A study on the loss factor identification for metallic materials and application for damping performance evaluation of laminated metal subject to heat treatment.

Abstract

Several standards or manuals are available for the test methods of damping capacity of damping materials such as composites or laminated damping steel sheets; however, few documents focus on lightly damped materials like metallic alloys. This study intends to provide a simple method for loss factor identification for metallic materials using typical vibration measurement setups. Also, influences on the identified loss factor due to the shape changes of the specimen and the difference of fixing conditions such as tightening torque and inserting shims are investigated. Vibration measurement using slender beam-shaped specimens and data processing procedures are studied to obtain loss factors with high reliability. It has been shown that applying a 6 dB bandwidth method together with the spline interpolation technique on the measured mechanical impedance leads to good results rather than the commonly used half-power bandwidth method. As for the specimen's shape change, numerical studies using finite element (FE) analysis are carried out, and it has been demonstrated that the warp up to 15 mm versus beam length 500 mm does not affect the loss factor largely. According to the test results, tightening torque variations and inserting shims influence little on the loss factor, too. As an application example of the proposed method, the change of loss factor underwent different heat treatments have been investigated for two-types laminated metallic materials.