Accession Number : AD0787086

Title :   Acoustic Emission and Microscopic Deformation and Fracture Processes.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV LOS ANGELES SCHOOL OF ENGINEERING AND APPLIED SCIENCE

Personal Author(s) : Ono,Kanji

Report Date : AUG 1974

Pagination or Media Count : 68

Abstract : This paper reviews diverse observations of acoustic emission from materials and attempt to interpret them on the basis of current knowledge of plastic deformation and fracture. Observed acoustic emission characteristics have been classified into five categories, which arises from heterogeneous and homogeneous yielding, dynamic strain aging, twinning and other heterogeneous deformation and strain induced transformation of acoustic emission during plastic deformation are examined in relation to these metallurgical aspects as well as the mechanical vibration viewpoint. For example, tensile deformation of magnesium is mainly via twinning, which generates shear mode acoustic emission. On the other hand, the yielding of a HSLA steel sample excites longitudinal resonances along the length of the sample. It is shown that the micro-yielding concept with suitable modifications best explains these acoustic emission behavior observed. This paper also reviews important aspects of measurement techniques and theoretical considerations of acoustic emission behavior.

Descriptors :   *Acoustic emissions, *Fracture(Mechanics), *Deformation, *Ultrasonic tests, Alloys, Metals, Defects(Materials), Instrumentation, Steel, Magnesium, Crack propagation

Subject Categories : Metallurgy and Metallography
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE