Modulus of Elasticity and Its Influence on the Performance of Flapper Valve Materials

Modulus of elasticity of flapper valve material is an important parameter for compressor design since it can affect efficiency and life time of the compressor. Modulus of elasticity is usually considered as a material constant. Actually, it can vary with material orientations and conditions and even environments such as temperature will also affect this value. Therefore, the parameters that can affect the modulus of elasticity of flapper valve material have been concerned. This paper provides an investigation on the parameters that may affect the modulus of elasticity and also the fatigue properties of the flapper valve materials. The results show that the modulus of elasticity of flapper valve material can vary with the orientation of the sample due to the presence of texture in the material. This variation is also different between different materials such as AISI 1095 and AISI 420. For AISI 1095, the modulus of elasticity increases slightly when increasing the angle to the rolling direction. For AISI 420, the modulus of elasticity is higher at 0° and 90o to the rolling direction, and lowest at 45o to the rolling direction. The heat treatment such as tempering can also affect the modulus of elasticity, but not significant. Surface treatment such as tumbling and cyclic loading also have a small influence on the modulus of elasticity. Cold rolled strip has lowest modulus of elasticity and highest anisotropy. Increase in temperature decreases the modulus of elasticity. Increase in modulus of elasticity will increase the initial impact stress. Therefore, the impact fatigue strength of the flapper valve steel is related to both the tensile strength and the E-modulus. For bending fatigue, the fatigue strength is however mainly related to the tensile strength and the ductility of the material.