Composite rock-breaking of high-pressure CO_(2)jet&polycrystallinediamond-compact(PDC)cutter using a coupled SPH/FEM model

CO_(2) 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 CO_(2) 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 CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.

Numerical simulation of rock-breaking and influence laws of dynamic load parameters during axial-torsional coupled impact drilling with a single PDC cutter

Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground.Still,the corresponding theory is not mature,and there are few correlative research reports on the rock-breaking mechanism of axial and torsional coupled impact drilling tools.Considering the influence of the impact hammer geometry and movement on the dynamic load parameters(i.e.,wavelength,amplitude,frequency,and phase difference),a numerical model that includes a hard formation and single polycrystalline diamond compact cutter was established.The Riedel-Hiermaier-Thoma model,which considers the dynamic damage and strength behavior of rocks,was adopted to analyze the rock damage under axial and torsional impact loads.The numerical simu-lation results were verified by the experimental results.It was found that compared with conventional drilling,the penetration depths of axial,torsional,and axial-torsional coupled impact drilling increased by 31.3%,5.6%,and 34.7%,respectively.Increasing the wavelength and amplitude of the axial impact stress wave improved the penetration depth.When the bit rotation speed remained unchanged,increasing the frequency in the axial and circumferential directions had little effect on the penetration depth.However,as the frequency increased,the cutting surface became increasingly smooth,which reduced the occurrence of bit vibration.When the phase difference between the axial and circumfer-ential stress waves was 25%,the penetration depth significantly increased.In addition,the bit vibration problem can be effectively reduced.Finally,the adjustment of engineering and tool structure parameters is proposed to optimize the efficiency of the axial-torsional coupled impact drilling tool.

Application of reaction nitrogen arc cladding TiCN/Fe composite coating on cutter of agricultural machinery

In order to solve the high-price and short-lifetime problems of the cutter of agricultural machinery,and improve the wear resistance of the cutter, the TiCN/Fe metal ceramic composite coating was prepared on the substrate of Q235 steel by reaction nitrogen arc cladding technique. The mixture powder of titanium and graphite was preplaced on the Q235 steel surface after intensive mixing by planetary ball mill and gluing with starch binder. The microstructure and phase of the coatings, interface behavior between coatings and the substrate were investigated by scanning electronic microscope and X-ray diffractometer. The micro-hardness distribution of the coating section was tested by micro-hardness tester. Friction coefficient and wear weight loss were measured by abrasion machine. Wearing surface morphology was investigated by scanning electronic microscope. The results show that an excellent bonding between the coatings and the Q235 steel substrate is ensured by the strong metallurgical interface and phase of the coatings. The coatings are mainly composed of TiCN. The highest micro- hardness of the coatings reaches 1 089 HV0. 2, while the micro-hardness of Q235 steel substrate is only about 286 HV0. 2. The anti-abrasive test results show that the wear resistance of the cladding coating is better than that of quenched and tempered 65 Mn steel which is often used as cutter of agricultural machinery. The field test results show that the TiCN/ Fe metal ceramic composite coating prepared by reaction nitrogen arc cladding is feasible to the manufacture and remanufacture of the cutter of agricultural machinery.

具有内阻的旋转锥形复合材料刀杆铣削过程稳定性的仿真分析

研究考虑材料内阻的旋转圆锥形复合材料刀杆铣削系统的再生颤振稳定性。基于复合材料粘弹性本构关系、Hamilton原理和Rayleigh梁理论,结合再生时滞铣削力模型,分别导出旋转坐标以及惯性坐标表示的颤振偏微分方程。采用Galerkin法对颤振偏微分方程进行离散化。基于自由振动分析和能量法计算复合材料刀杆的模态损耗因子;基于特征值分析技术计算旋转复合材料刀杆的临界速度和失稳阈。采用时域半离散法和频域零阶近似解法,预测切削系统的稳定性。分析锥度比、长径比、铺层角、铺层方式,以及内、外阻对切削稳定性的影响。计算结果表明,轴对称旋转刀杆铣削过程在两种坐标系下的稳定性预测结果是一致的。研究发现,在高转速下,由于旋转复合材料刀杆内阻的作用,切削系统出现新的不稳定区域。这些新的不稳定区域的起始转速等于旋转复合材料刀杆的失稳阈。

复合地层加强型盾构对比选型技术与滚刀磨损特征研究

为应对复杂地质条件下经验方法无法定量评价掘进机设备选型适应性和经济性的难题,提出盾构/TBM对比选型方法,基于地层综合组段划分技术,依据开挖面岩层性质、地下水情况、施工环境等因素将复杂地层划分成若干独立组段,计算不同类型掘进设备在各个组段内的施工效率和施工成本并作对比,综合汇总后给出各类设备施工定量化效率、工期和经济指标,决策者可根据项目主控因素作出选型结论。此外,同时结合包含硬岩和不良地质段的隧道工程掘进机选型实例,分析加强型盾构对此类地层的适应性,给出首例加强型盾构的配置参数和针对性设计,并对加强型盾构在硬岩段掘进时的滚刀磨损进行回归分析。研究结果表明:(1)盾构/TBM对比选型技术综合考虑不同设备在各隧道组段内的适用性、施工效率、施工成本,选型决策更具科学性和实用性;(2)加强型盾构配置6 r/min刀盘转速和19英寸大直径滚刀,可大幅提升掘进效率,因此对硬岩地层和不良地质段兼具适应性;(3)加强型盾构滚刀累计磨损量与其安装半径呈指数型相关性,边缘滚刀磨损速率最大,施工中应及时检修,保障开挖直径充足。

PCD刀具车削玻璃纤维增强复合材料切削温度研究

进行了PCD刀具车削玻璃纤维增强复合材料实验,研究了切削用量对切削温度的影响规律。研究结果表明:切削温度随着切削速度的增加而增大,随进给量的增加先增大后减小,随着背吃刀量的增加而增大。

Cr-C类石墨复合涂层制备表征及其在硬质合金铣刀上的应用

为了提高硬质合金铣刀的使用寿命,降低摩擦加工时的摩擦因数,本文结合Cr元素对涂层生长的促进作用与类石墨(GLC)涂层的优异性能,采用磁控溅射离子镀的方法,在硬质合金(YG8)上制备Cr-C类石墨复合涂层。通过拉曼光谱对复合涂层成分类石墨进行表征。利用扫描电镜观察涂层截面形貌,结合线扫描与面扫描结果对涂层元素成分分布进行表征。对复合涂层试样进行摩擦磨损试验,测定摩擦因数并计算磨损率,采用硬度测量仪测定复合涂层的硬度,使用自动划痕仪来评定复合涂层结合力。结果表明:Cr-C类石墨复合涂层具有典型的类石墨非晶碳结构特征,复合涂层整体厚度约为0.68μm;Cr元素主要分布在底层与过渡层,少量掺杂在工作层;C元素主要分布在工作层中,各层涂层内部没有裂纹、孔洞等缺陷,涂层的致密性较好。Cr-C类石墨复合涂层摩擦因数约为0.2,由磨痕形貌测得磨损体积为65.6651 mm^(3),磨损率为2.28×10^(-4) mm^(3)/(N·mm),复合涂层摩擦因数低,耐磨性好。复合涂层硬度可达824~986 HRV,与传统类石墨涂层相比,硬度提升28.22%~51.69%,复合涂层与基体之间的结合力为24 N,与同样应用于硬质合金铣刀的涂层相比,具有良好的结合性能。本文研究可为Cr-C类石墨复合涂层在硬质合金铣刀中的应用提供依据。

超大直径常压复合刀盘结构设计与分析

基于某过江隧道工程穿越的地质水文情况,并结合拟建工程区间大断面、长距离、高水压等特点,探讨了软硬不均等复合地层中盾构施工重难点,同时在借鉴国内外相应的理论研究成果和典型应用案例的基础上,着重对拟选超大直径盾构机的刀盘结构、刀具配置、中心冲刷等进行针对性设计分析,旨在设计出匹配拟建隧道工程施工的盾构刀盘,解决拟建区间面临的施工重难点、规避施工风险,并为后续类似工程盾构刀盘设计提供一定参考。

一种轮毂周圈孔的加工工艺方法优化

轮毂是汽车上必不可少的一种关键零部件,轮毂周圈孔精度不仅要求高,而且数量多,因此,其加工工艺方法及刀具的选择直接关系到轮毂周圈孔的加工精度及效率。文章采用工步合并的方法对一种轮毂周圈孔的加工工艺进行了分析与优化,且自主设计制作复合镗刀,在保证轮毂周圈孔精度的基础上,有效提高了轮毂的加工效率,降低了成本。

Rock deformation equations and application to the study on slantingly installed disc cutter

At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the func- tional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke＇s law and analyze the effect of the slanting installa- tion angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.

PDC单齿切削破碎非均质花岗岩性能的评价新方法

聚晶金刚石复合片(PDC)钻头在非均质、研磨性强的复杂地层存在破岩效率低、使用寿命短的问题,现有研究普遍孤立看待PDC齿的寿命和破岩效率。为此,根据PDC齿的攻击性能、受力状态及破岩效率间的关系,以2种花岗岩为研究对象,建立了非均质花岗岩的有限元模型,然后对3种PDC齿(锥形齿、鞍形齿和圆形齿)切削破碎非均质花岗岩的破岩效率的影响因素进行了研究,最后对3种齿的破岩性能进行了评价,对切削倾角进行了优选,最终提出一种评价PDC齿破岩性能的新方法。研究结果表明:①岩石细观矿物成分、强度、尺寸和含量会影响破岩效率,岩石的细观平均强度和岩石矿物泊松比的增加均会降低破岩效率;②围压的增加会降低齿的破岩性能,3种齿形的破岩性能从大到小排序为锥形齿、鞍形齿和圆形齿,且不受围压与切削倾角的影响;③当切削深度为1 mm,且仅考虑切削作用时,鞍形齿最优切削倾角范围为10°~15°,锥形齿的切削倾角优选范围为5°~10°,圆形齿的推荐切削倾角范围为0°~5°。结论认为,破岩性能评价新方法综合考虑了PDC齿的破岩效率、几何形状及其受力状态,能充分体现PDC齿的能耗经济性、寿命经济性及其切削参数的攻击特性差异,可为PDC齿形设计和参数优化提供新思路和新依据。

高温损伤岩石高压CO_(2)射流PDC齿联合破岩研究

欠平衡气体相比传统钻井液钻井技术,可提高机械钻速、减少和避免井漏和压差卡钻事故的发生。欠平衡钻井的井筒多相流及控压钻井工艺研究较为完善,但是围绕油气井欠平衡钻井中的CO_(2)气体射流-PDC齿联合破碎高温岩石问题尚不明确。通过单轴压缩与巴西劈裂试验测试高温损伤后岩石力学特性,然后在高压CO_(2)射流-PDC齿切削破岩试验破岩系统上进行联合破碎高温损伤后岩石试验,研究其破岩规律与切削力变化。力学特性测试试验结果表明,随加热温度的增大,砂岩加热后抗拉强度先减小后陡增,抗压强度先减小再增大。切削力与岩石力学参数相关性分析显示,岩石弹性模量与切削力关联度较强。联合破碎岩石的试验结果表明,高压CO_(2)射流能对岩石进行预打击,且射流强化齿前岩屑运移和齿后岩屑的排出,显著降低切削齿阻力,降低破碎岩石所需的切削力。进一步研究岩石加热温度、射流压力和喷嘴直径等工况参数的影响,当流体压力、喷嘴直径、射流温度分别为20 MPa、2 mm、45℃时,射流对砂岩的打击、携岩效果良好,切削力小,有利于破岩。本研究对指导高温井气体钻井技术和配套钻头研发具有重要指导意义。

油茶林立式螺旋松土除草机设计与试验

为实现低矮密集型油茶林松土、除草、除灌一体化作业,解决油茶林土壤板结、草灌杂生等问题,设计了立式螺旋松土除草机。通过对油茶林常见杂草、杂灌根系的物理力学特性分析,结合刀具运动分析,设计了立式螺旋耕刀。采用Hertz-Mindlin bonding接触模型建立了根土复合体模型,以降低功耗为目标对刀具参数进行了仿真优化,分析其对根土复合体的扰动情况,并试制样件进行了土槽试验,检验耕作效果,验证了仿真分析的可靠性。仿真结果表明:优化后立式螺旋耕刀对根土复合体的扰动率可达到91.41%,切削土壤时最大功耗为0.16 kW;切削根土复合体时最大功耗为0.77 kW。土槽试验表明:耕刀的耕深稳定性系数为92.34%,碎土率95.00%,除根率95.30%;螺旋耕刀在切削土壤时,实际测得最大转矩为7.93 N·m,比仿真值低6.57%;切削根土复合体时,实际测得最大转矩为34.84 N·m,比仿真值低4.91%,两者比较接近,验证了设计的正确性。设计的立式螺旋松土除草机满足丘陵山地油茶林松土、除草、除灌作业要求。

复合地层中不同刃形滚刀与岩石接触行为研究

目的滚刀截面形状即刃形对滚刀综合性能影响显著,研究不同刃形的滚刀在复合地层中的载荷变化特点,把握各型滚刀应用于复合地层时的优势与劣势,对于减少滚刀失效、降低刀盘偏载具有重要指导意义。方法通过滚刀破岩试验获取和对比3种刃形的滚刀(平顶、圆顶和螺旋槽滚刀)在软硬复合地层中的切削力、破岩体积等关键指标,同时建立滚刀破岩有限元数值模型,探究滚刀刃形影响其切削岩石性能的机理和规律。结果在复合地层中工作时,平顶滚刀所需的法向力均值最高,其余滚刀则相近。这是由于圆顶和螺旋槽滚刀破岩时仅有部分表面参与接触,接触面积均小于平顶滚刀,应力集中效应明显,从而降低破岩法向力。螺旋槽滚刀在切削不同强度岩石时的法向力差距最小;圆顶滚刀的法向力标准差的值最小。3种滚刀均形成了粉末状和片状岩石碎片,平顶和圆顶滚刀形成的岩石碎片总体积相近而螺旋槽滚刀略低。结论复合地层软硬岩强度相差较大时,可选用螺旋槽滚刀以减轻刀盘偏载;硬岩部分强度较高时,推荐选用圆顶滚刀,以减小切削力和载荷冲击。

复合地层小直径盾构刀具切削过程仿真及参数优化

基于ABAQUS有限元软件,以厦门地铁四号线滨海复合地层为依托,建立切刀切土、滚刀破岩过程仿真模型,对盾构刀具切削过程进行动态分析。通过对比、筛选切削力的影响因素,进行切刀、滚刀的多参数正交试验,获取不同因素的主次影响程度,进而得出优选刀具结构参数。研究结果表明,基于CEL法的切削仿真模型更符合实际的土体切削过程;刀具参数的最优组合为刀刃宽1 mm、刀刃角20°、刀刃圆弧半径为0.5 mm。

复合土质疏浚施工关键技术研究

在进行新港池开辟时,常常会遇到多种类型的土质复合在一起的情况,绞吸挖泥船在进行这类复合土质施工时往往效率较低,不能充分发挥船机设备的性能。依托莱基深水港工程,针对复合土质重新优化了绞吸船的挖掘系统和输送系统。经过在实际工程中应用,发现通过采用新型5臂绞刀挖掘系统、新型高效泥泵及复合材料输泥管线等措施能够大大提高绞吸船的施工效率和时间利用率,对节约成本和发挥船舶性能有重要意义。

大直径盾构常压复合刀盘滚刀刀筒结构设计与分析

为解决大直径盾构常压复合刀盘后置式滚刀刀筒在实际应用中螺栓受频繁交变应力影响易损坏的问题,通过借鉴国内外研究成果,设计前置式常压滚刀刀筒结构。将螺栓由受拉力承受滚刀推力的受力模式改变为刀筒直接承受滚刀推力,加强了对螺栓的防护。为验证该前置式常压滚刀刀筒的可靠性,通过理论与有限元分析相结合的方法,对前置式常压滚刀刀筒进行结构分析,包含静力学分析、模态分析及谐响应分析(静力学分析结果显示最大Mises应力未超过材料许用应力;模态分析与谐响应分析结果显示刀筒工作频率远小于结构自振频率,有效避免共振失效的发生),验证了刀筒设计的合理性。将该设计方案应用于实际工程项目,结果显示刀筒未出现螺栓松动、断裂现象,也未出现常压复合刀盘刀筒刀座压溃、刀筒失效等情况。理论分析与实践结果均显示该刀筒结构设计合理,可应对目标工程的地质情况,可为后续类似工程刀盘刀筒的选型设计提供参考。

软硬复合地层中盘形滚刀冲击载荷预测及影响因素分析

针对掘进机盘形滚刀在软硬复合地层中因受到冲击载荷而损坏的问题,利用科罗拉多矿业学院滚刀受力计算模型推导出楔形滚刀在软硬岩交界处垂直载荷随时间历程的解析表达式,并利用有限元数值模型试验验证其正确性,运用此解析表达式分析了关键因素对盘形滚刀所受冲击载荷的影响。结果表明:在软硬岩交界处滚刀垂直载荷的增长曲线为斜率逐渐增加的递增曲线;滚刀速度、贯入深度和刀间距的增大都会增加对滚刀的冲击破坏,故在软硬复合地层中应采取降低刀盘转速和贯入度等方法减小对盘形滚刀的不良影响。

富水复合地层掘进盾构刀具损坏控制技术

土压平衡盾构机在富水复合地层中掘进,由于穿越地层的不均匀性,加之地层溶洞发育,盾构刀具经常会出现非正常损坏的现象,从而降低盾构掘进功效,增加盾构施工成本,同时增加换刀安全风险,为此开展富水复合地层掘进盾构刀具损坏控制技术研究意义重大。以徐州城市轨道交通2号线周七区间隧道为工程实例,通过研究解决富水复合地层掘进盾构刀具损坏控制难题,为后续同类型工程提供参考与借鉴。

复合式土压平衡盾构盘形滚刀布置规律

根据目前常见复合式土压平衡盾构的结构特性,以刀盘开口特征为依据,对复合式土压平衡盾构进行分类并归纳出2种类型滚刀布置区域,建立其约束模型。通过分析盾构掘进时滚刀的受力情况,提出滚刀布置基本原则,在此基础上建立以滚刀极径与极角为设计变量的非线性多目标滚刀布置优化模型,分析模型的目标函数与约束条件,给出模型求解策略,并采用遗传算法求解得到滚刀布置参数。应用该优化设计方法对深圳地铁某施工标段所用盾构滚刀进行布置优化。研究结果表明:优化后刀盘的径向不平衡力下降10.1%,倾覆力矩下降9.4%,破岩量方差下降15.9%,表明所建立的数学模型及所使用的优化算法是正确、可行的。