Thrust Force In Drilling Research Articles

Cryogenic Drilling of AZ31 Magnesium Syntactic Foams.

Machined surface quality and integrity affect the corrosion performance of AZ31 magnesium composites. These novel materials are preferred for temporary orthopedic and vascular implants. In this paper, the drilling performance of AZ31-magnesium reinforced with hollow alumina microsphere syntactic foam under LN2 cryogenic, dry, and Almag® Oil is presented. Cutting tests were conducted using TiAlN physical vapor deposition (PVD) coated multilayer carbide and K10 uncoated carbide twist drills. AZ31 magnesium matrices were reinforced with hollow alumina ceramic microspheres with varying volume fractions (5%, 10%, 15%) and average bubble sizes. Experimental results showed that the drilling thrust forces increased by 250% with increasing feed rate (0.05 to 0.6 mm/tooth) and 46% with the increasing volume fraction of alumina microspheres (5% to 15%). Cryogenic machining generated 45% higher thrust forces compared to dry and wet machining. The higher the volume fraction and the finer the average size of hollow microspheres, the higher were the thrust forces. Cryogenic machining (0.42 µm) produced a 75% improvement in surface roughness (Ra) values compared to wet machining (1.84 µm) with minimal subsurface machining-induced defects. Surface quality deteriorated by 129% with an increasing volume fraction of alumina microspheres (0.61 µm to 1.4 µm). Burr height reduction of 53% was achieved with cryogenic machining (60 µm) compared to dry machining (130 µm). Overall, compared to dry and wet machining methods, cryogenic drilling can be employed for the machining of AZ31 magnesium syntactic foams to achieve good surface quality and integrity.

An experimental investigation of thrust force, delamination and surface roughness in drilling of jute/carbon hybrid composites

Purpose This paper aims to deal with the influence of cutting parameters on drill thrust force, delamination and surface roughness in the drilling of laminated jute/carbon hybrid composites. Design/methodology/approach The hybrid composites were fabricated with four layers of fabrics, which are arranged in different sequences using the hand-layup technique. Drilling experiments involved drilling of 6 mm diameter holes on the prepared composite plates using high-speed steel and solid carbide drill materials. Analysis of variance was used to find the influence, percentage contribution and significance of drilling parameters on drilling-induced damages. Scanning electron microscopy analysis was also conducted to understand the fracture behavior and surface morphology of the drilled holes. Findings The experimental study reveals that the most significant effect was the feed rate influenced the drill thrust force and the drill speed influenced both delamination factor and surface roughness of hybrid fiber-reinforced composites. From observations, the suggested combination for drilling jute/carbon hybrid composites is carbide drill, spindle speed of 1,750 rpm and feed of 0.03 mm/rev. Originality/value The new lightweight and low-cost hybrid composites were developed by hybridizing jute with carbon fabrics in the epoxy matrix with interplay arrangements. The influence of cutting speed and feed rate on delamination damage and surface roughness in the drilling of hybrid composites have been experimentally evaluated.

Mechanistic force modelling in drilling of AFRP composite considering the chisel edge extrusion

Aramid fiber–reinforced plastic (AFRP) composites have been widely used in automotive, aerospace, and defense industries. The common AFRP drilling process tends to cause damage to the composite structures which subsequently affects their fatigue lives and in-service performance. Understanding the mechanism of cutting force generation is crucial in controlling the cutting process for achieving desired hole quality and machining accuracy. This study proposes a novel mechanistic model considering both the cutting action and the extrusion action of the chisel edge. For the first time, the extrusion force generated by the chisel edge has been considered as a rigid wedge penetrating into an elastic half space based on the Hertz contact theory. The total thrust force in AFRP drilling is divided into three components: (i) thrust force generated by the cutting lips, (ii) thrust force generated by the chisel edge cutting action, and (iii) extrusion force generated by the chisel edge extrusion action. The proposed model was then validated by experiments and data was compared with the case where extrusion was not considered. The results show that our novel mechanistic model can provide a more accurate thrust force prediction. The average error of our model was 2.54% against the experimental data, whereas the error seen in conventional model without accounting extrusion was 8.22%. This suggests that the chisel edge extrusion plays a significant part in the drilling of AFRP and hence confirms the necessity of considering extrusion in establishing the associated mechanistic model.

Optimization of thrust force in drilling of carbon-basalt hybrid composites through Taguchi and RSM

The main object of the present work is to obtain better quality holes during drilling operation. Carbon-Basalt hybrid composite is a better performing composite with lesser price. For the present work, the hybrid composite test specimen was prepared by hand layup method. General purpose polyester resin is used as the matrix material. During the manufacturing process, alternate layers of carbon and basalt are stacked to prepare the composite. The maintained weight fraction of the fiber is 50%. The thickness of the obtained composite specimen is 6 mm. Delamination is the major reason for the rejection of drilled composites. The magnitude of delamination is directly proportional to the thrust force generated during drilling. Hence in the present work, an attempt has been made to reduce the thrust force to minimize the damage by optimizing the machining variables using Taguchi and RSM methods. The experiments were designed by DOE method. Taguchi’s 3 levels and 3 factors array was used to get the combination of parameters for each experiments. Totally 27 holes are drilled with different combinations of process parameters. The considered process parameters and their levels are: Drill diameter (6 mm, 8 mm & 10 mm), feed rate (50 mm/min, 75 mm/min & 100 mm/min) and spindle speed (750 rpm, 1000 rpm & 1250 rpm). Drilling process was carried out on a high precision CNC machine using HSS drill bits. The thrust force was measured by a Kistler dynamometer. Using ANOVA, the significant effect of considered parameters on the generated thrust force was also predicted. The result reveals that, the parameter feed rate has the most significant effect on thrust force, which is followed by the drill diameter. The least significant parameter is spindle speed. Both Taguchi and RSM methods suggest that, DD1, F1 and S3 combination parameters yields the lowest thrust value.

Control of Chip Formation and Improved Chip Ejection in Drilling With Modulation-Assisted Machining

Abstract Drilling with modulation-assisted machining (MAM) superimposes a low-frequency oscillation onto the drill feed motion. The otherwise continuous cutting in the drilling process is converted into a series of discrete cutting events. The result is a discrete chip formation process and concurrent improvement in chip ejection. The discrete chip formation and ejection in drilling with MAM were investigated via systematic experiments in OFHC Cu and Ti6Al4V using a two-flute twist drill and a single-flute gun drill. Drilling thrust force and chip morphologies for various modulation conditions are examined. The continuous cutting and discrete cutting regimes of modulation-assisted drilling are compared with conditions determined by a kinematic model. The results show that chip formation in the continuous cutting regime with MAM can influence chip breakage by random fracture at thin sections of the chip, but in this regime the resulting chip size is variable and not controlled. In contrast, when MAM conditions operate in the regime of discrete cutting, the deformed chip size can be directly controlled. The ability to control the chip size improves chip ejection and drilling process stability. A set of modulation conditions for enhanced performance of chip ejection are proposed. The study shows that modulation-assisted machining offers distinct advantages as a method for deep-hole drilling applications.

A prediction model of thrust force for drilling of bidirectional carbon fiber-reinforced carbon matrix composites.

Carbon fiber-reinforced carbon matrix composites have been widely used for the manufacturing of thermostructural parts for several industries such as the aerospace and automotive. Drilling is an extremely common method used in the machining of carbon fiber-reinforced carbon matrix composites before assembly. However, their non-homogeneous, anisotropic, and brittle nature make difficult to guarantee the hole quality in drilling. Some severe drilling defects, such as burrs, delamination, and tear, usually occur. In this regard, it is necessary to accurately predict the thrust force in drilling of carbon fiber-reinforced carbon matrix composites. Therefore, in this article, based on the cutting theory of fiber-reinforced polymer composites, an alternative thrust force prediction model for drilling of bidirectional carbon fiber-reinforced carbon matrix composites is proposed. The cutting force of the cutting lips is established by dividing the cutting deformation zone into three regions according to the machined material structure based on the Zhang's model in cutting of fiber-reinforced polymer. The periodic variation of fiber orientation is considered in detail. The experimental results show that the relative deviations of the predicted and experimental values of the thrust force are less than 14.36%.

Anisotropy of additively manufactured AlSi10Mg: threads and surface integrity

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In this experimental study, the objective was to evaluate anisotropy in part properties (i.e., flatness, surface roughness, surface porosity, surface hardness, pre-hole shrinkage, drilling thrust force, and thread-stripping force) when the part orientation (i.e., print inclination and recoater angle) was independently changed. This study developed and investigated an innovative procedure for determining anisotropy in part properties. The part properties were evaluated by designing specific features on a tailor-made flat plate. The replicas of the aluminum plate were additively manufactured at varying orientations using two commercial EOS parameter sets for the laser-based powder bed fusion technique. Conventional measurement equipment was used to analyze all the part properties, except the thread-stripping force, which was measured using a custom-made setup. All the part properties indicated a considerable degree of anisotropy, excluding the drilling thrust force. The printing parameters dictate the significance of the anisotropy. The anisotropy in flatness and pre-hole shrinkage decreases with an increased substrate temperature and a decrease in energy input and thermal gradient. The presence of surface overlapping contours in the scan strategy and an increased energy input can reduce anisotropy in surface roughness and hardness. No significant anisotropy was detected when the recoater angle was changed. This study helps designers establish and substantiate design for additive manufacturing that is within the limits of appropriate anisotropy for a robust design.

Evaluation of different tool geometries in the finite element simulation of ultrasonic-assisted drilling of Ti6A14V

This paper attempts to analyze the effect of various drilling parameters such as feed rate, spindle speed and vibration frequency on performance characteristics such as thrust force, effective stresses, temperature and chip morphology in conventional drilling (CD) and ultrasonic-assisted drilling (UAD) of Ti6A14V using three different point angle (140°, 120°, 90°) drill bits in order to optimize the chip breakability of Ti6A14V. The three different point angle drill bits are utilized to establish the finite element models (FEM) to simulate the drilling process with Lagrangian approach in DEFORM-3D software. The simulations are validated by the experimental findings and analytical data of thrust forces, and the percent errors in results range approximately between 3 and 7%. The results obtained prove that UAD can produce segmental discontinuous chip, lower thrust force, lower process temperature and lower effective stress. The point angle of 120° drill achieved the thinnest chip thickness and the excellent effects of chip breaking. The achieved results are assumed to help for the optimization of the drill tool geometries, drilling parameters and chip breakability.

MULTI-OBJECTIVE OPTIMIZATION FOR SURGICAL DRILLING OF HUMAN FEMURS: A METHODOLOGY FOR BETTER PULL-OUT STRENGTH OF FIXATION USING TAGUCHI METHOD BASED ON MEMBERSHIP FUNCTION

Drilling through bone is one of the common cutting processes involved in many of the orthopedic surgeries. In bone drilling, spindle speed, feed rate, diameter of the drill bit, drill bit geometry and method of cooling are the important parameters to influence the in-situ temperature, drill thrust force and quality characteristics of the drilled hole. Because of the selection of inappropriate drilling parameters, uncontrolled large drilling forces, continuous increase in temperature and mechanical damage to the local host bone were observed. As these adverse effects lead to poor bone–implant contact and often a revision surgery, performing a surgical drilling with optimal parameters is essential to succeed in the surgical procedure. It was observed that in addition to the variations in apparent bone density, the orientation of osteons influences the drilling thrust force and temperature in bone drilling. Ten adult cadaveric human femurs from the age group of 32–65 years were considered and drilling experiments were conducted on proximal-diaphysis, mid-diaphysis and distal-diaphysis regions in the longitudinal, radial and circumferential directions. Bone drilling with different spindle speeds (500, 1000 and 1500[Formula: see text]rpm), feed rates (40, 60 and 80[Formula: see text]mm/min), and apparent density in the range of 0.98[Formula: see text]g/cm3 to 1.98[Formula: see text]g/cm3 was investigated in this work using a 3.20[Formula: see text]mm diameter surgical drill-bit. The generation of in-situ temperature as well as thrust force at each target location was measured using [Formula: see text]-type thermocouple and Kistler[Formula: see text] dynamometer, respectively. Taguchi method based on membership function was used to optimize the drilling process. Then the efficacy of the method in reducing the in-situ temperature and thrust force, and quality of the drilled hole in respect of anatomical region and drilling direction was investigated using pull-out strength of the bone screws. Results revealed that the optimal parameters obtained from the Taguchi method based on membership function could simultaneously minimize the temperature as well as thrust force in bone drilling. The proposed method can be adopted to minimize the temperature and thrust force, and choose the best location nearest to the defect site for strong implant fixation by using CT datasets of the patient as the only input.

Evaluation of minimum quantity lubrication and minimum quantity cooling lubrication performance in hard drilling of Hardox 500 steel using Al2O3 nanofluid

The work in this study presents an experimental evaluation on minimum quantity cooling lubrication based on the Ranque–Hilsch vortex tube and minimum quantity lubrication performance in hard drilling of Hardox 500 steel (49–50 HRC) using coated carbide drills. Al2O3 nanoparticles are suspended in the based fluids including water-based emulsion and rice bran oil to enhance the cooling and lubricating effects. The response variables, consisting of drilling thrust force, surface roughness, surface profile and microstructure, and tool wear, are studied, and the analysis of variance is used for evaluating the input machining parameters under minimum quantity lubrication and minimum quantity cooling lubrication conditions. The results of this article indicate that minimum quantity cooling lubrication using Al2O3 nanofluid provides the better machining performance and gives out better surface quality and lower thrust force compared to minimum quantity lubrication with/without nanofluid and minimum quantity cooling lubrication with pure fluid. Also, based on the optimization results, the validation experiments are conducted to study more on drilling thrust force, chip morphology, and tool wear.

Effect of dipped cryogenic approach on thrust force, temperature, tool wear and chip formation in drilling of AZ31 magnesium alloy

Magnesium alloys tend to have inflammable nature and chip self-ignition at high cutting speeds under dry machining condition, although they can be easily machined with good surface quality. In the drilling process, cooling and lubrication have a critical impact as it controls heat generation, tool wear, surface quality, and cutting force. In the present study, drilling tests on AZ31 magnesium alloy were performed with dry and cryogenic conditions at various feed rates and cutting speeds. The effect of dipped cryogenic application during drilling on thrust force, temperature, tool wear, and chip formation were investigated. The results showed that the applied cryogenic drilling method provided less tool wear, smaller chips and reduced amount of adhesions. Drilling tests performed in the cryogenic environment increase the thrust forces by 32 %–39 % compared to dry cutting. Spark and chip ignition were not observed even at high cutting speeds during dry cutting.

Anisotropy of additively manufactured 18Ni-300 maraging steel: Threads and surface characteristics

The purpose was to evaluate part properties of additively manufactured 18Ni-300 maraging steel in a unified set-up when the printing orientation and the heat treatment were independently changed. Though the hardness, shrinkage, and drilling thrust force showed isotropic behavior to a certain extent, anisotropy was observed in the flatness, surface roughness, dross, and thread profiles. Solution treatment increases the surface roughness and reduces the flatness, surface hardness, drilling thrust force, and thread quality to some extent. Aging treatment significantly increases the surface hardness and yet still allows good-quality threads to be cut. The study aids designers in establishing and corroborating design for additive manufacturing.

Experimental study on drilling basalt with self-vibratory drilling head

Based on the goal of improving the rock breaking ability when drilling asteroid rock samples under limited energy conditions, this paper proposes a method of drilling rock using self-vibratory drilling head and develops a small self-vibratory drilling head for drilling rock. In order to analyze the dynamic characteristics of drilling rock with self-vibratory drilling head, a rock model hypothesis that the rock consists of a series of micro-segment uniform continuous media is put forward. Base on the hypothesis, the model of drilling rock is constructed, the stability lobes diagram of self-vibratory drilling head drilling basalt is plotted, and the energy mechanism of drilling rock system with self-vibratory drilling head is discussed. The comparison tests of drilling basalt by three kinds of self-vibratory drilling head with different spring stiffness and the conventional method are carried out. The rotational speed is a variable in the comparative tests. The test results show that under the specific rotational speed and spring stiffness, self-excited vibration is produced in self-vibratory drilling head drilling basalt. When self-excited vibration drilling is conducted, although the amplitude fluctuation range of the drilling thrust force is wider than that of conventional drilling, the average drilling thrust force is smaller than the conventional drilling. The amplitude of drilling thrust force increases with an increase in spring stiffness. The method of drilling rock by self-vibratory drilling head is proved to be a potential method for viable drilling of asteroid rock samples.

Effect of adding a woven glass ply at the exit of the hole of CFRP laminates on delamination during drilling

Composite materials are increasingly used in the aeronautical field. The assembly of structures requires usually drilling of composite parts. Drilling of composite materials generates defects, mainly delamination at the exit of the hole. This major defect diminishes the structure strength. Delamination is directly related to the drilling thrust force. Minimizing this force reduces the defects. Adding a woven glass ply at the exit of the hole is found to be another adequate solution to reduce the defects. In this paper, the drilling of carbon/epoxy thick composite structures with a woven glass ply at the exit of the hole is considered. An analytical model is developed to determine for a given tool geometry the critical delamination forces as function of the number of non-drilled plies remaining beneath the tool. The results are validated experimentally. These results show that adding a woven glass ply at the exit of the hole reduces delamination.

Study on ultrasonic-assisted drilling of Ti6Al4V using 3-flute drill in the finite element simulation

Continuous chip is one of the major problems during drilling Ti6A14V, and chip breaking is dependent on many factors such as drilling parameters, tool geometries and type of drill bits used. This paper attempts to analyze the effect of various drilling parameters such as feed rate, spindle speed on performance characteristics such as chip morphology, thrust force, temperature, and tool wear in conventional drilling and ultrasonic-assisted drilling of Ti6A14V using twist drill bit and 3-flute drill bit in order to optimize the chip breakability of Ti6A14V. The twist and 3-flute drill bit are utilized to establish the finite element models to simulate the drilling process with Lagrangian approach in DEFORM-3D software. The results of the simulations not only reveal obvious varying regular pattern of thrust force, temperature, tool wear depth, chip thickness and damage with the increasing of feed rates, spindle speeds, which confirm the capability and advantage of finite element model of the drilling process, but also provide a more profound knowledge about the drilling mechanism including the effect of 3-flute drill bit in ultrasonic-assisted drilling on chip breakability and tool wear.

Comparative study of minimum quantity lubrication and dry drilling of CFRP/titanium stacks using TiAlN and diamond coated drills

Although minimum quantity lubrication (MQL) has been proved beneficial for the machinability improvement of metallic materials, it is still not well understood whether or not to use the MQL when machining the composite-titanium stacks and whether the MQL can achieve a comparable effect as it operates in the metal cutting processes. The current work is aimed at revealing the underlying mechanisms of the MQL drilling on the CFRP/Ti6Al4V stacks. Both the MQL and dry conditions were examined using the TiAlN-coated and diamond-coated carbide drills to quantify how the MQL operates when compared with the conventional dry machining. The effects of the MQL environment on the machinability of the composite-titanium stacks were quantified in terms of drilling thrust forces, delamination damage of the composite phase and tool wear signatures. A particular emphasis is put on the wettability testing of cut stack hole surfaces versus the minimum quantity lubricants in terms of the contact angle. The results indicate that the machined composite surface shows a strong ability to absorb the lubricants under the MQL condition and fails to form a protective oil film at the drill-chip interface, resulting in an increase of thrust forces and delamination damage. Moreover, the MQL environment cannot prevent the drill bits from premature failures during the machining of CFRP/Ti6Al4V. It is indicated that the MQL fails to yield a comparable beneficial role as it operates in the machining of individual metal alloys in terms of the examined drilling responses.

Mechanics of thrust force on chisel edge in carbon fiber reinforced polymer (CFRP) drilling based on bending failure theory

CFRP (Carbon Fiber Reinforced Polymer) is widely used in the aerospace, automobile and construction industries. Its non-homogeneous and anisotropic nature often results in unfavorable hole quality during the drilling process, and exit delamination is a resulting phenomenon that has received much attention. Exit delamination occurs when the drilling thrust force exceeds the critical thrust force. It adversely affects product quality and may even result in rejection. The thrust force on the chisel edge is an important component of the total thrust force, and it helps to predict the total thrust force so that delamination can be reduced or avoided. In this study, noticing that the chisel edge has a certain length, the author puts forward the novel concept of the azimuth angle on the basis of the micro analysis of the contact state between the chisel edge and the carbon fiber. In addition to the orientation angle of the carbon fiber, the azimuth angle of the cutting edge is also an important factor that affects the thrust force. A single carbon fiber may be modeled as a beam on an elastic foundation, and the prediction model of thrust force on the chisel edge is established based on the theory of bending fracture. The model can reflect the influence of the material properties, cutting tool geometry parameters (including the length of chisel edge, rake angle and blunt radius of cutting edge), drilling process parameters, and ultrasonic vibration parameters on the thrust force on the chisel edge and quantitatively explain the reduction of thrust force and improvement of drilling quality during the longitudinal ultrasonic vibration drilling. The prediction model of the thrust force presented in this work can make up for the shortages of qualitative interpretation. The law of periodic variation of the chisel edge thrust force with the azimuth angle helps in developing a deep understanding of the CFRP drilling process and the material removal mechanism. The basis is provided in order to reduce and avoid the exit delamination defects in drilling, and to reasonably and quantitatively determine the spindle speed, feed rate, and drill bit geometry parameters. The reliability of the prediction model is verified by a drilling test.

Measurement and analysis of thrust force and torque in friction drilling of difficult-to-machine materials

Thrust force and torque applying in friction drilling contain some important information related to sufficient heat generation which can improve product quality and reduce tool wear. This concern becomes more challengeable when friction drilling is applied on difficult-to-machine materials. In the present study, temperature, thrust force, and torque for friction drilling of difficult-to-machine materials namely AISI304 and Ti-6Al-4V and Inconel718 are measured and analyzed. It contributes to provide an enhanced understanding of how friction in workpiece-tool interface increases the temperature. Subsequently, the sufficient heat generation, the effective thrust force, and torque that are needed to form a proper bushing with optimum features can be predicted. It is found that increasing in number of drilled holes reduces the quality of bushing shape. It is observed that thermal conductivity of workpiece material has significant effect on bushing formation quality. The findings indicate that better bushing formation and longer tool life are obtained from friction drilling of Inconel718. The microstructural changes of workpiece and tool wear are also analyzed and a relationship between them, temperature, thrust force, and torque, is explored. The maximum tool wear is observed on conical region where the process is in critical cycle time and temperature is on peak point.

Investigation on thrust force in rotary ultrasonic drilling of CFRP/aluminum stacks

The stacks of carbon fiber-reinforced polymer (CFRP) and aluminum are widely used in aviation industry due to its excellent mechanical and physical properties. Recently, rotary ultrasonic drilling technology which is recognized as a useful machining method has been introduced to machining these stacks. Thrust force influences the machinability directly such as tool wear, cutting temperature, and hole qualities. In this study, a theoretical model of thrust force for rotary ultrasonic drilling of CFRP/aluminum stacks is proposed. Based on the analysis of kinematic characteristics, the axial uncut chip thickness of rotary ultrasonic drilling is presented. Then the whole machining process of stacks is divided into five different states. Forces on cutting edge and chisel edge in different materials are modeled, respectively. After that, the thrust forces of five-state rotary ultrasonic drilling process are achieved by integrating with integral limits analysis in each state. Finally, verification experiments are conducted, and experimental results show that the trends of thrust forces agree well with the thrust force model. Therefore, this theoretical model can be used to evaluate the thrust force in rotary ultrasonic drilling of CFRP/aluminum stacks.

Investigation of minimum quantity lubrication effects in drilling CFRP/Ti6Al4V stacks

ABSTRACTMinimum quantity lubrication (MQL) has been extensively applied to the machining processes of various metallic materials; however, its impact on the drilling characteristics of metallic-composite stacks has not been thoroughly investigated. The present paper is thus aimed at identifying the influences of the MQL environments on the drilling process of one type of composite-titanium compound stacks constituted by T700/FRD-YZR-03 carbon/epoxy laminates and the Ti6Al4V sheets. A series of drilling trials were performed using tungsten carbide twist drills to investigate the feasibility of the MQL for the multilayer stack machining. A quantitative analysis was conducted on various drilling outputs including the drilling forces, surface morphologies of cut composite holes, hole defect extents, hole geometrical accuracy and tool wear signatures. A comparative investigation between the MQL and dry cutting conditions on the stack machinability was also carried out in order to quantify the potentials gained by the MQL machining process. The results indicate that the MQL drilling can yield several benefits in improving the surface morphologies of cut composite holes and in alleviating the drill wear severity, but it fails to reduce the drilling thrust forces, decrease the delamination extents and minimize the hole cylindricity errors when compared with the conventional dry cutting conditions.