When the fatigue life of C-type frame of huge pressure machine is estimated by nominal stress method, the fatigue comprehensive coefficient is a critical parameter. Based on the principle of fatigue simulation test and principle of similarity, the simulated scaled-model was established. On this basis, simultaneously considering interactions between three factors (stress concentration, size, and surface processing), a fatigue comprehensive coefficient modified expression was presented. A notched-sample fatigue life was analyzed and calculated by new expression, and it was basically accord with the test value. Furthermore, comparing modification results of the two coefficients, the new modified expression is more effective. The fatigue comprehensive coefficient of C-type frame can be conveniently obtained by new modification formula, which provides important basis for its fatigue life assessment.
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