Papers by Keyword: Convex

Abstract: In this paper, we study convex quadratic relaxation in polynomial programming. The goal is to solve polynomial programs through quadratic reformulation with the factorization method. The quadratization of monomials of degree more than two is carried out by replacing each pair of factors of the monomial with auxiliary variables. In this paper, each pair of factors of a monomial will be considered. The quadratic program obtained is convexified by using eigenvalues. As a result, the quadratic reformulation involving all factors of the monomial strengthens the information of the polynomial function but increases the dimensionality of the variables significantly. The next work is to develop a strategy to reduce the dimensions of the auxiliary variables.

Abstract: Through the analysis of processing 3D point cloud data obtained by laser radar and establishment of the point cloud model to calculate the volume and displacement to monitor the particular scene in accordance with the detection strategy of the dangerous situation, This article wants to develop a set of all-weather, real-time early monitor system, in order to timely risk information publish, reduce the losses caused by disasters. The system uses a modular design approach, which is divided into the information collection module, the information processing module, the analysis of early warning modules and information transmission module. The paper details the system design, and application in the design and implementation of technology and point cloud data processing algorithm. The system use serial programming techniques for laser radar data and control PTZ, and multi-threading technology to improve the efficiency of the serial communication and resolve the problem of multi-serial real-time data collection.

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: 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: High-quality stamped parts using cost-effective production technique are increasingly required, especially in parts with complex geometry wherein forming defects are easily generated. In this study, the concave and convex wall features were investigated for a stainless steel rectangular tray using the finite element method and related experiments. The concave and convex wall phenomena were theoretically clarified on the basis of stress distribution. The effects of tray geometry were also investigated. Increasing both the rectangle size and depth of tray, together with a decrease in the corner radius, resulted in an increase in concave wall generation. However, the effects of increasing the length or width of the rectangle affecting the concave wall were independent of each other. In addition, the application of a very large depth of tray resulted in a convex feature. The results showed that it is difficult to achieve a straight wall on both the ‘length’ and ‘width’ sides without the use of draw bead. The finite element simulation results showed a reasonable agreement with the experimental results, with reference to the material thickness distribution in both the cases of: absence of the draw bead formation; and presence of the draw-bead formation.