3D coupled thermo-mechanical FE analysis of roll size effects on the radial–axial ring rolling process

Radial–axial ring rolling is an advanced but complicated incremental metal forming technique with multi-factors coupling interactive effects. During the radial–axial ring rolling process, the deformation and thermal behaviors of the ring mainly occur in the roll passes which are constituted by rolls. So, the rolls sizes have enormous influence on the quality of the rolled ring as well as the stability of the process. In this paper, the ranges of rolls sizes and forming parameters are reasonably determined at first, then a 3D elastic–plastic and coupled thermo-mechanical FE model of radial–axial ring rolling is developed using the dynamic explicit code ABAQUS/Explicit, and its reliability is verified theoretically and experimentally. Based on the valid 3D FE model, the size effects of rolls on the radial–axial ring rolling process are investigated. The research results provide valuable guidelines for the design and optimization of the rolls sizes in the actual radial–axial ring rolling production.     

Modeling and experimental validation of the surface residual stresses induced by deep rolling and presetting of a torsion bar

During the production of torsion bars, two different mechanical processes of inducing the residual stresses into the torsion bar are used: the presetting of the torsion bar and the deep rolling of the torsion bar. The process of presetting the torsion bar is carried out by twisting the torsion bar to the desired angle and releasing it to the new residual angle position. With controlled overstraining, favorable residual shear stresses are induced into the torsion bar, so the material is strain hardened and the yield point of the material is shifted and increased in the stress and strain space. The objective of the deep rolling process is to introduce compressive residual stresses into near-surface regions in order to increase the fatigue strength of the torsion bar. These two processes influence each other. The final level of residual stresses depends on the production sequence of these two processes and the production parameters of each process. The correct production sequence of these two operations and distribution of beneficial residual stress was simulated using the finite element (FE) method. To validate this model, the predicted surface residual stresses were compared by the X-ray diffraction (XRD) measurements of residual stresses.     

Influence of the annealing cooling rate on the microstructure evolution and deformation behaviours in the cold ring rolling of medium steel

Pre-heat treatment is a necessary step of cold ring rolling that leads to different microstructure evolution processes and different macroscopic deformation behaviours of rings in the cold ring rolling process. In this paper, the cold ring rolling process of 1045 steel with different annealing cooling rates is studied because the annealing cooling rate is the factor with the greatest influence on the result of the pre-heat treatment. By subjecting 1045 steel to different annealing cooling rates, it is found that, within the experimental range, the grain size of the rings becomes smaller and the lamellar spacing of pearlite decreases as the annealing cooling rate increases, resulting in a stronger and tougher material. The ABAQUS finite element (FE) software was employed to simulate the cold ring rolling process. The simulations indicated that increasing the annealing cooling rate causes the stress in the rolled rings to increase, the strain to decrease and the cementite lamellae to become more fractured.     

FE analysis of coupled thermo-mechanical behaviors in radial–axial rolling of alloy steel large ring

Radial–axial rolling of alloy steel large ring (ASLR) is an advanced plastic forming process with complex coupled thermo-mechanical deformation behaviors which have significant influences on the microstructure and properties of the product. In this paper, the stable forming conditions and ranges of key forming parameters for the radial–axial rolling process of ASLR are determined reasonably. Then a 3D elastic–plastic and coupled thermo-mechanical FE model of radial–axial ring rolling is explored using the dynamic explicit code ABAQUS/Explicit, and its reliability is verified theoretically and experimentally. Using FE simulation and analysis, the effects of key forming parameters on the uniformity of deformation and temperature distribution of ASLR are investigated. The main results show that: (1) The deformation and temperature distribution of the ASLR are nonuniform in radial–axial ring rolling. The PEEQ gradually decreases from the surface region to the central region of the ASLR while the temperature distribution is reverse. The largest PEEQ and smallest temperature appear in the edge region of the ASLR. (2) With increasing the feed speeds of rolls, initial temperature of blank or decreasing the rotation speeds of rolls, the deformation of the ASLR becomes more uniform. (3) With increasing the feed speeds of rolls, rotation speeds of rolls or decreasing the initial temperature of blank, the temperature distribution of the ASLR becomes more homogeneous. (4) The friction coefficient has a slight effect on the uniformity of deformation and temperature distribution of the ASLR. The results provide an important basis for improving the microstructure and forming quality of ASLR through optimization of forming parameters.     

高性能环件辗轧成形智能仿真优化新思路与研究进展

面对环件辗轧成形过程有限元计算效率极低和成形成性难以一体化调控的挑战,提出了环件辗轧智能建模仿真优化的新思路和新方法。该方法能在有限元计算过程中,实现各轧辊运动的实时协调匹配和基于目标驱动的自动调控,只需要一次有限元计算就可直接获得满足控制量(环件长大速度、轧制力、温度、组织性能等)目标要求的环轧工艺路径;简介了超大型铝合金环件(10 m级)双向辗轧智能建模仿真、超大型筒节环件轧制智能建模仿真、基于力控的大型铝合金环件(5 m级)双向辗轧工艺路径智能仿真优化、基于温控的铸坯环件双向辗轧工艺路径智能仿真优化4个方面的最新研究进展。     

基于IITD模糊熵与随机森林的滚动轴承故障诊断方法

针对滚动轴承故障微弱振动信号特征提取后难以识别的问题,提出基于改进的固有时间尺度分解(IITD)和模糊熵(FE)输入随机森林(RF)模式识别的滚动轴承故障诊断方法。首先,利用轴承试验台采集正常、滚动体故障、内圈故障、外圈故障等4种状态下轴承的振动信号;通过IITD分解将采集到的振动信号分解成一组固有旋转分量(PRC),然后选取表征故障主要信息的有效分量计算其模糊熵值并构建特征向量,输入到随机森林分类器模型进行识别分类。实验数据分析结果表明,该方法可以有效地实现滚动轴承故障类别的诊断。     

空调室外机系统的实验模态分析与模型更新

有限元(Finite Element, FE)模型的正确性和可靠性对于确保结构仿真达到其分析目的相当重要。文章介绍了空调室外机(Outdoor Unit of Conditioner, OUC)有限元模型的建模技术与模型更新。建构OUC的有限元模型必须呈现结构的物理特性,包括几何形状、材料性质、接触接口和边界条件等,并施以实验进行验证。一般的方法是对结构进行实验模态分析(Experimental Modal Analysis, EMA)以获得结构模态参数。同时,也可由有限元模型的数值分析求得理论模态参数。模型更新是调整有限元模型参数,使分析模型和实际结构的结构模态特性相符。结果显示,更新后的有限元模型在结构模态和频率域特性上,能充分呈现空调室外机实际结构的振动特性。     

盒形件成形工艺分析

目的分析盒形件的成形规律,解决盒形件的成形问题。方法对毛坯展开料、拉伸次数、压边圈的选用、模具等几个主要参数及拉伸零件所需的冲床规格进行计算,制订加工工艺方案。分析零件在拉伸过程中有可能出现的皱痕、划痕、拉断等问题,从而采取合适的润滑剂。结果以典型盒形件为例,进行试加工,零件尺寸100%合格,零件表面质量良好。结论通过工艺参数计算原则及润滑剂的选用,能够保证盒形件的尺寸精度、表面质量,提高生产效率。该方法对类似零件的工艺计算和分析有一定的参考价值。     

Computational Intelligence-Based Process Optimization for Tandem Cold Rolling

The requirements for the manufacturers of steel have been increased in many respects in recent years. Harsh competition among manufacturers demands a continuous reduction of production costs and improvement of product quality. The work presented herein describes maximizing rolling mill throughput and minimizing processing costs and crop losses by computational intelligence-based process modeling and optimization. In this article, an intelligent searching mechanism is introduced to optimize the rolling schedule by assessing rolling constraints and the combined cost function of tension, shape, and power distribution. The optimization results have been compared with current rolling practices based on empirical models. It is shown that the proposed model can significantly reduce the power distribution cost, maximize the safe level of strip tension, and obtain good strip shape. The proposed model is generic for complex engineering problem optimization, and is capable of multiple-objective problem solving.     

Numerische Berechnung des Verschleißes an der Dornwalze eines Ringwalzprozesses in Abhängigkeit prozessrelevanter Parameter

Ring rolling is a forming process for the production of seamless rings. The process is characterized by a complex interaction of the shaping rollers and the centering rollers. In the design of a ring rolling process, it is necessary that the rolling and pre‐ring geometry strategy, i.e. the speeds and feeds of the individual rollers to align such that the required final shape is achieved optimally. Using the finite element simulation before starting the production optimizations concerning the process can be performed and thereby the number of costly rolling samples be kept to a minimum. The objective of the work focuses on the finite element modeling of a ring rolling process and the numerical calculation of the wear at the mandrel caused of the variation of process‐related parameters.     

Modelling of microstructure evolution during hot rolling of AA5083 using an internal state variable approach integrated into an FE model

Hot rolling, a critical process in the manufacturing of aluminum sheet products, can significantly impact the final properties of the cold rolled sheet. In this research, a mathematical model was developed to predict the through-thickness thermal and deformation history of a sheet undergoing single stand hot rolling using the commercial finite element (FE) package, ABAQUS^™. A physically based internal state variable microstructure model has been incorporated into the FE simulation for an AA5083 aluminum alloy to predict the evolution of the material stored energy and the subsequent recrystallization after deformation is complete. The microstructure predictions were validated against experimental measurements conducted using the Corus pilot scale rolling facility in IJmuiden, the Netherlands for an AA5083 aluminum alloy. The model was able to predict the fraction recrystallized as well as the recrystallized grain size reasonably well under a range of industrially relevant hot deformation conditions. A sensitivity analysis was carried out to determine the influence of changing the material constants in the microstructure model and deformation conditions on the predicted recrystallization behaviour. The analysis showed that the entry temperature was the most sensitive process parameter causing significant changes in the predicted driving force for recrystallization, nucleation density, fraction recrystallized, and recrystallized grain size.     

步长自适应技术在棒线材热连轧过程模拟中的应用

利用数值仿真技术建立平-立轧制三维热力耦合有限元模型,对304不锈钢棒线材热连轧过程粗轧6道次实际工况进行仿真计算.基于刚性体推动模型,采用步长自适应技术根据模型的运算需要选择适合的时间步长.步长自适应技术能够在轧件轧制过程时采用较小的时间步长,在道次间隙时使用较大的时间步长.计算结果表明,采用步长自适应技术所建立的有限元模型可以在保证计算结果精度的前提下,显著地提高运算效率.     

The effect of bulk nucleation parameters on the formation of macroscopic grain of the large-scale titanium slab ingot during EBCHM

The application of single electron beam cold hearth melting (EBCHM) to the production of large-scale rectangular titanium ingots has the potential to produce high-quality titanium strip coils and achieve significant cost reductions. In this study, multi-scale modelling of macroscopic grain formation in large-scale titanium slab ingots during EBCHM was carried out, by combining the finite element (FE) method on the macroscale with a cellular automaton (CA) model on the microscale. The effects of bulk nucleation parameters on the formation of macroscopic grains were studied, and the predictions arising from simulations were compared with experimental results. Based on the nucleation parameters that were investigated, the process parameters could be optimised during EBCHM to achieve a solidification structure favourable for rolling.     

Thermal-stress analysis of RC beams reinforced with GFRP bars

This paper aims to develop a 3D nonlinear finite element (FE) model that is capable of accurately predicting the performance of reinforced concrete (RC) beams reinforced with internal Glass Fiber-Reinforced Polymer (GFRP) bars when exposed to fire loading. The developed FE model is based on tested experimental data collected from the open literature. The model accounts for the variation in the thermal and mechanical constituent materials with temperature associated with the RC beam. To study the heat transfer mechanism and mechanical behavior of the RC beam, transient thermal-stress finite element analysis is performed using the ANSYS. It was shown that the FE predicted temperature and mid-span deflection results are in a good agreement with that of the measured experimental data. The validated FE model is used to conduct a parametric study to investigate the effect of the different parameters on the flexural performance of the reinforced beam specimens. The parametric study consisted of varying the concrete cover thickness as well as exposing the FE model to different fire curves. It is concluded that successful FE modeling of this structure would provide an economical and alternative solution to expensive and time consuming experimental testing. Other observations and recommendations are also discussed.     

TC4合金斜I型截面环件轧制工艺研究

目的 提升钛合金异型环轧制时的填充效果,提高成形精度,确定轧制型腔对环件成形质量的影响。方法 以TC4合金斜I型截面环件为研究对象,设计了开式与闭式2种轧制型腔,对该环件的轧制过程进行了研究。建立了斜I型截面环件的有限元模型,基于有限元模拟结果全面分析了不同轧制型腔对环件等效应变、温度分布以及型腔填充效果的影响规律。结果 与开式型腔相比,闭式型腔轧制的环件具有更优的等效应变和温度分布,型腔填充情况也明显更优,填充率在96%以上,进而确定了闭式型腔的轧制方式。采用设计的闭式型腔进行了环件轧制试验,试验环件尺寸与模拟结果吻合良好,误差在0.3%以内,同时组织性能均能够满足生产要求。结论 选择闭式型腔轧制可以有效提升钛合金异型环轧制时的填充效果,提高成形精度,提升环件成形质量。     

Research on deformation characteristics of JCOE forming in large diameter welding pipe

In the present work, the JCOE forming is investigated using the finite element (FE) method. A twodimensional FE model is established for the plane strain condition by FE code ABAQUS, and the FE model is validated by experiments. The aim of this research is to investigate forming quality states in the JCOE forming process; in particular, the effects of technological parameters on forming quality are evaluated. Taking the JCOE forming process of X80 steel φ1 219 mm×22 mm×12 000 mm welding pipe for instance, the deformation characteristics of JCOE forming are analyzed, in which the geometry of the formed pipe, residual stress distributions and effects of process parameters on JCOE forming quality can be obtained. Thus, the presented results of this research provide an effective approach to improve welding pipe forming quality.     

Role of Friction in Cold Ring Rolling

1. Introduction Cold ring rolling is a main technology used to manu- facture various precise seamless ring shape parts. It has been increasingly used in many industrial fields such as bearing, machine, automobile, petrochemicals, aeronau- tics, astronautics and atomic energy because of its many technical superiorities such as considerable saving in en- ergy and material cost, high quality, high efficiency, and low noise, etc. To research and develop advanced precise cold ring rolling technolog…     

Fastener pull-through in a carbon fibre epoxy composite joint

This paper considers the capability of finite element (FE) modelling to accurately predict fastener pull-through failure of composite laminates. Such failures are dominated by inter-ply delamination and through-thickness shear failure of the laminate and the common modelling approach is to use computationally expensive, detailed three-dimensional models that include delamination for every ply interface, fastener contact and prestress. This paper considers a simplified FE modelling strategy achieved through judicious use of symmetry boundary conditions, hybrid shell/solid modelling and reduced numbers of interfaces for delamination. The LS-DYNA FE software was used for this study using the available composite material and cohesive failure models. The conclusion drawn from this work is that the use of simplified FE models does have merit in modelling fastener pull-through provided the material is quasi-isotropic and the boundary conditions are uniform around a circular perimeter. Additional work is however required to determine suitable cohesive properties and progressive shear failure parameters.     

径-轴双向环轧工艺的研究进展

回顾了环件径-轴双向轧制锻透条件、咬入条件、刚度条件等相关理论研究进展,分析了工艺参数对轧制过程的影响及其确定准则,在此基础上引入轧制曲线的概念,并给出了径-轴双向环轧轧制曲线的设计原则,还探讨了在利用有限元方法模拟轧制过程、优化轧制工艺参数时存在的问题,并给出了对数值模型进行控制和处理的有效方法。     

An experimental and numerical investigation on micro rolling for ultra-thin strip

The demand for miniaturized parts and miniaturized semi-finished products is increasing nowadays, because microforming processes can improve production rate and minimize material waste due to less forming passes. However, traditional macro metal forming processes and modelling cannot be simply scaled down to produce miniaturized micro parts. In this study, a 2-Hi micro rolling mill has been successfully built. Experimental and numerical investigations on the micro rolling process for ultra-thin SUS 304 stainless steel strip have been conducted. The experimental results show that the micro rolling deformation of ultra-thin strip is influenced by size effect which results from the specimen size difference and this size effect is embodied in the flow stress and the friction coefficient. Analytical and finite element (FE) models in describing size effect related phenomena, such as flow stress, friction, rolling force and deformation behaviour, are proposed. The material surface constraint and the material deformation mode are critical in determination of material flow stress curve. The analysis of surface roughness evolution with rolling conditions has also been performed. The identified analysis on deformation mechanics provides a basis for further exploration of the material behaviour in plastic deformation of micro scale and the development of micro scale products via micro rolling.