金属构件在加工和服役过程中产生的残余应力会使其产生形变或应力疲劳,严重危害关键结构的安全性。现有超声应力检测技术存在温度耦合效应大且无法检测不同深度应力等问题,基于临界折射纵波的声弹性原理,设计并研制了四通道差分式超声应力检测仪。该仪器基于现场可编程门阵列(FPGA)设计,由超声发射电路、接收电路、信号处理电路和操作软件等部分组成。配合定制的组合式超声激励探头与双宽带接收探头,可以实现4个不同频率的超声临界折射纵波应力同步测量,有效地避免了温度耦合和不同频率探头声学耦合的问题。通过标准拉伸试验对铝合金和钛合金试样进行了应力测量,表明该仪器可以满足四通道应力测量。

The residual stress of metal components in the process of processing and service causes deformation and even stress fatigue, which seriously endangers the safety of the key structure. In order to avoid the effect of temperature and measure internal stress gradient at crucial components, a differential four-channel ultrasonic stress detector was designed based on acoustoelastic effect of longitudinal critical refraction wave. The detector was designed based on field programmable gate array (FPGA) and mainly consisted of ultrasonic transmitting and receiving circuit, signal processing circuit and operation software. The detector equipped four-frequency ultrasonic transmitter probe and two broadband receiver probes to eliminate coupling errors caused by temperature and probe replacement. The stress measurement of aluminum and titanium alloy structures was carried out by standard tensile test, and proved the capability of four-channel measurement of stress.