冷连轧机带钢表面振纹实测研究

针对某厂2180mm冷连轧机在轧制汽车面板时出现的振纹问题,进行了现场连续综合测试.基于对轧制周期内振动信号的分析、比较,掌握了该轧机的振动特征和振动形态,确定了轧机的起振次序.结合轧机的机械固有特性,找到了导致轧机振动的主要来源,即减速机中齿轮1和齿轮2的啮合冲击,据此提出了振纹的抑制措施.生产实际表明,抑振措施对振动及振纹的消除具有较好效果.     

The theory and development of user-friendly software for the measurement of surface roughness and geometrical parameters

Computers with analytical capabilities have proven their worth in sophisticated gaging applications, but they can intimidate operators. Dedicated keyboards with a logical button-to-button function connection present the user with multiple options. They can be cumbersome and often require adaptation for different parameters or program options. Standard P.C. keyboards do provide more programming flexibility but keys are not easily related to function. This paper discusses the development of a touch screen and related software functions as a dedicated keyboard which presents a very limited number of operating options at any one time. Using simple color graphic icons or “windows”, the described software guides the operator through the measurement process via a logical series of questions and menu operations. The program presents only specific questions or options that are relevant to the current measurement, which provides for a more friendly interface between operator and instrument.     

Cylindrical accuracy control based on stochastic modeling and forecasting compensation

A new compensatory control strategy has been developed for improving the form accuracy in real-time condition. This scheme is based on obtaining an error model of the tool error measured in-process then forecasting the error at the cutting point to compensate for it with the appropriate compensatory action. This approach is a combination of in-process gaging, stochastic modeling based on recursive parameter estimation, forecasting compensation with minimum variance, and real-time compensatory action. In order to demonstrate the feasibility of the proposed approach, a physical compensatory control system has been developed and implemented for the purpose of on-line control of cylindricity in boring operations. Basically, the overall control system involves a closed-loop system and consists of an in-process laser-based cylindricity measurement system, microcomputer and precise piezoelectric actuator systems. The effectiveness of this proposed strategy was confirmed through on-line cutting experiment.     

Calibrated method for ultrasonic on-line monitoring of gradual wear during turning operations

On-line tool condition monitoring is essential for modern machining systems, especially in the case of precision and unmanned machining. Knowledge of the condition and the expected life of the tool are very important inputs for determining the optimal machining parameters. Previous efforts have indicated that ultrasonic gaging methods can be used to directly measure in-process gradual tool wear during turning operations. Good correlation was shown between the level of gradual wear and the ultrasonic signals. However, the correlation was tool dependent. This was mainly attributed to variations in the tool materials and inconsistent coupling of the transducer to the tools. This paper describes a robust method for on-line gradual wear monitoring using normalized ultrasonic signals. A consistent calibration mark, cut in the lower comer of the tool nose, is used to generate a calibration echo. The calibration echo is affected by the same variations as that of the gradual wear and is used to normalize the nose and flank echoes. Experiments under various cutting conditions showed that the gradual wear measurements can be made tool independent by normalizing the measurements with the calibration mark. In addition, the variations in the signals which were previously reported are also eliminated.     

Metrology of freeform shaped parts

The scope of this keynote paper is to present the state of the art in the metrology of freeform shapes with focus on the freeform capabilities of the most important measuring techniques and on related metrological issues. Some examples of products are presented, for which the metrology of freeform shapes is important to guarantee the desired functional performance of the product. A classification of freeform measuring tasks and the corresponding metrological requirements are presented. A review of the most important measuring techniques is presented along with their capabilities for freeform measuring tasks. Specification and verification of freeform surfaces, including data evaluation and comparison to specifications are discussed, along with the measurement uncertainty and traceability of freeform measurements.     

Role of the solid/liquid interface faceting in rapid penetration of a liquid phase along grain boundaries

A model is developed for describing rapid penetration of a liquid phase along a grain boundary. It is based on the assumption of a highly faceted solid/liquid interface. Experiments showing the faceting of the solid/liquid interface in grain boundary penetration experiments are presented. The basic hypothesis of the model are an undersaturated solid and a positive spreading coefficient of the liquid phase along the grain boundary. The model explains the apparent concave shape of the tip of the groove and the reason why penetration also occurs if the liquid phase is pre-saturated with the material of the solid. Moreover it predicts a power law with an exponent close to unity for the time dependence of the depth of penetration of the liquid layer along the grain boundary.     

A molecular dynamics study of self-diffusion in the cores of screw and edge dislocations in aluminum

Self-diffusion along screw and edge dislocations in Al is studied by molecular dynamics simulations. Three types of simulations are performed: with pre-existing vacancies in the dislocation core, with pre-existing interstitials, and without any pre-existing defects (intrinsic diffusion). We find that diffusion along the screw dislocation is dominated by the intrinsic mechanism, whereas diffusion along the edge dislocation is dominated by the vacancy mechanism. Diffusion along the screw dislocation is found to be significantly faster than diffusion along the edge dislocation, and both diffusivities are in reasonable agreement with experimental data. The intrinsic diffusion mechanism can be associated with the formation of dynamic Frenkel pairs, possibly activated by thermal jogs and/or kinks. The simulations show that at high temperatures the dislocation core becomes an effective source/sink of point defects and the effect of pre-existing defects on the core diffusivity diminishes.     

Aligned rrP3HT film: Structural order and transport properties

Aligned regioregular poly(3 hexyl thiophene), rrP3HT, thin films have been fabricated by a rubbing technique. Structural studies indicate orthorhombic crystalline domains (CDs) with c-axis aligned principally along the rubbing direction. The backbones of the macromolecules are stacked along the b-axis, forming a plane of parallel backbones with π-electron overlap and with side chains between the planes (along the a-axis). There is no π-overlap between these planes due to the long side chains along the a-axis. The optical and electronic properties are correlated with the anisotropic structure. Both for light polarized parallel and for light polarized perpendicular to the chain direction, the onset of photocurrent coincides with the onset of absorption. The larger photoconductivity observed with light polarized along the c-axis suggests the films are of sufficiently high quality to reveal the intrinsic anisotropy of the electronic structure.     

Effects of grain-shape anisotropy and texture on balanced-biaxial creep of Ti and Zr alloys

Biaxial creep behaviors of stress-relieved and recrystallized thin-walled tubing of Ti-3Al-2.5V and Zircaloy-4 are considered under equal hoop and axial stresses by internal pressurization superimposed with axial load. Both hoop and axial strains were monitored and the ratio of the strain rate along the hoop to that along the axial directions is considered to represent the degree of anisotropy. In both of these alloys, relatively weak hoop direction in cold-worked stress-relieved (CWSR) materials became slightly stronger following recrystallization. Crystallographic texture was considered in terms of x-ray pole figures from which the crystallite orientation distribution functions (CODFs) were derived and crystal plasticity model with slip dominant on prism planes was combined with the CODFs to predict the creep anisotropy. While good correlation was noted for recrystallized materials, distinct deviations are observed for CWSR that are believed to arise from grain shape anisotropy. The relatively small (equiaxed) grain size along the hoop and radial directions results in grain boundary sliding leading to stress enhancements along these directions. This anisotropy in grain boundary sliding is shown to explain the observed deviations.     

Burrs—Analysis, control and removal

Increasing demands on function and performance call for burr-free workpiece edges after machining. Since deburring is a costly and non-value-added operation, the understanding and control of burr formation is a research topic with high relevance to industrial applications. Following a review of burr classifications along with the corresponding measurement technologies, burr formation mechanisms in machining are described. Deburring and burr control are two possible ways to deal with burrs. For both, an insight into current research results are presented. Finally, a number of case studies on burr formation, control and deburring along with their economic implications are presented.     

基于VPSC仿真的ZK60镁合金拉伸变形行为

通过实验和粘塑性自洽（VPSC）模型,研究了在室温下挤压态ZK60镁合金沿不同方向拉伸时的变形机制开动情况,及其与流动曲线、织构演变和显微组织的对应关系。通过调节VPSC模型的参数,建立了滑移和孪生耦合的晶体塑性力学模型。比较了不同方向拉伸过程中织构演变的差异,分析了变形机制对屈服不对称性的影响。实验和模拟结果表明：当沿垂直于挤压方向（PED）拉伸时,由于｛102｝孪晶开动,大部分晶粒发生大角度旋转（约90°）。柱面<a>滑移是导致ZK60合金沿不同方向拉伸时出现明显屈服不对称的主要变形机理。当ZK60合金沿挤压方向（ED）拉伸时,由于晶粒的择优取向分布,｛101｝孪晶难以开动,导致ZK60挤压态镁合金拉伸屈服强度较高。ZK60镁合金沿着与ED成45°的方向拉伸时,屈服应力高于沿PED拉伸,但随着拉应力逐渐增大,由于沿PED拉伸时柱面<a>滑移逐渐开动,沿PED应变后期的应力曲线逐渐高于沿与ED成45°方向应变的应力曲线。     

Feed optimization for five-axis CNC machine tools with drive constraints

Real time control of five-axis machine tools requires smooth generation of feed, acceleration and jerk in CNC systems without violating the physical limits of the drives. This paper presents a feed scheduling algorithm for CNC systems to minimize the machining time for five-axis contour machining of sculptured surfaces. The variation of the feed along the five-axis tool-path is expressed in a cubic B-spline form. The velocity, acceleration and jerk limits of the five axes are considered in finding the most optimal feed along the tool-path in order to ensure smooth and linear operation of the servo drives with minimal tracking error. The time optimal feed motion is obtained by iteratively modulating the feed control points of the B-spline to maximize the feed along the tool-path without violating the programmed feed and the drives’ physical limits. Long tool-paths are handled efficiently by applying a moving window technique. The improvement in the productivity and linear operation of the five drives is demonstrated with five-axis simulations and experiments on a CNC machine tool.     

磁力金属带传动压轴力的理论分析

对磁力金属带传动压轴力的基本公式及其影响因素进行了分析 ,并对压轴力随这些影响因素而变化的规律进行了数值模拟 ,从而可为传动轴及轴承的设计计算提供理论依据     

近全层组织γ-TiAl基合金的室温拉伸断裂机理

通过对直缺口近全层组织的扫描电镜原位拉伸实验以及相应的断裂表面观察，结合有限元计算了TiAl基合金近全层组织拉伸的断裂机理。研究表明：许多裂纹在塑性变形前沿着层间起裂和扩展，断裂过程的驱动力是拉应力。在直缺口试样中，许多裂纹直接起裂于缺口根部，并且沿着层间扩展。随着拉应力的增加，主裂纹和新裂纹也可以通过障碍晶粒的穿层解理断裂来连接。通过有限元计算得沿层断裂强度大约为50MPa，穿层断裂强度大约为120MPa。     

固溶温度对FGH95镍基合金持久断裂机制的影响

通过对不同温度固溶处理的FGH95合金进行组织形貌观察及持久性能测试,研究了组织结构对合金持久性能及其断裂机制的影响。结果表明:经1150℃固溶和时效处理后,合金中有粗大γ′相在较宽的边界区域不连续分布,其周围存在γ′相贫化区;经1160℃固溶及时效处理后,合金中粗大γ′相完全溶解,在晶内弥散分布高体积分数的γ′相,并有粒状(Nb,Ti)C碳化物在晶内及沿晶界不连续析出;经1165℃固溶和时效后,合金的晶粒尺寸明显长大,并有硬而脆的碳化物膜沿晶界连续析出。在650℃/1034MPa条件下,经1160℃固溶和时效的合金,由于在晶界处不连续析出的粒状碳化物对晶界具有钉扎作用,可有效阻碍晶界滑移,使合金具有较好的抗蠕变性能。合金蠕变后期的变形特征是晶内发生单取向和双取向滑移,随着蠕变进行,滑移迹线增多,并在晶界处引起应力集中,致使裂纹在晶界处萌生及扩展并最终导致断裂。     

Cascade of Peritectic Reactions in the B-Fe-U System

The solidification paths for UFeB₄, UFe₃B₂ and UFe₄B, ternary compounds, situated along the U:(Fe,B) = 1:5 line in the B-Fe-U phase diagram, are proposed based on x-ray powder diffraction measurements, differential thermal analysis, heating curves and scanning electron microscopy observations complemented with energy and wavelength dispersive x-ray spectroscopies. The compounds melt incongruently and are formed by peritectic reactions. The present work demonstrates the existence of a cascade of peritectic reactions along the U:(Fe,B) = 1:5 composition line, establishes peritectic temperatures and proposes an isopleth diagram along this line.     

无铰式斜轴泵的振动特性及减振

对无铰式斜轴泵缸体的振动特性和产生机理进行了分析研究。指出：泵在运转时,其缸体产生扭转振动,振幅随主轴盘转速改变而变化,随摆角增加而增加。扭振是因柱塞连杆对缸体的不均匀驱动而产生,受偏斜力矩的激励而加强,并引发共振。扭振会破坏泵的工作性能,降低其使用可靠性。探讨了可能的减振措施,并介绍了取得良好减振效果的干摩 察阻尼减振器的结构原理和设计要点。     

扫描方式对激光立体成形GH4169合金高温力学性能和热疲劳性能的影响

扫描方式是激光立体成形的一个重要工艺参数,选择3种不同的扫描方式对GH4169高温合金进行激光立体成形试验,并进行了500℃高温力学试验和1000次25~500℃冷热循环的热疲劳试验。结果表明:与沿长边平行往复扫描相比,长短边交替平行往复扫描时合金的抗拉强度和屈服强度分别增大了82和79 MPa,断后伸长率基本不变,热疲劳裂纹级别从7级变为2级。沿短边平行往复扫描时,合金力学性能和热疲劳性能介于沿长边平行往复扫描和长短边交替平行往复扫描之间。扫描方式优选为:长短边交替平行往复扫描。     

奥氏体不锈钢-铜钎料钎焊界面反应行为分析

针对电弧钎焊奥氏体不锈钢时,易产生裂纹的问题,采用316LN不锈钢母材和多种铜基钎料,研究了电弧钎焊、炉中钎焊和真空钎焊316LN不锈钢和铜基钎料时的界面反应行为.结果表明,电弧钎焊条件下钎料对母材的润湿性随着电流的加大而提高,钎料沿母材晶界的扩散不明显,在电流较高时母材局部熔化,且易形成沿晶界裂纹.炉中钎焊过程中钎料沿母材晶界扩散明显,但不易形成裂纹;真空钎焊过程中钎料沿母材晶界扩散显著,形成较厚的界面层,但无裂纹出现.较大的焊接热应力以及钎料沿母材晶界扩散造成的晶界弱化是形成界面裂纹的必要条件.     

CRYSTAL STRUCTURE AND MICROSTRUCTURE OF RAPIDLY SOLIDIFIED La(Ni, Sn)（5+x）(x=0.1---0.4) HYDROGEN STORAGE ALLOYS

采用常规熔铸和单辊快凝制备了CaCu5型贮氢合金La(Ni,Sn)5 x(x=0．1—0．4),用X射线衍射及扫描电镜分析了合金显微形貌、纳米晶粒和晶体结构的特征及相互间关系．XRD Rietveld分析表明,常规熔铸方法制备的La-Ni-Sn三元合金含有数量较多的沿C轴定向排列的Ni-Ni“哑铃”对,其纳米级晶粒呈扁平状,电镜观察显示该合金具有粗大的树枝状形貌,除La-Ni-Sn三元合金外,在熔铸合金中尚有一定量的LaNi5合金和单质Sn存在．单辊快凝制备的合金随着冷凝速度的加快,合金的纳米级晶粒沿(001)晶面法线方向明显变长,但沿(100)晶面法线方向的尺寸长大较慢,在高快凝速率下(10,15,20m／s),合金的显微形貌由细小的柱状与等轴状晶块组合而成．