Hole Bottom Surface Research Articles

A comparison of different heat flux density distribution models to predict the temperature in the drilling process

This work aims to improve heat flux distribution models to predict the temperature during drilling. The workpiece temperature is simulated by applying heat flux load only on the hole wall surface. Finite element method is used to simulate the temperature over process time. An iterative identification algorithm using particle swarm optimization (PSO) enables to identify the heat flux distribution parameters through the best fit of the experimental and calculated temperatures. Two heat flux density distributions presented in the literature, namely linear and polynomial, are investigated. A concentrated heat flux distribution is calculated based on measured torque and serves for a comparison purpose. Additionally, the polynomial approach is expanded by adding a concentrated heat flux in order to compensate the lack of hole bottom surface. The best results in terms of residual temperature are obtained for the hybrid heat flow distribution.

Analysis of the surface roughness for novel magnetorheological finishing of a typical blind hole workpiece

In modern high-performance machinery, parts which are highly finished and dimensionally accurate play a vital role. Surface finish enhances characteristics like wear, corrosion, pitting, and oxidation resistance of the surfaces. A novel magnetorheological polishing process using permanent magnets is developed to finish the internal cylindrical and bottom surfaces of the blind hole cylindrical workpiece. The process is capable of finishing the internal cylindrical and flat bottom surfaces of tubular and nontubular-shaped blind hole workpiece. Finishing of blind hole surfaces finds extensive application in dies and automotive components such as automobile actuators, cylinder body, valve seats, etc. In this study, two different tools for finishing the internal and flat bottom surfaces of blind hole cylindrical workpiece have been developed. The causal factor for material removal in the form of microchips is abrasive wear. The present study focuses on the calculation of forces acting on abrasive particles and mathematical modeling and simulation of the surface roughness. The performance of both newly developed tools for finishing the cylindrical blind hole mild steel workpiece is evaluated. After 275 finishing cycles, the Ra values improved by 55.2% in the internal cylindrical ferromagnetic workpiece and by 53.33% after 75,000 cycles on the flat surface of ferromagnetic blind hole workpiece. The theoretical and experimental values of the surface roughness are found to be consistent. The experimental surface roughness values of blind hole internal cylindrical surfaces are within 6.26% of the theoretical values, whereas in finishing the blind hole bottom surface it is found within 7.9% of the theoretical values.

Modeling of cavitating flow induced by an ultrasonic horn above a solid target with a microhole

Ultrasonic cavitation may be involved in many manufacturing-related applications, such as ultrasonic cleaning, ultrasonic cavitation peening, and ultrasound-assisted water-confined laser micromachining (UWLM). However, the previous physics-based modeling work has been very limited for cavitating flow induced by an ultrasonic horn near a solid target with a microhole. Such modeling work is reported in this paper, where two-dimensional compressible fluid mechanics equations, together with an equation governing the vapor-volume fraction evolution, are solved numerically. The model prediction shows reasonable consistency with experimental results in the literature for cavitating flow induced by an ultrasonic horn in water relatively far from a solid wall. Then the model is used to study the cavitating flow induced by a horn placed near a solid wall with a microhole. Under the studied conditions, the model calculations show that the horn-induced peak pressure magnitude at the microhole center decreases as the hole becomes deeper. On the other hand, the horn-induced temporal peak pressure at the hole bottom surface is spatially relatively uniform in the r (radial) direction, while the peak pressure on a solid surface without the hole decreases quickly with r. However, the peak pressure induced on the hole sidewall is not spatially uniform, and the largest peak pressure on the sidewall occurs at the hole bottom. The model may help future fundamental research work on ultrasonic horn-induced cavitating flow near a solid wall with a microhole, and may also provide a useful guiding tool for related manufacturing applications.

Magnetic fixtures for enhancement of smoothing effect by electron beam melting

In large-area electron beam (EB) irradiation method developed recently, high energy density EB can be obtained without focusing the beam. Therefore, large-area EB of 60mm in diameter can be used for instant melting and evaporation of the wide area material surface, and high efficient surface finishing is possible. However, if the workpiece has a hole shape, the EB concentrates in the entrance edge or inside wall of the hole. Thus, it is difficult to smooth the hole bottom surface. Previous study showed that the surface smoothing and micro-deburring effects for non-magnetic workpiece could be improved by setting a magnetic block under the workpiece, since the electrons tend to concentrate the magnetic block along magnetic lines. In this study, smoothing of hole bottom surface was experimentally investigated by setting a magnetic block under a workpiece in large-area EB irradiation. Expansion of smoothing area of the bottom surface was also tried by setting a through hole at the center of the magnetic block. It was clarified that wide area of hole bottom surface could be smoothed by large- area EB irradiation by setting the magnetic block under workpiece. The surface roughness decreased to less than 3.0μmRz at the area of hole bottom surface. When the hole diameter was 20mm and hole depth was less than 40mm, smoothing area of 10mm in diameter was obtained by using the magnetic block. Moreover, the smoothing area was sufficiently expanded by setting a through hole with an appropriate diameter in magnetic block.

Expansion of Smoothed Area on Hole Bottom Surface by Setting Magnetic Block in Large-area Electron Beam Irradiation

Expansion of Smoothed Area on Hole Bottom Surface by Setting Magnetic Block in Large-area Electron Beam Irradiation

An Inverse Heat Transfer Method for Determining Workpiece Temperature in Minimum Quantity Lubrication Deep Hole Drilling

This study investigates the workpiece temperature in minimum quantity lubrication (MQL) deep hole drilling. An inverse heat transfer method is developed to estimate the spatial and temporal change of heat flux on the drilled hole wall surfaces based on the workpiece temperature measured using embedded thermocouples and analyzed using the finite element method. The inverse method is validated experimentally in both dry and MQL deep-hole drilling conditions and the results show good agreement with the experimental temperature measurements. This study demonstrates that the heat generated on the hole wall surface is significant in deep hole drilling. In the example of deep hole drilling of ductile iron, the level of thermal power applied on the hole wall surface is about the same as that on the hole bottom surface when a 10 mm drill reached a depth of 120 mm.

Workpiece Thermal Distortion in Minimum Quantity Lubrication Deep Hole Drilling—Finite Element Modeling and Experimental Validation

This paper presents the three dimensional (3-D) finite element analysis (FEA) to predict the workpiece thermal distortion in drilling multiple deep-holes under minimum quantity lubrication (MQL) condition. Heat sources on the drilling hole bottom surface (HBS) and hole wall surface (HWS) are first determined by the inverse heat transfer method. A 3-D heat carrier consisting of shell elements to carry the HWS heat flux and solid elements to carry the HBS heat flux has been developed to conduct the heat to the workpiece during the drilling simulation. A thermal–elastic coupled FEA was applied to calculate the workpiece thermal distortion based on the temperature distribution. The concept of the heat carrier was validated by comparing the temperature calculation with an existing 2-D advection model. The 3-D thermal distortion was validated experimentally on an aluminum workpiece with four deep-holes drilled sequentially. The measured distortion on the reference point was 61 μm, which matches within uncertainty the FEA predicted distortion of 51 μm.

S134021 CFRP/Ti積層板のドリル加工面温度測定

Carbon reinforced plastics (CFRP) is increasingly being used in the aerospace industry because of the high strength-to-weight ratios. Material stacks comprising CFRP and titanium alloy are used for structures for aerospace applications, where high mechanical loads exist. Drilling is used to make holes for fastening the composites by bolting. The drilling temperature effects on the hole quality. In this study, the hole bottom surface temperature during drilling of CFRP/Ti composite is measured by using an infrared radiation pyrometer with an optical fiber. The optical fiber is inserted in the oil hole of carbide drill to measure the temperature. In the drilling of CFRP/Ti, the temperature is about 80 °C during drilling of CFRP, and the temperature rapidly increases to 270 C at the beginning of the drilling of titanium and it increases to 750 °C at the exit side of titanium. In the drilling of Ti/CFRP, the temperature is about 170 C at the beginning of the drilling of titanium and it increases to 700 °C at the exit side of the titanium, and the temperature is about 180 °C during drilling of CFRP.

Generalized modeling of drilling vibrations. Part I: Time domain model of drilling kinematics, dynamics and hole formation

This two part paper presents a comprehensive exercise in modeling dynamics, kinematics and stability in drilling operations. While Part II focuses on the chatter stability of drilling in frequency domain, Part I presents a three-dimensional (3D) dynamic model of drilling which considers rigid body motion, and torsional–axial and lateral vibrations in drilling, and resulting hole formation. The model is used to investigate: (a) the mechanism of whirling vibrations, which occur due to lateral drill deflections; (b) lateral chatter vibrations; and (c) combined lateral and torsional–axial vibrations. Mechanistic cutting force models are used to accurately predict lateral forces, torque and thrust as functions of feedrate, radial depth of cut, drill geometry and vibrations. Grinding errors reflected on the drill geometry are considered in the model. A 3D workpiece, consisting of a cylindrical hole wall and a hole bottom surface, is fed to the rotating drill while the structural vibrations are excited by the cutting forces. The mechanism of whirling vibrations is explained, and the hole wall formation during whirling vibrations is investigated by imposing commonly observed whirling motion on the drill. The time domain model is used to predict the cutting forces and frequency content as well as the shape of the hole wall, and how it depends on the amplitude and frequency of the whirling vibration. The model is also used to predict regenerative, lateral chatter vibrations. The influence of pilot hole size, spindle speed and torsional–axial chatter on lateral vibrations is observed from experimental cutting forces, frequency spectra and shows good similarity with simulation results. The effect of the drill–hole surface contact during drilling is discussed by observing the discrepancies between the numerical model of the drilling process and experimental measurements.