STRESS CONCENTRATION ON A PLATE WITH SINGLE AND MULTIPLE HOLES

CASE 1- For the first case in which we have a single hole of 60mm at the center

-I have the prepared the geometry of plate with single hole in solidworks rather than space claim because of lower version of ANSYS. So., I made the plate having single hole with dimensions according to the question and save it as Parasolid format.

-During meshing, I have taken the element size of 4mm rather than 2mm as it is getting too much fine and taking longer to solve the solution. Mesh method selected is tetrahedrons.

-Results- Deformation= 0.0002749mm

Equivalent stress= 0.602MPa

CASE 2- For the second case in which we have multiple holes of 60mm and 30mm.

-Prepared geometry same as that in case 1.

-Mesh is also generated as same as that in case 1.

-Results- Deformation=0.0002973mm

Equivalent stress=0.580MPa

Comparison of the deformation and equivalent stress between the two cases

	CASE 1	CASE 2
Deformation (mm)	0.0002749	0.0002973
Equivalent stress (MPa)	0.602	0.580

-Case 2 have lower equivalent stress as compare to that of Case 1 because of hole elongation in middle hole is relatively small than the two outer holes and lower tangential stress were exhibited at the middle hole leading to less likely the failure and fracture is initiated from middle hole in case 2. Thus case 2 have a better factor of safety.

-Case 2 have more deformation as compare to that of case 1 because in case 2 the tangential stress is acting on all three holes whereas in case 1 it is acting only one hole. Thus case 2 results in more deformation.

Selection of design on the basis of analysis standpoint

I will select case 2 as it has less equivalent stress due to low tangential stress (hoop stress) acting on the center hole as most stress acts on the outer holes. Due to this there will be less stress at the notch of center hole and can achieve better factor of safety. So, the chances of the failure of center hole get less and can be used in conditions have greater load than 500N. As the structural steel have maximum yield strength of 250MPa and factor of safety is equal to allowable stress/ applicable stress, thus case 2 have more FOS.

Selection of design on the basis of Manufacturer standpoint

I will select case 1 on the basis of manufacturer because as it consists of only 1 hole at center. So, during manufacturing this plate there will be these factors that are taken in consideration

-Wastage of material- As in case 2 there are two extra holes which has to be generated by drilling operation due to which material is wasted in drilling, whereas, in case 1 there is no such wastage of material as there is only one hole.

-Time of manufacturing- Case 1 take less time for manuufacturing due to the presence of one hole as compare to case 2 which have multiple holes, Thus in case 2 more time has to be invested in creation extra holes and results in increase of the price.

- Difficulty-In case 2 we have to create two holes at particular postions due to which difficulty increases as we have to take more dimensions and have to do drilling operation more precisely.