Drill Holes Research Articles

Theoretical study on the critical index of rock burst stress monitoring in coal seam drilling

Rock burst disasters severely restrict the safe and efficient mining of coal. The fundamental cause of their occurrence is the concentration of stress within the coal mass. Stress monitoring in coal seam drilling is widely used as an effective method for rock burst monitoring. However, how to scientifically and reasonably set the critical values of early warning indicators that match the conditions of each mine has always been a key issue restricting the accurate prediction of rock burst by the drilling stress method. This paper adopts a method combining theoretical analysis and field practice to conduct research on the critical values of drilling stress early warning indicators. Based on perturbation response instability theory, a mechanical model for the occurrence of impact ground pressure has been established. Based on the instability theory of disturbance response, a mechanical model for the occurrence of impact ground pressure has been established, leading to the derivation of the expression for the near-field critical stress of impact ground pressure events. The theoretical formula for the critical value of drilling stress early warning indicators was obtained based on the difference between the critical stress of rock burst occurrence and the actual stress in the roadway. This formula includes the mechanical parameters of the coal mass and its propensity for rock burst, roadway support stress, mining depth, stress concentration coefficient, and the initial installation pressure of the stress gauge. They can be determined by the geological and mining technical conditions of each mine. This theoretical formula breaks the uniformity of the critical values for stress warning indicators in various mine drill holes, allowing each mine to scientifically determine its critical value based on its own conditions. This theoretical method has been applied to a high-stress mine in Shanxi, China, and the critical values of drilling stress early warning indicators were obtained. When the monitored stress exceeded the critical value, dynamic phenomena of anchor rod and cable fractures occurred in the roadway roof. The distribution of microseismic events also shifted towards the warning area, and the microseismic monitoring indicators reached the warning values. This confirmed the engineering feasibility of the critical values for drilling stress early warning indicators determined by the theoretical method.

Subpectoral Biceps Tenodesis Using an All-Suture Anchor

Background: The long head of the biceps tendon (LHBT) has long been considered an intra-articular pain generator in the shoulder. While nonoperative treatment modalities can be acceptable for less severe presentations of LHBT pathology, surgical treatment options such as tenotomy and tenodesis remain controversial for recalcitrant cases. Open subpectoral biceps tenodesis allows for removal of all pathologic tissue from the bicipital groove, and all-suture anchor fixation utilizes a small caliber unicortical drill hole, which can potentially reduce the risk of a stress riser and iatrogenic fracture. Indications: In this study, we present a male patient with a history of left anterolateral shoulder pain worse overhead activities who has failed extensive physical therapy and other conservative measures. After extensive discussion regarding the treatment options, surgery in the form of shoulder arthroscopy, extensive debridement, rotator cuff repair, and open subpectoral biceps tenodesis was recommended and the patient had opted to proceed. For the purposes of this video, we focus on the open subpectoral biceps tenodesis portion of the procedure. Results: Open subpectoral biceps tenodesis can reduce pain with low complication and high satisfaction rates. Discussion: In this surgical technique study, we underline the importance position of the skin incision in axillary crease as well as skin tensioning when making the incision and retracting the conjoint tendon. We also highlight a locking lasso loop and double luggage tag fixation technique using a double-loaded all-suture anchor for the biceps tenodesis. We also provide technique commentary for appropriate restin tension of the LHBT. Finally, we review outcomes, postoperative management, rehabilitation protocol, and technique pearls and pitfalls. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Quantitative evaluation of the sealing effect of penetrating gas drilling and in situ repairing technology for smooth holes

AbstractIn this study, a new method is proposed to quantitatively determine the extraction of boreholes under the effect of time. The main purpose of this method is to divide the gas drilling holes in the monitoring time into two stages: the early stage of extraction and the middle stage of extraction. The early stage of extraction uses the gas pressure difference to detect the gas tightness of the drilling holes and determine the type of gas leakage of the drilling holes. Moreover, the unqualified drilling holes are repaired immediately to ensure that all the drilling holes in the middle stage of the monitoring are the qualified holes at the early stage of the inspection. In the middle of extraction, the average attenuation rate of the fitting attenuation curve of pure gas extraction in the extraction borehole is calculated by monitoring, the growth rate of the linear fitting of the pure air leakage is calculated, and their ratios are used as the basis for judging the repair value of the gas leak borehole and the gas leak borehole. This quantitative evaluation method is used to monitor the extraction effect of four test holes in a field test conducted at Ping Coal Mine 10. The results indicate that, after adopting in situ downhole repair technology in the early stage of extraction, the average air leakage of Borehole No. 4, which failed due to air leakage in the borehole, decreased from 9.33 to 1.26 L/min (a reduction of 86.5%). Similarly, that of Borehole No. 3, which failed due to penetration of fissures in the surrounding rock, had an air leakage drop from 8.35 to 1.34 L/min (a reduction of 84.0%). These improvements demonstrate the remarkable effectiveness of the method. The quantitative evaluation method established in this study is not only simple to operate but also stable and reliable. Thus, it is feasible to be applied in the field, which provides important technical support for the improvement in gas extraction effect during coal mine safety production.

VY-plasty for chronic quadriceps tendon rupture

Lengthening of the quadriceps tendon for dehiscence in chronic rupture. Chronic rupture of the quadriceps tendon with delayed diagnosis or failure of primary refixation with adehiscence between 1and 5 cm. Dehiscence of more than 5 cm. Reopen the old incision and lengthen it to about 20-25 cm if necessary. Visualize the rupture. Debridement of the tendon and the insertion. Measurement of the dehiscence. Creation of aV-flap and reinforcement with aholding seam. Gradual mobilization of the V‑flap distally and reinforcement with two strong suture cords (braided suture size5). Drilling of three obliquely ascending drill holes through the patella. Transosseous threading of the two reinforcement cords through the three drill holes. Knotting the reinforcement cords on the patella. Closure of the gap between the patella and the superficial tendon leaflet with a#2 braided suture. Closure of the gap between the V‑flap and the quadriceps tendon. Six weeks of partial weight-bearing with 20 kg in astraight orthosis. Mobility: weeks 1-4 E/F 0-0-60, weeks 5 and 6 E/F0-0-90. We were able to follow-up 8patients (mean age: 63.1 ± 4.5years), who underwent this surgery in the manner described. All patients were able to perform an active extension postoperatively. The Lysholm score increased from 46.4 (± 5.4) points preoperatively to 81.6 (± 6.5) points postoperatively. No further rupture was detectable in the ultrasound examination at latest follow-up after an average of 27 (18-36) months.

Whole rock lithogeochemical analysis of the Mount Read Volcanics: a new tool for geochemical exploration

The Mount Read Volcanics (MRV) of western Tasmania is a belt of Middle to Late Cambrian submarine volcanics and volcaniclastics and one of the major base and precious metal provinces within Australia. Exploration success in the MRV has been in decline in recent years due to a variety of challenges including intensely altered rocks with complex stratigraphy and lithofacies variation, and a lack of accessible outcrop. As a result, local and regional mapping of the MRV is often restricted to Group-level stratigraphy, rendering geological mapping ineffective for identifying decametre-scale mine stratigraphy. Surface rock chip and drill hole samples were collected and analysed using commercially available geochemical assays to create a regional geochemical dataset of the MRV, covering the entire province and all major stratigraphic units. From these data, a lithogeochemical methodology was developed, utilizing Ti/Nb and V/Sc systematics that effectively characterizes the samples according to composition and magmatic processes. This method is shown to be robust to biases due to alteration and lithofacies, eliminating the need for highly selective sampling or extensive data filtering. To demonstrate the utility of this method in an exploration context, data from the K-lens of the Rosebery polymetallic volcanic-hosted massive sulfide (VHMS) deposit was used as a case study. Using Ti/Nb–V/Sc systematics, a rock composition classification was developed that allowed for discrimination of the footwall, hanging wall and host stratigraphy of the Rosebery mine sequence. A geochemical fingerprint for the footwall stratigraphy to mineralization was developed, and by correlating this signature to the regional unclassified samples, geochemical analogues for the Rosebery footwall were readily identified. This approach rapidly reduces the exploration search space and provides valuable information for future mineral exploration. The methodology is applicable in other terrains; however, appropriate orientation studies are required to investigate potential biases due to lithofacies, alteration and mineralogical variability.

Explainable AI (XAI) Techniques for Convolutional Neural Network-Based Classification of Drilled Holes in Melamine Faced Chipboard

The furniture manufacturing sector faces significant challenges in machining composite materials, where quality issues such as delamination can lead to substandard products. This study aims to improve the classification of drilled holes in melamine-faced chipboard using Explainable AI (XAI) techniques to better understand and interpret Convolutional Neural Network (CNN) models’ decisions. We evaluated three CNN architectures (VGG16, VGG19, and ResNet101) pretrained on the ImageNet dataset and fine-tuned on our dataset of drilled holes. The data consisted of 8526 images, divided into three categories (Green, Yellow, Red) based on the drill’s condition. We used 5-fold cross-validation for model evaluation and applied LIME and Grad-CAM as XAI techniques to interpret the model decisions. The VGG19 model achieved the highest accuracy of 67.03% and the lowest critical error rate among the evaluated models. LIME and Grad-CAM provided complementary insights into the decision-making process of the model, emphasizing the significance of certain features and regions in the images that influenced the classifications. The integration of XAI techniques with CNN models significantly enhances the interpretability and reliability of automated systems for tool condition monitoring in the wood industry. The VGG19 model, combined with LIME and Grad-CAM, offers a robust solution for classifying drilled holes, ensuring better quality control in manufacturing processes.

Cu–Polymetallic Deposit Exploration under Thick Cover in Gucheng–Yaxi Area Using Audio-Magnetotelluric and Spread-Spectrum-Induced Polarization

Successful geophysical exploration projects in the Gucheng–Yaxi area located in Gaochun District, Jiangsu Province, China, have been limited partly due to the complex geological conditions of the area and high artificial noise in data acquired using electrical and electromagnetic methods. In this study, we deployed the new anti-interference spread-spectrum-induced polarization method (SSIP) and the audio-magnetotelluric (AMT) method to detect a copper–polymetallic deposit in the area. Two-dimensional inversion results in the Gucheng–Yaxi area revealed a high chargeability anomalous zone on the SSIP profile that coincided with a zone of moderate resistivity located between two resistor bodies on the AMT profile. A follow-up 1200 m drill hole was established at this high-chargeability, moderate-resistivity zone which encountered polymetallic (copper, lead, zinc, gold, and silver) mineralization at a depth of ≥400 m. Drill hole data analysis showed that mineralization occurred interspaced in the marble rock mass at varying depths. Furthermore, several low-resistivity, weak-chargeability sections were revealed and attributed to Cretaceous sediments and faults. These faults are thought to have played a critical role in the polymetallic mineralization genesis. In summary, this study demonstrated the successful of application of SSIP and AMT in detecting a metallic deposit in an area with high artificial noise. Hence, the geophysical prospection potential of the Gucheng–Yaxi area is great.

An insightful multicriteria model for the selection of drilling technique for heat extraction from geothermal reservoirs using a fuzzy-rough approach

Geothermal energy stands out as an exceptional renewable resource for power generation, offering a consistent power production without the intermittency issues. Despite its potential to deliver a consistent supply of electricity on demand, geothermal adoption is hindered due to substantial costs. Utilising the most effective drilling method can alleviate this challenge by boosting efficiency and reducing operational costs. The primary goal of this study is to identify the best drilling method for extracting heat from geothermal reservoirs. This optimised approach facilitates better access to geothermal reservoirs, leading to increased heat recovery rates and improved project viability. Traditional methods often fall short in evaluating optimal drilling alternatives due to uncertainties. To address this, our research introduces an innovative paradigm that integrates novel T-Spherical Hesitant Fuzzy Rough (T−SHFR) set, method for the removal effects of criteria with a geometric mean and ranking alternatives with weights of criterion hybrid Multiple Criteria Decision-Making (MCDM) techniques. By leveraging the novel T−SHFR concept, our approach allows for a comprehensive assessment of various factors. This holistic evaluation ensures an exhaustive comprehension of the decision-making environment. The study reveals that reservoir characteristics play a significant role in selecting a sustainable drilling alternative. Furthermore, directional drilling appears as the most promising method with higher energy yields followed by slim hole drilling. The robustness and credibility of these findings are established through sensitivity and comparative analyses, indicating the potential applicability of this MCDM method to analogous challenges in different contexts. The findings of the ranking techniques were validated using Spearman's rank correlation coefficient, which revealed a positive and notable correlation. This research will empower stakeholders to make informed decisions, thereby enhancing the overall efficiency and sustainability of geothermal energy projects.

TROCHANTERIC OSTEOTOMY AND TRANSFER DURING TOTAL HIP ARTHROPLASTY IN PATIENTS WITH DISLOCATED DYSPLASTIC HIPS: UNION RATE USING MONOFILAMENT TRANSVERSE WIRE CERCLAGE

Securing the osteotomized greater trochanter (GT) during total hip arthroplasty (THA) for dislocated dysplastic hips (DDH) poses a significant challenge. This study evaluates the union rate and effectiveness of a 2-strand transverse wiring technique utilizing the lesser trochanter for wire anchorage and tensioning.A digastric anterior slide trochanteric osteotomy was performed in 106 patients (118 hips) undergoing THA for DDH. Following uncemented stem insertion, the GT was transferred and fixed to the lateral cortex of the proximal femur using monofilament stainless steel wires. In 72 out of 106 patients (80 hips), the GT was fixed with 2 transverse wire cerclages threaded through 2 drill holes in the base of the lesser trochanter, spaced vertically 5–10 millimeters apart. The wires were wrapped transversely over the GT and tightened, avoiding contact with its tendinous attachments. Patients were regularly monitored, and GT union was assessed clinically and radiographically.Patient ages ranged from 20 to 57 years (mean 35.5), with a follow-up period ranging from 1.5 to 12 years (mean 6.2). The mean union time was 3.3 months (range 2–7). Among all hips, two developed stable nonunion and single wire breakage, but no fragment displacement (2.5%). Two hips exhibited delayed union, eventually healing at 6 and 7 months after surgery.Reattachment of the greater trochanter utilizing a 2-strand transverse wire cerclage anchored at the base of the lesser trochanter demonstrated a high rate of union (97.5%) following THA in dislocated DDH cases.

DEIT-Based Bone Position and Orientation Estimation for Robotic Support in Total Knee Arthroplasty-A Computational Feasibility Study.

Total knee arthroplasty (TKA) is a well-established and successful treatment option for patients with end-stage osteoarthritis of the knee, providing high patient satisfaction. Robotic systems have been widely adopted to perform TKA in orthopaedic centres. The exact spatial positions of the femur and tibia are usually determined through pinned trackers, providing the surgeon with an exact illustration of the axis of the lower limb. The drilling of holes required for mounting the trackers creates weak spots, causing adverse events such as bone fracture. In the presented computational feasibility study, time differential electrical impedance tomography is used to locate the femur positions, thereby the difference in conductivity distribution between two distinct states s0 and s1 of the measured object is reconstructed. The overall approach was tested by simulating five different configurations of thigh shape and considered tissue conductivity distributions. For the cylinder models used for verification and reference, the reconstructed position deviated by about ≈1 mm from the actual bone centre. In case of models mimicking a realistic cross section of the femur position deviated between 7.9 mm 24.8 mm. For all models, the bone axis was off by about φ=1.50° from its actual position.

Qualification Methodology for the Double Side Printed Substrate for Hybrid Microcircuits Application

Hybrid Microcircuits (HMCs) are always preferred over discrete versions due to small size, less weight, better performance and high reliability for space applications. Double side printed substrates realized using Thick film screen printing and Printed Through Hole (PTH) processes are being used in HMCs in order to achieve further miniaturization. This article details the newly developed innovative Thick film process technology involving drilling of holes and filling the through hole with gold conductive paste to connect the front and rear side of conductor patterns on an alumina substrate. The biggest challenge in the realization of double side printed substrates is creating multiple via holes and filling them with conductor paste. In addition, the limited ability to achieve substrate integration and uniformity pose additional challenges that require optimization of process parameters. A comprehensive test plan created to qualify this innovative method in terms of quality and reliability suitable for the aerospace industry is also presented.

In situ x-ray imaging to understand subsurface behavior during continuous wave laser drilling

A limited understanding regarding the underlying dynamics and mechanisms of material removal during continuous wave laser drilling has presented significant challenges in achieving precision and process control. To address this, we employed high-fidelity, in situ synchrotron x-ray imaging to reveal previously unknown material behaviors during continuous wave laser drilling with power modulation. Our findings highlight that high-aspect ratio drill holes are achieved when the laser modulation frequency falls within the range of 8–12 kHz, provided that the laser average power and modulation amplitude levels meet the specified limits. Under these conditions, we identified a material removal mechanism driven by incremental accumulation of recoil pressure that gradually pushes material upward from deep within the substrate to the surface. This mechanism manifested as a low-frequency fluctuation in the vapor depression depth, resulting in periodic instances of material ejection. Furthermore, our study underscores that rapid expansion of the melt pool and the widening of the drill hole opening can impede effective material removal by redirecting energy from material ejection to increasing the melt pool size. This investigation contributes essential insights into the subsurface dynamics involved in the drilling of high-aspect ratio holes, furthering our fundamental understanding of this intricate process.

Applying Knowledge-Based and Data-Driven Methods to Improve Ore Grade Control of Blast Hole Drill Cuttings Using Hyperspectral Imaging

Applying Knowledge-Based and Data-Driven Methods to Improve Ore Grade Control of Blast Hole Drill Cuttings Using Hyperspectral Imaging

Technical modifications to elbow interposition arthroplasty

Interposition arthroplasty of the elbow involves the interposition of afascia lata or dermis autograft or allograft between the distal humerus and the ulna or radius, while preserving the original form of articulation. Interposition arthroplasty is indicated for young patients with high functional demands who suffer from end-stage elbow arthritis and associated pain or joint stiffness. Contraindications include acute or subacute infection, skeletal immaturity, bone loss, deformity, or gross instability. Once the ulnar nerve has been secured, joint access is established via aposterior approach. The radial collateral ligament (RCL) and the common extensor tendon origin (CEO) are detached, while preserving the anconeus muscle and the lateral ulnar collateral ligament (LUCL). Subsequently, a capsular release is required to maintain adequate joint exposure and address the accompanying stiffness. Three to four transosseous drill holes are placed at the level of the distal humerus to secure the graft. After the graft has been positioned successfully within the joint space using two guide sutures, it can be secured to the distal humerus using ahorizontal mattress stitch. Finally, the detached tendon and ligament structures are reconstructed. After initial immobilization, early functional exercise of the elbow is performed in the motion orthosis, avoiding valgus or varus stress. The efficacy of elbow interposition arthroplasty has been demonstrated, particularly for young and active patients with severe inflammatory or post-traumatic osteoarthritis. Despite the results in terms of postoperative function and pain reduction are satisfactory, the current literature reports high complication, subsequent treatment, and revision rates. In the event of interposition arthroplasty failure, revision with another interposition procedure or conversion to endoprosthesis may be considered.

Central band reconstruction in Essex-Lopresti lesions

Restoration of longitudinal forearm stability by reconstruction of the central band (CB) of the interosseous membrane (IOM) of the forearm. Acute and chronic Essex-Lopresti lesions (EL) with longitudinal forearm instability. Absolute: acute/subacute infection. Relative: severe complex regional pain syndrome (CRPS), bony deformity/bone loss, pronounced osteoarthritis of the elbow and wrist. Ulnar approach with exposure of the ulna approximately 6 cm proximal to the ulnar styloid. Creation of a3.5 mm drill hole from ulnar-distal to radial-proximal. AFiberloop (Fa. Arthrex, Naples, FL, USA) is fixed to one end of the LARS (Ligament Advanced Reconstruction System, Fa. Corin Group, Cirencester, UK) in awhipstitch technique, is shuttled through the drill hole from radial to ulnar and fixed over aBicepsButton (Fa. Arthrex, Naples, FL, USA). Exposure of the radius through amodified Henry approach. A3.5 mm drill hole is made from radial-proximal to ulnar-distal approximately 12 cm proximal to the radial styloid. The graft is shuttled from the ulnar to the radial incision directly on the palmar surface of the IOM and shortened to the required length. Another Fiberloop is used to perform awhipstitch on the free end of the LARS. The final fixation of the CB reconstruction is achieved by shuttling the Fiberloop sutures through the radial drill hole with fixation over aBicepsButton. Short-term immobilization in along arm cast with subsequent early functional treatment. Mediocre to poor clinical results are reported in the literature for the treatment of chronic EL. Future research will tell whether the advanced surgical techniques with CB reconstruction will lead to better clinical outcomes.

Gravity and magnetic geophysical surveys for exploration of low sulphidation epithermal mining project. Marifil Complex, Chon Aike Igneous Province, Argentina

The Marifil Complex constitutes the early stage of the Chon Aike Igneous Province along eastern North Patagonia, Argentina. Geological, geochronological, and geochemical data indicate that this magmatism consists of two characteristic Lower Jurassic volcanic events (V0 and V1). The epithermal activity takes place in V1 as Au-Ag veins (Pavón Pivetta et al., 2024). Particularly, base metal veins are covered and masked by the important explosive volcanic activity related to the V1 volcanic stage. This makes geophysical exploration a highly recommended tool for interpreting subsurface geological features.With this in mind, we have carried out the acquisition and processing of gravity and magnetic data that is supported with drill holes and geochronological data. A series of gravity and magnetic highs and lows were recognized, together with major lineaments. Using Euler deconvolution, the depth of the sources that generate the anomalies was calculated. The analysis of these results allowed us to construct two perpendicular gravity 2D models for the calculation of thicknesses and depth of the rhyolitic coulée. The gravity lows were associated with the major thickness of rhyolitic coulée, reaching 290 m in the drill holes, and interpreted geophysically to have a deeper root. The gravity highs were interpreted in two possible ways: a basement depth decrease and/or the absence of the rhyolitic coulée. The minimum depth estimated for the basement highs is approximately 20 m. These interpretations are consistent with outcrop, drill hole and geochronologic data, and magnetic maps. The RMSE between the calculated and the observed anomalies of the models are about 0.316 and 0.519 mGal. Due to the shape of the anomalies obtained from the gravimetric maps, the structures that generate the anomalies were considered as generated by three-dimensional bodies. For this purpose, we created a 3D model that provides interesting data about the possible location of these non-outcropping gravity lows that are located in the first 200 m depth.These results demonstrate that the use of the gravity and magnetic method constitutes a useful, fast, economical, robust, and reliable tool for the identification of these volcanic structures.

Special MCP-N thermoluminescent detectors (TLD) with better angular dependence

One of the basic parameters in the use of thermoluminescent detectors is the angular characteristics, i.e. receiving different signals depending on the angle of radiation exposure. The TLD detector is typically installed in a slide/badge and here the angular characteristics may have an influence, adding non-uniform coverage of the detectors with filters for the correct determination of the dose as a function of energy, because the energy characteristics are usually not flat.As part of the work, special MCP-N (LiF:Mg, Cu, P) detectors of various shapes were prepared to improve the angular characteristics. The detectors were round pellets with the same circular shape with a diameter of 4.5 mm, and a modified form inside (large and small drilled holes) or a modified surface (cavity or hemisphere). For comparison, standard MCP-N type detectors were used. Detectors in special boxes were exposed to X-rays with an energy of 80 keV. The radiation beam was formed by a medical X-ray apparatus adapted for experiments at the Warsaw University of Technology in Warsaw. Exposures were made for angles of 0, 30, 45, 50, and 90° for a dose of 1.5 mGy.Results show that it is possible to improve the angular characteristics for detectors with modified shapes. Better angular characteristics will allow for more accurate measurements, in particular in comparison tests, for accreditation and other calibrations. Especially improved angular dependence detectors could be useful for H*(10) environmental measurements.

Effects of deep hole drilling processes on the fatigue strength of GTD-111 DS

The paper deals with the effects of electrochemical and electro-discharge deep hole drilling on the high-temperature fatigue behavior of a directionally solidified GTD-111 superalloy. High-temperature HCF tests were carried out at 800 °C on specimens having a coaxial hole drilled with the investigated processes. The hole diameter and length were 1.5 and 95 mm, respectively. The material’s high-temperature HCF S-N curve was also obtained to provide a reference curve. Despite the scatter caused by the material microstructure in the fatigue crack nucleation and propagation regime, the fatigue strength was found to be affected by the investigated hole drilling techniques. The electro-discharge deep hole drilling was found to lower the fatigue strength by 8%. Fractographic analyses showed that it can be attributed to the different hole surface roughness and microstructural alteration in the underlying material.

Mineral Magnetism in Relation to Thermal Thellier Palaeointensity Experimental Results of the Deccan Basalt Flows Along the Deep Drill Hole in Western India and Their Significance

Mineral Magnetism in Relation to Thermal Thellier Palaeointensity Experimental Results of the Deccan Basalt Flows Along the Deep Drill Hole in Western India and Their Significance

Residual stress determination in a C-C composite consisting of a carbonized elastomer matrix filled with graphite, carbon black and short carbon fibers

In this study, composites obtained through low-temperature carbonization of elastomeric matrix highly filled with graphite, carbon black and short carbon fibers were studied for the purpose of determining residual stresses at different scales using a combination of several complementary methods. The state-of-the-art techniques included X-ray stress analysis using the sin2⁡ψ method, the micro-ring-core technique via Focused Ion Beam milling and Digital Image Correlation (FIB-DIC), the contour method, the strain gauge method, and the hole drilling technique with digital laser speckle pattern interferometry (DLSPI). It was found that the contour method could not be used implemented for residual stress evaluation due to the low electrical conductivity of composite. Moreover, the DLSPI hole drilling method did not reveal any fringes indicating significant residual stress level exceeding a few MPa. The strain gauge method also revealed a narrow residual stress distribution with an average value of approximately zero. In contrast, the X-ray sin2⁡ψ method as well as FIB-DIC technique both returned values of about 150–250 MPa. A hierarchical model of the composite is proposed based on the Davidenkov Type I–II–III stress classification that provides an explanation of these observations.