Advanced Materials Research Vols. 690-693

Abstract: Pipe stamping processing is a new kind of processing method ,which is high efficiency, low cost, low energy consumption .It has the very high practical value. Aiming at the tube punching force and deformation characteristics, the application of plastic finite element method was used to study the tube punching main process parameters on forming after the influence of wall collapse. Research shows that: wall collapse as tool feed speed increases first increases, then decreases to a certain degree; Along with the fixed die mandrel increases ; With the increase of the wall inside diameter increases.

Abstract: 40 MN multi-cored die forging press is a bi-directional loading press machine designed by Tsinghua University. The main frame is made by combination of multi-components through bumpy-ridge contact face and wound steel wire, which will supply a solidity support to bi-directional working load, i.e., the vertical and horizontal. Due to combination of multi-components (blocks), the main frame must be wound by the tensioned steel wire, which will endure a strong pre-stress. When die forging press works, the complex loading cases will appear,for instance, the vertical and horizontal loading, the compound and the eccentric loading. This paper addresses whole finite element analysis of 40 MN die forging press in various cases. Especial attention is paid to stress, displacement and safety coefficient on bumpy-ridge contact face of main frame.

Abstract: By using finite element software, the paper establishes the main stand analysis model of the Ф140 pipe rolling mill and provides the model analysis of main stand in cases of full load. Verify the design of main stand fully comply with the technical requirements .In this paper, it provides the theoretical position of split casting and welding method using electric slag welding.

Abstract: Powder forming process can produce parts with homogeneous and satisfactory mechanical properties. Based on the assumption that the powder system is a compressive continuous material, the flow stress models used in powder forming were analyzed. The correspondent elasto-plastic constitutive model was derived from the yield criterion. Appropriate algorithm and mechanical models were applied. The program was developed and three-dimensional simulations for the powder compaction process of the iron matrix powder were performed. Effects of different flow stress models on simulation results were analyzed.

Abstract: Accurate prediction and controlling of spring-back within acceptable tolerance limits is absolutely essential for the design of bending die in order to produce sheet metal parts. This phenomenon which is defined as elastic recovery during unloading is one of the most important factors to influence the quality of sheet metal forming. This paper presents a study of spring-back in V-bending process of an isotropic CK67 steel sheet. In this investigation, in order to study the effects of significant parameters on spring-back, numerous simulations are performed using Finite Element Method (FEM). A two dimensional finite element model is developed using ABAQUS/Explicit intending to carry out a comprehensive study and prognosticate spring-back with variable parameters including punch load, punch tip radius (R _p) and thickness. Numerical results obtained from the simulations are discussed in details in several diagrams. These results represent verifiable and practical data that are in line with the results of previous researchers.

Abstract: This study proposes a parameter optimization system for a multi-LED lighting lens, which uses design of experiment (DOE) for screening the process parameters, computer-aided engineering (CAE) for mold flow analysis, analysis of variance (ANOVA) for determining the significant parameters, and response surface methodology (RSM) for finding the initial parameter settings in terms of multi-objective quality characteristics. In addition, two regression models, obtained from RSM, are employed as the quality predictors which are combined with the particle swarm optimization (PSO) to generate the optimal molding parameter settings. The numerical results show that the proposed approach, RSM with PSO, is beneficial to obtain the better process parameter settings in the injection molding process.

Abstract: The ring is subjected to the combined action of rolling deformation and guide rolls in radial ring rolling process. If the rolling process parameters are designed unreasonably, the ring may be deformed unexpectedly or squashed to waste product. In this article, equation of ring’s bending moment in rolling process is developed based on the mechanical model. Then the stress of ring at any point is analyzed and the maximum stress is found out. The plastic instability criterion of radial ring rolling is also proposed based on the analyses above.

Abstract: Pulse current effects during hot tensile process and superplastic forming process of AZ31 magnesium alloy and TA15 titanium alloy were investigated in this paper. The experimental results indicate that the current can produce polarity effect to coarse grain AZ31 magnesium alloy, but to fine grained TA15 titanium alloy, the polarity effect is not obvious. The impact of electron wind force can change the strength of material during tensile process and affect final shape of part, making the dome of AZ31 hemisphere part deviated from the axis to the side of positive pole during superplastic forming process. In addition, the impact of current depends on current density and dislocation density.

Abstract: This paper took the example of rolling force prediction in the cold rolling process to describe the establishment and application of BP neural network prediction system. This system is a prediction model for generic process. Users can select different parameters to train the network structure according to their needs, and can calculate relative rolling force parameters based on the known structure. This system can provide very valuable process information for workers and researchers .

Abstract: During the last years, some researchers have focused the development of ultrasonic microstructure refinement /modification techniques of die-casting aluminium alloys, to improve their properties. The developed techniques are highly efficient when applied to the die-casting process, but their capability with sand and ceramic moulding are unknown. Sand/ceramic aluminium castings are prone to coarse microstructure, porosities and inclusions due to low cooling rates and turbulent gravity pouring, and suitable processing techniques are required to eliminate those drawbacks. This article reports some results of a research work aiming the development of a reliable, low-cost and environmentally friend casting process, for geometrically complex and massive high strength sand/ceramic aluminium castings, to eliminate traditional soundness related defects and simultaneously promote the development of refined microstructures. The article presents the effect of applying ultrasound to AlSi₉Cu₃ alloy during solidification on a sand mould on the resultant microstructure. Results include microstructure characterization and its relationship with thermal analysis data collected from the center of the cast samples during cooling.