金属连接导管振动疲劳极限测试方法研究

为确定滚压和焊接钛合金导管的振动疲劳极限寿命,采用HB5277-84规定的振动疲劳试验方法和失效准则。分别利用激光位移传感器和电阻应变片测定了试件的第一阶频率和规定加速度载荷激励下的试件悬臂端位移及试件根部的应变。试验发现：对于具有连接特性的试件在进行定频振动疲劳试验初期,试件第一阶响应频率快速下降,此时试件并未发生裸眼可见破坏和裂纹。为满足产品定寿要求,采用逐级增加试验载荷进行扫频振动试验,直至试件频率稳定以及根部应变和端部位移达到试验要求后,再进行正式定频振动疲劳试验,仍采用依据频率下降1%作为失效准则完成了所用规定试验。

On the Vibration Fatigue Limit Test Method for Metal Connecting Pipe

In order to determine the vibration fatigue limit of titanium alloy pipes connected by welding and rolling respectively, fatigue tests were carried out based on Aero-Criterion HB5277-84, which defines the test method and failure criterion. One cantilever-beam specimen was fixed on the shaker by special fixture. In the test, laser-displacement-sensor was mounted at the free end of pipe and the strain-gauge at the root of the pipe. The first frequency of specimen was measured by sensors. The first resonance frequency drops rapidly along with the increase of excitation load and the failure rule (1% drop of resonance frequency) of Aero-Criterion is different from the fatigue limit test of these connected pipes at the test beginning stage. In order to define the fatigue limit of above mentioned 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 by using the failure criterion, which is defined as 1% drop of starting resonance frequency.