Applied Mechanics and Materials Vols. 217-219

Abstract: The welding which is used to seal the hole on the nuclear fuel rod is performed in a chamber which is filled with high-pressure helium. Experiments were done with different current and distance of tungsten and the end plug. Each current curve and voltage curve was analyzed. The results show that the effect of increasing the welding current or shortening the distance between the tungsten electrode and the end plug on the arc is that arc voltage is smaller and the arc stability is improved. The plan that positioning head is composed of two parts was put forward to control the fuel rod positioning accuracy. By means of properly choosing and controlling the parameters, the quality of welding is certainly improved and the rate of rejection is declined.

Abstract: In view of the situation that low quality and high cost of manual welded five-star feet, this paper proposed a new method to weld five-star feet. The method is compositing linear motion of welding torch and rotary motion of the workpiece to realize 3d welding track. After mathematic analysis and detailed calculation, the welding trajectory equation is obtained, and the speed matching relation between the welding torch and the workpiece is gained too.

Abstract: To improve the service life of roller, a kind of alloying powder materials with CeO2 was designed. And the surface of roller was alloyed by a 5kW CO2 laser. The effect of CeO2 on microstructure and properties was studied by means of OM, Micro-hardness Testing Machine, Friction and Wear Tester. The experimental results indicate that addition of CeO2 into coating materials can refine and purify microstructure. Microstructure in alloying layer is coarse without CeO2, when CeO2 is up to 2.0wt.%, microstructure in alloying layer becomes finest. And microhardness and wear resistance become largest.

Abstract: An ausform finishing process that integrates heat treatment, rolling finishing and hardening of steel components into single on-line manufacturing operation is discussed in this paper ,with the gear steel 20CrMo which is widely used in auto and precise machine industry as a example .the tooth engagement process is modeled ,and the formulas for calculating deformation are deduced.

Abstract: The phenomenon of tool wear and its generating reason and mechanism in ultrasonic milling are analyzed. Then, the effect of various process parameters on tool wear is researched. It is educed through analysis that compensation method of tool wear according to the path length of tool is more suitable for ultrasonic milling. The experimental results show that the mode of ultrasonic milling is completely feasible, and the compensation of tool longitudinal wear can be realized.

Abstract: The basic theory, process characteristics and advantages of high-pressure water jet incremental sheet metal forming were introduced. International research progresses in this field were summarized. The difficulty of straight-walled sheet metal part forming was analyzed, and a new method was researched, the result shows that the solution by regulating the contact angle which between sheet metal and water jet is practicable. The future developments were prospected.

Abstract: Ellipsoidal heads is a important composition of railways tank car. Sheet stamping process is a common method used for manufacturing ellipsoidal heads. An accurate and efficient finite element model was developed for analysis and prediction of ellipsoidal heads forming quality, with different degrees of reduction deformation at different binder forces considered, and self-adaptive mesh were adopted to improve computational efficiency and quality. And the results of simulation was validated by experimental results. Based on this finite element model, the distributions of stress, strain and wall thickness during this process were obtained.

Abstract: Samples of Q345 steel welded joints were tested to failure under low cycle fatigue(LCF),high cycle fatigue(HCF) and combined fatigue(CCF) using an apparatus that is capable of providing interactive LCF/HCF loading. The stress ratio R is 0.5 and the frequency of HCF is about 19kHz. The result indicates that not only high frequency minor cycles superimposed on low frequency major cycles , but also low frequency minor cycles superimposed on high frequency major cycles can do remarkable damage to fatigue performance of welded joints. The CCF strength is characterized by amplitude envelope. If CCF fatigue life is characterized by LCF life, adverse effect of HCF component is underestimated. If CCF fatigue life is characterized by HCF life, adverse effect of LCF component is overrated.

Abstract: Both to determinate the maximum diameter of cutting tool for a pocket, which is a common operation in CAM and feature representation, and to search an Optional Cutter Diameter Sequence (OCDS) for roughing, we introduce an approach using the Integrated Geometric Characteristics and Processing Rules (IGC&PR) algorithm. In IGC&PR algorithm, geometric characteristics includes accessible section (AS) calculated with rolling disk motion approach, ASs conjunction and narrowest convex hull for AS, also processing rules contains first cutting into condition and three AS index. Besides, the implement of this algorithm just needs simple geometric and mathematical calculation such as points, lines and vectors, rather than complex intersection computation and loop construction, which are needed in traditional methods (e.g., Offset and Voronoi Diagrams). As well, the AS computation can be used for machining cell building in further application. Finally, two examples are proposed to illustrate this algorithm, and the results show that the IGC&PR is implemented and tested successfully on real-world data.

Abstract: Present work applies the Upper-Bound Theorem (UBT) with Triangular Rigid Blocks (TRB) to metal forming compression processes like plane strain forge, offering an upper limit to required deformation energy. This analytical method, usually used by means of simplified models, is developed here incorporating different effects that impact in evolution of deformation process like shape factor and friction. By means of a new adaptive model, the shape and size of the rigid zones used for the UBT application are optimized according to the ratio of the width and the height of workpiece.