Rail defect inspection based on coupled structural–acoustic analysis

The inspection of rail defects is of importance in high-speed railway operation and maintenance. As a highly efficient method for both nondestructive testing and structural health monitoring of the rail, ultrasonic guided waves (UGWs) inspection provide increased sensitivity to smaller defects. These advantages can be fully exploited only if the complexities of UGWs propagation between the medium of air and rail are unveiled and managed for the given inspection method. The development and validation of modeling procedure for the rail based on coupled structural–acoustic model is presented in this paper. Acoustic–structure interaction between air and rail is simulated based on COMSOL Multiphysics software. The transient response and natural characteristics of UGWs in the rail was computed and predicted. Moreover, the displacement distribution of UGWs in the defective rail and nondefective rail are analyzed both in time and frequency domain. A feasible method for detecting small defects in the rail is proposed in the paper. The results indicated that a defect of 8 mm in rail head can be inspected effectively using UGWs with frequencies of 40 kHz and above. And for small defects in rail web, the X-crystallographic direction ultrasonic transducer should be chosen for inspection.

Adaptive Noise Cancellation System for Low Frequency Transmission of Sound in Open Fan Aircraft

This paper describes the use of a structural/acoustic model of a section of a large aircraft to help define the sensor/actuator architecture that was used in a hardware demonstration of adaptive noise cancellation. Disturbances considered were representative of propeller-induced disturbances from an open fan aircraft. Controller on and controller off results from a hardware demonstration on a portion of a large aircraft are also included. The use of the model has facilitated the development of a new testing technique, closely related to modal testing, that can be used to find good structural actuator locations for adaptive noise cancellation.

Lightweight Design Analysis Based on a Coupled Structural-Acoustic Model for Rectangular Enclosures

As an effort to reduce energy consumption and hazardous emissions, lightweight design has become more and more important for new vehicle developments. Substituting conventional steel material with other low-density materials in building vehicle structures is one typical approach for lightweight designs. To investigate the influence of the structural weight change on the noise, vibration and harshness (NVH) performance, this study presents a structural-acoustic coupled model of a rectangular shaped cavity enclosed by 1 or 2 flexible panels. Using this modal, parametric studies aiming at reducing the total structural weight and simultaneously improving the NVH performance are conducted. For the case of a single flexible panel subject to a point force excitation, it is found that substituting the heavier steel panel with a lighter Al panel may actually reduce the sound radiation inside the cavity at the low frequency range. On the other hand, at higher frequencies, the noise radiation level is roughly inversely proportional to the material density. For the case with dual flexible panels, although it is predicted that the two panels are weakly coupled through the acoustic cavity at most frequencies, the noise level may still be reduced at a lighter structural weight in certain cases.

A Structural-Acoustic Finite Element Method for Predicting Automobile Vehicle Interior Road Noise

A structural-acoustic finite element model of an automotive vehicle is developed and experimentally evaluated for predicting the structural-borne interior noise in the passenger compartment when the vehicle travels over a randomly rough road at a constant speed. The structural-acoustic model couples a structural finite element model of the vehicle with an acoustic finite element model of the passenger compartment. Measured random road profile data provides the prescribed power spectral density excitation applied at the tire-patch contact points to predict the structural-borne interior road noise. Comparisons of the predicted and measured interior noise for laboratory shaker excitation, tire patch excitation, and vehicle travel over a randomly rough road are used to assess the accuracy of the model.