平行辊矫直机压下量选择及矫直力计算

利用弯曲变形理论对平行辊矫直机压下量和矫直力的计算方法进行了研究,并模拟实际生产情况,进行仿真计算,计算结果接近于生产实际,可用于指导生产实践和设计工作。     

轨梁辊矫过程矫直力波形分析与工程算法

针对辊式矫直机常规理论计算方法的缺陷及矫直力实测中难于直接测量辊系中所有辊子矫直力的困难,通过对国内首台巨型1 300矫直机矫直力的工程测试和上排辊矫直力的波形分析,按压力阶梯（矫直力分量）剖析了矫直力和矫直过程,揭示了超静定矫直力系的建立过程和各辊矫直力之间的力学关系,拟定了矫直力系和矫直力分量的分割单元测量原理和总体便捷的工程测试方法,给出了以矫直力矩和压力阶梯表示的矫直力通式及其工程算法,并提供了计算工-56及轨-50矫直力的诺模图。这种确定矫直力的原理和方法,可供各种重型辊式矫直机工程应用。     

双金属复合板材辊式矫直的数值模型

将弯曲分层矫直数值计算和实验验证相结合,研究了双金属复合板材辊式矫直过程中的连续弯曲变形和力能参数。结果表明,使用弯曲分层矫直计算模型是计算双金属复合板材矫直过程的有效方法,分层算法的结果与实验数据有较好的一致性;双金属复合板材弯曲应变的中性层与几何中间层产生偏离,中性层位置随弯曲程度和材料比例而变化;同时,由于材料的力学性能不同,在同一弯曲单元内各组元材料的塑性层比例也不同;计算模型所给出的在双金属复合板材矫直过程中应力应变的演化,与单一材料有明显的不同;在不考虑原始曲率的前提下,矫后残余应力随着弯曲单元的增加而减小。     

一种新型双金属复合板弯曲矫直模型

因为传统的连续弯曲辊式矫直理论创建在单一金属反复连续弯曲变形的基础上,所以将该理论应用于双金属复合板连续弯曲矫直时,精度不高且无法保证双金属复合板的矫后平直度。为完善板材矫直力论,分析了双金属复合板矫直弯曲变形时的特点,提出了分层算法,并将模型计算数据与矫直实验数据进行了对比。结果表明:提出的方法可以在不同金属变形层上采用不同的计算方法和材料模型,比较适应于求解双金属复合板的辊式矫直问题;模型计算矫直力误差不大于5.73%。所得结论表明基于分层算法的数学模型在计算双金属复合板时具有良好的效果。      

针对大型型钢矫直压下的研究

通过对大型型钢矫直机压下量的计算,研究分析大型型钢矫直方案及压下规程。运用大变形矫直方案与小变形矫直方案的分析对比,得出了小变形矫直方案具有矫直轧件时消耗能量小以及作用轧件的总变形曲率较小的优点;大变形矫直方案具有使用较少的矫直辊却可达到较好矫直效果的特点。综合两种矫直方案的优点,制定出最佳的矫直规程。     

受压圆形层合板层间剥离的计算模拟

本文运用弹塑性有限变形理论讨论了受压层合圆板层间剥离的扩展。初始缺陷的层间裂纹有一段稳定期,当压缩量超过临界值后,裂纹首先在缺陷层内迅速扩展并很快涉及邻近的各层。文中给出了裂纹扩展情况及应力分布的有限元模拟结果。将剥离后的基体层用小模量的弹性体替代,可避免确定剥离面分离或接触的难点,使计算大为简化。     

一种轴类弯曲件矫直方法的研究与应用

航天产品中轴类工件因加工精度高、加工费用高,容易弯曲变形而成为机加行业中的一个难题。特别是一些粗长轴因某些原因而造成弯曲,处理起来十分困难。因次,研究如何采用有效方法矫直弯曲件有着十分重要的意义,本文通过研究与实际操作,得出了一种既经济又实惠的矫直方法——局部加热法,为一些粗长轴类弯曲件的矫直提供了依据。     

管材弯曲中应力中性层位移计算与影响因素分析

为研究管材弯曲成形过程中应力中性层位移及影响因素,基于塑性力学全量理论,分析了管材弯曲的应力应变规律,在考虑材料硬化特性和壁厚变化的情况下推导出应力中性层位移的近似计算公式,并利用正交设计法对应力中性层位移的影响因素进行了敏感性分析,认为相对弯曲半径和硬化指数是影响应力中性层位移最敏感的因素,其它参数无显著影响.通过与数值模拟结果对比,证明了理论分析的正确性和有效性.     

TC21钛合金热变形过程中片层α相动态球化行为研究

目的 定量分析不同热变形参数下片层α相的演化行为,探究不同热变形参数对TC21钛合金中片层α相动态球化行为的影响规律,并探讨片层α相在动态球化过程中的组织演变机理。方法 基于Thermecmastor-z热模拟试验机对TC21钛合金开展不同变形参数的热压缩试验,结合SEM-EBSD材料表征技术进行显微组织的表征。结果 随着温度从890℃升高至950℃,片层α相的平均厚度从0.65μm先增大至0.72μm后减小至0.16μm;在高温、低应变速率的条件下,片层α相球化百分数约为59%,而在低温、高应变速率条件下,片层α相球化百分数降至约26%;随着应变速率由0.001 s^-1升至1 s^-1,片层α相球化百分数的增量由10%减少至不足2%。结论 温度的高低主导了片层α相尺寸的变化趋势;变形温度的升高及应变速率的降低加速了片层α相的球化进程,而应变速率为主要影响因素;在α+β两相区变形过程中,LAGBs常形成于片层α相内部位错塞积程度较高的区域,并以此作为发生动态球化的界面。随着动态球化百分数的增大,α相中LAGBs的体积分数减小,而HAGBs的体积...     

金相样品制备过程中变形层的成因分析及对策

制备金相样品是金相检验中的必要步骤 ,而样品制备的质量受人为因素影响较大 ,在样品的切割、磨光和抛光过程中 ,若操作不当 ,极易使样品表面产生变形或使磨面产生变形层而影响检验效果。虽然在机械磨抛过程中产生变形层是不可避免的 ,但如果注意方法 ,可以将变形层的产生减至最小程度 ,便于在以后的侵蚀过程中完全去除掉 ,获得一个平整、真实的金相样品 ,提高制样的一次成功率。本文结合多年的制样经验 ,分析总结出磨抛过程中试样磨面产生变形层的原因及解决方法。1　磨制过程中变形层的产生与消除方法1 .1　接触压力在试样的磨制过程中 ,…     

Customized step coverage of copper seed layer using Eni-PVD (energetic neutral and ion physical vapor deposition)

PVD has usually poor step coverage control for high aspect ratio structures due to its high sticking coefficient and line of sight deposition characteristics. This study presents a novel PVD system, Eni-PVD, reporting customized step coverage with minimal overhang for copper seed layer. Energetic neutrals and ions controlled independently appear to have different angular flux distribution and show customized step coverage with proper mix. The technology can be effective to reduce RC delay through higher aspect ratio interconnect. It is capable of the Cu seed layer and barrier sputter deposition for 45 nm and beyond based on its critical minimum sidewall barrier/cladding thickness assessment. It can also be applied to other PVD areas where fine topography control is required.     

射频溅射ZnO作为GaN厚膜生长缓冲层的工艺研究

采用射频磁控溅射法制备出了适用于HVPE-GaN厚膜生长的ZnO缓冲层,利用X射线衍射(XRD)和原子力显微镜(AFM)和光致发光(PL)等分析方法表征了ZnO缓冲层以及HVPE-GaN厚膜的晶体性能。实验结果表明,采用溅射功率为60W、氩气压强为2.0Pa、蓝宝石衬底为室温条件下的溅射工艺获得了(0002)单一取向、晶界清晰、晶粒尺寸均一的ZnO薄膜,以它为缓冲层获得的GaN厚膜XRD的(0002)衍射峰半高宽(FWHM)为265secarc,室温PL谱未见明显黄光发射带。     

On the effective constitutive properties of a thin adhesive layer loaded in peel

An experimental method to determine the complete stress-elongation relation for a structural adhesive loaded in peel is presented. Experiments are performed on the double cantilever beam specimen, which facilitates a more stable experimental set-up as compared with conventional methods like the butt-joint test. The method is based on the concept of equilibrium of the energetic forces acting on the specimen. Two sources of energetic forces are identified: the start of the adhesive layer and the positions of the two acting loads. By use of the concept of equilibrium of energetic forces, it is possible to measure the energy release rate of the adhesive layer instantaneously during an experiment. The complete stress-elongation relation is found to be the derivative of the energy release rate with respect to the elongation of the adhesive layer at its start. By this procedure, an effective property of the adhesive layer is measured. That is, the fields are assumed to be constant through the thickness of the layer and only vary along the layer. To investigate the validity of this approach, experiments are performed on five different groups of specimens with different dimensions. This leads to large variations in the length of the damage zone at the start of the adhesive layer. Four of the experimental groups are used to determine the stress-elongation relation. This is found to be independent of the geometry. For the remaining experimental group, the adherends deform plastically and simulations are performed with the stress-elongation relation determined from the four elastic groups. It is found that the relation cannot be used to accurately predict the behaviour of the experiments where the adherends deform plastically. This indicates that the stress-elongation relation has limited applicability.     

Numerical analysis of AC tungsten inert gas welding of aluminum plate in consideration of oxide layer cleaning

A unified numerical simulation model of AC TIG welding of the aluminum plate considering energy balance among the electrode, the arc and the base metal and employing an analytical model for calculating cleaning rate of the oxide layer has been developed for investigating heat transport properties and weld pool formation process in AC TIG welding of aluminum plate. As a result of this simulation, it was shown that although the heat flux from the arc onto the base metal increases in EN (Electrode Negative) phase due to the electron condensation, that in EP (Electrode Positive) phase conversely decreases because mainly of cooling caused by the electron emission. Furthermore, the validity of the simulation model was confirmed by comparing to experimental results such as the arc voltage, the area of cleaning zone and the shape of weld pool.     

气球快速泄气过程动态面形测量方法

提出一种气球快速泄气过程中动态三维面形的测量方法。用正弦光栅投影到处于快速泄气 过程中的气球表面,使用高帧频CCD获取随时间变化的一系列变形条纹,再采用傅里叶变换轮廓术的方法进行处理,能再现气球快速泄气的整个变化过程。该方法为诸如爆轰、膨胀和萎缩等相关领域的动态过程的研究提供了一种新的方法。     

The role of trimethylgallium flow during nucleation layer deposition in the optimization of epitaxial GaN films

The effects of the trimethylgallium flow (14–55 μmol/min) during the deposition of the GaN nucleation layer on the structure and electronic properties of GaN epilayers were examined. X-ray and mobility studies indicate that GaN epilayers, grown using non-optimal trimethylgallium (TMG) flow, result in wide FWHM peak and low electron mobility. On the contrary, an optimal TMG flow during the nucleation layer growth leads to films with superior structural and electronic properties. Atomic force microscopy (AFM) was used to systematically investigate the morphological evolution of as-grown nucleation layers, and the nucleation layers were heated to 1000°C under different TMG flows.     

Numerical evaluation of inhomogeneity forces in a coating layer due to thermal loading

Abstract

In order to clarify the mechanical state at the interface between substrate and coating material, numerical analyses are implemented on model materials under thermal loads, and the possibilities of debonding are discussed from the configurational mechanics concept. The intensity of the interfacial singularity can be discussed in relation to the inhomogeneity force which is numerically evaluated in the course of thermal loading via finite element analysis. It is shown that interfacial roughness, a small perturbation at the interface, may have a dominant role in the evolution of inhomogeneity. Effects of initial defects, temperature gradient and additional external load are also evaluated. It is confirmed that the inhomogeneity force is a generalisation of the J-integral, i.e. the energy release rate in fracture mechanics, and this is also applicable to interfacial problems. A possible scenario of layer debonding is discussed in terms of the material inhomogeneity and the deformation characteristics of the thin coating layer under thermal loading.     

Dynamic observation of dislocation-free deformation process in Al, Cu, and Ni thin foils

Dislocation-free plastic deformation, which occurs under extraordinarily high internal stress comparable to ideal strength of metals, was discovered in thin foil portion produced by ductile fracture of fcc Au by dynamic observation of the deformation process [1, 2, 3, 4 and 5]. In the present study, the deformation process of thin foil portion in other fcc metals (Al, Cu, Ni) was examined in the same manner. In all these fcc metals, production of vacancy-type point defect clusters was confirmed during deformation without dislocations. Also, the dislocation-free deformation was found to progress under extraordinarily high internal stress levels corresponding to 14% elastic deformation in Ni, 12% in Cu, and 4% in Al. Especially in Al, as temperature decreased, the number density of stacking fault tetrahedra produced during deformation increased, along with increasing of the detected elastic deformation. These results indicate that internal stress level is a key factor in generalizing the new theory regarding dislocation-free plastic deformation.