Joint Mode Research Articles

Experimental and numerical study on the effect of load direction on the bolt loosening failure

The loosening is one of the main failure modes of bolted joints. Currently, researchers only focused on bolt loosening behavior under simple axial or transverse loads. Understanding the loosening failure mechanism of bolted joints under complex load is important for improving reliability. A multi-directional loading test device was designed, and bolt loosening experiments were conducted. The effect of load direction and amplitude on bolt loosening behavior were investigated. The results indicate that bolt loosening can be divided into two stages. Load direction and load amplitude are critical factors determining the loosening trend in the later stage. In addition, a refined finite element model of bolted joints was established to verify and explain the experimental results. The FEA results show that the relative sliding between internal and external threads and the stress redistribution on the threads are the main reasons for the bolt loosening. The smaller the angle between the load direction and the tangential direction of the contact surface, the relative sliding more likely to occur.

Cu array fabrication: An environmentally sustainable approach through bicontinuous microemulsion differential electrodeposition for advanced power device packaging

BackgroundThe demand for high-power density packaging and integration processes for third-generation semiconductors, like silicon carbide (SiC), necessitates advancements beyond conventional Si-based packaging technologies. Cu-Cu direct bonding emerges as a promising alternative in semiconductor packaging. However, achieving Cu-to-Cu direct bonding with low-temperature, low-pressure, and short-time poses significant challenges. Transient Liquid Phase Bonding (TLP) offers a low-temperature joining solution, but prolonged reflow time hinders its wide applications. MethodsThis study introduces a novel strategy utilizing bicontinuous microemulsion (BME) electrodeposition to fabricate micron-sized Cu arrays, addressing these challenges in achieving Cu bonding. The core of Cu array manufacturing lies in the differential electrodeposition rate of Cu ions in the aqueous and organic phases. This principle is rooted in the excellent conductivity of the aqueous solution compared to the non-conductivity of the organic solution. Significant findingsWe elucidate the growth mechanism and validate a theory for achieving void-free optimal growth of Cu arrays within BME and compared the cross-sectional morphology and fracture modes of TLP solder joints with micron and nano Cu arrays. Furthermore, the ability to recycle the BME soft template aligns with green chemistry principles, offering a sustainable die-attach approach for third-generation semiconductor device packaging.

Fatigue Analysis of Composite Bolted Joints under Random and Constant Amplitude Fatigue Loadings.

This paper attempts to analyze the random fatigue life and failure modes of joints using two calculation methods. Three kinds of tests were carried out, which were the static test, constant amplitude fatigue test and the random fatigue test, and four kinds of joints were designed. After the static test, the joint was subjected to a constant amplitude fatigue test by selecting different percentages of load according to the static strength. In order to predict the random fatigue life more precisely, two calculation methods were carried out, which were the linear cumulative damage method and the equivalent loading finite element method. Based on the linear cumulative damage hypothesis, the fatigue life of the joint was established as a function of the load amplitude, and then, the random life prediction was calculated by the amplitude distribution of the random loading. Another method was the equivalent loading method, which was to obtain the equivalent constant amplitude fatigue loading of the random loading spectrum. The finite element model was established based on the stiffness and strength degradation rule. The equivalent random life and fatigue failure modes of the joint were modeled. The two life prediction methods show good agreement with the fatigue experimental result, and all prediction results were included in a scatter band of the factor of 2.

Failure mechanisms in pre-tensioned bonded hybrid joints

ABSTRACT This study investigated the failure mode of pre-tensioned bonded hybrid joints in steel structures using Digital Image Correlation (DIC) alongside Finite Element Analysis (FEA) and compared the results with those of adhesive bonded joints of identical geometry. While all joint types initially exhibited ideal adhesive joint behaviour at low loading levels, with linear elastic response, differences emerged as loading increased. In particular, hybrid joints exhibited out-of-plane deformations near the ends of the splice plates, a feature not observed in bonded joints. Shear deformations consistently peaked at the ends of the overlap for all joint types and increased with increasing load levels. In contrast to bonded joints, hybrid joints demonstrated resilience under escalating loads, maintaining resistance due to the presence of bolts despite the increased deformations. This study contributes to the understanding of the observed failure mode: while hybrid joints initially resembled ideal bonded joints at lower loads, increasing loads caused critical cracks to initiate at the overlap ends in the adhesive layer, culminating in bonded joint failure. In conclusion, this study has elucidated the failure mode of hybrid joints, providing insights for modelling and dimensioning in steel structures.

Prediction of mechanical properties and fatigue life of nanosilver slurry in chip interconnection

This article investigates the failure mode and mechanism of copper pillar solder joints in temperature cycling experiments, focusing on a Cu/nano Ag/Cu solder joint structure. The hot pressing bonding condition at 300 °C with insulation for 10 s is chosen for the experiments. Based on the life test results, the thermal cycling fatigue life of the nanosilver solder joint is determined to be 2050 cycles. To gain further insights, finite element software ANSYS is employed to simulate nanosilver solder joints in flip chips, revealing the stress–strain distribution within the solder joints. The simulation utilizes the Anand viscoplastic constitutive model for the solder joint, providing a reasonable representation of the stress–strain behavior under thermal cycling load. Notably, the simulation highlights that the maximum stress and strain occur in the contact area between the solder joint and the copper column. To enhance accuracy, the calculation equation is refined using relevant experience, resulting in a prediction of the thermal fatigue life of nanosilver solder joints. This prediction aligns closely with the experimental results. The research outcomes not only contribute valuable insights into the behavior of nanosilver solder but also serve as a reference for its application in electronic packaging.

Effect of Matte-Sn Electroplating Parameters on the Thermo-mechanical Reliability of Lead-free Solder Joints

Most of the Cu/Cu alloy lead-frames of electronic components used for automotive applications contain electroplated matte-Sn terminal finish to improve the wettability of Sn-based Pb-free solders during reflow soldering process. When the solder joints are subjected to combined thermal and mechanical cyclic loading, the influence of matte-Sn electroplating parameters can lead to early and brittle failure of the solder joint. To test this hypothesis, a factorial design of experiments (DOE) has been conducted with LFPAK-MOSFET (hereafter referred to as LFPAK) components plated with different matte-Sn electroplating parameters and reflow soldered with two solder alloys (SAC 305 and Innolot). The LFPAK solder joints were then subjected to thermo-mechanical in-phase cyclic loading under different strain amplitudes. No electrical measurement is done to eradicate the effect of electrical current on the solder joint. The response to the DOE is the crack percentage obtained in the LFPAK solder joints after 1000 and 2000 cycles. The Innolot solder joints exhibited lower crack percentages than the SAC 305. The level of organic additives in the electroplating process of matte-Sn influences the failure mode of the solder joint. Microstructural investigation attributes the nature of failure to the morphology of the (Cu,Ni)6Sn5 IMC phase that forms on the component side of the solder joint.

Crashworthiness of AAG joints with a foam aluminum layer gusset plate

The gusset joint is the most widely used joint system in an aluminum alloy single-layer reticulated shell structure; it plays a vital role in the spatial grid structure. In this paper, the effects of different thicknesses of aluminum alloy gusset plates on the dynamic response and failure modes of aluminum alloy gusset (AAG) joints were studied by impact tests of three specimens. The test results show that the failure modes of AAG joints are a slight depression of the gusset plate, the local buckling of members, the local distortional buckling of members, and tearing of the lower flange and a web of members. The AAG joint inclines along the direction of the failed member and collapses. The finite element model of the AAG joint was established using ANSYS software. The stress, displacement, and deformation modes in the test and numerical simulation results were compared and analyzed, and the rationality of the numerical simulation results was verified. Based on the failure mode of the specimens, a design method for improving the impact resistance of AAG joints with aluminum foam layer gusset plate (AFLGP) is proposed. The numerical simulation results show that an AAG joint with an AFLGP effectively reduces the maximum peak value of impact loads through the deformation of the aluminum foam. In the elastic and elastic-plastic stages, AAG joint with AFLGP had better impact resistance, and the energy absorbed by its rods was 25.44% ∼ 30.36% lower than that of AAG joints alone. Finally, the influence of the thickness of the AFLGP on the impact force and energy absorption of the AAG joint was studied. The aluminum foam gusset layer plate is approximately twice as thick as the aluminum alloy gusset plate had the best protection effect on the AAG joint.

Joint mode selection and resource allocation for cellular V2X communication using distributed deep reinforcement learning under 5G and beyond networks

Vehicle-to-everything (V2X) communication via cellular networks is a promising technique for 5G and beyond networks. The cars interact directly with one another, as well as with the infrastructure and various vehicles on the road, in this mode. It enables the interchange of time-sensitive and safety-critical data. Despite these benefits, unstable vehicle-to-vehicle (V2V) communications, insufficient channel status information, high transmission overhead, and the considerable communication cost of centralized resource allocation systems all pose challenges for defense applications. To address these difficulties, this study proposes a combined mode selection and resource allocation system based on distributed deep reinforcement learning (DRL) to optimize the overall network sum rate while maintaining the reliability and latency requirements of V2V pairs and the data rate of V2R connections. Because the optimization issue is non-convex and NP-hard, it cannot be solved directly. To tackle this problem, the defined problem is first translated into machine learning form using the Markov decision process (MDP) to construct the reward function and decide whether agent would conduct the action. Following that, the distributed coordinated duelling deep Q-network (DDQN) method based on prioritized sampling is employed to improve mode selection and resource allocation. This approach learns the action-value distribution by estimating both the state-value and action advantage functions using duelling deep networks. The results of the simulation show that the suggested scheme outperforms state-of-the-art decentralized systems in terms of sum rate and QoS satisfaction probability.

Bond behavior of CFRP reinforcement systems with concrete under static and fatigue loading

In this research, the single lap shear tests were used to investigate the bond behavior of carbon fiber reinforced polymer (CFRP) sheets bonded to concrete blocks under static and fatigue loads. The magnitude of the fatigue load was considered as a parameter that varied from a minimum load of 10% of Pu to a maximum load of 60%, 70% and 80% of the ultimate static load. For both loading scenarios, the applied load versus slips curves and the profiles of the interface zone strain were presented. In addition, comparisons, and analyses of the failure mode of samples subjected to static and fatigue loading are presented. The experimental results demonstrate that the loading level has a significant impact on the failure mode, fatigue life and stiffness degradation of CFRP-concrete joints during the fatigue loading.Finally, a prediction model for the fatigue life of the CFRP-concrete joint was developed as part of this investigation.

Deep learning assisted InAs/InP quantum-dash laser structured light modes detection under foggy channel

This paper demonstrates L-band quantum-dash laser (QDL) based orbital angular momentum (OAM) structured light in a free space optics communication (FSO) system. A 4-ary OAM-shift-keying pattern coding communication system, based on Laguerre Gaussian (LG) and superposition LG (MuxLG) mode families, has been investigated under a foggy FSO channel. In addition, joint mode identification and channel condition estimation have been developed at the receiver side using advanced deep learning (DL) methods. We utilize and compare the performance of the convolutional neural networks (CNN) and UNET algorithms. An experimental setup has been conducted using an in-house controlled foggy chamber which allows an FSO transmission of 3-m length. Furthermore, we propose a data balancing approach to the experimental dataset by data augmentation. Visibility prediction results have shown a measured root mean square error of 17(18) m and 10(10) m for 4-ary LG(MuXLG) using CNN and UNET models, respectively. Moreover, the DL models provide an average mode classification accuracy of 94% under various channel visibility conditions.

Investigation on fatigue behavior of GFRP hybrid bonded/bolted joint under shear loading based on nondestructive monitoring test and numerical modeling

The GFRP (Glass Fiber Reinforced Polymer) is prospective in bridge and building engineering for its advantageous material property. The connection configuration of hybrid bonded/bolted joint of GFRP is thought superior in mechanical performance compared with the traditional bonded and bolted joints. However, the fatigue issue of this type of joint remains unclear which impedes its engineering applications. The presented work experimentally and numerically investigated the fatigue behavior of the GFRP hybrid bonded/bolted single-lap joints under shear loading. High-cycle fatigue tests on single-bolt, four-bolt, and nine-bolt specimens were conducted to study the failure process, rigidity degradation, failure mode, and fatigue life of the hybrid joints, where the nondestructive monitoring techniques of AE (Acoustic Emission) and 3D-DIC (Three-Dimensional Digital Image Correlation) were adopted, respectively to detect the material damages and overall deformation of specimens. Finite element modelling was further carried out to reveal the fatigue failure mechanism of hybrid joints, in which the property degradation of GFRP plates and adhesive layer were considered. Results showed that the failure process of GFRP hybrid single-lap joints under fatigue shear loading can be divided into four stages: (1) steady and (2) rapid development of adhesive damage, (3) steady and (4) rapid development of GFRP damage, of which the (2) and (4) stages account for less than 3% of the total fatigue life of joint, respectively. Stiffness degradation of 14–35% were read for the tested joints before final failure, and the joints with more bolts performed a superior degradation resistance compared to the less ones. Besides debonding and bolt inclination, the single-bolt joints failed with bearing failure of GFRP material, while the failure mode of multi-bolt joints were dominated by shear failure in GFRP plate with Y-shaped zone. The simulation results well supported the observations in experimental test. Based on the experimental results, the S-N curve of the GFRP hybrid single-lap joints is proposed, which can provide support for the engineering design of this type of joints.

Hybrid joints consisting of pre-tensioned bolts and a bonded connection—The influence of adhesives on the load-bearing capacity

This study explores the intricate mechanics of hybrid joints, which combine prestressed bolts and adhesive bonding, with a focus on increasing the joint capacity of steel structures. Despite their potential, the fundamental behaviour of these joints is not fully understood. The research focuses on unravelling the load-bearing capacity of these hybrid joints, emphasising the influence of the adhesive properties. The unique manufacturing process, involving the pre-tensioning of bolts while the adhesive is uncured, introduces additional dependencies not present in conventional adhesive joints. Analysis of the mechanical and physical properties of five adhesives provides key insights into the mechanics of load transfer and failure modes in hybrid joints, providing a comprehensive understanding. The study shows that load transfer occurs through micron-thin adhesive layers, highlighting the significant influence of adhesive properties on joint performance. Epoxies emerge as the top performers, with 2.5 times the average friction joint and more than five times the average bonded joint capacity, indicating their superiority in hybrid joint applications. Hybrid joints show significantly less variation than adhesive and friction joints, underlining their consistency and reliability in structural applications. When comparing hybrid and bonded joints with the same adhesive (SW7240), the variance was suppressed to one seventh by the application of preloaded bolts, with practical implications for design values based on quantiles. The study establishes correlations between joint strength and adhesive properties, emphasising the critical role of Young's modulus and tensile strength. It also finds that the elongation of hybrid joints at break is almost entirely dependent on load capacity, with viscosity having a lesser effect. Fracture surface investigations provide insight into the failure modes of hybrid joints, highlighting differences from those observed in frictional or purely bonded joints. This comprehensive study, combining experimental campaigns and in-depth analysis, provides valuable insights into the intricate relationships between joint capacity and adhesive properties in hybrid joints. The findings guide the selection of appropriate adhesives and provide the basis for the development of accurate load prediction methods, unlocking the full potential of hybrid joints and overcoming the limitations of conventional joining techniques in steel structures. Further research is encouraged to investigate the influence of adhesive class, post-tensioning stability and the nuanced mechanics of load transfer in these innovative joints.

Experimental investigation of aluminium alloy gusset joints’ dynamic response to lateral impact loads: Evaluating the influence of gusset plate bending stiffness

The traditional aluminium alloy gusset plate (AAG) joint is commonly regarded as a representative semi-rigid joint characterized by limited stiffness. This deficiency in stiffness significantly hampers its capacity for load transmission and resistance against progressive collapse in spatial grid structures. Notably, the dynamic response characteristics of semi-rigid joints, especially when subjected to short-term, highly intense loads such as impacts and explosions, deviate substantially from those of rigid joints. This research examines the dynamic failure behavior of six distinct traditional AAG joints with varying degrees of stiffness when subjected to impact loads. The first group comprises three specimens where the variance in AAG joint stiffness is achieved by altering the gusset plate’s diameter. The second group comprises three specimens aiming to manipulate the AAG joint’s stiffness by modifying the gusset plate’s thickness. The study yielded comprehensive data, including stress profiles, displacement patterns, acceleration time history curves, and failure modes of AAG joints. The experimental findings revealed that both groups of AAG joints under lateral impact loads exhibited brittle failure. The predominant failure modes included the rupture of the H-shaped aluminium alloy beam, distortional buckling of the beam, and warping of the thinner gusset plate. It is evident from the stress, displacement, and acceleration time history curves that the AAG joint adheres to the characteristics of a typical semi-rigid joint, and the diameter and thickness of the gusset plate exert significant influence on the AAG joint’s dynamic response. Subsequently, the six test conditions were simulated using ANSYS/LS-DYNA software. This simulation considered the stress distribution, impact force time history curves, and strain energy time history curves of AAG joints. It facilitated a detailed discussion of the failure mechanism underlying AAG joints when subjected to lateral impact loads.

Study on failure modes and calculation method of the cast steel joint with branches in treelike structure

The treelike structure links members and transfers loads via its solitary cast steel joint with branches. Therefore, the joint’s bearing capacity significantly affects the treelike structure’s stability, security, and economics. This paper utilized experimental verification and numerical modeling to examine the mechanical behavior of cast-steel joints with branches in the treelike structure under various loading conditions. Then, researchers investigated the failure process and mechanism of joints, and the three most common failure modes were outlined. Furthermore, the researchers proposed the bearing capacity calculation formula based on the common failure modes. The results show that the three common failure modes of the cast-steel joints with branches under different loading conditions are the failure in the joint core area under the axial load, the failure in the main pipe compression side under eccentric load, and the failure in the compression side of the single branch pipe root when the single branch pipe is under the uneven load. The suggested empirical calculation method can serve as a reference point for similar engineering practices design.

Probabilistic identification method for seismic failure modes of reinforced concrete beam-column joints using Gaussian process with deep kernel

Identifying the seismic failure modes of beam-column joints (BCJs) is crucial for the safety and integrity of reinforced concrete (RC) buildings or structures withstanding seismic forces. However, traditional identification methods fail to provide any indication about the uncertainties within their predictions, which is beneficial for evaluating, interpreting and improving these predictions. This study develops a probabilistic identification method for seismic failure modes of BCJs using Gaussian process (GP) with a deep kernel, which integrates the representational power of deep neural networks with the flexible structure of kernel functions to accurately represent the evolution characteristics of seismic failure modes of BCJs. Analysis results demonstrated the potential of the proposed method for improving the classification accuracy of traditional GPs, as well as its superiority over the prediction accuracy of traditional shear-resistance design methods and machine learning techniques. Furthermore, the proposed method also provides an efficient approach to estimate the uncertainties within their predictions for seismic failure modes of BCJs.

Numerical simulation and design method of dowel-type timber joints connecting laminated veneer lumber

Dowel laminated timber (DLT) is a structural engineering wood product composed of laminates connected by wood dowels. It has the characteristics of green, low-carbon, and a high degree of prefabrication. Wood dowel connection is the forming method of DLT, and its joint design is the key to DLT. The properties of laminates affect the mechanical properties of both DLT and dowel-type timber joints. Laminated Veneer Lumber (LVL) is an engineering wood product made by gluing veneers along a fixed grain direction, with excellent physical and mechanical properties. Utilizing small-thickness LVL as the laminates of DLT, a design method of dowel-type timber joints connecting LVL was explored through numerical simulation and theoretical calculation. A three-dimensional finite element model of dowel-type timber joints connecting LVL was presented, and experimental calibration were carried out. The parametric study was adopted to explore the influence of main variables on the shear performance of joints. The calculation formula for the shear capacity of joints was proposed and optimized, and the design method of joints was summarized. The results indicated that the failure mode and shear capacity of joints were dramatically influenced by two variables: the ratio of side laminate thickness to dowel diameter (n) and the thickness ratio of middle-to-side laminate (m). The two variables affected the shear capacity of joints by affecting the failure mode of joints. When the ratio of side laminate thickness to dowel diameter was 1 < n ≤ 3.75, the optimized Johansen theoretical formula could effectively predict the shear capacity of dowel-type timber joints connecting LVL.

Effect of laser micromachining crater-array–multi-grooves on the bonding strength and failure mode of aluminum alloy adhesive joints

The strength of aluminium (Al) alloy adhesive joints is essential for aerospace, ship and automotive applications. This study proposes the two-step laser processing of crater-array–multi-groove (CAMG) to maximize the shear strength of adhesive joints for 7075-T6 aluminum alloys. Firstly, the effects of CAMG feature parameters (groove pattern, groove spacing L, and groove depth Gp) on the surface roughness (Sa), shear strength (τ), and microscale failure mode were studied. The failure mode and anchoring structure reveal the influence mechanism of CAMG feature parameters on τ. Then, the parameters are optimized to obtain the best combination that maximizes τ. Finally, the advantages of CAMG were demonstrated by comparing it with a reference specimen and analyzing the surface morphology, wettability, chemical properties, and anchorage structure. The results show that for CAMG the surface had high cleanliness, wettability, and chemical modifications. The multi-scale anchoring structure formed by the grooves, craters, and micropores on the surfaces with the adhesive was sufficiently strong to allow cohesive failure (CF) to occur throughout the bonding region, maximizing τ. When the groove pattern is parallel-groove, L ≤ 100 μm, and the number of scans is N = 2–5, CAMG maximizes τ (∼29.34 MPa). To increase efficiency and save energy, the optimal combination of parameters for laser processing CAMG is parallel-groove, L = 100 μm, and N = 2. Compared with laser processing multi-grooves, CAMG improved the processing efficiency by 3.5 % and reduced the laser energy by 35.2 %. The proposed method shows great advantages in improvement of bonding strength.

Enhancing bond performance of CFRP-steel epoxy-bonded interface by electrospun nanofiber veils

The epoxy-bonded interfaces between carbon fiber reinforced polymer (CFRP) and steel usually have insufficient strength and toughness, and the toughening of bonded interface is a key problem for the usage of CFRP in steel structures. In this study, electrospun nanofiber veils were first proposed to enhance the bond performance of CFRP-steel epoxy-bonded interfaces. Firstly, shear tests were conducted on neat epoxy and nano-modified single-lap aluminum-aluminum joints to determine the optimal areal density and number of layers of nanofiber veils, as well as the optimal curing processes. Then, a series of neat epoxy and nano-modified CFRP-steel double-lap joints with different bond lengths were tested to investigate the size effect of the bond behavior. The displacement and strain field evolution of the joints were captured by the digital image correlation (DIC) technique, allowing for visualization of the detailed failure process. The failure modes, load-displacement curves, CFRP strain distributions, and bond-slip relationships of the CFRP-steel joints were obtained. Both the tests on aluminum-aluminum and CFRP-steel joints show that the optimal modification strategy is incorporating 3 layers of nanofiber wels with an areal density of 4.5 g/m2, with 5 h room-temperature and 2 h 80 °C high-temperature curing. The primary failure mode of CFRP-steel joints is CFRP delamination accompanied by CFRP-adhesive interface or steel-adhesive interface debonding. The bond strengths of the modified joints with 3 layers of 1.5 g/m2 and 4.5 g/m2 nanofiber veils are increased by 7 % and 25 % compared to those of un-modified joints, respectively. The 4.5 g/m2 nanofiber veils modified bonded interface has an effective bond length of about 152 mm, with a corresponding ultimate bearing capacity of 117 kN. Different from the triangular (brittle) shape of most neat epoxy interfaces, the nano-modified interfaces have trapezoidal (ductile) bond-slip relationships, providing superior cracking resistance. Moreover, a comparison with the bond strength of SiO2 nano-particles and carbon nanotubes (CNTs) modified joints revealed that nanofiber veil modification comes to higher bond strength in most cases. The proposed electrospun nanofiber veil modification technique provides a great insight into the interfacial toughening of CFRP-steel composite structures.

Adhesion improvement and strengthening mechanisms of ultrasonic adhesive-impact bonding process for CFRP/Ni bonded joints

The adhesively bonded structures of carbon fiber-reinforced polymers (CFRPs) and metals are extensively applied in various engineering fields. However, the inferior adhesion between metals (particularly such inert metals as nickel) and adhesives remains a significant challenge. In addition to surface pretreatment technology, ultrasonic vibration has been demonstrated to effectively enhance the flowability and permeability of liquid. In this paper, by implementing a novel ultrasonic adhesive-impact bonding process, the ultrasonic vibration was directly acted on adhesives to generate a violent high-frequency impact on the adherend surfaces of CFRP/Ni joints before the adhesive bonding process, resulting in an improvement of 17.2 % in the bonding strength. The optimal process parameters were determined through an orthogonal experiment, and the failure modes of joints were analyzed. The strengthening mechanisms were investigated by analyzing the microstructure and chemical components of both adherend surfaces and adhesive interfaces. The SEM image of the interface indicated that the high-frequency impact of adhesive caused by ultrasonic vibration facilitated its penetration into the microgrooves on the nickel surface, thereby increasing the effective bonding area and enhancing the mechanical anchoring. Furthermore, the FTIR spectra of the interface indicated the enlarged bonding area and the intense high-frequency collision between the adhesive molecules and the polar chemical groups on the nickel surface, which was introduced by atmospheric plasma treatment, enhanced the probability of the chemical reactions between them, thus strengthening the chemical bonding.

Bearing capacity of horizontal joints of UHPC prefabricated shear walls with vertical bars splicing by cold-extrusion sleeves

To study the shear performance of the horizontal joints of ultra-high-performance concrete (UHPC) prefabricated shear walls with vertical bars splicing by cold-extrusion sleeves, unidirectional loading tests for three samples have been conducted and a method to calculate the shear bearing capacity of the horizontal joint has been proposed. The influence of the reinforcement ratio and axial compression ratio on failure mode, cracking morphology, load-displacement curve, and shear bearing capacity of the horizontal joints has been analyzed in the tests. In addition, the failure process of the three samples has been simulated using finite element method. The results showed good agreement between the test results and numerical results, which certified the validity of the proposed calculation method for the shear capacity of the horizontal joint. The test results showed that the cold extrusion sleeve connection can effectively transmit the stress of the reinforcement, and the shear bearing capacity of the horizontal joints of the UHPC prefabricated shear wall can be enhanced by increasing the axial compression and reinforcement ratios.