Failure Analysis Of Bolts Research Articles

Failure analysis of bolts on fatigue test bench for excavator stick

In this study, a new bench device with full-scale fatigue test for excavator stick was designed. The test bench has the function of dynamic load self-balancing, because a part of the load applied to the specimen of stick is directly transferred to the pillars of the test machine through the high-strength bolts connection. Accordingly, the ground under the test machine was not affected by the test load. However, some bolts located on the fatigue test bench failed and fractured during fatigue testing for excavator stick. To determine the failure reasons of bolts, mechanical and scanning electron microscope (SEM) analyses were conducted. The tensile stress of bolt group under ultimate load was evaluated via finite element model (FEM) of test bench according to test load spectrum. Moreover, under the test load spectrum, the stress range of bolt group was obtained and the fatigue life prediction of bolts was conducted by referring to Eurocode 3. It should be noted that the results of numerical simulation of fatigue lives for failure bolts were consistent with the actual lives of failure bolts during test. A fractured surface on one of the failed bolts was examined by SEM observation to determine the failure initiation and failure mode.

Failure Analysis of a Reactor after Explosion Accident

Burst of a reactor occurred in an explosion accident during the production of antistatic agent process. According to the results of site survey, the current regulations and standards as well as the requirements of the accident investigation group, the reason of burst was discussed by failure analysis of the shell and bolts. The shell strength was analyzed by visual inspection, thickness measurement, and strength verification as well as estimating of bursting pressure. It can be concluded that the tank strength met the requirements of design condition. The bolts of the reactor was broken in the accident, so the failure analysis of bolts was carried out in detail, including visual inspection, fracture examination, chemical composition analysis, mechanical testing and strength verification. According to the results of the measured mechanical properties, the strength of the bolts was verified. It can be concluded that the bolts could bear the proof pressure test safely. Fracture analysis shows that no obvious metallurgical defects were found, the bolts were broken due to extreme overload. According to the technical analysis of the shell and the bolts, it can be concluded that the reactor could service safely under normal operating conditions. The cause of the bursting was transient extreme overpressure.

Failure analysis of bolts on an end flange of a steam pipe

This paper gives a case study about the failure of steam pipe fitting equipment in a chemical factory. The observation and analysis are done by way of SEM, EDS, tensile tests, and fracture mechanics. The reasons for failure, the fracture mechanisms, and the failure modes are revealed and discussed. A prediction of the fatigue life of a bolt of the fitting flange is made.