Thousands Of Holes Research Articles

Spot-checking machine learning algorithms for tool wear monitoring in automatic drilling operations in CFRP/Ti6Al4V/Al stacks in the aircraft industry

In aircraft manufacturing, where diverse materials, including Carbon Fiber-Reinforced Plastics (CFRP), aluminum, and titanium alloys, are employed, the assembly process heavily relies on creating thousands of holes. These holes accommodate bolts and rivets, facilitating the secure interlocking of structural components within the aircraft fuselage. The proliferation of sensor systems in this domain has led to a substantial increase in data generation during the hole-making process, offering a compelling opportunity to optimize the production system. In this context, this article is dedicated to harnessing the data collected from the production system of a commercial aircraft to refine the assembly process, with a specific focus on reducing consumable costs. The primary approach involves developing a real-time Tool Wear Monitoring System by comparing the performance of Linear Regression, Lasso Regression, Ridge Regression, k-Nearest Neighbors, Support Vector Regression, Decision Tree, Random Forest, and Extreme Gradient Boosting Machine Learning models. Using a scale of the general drill condition as an outcome, the Gradient Boosting Regressor has shown outstanding results. Notably, the residuals consistently exhibited zero-centered errors in training and test sets. However, it suggests that further enhancements are needed to surpass human-level performance in predicting tool conditions because of the quality and quantity of available data.

Investigation of Drilling Holes in CFRP for Aircraft Using cBN Electroplated Ball End Mill Using Helical Interpolation Motion

Investigation of Drilling Holes in CFRP for Aircraft Using cBN Electroplated Ball End Mill Using Helical Interpolation Motion

Research solution for automatic hole quality analysis when drilling fiber-reinforced composites

Fiber-reinforced polymers are highly demanding composites in aerospace and automotive areas because of their excellent mechanical properties such as stiffness and strength-to-weight ratio. The drilling remains the major machining operation applied to composites to provide high-quality holes for joints between parts. Due to composites plied structure, the drilling is accompanied with unusual form metal cutting defects such as delamination and uncut fibers around the drilled hole. Considering that the tool life of some drills reaches over thousands of holes, the research of composites machinability becomes difficult due to demanded labor intensity in manual inspection of the hole quality. Therefore, this paper develops the research solution for automatic analysis of the hole quality in drilled fiber-reinforced materials. The paper proposes a complex of solutions aimed to speed up the analysis of the hole quality when composites drilling. The solution consists of the developed vacuum table, robot arm with high-speed camera, developed top and bottom lightning systems, and Image Processing algorithms for defect detection from captured images. The paper results show how the developed solution can be used for high routine research activities. The output data, including tested 72 cutting data parameters and full-size tool life test, allowed identifying the operational window for high-speed steel drills and the range of tool life, where drill ensures a certain hole quality. The paper shows the efficiency of the developed research solution can reach 5 s per hole including drilling and full cycle of measurements having measurement error of 1–3%.

Integration of CVD graphene in gaseous electron multipliers for high energy physics experiments

To enhance the performance of micro-patterned gaseous detectors (MPGDs) to meet the challenging requirements of future high energy physics (HEP) experiments, two-dimensional (2D) materials are attractive candidates to address the back flow of positive ions, which affects detector performance by distorting electric field lines. In this context, graphene is promising to work as selective filter for ion back flow suppression, being transparent to electrons while at the same time blocking ions. Also, graphene membranes can physically separate drift and amplification regions of the detectors, offering additional flexibility in the choice of gas mixtures and allowing independent optimizations of detector sensitivity and electron multiplication processes. Here we present an approach to integrate graphene grown via chemical vapor deposition (CVD) on gaseous electron multiplier (GEM) prototypes via a wet transfer procedure in order to suspend graphene over thousands of holes with 60 μm diameter and overcome the challenges encountered due to process steps involving liquids, mostly related with the capillary effects during drying and evaporation of them. In order to overcome the risk of damaging the membrane and decreasing the yield of suspended 2D material membranes, critical point dryer (CPD) and inverted floating method (IFM) procedures are investigated. In addition to the necessity to cover the full holes in the active area, polymeric residuals have to be minimized in order to evaluate the graphene transparency at the electron energies (i.e., < 15 eV) typically obtained in the operating conditions, measurements in these energy ranges are still not deeply investigated.

Solitary wave interaction with upright thin porous barriers

The interaction of fluid flow with porous barriers has numerous practical applications, including as a partial barrier to water waves that damp some of the approaching energy at the same time as allowing environmental flow. However, surprisingly little effort has been expended on understanding the fundamentals of this interaction. Therefore, this study aims to model the interaction between waves and thin, upright porous barriers. This is undertaken by modelling the porous barrier empirically within a Smoothed Particle Hydrodynamics (SPH) framework that is then used to model wave flume experiments. Although detailed modelling of the interaction is possible at the laboratory scale, it is not feasible in practical settings where a barrier will contain many thousands of holes that cannot be individually modelled. The key information needed to model the barrier empirically is obtained from solitary wave-porous barrier interaction experiments. Our results indicate that, for each barrier, irrespective of the properties of the wave interacting with it, there is a coefficient value that is able to account adequately for the energy dissipation by the barrier. The reliability of the approach has been demonstrated by comparing SPH model predictions against companion sinusoidal wave-porous barrier experimental measurements. The SPH model was then used to determine the energy dissipation characteristics of porous barriers kept at different draught to water depth ratio, D/d, without reference to the wave flume experiments. Simulation results indicate that barriers are more effective in dissipating the incident wave energy if its draught is over 75% of the water depth.

Effect of Drilling Penetration Angle on Delamination for One-Shot Drilling of Carbon Fiber Reinforced Plastic (CFRP)

Carbon-fibre-reinforced plastic is prominent with superb specific mechanical properties that contribute to its application in high technology industries, such as aircraft and automobiles' mechanical structures. These materials are considered hard to cut. The delamination issues frequently arise due to their anisotropy and inhomogeneity. In aircraft manufacturing, thousands of holes are required to assemble the structural parts. Hole perpendicularity issues undoubtedly might happen during manual drilling. The main purpose of this work is to study the effects of various minor slant drilling angles on thrust force generation and delamination by using a special drill reamer. From the investigation, the drilling penetration angle significantly impacted the delamination. The delamination factor for the entry and exit sides of holes relatively decreased from 1.042 and 1.087 to 1.027 and 1.049, respectively, as the thrust force declined from 114.8 N to 106.5 N from 5° to 0° drilling angle.

Multi-spindle drilling of Al2024 alloy and the effect of TiAlN and TiSiN-coated carbide drills for productivity improvement

High precision drilling is required to ensure the structural integrity of the aircraft. Therefore, strict quality controls are required to ensure optimum hole quality since hundreds of thousands of holes are drilled into different aircraft structures. The large number of holes required for riveting means that their installation must be carried out in a fast and precise manner. This can be achieved using multi-head drilling tools that can drill several holes simultaneously. The current study investigated the use of a multi-spindle drill head that can produce three holes simultaneously. Uncoated carbide and TiAlN-coated and TiSiN-coated carbide drills were used to assess cutting forces, hole surface roughness, burr formations and tool condition when machining Al2024 aerospace alloy under dry machining conditions. Analysis of variance was employed for estimating the relationships between the input parameters (spindle speed, feed and tool coating) and the studied hole quality metrics. Furthermore, a regression model was developed with a regression coefficient (R2) of more than 90% for the prediction of measured responses. Interestingly, better results in lower thrust force and surface roughness were obtained using the uncoated carbide drills compared with TiAlN and TiSiN, while the performance of TiAlN was found to be better than those obtained from TiSiN.

Path optimization for multi-axis EDM drilling of combustor liner cooling holes using SCGA algorithm

Multi-axis electrical discharge machining (EDM) drilling technology is widely used in the manufacture of film cooling and jet cooling holes of combustor liners. However, there can be more than 3000 film cooling holes with variant orientations in a typical combustor liner. Drilling of thousands of holes without process planning will result in a low machining efficiency. Traditional path optimization methods are carried out in a workpiece coordinate system, which is usually not optimal when applied to multi-axis machining processes. Aiming at minimizing the total non-productive time in a combustor liner multi-axis EDM drilling process, a mathematic model, which takes tool traveling time, tool switching time, and compensation moving time into consideration, is firstly derived. To solve the optimization problem efficiently, a spectral clustering/genetic algorithm (SCGA) is applied as the model has a large number of 0–1 variables. To improve the search performance, pairwise inter-reshuffle (PIR) based initial population and modified mutation are utilized. The performance of SCGA is evaluated by solving a 3616-hole optimization problem and the results are compared with those by other heuristic methods. Comparison results show that the SCGA significantly outperforms other comparison algorithms in terms of minimum non-productive time and convergence speed.

An Experimental Comparative Analysis of Twist Drilling, Helical Milling and Pilot Hole Machining for Large Diameters in CFRPs

Carbon fiber-reinforced polymer (CFRP) large diameter hole drilling is certifiably not a broadly examined theme on account of their non-homogeneity and anisotropic highlights. In the scope of aerospace industrial uses of this material, thousands of holes have to be machined for purposes of assembly. The quality of this machined hole is influenced adversely by matrix grid cratering, thermal damage, spalling, surface delamination, and material debasement or fiber pullout. Among these different deformities, delamination is considered the most severe for CFRP composite. The main objective of this work is to compare twist drilling, helical milling and pilot hole machining technologies concerning unidirectional CFRP composite. In addition, the force modules were also discussed. In the scope of this work, numerous machining experiments were conducted in unidirectional CFRP composite: herein the impact of the type of cutting tool and of process parameters on the quality of machined holes are analysed and discussed (diameter of holes, circularity error and characteristics of uncut fibres). In other to achieve a better hole quality, the Scanning electron microscope (SEM) analysis and evaluation of acquired data were conducted. Experimental results show holes machined using twist drilling method present the lowest-quality, with damages present at the tool entry and exit as compared to the other studied methods. This study intended to help in assisting technicians working on assembly large structural parts in aircraft or automobile industries in choosing the best hole machining procedure when this three are in consideration.

Comparative analysis of wobble milling, helical milling and conventional drilling of CFRPs

Due to its excellent specific mechanical properties, carbon fibre-reinforced polymer (CFRP) composite is a widely used structural material in the aerospace industry. However, this material is difficult to cut, mainly due to its inhomogeneity and anisotropic features and because of the strong wear effects of its carbon fibres. In the scope of aerospace industrial uses of this material, thousands of holes have to be machined for purposes of assembly. Nevertheless, conventional drilling technology – even if special drilling tools are used – is only moderately able to manufacture good quality holes. Wobble milling is a novel advanced hole-making technology, which has been developed to minimize machining-induced geometrical defects like delamination or uncut fibres. The main objective of the present paper is to compare wobble milling, helical milling and conventional drilling technologies concerning unidirectional CFRPs. In addition, the kinematics of wobble milling technology is discussed in detail. In the scope of this paper, numerous machining experiments were conducted in unidirectional CFRPs: herein the impact of the type of cutting tool and of process parameters on the quality of machined holes are analysed and discussed (diameter of holes, circularity error and characteristics of uncut fibres). During these investigations, experimental data were evaluated with the help of digital image processing (DIP) and with the help of analysis of variance (ANOVA) techniques. Experimental results show that the amount of uncut fibres can significantly be minimized through the application of wobble milling technology.

Environmental Impact Assessment Due to Gas Seepage of Titas Gas Field, Bangladesh

The biggest gas field of Bangladesh, Titas in Brahmanbaria continues to face a possible disaster due to the seepage of the huge amount of gas mixed with water and oil through thousands of holes and cracks on the surface environment in and around this gas field. Gas is leaking through more than 3,000 big holes, including some 30-ft diameter ones, spreading in paddy fields, water bodies, and the Titas river. Approximately 1000 acres of virgin land with varieties of flora and fauna have been affected through seepage. Soil condition in the villages has degraded and still degrading to such an extent that it becomes unpredictable to comment on how many years it needs to regain fertility. Yet the present alarming situation is rippled with confusion about the actual source of seepage till now. To help the situation, an assessment of the impact of gas seepage from the Titas gas field on the surrounding environment was needed to evaluate the overall environmental condition at present and to propose adequate control measures for the abatement of the adverse impact on the environment. Therefore, the main objective of this research work is to assess the environmental impact of this seepage from the Titas Gas field. To fulfill the object of this study, we have developed a questionnaire including 18 parameters. These parameters encompassed all the aspects of ecology, socio-economic and so on. We visited the study area and made the gathering with affected peoples. The answer to each parameter of the questionnaire has been taken from people. From this study, it is found that all the tube wells of the villages are automatically emitting a huge quantity of natural gas. It is observed that the emitting of gas from the tube well-produced enormous irritating noise. The air is found polluted in and around the site visited. The most severe and alarming finding the health-related disease (skin disease, asthma, hair fall, water-born diseases e.t.c). It is summarized that about six square km of the area of Bakail, Suhilpur, Shampur and Anandapur villages, the Titas River and Loiska swamp are at high risk due the seepage.

Absorption characteristics of micro-perforated panels using scale modeling and microflown impedance gun

A theoretical and experimental comparison of the absorption characteristics of micro-perforated panels was undertaken. The micro-perforated panels were designed using the Sheffield University Java based website, constructed from 0.3 m by 0.3 m of acrylic, the thousands of holes were laser cut. The panels were large enough to be tested using the microflown impedance gun as well as a new scale model reverberation chamber based at London South Bank University. The 1:10 scale model reverberation chamber was constructed from acrylic materials and used a 3-D printed dodecahedron sound source. Data acquisition was through a ¼” microphone connected through a Nexus preamplifier to a 24 bit 192 kHz sound card. MATLAB code was used to acquire and process the signal in accordance to ISO 354 including air compensation for high frequencies. Results will be presented for theoretical, scale, and impedance based measurement of the absorption coefficients for the micro-perforated panels.

The Profile Error Feedback Optimization for the Design of a Showerhead System Controlling Gas Flow Uniformity in a Thin-Film Reactor

The design of a vector showerhead in a vertical reactor involves thousands of holes on the showerhead face plate and mass transport in the reactor, and the design variables and objective are always spatial related continuous characteristic, so the discretized sequence of the design variables has too many degrees of freedom that the needed sampling points of a design of experiment or heuristic algorithm methods are hardly acceptable. In order to solve this problem, a profile error feedback (PEF) optimization method was proposed. This method employed a loop-iteration-approximation mode, and started from a guessed initial model, and then fed back the profile error of design objective, according to a weight function, to continually adjusted the design variable sequence to make the gas flow uniformity in the new model continually approximate the perfect one. The optimization case of a vector showerhead system shown that the non-uniformity of the gas flow was reduced from 0.36% to 0.03% under a typical process condition.

Simulation-Based Optimization of a Vector Showerhead System for the Control of Flow Field Profile in a Vertical Reactor Chamber

Optimization of a vector showerhead in a vertical reactor involves thousands of holes on the showerhead face plate and the spatial distribution of physical fields, so parameterizing the geometry configuration of the holes in high resolution is very difficult, which makes the conventional optimization methods hard to deal with. To solve this problem, a profile error feedback (PEF) optimization solution was proposed to optimize a vector showerhead gas delivery system for the control of mass transport. The gas velocity profile in the reactor and the continuous-feature impedance distribution profile on the showerhead face plate are defined as design objective and variables, respectively. A cyclic iterative approximation idea was implemented in this solution. The algorithm was started from a guessed initial design model and then cyclically adjusted the design variables by the constructed PEF iterative formula to generate a better model and to make the gas velocity profile in the critical domain of the new model continually approximate to the expected profile, until it could be accepted. Finally, the optimized impedance profile was mapped to the holes geometry configuration through the established equivalent impedance model for the showerhead face plate.

The Fresnel interferometric imager

The Fresnel interferometric imager is a new kind of high angular resolution space instrument for the UV domain, and the related astrophysical targets. This optical concept is meant to allow larger and lighter apertures in space than solid state optics. It yields high dynamic range images and same resolution as that of a solid aperture of the same size. The long focal lengths of the Fresnel imager (a few kilometers) require operation by two-vessel formation flying in space. The first vessel holds a large and thin opaque foil punched with thousands of holes: the interferometric array, the second vessel holds the focal instrumentation. This Fresnel imager has been designed for mapping high contrast stellar environments: dust disks, close companions and (we hope) exoplanets. Compact objects such as large stellar photospheres may be imaged with array sizes of a few meters in the UV. Larger and more complex fields can also be imaged, although with a lesser dynamic range, such as small fields on galactic clouds or extragalactic fields, or in an other domain: small solar system bodies. We present the first images obtained on artificial sources with an 8 cm laboratory testbed array having 26680 apertures, the measured dynamic range of these images and their diffraction limited angular resolution. A 3 m class probatory space mission will be studied and follow a validation path, It has been submitted as a proposal to the ESA Cosmic Vision program.

Free jets spun from a prilling tower

A mathematical model of the dynamics of an inviscid liquid jet, subjected to both gravity and surface tension, which emerges from rotating drum is derived and analysed using asymptotic and computational methods. The trajectory and linear stability of this jet is determined. By use of the stability results, the break up length of the jet is calculated. Such jets arise in the manufacture of pellets (for example, of fertilizer or magnesium) using the prilling process. Here the drum would contain many thousands of holes, and the molten liquid would be pumped into the rotating drum. After the jet has broken up into droplets, these droplets solidify to form pellets. The jets in this prilling process are curved in space by both gravity and surface tension.

The tandem scanning reflected light microscope

AbstractReflected light microscopy of biological material has been a very difficult task and many different but hardly successful attempts have been made to get usable images. The main reasons for this state are: Weak reflections from the biologically important structures in the object as against strong reflection at its surface; reflections at optical surfaces in the microscope which cause a deterioration of contrast; and the mixing together of reflections from many levels in the object so that the signal coming from the focussed‐on level is lost in noise and d.c. components.We tried, and successfully, to reverse this situation and to make it possible for the signal to overwhelm spurious and scattered light using double, or, as we call it, tandem scanning. The object is illuminated only in small patches lying in one plane and moving across this plane, and only the light reflected from these illuminated patches is allowed to pass into the image plane and participate in image formation. The image consists of points which travel over the image plane and which are geometrical images of the illuminated patches in the focussed‐on object plane. To ensure that only the light belonging to these geometrical images be allowed to enter the image, the image plane is covered with an opaque diaphragm having holes in locations exactly corresponding to the locations of the geometrical images of the illuminated object points; this diaphragm travels in concordance with the first scanning and so the complete image of the focussed‐on object plane is formed successively.Both scans are performed by a single device, a Nipkow disc carrying in its annular periphery several ten thousands of holes arranged in Archimedean spirals. The disc is 100 mm in diameter and rotates about 100 rpm driven by an electric motor. On one side the disc is illuminated in a circle 18 mm in diameter, and the light transmitted through several hundred holes and reflected in a mirror system passes a microscope objective which forms the images of the disc holes in the object plane. The light reflected here passes through the same objective and mirror system (one mirror being a “limitlessly thin” beam splitter) to pass conjugate aperture holes on the observation side of the Nipkow disc. As the disc lies at the intermediate image plane of the objective lens on both its illuminating and observation sides, only light emanating from reflection or fluorescence in the plane of focus can contribute to the image. High contrast images of very thin focussed‐on layers are thus formed.The practical arrangements are such that very large specimens can be examined: The specimens for this microscope need not themselves be microscopic.

Simulation studies of improved die manufacturing techniques

In the production of an extrusion die, the step which consists of drilling thousands of holes into a steel hlank is extremely expensive. Several potential improvements for this drilling process have been proposed. This paper will attempt to evaluate the benefits of each proposed strategy using simulation. Substantial post-analysis of the simulation data is discussed to develop further potential improvements in the production process.

A Class of near-Perfect Coded Apertures

Coded aperture imaging of gamma ray sources has long promised an improvement in the sensitivity of various detector systems. The promise has remained largely unfulfilled, however, for either one of two reasons. First, the encoding/decoding method produces artifacts, which even in the absence of quantum noise, restrict the quality of the reconstructed image. This is true of most correlation-type methods. Second, if the decoding procedure is of the deconvolution variety, small terms in the transfer function of the aperture can lead to excessive noise in the reconstructed image. We propose to circumvent both of these problems by use of a uniformly redundant array (URA) as the coded aperture in conjunction with a special correlation decoding method. The correlation of the decoding array with the aperture results in a delta function with deterministically zero sidelobes. The properties of the encoding/decoding method are similar to those of the nonredundant pinhole array (NRA), however, the URA can be composed of thousands of holes whereas the NRA contains less than 40. In short, the URA offers the transmission advantage of the random array or Fresnel zone plate without introducing the artifacts typically seen when those apertures and others are used. It is shown that the reconstructed image in the URA system contains virtually uniform noise regardless of the structure in the original source. Therefore, the improvement over a single pinhole camera will be relatively larger for the brighter points in the source than for the low intensity points.