The elastic modulus of a special alloy material are measured by the ultrasonic pulse - echo method , when the temperature is changed from - 20 ~ 60 为实现超声声速的快速、精确测量应用数字相关法精确确定超声信号的传播时间。
Explain the characteristics of piezoelectric crystals and the factors relating to the resonant frequencies of a piezoelectric crystal , and the procedure of the pulse - echo method 说明压电晶体的特性和与压电晶体的共振频率有关的因数,以及脉波回波法的过程。