Papers by Author: Jian Feng Li

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Authors: Yan Le Li, Jie Sun, Jian Feng Li
Abstract: Investigation of forming forces in incremental sheet forming (ISF) is of great importance since it provides understanding of the deformation mechanics, monitoring of the forming process, failure prediction, and future means of on-line control and optimization. This paper provides a review of studies on the contact conditions and the effects of the process parameters on forming forces in ISF, followed by the current status on forming force prediction and its potential role in the improvement of ISF technology.
Authors: Xiao Wei Wang, Jian Feng Li, Jian Zhi Li, Rui Jun Zhang
Abstract: Because of the simplification for scenario choices and few reflections of space-time characters, product designers or police makers can’t reference effectively the results of LCA. This paper proposed a new LCA method for design scheme based on multi-scenarios coexistence. First, various life-cycle scenarios of product are summarized and the common attributes are extracted to generate the scenario model. Second, the choice matrix of multi-scenarios is founded based on product statistic. And the probabilities of scenarios calculated from the choice matrix are used to gather together the environmental impacts of multi-scenarios in proportion. Third, the inventory data are collected as per scenario including pollution emissions and character information. The later are used to generate personnel, spatial and temporal factors which reflect the diversity of environmental impacts in different scenarios. Finally, the related issues are discussed including matters needing attention in practical application and what need to research in future.
Authors: Dong Lu, Jian Feng Li, Yi Ming Rong, Jie Sun, Jun Zhou, Zhong Qiu Wang
Abstract: A burr formation process in micro-cutting of Al7075-T7451 was analyzed. Three stages of burr formation including steady-state cutting stage, pivoting stage, and burr formation stage are investigated. And the effects of uncut chip thickness, cutting speed and tool edge radius on the burr formation are studied. The simulation results show that the generation of negative shear zone is one of the prime reasons for burr formation. Uncut chip thickness has a significant effect on burr height; however, the cutting speed effect is minor. Unlike in conventional cutting, in micro-cutting the effect of tool edge radius on the burr geometry can no longer be neglected.
Authors: Fu Lai Sun, Jie Sun, Jian Feng Li, Liang Yu Song, Yu Guo Luo
Abstract: Linear expansion coefficient (CTE) is one of the important thermal parameters for materials, which has a great influence on the thermal deformation analyzing. Thermal Mechanical Analysis (TMA) is adopted to measure the CTE of pre-stretched aluminum alloy sheet 7050-T7451 in three vertical directions. The mathematical functions of CTE of aluminum alloy 7050-T7451 are established, which is with three directions and reflect the influence of the temperature. A comparison between the accurate CTE data and the CTE from reference is carried out .The reason of the CTE variation of aluminum 7050-T7451 with temperature also been explained qualitatively.
Authors: S.C. Wang, J. Han, Jian Feng Li, Zhi Nong Li
Abstract: Because of the deficiency of fixed kernel in bilinear time-frequency distribution (TFD), i.e. for each mapping, the resulting time-frequency representation is satisfactory only for a limited class of signals, a new adaptive kernel function named the radial parabola kernel (RPK), is proposed. The RPK can adopt the optimizing method to filter cross-terms adaptively according to the signal distribution, obtain good time-frequency resolution, and offer improved TFD for a large class of signals. Compared with traditional fixed -kernel functions, such as Wigner-Ville distribution, Choi-Willams distribution and Cone-kernel distribution, the superiority of the RPK function is obvious. At last, the RPK function is applied to the analysis of vibration signals of bearing, and the result proves the RPK function an effective method in analyzing signals.
Authors: Song Zhang, Jian Feng Li, Hong Gang Lv, Wei Dong Chen
Abstract: In the present research, an attempt has been made to experimentally investigate the cutting forces in hard milling of H13 steel with coated carbide tools under dry, MQL (minimum quantity lubrication) and MQCL (minimum quantity cooling lubrication) cutting conditions. Based on Taguchis method, four-factor (cutting speed, feed per tooth, radial depth of cut, and axial depth of cut) four-level orthogonal experiments were employed. It is found that the periodical fluctuation of the cutting forces caused by the variation of the undeformed chip thickness with the entry/exit of the cutting edge is an essential feature of the hard milling process. The empirical models for cutting forces are established, and ANOVA (analysis of variance) indicates that the quadratic models can well express the relationship between cutting forces and cutting parameters.
Authors: Peng Liu, Fang Yi Li, Jian Feng Li, Kai Kai Guan, Gang Li
Abstract: In order to study the recrystallization of the thermoplastic starch, this paper obtained the IR spectra of starch respectively plasticized by urea, glycerin and glycol. By analytical solutions spectra of vibration frequency of molecular groups, the paper studied the destructive effect of starch crystal structure, and plasticizer to form new hydrogen bonds with starch by hydroxyl group bonded. Excessive plasticizer was not suggested. When the ratio of starch and urea was 102, the thermoplastic starch was excellent in thermoplasticity and hot-workability.
Authors: Xiu Jie Jia, Jian Feng Li, Fang Yi Li
Abstract: Biomass cushioning packaging material has been gaining attention in the properties of the materials because of biodegradable and green environmental protection, and the starch plastics play an important role. Urea, formamide, glycerol, ethylene glycol four material compounded with starch respectively, for the purpose to forming hydrogen bonds by the test in this paper, the ability to hydrogen bond with the starch has been observed by infrared spectrum analysis. The results showed that urea, formamide as strong electronegative group stronger binding, glycerol and ethylene glycol are more preferably to form hydrogen bonds with the starch because of more hydroxyl group content.
Authors: G. Wang, Wan Jiang, Guang Zhao Bai, Jian Feng Li
Authors: Gang Cheng, Jian Feng Li, Wei Qiang Wang, Jie Sun
Abstract: In this paper, the finite element analysis is made to the modal analysis of the impeller, a finite element model of a impeller with cracks was established. This paper presents results of the modal of the compressor blade subjected to centrifugal force and aerodynamic equilibrium pressure. In this analysis, the numerical models without defects and also with cracks were defined. The simulation results showed that the centrifugal force due to rotational speed can greatly influence the frequency of the impeller. The distribution of two cracked blades effect the natural frequence of the impeller. When two cracked blades locate in the interval position, the increasing value of frequence is maximum. When the two cracked blades interval 150°, the increasing value of frequence is minimum. It provides a basis for modal calculation of the impeller.
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