Effect Of Work-piece Hardness On Peening Intensity Under Local Peening

Author:  Sharma, M. C.
Source:  Conf Proc: ICSP-3, (p.205-212)
Doc ID:  1987022
Year of Publication:  1987
Abstract:  
The time for peening a component depends upon the intensity of peening required. For which first peening intensity under a set of peening parameters such as stand off, shot size and its material, angle of impingement, air pressure and nozzle size (in pneumatic system) need to be established. Generally for establishing peening intensity Almen strips are peened under similar conditions as that of work piece for different time, and Almen arc height is measured. Saturation curves are then plotted as relationship between the Almen arc height and time of peening. The time necessary to produce saturation on the Almen strip is defined as the time required to produce a specific arc height at which doubling of the exposure time will not increase the arc height by more than 10%. However, the saturation curves must be obtained by peening one side of the Almen strip uniformly over the length which is achieved by providing relative movement between the nozzle and the strip. There may be cases like notches of the test pieces, roots of the small gear teeths, fillets, tips of the venting slots of the stator of turbogenerator etc. Where local peening over selected regions may serve the purpose. During local peening relative movement between surface to be peened and the peening nozzle may not be essential. This condition is referred here as local peening, it is further divided under two categories one for masked samples to expose small regions as well as to protect flow of metal at the edges, and other for unmasked samples. For work piece materials of similar hardness to that of Almen strip, the data of saturation curve obtained is applicable directly to component. However, where marked difference in hardness between the component material and test strip exist, some other method of determing the peening condition for obtaining saturation in component is required. Several methods are in use such as applying a suitable multiplication factor the use of test strips manufactured from the component in place of standard Almen test strips and the determination in the component by visual estimation of the time to produce complete coverage. All methods are in use. In the present investigation both the types of local peening over various hardness test strips were further explored.