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Abstract With the continuous development of underground engineering construction in China, it is particularly important to study the identification of structural plane characteristics of rock masses. In this study, three types of pseudo-rock specimens with structural plane interlayers were fabricated to analyze the patterns of drilling parameter changes in rock bodies with structural planes during the drilling process and to explore the characterization and identification methods of rock body structural planes. Gneiss, granite, and sandstone were used as rock materials, with gypsum mortar as the interlayer material for the structural planes in these three types of specimens. The indoor digital drilling equipment was utilized for conducting indoor digital drilling experiments. The variation patterns of drilling parameters in rock bodies with structural surfaces under different interlayer inclinations and thicknesses were analyzed. The relationship between the ratio of the change in rotational speed and drilling speed during the stable phase of the upper rock mass and the peak torque and peak drilling pressure has been established. The relationship between the structural plane inclination angle and the ratio of change in rotational speed and drilling speed has been determined. By utilizing the variation in these ratios, the impacts of the structural plane inclination angle and the thickness of the structural plane on the peak torque and peak drilling pressure have been elucidated. The research results provide a theoretical basis for the stability evaluation of rock masses with structural planes under drilling action.

With the continuous development of underground engineering construction in China, it is particularly important to study the identification of structural plane characteristics of rock masses. In this study, three types of pseudo-rock specimens with structural plane interlayers were fabricated to analyze the patterns of drilling parameter changes in rock bodies with structural planes during the drilling process and to explore the characterization and identification methods of rock body structural planes. Gneiss, granite, and sandstone were used as rock materials, with gypsum mortar as the interlayer material for the structural planes in these three types of specimens. The indoor digital drilling equipment was utilized for conducting indoor digital drilling experiments. The variation patterns of drilling parameters in rock bodies with structural surfaces under different interlayer inclinations and thicknesses were analyzed. The relationship between the ratio of the change in rotational speed and drilling speed during the stable phase of the upper rock mass and the peak torque and peak drilling pressure has been established. The relationship between the structural plane inclination angle and the ratio of change in rotational speed and drilling speed has been determined. By utilizing the variation in these ratios, the impacts of the structural plane inclination angle and the thickness of the structural plane on the peak torque and peak drilling pressure have been elucidated. The research results provide a theoretical basis for the stability evaluation of rock masses with structural planes under drilling action. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Martian rocks contain crucial information about the genesis of Mars and the historical evolution of Martian climate change. Consequently, extracting and examining Martian rocks are pivotal in advancing our comprehensive understanding of the red planet. However, the current core drill string is prone to wear and tear, and the samples are susceptible to thermal denaturation. To address these challenges, we introduce two novel types of drill bits, the conical straight junk slot and the conical spiral junk slot, both employing impregnated diamond as the primary material. Comparative experiments were meticulously conducted to evaluate the influence of different junk configurations on drilling parameters, including speed, abrasion resistance, drilling force loading, and sample temperature rise. The findings unequivocally demonstrate the superior performance of the spiral junk slot. Furthermore, simulations were performed to examine the drilling process on basalt using a fixed configuration drill bit, validating the occurrence of the sample temperature rise. The research presented in this paper offers valuable programmatic references and essential data support for future Martian rock coring drilling missions. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Under the conditions of drilling in gravel-bearing and heterogeneous stratas, the movement and force of the PDC bit during drilling are highly unstable. Irregular impact loads often cause fatigue failures such as tooth fracture, tooth breakage and delamination of the composite sheet. Dynamic impact load is the main cause of fatigue failure of cutting-tooth, which seriously affects the rock-breaking performance of PDC bits. This paper proposes a flexible cutting tooth unit consisting of a central tooth, an elastic element, and a base. The technical concept of flexible-cutting rock breaking is to reduce the impact load amplitude suffered during the cutting process to a certain threshold range by setting elastic elements or reducing the support stiffness of the cutting tooth, so as to inhibit the expansion of micro defects caused by the impact dynamic load of cutting teeth and prolong the service life of drill bits. The finite-element models of flexible cutting teeth for rock cutting were established. The influence of cutting depth, front rake angle and stiffness of elastic elements on the cushioning and vibration-absorption effect of flexible cutting was analysed. The results show that flexible cutting can reduce the peak and average value of von Mises stress at the cutting edge. Under different cutting-depth conditions, the decline rates were 21.45–49.02% and 9.42–17.8%, respectively. Then, under different front-rake-angle conditions, the decline rates were 20.51–24.02% and 9.41–17.8%, respectively. There is a suitable stiffness of the elastic element, which makes the peak and average value of von Mises stress at the cutting edge of the flexible cutting-tooth unit perform better and the effect of improving the uneven stress distribution at the cutting edge better. Flexible cutting technology can effectively improve the adaptability of the PDC bit in heterogeneous formations and reduce the occurrence of abnormal failure of cutting teeth. The research results of this paper can provide theoretical support for the drilling speed of PDC bits in hard formations. [ABSTRACT FROM AUTHOR]

Exploitation of polar resources and scientific research require efficient ice drilling technology. Thermal drilling is a common method for polar ice drilling, and is similar to the principle of ultrasonic assisted drilling; both are drilled by melting ice layers, but improving energy utilization has always been a challenge. In order to improve energy utilization and drilling efficiency, this paper proposes a method for ice drilling with ultrasonic frequency vibration. The mechanism of ultrasonic vibration drilling into ice was analyzed, the solid theoretical foundation for the application of ice melting efficiency under ultrasonic frequency vibration was determined and a series of indoor experiments were conducted. According to experimental data obtained, two conclusions were provided. First, different frequencies have distinct influence on power density, drilling speed and melting rate, and the optimum range excitation frequency for ultrasonic ice drilling is at least 30~32 kHz, under which the ice melting efficiency and drilling speed reached the peak value. Second, ultrasonic assisted drilling was verified to have the ability of improving the efficiency of ice breaking by comparing to thermal drilling under the same power density under 30 kHz. As an environmentally friendly and efficient drilling method, ultrasonic assisted ice drilling has great application prospects in the field of polar exploration. By using Ultrasonic assisted drilling, we demonstrate a strategy for a faster and more efficient drilling method, which is important for humankind.

Sand layer sampling is important in water conservancy and hydropower exploration, and the accurate identification of sand layers is the premise for foundation design and treatment. In this study, a new method for identifying sand layers based on key drilling parameters was proposed. Simulated formation laboratory experiments using a self-developed measurement-while-drilling system were first conducted to study the relationships between four drilling parameters and sand layers. Quantitative criteria based on key drilling parameters for sand layer identification were then proposed, followed by validation through three engineering projects. The results showed that bit pressure and drilling speed are sensitive to formation changes and can be used for sand layer identification. Specifically, in sand layers, the variation ratio of drilling speed is more than 150% and the variation ratio of bit pressure is less than 200%. Applications of the proposed method in Na water conservancy project, Sancha water conservancy project, and Tuodan reservoir project show satisfying accuracy, indicating that it can be used as an effective tool for sand layer identification in various engineering projects. [ABSTRACT FROM AUTHOR]

Martian rocks contain crucial information about the genesis of Mars and the historical evolution of Martian climate change. Consequently, extracting and examining Martian rocks are pivotal in advancing our comprehensive understanding of the red planet. However, the current core drill string is prone to wear and tear, and the samples are susceptible to thermal denaturation. To address these challenges, we introduce two novel types of drill bits, the conical straight junk slot and the conical spiral junk slot, both employing impregnated diamond as the primary material. Comparative experiments were meticulously conducted to evaluate the influence of different junk configurations on drilling parameters, including speed, abrasion resistance, drilling force loading, and sample temperature rise. The findings unequivocally demonstrate the superior performance of the spiral junk slot. Furthermore, simulations were performed to examine the drilling process on basalt using a fixed configuration drill bit, validating the occurrence of the sample temperature rise. The research presented in this paper offers valuable programmatic references and essential data support for future Martian rock coring drilling missions.

Ice cores from polar zones could determine ice dating and biodiversity. Ice cores retrieved in hot-water ice-coring drilling partly melted owing to moderate drilling speed of annular drill head with many nozzles, which was largely depended on the heat transfer efficiency of jet to ice at borehole bottom. To obtain the higher drilling speed and ice cores of good quality, this paper explored the influence of nozzle parameters on the heat transfer efficiency of annular jet to bottom ice. Main nozzle parameters affecting the heat transfer efficiency were theoretically determined firstly. Then influence law of nozzle parameters on the heat transfer were estimated by theoretical calculation and numerical simulation. The result showed the heat transfer of annular jet to bottom ice was positively correlated with the nozzle flow and negatively relevant with the nozzle diameter, nozzle angle and nozzle quantity, which was further compared with the drilling speed value in experiment to confirm its correctness. The angle was proved to be the most influential parameter, when it increased from 0° to 30°, the drilling speed decreased 75%. The result can provided reference for designers on how to promote the drilling speed in hot-water ice-coring drilling and improve ice core quality.

The vacuum impregnation method was employed to produce two batches of tubular drills, incorporating AS200 500/400 diamond grains in a Cu–15 wt.% Sn metal matrix. In one batch, ASM 1/0 ultradispersed diamond powders (UDDPs) were added as a reinforcement to matrices in some tools. In the other batch, the reinforcement was tin. The concentration of ASM 1/0 additives ranged from 1 to 11 wt.% and that of tin from 1 to 10 wt.%. Comparative laboratory tests for drilling porcelain, granite, and SiC-based abrasive stone were conducted using these diamond drills. Performance characteristics such as drill wear and drilling speed were examined. The hardness of matrix samples containing additives, but without AS200 500/400 diamond grains, produced by the vacuum fusion method was determined. In drilling the examined materials, UDDPs reduced the wear of diamond drills through the reinforcing effect and increased matrix hardness. The optimal concentration of UDDPs was found to be 5 wt.% (9 wt.% for porcelain). A further increase in the concentration of such additives led to higher wear of the drills as porosity that appeared in the matrix reduced diamond grain retention. The addition of tin to the matrix also decreased the wear of diamond drills, with the minimum wear observed when approximately 4 wt.% Sn was introduced into the matrix. Increasing the tin concentration in the matrix beyond this point resulted in higher drill wear because of brittle intermetallics, which also reduced the strength of diamond retention. The diamond drills with UDDP additives exhibited higher drilling speeds that those with tin additives. Furthermore, the drilling speed for porcelain and granite decreased with the introduction of tin up to 4 wt.% because of the 'blunting' effect. The diamond drills with a UDDP-reinforced matrix demonstrated better performance characteristics, including reduced wear and higher drilling speed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The significance of micro-destructive testing, which can estimate the durability of reinforced concrete structures with minimal damage and high accuracy, in the investigation and diagnosis of reinforced concrete structures has been increasing. This study aims to evaluate the quality of the surface layer of concrete structures via a small-diameter drilling test, which is one of the micro-destructive tests developed to estimate the strength of concrete. Hence, it would be possible to evaluate the quality and strength of concrete simultaneously, which is very important. In this study, the influence of the bleeding amount which affects the surface quality of concrete on the drilling speed, was experimentally studied, considering the water-cement ratio and unit water content as experimental factors. The influence of bleeding on the drilling speed of the specimen surface was also investigated through measurements at the top and bottom surfaces. The following points were clarified from the experimental results and their analysis. (1) The drilling speed changes depending on the water-cement ratio and the unit water content. (2) The amount of bleeding affects the drilling speed; however the drilling speed is affected by the volume of the fine aggregate in the specimen. Therefore, (3) there is a possibility that it can be used for surface quality evaluation of concrete by examining in detail the method for calculating and correcting the drilling speed.

The aim of this study was to measure the effect of drilling speed on heat generation in the cortical bone, on primary and secondary implant stability of implants and on early and late bone healing with micro-computerized tomography (micro-CT). Sixty implants were placed in the iliac crest of 6 sheep in order to form 5 different drilling protocols: 50 rpm without saline cooling, and 400, 800, 1200, and 2000 rpm with saline cooling. Simultaneous cortical bone temperature and primary stability at the time of placement; secondary stability and the ratio between relative bone and tissue volume (BV/TV) in 2D and 3D in micro-CT analysis were evaluated after 4 and 8 weeks. The 50-rpm group had the highest cortical bone temperature and the longest operation duration with the highest primary stability. Slightly higher values of secondary stability (T2) and subsequent 2D and 3D BV/TV values were found in 1200 rpm with irrigation at 8 weeks. All groups had sufficient ISQ values at 8 weeks for loading although the micro-CT analysis showed varying percentages of bone tissue around implants. The influence of drill speed for implant osteotomy and its irrigation is minimal when it comes to changes in temperature of the cortical bone, primary and secondary implant stability, and BV/TV. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate whether the drilling speed used during implant site preparation influences primary stability. Materials and Methods: Eighty tapered designed implants (3.8 x 10 mm) were inserted following osteotomies created in solid rigid polyurethane foam (simulating bone type II) and cellular rigid polyurethane foam (simulating bone type IV). Half were prepared using drilling speeds of 800 rpm (low speed), and the other half were prepared using speeds of 1,500 rpm (high speed). Following insertion, implant primary stability was measured using Periotest and Osstell (resonance frequency analysis [RFA]) devices. Results: Two-way analysis of variance (ANOVA) used for this study found that the drilling speed used to create the osteotomies appeared to have no significant impact on primary stability. Conclusion: The bone quality and not the osteotomy drilling speed seems to influence the implant primary stability. [ABSTRACT FROM AUTHOR]

Outburst prediction during coal roadway excavation, which is characterized by multiple prediction numbers and rapid cyclic construction, is a key link of outburst prediction in coal mines. This study is aimed at accurately predicting the outburst risk of coal roadway working face by the initial gas emission from boreholes (IGEB) indicator in the field. First, a theoretical calculation model for gas emissions from drill cuttings and borehole wall was established. Based on this model, it is concluded that the drilling speed significantly influences the critical value of IGEB for outburst prediction. Furthermore, the IGEB per meter was experimentally investigated at different drilling speeds and under different gas pressures with the aid of a self-developed IGEB outburst prediction device. The investigation results show that the value of IGEB is linearly correlated with the gas pressure at the same drilling speed, and it is also linearly correlated with the drilling speed. Besides, the values and critical values of IGEB at different drilling speeds were normalized to the values at the standard drilling speed, for the purpose of eliminating the influence of drilling speed on the determination of the critical value of IGEB for outburst prediction. Finally, a field test was carried out on the 3# coal seam of Xinjing Coal Mine, and a good application effect was achieved in the field test. [ABSTRACT FROM AUTHOR]

Bu çalışmada, altı farklı açık maden ocağında (4 adet kalker, 1 adet kil ve 1 adet feldspat ocağı) yapılan delme çalışmaları sırasında delici uç ve makine çalışma parametreleri (darbe miktarı, baskı kuvveti, hava basıncı ve dönme hızı) sabit tutularak delme hızları yerinde ölçülmüştür. Bu ocaklardan, laboratuvar deneyleri için şekilsiz bloklar ve delme işleminden çıkan kırıntılardan numuneler alınmıştır. Alınan kırıntı numunelerden pasa irilik katsayısı, blok numunelerden ise kayaçların fiziksel ve mekanik özellikleri belirlenmiştir. Ayrıca bu kaya birimlerinin delme oranı indeks (DRI) değerlerini belirlemek için Sievers minyatür delme deneyi ve kırılganlık deneyleri yapılmıştır. Çalışmalar sonunda, araziden alınan delme hızı verileri ile laboratuvarda yapılan deney sonuçları birlikte değerlendirilerek istatistiksel olarak irdelenmiştir. Arazi üzerinde ölçülen ilerleme hızları ile kayacın fiziksel ve mekanik özellikleri arasında anlamlı ilişkiler elde edilmiştir. Laboratuvar ortamında belirlenen delinebilirlik değerlerinin delme-patlatma çalışmalarında ilerleme hızının tahmin edilmesinde güvenilir bir şekilde kullanılabileceği belirlenmiştir.

Bu çalışmada, altı farklı açık maden ocağında (4 adet kalker, 1 adet kil ve 1 adet feldspat ocağı) yapılan delme çalışmaları sırasında delici uç ve makine çalışma parametreleri (darbe miktarı, baskı kuvveti, hava basıncı ve dönme hızı) sabit tutularak delme hızları yerinde ölçülmüştür. Bu ocaklardan, laboratuvar deneyleri için şekilsiz bloklar ve delme işleminden çıkan kırıntılardan numuneler alınmıştır. Alınan kırıntı numunelerden pasa irilik katsayısı, blok numunelerden ise kayaçların fiziksel ve mekanik özellikleri belirlenmiştir. Ayrıca bu kaya birimlerinin delme oranı indeks (DRI) değerlerini belirlemek için Sievers minyatür delme deneyi ve kırılganlık deneyleri yapılmıştır. Çalışmalar sonunda, araziden alınan delme hızı verileri ile laboratuvarda yapılan deney sonuçları birlikte değerlendirilerek istatistiksel olarak irdelenmiştir. Arazi üzerinde ölçülen ilerleme hızları ile kayacın fiziksel ve mekanik özellikleri arasında anlamlı ilişkiler elde edilmiştir. Laboratuvar ortamında belirlenen delinebilirlik değerlerinin delme-patlatma çalışmalarında ilerleme hızının tahmin edilmesinde güvenilir bir şekilde kullanılabileceği belirlenmiştir.

Study Design. An experimental investigation of a robot-assisted ultrasonic osteotome applied to vertebral cancellous bone. Objective. The aim of this study was to investigate the effect of various ultrasonic parameter settings on temperature in the drilling site and penetration time and determine the most suitable parameters for efficient and safe robot-based ultrasonically assisted bone drilling in spinal surgery Summary of Background Data. A robot-assisted ultrasonic osteotome device may be safe and effective for spinal drilling. Methods. Sixty specimens of bovine vertebral cancellous were randomly assigned to one of six groups, which varied by mode of ultrasonic vibration (L-T and L) and feed rate (one percent [0.8 mm/s], two percent [1.6 mm/s], and three pecent [2.4mm/s]). Maximum temperature in the drilling site and penetration time was recorded. Results. Maximum temperature in the drilling site decreased as output power increased for L-T and L modes, was significantly lower for L-T compared to L mode at each feed rate and power setting, was significantly different at feed rates of 1.6 mm/s versus 0.8 mm/s and 2.4 mm/s versus 0.8 mm/s for L-T mode at an output power of 60 W and 84 W, but was not influenced by feed rate for L mode. Penetration time did not significantly improve as output power increased for both L-T and L modes, was significantly decreased with increased feed rates, but was not significantly different between L-T and L modes. Conclusion. The optimal parameters for applying a robotassisted ultrasonic osteotome to vertebral cancellous bone are LT mode, maximum output power of 120 W, and maximum feed rate of 2.4 mm/s. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study presents the results of comparative laboratory tests of diamond tubular drills when drilling window glass, granite, and abrasive stones based on silicon carbide SiC. The tests were carried out in cold running water. Tin bronze containing micro- and ultradispersed diamond powders of ASM 40/28, ASM 10/7 (MDP), ASM 1/0 (UDDP) grades, and molybdenum powder were used as a matrix of the tool. Furthermore, the dependence of the hardness of specially prepared matrix samples on their composition was examined. With an increase in the ASM 1/0 concentration up to 5 wt.% in the reinforcement, the hardness of the matrix samples increased by one-third and reached a maximum of ~96.5 HRB. A further increase in the ASM 1/0 concentration led to a slight decrease in the hardness of the samples. The use of larger diamond powders required a higher concentration, providing high values of hardness. By adding ASM 10/7 in an amount of 10 wt.% and ASM 40/28 in the amount of 40–60 wt.% we managed to increase the hardness of the matrix to the same maximum. The introduction of a reinforcement in a bonding matrix of diamond tubular drills in amount ensuring its maximum hardness has significantly increased the efficiency of their operation. Thus, the wear of drills after glass processing decreased by 2–6 times, and the drilling speed increased by 3–4 times. Drill wear after granite processing has decreased by 50–84 times, and the drilling speed has increased 2.7–6 times, correspondingly. Finally, after processing of an abrasive stone based on silicon carbide SiC, the wear of diamond tubular drills decreased by 1.4– 2.9 times, and the drilling speed increased by 1.5–2.5 times. The effect of additives in the reinforcement of the tool depended on the choice of the diamond powder grade and their concentration. The best option was the introduction of ASM 1/0 (UDDP) powder in an amount of 5– 9 wt.%. The introduction of ASM 10/7, and especially ASM 40/28 (MDP), into the reinforcement required, firstly, their higher concentration (10–40 wt.%), and secondly, was not effective enough since the wear indicators of diamond tools were higher, and the drilling speed was lower. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the fragmentation capacity, clearance time, and drilling speed of combined ultrasonic with impact dual-energy and single energy ultrasonic lithotripter devices. Methods: Stone fragmentation and clearance tests were performed under direct view in an underwater layered hemisphere by four different operators using artificial stones (n = 10/operator). Time for complete clearance was measured. Drilling tests were performed using an underwater setup, consisting of a mounting rack for fixing the lithotripter handpiece with the probe in vertical position and in contact with the stone phantom placed on one side of a balance for defined and constant contact application pressure equivalent to 450 g load. Time until complete perforation or in case of no perforation, the penetration depth after 60 s into the stone sample was recorded. Four devices, one single energy device (SED), one dual-energy dual probe (DEDP), two dual-energy single probe (DESP-1, DESP-2), with different parameters were tested. Results: Stone fragmentation and clearance speed were significantly faster for dual-energy device DESP-1 compared to all other devices (p < 0.001). Using DESP-1, the clearance time needed was 26.0 ± 5.0 s followed by DESP-2, SED and DEDP requiring 38.4 ± 5.8 s, 40.1 ± 6.3 s and 46.3 ± 11.6 s, respectively. Regarding the drilling speed, DESP-1 was faster compared to all other devices used (p < 0.05). While the drilling speed of DESP-1 was 0.69 ± 0.19 mm/s, compared to 0.49 ± 0.18 mm/s of DESP-2, 0.47 ± 0.09 mm/s of DEDP, and 0.19 ± 0.03 mm/s of SED. Conclusions: The dual-energy/single-probe device combining ultrasonic vibrations with electromechanical impact was significantly faster in fragmentation and clearing stone phantoms as well as in drilling speed compared to all other devices. [ABSTRACT FROM AUTHOR]

The results of laboratory tests for drilling of corundum, chamotte, and porcelain with diamond tubular drills in running water, as well as the friction of cylindrical samples of the matrix against these materials, have been described. Bronze containing ultrafine ASM 1/0 diamond powders and molybdenum, as well as bronze without this reinforcement, served as the matrix for the drills and cylindrical samples. The speed of processing corundum, chamotte, and porcelain with diamond drills constantly increased when the concentration of diamond powders raised to 11 wt.%. At the same time, the tool wear significantly reduced, reaching the minimum at 5–9 wt.% of ASM 1/0 concentration (depending on the choice of the test material). The wear of diamond powder increased binsignificantly when the concentration of diamond powders grew to 11 wt.%. Similar results were obtained for the matrix of samples. Thus, the wear of the matrix samples decreased with an increase in the ASM 1/0 concentration. Such a decrease was observed even at 11 wt.% for friction against corundum. During friction against chamotte and porcelain, the wear of the samples reached the minimum at 7 wt.% diamond powders. As in the case with drills, a further increase in the content of ASM 1/0 in the reinforcement led to an increase in wear of the samples. High wear of the drills and samples at a relatively high content (11 wt.%) of ultrafine diamond powders was explained by the porosity that occurred in the matrix. The studies performed allowed concluding that reinforcement containing ultrafine ASM 1/0 diamond and molybdenum powders should be introduced into the matrix of diamond drills to improve their performance and decrease the consumption of abrasive material. The matrix samples containing up to 7 wt.% of ultrafine diamond powders can be successfully used as an abrasive tool for finishing (polishing) a series of nonmetallic materials, in particular, semiprecious and precious stones in jewelry production. [ABSTRACT FROM AUTHOR]

The Semmering Base Tunnel is being built by Austrian Federal Railways as part of the upgrading of the southern railway line. On contract SBT3.1, Züblin Spezialtiefbau Ges.m.b.H. was employed to undertake slope stabilization, piles dia. 1,500 mm embedded into the rock, as well as vertical and horizontal boreholes in the fault zones of Semmering. Due to the high requirements on drilling speed and accuracy of the boreholes, they were drilled as directional drilling with a hydraulic down‐the‐hole hammer. The vertical holes were used to install sleeve pipes for grouting works for the shaft Sommerau 2. The horizontal holes, also planned for the inclusion of sleeve pipes for grouting works, were used after on‐site rescheduling during the project for exploration and drainage of the rock mass. The drilling and survey data were subject to continual and thorough review to increase the efficiency of each control operation. [ABSTRACT FROM AUTHOR]

Residual stresses are induced in the material during manufacturing operations, which considerably affect the fatigue performance and the lifespan of a mechanical work piece. The nature, magnitude, and distribution of residual stresses decide their beneficial or detrimental effects. Past research efforts concluded that mechanical process parameters influence residual stress nature, distribution, and the magnitude. Nevertheless, how residual stress generation depends on the process parameters, is not well investigated especially in the case of a drilling operation. In fact, the residual stress field is required to be regulated near drilled holes to improve the fatigue strength of structural joints, especially in the aircraft industry. Accordingly, this work attempts to estimate the drilling-induced micro-residual stress distribution near the drilled hole. In addition, the effect of drilling speed on residual stress distribution has also been studied. A nanoindentation technique is used to follow-up precise distribution of micro-residual stresses near the holes drilled at three different drilling speeds of 700, 900, and 1100 r/min. The outcomes indicate the presence of compressive residual stresses near the hole. In addition, an increase in residual stress level is noticed with an increase in the drilling speed up to 900 r/min. A uniform distribution of residual stresses is observed near the hole when drilled at a higher drilling speed of 1100 r/min. These findings may be useful in planning an improved drilling operation to produce beneficial residual stress distribution. This may ultimately improve the fatigue strength and the service life of mechanical components or structures with drilled holes. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, drilling speeds were measured in situ by keeping the drill bit and machine working parameters (impact, pressure, air pressure and rotation) constant during drilling-blasting operations on six different open mines (4 limestones, 1 clay and 1 feldspar quarries). From these quarries, shapeless blocks samples and rock chipping specimens from blasting holes were taken for laboratory experiments. The physical and mechanical properties of the rocks from the block samples and coarseness index from chip samples were determined. Sievers miniature drilling tests and brittleness tests were also performed to determine the drilling rate index (DRI) values of the rocks. As a result, the results of the laboratory tests and insitu drilling data were evaluated statistically. Significant relationships were found between the physical and mechanical properties of the rock and the measured drilling speed. It has been determined that the drillability values determined in the laboratory can be reliably used in predicting the rate of penetration in drilling-blasting operations. [ABSTRACT FROM AUTHOR]

Highlights • A novel bone drilling system was designed to achieve high-energy ultrasonically assisted bone drilling. • The drilling temperature was compared with conventional bone drilling. • High-energy ultrasonically assisted bone drilling had slightly higher drilling temperature than conventional bone drilling. • The thermal effect of ultrasonic vibration was a main reason for this phenomenon. Abstract Ultrasonically assisted drilling as a new type of bone drilling technology has received increasing attention. However, the vibration energy of existing studies was limited. In this study, a robot-based ultrasonically assisted bone drilling experimental setup was designed, and high-energy ultrasonically assisted bone drilling (vibration frequency=24.1–41 kHz, and vibration amplitude=150–160 µm) was applied to bovine cortical bone to investigate the drilling temperature compared with conventional drilling. The effect of drilling speed on drilling temperature was also studied. The experiment results showed that, compared with the conventional bone drilling, high-energy ultrasonically assisted bone drilling had slightly higher drilling temperature (0.36–0.86°C), which is in direct contrast to previous reports. We hypothesized that this finding was due to the thermal effect of ultrasonic vibration, which the present study confirmed. Moreover, the drilling temperature increased with higher drilling speed. [ABSTRACT FROM AUTHOR]

Copyright of Selcuk University Journal of Engineering, Science & Technology / Selçuk Üniversitesi Mühendislik, Bilim ve Teknoloji Dergisi is the property of Selcuk University, Engineering & Architecture Faculty and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One of the most costly parameters in a mining operation is the raw material procurment. One of the most important parameters of raw material procurment cost is the drilling of blasting holes. If the drilling operations are not performed at the desired efficiency, both the working organization in business and the production cost will be significantly and adversely affected in the negative direction. In this study, the effect of drilling parameters on the fluid ambient pressure and rotational speed parameters of the Atlas Copco Flexi ROC T35 drilling machine used in the limestone quarry of DSİ 18th Regional Directorate was investigated. In order to determine the drilling speed, the drilling times of the working limestone in the limestone oven at Çavdır county in Burdur province were measured and clear and gross drilling speeds were calculated. The physicomechanical properties and chemical properties of the rocks were also determined in the laboratory environment. By evaluating all the data together, effect of fluid ambient pressure and rotating speed on drilling speed are examined. As a result, the best drilling speed at all fluid ambient pressure and at both rotational speeds was obtained at a rotational speed of 103 rpm. [ABSTRACT FROM AUTHOR]

The performed tests in this work include a wide range of rock masses of the Kopaonik massive of different strength (f = 2.3 - 16). Drilling was done with drill hammers VK-24 and RK-21 at optimum sharpening angle with different drill rod lengths (0.8, 1.2, 1.6, 2.4 and 3.2). Compressed air pressure is 0.60 MPa and diameter of drilling chisel d = 32 mm. The obtained results and analysis indicate that it is possible to determine the interdependence between the borehole length and drilling speed. The results of these tests are shown in Tables 1, 2, 3 and 4 and diagrams 1, 2, 3 and 4.

A survey done recently showed that almost 30 percent of the accidents occurred during oral implant surgery were concerned with the mandibular canal in the trabecular bone region and most of them were related to the drilling process. One of the reasons known is due to the clinicians' lack of knowledge and experience. In order to overcome the problem, through the educational approach, we proposed and developed a new system mainly for dental colleges' students, by focusing on drilling the mandibular trabecular bone. The system comes in the form of an oral implant surgery training simulator that enables student to sense the reaction force during drilling. The developed system was then evaluated by expert clinicians and dental college's students. A total of 8 clinicians and 24 students tested all three samples of drilling force database. The clinicians were asked to describe the drilling force based on a stiffness scale while the students are required to drill two samples first before drilling the third sample. They were asked to sketch the third samples based on the comparison of previous samples. Based on the evaluation done, it was found that the quantification of force sensed during drilling could be derived from the combination of drilling force and speed obtained through the relative value of comparison with the previous or accumulated experience of drilling. The results of this study also indicate that the oral implant surgery training simulator could help students learn the difference of drilling force sense dependent on the bone quality through repeated usage and practices.

The electrical discharge drilling could be applied in order to obtain cavities in workpieces made of materials difficult to be machined by classical machining methods. Distinct factors exert influence on the drilling speed. An experimental research was designed and developed by considering the depth of the cavity achieved by means of a tubular tool electrode. One used a machining scheme involving the achieving of the work movement by test piece to the tubular tool electrode clamped on the machine tool table. In this way, the influence exerted by the spurious electrical discharges facilitated by the presence in the work gap of the metallic particles detached from the two electrodes can be diminished. Empirical mathematical models were determined by mathematical processing of the experimental results and using specialized software. The empirical mathematical models proved a high influence exerted on the drilling speed by the peak current intensity.

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrical discharge drilling could be applied in order to obtain cavities in workpieces made of materials difficult to be machined by classical machining methods. Distinct factors exert influence on the drilling speed. An experimental research was designed and developed by considering the depth of the cavity achieved by means of a tubular tool electrode. One used a machining scheme involving the achieving of the work movement by test piece to the tubular tool electrode clamped on the machine tool table. In this way, the influence exerted by the spurious electrical discharges facilitated by the presence in the work gap of the metallic particles detached from the two electrodes can be diminished. Empirical mathematical models were determined by mathematical processing of the experimental results and using specialized software. The empirical mathematical models proved a high influence exerted on the drilling speed by the peak current intensity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Residual stress measurements on Titanium grade 5 specimen were carried out. [•] The effects of the choice of a proper analysis area are shown. [•] Effects of using different drilling speeds were examined too. [•] Higher scattering of the data was found for lower speeds. [•] Scattering at low speed was connected with the low quality of the drilled hole. [ABSTRACT FROM AUTHOR]