Experimental Studies on the Form Error Effect of the Part Mounting Surface on the Strength Quality Parameter of the Interference Fit Joints

Abstract

An experimental study was performed to investigate the effect of macrogeometric parameters of the mating surface forms on the strength of the cylindrical interference fit joint: taper, bow, barrel, and ovality. Fifteen couplings were made with a nominal diameter of 60 mm and a mating surface length of 70 mm. The bushings had a regular cylindrical form, and the CNC machining of shafts caused the geometry error. The relative geometric accuracy of the form was assumed to be the maximum allowable and was up to 60% of the tolerance zone. During modeling, the minimum allowable interference fit in the coupling Ø60 H8/u8 was assumed to be 0.04 mm to enhance the effect of form geometry errors. Ranked assembly was used to compensate for the interference fit in joints. The joints were assembled using thermal assembly. The strength was determined by axial pressing on the press with the press diagram recorded. The experiment results showed that form geometry error with maximum allowable values significantly affects the strength of the cylindrical interference fit. The taper reduces the strength to 0.87, barrel to 0.8, bow to 0.59, and ovality to 0.79 of coupling with perfect cylindrical surface geometry. Comparison of experimental results with those previously obtained by finite element modeling showed good agreement, within 10%. It is recommended that for critical couplings, a stricter limitation of the geometric error of the mating surfaces shall be provided.