Hi all, I am doing a High Velocity Impact testing using a gas gun I have to figure out a) is my test running well and I am not getting any reflection? Please correct me or help in calculating if I am wrong at any point. I guess, I can figure out by calculating the time required for the event and compare this with the experimental time caputured by the video cammeras, to see, is it insignifican or not?? Also do I need to calculte the time of wave to go there the sample and return, my sample is 4.7mm thick? b) If I get fracture on the outside of the surface, does this give any information about stress wave?? c)How do I know if the stress wave is going in compression ? d) How do I know if the stress wave is going in tension? What information/data I have at this point; I know Modulus=E=150Gpa, Density=p=157kg/m3 of my material I know the input energy given to the steel ball for the test is 12J and velcoity was captured 90m/sec , and time is 2.8micro second for the impact event as gas gun was used with a steel ball to impact the composite specimen. so the velocity of sound in steel is (from literature not measured) = 17000ft/sec or 5135m/sec I have worked out few relations and I guess these would fit well to workout further (you can varify these relations if feel doubt) speed of sound c is given by the Newton–Laplace equation=c= square root(modulus/density) elastic stress=density x c(is the above speed) x velocity of the impact i.e (90m/sec) and i guess time can be worked out as; time=distance/speed here distance is the thickness of the composite specimen=4.7mm or 0.0047m and speed I guess will be used "c" from above relation. Please reply me if you have any clue to solve the above metioned question? or If you need to know anything furher, please do not hesitate to ask me.