Effect of microstructure on modulus loss at flexural mode and stress in sensor materials

Anelastic behaviour of metals, resulting from internal friction and responsible of modulus loss, is one of the major mechanical properties of materials considered in the design of high accuracy measuring devices and sensors which are generally used in mass, force, pressure and dimensional metrology. The level of modulus loss is important when high accurate measurements are considered in view of metrology. Hysteresis error is the main source of uncertainty in the measurement devices and related with loading and unloading. Modulus loss causes the hysteresis error on measurement when sensor or flexural element is made of anelastic material. The value of modulus loss of a sensor material can be changed by the application of proper heat and/or thermo-mechanical treatments. This study covers the attempts of determining the modulus loss values of copper–beryllium (Cu–Be), 17-4 PH stainless steel and AISI 4340 steel that are commonly used as material of sensor. An inverted pendulum system is used for the measurements of modulus loss and determining anelastic effects for the different sensor materials. Results show that modulus loss is influenced by microstructure of same material and differs form each other for different materials even when all are of the same hardness level. It was concluded that dislocation and precipitation mechanisms and their interactions can be assumed to cause modulus loss and its level.