Ph.D. / Materials science / The influence of resonant and sub-resonant frequency vibration on the longitudinal residual stresses in A-36 mild steel weldments has been studied. Residual stress analysis was carried out using sectioning, x-ray and blind-hole-drilling techniques. The hole-drilling method was modified to take into account the effect of local plastic yielding due to stress concentration and the machining stresses, with a resultant accuracy comparable to that obtained by the sectioning method. As a result of the vibratory treatments, residual stress redistribution occurred near the weld; the peak stresses were decreased by up to 30%. The resonant frequency vibration had a more pronounced stress redistribution as compared to the sub-resonant frequency vibration. Transmission electron microscopy studies indicated local plastic deformation as the mechanism by which this stress reduction occurred. Constant amplitude axial fatigue experiments on samples machined from regions adjacent to the weld showed that both the vibratory techniques did not induce any fatigue damage.

Thesis (M.C.E.)--University of Delaware, 2009. / Principal faculty advisors: Dov Leshchinsky and Christopher L. Meehan, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 190-211).

Thesis--Teknillinen Korkeaukoulu, Otaniemi. / Includes bibliographical references.

Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2004. Directed by W. Steven Johnson. / Includes bibliographical references (leaves 261-271).

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 334-335).

Thesis (M. Phil.)--University of Hong Kong, 1972. / Mimeographed.

Thesis (M. Phil.)--University of Hong Kong, 1987.

Thesis--M. Phil., University of Hong Kong.

Thesis--M. Phil., University of Hong Kong. / Mimeographed.