Von Mises Stress Distribution Research Articles

NUMERICAL ANALYSIS OF SEISMIC RESPONSE OF STEEL CYLINDRICAL LNG STORAGE TANKS

Numerical analysis of the seismic response of steel cylindrical LNG (liquified natural gas) storage tanks is essential to designing such structures to ensure their safety and structural integrity during earthquake events. The seismic analysis involves the assessment of the tank's response to ground motion and evaluating its structural performance under seismic loads. The LNG storage tanks' seismic behavior is rarely reported when the tank is subjected to strong earthquakes. This paper evaluates the vibration characteristic (modal analysis) and the seismic response analysis, e.g., time history response, displacement vs. time, and distribution of the maximum Von-Mises stresses of the perfect cylindrical storage tanks. This paper uses the finite element analysis (FEA) technique using ABAQUS CAE-2019 to evaluate the seismic capacity in peak ground acceleration (PGA). Three perfect cylindrical tanks (PCT) have been considered first for modal analysis, with two having high-yielding strength and the rest with low-yielding strength. Then El-Centro 1940 seismic waves are applied as a horizontal ground motion at the fixed base of the tanks. Finally, the results from the modal analysis regarding the first natural frequency of the tank models are compared with those obtained from experiments. The result’s comparisons illustrate that the numerical simulation agrees well with the experimental test results.

A finite element analysis of stress distribution with various directions of intermaxillary fixation using orthodontic mini-implants and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy.

This finite element analysis (FEA) aimed to assess the stress distribution in the mandible and fixation system with various directions of the intermaxillary fixation (IMF) using mini-implants (MIs) and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy (BSSRO). A total of nine mandibular advancement models were set according to the position of the MIs (1.6 mm in diameter, 8 mm in length) and direction of the IMF elastics (1/4 inch, 5 oz). Major and minor principal stresses in the cortical and cancellous bones, von Mises stresses in the fixation system (miniplate and monocortical screws), and bending angles of the miniplate were analysed. Compressive and tensile stress distributions in the mandible and von Mises stress distributions in the fixation system were greater in models with a Class III IMF elastic direction and a higher IMF elastic force than in models with a Class II IMF elastic direction and a lower IMF elastic force. The bending angle of the miniplate was negligible. Stress distributions in the bone and fixation system varied depending on the direction, amount of force, and position of IMF elastics and MIs. Conclusively, IMF elastics in the Class II direction with minimal load in the area close to the osteotomy site should be recommended.

Mechanical influence of tissue scaffolding design with different geometries using finite element study.

The mechanical properties of tissue scaffolds are essential in providing stability for tissue repair and growth. Thus, the ability of scaffolds to withstand specific loads is crucial for scaffold design. Most research on scaffold pores focuses on grids with pore size and gradient structure, and many research models are based on scaffolding with vertically arranged holes. However, little attention is paid to the influence of the distribution of holes on the mechanical properties of the scaffold. To address this gap, this research investigates the effect of pore distribution on the mechanical properties of tissue scaffolds. The study involves four types of scaffold designs with regular and staggered pore arrangements and porosity ranging from 30% to 80%. Finite element analysis (FEA) was used to compare the mechanical properties of different scaffold designs, with von-Mises stress distribution maps generated for each scaffold. The results show that scaffolds with regular vertical holes exhibit a more uniform stress distribution and better mechanical performance than those with irregular holes. In contrast, the scaffold with a staggered arrangement of holes had a higher probability of stress concentration. The study emphasized the importance of balancing porosity and strength in scaffold design.

Seismic performance of bolted T-stub Beam-to-Box column connection

Using internal continuity plates in box columns due to accessibility problems and complicated detailing of connection was perceived as fraught with shortcomings and limitations. To overcome this deficiency, the effectiveness of external continuity plates in conjugation with T-stub connectors in I-beam to box-column connections under cyclic action is investigated in this study. Three damage control strategies based on the fuse action of T-stubs (T-F), strengthening the connections (T-S), and using reduced beam section (RBS) connections (T-R) are pursued and are compared to a corresponding end-plate connection (E). Nonlinear finite element analyses are conducted using the ABAQUS/STANDARD software on the connections under the qualification cyclic loading conditions to elucidate all the main seismic behavioral aspects, including the strength, initial stiffness, energy dissipation, ductility, von-Mises stress, and equivalent plastic strain distributions of models. First, the accuracy of numerical models is validated by a series of available experimental results. Then, a parametric study is performed on the effects of the moment ratio of the beam to column, the number of continuity plates, stiffeners embedded on the beam, and using high strength materials on the seismic performance of the connections. From the results, it is found that the T-S model was the most efficient among the different connections studied, supplying the stiffness, strength, energy absorption, and ductility increases by 2%, 21%, −17%, and 22%, respectively with respect to the E model, satisfying the requirements of AISC Seismic Provisions for SMF. Increasing the beam-to-column moment ratio and the number of continuity plates, had limited effects by less than 10% on the seismic performance of the connections. In the absence of continuity plates, the connections exhibited worse inelastic seismic performance with decreases in stiffness, strength, and energy dissipation up to 67%, 44%, and 74%, respectively. The T-F connection gained a 13% strength increase and satisfied the AISC requirements when high-strength T-stubs are used. Based on the numerical observations, design strength and rotational stiffness of the proposed connections on the component-based joint design strategies, are finally outlined.

Establishment of finite element model of varus-type ankle arthritis and biomechanical analysis of different correction models for tibial anterior surface angle

To establish the finite element model of varus-type ankle arthritis and to implement the finite element mechanical analysis of different correction models for tibial anterior surface angle (TAS) in supramalleolar osteotomy. A female patient with left varus-type ankle arthritis (Takakura stage Ⅱ, TAS 78°) was taken as the study object. Based on the CT data, the three-dimensional model of varus-type ankle arthritis (TAS 78°) and different TAS correction models [normal (TAS 89°), 5° valgus (TAS 94°), and 10° valgus (TAS 99°)] were created by software Mimics 21.0, Geomagic Wrap 2021, Solidworks 2017, and Workbench 17.0. The 290 N vertical downward force was applied to the upper surface of the tibia and 60 N vertical downward force to the upper surface of the fibula. Von Mises stress distribution and stress peak were calculated. The finite element model of normal TAS was basically consistent with biomechanics of the foot. According to biomechanical analysis, the maximum stress of the varus model appeared in the medial tibiotalar joint surface and the medial part of the top tibiotalar joint surface. The stress distribution of talofibular joint surface and the lateral part of the top tibiotalar joint surface were uniform. In the normal model, the stress distributions of the talofibular joint surface and the tibiotalar joint surface were uniform, and no obvious stress concentration was observed. The maximum stress in the 5° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress distribution of medial tibiotalar joint surface was uniform. The maximum stress of the 10° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress on the medial tibiotalar joint surface increased. With the increase of valgus, the stress of ankle joint gradually shift outwards, and the stress concentration tends to appear. There was no obvious obstruction of fibula with 10° TAS correction. However, when TAS correction exceeds 10° and continues to increase, the obstruction effect of fibula becomes increasingly significant.

Enhanced mechanical and tribological properties of polymer nanocomposites by improving interfacial properties by hexagonal boron nitride nanosheets: Molecular dynamics simulations

AbstractTo comparatively investigate the mechanical, tribological, and interfacial properties of polytetrafluoroethylene (PTFE) strengthened by graphene (Gr) and hexagonal boron nitride (h‐BN) nanosheets, molecular models of PTFE nanocomposites containing a similar weight fraction of Gr and h‐BN nanosheets were established. The constant‐strain approach, the three‐layer friction structures, and the pull‐out simulations were respectively employed to calculate the mechanical, tribological, and interfacial properties of the nanocomposites. Results indicate that the Young's, shear, and bulk moduli of the nanocomposites are increased by 17.22%, 20.72%, and 4.78%, respectively, by introducing h‐BN nanosheets than those by introducing Gr nanosheets. Meanwhile, a decrease of 8.49% in the friction coefficient of the nanocomposites is obtained by incorporating h‐BN nanosheets than that by incorporating Gr nanosheets. In addition, 84.71% and 5.18 times higher in the interfacial cohesive strength and interfacial shear strength, and 91.58% and 128.7% higher in the interfacial fracture toughness of PTFE nanocomposites in the normal separation and shear separation, respectively, are achieved by incorporating h‐BN nanosheets than those by incorporating Gr nanosheets. To provide a deeper understanding of the enhancement mechanisms of h‐BN nanosheets, the interfacial interaction energies, radial distribution functions, and von Mises stress distributions of the two PTFE nanocomposites were evaluated and interpreted accordingly.

Biomechanical Properties of Maxillary Second Molar with Different Endodontic Cavity Designs - A Finite Element Analysis.

To evaluate the biomechanical properties of maxillary second molars with three different cavity designs - Traditional, Conservative, and Extended - endodontic cavities using the finite element analysis method. Three finite element models of a maxillary second molar with three different types of endodontic cavities were designed and restored. Each model was subjected to three different force loads directed at the occlusal surface. The stress distribution patterns and the maximum von Mises (VM) stresses were calculated and compared. Vertical force of multipoint load on the occlusal surface and lateral forces to the palatal cusp showed the maximum stress values in the extensive cavity design, followed by the traditional cavity design and then the conservative cavity design. The VM stress distribution in the conservative endodontic cavity was minimal when compared to other access cavity designs.

Biomechanical analysis of different internal fixation methods for special Maisonneuve fracture of the ankle joint based on finite element analysis

ObjectiveThe objective of this study was to evaluate the biomechanical properties of different internal fixation methods for Maisonneuve fractures under physiological loading conditions. MethodsFinite element analysis was used to numerically analyze various fixation methods. The study focused on high fibular fractures and included six groups of internal fixation: high fibular fracture without fixation + distal tibiofibular elastic fixation (group A), high fibular fracture without fixation + distal tibiofibular strong fixation (group B), high fibular fracture with 7-hole plate internal fixation + distal tibiofibular elastic fixation (group C), high fibular fracture with 7-hole plate internal fixation + distal tibiofibular strong fixation (group D), high fibular fracture with 5-hole plate internal fixation + distal tibiofibular elastic fixation (group E), and high fibular fracture with 5-hole plate internal fixation + distal tibiofibular strong fixation (group F). The finite element method was employed to simulate and analyze the different internal fixation models for the six groups, generating overall structural displacement and Von Mises stress distribution maps during slow walking and external rotation motions. ResultsGroup A demonstrated the best ankle stability under slow walking and external rotation, with reduced tibial and fibular stress after fibular fracture fixation. Group D had the least displacement and most stability, while group A had the largest displacement and least stability. Overall, high fibular fracture fixation improved ankle stability. In slow walking, groups D and A had the least and greatest interosseous membrane stress. Comparing 5-hole plate (E/F) and 7-hole plate (C/D) fixation, no significant differences were found in ankle strength or displacement under slow walking or external rotation. ConclusionCombining internal fixation for high fibular fractures with elastic fixation of the lower tibia and fibula is optimal for orthopedic treatment. It yields superior outcomes compared to no fibular fracture fixation or strong fixation of the lower tibia and fibula, especially during slow walking and external rotation. To minimize nerve damage, a smaller plate is recommended. This study strongly advocates for the clinical use of 5-hole plate internal fixation for high fibular fractures with elastic fixation of the lower tibia and fibula (group E).

Experimental and Computer Simulation Studies on Badminton Racquet Strings.

This study investigates experimentally, numerically, and analytically the performance of different string materials (Kevlar, synthetic gut, natural gut, and polyester) on badminton racquets. Vibration and impact tests with a shuttlecock were performed using a racquet frame made of carbon graphite mixed with epoxy resin. Different string tensions were considered in the tests (20, 22, 24, 28, 30, and 34 lb), as well as different hitting locations on the racquet frame. The results show that, as the diameter of the strings increased, the elasticity of the string decreased from 0.529 to 0.447 for diameters ranging from 0.62 to 0.70 mm. Subsequently, a badminton racquet and shuttlecock were modeled using SolidWorks2018® software (version 26), and a maximum displacement was applied to the ball to simulate an impact on the string bed. The natural frequency, maximum deformation and maximum stress were calculated analytically, and a finite element analysis was also performed using ANSYS2022 R2® software (version 22.2). The analytical and numerical results from ANSYS® showed good agreement (within 5% accuracy). The results of the study show that the natural frequency of a racquet with Kevlar strings was significantly higher than that of racquets with synthetic gut, natural gut, or polyester string materials. Specifically, the natural frequency of a racquet made of carbon graphite and epoxy resin was 23.0%, 30.7%, and 36.2% higher than that of racquets with synthetic gut, natural gut, and polyester string material, respectively. On the basis of this finding, Kevlar was chosen as the preferred material for badminton racquets strings, and a parametric analysis was then conducted. The study showed that slightly lowering the tension of the off-centered strings had a minimal effect on the von Mises stress distribution of the ball and string bed. In addition to investigating string materials, this study also examined the effects of pull and diameter variations of racquet strings on vibrations during impact. This study contributes to the understanding of the role of racquet and strings in badminton, and it also provides new insights into the factors that can affect performance in the sport. By analyzing the performance of different string materials and examining the effects of pull and diameter variations of racquet strings, this study provides valuable information for players and manufacturers looking to optimize their equipment for maximum performance.

A finite element model of the elastic planar and spherical contact with hard and soft coatings

A finite element model of a rigid sphere contact with a deformable coating flat was used to study the elastic contact between the soft and hard coatings. Meanwhile, the contact of a rigid flat and a deformable coating sphere under the same condition was used for comparison. The contact area, load, interference, and maximum equivalent von Mises stresses in the coating system were normalized by the corresponding elastic contact parameters. The empirical expressions for the above two models which contained a wide range of the mechanical and geometric properties in soft and hard coatings were established by fitting the numerical results. The changes in the location of the maximum von Mises stress distribution in the models’ soft and hard coatings were compared when the displacement loads were used. The relationships between the dimensionless maximum von Mises stress on the substrate and coating and the dimensionless contact parameters were provided when the elastic limit (plastic yield onset) occurred. The range of the dimensionless coating thickness which led to the onset of plastic yield in the coating was determined when the rigid sphere was contacting with the deformable coating flat.

Analysis of Sealing Characteristics of Lip Seal Rings for Deep-Sea Separable Pressure Vessels

Deep-sea pressure vessels are specialized pressure vessels designed for automatic deployment from underwater to the surface. These vessels find extensive applications in underwater life-saving and transportation. Their interiors are furnished with a pair of sealing rings, one of which is lip-shaped, and the other is a convex shape, to ensure a dependable seal. With increasing water depth, the sealing rings experience augmented pressure, resulting in a gradual pressing of the rings into the sealing groove. Using ANSYS workbench finite element software, a two-dimensional axisymmetric lip seal finite element model using forces for overall constraint was established, the complete process of progressive pressing into the sealing groove was simulated, and the deformation, contact stress, maximum shear stress, and von Mises stress distribution was also simulated. We also conducted a comparative analysis of lip seals under low and high-water pressure sealing conditions. The findings of the study indicate that when subjected to a combined effect of the installation pre-tightening force and the working water pressure, the lip seal experiences complete compression into the sealing groove at a specific water depth. When subjected to the simultaneous influence of water pressure on the sealing ring material and friction force on the contact surface, two extremes of contact stress manifest in the primary sealing zone of the lip seal. These extremes have the capacity to elevate the contact stress and the effective sealing width, ultimately leading to an improvement in the sealing performance. Concurrently, as the water pressure gradually increases, the inner concave circle of the sealing ring experiences stretching, leading to a reduction in stress concentration, equivalent stress, and shear stress to a considerable extent. This mechanism ensures that the lip-shaped sealing ring retains sufficient strength. This study offers a viable solution for conducting sealing studies on deep-sea separable pressure vessels.

A novel electromagnetic micropump with PDMS membrane supported by a stainless-steel microstructure

As a main component, membrane micropumps play a key role in developing microfluidic systems. This part pumps fluids by deflecting a membrane using a micro-actuator with a deflection range of a few micrometers during a few seconds. Most electromagnetic micropumps have low lifetime and fracture toughness or low recovery speed. Micropumps with metallic mass-spring structures can overcome the mentioned disadvantages or limitations. This study investigated the fabrication and characterization of a novel electromagnetic micropump. The proposed micropump consists of a stainless-steel mass-spring structure, a polydimethylsiloxane body and membrane, a permanent NdFeB magnet, a micro-coil, and a 3D printed spacer. To characterize the micropump, the effects of the frequency and duty cycle of the electric current applied to the micro-coil on the micropump flow rate and the membrane deflection vs. time were investigated. A membrane deflection of ±8 µm was obtained in 4 s by applying 1000 mA electrical current to the micro-coil. The maximum volumetric flow rate of 523 nl s−1 was obtained at a frequency of 125 mHz and a duty cycle of 50%. The von Mises stress distribution in the micropump membrane and variations of the fluid velocity in the microchannels were analyzed using the finite element method.

A novel arc-cantilevers F-P filter with low stress applicated in infrared spectral integrated photodetector chip

Infrared spectral detector technology represents a novel detection strategy that combines spatial information with infrared spectral data, expanding the traditional light-intensity image detection in the spatial dimensions (x, y) to include the spectral dimension (x, y, λ). Conventional spectral detection methods often involve system integration grating on the spectrometer, which suffers from drawbacks such as large size and high-power consumption. To overcome these limitations and enable miniaturization application, it is necessary to investigate the development of spectral integrated infrared detector chips, which include a crucial component known as a tunable filter. Our previous experimental work identified an issue with the Fabry-Perot (F-P) filter based on the conventional cantilever beam structure, where excessive surface stress caused tilting of the bridge deck, adversely affecting the filtering quality. In this study, a new tunable F-P cavity filter structure with low surface stress by arc cantilevers was proposed. The Von Mises stress distribution of the bridge surface was analyzed, revealing a 50% reduction in surface stress compared to the traditional right-angle structure. The newly proposed structure demonstrates excellent performance in terms of tunable infrared transmission filtering spectrum. The tunable wavelength range covers 3-5 μm, and the structure achieves a transmission value of 70%. This work establishes valuable theoretical guidance for the fabrication of cantilever microbridge filters in experimental work and their potential future applications in spectrally integrated detector chips.

Graph Neural Networks (GNNs) based accelerated numerical simulation

Finite element method (FEM) based high-fidelity simulation can be computationally demanding and time-consuming as engineering problems become more complicated. It is thus necessary to develop a surrogate model that only requires a small amount of computational time but retains sufficient accuracy. A graph neural network (GNN) based framework is proposed as a general surrogate model for FEM to simulate the Von Mises stress distribution. The mesh body is embedded to a graph and a novel global attribute representation is introduced to capture the geometry and boundary conditions while overcoming the common problem of over smoothing in graph deep learning. The challenge to deal with varying geometry and boundary conditions is overcome by the proposed model and thus it outperforms existing methods such as proper orthogonal decomposition (POD) and greedy algorithm in terms of generalization. Numerical experiments are given to demonstrate the capability of the model developed and the results show that the proposed model not only accurately predicts the stress distribution but also speed-ups hundreds of times faster compared to a FEM-based simulator, enabling real-time structural response analysis for the application of digital twin and structural health monitoring. It is indicated that GNNs can be a powerful tool for resolving complex physical problems, thereby assisting in advancing science and enhancing engineering productivity.

Strain Retarding in Multilayered Hierarchical Sn‐Doped Sb Nanoarray for Durable Sodium Storage

AbstractAntimony (Sb) is a potential electrode material for sodium (Na) storage due to its high theoretical capacity of 660 mAh g−1. Yet, the alloy/dealloy reaction between Na and Sb induces detrimental structural strain that inevitably leads to electrode failure, further resulting in deteriorated rate performance and cycle life. Herein, inspired by the multilayered structure of the pine trees, 3D hierarchical multilayered tin (Sn)‐doped Sb nanoarray coated with a thin carbon (C) layer (Sb(Sn)@C) is developed. Density functional theory calculation results suggest that Sb(Sn)@C offers better kinetic properties for Na diffusion, and lower volume expansion upon sodium intercalation as compared to the counterparts without Sn dopant or carbon coating. Moreover, the simulation results based on finite element analysis suggest that the unique hierarchical multilayered construction not only provides highly efficient Na+ utilization, but also builds a uniform von Mises stress distribution that effectively confines structural strain induced during Na+ insertion. This is also verified by nanoindentation measurement that Sb(Sn)@C shows higher elastic modulus and hardness than Sb(Sn) and pure Sb, indicating best mechanical stability. As expected, Sb(Sn)@C achieves excellent electrochemical capability for sodium storage with high reversible capacity, enhanced cyclability, and remarkable rate performance.

Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEM) of a Customized Stent-Graft for Endovascular (EVAR) Treatment of Abdominal Aortic Aneurism (AAA)

Background: The treatment of abdominal aortic aneurysm (AAA) is today commonly treated by inserting a stent-graft by the endovascular route, without resorting to open surgery. However, some clinical cases do not allow this less invasive approach, meaning that the stent-graft cannot be inserted and open surgery is used. Methods: In the study, we propose a fluid–structure interaction (FSI) analysis of an aneurysmatic aorta that could not be treated with Endovascular Aneurysm Repair (EVAR). The vessel is reconstructed through segmentation from CT scans and subsequently modeled on CAD software to create the surface and thickness of the vessel itself. Subsequently, we proceeded to carry out Computational Fluid Dynamics (CFD) and FSI simulation. We propose a computational study on a vessel geometry that is faithful to reality and customized. Results: Hemodynamic variable results of the carried out simulations indicate that low velocity and consequently very low WSS areas located in aneurysmal site are no longer found when conventional or patient-specific grafts are inserted. The wall stress distribution of aorta FEM analysis enabled the identification of the area at risk of failure, that is, in the posterior part of the aneurysm (∼107 Pa), while FSI analysis of the patient-specific graft led to a uniform von Mises stresses distribution (∼105 Pa), except for the junctions where peak stress occurred. Conclusion: The importance of this study is to highlight the benefits of the personalized stent/graft. As the authors expected, the study shows the numerous benefits of the customized stent/graft in terms of blood flow trend and wall stress compared to a traditional stent/graft by supporting the tendency to want to shift the target towards customized stents/grafts, also in the vascular surgery sector.

Stress-based optimization of assembly surface mechanical properties oriented to stress-uniform assembly

Stress-uniform assembly is favorable for ensuring the precision and performance stability of precision electromechanical systems. Process compensation, assembly process optimization and assembly surface topography optimization are three typical ways to regulate the assembly stress distribution. Assembly surface mechanical properties optimization is a new and promising technique for achieving uniform stress distribution in assembled parts. This study takes that direction and investigates how variation in assembly surface material stiffness (i.e., Young's modulus) give rise to the variation in von Mises stress in assembled parts. To homogenize the von Mises stress distribution in assembled parts, the stress-uniform assembly-oriented material stiffness optimization model is constructed on the basis of finite element discretization. A stress-based material stiffness optimization method, which does not require sensitivity analysis, is developed by directly linking the amount of change in material stiffness to the value of von Mises stress. The feasibility and effectiveness of the stress-based assembly surface material stiffness optimization are demonstrated by a design case containing three elastic contact bodies, where both single-load and multi-loads conditions are considered. Some new phenomena during the assembly surface material stiffness optimization are also observed and explained.

Two-screw osteosynthesis of the mandibular condylar head with different screw materials: a finite element analysis

This study compared the biomechanical behavior of titanium, magnesium, and polylactic acid screws for two-screw osteosynthesis of mandibular condylar head fractures using finite element analysis. Von Mises stress distribution, fracture displacement, and fragment deformation were evaluated. Titanium screws performed the best in terms of carrying the highest load, resulting in the least fracture displacement and fragment deformation. Magnesium screws showed intermediate results, while PLA screws were found to be unsuitable with stress values exceeding their tensile strength. These findings suggest that magnesium alloys could be considered a suitable alternative to titanium screws in mandibular condylar head osteosynthesis.

Modeling the Crack Interference in X80 Oil and Gas Pipeline Weld.

Based on the numerical simulation method of the virtual crack closure technique (VCCT), an interference model was established to investigate the physical problem of two interacting cracks of different sizes in the welding zone of oil and gas pipelines. The obtained results of the current interference problem were compared with those of single crack case. Various crack configurations, such as different crack spacing and different crack sizes, were analyzed. The characteristic quantity fluid pressure load P during the crack propagation process, the peak value of the von Mises stress distribution field of the crack growth path, as well as the difference ∆Bx between the peak value of the magnetic induction intensity component at the crack and the value of the magnetic induction intensity component at its symmetrical position were calculated. The crack interaction scale factors, including γP, γMises, and γΔBx, were compared and analyzed. The numerical modeling results show that when the unequal-length double cracks interfere with each other, the cracks are more likely to propagate toward each other. The tendency of the double-cracks to propagate toward each other gradually weakens as the distance between the crack tips increases and is finally the same as that of single-crack cases. It was also found that the effect of large-sized cracks on small-sized cracks is greater than that of small-sized ones on large-sized ones. The numerical modeling results could be applied for the prediction and analysis of multicrack damage in oil and gas pipeline welds.

Nano-tribological behavior of CuCoCrFeNi high-entropy alloys at cryogenic temperature: A molecular dynamics study

High-entropy alloys exhibit great potential for cryogenic applications. This study investigates the nano-scratching behavior of CuCoCrFeNi high-entropy alloy at a cryogenic temperature (77 K) using molecular dynamics. Results show that compared with the single-grain model, the average friction coefficient (AFC) increases for all three polycrystalline models with different grain sizes d, but the anti-wear property can be improved by 28.5%, when grain size d = 10.7 nm. The smaller friction on the scratching surface of the single-grain model (AFC is 15.5% less than that of the model with d = 8.2 nm), which makes the overall temperature rise lower compared to that of the polycrystalline models. However, due to the stress concentration released when a complete stacking fault tetrahedron is produced, the single-grain model cannot significantly harden the surface and subsurface to a greater degree. In the polycrystalline models, dislocations are blocked at grain boundaries (GBs). However, the introduction of GBs changes the von Mises stress distribution. Finally, an attempt was made to reveal the role of yield pressure H3/E2 (H—hardness, E—elastic modulus) in friction-reducing and anti-wear properties.