Applied Mechanics and Materials Vol. 307

Abstract: In this paper, a model has been developed for calculating the Hertzian stress distribution of straight bevel gear. One pair of straight bevel gear teeth replaced with multiple pairs of spur gear teeth by using Tredgold approximation. The transmitted load and radii of curvature are evaluated and used to determine the stress distribution. The results show that these stresses are constant along the face width of tooth. Moreover, the magnitude of theses stresses are in good agreement with the simulation results using commercial ABAQUS software

Abstract: Punch forming is widely used in many fields such as car industry, aviation, and mechanical industry. Along with the new requirement such as velocity, efficiency, costing of punch forming, there is more and more failure appearance. For example, fracture, fold and spring back. In this paper, a detailed analysis of punch forming is done by FEM(finite element method), and the stresses of punch forming are obtained at every phase of punch. This work is very useful for mold design, punch forming parameters set and material properties test.

Abstract: For the Difficulties in fault diagnosis of tolerance analog circuit, a Wavelet Neural Network (WNN) diagnosis method based on Particle Swarm Optimization (PSO) algorithm is proposed. To overcome the deficiencies of the traditional BP algorithm using in WNN, PSO algorithm is introduced into the parameters optimization in WNN, and the velocity disturbance operator is embedded to ensure the particle out of the premature position for PSO algorithm performance. The simulation results show that the proposed method has the fast training rate, accurate diagnosis, without local convergence.

Abstract: In this paper, the dynamic behaviour of two degree of freedom building-like structure system against unexpected input such as seismic excitation is considered by experimentally. Proposed system consists of two floors structure with active mass damping (AMD) and shaker. Passive and active mode deflection responses of the floors are investigated and also a cart is used to suppress vibrations, which moves linear direction and is mounted on the second floor. PV (proportional and velocity) control of the cart is realized in passive mode. Moreover LQR (Linear Quadratic Regulator) control is designed to control the cart in active mode while system under excitation. For this aim a full-order observer is designed and implemented to control strategy. Displacements of cart, deflections and accelerations results of the floors are presented separately for passive and active mode responses of the system in the form of graphics.

Abstract: Phase unwrapping is one of the key technologies in electronic speckle pattern interferometry. A new phase unwrapping algorithm, based on windowed Fourier transform is proposed. The high noisy phase map is denoised by the window Fourier transform approach and then is uwrapped by the discrete cosine transform. The method is tested in this paper using a circumferentially fixed circular plate with a point load at the centre and compared with not denoised wrapped phase map and unwrapped phase map. The result shows the new proposed phase unwrapping method in denoising and improving image quality has obvious superiority.

Abstract: Because of the diversity and complexity of soft fault in analog circuit, the rapid and accurate diagnosis is very difficult. For this, an adaptive BP wavelet neural network diagnosis method of soft fault is proposed. It combines the time-frequency localization characteristics of wavelet and the self-learning ability of neural network in soft fault diagnosis of analog circuit, and by introducing the adaptive learning rate the diagnosis ability of BP wavelet neural network model can effectively be improved. In addition, PSPICE software is used to obtain the simulation data of actual analog circuit for the experiment. The results also verify the validity of the proposed method.

Abstract: Zinc oxide (ZnO) thin films were deposited on glass substrate by Radio frequency (RF) magnetron sputtering. The effect of substrate temperature on the microstructure of the ZnO films has been investigated. Crystal structure and surface morphology of the films were examined by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD patterns and AFM images show that the crystallinity and grain size are increasing with the increase of substrate temperature.

Abstract: Groove shape effect on wear behavior in PTFE radial bearings under rolling contact fatigue (RCF) was investigated. RCF tests in water-lubricated conditions were carried out at different loads and rotation speeds. The groove surfaces after testing were observed by using a laser confocal microscope and a two-dimensional shape measurement sensor. It was found that PTFE bearings under RCF generate wear debris, however no cracking or flaking failure could be observed. It is concluded that groove deformation depend on load rather than rotation speed. The biggest changes in groove profiles occurred when tested at loads close to 400N.

Abstract: A newly developed single-ball RCF testing machine was used in order to investigate crack initiation direction within SUJ2. From empirical data, it was found that the distribution of crack initiation direction at N = 1.0x106 cycles is very close to that at N = 1.0x107. This means that the cracks that do not cause failure stop growing by 1.0x106 cycles. Some cracks however continue to grow towards the surface, at an angle of 135 degrees.

Abstract: In our recent work, in order to realize joint element in lightweight and compact joints for tall humanoid robots, a new joint element was designed. It consists of a harmonic drive gearing device, a multi axis mechanism and a resin bush. The resin bush slides on a titanium crankshaft of the pole shape while the joint works. However, the bush was stuck, and stopped movement of the joint. In our present work, we observed the bush surfaces against two materials; the titanium and the 7075 aluminum alloy have been used. We could observe the differences between the titanium and the 7075 aluminum alloy by an optical microscope after the fatigue tests.