Modeling and Identification of Anisotropic Damping Property of Ni-Based Alloys by FEM-Simulation

The modeling and identification of anisotropic damping property of Ni based single crystal alloys are presented. The anisotropic material damping property is modeled by 3 D rheological equations and identified by using specimen modal damping ratios and FEM simulation. The measured damping ratios which exhibit strong anisotropy are predicted better by the method presented than by other methods.

FEM simulation of aluminum extrusion process in porthole die with pockets

In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.

FEM Simulation of Welding Quality in Porthole Die Extrusion

The effects of die structure such as the height of the welding,the welding angle and chamber the shape of the bridge on the welding quality of profiles were investigated by means of the commercial software DEFORM-3D.The numerical simulation results show that the welding quality of the hollow profiles has great sensitive to the die structure.With increasing the welding chamber height and decreasing the welding angle of the die leg can improve the welding quality.In addition,the welding quality index k of the new designed shape of the die leg is little down from 4.1 to 3.9 comparing the standard leg.

3D FEM Simulation of Milling Force in Corner Machining Process

To optimize milling force and machining accuracy quality in corner milling process, the changing law of milling force is revealed by Finite Element Method（FEM）. Based on DEFORM software a serial of 3D FEM models for corner milling process are devloped. Tool curved trajectory is achieved by establishing accurate relationship of tool location with milling time. Adaptive remeshing technique and iterative algorithm are adopted to ensure convergence of FEM model. Component force characteristics are revealed by analyzing FEM simulation results. It indicates that the milling force in Y direction becomes negative comparing with forces in X and Z direction. Magnitude of forces in three directions decreases with increase of spindle speed, while it increases with increase of milling feedrate. The simulation results for cutting force are in good agreement with those obtained from experiment. The FEM simulation model is first successfully established for corner milling process in this study, and the results provide a guide for optimizing cutting parameters in cutting process.

FEM Simulation on Artificial Freezing of Seepage Ground

The coupling mechanism in freezing process of seepage ground was studied and a simplified coupling math model was proposed. The nonlinear and coupling problems of PDEs were well solved using the exponential function, error function and normal distribution function, and a series of FEM equations of coupled fields of temperature and seepage were deduced and put forward. With the example of shaft ground freezing, the formation of freezing wall in seepage ground was simulated.

Quantitative Prediction of Fracture Distribution of the Longmaxi Formation in the Dingshan Area, China using FEM Numerical Simulation

Fracture prediction is a technical issue in the field of petroleum exploration and production worldwide.Although there are many approaches to predict the distribution of cracks underground,these approaches have some limitations.To resolve these issues,we ascertained the relation between numerical simulations of tectonic stress and the predicted distribution of fractures from the perspective of geologic genesis,based on the characteristics of the shale reservoir in the Longmaxi Formation in Dingshan;the features of fracture development in this reservoir were considered.3 D finite element method(FEM)was applied in combination with rock mechanical parameters derived from the acoustic emissions.The paleotectonic stress field of the crack formation period was simulated for the Longmaxi Formation in the Dingshan area.The splitting factor in the study area was calculated based on the rock breaking criterion.The coefficient of fracture development was selected as the quantitative prediction classification criteria for the cracks.The results show that a higher coefficient of fracture development indicates a greater degree of fracture development.On the basis of the fracture development coefficient classification,a favorable area was identified for the development of fracture prediction in the study area.The prediction results indicate that the south of the Dingshan area and the DY3 well of the central region are favorable zones for fracture development.

Three-Dimensional Rigid-Plastic FEM Simulation of Bulk Forming Processes with New Contact and Remeshing Techniques

Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.

FEM simulation and experimental verification of roll forming and springback process under complex contact conditions

The application of advanced high strength steel （AHSS） has an important significance in the development of the lightweight of automobile, but the parts made of AHSS usually have defects, such as fracture and large amount of springback, etc. In this paper, a model of multi-pass roll form- ing and springback process of AHSS is established with finite element software ABAQUS. Then a roll forming experiment is performed, and simulation and experimental results have been compared and analyzed. The model is established under complex contact conditions, including self-contact condi- tion. The results shows that during the process of sheet bending, large Mises stresses appear at ben- ding corners. The smaller the bending radius is, the larger the Mises stress and strain are. Thick- ness of sheet metal changes exceeds a certain limit, the differently if the bending radius is different. When the bending radius change tendency of the sheet thickness turns from increase to decrease.

FEM SIMULATION AND EXPERIMENTAL RESEARCH ON THE SHEET BLANKING

Both experiment and simulation are made on the AlMg4 . 5Mn0 .4 sheet blanking with 1 % , 10% and 20% relative clearance respectively. The cutting force curves and the cutting surface parameters which can be used to describe the quality of the blankings are measured. Simulation is accomplished by MARC Autoforge software package. Calculated cutting forces are always bigger than measured ones. All difference between experiment and simulation is not greater than 20% . It is feasible making virtual experiment on workstation to estimate the cutting force and to predict the quality of the workpiece for new material using certain blanking technical parameters.

3D FEM Simulation of Precision Forging Automobile Clutch Damping Spindle Sleeve

The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance for making decision on the optimal choice of process parameters and mould structure. Trial forging was used to verify the effectiveness of FEM simulation results.

FEM SIMULATION FOR LASER FORMING PROCESSING

Laser forming involves heating sheet metal workpiece along a certain path with adefocused laser beam directed irradiate to the surface. During laser forming, a tran-sient temperature fields is caused by the irradiation and travelling of a laser beam.Consequently, thermal expansion and contraction take place, and allows the thermal-mechanical forming of complex shapes. This is a new manufacturing technique thatforming metal sheet only by thermal stress. Therefore, the analysis of temperaturefields and stress fields are very useful for studying the forming mechanism and con-trolling the accuracy of laser forming. The non--liner finite element solver, MARC, isemployed to solve the thermal--mechanical analysis. Using this model, the stress andstrain distribution of pure aluminum plate with different thickness are analyzed. Theinfluence of scanning speed on temperature fields and plastic strain of metal sheet un-der the condition of constant line energy are also presented. Numerical results agreewell with the experimental results.

FEM NUMERICAL SIMULATION OF THE SOFT MEDIUM TUBE EXPANSION PROCESS

In this paper the soft medium tube expanding process of different loading case and tube sheet structure is simulated with FEM. The expanding patterns under different conditions are obtained. The correction of the Single-tube Model is verified, and cor- responding procedures are also proposed to correct the error.

FLOW STRESS MODELING FOR AERONAUTICAL ALUMINUM ALLOY 7050-T7451 IN HIGH-SPEED CUTTING

The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.

MATERIAL SURFACE THERMAL PROPERTY IDENTIFICATION USING HEAT FLUX TACTILE SENSOR

Eased on the mechanism of temperature tactile sensing of human finger,a heat flux tactile sensor com- posed of a thermostat module and a heat flux sensor is designed to identify material thermal properties. The ther- mostat module maintains the sensor temperature invariable, and the heat flux sensor（Peltier device） detects the heat flux temperature difference between the thermostat module and the object surface. Two different modes of the heat flux tactile sensor are proposed, and they are simulated and experimented for different material objects. The results indicate that the heat flux tactile sensor can effectively identify different thermal properties.

Hot deformation behavior of Ti-6Al-4V-0.1Ru alloy during isothermal compression

The hot deformation behavior of Ti-6 Al-4 V-0.1 Ru titanium alloy was investigated by isothermal compression tests on a Gleeble-3500 thermal simulator over deformation temperature range of 1023-1423 K and strain rate of 0.01-10 s-1.Arrhenius-type constitutive models were developed for temperature ranges of bothα+βdual phase andβsingle phase at strain of 0.1.Afterwards,a series of material constants(including activation energy Q,material constants n,αand ln A)as polynomial functions of strain were introduced into Arrhenius-type models.Finally,the improved Arrhenius-type models in temperature field ofα+βandβphase were constructed.The results show that the improved Arrhenius-type models contribute to the calculation of Zener-Hollomon(Z)parameter,and the microstructural evolution mechanism is uncovered by combining microstructure observations with Z-parameter.Furthermore,the improved Arrhenius-type models are also helpful to improve the accuracy of finite element method(FEM)simulation in the deformation process of Ti-6 Al-4 V-0.1 Ru titanium alloy.

Prediction of grain size for large-sized aluminium alloy 7050 forging during hot forming

A numerical approach for process optimization and microstructure evolution of lager-sized forging of aluminium alloy 7050 was proposed, which combined a commercial FEM code Deform 3D with empirical models. To obtain the parameters of empirical constitutive equation and dynamic recrystallization models for aluminium alloy 7050, the isothermal compression tests of 7050 samples were performed on Gleeble-1500 thermo-simulation machine in the temperature range of 250-450 ℃ and strain rate of 0.01-10 s-1, and the metallograph analysis of the samples were carried out on a Leica DMIRM image analyzer. The simulation results show that the dynamic recrystallization in the central area of the billet occurs more easily than that on the edge. Repetitious upsetting and stretching processes make the billet deform adequately. Among several forging processes e.g. upsetting, stretching, rounding and flatting, the stretching process is the most effective way to increase the effective strain and refine the microstructure of the billet. As the forging steps increase, the effective strain rises significantly and the average grain size reduces sharply. Recrystallized volume fractions in most parts of the final forging piece reach 100% and the average grain size reduces to 10 μm from initial value of 90 μm.

Finite element simulations on the mechanical properties of MHS materials

Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. The effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.

Adiabatic Shear Mechanisms for the Hard Cutting Process

The most important consequence of adiabatic shear phenomenon is formation of sawtooth chip. Lots of scholars focused on the formation mechanism of sawtooth, and the research often depended on experimental approach. For the present, the mechanism of sawtooth chip formation still remains some ambiguous aspects. This study develops a combined numerical and experimental approach to get deeper understanding of sawtooth chip formation mechanism for Polycrystalline Cubic Boron Nitride（PCBN） tools orthogonal cutting hard steel GCr15. By adopting the Johnson-Cook material constitutive equations, the FEM simulation model established in this research effectively overcomes serious element distortions and cell singularity in high strain domain caused by large material deformation, and the adiabatic shear phenomenon is simulated successfully. Both the formation mechanism and process of sawtooth are simulated. Also, the change features regarding the cutting force as well as its effects on temperature are studied. More specifically, the contact of sawtooth formation frequency with cutting force fluctuation frequency is established. The cutting force and effect of cutting temperature on mechanism of adiabatic shear are investigated. Furthermore, the effects of the cutting condition on sawtooth chip formation are researched. The researching results show that cutting feed has the most important effect on sawtooth chip formation compared with cutting depth and speed. This research contributes a better understanding of mechanism, feature of chip formation in hard turning process, and supplies theoretical basis for the optimization of hard cutting process parameters.

Optimization of extrusion process parameters of Incoloy028 alloy based on hot compression test and simulation

True stress?true strain curves of Incoloy028alloy at high temperature and strain rate were investigated by hot compression test.These curves show that the maximum flow stress decreases with the increase in temperature and the decrease in strain rate.FEM simulation was employed to investigate the influence of temperature,extrusion speed and friction coefficient on the extrusion load,stress,strain and strain rate in the extrusion process.The increase of extrusion temperature results in decrease of load and deformation resistance,but has little influence on strain and strain rate.When extrusion speed changes between200and350mm/s,no obvious change about extrusion load can be found.Sharp peak value up to42500kN emerges in the extrusion load curve and the extrusion process becomes unstable seriously when extrusion speed rises up to400mm/s.Both stress and strain rate increase with the raise of extrusion speed.When friction coefficient is between0.02and0.03,deformation resistance is about160MPa and the strain rate can be limited below70s?1.Successful production of Incoloy028tube verifies the optimized parameters by FEM simulation analysis,and mechanical tests results of the products meet the required properties.

Evaluation of mine scale longwall top coal caving parameters using continuum analysis

A mine-scale analysis of Longwall Top Coal Caving (LTCC) is performed using a continuum mechanics finite element solver called COSFLOW. The uniqueness of COSFLOW is that it incorporates Cosserat continuum theory in its formulation for describing the load deformation of bedded rocks. It is shown that such a continuum based code is valuable for assessing the feasibility of introducing LTCC in any mine. Various LTCC parameters, for example chock convergences, top coal failure behavior, strata cavingmechanism, abutment stresses and vertical stresses, were evaluated for a mine using COSFLOW.