Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the defo...Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.展开更多
Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge bas...Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge base in a fault diagnosis expert system that was based on machine learning by the four-layer perceptron neural network. An example was presented. By combining differential function with not differential function and back propagation of error with back propagation of expectation, the four-layer perceptron neural network was established. And it was good for solving such a bottleneck problem in knowledge acquisition in expert system and enhancing real-time on-line diagnosis. A method of synthetic back propagation was designed, which broke the limit to non-differentiable function in BP neural network.展开更多
This paper explains an integrated production inventory supply chain model,which consists of a supplier,a manufacturer and a retailer under two-level credit period.One is manufacturer’s credit period offered by the su...This paper explains an integrated production inventory supply chain model,which consists of a supplier,a manufacturer and a retailer under two-level credit period.One is manufacturer’s credit period offered by the supplier,and other is retailer’s credit period offered by the manufacturer.Here,the manufacturer replenishes raw materials from the supplier and produces non-deteriorating products in some cycles of equal length.It is noted that here four inventory structures have been considered to show the flow of the materials as either raw materials or finished products from supplier to retailer via manufacturer.Also in this model,manufacturer’s imperfect production has been considered.Here imperfect items are not repairable.The retailer receives good finished products from the manufacturer and sells these to his/her customers during some cycles of equal length in total time horizon.Our main objective is to find the optimal number of production and business cycles of the manufacturer such that the integrated system can get the maximum profit.The above discussed model is elaborated with the help of a numerical example,and a sensitivity analysis is done with respect to some parameters used in this model.展开更多
为探究配筋率和复合层厚度对ECC-NC(Engineered Cementitious Composites to Normal Concrete)复合梁抗弯性能的影响,设计了5根ECC-NC复合梁,通过四点弯曲试验,开展了ECC-NC复合梁抗弯性能研究,分析了复合梁破坏模式和裂缝发展规律,探...为探究配筋率和复合层厚度对ECC-NC(Engineered Cementitious Composites to Normal Concrete)复合梁抗弯性能的影响,设计了5根ECC-NC复合梁,通过四点弯曲试验,开展了ECC-NC复合梁抗弯性能研究,分析了复合梁破坏模式和裂缝发展规律,探讨了配筋率和复合层厚度对结构承载能力、韧性及延性的影响。研究结果表明:与普通混凝土梁相比,ECC-NC复合梁破坏模式不同,能有效发挥ECC材料特性,具有较好的抗弯性能;相同配筋率下,受拉区ECC层厚度增加,ECC-NC复合梁的抗弯承载力增强有限,弯剪区裂缝数量增多,延性增强,刚度退化缓慢,最佳复合层厚度为0.3h~0.5h;ECC层具有替代部分纵筋作用,受压与受拉区同时设置ECC层能极大地提高抗弯承载能力、延性及结构韧性;基于响应面法,配筋率对ECC-NC抗弯性能影响最大,最大配筋率与复合层厚度有关,0~0.5h呈负相关,0.5h~h间呈正相关,受压区设置ECC可提高界限配筋率,高配筋率有利于提高抗弯刚度,减缓裂缝扩展;弯曲荷载下,截面符合平截面假定,变形协调;基于条带法,建立了ECC-NC复合梁抗弯承载能力计算方法,与试验结果及已有文献数据校核,平均误差在6%以内,吻合度较高,可为工程应用提供理论支撑。ECC替代普通混凝土,不仅提高了结构抗弯承载力,还延缓了裂缝扩展,改善了复合梁带裂缝工作性能和抗裂性能,且抗弯性能较为优越。展开更多
基金the funds of the National Natural Science Foundation of China(No.51875456)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JM-450)+3 种基金the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20170518)the Key Laboratory of Advanced Manufacture Technology for Automobile Parts(Chongqing University of Technology),Ministry of Education(No.2018KLMT03)Materials Science and Engineering provincial-level superior discipline funding project of Xi'an Shiyou Universitythe Program for Young Innovative Research Team in Xi'an Shiyou University(No.2015QNKYCXTD02)。
文摘Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.
文摘Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge base in a fault diagnosis expert system that was based on machine learning by the four-layer perceptron neural network. An example was presented. By combining differential function with not differential function and back propagation of error with back propagation of expectation, the four-layer perceptron neural network was established. And it was good for solving such a bottleneck problem in knowledge acquisition in expert system and enhancing real-time on-line diagnosis. A method of synthetic back propagation was designed, which broke the limit to non-differentiable function in BP neural network.
基金This research work was supported by Council of Scientific and Industrial Research,Human Resource Development Group,India(No.25(0276)/17/EMR-II).
文摘This paper explains an integrated production inventory supply chain model,which consists of a supplier,a manufacturer and a retailer under two-level credit period.One is manufacturer’s credit period offered by the supplier,and other is retailer’s credit period offered by the manufacturer.Here,the manufacturer replenishes raw materials from the supplier and produces non-deteriorating products in some cycles of equal length.It is noted that here four inventory structures have been considered to show the flow of the materials as either raw materials or finished products from supplier to retailer via manufacturer.Also in this model,manufacturer’s imperfect production has been considered.Here imperfect items are not repairable.The retailer receives good finished products from the manufacturer and sells these to his/her customers during some cycles of equal length in total time horizon.Our main objective is to find the optimal number of production and business cycles of the manufacturer such that the integrated system can get the maximum profit.The above discussed model is elaborated with the help of a numerical example,and a sensitivity analysis is done with respect to some parameters used in this model.
文摘为探究配筋率和复合层厚度对ECC-NC(Engineered Cementitious Composites to Normal Concrete)复合梁抗弯性能的影响,设计了5根ECC-NC复合梁,通过四点弯曲试验,开展了ECC-NC复合梁抗弯性能研究,分析了复合梁破坏模式和裂缝发展规律,探讨了配筋率和复合层厚度对结构承载能力、韧性及延性的影响。研究结果表明:与普通混凝土梁相比,ECC-NC复合梁破坏模式不同,能有效发挥ECC材料特性,具有较好的抗弯性能;相同配筋率下,受拉区ECC层厚度增加,ECC-NC复合梁的抗弯承载力增强有限,弯剪区裂缝数量增多,延性增强,刚度退化缓慢,最佳复合层厚度为0.3h~0.5h;ECC层具有替代部分纵筋作用,受压与受拉区同时设置ECC层能极大地提高抗弯承载能力、延性及结构韧性;基于响应面法,配筋率对ECC-NC抗弯性能影响最大,最大配筋率与复合层厚度有关,0~0.5h呈负相关,0.5h~h间呈正相关,受压区设置ECC可提高界限配筋率,高配筋率有利于提高抗弯刚度,减缓裂缝扩展;弯曲荷载下,截面符合平截面假定,变形协调;基于条带法,建立了ECC-NC复合梁抗弯承载能力计算方法,与试验结果及已有文献数据校核,平均误差在6%以内,吻合度较高,可为工程应用提供理论支撑。ECC替代普通混凝土,不仅提高了结构抗弯承载力,还延缓了裂缝扩展,改善了复合梁带裂缝工作性能和抗裂性能,且抗弯性能较为优越。
