Tearing Process Research Articles

Fracture toughness and fracture mechanism of Al-Mg-Si alloy sheet subjected to pre-cryorolling and subsequent bake hardening

The fracture toughness of AA6061 sheets subjected to pre-cryorolling and room-temperature pre-rolling with varying reductions (5 %, 10 %, 15 %, and 20 %) followed by bake hardening was investigated. In the direction parallel to the rolling direction (R-T), the unit crack initiation energy (UIE) of the pre-cryorolled samples after bake hardening exhibited an increase of 0.8–6 % compared to samples without pre-rolling. In contrast, the UIE of the room-temperature pre-rolled samples displayed a varying degree of decrease. This difference can be attributed to the smaller mean grain size in the pre-cryorolled samples compared to the room-temperature pre-rolled samples. Due to work hardening, the crack propagation resistance of the pre-rolled samples was diminished, as evidenced by a decrease in crack propagation energy (UPE) with increasing reduction. The variation trends of UIE and UPE in the direction perpendicular to the rolling direction (T-R) were similar to those observed in the R-T direction. The fracture mechanism of the samples during the tearing process involves a combination of intergranular and transgranular fractures. However, samples in the R-T direction exhibit higher resistance to crack propagation compared to those in the T-R direction, which is reflected in the larger UIE and UPE. The greater resistance in the R-T direction can be attributed to the significant elongation of grains prior to fracture, resulting in a higher degree of plastic deformation in the region near the crack. Additionally, the proportion of transgranular fracture along the crack propagation path is greater in the R-T direction.

Accumulation of Hydrogen Bonds and van der Waals Interactions Determines Force Response between Two Parallel Cellulose Chains: Steered Molecular Dynamics Simulations.

We investigated the response forces between two parallel cellulose chains during the shearing and tearing processes by using steered molecular dynamics simulations. It was found that there are two logarithmic dependencies between response force and pulling speed in shearing processes but only one in tearing, according to Bell's equation by fitting the f-ln v curve. The mechanism is that there are 2-fold interactions determining the force response between two parallel cellulose chains resisting chain separation during a shearing process. Our results indicate that hydrogen bonds dominate the interchain interactions in the fast pull mode (FPM) for shearing, while van der Waals interactions dominate in the slow pull mode (SPM). For tearing, the one-by-one breaking of hydrogen bonds and van der Waals interactions plays a main role.

Comparison of tearing test methods for elastomers on trouser test pieces and determination of tear strength of plastics using a tearing element

The process of tearing on trouser test pieces was studied on four types of materials according to GOST 262-93 for elastomers and according to POLYPLASTIC Group standard STO 73011750-009-2012 [3] for testing thermoplastic materials. It has been shown that when tested according to the POLYPLASTIC Group standard on materials of polyethylene group (using a tearing element), it is possible to realize an area of continuous tearing. Data on tear resistance values were obtained on four materials: plasticized PVC, polyethylene of blow molding grades, PU and silicone.

Vertical tearing of subducting plates controlled by geometry and rheology of oceanic plates

Lateral non-uniform subduction is impacted by continuous plate segmentation owing to vertical tearing of the subducting plate. However, the dynamics and physical controls of vertical tearing remain controversial. Here, we employed 3D numerical models to investigate the effects of trench geometry (offset by a transform boundary) and plate rheology (plate age and the magnitude of brittle/plastic strain weakening) on the evolution of shear stress-controlled vertical tearing within a homogenous subducting oceanic plate. Numerical results suggest that the trench offset geometry could result in self-sustained vertical tearing as a narrow shear zone within the intact subducting oceanic plate, and that this process of tearing could operate throughout the entire subduction process. Further, the critical trench offset length for the maturation of vertical tearing is impacted by plate rheology. Comparison between numerical modelling results and natural observations suggests that vertical tearing attributed to trench offset geometry is broadly developed in modern subduction and collision systems worldwide.

Disc Tearing in a Be Star: Predicted 3D Observations

Abstract We build on our previous work involving smoothed particle hydrodynamic simulations of Be stars, by using the model that exhibited disc tearing as input into the three-dimensional Monte Carlo radiative transfer code hdust to predict observables from a variety of viewing angles throughout the disc tearing process. We run one simulation at the start of each orbital period from 20 to 72 orbital periods, which covers two complete disc tearing events. The resulting trends in observables are found to be dependent on the relative position of the observer and the tearing disc. The H$\rm \alpha$ equivalent width, V magnitude, and polarization can all increase or decrease in any combination depending on the viewpoint of the observer. The H$\rm \alpha$ line profile also displays changes in strength and peak separation throughout the tearing process. We show how the outer disc of the torn system can have a large effect on the H$\rm \alpha$ line profile, and also contributes to a wavelength-dependent polarization position angle, resulting in a similar sawtooth shape to the polarization percentage. Finally, we compare our predictions to Pleione (28 Tau) where evidence has suggested that a disc tearing event has occurred in the past. We find that our tearing disc model can broadly match the trends seen in Pleione’s observables, as well as produce the two-component H$\rm \alpha$ lines observed in Pleione. This is the strongest evidence, thus far, of Pleione’s disc having indeed experienced a tearing event.

Resistance and strain during tearing for tubular joints under reversed axial actions

This article aims to predict the load versus crack growth (P−Δa) and strain versus crack extension (ε−Δa) relations in the ductile tearing process of welded joints made from circular hollow sections (CHS). The experimental program includes fracture tests on monotonically and cyclically loaded CHS joints, with a fatigue crack near the weld toe, under axial loadings applied in the brace. Coupled with the tearing assessment diagram, this study integrates fracture resistance curves measured directly from joints and that from a fracture specimen under monotonic and reversed loadings in the experimental procedure. The tearing assessment estimates the evolution of the load resistance and the nominal strain versus the crack extension, both showing satisfactory agreement with the experimental results. This study translates the ductile tearing process into the load resistance and strain levels, which provides an interface between the fracture-mechanics based assessments and the engineering analysis and monitoring.

Ayurvedic concept of Ahara Rasa and Rasa Dhatu

According to Ayurveda, food is the main pillar of healthy life. Living body is continuously subjected to wear and tear process. Dhatus which are being lost in physiological activities are replenished by food and water. Man needs to eat food to build a new Dhatus and to repair damage Dhatus. After consumption food is digested in gastro intestinal tract. Fluid formed from the digested part of food is called as Ahara-Rasa. For growth, Dhatus needs nourishment, and these Dhatus are nourished by food and water. Aahar Rasa is formed in Annavaha Srotas. Aahar Rasa contains nutrients of seven Dhatus. Aahar Rasa is absorbed from Grahani (small intestine) and brought into heart. Heart is a root of Rasavaha Srotas, hence in heart, Rasa Dhatvagni transforms nutrients of Ahara Rasa into stable Rasa Dhatu. Rasa Dhatu is formed in Rasavaha Srotas. Rasa is the first Dhatu formed from Aahar-Rasa.

Improvement of lubrication performance of sliding pairs with multi-depth groove textures based on genetic algorithm

During the wear and tear process of bearings, the friction coefficient between the friction pairs can be effectively decreased by employing the suitable surface texture on the frition surface. In the study, the distribution and depth variation of the surface texture were used as variables, and the genetic algorithm was used for iterative optimization to obtain the optimal texture distribution and depth. The friction and wear performance of the rectangular texture bearing sliding blocks was optimized. The depth of the texture was represented by a 4-bit binary number, and different binary numbers were set to represent different texture depths. Finally, the genetic algorithm was used for continuous iteration and evolution to obtain the optimal texture combination. The study showed that, compared with the regular texture with a depth of 0.2 μm, the friction coefficient decreased by 15.0% under the optimal texture with a non-uniform depth. Simultaneously, compared with the regular 3 μm deep texture, texture with a optimized depth makes the friction coefficient decreased by 37.5%, and the minimum oil film thickness increased by 0.979 μm. The optimal texture and oil film thickness combination obtained from the study can effectively reduce solid contact force and alleviate mechanical wear.

Evidence of Vertical Slab Tearing in the Late Triassic Qinling Orogen (Central China) From Multiproxy Geochemical and Isotopic Imaging

AbstractThe process of slab tearing profoundly affects interchanges of material and energy between the lithosphere and asthenosphere and has been invoked as a trigger of magmatism in modern and ancient subduction‐collision systems. Horizontal slab tears may occur after continental collision and subsequent slab break‐off, whereas vertical slab tears may occur in response to along‐strike variations in rollback velocity, thereby ripping the subducting lithosphere. Previous studies have documented tearing of subducting slabs in modern convergent settings using geophysical methods, but in ancient collisional belts, where these methods cannot be applied, detection of slab tearing is more difficult, particularly if the oceanic plate was fully subducted and the geological evidence for subduction is limited. Here, we employ multiproxy element‐isotope imaging, as well as zircon petrochronology and whole‐rock geochemistry, to assess evidence of vertical tearing of the Mianlue slab in the Triassic Qinling Orogen in central China. Our results show evidence of anomalous, inferred tear‐related magmatism east of 107°E, at 225–210 Ma. Vertical tearing of the northward subducting Mianlue slab is recorded by geochemically anomalous igneous rocks, and the recognition of N–S to NE–SW trending boundaries defined by Sr‐Nd‐Hf isotopes, elemental ratios (Nb/Ta, and Ca/Al), Mg#, and reduced crustal thickness between 107° and 108°E. The inferred vertical tear may have been driven by slab rollback of the Mianlue slab at 225–210 Ma. The results show that multiproxy element‐isotope imaging (e.g., of εNd(t), εHf(t), (87Sr/86Sr)i, Nb/Ta, Mg#, and Ca/Al) can be used to reconstruct the evolution of fossil subduction systems.

Slab tearing in non-collisional settings: Insights from thermo-mechanical modelling of oblique subduction

The propagation of slab break-off (slab tearing) is usually attributed to laterally variable plate convergence systems with a spatial transition between simultaneous oceanic subduction and continental collision. To study the process of slab tearing in a non-collisional geodynamic context, here we use a 3D thermo-mechanical numerical approach to model the oblique subduction of a homogeneous oceanic plate. We investigate the effects of the following parameters: (1) subduction obliquity angle, (2) age of oceanic slab, and (3) partitioning of boundary velocities (i.e., the ratio between the subduction component and the advance of the overriding plate in the total convergence). In our simulations, the retreat of the subduction zone leads to a thinning of the fore-arc and back-arc lithosphere, which are decoupled from the subducting slab by the rise of the hot asthenosphere from the underlying mantle wedge. As a consequence of the initial obliquity of the active plate margin, slab roll-back velocities are subject to progressive along-trench variations. Consistent with the gradual rotation of the trench, the front of the decoupling between the overriding and downgoing plates (together with predicted magmatic activity and topographic uplift) migrates in a horizontal direction. In the experiments with low angles of subduction obliquity (< 15°), relatively old subducting plates (> 50 Ma), and in the absence of the subduction component in the overall shortening, slab detachment either develops simultaneously along the entire length of the subduction zone or does not occur at all. In contrast, with higher subduction obliquity (≥ 15°), younger slabs (≤ 50 Ma) and in the presence of a boundary push on the oceanic side, the initial slab break-off is followed by the gradual growth of the “tear” window in the direction opposite to the migration path of the previously established plates decoupling. The sharp contrast in trench retreat rates between subduction zone segments affected and unaffected by slab detachment results in the arcuate shape of the trench. Furthermore, the direction of slab tearing may change from horizontal to vertical, eventually leading to the formation of a transform fault on the subducting plate. Our results show striking similarities with several features – such as trench curvature, subduction zone segmentation, magmatic production, lithospheric stress/deformation fields, and associated topographic changes – observed in many subduction zones (e.g., Marianas, New Hebrides, Mexico, Calabrian).

A ductile tearing assessment diagram for cracked circular-hollow-section joints under reversed loadings

This paper proposes a ductile tearing assessment diagram (TAD) to predict the load resistance to the crack extension relationship during the stable tearing process of the circular-hollow-section (CHS) joints under the reversed in-plane bending actions. The tearing assessment diagram utilizes the envelope of the load-deformation curve from the fracture test under reversed loadings to build the connection among the fracture resistance, load resistance and crack extension. To verify the proposed approach, this study performs fracture experiments, imposing the reversed in-plane bending on the CHS X-joints, made of Q345 steel, with a surface crack near the weld toe. The experimental investigation reveals the effect of the reversed loading on the fracture resistance and validates the TAD-based assessment for tubular joints. Meanwhile, this study performs the cyclic fracture test on the single-edge-notched-tension [SE(T)] specimen made of Q345 steel and derives the TAD from the experimental record of the SE(T) specimen. The specimen-based assessment successfully predicts the load versus crack extension relation for the reported joints under reversed loadings. The study provides a basic framework to predict the joint response under reversed loadings by integrating the material fracture characteristics.

Origin of Late Triassic Granitoids of the Coastal Cordillera of Southern Central Chile (34°–37°S): Multi‐Isotopic Evidence of Slab Tearing Effects on Pre‐Andean Magmagenesis

AbstractThe Coastal Cordillera of Central Chile (34°–37°S) holds a series of Late Triassic granitoids classically interpreted as early Andean subduction‐related magmatism based on their arc‐like geochemical signature. Here, we present geochemical, isotopic, and geochronological data and a tomotectonic analysis that challenge this idea indicating a local interruption of the normal subduction process likely associated with a slab‐tearing event. Our results suggest that the source of the magmas is related to melting of asthenospheric mantle and crustal rocks of a metasedimentary Paleozoic complex. We suggest that partial melting of these sources was triggered by a slab tear‐related asthenosphere upwelling producing high‐silica S/I‐ and S‐Type granites of the Constitución and Hualpén areas, and anorogenic A‐Type granitoids in Cobquecura area. Also, partial melting of a metasomatized asthenospheric mantle plus continental crust that experienced previous high‐temperature hydrothermal alteration would have generated high‐silica magmas with low δ18O, high Pb, CHUR‐like 87Sr/86Sr, and 143Nd/144Nd ratios that originated La Estrella Granite. Our results offer an alternative explanation for the existence of subtle magmatic arc‐like geochemical signatures in the study area and support a segmentation of the active margin during the Late Triassic. The widespread upper‐plate magmatic record of slab‐tearing, spanning the Coastal Cordillera of Central Chile to the intraplate Neuquén basin in Argentina, and the lower mantle record of a slab gap, detected in ours and previous tomotectonic analyses, make the Late Triassic slab‐tearing event in southwestern Pangea the most robustly constrained pre‐Cenozoic slab tear process so far.

Hot Tearing analysis and process optimisation of the fire face of Al-Cu alloy cylinder head based on MAGMA numerical simulation

ABSTRACT This paper proposes a casting improvement process to enable the casting of Al-Cu alloy cylinder heads to achieve the required quality. The hot tearing defects generated in the fire face of the cylinder head during casting were simulated using MAGMA software. The simulation results show that the large wall thickness transition difference in the fire face of the cylinder head is the reason for the large temperature and stress gradient during solidification. Therefore, the first solution was optimised by forming the fire face as a whole into a flat plate, but the fire face centre area stress is still too high. The second optimisation option optimises the cold iron structure of the fire face, the probability of cracking in the fire face is reduced to 17%. These results have important reference significance for the optimisation of the Al-Cu alloy cylinder head hot tearing problem.

High-Speed Imaging Analysis of Laminated Fabric Tearing Behaviour

Laminated fabrics are widely used in diverse industries because of their ability to adapt to many different functions. Understanding their tear force behaviour is critical to evaluate their serviceability. The tearing behaviour of laminated fabrics can be examined using high-speed imaging and analyzed using image analysis techniques. This technique is an attractive tool to elucidate the tearing behaviour of laminated fabrics. Through high-speed imaging it is possible to observe the tearing process on the fabric (e.g., yarns bearing the load before failure, yarn breaking behaviour) and membrane (e.g., pop-in crack length, crack propagation, formation of wrinkles, thinning) sides of the laminated fabrics to understand the tearing behaviour. In addition, this technique helps quantify different phenomena such as the membrane pop-in crack length, and crack wake bridging width by yarns. High-speed imaging analysis is a promising technique to visualize the tear phenomena in laminated fabrics.

Extracorporeal Shockwave Treatment for Low Back Pain

Low back pain is a common symptom in patients with chronic musculoskeletal conditions, affecting several individuals. In most cases, low back pain can often prove to be nonspecific or even multifactorial. Current treatment approach is based on surgical and noninvasive interventions, including pharmacological, psychological, physiotherapeutic, or complementary strategies. Extracorporeal shock wave therapy (ESWT) is a type of noninvasive mechanotherapy that has become popular in recent years due to its applicability in the treatment of various musculoskeletal disorders, especially in the lumbar spine of individuals with osteopo-rosis, sacroiliitis, and even spinal cord disorders. The objective of this manuscript is to review the scientific evidence supporting the application of this therapy in the management of low back pain, and give a brief description of the treatment techniques used in clinical settings. The articles included in this descriptive review were selected from databases using the Google Scholar tool, from which a total of 13 applicable studies matching the topic were included. Despite the need for more clinical trials, shock waves have been applied in medical health for many years with satisfactory results. Its application in the treatment of lumbar spine disorders has been shown to be advantageous in the management of pathological progression, such as the natural wear and tear process of musculoskeletal structures. In this sense, shockwave therapy may represent a viable alternative for the treatment of lumbar spine disorders; however, its therapeutic effects andmechanisms require further elucidation.

Geochemistry and geochronology of the Miocene adakite-like potassic dikes in Tethyan Himalaya: New insights into Indian lithosphere slab tearing and breakoff

Adakitic and potassic magmatic rocks are widespread in the Himalaya and the Tibetan Plateau, and their petrogenesis might provide potential insights into the deep crustal processes. However, the detailed spatiotemporal distributions of these rocks and their controlling mechanisms remain ambiguous. Here we report geochemical data, zircon U-Pb ages and Hf isotopic compositions of east-west (E-W) directed Qunrang monzonite porphyry dikes located in the Tethyan Himalaya. These rocks are acid and potassic with low Mg, low abundances of compatible elements, low Y and HREE, but with high Al, high Sr (822–1386 ppm) and Ba (2027–6091 ppm), high Th (62–84 ppm), U (9–16 ppm) and Th/U ratios (4–7), and thus high Sr/Y and (La/Yb)N ratios. The above geochemical features, combined with their negative whole-rock εHf(t) values (−3.9 to −4) and negative to small positive zircon εHf(t) values (−7.2 to +0.5), suggest that they were derived from partial melting of a thickened lower continental crust consisting mainly of garnet-amphibolite which were triggered and hybridized by underplating enriched mantle-derived shoshonitic melts. Zircon U-Pb ages of the Qunrang monzonite porphyry yielded a weighted mean age of 10.02 ± 0.33 Ma. Based on these observations, synthesized with the spatiotemporal distribution of the Oligocene-Miocene adakitic and potassic rocks in the southern Tibet, we propose that lateral detachment and longitudinal tearing processes might be potentially accounted for the eastward and southward younging trend of these magmatic rocks, whereas slab rollback and hinge advance might result in the unique E-W directed Qunrang adakite-like potassic dikes and the northward reversal younging trend.

Study on fracture behavior of pipeline girth weld based on CTOD-Am method and Gurson ductile damage model

The mechanical properties of the materials in different regions of the pipeline girth weld are sometimes quite different, which will produce a more significant material constraint effect and complicate the fracture behavior of the girth weld. Therefore, this work adopts the finite element method combined with the material damage model to study the ductile tearing process of the weld. The results of the single edge notched bending (SENB) specimens with the weld center crack show that for the welds with different mismatch conditions, with the increase of the weld mismatch coefficient, the crack tip constraint decreases gradually, and the fracture toughness increases gradually. The smaller weld width will make this effect more significant. When the ratio of the weld width to the specimen width is larger than or equal to 0.43, the BM will basically no longer affect the crack tip constraint and the fracture toughness of the weld. The results of the SENB specimens with the interface crack show that for the overmatched weld, with the increase of the weld mismatch coefficient, the crack first grows along the interface and then deflects into the heat affected zone (base metal). When the weld mismatch coefficients are 1.44 and 1.86, the corresponding deflection angles are 14.84° and 24.61°. For undermatched weld, with the decrease of the weld mismatch coefficient, the crack growth will deflect into the weld metal. When the weld mismatch coefficients are 0.69 and 0.6, the corresponding crack growth deflection angles are 14.04° and 25.36°. The larger the degree of the weld mismatch, the more significant the deflection of the distribution of the equivalent plastic strain and the stress triaxiality ahead of the crack tip. The effect of the specimen thickness on the deflection angle of the interface crack growth is small. The verification shows that the numerical analysis results of this study are valid.

Analysis of wear surfaces on parts of revisionally removed implants

Nowadays, with increasing average age - and thus an increase in active years - and the heightened pace of life in our cruel, fast-paced world, our bodies are subjected to extreme stress for ever-longer periods. Unfortunately, this lifestyle does not go away without a trace - it can cause damage to everything from our skeletal system to our nervous system, and our joints are no exception - which is why arthroplasty procedures are becoming increasingly popular. Arthroplasty is one of the most successful surgical procedures, which seeks to re-condition, replace - in some cases remove - the joint surfaces to improve the function of the system or at least preserve its current status. The most common form of arthroplasty is the implantation of joint endoprostheses. These devices have a finite lifespan, like all engineering structures, so their replacement at certain intervals, by means of revision surgery, is essential. The prostheses removed in this way carry a wealth of essential information about their design, their manufacturer and even their user and implantor, which can be incorporated into the design of the next generation of systems using reverse engineering, thus moving closer to the development of the "gold standard" implant. The topic of our article is the analysis and exploration of the failure processes of hip, knee, and shoulder implants removed by revision. We will build a model that adequately represents the wear and tear processes of different types of prostheses, with the help of which the wear and tear processes can be determined and predicted, and the strengths and weaknesses of the constructs can be determined. We consider it essential to distinguish between the different types of damage since, without a comprehensive knowledge of their extent, it is impossible to prevent them effectively. Systems grouped according to implant type and implant modality were examined using 3-dimensional imaging. We determined the degradation of the polymer components caused by use, observing to distinguish between damage caused by revision surgery and damage caused by transportation and storage. During our measurements, particular care was taken to identify the exact extent of creep and wear in order to make the best possible recommendations for modifications to existing systems.

Design and application of a multichannel “cross” hot tearing tendency device: A study on hot tearing tendency of Al alloys

Hot tearing is one of the most serious defects during the casting solidification process. In this study, a new type of multichannel “cross” hot tearing device was designed. The hot cracks initiation and propagation were predicted by the relationship between temperature, shrinkage force and solidification time during the casting solidification process. The reliability and practicability of the multichannel “cross” hot tearing device were verified by casting experiments and numerical simulations. The theoretical calculation based on Clyne-Davies model and numerical simulation results show that the hot tearing tendency decreases in the order: 2024 Al alloy>Al-Cu alloy>Al-Si alloy at a pouring temperature of 670 °C and a mold temperature of 25 °C. Feeding of liquid films at the end of solidification plays an important role in the propagation process of hot tearing. The decrease of hot tearing tendency is attributed to the feeding of liquid film and intergranular bridging.

The experimental and numerical studies on load bearing capacity in lamellar tearing of friction stir lap weld

The load bearing capacity in lamellar tearing is one of the key mechanical properties for the friction stir lap welding which has not been investigated before. Both numerical model and experiments were used to study the load bearing capacity in lamellar tearing of friction stir lap weld. The constitutive model of the weld zone in the crack propagation model was obtained by the combination of the proposed precipitate evolution model and the moving heat source model, and the effectiveness of the model was verified by comparing the numerical data with the experimental data. Results indicate that the crack initiated from the keyhole and propagated on the centerline of weld along the weld direction. The rotation of the joint region in the tearing process is a key factor for the increase of the load capacity in the tearing test and the simulation. The joint region can be rotated in the tearing process and the rotation angle can be increased with the increasing of weld length. The load bearing capacity along the weld direction is linearly increased with the increasing of the weld length.