Stain measurement error near crankshaft fillet in bending fatigue test

Due to the complexity of shape and small fillet size, large error exists in the electrical measurement on strain near crankshaft fillet during bending fatigue test. Transient dynamic computation of fatigue test is carried out by modal superposition method, and the normal strains near critical position in fillet surface are obtained. The distribution of strain along the hoop direction of fillet section is expressed as the first-order Fourier series. Based on strain distribution regularity, the error due to the replacement of maximum stress by average strain in the sensitive grid field is analyzed. Result shows that this error can be controlled by choosing the foil gage with small size. Measurement error which caused by position offset of strain foil is discussed. Measurement error will be unacceptable as offset increases.