Study on Vibration Fatigue Limits Test Method for Metallic Joint Pipe
In order to determine the fatigue limits of two kinds of titanium alloy joint pipes connected by welding and rolling, the fatigue tests were carried out by test standard which defines the test method and failure rule. One cantilever-beam specimen was fixed on the shaker by the special fixture. The laser-displacement-sensor was fixed at the free end of pipe and the strain-gauge was adhesive at the root of the pipe. The first frequency of specimen was measured by these sensors. The first resonance frequency fell rapidly with the increment of the excitation loads of the shaker. The failure rule (1% drop of resonance frequency) of the standard was not same with the fatigue limit test of these connected pipes at the test beginning. In order to define the lives of two kinds of pipes, the stair method of sweep test was used to eliminate the effect of connection gap. Then the vibration fatigue of every specimen was tested at the last resonance frequency. And all the fatigue tests were finished using the failure rule which defines 1% drop of the steady resonance frequency.