Week 1 Stress Concentration on a Plate with hole
STRESS COCENTRATION ON A PLATE WITH A HOLE
Case 1
For case 1,static structural analysis is carried out on a plate with a single hole of dia 60mm. The material used is structural steel and the analysis carried out in Ansys workbench. The plate is first modified in Ansys SpaceClaim software and is shown in the figure below.
The dimensions of the plate are as follows:
Length 300mm
Breadth 120mm
Height 30mm
Hole dia 60mm
The 2d geometry is then extruded within SpaceClaim to get the model to be imported into ANSYS. The extruded model is as shown in the figure below
The properties of the material used are as follows :
Density 7.85e-006 kg mm^-3
Isotropic secant coefficient of thermal expansion 1.2e-005 C^-1
Specific heat constant pressure 1.34e+005 mJ kg^-1 C^-1
Isotropic Thermal conductivity 6.05e-002 W mm^-1 C^-1
Isotropic resistivity 1.7e-004 ohm mm
The model is meshed using an Ansys meshes with an element size of 0.5mm and a patch conforming method using tetrahedrons was employed.
A mesh metric that identifies elements according to their quality was employed and it can be seen that the elements of the lowest quality are minimal. Most of the elements have very high quality in the range of 0.6-0.8. Hence the mesh is of acceptable quality. The meshed model is shown in the image below.
The Simulation is then run with the settings applied and the results are obtained.
Case 2
For case 2 static structural analysis is carried out on a plate with 3 holes. It is a modification of the model used in case 1 such that there are 2 extra holes of 30mm dia placed 90mm away from the centre. The dimensions of the plate and the material used are the same as in case 1. The 3D model of the plate is as shown in the figure below:
The dimensions of the plate are as follows:
Length 300mm
Breadth 120mm
Height 30mm
Centre Hole Dia 60mm
2 holes from the centre 30mm
The model is meshed using Ansys mesher with an element size of 0.5mm and a patch conforming method using tetrahedrons was employed.
A mesh metric that identifies elements according to their quality was employed and it can be seen that the elements of the lowest quality are minimal. Most of the elements have very high quality in the range of 0.6-0.8.Hence the mesh is of acceptable quality. The meshed model is as shown in image below.
Fixed support is applied on one side of the model and a tensile load of 500n is applied on the other side. The simulation is then run and the results are obtained as below:
Results:
The Total Deformation for the two cases are compared first:
Time (s) minimum (mm) maximum (mm) Average (mm)
- 0 2.7495e-004 1.3832e-004
- 0 2.9732e-004 1.4562e-004
The Equivalent stress for the two cases are compared
Time (s) minimum (MPa) maximum (MPa) Average (MPa)
- 0 1.6828e-003 0.6746 0.17565
- 0 7.2453e-005 0.74345 0.17422
The Total deformation is plotted on the model and is as shown below:
The Equivalent stress is plotted on the model and is shown below:
Conclusion:
The analysis was run successfully the simulations for the 2 cases was examined. The mesh size that could be used In both the cases differed significantly as a result of the appearance of the two holes which resulted in lesser material and hence similar size mesh elements could be used.
On comparision of the Total deformation experienced by the model in the 2 cases only a slight difference in the average value is evident of the order of 0.04mm with case 2 having a higher value.Maximum deformation in two models have a difference of the order of 0.23mm.
On comparision of the equivalent stress experienced by the model in the case 2 a difference of 0.001Mpa is evident in the average value of equivalent stress. But the maximum and minimum value of stress experienced in case 2 is lesser than that in case 1.
On the basis of these results from an analysis point of view case 2 can be choosen because the stress undergone by it on application of the some amount of tensile force is lesser when compared to case 1 and there is not much improvement in performance when you consider the work that has to be done to make the model.