write:From this little exercise you should be able to see that the orientation of load to the specific geometry has a critical influence on the value of Kt. It should be obvious by now t

the dimensions “a” and “b” are equal
Kt is equal to 3 and the orientation of the load creating the stress is not important. This is not the case for elliptical holes. Sup-pose we change the dimensions of the hole to an ellipse whose dimen-sion “a” remains at one inch but whose dimension “b” is reduced to 1/4 inch. The elastic stress con-centration factor would increase to 9 (Kt=9) and the maximum local tension stress would increase to 160
000 psi. On the other hand
if we increased the “b” dimension to 4 inches while holding the “a” dimension at 1 inch
the elas-tic stress concentration factor be would only 1.5 and the maximum local tension stress would be only 30
000 psi. From this little exercise you should be able to see that the orientation of load to the specific geometry has a critical influence on the value of Kt.It should be obvious by now that the elastic stress concentra-tions generated by a component are a function of the design’s ba-sic geometry. Examples of how a component’s geometry can ex-acerbate or mitigate elastic stress concentrations are shown in Fig-ure 35-46.Looking at Figure 35-47
manu-facturing techniques used to fab-ricate a component can influence elastic stress concentrations. Some of the ways elastic stress concentra-tions can introduced during design are listed below:• Machining or grinding tool marks perpendicular to local ten-sion stress produced by applied loads. Marks which are parallel to tension stresses do not signifi-cantly increase elastic stress con-centrations. (Figure 35-48.)Burrs in drilled holes. Use of dull drill bits and failure to de-burr holes can result in notches in holes which greatly increase the elastic stress concen-trations caused by the original hole. (Figure 35-49.)Failure to prepare holes to the fit of fasteners which will be inserted into the holes. If a fastener with a fillet radius between its head and shank were inserted into a hole in which a chamfer or transition radius had not been machined
the hole’s sharp edge would cut into the fastener’s transition radius
creating an additional stress concentration in a area which already has a stress concentration. (Figure 35-50.)••Figure 35-48. Machine/Tool Marks Perpendicular to Local Tension Stress.Figure 35-49. Burrs in Drilled Hole.Figure 35-50. Sharp Corners on Holes into Which a Bolt with a Fillet Radius will be Inserted.