stress concentration on a plate with a hole
Objective: Static Structural analysis of a plate with a hole using ANSYS Workbench
Materials used for this case study is Structural Steel. The materials property are given below:
- Yield strength - 250 Mpa
- Ultimate strength - 460 Mpa
- Density - 7850 kg/m^3
Case1: This CAD model was designed using ANSYS design modeler. The geometric descriptions of the plate are - length= 300mm, height= 120mm, thickness=30mm, holes diameter=60mm
Case 2: The geometric description of the plate are - length =300mm, height =120mm, thickness =30mm, center hole dia=60mm, small holes = 2 holes of 30mm dia, 180mm away from each other and 90 mm away from the center.
Preprocessing step: Due to the limitation of the academic version of Ansys, the maximum node/element it can generate is 32000. Based on this limitation, an element size of 3.4mm and tetrahedron method with patch conforming algorithm is used to generate the mesh. Same mesh setting was taken for both the cases.
Application of load and constraints: Fixed support was given on the left face of this model and a force of 500N on the right face.
Post-processing step: After the result are solved, we need to analyze the result by observing the deformation and equivalent stress data.
Deformation Result: case 1 case 2
Equivalent stress result:
Results discussion:
From the deformation result, we can clearly see that deformation in case 2 exceeds a little as compared to case1. This is mainly due to the removal of material from the specimen by using two additional holes.
In case 1, the force flow line near the discontinuity get clustered and is not parallel to the edge. Hence stresses are accumulated near the discontinuity (holes). To reduce the stress accumulation two more additional holes are created for case 2 specimen, such that flow lines becomes more uniform and thus a better design. Based on the stress result, the value of stress in case 1 decreases to some amount after introducing the additional holes to a value given in case 2.
In both cases, the stress generated is much less than the yield strength. So, both the model are safe from failure point of view. From the design point of view, cases 2 will be a better design as it reduces stress concentration.
From the manufacturing point of view, case 1 specimen will be easy as it involves one operation.