可储能原则在一类岩爆问题中的研究和应用

从能量的角度对一类岩爆问题--应变型岩爆进行一些探讨.对此类岩爆能量的来源、能量的去处及能量释放的原因和大小进行了完整的论述.提出了岩体的可储能原则--岩体可存储的能量并非定值,而是随应力状态的变化而改变,当应力发生突变,岩体内实际存储的能量大于可储能时,多余的能量必将以各种形式瞬间释放,其中包括动能.根据此准则对简化了的一维、三维模型进行了详细的分析和计算,并结合离散元软件3DEC再现了三维卸载岩爆的破坏过程.     

Analytical analysis of the dual-phase-lag model of bioheat transfer equation during transient heating of skin tissue

Dual-phase-lag model of bioheat transfer equation is utilized in treating the transient heat transfer problems in skin tissue considering prevalent heating conditions in thermal therapy applications, namely, pulse train and periodic heat flux. Comparisons between the presented analytical results for limiting cases and previous studies display an excellent agreement. The effects of temperature gradient relaxation time on the tissue temperature, damage, and also on the blood perfusion in skin tissue are studied.     

Pressure Transient Analysis for Multi-stage Fractured Horizontal Wells in Shale Gas Reservoirs

This article presents the PTA on the multi-stage fractured horizontal well in shale gas reservoirs incorporating desorption and diffusive flow in the matrix. Currently, most PTA models are simply based on Darcy flow both in natural fractures and matrix without considering the mechanisms of desorption and diffusion in shale matrix. Source function and Laplace transform with the numerical discrete method are employed to solve the mathematical model. The solution is presented in the Laplace domain so that the wellbore storage effect and skin factor can be easily incorporated by convolution. Type curves are plotted with Stehfest algorithm and different flow regimes are identified. The presented model could be used to interpret pressure signals more accurately for shale gas reservoirs.     

高层建筑风振时地基土材料阻尼比取值范围的初探

高层建筑风振响应分析中考虑土与结构相互作用后地基土的材料阻尼比幅值是多少,这是考虑土与结构相互作用对高层建筑结构风振响应有利还是不利的关键问题.通过对无桩基桩架-剪力墙结构的顺风向风振响应分析,发现考虑土-结构相互作用时结构基础底面土体的动剪应变幅值处于弹性应变范围,根据土动力学中土的动剪应变与土的阻尼比的关系,土体的材料阻尼比较小,其值不超过0.03,据此计算出相应的结构最大层间位移和结构顶层的最大加速度比将地基视为刚性的结构有较大增长;因此,在高层结构风振响应分析中应考虑土-结构相互作用的影响.文章通过实例分析给出无桩基高层建筑土体材料阻尼比的建议值,该研究为有桩基高层建筑的土体材料阻尼比的计算提供了借鉴.     

Numerical well test for well with finite conductivity vertical fracture in coalbed

A new well test model is developed for the hydraulic fractured well in coalbed by considering the following aspects： methane desorption phenomena, finite conductivity vertical fractures, and asymmetry of the fracture about the well. A new parameter is introduced to describe the storage of the fracture, which is named as a combined fracture storage. Another new concept called the fracture asymmetry coefficient is used to define the asymmetry of the fracture about the well. Finite element method （FEM） is used to solve the new mathematical model. The well test type curves and pressure fields are obtained and analyzed. The effects of the combined fracture storage, desorption factor, fracture conductivity, and fracture asymmetry coefficient on the well test type curves are discussed in detail. In order to verify the new model, a set of field well test data is analyzed.     

去角质化妆品对皮肤摩擦性能的影响研究

采用UMT-Ⅱ多功能摩擦磨损试验机,模拟洗脸的摩擦条件,考察了微粒大小、数量和硬度不同的3种磨砂洗面奶介质对不同性别人体皮肤摩擦特性的影响.结果表明：由于在往复摩擦条件下磨砂洗面奶去除了皮肤表面老化角质层,皮肤的表面粗糙度下降,皮肤的电导、水合作用、黏着力及摩擦系数增加;含有2种微粒大小、数量和硬度适中的B组洗面奶介质摩擦去除老化角质较多,皮肤后续对保湿化妆品的渗透效果较好;由于不同性别皮肤表面结构的差异,磨砂洗面奶对男性皮肤表面结构的影响较女性大.     

Displacement of surrounding rock in a deep circular hole considering double moduli and strength-stiffness degradation

The problem of cavity stability widely exists in deep underground engineering and energy exploitation. First, the stress field of the surrounding rock under the uniform stress field is deduced based on a post-peak strength drop model considering the rock's characteristics of constant modulus and double moduli. Then, the orthogonal non-associative flow rule is used to establish the displacement of the surrounding rock under constant modulus and double moduli, respectively, considering the stiffness degradation and dilatancy effects in the plastic region and assuming that the elastic strain in the plastic region satisfies the elastic constitutive relationship. Finally, the evolution of the displacement in the surrounding rock is analyzed under the effects of the double modulus characteristics, the strength drop, the stiffness degradation, and the dilatancy. The results show that the displacement solutions of the surrounding rock under constant modulus and double moduli have a unified expression. The coefficients of the expression are related to the stress field of the original rock, the elastic constant of the surrounding rock, the strength parameters, and the dilatancy angle. The strength drop, the stiffness degradation, and the dilatancy effects all have effects on the displacement. The effects can be characterized by quantitative relationships.     

圆柱形弹性贮液容器的自振特性分析

贮液容器,无论是由钢材制成的或是由钢筋混凝土建造的。在工业或工程上都有着广泛的应用,如石油化工工业中的储油罐,给水工程中的水即为典型例子。在核动力工程中的压水堆或快增残堆,所用的主容器都可看成为一种特殊的贮液容器。它与一般容器很大的区别在于除贮液外,在堆内还设置一些构件。这对结构分析计算速写为不小的困难。本文根据剪切悬壁梁理论且考虑液动压力效应,建立了弹性圆柱形贮液容器的自振方程及相关特征值矩阵,     

Status of turbulence modeling for hypersonic propulsion flowpaths

This report provides an assessment of current turbulent flow calculation methods for hypersonic propulsion flowpaths, particularly the scramjet engine. Emphasis is placed on Reynolds-averaged Navier–Stokes (RANS) methods, but some discussion of newer methods such as large eddy simulation (LES) is also provided. The report is organized by considering technical issues throughout the scramjet-powered vehicle flowpath, including laminar-to-turbulent boundary layer transition, shock wave/turbulent boundary layer interactions, scalar transport modeling (specifically the significance of turbulent Prandtl and Schmidt numbers), and compressible mixing. Unit problems are primarily used to conduct the assessment. In the combustor, results from calculations of a direct connect supersonic combustion experiment are also used to address the effects of turbulence model selection and in particular settings for the turbulent Prandtl and Schmidt numbers. It is concluded that RANS turbulence modeling shortfalls are still a major limitation to the accuracy of hypersonic propulsion simulations, whether considering individual components or an overall system. Newer methods such as LES-based techniques may be promising, but are not yet at a maturity to be used routinely by the hypersonic propulsion community. The need for fundamental experiments to provide data for turbulence model development and validation is discussed.     

A solution including skin effect for stiffness and stress field of sandwich honeycomb core

Honeycomb sandwich panels have been increasingly used in every possible field, and their efficient load carrying capacity attributes have attracted considerable attention. All previous studies have been focused mainly on stiffness, neglecting for the most part skin effects. This paper represents an important further contribution by developing an analytical model that permits the computation of stiffnesses as well as interfacial stresses considering the skin-effect for hexagonal honeycomb sandwich, subjected to in-plane and out-of-plane forces. An explicit analytical model is derived based on equilibrium equations, where boundary conditions imposed by the skin effect are appropriately considered. The accuracy of the solution is verified through close correlations with existing stiffness formulations and finite element results. The skin effect on both stiffness and interfacial stress distribution is analytically defined. The present model is then used to carry out a parametric study on interfacial stresses, and to detect the critical sections in the structure where further consideration should be given for design purposes. The method provided in this study can be used for accurate analysis and design of sandwich structures.     

带腐蚀Euler-Bernoulli海洋管道模型在海波激励下的振动分析

研究了考虑腐蚀和海生物附着作用的海洋管道在海波激励下的动力学响应．采用欧拉-伯努利梁模型建立细长海洋管道动力学模型，利用格林函数法得到了该受迫振动问题的稳态响应．首先，推导了未腐蚀且考虑海生物附着的海洋管道在海波激励作用下的动力学响应．其次在考虑腐蚀、海生物附着情况下，利用前面未腐蚀模型的解得到腐蚀管道的动力学响应解析解．最后进行了数值讨论，分析了不同腐蚀深度、不同生物质量对管道固有频率的影响．研究了三种输流截面面积相同的环（圆、矩形、三角）模型在同一海波激励作用下的稳态位移响应．分析了不同海波高度、不同海波数目、不同海洋深度及腐蚀深度对管道模型位移的影响；对比了未腐蚀和有腐蚀深度时，某点随时间变化的位移效果．研究结果对海波激励下的管道响应分析和保护具有重要意义．     

Formulation of stress-strain relation for plastic deformation of mild steel for strain trajectory consisting of two straight branches

A relation between the stress and incremental strain deviators, which are not coaxial, is derived by considering the characteristics in tensor space. On the bases of this relation and of precise experimental results for mild steel, a specific plastic stress-strain relation is formulated for a strain trajectory with a comer in a 3D-vector space corresponding to the strain deviator, as a typical example of plastic behaviour under complex loading. It may be confirmed that the effects of plastic anisotropy and of the third invariant of the strain deviator on the plastic behaviour of mild steel under complex loading are expressed precisely by means of the above formulation.     

Visualizing surface strain distribution of facial skin using stereovision

An experimental technique has been developed for measuring and visualizing strain distribution on facial skin. A stereovision technique based on digital image correlation is employed for obtaining the displacement distribution on the human face. Time-variation of the movement of the facial skin surface is obtained from consecutive images obtained using a pair of high-speed cameras. The strains on the facial skin surface are then obtained from the measured displacements. The performance of the developed system is demonstrated by applying it to the measurement of the strain on facial skin during the production of sound. Results show that the strains on facial skin can be visualized. Further discussion on the relationship between the creation of wrinkles and strains is possible with the help of the developed system.     

汗液对皮肤摩擦特性的影响研究

采用人工汗液模拟人体汗液,在连续和间歇式往复摩擦运动模式下研究汗液对正常人体皮肤、穿戴假肢皮肤以及残肢疤痕皮肤摩擦性能的影响,并模拟假肢穿戴环境研究汗液对皮肤摩擦舒适度的影响. 结果表明:在法向载荷为0.2 N和0.7 N的连续和间歇式往复摩擦运动模式下,汗液均通过改变皮肤表面的物理化学性能而对皮肤的摩擦行为产生影响;在汗液逐渐干燥的过程中,皮肤的摩擦行为从粘着向相对滑移状态转变,摩擦系数变化经历从小到大再减小、最后达到稳定的过程;在法向载荷为8.0 N、模拟假肢穿戴环境的连续式往复摩擦运动模式下,汗液环境中的正常小腿皮肤、穿戴假肢皮肤和残肢疤痕皮肤的摩擦系数均大于干燥环境.根据皮肤在摩擦过程中的疼痛感、牵扯感和灼热感等同时提出皮肤摩擦舒适度概念,与干燥的假肢穿戴环境相比,汗液均加强了不同皮肤的摩擦不舒适感.     

Effects of Surface Waves and Marine Soil Parameters on Seabed Stability

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｆｏｒｃｅｓｅｘｅｒｔｉｎｇｏｎｃｏａｓｔａｌｓｔｒｕｃｔｕｒｅｓ,ｓｕｃｈａｓｏｆｆｓｈｏｒｅｄｒｉｌｌｉｎｇｒｉｇｓ,ｏｆｆｓｈｏｒｅｏｉｌｓｔｏｒａｇｅｔａｎｋｓ,ｂｕｒｉｅｄｐｉｐｅｌｉｎｅｓ,ｂｒｅａｋｗａｔｅｒｓ,ｅｔｃ .ａｒｅｄｕｅｔｏｗａｔｅｒｓｕｒｆａｃｅｗａｖｅｓ.Ｔｈｅｗａｔｅｒｗａｖｅｓｐｒｏｐａｇａｔｉｎｇｏｖｅｒｔｈｅｏｃｅａｎｃａｎｃｒｅａｔｅｔｒｅｍｅｎｄｏｕｓｄｙｎａｍｉｃｐｒｅｓｓｕｒｅ .Ｔｈｅｐｒｅｓｓｕｒｅ…     

Structural stability and failure analysis using peridynamic theory

The peridynamic theory has been successfully utilized for damage prediction in many problems. However, the elastic stability of structures has not been studied using the peridynamic theory. Therefore, this paper investigates the elastic stability of simple structures to determine buckling characteristics of the peridynamic theory by considering two sets of problems. The first set of problems involves rectangular columns under compression to find the effects of the cross-sectional area and boundary conditions on buckling load. The second set involves rectangular plates under a uniform temperature load to establish the effects of plate dimensions and material properties on the critical buckling temperature. The predictions of the peridynamic theory agree with those published in the literature. The solution method is based on reducing the peridynamic equations of motion to discrete forms by using collocation points. These discrete equations are then solved using adaptive dynamic relaxation. Furthermore, perturbation method using geometrical imperfections is utilized to trigger lateral displacements in the numerical solutions.     

散料在料仓内流动特性的实验研究

用振动筛测量多种散料的筛分尺寸，测量散料的容积密度、安息角，用应变直剪仪进行散料内摩擦角、壁面摩擦角的测量，分析了散料颗料的形状、尺寸对散料的安息角、内摩擦角、壁面摩擦角的影响。用示踪法进行了圆筒内散料重力场中颗粒流线和等时线的试验，以及出口直径与流量的关系、筒仓内散料高度对流量的影响的试验，流量与筒仓内散料高度关系的试验。分析了散料各物性参数对散料流动性的影响，为散料存贮和运输设备的结构设计提供实验依据。     

The exact analytical solutions to the new model of reservoir filtration problem

The present study has obtained the new model of the reservoir filtration problemby taking into account the effect of wellbore storage and skin and by making use ofthe coupled equations of doubled porous media filtration and consequently has got,through various forms of limits,the exact analytical solutions of the three commonreservoirs(fissure,homogeneous and the two-layered)pressure distribution under theconditions of three boundaries,i.e.,infinite boundary,sealed finite boundary and thefinite boundary at constant pressures.     

考虑破碎影响的颗粒材料亚塑性模型及应变局部化模拟

在基于2ndP-K应力率的亚塑性模型基础上,通过引入一个能够考虑颗粒破碎影响的孔隙比-平均压力临界状态方程,形成了一个能够模拟颗粒破碎影响的颗粒材料亚塑性模型,数值算例考查了颗粒破碎对应变局部化模式及位移-承载曲线的影响,结果表明,所建议模型具有模拟破碎对颗粒材料应变局部影响的良好性能。     

Predicting thermal shape memory of crosslinked polymer networks from linear viscoelasticity

The viscoelastic behavior of an amorphous shape memory polymer network and its dependence on time and temperature were measured by dynamic mechanical analysis. The resulting thermo-mechanical behavior was modeled and implemented in a commercial finite element code. The ability of the resulting thermomechanical model to simulate and, eventually, predict the shape storage and shape recovery of the material was evaluated against experimental shape memory thermomechanical torsion data in a large deformation regimen. The simulations showed excellent agreement with experimental shape memory thermomechanical cycle data. This demonstrates the dependence of the shape recovery on time and temperature. The results suggest that accurate predictions of the shape recovery of any amorphous polymer networks under any thermomechanical conditions combination solely depends on considering the material viscoelasticity and its time–temperature dependence.