High Temperature Characterization of the Stiffness Matrix of Different Steels

Abstract

The aim of this work is to acquire material data at elevated temperatures for different chemical compositions and phases as basis for numerical simulations incorporating the effect of crystalline texture. Several samples; AISI 304, interstitially free, low carbon, martensite, and pearlite, were measured in a Gleeble® Thermal-Mechanical Simulator 3800 in conjunction with LUS (GLUS®) during annealing from room temperature up to a maximum temperature in the range between 675 and 1000 °C. The laser ultrasonic measurements contain both pressure (P) and shear (S) waves. The arrival time of at least the first S-wave echo and two or more P-wave echoes were used. From the measurements it was observed that there was a slight tilt of the sample and misalignment of the centres of the generation and detection laser beams. An inversion scheme was implemented estimating the nine stiffness coefficients as well as the sample tilt and alignment error. The estimated stiffness coefficients as a function of temperature were successfully obtained from the measurements. Most of the coefficients decrease with increasing temperature, whereas C12, C13, and C23 remain relatively constant. The implemented inversion scheme successfully compensates for sample tilt and laser misalignment.