Advanced Materials Research Vols. 314-316

Abstract: The rheological behavior of two kinds Al-Zn-Mg-Cu aluminum alloy with different extrusion ratio was studied by thermal compression in 300°C~450°C and in strain rate range of 0.01 s-1~10s^-1 on Gleeble1500D simulator. The results show that: (1)the flow stress increases with de^{Superscript text}creasing deformation temperature and increasing strain rate, and the initial microstructure influence the rheological behavior, the flow stress with fine grain is higher than that with coarse one except in strain rate 0.01s-1 and 0.1s-1 in 450°C owing to deformation easily with more grain boundary sliding in high temperature and low strain rate.(2)The flow stress of Al-Zn-Mg-Cu aluminum alloy during hot compression can be expressed as hyperbolic sine constitutive equation with Arrhenius parameter, the apparent steady state activation energy for hot compression with coarse grain is of 181.51kJ/mol, while that with fine grain is of 203.02kJ/mol.(3) The apparent steady state activation energy decreases with increasing temperature and strain rate, and the value of fine initial microstructure is higher than the low extrusion ratio rod commonly.

Abstract: Aircraft dynamic systems digital simulation platform modeling was construct based on engineering needs and provide the basis of experimental data. Combined with dynamic system characteristics and saber software characteristics .In the Saber simulation software, used the schematic-based, based on functional requirements and the modeling method based on experimental data to establish a dynamic system of different parts of the device model, and according to different modeling methods established by the electrical load model and control model of power systems consisting of mixed-signal model. Finally, experimental verification of the whole system model, simulation results compared with the experimental results prove the accuracy of the system model, effective and practical.

Abstract: Integrated process planning and scheduling (IPPS) is a good way to achieve a global improvement for the performance of a manufacturing system, it has been extensively researched over the past years and it continues to attract the interest of both academic researchers and practitioners. This paper first summarizes the critical problems of IPPS and then a survey of the integrated model and optimal implementation method for IPPS is presented. The integrated model is categorized into interface-oriented integration and function-oriented integration two types based on the integration object and are discussed in detail respectively. The deficiencies of the current integrated models and the suggestion for further improvement are also given. The integration of process planning and scheduling has been implemented by variety methods and agent-based approach is discussed in more detail. Finally, future research directions and conclusions in IPPS research are discussed.

Abstract: Utilization of MSC.Marc FEM software, the typical warm compaction process of molybdeum powder was simulated. Influence of processing parameters of warm compaction on green density of molybdenum powder were studied. Furthermore, the commonly defect existing in green body were analyzed. The results show that compaction pressure is an important factor on green density. At the beginning of warm compaction, average relative density rises linearly along with the increasing pressure. The green density increases with the suppression speed increasing, when velocity value reaches 7mm/s the density will not increase anymore. After the value of friction coefficient is greater than 0.1,green density decreases with the friction coefficient increasing. Influence of temperature on compaction is improvement of the lubrication condition, and reduces the friction coefficient. The appearance of axial tensile stress is the important factor which causes delamination and cracks. Internal friction and lubrication condition of powder mixed system is the important reason results in defect.

Abstract: The thermal stress and strain, from the thermal mismatch of neighboring materials, are the major causes of fracture in InSb IRFPA. Basing on viscoelastic model describing underfill, the structural stress of 16×16 InSb IRFPA under thermal shock is studied with finite element method. Simulation results show that as the diameters of indium bump increase from 20μm to 36μm in step of 2μm, the maximum stress existing in InSb chip first increases slightly, and fluctuates near 28µm, then decreases gradually. Furthermore, the varied tendency seems to have nothing to do with indium bump standoff height, and with thicker indium bump height, the maximal Von Mises stress in InSb chip is smaller. All these mean that the thicker underfill is in favor of reducing the stress in InSb chip and improving the final yield.

Abstract: Deadlock prevention problem is an important issue in essence for flexible manufacturing systems (FMS). Many works make efforts in the issue. Theory of regions is recognized as one of the powerful deadlock prevention method for obtaining maximally permissive controllers. All legal and live maximal behavior of Petri net models can be preserved by using marking/transition-separation instance (MTSI) or event-state-separation-problem (ESSP) methods. However, solving all sets of inequalities are an extremely time consuming problem since all MTSIs and ESSPs need to be considered in the reachability graph of a deadlock FMS. In our previous work, we propose crucial MTSI (CMTSI) method to improve computational difficulty successfully. In this work, we further enhance the computational efficiency of CMTSI by combining critical markings and CMTSI methods. Experimental results reveal that this approach is more practical than the conventional methods.

Abstract: For hot rolling of large rings, determination of rolling force plays an important role in designing, choosing and optimizing of processing plan and rolling mill. The average shape parameter of the deformation zone of ring rolling is presented, and a reliable coupled thermo-mechanical three-dimensional (3D) finite element (FE) model for the process is developed. The effects of processing parameters on rolling force during hot rolling of titanium alloy large rings with different sizes are explored and the results obtained show that different rings follow a similar trend: increasing the relative reduction or rotational speed of the driver roll, or decreasing the feed rate of the idle roll is beneficial to a reduction in rolling force.

Abstract: The key components of the single screw compressor are rotor screw and two star-wheels which are symmetrical arrangement. The rotor screw and two star-wheels have composed a special spatial meshing pair. The high meshed precision is the guarantee of its excellent performance. In this paper, we will study the milling technology of screw milling cutter to the rotor screw, and establish the finite element model of the cutter, and analyze the cutter’s stress situation during the milling process, make the cutting parameters of the screw optimization, In this paper, we will also study the influence of the Milling depth and cutting width to tool in displacement and stress, in order to provide a theoretical reference of selecting of appropriate cutting parameters ,improving of processing quality and reducing wear of the tool.

Abstract: A feed-forward three-layer neural network was proposed to predict the fracture force of injection-molded parts’ weld line. Firstly, the most significant process parameters which affect the fracture force of weld line were analyzed. Secondly, melt temperature, injection pressure, holding pressure and holding time were chosen as import variables and the fracture force of weld line was chosen as output variable to construct artificial neural networks. Furthermore, the performance of ANN was evaluated and tested by its application to verification tests with process parameters randomly selected which all of them were not used in the network training. Results showed that the ANN predictions yield mean absolute percentage error (MAPE) in the range of 0.86％,and maximum relative error (MRE) in the range of 1.84％ for the test data set, and which can comparatively accurately reflect the influence relation of the injection process parameters on part’s quality index under the circumstance of data deficiencies.

Abstract: Taking a company’s automotive panel drawing die as an example, this paper numerically simulates the process of drawing forming based on finite element analysis (FEA) software ANSYS, the design rationality of die structure is analyzed combining distribution characteristics of stress and strain, the paper also proposes feasible improvment measures according simulation analysis to optimize the structure of drawing die. The study result shows that analysis results based on ANSYS can forecast defect and failure regions in the forming process of automotive panel drawing die, optimize the design of drawing die, prolong the die life effectively, and reduce production cost.