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CAD mesh model simplification with assembly features preservation

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Science China(Information Sciences) 2014年第3期57卷 119-129页

作者： XIAO Hong LI Yuan YU JianFeng ZHANG Jie The key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

This paper aims to investigate a CAD mesh model simplification method with assembly features preservation,in order to satisfy the requirement of assembly field for the information of 3D *** proposed method simplifies a CAD mesh model as ***,the notion of"conjugation"is incorporated into the definition of assembly features,with the purpose of benefitting the downstream applications such as assembly features recognition and ***,the attributed adjacency graphs(AAGs)of the regionlevel-represented parts are *** assembly features are automatically recognized by searching for conjugated subgraphs of every two AAGs based on subgraph isomorphism *** order to improve the efciency of assembly features recognition,the characteristics of conjugated subgraphs are adopted to initialize the mapping matrix,and the"verifying while matching strategy"is used to verify the validity of every two newly founded vertices which are correspondingly ***,simplified CAD mesh model with assembly features preserved is constructed after suppressing the common form *** method is applied successfully to simplify the CAD mesh model with assembly features well ***,the tradeof between the cost of time for conjugated subgraphs matching and the complexity of the to-be-matched parts is proven to be almost linear.

关键词： CAD mesh model model simplification assembly features feature recognition subgraph isomorphism

Dynamics modeling and pressure control of composites tape winding system based on LQSMC

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Chinese Journal of Aeronautics 2020年第2期33卷 740-748页

作者： Qi HONG Yaoyao SHI Danni LU The key laboratory of contemporary design and integrated manufacturing technology Ministry of Education Northwestern Polytechnical UniversityXi’an 710072China

Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin *** accuracy of pressure control systems is affected by nonlinear disturbances,such as friction,parameter perturbation,and measurement noise.A robust control algorithm based on linear quadratic optimal control and sliding mode control(LQSMC)is proposed to overcome these *** method is based on the system state space expression and linear quadratic optimal *** state space model of the system is improved by using a Kalman filter and control input for state estimation,and a new sliding surface equation is *** ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control(SMC)*** and experimental results show that LQSMC offers high control precision,much stronger antiinterference,and robustness,which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control(LQC).The winding pressure control precision is improved by 45%to 50%.The results show that the porosity of composite fiber tape winding products decreased thanks to our method.

关键词： Composites tape winding Dynamics modeling Kalman filter LQSMC Pressure control

Multiscale Analysis on Two-dimensional Nanoscale Adhesive Contacts

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Chinese Journal of Mechanical Engineering 2012年第3期25卷 446-455页

作者： TONG Ruiting LIU Geng LIU Lan key laboratory of contemporary design and integrated manufacturing technology of Ministry of Education Northwestern Polytechnical UniversityXi'an 710072China

Nanoscale adhesive contacts play a key role in micro/nano-electro-mechanical systems as the dimension of the components come to *** studies on nanoscale adhesive contacts are limited by some uncertain factors and the cost of experiments is too ***,nanoscale textured surfaces are difficult to process and nanoscale adhesive contacts of textured surfaces are still lack of *** using multiscale method,which couples molecular dynamics simulation and finite element method,two-dimensional nanoscale adhesive contacts between a rigid cylindrical tip and an elastic substrate are *** the contacts between the rigid cylindrical tip and smooth surface,Von Mises stress distributions,the maximum Von Mises stresses,and contact forces are compared for different radii to show the size effects and adhesive *** phenomena of hysteresis are observed and more obvious as the radii of the tip *** influences of indentation depth and indentation speed are also *** two series of textured surfaces are employed,and the influences of the texture asperity shape,asperity height,and asperity spacing on contact forces are *** contact forces comparisons show that textured surfaces can reduce contact forces effectively in the range of the two *** forces of textured surfaces increase as the asperity heights increase,and textured surfaces with smaller asperity spacing will get higher contact *** forces may be controlled through textured surfaces in the *** obtained results will help to improve contact condition and provide theory basis for texture design.

关键词： nanoscale adhesive contact multiscale method surface texture

Variable Tension Control for Discontinuous Tape Winding of Composites Based on Constant Extension Ratio

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Chinese Journal of Mechanical Engineering 2012年第5期25卷 1022-1028页

作者： SHI Yaoyao YAN Long HE Xiaodong key laboratory of contemporary design and integrated manufacturing technology Minnistry of EducationNorthwestern Polyteehnical UniversityXi'an 710072China

Discontinuous tape winding, which has obvious advantages in large extension ratio winding, is widely used in the molding of composites. Therefore, the research on technological parameters becomes the focus of many scholars. However, how to accomplish the variable tension control is usually not fully considered. Accordingly, the constant extension ratio and the smoothness of winding process cannot be ensured. Aiming at the problem of tension control, this paper first gives a comparatively deep research on the control method and the interaction mechanism of tension, extension ratio, automatic lap and automatic rectification. Then, according to the winding process features, the mechanical device and the mathematical model of tension control system are established respectively. With regard to the characteristics of PID controller and fuzzy controller, the fuzzy self-tuning PID controller is designed. As a result, the variable tension control is realized during the winding and lapping process, and the constant extension ratio is guaranteed. Finally, a sample application is presented for demonstration. By presenting the variable tension control techniques for discontinuous tape winding, the constant extension ratio of tapes is achieved, the consecution and the automation degree of winding process is improved as well. Thus, the quality of wound products is guaranteed.

关键词： tape winding tension control constant extension ratio automatic lap and rectification

Effects of Cutting Parameters on Tool Insert Wear in End Milling of Titanium Alloy Ti6A14V

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Chinese Journal of Mechanical Engineering 2017年第1期30卷 53-59页

作者： LUO Ming WANG Jing WU Baohai ZHANG Dinghua key laboratory of contemporary design and integrated manufacturing technology of Ministry of Education Northwestern Polytechnieal UniversityXi'an 710072China

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6A14V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6A14V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as： feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6A14V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.

关键词： tool wear Ti6A14V cutting parameter hard-to-cut material

Machining Error Control by Integrating Multivariate Statistical Process Control and Stream of Variations Methodology

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Chinese Journal of Aeronautics 2012年第6期25卷 937-947页

作者： WANG Pei ZHANG Dinghua LI Shan CHEN Bing key laboratory of contemporary design and integrated manufacturing technology Ministry of Education Northwestern Polyteehnical University Xi'an 710072 China

For aircraft manufacturing industries, the analyses and prediction of part machining error during machining process are very important to control and improve part machining quality. In order to effectively control machining error, the method of integrating multivariate statistical process control （MSPC） and stream of variations （SoV） is proposed. Firstly, machining error is modeled by multi-operation approaches for part machining process. SoV is adopted to establish the mathematic model of the relationship between the error of upstream operations and the error of downstream operations. Here error sources not only include the influence of upstream operations but also include many of other error sources. The standard model and the predicted model about SoV are built respectively by whether the operation is done or not to satisfy different requests during part machining process. Secondly, the method of one-step ahead forecast error （OSFE） is used to eliminate autocorrelativity of the sample data from the SoV model, and the T2 control chart in MSPC is built to realize machining error detection according to the data characteristics of the above error model, which can judge whether the operation is out of control or not. If it is, then feedback is sent to the operations. The error model is modified by adjusting the operation out of control, and continually it is used to monitor operations. Finally, a machining instance containing two operations demonstrates the effectiveness of the machining error control method presented in this paper.

关键词： machining error multivariate statistical process control stream of variations error modeling one-step ahead forecast error error detection

A high-order full-discretization method using Hermite interpolation for periodic time-delayed differential equations

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Acta Mechanica Sinica 2015年第3期31卷 406-415页

作者： Yilong Liu Achim Fischer Peter Eberhard Baohai Wu key laboratory of contemporary design and integrated manufacturing technology Northwestern Polytechnical University Institute of Engineering and Computational Mechanics University of Stuttgart

A high-order full-discretization method （FDM） using Hermite interpolation （HFDM） is proposed and implemented for periodic systems with time delay. Both Lagrange interpolation and Hermite interpolation are used to approximate state values and delayed state values in each discretization step. The transition matrix over a single period is determined and used for stability analysis. The proposed method increases the approximation order of the semidiscretization method and the FDM without increasing the computational time. The convergence, precision, and efficiency of the proposed method are investigated using several Mathieu equations and a complex turning model as examples. Comparison shows that the proposed HFDM converges faster and uses less computational time than existing methods.

关键词： Full-discretization method Time delay -Stability Chatter

New Cutting Force Modeling Approach for Flat End Mill

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Chinese Journal of Aeronautics 2007年第3期20卷 282-288页

作者： WAN Min ZHANG Wei-hong TAN Gang QIN Guo-hua Sino-French laboratory of Concurrent Engineering The Key Laboratory of Contemporary Design ＆ Integrated Manufacturing Technology Northwestern Polytechnical University Xi＇an 710072 China

A new mechanistic cutting force model for flat end milling using the instantaneous cutting force coefficients is proposed. An in-depth analysis shows that the total cutting forces can be separated into two terms: a nominal component independent of the runout and a perturbation component induced by the runout. The instantaneous value of the nominal component is used to calibrate the cutting force coefficients. With the help of the perturbation component and the cutting force coefficients obtained above, the cutter runout is identified. Based on simulation and experimental results, the validity of the identification approach is demonstrated. The advantage of the proposed method lies in that the calibration performed with data of one cutting test under a specific regime can be applied for a great range of cutting conditions.

关键词： runout cutting force flat end mill calibration cutting force coefficient

Geometric analysis of investment casting turbine blades based on digital measurement data

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China Foundry 2014年第1期11卷 20-27页

作者： Cheng Yunyong Wang Liya Zhu Zhenzhen Zhang Dinghua key laboratory of contemporary design and integrated manufacturing technology Ministry of Education Northwestern Polytechnical University

A turbine blade is one of the key components of the aero-engine. Its geometric shape should be inspected carefully in the production stage to ensure that it meets the tolerance specification. In the present paper, an approach for investment turbine blade geometric shape analysis based on multi-source digital measurement is presented. Its key technologies, such as measurement data collection, blade model reliable alignment, geometric shape deviation fast calculation and visualization, were investigated. Actual measurement data from a structure light measurement device and a Coordinate Measuring Machine(CMM) for turbine blades were used to validate the presented method. The experimental results show that the proposed method is accurate, quick and effective to implement.

关键词： turbine blade shape inspection model reliable alignment deviation visualization