The tension compression fatigue test of gray cast iron mainly studies the effects of loading frequency and surface roughness on the fatigue strength of gray cast iron at room temperature. The fatigue strength of three grades of gray cast iron samples is measured by lifting method, and the fatigue life curve is drawn. The fatigue samples are directly taken from the engine block body of the cooperative enterprise, and the dimensions of the tension compression fatigue samples are processed according to the standard sample drawings of the fatigue testing machine. The sample size is shown in the figure.
Requirements for fatigue sample processing: surface work hardening is not allowed during sample processing, and the final finishing direction of R35 arc surface is recommended to be longitudinal. The surface of the R35 arc section of the sample must be polished, and the surface is not allowed to leave machining marks, defects and rust, which will cause gaps on the sample surface and affect the accuracy of the test results.
The middle section of the sample is the working section, and the two ends are the clamping parts of the sample. Fillet transition is required for the transition between various parts of the sample to avoid stress concentration and fracture in other positions, which will affect the test results.