二维有模成形自适应数值模拟系统

本文给出完整的二维有模成形自适应数值模拟系统。该系统包括三个主模块，即有限元前处理、自适应有限元分析及有限元后处理。通过自适应网格生成实现了“三位一体”化，并用法兰成形实验验证了此系统的实用性及可靠性。

单点渐进成形工艺参数对正五边锥形件壁厚的影响

目的 利用数值模拟方法研究单点渐进成形工艺参数对制件成形区最小壁厚的影响规律,得出最优工艺参数组合,提高制件的成形质量。方法 在对2024铝合金正五边锥形件建立有模单点渐进成形数值仿真模型的基础上,对进给率、层间距、成形工具头直径和摩擦因数对制件成形区最小壁厚的影响进行单因素和正交试验分析,并通过物理试验对仿真优化后的工艺参数组合进行验证。结果 正五边锥形件单点渐进成形加工过程中,最小壁厚与进给率、层间距成反比,与成形工具头直径成正比,而摩擦因数对最小壁厚的影响较小;各工艺参数对最小壁厚的影响程度为进给率>层间距>成形工具头直径>摩擦因数;最佳工艺参数为成形头直径9 mm、进给率200 mm/min、加工层间距0.2 mm和摩擦因数0.1。结论 通过有限元仿真得出了单点渐进有模成形工艺对制件最小壁厚的影响规律,通过正交试验分析得出了正五边锥形件单点渐进有模成形最佳工艺参数组合,利用该参数组合可以得到壁厚较为均匀的正五边锥形件。

Numerical analysis of coupled finite element with element-free Galerkin in sheet flexible-die forming

A numerical method for coupled deformation between sheet metal and flexible-die was proposed. Based on the updated Lagrangian （UL） formulation, the elastoplastic deformation of sheet metal was analyzed with finite element method （FEM） and the bulk deformation of flexible-die was analyzed with element-free Galerkin method （EFGM）. The frictional contact between sheet metal and flexible-die was treated by the penalty function method. The sheet elastic flexible-die bulging process was analyzed with the FEM-EFGM program for coupled deformation between sheet metal and bulk flexible-die, called CDSB-FEM-EFGM for short. Compared with finite element code DEFORM-2D and experiment results, the CDSB-FEM-EFGM program is feasible. This method provides a suitable numerical method to analyze sheet flexible-die forming.

Flexible-die forming process with solid granule medium on sheet metal

Certain non-metallic granules （NMG） were selected as the research object. It was proposed to conduct the volume compression experiments as well as those on the NMG physical properties at high stress levels. Then, not only the volume compression ratio curve but also the extended Drucker-Prager linear model were obtained. In addition, through the friction strength tests, parameters of the Mohr-Coulomb model were gained, which proved in basic agreement with those of the extended Drucker-Prager linear model. Additionally, curves of the friction coefficients between the NMG and the sheet metal trader different pressures were also obtained. Based on the material performance experiments, numerical analysis in respect of flexible-die forming process with solid granule medium （SGM） was conducted. The die and device for experiments of solid granule medium forming （SGMF） on sheet metal were designed and manufactured. Typical parabolic parts were successfully trial-produced. The tests and simulation results show that the sheet formability is significantly improved for the extraordinary friction performance during interaction between the SGM and the sheet metal surface. The process control and die structure are simple, and the shaped work-pieces enjoy many advantages, such as satisfactory surface quality and favorable die fitability, which offers a brand-new method and means for processing and preparation of sheet metals.

Effect of geometrical parameters on forming quality of high-strength TA18 titanium alloy tube in numerical control bending

The forming quality of high-strength TA18 titanium alloy tube during numerical control bending in changing bending angle β, relative bending radius R/D and tube sizes such as diameter D and wall thickness t was clarified by finite element simulation. The results show that the distribution of wall thickness change ratio Δt and cross section deformation ratio ΔD are very similar under different β; the Δt and ΔD decrease with the increase of R/D, and to obtain the qualified bent tube, the R/D must be greater than 2.0; the wall thinning ratio Δto slightly increases with larger D and t, while the wall thickening ratio Δti and ΔD increase with the larger D and smaller t; the Δto and ΔD firstly decrease and then increase, while the Δti increases, for the same D/t with the increase of D and t.

Effects of parameters on rotational fine blanking of helical gears

The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking which combined the linear and rotational motion of punch and counterpunch was applied for the forming of helical gears.A three-dimensional(3D) rigid-plastic finite element model was developed on the DEFORM-3D platform.By finite element simulation and analysis,the influences of key parameters on the punch load and cut surface were investigated.It is shown that: 1) with increasing the counterforce or helical angle,the punch load and the depth of die roll increase; 2) with increasing blank holder force,the punch load increases while the depth of die roll decreases; 3) V-ring indenter facilitates an improvement in the quality.The results of this research reveal the deformation mechanism of rotational fine blanking of helical gears,and provide valuable guidelines for further experimental studies.

Modelling and simulation of contact force in cold rotary forging

Cold rotary forging is an advanced and complex metal forming technology with continuous local plastic deformation.Investigating the contact force between the dies and the workpiece has a great significance to improve the life of the dies in cold rotary forging.The purpose of this work is to reveal the contact force responses in cold rotary forging through the modelling and simulation.For this purpose,a 3D elastic-plastic dynamic explicit FE model of cold rotary forging is developed using the FE code ABAQUS/Explicit.Through the modelling and simulation,the distribution and evolution of the contact force in cold rotary forging is investigated in detail.The experiment has been conducted and the validity of the 3D FE model of cold rotary forging has been verified.The results show that: 1) The contact force distribution is complex and exhibits an obvious non-uniform characteristic in the radial and circumferential directions; 2) The maximum contact force between the upper die and the workpiece is much larger than that between the lower die and the workpiece; 3) The contact force evolution history is periodic and every period experiences three different stages; 4) The total normal contact force is much larger than the total shear contact force at any given time.

Design of relief-cavity in closed-precision forging of gears

To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.

3D modeling and deformation analysis for electromagnetic sheet forming process

Electromagnetic forming （EMF） is a high-speed forming method which can be quite effective in increasing the forming limits of metal sheet. However, the EMF process is complicated due to magnetic-structure coupling analysis. Numerical simulation offers an opportunity to overcome the problem. Nevertheless, most present models for EMF process are limited to 2D axisymmetric model. So, a three-dimensional （3D） finite element model was established to analyze the electromagnetic sheet bulging. The contact between the sheet and the die and the effect of sheet deformation on the magnetic field analysis were both taken into consideration during the forming process. The simulation results of deflection at the sheet center and 20 mm away from the center were in agreement with the experimental ones. The plastic strain energy and plastic strain were analyzed.

Effect of key factors on cold orbital forging of a spur bevel gear

Cold orbital forging is an advanced spur bevel gear forming technology. Generally, the spur bevel gear in the cold orbital forging process is formed by two steps: the preforming step and the final step. Due to the great importance of the final step to gear forming and its complication with interactive factors, this work aims at examining the influence of key factors on the final step in cold orbital forging of a spur bevel gear. Using the finite element(FE) method and control variate method, the influence rules of four key factors, rotation velocity of the upper tool, n, feeding velocity of the lower tool, v, tilted angle of the upper tool, γ, friction factor between the tools and the billet, m, on the geometry and the deformation inhomogeneity of the cold orbital forged gear are thoroughly clarified. The research results show that the flash becomes more homogeneous with increasing v, increasing m, decreasing n or decreasing γ. And the deformation of the gear becomes more homogeneous with increasing v, decreasing n or decreasing γ. Finally, a corresponding experiment is conducted, which verifies the accuracy of FE simulation conclusions.

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.

Finite element modeling and experiment for behavior estimation of AlMn0.5Mg0.5 sheet during electromagnetic forming

The electromagnetic forming is a procedure of high-speed processing,which favors the increase of the formability of some plastically deformed metals.In order to evaluate the capacity of some light metals,such as aluminum and its alloys,to be deformed through this procedure,it is useful to know the stress and strain state that occurs in the material during forming.In this work,the modeling of stresses and strains in electromagnetically deformed AlMn0.5Mg0.5 sheet was made.The modeling was achieved using the finite element method and it was verified through experimental tests.To determine the residual stresses,the X-ray diffraction method was used.The strains were established by measuring the displacements of the nodes in the network inscribed on the specimen by means of three coordinates measuring machine.A good agreement between the modeling results and experimental data was found.

Finite element simulation of aluminum alloy cross valve forming by multi-way loading

Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components.

Analysis and optimization of variable depth increments in sheet metal incremental forming

A method utilizing variable depth increments during incremental forming was proposed and then optimized based on numerical simulation and intelligent algorithm.Initially,a finite element method(FEM) model was set up and then experimentally verified.And the relation between depth increment and the minimum thickness tmin as well as its location was analyzed through the FEM model.Afterwards,the variation of depth increments was defined.The designed part was divided into three areas according to the main deformation mechanism,with Di(i=1,2) representing the two dividing locations.And three different values of depth increment,Δzi(i=1,2,3) were utilized for the three areas,respectively.Additionally,an orthogonal test was established to research the relation between the five process parameters(D and Δz) and tmin as well as its location.The result shows that Δz2 has the most significant influence on the thickness distribution for the corresponding area is the largest one.Finally,a single evaluating indicator,taking into account of both tmin and its location,was formatted with a linear weighted model.And the process parameters were optimized through a genetic algorithm integrated with an artificial neural network based on the evaluating index.The result shows that the proposed algorithm is satisfactory for the optimization of variable depth increment.

Plastic forming behavior of axisymmetric bimetal products with rotary swaging

In this paper,an elasto-viscoplastic three-dimension(3D) finite element model is developed to simulate the processing of bimetal tube with rotary swaging. Through simulation,the effects of high-frequency pulse stroking on the distribution and histories of stress,stain and loading are clarified. The stress in inner tube is compressive and higher than the minimum bonding force. Meanwhile,the stiffness of inner tube impacts outer tube extension in length.

A New Model for Simulation of Cold Roll-Forming of Tubes by Using Spline Finite Strip Method

A new model,called object model,for the simulation of cold roll-forming of tubes is presented.The model inherits the advantages of old models and is the embodiment of forming process that the strip is rolled step by step from feed rollers to last rolling pass.The elastic-plastic large deformation spline finite strip method based on updated Lagrangian method has been developed by improving the stiffness and transition matrix.Combined theory formulas and new analytical model,the forming process of a tube has been simulated successfully as an example.The analytical results are submitted and indicate that the proposed simulation method and new model are applicable.

A new pseudo rubrene analogue with excellent film forming ability

A novel pseudo rubrene analogue,6,11-di(thiophen-2-yl)-tetracene-5,12-dione (DTTDO) was synthesized,in which two thienyl groups and two carbonyl groups replacing four phenyl groups in the rubrene molecule were connected to the backbone of tetracene.This compound was characterized by single crystal X-ray structure analysis,thermogravimetric analysis,absorption spectra and electrochemical measurements.Unlike rubrene,DTTDO exhibited excellent film forming ability by normal vacuum deposition,indicating its promising applications in organic thin film transistors.