Abstract: Steel rods are widely used in the areas of petroleum, chemical, architecture and transportation, steel rods with cracks will cause terrible accident and great losses when working in production practice. In view of traditional Non-destructive Testing (NDT) method can only realize static detection, this paper provide the method based on modal calculate analysis, including the choice of damage index and the judgment of damage degree and damage location for cracks of steel rods. The damage location is judged by the strain mode shape difference curve and the function expression of damage degrees and mutation degrees of curvature mode shapes is acquired by the method of least square fitting, which can achieve quantitative analysis of single crack of steel rods, this provide theoretical support and technical reference for experimental modal analysis and dynamic NDT.
Abstract: At present, scratch on the wheel tread of train is detected mostly in low-speed circumstance in China. For this reason, a high-precision detection system for scratch on the wheel tread of train based on PSD which adapts to high-speed moving train is presented. Firstly, the principle of scratch detection based on PSD is given. Then, the acquisition and computing system for scratch on the wheel tread of train based on PSD is designed with TMS320F2812. Finally, the human-computer interaction system based on Visual Studio 6.0 is designed. The results show that the detection system for scratch on the wheel tread of train based on PSD can realize detection for scratch on the wheel tread of train and have advantages of high precision, high efficiency, high reliability and well human-machine interface.
Abstract: The effect of thermal radiation on free convection flow in unsteady Couette motion between vertical parallel plates has been investigated subject to a time dependent temperature boundary condition at the moving plate. Rosseland diffusion approximation is used to describe the radiative heat flux in the energy equation. Analytical solutions of the dimensionless governing equations are derived using the Laplace transform technique. The velocity and temperature profiles are shown on graphs, the variation of skin-friction, Nusselt number, volume flow rate and vertical heat flux are presented in tabular form. The effects of system parameters such as Grashof number, radiation parameter and time on the flow fields have been discussed in detail.
Abstract: Explosive blasting in rock and other media could induce strong shock wave. Near blasting zone, the blasting energy mainly break rock. Slightly far away from borehole, the blasting energy induces plastic damage. Farther afield, this kind of energy presents elastic deformation. In cut blasting, multi-boreholes initiate at the same time, multi-column stress waves occur superimpose and converge. Especially in multi-media, this process is extremely complex. Adopt numerical simulation method, set up multi-media model, which include weathered rock, highly weathered rock and plain fill. This paper simulated the propagation process of stress wave in these medias. Revealed the propagation mechanics of stress wave.
Abstract: In this paper, we analysed fractional dynamics behavior in metallogenic elements grade series, using detrended fluctuation analysis (DFA), with the objective to explore and understand the underlying dynamic mechanism. Our results show that the metallogenic elements grade series are the scale invariance and the long-range correlation. As in the case of element grade dynamics, the DFA scaling exponents can be used to discriminate mineral intensity.
Abstract: Bottom dead center repeat precision is the key evaluation standard of high-speed press, it’s an important index to judge production level and technical level. Use model RM-7201 testing apparatus to measure bottom dead center of high-speed press at different conditions, find out laws according to the test result. These findings may helpful in proving correctness of bottom dead center precision analysis and to control the B.D.C precision of the high-speed press. Provide practical guidance basis to improve the press structure and bottom dead center precision.
Abstract: Based on the theory of probabilistic fracture mechanics and Monte Carlo simulation, reliability analysis method for fatigue life of autofrettaged thick-walled cylinder was given. The forms of fatigue cracks in bore of autofrettaged thick-walled cylinder were considered as semi-elliptical cracks. The autofrettage residual stress solution was suitable for the thick-walled cylinder made of steel with strain hardening and Bauschinger effect. The stress intensity factors of thick-walled cylinder were calculated according to weight function method. The analysis of the examples showed that lognormal distribution is the best fit for fatigue life. Finally, the fatigue life of autofrettaged thick-walled on the condition of different reliabilities and confidences were presented.
Abstract: Aircraft icing cause significant degradation in aerodynamics performance and flight safety. Numerical methods are developed and presented to simulate two icing-related problems for airfoils, namely ice accretion and icing effects. Ice accretion on the leading edge of the NACA 0012 airfoil is predicted using CFD method based on spring analogy. A four-order Runge-Kutta method is used to solve the droplet trajectory equation. Besides, we use the integral form of Navier-Stokes equations and the Spalart-Allmaras turbulence model to study the icing effects. Designing three different icing models, the flow fields are analyzed. The results are in good agreement with the experimental data and show preliminarily that numerical method is feasible and effective.
Abstract: Ultrasonic infrared thermography is a novel nondestructive detection technique, which combines a short ultrasonic pulse excitation and infrared imaging to detect defects, such as crack, in materials and structures. A simplified one-dimension heat-conduction model excited by ultrasonic pulses is put forward in this paper. Based on this model, a serial of image processing methods for recognition and reconstruction of cracks were presented. Results obtained show that the proposed method is creditable and applicable.