THE PROBLEM OF PARAMETRIC INTEGRATION TO THE SLIP LINE FIELD IN THE COMPRESSION OF THICK WORKPIECE

An integration depending on a parameter to the compression of a thick workpiece has been obtained. For the conventional prevailing numerical formulaa definite functional relationship bet-ween and y is found. Therefore a parametric integration can be used to get an analytical solution. Take the slip line field for l/h= 0.121 as an example, the analytical solution is basically the same as the prevailing numerical one. It is justified theoretically that for the slip line field a parametric integration is perfectly possible for a satisfactory analytical solution.

The study of slip line field and upper bound method based on associated flow and non-associated flow rules

At present,associated flow rule of traditional plastic theory is adopted in the slip line field theory and upper bound method of geotechnical materials. So the stress characteristic line conforms to the velocity line. It is proved that geotechnical materials do not abide by the associated flow rule. It is impossible for the stress characteristic line to conform to the velocity line. Generalized plastic mechanics theoretically proved that plastic potential surface intersects the Mohr-Coulomb yield surface with an angle,so that the velocity line must be studied by non-associated flow rule. According to limit analysis theory,the theory of slip line field is put forward in this paper,and then the ultimate bearing capacity of strip footing is obtained based on the associated flow rule and the non-associated flow rule individually. These two results are identical since the ultimate bearing capacity is independent of flow rule. On the contrary,the velocity fields of associated and non-associated flow rules are different which shows the velocity field based on the associated flow rule is incorrect.

SLIP LINE METHOD FOR SINTERED POWDER MATERIALS UNDER CONDITION OF AXIAL SYMMETRY DEFORMATION

Slip line method for sintered powder materials under condition of axial symmetry is proposed based on the simplified yield condition of sintered powder materials and Haar-von Karman perfect plastic criterion. The equations of slip line and stress along slip line are derived, and numerical solutions are given. Deformation load in closed die upsetting of sintered copper cylinder is calculated by slip line method, and theoretical solutions are compared with experimental results.

Slip Line Field Solution for Second Pass in Lubricated 4-High Reversing Cold Rolling Sheet Mill

The development of a possible slip line field (slf) for theoretical calculations of the deforming pressure (load) in a second pass of a lubricated cold rolling sheet mill and validation using values from an aluminium sheet rolling mill was done in this work. This will be relevant in the manufacturing industries providing an easy method for determining necessary applied rolling load. Experimental rolling was carried out to observe the shear lines in the deformation field. Construction of possible slip line field model was developed adhering strictly to assumptions of rigid plastic model. Calculation of the deforming force/load was achieved using Hencky’s equation. Results showed that the load calculations for constructed slip line field using aluminium sheet rolling as an example tallied with values obtained from Tower Aluminium rolling mill. Slip line fields constructed for the second pass described adequately the rolling pressure in the cold rolling process, giving a valid solution of the exact load estimates on comparison with the industrial load values. Roll pressure along the arc of contact rose fairly linearly from the entrance to a maximum at the exit point. This work showed that slf for the first pass in a cold rolling mill cannot be used for subsequent passes;it requires construction of slfs for each pass in the cold rolling process.

Rolling Force and Rolling Moment in Spline Cold Rolling Using Slip-line Field Method

Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.

A challenge to the concept of slip-lines in extrusion tectonics

Wide-open V-shaped conjugate strike-slip faults in Asia are typically related to extrusion tectonics. However, the tectonic model based on the slip-line theory of plasticity has some critical problems associated with it. The conjugate sets of slip-lines in plane deformation, according to the theory of plasticity should be normal to each another but, in reality, the angles between the conjugate strike-slip faults, which are regarded as slip-lines in extrusion tectonics in the eastern Mediterranean, Tibet-middle Asia, China and the Indochina Peninsular regions, are always more than 90° （on average -110°） in the direction of contraction. Another problem is that the slip-line theory fails to explain how, in some cases, e.g., in the Anatolian area in the eastern Mediterranean, the extrusion rate is much higher than the indent rate. The two major problems are easy to solve in terms of the Maximum-Effective-Moment （MEM） Criterion that predicts that orientations of the shear zones are theoretically at an angle of 54.7° and practically at angles of 55°± 10° with the σ1- or contractional direction. The orientations of the strike-slip faults that accommodate extrusion tectonics are, therefore, fundamentally controlled by the MEM Criterion. When extrusion is along the MEM-orientations, the extruding rate is normally higher than the indenting rate.

Construction of improved rigid blocks failure mechanism for ultimate bearing capacity calculation based on slip-line field theory

Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.

A Slip-Line Method for Calculating Extrusion Force of Steel Helmet with Cold Extrusion Moulding

This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.

Slip-line field solution for ultimate bearing capacity of a pipeline on clayey soils

A slip-line field solution is presented for the ultimate bearing capacity of the pipeline on a purely-cohesive clay soil, taking into account the circular configuration of the pipe, the pipe embedment, and the pipe-soil interfacial cohesion. The derived bearing capacity factors for a smooth rigid pipe limit to those for the conventional rectangular strip footing while the pipe embedment approaches zero. Parametric studies indicate that, the pipe-soil interfacial properties have much influence on the bearing capacity for the pipe foundation on clayedy soils.

Axi-symmetric Active Earth Pressure for Layered Backfills Obtained by the Slip Line Method

The axi-symmetric active earth pressure for layered backfills was investigated using the slip line method. Due to different soil properties, the interfaces of the soil layers were considered as discontinuity surface. Accordingly, the change of the major principal direction was obtained and a new computation scheme was proposed to deal with the discontinuity in the calculation, finally the slip line method was extended to layered backfills. Results indicate that, the major principal direction, as well as the earth pressure, has a finite jump on passing the soil interfaces. The magnitude of the jump depends on the soil properties mainly. Generally, the active earth pressure when a strong layer is overlying a weak layer is much larger than that when the weak layer is lying on the strong layer. The present solution can be reduced to plane strain case and it has been compared with Rankine's and Coulomb's results, and a good agreement is observed.

Slip-Line Field Theory of Transversely Isotropic Body

A slip-line field theory of transversely isotropic body is proposed in the presentpaper in order to deal with problems in geology and geotechniques.The Goldenblat-Kopnov failure criterion is employed.The parameters in it are treated as functions of tempperature It is applicable to transverse isotropic media in non-uniform temperaturefield.The basic equtions of plastic deformation are developed while the associated ru-les of flow are derived.By means of characteristic line theory,slip-line slope formulasand laws of variation of stress and velocity along slip lines are obtained,The indenta-tion on semi-infinite media is calculated.The theory developed in this paper may be simplified into many classical theories such as Mises,Hill,and Coulomb ones,This complicated theory may be applied to geotechniques,geological structures,petroleumindustry,mining engineering,etc.

土与强风化岩双元边坡圆弧-平面破坏模式与支护设计方法

为了探究土与强风化岩边坡中强风化岩不破坏的临界坡率及稳定性判断方法,基于济南地层,得出适用于数值模拟的土层参数,并利用强度折减法求出边坡的临界坡率,为施工提供参考。针对强风化岩不破坏的边坡,运用改进的瑞典条分法求出边坡安全系数解析解,并利用滑移线场法求出滑移线,为安全系数解析解的应用提供依据。结果表明,岩层厚度超过边坡高度1/2或坡率大于1:0.5时,强风化岩一定破坏;解析解得出的安全系数偏小,有利于工程安全;针对土与强风化岩边坡,文中结果可确定边坡破坏区域,设计支护方案。

开洞刚性墙后土体破坏模式运动单元上限分析

超载作用下开洞地下刚性连续墙后土体稳定性问题具有广泛的工程应用背景。考虑墙体矩形开洞宽度足够大,且刚性墙与土体完全光滑接触等条件,参考构造刚性多块体上限法思路,预设墙后土体极简破坏机构并转化为初始三角网格,提出交替循环式新增节点、单元缩减、对角互换及成层加密等网格更新措施,同步开展基于刚体平动运动单元上限方法的刚性墙后土体破坏分析,通过多层级非线性规划运算获得高精度临界超载系数σ_(s)/c上限解,界定墙后土体滑移线网破坏模式及其定量范围与扩展边界。进一步依前述流程计算获得多参数影响下的临界超载系数σ_(s)/c上限解图表,结果表明:1)刚性墙后土体典型破坏特征表现为土体上方和开洞处的整体下沉刚性区域,开洞前方核心区域以密集滑移线网区隔的刚性滑块群,以及外围主要滑动面;2)临界超载系数σ_(s)/c随土体内摩擦角ϕ增大而增大,且后续增幅显著增加;3)σ_(s)/c随开洞深度比C/D的增大呈现出近似线性增大的趋势;4)相较于ϕ和C/D,土体重度参数γD/c的变化对于σ_(s)/c的影响不甚明显,σ_(s)/c随γD/c增大呈现近似线性减小的趋势;5)σ_(s)/c受剪胀角参数ψ/ϕ的影响与ϕ的增大程度密切相关。本研究结果可为开洞地下刚性连续墙后土体失稳破坏模式定量分析、破坏机理研究及工程措施制定等工作提供有力的数据支持。

深部矿井软底回采巷道底鼓机理及防治研究

针对山阳煤矿软底回采巷道严重底鼓的难题,采用理论分析、数值模拟和现场应用的方法,基于塑性理论建立了巷道底板岩体滑移线底鼓力学模型。研究表明,巷道底板破坏岩体主要分为3个区,分别为主动极限区、过渡区和被动极限区,推导了巷道底板岩体的最大破坏深度,提出了锚索+卸压槽联合控制底鼓的方法。采用数值模拟的方法验证了联合控制方案的可行性,现场应用效果表明该方法能够有效控制软底巷道底鼓,为相似地质条件底鼓问题的研究提供了一定的帮助。

穿越走滑断层隧道错动影响分区及隧道节段式衬砌抗错断性能控制

为了揭示中国西部地区穿越活动断裂公路隧道工程的变形及力学特性,通过数值模拟分析了断层左旋走滑运动对隧道结构产生的错动响应,建立隧道受断层错动影响分区,并提出隧道节段衬砌铰接设计这一抗错断措施。通过对比在影响区内设置不同长度节段衬砌时隧道结构的应力、位移响应规律,得出最优衬砌节段布置形式。研究结果表明:断层走滑错动2.5 m时,隧道结构受错影响范围为断层与活动盘交界面附近2.7 d(d为隧道跨径)内,定义1 d~2.7 d范围内为次要影响区,1 d范围内为主要影响区;通过对比分析发现3 m节段对衬砌结构水平位移和最大剪应力的控制效果最好,峰值最大降低率分别达到了3.38%和43.34%;隧道结构在断层交界面附近水平位移达到最大,随后向两侧较远位置变形不断减小至平稳;可见隧道结构沿纵向所受的最大剪应力值集中在错动影响区内,且在此范围内变化相较此范围外更加剧烈,错动影响区是抗断层错动设防重点关注对象。研究结果可为隧道抗错断设计提供参考。

穿插法应急整体修复市政污水总管的实践与分析

经长时间使用和自然因素的影响,市政排水管道不可避免会出现腐蚀、破裂、渗漏等结构性缺陷而突发险情,须对出险管段采取应急修复措施以消除安全隐患、恢复管道排水能力。以上海市沪南公路污水总管应急修复工程为例,介绍了穿插法在整体修复市政污水总管中的应用,包括管道规模及管材确定、过流能力验算、穿插轨迹设计、间隙注浆及检查井连接设计等方面。实践证明,穿插法修复排水管道具有施工速度快、环境影响小、质量可靠等优势,可为类似工程提供参考。

汽车后门外板腰线二次拉延技术研究应用

为了解决车身腰线锐利化带来的品质问题,以某车型后门外板为研究对象,文章展开了腰线二次拉延成形仿真以及冲压模具结构优化设计。在设计阶段对产品成形过程进行数值模拟。通过优选冲压方向、腰线二次拉延等方法优化冲压工艺,解决了腰线前端开裂、起皱以及优化了腰线滑移等质量问题。在冲压模具结构设计上,通过增加双导向、垫块和平衡块等方法,实现了模具实物上下型面间隙稳定,避免了由于工装精度不足导致的滑移线等质量问题。最终按照工艺方案用于模具制造,并根据仿真结果指导实物调试,得到了无开裂、起皱以及腰线滑移在基准内的合格零件。研究表明,该后门外板的二次拉延方案可实现锐利化腰线在后门外板上的工业化应用。

关于翼子板滑移线问题的研究

冲压件的滑移线是汽车覆盖件冲压生产中经常出现的一种表面缺陷,它严重影响了覆盖件的表面质量和车身的外观。对滑移线的产生机理、判定原则及其解决方法进行了全面的剖析,以实际生产中的实例为汽车覆盖件冲压生产时出现滑移线的整改提供了参考。

大尺寸厚层硅外延片表面滑移线缺陷检验研究

目前制约大尺寸厚层硅外延产品高质量生产的主要因素是表面滑移线,而滑移线的过程控制严重依赖于滑移线的完整、准确检验识别。通过对不同宏观显现的滑移线表征方法的研究,比较了各类检验的误差来源,分析出了影响硅外延滑移线量化计算的主要因素,制定了科学合理的检验策略,提高了批量生产过程中滑移线检验的准确性与稳定性,取得了显著成效。

正文煤矿采空区下回采巷道支护应用分析

为解决正文煤矿近距离煤层下方回采巷道围岩支护难题,以11107回采工作面为工程背景,综合运用理论计算、现场实测等方法,对回采巷道支护及应用进行了探讨;分析表明,9#煤层开采引起底板损伤破坏深度为4.69m,以层间岩层厚度是否大于5m为条件将其巷道围岩分为损伤间隔层、块裂间隔层两种类型,并采用不同的支护方案;应用表明,在掘巷阶段取得较好的围岩控制效果。