AUTOMOTIVE
TRANSMISSION
SYSTEMS PROJECT
TITLE Stress analysis of a rear
axle.
By: Akshay Singhvi 10BMA0059 Kartik Kabra 10BMA0026 Sagar Bhatt 10BMA0061 Siddharth Negandhi 10BMA0043
ABSTRACT: An axle is central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be
fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels
rotating around the axle. In any case, axle is one of the most important parts of a vehicle. [2,
3]
Simulation is carried out in 3 stages. First stage of the analysis is a forming simulation i.e. the
CAD, followed by service load simulation in second stage. The third stage is for fatigue
simulation.
Stress analysis was done on a given rear axle using ANSYS software. The modelling was done
in SolidWorks software.
Simulation results are validated by comparing them with the reference work.
The axle used in this report is a Ford 9 inch rear axle.
INTRODUCTION:
Axle is a very important load carrying component of the vehicle. It experiences many types of loads
during its operation. It must be able to endure such load and operate under such conditions. There
are two types of axles:
Fixed axle: axle that does not rotate with the wheel.
Rotating axle: axle that rotates with the wheel.
Now, the main load acts on the axle housing. It is vital that the housing resist against failure for
the predicted service life.
The forces acting on the rear axle are:
Longitudinal forces: It acts vertically downwards on either side of the differential case. It is a
result of the weight of the car and the additional load that the vehicle maybe carrying
(including passengers)
Lateral forces: It is the result of the reaction force from the drive shaft when the brakes are
applied or a pull force when the vehicle starts.
Torque reaction: It is the torsional reaction generated through the drive shaft and the
torque generated through the braking action on wheels.
CAD:
The CAD was made in SolidWorks 2012-2013.
The material was chosen as grey cast iron during CAD modelling.
MATERIAL PROPERTIES:
Gray Cast Iron
Density 7200 kg m^-3
Coefficient of Thermal Expansion 1.1e-005 C^-1
Specific Heat 447 J kg^-1 C^-1
Thermal Conductivity 52 W m^-1 C^-1
Resistivity 9.6e-008 ohm m
Gray Cast Iron > Compressive Ultimate Strength
Compressive Ultimate Strength Pa
8.2e+008
Gray Cast Iron > Compressive Yield Strength
Compressive Yield Strength Pa
0
Gray Cast Iron > Tensile Yield Strength
Tensile Yield Strength Pa
0
Gray Cast Iron > Tensile Ultimate Strength
Tensile Ultimate Strength Pa
2.4e+008
Gray Cast Iron > Isotropic Secant Coefficient of Thermal Expansion
Reference Temperature C
22
Gray Cast Iron > Isotropic Elasticity
Temperature C Young's Modulus Pa Poisson's Ratio Bulk Modulus Pa Shear Modulus Pa
1.1e+011 0.28 8.3333e+010 4.2969e+010
Gray Cast Iron > Isotropic Relative Permeability
Relative Permeability
10000
STRESS ANALYSIS:
The stress analysis on the axle was done in ANSYS 13 software. The loads on the axle were: the
normal stress due to the weight of the vehicle and a reaction force from the propeller shaft due to
sudden stopping of the vehicle.
The Ford 9 inch axle is an axle for small cars, hence we assumed the load to be 1000 Kg evenly
distributed as 5000N on each side of the differential case.
Then the stopping force was calculated assuming the velocity of the car to be 60 Km/h and stopping
distance to be 15 m. This force came out to be 9269 N which stopped the car in 1.78 s.
The CAD after being imported into ANSYS:
Meshed rear axle:
The loads described above were applied as follows:
A and B: equal forces of 5000 N evenly distributed on the surface.
C: Reaction force of 9269 N
D: Fixed support on both sides. (Assuming wheels as fixed support)
DETAILS OF THE GEOMETRY:
RESULTS:
The results of the analysis were:
Object Name
Maximum Principal Stress
Equivalent Stress
Total Deformation
Strain Energy
Structural Error
Results
Minimum -4.0392e+006 Pa 0. Pa 0. m 0. J
Maximum 1.3602e+007 Pa 1.148e+007 Pa 1.0944e-004 m 1.2004e-003
J 3.3276e-004
J
Bounding Box
Length X 0.28765 m
Length Y 0.28448 m
Length Z 1.0846 m
Properties
Volume 1.1626e-002 m³
Mass 83.706 kg
Scale Factor Value 1.
Statistics
Nodes 26077
Elements 13599
Mesh Metric None
Following were the contours generated:
Maximum principle stress:
Von-misses stress:
Total deformation:
Structural error:
Strain Energy:
Now, let us examine the critical points of the model, i.e. at the corners where structural failure might
occur due to high stress:
Max. Principle Stress Von misses stress
Now, following result was obtained for Mean Stress Theory for Googman, Soderberg and Gerber
equations:
CONCLUSION: Maximum deformation was found out in the analysis
Stress concentrated regions were predicted
Critical regions with high possibility of damage were determined
Increasing the thickness of crumples zones can be one of the solution
Reinforcement rings can be used in order to enhance the strength