玻璃钢复合材料夹层结构钻削试验研究

玻璃钢复合材料夹层结构凭借其优越的性能在航空航天、国防等领域得到了广泛应用,但在钻孔的过程中经常因钻削轴向力过大而出现分层、撕裂等缺陷.为此,利用正交试验方法,选用不同材质的钻头、不同切削参数对玻璃钢复合材料夹层结构进行钻削试验,分析这些因素与钻削轴向力之间的关系,得出最适合的切削参数.然后通过方差分析,得出各因素对钻削轴向力的影响程度.最后从钻削工艺角度提出改进措施,进一步提高钻孔质量.     

Comparison between response surface methodology and radial basis function network for core-center drill in drilling composite materials

Drilling using twist drill is the most frequently used secondary machining for fiber-reinforced composite laminates and delamination is the most important concern during drilling. The drill design and drilling parameters associated with thrust distribution on the drilling-induced delamination are presented. The core-center drill has been found to be more advantageous than the core drill in reference and practice experiences. Response surface methodology (RSM) is a very practical, economical, and useful tool for the modeling and analysis of experimental results using polynomials as local approximations to the true input/output relationship. Due to the radial basis function network’s (RBFN) fast learning speed, simple structure, local tuning, and global generalization power, researchers in the field of manufacturing engineering have been using RBFN in nonlinear manufacturing studies. The present paper compares these two techniques using various drilling parameters (diameter ratio, feed rate, and spindle speed) to predict the thrust force for a core-center drill in drilling composite materials. The obtained results indicated that RBFN is a practical and an effective way for the evaluation of drilling-induced thrust force.     

Thrust force and delamination of core-saw drill during drilling of carbon fiber reinforced plastics (CFRP)

Due to the inherent anisotropy and inhomogeneous nature of polymer-based composite materials, their cutting mechanism differs in many respects from conventional metallic materials. Amongst all machining operations, drilling using a twist drill is the most commonly applied method for generating holes for riveting and fastening structural assemblies. Most of the previous research correlates the drill geometry and feed rate to thrust force and delamination on the performance of a twist drill. The Taguchi method has been used to solve many engineering problems. In this investigation, drilling-induced thrust force and delamination by core-saw drill during drilling CFRP laminates were selected as quality character factors to optimize the drilling parameters to obtain the smaller-the-better characteristics. For thrust force and delamination quality character factors, the optimum conditions in drilling were also A₁B₁C₃, (i.e., diameter ratio = 0.55, feed rate = 8 mm/min and spindle speed = 1,200 rpm).     

Optimization of delamination factor in drilling medium-density fiberboards (MDF) using desirability-based approach

Medium-density fiberboards are finding increased applications in furniture and domestic industries. Drilling of these materials cannot be avoided. Delamination associated in drilling is the serious problem and this problem should be addressed further. This paper presents the systematic experimental investigation, analysis and optimization of delamination factor in drilling of medium-density fiberboards (MDF). Experiments were conducted on CNC drilling machine at various cutting conditions. The parameters considered for the experiments are cutting speed, feed rate and drill diameter. An empirical model has been developed for predicting the delamination factor at entry and exit of the holes in drilling of MDF boards. Desirability function based approach is employed for the optimization drilling parameters for minimizing the delamination factor at entry and exit in drilling of MDF boards. The influences of different parameters and their interactions are studied in detail and presented in this study.     

Experimental investigation and optimisation in drilling of GFRP composites

Glass fibre-reinforced polymer (GFRP) composite materials are one of the important materials and are economic alternative to engineering materials because of their superior properties. This paper presents an effective approach for the optimisation of drilling parameters with multiple performance characteristics based on the Tagugch’s method with grey relational analysis. Taguchi’s L₁₆, 4-level orthogonal array has been used for the experimentation. The drilling parameters such as spindle speed and feed rate are optimised with consideration of multiple performance characteristics, such as thrust force, workpiece surface roughness and delamination factor. Response table and response graph are used for the analysis. The analysis of grey relational grade indicates that feed rate is the more influential parameter than spindle speed. The results indicate that the performance of drilling process can be improved effectively through this approach.     

Effect of tool wear on delamination in drilling composite materials

Among all machining operations, drilling using twist drill is the most frequently applied for secondary machining of composite materials owing to the need for structure joining. Delamination is mostly considered as the principal failure model in drilling of composite materials. Drill wear is a serious concern in hole-making industry, as it is necessary to prevent damage of cutting tools, machine tools and workpieces. The industrial experience shows the worn drill causes more delamination. This paper presents a comprehensive analysis of delamination caused by the drill wear for twist drill in drilling carbon fiber-reinforced composite materials. The critical thrust force at the onset of delamination for worn drill is predicted and compared with that of ideal drill. The experimental results demonstrate that though the critical thrust force is higher with increasing wear ratio, the delamination becomes more liable to occur because the actual thrust force increases to larger extent, as the thrust factor (Z) illustrates. Compared to sharp drill, the worn twist drill allows for lower feed rate below which the delamination damage can be avoided.     

Drilling performance of functionally graded composite: Comparison with glass and carbon/epoxy composites

Functionally graded composite (FGC) materials are categorized as advanced materials that display different thermal and mechanical responses compared with well-known composites, such as carbon fiber or glass fiber-reinforced composites. This paper presents the experimental results for the drilling of three materials, namely glass/epoxy, carbon/epoxy, and FGC material. FGC was compared with carbon and glass/epoxy composites in terms of thrust force, delamination factor, diameter of hole, and roundness during drilling. This study illustrated that the drilling performance of FGC is considerably more complicated than that of more common composite materials, such as glass/epoxy and carbon/epoxy. Delamination factor at the exit of hole during drilling of FGC was mainly affected by the material placed at the exit of the hole. The proposed cutting parameters and drill geometries to minimize the occurrence of delamination during drilling of carbon/epoxy and glass/epoxy apparently does not meet the expectation in drilling FGC.     

平纹编织CFRP制孔分层形成机制的热-力学理论建模及试验分析

碳纤维增强复合材料(Carbon fiber reinforced plastics, CFRP)在航空航天领域获得了广泛应用,但由于各向异性和层间连接较差等特点,钻削过程中极易出现分层缺陷,严重影响构件的使用性能。为分析钻削温度对平纹编织CFRP制孔缺陷的影响机制,基于弹性地基梁理论、黏聚力学模型和热力学理论,建立了新钻型钻削平纹编织CFRP制孔分层形成的理论模型。结果表明：当新钻型多刃尖(Ⅲ)钻削孔边缘的最表层材料时,钻削温度达到最大值,对最终分层的形成最为关键;钻削温度和制孔分层随着主轴转速的增大而逐渐降低,随着进给速度的增大而逐渐升高。当纤维角度(θ)在0°/90°/180°/270°附近时,层间分层的临界轴向力达到最大值,分层相对较大,当纤维角度(θ)在45°/135°/225°/315°附近时,临界轴向力最小,分层并非极大。因此,临界力的大小只能反映产生分层缺陷的难易程度,不能决定分层的最终形状和大小。考虑温度影响时的制孔分层形态预测与试验观测基本吻合,而不考虑温度影响下所获得的预测值总体上偏小。此外,平纹编织CFRP分层形状基本呈近似圆形。     

奥氏体不锈钢1Cr18Ni9Ti的钻削试验研究

奥氏体不锈钢1Cr18Ni9Ti属较难加工材料,特别是较小孔钻削。为了得到钻头直径与钻削参数对钻削力和钻削温度的影响规律,故用高速钢标准钻头对1Cr18Ni9Ti与45钢进行了钻削对比试验,并用多元线性回归模型建立了钻削力和钻削温度的经验公式。结果表明:1Cr18Ni9Ti的扭矩和轴向力比45钢大,钻削参数对钻削力影响规律与45钢相同,即钻头直径对钻削力的影响最大,进给量次之,钻削速度最小;1Cr18Ni9Ti的钻削温度比45钢约高1.4倍,钻削速度对钻削温度影响最大,进给量次之,钻头直径最小。     

Prediction of thrust force of step drill in drilling composite material by Taguchi method and radial basis function network

Among material secondary machining, drilling is the most frequently applied factor to composites needing structure joining. Drill geometry is considered the most important factor that affects drill performance. A major concern in drilling of composite materials is the delamination that occurs in the exit as well as in the entrance planes. The delamination damage caused by the tool thrust is known as one of the major concerns during the drilling process. The thrust force of step drill with drilling parameters (step angle, stage ratio, feedrate and spindle speed) in drilling carbon fiber reinforced plastics (CFRP) laminates were experimentally investigated in this study. The experimental results indicate that the step angle, stage ratio, and feedrate are the most significant factors affecting the overall performance. The optimal combinations, such as A₂B₂C₁D₃ (i.e., step angle = 100 ° stage ratio = 0.4 mm/mm, feedrate = 0.01 mm/rev and spindle speed = 1,200 rpm), were used under the adopted drilling condition. An experimental approach to the prediction of thrust force produced by step drill using linear regression analysis of experiments and radial basis function network (RBFN) were proposed in this study. In the confirmation tests, RBFN (errors within 0.3%) has been shown to be a better predictive model than multi-variable linear regression analysis (errors within 28%) for quantitative prediction of drilling-induced thrust force in drilling of composite material.     

Application of grey fuzzy logic for the optimization of drilling parameters for CFRP composites with multiple performance characteristics

Carbon Fibre Reinforced Plastic (CFRP) composite materials have potential applications in various domains. In machining, drilling is essentially required to join different structures. But CFRP drilling poses many problems that decrease the quality of holes. In this paper, Taguchi’s L₂₇ orthogonal array is used to perform drilling of CFRP composite plates. To improve the quality of the holes drilled, the optimal combination of drilling parameters is chosen using grey relational analysis. Grey fuzzy optimization of drilling parameters is based on five different output performance characteristics, namely, thrust force, torque, entry delamination, exit delamination and eccentricity of the holes. Analysis of variance (ANOVA) is used to find the percentage contribution of the drilling parameters and found that feed rate is the most influential factor in drilling of CFRP composites.     

Investigation on delamination morphology during drilling composite laminates

Drilling-induced delamination of composite materials is a key factor that affects the quality of subsequent machining. To investigate the developing process of delamination, experiments with different drilling depth are conducted. In order to observe the delamination of different cross-sections in radial direction of the hole, the grinding method is adopted. Three-dimensional morphology of delamination at the exit of hole is obtained. The regularity of delamination with the change of drilling depth is analyzed, and the existence of “hidden delamination zone” is obtained finally. Due to the rebound effect of hole diameter and the inverted cone of drill guide section, the “hidden delamination zone” will be generated under the condition that the edge of delamination area is compressed tightly again. The critical thrust force of delamination is also studied, and it is proved to be correct.     

Drilling of woven glass fiber-reinforced plastic—an experimental and finite element study

Drilling in woven fiber-reinforced plastics is a well-known practice in modern-day manufacturing. The high fracture toughness of woven fiber-based composites over unidirectional counterparts is increasing demand in aviation and electronics industries. Hence, failure of these materials at harsh environments is a matter of concern. Very few numerical studies on drilling of these composites have been carried out; hence, the present scope may be considered as a trial de novo. Delamination was studied in the present work at different feed–speed combinations. Drilling responses were estimated using finite element as a numerical simulation tool. An equivalent elastic macromechanical model was assumed for the woven composite workpiece. A 3D drill bit was modeled using commercial CAD package Pro-Engineer and Ansys Autodyn was used as the solver environment. The simulation and validation experiments were carried out at planned feed–speed combinations. The effect of process parameters on exit and entry delamination is also documented. The thrust determined by finite element techniques showed good prediction with the experimental results.     

Regression modeling and optimization of machinability behavior of glass-coir-polyester hybrid composite using factorial design methodology

Polymer-based composite materials posses superior properties such as high strength-to-weight ratio, stiffness-to-weight ratio, and good corrosive resistance and therefore, are preferred for high-performance applications such as in the aerospace, defense, and sport goods industries. Drilling is one of the indispensable methods for building products with composite panels. In this present work, an investigation has been carried out to evaluate mechanical and machinability characteristics of hybrid composites, E-glass, and natural coir fiber abundantly available in India. A regression model is developed for correlating the interactions of some drilling parameters such as drill bit diameter, spindle speed and feed rate, and their effects on responses such as thrust force, torque, and tool wear during drilling of glass-coir fiber reinforced hybrid composites by Design of Experiment techniques. Results indicated that feed rate is playing major role on the responses than other two variables.     

Optimization of thrust force, torque, and tool wear in drilling of coir fiber-reinforced composites using Nelder–Mead and genetic algorithm methods

Machining of composite materials is an important and current topic in modern researches on manufacturing processes. Determination of optimal cutting parameters is one of the most important elements in the machinability study of composites. Optimization has significant practical importance particularly for operating the machineries. In order to increase the accuracy of drill holes, the tool must be in good condition always as much as possible. To achieve good condition of tool, the optimization of machining parameters like drill bit diameter, spindle speed, and feed rate are mandatory. The objective of this paper is to study the effect of these process parameters on thrust force, torque, and tool wear in drilling of coir fiber-reinforced composites. The optimal settings of the parameters were determined through experiments planned, conducted, and analyzed using the Box–Behnken design, Nelder–Mead, and genetic algorithm methods. This paper also aimed to increase the cutting condition of tool, i.e., minimization of tool wear by applying the optimized input parameters using Nelder–Mead and genetic algorithm techniques.     

ROTARY ULTRASONIC MACHINING OF CARBON FIBER-REINFORCED POLYMER: FEASIBILITY STUDY

Carbon fiber-reinforced polymer (CFRP) has been widely used in aircraft components, automotive parts, and sporting goods. Hole machining is the most frequently employed operation of secondary machining for fiber-reinforced composites. However, challenges (delamination, splintering, burr, short tool life, low machining precision, and low surface quality) still remain for their widespread applications. Rotary ultrasonic machining (RUM) is a non-conventional machining process that has been used to drill holes in composite materials. However, it has not been used to drill this type of CFRP. In this article, RUM is introduced into drilling holes in this type of CFRP for the first time. The feasibility to machine carbon fiber-reinforced epoxy using RUM is investigated experimentally. Chips, edge chipping, surface roughness, tool wear, and thrust force were measured. Effects of RUM process variables (rotation speed, vibration amplitude, and feedrate) on thrust force and surface roughness were studied. Results showed that RUM could be used to drill holes in CFRP with high productivity and low tool wear. A better surface was produced by higher rotation speed and lower feed rate.     

Experimental investigation and analysis of thrust force in drilling cast hybrid metal matrix (Al–15%SiC–4%graphite) composites

Composite materials are used in different engineering applications and are continuously displacing conventional materials due to their excellent properties. This paper discusses the influence of drilling parameter on thrust force in drilling Al 6061/15%SiC 4%Gr metal matrix composites. The composite materials are fabricated by stir casting method. The experiments are conducted on computer numeric control vertical machining centre using titanium nitride coated solid carbide twist drills of 4 mm, 8 mm and 12 mm diameter under dry conditions. A response surface analysis is carried out. The effect of drilling parameters on thrust force is studied and presented. The results indicated that feed rate is the main parameter which influences the thrust force in drilling of hybrid metal matrix composites.     

Experimental characterization and finite element modeling of critical thrust force in cfrp drilling

Composite laminates are used in many applications in ae-rospace/defense industries due to their high strength-to-weight ratio and corrosion resistance properties. In general, composite materials are hard-to-machine materials which exhibit low drilling efficiency and drilling-induced delamination damage at exit. Hence, it is important to understand the drilling processes for composite materials. This article presents a comprehensive study involving experimental characterization of drilling process to understand the cutting mechanism and relative effect of cutting parameters on delamination during drilling of carbon fiber reinforced plastic (CFRP). Thrust force and torque data are acquired for analyzing the cutting mechanism, initiation and propagation of delamination, and identification of critical thrust force below which no damage occurs. An FE model for prediction of critical thrust force has been developed and validated with experimental results. A [0/90] composite laminate is modeled simulating the last two plies in exit condition and a thin interface layer is inserted in between the plies to capture delamination extent. The tool geometry is modeled as “rigid body” with geometric features of twist drill used in experiments. The tool is indented on the workpiece to simulated tool feeding action into the workpiece. The FE model predicts the critical thrust force within 5% of the experimentally determined mean value.     

The influence of the cutting tool microgeometry on the machinability of hardened AISI 4140 steel

The aim of this work is to define the cutting conditions that allow the dry drilling of carbon fiber reinforced epoxy (CFRE) composite materials taking into consideration the quality of the drilled holes (the exit delamination factor and the cylindricity error) and the optimum combination of drilling parameters. A further aim is to use grey relational analysis to improve the quality of the drilled holes. The machining parameters were measured according to 3³ full factorial parameter designs (27 experiments with independent process variables). The experiments were carried out under various cutting parameters with different spindle speeds and feed rates. Drilling tests were done using WC carbide, high-speed steel (HSS), and TiN-coated carbide drills. The experiment design was accomplished by application of the statistical analysis of variance (ANOVA). Results show that the thrust force is mainly influenced by the tool materials and the feed rate, which has a strong influence on the exit delamination factor. On the other hand, the spindle speed particularly affects the cylindricity error of the holes. Correlations were established between spindle speed/feed rate and the various machining parameters so as to optimize cutting conditions. These correlations were found by quadratic regression using response surface methodology (RSM). Finally, tests were carried out to check the concordance of experimental results.     

Evaluation of the drilling-induced delamination of compound core-special drills using response surface methodology based on the Taguchi method

The hole-making process in composite parts today is required to be more accurate and efficient, which can affect the in-service life and decrease manufacturing cost. Thus understanding the key factors affecting their qualities is of vital importance to develop effective machining strategies. To this end, this study proposes a model with response surface methodology (RSM) based on the Taguchi method to evaluate the influence of drilling parameters on delamination by compound core-special drills. The model with RSM includes three steps: (1) design and experiments, (2) response surface modeling through regression, and (3) optimization. A series of experiments were conducted to test the proposed model. It was found that the key factors affecting drilling-induced delamination include: cutting velocity ratio, feed rate, inner drill type, and inner drill diameter. Therefore, some experimental implications can be proposed accordingly.