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Optimisation of Ratio of Center Distance of Adjacent Hole to Diameter of Pre-stressed Holes by FEA

Basavaraj Kawdi

Abstract


Residual compressive stress zone around a fastener hole is introduced by a process called pre-stressing. This is being done to reduce adverse effect of cyclic tensile stress and to restrict the fatigue crack growth due to material flaws or imperfect surfaces. The objective of this investigation is to optimize the inter-hole distance between adjacent cold expanded holes on a plate restricting the deformation of material between holes to the elastic range by stress application below the yield strength (compressive) of material. The ratio of center distance between holes to diameter of hole is observed and found that it has got considerable effect on stress contours induced for known expansion. Equations are derived for radial stress for a plate module as a thick cylinder. By using MATLAB, graphs are plotted for these equations. Finite Element Analysis, by ANSYS is carried out on two expanded holes of mild steel plate. The center distance between two holes was varied from 2.5D to 4D in steps of 0.25D to find optimum center distance between holes and it is studied. It is found from analytical and FE methods the stress pattern in the vicinity of holes is comparable, proving the approach used is correct. The relationship between percentage of expansion and the ratio of distance between holes and the diameter is analyzed to optimize the percentage of expansion needed for the given ratio.

Keywords


Expansion, pre-stressing, ratio, FEA, optimisation

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References


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DOI: https://doi.org/10.37628/ijsmfe.v6i2.1163

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