Design and fabrication of spur gear using metal matix composite using Aluminium silicon carbide..

1. DESIGN AND FABRICATION OF SPUR GEAR USING
METAL MATRIX COMPOSITE (Al-SiC)
Submitted by
Rakesh v (113014114075)
Nantha kumar M (113014114061)
Sanjeev M (113014114084)
GUIDE : ANBAZHAGAN (ME., M.B.A., Ph.D
Associate professor
Department of Mechanical Engineering
Vel Tech High Tech Dr.RR Dr.SS Engineering College
Chennai-62

2. ABSTRACT
 Metal matrix composites are gaining wider acceptance in aerospace and
defence industries due to their starving need for lightweight high strength
materials. In this project the influence of processing parameters on the properties
of SiC (7%wt) particle reinforced aluminium alloy (7050) composite spur gear
was fabricated. The composites are prepared by stir casting method.
 The control of processing parameters is very important in order to obtain
good quality casing with minimal defects. So that were investigated include melt
temperature and stirring speed. Specimens produced were subjected to mechanical
testing.
 This composite material is used to fabricate the spur gear by using gear
hobbing. It is proposed to use this material for power transmitting elements such
as gears which are subjected to continuous loading.

3. INTRODUCTION
 Since the early 1960, there is demand for new and improved engineering
materials with advancement of modern technology interest in the areas of
aerospace, automotive industries had forced a rapid development of metal matrix
composites.
 High demands on material for better overall performance has led to
extensive research and development efforts in the composites fields. Among the
composites field, the aluminium based metal matrix composite materials are
widely used.
 To meet emerging need, innovations in materials processing enabled
achieving an enhancement in stiffness, realization of high strength to weight ratio,
an improvement in wear resistance, maintaining strength at elevated temperatures.
 The utilization of AMCs in areas of aerospace and automotive industries
include performance, economic and environmental benefits. In AMC one of the
constituent is aluminum, which forms percolating network and is termed as matrix
phase. The other constituent is embedded in this aluminum and serves as
reinforcement, which is usually non-metallic and commonly ceramic such as SiC,
Al2O3 etc.,

4. LITERATURE REVIEW
ALUMINIUM ALLOY COMPOSITE PRODUCED BY STIR CASTING METHOD
 Metal matrix composites are acceptance in aerospace and defence industries due to
their lightweight — high strength materials. The control of processing parameters is very
important in order to obtain good quality casing with minimal defects.
 In this study the influence of processing parameters on the properties of SiC particle
reinforced aluminium alloy (Al- 10%Si- 0.6%Mg) composite was investigated. The
composites are prepared by stir casting method. The processing parameters that were
investigated include melt temperature and stirring speed.
 Microstructure observed through scanning electron microscope and optical
microscope was correlated to the observed mechanical behaviour. The results show that
the melt temperature appears to have little effect on the mechanical properties and particle
settling.

5. ALUMINIUM BASED SILICON CARBIDE PARTICULATE
METAL MATRIX COMPOSITE
 MMCs are made by dispersing a reinforcing material into a metal matrix.
They are prepared by powder metallurgy and casting, although several technical
challenges exist with casting technology.
 The aluminium alloy composite materials consist of high strength, high
stiffness, more thermal stability, more corrosion and wear resistance, and more
fatigue life. aluminium alloy materials found to be the best alternative with its
unique capacity of designing the materials to give required properties.
Hardness Test:
 The Brinell hardness measurements are carried out in order to investigate the
influence of SiC particulate weight fractions on the matrix hardness. The applied
load is 250N, and the indenter is a steel ball 5 mm in diameter. The hardness is
measured by Brinell Hardness Tester.

6. METHODOLOGY
MATERIAL USED
• ALUMINIUM
• SILICON CARBIDE
CASTING
• STIR CASTING
DESIGN
SPUR GEAR DESIGN
MACHINING PROCESS
TESTING

7. CHEMICAL COMPOSITION OF MMC
S.NO MATERIALS COMPOSITION
(%)
WEIGHT (gm)
1. Aluminium (Al) 89% 1200
2. Copper (Cu) 2.3% 28
3. Magnesium
(Mg)
2.3% 28
4. Zinc (Zn) 6.2% 74
5. Silicon carbide
(SiC)
7% 84

8. STIR CASTING
 Stir casting is an economical
process for the fabrication of aluminum
matrix composites. There are many
parameters in this process, which affect
the final microstructure and mechanical
properties of the composites. It is a
liquid state method of composite
materials fabrication, in which a
dispersed phase (ceramic particles, short
fibers) is mixed with a molten matrix
metal by means of mechanical stirring.

9. DESIGN OF SPUR GEAR
SPUR GEAR
Spur gears or straight-cut gears are the simplest
type of gear. They consist of a cylinder or disk
with teeth projecting radially, the edge of each
tooth is straight and aligned parallel to the axis of
rotation.These gears mesh together correctly only
if fitted to parallel shafts. No axial thrust is created
by the tooth loads. Spur gears are excellent at
moderate speeds.

10. GEAR MATERIALS
 When selecting the materials for toothed gears, it is necessary to ensure
sufficient beam strength of the-teeth and endurance of their surface layers.
 Based on the purpose and places of applications, gears made of various types
of materials can be employed.
THE MOST COMMON MATERIALS USED FOR MAKING GEARS ARE:
 Ferrous metals such as carbon steels, alloy steels of nickel, chromium and
vanadium, aluminium alloys and cast-iron of different grades.
 Non-ferrous metals such as brass, bronze, titanium etc.
 Non-metals such as plastic oriented materials like phenolic resins, nylon,
bakelite, mica etc.

11. GEAR FAILURES
TYPICAL FAILURE OF GEAR TOOTH ARE:
 Tooth breakage
 Pitting of tooth surface
 Abrasive wear
 seizing of teeth.
TOOTH BREAKAGE :
 Tooth breakage is the most dangerous kind of gear failure which may be the
result of high overloads of either impact or static action, repeated overloads
causing low-endurance fatigue. In order to escape from the gear tooth breakage,
gear material of sufficient beam strength may be selected.

12. PITTING
 Pitting of tooth surface may happen to gears which are enclosed, well lubricated and
protected against dirt. This kind of failure occurs due to over pressing of the tooth of one gear to
the tooth ofmating gear.During the continuous operation, a crack may be formed which may
increase in size and changed into the form of pits. To prevent pitting, the teeth are checked for
surface endurance.
ABRASIVE WEAR
 Abrasive wear is the principal reason for the failure of open gearing and the closed gearing
of machinery operated in a media, polluted by abrasive materials.Wear increases dynamic loads
and noise, weakens the teeth and finally, leads to tooth breakage. To prevent abrasive wear, the
gears can be protected from corrosive atmospheres.
SEIZING
 Seizing of the teeth is due to the crushing of oil film on the tooth surface under high
pressure. When the surfaces, which are tightly meshed by the oil film, are in relative motion, the
particles of softer material are detached from the tooth, leaving scores and scratches on its surfaces.
To event this, the operating temperatures and the properties of lubricants are properly maintained.

13. DESIGN CALCULATION OF SPUR GEAR
SELECTION OF MATERIAL
The pinion and gear are made of same material (Composite metal matrix Al-
SiC), the pinion is weaker than the gear. So we have to design only pinion.
Assumed metal matrix is hardened to 200 BHN.

14. MODULE (m)
m = d/Z
Where, d = Pitch circle diameter
Z = Number of teeth on pinion
m = 83/26
m = 3.19
From PSG DB page no 8.2, the nearest higher standard module value under choice 1 is 4
mm
m = 4 mm
CALCULATION OF 𝒁 𝟏 AND 𝒁 𝟐
Assuming Velocity ratio, i = 3.5
Number of teeth on pinion, 𝑍1 = 26
Number of teeth on gear , 𝑍2 = 91

15. CALCULATION OF 𝐅𝐭
Tangential load, F𝐭 =
p
v
×𝑘0
Where, p = Power transmitted in watts
v = Pitch line velocity =
𝜋𝑑𝑁
60
, in m/s
𝑘0 = Service / Shock factor.
Pitch line velocity, v =
𝜋𝑑𝑁
60
, in m/s
Where, d = Diameter of pitch circle
N = Speed of driving gear in rpm
Assuming, speed of driving gear = 900 rpm.
v =
𝜋×83×900
60×1000
m/s
v = 4 m/s
𝑘0 = 1.25, for medium shock condition
Tangential load, F𝐭 =
p
4
×1.25
Ft = 0.31 p

16. CALCULTION OF INITIAL DYNAMNIC LOAD 𝐅𝐝
Fd =
F 𝐭
𝑐 𝑣
Where, 𝑐 𝑣 = Velocity factor, assuming v = 12 m/s
=
6
6+𝑣
, for accurate hobbed and generated gears with v < 20 m/s
=
6
6+12
= 0.333
Fd =
0.31 𝑃
0.333
= 0.93 P
CALCULATION OF BEAM STRENGTH 𝐅𝐬
Beam strength, Fs = π.m.b.𝜎 𝑏.y
b = Face width = 10 × m = 10×4 = 40 mm
y = Form factor
= 0.154 -
0.912
𝑍1
, for 200 full depth system
= 0.154 -
0.912
26
= 0.118
Assuming maximum allowable stress, 𝜎 𝑏 = 157 N/𝑚𝑚2
Fs = π×4×40×157×0.118
Fs = 9385 N

17. Assuming maximum allowable stress, 𝜎 𝑏 = 157 N/𝑚𝑚2
Fs = π×4×40×157×0.118
Fs = 9385 N
CALCULATION OF POWER TRANSMITTED
Fs ≥ Fd
9385 ≥0.93 P
POWER TRANSMITTED, P = 10.091 kw
Thus, the power attained by our composite metal matrix spur gear is
10.091 kw

18. EXPERIMENTAL METHOD
The matrix material used for the current study was Al 7050 alloy,
having composition average values provided in weight percentage as
shown in Table 1. The Al – Zn based alloy has an excellent
combination of mechanical properties in the cast condition.
The matrix material was loaded in a graphite crucible and it was
placed inside a top loaded stir casting furnace at different temperature
level (700˚C, 750˚C, 800˚C, 850˚C). The SiC reinforcement (average
size 40 µm) was preheated at 1000˚C for two hours before added in
the matrix melt.
The 7% by volume of preheated SiC powder was added in the liquid
melt and the slurry was consciously stirred using a stirring.

19. EXPERIMENTAL SET UP

20. FABRICATION WORK
 The matrix material used in the present study is the commercial LM9
aluminium alloy. The nominal chemical composition in wt% of the matrix alloy is
given in Table 1. The reinforcement used is particulates of silicon carbide (hence
forth referred to as SiCp) of average size 35).im. In the present study, the
aluminium matrix composites with 7 wt% SiCp were prepared using stir casting
method. The experimental setup consists of an electrical resistance heating
furnace, a variable speed motor driven mechanical impeller with speed indicator, a
thermocouple for measurement of melt temperature.
 Approximately, 1200 gms of aluminium alloy was placed in a graphite
crucible and heated to 730°C. 7 wt% of SiCp were pre heated to 850°C in a
separate muffle furnace for a soaking period of one hour. The particles were then
added manually at a rate of 13-15 gms per minute using a feeder through the
vortex created by stirring the molten metal. The stirrer was placed at 0.75H from
the bottom of the crucible where H is the depth of the melt at rest. The stirrer
speed was varied between 400 to 500 rpm at an interval of 100 rpm.

21.  After completion of SiC addition, the stirring was continued for 20 minutes.
Prior to particle addition, 1 wt% of Mg powder was added in small packets
(wrapped in an aluminium foil) into the melt in order to improve the wettability.
The composite melt was finally poured into cast iron die preheated to 250°C. plate
specimens of 100mm width, 300mm length,10mm thickness were obtained.
Similarly, composite specimens were manufactured for melt temperatures 800°C
and 850°C.
 The amount of SiC particles in the matrix is estimated by chemical digestion
method. This involves dissolving the composite piece of known weight in
Hydrochloric acid solution. The residue collected was filtered, dried and weighed.
Weighing was carried out using electronic balance (METTLER model AE200)
with an accuracy of 0.0001gm. The weight fraction of SiC in - the composite
sample was then calculated.

22. GEAR HOBBING PROCESS
 Hobbing is a machining process for gear cutting, cutting splines, and
cutting sprockets on a hobbing machine, which is a special type of milling
machine. The teeth or splines are progressively cut into the work piece by a series
of cuts made by a cutting tool called a hob. Compared to other gear forming
processes it is relatively inexpensive but still quite accurate, thus it is used for a
broad range of parts and quantities.
 It is the most widely used gear cutting process for creating spur and helical
gears[ and more gears are cut by hobbing than any other process as it is relatively
quick and inexpensive.

23. ALUMINIUM METAL MATRIX COMPOSITE GEAR:

24. RESULTS AND DISCUSSION
 The incorporation of SiC in the matrix at different speeds were studied. It is
observed that with increase in stirring speed from 400 rpm, the amount of SiC
entrapped in the composite increases and reaches a peak value of 9.6 wt % at a
stirring speed of 500 rpm. Increasing the stirring speed further to 700 rpm, leads to
a reduction in amount of SiC incorporation. A similar variation has been
documented by for a composite produced by disintegrated melt deposition method.
 The development of vortex due to stirring is observed to be helpful for
transferring the particles into the matrix melt as the pressure difference between
the inner and outer surface of the melt sucks the particles into the liquid. However,
introducing the particles from air to the stirred melt through vortex sometimes
picks up atmospheric air, which must be removed by proper degassing, which
otherwise may result in porosity in the cast composite. In this study, at low stirrer
speed, the vortex formed was minimum owing to the reason that the mechanical
force in less to overcome the viscosity of the melt.

25. CONCLUSION:
1. Al-Zn alloy/7 wt% SiCp composites were fabricated using stir-
casting technique by varying the stirring speed and melt temperature.
2. Study on particle incorporation revealed that highest amount of
particles are entrapped and distributed uniformly at stirring speed range
of 500 —550 rpm.
3. Highest UTS was achieved when the melt temperature was 800°C
owing to proper wetting of the reinforcement by the melt and lesser
interfacial reaction.

26. REFERENCE
 Andrew Walker, J., The processing and properties of discontinuously
reinforced aluminium composites, Journal of Materials, 8-15 1991.
 Tham, L.M., Gupta, M., and Cheng, H., Influence of processing
parameters on the near net shape synthesis of aluminium — based metal
matrix composites, Journal of Materials Processing Technology, 89-90, 128-
134, 1999.
 Hashim, J., Looney, L., Hashmi, M.S.J., Metal matrix composites;
Production by stir casting method, Journal of Materials Processing Technology,
92-93, 1-7, 1999.
 Ourdjini, A., Chew, K.C., Khoo, B.T., Settling of silicon carbide particles
in cast metal matrix composites, Journal of Materials Processing Technology,
116, 72-76, 2001.
 Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and
Processes in Manufacturing (9th ed.), Wiley, p. 277, ISBN 0-471-65653-4

27. ANY QUESTION’S