Joint Performance Research Articles

Estimating the Single Shear Strength Performance of Joints Using Screws and Nails with Decayed Wood

To enable the long-term use of existing wooden structures, appropriately evaluating the extent of damage of the biodeterioration of structural performance, including members and joint systems, is necessary. To give one example, accurately estimating the single shear strength performance of nail and screw joints with decay is crucial. Therefore, this study proposes a method to model this by dividing wood into multiple layers with different strength performance, considering the grade of deterioration in a cross-section of decayed wood. The model was used to differentiate the sound layer and three decayed layers (multilayer) according to the extent of the damage. The estimated values, which were produced using the proposed model, were compared to the single shear strength of screw and nail joints with decay using two species of wood, namely Abies sachalinensis (Todomatsu) and Cryptomeria japonica (Sugi). The results point to a good fit between the average value of the experimental results and the estimated values of the proposed model. Compared with the existing (single-layer) model, the proposed model improved the accuracy of estimating the strength of wood undergoing early deterioration and therefore was considered usable.

Research on seismic performance of replaceable prefabricated RC beam-column joints

Based on the seismic design philosophy of recoverable functionality, this paper proposed a prefabricated concrete beam-column joint utilizing replaceable friction energy dissipation artificial plastic hinges (FAPH) as connecting devices. The connecting device comprised a pair of lugs and high-strength pins. This study analyzed the failure modes and hysteresis characteristics through cyclic loading tests performed on the precast beam-column joints. The results showed that the FAPH had a high peak capacity. However, the yield load was low, which reduced the energy-dissipation capacity of joints at the early stage. Therefore, lateral energy dissipation steel plates (EDPs) were added on both sides of the PAPH to improve bearing capacity. Then, utilizing ABAQUS finite element software, the mechanical behaviors of the optimized prefabricated joint such as the load-displacement curve, bearing capacity, ductility, and energy dissipation capacity were further analyzed. This paper also investigated the effect of the axial compression ratio, the friction coefficient, bolt preload, and connecting plate form of EDPs on the seismic capacity of the optimized joint. After optimization, the prefabricated joint exhibited a significant improvement in both yield capacity and cumulative energy dissipation, increasing by 47 % and 22 %, respectively. Additionally, there was a slight improvement in ductility. Increasing the axial compression ratio reduced the bearing capacity and ductility of prefabricated joints after the peak point. The specimen exhibited a significant increase in both peak capacity and cumulative energy dissipation as the friction coefficient increased. Additionally, the hysteresis curve of the joint became fuller with the increase in bolt preload. The connecting plates of EDPs mainly serve to transmit loads, and different forms of connecting plates had little effect on the bearing capacity and energy dissipation capacity of prefabricated joints.

The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance.

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near "in situ" structure around the exit hole, an "emergency stop" followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism.

Deformation ability of steel inner sleeve T-joint in modular gymnasia based on 3D-DIC method

Substantial loads the roofs bear exert stringent performance standards on connecting joints in movable modular gymnasiums. Previously, we introduced a novel joint design, utilizing internal sleeves and bolts to integrate the upper and lower columns of modular units. To explore the actual deformation behavior and force distribution of this joint, this study employed a three-dimensional digital image correlation (3D-DIC) measurement method to visualize its full-field displacement and strain distribution. The reliability of the 3D-DIC results was confirmed through comparison with traditional measurement methods. Building upon this solid foundation, this study proceeds to assess the static performance of this innovative joint in two distinct directions, successfully revealing micro-deformation and local buckling phenomena undetectable to the naked eye. Notably, the quality of the welds connecting the beams and columns plays a pivotal role in ensuring the overall structural integrity of the joint. Under lateral loading conditions, the destructive behavior of the joints is primarily governed by material strength. Moment-rotation curves were plotted to delve further into the mechanical characteristics of the joint, revealing that the inner-sleeve T-joint exhibits the attributes of a rigid joint. Moreover, the primary damage modes observed in the specimens were fractures at the beam root or buckling of the column, with the joint area remaining intact. Consequently, this joint qualifies as a full-strength connection. These findings will deepen knowledge and understanding of this novel joint for designers.

Coupling influence of laser-Nb interlayer on microstructure and performance of Ti/Al joint

Laser fusion welding of TC4 titanium (Ti) alloy and aviation 7075 aluminum (Al) alloy was conducted with the assistance of a niobium (Nb) interlayer. The effect of laser heat input and the alloying effect of Nb on the interfacial layer was analyzed. The study also investigated the coupling influence of the laser-Nb interlayer on the microstructure and performance of the Ti/Al joint. By utilizing a 0.1 mm-thick Nb interlayer and a welding velocity of 1800 mm/min, the results reveal an initial increase in tensile-shear force followed by a decline with the increase of laser power. The tensile-shear force reached a peak of 1663 N at 1.2 kW, representing a 36.76 % improvement over the 1 kW levels. Under appropriate laser power, the enhancement in joint performance is dominated by the controlled heat input and the effective Nb-alloying effect, which reduce the thickness and brittleness of the interfacial intermetallic layer, respectively. However, metallurgical regulation of Nb will be restricted by the insufficient Nb melting amount resulting from the low laser power, leading to a decrease in joint properties. Excessive laser power can lead to the formation of hot cracks and an excessive amount of Ti-Al intermetallic compounds, which can decrease the Nb content, thereby restricting the metallurgical regulation of Nb and the overall joint performance.

Experimental study on seismic performance of spatial and planar hoop-head mortise and tenon timber joints in historical architecture

This paper aims to present an experimental study investigating the seismic behaviour of spatial and planar hoop-head mortise and tenon (MT) timber joints in traditional Guangfu Ancestral Halls. The unique design of the external hoop head provides additional restraints for the tenon and mortise in these joints, endowing them with enhanced pull-out resistance and increased structural integrity compared to other types of MT connections commonly used in traditional timber-framed structures. The research commenced with material testing to determine the mechanical properties of Merbau wood used in this timber frame construction. Reversed cyclic loading tests were then performed on two planar and two spatial hoop-head MT timber joints. The experimental results demonstrated the favourable seismic performance of the hoop-head MT joints. All specimens failed within the MT joint area, exhibiting different failure modes based on varying connection configurations and tenon sizes. Furthermore, the spatial MT joints showed lower stiffness and bearing capacities compared to the planar MT joints of equivalent size. Their hysteresis curves, envelope curves, and cyclic stiffness degradation curves displayed greater asymmetry. These discrepancies can be attributed to the reduction in tenon sections necessary to accommodate the overlapping beams within the spatial joint core area.

Numerical simulation of the hybrid flat-clinching

The significance of mechanical joining continues to grow across various industrial sectors, including automotive and aerospace, Various processes, from traditional bolting and riveting to advanced techniques like welding, bonding and clinching, are used to assemble parts into a unified whole. One distinctive process is flat-clinching, particularly useful for joining two sheets by creating a geometrically interlocked joint, with its ability to create sturdy connections without the need for external elements, this process involves a punch pushing the sheets into a flat die, inducing local plastic deformation. Its advantages make it a valuable option in manufacturing. In this study, a numerical analysis using the finite element method was conducted, investigating the influence of several parameters as friction by taking many values, tool geometry by creating a new design and hybridization of materials on the flat clinching process. The focus was on evaluating the performance of joints formed by using three configuration of tool geometry by adding a shoulder on the holder and on the punch. lightweight materials, particularly Aluminum5754. Other commonly used materials were also considered as ETP copper, Brass CuZn37 and Mild steel, subjected to a tensile test for a comprehensive assessment. The findings offered understanding of how to enhance the flat-clinching process with regards to various materials depending on chosen parameters to maximize joint strength and reliability. Knowledge of these factors is important to manufacturers seeking to enhance productivity and performance of their products. In sum, this research adds to the general understanding of the mechanical joining methods and provides useful recommendations for companies that maybe interested in applying and optimizing flat-clinching for their joining tasks.

The Effect of High-Temperature Deformation on the Mechanical Properties and Corrosion Resistance of the 2024 Aluminum Alloy Joint after Friction Stir Welding.

The 2024 aluminum alloy is one of the high-quality lightweight materials. Friction stir welding (FSW) has shown advantages in reducing welding defects and improving welding quality in 2024 aluminum alloys. Currently, the research regarding FSW joint corrosion performance is mainly about the joint without plastic deformation. However, FSW joints often need to be formed into complex shapes by plastic deformation. The influence of plastic deformation on the corrosion performance of FSW joints is the focus of scientific research. To address this problem, the effect of high-temperature deformation on the mechanical properties and corrosion behavior of 2024 aluminum alloy joints was researched. The exfoliation corrosion test, scanning electron microscopy, energy-dispersive spectroscopy, and transmission electron microscopy were employed to analyze the corrosion mechanism and microstructure. The results show that high-temperature deformation of the weld nugget zone greatly affects the mechanical properties and corrosion behavior of the FSW joint. Compared with the 0% deformation specimen, the hardness and tensile strength of the 20% deformation FSW joint increased by 32% and 21%, respectively. The FSW joint with 20% deformation shows the best mechanical properties and corrosion resistance. The number of precipitated S' phases of the FSW joint increases when the deformation increases to 20%, and the shape of the S' phase is a regular round particle shape. The dislocation density of the FSW joint increases continuously during deformation, which provides a favorable nucleation location for the S' phase.

Simultaneous improvement in strength and ductility of friction stir welded Mg/Al joints by reducing micro-intermixing

Thread of pin has been proved beneficial to increasing shear action of tool and material intermixing, which however induces abundant formation of intermetallic compounds (IMCs) in Mg/Al dissimilar friction stir welding (FSW) leading to deteriorating the performance of joints. In this work, Mg alloy and Al alloy were well joined by threaded pin and unthreaded pin under the same welding parameters. For threaded pin joints, cracks occured in the banded structure (BS) region and bottom interface, then the main crack propagated along the Mg/Al interface, resulting in low strength and elongation. For unthreaded pin joints, necking and fracture occurred at the softened Al alloy to the retreating side (SAA-RS), and the fracture mode changed from brittle fracture (Mode I) to ductile fracture (Mode III). The tensile strength and strain of unthreaded pin joints are 201 MPa and 7.14 % respectively, significantly higher than those of threaded pin joints (i.e. 140 MPa and 1.15 %), and is the highest combination of strength and strain reported up until now. An unthreaded pin could reduce the local micro-intermixing between Mg and Al to suppress the formation of IMCs, which reduced the hardness in the BS region, preventing the formation and propagation of cracks.

Resources for action and organizational resilience in times of COVID‐19: A study in health care

AbstractThe COVID‐19 pandemic challenged health care organizations to cope with major disruptions, especially in the first waves. Several investigations were undertaken to understand how to support resilience during similar unexpected events. In this study, we attempted to unveil the resilient performance of health care organizations during the first waves of the COVID‐19 pandemic from the viewpoint of resources for action. Thus, the research objectives are twofold: (i) to evaluate organizational resilience in facing COVID‐19 by hospitals in Brazil and (ii) to evaluate the relationship between resources for action and resilient performance. Firstly, an online survey was sent to front‐line health care workers, resulting in 111 responses. Then, a questerview was undertaken through online interviews with some participants of the previous phase. Resources for action were interpreted as five aspects supporting decision‐making in health care organizations: information and communication; team, equipment, and tools; standard operating procedure (SOP); training; and built environment. Each resource was then unfolded based on the four potentials for resilient performance (i.e., anticipate, monitor, respond and learn). Respondents strongly agreed that their institutions are resilient (M = 4.15; standard deviation [SD] = 0.91). The potentials to learn (M = 4.23; SD = 0.96) and respond (M = 4.08; SD = 1.02) stood out, followed by monitoring (M = 3.85; SD = 1.07) and anticipating (M = 3.70; SD = 1.11). Although some differences stand out, findings corroborate with the joint performance of the resources for action to support resilience performance. Information and communication were the most present among the resources for action (M = 4.20). Making resources for action visible is a strategy for designing resilient systems, as it can be considered a bridge linking different resilience levels (micro, meso, and macro). Suggestions for future studies point out the need to promote the development and evaluation of resources for action in health care institutions.

Cracking characteristics and axial capacity degradation of precast segmental bridge piers connected with corroded tapered sleeve locking-type splicing

The tapered sleeve locking-type splicing (TSLTS) reinforcement joint is a new method of steel mechanical connection. When applying the TSLTS reinforcement joints to precast segmental bridge (PSB) piers in coastal environments, the durability need to be taken into account. After the TSLTS reinforcement joint is corroded, the connection performance of the TSLTS reinforcement joint is degraded. Therefore, the mechanical properties of PSB piers decrease due to the corrosion of the joints, which brings some potential hazards. In this paper, the durability of PSB piers with TSLTS reinforcement joints in coastal environments was studied. The corrosion-induced cracking characteristics, failure mode and axial capacity of PSB piers with TSLTS reinforcement joints were investigated by means of accelerated corrosion test and axial loading failure test. The results indicated that, with increasing corrosion time, the total length of the corrosion-induced cracks on the surface of the pier specimens increased, but the increasing rate of the total length decreased. The mass loss of TSLTS reinforcement joints increased linearly with the maximum width of longitudinal corrosion-induced cracks on the concrete cover of the self-compacting concrete (SCC) segment, and the critical mass loss of TSLTS reinforcement joints was approximately 4.0 % when longitudinal corrosion-induced cracks appeared. The probability distribution type of the width of longitudinal corrosion-induced cracks on the surface of pier specimens was mainly a lognormal distribution. When the mass loss of TSLTS reinforcement joints was less than 7.2 %, the damaged area of the pier specimens was mainly concentrated in the SCC segment, while when the mass loss of TSLTS reinforcement joints was higher than 8.8 %, the damaged area was located in the ordinary Portland concrete segment near the top of the pier specimens, and the corroded TSLTS reinforcement joints could still maintain their connection performance. With an increase in the corrosion degree of the steel bars, the axial capacity of the pier specimens decreased, and the equivalent stiffness also degraded. The degradation rate of the axial capacity of the pier specimens increased linearly with the mass loss of the TSLTS reinforcement joints, and the degradation of the axial capacity occurred only when the mass loss of the TSLTS reinforcement joints was greater than 4.6 %. The research results can provide a theoretical reference for the application of TSLTS reinforcement joints in PSB piers.

Finite Element Analysis of Prefabricated Semi-Rigid Concrete Beam–Column Joint with Steel Connections

This paper introduces a novel type of prefabricated semi-rigid concrete beam–column joint, aiming to examine its load-carrying capacity and seismic performance in comparison with a traditional cast-in-place joint. This study utilized the ABAQUS 2020 software to establish finite element models for both types of joints and conducted finite element analysis under low circumferential reciprocating displacement loads. When comparing the energy dissipation capacity, ductility, ultimate load-carrying capacity, stress mechanism, and damage mode, a comprehensive evaluation of the two types of joints was performed. Furthermore, this study investigated the impacts of various factors such as the axial compression ratio, concrete strength, reinforcement strength, and connector strength on the ultimate load-carrying capacity, ductility, and energy dissipation performance of the joints. Based on the findings, the newly combined joint exhibited a substantial 31.7% increase in its ultimate load-carrying capacity, along with a notable 7.23% enhancement in ductility and an improved energy dissipation capacity when compared with the cast-in-place joint. As a result, it can be concluded that the seismic performance of the new joint surpasses that of cast-in-place joints. Additionally, this study examined the impact of modifying relevant parameters on the seismic performance of the new prefabricated semi-rigid concrete beam–column joint.

Effect of die design on microstructure and mechanical joint strength in friction self-piercing riveted AA7055-T76 and AA7055-T76

In the present study, a unique friction self-piercing riveting (F-SPR) was applied to join high-strength, low-ductility aluminum alloy (AA) 7055-T76 and AA7055-T76 to mitigate a cracking issue. Also, the effect of die design on both joint formation and the mechanical joint performance were investigated. A crack-free joint was achieved when joining AA7055-T76 and AA7055-T76 by F-SPR. As the bottom diameter of the die increased, the mechanical interlocking distance initially increased then became almost saturated. At the same time, the solid-state bonding gradually disappeared, and the lap-shear fracture changed from bottom aluminum fracture to rivet pull-out with partial bottom aluminum fracture. The average maximum lap-shear joint strength of 11.57 kN and cross tension of 5.65 kN were achieved from the D2 die design owing to the combined contributions from high mechanical interlocking distance and good solid-state bonding at the joint interface. Ultrafine grain refinement was observed at the region next to the rivet shank outer surface and along the materials flow line between the top and bottom aluminum sheet in the rivet cavity. Because of the same joint-process parameters, the hardness profile at the joints made by different dies did not show obvious differences. As the distance from the base metal to the rivet outer surface decreased, frictional heat caused the hardness to initially decrease from 190 to 150 HV in the heat-affected zone. Hardness increased up to 175 HV in the thermomechanical affected zone (TMAZ-I) owing to large plastic deformation.

Seismic Performance of Steel-Reinforced High Strength Concrete Joints Considering Bond Slip Effect

This study presents a solution for push-out failure for the staged bond-slip constitutive relationship between the structural steel and high strength concrete, taking into account the concrete strength grade, anchoring length, and stirrup ratio. The critical point coordinates for different stages are determined by the tests of 14 steel-reinforced high strength concrete (SRHSC) specimens. It is observed that with the increase in the concrete strength grade and anchorage length, the ultimate load of the specimens increased significantly, but the influence on the residual bond strength was not significant. The effect of the stirring ratio was mainly manifested in a slight increase in the initial bond strength. The formula for calculating SRHSC characteristic bond strength and characteristic slip value is established, and the bond-slip constitutive relation of SRHSC is proposed based on the tests. The material constitutive model considering the effect of bond-slip is implanted into the software in the case of the ABAQUS finite element platform. The material is applied to the numerical simulation analysis of the SRHSC exterior joints. The rationality and accuracy of the new material are verified by comparing the simulation results with the test results.

Investigation on submerged friction stir welding of AZ31B magnesium alloy under the influence of rotation speed

In this study, submerged friction stir welding (SFSW) was performed to weld 6 mm thick AZ31B Mg alloy plates, aiming to explore the impact of rotation speed on microstructure and tensile behavior. The water medium was used to submerge the samples. The SFSW was conducted at three different speeds (815, 960, and 1200 rpm), to assess the impact of rotation speed on SFSWed joint performance. As the rotation speed increased from 815 to 960 rpm, tensile strength increased plateauing over a range of the rotation speed. However, a significant drop in tensile strength occurred at 1200 rpm due to the formation of void defects. The SZ exhibits a size and width increment in the lower part with increasing rotation speed. The hardness of the stir zone (SZ) gradually rose with increasing rotation speed from 815 to 960 rpm. Fracture locations were observed in the thermal-mechanically affected zone (TMAZ) adjacent to the SZ at a rotation speed of 815 rpm, and in the heat-affected zone (HAZ) adjacent to the TMAZ at a rotation speed of 960 rpm. The joint welded at 1200 rpm fractured within the SZ. This study offers valuable insights into the welding and joining field, particularly regarding their mechanical characteristics.

Optimization and experimental study on seismic performance of precast dry-wet hybrid beam-column joint with local prestressing

In order to improve the seismic performance, a novel dry-wet hybrid beam-column joint was optimized based on the findings of the preliminary experiment. Four full-scale prefabricated specimens were tested under cyclic loading to further investigate their seismic behavior and explore the various factors, including the connection methods for beam top longitudinal reinforcement in the joint core, magnitude of prestressing force, forms of hoop reinforcement at beam ends, and types of grouting material used in corrugated steel ducts. The results indicate that the new joint failed in the flexural mode, and its experimental bearing capacity value was consistent with the theoretical value, indicating a good safety margin. Additionally, it exhibited remarkable ultimate deformation capacity and displacement ductility coefficient exceeding 3, comparable to cast-in-place structures. The performance indicators of post-tensioned (PT) bar specimens were similar to those of cast-in-place structures and superior to PT rod specimens. The energy dissipation of PT rod specimens accounted for approximately 80 % to 90 % of that of the PT bar specimen. The viscous damping ratios of specimens with PT bars and PT rods were approximately 20 % and 15 %, respectively. Two methods of connecting beam top longitudinal bars by grouting or couplers, accompanied by a local unbonded treatment, could both fulfill anchorage requirements. However, the later one resulted in loosening of steel bars within the connector during late loading stages. The anchoring performance of prestressed grouting material could satisfy the anchoring requirements of PT bars, but still failed to meet the slippage resistance requirements of PT rods. Increasing the prestressing force can enhance the initial stiffness, significantly reduce yield displacement, and improve ductility coefficient, while having minimal impact on strength and energy dissipation. The open composite stirrups at beam ends do not significantly impact overall performance of the joint. The optimal details for the novel joint involves a combination of high-strength PT bars, grouting in corrugated ducts with local debonding treatment, and open composite stirrups at beam ends.

Process defect analysis and visual detection of aluminum/copper cable joints with magnetic pulse crimping

Magnetic pulse crimping (MPC) has been demonstrated to enhance the electrical and mechanical performance of the aluminum/copper cable joints compared to traditional mechanical crimping. However, little attention has been given to the impact of defects during the manufacture on the performance. This paper uses MPC technology to connect joints and investigates the influence of various defects (including scratches, skew, length inadequate, wire broken, and depth inadequate), on the electrical and mechanical performance of the joints. The results indicated that the defects lead to significant changes performance of joints. Compared to the normal joint, skew, length inadequate, wire broken, and depth inadequate contributed to decreased tightness and the strength of the joints, resulting in an increase in the average resistance by 518.8 %, 1133.2 %, 1533.8 %, and 1377.9 %. Simultaneously, average loads of joints decrease by 16.4 %, 23.5 %, 28.8 %, and 91.3 %, respectively. Scratches have no discernible impact on performance. To address these defects systematically, a hierarchical defect detection approach was proposed. Faster R-CNN was employed to search three distinct regions: a large region (L), a middle region (M), and a small region (S), each associated with different defects that proved to impact performance via previous experiments. A COCO metric of 84.85 % was achieved. Four ResNet models were then utilized to classify defects within these regions. ResNet50 exhibited the best overall performance: 95 % accuracy for L, 100 % for M, and 87 % for S.

Evaluation of shear performance of timber-timber composite joints

The mechanical performance of timber composite floors is influenced by the degree of composite action between the components. In this study, the shear strength performance of cross-laminated timber and glued laminated timber composite floors based on the joining method was evaluated by push-out test. Eight types of timber-timber composite joints were evaluated using three different methods: lag screw joints, glued-in rod joints using fully threaded bolts and glass fiber reinforced plastic, and hybrid joints. Strength characteristics were derived to make theoretical predictions on the load-carrying capacity of the joints. The results showed that the glued-in rod joints were superior to the lag screw joints, with slip coefficients and ductility measured as 10 times and 2.5 times higher, respectively. The reliability of the strength characteristics of the glued-in rod joints was remarkably different depending on the presence or absence of anti-adhesive tape applied to the timber-to-timber joint surface. The load capacity of the hybrid joint, which combines mechanical and glued-in rod joining methods, was 47% higher than that of the lag screw joint and 38% higher than that of the glued-in bolt joint. In the European Yield Model modified to estimate the load capacity of joints, the rope effect and the yield moment of the fasteners had a remarkable impact on the predicted load capacity.

Experimental and simulation study on seismic performance of the new beam-column transfer joint as the embedded part of the basement roof

A new beam-column transfer joint is proposed, which consists of an upper column with a concrete-filled steel tube column (CFST), a lower column with a variable-diameter steel-concrete column (SRC), and a reinforced concrete beam. The new transfer joint is mainly set on the roof of the basement of a high-rise building structure. Compared with traditional transfer joints, it reduces the amount of steel used, increases the use space of the basement, and improves the seismic performance of the structure. New transfer joint and traditional joint were tested under cyclic loading to investigate response of the proposed joint. The main performance indicators studied are hysteretic response, energy dissipation, ductility, and stiffness degradation. Research results show that the energy consumption and carrying capacity of the new transfer joint are higher than those of the traditional joint. The correctness of the finite element analysis was verified through the test results, and a parametric analysis was carried out on this basis. It was found that the diameter reduction position of the steel tube and the length of the corbels of the lower column have little impact on the seismic performance of the new transfer joint. The thickness of the steel tube has a greater impact on the seismic performance of the new transfer joints. The peak bearing capacity is increased by about 17 %. Finally, according to the formula given by the specification, the embedding effect of the new transfer joint and the traditional joints are compared. The effect of the new transfer joints is better than that of the traditional one, which can provide a reference for future basement design of high-rise building structures.

Ag-based filler metal wetting behavior and brazed joint performance on SLMed Ti/TiB2 substrate

PurposeThis study aims to investigate the wetting behavior of AgCuTi and AgCu filler metals on selective laser melting (SLMed) Ti/TiB2, and to analyze the microstructure and fracture characteristics of SLMed Ti/TiB2/AgCuTi or AgCu alloy/SLMed Ti/TiB2 brazed joints. The wetting behavior of AgCuTi and AgCu filler metals on the selective laser melted (SLMed) Ti/TiB2 has been studied. The analysis of microstructures and fracture characteristics in vacuum-brazed SLMed Ti/TiB2 substrate, using AgCuTi and AgCu filler metals, has been conducted to elucidate the influence of brazing temperature and alloy composition on the shear strength of the brazed joints.Design/methodology/approachBrazing SLMed-Ti/TiB2 in a vacuum using AgCuTi and AgCu filler metals, this study aims to explore the optimal parameters for brazed joints at various brazing temperatures (800°C−950°C).FindingsThe findings suggest that elevated brazing temperatures lead to a more extensive diffusion region in the joint as a result of the partial melting of the filler metal. The joint composition changes from distinct Ti2Cu layer/TiCu layer/filler metal to a-Ti (ss) + ß-Ti (ss)/TiCu. As the brazing temperature increases, the fracture mode shifts from brittle cleavage to ductile fracture, mainly attributed to a decrease in the CuTi within the brazed joint. This change in fracture behavior indicates an improvement in the ductility and toughness of the joint.Originality/valueThe originality of this study lies in the comprehensive analysis of the microstructure and shear strength of vacuum brazing SLMed Ti/TiB2 using AgCuTi and AgCu filler metals.