程序化计算端面移动量在多楔模具参数化设计上的应用

精确地计算出楔横轧轧制过程中轧件端面移动量 ,对于楔横轧多楔模具设计合理确定楔与楔之间的相对位置起着至关重要的作用。在综合楔横轧轧制过程不同阶段端面移动量计算规律的基础上 ,开发并编制出楔横轧端面移动量计算机源程序 ,并应用于楔横轧多楔模具参数化设计。通过实际轧制实验证明 ,该程序计算结果正确、计算效率高 ,为楔横轧多楔模具参数化设计提供了良好的前处理通用程序     

楔横轧多楔轧制展宽段应力与应变有限元分析

楔横轧多楔轧制是主楔和侧楔同时对轧件进行径向压下、横向扩展并轴向延伸的塑性成形。多楔轧制与单楔轧制相比 ,其成形过程中应力场、应变场变化规律更加复杂。针对楔横轧多楔轧制特点 ,在LS/DYNA有限元软件基础上进行二次开发 ,成功地仿真了楔横轧多楔轧制过程 ,并对其展宽段的应力、应变场变化规律进行详细分析 ,得到了在料既不堵又不拉情况下多楔轧制应力比单楔轧制应力变化时间长、变化幅度大的结论     

楔横轧技术用于铝合金加工的研究

对楔横轧技术进行了简单介绍，重点介绍了铝合金在楔横轧加工的材料流动和应力应变场分布，内部损伤量随模具工艺参数变化的规律；提出了铝合金在楔横轧加工方面发展的新方向。     

工艺参数对楔横轧特大型轧件内部应力影响分析

楔横轧成形特大型轧件为复杂的三维变形，其内部应力变化规律复杂，至今缺乏深入研究与本质理解，严重影响楔横轧的应用与发展。采用有限元先进数值方法模拟楔横轧特大型轧件成形过程，详细分析成形过程中轧件内部中心点的应力变化规律，阐明成形角、展宽角和断面收缩率三个主要工艺参数对特大型轧件内部应力的影响关系，为合理选取楔横轧特大型轧件模具工艺参数、开发设计特大型楔横轧机提供重要的理论依据。     

板式楔横轧轧件成形过程几何模拟

在对板式楔横轧轧制过程分析的基础上,建立了楔横轧入轧制和展宽轧制过程轧件变形的数学模型。探讨了轧制过程中轧件滚动半径的确定方法,对轧件端面移动理论进行了研究,建立了轧件端面移动数学模型。最后利用计算机画技术,交 轧制过程中轧件成形过程进行了模拟,实现了模拟轧制。     

基于特征的楔横轧模具CAD/CAPP信息模型

针对楔横轧模具的特点，提出了基于特征的楔横轧模具CAD／CAPP信息模型的建模方法及其结构。     

楔横轧梯形螺纹轴成形机理

通过分析螺纹轴齿形成形过程,并结合金属流动特点,获得楔横轧梯形螺纹轴的成形机理.考虑到轧制过程轧件螺旋升角瞬时变化特点和成形段齿形截面变化等因素设计了楔横轧模具,采用有限元分析软件Deform-3D对楔横轧梯形螺纹轴齿形成形过程进行模拟,得到精度较高的梯形螺纹轴轧件.利用有限元点跟踪功能,对轧件多个点进行跟踪,详细分析了轧件螺纹不同位置各点的径向、轴向位移变化情况,从中获得螺纹段各处金属流动规律.采用软件模拟参数进行了相应的楔横轧实验,得到的梯形螺纹轴实验轧件与有限元模拟结果相同.模拟和实验结果表明,模具螺旋升角采用轧件瞬时半径对应螺旋升角时,能够轧制出形状精确的螺纹轴.      

楔横轧模具脱空对轧制力影响规律研究

减小设备在现有工艺下的受力,是提高轧机轴承等关键零部件寿命和产品质量的有效方法之一。为此,采用有限元法对楔横轧模具在不脱空和脱空情况下进行了轧制过程数值模拟,详细分析了模具脱空对轧制力影响的规律,得到了在一定断面收缩率范围内模具脱空有利于减小轧制力的研究结果,并与测试结果进行比较。研究结果为合理设计楔横轧模具、改善轧机受力状况提供了重要的理论依据。     

楔横轧模具脱空对轧制力影响规律研究

减小设备在现有工艺下的受力,是提高轧机轴承等关键零部件寿命和产品质量的有效方法之一。为此,采用有限元法对楔横轧模具在不脱空和脱空情况下进行了轧制过程数值模拟,详细分析了模具脱空对轧制力影响的规律,得到了在一定断面收缩率范围内模具脱空有利于减小轧制力的研究结果,并与测试结果进行比较。研究结果为合理设计楔横轧模具、改善轧机受力状况提供了重要的理论依据。     

楔横轧特大型轴类件变形特征研究

通过有限元Ansys/Ls-Dyna分析软件,对特大型轴类件和小轴类件分别进行楔横轧数值模拟,分析特大型轴类件的应力应变规律,并与小轴类件比较,阐明楔横轧特大型轴类件变形特征研究,为合理选择模具工艺参数,实现特大型轴类件楔横轧精确成形提供重要的理论依据.     

芯棒直径对楔横轧5Cr21Mn9Ni4 N空心气门壁厚均匀性的影响规律

楔横轧空心轴类件存在壁厚分布不均问题,特别是在小直径大长径比空心件楔横轧成形中更为突出.本文在Gleeble-1500D热模拟实验机上进行了5Cr21Mn9Ni4N耐热钢的热压缩实验,得到了5Cr21Mn9Ni4N的热变形本构方程.通过改变芯棒直径,采用有限元仿真和实验相结合的方法,研究了楔横轧轧制空心气门过程中的壁厚变化规律.研究结果表明,带芯棒轧制时,芯棒直径存在临界值,在该值下进行轧制,空心气门预制坯壁厚均匀性最优;楔横轧空心件时,金属轴向均匀流动是壁厚均匀的必要条件;轧件轴向拉应变减小,径向压应变变大,周向应变在0附近且为拉应变时,壁厚较为均匀.      

Antiproliferative and cytotoxic effects of geldanamycin, cytochalasin E, suramin and thiacetazone in human prostate xenograft tumor histocultures

PURPOSE: We have shown that the three human prostate xenograft tumors, i.e. the androgen-dependent CWR22 tumor, and the androgen-resistant CWR22R and CWR91 tumors, are comparable to patient tumors in their expression of prostate specific antigen, multidrug resistance p-glycoprotein, p53 and Bcl-2 and in their sensitivity to doxorubicin and paclitaxel. The present study used histocultures of these xenograft tumors to evaluate the antiproliferative and cytotoxic effects of several drugs (geldanamycin, cytochalasin E and thiacetazone), which have diverse action mechanisms and have shown activity against primary cultures of human prostate cancer cells. Suramin, a clinically active compound was included for comparison. Methods. The antiproliferative effect of 96 h drug treatment was measured by inhibition of DNA precursor incorporation, and the cytotoxic or cell kill effect was measured by in situ DNA end labeling of apoptotic and necrotic cells and by reduction of live cell density. RESULTS: The rank order of molar potency was geldanamycin > cytochalasin E > suramin > or = thiacetazone. Thiacetazone produced antiproliferation only in CWR22 tumor and had no cytotoxicity, whereas the other three drugs produced both antiproliferation and cytotoxicity in all three tumors. Geldanamycin, but not cytochalasin E and suramin, showed greater antiproliferation and cytotoxicity in tumor cells compared to normal stromal cells. The two androgen-resistant tumors were 4 to >40-fold less sensitive than the androgen-dependent tumor to drug-induced antiproliferation but were about equally or 4 to >20-fold more sensitive to drug-induced cytotoxicity. The ratios of drug concentrations that produced 50% antiproliferation to the concentrations that produced 50% cytotoxicity ranged from <0.04 to 0.3 in CWR22 tumor, but ranged from 0.3 to 2.7 in CWR22R and CWR91 tumors, indicating a shift from antiproliferation as the predominant drug effect in the androgen-dependent tumor to cytotoxicity in the androgen-resistant tumors. CONCLUSIONS: Our results indicate (a) differential drug effects in human prostate xenograft tumors with antiproliferation and cytotoxicity as the predominant drug effect in the androgen-dependent and androgen-resistant tumors, respectively, (b) that progression of tumors from androgen-dependent state to androgen-resistant state appears to be associated with a lower sensitivity to drug-induced antiproliferation and an equal or greater sensitivity to drug-induced cytotoxicity, and (c) that geldanamycin but not thiacetazone warrants further development.     

Different functions for the thyroid hormone receptors TRalpha and TRbeta in the control of thyroid hormone production and post-natal development

Par-4 is a widely expressed protein that sensitizes both prostatic and non-prostatic cells to apoptosis. Constitutive- or regulated- overexpression of Par-4 caused a reduction in the levels of the anti-apoptotic protein Bcl-2. Replenishment of Bcl-2 levels abrogated susceptibility to Par-4-dependent apoptosis, suggesting that Par-4-mediated apoptosis requires downmodulation of Bcl-2 levels. The inverse correlation between Par-4 and Bcl-2 expression was recapitulated in human prostate tumors. Par-4 but not Bcl-2 was detected in the secretory epithelium of benign prostatic tumors and in primary and metastatic prostate cancers that are apt to undergo apoptosis. Moreover, xenografts of human, androgen-dependent CWR22 tumors showed Par-4 but not Bcl-2 expression. By contrast, androgen-independent CWR22R tumors derived from the CWR22 xenografts showed mutually exclusive expression patterns of Par-4 and Bcl-2. These findings suggest a mechanism by which Par-4 may sensitize prostate tumor cells to apoptosis.     

二辊楔横轧轧件的微观组织

 为了研究楔横轧条件下工件的性能,在考虑原始棒料直径、变形温度、断面收缩率以及工件轧后热处理状态等的基础上,利用二辊楔横轧机进行了系列楔横轧轧制实验。对轧后工件进行指定位置线切割取样,并用金相分析法得到变形后工件的高温奥氏体晶粒尺寸分布及低温相组成。实验结果表明：降低轧制温度有利于得到较细小的高温奥氏体晶粒,是一种提高工件综合性能的新工艺。对于直径较细的工件,轧后立即淬火几乎可得到全部马氏体。     

Analysis of Metal Forming in Two-Roll Cross Wedge Rolling Process Using Finite Element Method

A simulation model for two-roll cross wedge rolling (CWR) was presented by using three-dimensional rigid-plastic finite element method (FEM).The whole forming process of CWR,including knifing zone,guiding zone,stretching zone,and sizing zone,was simulated using the model in which dynamic adaptive remeshing technology for tetrahedral solid elements was used to fix element distortion.Based on the simulation results,the distributions of metal flow field,strain field,and damage field,and the geometry of the workpiece's end were analyzed.These results could provide theoretical guidance for realizing net shaping and reasonable design of tools.     

楔横轧内直角小台阶精确轧齐曲线

内直角台阶的轧齐一直是楔横轧的关键技术之一,一般内直角台阶的轧齐曲线公式和算法不适合小台阶的生产应用。为了解决这一问题,通过改进几何模型,针对内直角小台阶的螺旋体体积提出一种新的计算方法。根据楔横轧工艺的特点,比较轧件初始半径与对应辅助圆半径的大小关系,指出了二辊轧齐过程中内直角小台阶的判断条件。根据轧件大端半径与旋转角度的关系,将轧齐过程分成了三个阶段。通过对小台阶螺旋体的分块,将其近似成三个规则体积的组合,推导出了轧齐过程中各个阶段的体积公式。依据体积平衡原理和楔横轧模具特点,得到了二辊楔横轧内直角小台阶随轧件旋转角度变化的轧齐曲线。最后采用刚塑性有限元软件Deform-3D对一定断面收缩率范围内的轴类件进行楔横轧数值模拟,验证了本文所提出的轧齐曲线计算方法的适用性。同时通过对比分析,发现在小断面收缩率轴类件直角台阶成形时展宽角应尽量取小。      

Nonlinear Rail-Structure Interaction Analysis of an Elevated Skewed Steel Guideway

The use of continuous welded rail (CWR) with direct fixation of track on concrete deck is typical of most modern light-rail aerial structures. The interaction between the CWR and the elevated structure takes place through direct-fixation rail fasteners, which have a nonlinear force-displacement relationship. Factors that have significant influence on this interaction include the following: the bearing arrangement at the substructure units, trackwork terminating on the aerial structure, type of deck construction, and type of rail fasteners. To better understand the interaction mechanism, a nonlinear three-dimensional (3D) finite-element analysis of a straight, skewed, elevated steel guideway was carried out using the commercially available software GT STRUDL. The load cases considered in this study are temperature change, temperature change with rail breaking, and train braking. Results are presented in the form of rail axial stresses along the length of the bridge and normal bearing forces at both abutments and at all pier locations. The study shows that nonlinear 3D modeling can give a comprehensive insight into the rail-structure interaction (RSI) forces.     

Cross-Wedge Rolling of Shafts With an Eccentric Step

 A new concept for forming eccentric shafts on the basis of the cross wedge rolling (CWR) process was presented. This concept was based on the application of special guides, which, by acting on a billet, lead to its controlled movement in the vertical direction. This movement made possible eccentric cutting of tools into the billet. FEM calculations and experimental rolling tests clearly confirmed the effectiveness of the proposed forming method.     

楔横轧反楔堆轧改善空心零件过渡轴肩的壁厚减薄

楔横轧随形轧制空心零件在过渡轴肩位置会产生壁厚减薄,降低零件的力学强度,改善轴肩的壁厚状况是必须解决的问题.本文基于有限元模拟方法,揭示空心零件成形时壁厚减薄的产生原因,提出采用楔横轧反楔堆轧改善轴肩壁厚的成形方法,分析反楔堆轧增加轴肩壁厚的主要影响因素,从而获得轴肩壁厚增厚的成形方法和最佳条件,实现了楔横轧随形轧制空心零件轴肩位置的显著增厚.通过轧制试验,验证了有限元模拟分析模型的可靠性.