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1.
The special contact conditions in skin-pass rolling of steel strip are examined by experimental as well as numerical analysis studying plane strain upsetting of thin sheet with low reduction applying long narrow tools with smooth and roughened surfaces under dry friction and lubricated conditions. The influence of friction on the extent of a central sticking region is determined by an elasto-plastic FEM analysis of the plane strain upsetting. The experimental results obtained by measuring the local surface extension using markers made by Micro Vickers indentation verify the FE analysis and show significant influence of tool roughness and lubrication on the contact conditions for varying pressure. The central sticking region was larger for larger friction or tool roughness. At increasing pressure a sudden change in deformation pattern appeared with drastic elongation and sliding in case of lubrication. This deformation pattern is also affected by the tool roughness. 相似文献
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Hideo Kijima 《Journal of Materials Processing Technology》2013,213(10):1764-1771
Skin-pass rolling (or temper rolling) is the final forming step in the production of cold rolled steel sheets. Although a large roll radius compared to the contact length is one of the characteristics of skin-pass rolling conditions, numerous studies have been conducted thus far using laboratory mills with small radius rolls. In this paper, the influence of roll radius on the contact condition and material deformation in skin-pass rolling is examined and clarified by numerical analysis by an elastic–plastic FEM analysis as well as experimental rolling tests, which were performed to verify the result of the analysis. Some characteristics of skin-pass rolling related to pressure distribution, contact condition and material deformation are not properly simulated using small radius rolls. Considering characteristic skin-pass rolling conditions, two cases using simplified models, i.e., vertical compression and rolling with a circular, rigid roll, were analyzed. 相似文献
3.
《Journal of Materials Processing Technology》2014,214(5):1111-1119
Skin-pass rolling (or temper rolling) is usually the final process in the production of cold-rolled steel sheets. One of the main objectives in skin-pass rolling is to obtain a certain surface roughness profile. Although a large roll radius compared to the contact length and the reduction in thickness is one of the characteristics of skin-pass rolling conditions, numerous studies have been conducted thus far using laboratory mills with small radius rolls. In this paper, the influence of roll radius on roughness transfer in skin-pass rolling is investigated by experimental rolling tests as well as numerical analysis by elastic–plastic FEM. A simple but useful method of estimating roughness transfer is suggested. It was found that some characteristics of skin-pass rolling related to roughened rolls are not properly simulated using small radius rolls. 相似文献
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Yuepeng Song Wenke Wang Dongsheng Gao Eun Yoo Yoon Dong Jun Lee Hyoung Seop Kim 《Metals and Materials International》2014,20(3):445-450
High pressure torsion (HPT) is one of the most important techniques among various methods that create severe plastic deformation in the production of bulk materials with nano/ultrafine grained microstructures. Since the driving force in deforming the workpiece in HPT is surface friction, understanding of the friction effect is critical for successful application of HPT. In this study, the friction effect in HPT was analyzed using the finite element method. The distribution of effective strain on the contact surface of the HPT samples under different friction conditions was investigated. The friction force influenced the effective strain more in the middle and edge regions than in the central region. The condition for the minimum friction factor that could achieve a sticking condition between the surfaces of the dies, and the samples in the middle and edge regions, was investigated. There was a critical friction coefficient in which the effective strain varies sharply with an increasing friction coefficient. 相似文献
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A numerical solution for plane strain Steckel rolling using an experimentally determined stress-strain curve and measured roll-work interface velocities is presented. The solution is based on rate formulation of the constitutive equations for an isotropic elastic plastic work hardening material with von Mises yield condition and on an incremental finite element analysis employing constant strain increment triangles. Interfacial velocities are measured and used as prescribed boundary conditions in the numerical model of the deformation process. Some predictions are presented such as distributions of normal pressure in the contact region of the roll and drawing stress. For several reductions, the drawing force compares favorably with experimental values. 相似文献
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This paper presents a methodology to determine simultaneously (a) the flow stress at high deformation rates and temperatures that are encountered in the cutting zone, and (b) the friction at the chip–tool interface. This information is necessary to simulate high-speed machining using FEM based programs. A flow stress model based on process dependent parameters such as strain, strain-rate and temperature was used together with a friction model based on shear flow stress of the workpiece at the chip–tool interface. High-speed cutting experiments and process simulations were utilized to determine the unknown parameters in flow stress and friction models. This technique was applied to obtain flow stress for P20 mold steel at hardness of 30 HRC and friction data when using uncoated carbide tooling at high-speed cutting conditions. The average strain, strain-rates and temperatures were computed both in primary (shear plane) and secondary (chip–tool contact) deformation zones. The friction conditions in sticking and sliding regions at the chip–tool interface are estimated using Zorev's stress distribution model. The shear flow stress (kchip) was also determined using computed average strain, strain-rate, and temperatures in secondary deformation zone, while the friction coefficient (μ) was estimated by minimizing the difference between predicted and measured thrust forces. By matching the measured values of the cutting forces with the predicted results from FEM simulations, an expression for workpiece flow stress and the unknown friction parameters at the chip–tool contact were determined. 相似文献
8.
本研究针对镁合金热轧制工艺,通过协调有限元分析结果及物理试验数据,提出一种关于热轧制接触摩擦因子的确定方法,耦合多轧制工艺参数进一步拟合出其求解关系式,工艺参数包括:轧制温度,轧制速度以及压下率。在之前对AZ31B镁合金板材轧制过程轧制力预报模型及温度场数学模型建立研究的基础上,综合考虑接触单位压力及摩擦应力两方面因素的作用,对前期轧制力预报模型进行了优化重构,经确定接触摩擦作用到轧辊的压力约占整体轧制力的4.36%。 相似文献
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In this work, a model for steady-state plane strain cold rolling of a strain hardening material is proposed. The mixed pressure and velocity formulation is used and front and back tensions are included in the model. Roll deformation is taken into account by Hitchcock's formula and the friction model of Wanheim and Bay is used. Comparisons with the experimental results found in the literature are made to evaluate the accuracy of the present model. In the rolling process, material properties and friction coefficients are not known precisely and hence they can be treated as fuzzy numbers. Analysis with the fuzzy parameters is carried out to highlight the usefulness of such an analysis. A method to assess the reliability of a design is also proposed. 相似文献
10.
X. Q. Zhang Y. H. Peng X. Y. Ruan M. Q. Li S. C. Wu 《Journal of Materials Engineering and Performance》2000,9(2):164-169
Workability limits must be considered when designing powder metallurgy (PM) forging processes. This research successfully
applied the general upsetting experiment method to the deformation of porous materials. Based on the plastic theory of porous
materials, the compressible rigid plastic finite element method is used to simulate the deformation processes of cold upsetting
of disks and rings for porous metal materials with a full account of contact friction boundary conditions, the height-to-diameter
ratio, the initial relative density, and the die and workpiece geometry. Furthermore, a successful analysis of the cold forging
process results in the prediction of the stress, the strain, and the density field. By coupling with the ductile fracture
criterion, which is a strain-based criterion obtained by Lee and Kuhn, possible defects leading to material failure have been
checked. This research reveals that larger height to diameter and a lesser friction factor can delay the local strain locus
to intersect with the Lee and Kuhn’s fracture line and restrain formation of the surface crack. Meanwhile, it reveals that
the initial relative density has only a very small influence on the strain to fracture in compression, and it shows the forming
behavior of the ring and disk with the curved die. According to Lee and Kuhn’s results, the calculated results agree well
with the experimental results. 相似文献
11.
NUMERICAL SIMULATION OF ROUND TO OVAL ROLLING PROCESS 总被引:5,自引:0,他引:5
Y. W. Wang Y. L. King D. H. Yuan S. G. Liu Z. Y. Yu ) University of Science Technology Beijing Beijing China ) Daye Special Steel Co. Huangshi China 《金属学报(英文版)》2000,13(2):428-433
1.IntroductionInthebarrollingprocess9ovalpassiswidelyused.Averycomplexthree--dimensionalInaterialflowtakesplaceinthepass.DuetothedifficLiltyofdevelopingtheoreticalanalysisforthree--dimensionalplasticdeformation,mosteffortsmadeonthissubjecthavebeeneitherempiricaloreXPerimental.Recently,withthedevelopmentofcomputers,thefiniteelementmethodhasbeenusedforthree--dimensionalrollingprocesssimulation.aam-etal.,simulatedsingleandmulti--passshaperollingusingfiniteandslabelementmethodll--3].Glowackietal… 相似文献
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Initial surface micro-scratches due to cropping, rolling or handling change that cause crack or lap defects during forging and reduce the quality of forged products. Elimination of surface micro-defects in forging is pressing problem in forging industry. A new method of finite element analysis featuring effective meshing and an adaptive remeshing system is applied to clarify the mechanism of the formation or the disappearance of surface micro-defects in forging. V-shaped and rectangular scratches on the surface of billet are simulated under the axisymmetric assumption and the basic deformation of scratch during upsetting and the influence of friction on the deformation of micro-defects are discussed. Shallow V-shaped scratch on the top surface of billet tends to disappear and deep scratch becomes lap defect during upsetting. Defects are more likely to disappear under low friction. It is possible to predict that an initial surface micro-scratch on the billet remain or not as a defect after forging. 相似文献
13.
Chi Zhang Zhenyu LiuYang Xu Guodong Wang 《Journal of Materials Processing Technology》2012,212(11):2183-2192
During hot rolling of ferritic stainless steels (FSSs), sticking can cause severe surface defects both on work rolls and strips especially for ultra purified FSSs with the total amount of carbon and nitrogen being less than 150 ppm. In the present paper, high temperature oxidization behavior of the ultra purified FSSs was characterized. A new experimental method was invented to simulate the sticking behavior of ultra purified 21%Cr FSS, by which specially designed specimens were hot compressed with different processing parameters to simulate hot strip rolling process. The specimens were surface conditioned prior to the simulation test, either by mechanically polishing or by pre-oxidization to form oxide scales with certain thickness. Observation on the cross-section of sticky regions indicated that cracks had been formed by cyclic heating and cooling during hot deformation had been acting as nucleation sites for sticking particles. The results indicated that oxide scale could avoid the direct contact between roll surfaces and rolled materials to help reducing the sticking occurrence. The temperature region for easy sticking occurrence in the ultra purified 21%Cr FSS has been measured to be from 900 to 1100 °C, which is enlarged as compared to other plain FSSs. The tendency for sticking occurrence decreased with increasing strain rate and decreasing the hammer or work roll surface roughness. 相似文献
14.
Using rigid-plastic finite element DEFORM-2D and -3D software, this study simulates the plastic deformation of metal sheets at the roll gap during the sheet rolling process. The study focuses specifically upon the deformation of porous metal sheets containing internal void defects. The present numerical analysis investigates the relative density distributions, the void closure behavior, the deformation mechanisms and the stress–strain distributions around the internal voids for various rolling conditions. The influences on the dimensions of the final void of the thickness reduction, the initial internal void dimensions, the friction factors and the relative density are systematically discussed. The critical rolling conditions also investigated. A series of sheet rolling experiments are performed in order to verify the validity of the simulation results. The current numerical results provide a valuable source of reference for the design of pass schedules for porous metals undergoing rolling processes. 相似文献
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The hot compression tests of 42CrMo steel were performed in the temperature range of 850–1150 °C at strain rates of 0.01–10 s?1 and deformation degrees of 10–60% on Gleeble-1500 thermo-simulation machine. The optical microstructures in the center region of the section plane were examined. Based on the results from thermo-simulation experiments and metallographic analysis, the dynamic recrystallization mathematical models of 42CrMo steel were derived. The effects of processing parameters, including the strain rate and deformation temperature, on the microstructure evolution of 42CrMo steel hot upsetting process were discussed by integrating the thermo-mechanical coupled finite element method with the derived microstructure evolution models. The fraction of dynamic recrystallization and dynamic recrystallization grain sizes during the hot upsetting process of 42CrMo steel were predicted. The results show that the effects of strain rates and deformation temperatures on the microstructure evolution of 42CrMo steel hot upsetting process are significant, and a good agreement between the predicted and experimental results was obtained, which confirmed that the derived dynamic recrystallization mathematical models can be successfully incorporated into the finite element model to predict the microstructure evolution of hot upsetting process for 42CrMo steel. 相似文献
18.
An experimental investigation on the deformation behavior during wire flat rolling process 总被引:5,自引:0,他引:5
In the present study a laboratory flat rolling machine is utilized to assess the deformation behavior of low and high carbon steel wires in wire flat rolling process. The effects of friction coefficient, rolling reduction and roll speed on rolling force and deformation behavior of the wires are experimentally investigated. It is found that the roll speed affects considerably the rolling force but a negligible effect on deformation behavior. It is noted that by increasing the roll speed, the rolling force may decrease or increase depending on the magnitude of the roll speed. Also, the deformation behavior of the wires in flat rolling is formulated. A relationship is developed for calculating the width of contact area between the wire and rolls as a function of rolling reduction. This relationship depicts that the width of contact area is proportional to square root of rolling reduction. Furthermore, two relationships are derived to predict the spreading of the wires after flat rolling. It is found that the relationships are applicable for both the low and high carbon steel wires. 相似文献
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黄永明 《中国有色金属学会会刊》2008,18(3):665-673
The flow rule of Prandtl-Reuss was adopted and incremental elasto-plastic finite-element analysis formulation of Coulomb's friction law combining the finite deformation theory was established, and Lagrangian formulation for simulating the squaring process of circular tube was updated. Incremental Coulomb's friction law was used in the global stiffness matrix to solve the sliding-sticking state of friction at the boundary contact interface. During the squaring process, the linear factor rmin was adopted to solve the non-linear boundary problems of changing node contact and separation, elasto-plastic transient situation in an element and the non-linear constitutive behavior of material so as to make each reasonable increment of the punch meet the demand of calculation for linear increment. The squaring process of circular tube, load distribution and final shape of work piece after unloading were simulated by this mode and compared with research data. It is known that the circular tube with higher geometrical ratio (R/t) could be pressed into symmetric square tube without collapse. This result can provide reference for the analysis of this process and evaluation and improvement of product defects. 相似文献