Mathematical Model of Properties and Experimental Fatigue Investigation at Elevated Temperatures of Functionally Gradient Materials

Abstract

 Manufacturing of functionally graded materials by the permanent casting method was studied.  Installing and equipping a fatigue tester with a thermal chamber was employed.  Fatigue analysis for functionally gradient materials was conducted using ANSYS at elevated temperatures.Fatigue that occurs at elevated temperatures is called thermal fatigue. High temperatures and cycling loads cause thermal fatigue that can cause component failures. In this paper, induced the mathematical models for functionally gradient materials and three models of functionally gradient materials (FGMs) manufactured by permanent casting were tested to predict their thermal fatigue life. FGMs have been tested to determine the effect of fatigue and temperature interactions. FGMs models were of FGM1, FGM2, and FGM3 respectively, with the following volume fractions and gradations: [100%Al-50%Al50%Zn-50%Zn50%Al-100%Zn], [100%Al-30%Zn70%Al-70%Zn30%Al-100%Zn] and [100%Al-70%Zn30%Al-30%Zn70%Al-100%Zn]. The experimental procedure presented the mechanical properties as modulus of elasticity at two levels of temperatures (80 o C, and 160 o C).Through the results of the tensile test at high temperatures, it was noted that the reduction percentage was high in the second type. This was especially for the yield strength value, where the percentage reached 43% at 160 °C. In the second type, the ultimate strength was affected more at 160 °C: the decrease percentage reached 33%, and the elastic modulus at the same temperature fell by 32%. The third type is the least affected at high temperatures, as the percentage of properties decrease at 160 °C reached 16, 17, and 16% for modulus of elasticity, ultimate strength, and yield strength, respectively. Fatigue strength is the most significant among the mechanical properties, where the highest value of the fatigue limit for the third type was experimentally 149.68 MPa. While the lowest value of fatigue strength was the second type, and at the same time, on the contrary, it was less affected at high temperatures, with a rate of 8%, which reached the decrease. The simulation results from the ANSYS program regarding fatigue at high temperatures were acceptable and gave reasonable variation ratios and were very close to the experimental results.