Numerical Modeling of Exit-Ply Delamination During Drilling of CFRPs Considering Thermal Effects

Abstract

A finite element (FE) model for exit-ply delamination during drilling carbon fiber reinforced polymers (CFRPs) laminates is presented. The current FE model is developed to predict critical thrust force at the onset of delamination for 1 and 2 plies under the twist drill for various cutting temperatures. The interface behavior for delamination onset is modeled using surface based cohesive zone model (CZM). The numerical predictions for critical thrust force are compared with experimental thrust forces for various number of plies under the twist drill over a range of cutting temperature. Thrust force predictions were found to match with experimental data.     

Application of Deep Hole Drilling to the Measurement and Analysis of Residual Stresses in Steel Shrink‐Fitted Assemblies

Abstract: Residual stress measurement of shrink‐fitted assemblies was achieved through finite element simulations and experiments using the deep hole drilling technique. Shrink‐fitted assemblies using stainless steel and cast iron were manufactured and residual stresses measured using a combination of deep hole and centre hole drilling. The results from the finite element simulations demonstrated that modifications to the deep hole drilling method were required to account for plastic relaxation during the measurement process. This was verified through the experimental measurements. The results from both the stainless steel and cast iron assemblies provided a clear demonstration that the final residual stress state was a consequence of the machining and assembly of the components.     

信道阻尼边界对井下钻杆声传输的影响

为改善低频声波沿钻杆管肇的传输性能，分析了影响声遥测的阻尼机制。考虑钻杆内外沿轴向流动的钻井液的阻尼影响，引入流体的粘性阻尼力，建立了一维纵波波动方程。基于圆柱源辐射理论，研究纵波的径向耦合损耗，并将地层等效为Kelvin粘弹性介质，应用有限单元法求解时域波动方程，讨论了钻井液粘性阻尼和粘弹性地层边界对行波传播特性的影响。理论分析表明，径向辐射和由此产生的波型耦合是声阻尼损耗的主要形式，地层粘弹性系数的变化列低频特性影响很大，但并不改变信道通阻带交替的梳状滤波器频谱。     

Experimental investigation and optimization of machining parameters in drilling of fly ash-filled carbon fiber reinforced composites

Particle-filled polymer composites have become attractive because of their wide applications and low cost. Carbon fiber reinforced polymer (CFRP) is well known as a difficult-to-cut material, which has very strong physical and mechanical characteristics. Machining of carbon fiber reinforced composites is essential to have functional upshots, out of which drilling is the key operation needed for fabrication. In this paper Taguchi L₂₇ experimental design is coupled with grey relational analysis (GRA) to optimize the multiple performance characteristics in the drilling of fly ash-filled carbon fiber reinforced composites. Experiments were conducted on a vertical machining center, and Taguchi L₂₇ experimental design was chosen for the experiments. The drilling parameters, namely spindle speed, feed rate, drill diameter and wt% of fly ash, have been optimized based on the multiple performance characteristics including thrust force, surface roughness, and delamination. The GRA with multiple performance characteristics indicates that the wt% of fly ash and drill diameter are the most significant factors that affect the performance. Experimental results have shown that the performance in the drilling process can be improved effectively by using this approach.     

月面采样钻具锁合随动式限幅机构研究

中国探月三期工程将采用无人探测器开展月面采样探测,利用中空外螺旋钻具开展预计深度为2 m的连续钻取采样。在轨作业期间,航天器发射段和飞行段产生的随机振动负载及钻具在采样过程中存在的横向负载等附加负载会引起钻杆挠曲变形,严重时可能会导致钻取采样作业失败。在不修改取芯钻具的前提下,参考地面油田钻井工程中的相关技术,提出了一种月面采样钻具锁合随动式限幅机构。该机构主要由主支撑架、对接锁合组件和钢球锁释组件组成。在限幅机构工作过程中,其主支撑架在钻杆的中部位置提供外部支撑,减小由于飞行振动引起的挠曲变形,当钻具钻进一定深度后,对接锁合组件和钢球锁释组件实现锁合与解锁的功能,并随钻具同步向下进尺,为钻具后续的钻进动作提供空间。通过有限元分析手段,对限幅机构的强度和刚度进行校核与分析。通过试验件研制以及地面钻取采样试验验证可知：锁合随动式限幅机构作为外部支撑,能提高中空外螺旋钻具的刚度,且不会影响钻取采样的正常作业过程。研究结果表明锁合随动作业方式与当前取芯钻具的配合程度较好,提高了钻取采样作业性能及其可靠性,为完善我国探月三期工程钻取采样系统提供了参考。     

Residual stresses due to gas arc welding of aluminum alloy joints by numerical simulations

This study deals with the numerical simulation of the gas arc welding process of Aluminum tee joints using finite element analysis and evaluation of the effect of welding parameters on residual stress build up. The 3D simulations are performed using ABAQUS code for thermo-mechanical analyses with moving heat source, material deposition, solid-liquid phase transition, temperature dependent material properties, metal elasticity and plasticity, and transient heat transfer. Quasi Newton method is used for the analysis routine and thermo-mechanical coupling is assumed; i.e. the thermal analysis is completed before performing a separate mechanical analysis based on the thermal history. The residual stress build up and temperature history state in a three-dimensional analysis of the tee joint is then compared to experimental results. Hole drilling method is used for measuring the residual stress, while temperature history is measured by thermocouples. After carrying out numerical simulations, the effects of voltage/current, welding speed, material thickness and size of electrode on residual stress build-up and resulting distortions are evaluated.     

汽车轻量化连接用自流钻螺钉挤压成形工艺研究

目的 针对自流钻螺钉现有工艺生产效率低、易产生晶粒粗大等问题,提出了一种新的多工步冷挤压成形工艺——利用模腔控制螺钉尾部形状,并验证了该工艺的可行性。方法 利用有限元软件DEFORM- 3D对提出的3种不同冷挤压方案成形过程中的金属流动规律、材料填充情况、成形力进行了数值模拟,讨论了方案一和方案二中锻造缺陷产生的原因,最后根据方案三的模拟结果设计了相应模具并进行了试验验证。结果 根据方案三成形出的自流钻螺钉充填饱满,第一道工序是将圆棒坯料一端直接挤压成螺钉特定的尾部形状,该工序所需成形力为42.4 kN。第二道工序是将螺钉头部镦粗,该工序所需成形力为58.2 kN。第三道工序是终锻成形,该工序所需成形力为287.4 kN。结论 通过有限元模拟,确定了自流钻螺钉三工步冷挤压成形工艺,提出了能够避免折叠产生的预制坯形状和模具结构,实现了自流钻螺钉尾部的可控成形。通过试验验证,形成了稳定的成形工艺窗口和可靠性较高的模具结构,实现了该产品的批量生产。     

混合式单牙轮钻头破岩性能研究

在石油钻探过程中,优质的钻头对于降低钻井成本和提高钻井效率至关重要。通过设计,将牙掌结构与牙轮结构相连接,并且分别在牙轮和牙掌上安装锥形齿和PDC齿,从而设计出一种新型的混合式单牙轮钻头。该混合式单牙轮钻头较一般单牙轮钻头多了PDC齿,利用冲击和剪切原理破岩。牙轮大端通过井底中心,所有齿圈与井壁接触,在破岩的同时可以起到保径作用。建立了混合式单牙轮钻头与岩石相互作用的有限元模型,并对钻头井底模型、牙齿主切削力和破岩体积进行了仿真分析。通过台架实验对数值模拟得到的钻压和进尺量进行验证。研究结果表明,数值模拟得到的钻压和进尺量与台架测试结果相符,破岩载荷规律与钻头结构设计特点一致。混合式单牙轮钻头与球形单牙轮钻头相比,侧向力减小39.6%,破岩效率提高37%。使用该混合式单牙轮钻头钻井时稳定性更高,可以减小井斜发生的概率。根据结果可知,数值模拟在研究该混合式单牙轮钻头破岩规律中是有效的,该方法为钻头进一步设计及其工作特性的评估提供了依据。     

Experimental and finite element predictions of residual stresses due to orthogonal metal cutting

The development and implementation of a finite element method for the simulation of plane-strain orthogonal metal cutting processes with continuous chip formation are presented. Experimental procedures for orthogonal metal cutting and measurement of distributions of residual stresses using the X-ray diffraction method are also presented. A four-node, eight degree-of-freedom, quadrilateral plane-strain finite element is formulated. The effects of elasticity, viscoplasticity, temperature, friction, strain-rate and large strain are included in this formulation. Some special techniques for the finite element simulation of metal cutting processes, such as element separation and mesh rezoning, are used to enhance the computational accuracy and efficiency. The orthogonal metal cutting experiment is set-up on a shaper, and the distributions of residual stresses of the annealed 1020 carbon steel sample are measured using the X-ray diffraction method. Under nominally the same cutting conditions as the experiment, the cutting processes are also simulated using the finite element method. Comparisons of the experimental and finite element results for the distributions of residual stresses indicate a fairly reasonable level of agreement. The versatility of the present finite element simulation method allows for displaying detailed results and knowledge generated by orthogonal metal cutting processes, such as the distribution of temperature, yield stress, effective stress, plastic strain, plastic strain-rate, hydrostatic stress, deformed configuration, etc. Such knowledge is useful to provide physical insights into the process as well as to better design the process for machining parts with improved performance.     

Failure analysis and appropriate design of drill pipe upset transition area

In recent years, the drill pipe failures often happen in the case of ultra deep well drilling and complex geological conditions drilling. One of the main failure types is the stress concentration at the upset transition area of the drill pipe. Based on the elastic–plastic mechanics, finite element theory, and application of numerical simulation analysis for the actual mechanical properties of three-dimensional simulation analysis of drill pipe in the well, the finite element analysis (FEA) model of 5″ API standard drill pipe is established. The mechanical characteristic of API standard drill pipe upset transition area is simulated, which can provide a reasonable reference for the optimization of the size of new types 5″ drill pipe upset transition as well as the practical application. Based on the simulation model, the factors affecting the stress distribution of the drill pipe upset transition area are obtained, and the new type of upset is developed.     

强研磨性地层中PDC钻头井底热-流-固三场耦合研究

PDC（polycrystalline diamond compact， 聚晶金刚石复合片）钻头在强研磨性地层中破岩时，其钻齿在刮切破碎岩石的同时与岩屑、岩石剧烈摩擦，产生的局部高温加快了钻齿的磨损失效，这会极大地缩短整个钻头的使用寿命。因此，探究温度对PDC钻头磨损的影响并改进其水力结构对提升单个钻头的进尺深度和降低钻井经济成本有显著意义。为此，通过钻齿切削实验来验证其温度与磨损之间的关系，并在考虑井底钻井液流动状态及其与钻齿之间对流换热的基础上，建立了PDC钻头井底热?流?固三场耦合模型，分析了井底钻井液与PDC钻头之间的相互作用，同时针对原有的PDC钻头水力结构提出了优化措施。结果表明：1）在钻齿切削过程中温升现象十分明显，说明温度是影响PDC钻头磨损的重要因素；2）PDC钻头井底流场呈热?流?固耦合状态，且钻井液流动状态对其钻齿换热的影响大，这为钻头水力结构的优化提供了方向；3）通过调整喷嘴的流量及角度等水力结构，降低了钻齿的平均温度，可有效改善PDC钻头的磨损情况。研究结果对强研磨性地层中钻头的优化设计有重要指导意义。     

基于光纤光栅传感的螺纹钻杆复合载荷多节点检测技术

引入光纤光栅应变传感器和温度传感器,结合螺纹钻杆复合载荷（轴向压力、弯矩和扭矩）分离理论,实现对钻进过程中螺纹钻杆多节点处复合载荷自动分离与在线检测,同时对钻进过程中出现的温升进行了补偿。将检测结果与电机施加的载荷（压力和扭矩）进行对比分析,认为螺纹钻杆前端（靠近钻头一侧）受到被钻物侧向挤压和摩擦阻力较大,使得电机施加的压力和扭矩传递损耗较多,导致易磨损、变形;而螺纹钻杆中段和末端只是短暂甚至未进入被钻物,传递损耗相对较少,受弯矩的影响较大。该检测技术为钻杆材料的选择、结构优化和钻进参数的选定提供技术支撑。     

钻杆扭矩法预测冲击地压的研究

钻杆扭矩法是通过测试钻孔过程中钻机对钻杆输出扭矩的大小来判断煤矿冲击地压危险性的方法,具备许多传统方法不可替代的优点,是一种很有发展的预测预报方法。该文建立了钻屑过程中钻杆的力学模型,得出钻杆扭矩与煤体应力、煤体性质及钻进速度的关系,分析表明:钻屑过程中,煤体应力增大时,钻杆扭矩增大,钻屑推进力减小;钻屑推进速度增加时,钻杆扭矩增加,钻屑推进力增大;煤体强度增大时,钻杆扭矩增加,钻屑推进力增大。利用钻杆扭矩测试装置,测试了不同煤体应力条件下钻屑扭矩的变化规律。理论和实验结果均表明:使用相同的钻机及钻具,按照指定速度对同一性质的煤层打钻时,钻杆扭矩随着煤体应力的增大而增大,钻杆扭矩变化规律与煤体应力及钻屑量具有较好的一致性,通过测试钻杆扭矩的变化规律,得出钻孔处煤体应力场的分布化规律,进而预测煤层冲击危险性。研究结果为煤矿动力灾害预测预报提供一定的理论与实验基础。     

Hole drilling in ceramics/Kevlar fiber reinforced plastics double-plate composite armor using diamond core drill

Both engineering ceramics and Kevlar fiber reinforced plastics (KFRPs) are difficult to cut, so is the ceramics/KFRP double-plate composite armor. In this work, an experimental study of drilling the ceramics/KFRP double-plate composite armor by using a special sintering diamond core drill has been carried out on a general-purpose drilling machine. Machining mode, drilling sequence, and machining efficiency have been discussed based on drilling experiments. According to the discussed experimental results, machining using manual step feed, drilling the KFRP backboard firstly, and selecting the reasonable technical parameters could greatly facilitate the hole drilling in the ceramics/KFRP double-plate composite armor. The results achieved show that the machining method presented in this work is applicable for small order production.     

Finite element sintering analysis of metal injection molded copper brown body using thermo-physical data and kinetics

A finite element analysis based on a thermo-kinetic model was established to describe the densification process of a MIM copper brown body during sintering. This finite element analysis does not require a constitutive law; rather the thermo-physical data (density, thermal conductivity, specific heat as a function of temperature) and kinetics are used to predict sintering deformation. The thermo-physical data were obtained by measuring the brown MIM copper compacts using dilatometer (DIL), laser flash (LFA) and differential scanning calorimeter (DSC). These aspects are included in our work with emphasis on the development of a numerical model which is made possible by the commercial finite element software ANSYS@. To verify the densification-based finite element method, two case studies are made and discussed. The numerical predictions were compared with experimental measurements, and it is shown that the results numerically simulated by FE agree well with those experimentally observed by furnace sintering. Furthermore, some enhancements are suggested in temperature field calculation of FE model in order to draw a real furnace conditions.     

灰铸铁和球墨铸铁前托架钻削性能评价

从导热系数、铁屑形貌、钻孔内表面粗糙度、钻头顶部温度、钻削负载(扭矩、进给力)等方面,评价了QT450和HT250材质拖拉机前托架的钻削性能,并分析了钻削性能与微观组织的关系。结果表明,对HT250和QT450前托架钻削加工时,两者钻削负载没有明显差别;与HT250相比,QT450的石墨对基体的分割作用小,其基体组织中较多的铁素体,造成钻削加工时断屑和排屑困难,导致钻孔内表面粗糙度大;QT450导热系数低、铁屑与钻头摩擦严重,使得钻头温度较高;QT450有较小的切削力和铁屑对钻头较大的摩擦力,在这2个力作用下,QT450钻削负载与HT250基本相同。     

月壤钻进取心过程钻具热特性研究

我国探月三期工程采用回转冲击钻对月表月壤进行预计深度为2米的采样作业，采样过程中钻头由于钻削产生的切削热完全由钻具本身导热传递。由于月球的超高真空度以及苛刻的温度环境，导热效率相较于地面钻探低。同时，由于钻进工况的未知性，钻具可能会形成局部高温区域，这会使钻具的整体性能降低，尤其对钻具的取心性能影响最大。通过EDEM软件，建立不同形状及颗粒大小的月壤颗粒微元模型，组成月壤仿真模型，基于高温小颗粒群法，开展钻进过程月壤热特性仿真研究，研究温升颗粒的分布规律，并根据这一分布规律建立温升颗粒数量与温升之间的关系式。另外，在模拟月壤钻进实验中，在原有的取芯钻具上补充若干温度测量点，通过光纤光栅传感技术，开展钻具热特性实验研究，获得了钻头不同位置区域的温升规律，以及回转转速、进给速率对钻具温度的影响规律。温升颗粒数量模型以及常规热特性实验均能实现钻具温升情况的预测，为后续钻具在拟实月球环境及恶劣工况下的热安全性研究提供依据。     

3D numerical analysis of drilling process: heat,wear, and built-up edge

In this study, a 3D finite element model is developed to investigate the drilling process of AISI 1045 steel, and particularly, the heat and wear on the drill faces. To model drill wear, a modified Usui flank wear rate is used. Experiments are used for the verification of the simulated model and the evaluation of the surface roughness and built-up edge. A comparison of the predicted and experimental thrust forces and flank wear rates revealed that the predicted values had low errors and were in good agreement with the experimental values, which showed the utility of the developed model for further analysis. Accordingly, a heat analysis indicated that approximately half the generated heat in the cutting zone was conducted to the drill bit. Furthermore, material adhesion occurred in localized heat areas to a great extent, thus resulting in wear acceleration. A maximum flank wear rate of 0.026 1 mm/s was observed when the rotary speed and feed rate were at the lowest and highest levels, respectively. In the reverse cutting condition, a minimum flank wear rate of 0.016 8 mm/s was observed.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0223-z     

Selection of drilling conditions for glass fibre reinforced plastics

An experimental investigation has been carried out into the drilling of glass fibre reinforced plastics using HSS twist drills. A test series was conducted using a wide range of cutting conditions and drill geometry, namely cutting speed, feed rate, point angle and helix angle. Decisions relating to the ‘optimum’ drilling conditions were based on the geometrical accuracy and appearance of the produced holes. Drill wear was measured during the test trials and used as a further constraint in ‘optimum’ cutting conditions selection. Speed, feed rate and drill point angle were found statistically to be the most significant parameters influencing hole quality. Drill wear can be successfully correlated to the level of the thrust force. A simple nomogram is included to predict drill wear level from the thrust level or the amount of material removed.     

Research on damage distribution and permeability distribution of coal seam with slotted borehole

In order to study the effect of high pressure water jet cutting technology on the permeability of single coal seam, we use the damage variable to describe the fracture distribution of coal seam, develop the 3-D finite element program based on the damage theory, and then analyze the damage distribution of coal seam after drilling and slotting. Using MTS815 rock mechanics testing system and the permeability test system, we conduct the permeability test and get the relationship between permeability and damage. Based on the damage distribution of coal seam after drilling and slotting and the permeability change law, we analyze the permeability distribution of coal seam after drilling and slotting. The results show that: after slotting high damage appears in the coal seam around the slot, which is advantageous for gas flow and expands the effect range of the drill. The slot width has little effect on the permeability of coal seam while the slot height has the obvious effect on permeability of coal seam. It is necessary to expand the slot height for increasing the effect range of the drill.