Xiao S.,Northwestern Polytechnical University |
Sun S.,Northwestern Polytechnical University |
Guo H.,Northwestern Polytechnical University |
Jin M.,Xian Aerospace engine Group LTD |
Yang H.,Northwestern Polytechnical University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2015
A hybrid estimation of distribution algorithm (EDA) is proposed to solve the stochastic job shop scheduling problem (SJSSP) with stochastic processing times. The mathematic model of the SJSSP and the evaluation method of stochastically expected model are constructed. To enhance the population diversity, the recombination and mutation process of (μ+λ)-Evolutionary strategy are incorporated in the EDA, thus a hybrid EDA, i.e. ES-EDA is constructed. Based on the encoding method of chromosome adopted in this research, the concept of Inherit rate of the operations in parent individual is defined. Then a new recombination method based on the Inherit rate of the operations in parent individual is designed. This recombination method can not only make the offspring inheriting the excellent characteristics of the parent effectively, but also avoiding infeasible solutions. Three problem instances with stochastic processing times for simulation experiment are constructed based on the benchmark instances FT06, FT10 and FT20, the comparison with the simulation results obtained by the 5 algorithms in literatures shows that the ES-EDA has significant advantages in aspect of optimal performance. © 2015 Journal of Mechanical Engineering.
ZHANG Q.-C.,Nanjing University of Aeronautics and Astronautics |
CHEN M.-H.,Nanjing University of Aeronautics and Astronautics |
WANG H.,Nanjing University of Aeronautics and Astronautics |
WANG N.,Nanjing University of Aeronautics and Astronautics |
And 2 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2016
The deformation behavior and mechanism of Ti2AlNb-based alloy were experimentally investigated at elevated temperatures. Firstly, the stress–strain relationships at different temperatures and strain rates were investigated via uniaxial tensile testing. Then, formability data, as determined by examining the deep drawing and bending abilities, were obtained through limiting draw ratio (LDR) and bending tests. Finally, metallographic experiments and fracture morphology investigations were conducted to examine the thermal deformation mechanism of the alloy. The results showed that as the temperature increased, the total elongation increased from 13.58% to 97.82% and the yield strength decreased from 788 to 80 MPa over the temperature range from 750 to 950 °C at a strain rate 0.001 s−1. When the temperature reached 950 °C, the strain rate was found to have a great influence on the deformation properties. The plastic formability of the sheet metal was significantly improved and a microstructural transformation of O to B2 and α2 occurred in this temperature region, revealing the deformation mechanism of its plasticity. © 2016 The Nonferrous Metals Society of China
Dong H.,Nanjing University of Aeronautics and Astronautics |
Yang C.,Nanjing University of Aeronautics and Astronautics |
Yang C.,Jiangsu Key Laboratory of Advanced Numerical Control Technology |
Gao S.,Nanjing University of Aeronautics and Astronautics |
And 3 more authors.
Jingangshi yu Moliao Moju Gongcheng/Diamond and Abrasives Engineering | Year: 2016
For typical difficult-to-machine materials of nickel-base superalloy GH4169, honing experiments are carried out to study the hole surface roughness and cylindricity. Results show that the surface roughness decreases gradually and tends to be stable as honing continues when honing GH4169 using metal bonded CBN oilstone. The best surface roughness is Ra 0.7 μm when using the grit size 100 μm oilstone, Ra 0.3 μm using 34 μm oilstone and Ra 0.1 μm using 8 μm oilstone. Based on the results, two prediction models, namely the minimum bottom hole machining allowance prediction model and the maximum allowable deviation of cylindricity prediction model, are established and verified by relevant experiments. It turns out that the errors of the models are less than 10%. © 2016, Diamond & Abrasives Engineering Editorial Office. All right reserved.
Zhao Z.,Nanjing University of Aeronautics and Astronautics |
Fu Y.,Nanjing University of Aeronautics and Astronautics |
Xu J.,Nanjing University of Aeronautics and Astronautics |
Zhang Z.,Nanjing University of Aeronautics and Astronautics |
And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015
Profile grinding is an established technology for manufacturing aircraft engine components with a high surface quality and a high dimensional accuracy, for instance, the dovetails of gas turbine blades. In spite of recent advantages, the employment of profile grinding has been impeded by drastic wheel wear and thermal damage, especially when machining difficult-to-cut materials such as titanium and nickel alloys. In this study, grinding experiments with directional solidified nickel-based superalloy DZ125 were performed with the aim to enhance the wheel shape retention, suppress thermal damage, and increase the material removal rate. Instead of conventional abrasive wheels, a monolayer electroplated cubic boron nitride (CBN) profile wheel was employed, and the measurement results showed that the dimensional deviation of the machined surface profile was within tolerance. An analysis of the specific grinding energy revealed that a low specific grinding energy can be achieved by effectively controlling the maximum chip thickness. Only a slight variation of the grinding temperature was measured in the grinding zone between different points along the profile when using a profile-adapted needle nozzle. For the grinding parameters used in this study, a high shape accuracy and a good surface integrity was obtained even at a specific material removal rate of 50 mm3/mm s and grinding in a single pass. © 2015 Springer-Verlag London
Zhang X.Y.,Northwestern Polytechnical University |
Li M.Q.,Northwestern Polytechnical University |
Li H.,Northwestern Polytechnical University |
Luo J.,Northwestern Polytechnical University |
And 2 more authors.
Materials and Design | Year: 2010
Isothermal compression of the TC11 titanium alloy has been conducted on Gleebe-1500 hot-simulator at the deformation temperatures ranging from 1023 K to 1323 K, the strain rates ranging from 0.001 s-1 to 10.0 s-1, and the height reductions ranging from 50% to 70%. The effect of deformation temperature, strain rate and strain on the flow stress and the apparent activation energy for deformation is in depth analyzed. The experimental results show that the apparent activation energy for deformation in isothermal compression of the TC11 titanium alloy decreases with the increasing of strain. Moreover, the apparent activation energy for deformation in α + β two-phase region of the TC11 titanium alloy increases with the increasing of deformation temperature and decreases with the increasing of strain rate. A power dissipation efficiency map in isothermal compression of the TC11 titanium alloy is constructed at a strain of 0.6, in which three domains with higher power dissipation efficiency are observed, and deformation characteristics of the above-mentioned domains are analyzed. Finally, optical micrographs of the TC11 titanium alloy obtained on a Leica DMLP microscope showed the evidence of deformation in three domains. © 2010 Elsevier Ltd. All rights reserved.