Forum Technical Discussions      Re: equivalent wedge delay calculation in DGS curves Posted by: Gerhard Splitt    (PID_187), E-mail: Address, on December 02, 2008 at 18:00 : In Reply to: equivalent wedge delay calculation in DGS curves posted by : XiangYan , E-mail: Address, on December 02, 2008 at 16:41 : ----------- Start Original Message ----------- : According to EN583-2, when plotting the DGS curves for angle beam transducer, there is an equivalent wedge delay that added to the steel path, which is: : equivalent wedge delay=wedge path*Cwedge/Csteel. : I am not sure of the derivation of this formula, but if I use the equal phase method, I got: : equivalent wedge delay=wedge path*Csteel/Cwedge. : Does anyone look into this problem? I don't know which answer is correct. : Thanks! : Xiang Yan ------------ End Original Message ------------ Hi Xiang, the first formula, equivalent wedge delay=wedge path*Cwedge/Csteel, is the correct one. We are looking for the near field equivalent of the wedge length. As the sound velocity v stands in the denominator of the Near field length calculation N=D^2*f/4v, the near field length in the plastic wedge is bigger than in steel, meaning that the near field equivalent part of the wedge in steel is shorter than the mechanical length of the wedge. The other formula, equivalent wedge delay=wedge path*Csteel/Cwedge, is for calculation of the steel equivalent time of flight of the wedge. Follow Ups: Re: equivalent wedge delay calculation in DGS curves Udo Schlengermann 18:56 Dec-03-2008 (0) Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : : According to EN583-2, when plotting the DGS curves for angle beam transducer, there is an equivalent wedge delay that added to the steel path, which is: : : equivalent wedge delay=wedge path*Cwedge/Csteel. : : I am not sure of the derivation of this formula, but if I use the equal phase method, I got: : : equivalent wedge delay=wedge path*Csteel/Cwedge. : : Does anyone look into this problem? I don't know which answer is correct. : : Thanks! : : Xiang Yan : Hi Xiang, : the first formula, equivalent wedge delay=wedge path*Cwedge/Csteel, is the correct one. We are looking for the near field equivalent of the wedge length. As the sound velocity v stands in the denominator of the Near field length calculation N=D^2*f/4v, the near field length in the plastic wedge is bigger than in steel, meaning that the near field equivalent part of the wedge in steel is shorter than the mechanical length of the wedge. : The other formula, equivalent wedge delay=wedge path*Csteel/Cwedge, is for calculation of the steel equivalent time of flight of the wedge. ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help