An investigation of the effects of weight geometry and time in repeated tension impact testing

• Main Authors: Ours, S. R., Jackson, William G.
• Format: Others
• Published: 1944
• Online Access: https://thesis.library.caltech.edu/4665/1/Ours_sr_1944.pdf; Ours, S. R. and Jackson, William G. (1944) An investigation of the effects of weight geometry and time in repeated tension impact testing. Engineer's thesis, California Institute of Technology. doi:10.7907/G8NX-JD54. https://resolver.caltech.edu/CaltechETD:etd-11252008-093713 <https://resolver.caltech.edu/CaltechETD:etd-11252008-093713>

The investigation covered in this report was conducted with the Falling-Carriage Repeated Tension Impact Machine at the Guggenheim Aeronautical Laboratory, California Institute of Technology, Pasadena, California. Twenty-eight aluminum alloy test specimens were subjected to a total of 7,834 impacts in the GALCIT Falling-Carriage Repeated Tension -impact Machine. Since the average number of impacts per specimen was about 280 it is believed that this investigation covered a regime different from other investigations made with this equipment. The effect of elapsed time between series of impacts was not established. The results obtained were contradictory, and it is believed that this was due to the energy per impact being variable and unknown. It is established that the geometry of the weight used in this type of test has some influence upon the elongation produced. It is shown that 17S-T duralumin is relatively sensitive to stress concentrations caused by change in cross-section and strain wave reflection, and relatively insensitive to stress concentrations due to small scribe marks. Evidence is presented to indicate that the elongation at fracture of a specimen subjected to repeated tension impact is inversely proportional to the number of impacts required to produce fracture. Suggestions are offered for improving the test equipment so as to obtain more nearly consistent results.