金属粉末轧制工艺及装置研究

概述金属粉末轧制工艺,分析金属粉末的性能、轧制速度、辊径、辊缝、给料方式等工艺参数对粉末轧制性能的影响。设计一台金属粉末专用轧制试验装置,采用有限元软件对轧制装置进行模态分析和静力分析,计算结果表明,轧制装置工作时的变形趋势小,对轧件精度影响小,装置机械结构满足材料的强度条件和刚度条件要求。     

薄板轧制参数数学模型优化设计

分析了薄板轧制过程中的轧件受力情况,由轧件稳定轧制过程的平衡条件,得到轧制力与张力之间的函数关系,建立了基于稳定轧制过程中的张力的数学模型,运用数学软件Mathematical及Fortran语言编程对轧制张力进行优化设计,通过实例仿真分析,得出了薄板轧制过程合理的张力,为薄板轧制过程及张力的调节提供了理论依据和重要的参数。在生产中应用优化设计结果,确保了稳定的轧制过程,使薄板轧制质量显著提高。该方法还可应用在相似工况的轧件分析及优化设计中。     

无缝钢管连轧机组的自激振动分析

无缝钢管的轧制变形区作为轧制过程的工作界面,其动力学特性对连轧管机的轧制振动有决定性影响.文中分析了动态情况下轧制界面上的界面摩擦、轧制变形参数、轧辊运动等行为机理及其耦合特性,建立了轧制界面的动力学模型.通过模型研究轧制工艺参数与轧制力能参数的关系,分析了连轧管机自激振动发生的原因,并用数值模拟方法分析了不同轧制条件下轧制变形区的工艺参数与连轧管机自激振动的关系,为解释连轧管机的自激振动机理提供了理论基础.     

高颈法兰封闭轧制的数值模拟研究

基于DEFORM有限元软件建立了高颈法兰封闭轧制过程的仿真模型,对整个周期的动态轧制过程进行数值模拟分析,分别分析了驱动辊转速、芯辊进给速度对轧制过程以及轧制力的影响规律,并获得了工艺参数的优化指标。研究结果表明,计算机数值模拟对优化工艺参数、提高轧制效率具有重要的意义。     

张力在轧制过程中对轧制力影响的有限元模拟

轧制张力是冷轧带钢生产过程中非常重要而且必须严格控制的参数,研究轧制张力可以为企业生产实践提供理论依据。采用有限元显式动力学分析软件ANSYS/LS-DYNA建立三维实体模型,并模拟分别改变前张力和后张力板带的轧制过程。通过分析轧制过程中轧制力以及轧制后板形的变化,得出结论:张力的变化可以显著改变轧制压力,后张力对轧制力的影响幅度要大于前张力。     

钎钢轧制过程主要工艺参数对成品质量的影响

利用ANSYS/LS-DYNA有限元分析软件,对钎钢轧制过程进行三维数值模拟,获得了三个主要轧制工艺参数对成品质量的影响规律。以铅管为材料,对钎钢的轧制过程进行了试验研究,分析了轧制工艺参数及管坯尺寸对成品外形的影响,并与数值模拟结果进行了对比,两者吻合较好,从而验证了钎钢轧制过程模拟结果的正确性和可靠性,为确定合理的轧制工艺参数提供了理论依据。     

一种基于数值模拟的金属粉末轧制力能参数计算方法

对金属粉末轧制的成形特点进行分析。基于可压缩连续体力学对金属粉末轧制的有限变形弹塑性本构模型进行推导,并编制了计算模块,利用该模块对铝粉轧制过程进行数值模拟。分析成形区域的特征,结果表明压实区所对应的等效应力、等效应变与相对密度都达到最大值,进入稳定轧制阶段后轧制力趋于平稳。结合对轧制变形的区域划分,根据应力、应变及密度等参数的分布,确定咬入角和中性角的位置。对轧制力和相对密度的实验和模拟结果进行对比分析,表明所提出的理论模型及计算模块稳定可靠。     

环件辗轧过程建模

在论述环件轧制过程与特征的基础上,对热态矩形截面环轧制的数学模型作了初步探讨,分析了液压伺服控制系统与环件轧制的关系。所建立的轧制模型可用于环轧控制系统的设计与轧制规程的优化,对环件轧制预测和实际生产有重要的指导意义。     

高精度扁钢轧制压力分析

在分析了轧机在轧制过程中的力能参数基础上，测量并计算了500mm轧机的轧制力和轧制力矩。探讨了用力学模型确定轧制力的方法。用力学理论计算了轧制力和轧制力矩，并对轧制力和轧制力矩进行了比较分析。结果表明计算结果可以较好地反映实际轧制过程的特征。     

钢坯无头轧制设备与关键技术分析

总结了无头轧制技术的发展情况与技术特点,介绍了无头轧制设备的主要组成部分,详细阐述了各部分的功能与特点,同时分析了闪光焊接的工艺过程,并着重分析了无头轧制关键技术,并对无头轧制技术的优越性与应用前景作了简要分析.     

热轧板坯库出库计划编制模型与算法研究

为了解决板坯库出库计划的编制问题,提出了将板坯库出库计划分解为板坯出库优化决策和板坯最优倒垛决策组合优化问题,分别建立了板坯出库优化决策模型和板坯最优倒垛决策模型,利用两个模型分层协作完成出库计划的编制。为求解模型,构造了一种离散粒子群优化算法,采用适合模型的粒子取值方式和粒子速度变化方式。实际排产的结果表明,所建立的模型和算法切实可行。     

激光二极管阵列侧泵浦Nd:YAG板条热效应的研究

为了解决激光二极管阵列侧面泵浦激光板条引起的热效应问题,对于激光板条温度模式分布进行了研究。通过激光板条工作特点分析,建立了符合实际情况的热模型。基于热传导理论,建构了Poisson方程新的求解方法,得出了侧泵板条温度场与热形变场的一般解析表达式。该解析方法不仅解决了将板条内部热流线径向假设造成的温场计算误差问题,而且解决了数值分析方法带来的计算精度不高的问题。研究结果表明：使用输出功率为30W的激光二极管阵列侧面泵浦Nd:YAG板条,考虑耦合到板条侧面的高斯光斑半径为150μm、板条钕离子掺杂质量分数为1.0at.%,板条泵浦面具有102.3 oC的最高温升,泵浦面与通光端面同时发生1.54μm和2.66μm的最大热形变。并定量研究了激光二极管阵列不同泵浦功率以及不同泵浦光斑下Nd:YAG板条温度场的分布情况。研究结果可以用于侧泵板条激光器谐振腔的设计之中,为减小激光系统的热效应提供了理论依据。     

Optimum residence time for steel productivity and energy saving in a hot rolled reheating furnace

A mathematical model is developed to calculate temperature distribution of a slab in a hot rolled reheating furnace by considering thermal radiation in the furnace and transient conduction in the slab. The furnace is modeled as a radiating medium with spatially varying temperature. Radiative heat flux within the furnace, including the effects of the furnace walls, combustion gases, skid beams, and buttons, is calculated through finite volume method with weighted sum of gray gases model and is applied as the boundary condition in the transient conduction equation of the slab. After validating the predictions of the present models with experimental data, the variations in the heating characteristics of the slab are investigated with residence time in the furnace at two different charging and furnace gas temperatures. The optimum residence time for the slab in the furnace is examined with regard to slab exit temperature, temperature difference between the upper surface and centerline of the slab, and skid mark.     

连铸板坯的粘弹性板模型及鼓肚变形分析

从坯壳材料的粘弹性 (Maxwell模型 )畸变关系和弹性体变关系出发 ,建立了连铸板坯鼓肚变形的粘弹性薄板计算模型。根据弹性—粘弹性的相应原理 ,得到了板坯鼓肚变形的解析解。与宝钢板坯连铸机鼓肚变形的设计公式及现有的其他公式相比 ,该解包含有弹性变形、粘性变形和弹性、粘性的耦合变形 ,能求出在任一时刻板坯内任一点的弯曲变形及鼓肚变形 ,并讨论了材料的松弛时间对板坯鼓肚变形的影响     

Dynamic characteristics and model updating of damaged slab from ambient vibration measurements

This paper reports a field investigation using ambient vibration testing on a damaged floor slab of a reinforced concrete frame building. Due to unexpected heavy rainfall, the hill slope at the rear of building failed triggering a major landslide and causing major damage to the perimeter beams and parts of the slab on the first floor. The modal parameters namely natural frequencies and mode shapes were acquired using output only identification technique and the results obtained from the undamaged and damaged floor slabs were compared. It was observed that there was a 25–53% drop in natural frequencies of the damaged slab compared to the undamaged slab, with a much bigger drop for the lower modes. The irregularities in mode shapes identified correlates with the location of the cracks as revealed from visual examination on the damaged slab. Two finite element models of the slab were created using a finite element software package. The damaged slab was updated manually so as to match the modal parameters obtained experimentally. The results from this study further highlight the possibility and feasibility of using non-destructive vibration testing for condition monitoring of structures over more conventional testing techniques.     

Unsteady state work-roll temperature distribution during continuous hot slab rolling

Predicting temperature distributions in the work-rolls during the hot slab rolling process is of great importance to mill designers. This is because the temperature distribution and the dimensional accuracy of the slab being rolled are both dependent on the work-roll temperature. In addition, the life of the roll is also a function of its own temperature distribution. In this paper, the unsteady state heat transfer equations with time dependent boundary conditions are coupled with a two-dimensional finite element method to predict the work-roll temperature distribution during the continuous hot slab rolling process. To achieve an accurate temperature field, the effects of various factors including the thermal relationships of the work-roll and the metal slab, the idling work-roll revolutions, the rolling speed, the slab/roll interfacial heat transfer coefficient, and the magnitude of the thickness reduction of the slab at each deformation pass are taken into account. Comparisons between the predicted and published experimental results are used to illustrate the validity of the mathematical model.     

Thermal and stress analyses in an end-pumped Nd:YAG slab laser using finite element method

The increasing application on high laser power in industries required studies in the portion of pump radiation absorbed by laser media that exchanges to heat. Heat may cause thermal stress, stress birefringence and thermal lens effects. These effects can destroy the optical properties of the laser medium, decrease the beam quality and may lead to medium break. In this paper, the thermal and stress analyses of continuous and pulsed end-pumped Nd:YAG slab laser are studied using finite element method. Heat deposited in the slab is removed by cooling water, flowing on the largest faces of the slab, which surrounds the active media. The temperature and stress distributions of the end-pumped Nd:YAG slab are defined by coupled field methods in the ANSYS commercial finite element software. The value of maximum temperature and stress in the slab which is affected by an end-pumping are calculated. Finally the maximum pump-power range which can be applied to the slab is determined using the limit of maximum stress in the slab. The analyses are done in from transient to steady-state regimes for continuous pumping. Results show that deposited heat due to the pulsed pumping acts like a mechanical impact.     

连铸板坯倒角结晶器的应用实践

通过对连铸板坯角部横裂纹形成机制分析,提出采用倒角结晶器解决连铸板坯角部横裂纹缺陷问题。倒角结晶器已成功应用于首秦连铸板坯生产,生产钢种的连铸板坯角部横裂纹缺陷明显降低,提高了钢材的成材率。     

基于辛几何法分析连铸板坯的黏弹性鼓肚变形

对板坯连铸机中板坯(坯壳)的鼓肚变形问题,考虑了坯壳在高温下呈现黏弹性性态以及弹性变形与黏性变形的耦合特性,提出了连铸板坯鼓肚变形的四边固支黏弹性矩形板模型。根据Laplace变换和弹性-黏弹性相应原理,导出了黏弹性板柸在拉氏域内的四阶偏微分方程,再将其导入拉氏域内的哈密顿正则方程。对全状态矢量利用分离变量法、本征函数展开法、共轭辛正交归一化关系和Laplace逆变换,得到了四边固支黏弹性矩形坯壳在时域内的挠度解析解。以某板坯连铸机为例,分析了弹性变形、蠕变变形和松弛时间对鼓肚变形的影响,以及坯壳中点的单位长度弯矩随时间的变化情况。     

Mechanical modelling of friction variation in slab edging with a finite element method approach

Friction variation at the interfaces between two vertical rolls and a slab being plastically deformed by the vertical rolls is considered by both theoretical modelling and practical simulation. In this paper, the authors analyzed and simulated the slab edging process, employing the constant friction and friction variation models. Programming was performed on a PC, and the shape of the slab, the roll separating force, the distribution of rolling pressure, strain and strain rate are obtained. Simulation results show that when the friction variation is considered, the computed roll separating force and shape of slab are in good agreement with the experimental values, and the developed numerical model is efficient and stable.