Adiabatic shear band localization of inelastic single crystals in symmetric double-slip process

Summary The main objective of the present paper is the development of a viscoplastic regularization procedure valid for an adiabatic dynamic process for multi-slips of single crystals. The next objective is to focus attention on the investigation of instability criteria, and particularly on shear band localization conditions.To achieve this aim, an analysis of acceleration waves is given, and advantage is taken of the notion of the instantaneous adiabatic acoustic tensor. If zero is an eigenvalue of the acoustic tensor, then the associated discontinuity does not propagate, and one speaks of a stationary discontinuity. This situation is referred to as the strain localization condition, and corresponds to a loss of hyperbolicity of the dynamical equations. It has been proved that for an, adiabatic process of rate-dependent (elastic-viscoplastic) crystal, the wave speed of discontinuity surface always remains real and different from zero. It means that for this case the initial-value problem is well-posed. However, for an adiabatic process of rate-independent(elastic-plastic) crystal, the wave speed of discontinuity surface can be equal zero. Then the necessary condition for a localized plastic deformation along the shear band to be formed is as follows: the determinant of the instantaneous adiabatic acoustic tensor is equal to zero. This condition for localization is equivalent to that obtained by using the standard bifurcation method. Based on this idea, the conditions for adiabatic shear band localization of plastic deformation have been investigated for single crystals. Particular attention has been focused on the discussion of the influence of thermal expansion, thermal plastic, softening and spatial covariance effects on shear band localization criteria for a planar model of an f.c.c. crystal undergoing symmetric primary-conjugate double slip. The results obtained have been compared with available experimental observations.Finally, it is noteworthy that the viscoplasticity regularization procedure can be used in the developing of an unconditionally stable numerical integration algorithm for simulation of adiabatic inelastic flow processes in ductile single crystals, cf. [21].The paper has been prepared within research programme sponsored by the Committee of Scientific Research under Grant 3 P404 031 07.     

连铸结晶器内部流场及熔渣卷入的数值模拟

针对连铸结晶器内部流场及熔渣卷入过程 ,提出了两方程k -ε湍流模型和充填法数值计算模型 ,并采用硅油 /水模拟体系代替熔渣 /钢液体系 ,进行了模拟试验和数值计算。对充气造成的浸入式水口水流脉动的影响进行分析。计算结果与试验结果符合良好 ,表明本文所采用的数值模拟方法是适用的     

作动器参数对结构性能的影响和调整受力状态的实施策略模拟

基于规划法研究了作动器各参数对自适应超静定桁架性能的影响。该规划法能够使结构工作状态更合理化。这一方法能够改善自适应结构的工作状态因而提高承载能力。以此为基础，研究了具有作动器的组合杆的有关参数诸如变形上限、刚度和承载力上限对于控制效果的影响。从而为作动器的合理选择提供了理论根据。对于调整作动器变形以控制结构强度的实施策略进行了模拟和分析。该策略包括3部分：1．模拟和分析了“加载、调控、卸载”重复循环直至调控的完成；2．不同作动器按比例同时放大变形直到调控实现；3．多次加载、调控同一次加载、调控结构的等价性。研究表明本文提出的使结构工作状态合理化的调控过程是安全、可靠和灵活的。     

Order and Pattern Formation in Psychotherapy

In an empirical analysis of the dynamics of psychotherapy processes, concepts and tools from self-organization theory are applied. Our focus is on pattern formation in the therapy system, i.e. the system constituted by the interaction dynamics of therapist and patient. The hypothesis of pattern formation explored is based on data sets of 28 psychotherapy courses (10 behavioral, 3 client-centered, 9 heuristic, 6 schema-oriented; 40 to 90 weekly sessions). Patients' and therapists' therapy session records are analyzed (33 variables addressing various aspects of the therapeutic relationship, of progress within and outside the therapy setting). Multivariate methods are implemented to test the key hypothesis of self-organization theory, namely the reduction of degrees of freedom of a system. Consistent with this hypothesis, a significant reduction of degrees of freedom is found when the initial and final sessions of the therapies are compared. Correspondingly, Landsberg order increased significantly in the course of therapies. Given these findings, the explorative question of how this self-organizing property relates to therapy outcome is investigated. We find a significant positive association with various outcome measures, such as: therapist's and client's evaluations of success (direct change measures), feelings of guilt, anxiety, social potence, depression (pre-post effect sizes), and others. These results suggest that order is related to therapy outcome. In our interpretation, order is a dynamical attribute of the therapeutic alliance to be considered as a promising therapy process variable.     

单轴条件下砂岩三维破裂过程的CT观测

岩石破裂过程研究一直是岩石力学专家关注的重要问题。本文采用特制的三轴压力仪与医用西门子SOMATOM -plusCT扫描仪结合 ,对砂岩进行了室内单轴压缩试验。通过对砂岩的CT图像和密度损伤增量与应力关系曲线分析 ,结果显示 ,砂岩的破裂演化过程可分为初始损伤的压密、裂纹出现—扩展、裂纹归并—分岔、裂纹重分岔—扩展以及裂纹惯通—宏观破坏等五个阶段。在初始损伤的压密阶段 ,砂岩的密度损伤增量为正值 ,速率也为正 ;在裂纹出现—扩展阶段 ,砂岩出现局部密度损伤增量减小 ,并随应力增加而由正值转为负值 ,速率也由正变负 ;在裂纹归并—分岔阶段 ,砂岩的密度损伤增量全为负值 ,速率也变快 ;在裂纹重分岔—扩展阶段 ,砂岩的密度损伤增量继续变负 ,但速率变慢 ;在裂纹惯通—宏观破坏阶段 ,砂岩的密度损伤增量继续变负 ,速率变的更快。     

砖砌烟囱爆破拆除倾倒过程的观测分析

本文通过对砖砌烟囱爆破拆除的实例分析得到,在砖砌烟囱的爆破拆除倾倒过程中,其倾倒支点是不断移动的,随着烟囱主体的不断下沉,相对于未垮部分的烟囱主体来说,该支点沿烟囱筒体不断向上移动。这表明,不能简单地按刚体模型描述砖砌烟囱的倾倒运动。     

Beitrag zur Prüfung metallischer Werkstoffe im Torsionsversuch

Zusammenfassung Der Torsionsversuch eignet sich zur Untersuchung des plastischen Verhaltens von Metallen bei erhöhten Temperaturen, wenn die Fließspannung stark von der Umformgeschwindigkeit abhängt. Aus der gemessenen Drehmoment-Drehwinkel-Kurve wird die Fließkurvek _f () berechnet. Hierfür wird ein Fließkriterium benötigt, dessen Unsicherheit im allgemeinen größer ist als alle Meßfehler. Diese Unsicherheit geht aber nicht in die berechnete Dehngeschwindigkeitsempfindlichkeit ein, die somit als Hauptergebnis des Versuches anzusehen ist.Um die Bedingungen technischer Warmumformung zu simulieren, wird die Verwendung extrem kurzer Proben (flacher Scheiben) empfohlen, womit sehr hohe Umformgeschwindigkeiten erreicht werden können. Für die Auswertung derartiger Versuche ist die wirksame Länge der kurzen Proben — experimentell oder semiempirisch — zu bestimmen und die Kerbwirkung zu berücksichtigen. Im Gegensatz zur herkömmlichen Vorgehensweise wird empfohlen, die örtliche Spannung und Verzerrung nicht für die Mantelfläche der Probe zu berechnen, sondern für einen kritischen Radialabstand im Innern der Probe, für den die Schiebung von der Kerbwirkung unabhängig ist, so daß sich die zuverlässigsten Werte ergeben.

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Summary The torsion test is often used for studying the plastic deformation of metals at elevated temperatures when stress depends strongly on the strain rate. From the measured torque-twisting angle curve, the stress-strain curvek _f () has to be calculated. For this purpose a yield criterion has to be used the uncertaintly of which normally exceeds all experimental errors. This uncertaintly, however, does not propagate into the calculated strain rate sensitivity which therefore may be considered as the main result of the torsion test.For simulating the conditions of technical hot forming processes, the use of extremely short test pieces (flat discs) by which very high strain rates can be obtained is recommended. For evaluating the test data the efficient lenght of short specimens has to be determined. In opposition to the conventional procedure of test evaluation, it is recommended not to calculate stress and strain for the surface of the specimen but for a critical radius for which strain is independent of the notch effect so that the most reliable values are obtained.

Mit 5 Abbildungen     

管流系统的可控扰动装置及其应用

阐述了具有可控人工扰动装置的低背景湍动液体管流系统的研制和评价要点在及在高分子减阻液研究中的应用，并指出了这种实验系统在液体内流研究中的重要意义。     

不同围压作用下非均匀岩石水压致裂过程的数值模拟

从岩石细观非均匀性的特点出发，提出一个描述非均匀材料渗流和破裂相互作用的数值模型。在这个数值模型中，单元的力学、水力学性质根据统计分布而变化，以体现材料的随机不均质性，材料在开裂破坏过程中流体压力传递通过单元渗流，损伤耦合迭代来实现。算例表明，该模型能较好地模拟出岩石类材料在水力压裂作用下，微结构非均匀分布和不同围压比对破裂模式、失稳压力的影响，非均匀性导致试件的开裂压力、失稳压力明显不同，裂纹扩展路径不规则发展，模拟结果和实验结果较为一致。     

汶川震区北川9.24暴雨泥石流特征研究

2008年9月24日汶川震区的北川县暴雨导致区域性泥石流发生,这次9.24暴雨泥石流灾害导致了42人死亡,对公路和其他基础设施造成严重损毁。本研究采用地面调查和遥感解译方法分析地震与暴雨共同作用下的泥石流特征,获取的气象数据用于分析泥石流起动的临界雨量条件。本文探讨了研究区泥石流起动和输移过程,并根据野外调查,分析了泥石流形成的降雨、岩石和断层作用,特别是强降雨过程与物源区对泥石流发生的作用。根据应急调查发现北川县境内暴雨诱发的泥石流72处,其分布受岩石类型、发震断层和河流等因素控制。根据对研究区震前和震后泥石流发生的临界雨量和雨强的初步分析,汶川地震后,该区域泥石流起动的前期累积雨量降低了14.8%～22.1%,小时雨强降低25.4 %～31.6%。震区泥石流起动方式主要有二种,一是由于暴雨过程形成的斜坡表层径流导致悬挂于斜坡上的滑坡体表面和前缘松散物质向下输移,进入沟道后转为泥石流过程;二是"消防水管效应"使沟道水流快速集中,并强烈冲刷沟床中松散固体物质,导致沟床物质起动并形成泥石流过程。调查和分析发现沟内堆积的滑坡坝对泥石流的阻塞明显,溃决后可导致瞬时洪峰流量特别大。研究结果表明了汶川震区已进入一个新的活跃期。因此,应该开展对汶川地震区的泥石流风险评估和监测、早期预警,采取有效的工程措施控制泥石流的发生和危害。