Experimental and numerical studies of friction-induced vibration and noise and the effects of groove-textured surfaces

An experimental and numerical study of friction-induced vibration and noise of a system composed of an elastic ball sliding over a groove-textured surface was performed. The experimental results showed that the impact between the ball and the edges of the grooves may significantly suppress the generation of high frequency components of acceleration and reduce the friction noise. Groove-textured surfaces with a specific dimensional parameter showed a good potential in reducing squeal. To model and understand this noise phenomenon, both the complex eigenvalue and dynamic transient analysis were performed. The dynamic transient analysis for the cases of groove-textured surface with/without filleted edges validated the role of the impact between the ball and the groove edges. Furthermore, a self-excited vibration model with three degrees of freedom was proposed to capture the basic features of the friction system. A small contact angle between the ball and the groove edges, corresponding to the relatively small groove width used in this study, would not cause any instability of the system

Contact behaviour and vibrational response of a high-speed train brake friction block

Brake experiments were conducted on a typical kind of friction blocks of a high-speed train. The friction and wear, interfacial temperature, vibration, and noise generated at or by the brake interface were investigated, and the interrelationship between the vibration response and the contact behaviour of interface was analysed. The results showed the friction coefficient, vibration energy, and noise intensity were lower when the block surface experiences less wear; the friction coefficient and contact angle of the block were important factors affecting the vibration characteristics of the brake system. Moreover, the contact inclination angle increased with the increase in the friction coefficient, and mode coupling of the brake system occurred; as a result, the vibration intensity increased, and squeal occurred

Geometric modeling of 3D woven preforms in composite T-joints

A common method to fabricate net-shaped three-dimensional (3D) woven preforms for composite T-joints is to weave flat 3D preforms via a standard weaving machine with variation in binder yarn path and then separate the preform in the form of a bifurcation. Folding introduces fiber architecture deformation at the 3D woven bifurcation area. In this paper, a geometric modeling approach is proposed to represent the realistic fiber architecture, as a preprocessor for finite element analyses to predict composite structural performance. Supported by X-ray micro-computed tomography (mCT), three important deformation mechanisms are observed including yarn stack shifting, cross-section bending, and cross-section flattening resulting from the folding process. Furthermore, a set of mathematical formulae for simulation of the deformations in the junction region are developed and satisfactory agreement is observed when compared with mCT scan results

SnO2Nanowire Arrays and Electrical Properties Synthesized by Fast Heating a Mixture of SnO2and CNTs Waste Soot

SnO2nanowire arrays were synthesized by fast heating a mixture of SnO2and the carbon nanotubes waste soot by high-frequency induction heating. The resultant SnO2nanowires possess diameters from 50 to 100 nm and lengths up to tens of mircrometers. The field-effect transistors based on single SnO2nanowire exhibit that as-synthesized nanowires have better transistor performance in terms of transconductance and on/off ratio. This work demonstrates a simple technique to the growth of nanomaterials for application in future nanoelectronic devices