Application of nonlinear ultrasonic technique to characterize the microresidual strain in metal
- PDF / 1,163,098 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 59 Downloads / 172 Views
Department of Engineering Physics, Tsinghua University, Beijing 100084, China Guodian Boiler and Pressure Vessel Inspection Co., Ltd., Guodian Science and Technology Research Institute, Beijing 102209, China 3 Department of Aerospace electronic technology, Shanghai Academy of Spaceflight Technology, Shanghai 201109, China a) Address all correspondence to this author. e-mail: [email protected] b) Present address: Room1003, building Liu Qing, shuangqing road, Tsinghua University, Beijing 100084, China. 2
Received: 15 February 2019; accepted: 15 April 2019
Residual strain often occurs in metal when it was subjected to the tension load, random vibration, or high impact. The mild steel was selected as the research object, and the feasibility of using nonlinear ultrasonic technique to characterize the residual strain was investigated in this paper. First, the mild steel specimens were stretched to several different kinds of stress, then the nonlinear effect as well as the microstrain of each sample was measured. The results indicate that the microstrain increases with increasing applied stress and reaches a maximum value of about 0.036% as the tensile stress increases to the elastic limit. Compared with the original specimen, the nonlinear parameter of tensile specimen gradually increased within the elastic limit. This result reveals that the variation of nonlinear parameter was related to microstrain in mild steel, because the microstructure observation demonstrated that the dislocation structure was basically unchanged within the elastic limit. This research indicates that the nonlinear ultrasonic method has the promising potential to characterize the microstrain in metals.
Introduction Residual strain is the strain that remains after the original cause of the external stress has been removed [1]. Residual strain occurs for a variety of reasons, such as when materials were subjected to the tension load, random vibration, or high impact [2]. Residual strain is a significant factor for assessing the deformation and failure of materials [3]. Simultaneously, the residual strain in metal could make significant effect to the change of measured lattice parameters, which potentially leads to inaccurate structural integrity evaluation and determination [1]. The nonlinear ultrasonic technique is a novel method emerging in recent years [4, 5, 6, 7, 8], and now it has been recognized as a powerful method for characterizing the microstructural features in solids. With respect to its application in metal, a review of this technique was provided by Matlack [9]. Recently, Apple et al. [10] studied the nonlinear effect in single crystal copper during the fatigue process and found that the variation of nonlinear parameter was related to the presence of secondary dislocations in the samples. Xiang et al. [11] studied the thermal degradation in ferritic Cr–Ni alloy steel and revealed that the acoustic nonlinearity increases due to the second phase
ª Materials Research Society 2019
precipitates in the early stage; Marino et al.
Data Loading...
