Papers by Author: Aaron Krawitz

Abstract: In the present study, the evaluation of the deformation and the determination of the first order residual stresses in shot peened aluminium plate have been performed by neutron diffraction on the strain imaging instrument SALSA at the Institut Laue Langevin, Grenoble, France, in order to validate a model of finite element analysis permitting to predict the final deformation. The sample used in this study is a rolled aluminium sheet (Al 2024 T3 alloy) which was clamped in a steel frame and peened following exactly the industrial production process. The first measurements were performed on the sample while it was still clamped. The second set was made after removing it from the frame. For each case, we measured the lattice strains and determined the stress repartition in the three principal directions.

Abstract: The early years of neutron stress measurements are recounted using published documents and input from workers in the field. The circumstances and motivations of the early workers in the field are discussed, and some general conclusions are drawn. The first known reference is from the US National Bureau of Standards (NBS), now the National Institutes for Science and Technology (NIST), in 1976. In Europe, in the 1970s, materials scientists and engineers were encouraged to use neutrons to study applied problems after the ILL was commissioned, and this outreach effort was productive. The idea was also discussed in Australia at this time. Actual depth-probing measurements of stress began in 1979 at Missouri and Karlsruhe, then Harwell in 1980. The 1980s saw dramatic growth in the number and kinds of measurements, including initial pulsed source studies at IPNS and commercial work at Harwell and Chalk River. Two meetings are particularly significant: the 28th Sagamore Army Materials Research Conference on Residual Stress and Stress Relaxation, held in July, 1981, in Lake Placid, New York, and the NATO Advanced Research Workshop on Measurement of Residual and Applied Stress Using Neutron Diffraction, held in March, 1991, in Oxford. At the Sagamore Conference, the first workers to make successful measurements met. At the NATO Workshop, the neutron stress measurement community essentially came into existence.