PREDICTION OF TRUE COMPRESSIVE FLOW STRESS OF AA 6063 THROUGH ULTRASONIC ATTENUATION
By Kuenzang Jurmey, Nishan Sharma Ghimire, Vigneswaran Sivahar, Gayan Aravinda Abeygunawardane, Miyuru Piyathilaka of Department of Materials Science and Engineering, University of Moratuwa
This research work is based on prediction of true compressive flow stress of AA 6063 through ultrasonic attenuation. AA 6063 specimens were compressed to obtain compressive flow stress and strain. Ultrasonic attenuation coefficient of the each compressed specimens were measured to correlate the variation of stresses with it. Finite Element Analysis (FEA) was performed to validate the frictional and misalignment effect during compression testing and to obtain true compressive flow stress.
The true compressive flow stress of metal cannot be determined due to the misalignment of test specimen and friction at the interface of specimen platens surfaces leading to barreling as shown in figure 1. Validation of frictional effect was made through FEA model shown in figure 3a with friction coefficient (penalty) of 0.45. It shows that the deformation is maximum at mid height position and minimum or zero near the specimen platen interfaces. With zero friction and zero misalignment in figure 3b, no barreling was observed. The flow of material and the stress distribution were uniform throughout the specimen irrespective of its position.
The relation between compressive flow stress from FEA and ultrasonic attenuation was obtained to predict the true compressive flow stress of AA 6063 through ultrasonic attenuation coefficient.