镐型截齿截煤过程及受力分析

为进一步了解镐型截齿的磨损原因，对截齿截割煤岩过程和受力情况进行分析，将截齿看成是悬臂梁，进行受力计算和结构分析，所得结果为截齿的结构设计提供了重要的参考。     

截齿截割煤岩的LS_DYNA仿真模拟

研究应用LS_DYNA软件进行煤岩截割破碎仿真的程式与方法,对悬臂式掘进机截割头上镐形截齿截割煤岩进行仿真模拟,在hypermesh中建立有限元网格模型,调用LS_DYNA971求解器进行求解,研究不同切削角对截齿截割阻力的影响以及切削厚度与比能耗之间的关系,并与常用的截齿截割阻力公式计算结果相比较,仿真结果证明了建模...     

截割厚度与截线距对镐型截齿破岩力学参数的影响

基于对一种砂岩的直线截割试验,研究截割厚度和截线距对镐型截齿破岩力学参数的影响。单因素回归表明:截割力、法向力与截割厚度成正比,线性拟合和幂函数拟合均能很好地描述它们之间的统计学关系;随着截割厚度的增加,法向力截割力比值呈线性减小;随着截线距的增加,截割力和法向力呈线性增加,法向力截割力比值呈幂函数减小。载荷波动性系数随着截线距与截割厚度比值的增大呈线性减小。多元线性回归表明:截割力、法向力与截割厚度和截线距之间有极强的统计学关系;载荷波动性系数与截割厚度及截线距之间存在显著的统计学关系,且与截割厚度成正比,与截线距成反比。对比发现,Evans的理论模型较Roxborouth等、Goktan的改进模型对截割力有更好的预测性能。     

掘进机截割头镐齿设计与有限元分析

按照掘进机截割头设计要求完成截割头运动规律分析，镐齿的空间排列与载荷计算，并对镐齿进行有限元分析。     

掘进机截割头体、截齿座焊接组对工装的设计

在煤炭、铁路、公路、水利等行业高效自动化、智能化采掘的今天已广泛使用掘进机进行巷道掘进。截割头是掘进机进行截割煤岩、半煤岩、岩石的关键部件。随着研发人员对煤岩、半煤岩、全岩破岩机理的不断深入研究，对截割头的设计要求更加科学化、合理化，对制造的要求更为精细化。为适应不同型号截割头的设计要求，针对满足小批量多品种生产的需要。设计出满足各种参数要求的截割头体、截齿座焊接组对工装，解决了工装定位准确性、通用性的难题。     

采煤机截齿三向力测试方案设计及实验研究

为研究采煤机工作状态下截齿负载特性,设计了截齿三向力测试方案,并应用该测试方案对MG400/930-WD型采煤机进行了相关实验研究,得到了采煤机截割某实验室模拟煤壁时的截齿三向力曲线,并对实验结果和理论计算结果进行了对比分析.考虑误差和随机因素的影响,可以认为实验结果与理论分析是一致的,验证了测试方案的可行性,能为采煤机截齿相关参数的改进及采煤机截割部的设计提供实验数据和理论依据.     

镐型截齿温度场数值模拟与试验研究

以镐型截齿及其深冷处理环境为研究对象,基于Solidworks软件建立截齿的三维几何模型,基于ANSYS Fluent软件建立了镐型截齿深冷处理温度场数值模型。完成了某型截齿的温度场数值模拟,为验证该模型的合理性,完成了镐型截齿的深冷处理试验,通过截齿温度场模拟数据与试验数据对比,得出数值模拟温度与试验温度下降趋势一致,且时间相差8 min左右,表明镐型截齿温度场数值模拟具有一定的可行性。     

掘进机截割速度变化过程分析

为更准确地探讨截割头对掘进机截割性能的影响规律,提高掘进机截割效率,延长截割头及截齿使用寿命,该文用显示动力学对掘进机截割头截割煤岩时过程进行分析。以Creo、ANSYS/LS＿DYNA为模拟计算程序,截割头平行截割工况下进行模拟,利用不同速度进行分析比较,通过观察截割头的应力云图及受力情况,做出了梳理及总结,为掘进机截割头的设计工作及使用效率优化提供了理论依据。     

滚筒式采煤机煤岩截割力学特性及测试系统研究

为实现采煤机在煤岩截割过程中滚筒载荷受力的测试与分析,现场建立等比例大型采煤机力学特性分析研究实验平台,采用等效结构惰轮轴传感器测试方法,针对滚筒式采煤机在煤岩截割过程中采煤机滚筒载荷变化进行实时动态在线监测,采用无线信号发射装置实现测试数据的实时传输。现场截割实验结果表明,在采煤机截割煤岩过程中,滚筒x,y,z三向上的载荷峰值差分别为29.941,17.459和7.371kN,载荷变化显著,测试结果符合现场实际工况,为实现采煤机煤岩动态识别以及自动调高控制提供了重要的理论和数值依据。     

基于ANSYS的纵轴式掘进机单个截齿分析

悬臂纵轴式掘进机在半煤岩巷或中硬及以下的全岩巷道掘进中有着广泛的应用。本文针纵轴式掘进机，基于ANSYS有限元分析方法，结合EBZ-75型掘进机的工况，对其在截割工作时的重要受力部分截齿进行研究，建立了单个截齿的分析模型，对其受力变形及应力云图进行分析。为生产实践及截割部的设计奠定基础。     

岩石控界切割锥形聚能射流的优化设计及试验

对聚能装药形成射流冲击岩石展开研究,通过线性聚能装药和锥形罩聚能装药的爆炸破岩对比试验、数值模拟以及岩石断裂力学分析认为,采用锥形罩聚能装药结合初始裂纹形式时,能量利用率更高,能对岩石产生更好的劈裂效果。为得到高速锥形射流,运用正交分析和数值仿真对聚能装药进行了优化设计,优化后的锥形罩聚能装药的参数为:炸高15 mm、药型罩锥角84°、药型罩厚度1.35 mm。优化后的岩石劈裂试验中,两个锥形罩聚能装药同时爆炸作用于岩石,在初始裂缝的引导下形成了长度达120 cm的定向平直裂纹。该试验验证了多点锥形罩聚能装药应用于岩石控界切割技术的有效性,可应用于精细化要求的边界控制爆破。     

Deformation and fracture of rocks loaded with spherical indenters

The response of four rocks, namely granite, rhyolite, limestone and schist, to indentation by blunt cutting tools is discussed from a contact mechanics point of view. Contact forces between 0.1 kN and 2.45 kN are applied; indenter sizes are 1.0 and 5.0 mm, respectively. A transition from elastic to elastic-plastic response exists which depends on rock hardness and on indenter size. Blunt indenters promote elastic response; soft rocks tend to elastic-plastic response. In the elastic-plastic range, depression radius has a linear relationship to the indenter radius. Radial cracking occurs in soft rocks leading to strength degradation in the near surface regions. Sharp indenters promote radial cracking. The relationship between length of radial cracks and contact force is non-linear. Lateral cracking occurs in soft rocks leading to material removal. Sharp indenters promote lateral fractures. Anisotropy and non-homogeneity affect the material response notably. The ratio between fracture toughness and hardness (`index of brittleness') is a promising parameter to evaluate the behaviour of rock materials in excavation, drilling and fragmentation processes.     

Elasto-plastic analysis of a circular opening considering material dilatancy and elasto-plastic coupling effects

The deformation and fracture of a surrounding rock mass are important bases of underground engineering stability evaluation and bolting design. In this paper, an improved elastic-perfectly plastic-brittle model is employed to analyze the mechanical property weakening behavior of surrounding rock, including the elastic zone, plastic zone, and fracture zone. Examining a circular opening under hydrostatic pressure, material dilatancy, and elasto-plastic coupling were considered for an analytical study of stress and displacement of the surrounding rock. The influences of the supporting force, dilatancy, and elasto-plastic coupling were analyzed for a deep coal mine tunnel. It is shown that the supporting force cannot significantly change the state of the stress distribution, but it has an outstanding influence on the displacement of the surrounding rock. Dilatancy and elasto-plastic coupling can both cause a rapid increase of fractured zone deformation of the surrounding rock. Additionally, the majority of deformation within the surrounding rock was derived from expansion-related deformation of the fractured zone in a residual-strength state.     

切缝药包岩石定向断裂爆破的研究

以爆炸力学、岩石断裂力学理论为原理，对切缝药包在岩石定向断裂爆破中的切缝产生及裂纹起裂和扩展进行了一定的研究。同时对该法的爆破参数进行了设计，并在实验室进行模型试验验证其正确性。实验结果表明切缝管能使爆炸后的能量有方向性地集中，裂纹的定向断裂控制效果良好，现场初步试验也表明该法是一种比较理想的断裂控制爆破技术。最后还指出了该技术还需要有待研究的方向，这些对相关理论研究和现场应用均有一定的指导意义。     

Coupled poromechanics-damage mechanics modeling of fracturing during injection in brittle rocks

Subsurface injection of fluids in a stress-sensitive naturally fractured rock faces the problem of near-wellbore fracture evolution and associated changes in rock properties. Numerical modeling of the changes in permeability and poroelastic properties of the near-wellbore region is challenging due to the coupling between fracture dynamics and poromechanics across multiple length scales of fractures and the host rock. We present a numerical framework to model anisotropic and dynamic evolution in rock properties based on a coupled formulation of fluid flow, rock mechanics, and fracturing, where fracturing-induced damage is used to update the rock properties. A generalized fixed-stress method, which accounts for damage-induced anisotropy in flow and deformation processes, is developed to sequentially solve the equations of flow, mechanics, and fracture evolution. We demonstrate the usefulness of our framework in quantifying the effects of injection rate variability, initial fracture distribution, and in-situ stress state on the evolution in permeability, elastic stiffness, and the Biot parameters. Our framework does not require the computational mesh to conform to existing or future fractures, allows simultaneous growth of multiple randomly distributed fractures, and can be implemented relatively easily in existing coupled flow-geomechanics simulators to extend them to model fracturing at the reservoir scale.     

ON THE RELATION BETWEEN STABLE CRACK GROWTH AND FATIGUE

Abstract— Fatigue crack growth in the intermediate range can be described by the Paris law of linear elastic fracture mechanics. However, if gross plastic deformation is involved, the crack growth rate is often underestimated by LEFM. In the present study the increased crack growth rate due to plastic deformation is determined by using the J–R curve. This model was found to give very good results over a wide range of high crack growth rates for three different geometries of two different steels. A way to predict instability under controlled cyclic load is discussed and is proved to work well in practice. Instability under displacement control is also discussed.     

The transition between stress corrosion crack growth and plastic fracture—II. The effect of loading pattern

The paper addresses the problem of predicting the onset of plastic fracture at the tip of a growing stress corrosion crack, using data from laboratory fracture mechanics tests. A theoretical analysis for a particular model: namely that of the place strain deformation of a solid with two symmetrically situated deep cracks, and with tension of the small remaining ligament, shows that plastic fracture occurs at a $\text{J}$ value that is not constant, but depends on whether the loading is load or displacement control. This result, which is valid for materials for which the onset of crack extension and unstable fracture are coincident in a rising load fracture mechanics test, provides valuable support for the view that great care must be exercised when using fracture mechanics procedures to predict the transition between stress corrosion crack growth and plastic fracture in such materials.     

Thickness effect of notched metal sheets on deformation and fracture under tension

The deformation field in notched metal sheets stretched under tension was analysed experimentally. The results of strain distribution were explained by using the result of the near-tip deformation field of non-linear elastic material, combined with a simple model of the plastic state under a mixed plane stress and plane strain condition. Next, the relationship among fracture mechanics parameters, i.e. the notch-tip opening displacement, the notch-tip contraction and $\text{J-}\text{integral}$ was established based on the rigid plastic strip model. Finally, the effect of the specimen thickness on the toughness value at crack initiation and instability was discussed by improving Bluhm's idea that the total fracture resistance was the sum of the fracture work for slant and flat fractures.