The microstructure of surface peeling in finish rolled Cu-0.1Fe-0.03P sheetis analyzed by scanning electron microscope and energy dispersive spectroscope. Fe-rich areas ofdifferent contents are observed in the matrix....The microstructure of surface peeling in finish rolled Cu-0.1Fe-0.03P sheetis analyzed by scanning electron microscope and energy dispersive spectroscope. Fe-rich areas ofdifferent contents are observed in the matrix. The stress distributions and strain characteristicsat the interface between Cu matrix and Fe particle are studied by elastic-plastic finite elementplane strain model. Larger Fe particles and higher deforming extent of finish rolling are attributedto the intense stress gradient and significant non-homogeneity equivalent strain at the interfaceand accelerate surface peeling of Cu-0.1Fe-0.03P lead frame sheet.展开更多
Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/t...Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/titanium alloy ultrasonic welding has not been defined clearly. In this paper, the experimental and the finite element analysis were adopted to study the thermal mechanism during welding. Through the test, the temperature variation law during the welding process is obtained, and the accuracy of the finite element model is verified. The microscopic analysis indicates that at the welding time of 0.5 s, the magnesium alloy in the center of the solder joint is partially melted and generates the liquid phase. Through the finite element analysis, the friction coefficient of the magnesium–titanium ultrasonic welding interface can be considered as an average constant value of 0.28. The maximum temperature at the interface can exceed 600 ℃ to reach the melting point temperature of the magnesium alloy. The plastic deformation begins after 0.35 s and occurs at the magnesium side at the center of the interface.展开更多
This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stif...This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.展开更多
Metal magnetic memory （MMM） signals are difficult to be analyzed due to noise interfer- ence, which limits its practical engineering application. A method of improving the magnetic signals is proposed in this paper ...Metal magnetic memory （MMM） signals are difficult to be analyzed due to noise interfer- ence, which limits its practical engineering application. A method of improving the magnetic signals is proposed in this paper by placing the excitation device which generates a weak external magnetic field about 100 A/re. The effect of the external magnetic field on the magnetic signals is studied using both finite element method （FEM） and uniaxial tensile tests. Comparison of the test data with the simulation ones of stress-magnetic coupling shows that the magnetic signals are strengthened and the measurement sensitivity of the detection system is greatly improved through the external magnetic excitation. Moreover, the FEM result has a good agreement with the testing results of No. 20 steel plate. The proposed method has laid a foundation for further practical engineering application.展开更多
Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo th...Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo three-dimensional （3D） ONH model was reconstructed by optical coherence tomography （OCT） images and magnetic resonance imaging （MRI） images. Materials and Methods： A human eye was scanned by MRI and OCT in serial imaging protocol. The sclera and ONH were segmented from the images, and 3D models were reconstructed by multimodality image registration. Through the morphological segmentation, part of lamina cribrosa （LC） was acquired and reconstructed in combination with the ONH and sclera. Results： The models of ONH and sclera were got, the part of LC was included in the model. In the analysis of FEM, the ONH was compressed and the cup/disk ratio was changed obviously in high glaucomatous IOP. Discussion： This study described a method to build a 3D in vivo ONH model by image processing. It can be used in biomechanieal analysis, and provide the stress state of ONH for the research about the fundus damage of glaucoma.展开更多
Finite element analyses including a cohesive zone model （CZM） were conducted to investigate the role of corrosion product films （CPFs） in stress corrosion cracking （SCC） for copper in an ammoniacal solution. It ...Finite element analyses including a cohesive zone model （CZM） were conducted to investigate the role of corrosion product films （CPFs） in stress corrosion cracking （SCC） for copper in an ammoniacal solution. It is found that a tensile CPF-induced stress generates near the interface between the CPF and the copper substrate at the substrate side in front of the notch tip for a U-shaped edgenotched specimens. The CPF-induced stress is superimposed on the applied stress to enhance emission and motion of dislocations. The peak opening stress （S11） increases with an increase in CPF thickness and a decrease in CPF Young＇s modulus. Damage mechanics based on the CZM was applied to study the stress corrosion crack initiation and propagation by analyzing the stress redistributions and load-displacement curves. The results show that the crack initiates first in the CPF and then propagates to the copper substrate. The fracture strain of the specimen covered a CPF is lower than that without a CPF. Based on the simulation results, the mechanism of the CPF-induced SCC, which promoted the initiation and propagation of the stress corrosion cracks, was discussed.展开更多
A damage identification system of carbon fiber reinforced plastics （CFRP） structures is investigated using fiber Bragg grating （FBG） sensors and back propagation （BP） neural network. FBG sensors are applied to c...A damage identification system of carbon fiber reinforced plastics （CFRP） structures is investigated using fiber Bragg grating （FBG） sensors and back propagation （BP） neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis （FEA）. At last, the damage identification system is verified on a CFRP plate with 300mm × 300mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.展开更多
Three friction welding processes are compared for temperature, stresses and strains, as well as strain rates developed in the early phases of the processes, which are essential in their successful development. These a...Three friction welding processes are compared for temperature, stresses and strains, as well as strain rates developed in the early phases of the processes, which are essential in their successful development. These are friction stir welding （FSW）, linear friction welding （LFW） and rotary friction welding （RFW）. Their common characteristic is the use of friction to generate adequate energy and raise temperature locally in order to create favorable conditions for welding at the interface between two parts. Although the mode of movement is different for each one of them, welds are produced through plastic deformation. The Lagrangian and coupled Eulerian-Lagrangian numer- ical models developed have produced results which are in qualitative agreement with experiments and have shed a light on the commonalities of these friction welding processes展开更多
This paper investigates the particle fracture and debonding during machining of metal matrix composite （MMC） due to developed stress and strain, and interaction with moving tool by finite element analysis. The machi...This paper investigates the particle fracture and debonding during machining of metal matrix composite （MMC） due to developed stress and strain, and interaction with moving tool by finite element analysis. The machining zone was divided into three regions： primary, secondary and tertiary deformation zones. The tendency of particles to fracture in each deformation zone was investigated. The findings of this study were also discussed with respect to the experimental results available in the literature. It was found that particles at the cutting path inthe tertiary deformation zone fractured as it interacted with tool. In the secondary deformation zone, particles interacted with other particles as well as cutting tool. This caused debonding and fracture of huge number of particles as those were moving up along the rake face with the chips. No particle fracture was noted at the primary deformation zone. The results obtained from finite element analysis were very similar to those obtained from experimental studies.展开更多
A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help o...A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking NDa molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 inK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.展开更多
This paper highlights the available numerical computation techniques in mechanical engineering field with focus on application of modeling and simulation within renewable energy conversion machines as a particular res...This paper highlights the available numerical computation techniques in mechanical engineering field with focus on application of modeling and simulation within renewable energy conversion machines as a particular research case. The study makes special focus on simulation approaches based on finite elements and multibody dynamics that are currently focused within the research community. Developing the simulation model in a computer-aided design （CAD） tool is a precondition for a successful simulation-based mechanical system research. The article discusses and elaborates the methods imple- mented to integrate design data with other computer-aided engineering functions. The motivation is the fact that simulation-based research is useful for design optimization of mechanical systems that operate in harsh and unfriendly environment where conducting physical testing of proto- types is difficult. In addition, the manufacturing environ- ment is benefiting from the developments in numerical computation techniques through machining simulation that significantly reduce the time-to-market and thus increase competitiveness. The study is also intended to explore the existing gaps of capabilities in current approaches in application of computational techniques in order to draw at- tention to future challenges and trends.展开更多
基金This project is supported by 863 Program of China (N0.2002AA331112)Doctoral Foundation of Northwestern Polytechnical University.
文摘The microstructure of surface peeling in finish rolled Cu-0.1Fe-0.03P sheetis analyzed by scanning electron microscope and energy dispersive spectroscope. Fe-rich areas ofdifferent contents are observed in the matrix. The stress distributions and strain characteristicsat the interface between Cu matrix and Fe particle are studied by elastic-plastic finite elementplane strain model. Larger Fe particles and higher deforming extent of finish rolling are attributedto the intense stress gradient and significant non-homogeneity equivalent strain at the interfaceand accelerate surface peeling of Cu-0.1Fe-0.03P lead frame sheet.
基金Supported by National Natural Science Foundation of China(Grant Nos.U1764251,51775160)Fundamental Research Funds for the Central Universities of China(Grant No.DUT19LAB24)
文摘Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/titanium alloy ultrasonic welding has not been defined clearly. In this paper, the experimental and the finite element analysis were adopted to study the thermal mechanism during welding. Through the test, the temperature variation law during the welding process is obtained, and the accuracy of the finite element model is verified. The microscopic analysis indicates that at the welding time of 0.5 s, the magnesium alloy in the center of the solder joint is partially melted and generates the liquid phase. Through the finite element analysis, the friction coefficient of the magnesium–titanium ultrasonic welding interface can be considered as an average constant value of 0.28. The maximum temperature at the interface can exceed 600 ℃ to reach the melting point temperature of the magnesium alloy. The plastic deformation begins after 0.35 s and occurs at the magnesium side at the center of the interface.
文摘This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.
基金Supported by the National Natural Science Foundation of China(51275048)
文摘Metal magnetic memory （MMM） signals are difficult to be analyzed due to noise interfer- ence, which limits its practical engineering application. A method of improving the magnetic signals is proposed in this paper by placing the excitation device which generates a weak external magnetic field about 100 A/re. The effect of the external magnetic field on the magnetic signals is studied using both finite element method （FEM） and uniaxial tensile tests. Comparison of the test data with the simulation ones of stress-magnetic coupling shows that the magnetic signals are strengthened and the measurement sensitivity of the detection system is greatly improved through the external magnetic excitation. Moreover, the FEM result has a good agreement with the testing results of No. 20 steel plate. The proposed method has laid a foundation for further practical engineering application.
基金National Natural Science Foundation of Chinagrant number: 31070840 and 11102123+3 种基金Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipalitygrant number: PHR201110506General Program of Science and Technology Development Project of Beijing Municipal Education Commissiongrant number: KM201110025009
文摘Introduction： The human optic nerve head （ONH） is vulnerable to the damage in glaucomatous high intraocular pressure （IOP）. In order to analyze the human ONH head stress and deformation in high IOP, an in vivo three-dimensional （3D） ONH model was reconstructed by optical coherence tomography （OCT） images and magnetic resonance imaging （MRI） images. Materials and Methods： A human eye was scanned by MRI and OCT in serial imaging protocol. The sclera and ONH were segmented from the images, and 3D models were reconstructed by multimodality image registration. Through the morphological segmentation, part of lamina cribrosa （LC） was acquired and reconstructed in combination with the ONH and sclera. Results： The models of ONH and sclera were got, the part of LC was included in the model. In the analysis of FEM, the ONH was compressed and the cup/disk ratio was changed obviously in high glaucomatous IOP. Discussion： This study described a method to build a 3D in vivo ONH model by image processing. It can be used in biomechanieal analysis, and provide the stress state of ONH for the research about the fundus damage of glaucoma.
基金financially supported by the National Natural Science Foundation of China(No.51371035)the National High Technology Research and Development Program of China(No.2013AA031104)
文摘Finite element analyses including a cohesive zone model （CZM） were conducted to investigate the role of corrosion product films （CPFs） in stress corrosion cracking （SCC） for copper in an ammoniacal solution. It is found that a tensile CPF-induced stress generates near the interface between the CPF and the copper substrate at the substrate side in front of the notch tip for a U-shaped edgenotched specimens. The CPF-induced stress is superimposed on the applied stress to enhance emission and motion of dislocations. The peak opening stress （S11） increases with an increase in CPF thickness and a decrease in CPF Young＇s modulus. Damage mechanics based on the CZM was applied to study the stress corrosion crack initiation and propagation by analyzing the stress redistributions and load-displacement curves. The results show that the crack initiates first in the CPF and then propagates to the copper substrate. The fracture strain of the specimen covered a CPF is lower than that without a CPF. Based on the simulation results, the mechanism of the CPF-induced SCC, which promoted the initiation and propagation of the stress corrosion cracks, was discussed.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos. 41472260 and 51373090, the Natural ScienceFoundation of Shandong Province, China under Grant Nos. 2014ZRE27372 and ZR2017BF007, the Fundamental research funds of Shandong University, China under Grant No. 2016JC012, and the Young Scholars Program of Shandong University under Grant No. 2016WLJH30.
文摘A damage identification system of carbon fiber reinforced plastics （CFRP） structures is investigated using fiber Bragg grating （FBG） sensors and back propagation （BP） neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis （FEA）. At last, the damage identification system is verified on a CFRP plate with 300mm × 300mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.
文摘Three friction welding processes are compared for temperature, stresses and strains, as well as strain rates developed in the early phases of the processes, which are essential in their successful development. These are friction stir welding （FSW）, linear friction welding （LFW） and rotary friction welding （RFW）. Their common characteristic is the use of friction to generate adequate energy and raise temperature locally in order to create favorable conditions for welding at the interface between two parts. Although the mode of movement is different for each one of them, welds are produced through plastic deformation. The Lagrangian and coupled Eulerian-Lagrangian numer- ical models developed have produced results which are in qualitative agreement with experiments and have shed a light on the commonalities of these friction welding processes
文摘This paper investigates the particle fracture and debonding during machining of metal matrix composite （MMC） due to developed stress and strain, and interaction with moving tool by finite element analysis. The machining zone was divided into three regions： primary, secondary and tertiary deformation zones. The tendency of particles to fracture in each deformation zone was investigated. The findings of this study were also discussed with respect to the experimental results available in the literature. It was found that particles at the cutting path inthe tertiary deformation zone fractured as it interacted with tool. In the secondary deformation zone, particles interacted with other particles as well as cutting tool. This caused debonding and fracture of huge number of particles as those were moving up along the rake face with the chips. No particle fracture was noted at the primary deformation zone. The results obtained from finite element analysis were very similar to those obtained from experimental studies.
基金This work was supported by the Young Scientists Fund of the National Natural Science Foundation of China （Grant No. 11504318）.
文摘A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking NDa molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 inK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.
文摘This paper highlights the available numerical computation techniques in mechanical engineering field with focus on application of modeling and simulation within renewable energy conversion machines as a particular research case. The study makes special focus on simulation approaches based on finite elements and multibody dynamics that are currently focused within the research community. Developing the simulation model in a computer-aided design （CAD） tool is a precondition for a successful simulation-based mechanical system research. The article discusses and elaborates the methods imple- mented to integrate design data with other computer-aided engineering functions. The motivation is the fact that simulation-based research is useful for design optimization of mechanical systems that operate in harsh and unfriendly environment where conducting physical testing of proto- types is difficult. In addition, the manufacturing environ- ment is benefiting from the developments in numerical computation techniques through machining simulation that significantly reduce the time-to-market and thus increase competitiveness. The study is also intended to explore the existing gaps of capabilities in current approaches in application of computational techniques in order to draw at- tention to future challenges and trends.
