The measurement accuracy of acoustic time difference directly affects the reliability of ultrasonic stress test results. The threshold method was proposed to be used for measuring acoustic time difference. The new method compares the time at the optimal threshold of two periodic signals with definite time-delay, the time interval at an optimal threshold is the acoustic time difference. The mathematical model of error analysis for measuring acoustic time difference by threshold method was established, and the optimal threshold value is determined according to the model. The noise is inevitable in the process of stress measurement; the ultrasonic signals with different signal-to-noise ratios were stimulated to verify the reliability of the optimal threshold method. The simulation results show that the method has a high antinoise capability, higher detection accuracy, and better adaptiveness to the ultrasonic signal of the time change.

声时差的测量精度直接影响超声应力测试结果的可靠性。提出了阈值法用于测量声时差。新方法将两个周期信号的最佳阈值处的时间与确定的时延进行比较，最佳阈值处的时间间隔为声学时间差。建立了用阈值法测量声时差的误差分析数学模型，并根据模型确定了最佳阈值。应力测量过程中不可避免地会产生噪声。刺激不同信噪比的超声信号，以验证最佳阈值方法的可靠性。仿真结果表明，该方法具有较高的抗噪能力，