This document discusses the materials and manufacturing process used for the Brodie steel helmet from World War 1. It then evaluates potential alternative materials for military helmets.
The Brodie helmet was made of Hadfield steel through a deep drawing process to form its distinctive shape. This provided ballistic protection from shrapnel through a combination of hardness from work hardening during forming and toughness in the inner layer. However, steel helmets are heavy, can transmit impact forces, and are susceptible to corrosion.
The document then evaluates properties required for helmet materials, including energy absorption capacity. Carbon fiber composites and boron carbide are identified as alternatives with advantages over steel such as lower weight and ability to dissipate impacts without
This study investigated the effect of three iron-based hardfacing electrodes - Hard Alloy 400, Hardloy III, and Hardloy V - on the properties of stainless steel when applied using shielded metal arc welding. Single and double layers of each electrode were deposited. Microhardness, wear resistance, and microstructure of the samples were then analyzed. Microhardness was found to increase by 1.7x, 2x, and 2.4x for the three electrodes respectively. Wear resistance improved by 29%, 60%, and 66% respectively. Microstructure analysis revealed that Hardloy V samples had the finest and most uniform grain structure, corresponding to the highest hardness and lowest wear rate. In conclusion, Hardloy V electrode
Effect of silicon carbide percentage on fracture toughness of aluminium silio...eSAT Journals
Abstract Metal matrix composites are composites in which one component will be a metal and other metal or non metal. It has wide applications in various fields like automobile, turbines blades etc which needs good mechanical properties. This thesis work studies about Aluminium Silicon Carbide metal matrix composites and their properties. Earlier studies revealed that as the percentage of Silicon Carbide is increased the properties get increased up to a limit and fracture toughness gets reduced beyond that. Here, in this work different percentage of SiC is added and fracture toughness is analyzed in terms of Stress intensity factor since fracture toughness cannot be calculated directly. Both software simulation and experimental methods has been done to find out the best percentage composition. Keywords: Metal matrix composites, Aluminium Silicon Carbide, Fracture Toughness, Stress Intensity Factor
Analysis of mechanical properties of heat treated mild steelSaugata Chowdhury
The aim of this project was to make a comparison between the changes in mechanical properties of mild steel quenched in various quenching mediums namely Vegetable oil, Brine solution, NaOH solution and Super-quenchant. Mild-Steel specimens for hardness test, tensile test and impact test were prepared and heated upto the austenizing range of temperature. After holding at that temperature for the necessary sintering time, they were immediately quenched in the four mediums.
Upon carrying the various tests, it was observed that hardness of all the specimens increased at the expense of toughness. Further the rate of cooling influenced the hardness of the specimens. Specimens quenched in NaOH exhibited maximum increase in hardness and tensile strength of steel. Oil quenched steel showed rise in hardness and tensile strength with least decrease in toughness among the four mediums. Brine also improved the hardness and tensile strength but maximum reduction in toughness was encountered. Finally, superquenchant was found to be the best quenching medium with appreciable rise in the hardness and tensile strength at very less reduction in toughness.
Proper heat treatment of steels is one of the most important factors in determining how they will
perform in service. Engineering materials, mostly steel, are heat treated under controlled sequence of
heating and cooling to alter their physical and mechanical properties to meet desired engineering
applications. In this study we have chosen AISI 1020 steel as for our research work and we have tried to
find out the mechanical properties (hardness) and micro structural properties (martensite formation,
carbon self-locking region) by means of appropriate heat treatment process (annealing, normalizing &
hardening). Here the steel specimens were heat treated in a furnace at different temperature levels and
soaking time; and then cooled in various media (air, ash, water). After that the hardness of the specimens
were rechecked for the comparison with previous data and the microstructures of the specimens were
examined using metallurgical microscope equipped with camera. These results showed that the hardness
of AISI 1020 steel can be changed and improved by different heat treatments for a particular application.
From the microstructures we have found that the annealed specimens with mainly ferrite structure give the
lowest hardness value and highest ductility while hardened specimens which comprise martensite give
the highest hardness value and lowest ductility. On the other hand, normalized specimens have given the
moderate hardness and ductility comparing with hardened and annealed specimens
Shell moulding is a casting process where a thermosetting resin-sand mixture is allowed to adhere to a heated metal pattern, forming a shell. The shell is then removed from the pattern. Molten metal is poured into the shell mould to form the casting. Shell moulding can produce complex parts with good dimensional accuracy and surface finish, reducing machining needs. Common materials cast are iron, aluminum, and copper alloys. Advantages include close tolerances and smooth surfaces, while limitations include expensive patterns and size restrictions. Applications include engine parts like cylinders and heads.
This document provides an overview of duplex stainless steel, including its metallurgy, corrosion resistance, welding practices, and design code requirements. It discusses the four main types of duplex stainless steel based on chromium content and their applications. Key points covered include the dual ferritic-austenitic microstructure of duplex stainless steel, how alloying elements like chromium, molybdenum, and nitrogen contribute to its properties, and metrics like PREN and CPT/CCT that evaluate its corrosion resistance. Welding guidelines and common processes for duplex stainless steel are also summarized.
This document provides an overview of various materials testing methods for steel, including microstructure, heat treatment, hardenability, hardness, tensile, impact, fatigue, and creep testing. It defines key terms for each test, describes the testing procedures and purposes. Microstructure of steel depends on carbon content and other alloying elements. Heat treatment involves controlled heating and cooling to modify properties. Hardenability testing determines how deep steel can harden during quenching. Hardness, tensile, impact, fatigue, and creep tests evaluate mechanical properties under different loading conditions.
This document provides an overview of materials used in fertilizer plants, including their classification, properties, and applications. It discusses various types of metals and alloys used, including carbon steel, cast iron, stainless steel, and others. Key points covered include:
- Classification of materials into ferrous, non-ferrous, metallic, and non-metallic categories.
- Properties of materials like strength, hardness, ductility, and toughness.
- Types of steel alloys and role of elements like chromium, nickel, molybdenum, and carbon.
- Applications of materials for cooling water networks, steam lines, and urea service equipment.
- Stainless steel
This study investigated the effect of three iron-based hardfacing electrodes - Hard Alloy 400, Hardloy III, and Hardloy V - on the properties of stainless steel when applied using shielded metal arc welding. Single and double layers of each electrode were deposited. Microhardness, wear resistance, and microstructure of the samples were then analyzed. Microhardness was found to increase by 1.7x, 2x, and 2.4x for the three electrodes respectively. Wear resistance improved by 29%, 60%, and 66% respectively. Microstructure analysis revealed that Hardloy V samples had the finest and most uniform grain structure, corresponding to the highest hardness and lowest wear rate. In conclusion, Hardloy V electrode
Effect of silicon carbide percentage on fracture toughness of aluminium silio...eSAT Journals
Abstract Metal matrix composites are composites in which one component will be a metal and other metal or non metal. It has wide applications in various fields like automobile, turbines blades etc which needs good mechanical properties. This thesis work studies about Aluminium Silicon Carbide metal matrix composites and their properties. Earlier studies revealed that as the percentage of Silicon Carbide is increased the properties get increased up to a limit and fracture toughness gets reduced beyond that. Here, in this work different percentage of SiC is added and fracture toughness is analyzed in terms of Stress intensity factor since fracture toughness cannot be calculated directly. Both software simulation and experimental methods has been done to find out the best percentage composition. Keywords: Metal matrix composites, Aluminium Silicon Carbide, Fracture Toughness, Stress Intensity Factor
Analysis of mechanical properties of heat treated mild steelSaugata Chowdhury
The aim of this project was to make a comparison between the changes in mechanical properties of mild steel quenched in various quenching mediums namely Vegetable oil, Brine solution, NaOH solution and Super-quenchant. Mild-Steel specimens for hardness test, tensile test and impact test were prepared and heated upto the austenizing range of temperature. After holding at that temperature for the necessary sintering time, they were immediately quenched in the four mediums.
Upon carrying the various tests, it was observed that hardness of all the specimens increased at the expense of toughness. Further the rate of cooling influenced the hardness of the specimens. Specimens quenched in NaOH exhibited maximum increase in hardness and tensile strength of steel. Oil quenched steel showed rise in hardness and tensile strength with least decrease in toughness among the four mediums. Brine also improved the hardness and tensile strength but maximum reduction in toughness was encountered. Finally, superquenchant was found to be the best quenching medium with appreciable rise in the hardness and tensile strength at very less reduction in toughness.
Proper heat treatment of steels is one of the most important factors in determining how they will
perform in service. Engineering materials, mostly steel, are heat treated under controlled sequence of
heating and cooling to alter their physical and mechanical properties to meet desired engineering
applications. In this study we have chosen AISI 1020 steel as for our research work and we have tried to
find out the mechanical properties (hardness) and micro structural properties (martensite formation,
carbon self-locking region) by means of appropriate heat treatment process (annealing, normalizing &
hardening). Here the steel specimens were heat treated in a furnace at different temperature levels and
soaking time; and then cooled in various media (air, ash, water). After that the hardness of the specimens
were rechecked for the comparison with previous data and the microstructures of the specimens were
examined using metallurgical microscope equipped with camera. These results showed that the hardness
of AISI 1020 steel can be changed and improved by different heat treatments for a particular application.
From the microstructures we have found that the annealed specimens with mainly ferrite structure give the
lowest hardness value and highest ductility while hardened specimens which comprise martensite give
the highest hardness value and lowest ductility. On the other hand, normalized specimens have given the
moderate hardness and ductility comparing with hardened and annealed specimens
Shell moulding is a casting process where a thermosetting resin-sand mixture is allowed to adhere to a heated metal pattern, forming a shell. The shell is then removed from the pattern. Molten metal is poured into the shell mould to form the casting. Shell moulding can produce complex parts with good dimensional accuracy and surface finish, reducing machining needs. Common materials cast are iron, aluminum, and copper alloys. Advantages include close tolerances and smooth surfaces, while limitations include expensive patterns and size restrictions. Applications include engine parts like cylinders and heads.
This document provides an overview of duplex stainless steel, including its metallurgy, corrosion resistance, welding practices, and design code requirements. It discusses the four main types of duplex stainless steel based on chromium content and their applications. Key points covered include the dual ferritic-austenitic microstructure of duplex stainless steel, how alloying elements like chromium, molybdenum, and nitrogen contribute to its properties, and metrics like PREN and CPT/CCT that evaluate its corrosion resistance. Welding guidelines and common processes for duplex stainless steel are also summarized.
This document provides an overview of various materials testing methods for steel, including microstructure, heat treatment, hardenability, hardness, tensile, impact, fatigue, and creep testing. It defines key terms for each test, describes the testing procedures and purposes. Microstructure of steel depends on carbon content and other alloying elements. Heat treatment involves controlled heating and cooling to modify properties. Hardenability testing determines how deep steel can harden during quenching. Hardness, tensile, impact, fatigue, and creep tests evaluate mechanical properties under different loading conditions.
This document provides an overview of materials used in fertilizer plants, including their classification, properties, and applications. It discusses various types of metals and alloys used, including carbon steel, cast iron, stainless steel, and others. Key points covered include:
- Classification of materials into ferrous, non-ferrous, metallic, and non-metallic categories.
- Properties of materials like strength, hardness, ductility, and toughness.
- Types of steel alloys and role of elements like chromium, nickel, molybdenum, and carbon.
- Applications of materials for cooling water networks, steam lines, and urea service equipment.
- Stainless steel
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Microstructure and chemical compositions of ferritic stainless steelGyanendra Awasthi
This document discusses the microstructure and chemical compositions of ferritic stainless steel. It begins by defining ferrite as the body-centered cubic crystal structure of pure iron that gives steel and cast iron their magnetic properties. It then discusses how adding nickel changes the crystal structure from body-centered cubic to face-centered cubic. The document also examines the different groups of ferritic stainless steels based on their chromium content, from 10-14% chromium to those with over 18% chromium. It notes that ferritic stainless steels have lower strength at temperatures over 600°C but greater resistance to thermal shocks than austenitic stainless steels.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
IRJET- Development of Low Weight Magnesium Composite and its CharacterisationIRJET Journal
This document summarizes research into developing a low-weight magnesium composite material and characterizing its properties. Magnesium alloy AZ91D was processed with silicon carbide as reinforcement using stir casting. Specimens with varying silicon carbide composition from 3-12% were tested. Tensile testing showed that yield stress, ultimate tensile strength, and toughness increased with higher silicon carbide content. Microstructural analysis found smaller grain sizes and better reinforcement distribution with smaller silicon carbide particle sizes. X-ray diffraction testing identified the crystal structures and confirmed no stress concentration in the composites.
This document provides information on various metalworking processes including cold working, hot working, rolling, extrusion, casting, and heat treatments. It discusses:
1) Cold working processes like rolling, drawing, and pressing that permanently deform and strengthen metals below the recrystallization temperature.
2) Hot working processes like forging, rolling, and extrusion that deform metals above the recrystallization temperature for easier shaping.
3) The sand casting process which is used to produce small quantities of identical castings through the use of sand molds. Molten metal is poured into a mold cavity and allowed to solidify.
This document reviews the deformation processes of porous metals and metallic foams. It discusses that porous metals have large pore volumes, while metallic foams refer to porous metals created through foaming processes. Forming porous metals into shapes allows for control of porosity and morphology, work hardening of the metal matrix, and creation of unusual microstructures. Forming can also improve properties like strength and sound absorption. Porous metals are also able to take on more complicated shapes than solid metals. Overall, forming processes can enhance properties but also reduce porosity, and porous metals may have applications where solid metals cannot be used.
Effects Of 600 Microns Particles of Eggshell on Tensile Strength of Zinc-Alum...IJMREMJournal
The study investigates the effects of eggshell particulate and particulate sizes on tenstile strength of ZA27 MMC
where eggshell served as particulate reinforcement. ZA27 MMC was produced by melting and casting ZA27
alloy and particulate eggshell in a lift-out crucible furnace, to produce rods of ZA27 MMC. Control sample rods
which have no eggshell content were also produced by melting and casting in sand molds. The tensile strength
of the produced rods were tested, and the results show a significant dependence of this property on added
particulate eggshell content.
IRJET- Effect of Soft Annealing on Copper, Brass and GunmetalIRJET Journal
The document analyzes the effect of soft annealing on copper, brass, and gunmetal samples. Rockwell hardness tests were performed before and after annealing samples at 850°C. Brass was found to be the hardest before annealing, while copper was hardest after annealing. Microstructure images showed grain refinement in copper after annealing but no visible changes in brass. Gunmetal samples developed cracks and pores after annealing. Wear tests found copper to be most resistant to wear, followed by brass, with gunmetal being the least resistant due to cracks and pores developed during annealing. In conclusion, annealing increased ductility and workability while decreasing hardness, with copper retaining higher hardness and wear resistance compared to brass and gunmetal after annealing.
Dr.R.Narayanasamy - Effect of Microstructure on formability of steels - Modif...Dr.Ramaswamy Narayanasamy
The document discusses the effect of microstructure on the formability of steels. It states that the amount of pearlite and ferrite phases affect formability, with pearlite decreasing ductility and ferrite increasing it. Finer pearlite and ferrite grain sizes increase strength but decrease formability. Spheroidizing pearlite increases ductility. The presence of inclusions like oxides and sulfides reduces ductility depending on their shape, size, and distribution. Globular inclusions perform better than elongated ones. The document also discusses how these microstructural factors affect the formability of different steel types like austenitic stainless steels.
The document discusses various types of cast iron, their microstructures, properties, production methods and applications. It describes the microstructures of gray cast iron, white cast iron, ductile cast iron and malleable cast iron. The key types are defined by the form of carbon in the microstructure, such as graphite flakes, nodules or carbide phases. The document also examines the solidification and processing factors that determine the carbon structure.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
This document summarizes research on using the Taguchi method to optimize metal inert gas (MIG) hardfacing welding parameters. The Taguchi method uses orthogonal arrays to minimize the number of experimental runs needed. In the study, different welding parameters including voltage, wire feed rate, nozzle-to-plate distance, welding speed, and gas flow rate are considered as control factors. An L25 orthogonal array is used to conduct the experiments according to the design matrix. Hardness and impact toughness tests are performed on the hardfaced samples, showing improvements in the properties. Grey relational analysis and desirability functions are also discussed as part of the Taguchi method optimization approach.
Mechanical Engineering Technical Interview Q & A Material science And Heat Tr...Er. Bade Bhausaheb
Material Science (MS) and Heat Treatment (HT) discusses various metal properties and heat treatment processes. It defines terms like specific gravity, tenacity, machinability, malleability, hardness, and toughness. It describes processes like annealing, normalizing, hardening, tempering, and case hardening. Key points covered include how carbon affects steel properties, uses of cast iron and different alloys, heat treatment purposes, and identifying metals based on sparks from grinding.
This document explores material and casting process options for manufacturing a hypothetical tap and faucet design. It considers stainless steel, copper, brass, and aluminum alloys as potential materials. Brass is selected due to its corrosion resistance, machinability, ability to be plated, and cost effectiveness. The permanent mould casting process is chosen as it produces a smooth finish at low cost while allowing high production volumes without die replacement. This process and DCB3 die casting brass meet the design requirements of affordability, quality, lifespan, and production timelines for the mid-market brand.
IRJET - Influence of Temperature on Tensile Properties and Fracture Behavior ...IRJET Journal
This document summarizes research on the influence of temperature on the tensile properties and fracture behavior of high-strength stainless steel 2304. Tests were conducted on specimens at room temperature and 200°C. The microstructure was examined and tensile tests were performed on an automated test machine. Failed samples were also examined under a scanning electron microscope. The research aims to understand how temperature affects tensile behavior and fracture in the stainless steel.
Ch2 foundaryproc Erdi Karaçal Mechanical Engineer University of GaziantepErdi Karaçal
This document provides an overview of foundry processes. It discusses how molds are made by preparing sand and pouring molten metal into prepared molds. Key steps include making molds and cores, melting and pouring metals, and allowing the casting to solidify. Molds are prepared using patterns and sand, and may use cores to create internal cavities. The document outlines important mold characteristics and different types of molds, cores, and sand used in the casting process.
A is true, R is false. Electric arc furnace can be used for both acid and basic steel making. However, impurities are not eliminated extensively in acid method using electric arc furnace. Impurities are eliminated extensively in basic oxygen furnace process, not in acid method.
Hence, A is true but R is false.
Stainless steel alloys are used widely in orthodontics. They contain 12-30% chromium which gives corrosion resistance. There are three main types - ferritic, austenitic and martensitic - depending on crystal structure. Austenitic stainless steel like 18-8 is most common due to good ductility. It can be work hardened or hardened by rapid cooling to form martensite. Heat treatments like annealing can relieve stresses from work hardening. Stainless steel is joined by silver soldering or spot welding in orthodontics.
This document discusses the development of an in-situ repair welding procedure for cracks found in steam turbine shrouds and blades made of martensitic stainless steel. Researchers at Indira Gandhi Centre for Atomic Research developed a procedure using gas tungsten arc welding and an austenitic stainless steel filler wire. Localized post-weld heat treatment was also conducted on the repair welds. This procedure was then successfully used to repair cracks in several power plants, and the repaired components performed satisfactorily for over three years of service.
This chapter discusses principles of solidification as they apply to pure metals. It examines mechanisms of solidification such as nucleation and growth, and applications like welding. The chapter outlines solidification processes, defects, and casting techniques. It provides examples calculating critical nucleation radius, redesigning a casting, and designing a riser. Diagrams of cooling curves and cast microstructures are also presented.
Development of WC-Feal Composite by Stir Casting MethodDr. Amarjeet Singh
In this paper author make an effort to develop a new
material for fulfill the need of present requirement. This
material is developed by the using of stir casting method. A
AMMC’s composite are developed to fulfill the need of present
requirements. This composite material is prepared by the use
of 3 metals. These metals are iron (Fe), aluminum (Al) and
tungsten carbide (WC).Thus this composite come under metal
matrix composite. This composite is WC – FeAl composite.
This is prepared by the use of stir casting method. The base
metals are iron and aluminum. These are having equal
quantity by weight. In this the sample is prepared by the
change the of percentage reinforcement. This is varying from
0 to 3%. A test is conduct to check their tensile strength as
well as compressive strength. By these test it is confirm that
with the increase the percentage of reinforcement in the
composite their tensile strength is decrease but their
compressive strength is increase.
Fabrication and compression of mechanical PROPERTIES OF AL7075 BY STIR CASTINGVenugopalraoSuravara
This document discusses the fabrication and testing of aluminum 7075-silicon carbide (SiC) metal matrix composites produced via stir casting. Al 7075 and SiC powders were mixed in varying weight ratios and cast into cylinders. Testing showed that hardness increased with higher SiC content and heat treatment. Wear resistance also improved with more SiC added. The composites demonstrated enhanced mechanical properties over the base aluminum alloy.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Microstructure and chemical compositions of ferritic stainless steelGyanendra Awasthi
This document discusses the microstructure and chemical compositions of ferritic stainless steel. It begins by defining ferrite as the body-centered cubic crystal structure of pure iron that gives steel and cast iron their magnetic properties. It then discusses how adding nickel changes the crystal structure from body-centered cubic to face-centered cubic. The document also examines the different groups of ferritic stainless steels based on their chromium content, from 10-14% chromium to those with over 18% chromium. It notes that ferritic stainless steels have lower strength at temperatures over 600°C but greater resistance to thermal shocks than austenitic stainless steels.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
IRJET- Development of Low Weight Magnesium Composite and its CharacterisationIRJET Journal
This document summarizes research into developing a low-weight magnesium composite material and characterizing its properties. Magnesium alloy AZ91D was processed with silicon carbide as reinforcement using stir casting. Specimens with varying silicon carbide composition from 3-12% were tested. Tensile testing showed that yield stress, ultimate tensile strength, and toughness increased with higher silicon carbide content. Microstructural analysis found smaller grain sizes and better reinforcement distribution with smaller silicon carbide particle sizes. X-ray diffraction testing identified the crystal structures and confirmed no stress concentration in the composites.
This document provides information on various metalworking processes including cold working, hot working, rolling, extrusion, casting, and heat treatments. It discusses:
1) Cold working processes like rolling, drawing, and pressing that permanently deform and strengthen metals below the recrystallization temperature.
2) Hot working processes like forging, rolling, and extrusion that deform metals above the recrystallization temperature for easier shaping.
3) The sand casting process which is used to produce small quantities of identical castings through the use of sand molds. Molten metal is poured into a mold cavity and allowed to solidify.
This document reviews the deformation processes of porous metals and metallic foams. It discusses that porous metals have large pore volumes, while metallic foams refer to porous metals created through foaming processes. Forming porous metals into shapes allows for control of porosity and morphology, work hardening of the metal matrix, and creation of unusual microstructures. Forming can also improve properties like strength and sound absorption. Porous metals are also able to take on more complicated shapes than solid metals. Overall, forming processes can enhance properties but also reduce porosity, and porous metals may have applications where solid metals cannot be used.
Effects Of 600 Microns Particles of Eggshell on Tensile Strength of Zinc-Alum...IJMREMJournal
The study investigates the effects of eggshell particulate and particulate sizes on tenstile strength of ZA27 MMC
where eggshell served as particulate reinforcement. ZA27 MMC was produced by melting and casting ZA27
alloy and particulate eggshell in a lift-out crucible furnace, to produce rods of ZA27 MMC. Control sample rods
which have no eggshell content were also produced by melting and casting in sand molds. The tensile strength
of the produced rods were tested, and the results show a significant dependence of this property on added
particulate eggshell content.
IRJET- Effect of Soft Annealing on Copper, Brass and GunmetalIRJET Journal
The document analyzes the effect of soft annealing on copper, brass, and gunmetal samples. Rockwell hardness tests were performed before and after annealing samples at 850°C. Brass was found to be the hardest before annealing, while copper was hardest after annealing. Microstructure images showed grain refinement in copper after annealing but no visible changes in brass. Gunmetal samples developed cracks and pores after annealing. Wear tests found copper to be most resistant to wear, followed by brass, with gunmetal being the least resistant due to cracks and pores developed during annealing. In conclusion, annealing increased ductility and workability while decreasing hardness, with copper retaining higher hardness and wear resistance compared to brass and gunmetal after annealing.
Dr.R.Narayanasamy - Effect of Microstructure on formability of steels - Modif...Dr.Ramaswamy Narayanasamy
The document discusses the effect of microstructure on the formability of steels. It states that the amount of pearlite and ferrite phases affect formability, with pearlite decreasing ductility and ferrite increasing it. Finer pearlite and ferrite grain sizes increase strength but decrease formability. Spheroidizing pearlite increases ductility. The presence of inclusions like oxides and sulfides reduces ductility depending on their shape, size, and distribution. Globular inclusions perform better than elongated ones. The document also discusses how these microstructural factors affect the formability of different steel types like austenitic stainless steels.
The document discusses various types of cast iron, their microstructures, properties, production methods and applications. It describes the microstructures of gray cast iron, white cast iron, ductile cast iron and malleable cast iron. The key types are defined by the form of carbon in the microstructure, such as graphite flakes, nodules or carbide phases. The document also examines the solidification and processing factors that determine the carbon structure.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
This document summarizes research on using the Taguchi method to optimize metal inert gas (MIG) hardfacing welding parameters. The Taguchi method uses orthogonal arrays to minimize the number of experimental runs needed. In the study, different welding parameters including voltage, wire feed rate, nozzle-to-plate distance, welding speed, and gas flow rate are considered as control factors. An L25 orthogonal array is used to conduct the experiments according to the design matrix. Hardness and impact toughness tests are performed on the hardfaced samples, showing improvements in the properties. Grey relational analysis and desirability functions are also discussed as part of the Taguchi method optimization approach.
Mechanical Engineering Technical Interview Q & A Material science And Heat Tr...Er. Bade Bhausaheb
Material Science (MS) and Heat Treatment (HT) discusses various metal properties and heat treatment processes. It defines terms like specific gravity, tenacity, machinability, malleability, hardness, and toughness. It describes processes like annealing, normalizing, hardening, tempering, and case hardening. Key points covered include how carbon affects steel properties, uses of cast iron and different alloys, heat treatment purposes, and identifying metals based on sparks from grinding.
This document explores material and casting process options for manufacturing a hypothetical tap and faucet design. It considers stainless steel, copper, brass, and aluminum alloys as potential materials. Brass is selected due to its corrosion resistance, machinability, ability to be plated, and cost effectiveness. The permanent mould casting process is chosen as it produces a smooth finish at low cost while allowing high production volumes without die replacement. This process and DCB3 die casting brass meet the design requirements of affordability, quality, lifespan, and production timelines for the mid-market brand.
IRJET - Influence of Temperature on Tensile Properties and Fracture Behavior ...IRJET Journal
This document summarizes research on the influence of temperature on the tensile properties and fracture behavior of high-strength stainless steel 2304. Tests were conducted on specimens at room temperature and 200°C. The microstructure was examined and tensile tests were performed on an automated test machine. Failed samples were also examined under a scanning electron microscope. The research aims to understand how temperature affects tensile behavior and fracture in the stainless steel.
Ch2 foundaryproc Erdi Karaçal Mechanical Engineer University of GaziantepErdi Karaçal
This document provides an overview of foundry processes. It discusses how molds are made by preparing sand and pouring molten metal into prepared molds. Key steps include making molds and cores, melting and pouring metals, and allowing the casting to solidify. Molds are prepared using patterns and sand, and may use cores to create internal cavities. The document outlines important mold characteristics and different types of molds, cores, and sand used in the casting process.
A is true, R is false. Electric arc furnace can be used for both acid and basic steel making. However, impurities are not eliminated extensively in acid method using electric arc furnace. Impurities are eliminated extensively in basic oxygen furnace process, not in acid method.
Hence, A is true but R is false.
Stainless steel alloys are used widely in orthodontics. They contain 12-30% chromium which gives corrosion resistance. There are three main types - ferritic, austenitic and martensitic - depending on crystal structure. Austenitic stainless steel like 18-8 is most common due to good ductility. It can be work hardened or hardened by rapid cooling to form martensite. Heat treatments like annealing can relieve stresses from work hardening. Stainless steel is joined by silver soldering or spot welding in orthodontics.
This document discusses the development of an in-situ repair welding procedure for cracks found in steam turbine shrouds and blades made of martensitic stainless steel. Researchers at Indira Gandhi Centre for Atomic Research developed a procedure using gas tungsten arc welding and an austenitic stainless steel filler wire. Localized post-weld heat treatment was also conducted on the repair welds. This procedure was then successfully used to repair cracks in several power plants, and the repaired components performed satisfactorily for over three years of service.
This chapter discusses principles of solidification as they apply to pure metals. It examines mechanisms of solidification such as nucleation and growth, and applications like welding. The chapter outlines solidification processes, defects, and casting techniques. It provides examples calculating critical nucleation radius, redesigning a casting, and designing a riser. Diagrams of cooling curves and cast microstructures are also presented.
Development of WC-Feal Composite by Stir Casting MethodDr. Amarjeet Singh
In this paper author make an effort to develop a new
material for fulfill the need of present requirement. This
material is developed by the using of stir casting method. A
AMMC’s composite are developed to fulfill the need of present
requirements. This composite material is prepared by the use
of 3 metals. These metals are iron (Fe), aluminum (Al) and
tungsten carbide (WC).Thus this composite come under metal
matrix composite. This composite is WC – FeAl composite.
This is prepared by the use of stir casting method. The base
metals are iron and aluminum. These are having equal
quantity by weight. In this the sample is prepared by the
change the of percentage reinforcement. This is varying from
0 to 3%. A test is conduct to check their tensile strength as
well as compressive strength. By these test it is confirm that
with the increase the percentage of reinforcement in the
composite their tensile strength is decrease but their
compressive strength is increase.
Fabrication and compression of mechanical PROPERTIES OF AL7075 BY STIR CASTINGVenugopalraoSuravara
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helmets
1. i
INTRODUCTION1
MK 1 “BRODIE HELMET” TYPE B....................................................................................................1
Material Composition ...................................................................................................................1
Manufacturing Process................................................................................................................2
Forming the Steel.........................................................................................................................2
Shaping the Helmet .....................................................................................................................2
Material Properties.......................................................................................................................2
Environmental Impact..................................................................................................................3
Causes of in-Service Failure........................................................................................................4
Causes of Early Failure ...............................................................................................................6
ALTERNATIVE MATERIAL SELECTION FOR HELMET DESIGN..................................................6
Requirements of Helmets and Their Materials............................................................................6
Material Choice ............................................................................................................................6
Selection of a New Material.........................................................................................................8
COMPARISON OF MATERIAL PROPERTIES................................................................................10
Carbon Fibre Reinforced Composite (CFRP) ...........................................................................10
Boron Carbide............................................................................................................................10
Processes ..................................................................................................................................12
Conclusion of Alternative Materials ...........................................................................................14
IMPROVEMENTS TO SERVICE LIFE..............................................................................................15
CONCLUSION...................................................................................................................................16
2. ii
Abbreviations/Glossary
BC Boron Carbide
CES Cambridge Engineering Selector
CFRP Carbon Fibre Reinforced Plastic
CO2 Carbon Dioxide
FCC Face Centred Cubic
IED Improvised Explosive Device
ISAF International Security Assistance Force
J Joules. Unit of energy
K Kelvin. Temperature in degrees centigrade + 273
KE Kinetic Energy
MK Mark
UTS Ultimate Tensile Strength
3. 1
INTRODUCTION
1. For this assignment I will be looking at the materials and the processes of military combat
helmets. I will first look at one from the First World War and then use the Cambridge Engineering
Selector (CES) to select an alternative material that helmets could be made from and compare
them against each other.
MK 1 “BRODIE HELMET” TYPE B
2. This helmet was bought into service in 1915, it was brought into service to reduce the
number of casualties caused by shrapnel from enemy artillery. The MK 1 (fig 1) was the first steel
helmet issued to British troops since the early 1700s and its introduction reflected the increase in
firepower and artillery tactics of the WW1. The “soup bowl” shape provided protection from artillery
shells bursting above the trenches, this one piece design allowed for the use of steel that could be
made from a single pressing. A leather liner provided cushioning and a simple strap attached it to
the user. They were finished with a simple coat of paint.
Fig 1. British Army Mk1 Helmet
Material Composition
3. The type B was made out of steel with a manganese content of 12% and carbon content of
1%, this was known as “Hadfields Steel” after its inventor Sir Robert Hadfield. The harder steel
had increased ballistic protection, was non-magnetic and weighed 2.4 lbs or 1.1kg, by the authors
assumption it was required to operate under the following conditions shown below:
Table 1 physical and environmental conditions
Temperature (+/-) 323 Kelvins
Weather
Prolonged exposure to
light and heavy rain
Ballisitc Protection
Shrapnel projectiles (KE up
to 600 Joules)
User Requirements
Potect from general bumps
and impacts, be light and
comfortable enough for
prolonged wearing
4. 2
Manufacturing Process
Forming the Steel
4. The steel and its alloying elements are heated to an austenitic state at 1050 degrees C, it is
then quenched rapidly. Because the steel contains such a high percentage of manganese, this
has the effect of reducing the transformation temperature to such an extent that austenite is formed
at room temperature, this produces austenitic steel which gives good hardness and ductility
making the steel tough.
Shaping the Helmet
5. The helmet was deep drawn from 20 gauge (0.36in) sheets. Deep drawing is done by
forming flat sheet metal into a shape by pulling it through a die (fig 2). The process depends on
the materials ability to plastically stretch and deform into shape and is limited by the materials draw
ratio.
Fig 2. Drawing process
6. The term deep drawing is mainly used when the depth of draw exceeds the diameter by one
or more, anything less is termed stamping however the operations are the same. Once this
process was complete, the part would’ve been cut out to produce a finished helmet.
7. An alternative method to this could have been to cast the compartment. In this case 2 dies
would be needed to form the shape required when molten metal is poured in and allowed to cool,
using sand casting would’ve been too costly to produce the helmets in the quantity required but a
die cast machine could’ve been used. Casting would’ve offered the benefit that the cast part
would’ve required no further machining and the accuracy of the helmet would’ve been consistent.
The downside of casting would’ve been the fact that the drawing process was key to enhancing the
helmets armour qualities which is explained below.
Material Properties1
8. Hadfield is a steel/manganese alloy, manganese is used in all steels to de-oxidise it, and it
reduces the problems caused by sulphur and improves the strength and wear resistance. Tensile
strength increases up to about 8% manganese before dropping off. Hadfield steel contains 10% or
more manganese and has an austenitic phase with a face centred cubic (FCC) lattice (fig 3), the
austenite structure comprises large grains which allows the material to deform as the grains can
1
http://www.acmealloys.com/Austenitic%20Manganese%20Steels.PDF
5. 3
move a large amount. The steel is strengthened due to the interstitial carbon atoms and the
substitutional manganese atoms (fig 4).
Fig 3: Face Centred Cubic Lattice Fig 4. Alloying arrangements
9. The FCC has 12 equivalent slip systems and deformations and when the material is work
hardened these cause some of the austenite to form into martensite, as martensite is a hard
substance Hadfield steel therefore has a hard outer surface and a tough inner. This hardening of
the outer layer is further beneficial if a crack in the outer layer should occur, the crack propagation
is stopped by the tough inner core.
10. The drawing process was key to the helmets armour qualities, when the metal is drawn it is
work hardened, as mentioned this has the effect of changing the austenitic steel into martensitic
steel on the outer edge (the part that is drawn into the die), the helmet therefore had a hard outer
and tough inner, the hardness gave the helmet a first layer of ballistic resistance and the tough
inner could absorb the energy, it also got harder over time with each successive hit.
11. Helmet attachments. The helmet had internal welded lugs through which a leather strap
was fitted which was in contact with the wearer and allowed a chin strap to be fitted. Leather is a
natural material with good thermal properties but can become slippery when wet and quickly
degrades.
Environmental Impact
12. Due to the number of men in the army at the time well over 1 million helmets were
manufactured, this required about 4000 tonnes of steel, equivalent to around 140 thirty tonne tanks
of the period. As steel at this time was the single most important material for both industry and the
war effort this was clearly a large strain on production.
13. To turn raw steel into a helmet requires a lot of energy, because of that we produce Carbon
dioxide (CO2). The table below demonstrates the cost of energy and CO2 production for
equipping an army of 1 million soldiers with a high carbon steel helmet. Due to lack of information
on the energy and CO2 usage of Hadfield steel I have used CES to find a comparable high carbon
steel.
6. 4
Table 2. Energy use and CO2 production
14. This table demonstrates the high levels of energy needed to turn raw materials into useful
objects and the negative effect of doing that in terms of CO2 produced, of interest is the amount of
water required for making the helmets, over 68 million litres which again has a big effect on the
environment and on an island country at war.
15. Due to the pressures placed on the country during a time of war there was a need to reduce
costs wherever possible, the armour qualities of the helmet could’ve been increased with an
increase in thickness, however this would have required more steel and more expense. Another
means of reducing the costs was in the corrosion protection, the finished helmet was painted in
olive drab which was a quick and cheap method but which did not offer the long term corrosion
benefits that could’ve been offered by first galvanising the helmet and then painting it. This led to
the possibility of an increase failure due to corrosion if the paint became damaged.
Causes of in-service failure
16. Impact. For an item that is designed to be worn during combat the biggest threat of failure
is likely to be from impact, typical impacts would have been from shrapnel and bullets but also from
blunt hits such as from a rifle butt or similar objects during trench raids.
17. When a projectile hits the helmet it contains kinetic energy based on its mass and velocity. A
typical fragment of shell is 1.2 grams and travels at 1000 metres per second, this contains kinetic
energy (KE) as calculated by KE=0.5mv², therefore:
KE =
1
2
𝑋 0.0012 𝑋1000² = 600 Joules2
18. As the shrapnel hits the helmet, its material will start to absorb that energy by changing it into
heat and sound. The ability of the material to absorb energy depends on its ultimate tensile
strength and its ability to elastically and plastically distort. Fig 5 shows these regions, as the
2
(Farrar, CL; Leeming, DW; Royal Military College of Science, Shrivenham, 1982)
Energy Ammount
Mass of
Helmet Per unit Per 1 million units
Embodied Energy, Primary Production (MJ/Kg) 34.2 1.1 37.62 37,620,000.00
Drawing Energy (MJ/Kg) 124 1.1 136.40 136,400,000.00
Recycling energy (MJ/Kg) 9.01 1.1 9.91 9,911,000.00
Total 183.93 183,931,000.00
CO2 footprint, primary production (Kg/Kg) 2.34 1.1 2.57 2,574,000.00
C02 footprint, drawing process (Kg/Kg) 9.32 1.1 10.25 10,252,000.00
CO2 footprint, recycling (Kg/Kg 0.708 1.1 0.78 778,800.00
Total 13.60 13,604,800.00
Water Usage (l/Kg) 62.3 1.1 68.53 68,530,000.00
Environmental impact of the Brodie Helmet
(Steel AISI A4 air-hardening cold worked suitable for deep drawing 1.05% carbon and 2.2% manganese)
Energy Usage
Recycling
7. 5
projectile hits the material the stress in it increases disproportionally to the strain (energy is being
absorbed without a change in material shape), it then reaches a point where the material gives up
under the stress and plastically deforms. The area under the curve can be considered work done
or the energy required to break it. If there is enough energy in a projectile it will break the material
it hits. Due to the proximity of the helmet to the head plastic deformation may also cause injury.
Fig 5. Elastic and Plastic deformation
19. Hadfield steel was designed to absorb the energy from relatively small objects like shrapnel
as this was the biggest cause of fatalities in the trenches, however, if the helmet was hit from a
bullet fired by an enemy sniper than the KE could surpass the ability of the helmet.
20. For example, a bullet with a mass of 5g travelling at 920 m/s has KE of 2116 J, this would hit
the helmet, rapidly surpass the tensile strength of the steel and penetrate it killing the soldier, even
if the bullet lost a lot of energy due to the shape of the helmet and failed to penetrate their could
still be enough energy to transmit a shockwave through the material and injure or kill the soldier.
Very few helmets even today can withstand a hit from a high velocity bullet. Other factors can also
affect the point at which the material fractures under impact, these being:
a. Presence of stress concentrations. Either caused during manufacture or by
environmental factors, a small hole or notch can raise the stress
b. Speed with which the projectile hits the material. This may result in the material
not having time to plastically deform and so it fails in a brittle manner instead.
c. Temperature. Metal can behave in a more brittle manner as temperature decreases,
although as Hadfield steel has a Face Centred Cubic structure it is not affected by this
ductile-brittle transition.
21. Other methods of failure such as creep and fatigue were unlikely to cause failure in the Mk1.
Creep will only occur if a continuous force is applied to the helmet and the temperature is within 0.3
to 0.4 of the metals meting temperature, our steel has a melting point of 1773 K which means our
creep value is around 531.9K, the helmets working environment would not have got to that
temperature.
22. Fatigue failures require the constant loading and unloading of a material, again this is not
something that would be expected for a helmet as we would not expect a soldier to either
repeatedly hit his helmet or allow it to be shot over and over again. Furthermore our helmet’s strap
was connected to welded lugs as opposed to drilled holes (which could’ve acted as stress raisers)
so we would not expect fatigue failure to be significant in the Mk1.
8. 6
Causes of Early Failure
23. Corrosion. As steel is iron based it can be susceptible to rusting, if unprotected iron is
exposed to oxygen and water then rusting can take place, both these conditions were present on
the western front. The helmet was delivered to troops painted in an olive drab paint, painting
protected the metal by providing a cover over the helmet through which water cannot penetrate.
However, during use the helmet would be dropped and scratched, and this exposed the metal.
24. When steel comes into contact with water and oxygen, the oxygen combines with the steel
atomically and creates a new compound called an oxide which weakens the bonds of it. Rusting is
an electro-chemical process which causes the iron to lose electrons to the oxygen surrounding it
dependant on the presence of water. The chemical process is shown below.
O2 + 4e-
+ 2H2O = 4OH-
25. This problem could’ve been reduced by adding protective measures such as galvanising
which creates another layer of zinc which protects the steel, however this would’ve been too
expensive for so many helmets.
ALTERNATIVE MATERIAL SELECTION FOR HELMET DESIGN
Requirements of helmets and their materials
26. The ability of a projectile to cause damage or injury is determined by its kinetic energy, the
helmet must resist penetration of the projectile and dissipate as much of the kinetic energy as
possible. Additionally, as the helmet is in close contact with the head which can be damaged by
even small amounts of movement, it must also minimise the effects of secondary damage. A
helmet that deforms plastically therefore may still cause injury or death to the wearer even if it
absorbs the energy it was hit with.
27. To absorb energy we require a material that is tough, toughness is defined as a materials
ability to resist crack propagation3
or its ability to absorb energy without fracturing. It requires a
balance of strength and ductility. Toughness is measured in Joules per cubic metre. We could
also use a very hard material to reject all the energy of the projectile.
28. A further requirement of helmet materials is to protect the soldier from everyday knocks and
scrapes when entering or leaving armoured vehicles. Pertinent to today is the need for the helmet
to protect the head against injury from flying projectiles during a vehicle accident/IED strike or from
hitting the ground after a fall as a result of an explosion.
Material Choice
29. Metallic Armour. Metallic armour works by preventing any penetration of the projectile, it
does this by breaking it up and dissipating the energy over a large surface area, this requires
hardness. It is generally successful in withstanding high velocity bullets and multiple hits in the
same area, this is a very strong factor in helmet design and one of the reasons Hadfield steel was
used in the MK1.
30. However, when metallic armour is placed in contact with the body it has the disadvantage
that on impact a shock wave can be transmitted through the material to the body causing cavitation
which then leads to secondary injuries (fig 6).
3
(W.Bolton, 1998)
9. 7
Fig 6 4
31. Metallic armour is normally heavier and this can cause injury when the head is moved rapidly
by impact as well as adding to the weight carried by soldiers, this was a key reason for the
exploration of other materials.
32. Polymer Composite Armour. An interwoven fibre laid into shape and then made hard with
a resin. When the projectile hits, it is trapped by the fibres, each fibre pulls every other fibre
connected to it and so the energy is dissipated across a large surface area, this is similar to a
football being stopped by the goals net.
33. However, this means that each hit weakens the material and so its ability to defeat multiple
hits is reduced. It is not able to resist high velocity bullets but is particularly good at defeating
shrapnel as this presents a larger surface area to get trapped in the fibres. Its low mass (less
mass on the head) and ability to be moulded to shape are its main benefits.
Fig 7. Mk 6 helmet
34. This material is the current common choice for combat helmets such as the British Army Mk
6 helmet (fig 7), this is made from a ballistic nylon fibre hardened with a resin, another common
material is Kevlar which is used to reinforce a plastic material, Kevlar is an aramid with specific
ballistic enhancing properties.
4
(Farrar, CL; Leeming, DW; Royal Military College of Science, Shrivenham, 1982)
10. 8
35. Ceramic Armour. Ceramics (specifically engineered ceramics) are hard materials with low
density, they defeat projectiles by being harder than the projectile which is forced to distort itself on
impact with the ceramic thereby reducing its kinetic energy by itself (fig 8), and although they fail in
a brittle manner they are still justifiable due to the extremely high hardness levels.
Fig 8. Impact of projectile on ceramic5
36. For this reason it is able to resist penetration from high velocity projectiles. However it does
need an additional material such as a composite to hold it together if it shatters after the projectile
hits, this actually allows the armour to continue to defeat the projectile as the ceramic dust will
wear away at the bullet. The additional material then dissipates the remaining energy to an
acceptable level.
Selection of a new material
Based on this ballistics information of materials, I will look for a composite and a ceramic material
that can offer similar ballistic protection to that offered by steel but that is also lighter. A lighter
helmet will mean less weight for the soldier to carry and will minimise the damage caused by
injuries such as whiplash during an IED explosion or vehicle roll-over.
37. To do this I will use CES to compare yield strength versus density for a composite material
and hardness verses density for a ceramic option. I will use yield strength as a guide of a
materials ability to elastically deform, the ultimate yield point being an indicator of the point to
which the material will elastically deform. Hadfield steel is not included in CES so for comparisons
I shall use high carbon steel.
5
(Fundus, 2013)
Composite
Ceramic
Ceramic
11. 9
Graph 1 Material selection based on elastic limit
Graph 2 Material selection based on Hardness
12. 10
38. By using CES I have established that two suitable materials for helmets might be Carbon
Fibre Reinforced Plastic (CFRP) and Boron Carbide (BC). CFRP is a material from the
plastic/composite category and BC is a material from the ceramic category, these both differ from
Hadfield steel which is of the metal category.
39. These two materials should match my requirements of finding a new material with
comparable ballistic qualities of steel but with a reduced weight. CFRP has a comparable yield
strength to steel, and BC has a much higher hardness value to steel so I am justified in choosing
these materials.
COMPARISON OF MATERIAL PROPERTIES
Carbon Fibre Reinforced Composite (CFRP)
40. This composite material consists of fibres of carbon added to a polyester or epoxy resin, the
epoxy holds the materials in the desired shape and transfers the loads to the carbon fibres which
do all of the work, the resin allows for ductility and toughness and protects the fibres, the epoxy
also keeps the fibres apart which helps to reduce crack propagation.
41. Carbon fibre is first spun into filament yarns, this yarn is then heated to get rid of any non-
carbon atoms and then wound onto bobbins. Unidirectional sheets can then be made. The
sheets are laid into a mould pre-coated with resin, after each layer is aligned it is coated with more
resin and rolled to distribute the resin fully throughout the fibres in a hand layup technique (fig 9),
this is then repeated until the required thickness is reached. Once complete it is either air-cured or
put into an autoclave to heat and set the epoxy.
Fig 9. Hand layup technique.
42. Much of the strength depends on the orientation and type of the fibres. Aligning the fibres in
a continuous length will give the highest strength against a force applied in line with the fibres but
reduces performance when it is placed against them, randomly arranging them will give less
performance than continuous but the performance is achieved in all directions.
43. This material offers reduced weight but comparable tensile strength when compared to steel,
it is more likely to fail in a brittle manner than steel but the reduced weight is such a big factor that
this could still be acceptable. A more common material added to plastic helmets is Kevlar which is
a poly-aramid fibre with increased ballistic properties but this was not shown on CES. However,
CFRP helmets are used by Special Forces teams were its lightweight is more beneficial than its
outright ballistic protection. The big downside with CFRP is the difficulty of manufacture due to the
lengthy hand layup technique
Boron Carbide
44. Boron Carbide (BC) is a very hard material that exceeds the hardness offered by steel.
Graph 2 shows BC having a Vickers hardness level of 1300 HV and a density of 1200 kg/m3. BC
13. 11
has strong covalent bonds (atoms sharing electrons) which means they require a lot of energy to
break them. It consist of a complex crystal structure of boron and carbon atoms (fig 10).
Fig 10. Boron-carbide
45. It is formed by pressing BC powder into the desired shape, a polymer binder is added to hold
its shape and then the whole thing is fired at a high temperature which burns off the polymer and
causes the powder particles to coalesce and fuse together in a process known as sintering (fig 11),
the temperature is typically around 1550 -1700 o
C and continues for up to 20 hours, this process
has the negative effect of causing the shape to shrink by around 20%, this means the initial
shaping must be done above the desired end shape. The process and in particular the
temperature and time need to be sufficiently high in order to reduce the porosity of the material.
Fig 11. Sintering and pressing technique.
46. The ability of this material to defeat projectiles depends on it having a very low porosity,
porosity (holes) in ceramics is what gives them the ability to shatter easily, the pressing and
sintering process reduces the porosity but, if this is not done correctly or isn’t successful than a
very porous material will be produced which could shatter easily when hit. Because of the constant
equal pressure needed to form a non-porous material it is difficult to form anything other than
simple shapes such as squares or rectangles.
47. With research this is not often used for helmet manufacture due to the difficulties in forming it
into a single curved shape, however it is being investigated and is a potential future technology.
Also, due to the relatively poor ability of this armour to survive multiple hits without cracking it is
perhaps not ideally suited for use by soldiers as replacement of the damaged helmet on the
Boron
atom
Carbon
atom
14. 12
battlefield may be problematic. However, it could be justified based on its ability to defeat high
kinetic energy projectiles such as those from a high velocity sniper rifle.
48. Another alternative could be for this type of material to be fitted as a temporary removable
extra piece of armour on a composite helmet as and when the threat level requires it, such as on
static guard duty in a Sanger with the main threat coming from sniper fire. If the BC was formed
into small square or diamond shapes they could be added to a helmet in a similar fashion to how
ceramic armour is fitted to armoured vehicles currently. Being small they could be easily replaced
when hit.
49. This material offers reduced weight but increased protection compared to steel, the downside
is the difficulty in manufacture and it’s potential for brittle failure. It could however be combined
with CFRP to provide protection from cracking, this would be a much better solution.
Processes
50. To compare these materials with meaningful comparisons I will design a basic helmet shape
based on the circumference of my own head. I can then use these measurements to compare
cost, weight and environmental conditions by comparing the materials like for like.
51. Circumference of head plus air gap is 62cm, therefore diameter = 62 / 3.14 =19.7cm.
Simplified helmet shape is a hollowed out half sphere (Volume outer (Vo) – Volume Inner (Vi)) with
thickness of 0.9cm (based on the thickness of current combat helmets such as the Mk 6) therefore
volume of helmet is:
Vo
1
2
(
4
3
𝜋𝑟3) – Vi
1
2
(
4
3
𝜋𝑟3) = 500cm3
or 0.0005m3
Fig 12. Example helmet design for material comparison
52. I will base the cost on equipping an army of 100,000 soldiers with the new helmet. Figures
taken from CES are the highest ones given. As before, in place of Hadfield steel I have used Steel
AISI A4 air-hardening cold worked suitable for deep drawing with 1.05% carbon and 2.2%
manganese. I would expect Hadfield steel to have a higher cost than plain high carbon steel due
to the extra manganese in it.
53. It should be noted that these dimensions and figures serve to illustrate the difference in costs
only, they do not reflect the actual dimensions required of a helmet, the MK1 steel helmet had a
much thinner dimension of .09cm as opposed to .9cm and a mass of 2.2kg as opposed to 4kg, this
means our figures our accounting for more material than may be necessary. The reason for this is
that making accurate figures for ballistic protection is very complicated and out of the scope of this
assignment, however, they are still justifiable for comparing the costs of materials. We would
expect that a steel helmet could be made thinner than its CFRP or BC counterpart.
15. 13
54. The figures below are calculated from the information on CES, manufacture costs are then
calculated by CES which gives a high and low relative cost index per batch size, the average
between high and low was then taken.
Table 3. Cost comparison
55. These figures show the cost of manufacture of up to 100,000 helmets, at this stage the price
per helmet is relatively fixed and no further reduction in cost per unit can be made. Of interest is
the difference in price per single helmet and price per 100,000 helmets, this shows the expense
incurred in starting up a new business such as the cost of the machinery.
56. Another interesting point is that despite CFRP having the lowest overall mass and the lowest
cost per single unit of all three it remains by far the highest cost per unit, this is due to the complex
manufacturing process which is difficult to automate.
57. We can now look at how our materials compare against in each other in terms of energy use
and CO2 levels. Due to the difficulties in obtaining accurate figures for BC we will look at the
energy and CO2 levels for primary production only.
HIGH CARBON
STEEL
CFRP Boron Carbide
Density (KG/m3) 7999 1600 2550
Volume of
example helmet
(m3)
0.0005 0.0005 0.0005
Mass of example
helmet (kg)
4.00 0.80 1.28
Price (kg/m3) 0.39 26.20 56.20
Type of
manufacture
Deep Drawing Lay-up
Pressing and
Sintering
Cost with
manufacture
(per unit) (£)
7250.00 2705.00 5250.00
Cost with
manufacture
(per 100,000
units) (£)
6.25 395.00 55.00
16. 14
Table 4. Comparison of energy use and CO2 production
58. Of interest is the high numbers for CFRP, they show how much energy is required for
producing the material coupled with the high amount of CO2 produced as a result, although the
figures aren’t shown we would also expect high figures for manufacturing energy and CO2 footprint
from CFRP, again this is due to the complex nature of making the CFRP sheets and the lengthy
time required in the “hand layup” techniques.
59. The other interesting point is the lack of ability to re-cycle CFRP or BC, this is because once
formed the energy required to try and convert them back into their base components would be far
too excessive, steel on the other hand can be melted back.
Conclusion of alternative materials
60. The two materials I have chosen offer the benefits of reduced helmet mass compared to
steel, for this reason both materials are justified in their selection if mass is our only consideration.
However, steel offers a more versatile material to work with, and pertinent to today, can be
recycled with relative ease.
61. If we were selecting a material based on its ballistic protection then Boron Carbide would be
the best selection as this offers a higher hardness value then steel but at a reduced mass, this
makes it very attractive for armour but, the ability to form it into a complex shape and its brittleness
makes it a possibility for future or specialised helmets only.
62. If cost, energy consumption and CO2 levels were of less concern than protection then
combining a BC core with inner and outer layers of CFRP would offer a lightweight, high tensile
strength and extremely hard helmet that could offer greatly increased ballistic protection compared
to steel.
Energy Ammount Mass of Helmet Per unit Per 100,000
Embodied Energy, Primary Production (MJ/Kg) 34.2 3.95 135.09 13,509,000.00
CO2 footprint, primary production (Kg/Kg) 2.34 1.28 3.00 299,520.00
RECYCLE YES
Embodied Energy, Primary Production (MJ/Kg) 500 0.8 400.00 40,000,000.00
CO2 footprint, primary production (Kg/Kg) 36.4 0.8 29.12 2,912,000.00
RECYCLE NO
Embodied Energy, Primary Production (MJ/Kg) 169 1.28 216.32 21,632,000.00
CO2 footprint, primary production (Kg/Kg) 9.1 1.28 11.65 1,164,800.00
RECYCLE NO
STEEL
CFRP
BORON CARBIDE
17. 15
IMPROVEMENTS TO SERVICE LIFE
63. The MK1 steel helmet was a critical part of a soldier’s equipment when in the trenches,
however, it was not without criticisms. If we were to improve the service life of it we could look at
the following improvements.
64. Materials Composition. Hadfield steel proved to be very efficient at protecting the soldiers
from enemy shrapnel, however it was not as good at protecting them from rifle rounds, as these
projectiles carry so much kinetic energy the only way to improve the helmet with the technology of
the time is to add more steel to vulnerable areas.
Fig 13. Increased ballistic protection6
65. Figure 13 shows this concept as used by the German army, an extra steel plate which could
be added to the front of the helmet to protect men when on sentry duty, this increased the ballistic
protection against frontal attack. However, the extra weight meant it was tiresome to wear for
anything but short periods.
66. Design. The design of the Mk 1 helmet was designed to protect against shrapnel, for this
reason a large rim was added to cover not just the head but also part of the shoulders from artillery
rounds exploding overhead.
67. An improvement could have been made by adding a neck shield at the back, this would
protect the extremely vulnerable area around the spine and could have reduced the number of
spinal injury to troops. However, due to the material technology at the time this could only have
been done with an extra steel plate, this would’ve been very inflexible and could have hindered
movement when taking up a firing position.
68. One key improvement that was made was to redesign the chin strap attachment with a brass
screw attachment on the helmet, this meant that a damaged liner could be changed far easier and
quicker in the field.
69. Corrosion Protection. The materials were only painted in standard army olive drab due to
costs. This meant that if the helmet was dropped or hit then some paint could flake off which
would result in corrosion through rusting. A better method would have been to galvanise the metal.
6
http://www.iwm.org.uk/collections/item/object/30100401
18. 16
Fig 14. Galvanising process
70. Galvanising involves degreasing the metal and then dipping it into liquid zinc, it is then
cooled in air. The process allows the molten zinc to alloy itself with the steel which forms a thin
coat around it (fig 14). Then if the helmet is scratched it the zinc that is scratched rather than the
steel underneath.
71. Working conditions/environment. The working conditions of the mk1 would be difficult to
alter, however a big problem with a helmets lifespan is due to user error, this could be soldiers
throwing it around and causing dents and scratches. The only way to improve the working
conditions is to better educate the user.
CONCLUSION
72. The mk1 helmet was the first ballistic helmet issued to the British Army since medieval ages,
it was rushed into service as what would today be termed an “urgent operational requirement” in
response to the increase in injuries from overhead artillery fire. Many soldiers and officers were
initially dubious about it and failed to understand its abilities, this led to misuse or over confidence
in it, coupled to this was the fact that injuries actually increased after it was introduced (due to the
reduction in deaths which would’ve occurred) meant that its issue required a change in thinking for
the British Army.
73. This was mirrored nearly 60 years later with the issue of the MK6 helmet, the first plastic
helmet issued to British soldiers was problematic as again a change in thinking was required to
accept plastic helmets after so many years with steel ones, the heavy weight of steel was more
reassuring than plastic and as everyone “knows” steel is hard and plastic is weak.
74. So, despite the increased benefits that material technology can bring, the most important
aspect to remember is what the customer wants or is willing to accept. Without trust or
understanding of the material in question, the customer is unlikely to use it, perhaps this is the
biggest problem armour manufacturers will face as they introduce ever lighter and different armour
materials.
75. As someone who has used helmets repeatedly on operations but never really thought about
how it works or what it is capable of, I found this assignment very interesting. I think there is a real
need for the development of helmets with increased ballistic protection. The use of single shot
attacks on ISAF troops in Afghanistan demonstrates the need for head protection from high
velocity, high kinetic energy rounds.
19. 17
Bibliography
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Ballistics-A basic manual. Oxford: BRASSEYS.
Fundus, M. (2013). Ballistic Protection-Trends in Body Armour and Helmets. Berlin: ESK Ceramics
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http://eandt.theiet.org/magazine/2014/06/putting-a-lid-on-it.cfm. (2014, November 12). Retrieved
from the IET.
W.Bolton. (1998). Engineering Materials Technology (Third ed.). Oxford: Butterworth-Heinemann.
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