Numerical simulation of involutes spline shaft in cold rolling forming

Design of forming dies and whole process of simulation of cold rolling involutes spline can be realized by using of CAD software of PRO-E and CAE software of DEFORM-3D. Software DEFORM-3D provides an automatic and optimized remeshing function, especially for the large deformation. In order to use this function sufficiently, simulation of cold rolling involutes spline can be implemented indirectly. The relationship between die and workpiece, forming force and characteristic of deformation in the forming process of cold rolling involutes spline are analyzed and researched. Meanwhile, reliable proofs for the design of dies and deforming equipment are provided.

Influence of deformation path on the forming effect in a multistep flexible rolling process

The flexible rolling process(FRP) is a novel three-dimensional(3 D) forming process that combines the multipoint and traditional rolling forming. The principle of FRP is based on thickness thinning, so the deformation path significantly impacts the forming effect. In this study, the multistep forming process with different deformation paths was introduced to improve the forming effect of FRP. For instance, with the convex surface part, three finite element models of multistep FRP(MSFRP) were established. The corresponding numerical simulations and forming experiments performed among different deformation paths showed the surface part with a longer effective forming region was obtained and the forming regions with more steps in MSFRP were smoother. Thus, the sheet-metal utilization rate was greatly improved. Moreover, the MSFRP can improve the longitudinal bending effect dramatically and thereby endowing the forming part with a better forming effect. Therefore, MSFRP is a prospective method for broad applications.

Key technologies of roll forming automobile components with AHSS

Lightweight design is one of the development trends of the automobile industry. An effective way to achieve lightweight auto bodies is to use AHSS （advanced high strength steel ） for the safety components of automobiles. This study has taken doorsill reinforcements made of martensite AHSS as the object ,and performed research on the AHSS roll forming technologies and prototype development of typical asymmetric open components. By means of finite element analysis （FEA） and simulation,studies have been carried out on the springback and edge wave defects during AHSS roll forming ,and an optimized process design has been achieved. The generation mechanisms of vertical bows ,horizontal cambers, twists,pre-punched hole distortion and cut end flare have been analyzed,and solutions to these defects have been given. In addition,tesing of the roll forming process for AHSS has been conducted and typical samples with required dimensional accuracy have been manufactured. This study has provided technical support for the large-scale application of AHSS.

Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

Mechanism investigation and strategies for reducing residual stress at open ends of the roll-formed part

Increasing geometrical accuracy at open ends of the roll-formed part is difficult due to the release of residual stress after end cutting.In this work,a typical rail with a high requirement of geometry accuracy was selected to realize the behaviors of residual stress release.First,residual stress distribution after roll forming is discussed in detail by finite element analysis with ABAQUS.In addition,two different approaches are proposed to check their capabilities in reducing the residual stress level.The results indicate that both additional rolling passes and multiple bending processes are beneficial to reducing uniform residual stress.

FEM simulation of flexible roll forming based on different material models

Flexible roll forming is a new roll forming process that produces parts with variable cross sections. This forming process is proposed to meet the demand of weight reduction of automobile industry. In order to study the mechanisms and material flow rules in this new forming process,the finite element mothod( FEM) model of a nine-step flexible roll forming of an ultra-high-strength steel bumper is established based on deep understanding and reasonable simplification of the process.Given that the material model is an important factor that influences the simulation accuracy,three material models which consist of different yield criteria and hardening models are adopted in the FEM models. Sheet thickness and springback amount calculated with three material models are studied comparatively. According to sheet thickness reduction and springback amounts,it is found that the MKi( Mises yield criterion and kinematic hardening law) model's result is larger than MI( Mises yield criterion and isotropic hardening law) model and HI( Hill's yield criterion and isotropic hardening law) model. Therefore,it is concluded that material models do have influences on the flexible roll forming simulation and need to be determined carefully.

Metal Flowing of Involute Spline Cold Roll-beating Forming

The present research on involute spline cold roll-beating forming is mainly about the principles and motion relations of cold roll-beating,the theory of roller design,and the stress and strain field analysis of cold roll-beating,etc.However,the research on law of metal flow in the forming process of involute spline cold roll-beating is rare.According to the principle of involute spline cold roll-beating,the contact model between the rollers and the spline shaft blank in the process of cold roll-beating forming is established,and the theoretical analysis of metal flow in the cold roll-beating deforming region is proceeded.A finite element model of the spline cold roll-beating process is established,the formation mechanism of the involute spline tooth profile in cold roll-beating forming process is studied,and the node flow tracks of the deformation area are analyzed.The experimental research on the metal flow of cold roll-beating spline is conducted,and the metallographic structure variation,grain characteristics and metal flow line of the different tooth profile area are analyzed.The experimental results show that the particle flow directions of the deformable bodies in cold roll-beating deformation area are determined by the minimum moving resistance.There are five types of metal flow rules of the deforming region in the process of cold roll-beating forming.The characteristics of involute spline cold roll-beating forming are given,and the forming mechanism of involute spline cold roll-beating is revealed.This paper researches the law of metal flow in the forming process of involute spline cold roll-beating,which provides theoretical supports for solving the tooth profile forming quality problem.

The development of real time data driving multi-axis linkage and synergic movement control system of 3D variable cross-section roll forming machine

The three dimensional variable cross-section roll forming is a kind of new metal forming technol- ogy which combines large forming force, multi-axis linkage movement and space synergic movement, and the sequential synergic movement of the ganged roller group is used to complete the metal sheet forming according to the shape of the complicated and variable forming part data. The control system should meet the demands of quick response to the test requirements of the product part. A new kind of real time data driving multi-axis linkage and synergic movement control strategy of 3D roll forming is put forward in the paper. In the new control strategy, the forming data are automatically generated according to the shape of the parts, and the multi-axis linkage movement together with cooperative motion among the six stands of the 3D roll forming machine is driven by the real-time information, and the control nodes are also driven by the forming data. The new control strategy is applied to a 48 axis 3D roll forming machine developed by our research center, and the control servo period is less than 10ms. A forming experiment of variable cross section part is carried out, and the forming preci- sion is better than ＋ 0.5mm by the control strategy. The result of the experiment proves that the control strategy has significant potentiality for the development of 3D roll forming production line with large scale, multi-axis ganged and svner^ic movement

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.

Modeling of the Shape Forming of Composite Roll

A shape modeling of spray formed composite roll, which is utilized to predict the shape and dimension of roll during spray forming process, is developed in this paper. The influences of the principal spray forming parameters, such as the spatial distribution of melt mass flux, spray distance, rotating and translating speeds of substrate bar etc. , on the geometry and dimension of spray formed product were investigated.

VISUAL SIMULATION OF COLD ROLL-FORMING BASED ON OBJECT ORIENTED PROGRAMMING

To simulate the process of cold roll-forming process, a new method isadopted. The theoretical foundation of this method is an elastic-plastic large deformation splinefinite strip method based on object-oriented programming. Combined with the computer graphicstechnology, the visual simulation of cold roll-forming is completed and the system is established.By analyzing common channel steel, the process is shown and explained including theory method, modeland result display. So the simulation system is already a kind of mature and effective tool toanalyze the process of cold roll forming.

NUMERICAL SIMULATION OF ROLL FORMING FORCHANNEL SECTION WITH OUTER EDGE

The finite strip method in structural analysis has been extended, and elastic-plastic large deformation spline finite strip method based on the Updated-Lagrange method (U. L. method) was established to simulate roll forming process of channel section with outer edge. The deformation characteristics of strip was analyzed, and the three-dimensional displacement field, strain field and stress field of deformed strip were got. The calculation example proves that the peak transverse pressing membrane strain is on the corner part of the deformed strip, and the peak longitudinal stretching strain is on the outer edge part of the deformed strip in front of rolls. In addition, the transverse deformation of the deformed strip is principal, and the longitudinal deformation is small.

汽车B柱Rollforming成型的有限元仿真

在汽车车体构件制造中的辊弯成型工艺应用项目研究中,利用大型非线性有限元分析软件MSC.Marc研究了汽车B柱变截面辊弯成型仿真的有限元建模方法,主要包括板料模型和成型辊模型的建立、单元选择、边界条件、各种参数的设置及成型辊的速度加载等内容,然后采用刚性轧辊沿板料长度方向平动的方式对板料成型过程进行仿真模拟,分析了板料在成型初期、成型中期、变截面成型期三个阶段的变形特点及应力应变分布,得出了与实际成型规律相符合的结论,验证了模型的正确性,为辊弯成型FEA研究提供技术支持。

SIMULATION OF ROLL-FORMING PROCESSES OF WELDED PIPE

A multi- pumose simulation method for the roll- formign is proposed. The forming pro- cesses of welded pipes are systematically simulated by using the method. The three-dimensional cu rved surfaces of sheet metals in forming processes are mathema tically expressed by using the shape fonction S(X) which represents flow pattern of each part of sheet metal. Through optimis- ing t e parameter n in s(X), the best approximation of the deformation of sheet metal is derived and the minimum power of deformation is obtained. A mathematical procedure of this analysis is systematically foimulated. The simulation method can be applied to the analysis and simulation for various roll- forming processes of welded pipes observed in commercial production line.

A novel micro-rolling&incremental sheet forming hybrid process:Deformation behavior and microstructure evolution

Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.

Graphitization of Spray-formed Ultrahigh Carbon Steels Containing Si during Hot Rolling

The graphitization behavior of ultrahigh carbon steels containing Si in hot rolling processes was investigated. The graphite stringers went mostly through the small pores and generally paralleled to the rolling direction. The influence of alloy elements on graphitization was estimated based on thermodynamics, which showed that Si content was important for graphitization. Graphite stringers nucleated at small pores and grew with carbon diffusion during hot rolling. Alloy contents, pores and hot deformation at γ+Fe3C phase range were the key factors for the formation of graphite. The probable effect of deformation on graphite formation during hot rolling was discussed in this paper.

Microstructure evolution and strengthening mechanisms of spray-formed 5A12 Al alloy processed by high reduction rolling

The extrusion preform of the spray-formed5A12Al alloy was hot rolled using high reduction rolling technology.By means of transmission electron microscopy(TEM),electron backscatter diffraction(EBSD)and energy dispersive spectroscopy(EDS),the microstructure evolution was studied and the strengthening and toughening mechanism was thereby proposed.The results indicate that discontinuous and continuous dynamic recrystallization occurred during the hot rolling deformation of the spray-formed5A12Al alloy.The grain size was significantly refined and the micro-scale grains formed.Partial dynamic recrystallization leads to a significant increase of dislocation density and cellular structure.The Mg atoms were distributed in the Al matrix mainly in the presence of solid solution rather than the formation of precipitate.High solid solution of Mg atoms not only hindered the dislocation motion and increased the density of dislocation,but also exhibited a remarkable solid solution strengthening effect,which contributes to the high strength and high toughness of the as-rolled sheets.The tensile strength and elongation of spray formed5A12Al alloy at room temperature after3passes hot rolling were622MPa and20%,respectively.

Developments and perspectives on the precision forming processes for ultra-large size integrated components

In order to meet the requirements of high reliability,long-lifetime and lightweight in a new generation of aerospace,aviation,high-speed train,and energy power equipment,integrated components are urgently needed to replace traditional multi-piece,welded components.The applications of integrated components involve in a series of large-size,complex-shaped,highperformance components made of difficult-to-deform materials,which present a huge challenge for forming ultra-large size integrated components.In this paper,the developments and perspectives of several extreme forming technologies are reviewed,including the sheet hydroforming of ultra-large curved components,dieless hydroforming of ellipsoidal shells,radial-axial ring rolling of rings,in situ manufacturing process of flanges,and local isothermal forging of titanium alloy components.The principle and processes for controlling deformation are briefly illustrated.The forming of typical ultra-large size integrated components and industrial applications are introduced,such as the high strength aluminum alloy,3m in diameter,integrated tank dome first formed by using a sheet blank with a thickness the same as the final component,and a 16m diameter,integrated steel ring rolled by using a single billet.The trends for extreme forming of ultra-large size integrated components are discussed with a goal of providing ideas and fundamental guidance for the further development of new forming processes for extreme-size integrated components in the future.

Technology and Experiments of 42CrMo Bearing Ring Forming Based on Casting Ring Blank

Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named ＂casting-rolling compound forming technology＂ is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.