安装参数与掘进参数对滚刀破岩阻力的影响

为获得不同切削顺序下盘形滚刀安装参数与掘进参数对其破岩阻力的影响,通过建立多滚刀破岩数值模型,研究不同切削顺序下滚刀贯入度、刀间距、安装半径与刀盘转速等参数对滚刀破岩阻力的影响规律,采用多因素正交实验法分析各因素对破岩阻力的影响显著性,并通过滚刀破岩试验验证数值分析结果的正确性.研究结果表明：滚刀破岩阻力总体上随贯入度、切削速度、刀间距与安装半径的增加而增大;不同切削顺序下,滚刀破岩阻力各不相同,其差异性随贯入度增加以及刀间距减小而逐渐增大;3种不同切削顺序下,贯入度对滚刀破岩阻力影响均为非常显著,刀盘转速和滚刀安装半径对破岩阻力影响较小,刀间距对破岩阻力的影响随切削顺序变化而有明显差异,破岩试验结果与仿真基本一致.     

混合遗传算法求解包含柔性工艺的作业车间调度问题

针对离散制造企业中通常采用柔性工艺设计这一类新的作业车间调度问题,对传统的柔性作业车间调度问题进行了扩展,建立了包含柔性工艺的作业车间调度问题的数学模型.针对问题中在作业调度同时进行柔性工艺选择的特点,设计了改进的遗传算法染色体编码方式和遗传算子,在此基础上,结合变邻域搜索算法,设计了4种不同的邻域结构以产生邻域解,从而提高遗传算法的邻域搜索性能.最后以某轴承公司的实际调度数据为实例,将该算法进行实例测试,并与其他现有的方法相比较,验证了所设计算法的有效性.     

双节理岩体TBM滚刀破岩过程数值模拟

为了研究节理特征对全断面掘进机(tunnel boring machine, TBM)盘形滚刀破岩的影响,采用颗粒流方法建立盘形滚刀与含平行双节理岩体的二维数值模型,进行不同节理倾角和间距的30组数值试验,根据数值试验结果研究岩体破裂模式、滚刀竖向接触力峰值随节理倾角和间距的变化规律、滚刀破岩过程中细观裂纹扩展规律。研究结果表明:不同的节理特征下,滚刀破岩可以分为4种基本的破裂模式;滚刀竖向接触力峰值随节理倾角的增大呈现先减小后增大的趋势,在节理倾角为30°或45°时最小,在节理倾角为90°时最大;滚刀竖向接触力峰值随节理间距的增大总体上呈现增大趋势;随滚刀的贯入,滚刀竖向接触力与细观裂纹个数有3个关联的变化阶段。通过研究TBM滚刀与节理岩体相互作用机制,揭示不同节理特征对滚刀破岩的影响规律,对TBM滚刀的合理设计和施工有一定的指导意义。     

EPB盾构掘进机刀具运动学建模分析

EPB盾构掘进机的刀盘上可根据切削土质的软硬而选择安装硬岩刀具和软土刀具。通过运用空间几何理论以及空间运动学的坐标变换矩阵法对刀盘上安装的正滚刀、边滚刀以及切刀的破岩过程进行分析,得出了刀具破岩的运动规律,建立了刀具工作刀刃的破岩运动学模型。模型的建立有利于对刀具进行磨损和破岩机理以及刀具优化设计的研究。     

薄板冷轧过程中宽展的变化规律及其影响因素

基于金属流动原理,采用显式动力学有限元软件ANSYS/LS-DYNA模拟薄板轧制过程,研究轧制力、摩擦系数、压下率对轧件宽展变化的影响。结果表明,摩擦系数越大,轧件宽展也越大;轧件的最大宽展随着轧制力的增加而增大,轧制力对轧件后端部分宽展影响程度较大;压下率增大,轧件宽展随之增大,轧件各部分宽展的不均匀程度也在增加。     

岩石特性对掘进机破岩的影响

目的研究岩石特性对掘进机破岩的影响,提高掘进机施工效率,延长滚刀使用寿命．方法将滚刀及其掘进的岩石作为一个整体,模拟破岩过程中滚刀和岩石的应力分布,并通过实验测量了滚刀破岩时滚刀受力和切深等参数,分析了不同硬度的岩石、切深和滚刀施加力对滚刀及岩石受力的影响．结果岩石反作用于滚刀的力和岩石的切深沿切割方向呈波浪型水平线;岩石抗压强度增大,岩石的切深和破碎区体积降低．结论同种岩石破碎程度与滚刀切割力大小成正比;切割力相同时,岩石破碎程度与岩石抗压强度成反比;研究结果对提高岩石掘进机的破岩效率,及其对地质的适应性具有重要作用．     

Experimental investigation on hard rock fragmentation of inserted tooth cutter using a newly designed indentation testing apparatus

This investigation aims to explore the effects of stress conditions and rock cutting rates on hard rock fragmentation through indentation tests on a newly designed triaxial testing apparatus. This apparatus was designed to realize a triaxial loading and indentation test of cylindrical specimens using inserted tooth cutter. The boreability and crushing efficiency of granite rock was investigated by analyzing the change rules of the thrusting force, penetration depth, characteristics of chippings and failure patterns. Several quantitative indexes were used to evaluate rock boreability in this investigation. The granite rock samples all had a chiselled pit and a crushed rock core. Under initial stress conditions, only flat-shape chippings were stripped from the rock surface when the thrusting force reached 20 kN. The rock cutting special energy had a close correlation with the initial stress conditions and inserted tooth shape. Moreover, a thrusting force prediction model was proposed in this paper. The contribution of this study is that for the first time the influence mechanism of the initial triaxial stress conditions on rock fragmentation is investigated using an inserted tooth and the newly designed testing apparatus. This study has a crucial importance for practical underground hard rock crushing in geoengineering.     

基于载荷转移的爆胎汽车操纵动力学研究

通过分析爆胎引起的车轮半径变小进而引起汽车载荷转移的过程,建立爆胎汽车方向失稳动力学模型.通过研究汽车爆胎后车轮的滚动半径变化的影响,对爆胎汽车姿态变化而引起的载荷转移进行分析;及通过载荷转移结合轮胎特性所导致的各个车轮上的侧偏力大小对汽车行驶方向失稳影响的研究;根据轮胎模型应用魔术公式建立侧偏角与侧偏力的对应关系并建...     

数控系统的刀具半径补偿技术研究

数控系统的刀具半径补偿是在CNC系统内部由计算机自动完成的.在加工过程中,CNC系统根据零件轮廓尺寸、刀具运动的方向指令(G40,G41,G42)以及实际加工中所用的刀具半径值自动计算出刀具中心轨迹,完成对零件的加工.介绍了C功能刀具半径补偿原理,根据平面内刀具半径补偿转接过渡的不同转接类型,针对C功能刀补的工程实际应用,提出了交角转接及直接转接两程序段间的软件实现方法.针对实际轮廓加工过程中刀具半径补偿的执行过程:刀具补偿建立、刀具补偿维持及刀具补偿撤消,结合所用的数控系统和刀具,编制了凸轮轮廓的加工程序.实践证明,C功能刀具半径补偿方法切实可行,且效率高.     

Effect of pre-tensioned rock bolts on stress redistribution around a roadway-insight from numerical modeling

The importance of the pre-tensioned force of rock bolts has been recognized by more and more researchers. To investigate the effect of pre-tensioned rock bolts on stress redistribution around roadways, a numerical analysis was carded out using FLAC3D and a special post-process methodology, using surfer, is proposed to process the numerical simulation results. The results indicate that pre-tensioned rock bolts have a significant effect on stress redistribution around a roadway. In the roof, pre-tensioned rock bolts greatly increase vertical stress; as a result, the strength of the rock mass increased significantly which results in a greater capacity of bearing a large horizontal stress. The horizontal stress decreases in the upper section of the roof, indicating that pre-tensioned rock bolts significantly reduce the coefficient and the size of the region concentration of horizontal stress. At the lateral side, pre-tensioned rock bolts greatly increase the horizontal stress; therefore, the rock mass strength significantly increases which results also in a greater capacity of bearing a large vertical stress. The greater the size of pre-tensioned force, the larger the region of stress redistribution around a roadway is affected and the higher the size of the stress on the roadway surface the more the rock mass strength increases.     

Gauge-meter model building based on the effect of elastic deformation of rolls in a plate mill

The calculation error of the gauge-meter model will affect the gap setting precision and the self-learn precision of rolling force. The precision of the gauge-meter model is strongly influenced by plate width, working roll radius, backup roll radius, working roll crown, backup roll crown, and rolling force. The influence rules are hard to get by measuring. Taking a conventional 4-h plate mill as the research subject, these influences were transferred into the calculation of roll deflection and flattening deformation. To calculate these deformations, the theory of the influence function method was adopted. By modifying the traditional gauge-meter model, a novel model of the effect of roll elastic deformation on the gap setting was built by data fitting. By this model, it was convenient to analyze the variation caused by the rolling condition. Combining the elastic deformation model of rolls with the kiss-rolls method, a gauge-meter model was put forward for plate thickness prediction. The prediction precision of thickness was greatly improved by the new gauge-meter model.     

Hoek-Brown破坏准则求解圆形硐室塑性区半径与修正的芬纳公式比较

目的 为定量确定围岩塑性区半径和给支护锚杆的深度设计提供科学依据.方法 以Hoek-Brown破坏准则为极限平衡条件,推求侧压力系数为1.0时圆形硐室理想弹塑性围岩的弹塑性应力和塑性区半径,运用Mohr-Coulomb准则直线拟合Hoek-Brown准则曲线和面积差补方法 ,求取等效的岩体Mohr-Coulomb强度参数后,建立相对塑性区半径随支护力和地质强度指标变化的二元非线性回归数学模型,并与源自于Mohr-Coulomb强度准则为屈服条件的修正的芬纳公式进行比较研究.结果 支护力每增加1.0 MPa,就可确保地质强度指标降低10～20的岩体中不会出现塑性区.在支护力较小和岩体质量较差情况下,采用Hoek-Brown破坏准则推导得出的塑性区半径和修正的芬纳公式计算得出的塑性区半径差别稍大.相对塑性区半径与地质强度指标都呈负乘幂函数关系,随着支护力的增大,塑性区半径随着岩体质量等级的升高而下降的趋势逐渐变缓.建立的相对塑性区半径随地质强度指标和支护力变化的二元非线性回归数学模型简明,使支护力连续变化,提高了工程实用性.结论 在岩体质量较差情况下,锚杆深度取1.8～3.0倍硐半径为宜.     

全断面硬岩TBM滚刀磨损关键技术分析

目的研究全断面硬岩掘进机（TBM）刀盘上滚刀的相关关键技术,分析破岩机理及滚刀的磨损问题.方法以双护盾TBM刀盘为研究对象,将岩石的硬脆特性与压痕断裂力学相结合,确定破岩机理及影响滚刀磨损的因素.确定滚刀布置原则、运动特性、破岩机理和滚刀磨损形式及其主要影响因素.结果结果表明,TBM刀盘设计制造要满足耐磨性的要求,滚刀布置要符合空间力系平衡,刀具高度应一致,高度差不应大于15 mm,防止刀盘滚刀会发生大面积磨损.除常规的检测刀具磨损外还要注重掘进过程中的参数观测,一旦发生特殊情况,应及时检测及更换刀具,防止其他刀具也受到损坏.结论刀盘设计要符合耐磨性要求,同时应增强对常规磨损参数检测和掘进参数的观测,控制滚刀磨损量,优化TBM掘进参数,防止大面积刀具磨损发生.     

基于应力场的高速面铣刀安全性研究

针对高速面铣刀切削加工过程的特点,在刀具可靠性分析基础上建立了高速可转位面铣刀的应力场模型和刀具及其组件的安全性判据.通过有限元分析,获得了切削力和离心力对高速面铣刀应力场影响规律,并获得了刀具安全转速.高速面铣刀切削试验结果表明:基于应力场分析开发的高速面铣刀,在其安全转速范围内应力场分布状态较好,并在切削速度为2 010 m/min时达到最佳的切削性能.     

多滚刀顺次作用下岩石破碎模拟及刀间距分析

相邻滚刀刀间距设计是全断面岩石掘进机(TBM)刀盘设计的关键技术之一,刀间距设计的合理与否直接关系到刀盘刀具掘进效率和寿命.刀间距设计不仅与岩石边界条件、刀盘掘进参数及刀具参数有关,而且与刀盘结构相互耦合相互影响,且相邻滚刀之间是一种顺次破碎岩石的过程.基于有限元岩石破碎仿真平台RFPA2D,考虑相邻多滚刀的顺次约束关系,分别以2种典型岩石(泥质粉沙岩和花岗片麻岩)为边界条件,建立多滚刀顺次作用下垂直压入岩石的破碎仿真模型,模拟多滚刀在顺次压入和同时压入岩石的仿真过程,建立了刀间距与岩石破碎能量之间的映射关系,进而建立了多滚刀最优刀间距下顺次角度与岩石破碎能量之间的映射关系,通过此映射关系可以确定滚刀在刀盘上不同位置的最优刀间距和最优的顺次角度,并为下一步滚刀在刀盘盘面上的布置设计提供设计依据.     

横风对高速动车组直线运行动力学性能的影响

通过建立高速动车组动力学仿真模型,分析了高速动车组在所受气动升力、侧力和倾覆力矩作用下的运行安全性.以某350 km/h动车组为原型,采用动拖动的编组方式,建立了列车动力学模型.动车转向架采用转臂式轴箱定位结构,二系悬挂由空气弹簧与横向减振器、抗蛇行减振器组成.研究常速横风及阵风对动车组各车的影响.仿真结果表明:横向风对脱轨系数、轮重减载率及轮轨横向力均有很大的影响,尤其是轮重减载率,在所计算的工况下,几乎所有的轮重减载率均超出了标准要求,因此在横向阵风的作用下,动车必须限速运行,否则会有脱轨的危险;另外,阵风对动车组的影响要大于常值侧风,并且横风对头车的影响比其他车辆要大很多.     

基于余弦速度场的厚板轧制力能参数建模

为建立一个预测精度可靠的轧制力模型,根据轧件变形时金属流动的特点提出了一个余弦速度场,并基于该速度场进行了相应的能量解析。该速度场能够严格满足体积不变条件、出入口速度边界条件以及几何方程,较好地满足了运动许可条件。建模过程中,基于分矢量内积加和法导出了轧制内部变形功率,解决了非线性Mises比塑性功率带来的积分问题。同时,基于该速度场也导出了摩擦功率、剪切功率的数学表达式。在此基础之上,依据刚塑性变分原理获得了轧制力能参数的解析模型。利用国内某厂现场轧制数据对建立的轧制力模型进行了验证。结果显示,各道次轧制力预测值与实测值的误差均在7.55%以内,具有较高的精度。将所建模型与经典的Sims模型和Tselikov模型进行了对比,也显示了较好的优越性。此外,为了研究厚板轧制过程中的参数变化规律,本文也先后分析了压下率、形状因子、摩擦因子、径厚比、轧辊半径对应力状态系数和中性点位置的影响。     

曲线地段直线电机轮轨列车动力学响应

为研究直线电机轮轨列车行驶于曲线段线路上时,铁路线路条件对列车动力响应的影响规律,以便为修改线路设计规范提供理论依据.建立直线电机轮轨交通列车线路动力学模型,模型中直线电机所受垂向电磁力大小随列车牵引速度和电机气隙的变化而时刻改变.仿真模拟并分析垂向电磁力、车速、曲线半径、超高、轨道不平顺对系统动力响应的影响.结果表明:轨道垂向不平顺和高车速对气隙影响显著;列车通过小半径曲线段时,垂向电磁力对脱轨系数和轮重减载率的消减作用显著;脱轨系数、轮重减载率、轮轨横向力、车体横向加速度、车体横向位移这5类动力响应的最大值,同时受车速、曲线半径、超高影响显著.基于5类动力响应最大值的拟合公式,可对车速、曲线半径、超高取值范围进行合理匹配,并确定曲线地段的合理车辆限界.     

Numerical analysis of the effects of rock bolts on stress redistribution around a roadway

Besides opening geometry, in situ stress and material properties, opening support also has significant effects on stress redistribution around a roadway. To investigate these effects of rock bolts on the stress redistribution around a roadway, a series of numerical studies were carried out using the finite difference method. Since the stress changes around a roadway caused by rock bolting is small relative to the in situ stress, they cannot obviously be observed in stress contour plots. To overcome this difficulty, a new result processing methodology was developed using the contouring program Surfer. With this methodology, the effects of rock bolts on stress redistribution can obviously be analyzed. Numerical results show that in the three patterns of rock bolts installed in the roof, in the roof and the two lateral sides, and in all the four sides of the rectangular roadway, the maximum stress magnitude of the increase is 0.931 MPa, 2.46 MPa,and 6.5 MPa, respectively; the bolt number of 5 can form an integrated ground arch; the appropriate length and pre-tensioned force of the rock bolt is 2.0 m and 60 k N, respectively. What is more, the ground arch action under the function of rock bolting is able to be effectively examined. The rock bolts dramatically increase the minor principal stress around a roadway which results in significant increase in material strength. Consequently, the major principal stress that the material can carry will greatly increase.With adequate supports, an integrated ground arch which is critical for the stability of roadway will be formed around the roadway.     

Composite rock-breaking of high-pressure CO2 jet & polycrystalline-diamond-compact(PDC) cutter using a coupled SPH/FEM modelOA

CO₂ drilling is a promising underbalance drilling technology with great advantages, such as lower cutting force, intense cooling and excellent lubrication. However, in the underbalance drilling, the mechanism of the coupling CO₂ jet and polycrystalline-diamond-compact(PDC) cutter are still unclear. Whereby, we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM) model to simulate the composite rock-breaking of high-pressure CO₂ jet...