Estimation o inside stress distribution and destruction of metal using nonlinear dependency of sound velocity on stress

该研究的目的是开发新技术，通过使用超声速度对应力的非线性依赖性来评估金属的状况。特别是利用应力扰动产生的泵浦波和速度变化检测的超声探测波是从检测两波交叉区域的相互作用来定位或成像金属内部状态的关键点。首先，用新得到的应力-应变系统和50 MHz超声波系统研究了声速与应力的非线性关系，然后用等效线性和二阶、三阶非线性弹性常数建立了声速与应力的非线性关系，并由实验结果导出了这些值。（3）建立了能在金属内部产生约1 MPa、5 μ sec持续时间的应力扰动的抽运系统和能探测0.01度动态相变的50 MHz探测波。iv）它们用于测量金属的局部非线性弹性常数。（5）引入了一个新的表征金属状态的特征值作为非线性弹性常数的函数。最后，作为一个例子，vi）将其应用于金属内部弹性变形极限应力值的估算，并证明了其对金属破坏预测的实用性。

The objective of the research was the development of new techniques for evaluation of the condition of metals by using nonlinear dependence of ultrasound velocity on the stress. Especially the use of stress perturbation generating pumping waves and the velocity change detecting ultrasonic probing waves is key point for localization or imaging of the condition inside of metals from the detection of the interaction at the crossing region of the two waves. First, i) the nonlinear dependency of sound velocity on stress is examined by using newly obtained stress-strain system and ultrasonic wave system of 50 MHz, then ii) the nonlinear relation is formulated by using equivalent linear and 2nd and 3rd order nonlinear elastic constants and these values are derived from the experimental results. iii) The pumping system which gives about 1 Mpa stress perturbation of 5 musec duration inside metal is constructed and the probing wave of 50 MHz which can detect 0.01 degree of dynamic phase change is also constructed. iv) They are used to measure local nonlinear elastic constants of metal. v) A new characteristic value to evaluate the state of metal is introduced as a function of the nonlinear elastic constants. Finally, as an example, vi) it is applied for the evaluation of elastic deformation limiting stress value inside of metal and the usefulness for the prediction of destruction of metal is demonstrated.