Hole Wall Research Articles

The characteristics of natural open fractures in acoustic borehole image logs from the pre-salt Barra Velha formation, Santos Basin, Brazil

Natural open fractures have been reported in the Barra Velha Formation (BVE) in the pre-salt lacustrine carbonate reservoirs in the Santos Basin offshore Brazil. These fractures contribute to excess permeability i.e., well test permeability is significantly larger than core permeability or log derived permeability, and they are therefore important for the fluid flow in the reservoirs during production and injection. In this paper we summarize the characteristics of natural open fractures in acoustic borehole image logs (BHI) in 19 wells from the BVE reservoirs and discuss their distribution, occurrences and formation. The data quality is overall good and consistent so that results can be compared between wells. The P21 fracture intensity, which is fracture trace length per area (bore hole wall) was used, instead of Terzaghi corrected P10 fracture intensity which do not distinguish between minor and major fractures. Mean P21 fracture density shows a variation of 2 orders of magnitude between interpreted wells. Data binning was used in the analysis of P21 fracture intensity vs petrophysical parameters to reduce the effect of sampling volume being much smaller than the representative elementary volume (REV) of the fracture pattern. P21 fracture intensity shows a positive correlation with silica content, which varies in the carbonates, whereas the porosity is less important for fracture intensity. The occurrence of fractures is also associated with vug-fraction estimated from the acoustic BHIs. Fractures are also frequent in fault damage zones, above and below cavities. The main orientation of the fractures is NNW-SSE, that is in the same direction as the dominating fault trend, and this indicates a structural control on fracture formation. Natural open fractures are rare in high porosity rocks with a shrubby or grainy texture, and also in intervals with a conglomeratic appearance in the BHI image logs.

Field concentration and distribution in three-dimensional magneto-electro-elastic plates with open holes

In this work, the field concentration and distribution along the wall of elliptic holes in three-dimensional thick plates of anisotropic magneto-electro-elastic (MEE) materials are systematically analyzed using a three-dimensional weak finite-element formulation implemented in the COMSOL software. The proposed model is validated against existing solutions, and then applied to the analysis and design of multiferroic composites with an open hole, including multicoated circular fibrous MEE composites and MEE sandwich made of piezoelectric (BaTiO3) and magnetostrictive (CoFe2O4) materials. The distribution of field concentration factor, hoop stress, radial stress, and out-of-plane stress along the wall of elliptic holes for MEE plates under typical far-field uniform loads are analyzed, as well as the influence of hole shape, plate thickness and stacking sequence. Under far-field electric or magnetic fields, various unique features are observed which should be very helpful for strength and fatigue designs of MEE materials with notches and holes. An empirical formula is derived to predict accurately the maximum stress concentration factor along the thickness direction of the elliptical hole.

Preparation and investigation of high-performance 3D Ag/SiO2 nanohole array substrate based on cicada wing

In this paper, SiO2 support with 3D ordered nanohole structure was developed by using the nanopillars naturally created on the surface of the cicada wing as the template through a simple strategy of tetraethyl orthosilicate (TEOS) hydrolysis. Then 3D Ag/SiO2 substrate with a high density of hot spots was subsequently obtained by thermal deposition of Ag onto the SiO2 support. SEM and AFM observation reveal the hole walls of SiO2 were covered densely with large Ag particles whose surface was composed of lots of tiny Ag NPs. Especially at the top of the hole walls, six adjacent large Ag particles surrounded each hole. FDTD simulation demonstrated both the gaps between the tiny Ag NPs and those between large Ag particles were efficient hot spots, which could concentrate the electric field effectively. By using crystal violet (CV) as the probe molecule, the proposed Ag/SiO2 substrate could detect 10−9 M CV easily and the enhancement factor (EF) was calculated to be 1.7 × 107 due to the combined effect of hot spots and the 3D structure. The hexagonally arrayed nanohole structure endowed the proposed Ag/SiO2 substrate with good uniformity and the relative standard deviation (RSD) was estimated to be as low as 5.79%. The great potential of this substrate in practical applications was demonstrated by the successful detection of tricyclazole down to 0.01 ppm which lived up to the EU standard.

Effects of in-nozzle flow and low-pressure zone on spray targeting of multi-hole gasoline direct injection injector

The purpose of this study is to reveal the effect of In-nozzle flow and low-pressure zone near the nozzle exit on the spray targeting of a multi-hole gasoline direct injection injector using a numerical simulation. The change in spray targeting owing to in-nozzle flow and the distribution of the liquid phase at the hole exit were analyzed through a multi-phase flow simulation. A volume of fluid (VOF) model was used to effectively distinguish between the liquid flow and cavitation region. Results of the numerical simulation at the internal and near-field show that cavitation occurred at a sharp corner with a high flow velocity. Moreover, the low liquid rebounded at the hole wall, and the flow was bent in the direction of cavitation. The results of the spray simulation indicated that an increase in the injection pressure reduced the minimum pressure in the low-pressure zone. By contrast, the increase in ambient pressure not only decreased the pressure in the low-pressure zone, but also caused the low-pressure zone to form closer to the hole exit. In most cases, the low-pressure zone had a greater effect on plume bending than on in-nozzle flow, which was further enhanced as the ambient pressure increased.

GaN-полевой транзистор с эффективным теплоотводом на Si-подложке

A simple design of a GaN field-effect transistor on a Si substrate with efficient heat removal through polydiamond layers formed on the walls of grounding holes is proposed. According to calculations, as a result of the introduction of such a heat sink with the same average distance between the gate sections, the maximum temperature in the channel of the GaN transistor on the Si substrate decreases significantly and becomes comparable to the maximum temperature in the channel of the GaN transistor on the SiC substrate.

GaN field-effect transistor with efficient heat dissipation on Si substrate

A simple design of a GaN field-effect transistor on a Si substrate with efficient heat removal through polydiamond layers formed on the walls of grounding holes is proposed. According to calculations, as a result of the introduction of such a heat sink with the same average distance between the gate sections, the maximum temperature in the channel of the GaN transistor on the Si substrate decreases significantly and becomes comparable to the maximum temperature in the channel of the GaN transistor on the SiC substrate.. Keywords: GaN FET, ground hole, channel temperature, polydiamond.

Investigation into temperature and its effects on hole wall quality in rotary ultrasonic countersinking of thin-walled CFRP/Al stacks

Carbon fiber-reinforcement plastics (CFRP) have been widely applied in modern aerospace industry with aluminum alloy in the form of thin-walled stacks due to their superior mechanical and physical properties. However, for CFRP, the heat accumulation occurs easily during countersinking process in consequence of low thermal conductivity. The surface thermal damage of CFRP caused by excessive heat would affect the fatigue and stealth performance of aircraft. Consequently, the countersinking temperature is an important indicator to judge the feasibility of CFRP countersinking process. In this paper, to investigate temperature of countersinking process, the application of rotary ultrasonic machining technology to CFRP/Al thin-walled stacks countersinking process under different stiffness conditions with drilling-countersinking integrated tool is carried out by FEA (Finite element analysis) and experiments. And the influences of cutting temperature on countersunk wall quality are discussed. The results demonstrate that the maximum countersinking temperature increases with the decrease of axial stiffness, and the ultrasonic vibration can effectively reduce maximum countersinking temperature by 22.9%-26.2%. Furthermore, analysis of the surface quality of countersunk wall shows that the countersunk wall roughness and defects gradually deteriorate with the increase of the maximum countersinking temperature. Meanwhile, the ultrasonic vibration can improve countersunk surface quality by reducing maximum countersinking temperature effectively.

Seismic behavior of the assembled walls using uniform precast hollow-core concrete panels restrained by cast-in-place boundary elements in single-story buildings

To achieve efficient construction of single-story buildings and increase economic efficiency while ensuring safety, low-cost, easy-to-assemble, and good seismic performance assembled walls using uniform precast hollow-core concrete panels restrained by cast-in-place boundary elements were designed. Through the low-cyclic loading test of three specimens, the safety and reliability of the connection between the components were verified, the good seismic performance of the structure was proved, and the influence of the number (2, 3, 4) of panels contained in the specimens, that is the shear span ratio (SSR) of the specimens, on their seismic performance was investigated. The study found that all specimens finally show shear-slip damage, and with the decrease of SSR, the ultimate shear-bearing capacity of the specimen increases, the deformation capacity decreases, and the energy dissipation capacity increases. Compared with the specimen of 2 panels, the ultimate shear bearing capacity of 3 panels and 4 panels is increased by 39.2% and 88.9% respectively. The ultimate deformation capacity of 2 panels is similar to that of 3 panels, but that of 4 panels is reduced by 23.3%. In addition, these three specimens are simulated using the finite element analysis software ABAQUS. The stress nephogram of each specimen reflects the presence of vertical shear along the thin wall of the circular hole of the panels under horizontal load, and the vertical shear surface will be linked into the shear belt along the diagonal of the specimen. Combined with experiment and finite element simulation, the calculation method of the ultimate lateral bearing capacity of the structure is established. The ratio of the measured value to the calculated value is greater than 1.0, and the maximum relative error of them is only 6.85%, which proves that the calculation method is safe and reliable. The research results of this paper can provide the necessary basis for the engineering application in single-story buildings.

Experimental research on new hole-making method assisted with asynchronous mixed frequency vibration in TiBw/TC4 composites

With the gradual promotion and the application of difficult-to-machine materials such as titanium matrix composites in the aerospace field, high-quality hole-making technology has become a major demand in aviation manufacturing. In order to improve the hole-making quality of TiBw/TC4 composites, asynchronous mixed frequency vibration-assisted hole-making (AMFVAHM) method is proposed. The process consists of two steps: ultrasonic vibration-assisted drilling (UVAD) base hole and low-frequency torsional vibration-assisted helical milling (LFTVAHM) target hole. Based on this process, the cutting trajectory modeling is established, and the hole-making experiment on TiBw/TC4 composites is conducted. The experimental data show that during the hole expansion stage, the maximum XY-plane average milling force decreases by 30.96% and the maximum axial average milling force decreases by 24.49% compared with conventional helical milling (HM) when the torsional vibration frequency and the milling frequency are the same in LFTVAHM. The hole-making experiment shows that AMFVAHM can reduce the chip size, tool wear, and some other defects such as entrance/exit burrs, scratches, and fractures of the hole wall. Comparing with HM and UVAD, the verticality of hole wall increases by 71.43% and 86.21%, the inlet damage decreases by 27.98% and 31.60%, the outlet damage decreases by 2.80% and 14.47%, the hole wall roughness (Ra) decreases by 36.29% and 63.43%, and the maximum white layer thickness decreases by 19.99% and 67.66%. Meanwhile, AMFVAHM process not only reduces the cutting force and cutting temperature but also improves the hole-making quality due to the fretting friction effect of LFTVAHM in secondary hole expansion, which meets the need for high-quality hole-making of difficult-to-machine materials in practical engineering applications.

A twisted yieldable rock bolt as a tool for dissipation of the ground pressure energy

An innovative design of a twisted yieldable rock bolt has been developed using the system analysis of conventional rock bolt technology, a thermodynamic approach, and a theory of technical creativity. This bolt consists of one single piece of a metal cylindrical rod having longitudinal feathers that provided its maximal reliability and minimized the cost. The bolt can be driven into a hole with a pneumatic hammer and creates a set of dissipative structures during rock mass deformation that facilitates and intensifies the dissipation of ground pressure energy causing stress relief around an underground opening. A 30 cm section of the bolt was successfully tested in special laboratory equipment, one 1.8 m bolt in a mechanic workshop, and fifty-five 1.8 m bolts in an underground entry of a coal mine. The behavior of this bolt was simulated on the FLA3D model to verify its basic parameters and to understand deeper abilities to yield and resist rock mass deformation. This bolt is fastened to the hole's wall for its entire length, thus the resistance and the energy dissipation indicators of this bolt are extensive parameters, hence the 2-m-length bolt can exceed the performance of the best modern prototypes. This bolt is relevant to provide stability to underground openings in hard squeezing conditions.

An experimental investigation on press joining mechanism and bearing behavior of single-lap composite riveted joints

This paper reports an experimental study on the forming mechanism and bearing behavior of single-lap composite riveted joints with different hole diameters (4.82 mm and 4.9 mm) and squeeze forces (15 KN, 18 KN, 20 KN, and 23 KN). Pressure riveting and tensile tests are conducted to composite riveted joints to obtain the joint interference, joint stiffness and bearing strength needed to quantitatively evaluate their deformation features and mechanical properties. Furthermore, microscopic studies on damaged areas using applying ultra-depth three-dimensional microscope to monitor damage evolution are conducted to comprehend the joint shear failure mechanism. Results show that the hole diameter and riveting force have a significant effect on the performance of the joint. The forming damage occurs mainly in the hole wall near the driven head and is dominated by fiber crushing and interfacial shear cracks. The radial expansion of the rivet shank is not uniform under the riveting force and the whole is drum shaped. But the hole expansion of the joint at 4.82 mm hole diameter is more uniform than 4.9 mm, which would lead to better joint stiffness and bearing strength. Moreover, high interference fit would cause the shear fracture of the rivet, while lower interference joints are dominated by compression-pull mixed failure. In general, the size of interference fit is an unneglectable factor in the composite riveted joints that should be thoroughly investigated.

Broadband optical transmission through two-dimensional hole arrays

We suggest that a metal film perforated with two-dimensional (2D) hole arrays can support broadband optical transmission. This phenomenon is based on the impedance matching between the perforated metal film and incoming light waves at oblique incidence. Theoretical formulas for the effective impedance of the hole arrays and Brewster angle of broadband transmission have been derived in the infrared regime, taking account of the field penetration effect on the hole walls. With the numerical simulations, the predicted optical effect has also been demonstrated. Compared with the narrow transmission band due to surface-plasmon polariton resonance, our results present a non-resonant, broadband, and robust transmission channel for the 2D hole arrays.

Optimization of High Temperature-Resistant Modified Starch Polyamine Anti-Collapse Water-Based Drilling Fluid System for Deep Shale Reservoir.

During drilling in deep shale gas reservoirs, drilling fluid losses, hole wall collapses, and additional problems occur frequently due to the development of natural fractures in the shale formation, resulting in a high number of engineering accidents such as drilling fluid leaks, sticking, mud packings, and buried drilling tools. Moreover, the horizontal section of horizontal well is long (about 1500 m), and the problems of friction, rock carrying, and reservoir pollution are extremely prominent. The performance of drilling fluids directly affects drilling efficiency, the rate of engineering accidents, and the reservoir protection effect. In order to overcome the problems of high filtration in deep shale formations, collapse of borehole walls, sticking of pipes, mud inclusions, etc., optimization studies of water-based drilling fluid systems have been conducted with the primary purpose of controlling the rheology and water loss of drilling fluid. The experimental evaluation of the adsorption characteristics of "KCl + polyamine" anti-collapse inhibitor on the surface of clay particles and its influence on the morphology of bentonite was carried out, and the mechanism of inhibiting clay mineral hydration expansion was discussed. The idea of controlling the rheology and water loss of drilling fluid with high temperature resistant modified starch and strengthening the inhibition performance of drilling fluid with "KCl + polyamine" was put forward, and a high temperature-resistant modified starch polyamine anti-sloughing drilling fluid system with stable performance and strong plugging and strong inhibition was optimized. The temperature resistance of the optimized water-based drilling fluid system can reach 180 °C. Applied to on-site drilling of deep shale gas horizontal wells, it effectively reduces the rate of complex accidents such as sticking, mud bagging, and reaming that occur when resistance is encountered during shale formation drilling. The time for a single well to trip when encountering resistance decreases from 2-3 d in the early stages to 3-10 h. The re-use rate of the second spudded slurry is 100 percent, significantly reducing the rate of complex drilling accidents and saving drilling costs. It firmly supports the optimal and rapid construction of deep shale gas horizontal wells.

Study on the mechanism affecting the quality of micro-hole in ultrasonic-assisted drilling of high-speed circuit boards

High-speed circuit boards are created to meet the high-speed signal transmission requirements of 5G communication technology, but the non-polar resins, flat glass fibers, and multiple and hard fillers used for this purpose have posed new challenges to their micro-hole processing. The quality of micro-hole has always been a decisive factor in board performance. Therefore, this paper aims at proposing a new processing method for improving the micro-hole drilling quality of high-speed circuit boards. By establishing an ultrasonic-assisted drilling tool motion model, analyzing the changes in drilling method, material deformation, chip breakage, and chip removal during ultrasonic-assisted drilling of printed circuit boards, the influence mechanism on micro-hole quality during ultrasound-assisted drilling is studied prudently. Besides, an experimental platform for ultrasonic-assisted drilling is designed and built, and single-factor experiments for verification of ultrasonic effects, optimization of drilling parameters, and orthogonal experiments for ultrasonic-assisted drilling of high-speed circuit boards are conducted on this platform. The experimental results show that the loading of ultrasonic vibration has made an obvious improvement on several machining defects including hole wall roughness, entrance burr, and nail head in micro-hole drilling of high-speed circuit boards. In addition, the influence order of each processing parameter and a better combination of them are discovered, which provides a theoretical research basis and instructions for the improvement of micro-hole quality of high-speed circuit boards.

Powder mixed electrochemical discharge process for micro machining of C103 niobium alloy

This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining (PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications. Three processes are involved simultaneously i.e. spark erosion, chemical etching, and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions i.e. spark erosion, and chemical etching. The powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical micro-electrochemical discharge machining (MECDM). Further, the results are optimized through a multi-objective optimization approach and study of the surface topography of the hole wall surface obtained at optimized parameters. In the selected range of experimental parameters, PMECDM shows a higher material removal rate (MRR) and lower surface roughness (Ra) (MRR: 2.8 mg/min and Ra of 0.61 μm) as compared to the MECDM process (MRR: 2.01 mg/min and corresponding Ra of 1.11 μm). A detailed analysis of the results is presented in this paper.

Fatigue behavior analysis and life prediction of all-composite joint

In this study, we join the thermoplastic composite using thermoplastic composite fastener (TPCF), and a physics-guided neural network is designed to predict the fatigue life of the all-composite joint. The experimental results show that TPCF is only 19.0% of the weight of the titanium rivet. Under a proper joining pressure of 1.50 MPa, the all-composite joint is well connected by an ‘S-shape’ interlayer, the fatigue resistance is improved. After hot-press joining, the lower cooling rate of 1 °C/min prolongs the crystallization process of TPCF and composite hole wall, thus enhancing the fatigue life to 105.8 cycles. The experimental results are summarized as physics constraints guiding the neural network. Similar fatigue data are migrated by producing a significant constraint. The loss function is the negative logarithm of the likelihood, which can predict both mean and deviation of fatigue life. The predicted results agree well with the experiments.

Experimental study on longitudinal-torsional ultrasonic vibration drilling of carbon fiber–reinforced plastics/titanium alloy stacks

Carbon fiber–reinforced plastics (CFRP)/titanium alloy (Ti) stacks are extensively applied in the aerospace industry due to their excellent mechanical properties. However, their poor machinability poses great challenges. In this study, longitudinal-torsional ultrasonic vibration drilling (LT-UVD) is innovatively introduced to improve the quality of CFRP/Ti drilling. First, the separation mode of LT-UVD is analyzed by kinematic equations. Then, an experimental platform is built based on the LT-UVD vibration actuator to perform CFRP/Ti drilling experiments. The thrust force, interface temperature, hole wall quality, hole defects, Ti chip morphologies, and tool wear in LT-UVD are experimentally compared against conventional drilling (CD) and longitudinal ultrasonic vibration drilling (L-UVD). The experimental results show that, compared with CD and L-UVD, the thrust force of CFRP in LT-UVD decreases by 20.36–40.55% and 2.04–14.61%, while the thrust force of Ti decreases by 19.08–24.83% and 1.95–9.34%. Moreover, a relatively low maximum interface temperature is achieved in LT-UVD. In addition, the hole size accuracy, surface roughness for the hole’s inner surface, and delamination factor are improved in LT-UVD. Fiber pullout defects, chip-breaking performance, and tool wear of CFRP are improved due to torsional vibration in LT-UVD. Finally, according to the high-speed camera, damage forms of the interface area are different when drilling CFRP/Ti stacks with various drilling sequences.

BTA Deep Hole Vibration Drilling for Nickel-Based Alloys: Cooling Patterns and Cutter Tooth Wear Mechanisms.

The high cutting temperature and poor thermal diffusion efficiency of nickel-based alloys during deep hole machining have become technical challenges in the hole machining field. In this paper, a finite element simulation model of Inconel-718 BTA ordinary drilling and vibration drilling processes was established by using Deform-3D finite element simulation software. The variations in the temperatures of the tool teeth and the workpiece at different positions of the nickel-based alloy under ordinary drilling and vibration drilling were investigated. Additionally, the wear pattern of each tool tooth under the two drilling methods was further analyzed by building an experimental platform for workpiece temperature detection, which reveals the wear and cooling mechanism of nickel-based alloy BTA deep hole drilling. The results show that the average temperatures of the external, intermediate, and central teeth were reduced by 18.1%, 21.1%, and 17.8%, respectively, during vibration drilling. In addition, the workpiece hole wall and hole bottom temperatures were reduced by 5.7% and 4.6%, respectively. To conclude, the experimental tests were consistent with the simulated temperature trends. BTA vibration drilling optimizes the heat exchange conditions between the cutter teeth and the workpiece during the drilling of nickel-based alloys, which effectively reduces the cutting temperature and, thus, improves the wear resistance of the cutter teeth.

Machining Performance Analysis of Rotary Ultrasonic-Assisted Drilling of SiCf/SiC Composites

An SiCf/SiC composite has the following excellent properties: high strength, low specific gravity, and high temperature resistance, which has great prospects in the combustion chamber of rockets or aero engines. Hole-making in SiCf/SiC parts is an important processing method. Generally, water-based or oil-based coolants are avoided, so dry drilling is the primary hole-making approach for SiCf/SiC. However, the abrasion resistance and high hardness of SiCf/SiC often lead to fast tool wear as well as serious damage to the fiber and matrix during dry drilling. This study proposes an innovative strategy for hole-making in SiCf/SiC parts—rotary ultrasonic-assisted drilling (RUAD) using an orderly arranged brazed diamond core drill. The influence of tool life and wear on drilling accuracy is analyzed. Additionally, the impacts of the process parameters of conventional drilling (CD) and RUAD on drilling force, torque, the surface roughness of the hole wall, and the exit tearing factor are investigated. The results show that the orderly arranged brazed diamond core drill exhibits longer tool life and higher accuracy in hole-making. Meanwhile, compared with CD, RUAD with the proposed core drill effectively improves the drilling quality and efficiency, and reduces the force and torque of drilling. The range of process parameters for dry drilling is broadened.

Effect of cooling strategy on the bearing capacity of CF/PEEK composite hole

Currently, carbon fibre-reinforced polyetheretherketone (CF/PEEK) hole-making process employs the same fast cooling strategy as in a traditional thermosetting composite to avoid hole wall burns. However, owing to the characteristics of thermoplastic resins, excessive cooling adversely affects the recrystallisation process of PEEK resins in the high-temperature region. This poses questions against the conventional perception that “cooling is beneficial.” To address this issue, mechanical parameters of the samples treated at different cooling rates were measured. The mechanical response and material damage of the holes under load were analysed, and the relationship between material cooling rate, crystallinity, and mechanical properties was established. A retarded cooling strategy was proposed to actively control the temperature after the hole-making. The effects of fast cooling, natural cooling, and retarded cooling on the quality of CF/PEEK holes were analysed by differential scanning calorimetry (DSC), tensile, and fatigue tests, and the detrimental effect of fast cooling on the quality of the hole structure was confirmed. The results reveal that compared with fast cooling, the ultimate tensile strength of the retarded cooling components is increased by 23.64%, and the fatigue life is increased by more than 10 times at 65% σult. The retarded cooling strategy improved the quality of CF/PEEK holes.