Fig 4 3320 11 Important parameters of shot peening and standardization Shot

Fig 4 3320 11 important parameters of shot peening

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Fig 4 3/3/20 11
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Important parameters of shot peening and standardization Shot peening intensity is a measure of relative work done on the surface of material during the process This shot peening intensity will be propositional to the residual stress imparted. In order to obtain the shot peening intensity, standardized testing has to be carried out . It was developed by Jhon O Almen and named it as Almen test. Resulting intensity is also called as Almen Intensity. 3/3/20 12
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Almen Test Fig 5 Schematic representation of Almen test procedure/Steps 3/3/20 13
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Almen Test Almen intensity is a measure of the resulting degree of curvature when a SAE grade 1070 steel made strip with predetermined dimensions and hardness of 45HRC (Almen Strip) placed as a target of shot peening Almen strip was classified in to N, A and C according to there thickness Entire procedure is given in Fig 5 3/3/20 14
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Peening Saturation After a specific point, increasing exposure time will not have considerable effect on increasing the intensity (Arc height), that point is called saturation point After saturation point, Increase in intensity can be achieved only by means of the increasing the shot peening pressure or shot size In practice this saturation values are taken to specify the peening intensity. Fig 6 explains the saturation point Fig 6 3/3/20 15
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Peening media In shot peening, shots with different size , shots of different material were used according to the requirement of the material and application Classification of shots (by materials) Material Remarks Cast steel shots peening the ferrous components Ex : leaf or coil springs Glass beads shots peening the non ferrous components Where the very low Intensity is required. Example: Aluminum and its Alloys, Titanium alloys., Cut Wire shots Initially it won’t be round in shape so it should be blasted against the scrap steel to make shots round as per the requirements. 3/3/20 16
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4. Materials that go well with Shot peening High strength steels In high strength steels High fatigue strength is obtained through the shot peening As this type of steel posses more hardness which will in turn reduce the fatigue strength. Hence shot peening is utilized beneficially in obtaining the high fatigue strength. Fig 7 explains effect of shot peening on the high strength steel’s fatigue strength as a function of ultimate tensile strength. Fig 7 3/3/20 17
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Aluminum alloys Aluminum alloys plays an imperative role in the aerospace application S-N curve of the reversed bending fatigue tests on unpeened and peened specimen of the 7075 T6 aluminum alloy is shown in the Fig 8. shot peening is used to improve the fatigue life of Al alloy Fig 8 3/3/20 18
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Beneficial effect of the shot peening will not have significant difference in enhancing the fatigue resistance for various aluminum alloys S-N curve of the Al-Li alloy(Data points) and conventional 7075 T6 alloy(solid lines) at various condition are given in the Fig 9 Fig 9 3/3/20 19
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Austempered ductile iron This type of material is generally used in manufacturing the crank shaft, cam shaft and gears.
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