Ameer Hamza 18R/17-ME-23
Stress Analysis of a Shaft Using ANSYS
Ameer Hamza
Department of Mechanical Engineering,
University of Engineering & Technology, Taxila
Abstract: This report deals with the stress analysis of a shaft using Ansys. The shaft which is fixed at one en d
is selected and forces are given at particular points. The reactant forces act in opposite directions. Torque act s
at two points in opposite directions. The reactant forces and bending moments are initially calculated. B ased
on these parameters, the maximum shear stress, normal stress are calculated. The sa me v alu es a re u sed t h en
calculated by using ANSYS software. Finally, the theoretical and analytical results are compared and
verified.
Key words: Splines Keyways Gears Pulleys Bearings
INTRODUCTION For Power Transmission:
Shaft: A shaft is a rotating member which transmits Line shafts
power. A shaft may be subjected to bending moment as Contour shafts
well as twisting moment. Gears, pulleys etc are usually
keyed to the shaft and the shaft rotates in the bearings. Materials: Mild-steel for ordinary shafts. Allo y st eel
An axle is chiefly subjected to bending moment. It nickel, nickel-chromium and nickel-vanadiu m st eels)
may carry freely rotating parts (without key) pulleys, when greater strength is required, as in high sp eed
gears etc. (e.g., industrial car wheels freely rotates on machinery. Alloy steel shafts are a lwa y s h ea t -treated
their axle). Sometimes, wheel is fastened rigidly to the (surface hardening).
axle rotates in the bearings. No torque is transmitted.
The rear axle of the wheel drive of the automobile is really Manufacture of Shafts:
a shaft, because it transmits torque to transmit propelling
force for the vehicle. Such shaft in the machinery is called Hot rolled bar is turned and ground.
spindles. Cold rolled or cold drawn shafts are of fairy uniform
A line shaft or transmission shaft, is a comparatively diameter and good surface finish. They can be
long shaft which is driven by the motor. The line shaft directly used for transmission shafting without
transmits motion to various machines through various machining. Machinery shafts are made of stepped to
machines through counter shafts. provide shoulders for locating gears, pulleys,
Front wheels of rear wheel drive vehicles are bearings etc. Splines, keyways etc., are machined
on supported on the stub axles. the shafts to secure gear wheels, pulleys etc.
Classification of Shafting:- Design of Strength: At various sections of the shaft will
For Prime Movers: lead to misalignment of mating parts and non uniform
distribution of loads. In machine tool spindles deflection
Engine shafts will affect the accuracy of parts machined. In these cases,
Generator shafts strength as well as bending stiffness and torsional
Turbine shafts stiffness are the criteria for design. While designing as per
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Ameer Hamza 18R/17-ME-23
standards, for line shafting, deflection should not exceed Force at the point B = 5.4 KN
0.2 mm per metre length of the shaft. Twist should not Torque = 600 Nm
exceed 0.25 degrees per metre for machine tools. Bendin g Equivalent force
deflection is inversely proportional to EI (flexural rigidity ) RO + RB -FA-FC = 0
and torsional twist is inversely proportional to to GJ RO + RB = FA + FC
(torsional rigidity).
Wear Resistance: Wear resistance is obtained by
hardening shaft surface. Low carbon steel shafts are
carburized or nitride. If the steel has sufficient carbon
content, surface hardening is given.
Hollow Shafts: For the same cross sectional area (weight),
hollow shafts are stronger and more rigid than solid
shafts. But hollow shafts are more expensive.
Critical Speed Shafts:
SHAFT
The centre of gravity of the loaded of the loaded
shaft will be displaced from the axis of the rotation
due to one or more of the following reasons.
Eccentric mounting of rotors
Lack of straightness of the shaft
Bending under the action of gravity in case of a
horizontal shaft
When the shaft begins to centrifugal force is
balanced by the inward elastic pull. The shaft deflection
is a function of shaft speed and it reaches maximum valu e
at a particular speed known as the critical speed. The
natural frequencies of lateral vibrations of the shaft is
same as that of critical speed. The shaft should not b e ru n
at the critical speed. Because excessive deflection will SHEAR STRESS
result in the failure of the shaft. Due to damping, friction
in bearings and effect of environment the shaft d o es n o t
fail instantaneously. If the shaft passes quick ly t h ro ugh
the zone of critical speed, no damage will be done.
Objective of the Project: The objective is stre analysis
and to calculate various stress acting on it by the given
values. Then, the dimensions are introduced in the An sy s
software and then the results are tabulated. Finally the
theoretical and analytical results are compared an d t h en
concluded.
Design Calculation: Dimensions:
Diameter of the shaft = 32 mm
Length of the shaft = 750 mm
Force at the point A = 5.4 KN NORMAL STRESS
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Ameer Hamza 18R/17-ME-23
CONCLUSION REFERENCES
The design parameters of the shaft has been taken 1. Joseph E. Shigley, “Mechanical engineering design”
from standard values and it has been designed to ANSYS (6 TH Edition).
It was found that the maximum shear stress value found 2. “Fundamentals of machine design” BY T.J. Prabhu.
by theoretically is 8.01 MPa and by ANSYS is 8.09 MPa. 3. Khurmi, R.S., “A Textbook of Machine Design”.
Therefore, the stress values are with the permissible limit 4. “Strength of materials” by R.K. Bansal.
and the design is safe.
