Experimental Investigation on Structure Dynamic Stress Based on OBMA and FEA

Rotating machinery is often subject to cyclic loads in operating conditions, which may lead to a sharp increase in structural stress and cause high cycle fatigue. In this paper, structure dynamic stress analysis method based on Finite Element Analysis (FEA) and Order Based Modal Analysis (OBMA) is applied to a rotor test rig foundation to identify area of high stress induced by vibration. Firstly, dynamic parameters of the system are identified with Experiment Modal Analysis (EMA) method. The FE model is updated based on the modal identification results to make it corresponding to the actual operating conditions. Afterwards, OBMA method is applied to extract vibration acceleration response spectrum and dynamic parameters of the test rig, then FEA is used to estimate the stress of the structure. It is concluded that this method can be used for structural dynamic stress monitoring of rotating machinery under variable speed conditions, ensuring that it does not exceed the warning level.