The document discusses environment stress cracking (ESC) failures in plastic components caused by the combined effect of environmental exposure and stress over time. It analyzes the stresses in a secondary coil bobbin made of Noryl GFN3 PPE + PS plastic using finite element analysis (FEA) under thermal cycling conditions. The FEA results show zones of tensile stress concentration near fillets at low temperatures that could lead to slow crack growth. A new material with higher molecular weight and crystallinity than Noryl is proposed to improve resistance to ESC.
The experiment measured mechanical properties of annealed and unannealed brass rods as well as borate glass rods of varying compositions. It found that annealing decreased the yield strength of brass rods by increasing grain size and reducing dislocation density. Borate glass became more brittle at lower alkali concentrations due to being below its glass transition temperature. Young's modulus was measured through tensile testing, 3-point bending, and measuring speed of sound, with varying results found between annealed and unannealed brass.
This document discusses adaptive abrasive composites and their ability to combine high material removal rates with high surface integrity in grinding processes. Adaptive composites can self-tune their properties in response to cutting conditions, exhibiting inverse feedback where increased cutting forces and temperatures lead to increased bond rigidity rather than deformability. This allows for high energy transfer without excessive plastic deformation or heat, enabling both high removal rates and smooth surfaces. Experiments show reversible structural changes in adaptive composites under varying loads and vibrations, as measured by luminescence intensity from contact areas. Adaptive composites distribute energy more evenly across contact points compared to traditional bonds, transferring more energy per unit area.
Minimization of the grain boundary resistance in YSZ thin filmsEdmund Mills
The document discusses nano-columnar yttria-stabilized zirconia (YSZ) thin films. Thinner films showed enhanced conductivity, nearly matching that of single-crystal YSZ when less than 10 nm thick. An interfacial layer model predicted a 7.6 nm thick conductive layer. Secondary ion mass spectrometry revealed magnesium ions diffused from the magnesium oxide substrate into the grain boundaries and up to the film surface, creating conductive layers with a combined thickness matching the model. The magnesium doping nearly eliminated grain boundary resistance, explaining the enhanced conductivity.
Electrical Properties of Thermally Evaporated In40 Se60 Thin Filmsiosrjce
In40 Se60 thin films with different thicknesses (300,500, and 700nm) have been deposited by single
source vacuum thermal evaporation onto glass substrates at ambient temperature to study the effect of thickness
and on its structural morphology, and electrical properties. AFM study revealed that microstructure parameters
such as crystallite size, and roughness found to depend upon deposition conditions. The DC conductivity of the
vacuum evaporated In40 Se60thin films was measured in the temperature range (293-473)K and was found to
increase on order of magnitude with increase of thickness. The plot of conductivity with reciprocal temperature
suggests, there are two activation energies Ea1and Ea2 for In40 Se60 for all thicknesses which decreases with
increasing thickness .Hall effect measurement showed that low thickness In40 Se60 film exhibit p-type
conductance whereas the film exhibit n-type towards the higher thickness. The electric carrier concentration
and mobility show opposite dependence upon thickness.
s32p01 Bchir Cu Plating Impact to Warpage ECTC 2014Omar Bchir
This document summarizes research on improving substrate and package warpage through optimization of the copper plating process. The key findings are:
1) The copper plating solution and plating rate can significantly impact package warpage, with up to a 27% reduction in warpage achieved through optimization.
2) A lower copper plating rate and solution B provided the lowest warpage. Solution B deposited copper with higher initial compressive stress that relaxed more slowly over time.
3) Balancing the plating current density between inner and outer substrate layers also improved warpage, with lower current density on outer layers performing best.
Microstructural and Nonlinear Properties of Zn-V-Mn-Nb-O Varistor Ceramics wi...nor hasanah isa
This document summarizes a study on the effect of Gd2O3 substitution on the microstructure and electrical properties of Zn-V-Mn-Nb-O varistor ceramics for low voltage applications. XRD and SEM analysis showed the formation of secondary phases like GdMnO3 and GdVO4 at grain boundaries. Gd2O3 substitution decreased grain size from 3.85 to 3.06 μm and increased density from 5.12 to 5.19 g/cm3. Samples with 0.03 mol% Gd2O3 exhibited the optimal nonlinear coefficient of 9.91, highest breakdown field of 88.48 V/mm, and lowest leakage current density of 0.
Dielectric Properties of ZrO2/ PMMA NanocompositesIOSR Journals
The document studies the dielectric properties of Zirconia (ZrO2)/Poly(methyl methacrylate) (PMMA) nanocomposites. PMMA/ZrO2 composites were prepared using various ZrO2 volume fractions. Dielectric properties including dielectric constant, dissipation factor, and dielectric loss were measured from 50Hz to 5MHz. The dielectric constant decreased with increasing frequency but increased with higher ZrO2 content, peaking at 2.5% ZrO2. The dissipation factor and dielectric loss decreased up to 3MHz and remained constant at higher frequencies. They also increased with greater ZrO2 volume fraction. The document concludes that dielectric properties depend on frequency and
Presentation at icotom17 dresden 20140826Xiaodong Guo
ICOTOM stands for International Conference on Textures of Materials. it is the biggest conference in the field of texture and microstructure of materials in the world.
The experiment measured mechanical properties of annealed and unannealed brass rods as well as borate glass rods of varying compositions. It found that annealing decreased the yield strength of brass rods by increasing grain size and reducing dislocation density. Borate glass became more brittle at lower alkali concentrations due to being below its glass transition temperature. Young's modulus was measured through tensile testing, 3-point bending, and measuring speed of sound, with varying results found between annealed and unannealed brass.
This document discusses adaptive abrasive composites and their ability to combine high material removal rates with high surface integrity in grinding processes. Adaptive composites can self-tune their properties in response to cutting conditions, exhibiting inverse feedback where increased cutting forces and temperatures lead to increased bond rigidity rather than deformability. This allows for high energy transfer without excessive plastic deformation or heat, enabling both high removal rates and smooth surfaces. Experiments show reversible structural changes in adaptive composites under varying loads and vibrations, as measured by luminescence intensity from contact areas. Adaptive composites distribute energy more evenly across contact points compared to traditional bonds, transferring more energy per unit area.
Minimization of the grain boundary resistance in YSZ thin filmsEdmund Mills
The document discusses nano-columnar yttria-stabilized zirconia (YSZ) thin films. Thinner films showed enhanced conductivity, nearly matching that of single-crystal YSZ when less than 10 nm thick. An interfacial layer model predicted a 7.6 nm thick conductive layer. Secondary ion mass spectrometry revealed magnesium ions diffused from the magnesium oxide substrate into the grain boundaries and up to the film surface, creating conductive layers with a combined thickness matching the model. The magnesium doping nearly eliminated grain boundary resistance, explaining the enhanced conductivity.
Electrical Properties of Thermally Evaporated In40 Se60 Thin Filmsiosrjce
In40 Se60 thin films with different thicknesses (300,500, and 700nm) have been deposited by single
source vacuum thermal evaporation onto glass substrates at ambient temperature to study the effect of thickness
and on its structural morphology, and electrical properties. AFM study revealed that microstructure parameters
such as crystallite size, and roughness found to depend upon deposition conditions. The DC conductivity of the
vacuum evaporated In40 Se60thin films was measured in the temperature range (293-473)K and was found to
increase on order of magnitude with increase of thickness. The plot of conductivity with reciprocal temperature
suggests, there are two activation energies Ea1and Ea2 for In40 Se60 for all thicknesses which decreases with
increasing thickness .Hall effect measurement showed that low thickness In40 Se60 film exhibit p-type
conductance whereas the film exhibit n-type towards the higher thickness. The electric carrier concentration
and mobility show opposite dependence upon thickness.
s32p01 Bchir Cu Plating Impact to Warpage ECTC 2014Omar Bchir
This document summarizes research on improving substrate and package warpage through optimization of the copper plating process. The key findings are:
1) The copper plating solution and plating rate can significantly impact package warpage, with up to a 27% reduction in warpage achieved through optimization.
2) A lower copper plating rate and solution B provided the lowest warpage. Solution B deposited copper with higher initial compressive stress that relaxed more slowly over time.
3) Balancing the plating current density between inner and outer substrate layers also improved warpage, with lower current density on outer layers performing best.
Microstructural and Nonlinear Properties of Zn-V-Mn-Nb-O Varistor Ceramics wi...nor hasanah isa
This document summarizes a study on the effect of Gd2O3 substitution on the microstructure and electrical properties of Zn-V-Mn-Nb-O varistor ceramics for low voltage applications. XRD and SEM analysis showed the formation of secondary phases like GdMnO3 and GdVO4 at grain boundaries. Gd2O3 substitution decreased grain size from 3.85 to 3.06 μm and increased density from 5.12 to 5.19 g/cm3. Samples with 0.03 mol% Gd2O3 exhibited the optimal nonlinear coefficient of 9.91, highest breakdown field of 88.48 V/mm, and lowest leakage current density of 0.
Dielectric Properties of ZrO2/ PMMA NanocompositesIOSR Journals
The document studies the dielectric properties of Zirconia (ZrO2)/Poly(methyl methacrylate) (PMMA) nanocomposites. PMMA/ZrO2 composites were prepared using various ZrO2 volume fractions. Dielectric properties including dielectric constant, dissipation factor, and dielectric loss were measured from 50Hz to 5MHz. The dielectric constant decreased with increasing frequency but increased with higher ZrO2 content, peaking at 2.5% ZrO2. The dissipation factor and dielectric loss decreased up to 3MHz and remained constant at higher frequencies. They also increased with greater ZrO2 volume fraction. The document concludes that dielectric properties depend on frequency and
Presentation at icotom17 dresden 20140826Xiaodong Guo
ICOTOM stands for International Conference on Textures of Materials. it is the biggest conference in the field of texture and microstructure of materials in the world.
Growth and Magnetic properties of MnGeP2 thin filmsinventy
We have successfully grown MnGeP2 thin films on GaAs (100) substrate. A ferromagnetic transition near 320 K has been observed by temperature dependent magnetization and resistance measurements. Field dependent magnetization experiments have shown that the coercive fields at 5, 250, and 300 K are 3870, 1380 and 155 Oe, respectively. Magnetoresistance and Hall measurements have displayed that hole conduction is dominant in MnGeP2. PACS: 75.50.Pp, 75.70.-i, 85.70.-w, 73.50.-h
The document summarizes research on developing a synthetic gecko tape adhesive by microfabricating arrays of flexible plastic pillars that mimic the structure of gecko foot hairs. Key findings include:
1) Initial attempts using rigid pillar arrays failed to achieve strong adhesion due to uneven surfaces preventing contact.
2) Flexible polyimide pillars were optimized through testing different diameters, heights, and densities.
3) Transferring the flexible pillar array to a soft backing dramatically improved adhesion by allowing more hairs to contact surfaces.
4) The synthetic gecko tape achieved adhesion forces comparable to geckos and could support weights, though durability requires further improvement.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Grain size dependence of fracture toughness and crack-growth resistanceAslan Ahadi
1) The fracture toughness (KIC) and crack growth resistance (KR) of superelastic NiTi decrease with reductions in grain size from the micrometer to nanometer scale.
2) In-situ digital image correlation and infrared thermography during crack opening tests show that the size of the crack-tip phase transformation zone and maximum force also decrease with smaller grain sizes.
3) Both intrinsic and extrinsic toughening mechanisms are influenced by grain size, as nanocrystalline NiTi exhibits less ductility and constrained phase transformation compared to larger grain sizes.
- Experimental tests were conducted on double lap timber joints bonded with different adhesives, including stiff epoxy and softer plastic adhesives.
- The tests found no significant differences in load-displacement curves or influence on strength between the different adhesives. Failure occurred brittlely in the timber.
- Numerical modeling confirmed the softer adhesives reduced stress magnitudes but also increased the stressed volumes.
- A probabilistic approach is needed to explain the relationship between stress and strength, rather than a direct correlation, due to size effects and the brittle nature of timber.
- While ductile adhesives reduce stresses, they do not necessarily increase joint strength as expected based on a stress-
This document describes Standard Test Method E 384 for determining microindentation hardness of materials. The standard covers using Knoop and Vickers indenters to make indentations between 1-1000 gf force. Hardness is calculated based on indentation size and geometry. Key points:
- Hardness is determined by dividing force by projected area or surface area of indentation for Knoop or Vickers respectively.
- Equipment must precisely control low forces and indentation size must be measured via microscope.
- Specimens must be flat and polished to accurately measure indentation diagonals and calculate hardness.
- Multiple sources of error exist and can affect accuracy of results, including force variation, indenter geometry, and measurement errors. Standard aims
This document provides details on PC steel bar including its chemical composition, sizes available, standards that apply, and mechanical properties including tensile strength, yield strength, and elongation. PC steel bars are mainly used in prestressed concrete applications like pipes, poles, railway sleepers, and viaduct piers. The bars are packaged in coils between 1000-1100kg that are wrapped in anti-rust paper and strapped securely.
1. Laser pulses were used to generate shock waves in solids with peak pressures ranging from 5 to 120 kilobars. Peak pressures of around 35 kilobars were achieved at a fluence of 1000 J/cm2, while applying a transparent overlay increased the peak pressure to 120 kilobars.
2. Measurements found that plasma initiation occurred around 8 nanoseconds into a laser pulse when exposing a graphite coating. The resulting shock wave rose sharply at 37 nanoseconds, with only a small precursor pressure seen earlier.
3. Precursor pressures seen with carbon-resin coatings but not with pure graphite coatings, supporting the idea that precursors are due to surface ablation pressures before plasma formation
Engineering Fracture Mechanics. Engineers try to have high-strength, high ductility, high crack resistance, and faultless structures. The most reliable approach is "No cracks - no problems,"
When all is not possible, there are different methods of prevention of catastrophic failure: increase crack resistance by ductile material, by local heating; decrease SIF by placing holes on the crack path, by patching, by stiffing elements or by using composite materials. "Leak-before-break" is an effective strategy to prevent catastrophic failure of pressure vessels. It is better to allow a semi-elliptical crack to grow through the wall and to detect it by leaking than to have the dynamic start and failure of the whole vessel. There are two characteristics of the material: crack resistance for semi-elliptical crack and crack resistance for through crack.
Stress concentrations produced by discontinuities in structures such as holes, notches, and fillets will be introduced in this section. The stress concentration factor will be defined. The concept of fracture toughness will also be introduced.
This document discusses fracture mechanics and provides background information on the topic. It introduces key concepts in fracture mechanics including stress intensity factor, linear elastic fracture mechanics (LEFM), ductile to brittle transition, and fracture toughness. Applications of fracture mechanics are described such as its use in analyzing cracking in pavement systems. The document also covers probabilistic fracture of brittle materials and how their strength is affected by the presence of flaws.
Macro-mechanism of polyvinyl chloride shrink sleevesJia Chen
This document summarizes research on the macro-mechanism of relief formation in polyvinyl chloride (PVC) shrink sleeves during the embossing process. Key findings include:
- Relief height depends on the size of the locally heated zone used to form tactile dots, with larger heated zones producing greater relief.
- A gap of at least 15 mm between the film and substrate is needed during heating for the relief to form, as less than 30% shrinkage prevents relief emergence.
- Thicker films produce greater relief heights, with 0.1 mm PVC film yielding 0.4 mm dots and 0.45 mm film producing 1.1 mm dots under identical heating conditions.
The document compares the mechanical and physical properties of low density polyethylene (LDPE) thin films and sheets reinforced with graphene nanoparticles. LDPE/graphene thin films were produced via solution casting, while sheets were made by compression molding. Testing showed that the thin films had enhanced tensile strength, lower melt flow index, and higher thermal stability compared to sheets. The tensile strength of thin films increased by up to 160% with 1% graphene, while sheets increased by 70%. Melt flow index decreased more for thin films, indicating higher viscosity. Thin films also showed greater improvement in glass transition temperature. These results demonstrate that processing technique affects the properties of LDPE/graphene nanocomposites.
The document discusses the failure of a rolled slab due to improper cooling. Specifically:
1) A crack was found in the middle slab after air cooling, but not in the top or bottom slabs.
2) Analysis showed the middle slab cooled more slowly due to being sandwiched, allowing embrittling Ni4Mo phases to precipitate.
3) This embrittlement, combined with tensile stresses from the slab weight, caused the crack to form intergranularly in the middle slab. Proper cooling of each slab individually is the recommended solution.
This document discusses warpage of microelectronic packages. It begins with an introduction to the importance of controlling warpage, especially in package-on-package configurations where tight warpage specifications are required. The key factors that influence warpage are identified as the die size/thickness, substrate properties and thickness, and underfill material properties. The document then examines warpage fundamentals using the bimetallic strip theory in 2D and finite element modeling in 3D. It identifies glass transition temperature, coefficient of thermal expansion, viscosity, and filler content as important underfill properties for controlling warpage. Solutions for reducing warpage through underfill design and other techniques are proposed.
This document discusses bulk workability and how it differs from ductility. Bulk workability considers the amount of deformation a material can undergo under multiaxial stresses, while ductility is defined under uniaxial tension. Good bulk workability requires high ductility and compressive hydrostatic stress. Various processes like extrusion and wire drawing induce different stress states, with extrusion having better bulk workability due to being fully compressive. The document also discusses models for quantifying bulk workability and modeling friction in bulk forming processes using concepts like shear yield stress and Coulomb friction models.
This document summarizes research on the structural, optical, and electrical properties of flower-like zinc oxide (ZnO) thin films deposited by chemical bath deposition. X-ray diffraction analysis showed the films had a hexagonal wurtzite crystal structure. The crystallite size increased slightly with higher annealing temperatures from 47.6-50.3 nm. Optical transmission was over 60% in the visible range and bandgap decreased from 3.23 to 3 eV with increasing annealing temperature. Scanning electron microscopy revealed flower-shaped grains several nanometers in size. Electrical conductivity increased with higher annealing temperature as measured by four-probe method.
This document discusses size reduction and comminution. It outlines the objectives of size reduction such as improving flow properties and increasing surface area. It examines how material properties like brittleness, toughness, and hardness influence size reduction. Different size reduction methods are described, including cutting, compression, impact, attrition, and combined impact/attrition. Specific equipment like ball mills, hammer mills, and fluidized mills are discussed in terms of how they achieve size reduction through impacts and attrition. Factors that influence particle size distribution changes during milling are also covered.
The document discusses nanoindentation and nanoscratch testing of thin films of Indium Tin Oxide (ITO) coated on polymer substrates like PET. Spherical indentation was used to promote circumferential cracking of the brittle ITO layers. Low load nanoscratch testing showed two failure mechanisms: rupture of the ITO layer and spallation of the coating from the substrate. Critical loads and scratch widths were measured and compared for different ITO thicknesses. Acoustic emission measurements during indentation provided insight into failure events in the coatings.
Tunability of Thin Film Tantalum Nitride Grown by SputteringOnri Jay Benally
This document provides a literature review on the tunability of thin film tantalum nitride grown by sputtering. It discusses how the nitrogen concentration in TaN can be varied to achieve different material properties. Lower nitrogen concentrations produce metallic and electrically conductive TaN, while higher concentrations result in an insulating material. The document outlines common deposition methods for TaN including facing-target, direct current, and radio frequency magnetron sputtering. It reviews how nitrogen concentration affects the surface roughness, crystal structure, electrical resistivity, and mechanical hardness of sputtered TaN films.
Growth and Magnetic properties of MnGeP2 thin filmsinventy
We have successfully grown MnGeP2 thin films on GaAs (100) substrate. A ferromagnetic transition near 320 K has been observed by temperature dependent magnetization and resistance measurements. Field dependent magnetization experiments have shown that the coercive fields at 5, 250, and 300 K are 3870, 1380 and 155 Oe, respectively. Magnetoresistance and Hall measurements have displayed that hole conduction is dominant in MnGeP2. PACS: 75.50.Pp, 75.70.-i, 85.70.-w, 73.50.-h
The document summarizes research on developing a synthetic gecko tape adhesive by microfabricating arrays of flexible plastic pillars that mimic the structure of gecko foot hairs. Key findings include:
1) Initial attempts using rigid pillar arrays failed to achieve strong adhesion due to uneven surfaces preventing contact.
2) Flexible polyimide pillars were optimized through testing different diameters, heights, and densities.
3) Transferring the flexible pillar array to a soft backing dramatically improved adhesion by allowing more hairs to contact surfaces.
4) The synthetic gecko tape achieved adhesion forces comparable to geckos and could support weights, though durability requires further improvement.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Grain size dependence of fracture toughness and crack-growth resistanceAslan Ahadi
1) The fracture toughness (KIC) and crack growth resistance (KR) of superelastic NiTi decrease with reductions in grain size from the micrometer to nanometer scale.
2) In-situ digital image correlation and infrared thermography during crack opening tests show that the size of the crack-tip phase transformation zone and maximum force also decrease with smaller grain sizes.
3) Both intrinsic and extrinsic toughening mechanisms are influenced by grain size, as nanocrystalline NiTi exhibits less ductility and constrained phase transformation compared to larger grain sizes.
- Experimental tests were conducted on double lap timber joints bonded with different adhesives, including stiff epoxy and softer plastic adhesives.
- The tests found no significant differences in load-displacement curves or influence on strength between the different adhesives. Failure occurred brittlely in the timber.
- Numerical modeling confirmed the softer adhesives reduced stress magnitudes but also increased the stressed volumes.
- A probabilistic approach is needed to explain the relationship between stress and strength, rather than a direct correlation, due to size effects and the brittle nature of timber.
- While ductile adhesives reduce stresses, they do not necessarily increase joint strength as expected based on a stress-
This document describes Standard Test Method E 384 for determining microindentation hardness of materials. The standard covers using Knoop and Vickers indenters to make indentations between 1-1000 gf force. Hardness is calculated based on indentation size and geometry. Key points:
- Hardness is determined by dividing force by projected area or surface area of indentation for Knoop or Vickers respectively.
- Equipment must precisely control low forces and indentation size must be measured via microscope.
- Specimens must be flat and polished to accurately measure indentation diagonals and calculate hardness.
- Multiple sources of error exist and can affect accuracy of results, including force variation, indenter geometry, and measurement errors. Standard aims
This document provides details on PC steel bar including its chemical composition, sizes available, standards that apply, and mechanical properties including tensile strength, yield strength, and elongation. PC steel bars are mainly used in prestressed concrete applications like pipes, poles, railway sleepers, and viaduct piers. The bars are packaged in coils between 1000-1100kg that are wrapped in anti-rust paper and strapped securely.
1. Laser pulses were used to generate shock waves in solids with peak pressures ranging from 5 to 120 kilobars. Peak pressures of around 35 kilobars were achieved at a fluence of 1000 J/cm2, while applying a transparent overlay increased the peak pressure to 120 kilobars.
2. Measurements found that plasma initiation occurred around 8 nanoseconds into a laser pulse when exposing a graphite coating. The resulting shock wave rose sharply at 37 nanoseconds, with only a small precursor pressure seen earlier.
3. Precursor pressures seen with carbon-resin coatings but not with pure graphite coatings, supporting the idea that precursors are due to surface ablation pressures before plasma formation
Engineering Fracture Mechanics. Engineers try to have high-strength, high ductility, high crack resistance, and faultless structures. The most reliable approach is "No cracks - no problems,"
When all is not possible, there are different methods of prevention of catastrophic failure: increase crack resistance by ductile material, by local heating; decrease SIF by placing holes on the crack path, by patching, by stiffing elements or by using composite materials. "Leak-before-break" is an effective strategy to prevent catastrophic failure of pressure vessels. It is better to allow a semi-elliptical crack to grow through the wall and to detect it by leaking than to have the dynamic start and failure of the whole vessel. There are two characteristics of the material: crack resistance for semi-elliptical crack and crack resistance for through crack.
Stress concentrations produced by discontinuities in structures such as holes, notches, and fillets will be introduced in this section. The stress concentration factor will be defined. The concept of fracture toughness will also be introduced.
This document discusses fracture mechanics and provides background information on the topic. It introduces key concepts in fracture mechanics including stress intensity factor, linear elastic fracture mechanics (LEFM), ductile to brittle transition, and fracture toughness. Applications of fracture mechanics are described such as its use in analyzing cracking in pavement systems. The document also covers probabilistic fracture of brittle materials and how their strength is affected by the presence of flaws.
Macro-mechanism of polyvinyl chloride shrink sleevesJia Chen
This document summarizes research on the macro-mechanism of relief formation in polyvinyl chloride (PVC) shrink sleeves during the embossing process. Key findings include:
- Relief height depends on the size of the locally heated zone used to form tactile dots, with larger heated zones producing greater relief.
- A gap of at least 15 mm between the film and substrate is needed during heating for the relief to form, as less than 30% shrinkage prevents relief emergence.
- Thicker films produce greater relief heights, with 0.1 mm PVC film yielding 0.4 mm dots and 0.45 mm film producing 1.1 mm dots under identical heating conditions.
The document compares the mechanical and physical properties of low density polyethylene (LDPE) thin films and sheets reinforced with graphene nanoparticles. LDPE/graphene thin films were produced via solution casting, while sheets were made by compression molding. Testing showed that the thin films had enhanced tensile strength, lower melt flow index, and higher thermal stability compared to sheets. The tensile strength of thin films increased by up to 160% with 1% graphene, while sheets increased by 70%. Melt flow index decreased more for thin films, indicating higher viscosity. Thin films also showed greater improvement in glass transition temperature. These results demonstrate that processing technique affects the properties of LDPE/graphene nanocomposites.
The document discusses the failure of a rolled slab due to improper cooling. Specifically:
1) A crack was found in the middle slab after air cooling, but not in the top or bottom slabs.
2) Analysis showed the middle slab cooled more slowly due to being sandwiched, allowing embrittling Ni4Mo phases to precipitate.
3) This embrittlement, combined with tensile stresses from the slab weight, caused the crack to form intergranularly in the middle slab. Proper cooling of each slab individually is the recommended solution.
This document discusses warpage of microelectronic packages. It begins with an introduction to the importance of controlling warpage, especially in package-on-package configurations where tight warpage specifications are required. The key factors that influence warpage are identified as the die size/thickness, substrate properties and thickness, and underfill material properties. The document then examines warpage fundamentals using the bimetallic strip theory in 2D and finite element modeling in 3D. It identifies glass transition temperature, coefficient of thermal expansion, viscosity, and filler content as important underfill properties for controlling warpage. Solutions for reducing warpage through underfill design and other techniques are proposed.
This document discusses bulk workability and how it differs from ductility. Bulk workability considers the amount of deformation a material can undergo under multiaxial stresses, while ductility is defined under uniaxial tension. Good bulk workability requires high ductility and compressive hydrostatic stress. Various processes like extrusion and wire drawing induce different stress states, with extrusion having better bulk workability due to being fully compressive. The document also discusses models for quantifying bulk workability and modeling friction in bulk forming processes using concepts like shear yield stress and Coulomb friction models.
This document summarizes research on the structural, optical, and electrical properties of flower-like zinc oxide (ZnO) thin films deposited by chemical bath deposition. X-ray diffraction analysis showed the films had a hexagonal wurtzite crystal structure. The crystallite size increased slightly with higher annealing temperatures from 47.6-50.3 nm. Optical transmission was over 60% in the visible range and bandgap decreased from 3.23 to 3 eV with increasing annealing temperature. Scanning electron microscopy revealed flower-shaped grains several nanometers in size. Electrical conductivity increased with higher annealing temperature as measured by four-probe method.
This document discusses size reduction and comminution. It outlines the objectives of size reduction such as improving flow properties and increasing surface area. It examines how material properties like brittleness, toughness, and hardness influence size reduction. Different size reduction methods are described, including cutting, compression, impact, attrition, and combined impact/attrition. Specific equipment like ball mills, hammer mills, and fluidized mills are discussed in terms of how they achieve size reduction through impacts and attrition. Factors that influence particle size distribution changes during milling are also covered.
The document discusses nanoindentation and nanoscratch testing of thin films of Indium Tin Oxide (ITO) coated on polymer substrates like PET. Spherical indentation was used to promote circumferential cracking of the brittle ITO layers. Low load nanoscratch testing showed two failure mechanisms: rupture of the ITO layer and spallation of the coating from the substrate. Critical loads and scratch widths were measured and compared for different ITO thicknesses. Acoustic emission measurements during indentation provided insight into failure events in the coatings.
Tunability of Thin Film Tantalum Nitride Grown by SputteringOnri Jay Benally
This document provides a literature review on the tunability of thin film tantalum nitride grown by sputtering. It discusses how the nitrogen concentration in TaN can be varied to achieve different material properties. Lower nitrogen concentrations produce metallic and electrically conductive TaN, while higher concentrations result in an insulating material. The document outlines common deposition methods for TaN including facing-target, direct current, and radio frequency magnetron sputtering. It reviews how nitrogen concentration affects the surface roughness, crystal structure, electrical resistivity, and mechanical hardness of sputtered TaN films.
FRACTURE BEHAVIOUR OF NANOCOMPOSITES -FATIGUEArjun K Gopi
This document discusses the fracture and fatigue behavior of polymer nanocomposites. It notes that nanoparticles have higher specific surface areas than microparticles, which can improve stress transfer and that nanoparticles can be added at lower loadings while retaining properties of the neat polymer matrix. The document covers different types of fractures like brittle and ductile, and describes how the addition of nanoparticles up to 5 wt% can improve the fatigue resistance of polyamide nanocomposites by inhibiting crack propagation, but higher loadings may embrittle the material. TEM images show the differences in clay dispersion with varying nanoparticle content.
This document summarizes an experimental study on the flexural fatigue behavior of carbon/epoxy angle ply laminates. Flexural fatigue tests were conducted on laminate composites with different fiber orientations: [00]4, [±450]4, [±550]4, and [00, 900]4. The tests measured the stiffness degradation of the laminates as a function of the number of load cycles applied. The results showed that stiffness reduced rapidly at first as the top and bottom layers were damaged, then the rate of reduction slowed as a "pivoting effect" limited further damage. Numerical models were able to describe the stiffness degradation curves.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
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Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
CHAPTER 6 Strength, creep and fracture of polymers.pptWeldebrhan Tesfaye
This document discusses creep, recovery, and stress relaxation in polymers. It begins with an introduction to deformation mechanisms in polymers and factors that influence polymer strength. It then covers stress-strain curves in polymers and different deformation modes. Specific topics discussed in more detail include glassy polymers, semicrystalline polymers, viscous flow, creep in polymers, stress relaxation, creep failure of polymers, creep modulus, and factors that influence creep resistance in plastics. Examples are provided to illustrate concepts.
L’importanza dell’approccio Lean sui sistemi qualità delle organizzazioniFederico フェデリコ Guidi
La progressiva diffusione del concetto di azienda snella in molte realtà industriali italiane ha portato immediatamente alla contrapposizione “ideologica” fra “esperti”. Da un lato coloro che ritengono i Sistemi di Gestione per la Qualità, e le relative certificazioni ISO 9001, inutili, inefficaci ed incompatibili con l’approccio Lean. Ad essi si oppongono coloro che individuano nei SGQ l’unico strumento concreto e veramente efficace per incrementare la competitività delle imprese.
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INDEX
FIGURES 4
TABLES 4
1 ABSTRACT 5
2 SUBJECT 6
3 FAILURE TYPE 6
4 CRAZING AND CRACKING IN AIR 6
5 STRESS ANALYSIS IN SECONDARY COIL BOBBIN 9
5.1 CURRENT MATERIAL (NORYL GFN3 PPE + PS) 9
5.2 DATA SHEET OF NORYL GFN3 PPE + PS 10
5.3 FEA ANALYSIS 11
5.3.1 FEA MODEL 11
5.3.2 FEA DESCRIPTION OF CURRENT MATERIAL 12
5.3.3 FEA CONSTRAINT CONDITION @ LOW TEMPERATURE 12
5.3.4 FEA CONSTRAINT CONDITION @ HIGH TEMPERATURE 13
5.3.5 FEA LOAD CONDITION 13
5.3.6 FEA RESULTS @ LOW TEMPERATURE (-30°C) 14
5.3.7 FEA RESULTS @ HIGH TEMPERATURE (+100 °C) 16
6 MATERIAL SELECTION 16
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6.1 POLYMER MOLECULAR WEIGHT 16
6.2 CRYSTALLINE VS. AMORPHOUS MATERIAL 18
6.3 TECHNICAL PROPOSAL 19
6.4 NEW MATERIAL (POCAN T 739I PBT) 19
6.5 DATA SHEET OF POCAN T 739I PBT VS. NORYL GFN3 PPE + PS 20
7 NEW ACTIVITIES 21
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FIGURES
Figure 1: sample ............................................................................................................... 6
Figure 2: the sequence leading to slow crack growth....................................................... 7
Figure 3: ESC result ......................................................................................................... 8
Figure 4: FEA model...................................................................................................... 11
Figure 5: FEA description of current material................................................................ 12
Figure 6: FEA constraint condition @ low temperature ................................................ 12
Figure 7: FEA constraint condition @ high temperature ............................................... 13
Figure 8: FEA results @ low temperature - minimum CTE (30×10-6
1/°C)................... 14
Figure 9: FEA results @ low temperature (fillet detail) minimum CTE..................... 15
Figure 10: FEA results @ low temperature (fillet detail) maximum CTE.................. 15
Figure 11: FEA results @ high temperature - minimum CTE (30×10-6
1/°C)................ 16
Figure 12: crystalline Vs. amorphous............................................................................. 18
TABLES
Table 1: summary of NORYL GFN3 PPE + PS data sheet ........................................... 10
Table 2: thermal cycles Nr.1 (specs.) ............................................................................. 13
Table 3: thermal cycles Nr.2 (specs.) ............................................................................. 14
Table 4: significance of the molecular weight................................................................ 17
Table 5: summary of POCAN T 739I PBT Vs. NORYL GFN3 PPE + PS ................... 20
Table 6: thermal cycle (compressive load)..................................................................... 21
Table 7: thermal cycle (tensile load) .............................................................................. 21
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1 ABSTRACT
Environment Stress Cracking (ESC) is one of the main causes of failure of injection
moulded plastic components. Failure occurs as a result of the accelerated fracture of
polymeric materials due to the combined action of environmental exposure and stress.
A low temperature condition combined with a particular constraint condition produces a
critical tensile stress distribution that culminates in a slow crack growth: the material
used for moulded plastic component is not suitable for a creep condition.
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2 SUBJECT
The subject of this document is the high tension coil made by confidential
informations : the analysis will investigate the material of high tension coil secondary
coil bobbin.
3 FAILURE TYPE
Thermal cycles produce a crack in high tension side of secondary coil bobbin: through
this crack occurs a spark that reduces high tension coil performances.
Figure 1: sample
4 CRAZING 1
AND CRACKING IN AIR
Modest levels of stress applied over long periods of time induce purely mechanical
degradation in the form of crazes and cracks. This is the underlying cause of the long-
term transition from ductile to brittle behaviour.
The sequence that culminates in slow crack growth is illustrated in Figure 2.
1
A network of fine cracks on or under the surface of a material.
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Figure 2: the sequence leading to slow crack growth
At the microscopic level, polymer surfaces unavoidably contain a high density of stress
concentrating defects. Typically these range in stress concentration factor from 1 to ~
50. Under modest tensile stresses (a few MPa), the yield strength (typically < 100 MPa)
will be locally exceeded. The micro-yielded zones blunt the defect and the feature is
initially stabilised. The size and shape of a yielded zone are determined by the yield
stress contour of the local stress field. However the yield strengths of all polymers
decline with time under stress, and the rate of decline is increased with increasing
temperature. Therefore with time under stress, the size of the micro-yielded zones
increases. Thin plate like zones grow in area in a plane normal to the principal tensile
stress direction. As they do so the zones increase in thickness. Eventually volume
expansion induces cavitation within the zone. The feature can now be described as a
craze.
With further growth of the zone and zone cavities, the inter-cavity material stretches to
form highly oriented, load-bearing fibrils. Voids and fibrils are typically of the order of
tens of nanometres in diameter. With further growth of the craze, a point is reached
when the most highly stretched fibrils (generally those nearest the polymer surface) will
rupture. This will lead to an increase in stress at the craze tip, a transient increase in
craze growth rate, and an increase in the extension of adjacent fibrils. The sequence is
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repeated. The now unsupported portion of the craze is called a crack. The crack
advances behind a craze of reasonably constant length. The part fractures when the
crack reaches a critical length. On examination of fracture surfaces the slow crack
growth region (the initial stage up to the critical length) will be macroscopically flat and
microscopically 'pimpled'. The pimples are the remnants of ruptured fibrils. The fast
crack growth region will be macroscopically uneven (hackle marks, bifurcation etc.) but
microscopically smooth.
The progress of slow crack growth (and consequently the durability of the stressed part)
depends primarily upon the strength and stability of the craze material, and therefore
upon the ultimate properties of the bridging fibrils. Semi-crystalline plastics generally
form higher tenacity fibrils than amorphous plastics. Higher molecular weight plastics
are also superior in this respect. Therefore high molecular weight grades of semi-
crystalline thermoplastics generally offer the best resistance to slow crack growth and
such associated phenomena as ESC, dynamic fatigue fracture, and fretting wear.
Figure 3: ESC result
START POINT
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5 STRESS ANALYSIS IN SECONDARY COIL BOBBIN
The key point in the sequence leading to a slow crack growth is a tensile load condition.
During thermal cycles the secondary coil bobbin it could be loaded by a tensile load?
In order to answer this question, it is necessary a Finite Element Analysis (FEA) of
secondary coil bobbin: the first step is a very simple FEA in which we do not consider
potting resin (the CTE ratio between NORYL and potting resin is ~ 1¸2.5)2
and copper.
Anyway, the presence of potting resin and copper does not introduce a tensile load but
only a compressive load if CTE ratio is higher than 1. Regarding the magnet inside the
secondary coil bobbin, we consider it a rigid solid (the CTE ratio between NORYL and
ferrite is ~ 10): this is one safety hypothesis.
5.1 CURRENT MATERIAL (NORYL GFN3 PPE + PS)3
General Class: PPE/PPO (Polyphenylene Ether Blends).
Company: GE Plastics.
Trade Name: NORYL GFN3 PPE + PS, Grade with 30% glass fibers.
Application: household appliances, electrical applications such as control housings,
fibre-optic connector, etc.
Note: PPO is a poly (2,6 dimethyl p-phenylene) oxide. The ether linkages offer easier
processibility. Copolymers are referred to as PPEs (Polyphenylene Ethers). Typically,
the commercially available PPOs (PPEs) are blended with other thermoplastic materials
such as PS (or HIPS), Nylon, etc. These blends are still referred to as PPOs or PPes. The
blends offer superior processibility compared to pure PPOs. Their viscosities are lower.
2 It depends from the direction that we consider.
3 Dr.C-Mold user s Guide Molding Intelligence for Plastics Professionals C-Mold, Ithaca, New York,
USA, 1996.*
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Blends with Nylons are crystalline. They offer improved chemical resistance and
perform well at high temperatures. The water absorption is low and the moulded
products have excellent dimensional stability.
Blends with PS are amorphous. The addition of glass fibres reduces shrinkage levels to
0.2%. These materials have excellent dielectric properties and a low coefficient of
thermal expansion. The viscosity level depends on the ratio of the components in the
blend: higher PPO levels increase the viscosity.
5.2 DATA SHEET OF NORYL GFN3 PPE + PS
Information provided by GE Plastics for their European product line. This product is
also a part of their North American product line.
PHYSICAL PROPERTIES METRIC COMMENTS
Density 1.3 g/cm3
ISO 1183
Tensile modulus (E) 8 GPa ISO 527
Poisson s ratio 0.365 ASTM D 368
Ultimate tensile strength 100 MPa ISO 527
Elongation at break 1.5 % ISO 527
CTE, linear 20°C in flow direction 30×10-6
1/°C ISO 11359-2
CTE, linear 20°C transverse to flow 70×10-6
1/°C ISO 11359-2
Thermal conductivity 0.28 W/m°C ISO 8302
Dielectric strength 22 kV/mm Short time, 3.2 mm - ASTM D 149
Table 1: summary of NORYL GFN3 PPE + PS data sheet
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5.3 FEAANALYSIS
The FEA analysis has been performed with the software ProMechanica integrated with
the design software ProEngineer.
In the following paragraphs they will be described all elements necessary to perform
FEA analysis.
5.3.1 FEA MODEL
The FEA model is in agreement with confidential informations : the model has been
simplified where the details are not important for the analysis.
Figure 4: FEA model
The FEA model is referred to a cylindrical coordinate system (CS1) in which the z
direction corresponds to the axis of FEA model (positive direction is from low voltage
side to high voltage side). The plane z = 0 corresponds to the bottom plane of secondary
coil bobbin (low voltage side).
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5.3.2 FEA DESCRIPTION OF CURRENT MATERIAL
The FEA analysis has been performed using the following material model.
Figure 5: FEA description of current material
5.3.3 FEA CONSTRAINT CONDITION @ LOW TEMPERATURE
At low temperature (under the reference temperature) it is a good hypothesis to suppose
that only the inner surface of secondary coil
bobbin will be constrained: as shown in the
picture (Fig.6), on the red surface they have
been applied the constraints in r direction and
on the blue surface they have been applied the
constraints in z direction. The constraint
condition is doubly symmetrical, like the load
condition, and therefore the FEA model can be
simplified: on the green surfaces they have been
applied the symmetric constraints (mirror).
Figure 6: FEA constraint condition @ low temperature
MINIMUM CTE
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5.3.4 FEA CONSTRAINT CONDITION @ HIGH TEMPERATURE
At high temperature (over the reference temperature) it is a good hypothesis to suppose
a constraint distribution as shown in the picture (Fig.7): on the red surfaces they have
been applied constraints in r direction, on the blue surfaces they have been applied
constraints in z direction and on the magenta surfaces they have been applied
constraints in r and z . The constraint condition is doubly symmetrical, like the load
condition, and therefore the FEA model can be simplified: on the green surfaces they
have been applied the symmetric constraints (mirror).
Figure 7: FEA constraint condition @ high temperature
5.3.5 FEA LOAD CONDITION
LOW TEMPERATURE
(°C)
TIME
HIGH TEMPERATURE
(°C)
TIME
-30 3 hrs +80 3hrs
x 10 times (60 hrs)
Table 2: thermal cycles Nr.1 (specs.)
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LOW TEMPERATURE
(°C)
TIME
HIGH TEMPERATURE
(°C)
TIME
-30 1 hr +100 1hr
x 200 times (400 hrs)
Table 3: thermal cycles Nr.2 (specs.)
The reference temperature for thermal properties of materials is 20°C.
5.3.6 FEA RESULTS @ LOW TEMPERATURE (-30°C)
Figure 8: FEA results @ low temperature - minimum CTE (30×10-6
1/°C)
The FEA results for the low temperature condition show that there is a zone around the
fillet in the high voltage side critical regarding the stress: the Von Mises stress
distribution points out that around the fillet there is a wide zone in which the SF is about
1.76 ÷ 3. This SF in not enough first of all because typically the stress concentration
factor ranges from 1 to ~ 50, beside this because the yield strengths of all polymers
TENSILE STRESS
ZONE
TENSILE
STRESS ZONE
TENSILE STRESS
ZONE
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decline with time under stress and finally because the material used for the FEA
analysis has been described with the minimum CTE (30×10-6
1/°C).
Figure 9: FEA results @ low temperature (fillet detail) minimum CTE
Figure 10: FEA results @ low temperature (fillet detail) maximum CTE
MAXIMUM STRESS (56.8 MPa)
SF = 1.76
MAXIMUM STRESS (132.6 MPa)
SF = 0.75
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5.3.7 FEA RESULTS @ HIGH TEMPERATURE (+100 °C)
Figure 11: FEA results @ high temperature - minimum CTE (30×10-6
1/°C)
The FEA results for the high temperature condition show that the zone around the fillet
in the high voltage side is in a condition of compressive stress. Regarding the sequence
that culminates in a slow crack growth, a compressive stress is a favourable condition
because it closes the crack. However if the compressive stress exceeds the compressive
yield stress, it could produce the micro-yielded zones from which in the next low
temperature cycle it could start the sequence that culminates in a slow crack growth.
6 MATERIAL SELECTION
6.1 POLYMER MOLECULAR WEIGHT
The molecular weight is expressed in grams/mole.
The most important useful properties of polymers arise primarily from the high
molecular weight and extended chain length of the polymer molecules:
COMPRESSIVE
STRESS ZONE
COMPRESSIVE
STRESS ZONE
COMPRESSIVE
STRESS ZONE
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- improves impact resistance;
- lowers the brittleness temperature;
- increases melt viscosity;
- improves long-term performance
o fatigue;
o ESC resistance;
o chemical resistance.
Lower Molecular Weight Higher
Broader Molecular Weight Distribution Narrower
Higher Crystallinity Lower
Faster Rate of Loading Slower
Lower Temperature Higher
Higher Filler Content Lower
Lower Filler Aspect Ratio Higher
Higher Applied Load Lower
Higher Internal Stresses Lower
Abrupt Wall Thickness Transition Gradual
Concentrated Chemical Exposure Dilute
Brittle Ductile
Table 4: significance of the molecular weight
Causes of low molecular weight:
- specification viscosity too low in initial material;
- specification blended materials;
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- thermal degradation high melt temperatures and/or long residence time;
- hydrolytic degradation excess moisture in the raw material during processing
- drying oxidation due to aggressive drying conditions;
- environmental influences heat aging, UV degradation, chemical exposure.
6.2 CRYSTALLINE vs. AMORPHOUS MATERIAL
Figure 12: crystalline Vs. amorphous
Performance differences:
- a semi-crystalline structure provides better chemical resistance;
- a semi-crystalline structure provides better ESC resistance (ESCR);
- a semi-crystalline structure provides better resistance to fatigue failure;
- a semi-crystalline structure benefits more from the incorporation of fillers;
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- a semi-crystalline structure generally has lower impact performance;
- a semi-crystalline structure generally has a good dimensional accuracy and a
good dimensional stability but not quite for achieving the same level of
amorphous structure.
6.3 TECHNICAL PROPOSAL
In the previous paragraphs it has been shown that the best solution for the new material
will be a compromise between an amorphous structure and a semi-crystalline structure.
For the semi-crystalline structure it will be chosen a polyester like PBT and for the
amorphous structure it will be chosen a polycarbonate (PC): the new material will be a
PBT/PC blend. Polycarbonate has been chosen first of all because it shows a good creep
resistance, beside this it is fine for all precision parts and finally it has a temperature-
independent dielectric constant, as well as good insulating properties.
Regarding stress analysis in secondary coil bobbin, the FEA results point out that the
new material must have first of all a lower CTE, beside this a higher ultimate tensile
stress and finally a good creep behavior in order to have a lower yield strengths
reduction with time under stress and therefore to support a higher number of thermal
cycles (specs.).
6.4 NEW MATERIAL (POCAN T 739I PBT)
General Class: PBT + PC blend.
Company: LANXESS.
Trade Name: POCAN T 739I PBT, Grade with 45% glass fibers.
Application: automotive sector.
Note: very good surface finish, low warpage, very high strength and stiffness, good
creep behavior, low thermal expansion.
20. Environment Stress Cracking
SUBJECT: confidential information rev. 0 Pag. 20 di 21
6.5 DATA SHEET OF POCAN T 739I PBT Vs. NORYL GFN3 PPE + PS
Information provided by Lanxess for POCAN T 739I PBT and GE Plastics for NORYL
GFN3 PPE + PS.
PHYSICAL PROPERTIES
METRIC
COMMENTS
CURRENT
MATERIAL
NEW
MATERIAL
Density 1.3 g/cm3
1.67 g/cm3
ISO 1183
Tensile modulus (E) 8 GPa 17 GPa ISO 527
Poisson s ratio 0.365 0.365 ASTM D 368
Tensile Creep modulus (E)
1hr
n.a. 16.5 GPa n.a.
Tensile Creep modulus (E)
1000 hrs
n.a. 15 GPa n.a.
Ultimate tensile strength 100 MPa 165 MPa ISO 527
Elongation at break 1.5 % 1.7 % ISO 527
CTE, linear 20°C
in flow direction
30×10-6
1/°C 20×10-6
1/°C ISO 11359-2
CTE, linear 20°C
transverse to flow
70×10-6
1/°C 50×10-6
1/°C ISO 11359-2
Thermal conductivity 0.28 W/m°C n.a. ISO 8302
Maximum service temperature, Air n.a. 210 °C n.a.
Dielectric strength 22 kV/mm 27 kV/mm
Short time, 3.2 mm
ASTM D 149
Table 5: summary of POCAN T 739I PBT Vs. NORYL GFN3 PPE + PS
21. Environment Stress Cracking
SUBJECT: confidential information rev. 0 Pag. 21 di 21
7 NEW ACTIVITIES
It has been verified, only with a FEA analysis, that thermal cycles are able to generate a
tensile load in high voltage side of secondary coil bobbin: the FEA analysis results point
out that it is the low temperature the responsible of the sequence that culminates in slow
crack growth. In order to verify this hypothesis, a very easy activity it could be to
perform two different thermal cycles:
LOW TEMPERATURE
(°C)
TIME
HIGH TEMPERATURE
(°C)
TIME
+20 3 hrs +100 3hrs
x 10 times (60 hrs)
Table 6: thermal cycle (compressive load)
LOW TEMPERATURE
(°C)
TIME
HIGH TEMPERATURE
(°C)
TIME
-30 3 hrs +20 3hrs
x 10 times (60 hrs)
Table 7: thermal cycle (tensile load)
if the hypothesis is correct, the high tension coils that have been loaded by the first
thermal cycle (table 6) will not be damaged whereas the others (table 7) will be
damaged.