Polyhedral surfaces are used as representation model for CAM and process planning purposes because of its simplicity for data exchange and geometric computation. However, there is few tool path planning strategies for such surfaces but the iso-plane method. In this paper, contour parallel path are generated for three-axis ball-end milling. This tool path is based on a novel algorithm for offsetting curves on polyhedral surfaces presented in this paper. It reduces the task of removing complex interfering of offset curve from 3D surface to 2D plane by flattening mesh surface, and avoids costly 3D Boolean set operations and expensive distance calculation. This results in an efficient tool-path generation. Empirical examples illustrate the feasibility the proposed method.
The CTOD (Crack Tip Opening Displacement) evaluation and control for HAZ (Heat Affected Zone) toughness of welded joints are the most effective measures to the security of steel structures. This paper address the problem of the newly developed offshore structure steel API 2W 50Z with heavy thickness of 100mm. In accordance with the American Petroleum Institute standard Recommended Practice 2Z (API PR 2Z), the CTOD tests of two critical positions of HAZ in three kinds of heat inputs were carried out in low temperature (-10°C). All of these CTOD testing and assessments are finished under the witness of American Bureau of Shipping (ABS). The result shows that all of the CTOD values are greater than the required value (0.38mm) in API RP 2Z. This indicates that the newly developed offshore structure steel (API 2W 50Z) meet the requirement of the toughness. Further, the CTOD testing and assessments in several international standards about weld joints of steel plates are also compared and discussed in this paper.
In this paper we use AHP mathematical theory, combining with VB6.0 software, and establish preschool children's psychological development model, and design preschool children's psychological development analysis system. In the first part of this paper we introduce the AHP structure, and discuss the principle and process of hierarchical analysis; in the second part, combining with the matrix theory we establish the mathematical model of objective function layer approximation. In order to verify the effectiveness and reliability of model, we use the VB software to do numerical simulation on preschool children's psychological development, and obtain the level nephogram and children's psychological maturity index curve of children's psychological development. It provides technical reference and the theory basis for the effect of preschool physical education on the psychological development of children.
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