Thrust Force Reduction Research Articles

An optimization technique on ultrasonic and cutting parameters for drilling and deep drilling of nickel-based high-strength Inconel 738LC superalloy with deeper and higher hole quality

In this research work, an ultrasonic assisted drilling system is employed to apply both rotation and vibration to drill bits. The transducer horn transfers power very efficiently and changes tools effortlessly. The setup used to conduct drilling tests is Inconel 738LC with depth-to-diameter ratios from 2 to 10 by conventional drilling (CD), ultrasonic assisted drilling (UAD), and electro discharge drilling (EDD). The effects of ultrasonic vibration amplitude, spindle speed, and number of steps to drill each hole on machining force and surface roughness in UAD are investigated. The results demonstrate not only a significant improvement in tool life (by applying ultrasonic vibration to the drilling process) but also a 40 % reduction in thrust force compared to CD. The UAD technique seems more appropriate than the EDD method due to the ability to reduce machining process time by up to 90 %, improve cylindricity by roughly 50 %, increase hole dimension accuracy by up to 80 %, and reduce surface roughness by 52 %.

Thrust Force Analysis in Drilling Glass Fiber Reinforced/Polypropylene (GFR/PP) Composites

Glass fiber reinforced thermoplastic (GFRTP) composites are an important alternate to the conventional engineering materials owing to their good application-oriented properties. Drilling is unavoidable and an important operation used in automotive and aerospace industries in the assembly stage. The reduction of thrust force is required to minimize delamination. This paper examines the parameters that influence the thrust force on drilling glass fiber reinforced polypropylene (GFR/PP). The experiments are conducted using the Box–Behnken experimental design method. An empirical relation is established for determining the thrust induced in the drilling of GFRTP. The factors that affect the drilling process and their interaction are analyzed and presented in detail.

Multi Response Optimization of Drilling Parameters during Drilling of Particle Board Using Grey Relational Analysis

Particle board serves numerous functions such as cabinetry, tabletops, shelving, wall & floor panels, etc. Though Particle boards are much cheaper compared to solid wood, machining the material by optimizing the process parameters is a big challenge. Drilling is the major operation during final assembly of particle board, where fasteners are used to join together to bring final shape to the product. In this paper, the operation parameters such as speed, feed, drill diameter has been considered during drilling operation performed on Particle board and the output responses-surface roughness of the drilled hole and the Thrust force acting on the board during drilling are measured. Good surface finish of the hole ensures reduction of localised stresses around the hole due to fastening. Reduced Thrust force contributes to lesser delamination in particle board. Hence minimisation of both surface roughness and delamination is desired and hence optimisation of both responses is done simultaneously using grey relational analysis.

Disturbance Compensation by Wind Speed Reconstruction based on a Takagi-Sugeno Wind Turbine Model

In this work, the nonlinear Tagaki-Sugeno modelling method is utilised to set up an observer-based feed-forward control scheme for wind turbines, which can compensate for the influence of the disturbing wind variation on the rotational speed. The applied scheme leads to a reduced thrust force acting on the rotor.

Experimental investigation on drilling of high strength T800S/250F CFRP with twist and dagger drill bits

T800S/250F lamination is a new high strength carbon fibre reinforced plastic (CFRP) material, which is usually defined as difficult-to-machine material and used to manufacture the key load-bearing structural components of large commercial aircrafts. Drilling is the most frequently operation used as the final assembling process for CFRP components, while the hole defects, such as delamination and burr, always occur at the exit of hole in the CFRP laminate. In this paper, the machinability of T800S/250F was investigated in term of drilling force, burr morphology and delamination factor by using uncoated carbide twist and dagger drill bits. The experimental results indicated that high spindle speed and low feed rate favour the reduction of thrust force for both drill bits. It was also identified that the dagger drill showed good performance with smaller burr defect and lower delamination factor as compared with the twist drill.

Experimental Investigation on Drilling Force and Hole Quality when Drilling of T800S/250F CFRP Laminate

High-strength carbon fiber reinforced plastic (CFRP) T800S/250F is used as the large commercial aircraft material for manufacturing the main load-bearing structural components. Drilling is the mostly used in final machining process of CFRP laminates, while the delamination and burrs occur frequently at the drill exit in the CFRP laminate. In this paper, the machinability of T800S/250F was investigated in term of drilling force and hole quality by using a twist drill and a dagger drill. The experimental results indicated that high spindle speed and low feed rate favor the reduction of thrust force for both drill bits. High spindle speed is a preference to gain the good hole quality at drill exit especially for the dagger drill, which also shows excellent drilling performance than the twist drill and was more suitable for drilling of T800S/250F CFRP laminate.

Ultrasonically assisted drilling: A finite-element model incorporating acoustic softening effects

Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drilling in hard-to-machine quasi-brittle materials such as carbon fibre reinforced polymer composites (CFRP). UAD has been shown to possess several advantages compared to conventional drilling (CD), including reduced thrust forces, diminished burr formation at drill exit and an overall improvement in roundness and surface finish of the drilled hole. Recently, our in-house experiments of UAD in CFRP composites demonstrated remarkable reductions in thrust-force and torque measurements (average force reductions in excess of 80%) when compared to CD with the same machining parameters. In this study, a 3D finite-element model of drilling in CFRP is developed. In order to model acoustic (ultrasonic) softening effects, a phenomenological model, which accounts for ultrasonically induced plastic strain, was implemented in ABAQUS/Explicit. The model also accounts for dynamic frictional effects, which also contribute to the overall improved machining characteristics in UAD. The model is validated with experimental findings, where an excellent correlation between the reduced thrust force and torque magnitude was achieved.

Vibration Drilling of Al2024-T6

Vibration drilling (VD) is a process in which longitudinal wave is used to improve drilling conditions. In this process, longitudinal wave with high frequency and low amplitude is applied on tool while engagement between tool and workpiece during machining process is connected and disconnected. In this study, a rotary VD tool was designed and fabricated for performing VD. This tool is able to apply longitudinal wave through an ultrasonic transducer and horn to a drill in a rotary mechanism. After primary tests and confidence from proper design and fabrication of this tool, the effect of longitudinal wave in VD of Al2024-T6 was studied and compared with ordinary drilling (OD). Some parameters such as the thrust force, chip, and burr were measured and compared together in both conventional and ultrasonic methods. The obtained results demonstrate a substantial reduction in thrust force with VD rather than OD.

Applying Ultrasonic Vibration to Decrease Drilling-Induced Delamination in GFRP Laminates

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, and ultrasonic vibration amplitude as control factors. The results show that applying ultrasonic vibration reduces the thrust force and therefore the drilling induced delamination dramatically.

A Finite Element Model of Ultrasonically Assisted Drilling in Carbon/Epoxy Composites

Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drilling difficult-to-machine materials such as carbon/epoxy composites, where ultrasonic vibrations are superimposed on the tip of the revolving drill bit. Recently, UAD has been shown to possess several advantages in comparison to conventional drilling, including a reduced thrust force and torque, reduced drilling-induced damage and overall improvement in roundness and surface finish of the drilled hole. Here, a finite element model of UAD in carbon/epoxy composite is presented. This model accounts for volumetric and thermal softening phenomena in the workpiece material under the influence of localized vibro-impacts, which is a characteristic feature of UAD. The model was implemented in Abaqus/Explicit and validated with results from experiments, demonstrating a reasonable correlation between them. A parametric study was also carried out to examine the effect of variation in intensity of ultrasonic energy on the extent of softening in the carbon/epoxy composite for UAD.

Cutting forces in ultrasonically assisted drilling of carbon fibre-reinforced plastics

Ultrasonically assisted drilling (UAD) is a non-traditional hybrid machining process, which combines features of conventional drilling and vibratory machining techniques to obtain remarkable improvements in machinability of advanced materials. The experiments are conducted on commercially available samples of a carbon fibre-reinforced plastic (CFRP) at a feed rate of 16 mm/min. In this study, a thrust force reduction in excess of 60% is observed in UAD when compared to conventional drilling (CD). Lower delamination was observed when compared to CD techniques. Optical microscopy revealed that the material is removed as a continuous chip in UAD whereas in case of CD we observe powdered dust. Light and scanning electron microscopy of CFRP chips obtained in drilling elucidate fundamental differences in the underlying machining processes in UAD of CFRP.

Ultrasonically Assisted Drilling of Carbon Fibre Reinforced Plastics

Carbon fibre-reinforced plastics (CFRPs) gained substantial acclaim in recent decades and are used in aerospace, automotive and structural applications due to their high strength-to-weight ratio, high stiffness, high fatigue and corrosion resistance. CFRPs are manufactured near to net shape but some machining processes such as drilling cannot be avoided. Drilling induces damage (delamination, matrix cracking, matrix burning, lamina cracking and fibre pull out) in CFRP because of high axial thrust forces and a temperature rise. In this research an attempt is made to use ultrasonically assisted drilling (UAD) to reduce the axial thrust forces. In UAD high frequency (~ 20 kHz) vibrations are superimposed on a drill bit, preferably in axial direction, to reduce the thrust forces. In this study, experiments are conducted in two stages. At the first stage an initial setup with an existing UAD transducer is used to compare UAD with conventional drilling (CD) of CFRP. A reduced thrust force is experienced in case of UAD when compared to CD. At the second stage, drilling dynamics, i.e. feed speed, is changed along with the improvement of the transducer, and an enormous amount of force reduction (>80%) is observed in case of UAD (as compared to CD).

Experimental and Numerical Investigations in Conventional and Ultrasonically Assisted Drilling of CFRP Laminate

Carbon fiber-reinforced plastic (CFRP) composites are attractive for many industrial applications due to their superior properties. The parts made from CFRP are usually manufactured to a near-net shape; however, various machining processes, such as drilling, are often required to facilitate component assemblies. Conventional Drilling (CD) of CFRP induces high stresses in the vicinity of the drilled hole; along with high thrust forces on a drilling tool. An advanced drilling technique known as Ultrasonically Assisted Drilling (UAD) has been used to demonstrate its several advantages over CD including a reduced thrust force. A 3D finite element (FE) models simulating CD and UAD techniques for drilling in CFRP laminates were developed using the general-purpose FE software ABAQUS/Explicit. The numerical results obtained with the FE model were found to be in a good agreement with the experimental data.

Comparative analysis of drills for composite laminates

The characteristics of carbon fiber-reinforced plastics allow a very broad range of uses. Drilling is often necessary to assemble different components, but this can lead to various forms of damage, such as delamination which is the most severe. However, a reduced thrust force can decrease the risk of delamination. In this work, two variables of the drilling process were compared: tool material and geometry, as well as the effect of feed rate and cutting speed. The parameters that were analyzed include: thrust force, delamination extension and mechanical strength through open-hole tensile test, bearing test, and flexural test on drilled plates. The present work shows that a proper combination of all the factors involved in drilling operations, like tool material, tool geometry and cutting parameters, such as feed rate or cutting speed, can lead to the reduction of delamination damage and, consequently, to the enhancement of the mechanical properties of laminated parts in complex structures, evaluated by open-hole, bearing, or flexural tests.

Finite element modeling of a micro-drill and experiments on high speed ultrasonically assisted micro-drilling

Modal characteristics of a generic micro-drill and experiments on the micro-drilling with superimposing of longitudinal ultrasonic vibration are presented. Finite element (FE) analysis is used for identification of eigenfrequencies and modes of the drill. Dynamic influence of the drill shank is discussed and a hybrid model is proposed to account for it. The model is proven to be efficient for complicated drill models and advanced analysis. A high speed ultrasonically assisted micro-drilling (UAMD) system is established with air bearings and longitudinally vibrating workpiece. During the experiments the thrust force reduction is studied as well as effects of ultrasonic vibration frequency and rotational speed. A correlation study was conducted between the thrust force measurements and simulations from a nonlinear force model. It can be seen that the current one-dimensional model is not sufficient to describe the complete behavior of the drill. The FE model and force experimental results can be utilized for a full dynamic model of the UAMD system to study vibration and the cutting mechanism in the future.

Study on Thrust Force Reduction of Tripod Constant Velocity Joint

Tripod constant velocity joints are used in the driveshafts of front wheel drive vehicles. Thrust force generated by this joint causes lateral vibration in these vehicles. This paper surveys some methods for reducing the thrust force based on the mechanisms inducing the thrust force, focusing on a method that creates dual contact between a roller and groove. This method has the advantage of requiring only a few design modifications, but its thrust force reduction mechanism has yet to be clarified. Therefore, a theory was constructed to describe the induction of thrust force by this method through the application of sliding velocities generated between the roller and dual contact groove. Subsequently, the effect of the thrust force reduction was investigated. This paper also describes the appropriateness of this theory. It was validated by comparing theoretical results with computational results based on a multibody dynamics approach and with experimental results of a prototype joint equipped with the dual contact grooves.

Study on Thrust Force Reduction of Tripod Constant Velocity Joint

A tripod constant velocity joint is used in the driveshaft of front wheel drive vehicles. Thrust force generated by this joint causes lateral vibration in these vehicles. In this paper, in order to reduce the thrust force, some reduction methods are surveyed based on mechanisms inducing the thrust force. In these methods, the dual-contact method between a roller and a groove is focused. This method has the advantage of only a few design modifications, but reduction mechanisms have not been clarified. Therefore, a theory inducing the thrust force in this method is constructed by applying sliding velocities caused between the roller and this dual-contact groove, and the effectiveness of the thrust force reduction is studied. This paper also describes the appropriateness of this theory. It is verified by comparing these theoretical results with computational results by utilizing multibody dynamics approach and experimental results by using a prototype joint equipped with the dual-contact grooves.

507 トリポード形等速ジョイントのスラスト力低減に関する研究(ジョイントのモデリングとその応用,OS-19 マルチボディダイナミクス,総合テーマ「伝統を,未来へ!」)

To achieve reduction of thrust force of a tripod constant velocity joint, some reduction methods are determined based on mechanisms inducing the thrust force. In these methods, a dual-contact method is selected because of very few design change. A theory inducing the thrust force between a roller and this dual-contact groove is constructed. By comparing theoretical results with computational ones using multibody dynamics approach, the appropriateness of this theory is verified. This paper also describes the effectiveness of the thrust force reduction by testing a prototype joint equiped with the dual-contact groove.

High-Aspect-Ratio Microdrilling of Cobalt-Based Superalloy

It is necessary to develop a high-aspect-ratio microdrill method with a diameter of 0.2mm and a depth of 4mm (aspect ratio 20) that can be applied to the fuel injection nozzle of a marine diesel engine. However, the injection nozzle is made of cobalt-based superalloy, which is a difficult-to-cut material. In this study, the drilling conditions from viewpoints of thrust force and torque for the cobalt-based superalloy are determined. In addition, a thinning machine is developed for the convenient precise thinning of the microdrill. The effects of the thinning of the microdrill are verified to measure thrust force and torque during drilling. The following results are obtained. The thinning of the microdrill with a diameter of 0.2mm results in a reduction in thrust force by 20% and that in chip adherence to the drill by 25% during drilling.

Study on the effect of frequency tracing in ultrasonic-assisted drilling of titanium alloy

Drilling titanium alloys are difficult because of the inherent material properties, particularly the low thermal conductivity and high chemical reactivity. This paper presents the design of a frequency tracing system and the experimental investigation in ultrasonic-assisted drilling (UAD) of titanium alloy. In order to realize the degree of influence between developed frequency tracing system and cutting parameters (frequency tracing, operating voltage, drill diameter, feed rate, and spindle speed) in UAD of titanium alloy, a L18 (2 × 37) orthogonal array was employed. Based on the experimental results, the importance of drill diameter, feed rate, and spindle speed in assessing thrust force is highlighted. On the other hand, average thrust force reduction of 3.2% was realized with frequency tracing compared to without the frequency tracing counterpart in UAD of titanium alloy. Moreover, the best combination to get lower thrust force in UAD of titanium alloy is A2B2C3D1E3 (i.e., frequency tracing = YES, operating voltage = 500 V, drill diameter = 3 mm, feed rate = 10 mm/min, and spindle speed = 1,000 rpm) within the selected test range.