Elasto-plasticity and pore-pressure coupled analysis on the pullout behaviors of a plate anchor

A numerical method is proposed for the elasto-plasticity and pore-pressure coupled analysis on the pull- out behaviors of a plate anchor. The bounding-surface plasticity （BSP） model combined with Blot＇s consol- idation theory is employed to simulate the cyclic loading induced elasto-plastic deformation of the soil skeleton and the accompanying generation/dissipation of the excess pore water pressure. The suction force generated around the anchor due to the cyclic variation of the pore water pressure has much effect on the pullout capacity of the plate anchor. The calculated pullout capacity with the proposed method （i.e., the coupled analysis） gets lower than that with the conventional total stress analysis for the case of long-term sustained loading, but slightly higher for the case of short-term monotonic loading. The cyclic loading induced accumulation of pore water pressure may result in an obvious decrease of the stiffness of the soil-Plate anchor svstem.

Experimental Study on Anchoring Physical Properties of Different Anchoring Lengths Coupled with Temperature and Pressure

Aiming at deep roadway anchorage solids, laboratory similar model tests were used to reveal the mechanical properties of anchorage solids with different anchorage lengths under the coupling effect of temperature and pressure, and SPSS statistical analysis software was used to conduct linear regression analysis of the ultimate anchorage force obtained from the tests. The results show that: through multiple linear regression analysis, the influence degree of temperature and pressure coupling on the ultimate anchorage force is arranged in order of anchoring length > surrounding rock strength > temperature > side pressure coefficient, and the linear regression equation of the model is obtained. Compared with the linear regression equation of simulation results, the model has a high explanatory ability.

Pore pressure fluctuations of overlying aquifer during residual coal mining and water-soil stress coupling analysis

Three test models and a simulation model were constructed based on the prevailing conditions of the Taiping coalmine in order to analyze pore pressure fluctuations of an overlying aquifer during residual coal mining. As well, the relation between pore pressure and soil stress was evaluated. The model tests show the vibrations of pore pressure and soil stress as a result of mining activities. The simulation model tells of the response characteristics of pore pressure after mining and its distribution in the sand aquifer. The comparative analysis reveals that pore pressure and soil stress vibration are activated by unexpected events occurring in mines, such as collapsing roofs. An increased pore pressure zone always lies above the wall in front or behind the working face of a mine. Both pore pressure and vertical stress result in increasing and decreasing processes during movements of the working face of a mine. The vibration of pore pressure always precedes soil stress in the same area and ends with a sharp decline. Changes in pore pressure of sand aquifer are limited to the area of stress changes. Obvious changes are largely located in a very small frame over the mining face.

Numerical analysis on coal-breaking process under high pressure water jet

Based on the theory of nonlinear dynamic finite element,the control equation ofcoal and water jet was acquired in the coal breaking process under a water jet.The calculationmodel of coal breaking under a water jet was established;the fluid-structure couplingof water jet and coal was implemented by penalty function and convection calculation.The dynamic process of coal breaking under a water jet was simulated and analyzed bycombining the united fracture criteria of the maximum tensile strain and the maximal shearstrain in the two cases of damage to coal and damage failure to coal.

Forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by CNTs based on MCST with temperature-variable material properties

In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.

FEM analyses for influences of pressure solution on thermo-hydro-mechanical coupling in porous rock mass

The model of pressure solution for granular aggregate was introduced into the FEM code for analysis of thermo-hydro- mechanical （T-H-M） coupling in porous medium. Aiming at a hypothetical nuclear waste repository in an unsaturated quartz rock mass, two computation conditions were designed： 1） the porosity and the permeability of rock mass are fimctions of pressure solution; 2） the porosity and the permeability are constants. Then the corresponding numerical simulations for a disposal period of 4 a were carried out, and the states of temperatures, porosities and permeabilities, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show that at the end of the calculation in Case 1, pressure solution makes the porosities and the permeabilities decrease to 10%-45% and 0.05%-1.4% of their initial values, respectively. Under the action of the release heat of nuclear waste, the negative pore pressures both in Case 1 and Case 2 are 1.2-1.4 and 1.01-l.06 times of the initial values, respectively. So, the former represents an obvious effect of pressure solution. The magnitudes and distributions of stresses within the rock mass in the two calculation cases are the same.

Numerical analysis of rapid drawdown: Applications in real cases

In this study, rapid drawdown scenarios were analyzed by means of numerical examples as well as modeling of real cases with in situ measurements. The aim of the study was to evaluate different approaches available for calculating pore water pressure distributions during and after a drawdown. To do that, a single slope subjected to a drawdown was first analyzed under different calculation alternatives, and numerical results were discussed. Simple methods, such as undrained analysis and pure flow analysis, implicitly assuming a rigid soil skeleton, lead to significant errors in pore water pressure distributions when compared with coupled flow-deformation analysis. A similar analysis was performed for the upstream slope of the Glen Shira Dam, Scotland, and numerical results were compared with field measurements during a controlled drawdown. Field records indicate that classical undrained calculations are conservative but unrealistic. Then, a recent case of a major landslide triggered by a rapid drawdown in a reservoir was interpreted. A key aspect of the case was the correct characterization of permeability of a representative soil profile. This was achieved by combining laboratory test results and a back analysis of pore water pressure time records during a period of reservoir water level fluctuations. The results highlight the difficulty of predicting whether the pore water pressure is overestimated or underestimated when using simplified approaches, and it is concluded that predicting the pore water pressure distribution in a slope after a rapid drawdown requires a coupled flow-deformation analysis in saturated and unsaturated porous media.

大气压固体分析探针结合单四极杆质谱仪快速检测18种合成大麻素

本研究建立了一种大气压固体分析探针结合单四极杆质谱仪(ASAP-MS)快速检测18种合成大麻素(SCs)的方法。通过优化ASAP-MS锥孔电压,确定4种优化电压为15、25、35和50 V,以提供化合物全面的质谱信息。在优化条件下对一系列SCs标准溶液进行分析,建立了18种SCs的质谱库,并对本方法进行方法学验证,得到18种SCs的检出限为10~20 mg/L。应用该方法对缴获的15批次未知样品进行检测,9批次呈阳性。该方法具有前处理简单、分析速度快、匹配高效精准、定性准确的优势,可用于基层公安禁毒部门的分析检测。

反应堆压力容器“set-on”集成化锻造结构多物理场耦合模拟研究

核反应堆压力容器(RPV)传统采用独立锻件通过焊缝连接的结构形式,由于焊缝为铸态金属组织,属失效分析中的薄弱环节,因此采用集成化锻造结构,确保承压焊缝质量,是提升RPV安全可靠性的重要方法。但是,集成化后的锻造结构存在几何异形、结构复杂、壁厚差异大等问题,其材料组织与性能调控难度大幅增加。针对上述问题,以核电RPV接管“set-on”结构形式为对象,基于结构导热微分及等温转变叠加理论,建立了锻造结构温度-组织-应力的多物理场耦合模型,以调质热处理的奥氏体化及淬火冷却两个阶段为对象,结合淬火冷却介质流-固耦合分析方法,获得锻造结构不同位置处材料组织与性能变化的定量规律,并明确了其关键影响因素。

温压耦合作用下锚固界面变形失效机理

深部地层高地温、高地应力环境使巷道围岩树脂锚固支护结构稳定性降低,围岩变形有效控制问题亟待解决。因此,研究温度与压力耦合作用下锚杆杆体-树脂锚固剂界面变形破坏机理十分必要。首先,根据两淮矿区深部支护工程现状并结合室内不同温度环境下拉拔试验结果,发现高地温环境下树脂锚固体变形破坏加剧;进一步分析锚固体受拉拔荷载作用轴向、径向破坏模式,将第一锚固界面破坏分为弹性围岩-剪切-滑移型、未贯穿-剪胀滑移破坏及贯穿-剪胀滑移破坏等3种模式。其次,基于弹塑力学分析受围岩应力作用锚固界面不同破坏类型的界面受力状态,考虑高温环境下树脂锚固剂层力学强度弱化,建立温度-围岩应力耦合作用的第一界面失效破坏力学计算模型;分析围岩应力、环境温度及弹性模量比等因素变化对第一界面锚固性能影响的规律,发现第一界面极限轴向荷载随温度升高而降低,围岩处于裂隙发育或裂隙贯穿状态时,围岩应力对第一锚固界面剪切破坏影响程度较未产生裂隙时大幅度增高。最后,结合室内拉拔试验数据对比验证所推导计算方程式的合理性。研究可为深部巷道围岩稳定性控制及锚固支护参数设计提供理论依据。

湿热耦合条件下混凝土墙内的孔隙压力研究

基于高温下混凝土的湿热本构模型对火灾下混凝土墙内孔隙压力的发展及其影响因素进行研究.主要采用ABAQUS对墙体进行热分析,并在分析步中调用子程序进行湿热耦合,求解墙体内部孔隙压力的分布.在该计算模型中,考虑了高温下混凝土内部孔隙中水的相态转变及质量守恒、水泥浆体的脱水、混凝土的高温热损伤等因素.在与试验结果对比验证模型的有效性与准确性后,给出了一个案例研究以对火灾下混凝土墙内孔隙压力的发展进行分析,并评估了由孔隙压力导致混凝土发生爆裂的可能,最后探讨了升温制度、混凝土骨料类型、初始渗透率、初始孔隙率等因素对火灾下混凝土墙内孔隙压力的影响.研究结果表明:混凝土墙体受火后,其内部的孔隙压力会在较短的时间内迅速上升,这导致墙体在火灾前期可能出现较大的剥落风险;受火后墙体在厚度方向上往往存在着两处可能由孔隙压力触发墙体剥落的点.研究结果还表明火灾作用下混凝土墙体的孔隙压力发展受升温制度的影响显著,在升温速率最快的炔类火作用下的混凝土墙体最快到达了孔隙压力峰值,且相较于ASTM-E119和ISO-834升温制度,炔类火灾作用下混凝土墙内的孔隙压力峰值分别提高了16.82%和5.81%;混凝土骨料类型对混凝土墙内的孔隙压力发展的影响相对较小;采用硅质骨料的混凝土墙体内部产生的孔隙压力峰值仅高出钙质骨料混凝土3.14%;混凝土初始渗透率同样对混凝土墙内孔隙压力的发展影响显著,混凝土初始渗透率越小,墙体内部产生的孔隙压力越大;混凝土的内部初始孔隙率对受热后墙体内部孔隙压力发展的存在次要影响,随着初始孔隙率的增大,墙体的孔隙压力呈现非线性下降趋势.

基于双向流固耦合的倒虹吸管道水击压力波与拱式桥架组合结构动力响应分析

在大跨度倒虹吸管道中有压闸阀关闭时通常伴随着水击现象,当水击发生时,流体与固体的耦合作用同时存在。为研究发生水击时,不同关阀时间下的压力波与考虑耦合作用时结构的动力响应情况,以大跨度倒虹吸管道与拱式桥架结构为研究对象,进行整体水力计算,基于流固耦合分析理论,将整体水力模型计算得到的水击压力波作为流体部分加载条件,在workbench平台上进行双向流固耦合分析求解桥架结构的位移、内力及应力动力响应结果。结果表明:不同关阀时间工况下,水击压力波曲线的变化趋势大致相同,结构各监测点的位移时程曲线同水击压力波曲线规律基本吻合;阀门匀速关闭时,增加闸阀的关闭时间可以作为降低倒虹吸管道水击压强的有效措施;水击力对桥架管道的影响最大,盖梁次之,拱圈最小,结构以发生顺桥向动力响应为主。

基于协同优化的耐压柱壳多学科多目标优化

为提高耐压柱壳的设计效率和结构性能,本文基于多学科设计优化思想,进行了耐压柱壳多学科设计优化的学科分解,确定了耐压柱壳多学科优化设计的设计参数,明确了设计变量间的耦合关系,设计了耐压柱壳参数化分析流程,进行了设计变量灵敏度分析。在利用响应面模型建立了具有较高拟合精度耐压柱壳近似模型的基础上,以质量排水量比和极限载荷为目标函数,建立了基于协同优化方法的耐压柱壳多学科多目标优化模型,在确定了系统层和学科层的优化求解方法基础上,设计了基于协同优化的耐压柱壳多学科多目标优化框架,进行了优化的求解工作,得到了优化方案。与初始方案的对比表明:所得到的Pareto解集中,部分方案在2个目标函数上均得到了优化,验证了优化框架的有效性。

高压反应釜螺纹式快开结构强度分析

为了解决工程中常用的卡箍式及齿啮式快开结构反应釜难于满足介质操作过程中均温性要求的问题,笔者设计了一种均温性能良好的螺纹式快开结构反应釜装置,用于热塑性聚氨酯弹性体(thermoplastic polyurethane elastomer,TPU)材料生产以提高其生产质量。分别建立平盖、碗形盖和凸形盖3种快开结构有限元模型,分析螺纹应力分布情况并进行设计压力工况及热-力耦合工况的应力强度评定。结果表明:3种快开结构的筒体端部内螺纹根部应力整体高于釜盖外螺纹,其应力均随着螺纹扣数增加而减小;2种工况下3种快开结构的最大应力均出现在第1扣螺纹根部,当考虑温度载荷影响时,热应力分别增大了13.97%,9.30%和4.79%,应力和疲劳强度均满足要求。对比表明凸形盖螺纹式快开结构承压承温的综合性能较好。

基于CFD-DEM耦合的装车站溜槽设计参数优化

为提高装车站溜槽的物料分布均匀性,降低粉尘质量浓度,提出基于CFD-DEM耦合的装车站溜槽设计参数优化方法。分析装车站溜槽的工作流程,采用CFD-DEM耦合的方法建立装车站溜槽有限元模型;建立卸料方程、物料与溜槽、挡板的撞击方程、滑行方程和运动方程,同时结合有限元模型展开颗粒运动分析和压力流场分析;根据分析结果优化装车站溜槽物料对应的动堆积角参数、流线控制参数、物料入射角参数、挡板与物料之间的摩擦角参数,实现优化物料流、物料速度、溜槽横截面积和物料重力分布。实验结果表明:所提方法设计溜槽的物料分布均匀性高,并且粉尘质量浓度降低至912 mg/m 3。

汽车空调管路的流固耦合振动特性分析

为研究汽车空调管路的振动特性,对比分析了汽车空调管路在空管和考虑流固耦合特性下两种管路的振动特性。借助有限元分析软件对比分析空管和考虑流固耦合状态下管路系统的固有频率和振型图,根据分析结果可知,在考虑流固耦合后管路的固有频率值有明显的提高;为进一步研究管路振动特性,还对管路进行了谐响应分析,通过分析结果可知,当频率接近5 Hz时,空管和考虑流固耦合管路的振幅达到最大值,即在5 Hz附近容易出现共振现象,因此需要避开这个频率。

耦合气阀故障的往复压缩机性能分析

可靠性、容积流量、能耗是评价往复压缩机性能的重要指标,压缩机性能与气阀有着密切关系,气阀工作在高频、高冲击等恶劣条件下,极易损坏,不仅影响压缩机运转率,而且导致指示功增多,排气量减少。因此,通过建立正常工况及气阀故障工况下的往复压缩机数学模型,获取不同工况下的动态压力数据,开展基于动态压力数据的往复压缩机性能分析,对比正常工况与气阀故障工况性能参数,从而获取压缩机机组的气阀故障特征,为之后的故障诊断奠定基础。

SECTIONAL FINITE ELEMENT ANALYSIS OF COUPLED DEFORMATION BETWEEN ELASTOPLASTIC SHEET METAL AND VISCO-ELASTOPLASTIC BODY

The present paper is devoted to developing a new numerical simulation method for the analysis of viscous pressure forming （VPF）, which is a sheet flexible-die forming （FDF） process. The pressure-carrying medium used in VPF is one kind of semisolid, flowable and viscous material and its deformation behavior can be described by the visco-elastoplastic constitutive model. A sectional finite element model for the coupled deformation analysis between the viscoelastoplastic pressure-carrying medium and the elastoplastic sheet metal is proposed. The resolution of the Updated Lagrangian （UL） formulation is based on a static explicit approach. The frictional contact between sheet metal and visco-elastoplastic pressure-carrying medium is treated by the penalty function method. Coupled deformation between sheet metal and visco-elastoplastic pressure-carrying medium with large slip is analyzed to validate the developed algorithm. Finally, the viscous pressure bulging （VPB） process of DC06 sheet metal is simulated. Good agreement between numerical simulation results and experimental measurements shows the validity of the developed algorithm.

压裂工况下高压管汇的振动特性分析

压裂车泵头体里面的柱塞泵以及连杆会产生较大振动,与泵头体相接的高压管汇在工作时会产生共振等危险。对于高压管汇流固耦合分析和改进安装约束方式综合考量的研究鲜有涉及,且在固有频率附近的响应情形尚不明确。为此,基于空挡位和单向流固耦合的模态分析方法,对比分析高压管汇的固有频率和振型,并对工况丁进行谐响应分析,揭示了改进约束方式对提高固有频率的影响规律。研究结果表明:无论是否增加固定约束,在流固耦合模态下比在空模态下的固有频率均要高2%~6%;改进约束方式后管汇的前3阶固有频率是改进前的2~3倍;管汇在改进前主要在中间直管段的上下、前后弯曲摆动,改进后变为上下、左右摆动,且管汇振动主要集中在中间直管段;在X方向上的位移、加速度、应力和应变谐响应峰值均比在Y和Z方向上的要高。研究结果可为高压管汇的设计以及增加固定约束的方式提供理论依据。

基于流固耦合的骨架膜结构优化

为了实现骨架膜结构的优化设计,基于ANSYS平台考虑了膜结构在风荷载作用下的结构变形对建筑表面风压分布的影响,采用双向流固弱耦合的方法对某低矮类膜建筑在不同风向角下的定常风场特性与其围护骨架膜结构的风致结构受力进行了研究,并以此为依据采用响应面法对骨架膜结构中各杆件的截面尺寸进行了优化.结果表明:仿真所得建筑表面风压分布与同类模型风压实测数据、风洞试验数据以及国家相应规范吻合较好;不同风向角下骨架膜结构的受力状态不同,其中90°风向为该结构的最不利工况;采用响应面法得到了该骨架膜结构中各杆件的截面尺寸对结构受力的影响关系,并将该结构整体质量降低了14.73%.