title: Guided torsional wave generation of a linear in-plane shear piezoelectric array in metallic pipes.
abstract: Cylindrical guided waves based techniques are effective and promising tools for damage detection in long pipes. The essential operations are generation and reception of guided waves in the structures utilizing transducers. A novel in-plane shear (d36 type) PMNT wafer is proposed to generate and receive the guided wave, especially the torsional waves, in metallic pipes. In contrast to the traditional wafer, this wafer will directly introduce in-plane shear deformation when electrical field is conveniently applied through its thickness direction. A single square d36 PMNT wafer is bonded on the surface of the pipe positioned collinearly with its axis, when actuated can predominantly generate torsional (T) waves along the axial direction, circumferential shear horizontal (C-SH) waves along circumferential direction, and other complex cylindrical Lamb-like wave modes along other helical directions simultaneously. While a linear array of finite square size d36 PMNT wafers was equally spaced circumferentially, when actuated simultaneously can nearly uniform axisymmetric torsional waves generate in pipes and non-symmetric wave modes can be suppressed greatly if the number of the d36 PMNT wafer is sufficiently large. This paper first presents the working mechanism of the linear d36 PMNT array from finite element analysis (FEA) by examining the constructive and destructive displacement wavefield phenomena in metallic pipes. Furthermore, since the amplitude of the received fundamental torsional wave signal strongly depends on frequency, a series of experiments are conducted to determine the frequency tuning curve for the torsional wave mode. All results indicate the linear d36 PMNT array has potential for efficiently generating uniform torsional wavefield of the fundamental torsional wave mode, which is more effective in monitoring structural health in metallic pipes.
authors.affiliation: Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China; School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China. Electronic address: zhouwensong@hit.edu.cn.
authors.forename: Wensong
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA; College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China. Electronic address: yuan@ncsu.edu.
authors.forename: Fuh-Gwo
authors.initials: FG
authors.lastname: Yuan
authors.affiliation: Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China; School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors.forename: Tonglu
authors.initials: T
authors.lastname: Shi
keywords: Frequency tuning curve; Guided wave; In-plane shear transducers; Piping structure; Torsional wave mode