PARAMETRIC STRESS ANALYSIS OF HELICAL GEAR USING FEA Finite Element Analysis

1. SANT GAHIRA GURU UNIVERSITY AMBIKAPUR
Department of Mechanical Engineering
(M-Tech Machine Design)
A Presentation on
PARAMETRIC STRESS ANALYSIS OF HELICAL
GEAR USING FEA
by
BAPI BISWAS
(Enrolment No- SUT16R1003)
Guided By - Prof. Pankaj Sidar

2. Contents:
 Introduction
 Types of Gears
 Causes of gear failures
 Experimental Procedure
 Design of Helical Gear Pair
 Static Structural Analysis in ANSYS
 Result
 Conclusion

3. LITERATURE SURVEY
 Rao and Muthuverrappan explained about the geometry of
helical gears by simple mathematical equations, the load
distribution for various positions of the contact line and the stress
analysis of helical gears using the three dimensional finite element
methods.
 Hedmund and Lehtovaara study the Modelling of helical gear
contact with tooth deflection.
 P. Sidar Presented multi-point constraint method (MPCM) to find
the actual load shared among the paired teeth. A calculation model
for helical gear for contact stress analysis is introduced. The
coordinates of the points of the helical gear tooth profile in the first
face were computed with the transverse module of the helical gear
by using MATLAB code. The average load shared by teeth during
the mesh cycle of gear can calculate the load-sharing ratio of the
pair of helical gear teeth in one mesh cycle.

4. Introduction:
Gears are used for transmitting power between the
shafts. It is one of the best methods for transmit
torque, power, angular velocity and motion. Helical
gear is used to transmit motion and power between
parallel, non-parallel and intersecting shafts.

5. Investigates the maximum contact stress, which
improve load sharing capacity .
Contact stresses are calculated by using multi-pair
constraint method (MPCM)
Modelling of gear pairs using Solid Works 2016
Meshing through ANSYS 18.1
Analysis to evaluate the contact stresses using
Ansys 18.1
Find stresses for different position of the contact
line
Main Step

6. Types of Gears:
1. Spur Gears - Spur gears belong to the parallel shaft gear
group and are cylindrical gears with a tooth line which is
straight and parallel to the shaft. Spur gears are the most
widely used gears that can achieve high accuracy with
relatively easy production processes.

7. 2. Bevel Gears - Bevel gears have a cone shaped
appearance and are used to transmit force between
two shafts which intersect at one point (intersecting
shafts). A bevel gear has a cone as its pitch surface
and its teeth are cut along the cone.

8. 3. Helical Gear - Helical gears are used with
parallel shafts similar to spur gears and are
cylindrical gears with winding tooth lines. They
have better teeth meshing than spur gears and
have superior quietness and can transmit higher
loads, making them suitable for high speed
applications. When using helical gears, they
create thrust force in the axial direction,
necessitating the use of thrust bearings. Helical
gears come with right hand and left hand twist
requiring opposite hand gears for a meshing pair.

9. TYPES OF GEAR FAILURES
• Fatigue
• Impact
• Fracture
• Wear
• Stress Rupture
• Surface contact fatigue- pitting, spalling

10. Photograph indicate that teeth of the helical gear failed
by fatigue with a fatigue crack initiation from destructive
pitting and spalling region at one end of tooth in the
vicinity of the pitch line because of misalignment.
FATIGUE FAILURE

11. Photograph of Pitted gear teeth

12. CAUSES FOR FAILURE
Poor design of gear set
Misalignment of gears
Overloads
Subsurface defects in internal areas
Use of incorrect materials and heat treatment

13. AISI 8620 Steel
Elastic Modulus 210000 N/mm2
Poisson's Ratio 0.28 -
Shear Modulus 79000 N/mm2
Mass Density 7700 kg/m2
Tensile Strength 723.8256 N/mm2
Yield Strength 620.422 N/mm2
Thermal Expansion Coefficient 1.3e-005 /K
Thermal Conductivity 50 W/(m·K)
Specific Heat 460 J/(kg·K)

14. Parameters Value
Number of teeth helical gear 20
Helix angle 120
Module, normal (mm) 1, 1.125 & 1.25
Pitch 1mm
pd 20.4468deg
Face width (mm) 8.4 & 10
Addendum 1
Dedendum 1.25
whole depth 2.25
Transverse pressure angle 20.4103deg
Transverse pitch 0.978148deg
Transverse tooth thikness 1.60589

15. Solid model with involute profile

16. Solid Model of Gear Pairs

17. MESHING:
Meshing is an integral part of the computer-aided engineering simulation process. The
mesh influences the accuracy, convergence and speed of the solution. a user can put
the right mesh in the right place and ensure that a simulation will accurately validate
the physical model. We put element size is 0.1mm and contact sizing meshing method
was used for this analysis.

18. Contact Region

19. RESULTS AND ANALYSIS
 For this analysis MPC based approach was used for contact
algorithm and Contact detection at nodal point is normal to target
surface.
 The load sharing ratio of the helical gear pair teeth in one mesh cycle
can be calculated by average load shared by teeth during the mesh
cycle of gear.
 The load shared among the contact element of the paired teeth can be
obtain by applying force 10 KN on the nodes of inner radius of the
rim in tangential direction.
𝐋𝐒𝐑 𝟏 =
𝐂𝐨𝐧𝐭𝐚𝐜𝐭 𝐥𝐨𝐚𝐝 𝐚𝐭 𝐩𝐚𝐢𝐫 𝟏
𝐂𝐨𝐧𝐭𝐚𝐜𝐭 𝐥𝐨𝐚𝐝 𝐚𝐭 𝐩𝐚𝐢𝐫 𝟏 + 𝐂𝐨𝐧𝐭𝐚𝐜𝐭 𝐥𝐨𝐚𝐝 𝐚𝐭 𝐩𝐚𝐢𝐫 𝟐 + 𝐂𝐨𝐧𝐭𝐚𝐜𝐭 𝐥𝐨𝐚𝐝 𝐚𝐭 𝐩𝐚𝐢𝐫 𝟑

20. Module Type For Module 1 For Module
1.125
For Module
1.25
Von-Misses
Stress
124.41 MPa 125.03 MPa 125.73 MPa
Output from FEA (Ansys)

21. Equivalent von-mises Stress Ansys18.1 for module 1

22. Equivalent von-mises Stress Ansys18.1 for module 1.125

23. Equivalent von-mises Stress Ansys18.1 for module 1.25

24. Form load sharing plots of helical gear for the three modules of gear
pair, it is observed that increase in module decreases the three tooth
contact region which increases the stress developed in the contact
region.
GRAPHICAL REPRESENTATION OF LOAD
SHARING RATIO
LSR Vs Contact Position (X/Pbt) plot for module 1, 1.125 & 1.25 for b= 8.4

25. Form load sharing plots of helical gear for the three modules and three
different face width of gear pair, it is observed that increase in face
width increases the three tooth contact region which decreases the
stress developed in the contact region.
LSR Vs Contact Position (X/Pbt) plot for module 1, 1.125
& 1.25 for b= 10

26. CONCLUSION
The attempt is made to determine the contact stresses in helical gear by
considering the load sharing ratio between the pair of teeth in
simultaneous contact. The following observations are made from the
FEM analysis of helical gear.
 The maximum contact stress in the contact region of helical gear is
developed at the pitch point of helical gear because of high load
sharing ratio.
 The contact stress near tip and the root is less as compared at pitch
point because of less load sharing ratio.
 The maximum contact stress is decreases with the increase in the face
width of helical gear.
 The maximum contact stress in the contact region is increase with
increase in module.
 The maximum contact stress is maximum for module 1.25.

27. THANK YOU!