Papers by Keyword: Concave

Abstract: In this paper, we have started from the point of view of bionics, doing surface bionic non-smooth design at the standard No.16 animal syringe needles. Then treating the concave as the bionic unit, we worked out the concave bionic drag reduction needles by use of the laser material remove processing means. In accordance with the national standard on the injection drag test of disposable needles, we did the puncture drag comparative test of the smooth needles and the bionic needles, getting the correspondence relationship between the drag reduction rate and the bionic unit parameters. We found that the maximum drag reduction rate up to 44.05%, and it appeared when the concave interval was 0.9mm and the concave diameter was 0.09mm. Then through discussing the drag reduction mechanism of the bionic needles, we knew that the bionic units reduced the actual contact area between the needle outer wall and the simulation skin, and it was the main reason of bionic needles puncture drag decreases.

Abstract: A faster algorithm for calculating the shortest distance between two spatial bodies based on existing algorithms was presented. A simulation analysis of missile models separation process was built by using this algorithm. The simulation proved that this algorithm has the same precision and faster speed compared with other existing algorithms.

Abstract: In recent years, the requirements on the complicated deep-drawn parts with the high dimension precision are increasingly. As the major defect, the concave wall feature which commonly encounter in the complicated deep-drawn parts of the difficult-to-deep draw material is focused. In this research, the effects of draw-bending characteristics on concave wall feature during deep-drawing process are clearly identified. The mechanism of concave wall feature related to the draw-bending characteristic was investigated and clearly identified by using the finite element method (FEM) and the experiments were also performed to validate the FEM-simulation results. On the basis of stress distribution, the effects of draw-bending characteristics on the concave wall feature could be clearly identified via the changes of stress distributions on the wall, convex feature and spring-go feature on the bottom surface, and spring-back feature on the top surface. However, comparing with U-draw bending model, the effects of draw-bending characteristics was decreased and the concave wall feature in the case of deep-drawing model was smaller than that in the case of U-draw bending model. The experiments were carried out in both cases of the deep-drawing and U-draw bending models to validate the FEM-simulation results. The FEM-simulation results showed a good agreement with the experimental results with reference to the distribution of material thickness.

Abstract: The paper presents the researches to determine the best technologies to improve the lifetime of the corner welding. Generally it is says that the convex corner welding presents high mechanical properties because of the greater area section. The practice activity shows that in fact, because of the stress concentrators, these shapes of the welding are not the best solution. A better shape of the corner welding is the concave one that provides better results in the working conditions. To provide better results of the convex shape corner welding different recondition techniques are known. The paper is focused on fatigue testing performed on different samples realized with different beads on different working parameters. There are studied different reconditioned probes and the results are reported in fatigue curves.

Abstract: An object’s fine surface can change the object's surface friction property. So this paper aims to study the friction property of concave laser-textured surface through experiment. First, the Nd:YAG laser is used to generate micro-pores on Cr12 steel surface in the research and then its impact on object's surface friction property is studied. The test result shows that compared with the non-textured surfaces, the concave surface with area density of 5% and depth of I10.8 can reduce the friction coefficient significantly.

Abstract: The flow field of lubrication film under the bottom of the slipper was analyzed particularly. Taking into account of the rotation and self-rotation of the slipper, got the velocity of lubrication film under the bottom. By machining some regular concaves convergenting along radial in slipper’s bottom face，to enhance lubrication effect ,and improve the wear and tear situation in the outer fringe.

Abstract: The flow field of lubrication film under the bottom of the slipper is analyzed particularly. The velocity in different points of the lubrication film on the bottom of the slipper is solved based on the premise that the rotation and self-rotation of the slipper has been taken into account of. This paper puts forward that regular concaves converging along the radial direction be set up in the cyclic zone of slipper’s bottom surface to enhance the lubrication effect and improve the overwear situation in the peripheral parts of the slipper.

Abstract: Concave/convex wall features are usually generated in the deep-drawn parts with complicated geometry, especially the difficult-to-deep draw materials. The application of the draw bead could reduce the concave/convex wall features. However, it is difficult to determine the suitable draw bead geometry and its position to obtain a straight wall. In this study, the effects of draw bead height were investigated using the finite element method (FEM) and experiments. The application of the draw bead and the effects of its height on the concave/convex wall features could be theoretically clarified on the basis of principal stress distribution. The application of draw bead led to the decrease in tensile stress in the direction of punch movement and also increased in the tensile stress distributed to the corner zone; therefore, the concave wall feature decreased. In addition, this feature decreased as the draw bead height increased. However, the application of a very large draw bead height resulted in a convex feature. The FEM simulation results were validated by experiments in the following two cases, i.e., without and with draw bead formations. With reference to the material thickness distribution, the FEM simulation results showed a good agreement with experimental results.

Abstract: The application of the draw bead could reduce the concave/convex wall features. However, it also affected the wall thinning. Therefore, it is difficult to determine the suitable draw bead geometry to obtain a straight wall without the wall thinning. In this study, the effects of draw bead geometry of height and width on concave/convex wall feature and wall thinning were investigated by using the finite element method (FEM) and experiments. Based on the stress distribution analysis, the increasing in draw bead width and the decreasing in draw bead height lead to the concave wall feature increased; however, the application of the too small draw bead width and the too large draw bead height generated the convex wall feature. The wall thinning also decreased as the draw bead width increased as well as the draw bead height decreased. Therefore, the application of suitable draw bead height and width significantly suppressed the concave/convex wall feature and wall thinning, which resulted in the straight wall with the smallest wall thinning could be achieved.

Abstract: The production method of a driving axles used in gearbox is presented in this paper. A five-stage cold extrusion technology for forming the driving axle was made. First, simulations based on thermal-mechanical coupling finite element model were performed with Deform_2D. During the forming process, the concave appeared at the shaft end. And its formation mechanism was studied. Then the forming rules were obtained. Corresponding experiments were carried out and quality forging was achieved. Simulation and experimental results both indicate that the five-stage cold extrusion technology was feasible.