Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of...Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.展开更多
An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress dif...An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress difference was developed as an indicator of the degree of springback instead of implicit springback analysis.Explicit finite element method(FEM)was used to analyze the forming process and to provide the stress distribution for calculating the amount of the stress indicator.In addition,multi-island genetic algorithm(MGA)was employed to seek the optimal loading condition.A case study was performed to demonstrate the potential of the suggested method.The results show that the optimization design of process parameters effectively reduces the amount of springback and improves the part shape accuracy.It provides a guideline for controlling springback in stretch forming of aircraft skin.展开更多
Yarn quality characteristics are affected by processing parameters. A 36 tex rotor spun yarn of 50/50 Basofil/ cotton （B/C） blended yarn was spun, and the spinning process optimised for rotor speed, opening roller s...Yarn quality characteristics are affected by processing parameters. A 36 tex rotor spun yarn of 50/50 Basofil/ cotton （B/C） blended yarn was spun, and the spinning process optimised for rotor speed, opening roller speed and twist factor. Selected yarn characteristics were studied during the optimization process. During the optimizations process yarn elongation and hairiness reduced with increase in rotor speed. Tenacity increased with increase of rotor speed. The increase in TF caused tenacity and CV of count to increase up to a peak and then started to decrease with further increase of TF.While TF caused an increase in yarn hairiness, elongation decreased to a minimum level and then started to increase with further increase of TF. CV of count and hairiness increased with increase in opening roller speed, but tenacity and elongation decreased with increase in opening roller speed. The optimization process yielded the optimum levels for rotor speed, opening roller speed and twist factor （TF） as 45,000 rpm, 6,500 rpm and 450 respectively. As per uster Standards the optimum yam showed good results for CV of count, CV of tenacity and thin places/km.展开更多
基金Projects (50905144, 50875216) supported by the National Natural Science Foundation of ChinaProject (09-10) supported by the State Key Laboratory of Materials Processing and Die & Mould Technology, ChinaProject (JC201028) supported by the Northwestern Polytechnical University Foundation for Fundamental Research, China
文摘Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.
基金Project(50905008)supported by the National Natural Science Foundation of ChinaProject(2007AA041905)supported by the National High-tech Research and Development Program of ChinaProject(YWF-10-01-B08)supported by the Fundamental Research Funds for the Central Universities,China
文摘An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback.In the optimization model,a mathematical formulation of stress difference was developed as an indicator of the degree of springback instead of implicit springback analysis.Explicit finite element method(FEM)was used to analyze the forming process and to provide the stress distribution for calculating the amount of the stress indicator.In addition,multi-island genetic algorithm(MGA)was employed to seek the optimal loading condition.A case study was performed to demonstrate the potential of the suggested method.The results show that the optimization design of process parameters effectively reduces the amount of springback and improves the part shape accuracy.It provides a guideline for controlling springback in stretch forming of aircraft skin.
文摘Yarn quality characteristics are affected by processing parameters. A 36 tex rotor spun yarn of 50/50 Basofil/ cotton （B/C） blended yarn was spun, and the spinning process optimised for rotor speed, opening roller speed and twist factor. Selected yarn characteristics were studied during the optimization process. During the optimizations process yarn elongation and hairiness reduced with increase in rotor speed. Tenacity increased with increase of rotor speed. The increase in TF caused tenacity and CV of count to increase up to a peak and then started to decrease with further increase of TF.While TF caused an increase in yarn hairiness, elongation decreased to a minimum level and then started to increase with further increase of TF. CV of count and hairiness increased with increase in opening roller speed, but tenacity and elongation decreased with increase in opening roller speed. The optimization process yielded the optimum levels for rotor speed, opening roller speed and twist factor （TF） as 45,000 rpm, 6,500 rpm and 450 respectively. As per uster Standards the optimum yam showed good results for CV of count, CV of tenacity and thin places/km.
