Cone Fracture Research Articles

Drilling- and coring-induced artefacts in poorly indurated clays

Macroscopic and microscopic drilling-induced deformation structures were documented in cores of Ypresian Ieper Group and Rupelian Boom Formation clays using macro-polished slabs and polarizing microscopy of thin sections. The cores were recovered in north Belgium from a depth of a few hundred metres by pushing a steel barrel with a cutting shoe into the non-indurated clays that are in a ductile to brittle transition state. The outer border of the clay cores was bent downwards due to the pushing action. The geometry of the drilling-induced fractures can be described as vertically stacked axisymmetrical conical fractures complexed by a general concave and undulating shape, and by fractures splaying from other fractures. At the microscopic scale (2D), the fractures are micro-faults that produce a breccia texture and which consist of thin planes, lines in 2D, of orientated clay minerals. The preferred orientation of these clay minerals in the fractures point to shear movement and explain the shiny appearance of these slickenside-like fractures when viewed in 3D. The micro-faults produce clay domains tilted with respect to each other. Recognizing exclusively drilling-induced structures helps in the selection of cores and core fragments for further laboratory testing, and may be of help in distinguishing them from regional faults or fracture systems in homogeneous clays. Thematic collection: This article is part of the Sustainable geological disposal and containment of radioactive waste collection available at: https://www.lyellcollection.org/topic/collections/radioactive

Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling

Mayotte island experienced a large volcanic eruption 50 km offshore in 2018–2021, creating the submarine volcano “Fani Maoré”. The eruption was accompanied by intense seismicity at mantle depths (20–45 km), divided into a “proximal” and a “distal” cluster centered 10 and 30 km east from the island, respectively. Previous studies suggest that two separate magma reservoirs may lie at the top and bottom of the proximal cluster. Here, we assess whether two reservoirs are a mechanically viable explanation for the proximal cluster's truncated conical shape. We developed finite-element models of pressurized magma reservoirs in a 2D axisymmetric domain, modeling the reservoirs as compliant elastic ellipsoids embedded in an elastoplastic host rock. We find that, at these depths, extremely low friction is required to generate failure at realistically low reservoir pressures. This implies in turn that mechanical weakening must occur at these depths. The weakening could be induced by fractures or pore fluid overpressure in the volcanic system. We find that two superimposed reservoirs can generate a plastic domain between them, if they are spatially close enough. Several reservoir geometries (from spherical to sill-like) are plausible. A conical fracture domain is more likely to appear for reservoirs with opposite pressure loads (i.e. one inflating, one deflating). Given the geometrical match with the proximal seismicity cluster at Mayotte, we suggest that the shallower (Moho-depth) reservoir is inflating, creating a potential hazard for Mayotte island.

Subsurface fracturing of sedimentary stones caused by bullet impacts.

The immovable nature of built heritage means that it is particularly vulnerable during times of armed conflict. Although impacts from small arms and shrapnel leave relatively inconspicuous impact scars, they elevate the risk of future stone deterioration. This study investigates the subsurface damage caused by bullet impacts, which is not apparent from surface inspection, in order to better understand the geometry and mechanics of this form of conflict damage to heritage. Controlled firearm experiments were conducted to simulate conflict damage to sandstone and limestone buildings. The bullet impacts created conical fractures or zones of increased fracture intensity below the impact, radial fractures, and spallation, in addition to a crater. Dynamic fracture distinguishes the formation of these features from quasi static cone crack experiments, while the lack of a shockwave differentiates these bullet impacts from hypervelocity experiments. Damage was created by momentum transfer from the bullet, so that differences in target properties had large effects on the nature of the damage. The crater in the limestone target was almost an order of magnitude deeper than the sandstone crater, and large open fractures formed in the limestone below the crater floor, compared with zones of increased fracture intensity in the sandstone target. Microstructural analysis of subsurface damage showed that fracture intensity decreased with increasing distance from the impact centre, suggesting that regions proximal to the impact are at increased risk of future deterioration. Conical subsurface fractures dipping away from the impact beneath multiple impact craters could link up, creating a continuous fracture network. By providing pathways for moisture and other weathering agents, fractures enlarge the region at increased risk of deterioration. Their lack of surface expression makes understanding their formation a vital part of future surveying and post conflict assessments.

Mechanical Response of CNT/2024Al Composite to Compression and Tension at Different Strain Rates

Compressive and tensile properties of a carbon nanotube (CNT) reinforced 2024Al composite are investigated under quasi-static and dynamic compression as well as quasi-static tension, along three different directions (extrusion, normal and transverse directions). Upon compression, yield and fracture strengths of the composite show negligible strain rate effect and mechanical anisotropy as manifested in the compressive stress–strain curves. Fractography and profilometry show that fracture surfaces are rough shear fracture planes for quasi-static compression; however, smooth conical fracture surfaces are observed for dynamic compression as a result of more homogeneous damage nucleation and growth, leading to high ductility under high strain rate loading. Pronounced mechanical anisotropy is observed for the composite under quasi-static tensile loading. Ductility or fracture strain is the highest along the normal direction, because debonding along the particle and lamellar interfaces is suppressed along this direction. In situ optical imaging along with digital image correlation is utilized to obtain the deformation dynamics of the composite along the three different directions. Stripe-shaped strain localizations appear in the strain fields along the extruded and tangential directions, while the strain fields are approximately uniformly distributed along the normal direction, consistent with the stress–strain curves.

Experimental investigation on the anchorage performance of hooked high-strength steel strands for beam-to-column connection

To explore the anchorage performance of hooked steel strands used in the beam-to-column connection of the precast prestressed assembled structural (PPAS) system, considering the influence of the various research variables, such as anchorage length and the length of the vertical segment of the steel strand, 16 specimens were designed and tested under the pull-out loading. The failure modes, pull-out load-slip curves, peak point loads, and the corresponding slips of the tested specimens were obtained accordingly. Besides, by means of portable X-ray detection technology, the shape evolution of hooked steel strands in the concrete columns under various pull-out loads were imaged and compared, and the anchorage failure mechanism of hooked steel strands was further clarified. The test results demonstrated that three failure modes were observed in all test specimens. Besides, the hooked steel strands can significantly improve its ultimate anchorage capacity and material strength utilization efficiency. When the anchorage length is not less than 500 mm, and the length of the vertical segment is 5d, 10d and 15d, the conical fracture failure of the steel strand always occurs in the test specimens, and the material strength utilization efficiency is always not less than 90 %, far higher than that of the straight steel strands. In addition, the relative slip at the loaded end is obviously related to the anchorage parameters of the steel strands. In details, whether the length of the vertical segment is 5d, 10d or 15d, the relative slip of the hooked steel strand is significantly lower than that of the straight steel strand, which is strongly related to the unique anchoring mechanism of hooked steel strand. However, the necessary anchorage length is needed for hooked steel strands to achieve the ideal anchorage effect, which should generally not be less than 500 mm.

Traumatic fracture of the polyethylene tibial post and cone in a posterior-stabilized total knee arthroplasty: A case report.

Introduction and importanceVery few reports addressed polyethylene tibial post and cone fractures requiring revision surgery. Up to our knowledge, this particular pattern of wear, involving 2 fracture areas simultaneously, has not been previously described.Case presentationA 70 year-old female developed a fracture involving both the tibial insert post and cone after a minor trauma after undergoing posterior-stabilized total knee replacement 4 years prior.Clinical discussionThis unique pattern of wear may occur even after minor trauma.ConclusionWe recommend having a low threshold to investigate minor trauma in this patient population, even years after undergoing primary knee arthroplasty.

Importance of Hardening Effect and Its Analysis on Diametrical Fractured Ends of Tensile Testing of Al and Steel

The hardening effect varies deliberately to elevate the properties of alloy specimens either in ferrous or nonferrous materials. The cup and cone fracture theory explains the effect of hardening through heat treatment of the specimen. The hardening effects are imposed on the specimen by the furnace heating and hot pressing method. The neck formation and the elongation levels are evaluated and compared for both heat-treated and non-heat-treated specimens of steel and aluminum alloys. The simulation tools are used to predict the compressive and elongation levels by obtaining the stresses and deflections at various nodal points. The suitable heat treatment was indicated by the single or twice method of heat adoption over the steel and aluminum specimens. The fracture analysis and experimental results are compared among the hardened or non-heat-treated specimens.

A two characteristic length nonlocal GTN model: Application to cup–cone and slant fracture

Ductile failure prediction is essential to avoid loss of structural integrity or to control crack propagation during forming processes. One of the main difficulties is the prediction of complex crack paths. This study proposes a nonlocal extension of a local Gurson–Tvergaard–Needleman (GTN) ductile damage model at finite strains able to capture cup–cone or slant fracture. The proposed model is based on an implicit gradient formulation which enables to solve the problem of spurious strain and damage localization. The model integrates two different material characteristic lengths, which are used to separately regularize damage by void growth and damage by damage nucleation. After parameter fitting using data for a line pipe steel, conditions to obtain converged solutions are studied, which can be used to select the mesh size in the localization band. With the appropriate mesh design, it was possible to study the effect of the characteristic lengths on the formation of cup–cone fracture and slant fracture. It is observed that, for a given specimen size, larger characteristic lengths favor flat crack advance. Similarly, for given material lengths, size effects can be predicted with small specimens being more prone to flat fracture. This paves the way to a more direct determination of material lengths by using homothetic specimens so as to obtain different crack paths.

Application of parabolic cracks in determining handedness in archaeological remains. The case study of the Axlor site (Bizkaia, Iberian Peninsula)

Lithic artefacts are a potential source of information for the study of handedness in different human species. In flint flakes, a system of fractures is developed (parabolic cracks) around the point of percussion in connection with the cone of percussion and the conical fracture of the flint. The orientation of these fractures is linked to the direction of percussion, and therefore to the knapper's handedness. The archaeological remains from Levels III, IV, V and VI at Axlor (Bizkaia, Iberian Peninsula) are studied here in order to determine how well parabolic cracks are preserved in archaeological remains, and whether it is possible to study them if the remains are covered with a patina or damaged.

The Role of Extracellular Vesicles in Osteoporosis: A Scoping Review.

As an insidious metabolic bone disease, osteoporosis plagues the world, with high incidence rates. Patients with osteoporosis are prone to falls and becoming disabled, and their cone fractures and hip fractures are very serious, so the diagnosis and treatment of osteoporosis is very urgent. Extracellular vesicles (EVs) are particles secreted from cells to the outside of the cell and they are wrapped in a bilayer of phospholipids. According to the size of the particles, they can be divided into three categories, namely exosomes, microvesicles, and apoptotic bodies. The diameter of exosomes is 30–150 nm, the diameter of microvesicles is 100–1000 nm, and the diameter of apoptotic bodies is about 50–5000 nm. EVs play an important role in various biological process and diseases including osteoporosis. In this review, the role of EVs in osteoporosis is systematically reviewed and some insights for the prevention and treatment of osteoporosis are provided.

Effect of post–weld heat treatment on multi-scale microstructures and mechanical properties of friction stir welded T-joints of Al–Mg–Si alloys

Defect-free T-joints of Al–Mg–Si plates were successively welded using a friction stir welding (FSW) process. Multi-scale microstructure analysis was performed to investigate the metallography of FSW T-joints and comprehend the clustering behavior of base metals (BM) and stir zones (SZ). The mechanical properties of T-joints were evaluated during post–weld heat treatment (PWHT) using tensile tests.BM with a 47.3 μm average grain size was transformed into approximately 2.6 μm fine equiaxed grains in the SZ. Simultaneously, dissolution of clusters and/or precipitates in the SZ was related to the decrement of the mechanical properties of the joints. Softening was confirmed in the SZ due to the peak-heat by friction stirring of the FSW tool. Thinning of the plate on the advancing side (AS), which was affected by the shoulder zone of the FSW tool, acts as a weak spot for crack initiation. There was a cup and cone fracture on heat affected zones (HAZ) of the plate in the AS.Nanocluster formation was quantitatively analyzed during PWHT using a three-dimensional atom probe (3DAP). Small nanoclusters with approximately 0.6 nm were dominantly formed in the SZ than the BM. Nanoclusters with higher Mg/(Mg + Si) were predominantly generated in the BM. The number densities of the clusters in the BM and SZ were 15.10 × 1023 m−3 and 38.60 × 1023 m−3, respectively. This study confirmed that FSW facilitates better the formation of refined nanoclusters and precipitates in the SZ with smaller size and higher number density compared to BM.

New zooarchaeological perspectives on the early Upper Paleolithic Rostamian sequence of Ghar-e Boof (southern Zagros Mountains, Iran)

Ghar-e Boof is a Paleolithic cave site in Iran, known for being the type locality for the early Upper Paleolithic (UP) Rostamian lithic industries. Defining the Rostamian cultural group has significant archaeological implications for the Zagros Mountains. First, it highlights the cultural diversity of the UP in the Zagros. Second, it evinces a more complex scenario for the spread of anatomically modern humans (AMHs) across Southwest Asia. Despite this, little is known about human subsistence strategies during the Rostamian. In this paper, we present the results of a zooarchaeological analysis that allows us to reconstruct prey choice, transport decisions, and carcass processing at Ghar-e Boof. Wild sheep/goat was the main prey at the site, but other taxa such as partridges, tortoises, and gazelles represented important dietary supplements. Mortality data indicate that Rostamian hunters primarily targeted prime-aged adult ungulates. Anatomical representation also shows that there was no selective transport of animal carcasses to the site, so hunting activities most likely took place nearby. Although many specimens in the assemblage were covered by thick concretions, the presence of cut marks demonstrates defleshing, filleting, dismemberment, and even the removal of internal organs of prey. Percussion impacts and cone fractures also suggest the processing of bones for marrow. Chronologically, moving from the oldest to the youngest layers, there is a decrease in large game in parallel with a progressive increase in small, fast-moving animals. Following the prey choice model of optimal foraging theory, this diachronic variation might track regional resource stress or an increase in hunting pressure. Our results, along with the analysis of lithic artifacts and changes in the rates of sedimentation during the Rostamian sequence, indicate an increase in occupation intensity through time. Thus, the archaeological record of Ghar-e Boof and the ubiquity of UP sites across the Dasht-e Rostam region most probably reflect population growth within a few millennia after the arrival of AMHs.

A novel approach to producing architectured ultra-high strength dual phase steels

An ultrafine-grained dual phase (DP) microstructure has been produced in a steel that contains a combination of composition and deformation gradients. A carbon gradient was created by controlled decarburization of the steel. The compositionally graded steel was cold rolled to produce a large number of shear bands prior to recrystallization annealing at 650 °C for 5 h followed by intercritical annealing at 740 °C for 10 min. Microstructural characterization reveals a very fine heterogeneous dual phase microstructure with submicron grains appearing along the traces of the prior shear bands that had developed during rolling. Martensite volume fraction changes from the surface to the center and also within these shear band traces. Tensile tests of the new dual phase structure reveal that the work hardening rate changes spatially with martensite volume fraction. Detailed fractography using ex-situ X-ray computed tomography (XCT) reveals a unique form of multiple cup and cone fracture features that can be related to the evolution of damage along the shear band traces with a gradient of void density from the surface to the center. This strategy for fabricating dual phase steels enables the development of architectured ultra-high strength DP steels with different properties that can be tailored by controlling the composition and deformation gradients and subsequent annealing treatments.

Forensic Investigation of Bullet Holes for Determining Distance from Glass Fracture Analysis

The study of glass fracture patterns has been of long interest to the forensic community. Fragments of glass can be significant evidence found in the investigation of various types of offenses especially where armed violence is involved on automobiles. Figuring out, whether glass fragments present on crime scene share the same origin as per glass that has been hit by a projectile or any substrate, is quite a success to an examiner because that further leads to the investigation of how and by which means it has done. Holes occurred in the glass at the crime scenes have much importance and many attempts are taken to investigate the properties of these glass holes to find the type, speed, and angle of the projectile which probably produce the hole. For highvelocity projectiles including bullets, these bullet holes in glass can exhibit certain features and fractures. The objective of this research was to determine the distance of shooter from the bullet hole on glass used in automobiles. Bullet holes were prepared and different parameters of glass fractures like bullet hole diameter, cone fractures radius, cone fractures diameter, radial, and concentric fracture count were considered from both front and the backside of the glass. These parameters were observed and analyzed to determine the dependency of these parameters on the variable “distance”. The consistency found in the measurements to conclude our results were checked by goodness of fit test. The study bears great significance as it could lay down a foundation to set a standard parameter to estimate distance of bullet hole from shooter in firing incidents involving glass fracture. This will provide a blueprint to crime scene investigators in order to reconstruct the crime scene for understanding and to take investigation to logical conclusion.

Effect of tool pin geometry on microstructure and mechanical properties of friction stir spot welds of 7075-T651 aluminium alloy

7075-T651 aluminium alloy sheets were overlapped and friction stir spot welded using two welding tools having different pin geometries (one with a conical pin and other with a triangular pin) and 800, 1200 and 1600 revolution per minute (rpm) tool rotation speeds at a constant tool plunge and removal speed of 7.3 mm/min, tool plunge depth of 3.8 mm and tool dwell time of 5 s. Microstructure, Vickers microhardness, tensile shear strength, fracture surface after tensile shear test and impact energy of the produced friction stir spot welds were examined. As a result, the welds made via triangular pin tool had considerably higher tensile shear loads than the welds made via conical pin tool since the weld bond widths (stir zones) of the welds made via triangular pin tool were larger. The strongest welds made at 1200 rpm for conical pin tool and triangular pin tool. The tensile shear loads of the welds increased significantly when tool rotation speed increased from 800 to 1200 rpm for both welding tools and then decreased slightly for triangular pin tool and dramatically for conical pin tool with further increasing tool rotation speed from 1200 to 1600 rpm. Maximum tensile shear load of 7.776 kN and impact energy of 16 J obtained in the weld made at 1200 rpm using triangular pin tool. The welds made at 800 rpm had lowest impact energy. The lowest hardness values found in the heat affected zones of the welds. Circumferential fracture mode for conical pin tool welds and nugget pull-out fracture mode for triangular pin tool welds observed after tensile tests.

Fatigue Life of Aluminum Alloys Based on Shear and Hydrostatic Strain.

The main purpose of this paper is to propose, based on the literature review, a new multiaxial fatigue strain criterion, analogous to the Dang Van stress criterion, considering the maximum amplitude of the shear strain and volumetric strain. The proposed strain criterion was successfully verified by fatigue tests in cyclic bending with torsion of specimens made of 2017A-T4 and 6082-T6 aluminum alloy. The scatter of test results for cyclic bending and the combination of cyclic bending and torsion is included in the scatter of tests for the cyclic torsion of the analyzed materials. Fracture surfaces for respective bending and torsion in the 6082-T6 aluminum test with strain control showed that, in the case of bending, cracks can be observed that develop from the surface of the specimen towards the bending plane. They are inclined from the fatigue crack at an angle of 45° in relation to the crack surface and the remaining cracks come from the static fracture. In the case of torsion, however, a conical fracture at 45° and a static torsion zone can be observed.

Scaling effects and brittle fracture mechanisms in laser punching of PECVD SiO2 films

We experimentally investigate the removal of several microns thick plasma-enhanced chemical vapour deposition SiO2 films by a localized dynamic fracture due to confined laser–matter interaction with the silicon substrate (punching) using 10 ps laser pulses at 355 nm. A near order of magnitude increase in the punching threshold fluence (from ∼0.1 to ∼1 J cm−2) is observed as the ratio between the spot size and the film thickness is scaled down, in order to produce high aspect ratio openings in the film. An opening radius of about twice the film thickness appears to be an approximate practical limit. A high aspect ratio opening is created by a cone fracture of the film and the ejection of a conoid film segment (flyer). We discuss mechanisms of brittle fracture that may lead to the observed patterns.

A 1.4-million-year-old bone handaxe from Konso, Ethiopia, shows advanced tool technology in the early Acheulean

In the past decade, the early Acheulean before 1 Mya has been a focus of active research. Acheulean lithic assemblages have been shown to extend back to ∼1.75 Mya, and considerable advances in core reduction technologies are seen by 1.5 to 1.4 Mya. Here we report a bifacially flaked bone fragment (maximum dimension ∼13 cm) of a hippopotamus femur from the ∼1.4 Mya sediments of the Konso Formation in southern Ethiopia. The large number of flake scars and their distribution pattern, together with the high frequency of cone fractures, indicate anthropogenic flaking into handaxe-like form. Use-wear analyses show quasi-continuous alternate microflake scars, wear polish, edge rounding, and striae patches along an ∼5-cm-long edge toward the handaxe tip. The striae run predominantly oblique to the edge, with some perpendicular, on both the cortical and inner faces. The combined evidence is consistent with the use of this bone artifact in longitudinal motions, such as in cutting and/or sawing. This bone handaxe is the oldest known extensively flaked example from the Early Pleistocene. Despite scarcity of well-shaped bone tools, its presence at Konso shows that sophisticated flaking was practiced by ∼1.4 Mya, not only on a range of lithic materials, but also occasionally on bone, thus expanding the documented technological repertoire of African Early Pleistocene Homo.

Fracture characteristics of coal jointly impacted by multiple jets

Drilling technology using multiple jets can achieve an ultra-small hole radius or well, and achieves good engineering results in soft rock such as coal. In this study, multiple jet impingement experiments were conducted to reveal the rock-breaking mechanism for coal. Computed tomography scanning was applied to observe the propagation law of internal rock fractures formed by the impact of multiple jets. By analyzing the relationship between the angle and length of a conical fracture and the arrangement mode of multiple jets, two types of interference fracture propagation laws were obtained. Combined with scanning electron microscope images of the impact debris, the fracture characteristics of coal impact by multiple jets is revealed, and a novel rock-breaking mode for multiple jets containing a center jet based on the combined impingement fracture propagation is proposed. The pilot hole formed by the center jet provides a free boundary for the side jet impact to avoid interference between adjacent jets. A conical fracture on the side near the center jet can also expand on the other side. When the cone length reaches the distance between the side jet and center jet, the erosion pits respectively generated by the adjacent jets will be connected, thus forming a joint erosion pit. Compared with multiple jets without a center jet, the rock-breaking efficiency of multiple jets containing a center jet can be improved by 47.3%. The present research results are a supplement to the rock-breaking theory of water jet impingement, providing theoretical support for the design of a multi-orifice nozzle.

Simulation and Experimental Validation of EBW Studies in Austenitic Stainless Steel AISI-321

Electron beam welding of austenitic stainless steel AISI-321 has been studied with butt weld configuration. The numerical simulation is done in both thermal and structural analysis modes using ANSYS™ software for welding as well as tensile testing. Optimization of the process parameters such as the welding speed, power, beam offset and number of passes was carried out to obtain a sound weld joint using bead on trials and also through welding simulation to get a full penetration weld. Voltage of 60 kV with current of 90–95 mA was found to be optimum parameters for electron beam welding for the welding of a 4-mm-thick plate. The microstructure examination of various weld zones has been carried out. The tensile tests were carried out on the welded samples at room temperature and elevated temperatures (1173 K, 1223 K and 1273 K). It is observed that, with increasing strain rate, there is an increase in strength of the weldment at elevated temperatures indicating positive strain rate sensitivity. Further, a comparative study between the simulated and experimental results of room temperature tensile tests has been carried out. A good match in ambient temperature engineering stress–strain curves obtained through simulation and experimentation has been observed. The fractography analysis of the ambient temperature tensile tested specimens was carried out. It has been observed that the material exhibits necking and a cup cone fracture with fine dimples indicating a ductile fracture.