Showing papers on "Peening published in 1976"

A new technique in the application of high-speed water jet

Abstract: The energy of the high-speed water jet is usually utilized for cleaning, penetrating, fracturing or cutting of different materials. This study introduces a new application, i.e. the modification of surfaces through pressure-induced plastic flow. The experimental parameters, such as stand-off distance, feed-rate and pressure, can be controlled, so that no destructive effects can be detected on the surface of treated materials. Under these controlled conditions, there is a marked improvement in the mechanical properties, e.g. surface hardness, yield strength and fatigue strength of mild steel used as a target material. The method is similar in many ways to the well-known shot peening and abrasive cleaning methods. A comparative study, using annealed aluminum as a model material, was carried out between shot peening and water blasting. Using previously determined water jetting parameters, the improvement in fatigue strength attainable from water blasting is not as good as that for shot peening. The reasons for this and the interpretation of X-ray back reflection data are discussed. Order from: BSRA as No. 48,045.

An investigation of three methods of repairing fatigue cracks at fillet welds

Abstract: Three methods of repairing fatigue cracks at fillet weld toes were investigated to determine their effectiveness on defects of different severity and under different loading conditions. The repair methods which included grinding, peening, and gas tungsten-arc remelting, were applied to the fillet welds attaching coverplates to full-size I-beams. Repairing was performed at one of three times in the life of the beams; before cyclic loading, after a predetermined number of cycles, and after cracks were visible. Cyclic loading was done at three stress ranges and two minimum stresses to determine the effect of loading conditions. Gas tungsten-arc remelting was shown to be the most consistent and effective repair for all defect severities and loading conditions. Fatigue lives of three to four times that of non-repaired beams were not uncommon. Peening was shown to be most effective when performed while the minimum load was applied. When performed under no-load conditions, the effectiveness wasstrongly dependent on loading conditions, with low minimum stress and stress range resulting in longest life. This is due to the cancelling of the compressive residual stress field due to peening by the large tensile stresses due to loading.