煤岩力电耦合模型及其参数计算

电磁辐射技术已经在矿山煤岩动力灾害预报中得到了应用，根据煤岩强度的统计理论和损伤力学理论，建立了受载煤岩的力电耦合模型，推导得到了该模型中参数的确定方法，并结合实验结果对其中的参数进行了计算．结果表明：煤岩材料的破坏是内部代表性体元微损伤累积的结果，电磁辐射可以反映煤岩体的损伤程度，力电耦合模型能够较好地描述煤岩变形破裂过程的电磁辐射规律，参数的拟合相关系数较大说明该方法合理可行．     

基于有限元模型修正技术的结构损伤检测

结构损伤检测已成为工程领域中的前沿性课题之一.由于联合静动法模型修正技术包含了结构的众多信息,因此利用联合静动法模型修正技术进行结构损伤检测时能够得到较好的结果.在传统的联合静动法基础上,提出了一种基于有限元模型修正技术的新式联合静动法.结合一个简支梁的算例,讨论研究了该方法实现过程.仿真计算结果表明了该新式联合静动法模型修正技术的有效性.     

水压轴压联合作用下煤岩的统计损伤本构模型研究

从煤岩内部节理、裂隙和物质分界面等缺陷的随机性分布特征出发,基于反映煤岩内部缺陷的微元强度服从weibull分布的概念,建立了水压和轴压联合作用下煤岩的损伤本构模型.以东庞北井9#煤静态压缩试验为基础确定了模型里面的相关参数,并得出了与峰值应力对应的累积损伤度(即临界损伤度).研究结果表明:(1)模型参数少且易于确定;(2)模型能反映围压效应,即可以体现煤岩体强度随水压变化的规律;(3)模型参数确定方法揭示了模型参数的物理意义;(4)可以通过不同围压下煤岩体应力-应变全曲线特征及在不同围压下峰值应力与应变之间的关系来确定模型参数;(5)在弹性矩阵中引入孔隙水压力影响因子来考虑孔隙水压力对煤岩损伤本构模型的影响,这种方法被证明是可行的.     

对铰杆增力机构中滑柱力学模型的修正

对<机床夹具设计>[1,2]中抽象的滑柱力学模型,进行了分析,指出其错误在于滑柱承受的是一个非平衡力系,建立了基于平衡力系的力学模型,并推演出了相应的力学计算公式.     

对铰杆增力机构中滑柱力学模型的修正

对《机床夹具设计》[1,2 ]中抽象的滑柱力学模型 ,进行了分析 ,指出其错误在于滑柱承受的是一个非平衡力系 ,建立了基于平衡力系的力学模型 ,并推演出了相应的力学计算公式     

对铰杆增力机械中滑柱力学模型的修正

对《机床夹具设计》＾「１,２」中抽象的滑柱力学模型,进行了分析,指出其错误在于滑柱承受的是一个非平衡力系,建立了基于平衡力系的力学模型,并推演出了相应的力学计算公式。     

损伤塑性模型的耦合关系

由于ABAQUS软件的强大分析能力和模拟复杂问题的可靠性,已经在土木领域中得到广泛应用。分析了软件中能有效模拟混凝土非线性行为的损伤塑性模型(CDP)的耦合关系,并总结比较两种模型理论中损伤的物理意义。     

建筑物夜景亮度计算模型及修正系数

为了解决国际照明委员会（CIE）推荐的照明计算公式不适合具有混合光反射性质的现代建筑饰面材料的问题,寻找一个能符合现代建筑饰面材料的亮度计算方法,达到建筑节能与城市夜景亮度控制目的。在光度学实验室对30种常用建筑饰面材料不同方向的亮度进行了测量,用测量获得的不同方向亮度值计算出亮度修正系数K（i,β）,还分析了光在传播过程中受大气影响衰减与反射亮度的关系。将K（i,β）值与视看距离、光源种类、灯具利用、材料清洁程度、照明系统维护等作为修正系数补充CIE计算公式,建立一个新的计算模型。通过计算比对,新模型计算的照度值仅为传统公式计算的1/3。     

耐热钢蠕变损伤力学模型研究

在理论推证和试验的基础上,建立了一种崭新的蠕变损伤强度理论,引入了一个新的强度指标,即材料的极限有效损伤应力强度。实验证明它较之传统强度理论中的屈服极限或强度极限更具有合理性,实验测定结果的稳定性更好。因此,依据该强度理论,可对发生蠕变损伤的耐热钢构件或耐热钢结构的有效使用寿命,作出更加合理的估计。     

混凝土塑性损伤模型损伤因子研究及其应用

在有限元软件ABAQUS中,为混凝土材料定义了一种材料模型:塑性损伤模型,它可以模拟混凝土材料的拉裂和压碎等力学现象,而且使用也较为方便.本文基于能量损失原理,编制相关的计算程序,获得了现行《混凝土结构设计规范》提供的混凝土受压和受拉应力-应变关系曲线对应的混凝土损伤因子随应变增长的变化曲线.基于本文的研究成果,介绍了损伤因子在钢筋混凝土构件、新型钢管混凝土-钢筋混凝土梁节点和整体结构弹塑性分析中的应用实例.本文的有关论述和方法可为同类研究提供参考.     

A damage-based constitutive model for rock under impacting load

Using the Splitting Hopkinson Pressure Bar (SHPB) experimental system, investigations were made into the dynamic mechanical performances of underground soft rocks. The experiments proved that the measured stress–strain curves display the characteristics of plastic deformation. By making use of a revised overstress constitutive formula for the stress model and by taking into account that the strain rate and strain are a function of 1 − E(t)/E₀, a revised overstress constitutive formula for the stress model was simplified by applying dimensional analysis and consequently, a simplified overstress formula was obtained for the stress model. Then, by taking into consideration the effects of damage under a dynamic load on the dynamic loading strength of the rock, the continuous damage theory and the statistical strength theory were introduced into the development of the simplified overstress constitutive formula for the stress model. Hence, a damage-based constitutive formula for an overstress model, which can be appropriately applied to the analysis of full dynamic stress–strain curves, was developed. By using the simplified damage-based constitutive formula for an overstress model, the actually measured curves are fitted, indicating that the fitting curves and those actually measured are in good agreement.     

岩石在压应力作用下的裂纹扩展模型

在分析压应力作用下裂纹扩展模型的基础上,指出了目前几种常用的岩石中平面分支裂纹尖端应力强度因子的近似解析式所存在的问题,并给出了应力强度因子的较为简便且合理的近似表达式.     

冻融荷载下节理岩体的复合损伤模型

针对工程实际中的冻融受荷岩体,以岩石初始损伤状态为参考状态,将冻融与荷载作用引起的损伤视为细观损伤,节理引起的损伤视为宏观损伤,根据Lemaitre应变等效性假设,推导建立考虑宏细观缺陷的节理岩体复合损伤模型.应用该模型分析贯通率和冻融次数分别对岩体力学性质劣化的影响,结果表明:在贯通率一定时,损伤演化曲线随冻融次数的增加而增加,试验与理论峰值强度(或弹性模量)曲线随冻融循环次数增加而降低;在冻融次数一定时,损伤演化曲线与贯通率呈正相关关系,试验与理论峰值强度(或弹性模量)与贯通率呈负相关关系.说明贯通率与冻融次数对岩体的劣化产生一定影响,且饱和试验组受冻融效应较天然试验组力学性能劣化严重.将所建模型计算结果与试验值进行比较,理论曲线与试验曲线吻合良好,验证了所建模型的合理性与有效性.     

冻融受荷岩石唯象损伤扩展特性探讨

针对工程地质和岩土工程中所涉及到的冻害问题,从细观力学机理出发,将冻融循环次数及应变和岩石的损伤变量联系起来,得到宏细观相结合的冻融受荷岩石损伤演化方程及损伤扩展本构关系;对冻融荷载作用后的岩石进行唯象损伤扩展特性分析.研究发现:岩石的冻融损伤是一个疲劳损伤破坏过程,在寒区岩体工程设计和施工中,必须考虑冻融损伤的影响;寒区工程结构受荷岩石的岩性、初始损伤状态及力学性质的不同,造成冻融循环和荷载对损伤扩展的影响差别非常大,并表现出终态的宏观差异.     

岩石软化的细观损伤模型

通过分析岩石材料应变软化的细观损伤力学过程 ,建立了岩石软化阶段的细观损伤力学模型 ,从而得到单向拉伸状态下岩石软化过程的应力应变本构关系 .     

Stochastic fatigue damage model for concrete under complex stress states

This paper presents a stochastic fatigue damage model for concrete subjected to complex stress states. A constitutive framework considering the tensile and shear damage mechanisms and elastic and plastic energy dissipations is employed. The damage law is established through a multiscale analysis of the damage evolution mechanism. Validation results against test data show that the model can effectively predict the static strength, stress-strain curve, fatigue life, and scattering range of concret...     

Catastrophe model and its experimental verification of static loading rock system under impact load

According to the catastrophe model for impact buckling of static loading structures, a new catastrophe model for impact loading failure of a static loading rock system was established, and one dimension （1D） catastrophe model was analyzed. The analysis results indicate that the furcation collection where catastrophe may take place is not only decided by mechanical system itself but also relates to exterior loading, which is different from the results obtained under mono-static loading where the bifurcation collection is only determined by mechanics of the system itself and has nothing to do with exterior loading. In addition, the corresponding 1D coupled static-dynamic loading experiment is designed to verify the analysis results of catastrophe model. The test is done with Instron 1342 electroservo controlled testing system, in which medium strain rate is caused by monotony rising dynamic load. The parameters are obtained combining theoretical model with experiment. The experimental and theoretical curves of critical dynamic load vs static load are rather coincided, thus the new model is proved to be correct.     

Thermal-hydro-mechanical coupling damage model of brittle rock简

Based on fluid mechanics, thermodynamics and damage mechanics, thermal-hydro-mechanical （THM） coupling damage model of brittle rock is established by analyzing THM coupling mechanism, where THM coupling damage variable DTHM is dominated by TH coupling damage variable DTH, TM coupling damage variable DTM and HM coupling damage variable DHM, and DTH is firstly expressed in term of dimensionless total thermal conductivity of the water Nu. Permeability test, uni-axial compression test and THM coupling test are conducted to measure the permeability, elastic modulus and THM coupling stress-strain curves of brittle rock. The tested values of THM coupling elastic modulus E＇HM are in good agreement with the predicted values of THM coupling elastic modulus ETHM, which can verify the newly established THM coupling damage model.     

Damage statistical mechanics model of top coal in steep top caving coal

Damage statistical mechanics model of horizontal section height in the top caving was constructed in the paper. The influence factors including supporting pressure, dip angle and characteristic of coal on horizontal section height were analyzed as well. By terms of the practice project analysis, the horizontal section height increases with the increase of dip angle β and thickness of coal seam M. Dip angle of coal seam β has tremendous impact on horizontal section height, while thickness of coal seam M has slight impact. When thickness of coal seam is below 10m, horizontal section height increases sharply. While thickness exceeds 15m, it is not major factor influencing on horizontal section height any long.     

极温冻融-荷载作用下碳纤维复合材料修复试件损伤分析

为了研究碳纤维复合材料(CFRP)对冻融损伤混凝土柱的修复效果,按照混凝土耐久性及碳纤维加固规范要求,对混凝土试件进行冻融0、50、100、150、200次后,采用不同修复间距、不同纤维量CFRP,对其进行修复,再进行轴压试验,以压缩荷载、竖向整体位移、膨压比等为参数研究试件微观结构下CFRP修复冻融损伤受压性能,提出了CFRP修复冻融损伤混凝土受压模型.试验结果表明:冻融循环对混凝土抗压性能影响很大,CFRP修复技术能够有效提高冻融损伤混凝土抗压承载力,最大可提高630.6％,同时,CFRP修复试件承载力的提高与修复间距无关,而与CFRP的纤维量有关.修复试件的竖向整体位移随着冻融次数的增加而增大,随着CFRP修复间距的增大而减小.膨压比随着冻融循环先减小后增大再减小,膨压比峰值从"凸"型逐渐变为"凹"的塌陷底峰值,且峰值距离逐渐减小.通过纤维修复混凝土冻融损伤微观分析,建立了混凝土粘塑性损伤模型,研究了混凝土破坏过程及荷载-应变关系,验证了模型合理性.