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Closed T-Spline Surface Reconstruction from Medical Image Data
Ce Shang,Jianzhong Fu,Zhiwei Lin,Jiawei Feng,Bin Li 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.11
The reconstruction from medical image data to CAD model is an essential process of Bio-medical engineering. So far, it is still challenging to create medical model which is suitable for both design and manufacturing. This paper introduces a process of constructing a single-patched closed T-spline surface model based on medical image data. The image data is first converted into triangular mesh and then parameterized onto a rectangular domain. An iterative least-squares fitting process is proposed to finally obtain the T-spline surface model with a user-specified tolerance. In this fitting process, the smoothing part of the algorithm is redesigned, considering the flexible structure of T-mesh and the geometric complexity of the T-spline surface. Local smoothness weighting factors are introduced to the fitting formula to locally adjust the smoothness of the surface. An adaptive smoothness checking points distribution method is proposed to reduce the computational cost. These algorithms are easy to implement and the obtained model is simple in form. Compared with the STL and NURBS model, the T-spline surface model requires less storage space and can be easily modified. The obtained model is suitable for Bio-medical engineering applications like bone scaffolds design, surgical planning and related manufacturing process.
Thermal Effects on the Enhanced Ductility in Non-Monotonic Uniaxial Tension of DP780 Steel Sheet
Omid Majidi,Frederic Barlat,Yannis P. Korkolis,Jiawei Fu,Myoung-Gyu Lee 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.6
To understand the material behavior during non-monotonic loading, uniaxial tension tests were conducted inthree modes, namely, the monotonic loading, loading with periodic relaxation and periodic loading-unloadingreloading,at different strain rates (0.001/s to 0.01/s). In this study, the temperature gradient developing duringeach test and its contribution to increasing the apparent ductility of DP780 steel sheets were considered. In order toassess the influence of temperature, isothermal uniaxial tension tests were also performed at three temperatures(298 K, 313 K and 328 K (25 °C, 40 °C and 55 °C)). A digital image correlation system coupled with an infraredthermography was used in the experiments. The results show that the non-monotonic loading modes increasedthe apparent ductility of the specimens. It was observed that compared with the monotonic loading, the temperaturegradient became more uniform when a non-monotonic loading was applied.