Dear Rushna, I have come across a review paper by Sansalone, M. from Cornell University titled "Impact-echo: The complete story". I think it would be of your interest. Here is its abstract and source: Title: Impact-echo: The complete story Author: Sansalone, Mary. Source: ACI Structural Journal. v 94 n 6 Nov-Dec 1997. p 777-786. (ACI = American Concrete Institute) Abstract: Impact-echo's history is an interesting story of how a real need for nondestructive test methods for flaw detection in concrete structures led to a systematic and sustained basic and applied research effort to develop such a method, beginning in 1983, at the National Bureau of Standards, and continued since 1987 at Cornell University. This paper discusses the contributions of the people and the organizations who carried out the theoretical, numerical, laboratory, and field studies that established the method and who developed the software and instrumentation that gave rise to a patented impact-echo field system. It also documents how this effort was undertaken and sustained with government and industry funding. Subsequently, this paper draws on knowledge gained over twelve years of research to provide, for the first time, a unified explanation of impact-echo theory as it applies to the testing of structural elements, including plates (slabs, walls, bridge decks, pavements, etc.), bars (beams and columns), and hollow cylinders (pipes and tunnel and mine shaft liners) and to the detection of flaws within these elements. The last key pieces fell into place in 1995, and it is now possible to explain in a concise and coherent way the principles upon which impact-echo testing is based. (Author abstract) [References: 33] Sincerely, Kamaiton Wongkaew Ph.D. Candidate Structures Area School of Civil Engineering Purdue University West Lafayette, IN 47907 USA On Tue, 7 Sep 1999, Begum RB wrote: > > I have modelled the impact echo system using ANSYS. I have simulated a > crack in concrete, and applied an impact of 1/2 sin wave, the results are > good. I want to know if anybody has done something similar. > > Rushna > > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%