【作者】 姬国强；

【导师】 廉自生；

【作者基本信息】 太原理工大学 ， 机械设计及理论， 2008， 硕士

【摘要】 采煤机截割过程是一个复杂的过程,其根本原因在于煤岩结构及性质的复杂性。煤岩不是完整的质料均匀的各向同性体,它既不是完整弹性体,也不是理想塑性体,而具有明显的脆性。分析了煤岩在截割破碎过程中的物理和力学性质及破坏准则,这些是进行计算机模拟的基本前提。通过对采煤机截割理论的分析,认识到采煤机截割过程主要包括四个阶段:变形阶段、裂纹阶段、压实核形成阶段及裂纹扩展及崩裂阶段,这四个阶段不断重复实现了煤岩的不断破碎和脱落。在截割过程中,作用在截齿上的载荷是在各种复杂且在空间上不断变化的条件下形成的,伴随大量的随机因素,可将截齿的受力简化为三向力:截割阻力、牵引阻力和侧向力。对截割过程影响的主要因素包括:截齿形状、截割速度、截割厚度、安装角及截槽形状等。本文运用LS-DYNA对煤体的截割过程进行模拟,在模拟中由于模型相对简单,选择直接在ANSYS环境下直接建模。在模拟前还需对模型配置各自的材料模型、材料参数、约束条件及载荷等,其中材料模型的选择是个至关重要的问题,直接关系到模拟结果的可靠性。在模拟时选择了四种方案:变换截割速度、变换截割厚度、变换截齿锥角及变换安装角。通过模拟得到了各种截割条件下的三向阻力,对比分析同种方案中不同阻力的统计值,总结出了一定规律。运用Matlab对三向阻力结果进行了频谱分析,得到了频域中各载荷的能量分布曲线,从中分析出了各向载荷的主要频率,主要频率对截割过程的影响最大,关系到采煤机震动的剧烈程度和工作的稳定性,从而在进行采煤机结构的设计时要尽可能使采煤机的固有频率远离这些主要频率。通过对截割过程模拟的应力云图动画分析,展现了截割过程中煤体应力分布情况,加深了对截割过程的认识。更多还原

【Abstract】 The cutting process of shearer is a complex process, because the strucrure and nature of coal is complex. The coal is not the entity of the same nature in every direction with regular qulity. It is neither the full elastic entity nor the complete plasticity entity, and it is obviously brittle.The paper analyses the physical, mechanics character and damage rule in cutting process, which provides the basic requirement for computer simulation.Through analysis for the cutting theory of shearer,it is realized that the cutting process of shearer involves four periods: the deform period, the crack period, the compaction core forming period, the crack expandition and crumble period. The coal is constantly broken and falls off when the four periods continuously appear. In the cutting process, the loads on pick form in all kinds of complicated and constantly changeable space conditions which accompanies with many random factors. The forces on the pick is simplified to three direction forces: the cutting resistance, the pulling resistance and the side resistance. The main factors affecting the cutting process involves : the shape of pick, the cutting velocity, the cutting thickness, the install angle and the shape of cutting groove. The paper simulates the cutting process of coal with LS-DYNA.The model is directly set up in ANASYS environment for the model is relatively simple in simulation.Before the simulation, it is necessary that material model ,material parameter, restrain qualification and loads should be offered. The choice of the material model is an important problem,it affects the reliability of simulation result.In simulation four schemes are chosen: the different cutting velocities, the different cutting thicknesses, the different cone angles and the different install angles. By simulation the three direction resistances in every cutting conditions are got. Compared with the statistics values of different resistances in the same scheme, some rules are concluded. With Matlab,the frequency spectrum of three direction resistances results are analysed, and energy distribution curves of every load in the frequency field are received. The main frequencies of every load are found out from the curves. The main frequency affects the cutting process greatly, it is attached with the fierce of vibration and work stabilization of the shearer. So inherent frequency of shearer should be far away from these main frequencies in the design of the shearer structure.By dynamic analysis of the stress distribution for the simulation of cutting process, the stress distribution of the coal model is found out, which makes the cutting process realized deeply.更多还原