Advanced Materials Research Vols. 189-193

Abstract: A new simple methodology to determine the flow stress of material is presented and Johnson–Cook (JC) constitutive model of titanium alloy Ti6Al4V is obtained via this approach. The JC model is verified by comparison between simulations and experiments. The results show that the model is suitable for cutting simulation. This simple method can be used to determine conveniently JC model not only in the scientific research but also in the workshop production.

Abstract: To reveal the mechanism of the impactor-bit-rock interaction in geophysical prospecting percussion drilling, considering the coupling effect of the static pressure, impact force and rotary cutting, constructing the physical model of the impactor-bit-rock interaction, and using the finite element methods (FEM), three-dimensional (3D) model of the impactor-bit-rock interaction is established. Using the finite element analysis software (ANSYS/LS-DYNA), the 3D FEM analysis of the impactor-bit-rock interaction is carried out when compressed air pressure is 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa and 1.2 MPa respectively. The results show that: the energy transmission efficiency when piston impacts bit under different air pressure is not high and it should be improved further, bit can not fragment rock until it is impacted by piston, it is found that the best air pressure is 1.0 MPa when the impactor and bit are used to drill granite according to the volume of the fragmented rock and the depth of the crater, the speed and displacement on the radial direction of the piston which should be reduce even eliminate are very harmful. The results are further useful to extend the applications of the geophysical prospecting impactor and hammer bit.

Abstract: Flow features, specially, flow rate, discharge coefficient and efflux angle under different operating conditions are numerically simulated, and the effects of shapes and the number of notches on them are analyzed. To simulate flow features, 3D models are developed as commercially available fluid flow models. Most construction machineries in different conditions require different actions. Thus, in order to be capable of different actions and exhibit good dynamic behavior, flow features should be achieved in designing an optimized proportional directional spool valve.

Abstract: Based on viscoplastic Anand’s model, the structural stress of 8×8 InSb array detector with underfill dependent on indium bump sizes is systemically researched by finite element method. Simulation results show that as the diameters of indium bump decrease from 36μm to 20μm in step of 2μm, the maximum stress existing in InSb chip first reduces sharply, then increases flatly, and reaches minimum with indium bump diameter 32μm. The maximum stress in Si readout integrated circuit (ROIC) fluctuates at 320MPa with amplitude less than 50MPa, almost half stress in InSb chip. Yet the maximum stress in the indium bump array is almost unchangeable and keeps at 16.3MPa. When the height of indium bump increases from 9μm to 21μm in step of 6μm, the maximal stress in InSb chip first reduces sharply from 800MPa to 500MPa, then almost retains constant. With indium bump diameter 32μm and height 21μm, the maximum stresses in whole 8×8 InSb array detector reaches minimum 458MPa, besides, the stress distribution at the contacts areas is uniform and concentrated, the stress value is smallest and this structure is promising to avoid device invalidation.

Abstract: The heat transfer coefficient between the alloys and cooling water is affected by a lot of factors and hard to measure, a new method was investigated with a self-designed system ultilizing SP-15 high-frequency inductive heating unit. Based on measured temperature curves and Fourier heat transfer model, quantitative correlation between heat transfer coefficient and temperature was obtained by inverse algorithm method of iterative simulation and automatic optimization. The results showed that in submerged water-cooling process, the heat transfer coefficient reached to a peak value at the beginning and then decreased with increasing temperature. A decrease of cooling water temperature increased the peak value of the heat transfer coefficient, but did not change temperature range of the peak value from 200°C to 225°C . The heat transfer coefficient was mainly dependent of interfacial temperature between the Al-Cu alloys and the cooling water.The temperatures range from 200°C to 225°C gave the highest heat flux transfer.

Abstract: In order to accurately analyze the dynamic damage process of three-point-bending concrete beam with offset notch, the multiscale numerical model of time and space by coupling Discrete Element Method (DEM) and Finite Element Method (FEM) of three-point-bending concrete beam with offset notch was established. Using the multiscale numerical model of three-point-bending concrete beam, the generating and the extending processes and rules of cracks in concrete beam under condition of different offset distances of notch were analyzed at macro- and meso-levels. The simulated results are in accordant with the experimental ones. Comparing the computation time of the multiscale model and that of the DEM model in the example of three-point-bending concrete beam, the former accomplished the heterogeneous mesoscopic simulations of the latter, at the same time, the former was much more efficient than the latter.

Abstract: A linear elastic fracture mechanics (LEFM) approach to the debonding analysis of concrete beams strengthened with externally bonded fiber-reinforced-polymer (FRP) strips are studied. The analytical models based on the LEFM approach are presented and discussed. The fracture analysis has adopted the energy-release-rate approach and the J-integral formulation. In addition, an algorithm for the construction of the equilibrium path that describes the debonding process in the FRP strengthened beam has been developed. The approach and its applicability to the debonding analysis of the FRP strengthened beam has been examined through three cases that include a single shear test, an edge peeling test, and a beam specimen strengthened with FRP. In cases where qualitative information regarding the initiation and progress of the debonding process is available, the LEFM model can be used for a reasonable quantitative appraisal of the debonding mechanism.

Abstract: To reduce the ladder axis machining error, in this paper, the finish turning of a machine tool spindle and the rough turning process is analyzed, were calculated the change of step-axis contour deformation in the process of the finish turning and rough turning with limited difference method and the finite element method (the elastic constraint and inelastic constraint in both ends ). Comparison of the deformation of the three profile, to find more realistic results, and simulate the spline of shaft ladder deformation, using Compensation method to process NC programming. To improve the processing quality of stepped shaft.

Abstract: Synchronizing ring, an important component of automotive synchronizer, uses the friction torque generated on its conical surface to synchro-mesh the two meshing components to realize gear shift. In the paper the forming of the hot precision forging of the new synchronizing ring is analyzed based on the finite element numerical simulation method, which provides evidence for processing optimization and mould modifying to get an accurate blank. In addition, the one-step forming processing for the synchronizing ring is analyzed, and the flow of the material, forming process, flaw prediction and the optimization of the mould structure is studied as well. The result indicates that it is more reasonable of the distribution of the material and it is more satiation filled of the cavities. The cycle life of new product development is reduced greatly by forming process analyzing and flaw prediction of the synchronizing ring.

Abstract: Spinning is the main process of making the tubeless steel wheel, which is a key factor to the outline dimension and use performance. It offers reliable technology for manufacture and use of tubeless steel wheel. We make a list of experiment by number simulation to the spinning process of tubeless steel wheel using Deform-3D，and get the result which is that a well quality steel wheel can be formed under the condition of r=1,2rad/sec and f=0.7. It provide reliable basis for the manufacture of tubeless steel wheel.