Now showing 1 - 8 of 8
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    Effect of oil jet peening duration on surface modification and fatigue behavior of medium carbon steel, AISI 1040
    (15-05-2007)
    Grinspan, A. Sahaya
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    Introduction of compressive residual stress on the surface of dynamically loaded structural members improves the fatigue life. Oil jet peening is a new surface modification technique that can be potentially applied to introduce compressive residual stresses. Effect of oil jet peening on the surface modification and fatigue behavior of medium carbon steel, AISI 1040, is reported. The compressive residual stress on the surface of oil jet peened specimen was in the order of 332 MPa and the depth of compressive stress induced was about 50 μm. The surface hardness increased due to the oil jet peening. Oil jet peening improved the fatigue strength under cantilever-bending conditions to about 19% compared to unpeened specimens. © 2006 Elsevier B.V. All rights reserved.
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    Publication
    A novel surface modification technique for the introduction of compressive residual stress and preliminary studies on Al alloy AA6063
    (05-10-2006)
    Grinspan, A. Sahaya
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    A new peening process for introducing compressive residual stresses with less erosion and good surface finish using a high pressure oil jet was developed. Aluminium alloy, AA 6063 was peened with an oil pressure of 50 MPa at different stand-off-distances. Residual stresses measured using X-ray diffraction indicated the induction of about 50 MPa (compressive) residual stresses on the surface. The depth of compressive residual stress developed was about 250 μm. The surface roughness of the oil jet peened surface depends on the stand-off-distance. Significant work hardening was observed at low stand-off-distances. The temperature rise during the process was marginal and doesn't contribute to stress relaxation. Erosion during the process was also reported based on the mass loss rate measured. © 2006 Elsevier B.V. All rights reserved.
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    Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Residual stress and hardness
    (15-11-2006)
    Grinspan, A. Sahaya
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    The life of structural members that experience cyclic loading is improved by the introduction of surface compressive residual stresses. A high-pressure oil jet is used for the introduction of surface compressive residual stresses in aluminum alloys, AA6063-T6 and AA6061-T4. The peening machine designed and developed in the laboratory is capable of generating high pressures using hydraulic oil. The magnitude of residual stress developed depends upon the stand-off distance and yield strength of the material. A hardened layer up to a depth of about 350 μm was developed in the materials investigated. The residual stresses and surface hardening induced are comparable to that produced by other peening processes. An analytical model is proposed to predict the impact pressure. © 2006 Elsevier B.V. All rights reserved.
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    Effect of nozzle-traveling velocity on oil cavitation jet peening of aluminum alloy, AA 6063-T6
    (01-01-2007)
    Grinspan, A. Sahaya
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    A new surface modification process was developed to introduce compressive residual stresses at the surface of components. In this process, instead of oil droplets a high-velocity cavitation jet (cloud of oil bubbles) impinges on the surface of the component to be peened. The impact pressure generated during implosion of cavitation bubbles causes severe plastic deformation at the surface. Consequently, beneficial compressive stresses are developed at the surface. In order to find the potential of this process, aluminum alloy AA6063-T6 specimens were peened at a constant cavitation number with various nozzletraveling velocities. Residual stress induced by oil jet cavitation peening was measured using X-ray diffraction. Oil cavitation jet peening results in a smooth and hard surface. The developed compressive residual stresses at the peened surface are about 52%, 42%, and 35% of yield strength in samples for peened at nozzle traveling velocities of 0.05 mm/s, 0.10 mm/s, and 0.15 mm/s, respectively. Copyright © 2007 by ASME.
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    Surface nanocrystallization of aluminium alloy by controlled ball impact technique
    (15-10-2012)
    Prakash, N. Arun
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    A novel surface modification process namely controlled ball impact peening was developed for synthesizing a nanostructured surface layer and to impart compressive residual stresses on metallic materials in order to enhance the overall surface properties. This article demonstrates the microstructural evolution, surface hardening and introduction of the residual stresses in the ball impact peened aluminium alloy surfaces, AA6063-T6. Hardened steel balls were impinged in controlled manner inducing high strain rates on the aluminium samples which are precisely moved using independent programmable logic controlled linear actuators in the controlled ball impact peening process. Mechanical properties of the nanocrystalline surface layer were investigated using dynamic ultra micro-hardness tester. The hardness of the nanocrystalline surface layer is (~. 1.3. GPa) improved compared to the matrix (~. 0.58. GPa) and the depth of the hardened layer is about ~. 350 μm depending upon the peening conditions. The amount of compressive residual stress developed by the treatment is also studied using depth sensing indentation method. The surface compressive residual stresses induced in the ball impact peened samples is about 70-127% of yield strength of the target material depending upon the peening conditions. X-ray diffraction analysis and transmission electron microscope analysis revealed the formation of nanograin crystalline structure on the ball impact peened surface layer. The mean grain size of the peened sample determined by transmission electron microscope is about 8 ± 2. nm in the top surface layer. High strain rate and repeated directional loading imparted in the contact zone generates the various dislocation activities and microstructural features which were responsible for the formation of the randomly oriented nanostructured grains on the metallic materials. With increasing strain, the various microstructural features produced in the ball impact peened aluminium samples are deformation twins, multiple shear bands, high density dislocation and dislocation pile-up at the grain boundaries as investigated by transmission electron microscope. Grain refinement on the ball impact peened aluminium surfaces resulted in the formation of high density dislocation associated with the subdivision of original grains into subgrains. The peening coverage and number of overlapping impacts depend upon the sample travelling velocity, which in turn affects the hardness, compressive residual stresses induced and grain size formed for a given ball diameter and impact velocity. © 2012.
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    Fretting wear behavior of fine grain structured aluminium alloy formed by oil jet peening process under dry sliding condition
    (30-07-2012)
    Arun Prakash, N.
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    Use of aluminium alloy in aerospace and automotive industry has increased due to their high strength to weight ratio. Oil jet peening, a surface modification process is developed to impart compressive residual stresses on the surface of the metallic materials and resulted in significant surface hardening with associated grain refinement. Unlubricated fretting tests were performed on the oil jet peened and unpeened aluminium samples using ball-on-flat configuration at constant slip amplitude and at different applied normal loads. At low applied normal loads, the contact region between the mating surfaces makes the asperities interlock each other resulting in high tangential force coefficient. Due to micro-displacement between the interfaces of two mating members, cracks initiate and cause debris formation. The steady state tangential force coefficient, wear volume and specific wear rate of the oil jet peened samples were lower than those of the unpeened (as-received) samples for all the conditions tested and this is mainly attributed to increased substrate strength. A complex adhesion and oxidation type of wear mechanism was observed at low applied normal loads and at high applied normal loads abrasion was found to be a dominant wear mechanism. © 2012 Elsevier B.V.
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    Surface modification of steel using liquid jet peening (fatigue performance)
    (01-01-2007) ;
    Grinspan, A. Sahaya
    Oil jet peening is a surface modification process developed for the introduction of compressive residual stresses. In this process, a high-pressure oil jet impinges on the surface to be peened. Specimens made of AISI 1040 steel were peened at oil pressure of 50 MPa. Residual stresses induced on the oil jet peened specimen was in the order of -200 MPa. Standoff distance influenced the residual stress induced and also the erosion and surface roughness. Fully reversed cantilever bending tests conducted on the peened and unpeened conditions revealed the improved performance of the oil jet peened specimens.
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    Publication
    Surface modification and fatigue behavior of high-pressure oil jet-peened medium carbon steel, AISI 1040
    (01-01-2007)
    Sahaya Grinspan, A.
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    Introduction of compressive residual stresses on the fatigue-loaded components is one of the techniques followed to improve the fatigue life of industrial components. Oil jet peening is a surface modification process for the introduction of compressive residual stresses. A high-pressure oil jet is made to impinge on the surface to be peened. Preliminary studies were carried out on the medium carbon steel at the oil pressure of 50 MPa. The compressive residual stress induced on the surface of unpeened and oil jet-peened AISI 1040 steel was 21 MPa and 200 MPa, respectively. Fully reversed cantilever bending fatigue behaviors of medium carbon steel in both under peened and unpeened conditions were evaluated at room temperature. Oil jet-peened specimens exhibited superior fatigue performance compared to the unpeened specimens. Fractographical analyses were carried out for specimens broken at several tested stress levels using optical microscope. Copyright © 2007 by ASME.