Characteristics Of Joints Research Articles

Shear mechanism and bearing capacity calculation of steel fiber reinforced concrete beam-column joints

Based on the strut-and-tie model, the shear mechanism of steel fiber reinforced concrete (SFRC) beam-column joints is analyzed. In addition, based on the stress characteristics of SFRC beam-column joints, the influence of randomly distributed steel fibers at the cracks is equated to the effective bond stress of the steel fibers. Consequently, a formula for calculating the shear capacity of SFRC beam-column joints is proposed. Furthermore, a database of 132 SFRC beam-column joints is compiled. Based on the database, the proposed calculation method is optimized using statistical analysis method. Furthermore, the contributions of concrete, stirrups, and steel fibers to the shear bearing capacity are discussed. Finally, the proposed calculation method is compared with the existing calculation methods to validate the accuracy of the model. The results indicate that the shear bearing capacity provided by concrete can reach 90% of the total shear bearing capacity. The maximum shear bearing capacity provided by stirrups and steel fibers is 27% and 26% of the total shear bearing capacity respectively. When the stirrup ratio exceeds 1%, the enhancement of shear bearing capacity by the stirrups becomes more pronounced. Compared to straight steel fibers, hooked-end steel fibers can better enhance shear capacity. The proposed calculation method demonstrates higher accuracy compared to existing calculation methods, which can be used to predict the shear bearing capacity of SFRC beam-column joints.

Deformation behavior study of SAC305 solder joints under shear and tensile loading by crystal plasticity finite element method.

Micro solder joints experience various loads during operation, and the failure of a single micro solder joint can impact the overall reliability of the entire microsystem. This study utilized the Crystal Plasticity Finite Element Method (CPFEM) to create a polycrystalline model that accurately represents the shape of solder joints. By calibrating the crystal plasticity characteristics of SAC305 material solder joints using macroscopic stress-strain curves, the model successfully simulates the deformation mechanisms of micro-solder joints under both tensile and shear loads. This paper highlights that equivalent plastic strain serves as a key indicator of solder joint fracture behavior, revealing that strain components have varying effects on cracking: shear strain was found to cause crack initiation, while normal strain was found to promote crack extension. Moreover, Grain boundary features and orientation lead to uneven plastic strain by affecting the slip system and the Schmidt factor, especially small Schmidt factor grains at triple grain boundary intersections are more susceptible to crack initiation. Additionally, the study found that solder joints exhibit more pronounced mechanical responses under tensile loading compared to shear loading. These insights offer valuable guidance for the design and manufacturing of micro-solder joints.

Shared lung and joint T cell repertoire in early rheumatoid arthritis driven by cigarette smoking

ObjectivesSmoking has been associated with an increased risk of developing rheumatoid arthritis (RA) in individuals carrying shared epitope (SE) HLA-DRB1 alleles. Yet, little is known about the regional and systemic...

Motion controller for multi-joint robotic arm with deep cascade gated Bayesian broad learning system

Intelligent controllers based on the broad learning system can simplify the process of model parameter adjustment, finding wide applications in the motion control of multi-joint robotic arms. However, motion controllers for multi-joint robotic arms based on broad learning system exhibit insufficient precision and overlook the impact of joint motion commonalities on controller design. Therefore, this paper proposes a novel motion control strategy for a multi-joint robotic arm based on a deep cascade feature-enhancement gated Bayesian broad learning system. Firstly, the motion controller of the deep cascade feature-enhancement Bayesian broad learning system is constructed to enhance the robotic arm motion control precision. Secondly, an incremental node generation module with an attention-gated mechanism is constructed to capture the unique motion characteristics of the target joints, which is further combined with model generalization to simplify the motion control process of the multi-joint robotic arm. Finally, controller convergence is enhanced by combining it with the Lyapunov theory to constrain the learning parameters. Simulations and physical experiments are designed to verify the feasibility and superiority of the proposed motion control strategy. The results demonstrated that the strategy improved the accuracy of robotic arm motion control, with the root mean square error in position tracking reduced to 0.0019 rad. This represents a 93.39% reduction in error compared to existing techniques.

Reliability-based capacity safety factor for G20Mn5 cast steel joints

Cast steel joints have complex geometries and great load-carrying capacity, and hence their resistances are commonly determined through FE simulations. Considering the significant variability in the material mechanical properties (that in fracture strains, in particular) and the model uncertainty inevitably involved in the FE analysis, a large safety factor (γR) should be adopted for the FE simulation-based design of cast steel joints. However, the γR-values specified by the current design specifications, e.g. the Chinese standard CECS 235: 2008 in which γR = 3.0, are deemed to be overly conservative. This paper examined the structural reliability of G20Mn5 cast steel joints to provide a rational γR-value for the practical joint design. The above-mentioned uncertainty of the material and geometric properties as well as the model uncertainty related to FE simulations are evaluated, and Monte Carlo simulations were conducted on nine representative joints to obtain the statistical characteristics of cast steel joints’ ultimate resistance, allowing for both failure modes of material fracture and instability caused by large-scale yielding. FORM was adopted to calculate the reliability index β for the assumed γR-values and different loading scenarios, and the recommended values for γR under target reliability indices are proposed. For snow load-dominant and wind load-dominant load combinations, the recommended γR corresponding to β = 4.2 are 2.29 and 2.16, respectively, and the recommended γR corresponding to β = 3.7 are 2.01 and 1.90, respectively.

The influence of external and internal factors on ensuring adhesive interaction of a polymeric sealant with a substrate surface (a review)

This paper analyzes literature data on the influence of various factors affecting the strength and durability of adhesive bonds, as well as presents a characterization of the methods described in the literature for conducting relevant studies. It is shown that one of the main characteristics of adhesive joints is the interaction at the interface between the substrate and the adhesive. The adhesive capability of a sealant largely depends on the structure of the polymer component, as well as the presence of components in the sealant that enhance this property. The structure and condition of the substrate surface significantly affect the nature of the interaction between the adhesive and the substrate. Various methods are used to determine the strength of the adhesive bond, differing in the type of applied loads and the nature of the surface fracture. An important indicator is the determination of the wetting angle of the substrate by the sealant, which characterizes the surface energy. The durability of adhesive bonds is significantly influenced by environmental factors as well as operational conditions. Moisture, atmospheric oxygen, ultraviolet radiation, and microorganisms have a particularly strong effect on the properties of polymeric sealants.

Population-based in silico modeling of anatomical shape variation of the knee and its impact on joint loading in knee osteoarthritis.

Anatomical knee joint features and osteoarthritis (OA) severity are associated, however confirming causals link to altered knee loading is challenging. This study leverages statistical shape models (SSM) to investigate the relationship between joint shape/alignment and knee loading during gait in knee OA(KOA) patients to understand their contribution to elevated medial knee loading in OA. Musculoskeletal (MSK) models were created for the mean as well as the first eightSSM principal modes of variation (-3,-2,-1, +1, +2, +3 standard deviations for each mode) and used as input to a MSK modeling framework. Using an identical KOA gait pattern (i.e., joint kinematics and ground reaction forces), we ran simulations for each MSK model and evaluated medial compartment loading magnitude and contact distribution at the instant of first and second peak of knee joint loading. An increase in external rotation, posterior tibia translation and a decrease in medial joint space and medial femoral condylar size predisposed the medial compartment knee joint to overloading during gait. This was coupled with an anterior and medial shift in contact location with increasing external rotated tibial position and increasing posterior tibial translation with respect to the femur. Next, results also highlighted a posterior shift of the medial compartment loading location with decreasing medial joint space. This study provides important population-based insights on how knee shape and alignment predispose individuals with KOA to elevated medial compartmental knee loading. This information can be crucial in assessing the risk for medial KOA development and progression.

Reliability analysis of support strategies in tunnel construction: Insights from geomechanical analysis of jointed rock masses

In this study, the dynamics of jointed rock masses in the challenging geological setting of the Himalayas, with a focus on tunneling activities and recommendations of support for jointing rock mass, were investigated. The jointing in Himalayan rocks mass poses significant implications for tunnel stability, demanding a detailed analysis of joint characteristics, such as joint connectivity and spacing. The parameter of joint connectivity rate along the Himalayas becomes a key focus, impacting rock mass strength for tunneling. The study utilized quadratic polynomial and reciprocal expressions of power functions, to characterize the nonlinear variation of jointed rock mass strength concerning joint connectivity rate. Integration of these results leads to unified equations that consider rock type dependence, having a realistic representation of jointed rock behavior. Numerical analysis reveals that jointing in rock affects instability through complex stress regimes, identifying critical stress concentration points. The effectiveness of support measures like rock bolts and shotcrete are validated, demonstrating their role in reducing displacements in tunnels.

Atomistic insights into cold welding process of high-entropy alloy nanowires

This research applied molecular dynamics (MD) simulations to investigate the influences of contact pressure, temperature, crystal orientation, and chemical composition on the characteristics of the cold welding joints of CoNiCrFeMn high-entropy alloy (HEA) nanowires. The findings indicate that defect-free cold welded joints can be successfully formed within a contact pressure range of 10 to 10,000 Pa. In addition, changing the contact orientation could cause a significant change in the structure transformation level. The dislocation distribution is continuous when the top and lower blocks are oriented in the same direction. Dislocation lines, on the other hand, stop at the interfacial area and have a discontinuous shape when the weld joints are formed from different orientations. Furthermore, creating from the same orientations leads to a higher ultimate tensile strength (UTS) value than the different orientation cases. In the temperature range of 150 K–350 K, the deformation behaviors of the cold weld joint are stable. Besides, there was no noticeable change in the weld joint when the composition changed. Because of the strong crystal structure of the cold welding joints, the UTS values of the cold-welded joints range from 13.2 to 17.4 GPa, comparable to the bulk samples.

Joint morphology, characteristics, and role of intermetallics in AA7075 friction stir lap joints with copper interlayer

Joint morphology, characteristics, and role of intermetallics in AA7075 friction stir lap joints with copper interlayer

Microstructure and mechanical properties of ultrasonically welded aluminum to Zn–Mg–Al coated and uncoated mild steels

The gaining popularity of aluminum alloys in the automotive industry demand the development of energy efficient joining methods of Al with other metals such as steel. Among such joining methods, ultrasonic welding is advantageous because it is cost effective and prevents metallurgical defects because of the low welding energy involved. This study evaluates the microstructural changes and mechanical properties of dissimilar ultrasonic welding of Al to Zn–Mg–Al-coated and uncoated mild steels. Various intermetallic compounds (IMCs), such as FeAl3, and Fe2Al5 with different thicknesses and morphologies were observed at the joint interfaces. The Al-to-Zn-Mg-Al-coated steel exhibited mechanical properties that are superior to those of Al-to-uncoated mild steel. The results are discussed in terms of microstructure evolution, joint characteristics, and interfacial reactions in the welds. This study contributes to the understanding of the mechanisms behind strong ultrasonic welding of dissimilar metals.

Which direction will electronic word-of-mouth (eWOM) choose? Dance drama eWOM's spatiotemporal characteristics and influencing factors

Compared with movie electronic word-of-mouth (eWOM) with concentration, retail eWOM with continuity, and accommodation eWOM with locality, dance drama eWOM is specific to time and space because of the performance of offline single-threaded touring. Dance drama is associated with a special cultural output function, with a focus on potential development value rather than apparent sales revenue. To explore the eWOM generated by dance dramas with specific spatiotemporal characteristics, two vector autoregressive models for megacities and other cities are developed based on the online review data of the representative dance drama The Journey of a Legendary Landscape Painting, and the dynamic relationships among eWOM reviewer characteristics, rating characteristics, and online buzz are investigated. The results of the study show that in terms of spatial characteristics, dance drama eWOM displays significant differences across different city types, and the relationships among eWOM reviewer characteristics, rating characteristics, and online buzz are causally inverted in megacities and other cities. In terms of temporal characteristics, dance drama eWOM exhibits long-term an fluctuating characteristics, and the cycle of dance drama eWOM spans approximately 10 months. In terms of spatiotemporal joint characteristics, the spatial distributions of dance drama eWOM and dance drama background culture remain consistent. Specifically, the eWOM for The Journey of a Legendary Landscape Painting moves from south to north, but for the Spring Festival, Gala eWOM moves from east to west.

Laser-Induced Self-Limiting Welding of Ag Nanowires with High Mechanical and Electrical Performance.

The high-efficiency and high-precision welding technology of Ag nanowires is of great engineering significance for the integration of new-generation micro- and nanodevices, and the mechanical behavior of its interconnect joints is also essential for their reliable application, especially for some flexible device. In this paper, based on the nano-focusing and localized plasma enhancement properties of Ag nanowires under laser irradiation, Ag nanowire self-limiting joints with mechanical and electrical properties comparable to those of the base material are obtained. At the same time, the local plasma enhancement characteristics of Ag nanowire joints are scanned and analyzed with nanoscale resolution by using cathodoluminescence technology, and the local multi-physical field coupling regulation mechanism of Ag nanowire joints induced by different laser parameters is systematically investigated by combining theoretical simulations. Meanwhile, based on the in situ laser welding and nanomechanical tensile experiments, the mechanical properties of single Ag nanowires and their welded joints are systematically analyzed, and the characteristics of the interfacial atomic behaviors and the evolution process during the welding and tensile processes are investigated.

Design of flat hole-clinching for joining polymer and metal sheets

There is a growing need for joining processes capable of joining dissimilar materials, specifically lightweight materials. In this study, flat hole-clinching (FHC) is developed for joining polycarbonate and AZ31 magnesium alloy sheets. A ductile fracture criterion is calibrated using tensile tests and employed in the finite element analysis of the process to investigate the effect of geometric parameters on the joint characteristics and strength. A tool concept is also proposed for the FHC process. Results show that the FHC process enables to successfully connect these sheets without fracture. The flat hole-clinched joint resisted the maximum force of 0.9 kN in the pull-out test, and failed with bottom separation mode.

Simulation of Friction Stir Welding of AZ31 Mg Alloys.

Friction stir welding has been extensively applied for the high-quality bonding of Mg alloys. The welding temperature caused by friction and plastic deformation is essential for determining the joint characteristics, especially the residual stress and weld microstructure. In this work, a modified moving heat source model was proposed by considering the variations in heat generation caused by friction shear stress at both the side and bottom surfaces of the tool. The application of this model was further extended to the entire welding process, especially in the plunging stage. The relative errors between the experimental and simulated peak temperatures at characteristic points were small, with a maximum of 10%, thereby validating the model for accurate temperature prediction. Furthermore, the influence of welding and rotational speed on temperature fields was systematically investigated. At relatively low welding and rotational speeds, the welding temperature increased significantly with either an increase in rotational speed or a decrease in welding speed. However, this effect gradually diminished at higher welding and rotational speeds. These results provide some valuable guidelines for controlling heat generation to improve the quality of Mg alloy welds.

Coal Mine Slope Stability Analysis Using the Rock Mass Rating (RMR), Slope Mass Rating (SMR) Method, and Morgenstren-Price Limit Equilibrium for the Low Wall Pit Area Y PT. Bina Sarana Sukses, Lahat Regency, South Sumatra

Open pit mining has a complex connection to excavation and stockpiling operations, which can potentially induce slope instability. The analysis of slope stability is crucial to prevent slope failure, which has the potential to result in major losses. The study on slope stability was performed at the low wall pit Y area of PT. Bina Sarana Sukses site MAS in Lahat Regency. This research aimed to analyze the rock mass classifications, determine the safety factor values, and provide recommendations for mitigating landslide occurrences. The techniques employed in this study include the RMR and SMR methods for assessing the susceptibility of landslides, collectively with the Morgenstern-price limit equilibrium approach for estimating the stability of the slope. Based on the analysis of the rock mass rating (RMR) and slope mass rating (SMR), Block B2 exhibits a 20% likelihood of experiencing landslides, specifically due to block joint characteristics. On the other hand, Blocks B4 and B5 show a 40% potential for landslides, primarily associated with flat or wedge-type block joints. The force produced by friction under saturated conditions is comparatively lower than that observed under dry conditions. During the final design phase in 2022, it was observed that Blocks B4 and B5 exhibit critical and dangerous safety factors when saturated. Hence, the proposal has been suggested to enhance slope stability. Further, it is recommended to monitor the geotechnical piles periodically. We hope this research results as a valuable resource for evaluating and assessing slope stability, including artificial and natural slopes.

Bionic Design of High-Performance Joints: Differences in Failure Mechanisms Caused by the Different Structures of Beetle Femur-Tibial Joints.

Beetle femur-tibial joints can bear large loads, and the joint structure plays a crucial role. Differences in living habits will lead to differences in femur-tibial joint structure, resulting in different mechanical properties. Here, we determined the structural characteristics of the femur-tibial joints of three species of beetles with different living habits. The tibia of Scarabaeidae Protaetia brevitarsis and Cetoniidae Torynorrhina fulvopilosa slide through cashew-shaped bumps on both sides of the femur in a guide rail consisting of a ring and a cone bump. The femur-tibial joint of Buprestidae Chrysodema radians is composed of a conical convex tibia and a circular concave femur. A bionic structure design was developed out based on the characteristics of the structure of the femur-tibial joints. Differences in the failure of different joint models were obtained through experiments and finite element analysis. The experimental results show that although the spherical connection model can bear low loads, it can maintain partial integrity of the structure and avoid complete failure. The cuboid connection model shows a higher load-bearing capacity, but its failure mode is irreversible deformation. As key parts of rotatable mechanisms, the bionic models have the potential for wide application in the high-load engineering field.

Fault diagnosis of rolling bearing under complex working conditions based on time-frequency joint feature extraction-deep learning

The same independent distribution is not obeyed for the data collected under complex working conditions such as time-varying speed or loading, and the fault characteristic information is insufficient, resulting in low accuracy by using traditional methods. To solve the above problem, a fault diagnosis method based on time-frequency joint feature extraction combined with deep learning is proposed. Firstly, the original vibration signal is processed by variational mode decomposition (VMD) to obtain several intrinsic mode functions (IMFs), then the sensitive components are selected by calculating the steepness values of each IMF. Subsequently, the characteristic features of the selected sensitive component in time-domain, frequency-domain and time-frequency domain are calculated to form the time-frequency joint feature. The sparse attention mechanism (SAM) is combined with the advantages of recurrent neural network (RNN) and convolutional neural network (CNN) to form a hybrid deep learning model (SAM-RNN-DCNN). Finally, the time-frequency joint features are combined with the hybrid model for fault diagnosis. Experimental verifications are carried out by using data sets under variable rotational speed, variable load and strong noise interference, and the analysis results show that the proposed method has high diagnostic accuracy, good diagnostic performance and robustness under complex working conditions.

Radiographic Measurements of the Hip Joint in Capuchin Monkeys (Sapajus spp.).

Radiographs are useful for the initial evaluation of the hip joints. The information can be utilized for the betterment of animal health or other goals such as anatomic studies and gait analysis, among others. Therefore, this study aimed to evaluate radiographic measurements of the hip joint in capuchin monkeys, kept under human care at a reference center for wildlife. Twelve capuchin monkeys (Sapajus spp.) (three adult males, seven adult females, and two sub-adult females) were evaluated. Ventrodorsal radiographic views were taken under chemical restraint. All measurements on the digital images were performed in triplicate by one examiner. None of the measurements evaluated were statistically different between males and females. No statistical differences were found between hind limbs. The mean (±SD) Norberg angle was 104.92° (±2.82°) and the Wiberg angle was 15.26° (±1.86°). The percentage of the femoral head covered by the acetabulum was 68.57% (±3.65%) and the acetabular index depth to width ratio was 54.66% (±3.85%). In conclusion, the radiographic measurements showed certain morphological features of the hip joint in Sapajus spp. that contribute to improving species knowledge.

Mechanical and failure behaviors of adhesively bonded dissimilar materials joints incorporating bio-inspired morphological irregularities

Adhesive dissimilar material joints between stainless steel grade 316L and polyethylene terephthalate glycol (PETG) plastic were examined, in which irregular interface morphologies inspired by natural sutures were incorporated. The joint interfaces exhibited various teeth-like, non-repetitive zigzag patterns based on a pseudo-randomization method and sutural interdigitation index. Effects of their irregularities on mechanical and failure characteristics of adhesive butt joints were studied by means of experiments and FE simulations. The cohesive zone model, Drucker-Prager plasticity model and ductile failure criterion were applied for the interface and PETG, respectively. Predicted load-displacement curves of joints with different teeth profiles were well validated. The degree of irregularity became higher to 20%, 40%, and 60%, the joint strengths decreased by 1.47%, 5.39%, and 11.95%, while the total energies to failure increased by 110.74%, 129.33%, and 161.23%, accordingly. More inhomogeneous morphologies led to earlier local damage initiation, but enhanced damage evolution range by impeding abrupt joint separation. Smaller teeth angles provided higher joint strength, whereas significant declines of bonding strength were observed by too acute teeth angle due to excessive stress localization and resulting teeth breakage. The teeth angle of 45º enabled the superior joint performance owing to a proper combination of interlocking and large adhesive force under shear stress state. Finally, a key insight for designing an optimal dissimilar joint with morphological irregularities was provided.