Modelling and Prediction of Low Temperature Fatigue Life of 7075-T651 Aluminium Alloy

Abstract

Half of the mechanical failures are due to fatigue loading associated with it. Fatigue in structure can be defined as a structural damage which occurs when a material is subjected to cyclic or fluctuating strains at nominal stress that has the maximum value less than the yield strength of the material. Fatigue life of material also depends upon the operating temperature. Since 7075-T651 aluminium alloy is widely used in aircraft and aerospace industries where low temperatures are achieved on regular basis, fatigue behaviour 7075- T651 aluminium alloy under low operating temperatures is matter of concern.
In the present investigation an attempt has been made to study the effects of constant amplitude loading on fatigue crack growth behaviour of 7075-T651 aluminium alloy at low temperature (0°C,-10°C ,-20°C,-40°C and -60°C) under mode I loading condition. It is observed that crack growth rate decreases with lowering of temperature which can be attributed to increase in density of secondary crack and properties of aluminium at low temperature. Exponential and Artificial Neural Network (ANN) models have been developed to predict residual life at low temperature. The predicted results by both the models are found to be in good agreement with the experimental data.