Spur Gear detailed analysis with cast iron, cast steel and cast bronze using Ansys

Objective: Write a detailed report comparing the results of the three cases mentioned below and conclude which material would you recommend based on these results. 

• Case 1: Using Cast Iron(ductile) as a material, carry out a static structural analysis to find out Equivalent stress, Total deformation, and Stress intensity Find a location for possible fracture

• Case 2: Using Cast Steel as material, perform the same analysis for the results as in Case 1.

• Case 3: Using Cast Bronze as material, perform the same analysis for the results as in Case 1.

Theory: 

Equivalent Stress: It is used when there is a multiaxial stress state with multiple stress components acting at the same time in the structure. In such cases, we can use selected criterion to transform the whole stress tensor into a single equivalent component that can be treated as tensile stress and thus compared with material’s strength easily.

Total Deformation:  Total deformation gives a square root of the summation of the square of x-direction, y-direction, and z-direction.

Stress Intensity: 1. Stress intensity factor accounts for asymptotic stress variation. How stresses vary near the crack tip. 

2. It is a dimensionless quantity that varies with the load and geometry.

3. Stress intensity at a kinked crack tip determines the crack deflection at the load when the crack starts to propagate.

Model given:

============================================================================================================

Simulation:

Material Selection:

Time Step detail analysis settings:

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Cast Iron:

                                                                                    Equivalent stress animation (Cast Iron)

Total Deformation:

Equivalent Stress:

                                                                      Graph Equivalent Stress  (Cast Iron)

Stress Intensity:

                                                                           Stress Intensity (Cast Iron)

====================================================================================================================

Case 2. Cast Steel

                                                    Equivalent stress animation (Cast Steel)

Total Deformation (Cast Steel)

                                                                      Equivalent Stress (Cast Steel)

                                                             Graph Equivalent Stress  (Cast Steel)

Stress Intensity:

Graph Stress Intensity (Cast Steel)

=============================================================================================================

Case 3: Cast Bronze

                                                            Equivalent Stress (Cast Bronze)

                                                        Graph Equivalent Stress  (Cast Bronze)

Total Deformation:

Stress Intensity:

                                                                   Graph Stress Intensity (Cast Bronze)

===========================================================================================================

Conclusion:    Casting Material        Equivalent Stress(Max)              Stress Intensity(Max)

                                                                          (MPa)                                     (MPa)

                          Iron                                        425.21                                    466.19

                          Steel                                       428.36                                    472.25

                          Bronze                                    427.84                                    478.1

It can be observed that cast iron is less ductile among all so it can't be selected and its resistance is low. Cast bronze is highly ductile and its fracture rate is lowest.

In this particular case, we would prefer to Cast steel due to its high stress intensity factor also strength and availability of the material are high.

In general case due to good vibration damping, good wear resistance, good maintainability, low notch sensitivity cast Iron is preferred.