Nondestructive Ultrasonic Near-Surface Residual Stress Measurements in Aircraft Wheels

An ultrasonic Rayleigh surface wave method is propose to determine residual stress depth profile in aluminum aircraft wheels. The Rayleigh wave method has several distinct advantages. The residual stress depth profile can be easily obtained by altering the penetration depth of the Rayleigh wave. The Rayleigh wave is bound to the surface of the wheel, enabling measurements on curved and other irregularly shaped surfaces. Also, the Rayleigh wave approach can discriminate between tensile and compressive residual stresses and eliminate the effect of texture on the residual stress determination. Initial measurements have demonstrated these capabilities on non-ferrous and ferrous metals. The result of the proposed research program will be a field portable inspection system based on a portable computer that can be operated remotely by a single user. This will enable the stress levels and their variation with subsurface depth to be determined rapidly and the data to be stored for later analysis. The results obtained from this instrument will enable the fatigue life of the aircraft wheels to be predicted and incorporated into appropriate design models. Preliminary contacts with commercial users have demonstrated a significant interest in this proposed system, simplifying the commercialization process.