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Frontiers of Mechanical Engineering

, Volume 14 Issue 4

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A naive optimization method for multi-line systems with alternative machines
Weichang KONG, Fei QIAO, Qidi WU
Front. Mech. Eng.. 2019, 14 (4): 377-392.
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The scheduling of parallel machines and the optimization of multi-line systems are two hotspots in the field of complex manufacturing systems. When the two problems are considered simultaneously, the resulting problem is much more complex than either of them. Obtaining sufficient training data for conventional data-based optimization approaches is difficult because of the high diversity of system structures. Consequently, optimization of multi-line systems with alternative machines requires a simple mechanism and must be minimally dependent on historical data. To define a general multi-line system with alternative machines, this study introduces the capability vector and matrix and the distribution vector and matrix. A naive optimization method is proposed in accordance with classic feedback control theory, and its key approaches are introduced. When a reasonable target value is provided, the proposed method can realize closed-loop optimization to the selected objective performance. Case studies are performed on a real 5/6-inch semiconductor wafer manufacturing facility and a simulated multi-line system constructed on the basis of the MiniFAB model. Results show that the proposed method can effectively and efficiently optimize various objective performance. The method demonstrates a potential for utilization in multi-objective optimization.

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Hybrid forming mechanism of patternless casting and laser cladding
Zhongde SHAN, Fuzhen SUN, Yang LIU
Front. Mech. Eng.. 2019, 14 (4): 393-401.
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In accordance with the requirement of manufacturing dies quickly and economically, a hybrid forming method of stamping dies for automobile panels is proposed. The method combines digital patternless casting and high-power laser cladding. An experimental study is conducted on the hybrid forming process and its trial production and application in the manufacturing of stamping dies for typical panels. Results prove that the laser cladding layer exceeds HRC60 (Rockwell hardness) and thus meets the production efficiency requirement of automobile dies. The rate of defects is well controlled. Compared with traditional technology, this technology has remarkable advantages and advancement.

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Damage mechanism and evaluation model of compressor impeller remanufacturing blanks: A review
Haiyang LU, Yanle LI, Fangyi LI, Xingyi ZHANG, Chuanwei ZHANG, Jiyu DU, Zhen LI, Xueju RAN, Jianfeng LI, Weiqiang WANG
Front. Mech. Eng.. 2019, 14 (4): 402-411.
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The theoretical and technological achievements in the damage mechanism and evaluation model obtained through the national basic research program “Key Fundamental Scientific Problems on Mechanical Equipment Remanufacturing” are reviewed in this work. Large centrifugal compressor impeller blanks were used as the study object. The materials of the blanks were FV520B and KMN. The mechanism and evaluation model of ultra-high cycle fatigue, erosion wear, and corrosion damage were studied via theoretical calculation, finite element simulation, and experimentation. For ultra-high cycle fatigue damage, the characteristics of ultra-high cycle fatigue of the impeller material were clarified, and prediction models of ultra-high cycle fatigue strength were established. A residual life evaluation technique based on the “b-HV-N” (where b was the nonlinear parameter, HV was the Vickers hardness, and N was the fatigue life) double criterion method was proposed. For erosion wear, the flow field of gas-solid two-phase flow inside the impeller was simulated, and the erosion wear law was clarified. Two models for erosion rate and erosion depth calculation were established. For corrosion damage, the electrochemical and stress corrosion behaviors of the impeller material and welded joints in H2S/CO2 environment were investigated. KISCC (critical stress intensity factor) and da/dt (crack growth rate, where a is the total crack length and t is time) varied with H2S concentration and temperature, and their variation laws were revealed. Through this research, the key scientific problems of the damage behavior and mechanism of remanufacturing objects in the multi-strength field and cross-scale were solved. The findings provide theoretical and evaluation model support for the analysis and evaluation of large centrifugal compressor impellers before remanufacturing.

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Timing decision-making method of engine blades for predecisional remanufacturing based on reliability analysis
Le CHEN, Xianlin WANG, Hua ZHANG, Xugang ZHANG, Binbin DAN
Front. Mech. Eng.. 2019, 14 (4): 412-421.
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A timing decision-making method for predecisional remanufacturing is presented. The method can effectively solve the uncertainty problem of remanufacturing blanks. From the perspective of reliability, this study analyzes the timing decision-making interval for predecisional remanufacturing of mechanical products during the service period and constructs an optimal timing model based on energy consumption and cost. The mapping relationships between time and energy consumption are predicted by using the characteristic values of performance degradation of products combined with the least squares support vector regression algorithm. Application of game theory reveals that when the energy consumption and cost are comprehensively optimal, this moment is the best time for predecisional remanufacturing. Used engine blades are utilized as an example to demonstrate the validity and effectiveness of the proposed method.

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Optimization of remanufacturing process routes oriented toward eco-efficiency
Hong PENG, Han WANG, Daojia CHEN
Front. Mech. Eng.. 2019, 14 (4): 422-433.
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Remanufacturing route optimization is crucial in remanufacturing production because it exerts a considerable impact on the eco-efficiency (i.e., the best link between economic and environmental benefits) of remanufacturing. Therefore, an optimization model for remanufacturing process routes oriented toward eco-efficiency is proposed. In this model, fault tree analysis is used to extract the characteristic factors of used products. The ICAM definition method is utilized to design alternative remanufacturing process routes for the used products. Afterward, an eco-efficiency objective function model is established, and simulated annealing (SA) particle swarm optimization (PSO) is applied to select the manufacturing process route with the best eco-efficiency. The proposed model is then applied to the remanufacturing of a used helical cylindrical gear, and optimization of the remanufacturing process route is realized by MATLAB programming. The proposed model’s feasibility is verified by comparing the model’s performance with that of standard SA and PSO.

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Review of the damage mechanism in wind turbine gearbox bearings under rolling contact fatigue
Yun-Shuai SU, Shu-Rong YU, Shu-Xin LI, Yan-Ni HE
Front. Mech. Eng.. 2019, 14 (4): 434-441.
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Wind turbine gearbox bearings fail with the service life is much shorter than the designed life. Gearbox bearings are subjected to rolling contact fatigue (RCF) and they are observed to fail due to axial cracking, surface flaking, and the formation of white etching areas (WEAs). The current study reviewed these three typical failure modes. The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs. Although numerous studies have been carried out, the formation of WEAs remains unclear. The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors. WEAs were compared with adiabatic shear bands (ASBs) generated in the high strain rate deformation in terms of microstructural compositions, grain refinement, and formation mechanism. Results indicate that a number of similarities exist between them. However, substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.

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Key point selection in large-scale FBG temperature sensors for thermal error modeling of heavy-duty CNC machine tools
Jianmin HU, Zude ZHOU, Quan LIU, Ping LOU, Junwei YAN, Ruiya LI
Front. Mech. Eng.. 2019, 14 (4): 442-451.
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Thermal error is one of the main factors that influence the machining accuracy of computer numerical control (CNC) machine tools. It is usually reduced by thermal error compensation. Temperature field monitoring and key temperature measurement point (TMP) selection are the bases of thermal error modeling and compensation for CNC machine tools. Compared with small- and medium-sized CNC machine tools, heavy-duty CNC machine tools require the use of more temperature sensors to measure their temperature comprehensively because of their larger size and more complex heat sources. However, the presence of many TMPs counteracts the movement of CNC machine tools due to sensor cables, and too many temperature variables may adversely influence thermal error modeling. Novel temperature sensors based on fiber Bragg grating (FBG) are developed in this study. A total of 128 FBG temperature sensors that are connected in series through a thin optical fiber are mounted on a heavy-duty CNC machine tool to monitor its temperature field. Key TMPs are selected using these large-scale FBG temperature sensors by using the density-based spatial clustering of applications with noise algorithm to reduce the calculation workload and avoid problems in the coupling of TMPs for thermal error modeling. Back propagation neural network thermal error prediction models are established to verify the performance of the proposed TMP selection method. Results show that the number of TMPs is reduced from 128 to 5, and the developed model demonstrates good prediction effects and strong robustness under different working conditions of the heavy-duty CNC machine tool.

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Effect of TGO on the tensile failure behavior of thermal barrier coatings
Le WANG, Yuelan DI, Ying LIU, Haidou WANG, Haoxing YOU, Tao LIU
Front. Mech. Eng.. 2019, 14 (4): 452-460.
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Thermally grown oxide (TGO) may be generated in thermal barrier coatings (TBCs) after high-temperature oxidation. TGO increases the internal stress of the coatings, leading to the spalling of the coatings. Scanning electron microscopy and energy-dispersive spectroscopy were used to investigate the growth characteristics, microstructure, and composition of TGO after high-temperature oxidation for 0, 10, 30, and 50 h, and the results were systematically compared. Acoustic emission (AE) signals and the strain on the coating surface under static load were measured with AE technology and digital image correlation. Results showed that TGO gradually grew and thickened with the increase in oxidation time. The thickened TGO had preferential multi-cracks at the interface of TGO and the bond layer and delayed the strain on the surface of the coating under tensile load. TGO growth resulted in the generation of pores at the interface between the TGO and bond layer. The pores produced by TGO under tensile load delayed the generation of surface cracks and thus prolonged the failure time of TBCs.

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New analysis model for rotor-bearing systems based on plate theory
Zhinan ZHANG, Mingdong ZHOU, Weimin DING, Huifang MA
Front. Mech. Eng.. 2019, 14 (4): 461-473.
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The purpose of this work is to develop a new analysis model for angular-contact, ball-bearing systems on the basis of plate theory instead of commonly known approaches that utilize spring elements. Axial and radial stiffness on an annular plate are developed based on plate, Timoshenko beam, and plasticity theories. The model is developed using theoretical and inductive methods and validated through a numerical simulation with the finite element method. The new analysis model is suitable for static and modal analyses of rotor-bearing systems. Numerical examples are presented to reveal the effectiveness and applicability of the proposed approach.

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Energy-aware fuzzy job-shop scheduling for engine remanufacturing at the multi-machine level
Jiali ZHAO, Shitong PENG, Tao LI, Shengping LV, Mengyun LI, Hongchao ZHANG
Front. Mech. Eng.. 2019, 14 (4): 474-488.
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The rise of the engine remanufacturing industry has resulted in increased possibilities of energy conservation during the remanufacturing process, and scheduling could exert significant effects on the energy performance of manufacturing systems. However, only a few studies have specifically addressed energy-efficient scheduling for remanufacturing. Considering the uncertain processing time and routes and the operation characteristics of remanufacturing, we used the crankshaft as an illustrative case and built a fuzzy job-shop scheduling model to minimize the energy consumption during remanufacturing. An improved adaptive genetic algorithm was developed by using the hormone modulation mechanism to deal with the scheduling problem that simultaneously involves parallel machines, batch machines, and uncertain processing routes and time. The algorithm demonstrated superior performance in terms of optimal value, run time, and convergent generation in comparison with other algorithms. Computational results indicated that the optimal scheduling scheme is expected to generate 1.7 kW∙h of energy saving for the investigated problem size. In addition, the scheme could improve the energy efficiency of the crankshaft remanufacturing process by approximately 5%. This study provides a basis for production managers to improve the sustainability of remanufacturing through energy-aware scheduling.

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Hot deformation behavior of a novel bimetal consisting of BTW1 and Q345R characterized by processing maps
Pengtao LIU, Lifeng MA, Weitao JIA, Tao WANG, Guanghui ZHAO
Front. Mech. Eng.. 2019, 14 (4): 489-495.
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Only a few studies have been conducted on the flow behavior of the novel BTW1/Q345R bimetal, which is widely used in coal equipment. In this work, compression tests were conducted on BTW1/Q345R bimetal at a temperature range of 950 °C–1200 °C and strain rates of 0.05, 0.5, 5, and 15 s1 by using a Gleeble-3800 thermomechanical simulator. A constitutive equation was validated by referring to the Arrhenius equation during the characterization of hot workability. The computed apparent activation energy of the BTW1/Q345R bimetal was 360 kJ/mol, and processing maps under different strain conditions were drawn. Analysis of the stress-strain relationship revealed that work hardening exerted a dominant effect on the thermal deformation of the BTW1/Q345R bimetal. The processing maps predicted that the optimal processing interval will increase with strain. Results showed that thermal deformation of the BTW1/Q345R bimetal should proceed when the temperature range varies from 1182 °C to 1200 °C and the strain rate interval is from 4.2 to 15 s1.

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11 articles