Peening

About: Peening is a research topic. Over the lifetime, 5538 publications have been published within this topic receiving 73073 citations.

Microscale Laser Shock Peening of Thin Films, Part 2: High Spatial Resolution Material Characterization

Abstract: Microscale Laser Shock Peening (LSP) is a technique that can be potentially applied to manipulate the residual stress distributions in metal film structures and thus improve the reliability of micro-devices. This paper reports high-spatial-resolution characterization of shock treated copper thin films on single-crystal silicon substrates, where scanning x-ray microtopography is used to map the relative variation of the stress/strain field with micron spatial resolution, and instrumented nanoindentation is applied to measure the distribution of hardness and deduce the sign of the stress/strain field. The measurement results are also compared with 3-D simulation results. The general trends in simulations agree with those from experimental measurements. Simulations and experiments show that there is a near linear correlation between strain energy density at the film-substrate interface and the X-ray diffraction intensity contrast.

Effect of Ultrasonic Shot Peening on Fatigue Strength of High Strength Steel

Abstract: A study had been made to evaluate the effect of the Ultrasonic shot peening treatment, developed by SONATS, on fatigue strength. This new shot treatment could give the smooth surface after shot peening because of using the polished ball bearings. To investigate the effect and the merit of new treatment, fatigue test were conducted on cantilever type rotating bending fatigue testing machine. It was colifirmed that fatigue streilgtli peened by ultrasonic shot treatliient is almost the same as that peened by convelitional air peening device. Ful-ther, mechanism of the fracture was confirmed between roughed specimens by conventioilal peening and the smooth one by ultrasonic peening.

Effects of post-processing route on fatigue performance of laser powder bed fusion Inconel 718

Abstract: Fatigue performance of Inconel 718 (IN718) parts built using laser powder bed fusion (L-PBF) is often poorer than that of the cast and wrought alloy parts. This is because of detrimental effects arising from the microstructures such as brittle phases and anisotropy as well as porosities. To improve fatigue performance of L-PBF IN718, two types of post processes namely hot isostatic pressing (HIP) (performed at 980 °C, 100 MPa and 4 h) and shot peening (performed at 0.45 mmA intensity and 200 % coverage) were employed individually as well as sequentially on different specimens in addition to a standard processing route consisting of L-PBF build followed by solution annealing and double aging heat treatment. Porosities were considerably reduced by HIP-ing (from 0.39 % to 0.08 % porosity volume ratio) but this did not translate to improvements in fatigue performance. This can be attributed to the presence of inclusions and yield strength reduction resulting from γ” solutionisation. High compressive residual stresses of close to 1 GPa were recorded following shot peening regardless of whether HIP-ing was carried out prior to the shot peening. Improvement in fatigue lives particularly at high stress levels was observed on shot peened specimens without HIP-ing (H + SP) which can be explained by the compressive residual stresses that delay the onset of fatigue crack initiation. Shot peening applied on the HIP-ed specimens (H + HIP + SP) however, resulted in fatigue performance deterioration. This is related to the harmful tensile stresses that must exist alongside the compressive residual stresses in a shot peened surface, as evident from the location of the sub-surface crack initiations near the residual stress transition region approximately 300 μm from the free surface. In this case, detrimental effects arising from tensile stresses appear to have outweighed the benefits from compressive stresses on fatigue performance.

Method for monitoring and controlling laser shock peening using temporal light spectrum analysis

Abstract: A method for quality assurance of a laser shock peening process of workpieces includes measuring and recording or temporal light intensity data over a short period during the duration of a plasma associated with the vaporized material from laser shots fired during a production laser shock peening process. The recorded temporal data is then analyzed to obtain an instantaneous optical spectrum of the plasma and then used to provide statistical control of the production laser shock peening process. One correlation function of the present invention is based on a time integrated spectral peak intensity wavelength curve for each of the laser firings and for which a peak intensity wavelength is determined for a plurality of times during each plasma of a plurality or all of the firings. Production results from the analysis of the instantaneous optical spectrum is used to determine whether the production laser shock peening process is acceptable. One embodiment of the method compares the production results from the analysis of the instantaneous optical spectrum to a correlation of test results from the analysis of instantaneous optical spectrum and high cycle fatigue failure based on high cycle fatigue tests of test workpieces that are the same or related to the production workpieces and that were laser shock peened in the same or similar laser shock peening apparatus.