摘要
从理论上分析了采用非线性超声兰姆波方法准确评价固体板材疲劳损伤的可行性。对于未承受周期性载荷作用的航空铝板,采用已建立的超声兰姆波实验系统测量了在其中传播的超声兰姆波的基波和二次谐波的幅频曲线,并对所测得结果给予了合理的物理解释。对两块给定的航空铝板试件施加拉-拉疲劳载荷作用,在超声兰姆波具有强烈非线性效应的条件下,对于不同的载荷循环次数,分别对两试件中超声兰姆波的基波和二次谐波的幅频曲线进行了测量。结果表明,在板材疲劳损伤的初期,超声兰姆波基波的应力波因子随循环次数的改变并不明显,且与循环次数的对应关系也不确定;然而,在周期性载荷作用的最初阶段,超声兰姆波二次谐波的应力波因子随循环次数的变化非常显著,并表现出明显的单调对应关系,表明超声兰姆波的非线性效应及相应的超声兰姆波二次谐波的应力波因子,可望能为固体板材早期疲劳损伤的准确评价提供一条有效途径。
The feasibility of using a nonlinear ultrasonic Lamb wave approach for accurately evaluating fatigue damage in solid plates was theoretically analyzed. With the established experimental system for ultrasonic Lamb waves, the fundamental- and second-harmonic amplitude-frequency curves of Lamb waves, propagating in an aeronautic aluminum sheet without being subjected to any cyclic loading, were measured. Reasonable physical explanations were given for the data measured. The tension-tension fatigue loading was respectively applied to the two given aeronautic aluminum sheets. The fundamental- and second-harmonic amplitude-frequency curves of ultrasonic Lamb waves, propagating in the two specimens subjected to tension-tension fatigue loading for different numbers of loading cycles, were measured under the condition that ultrasonic Lamb waves had a strong nonlinearity. It was found, in the early stages of fatigue damage in the specimens, that the change in the Stress Wave Factor （SWF） of the fundamental waves of ultrasonic Lamb waves with the number of loading cycles （N） was not obvious, and that there was not a clear monotonic relationship between the SWF of the fundamental Lamb waves and N. In the initial stage of cyclic loading, however, the change in the second-harmonic SWF of ultrasonic Lamb waves was very sensitive to N, and there was a clear monotonic relationship between second-harmonic SWF of ultrasonic Lamb waves and N. It could be concluded that the nonlinear effects of ultrasonic Lamb waves and the corresponding second-harmonic SWF might offer a potential for accurately evaluating the early stages of fatigue damage in solid plates.
出处
《声学学报》
EI
CSCD
北大核心
2008年第4期360-369,共10页
Acta Acustica
基金
国家自然科学基金(10674180)
教育部新世纪优秀人才支持计划(NCET-05-X)资助项目
关键词
超声兰姆波
非线性效应
疲劳损伤
无损评价
板材
固体
应力波因子
载荷作用
Aerodynamics
Alumina
Aluminum
Aluminum sheet
Cracks
Cyclic loads
Dynamic loads
Harmonic analysis
Light metals
Loading
Plates (structural components)
Stages
Ultrasonic waves
Ultrasonics
