【作者】 计三有；

【导师】 孙国正；

【作者基本信息】 武汉理工大学 ， 机械设计及理论， 2002， 博士

【摘要】 散体材料是许多工程机械与散货装卸机械的工作对象与工作介质，散体结构的挖掘与破坏是散体工程中的一个主要工作方式与目的。在挖掘过程中，散粒物料的挖掘阻力直接影响其工作机械的性能与效率，由于散体材料力学特性的复杂性，给挖掘阻力的研究及工程实际应用带来了很大的困难。因此，散体力学特性及挖掘阻力的研究具有重要的理论意义和工程实用价值。 针对散体工程中散体的挖掘与破坏课题，本文从以下三个大方面开展了研究：1．研究散粒体的力学特性并探讨其本构关系；2．研究挖掘阻力并建立工程实用的计算模型；3．抓斗取料装置挖掘过程的计算机仿真模型及挖掘过程的实验研究。在理论及实验研究的基础上，取得了一些具有理论意义和工程应用价值的研究成果。本文具体研究内容如下： 1)．分析了散粒体临界状态下的变形特征，应用能量平衡原理导出了临界状态下的变形规律，即散粒体临界状态下的本构关系。该本构模型反映了散体材料的非相关塑性流动，取代了散体极限平衡理论中散体材料服从相关流动法则的假定。指出散粒体临界状态下的主应变率与主应力共轴，而与临界应力面形状无关。给出了临界状态下的能量平衡方程及塑性功与临界应力面的关系。 2)．提出了一种含4个材料常数的亚弹性本构模型，来描述散粒体在加载时的力学行为，本模型的分析结果与不同相对密度下标准砂的三轴实验可较好地吻合，能反映散粒体的剪缩、剪胀现象，还对如何用三轴实验数据来确定这4个材料常数，给出了适宜的计算方法。该模型与W Wu.和D Kolymbas提出的亚塑性本构模型相比，具有形式简单的优点，所提供的材料常数确定方法，克服了亚塑性模型中因选取参考点的不同所确定的材料常数值变化大的弊病。 3)．从理论上论证了经典的塑性极限分析理论中的上、下限定理对散体材料的适用性，并给出了相应的限制条件。建立了挖掘过程推压阻力的计算模型，该模型适用面广、计算较简便，既避免了滑移线适用面窄的局限性、也避免有限元分析对散体渐近破坏过程模拟的复杂计算过程，计算结果与工程实际吻合，具有工程实用价值。 4)．分析了各因素对挖掘过程推压阻力的影响，在此基础上，提出了一武汉理工大学博士学位论文个更为简化的推压阻力计算模型;以该模型为基础，建立了推压阻力系数表，为工程应用提供了方便。同时也得出了一些具有工程实用价值的结论:(1).挖掘过程中存在着一个最优挖掘角度;(2).散体容重y、散体粘结力。联合产生的推压阻力值尸可以近似地表示为散体容重r独立产生的推压阻力值与散体粘结力c独立产生的推压阻力值的迭加。 5).提出了抓斗取料装置挖掘过程中散粒物料破坏模式及其判断准则;提出了斗刃的运动方向与破坏模式的关系;给出了抓斗斗体推压阻力的力学模型。以港口常用的长撑杆双颗板抓斗为典型，建立了力学模型与计算机仿真的数学模型，并编制了相应的计算机仿真程序。挖掘过程仿真结果表明:本文所建立的挖掘过程仿真模型可以反映抓斗实际抓取过程中初始阶段的下挖现象及后期阶段的上移趋势。 6).设计并建立了抓斗挖掘过程及抓取量的实验台，并对抓斗取料过程及抓取量进行了实验研究，得到了抓斗的实际挖掘曲线。实验结果表明:本文所建立的抓斗挖掘过程计算模型与实验结果能较好吻合。更多还原

【Abstract】 Granular materials is the object or medium actuated by lots of engineering machinery and bulk solids handling machinery. Digging and breakdown of the granular structure is a major actuating mode or objective in granular engineering. The digging resistance of granular materials affects directly function and efficiency of the working machine in the process of the digging materials. Because of the complicated mechanical behaviors of granular materials, we come up against difficulties in study of digging resistance and its actual engineering application. So that research on the mechanical behavior of granular materials and its digging resistance have important theoretical significance and engineering application value.Aiming at the problem of the digging and breakdown of the materials in granular engineering, this paper has carried out the research in the following three fields: 1. Research on the mechanical behaviors of granular materials and establishment of its constitutive models. 2. Research on the digging resistance of granular materials and establishment of its engineering applicable models. 3. Research on computer simulation models of the grab in the process of its digging the materials and experiment research on process of grab digging the materials. On the basis of the theoretical and experimental research, a lot of the research achievements have been obtained which have theoretical significance and engineering application value. The research contents in detail are following:1). This dissertation analyses the deformation characteristics of granular materials at critical state, and the deformation regulation is derived on the principle of energy equilibrium, i. e. the constitutive relationship of granular material at critical state. This constitutive model describes the non-associated plastic flow of granular material, and replaces the assumption that granular material complies with associated flow rule in the limit" equilibrium theory of granular material. It points out that the principal strain rate is coaxial with the principal stress at critical state and is independent of the critical stress surface. The energy equilibrium equation and the relation between plastic work and thecritical stress surface are given.2). This dissertation presents a hypoelastic constitutive model with four material constants in describing the mechanical behavior of granular materials under loading. Analysis results of the model have good coincidence with those of triaxial experiment of the standard sand under different relative density. The model can describe the contractant and dilatant phenomena of granular materials. A suitable calculation method is given to identify the fore material constants using trialxial tests. In comparison with the hypoplastic constitutive model presented by W. Wu and D. Kolymbas, this model has the advantage of form simplicity. The determination method of material constants presented in this dissertation avoids disadvantage that material constants vary with the chosen reference point.3). This dissertation verifies the applicability of the upper limit theorem and the lower limit theorem in the classical plastic limit analysis theory, and gives correspondingly constrained conditions. The pushing resistance model in digging process is set up. This model has wide-ranging application and simple computing procedure. It avoids the narrow-ranging limitations of slide line method, as well as avoids the complicated computing procedure in the simulation of the gradual breakdown process for the granular structure by FEM. Its analysis results are identical with those of the practical engineering, this model has engineering application value.4). On the basis of affection factor analysis of the pushing resistance in digging process, the dissertation brings up the more simplified resistance model. On the basis of the model, the factor table of the pushing resistance is set up for convenient engineering application. Furthermore some conclusions having engineering application value are obtained:更多还原