Stress Concentration on a Plate with hole

Results:

After solving the model, the following results are obtained.
The Total Deformation Results for both the cases-
Case 1 Case 2
Min Deformation (mm) 0 0
Max Deformation (mm) 2.74e-004 2.97e-004
Avg. Deformation (mm) 1.35e-004 1.45e-004

The Equivalent Von-Mises Stress for both the cases-
Case 1 Case 2
Min Equivalent Stress 1.735e-002 2.367e-003
(MPa)

Max Equivalent Stress 0.598 0.577
(MPa)

Avg. Equivalent Stress 0.161 0.168
(MPa)

Total deformation for Case 1

Total deformation for Case 2

Equivalent Von Mises Stress for Case 1

Equivalent Von Mises Stress for Case 2

Discussion

The simulation was run successfully without any errors. As discussed earlier in case 2, finer element size could be used for the Case 2 as it contains two extra holes and hence has a reduction in area. This allowed finer element size within the limits of ANSYS Student version.
On comparing the Total Deformation for both the cases, there is only a slight change in the values with only the Avg. Value is evident. The case 2 has greater values and the Max Deformation for the Case 2 is only bigger by the order of 0.23 mm. The reason Case 2 has higher Deformation than Case 1, because the reduction in material in Case 2 reduced the stiffness of the plate.
On comparing the Equivalent Stress results, the sudden change in the geometry causes a stress concentration around the holes. Case 2 has lower Max Stress as compared to Case 1 because the extra 2 holes in Case 2 evenly spreads the stress and stress concentration. With the use of adequate holes, stress concentration can be further reduced. Case 1 has 0.598 MPa of Max stress around the hole and is greater than Case 2 Max stress by 0.021 MPa. It is also observed that Case 1 has higher Min Stress compared to Case 2, as stress concentration is distributed in Case 2 due to holes.

From an analysis standpoint, Case 2 design must be used as it reduces the stress concentration around a single hole. Case 2 design will have a longer operational life and Case 1 design may fail early due to stress concentration.

From a Manufacturing standpoint, Case 1 design shall be used as less manufacturing operations are involved which will also prevent material wastage and associated costs. Besides, there is no significant difference in both the designs.