A brief analysis on unexpected damages to machinery during short distance transportation by low-cycle tensile fatigue fracture

摘要

As is well known, imported equipment is often damaged due to improper installation, fixing and packaging or loosening of some connected parts; such damages are usually attributed to inadequate steel strength of some parts or some kind of unexpected external force. In this article, we will analyze, mechanically and fractographically, a fracture of U-bar during short-distance transportation of a set of equipment and consequently conclude that the fracture arises from a kind of special metal fatigue which stretches quickly (subcritical stretching) on a low-cycle basis. Therefore, special attention must be paid to "suspension-style" installation and fixing of the structure to reduce the unexpected damages during short-distance transportation. It is hoped that such an analysis will provide some useful experience for the inspection of imported equipment.