Strain-based design for buried pipelines subjected to landslides

Landslides are one of the key problems for stability analysis of pipelines in the western region of China where the geological conditions are extremely complicated. In order to offer a theoretical basis for the pipe-soil interaction, the general finite element program ABAQUS is used to analyze the distribution of pipe strain caused by landslide through which the pipeline passes. In this paper the Ramberg-Osgood constitutive equation is used to study the strain-based mechanical characteristics of pipelines. Different calculation schemas are designed by considering the change of spatial relationship between pipeline and landslide, and the change of D/t, diameter-thickness ratio of pipeline. The results indicate that the pipeline is primarily subjected to tension stress when the landslide crosses the pipeline perpendicularly, the pipe strain is a maximum along the central axis of the landslide, and reverse bending occurs on pipeline at both edges of the landslide. The pipeline is primarily subjected to friction force caused by the downward movement of the landslide, and the friction force is relatively small when the landslide is parallel to the pipeline. The pipe strain is in proportional to D/t, and this means decreasing D/t can help to improve security of pipelines subjected to the landslide.

Topology Optimal Design of Material Microstructures Using Strain Energy-based Method

Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.

Using strain energy-based prediction of effective elastic properties in topology optimization of material microstructures

An alternative strain energy method is proposed for the prediction of effective elastic properties of orthotropic materials in this paper. The method is implemented in the topology optimization procedure to design cellular solids. A comparative study is made between the strain energy method and the well-known homogenization method. Numerical results show that both methods agree well in the numerical prediction and sensitivity analysis of effective elastic tensor when homogeneous boundary conditions are properly specified. Two dimensional and three dimensional microstructures are optimized for maximum stiffness designs by combining the proposed method with the dual optimization algorithm of convex programming. Satisfactory results are obtained for a variety of design cases.

Optimal Preform Die Design through Controlling Deformation Uniformity in Metal Forging

A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the deformation uniformity. The objective function expressed by the effective strain is constructed. The sensitivity equations of the objective function, elemental volume, elemental effective strain rate and the elemental strain rate with respect to the design variables are constituted. The preform die shapes of an H-shaped forging process in axisymmetric deformation are designed using this method.

Design and Performance Evaluation of a Sustained Load Dual Grip Creep Testing Machine

The design and performance evaluation of a sustained load creep testing machine was undertaken in this research. The design was motivated by the need to make locally available, a cost effective, technically efficient, and easily operated creep testing facility;for creep behaviour studies of materials. Design drawings and purchase of materials and components for the design were undertaken after thorough evaluation of the following design and materials selection criteria: design principle and theory, local availability of raw materials and components required for the design, material properties, cost of materials and design, ease of utilization and maintenance, and basis of testing and data capture. The machine casing and frame, heating chamber (consisting of the furnace and a dual specimen mounting stage), load lever and hanger system, and the electro-technical components;were fabricated and coupled following the produced design specifications. The machine was tested and its performance was assessed using its heating efficiency, repeatability and reproducibity of experimental test results, maintainability and cost-effectiveness as criteria. It was observed from repeat tests that the machine has the capacity of generating reliable data for computing creep strain-time results. The efficiency and temperature regulating capacity of the heating unit of the machine were also observed to be very satisfactory. The cost of the design was about 112,000 Naira ($700.00) which is cheaper in comparison to similar commercial creep testing machines from abroad. The machine was also found not to pose maintenance or repairs challenges.

巷道围岩应力应变仿真系统设计与教学探索

为了获得采动条件下巷道围岩应力应变演化特征,通过复变函数换算结合工程实践经验,运用科学计算软件编程对巷道围岩受力模型进行求解,获得巷道围岩主应力和主应力集中系数分布规律。采用MATLAB对巷道受力模型进行模拟演算,获得工程开采参数与巷道围岩应力应变的关系规律,由此设计了一种采动影响下巷道围岩应力应变模拟仿真系统。该系统可对多种巷道断面进行计算和模拟,进而呈现出多种信息仿真演示,解决了以往软件适用巷道类型单一、应力求解不具体且结果呈现单一化缺点,可为回采巷道支护设计提供相应的理论依据,有利于矿山工程技术人员及实验室技术人员开展模拟仿真教学。

Advanced test methods of material property characterization:high strain-rate testing and experimental simulation of multiaxial stress states

Optimum utilization of the loading capability of engineering materials is an important and active contribution to protect nature's limited resources,and it is the key for economic design methods.In order to make use of the materials' resources,those must be known very well;but conventional test methods will offer only limited informational value.The range of questions raised is as wide as the application of engineering materials,and partially they are very specific.The development of huge computer powers enables numeric modelling to simulate structural behaviour in rather complex loading environments-so the real material behaviour is known under the given loading conditions.Here the art of material testing design starts.To study the material behaviour under very distinct and specific loading conditions makes it necessary to simulate different temperature ranges,loading speeds, environments etc.and mostly there doesn't exist any commonly agreed test standard.In this contribution two popular,non-standard test procedures and test systems will be discussed on the base of their application background,special design features as well as test results and typically gained information:The demand for highspeed tests up to 1000 s^(-1) of strain rate is very specific and originates primarily in the automotive industry and the answers enable CAE analysis of crashworthiness of vehicle structures under crash conditions.The information on the material behaviour under multiaxial loading conditions is a more general one.Multiaxial stress states can be reduced to an equivalent stress,which allows the evaluation of the material's constraint and criticality of stress state.Both discussed examples shall show that the open dialogue between the user and the producer of testing machines allows custom-tailored test solutions.

不同缺陷类型双层石墨烯旋转摩擦特性

采用分子动力学模拟方法,构建双层石墨烯旋转摩擦的原子模型,研究缺陷类型、浓度、尺寸效应、石墨烯堆叠方式等因素对其层间旋转摩擦特性的影响,并探讨应变工程的减摩效应.实验结果表明,缺陷类型和堆叠方式对石墨烯旋转摩擦特性的影响较为显著,缺陷类型的影响程度最高.当对底层石墨烯引入拉伸应变后,其旋转摩擦阻力发生衰减,且单空位缺陷与无缺陷模型的力矩递减趋势最为相似.对比研究底层石墨烯的压缩应变,发现其在一定范围内使得层间摩擦增大.本研究有助于缺陷石墨烯层间旋转摩擦特性理论的进一步完善.

考虑应变率效应的金属爆炸容器初始设计方法

针对爆炸容器初始设计常用的动力系数法存在的设计余量过大问题,通过将Johnson-Cook本构模型的应变率项纳入结构振动方程,推导出考虑应变率效应的等效静载荷计算方法。采用本文方法及常规动力系数法对不同半径的球形容器在1 kg TNT炸药加载下的壁厚进行了理论设计,并通过高置信度数值模型对两种方法所设计的容器的结构响应进行了数值计算。结果显示,两种方法所设计的容器均在弹性范围,但是本文方法的容器壁厚更小、结构应力更大。这表明通过考虑应变率效应,本文方法可合理降低设计载荷以减小设计余量,进而更充分地发挥材料与结构的力学性能,并可用于金属爆炸容器的初始设计。

超高压爆破片设计爆破压力的半经验计算公式

针对超高压正拱型爆破片提出设计爆破压力的半经验计算公式,开展超高压爆破片预拱变形后非均匀减薄壁厚的测量试验,借助试验数据对爆破片变形后非均匀减薄壁厚的理论计算公式进行修正,同时,为进一步简化半经验公式及过程,选取不同材料、爆破压力和挠曲高度的试验数据,建立爆破片挠曲高度和材料应变硬化指数之间的关联关系,对设计爆破压力半经验公式化繁为简,利用试验方法,对爆破片的爆破压力进行试验验证,试验结果与理论计算结果吻合较好,其误差分别为3.72%和6.59%,对实际工程应用具有指导意义。

压缩浇筑混凝土的应力-应变关系

压缩浇筑可以显著提高混凝土的强度和耐久性,无需添加任何化学添加剂和矿物掺料.采用压缩浇筑方法制作压缩浇筑混凝土试件,并开展单轴受压试验.试验结果表明,相比于普通混凝土,压缩浇筑混凝土的抗压强度和弹性模量显著提高,而峰值应力对应的应变稍有减小.基于现有混凝土应力-应变模型对试验结果进行回归分析,得到压缩浇筑混凝土的应力-应变关系模型.在此基础上,利用受弯定理推导了压缩浇筑混凝土受弯构件的等效矩形应力块参数模型.研究成果可为压缩浇筑混凝土构件的抗弯设计和分析提供理论依据.

微尺度3D打印柔性传感器创新实验设计与实践

介绍了一种利用微尺度3D打印柔性应变传感器的实验设计及实践,旨在培养学生的创新意识和实践能力,提高教学质量和水平。该实验借助微尺度3D打印技术,实现了传感器微型化和高精度制备,有效地提升了传感器的灵敏度和稳定性。在实践过程中,学生需要独立进行实验设计、制备和测试,注重实验数据的统计和分析,培养了学生的创新思维和实践操作能力。

面向东北人工林的辊式清林切削装置设计及试验

从加强东北地区人工林利用角度出发,需要对森林资源进行合理采伐。但由于林内杂草丛生,以致对采伐工人的视线造成严重干扰,给采伐工作带来了不良影响。故需要对面向人工林的清林装置按照我国东北地区人工林的相关特点进行设计。通过进行实地调查,提出一种辊式清林装置,并根据相关数据完成了辊式清林装置切削结构的设计。首先,对关键部件,如刀辊、刀座、刀具进行参数设计和分析,并确定切削装置的功率需求;随后,根据计算得出的关键设计参数进行3D建模,并基于ANSYS进行应力应变分析,基于ADAMS软件进行动平衡仿真分析,结果显示,刀辊设计与有关标准及设计要求一致,应力和应变分析得出的结果表明刀座设计符合要求;接着,对刀辊进行了动平衡测试,结果表明刀辊的纵向最大振动速度1.54 mm/s,噪声小于95 dB,依照ISO标准进行划分,属于允许振动的B级;最后,设计制作样机,并通过试验得出,该装置可以完成灌木密度为11根/m^(2)的伐区清林作业,清林效果符合设计要求。

地质灾害作用下埋地管道力学响应数值分析进展及问题探讨

断层、滑坡、泥石流、局部沉陷、隧道开挖等引起的管周土体失稳严重威胁埋地管道的稳定性,避免因为地质灾害的影响而造成管道破坏,是城市和油气田地下生命线工程急需解决的问题。数值模拟作为埋地管道与管周土相互作用分析的主要技术手段,可为埋地管道的全寿命设计提供更为快捷准确的指导。该文简述了地质灾害作用下埋地管道力学响应数值分析的研究进展,主要包括埋地管道典型地质灾害特点、管土相互作用单元及管道穿越地质灾害区有限元模型,并针对地质灾害作用下管道力学行为研究中所存在的问题,提出今后应开展基于壳式模型的管土相互作用、多种地质灾害耦合作用下管道力学行为和基于应变设计与评估准则的研究。

基于ABAQUS的曳光管套结构设计与强度分析

曳光弹丸发射过程中,在高过载和高膛压作用下曳光管壳可能发生大的塑性变形甚至断裂,影响曳光药剂正常燃烧,因此设计了用来固定和保护曳光管的管套。压螺与弹体螺纹连接和曳光管壳在高过载作用下的强度校核结果满足要求的前提下,利用ABAQUS软件仿真分析曳光管壳和管套在360 MPa膛压作用下的应力应变,结果显示:曳光管与方案1管套配合时的最大应力为1026 MPa,最大应变为0.8;与方案2管套配合时的最大应力为844.7 MPa,最大应变为0.05。经分析可知,采用方案1管套时,曳光管壳的局部变形量可使曳光药剂断层、松散;而采用方案2管套时,曳光药剂强度不会发生破坏性变化。通过曳光性能射击试验验证了ABAQUS软件仿真分析结果。

基于应变设计X80钢管性能关键影响因素分析及模拟评价

针对基于应变设计管线钢对应变容量的需求,阐述了材料的屈强比、应力比、屈服强度和抗拉强度、均匀延伸率、塑性各向异性等对钢管屈曲应变容量的影响,以及目前在管道材料方面的研究及取得的技术成果。以中石化新疆煤制气外输管道工程为例,对X80M钢级Φ1 219 mm×26.4 mm规格钢管采用数值模拟、性能测试等方法,建立了管道屈曲应变量与力学性能指标的关系式,并采用全尺寸弯曲试验对拟合结果进行了验证,从工程应用角度提出了基于应变设计X80钢管的各项性能指标。结果表明,该项目用管材最小应力比R_(t2.0)/R_(t1.0)为1.033,纵向屈服强度为530~630 MPa,纵向抗拉强度为625~770 MPa,最大屈强比为0.85,最小均匀延伸率为6%。

全厚式沥青路面结构设计与优化

为探究抗疲劳结构层等功能层在全厚式沥青路面结构中所发挥的作用,设计了以级配碎石为底基层,细粒式密集配沥青混合料结构层为抗疲劳层的全厚式沥青路面结构,以改变结构层厚度和设计轴载的方式计算了不同因素组合下路面结构的沥青层层底拉应变、路基顶面压应变及预估使用寿命,使用方差分析法确定了不同因素对路面结构使用性能的影响,最后对设计的路面结构进行了优化。结果表明:细粒式密集配沥青混合料结构层和级配碎石结构层厚度的增加对保证路面结构耐久性有着积极作用,重复重载作用是影响路面结构使用性能和耐久性的主要因素。

围堰封底混凝土钢护筒应力应变分析及厚度设计方法研究

桥梁是国民经济建设和社会发展的重要基础设施,提升封底混凝土与钢护筒之间的界面黏结力对巩固桥梁基础中的围堰受力至关重要。钢护筒界面的环向变形和膨胀作用使混凝土处于局部受压的状态,对二者界面的黏结力起决定性作用。目前钢护筒厚度设计尚无完整明确的计算方法,仅依靠规范厚度取值过于保守。文章基于弹性体广义虎克定律,结合轴对称体系应力应变关系的对称性,建立轴向荷载下轴对称薄壁钢护筒的应变场数学模型。通过构建微元体的平衡微分方程、几何方程及本构方程,分析薄壁钢护筒在轴向荷载下的环向应变与位移关系,提出围堰封底混凝土钢护筒厚度参数设计方法,并通过ABAQUS大型通用有限元软件模拟验证了该设计方法的合理性。

基于蓝牙无线传输技术的液压导管应变测量系统

液压导管应变检测是保证液压系统安全可靠运行和判断系统结构健康状况的关键,针对有线应变测试设备存在的问题,设计了一套基于蓝牙无线传输技术的应变测量系统。系统设计遵循体积小、低功耗的原则,基于蓝牙低功耗、高信号质量的无线传输技术,根据一主多从模式架构设计了主从机电路,设计完成液压导管应变采集和无线通信等功能需求,另外设计配套数据传输与处理软件,在交互界面实现数据实时显示与分析。通过有线采集设备与无线测量系统的应变测量对比实验,证明本文设计的基于蓝牙无线传输技术的应变测量系统能够准确有效测得液压导管应变。

基于平面应变比的深基坑工程支护结构优化设计研究

基坑开挖是一个三维空间过程。以实际深基坑工程为背景,借助岩土工程有限元分析软件PLAXIS 3D进行三维建模,分析了基坑工程在三维条件下的变形特性,并引入平面应变比概念对支护结构进行优化。结果表明:基坑拐角效应对变形存在显著影响,通过考虑平面应变比对基坑支护结构进行优化设计,能够在保证安全的前提下节约成本,优化效果显著。研究成果可为类似工程的设计、优化提供参考。