The elastic property of a copper (Cu) thin film was investigated using the surface acoustic wave (SAW) measurement technique. The Cu film was deposited on a quartz substrate using a direct current magnetron sputter and its surface morphology was inspected using atomic force microscopy. Time-domain waveforms of the SAW on the film were acquired at different propagation distances to estimate the Young’s modulus of Cu such that the experimentally-obtained dispersion curve can be compared to the analytical result calculated using the Transfer Matrix method for curve-fitting. Results showed that the film’s elastic property value decreased by 18.5% compared to that of the bulk state, and the scale effect was not significant in the thickness range of 150-300 nm, showing good agreement with those by the nanoindentation technique. The property, however, increased by 15.5% with the grain coarsening.

In this paper, a study on the effectiveness of micro-peening was accomplished for improvement of fatigue characteristics for reduction gear of manned and unmanned aircraft. The Almen saturation curve was obtained by various peening injection pressure supplied from a commercial air jet peening machine. The effective micro-peening process condition was adopted as five bar. The four points rotary bending fatigue test was conducted by using test specimen made of AISI alloy that was carburized based on AMS standard in this work. From the fatigue test result, the fracture life of specimen peened by nozzle pressure with five bar and six bar was higher than the un-peened specimen by approximately 323 percent and 146 percent respectively. However, the fracture life of specimen peened by the nozzle pressure with six bar was lower by approximately 221 percent than the peened specimen by five bar. For this reason, the peening nozzle pressure with five bar was decided as the optimum micro-peening condition. Effectiveness of micro-peening was validated and this micropeening technique will be used for real manned and unmanned aircraft gear parts or other durability mechanical parts.

Shot peening is widely used to improve the fatigue life and strength of various mechanical parts and an accurate method is important for the prediction of the compressive residual stress caused by this process. A finite element (FE) model with an elliptical multi-shot is suggested for random-angled impacts. Solutions for compressive residual stress using this model and a normal random vertical-impact one with a spherical multi-shot are obtained and compared. The elliptical multi-shot experimental solution is closer to an X-ray diffraction (XRD) than the spherical one. The FE model’s peening coverage also almost reaches the experimental one. The effectiveness of the model based on an elliptical shot ball is confirmed by these results and it can be used instead of previous FE models to evaluate the compressive residual stress produced on the surface of metal by shot peening in various industries.