Advances in Manufacturing

A novel method for workpiece deformation prediction by amending initial residual stress based on SVR-GA

Jiang Guo, Bin Wang, Zeng-Xu He, Bo Pan, Dong-Xing Du, Wen Huang, Ren-Ke Kang

2021, 9(4): 483-495. doi:10.1007/s40436-021-00368-9

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High-precision manufactured thin-walled pure copper components are widely adopted in precision physics experiments, which require workpieces with extremely high machining accuracy. Double-sided lapping is an ultraprecision machining method for obtaining high-precision surfaces. However, during double-sided lapping, the residual stress of the components tends to cause deformation, which affects the machining accuracy of the workpiece. Therefore, a model to predict workpiece deformation derived from residual stress in actual manufacturing should be established. To improve the accuracy of the prediction model, a novel method for predicting workpiece deformation by amending the initial residual stress slightly based on the support vector regression (SVR) and genetic algorithm (GA) is proposed. Firstly, a finite element method model is established for double-sided lapping to understand the deformation process. Subsequently, the SVR model is utilized to construct the relationship between residual stress and deformation. Next, the GA is used to determine the best residual stress adjustment value based on the actual deformation of the workpiece. Finally, the method is validated via double-sided lapping experiments.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00368-9

Multi-person vision tracking approach based on human body localization features

Ao-Lei Yang, Hai-Yan Ren, Min-Rui Fei, Wasif Naeem

2021, 9(4): 496-508. doi:10.1007/s40436-021-00363-0

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This paper presents a multi-person vision tracking approach based on human body localization features to address the problem of interactive object localization and tracking in a home monitoring scenario. Firstly, the human body localization model is used to obtain the 3D position of the human body, which is then used to construct the human body motion model based on the Kalman filter method. At the same time, the human appearance model is constructed by fusing human color features and features of the histogram of oriented gradient to better characterize the human body. Secondly, the human body observation model is constructed based on the human body motion model and appearance model to measure the similarities between the human body state sequence in the historical frame and the human body observation result in the current frame, and the cost matrix is then obtained. Thirdly, the Hungarian maximum matching algorithm is employed to match each human body in the current and historical frames, and the exception detection mechanism is simultaneously constructed to further reduce the probability of human tracking and matching failure. Finally, a multi-person vision tracking verification platform was constructed, and the achieved average accuracy was 96.6% in the case of human body overlapping, occlusion, disappearance, and appearance; this verifies the feasibility and effectiveness of the proposed method.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00363-0

Effects of assembly errors and bonding defects on the centroid drift of a precision sleeve structure

Jian-Hua Liu, Xia-Yu Li, Huan-Xiong Xia, Lei Guo

2021, 9(4): 509-519. doi:10.1007/s40436-021-00346-1

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Adhesive joints are widely used in precision electromechanical products, and their bonding process has significant effects on the performance of an assembled product. This paper presents a numerical study on the bonding assembly of a sleeve structure of a precision inertial device using a finite element method, where the stresses due to curing and relaxation behaviors are considered. The effects of assembly errors and bonding defects on the centroid drift of the sleeve structure were found and analyzed quantitatively. This study can help understand the zero-drift mechanism of the precision inertial device and contribute valuable data for its error compensation.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00346-1

Microstructural evolution and mechanical properties of 55NiCrMoV7 hot-work die steel during quenching and tempering treatments

Xing-Sheng Yu, Chuan Wu, Ru-Xing Shi, Ya-Sha Yuan

2021, 9(4): 520-537. doi:10.1007/s40436-021-00352-3

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55NiCrMoV7 hot-work die steel is mainly used to manufacture heavy forgings in the fields of aerospace and automobile. This study aims to clarify the effects of heat treatment on the microstructural evolution and mechanical properties of the steel, in order to find out an optimal heat treatment scheme to obtain an excellent balance of strength, ductility and toughness. The steel was quenched at temperature from 790 C to 910 C followed by tempering treatments of 100-650 C for 5 h. The mechanical property tests were carried out by tensile, impact toughness and hardness. Optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the austenite grains, lath martensite, carbides and fracture morphology. The results show that the quenching temperature mainly influences the austenite grain size and the volume fraction of undissolved carbides (UCs), while the tempering temperature mainly influences the size and morphology of the martensite with a body centered cubic (BCC) and the carbides with a face centered cubic (FCC). The mechanical properties of the steel, including yield and tensile strength, ductility, impact toughness and hardness, get an excellent balance at a quenching range of 850-870 C. As the tempering temperature increases, the yield and tensile strength and hardness decrease, while the ductility and impact toughness increase. These variation trends can be further verified by fracture SEM observation and analysis. Combined with a macro-micro coupled finite element (MMFE) modeling technique, the cooling rate, microstructural evolution and yield strength of the steel were predicted and compared with the tested data.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00352-3

Theoretical and experimental study of surface texturing with laser machining

Ya-Zhou Mao, Jian-Xi Yang, Jin-Chen Ji

2021, 9(4): 538-557. doi:10.1007/s40436-021-00355-0

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To explore the forming process and mechanism of the surface texture of laser micropits, this paper presents the thermal model of laser machining based on the Neumann boundary conditions and an investigation on the effects of various parameters on the processing. The surface profile and quality of the formed micropits were analyzed using NanoFocus 3D equipment through a design of experiment (DOE). The results showed that more intense melting and splashing occurred with higher power density and narrower pulse widths. Moreover, the compressive stress is an important indicator of the damage effects, and the circumferential thermal stress is the primary factor influencing the diameter expansion. During the process of laser machining, not only did oxides such as CuO and ZnO generate, the energy distribution also tended to decrease gradually from region #1 to region #3 based on an energy dispersive spectrometer (EDS) analysis. The factors significantly affecting the surface quality of the micropit surface texture are the energy and pulse width. The relationship between taper angle and energy is appropriately linear. Research on the formation process and mechanism of the surface texture of laser micropits provides important guidance for precision machining.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00355-0

Material removal mechanisms and characteristics of potassium dihydrogen phosphate crystals under nanoscratching

Ning Hou, Yong Zhang, Liang-Chi Zhang, Ming-Hai Wang

2021, 9(4): 558-567. doi:10.1007/s40436-021-00356-z

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Potassium dihydrogen phosphate (KDP) crystals are important materials in high-energy laser systems. However, because these crystals are brittle and soft, machining-induced defects often emerge in KDP components. This study aimed to investigate the material removal mechanisms and characteristics of KDP during nanoscratching using Berkovich, spherical, and conical indenters. We found that KDP surface layers could be removed in a ductile mode at the micro/nanoscale and that dislocation motion was one of the main removal mechanisms. Removal characteristics are related to the stress fields generated by indenter geometries. The spherical indenter achieved a ductile removal mode more easily. The lateral force of nanoscratching increased with an increase in the normal force. The coefficient of friction (COF) followed the same trend as the lateral force when spherical and conical indenters were used. However, the COF was independent of the normal force when using a Berkovich indenter. We found that these COF variations could be accurately described by friction models.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00356-z

Regularization of mathematical model for chip flow angle catastrophe

Shao-Nan Zhang, Dong-Dong Cheng, Liang-Shan Xiong

2021, 9(4): 568-579. doi:10.1007/s40436-021-00369-8

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The chip flow angle (CFA) catastrophe in double-edged cutting results in a significant reduction in the cutting force, which can benefit the applications. However, established potential functions (i.e., cutting power calculation functions) of mathematical models for the CFA catastrophe are presented in the form of transcendental functions with two control parameters and one state parameter, which are extremely complex. A method is proposed herein to realize the regularization of the potential functions and establish mathematical models in a standard form and with complete content for the CFA catastrophe. Using this method, the potential function of the CFA catastrophe is expanded into a k-order Taylor polynomial at each midpoint of N end-to-end equally partitioned intervals of the state parameter using the Taylor function provided in MATLAB. The potential function after piecewise Taylor expansion is transformed into the same form as the potential function of the standard cusp catastrophe model by truncating the first five terms of the Taylor polynomial and eliminating the third-order term of the state parameter with elementary transformation. Hence, the regularization of potential function is realized. Subsequently, the regularization of equilibrium surface and bifurcation set can be realized based on the conclusions of the catastrophe theory. Regularization errors of the potential function, equilibrium surface, and bifurcation set are defined to evaluate the effectiveness of this regularization method. The problem of calculating regularization errors is regarded as an optimization problem. The "simulannealbnd" function provided in MATLAB is used to solve the problem. Applying the proposed method, the regularization of a mathematical model for the CFA catastrophe established by the predecessor is completed; a mathematical model (i.e., standard cusp catastrophe model) in a standard form and with complete content for the CFA catastrophe is established; and the corresponding regularization errors are analyzed. The regularization errors of the potential function, equilibrium surface, and bifurcation set curves are 5.485 5 9 10^-4%, 0.320 6%, and 4.653 9%, respectively. Based on the equilibrium surface and the bifurcation set curves constructed using the regularized mathematical model for the CFA catastrophe, the mechanism of the CFA catastrophe and the specific approach to render the cutting system operable in a low-energy consumption state by controlling the historical change path of the control point are analyzed. This study will promote the rational use of the CFA catastrophe.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00369-8

Performance evaluation of nanofluid-based minimum quantity lubrication grinding of Ni-Cr alloy under the influence of CuO nanoparticles

Roshan Lal Virdi, Sukhpal Singh Chatha, Hazoor Singh

2021, 9(4): 580-591. doi:10.1007/s40436-021-00362-1

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In machining processes, researchers are actively engaged in exploring minimum quantity lubrication (MQL) as a possible alternative to traditional flood cooling owing to economic and ecological concerns. The search for ecologically safe lubricants has attracted the attention of scientists looking to use vegetable oil as a lubricant. The nanofluid MQL technique with biodegradable oils as the base is a relatively new method with the potential to replace mineral oils. In the present study, the grinding of Inconel-718 alloy was investigated using nanofluid MQL (NFMQL) with biodegradable oils as the base. Nanofluids are composed by dispersing 0.5% (mass fraction) and 1% (mass fraction) of CuO nanoparticles in vegetable oil. The surface morphology, G-ratio, forces, and grinding energy were examined under pure MQL, NFMQL, and dry and flood lubrication conditions. The experimental results indicated that the nanofluid MQL significantly improved the machining performance. Owing to the polishing and rolling effect of nanoparticles on the tool work interface, a surface finish under a 0.5% (mass fraction) nanofluid was found to be better than pure MQL-dry and flood lubrication conditions. The NFMQL technique with 1% (mass fraction) CuO nanoparticles with palm oil as the base helped in achieving a better evacuation of chips from the grinding zone, leading to a better surface finish with a high material removal rate along with less energy consumption compared to flood and dry grinding.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00362-1

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