Stress distribution in gudgeon pins

Abstract

Frozen stress photoelastic tests were carried out on four shapes of gudgeon pins, loaded in a piston of realistic shape by a realistic connecting rod. The results showed that the greatest stresses occurred in the gaps between the piston and connecting rod at the horizontal position in the bore. Measured compressive hoop stresses and calculated shear stresses there were up to 2 1/2 times the mean shear stress. Thick ring calculations slightly overpredicted the compressive stresses and the tensile hoop stresses at the vertical position, i.e. they are 'safe’. The greatest axial stresses were smaller than the above. Measured pin deflections between the piston bosses were less than the results of simple beam calculations, which ignored the restraints exerted by the piston. Ovalization of the cross-section was largest in the middle.