Railway axle modified KT figure acquiring method and damage tolerance design method

Abstract

The invention relates to a railway axle modified Kitagawa-Takahashi (KT) figure acquiring method and a damage tolerance design method thereof. The railway axle fixation KT graph acquiring method comprises the following steps: S1, getting the fatigue limit sigma(c) of an axle; S2, cutting out a 0.5-2mm deep semi-elliptical crack perpendicular to the axis at a research position of the axle, and drawing a line A on a log(delta sigma)~log(a) coordinate system; S3, drawing a line B on the log(delta sigma)~log(a) coordinate system; S4, fitting out a contour line of the crack length d1-d2 on the log(delta sigma)~log(a) coordinate system; and S5, determining the rules of fatigue crack growth at different load levels, drawing a contour line between 0 and d1, and getting a modified KT figure considering the effect of short fatigue crack. According to the modified KT figure designed in the invention, a corresponding fatigue limit can be read by measuring a crack length at a position of an axle. The service reliability of axles is ensured. A scheme for appropriately extending or shortening the nondestructive detection period can be obtained according to the long-term operation experience.

Description

technical field [0001] The invention relates to the technical field of fatigue damage analysis, in particular to a method for obtaining a modified Kitagawa-Takahashi (KT) diagram of a high-speed railway axle and a damage tolerance design method. Background technique [0002] At present, the hollow axle design of domestic and foreign motor axles is based on the traditional safety strength design theory (or nominal stress method), which does not take into account the evolution characteristics of defects (or cracks) and their stress amplification effects during actual material manufacturing and operation. Although fatigue fracture mechanics has been paid attention to and applied in the formulation of the non-destructive testing cycle plan and life evaluation of axles in recent years, the assumed cracks are generally larger than 2mm, and the crack growth life only accounts for a small part of the total service life, resulting in the safety limit of the axle is too large , causin...

AI Technical Summary

Problems solved by technology

On the one hand, the traditional strength evaluation method does not consider the inherent discontinuity of the matrix material and structural geometry, ignores the local increase in stress caused by it, and gives an overly conservative design conclusion; on the other hand, the axle in the manufacturing, Minor defects such as bumps, scratches, foreign body impact pits, environmental corrosion pits, and wear of the press-fitting parts are inevitable during transportation, service, and maintenance, which have become huge safety hazards for trains running at high speeds

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