Plate Joints Research Articles

Experimental and numerical investigations of seismic performance of stepped beam-column joints with different connection forms

The seismic resilience of prefabricated steel structures significantly depends on the design and construction of beam-column joints. To address the challenges related to the installation of prefabricated wall panels and overall system assembly, this study introduces a novel stepped beam-column joint. The effectiveness of different connection configurations on the seismic behavior of the joints was investigated. A series of cyclic tests were conducted on four joint specimens with different configurations, and their failure mechanisms, hysteretic curves, skeleton curves, stiffness degradation, load-bearing capacity, and energy dissipation capacity, were revealed. The experimental results showed that the stepped joint configuration offers favourable seismic performance, with notable asymmetry observed in the response patterns under positive and negative loading directions. Reducing the height of the stepped segment or the thickness of the end plate adversely affected the seismic performance, leading to early bolt failure. Consequently, a detailed finite element model of the stepped joint was developed and the model demonstrated satisfactory agreement with the experimental results. Furthermore, a parametric analysis focusing on variations in stepped segment's height was conducted, providing insights into optimization of the load-bearing capacity of the stepped joint. The difference in the performance between the stepped joints and traditional flush end plate joints is also highlighted.

Evolution of microstructure and mechanical properties of GTAW joint for magnesium alloy thin plate by post-weld reinforcement compression treatment

Gas tungsten arc welding (GTAW) joints of magnesium alloy thin plates generally exhibit low welding coefficients. Therefore, post-weld reinforcement compression treatment is utilized to improve mechanical properties of the joints in this experiment. The study shows that the grain shapes and sizes in various zones of the treated welded joints alter significantly, and the presence of twins is also detected especially in the base material (BM) and heat-affected zone (HAZ). The strength of the welded joints progressively rises with the increase in the compression reduction. The welding coefficient of the C3-joint reaches 91.6% when the compression reduction is 1 mm. The ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) are 271 MPa,173 MPa and 7.2% respectively. The post-weld reinforcement compression treatment introduces abundant dislocations in the fusion zone (FZ), contributing significantly to the increase in joint strength. In addition, solid solution strengthening and texture strengthening also exert a role.

Study of microstructure and mechanical properties of SA553/SA537 steels joints using multi-pass welding for pressure vessels application

In this study, gas metal arc welding (GMAW or MIG) process was investigated for similar and dissimilar joints of SA553 and SA537 steel plates in different thicknesses with E NiCrMo-3 filler metal and 0–3 panel joint design that joined pressure vessels body to manholes. In order to examine the metallurgical behavior of the weld, optical and scanning electron microscopies were used. The effect of cooling rate (∂T∂t) on microstructure, strength and impact energy (cryogenic fracture toughness) were examined. By doubling the thickness (6–12 mm), the heat transfer rate or cooling rate (∂T/∂t) increased 4 times. Therefore, the strength and impact energy for the similar welding joint SA553 increased by about 8 % and for the similar welding joint SA537 by about 5 %. For dissimilar weld joints with different thicknesses, strength and impact energy are caused by the type of base metals and the different cooling rates of each base metal. Due to the high elongation of the E NiCrMo-3 electrode (30 %), there was continuous plastic deformation during bending tests. Also, by carrying out radiographic tests, the absence of cracks in welding structures was confirmed.

Nonlinear vibrations of bolted flange joint plate system considering the stick–slip–separation state: theory and experiment

Nonlinear vibrations of bolted flange joint plate system considering the stick–slip–separation state: theory and experiment

Effect of the Energy Director Material on the Structure and Properties of Ultrasonic Welded Lap Joints of PEI Plates with CF Fabric/PEI Prepreg

To estimate the possibility of using both low-melting TecaPEI and neat PEI films as energy directors (EDs) for ultrasonic welding (USW) of carbon fiber (CF) fabric–polyetherimide (PEI) laminates, some patterns of structure formation and mechanical properties of their lap joints were investigated by varying the process parameters. The experiment was planned by the Taguchi method with the L9 orthogonal matrix. Based on the obtained results, USW parameters were optimized accounting for maintaining the structural integrity of the joined components and improving their functional characteristics. The use of the low-melting EDTecaPEI film enabled US-welding the laminates with minimal damage to the fusion zone, and the achieved lap shear strength (LSS) values of ~7.6 MPa were low. The use of EDSolverPEI excluded thermal degradation of the components as well as damage to the fusion zone, and improved LSS values to 21 MPa. With the use of digital image correlation (DIC) and computed tomography (CT) techniques, the structural factors affecting the deformation behavior of the USW lap joints were justified. A scheme was proposed that established the relationship between structural factors and the deformation response of the USW lap joints under static tension. The TecaPEI film can be used in USW procedures when very high interlayer adhesion properties are not on demand.

Crack generation and propagation mechanism of Mo[sbnd]14Re alloy laser welding

This paper investigates the mechanism of crack generation and propagation in laser-welded joints of Mo14Re alloy plates. The study utilized optical microscopy (OM) and scanning electron microscopy (SEM) to examine the microstructure and morphology of the crack area in the Mo14Re laser-welded joint. Additionally, energy dispersive spectroscopy (EDS) was employed to characterize the elements at the crack defect, while electron backscatter diffraction (EBSD) was utilized to analyze the grain boundary and crystal orientation at the crack defect.The analysis of crack formation and propagation considered various factors, including grain boundary segregation, characteristics of grain boundaries and crystal orientation, and the Schmidt factor. The findings revealed that cracks formed in the weld area exhibited distinct characteristics of brittle fracture along the grain. Notably, these cracks displayed evident carbon and oxygen segregation attributed to the presence of a low melting point eutectic liquid film. The segregation, along with high-temperature compounds on the fracture surface, emerged as the primary factors contributing to crack formation.In the proximity of the crack, there exists a concentration of strain, inducing plastic deformation and thereby facilitating crack initiation. Cracks exhibit a tendency to originate along large-angle grain boundaries and deflect along these boundaries. Owing to the difference in atomic slip characteristics on both sides of the crack, the direction of crack propagation is more inclined to deflect towards grains with a smaller Schmidt factor.

Microstructure and Micro-texture Development of Variable Frictional Heat Input Friction Stir Welded Joints of Laser Powder Bed Fusion-Made AlSi10Mg Plates

Microstructure and Micro-texture Development of Variable Frictional Heat Input Friction Stir Welded Joints of Laser Powder Bed Fusion-Made AlSi10Mg Plates

Non-destructive detection and analysis of weld defects in dissimilar pulsed GMAW and FSW joints of aluminium castings and plates through 3D X-ray computed tomography

AbstractThis work focuses on porosity formation during the welding of dissimilar aluminium alloys (cast and sheet) by pulsed gas metal arc welding (GMAW) with different travel speeds (12–14 mm/s) and by friction stir welding (FSW). The case study concerns the assembling of a battery-pack enclosure prototype. The welded specimens were scanned by 3D X-ray computed tomography. The cast base material (BM) shows a porosity percentage of 1.45%, and it is characterized by pores with a strong hyperbolic relationship between equivalent diameter and sphericity. Considering the GMAW beads, porosity rises with the travel speed (from 1.80 to 5.12%), due to the reduction of the opening window in which pores can escape. Pores with volume higher than 0.10 mm3 rise with the travel speed, representing from 9.75 to 32.98% of the total porosity. These pores are responsible for the weaker hyperbolic connection for sphericity found for the GMAW beads. On the other hand, FSW mixes and homogenizes the pores in the cast BM. The novelty of the paper lays in proving the strong potentialities of FSW for weld porosity reduction. A re-designing of the battery-pack enclosures is necessary to limit arc welding in marginal areas, which are not crucial for sealing but necessary to create a stable platform to be subsequently sealed with FSW.

ANALYSIS OF THE PERFORMANCE OF A JOINT THAT COMBINES HIGH-STRENGTH BOLTS AND WELDING

In steel constructions, sometimes, it is necessary to combine bolts and welds in a single joint. While some design provisions for these combination joints appear in current standards, there have been no design rules generally verified by physical tests. In addition, the rules appear illogical in some cases, possibly leading to unconservative designs. The need for a combined joint in steel structures can arise for several reasons. For example, load requirements for an existing bolted joint may change, necessitating the joint redesign. As a result of bolt clearance requirements or limitations due to the existing joint plate size, there may not be sufficient space to add more bolts. Also, drilling a new bolthole in the field may not be possible because of space restrictions. For this situation, adding welds to the joint is the only practical option to give the joint the necessary increase in load resistance. The need for a combination joint may also arise in new construction. Another situation often requiring a combination joint is repairing a riveted joint. The assumption that the ultimate strength of a connection is the sum of the ultimate strength of each mechanical fastening element present in the connection is an unconservative approach to the design of the connection. In contrast, only accounting for the ultimate strength of one of the individual types of mechanical fastening elements in a combination joint is a very conservative approach. In the design of steel structures, it may be necessary to use a combined joint in which bolts and welds take up the force flow. Guidelines for the design of such a combined joint are available in the current DBN B.2.6-198:2014 ‘Steel structures. Design standards’. However, there are no practical examples and recommendations for calculating this type of joint in the scientific and technical literature. This article is devoted to studying the combined joint to improve understanding of the nature of its operation. The authors achieved the goal by numerical modelling of combined joints. Numerical experiments have shown that the welds’ orientation and the bearing capacity of bolts are two key factors to consider when determining the proportion of force acting on welds and bolts. Keywords: high-strength bolt, welds, combined joint, stress-strain state.

Ultrasonography-Based Quantitative Evaluation of Second Metatarsophalangeal Joint Instability in Female Patients With Hallux Valgus.

Patients with moderate to severe hallux valgus (HV) sometimes exhibit second metatarsophalangeal (MTP) joint dislocation. Second MTP joint instability due to plantar plate (PP) injury has been suggested as one of the causes. However, there have been no reports that quantitatively evaluate this instability. This study aimed to evaluate second MTP joint instability in patients with HV without dislocation via ultrasonography and investigate its relationship with the presence of PP injury or foot form. Between May 2018 and July 2023, symptomatic female patients with HV without any lesser toe deformity were included in this study. Second MTP joint instability was defined as the dorsal displacement ratio (DDR) of the passively subluxated proximal phalangeal articular surface on the metatarsal head articular surface. The presence of PP injury was assessed using ultrasonography. Foot "form" was determined by measuring standard foot bony angles on weight-bearing foot-ankle radiographs. The relationship between DDR or PP injury and radiographic measurements was investigated. Sixty-four patients (100 feet) were included. The average DDR of the second MTP joint in patients with HV without dislocation was 35.7%. There was an increase in the probability of PP injury, above a cutoff DDR value r of 35.4% (area under the curve = 0.712). The sensitivity, specificity, positive predictive value, and negative predictive value for the presence of PP injury based on this cutoff level were 63.9%, 74.4%, 79.6%, and 56.9%, respectively. Metatarsalgia was reported in 21 feet (21.0%), of which 15 feet (71.4%) showed PP injury. An increase in DDR was weakly associated with increased metatarsus adductus angle and decreased second metatarsal height. In female patients with HV without second MTP dislocation, we found ultrasonographic evidence of second MTP plantar plate injury and joint instability to be a relatively common finding with a high prevalence in those with localized metatarsalgia. Level II, development of diagnostic criteria based on consecutive patients.

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.

A digital twin approach toward unlocking elasto-plastic fatigue crack growth rates under negative load ratios

This paper introduces a novel digital twin solution for unlocking the elasto-plastic fatigue crack growth within an S550 steel under negative load ratios. The digital twin transforms solely strain data from a strain-interfaced welded plate joint specimen to the load–displacement curve to compute cyclic J-integral values using the η approach, eliminating the need for load and displacement measurements. The accurate computation of the elasto-plastic ΔJ effectively extends the fatigue crack growth relationship derived from standard fracture specimens. The extended fatigue crack growth relationship accurately predicts the fatigue life of specimens under separate step-up and step-down variable amplitude loading regimes.

Ultrasonic welding of lap joints of PEI plates with PEI/CF-fabric prepregs

In this study, ultrasonic welding (USW) of lap joints of polyetherimide (PEI) plates (adherends) with carbon fiber (CF) prepregs impregnated with PEI was investigated. No energy director (ED) was used, so binder contents were varied in the prepregs to compensate for the lack of the polymer in the fusion zone. In addition, the effect of the USW parameters on the structure and the mechanical properties of the lap-joints were analyzed. The most homogeneous macrostructure, the maintained structural integrity of both the CF-fabric in the prepregs and the lap-joined PEI adherends, as well as the maximum strength properties (tensile strength) were revealed for the USW joints with the minimum polymer content in the prepreg. In this case, rising the USW time from 400 up to 800 ms radically changed the macrostructure of the fusion zone, while the strength properties did not vary significantly (shear stresses were 42–48 MPa). Computer simulation of the influence of the PEI/CF-fabric ratios in the prepregs on the deformation response of the USW joints showed that the prepreg thicknesses and, accordingly, the PEI/CF ratios did not exert a noticeable effect on the strain–stress (tensile) diagrams, while the determining factor was the adhesion level.

Low-cycle fatigue behaviour of magnesium alloy thick plate joints fabricated via differential double-shoulder friction stir welding

Magnesium (Mg) alloy thick plates welded by friction stir welding (FSW) often exhibit poor formability and uneven microstructures, leading to a significant deterioration in the mechanical properties. In this work, AZ31 Mg alloy plates with a thickness of 20 mm were successfully welded by differential double-shoulder friction stir welding (DDS-FSW). The low-cycle fatigue response behaviour was characterised, and the damage mechanism of the joints were studied. The results indicated that the fatigue life of the DDS-FSW joints in both parameters exceeded that of the FSW joint at 0.3 % strain amplitude, with increases of 200 % and 82 %, respectively. The predominant deformation mechanisms are basal slip and {10 1¯ 2} twinning. Basal slip is more likely to be activated in the FSW joint, whereas {10 1¯ 2} twinning is more easily activated in the DDS-FSW joints. Furthermore, the fatigue toughness (W0) and damage transition exponent (β) could be increased by improving the asymmetric distribution of the stir zone in the joint, the strength of “orientated micro-interface”, and the proportion and distribution uniformity of twins.

Vision‐based robust missing and loosened bolt detection for splice plate joints

SummaryVision‐based bolt defect detection methods based on feature changes have been reported. However, the robustness of key feature extraction and bolt detection requires improvement. This paper proposes a robust missing and loose bolt defect detection approach. The key features—reference points for perspective correction and the straight lines of the bolt edges—are extracted from the masks obtained by semantic segmentation models. The true and false bolt discrimination approach based on the mask shape can help improve bolt object detection accuracy. Overlapping between the bolt bounding boxes in the reference and detection images indicates missing bolts. The rotation angles reveal loosened bolts. The proposed approach was tested on fabricated bolted joint specimens and a steel railway bridge. The results suggest that these improvements ensure defect detection accuracy, with a miss rate of only 1% for missing bolt detection. Moreover, a loosened bolt with only 3° rotation is successfully detected. This approach has promising potential applicability in automatically detecting bolt defects in large steel structures.

Study on the Seismic Performance of High-Speed Railway Extradosed Cable-Stayed Bridge Considering CRTS III Slab Ballastless Track Structure

This paper explores the seismic damping mechanism and performance of CRTS III slab ballastless track on an isolation system extradosed cable-stayed bridge during rare earthquakes. It serves as a guide for designing slab ballastless tracks on high-speed railway extradosed cable-stayed bridges. Using a high-speed railway extradosed cable-stayed bridge as a case study, we established a Midas finite element model to optimize the track plate parameters by adjusting the fastener stiffness and plate joint length. The optimization process and method can be applied as a reference for similar bridge designs. The research findings reveal that, under rare earthquake conditions, the CRTS III slab ballastless track model (with a plate joint length of 90mm and fastener stiffness of 30kN/mm) has a minimal impact on increasing the longitudinal internal force at the pier’s base. It, at most, raises the earthquake internal force response by 5%. The model significantly reduces the overall relative displacement of the bridge pier and girder, with a notable 15.5% reduction in the relative displacement of pier 143# on the side pier. Therefore, when conducting internal force tests for the bridge, it is crucial to consider the influence of track plate restraint.

Open reduction and internal fixation in treatment of four cases of bipolar clavicle dislocations

To summarize the method and effectiveness of open reduction and internal fixation in the treatment of 4 cases of bipolar clavicle dislocations. Between June 2017 and June 2022, 4 patients with bipolar clavicle dislocations were admitted. There were 3 males and 1 female. The age ranged from 27 to 63 years, with an average age of 45 years. There were 2 cases of crushing injury of mine car, 1 case of traffic accident injury, and 1 case of heavy object injury. The time from injury to operation was 3-7 days, with an average of 5.0 days. The sternoclavicular joint dislocations were classified as Grade Ⅱ in 1 case and type Ⅲ in 3 cases, and anterior dislocation in 3 cases and posterior dislocation in 1 case. The acromioclavicular joint dislocations were classified as Tossy type Ⅱ in 2 cases and type Ⅲ in 2 cases. After open reduction, the sternoclavicular joint and acromioclavicular joint were fixed with lateral malleolus locking titanium plate and clavicular hook plate, respectively. All operations were successfully completed without vascular or nerve injury. All incisions healed by first intention. All patients were followed up 12-18 months, with an average of 14 months. At last follow-up, the shoulder joint functions were rated as excellent in 3 cases and good in 1 case according to Rockwood score. During follow-up, there was no loosening of internal fixator or fracture. The internal fixators were removed in all patients at 5-7 months after operation (mean, 6 months), and no re-dislocation occurred after removal. For bipolar clavicle dislocation, open reduction combined with lateral malleolus locking titanium plate fixation of the sternoclavicular joint and clavicle hook plate fixation of the acromioclavicular joint can achieve good effectiveness. It has the advantages of simple operation, high safety, firm fixation, and fewer complications, and the shoulder function recovers well.

Correlation of microstructure, texture, and mechanical properties of friction stir welded Joints of AA7075-T6 plates using a flat tool pin profile

This study investigates the influence of square and hexagon tool pin profiles on the butt joint of AA7075-T6 plates through friction stir welding. In contrast to the AA7075-T6 base metal with a grain size of 32.736 μm, both square (4.43 μm) and hexagon (5.79 μm) pin profiles led to a significant reduction in grain size within the stir zone (SZ) of the weld cross-section. The SZ region exhibited a gradient in recrystallization and a notable fraction of high angle grain boundaries, attributed to continuous dynamic recrystallization influenced by variations in temperature and strain rate. Pole figure analysis revealed predominant shear texture elements (B/ B‾ and C) with minor A1*/A2* and A/ A‾, indicating elevated strains within the SZ. Orientation distribution function (ODF) analysis identified recrystallization texture elements such as Goss {110} <001>, cube {001} <101>, and P {011} <112>, along with shear texture components F {111} <112> and rotating cube (H) {001} <110>. Tensile and nanoindentation analyses demonstrated that the weld joint using a square-shaped pin profile exhibited higher strength, elongation, and elastic modulus compared to other weld joints. These findings suggest that the square tool pin geometry enhances material flow and grain refinement during welding, thereby improving the mechanical properties of the joint.

One-sided friction stir welding of 1565сhM alloy plates

The results of experimental studies of the features of the structure of butt joints of 1565chM alloy plates with a thickness of 25 mm obtained by one-sided friction stir welding are presented. It is established that the structure of the mixing zone (weld metal) is a dynamically and primarily recrystallized region. The grain size in the weld metal varies depending on the distance from the front surface of the weld from 5.16 μm (upper part of the joint) to 2.93 μm (root part of the joint). The separation of intermetallic compounds in the mixing zone for Al—Mg system alloys helps to reduce the average grain size. In the bodies of grains at the level of half the thickness of the plate, there are both chaotically distributed dislocations and dislocation clusters mainly in the form of dislocation walls. In this case, the scalar density of dislocations at this level exceeds the values of the scalar density of dislocations in the upper and root parts of the weld. In the mixing zone of the joints of the 1565chM alloy plates the microstructure at different levels of horizontal sections along the thickness of the plate is very homogeneous, which indicates the mechanism of layer-by-layer transfer, which is macroscopic.

Analyzing Thermal Images to Evaluate Thermal Protection in Residential Structures: Lessons from Russian Practices

Building thermography is a non-destructive and effective method for diagnosing the thermal insulation of buildings with various purposes. Regardless of the specifics of conducting thermographic surveys, the obtained thermal images (thermograms) can be analyzed both qualitatively and quantitatively. The first method of analyzing thermal images is implemented using specialized software typically provided with the thermal imaging camera. The second method is carried out based on the results of thermographic surveys following the methodologies regulated by the country’s normative documents. Using the example of thermographic inspection of enclosing structures in a multi-story residential building constructed from reinforced concrete panels, a qualitative assessment of thermal images was conducted to identify potential thermal defects. Thermal bridges were detected in the area of vertical joints of panel plates, and excessive heat losses were identified in the region where the heating device niche is located.Quantitative assessment of thermal images revealed that the thermal resistance in the temperature anomaly area is nearly twice as low as the thermal resistance in the baseline section of the thermogram. One of the variations for evaluating the error of indirect measurements of relative thermal resistance is presented, taking into account the range of measuring instruments used. Verification of the thermal resistance of the enclosing structure of the external wall of the residential building was conducted to ensure compliance with sanitary and hygienic requirements. According to the results of in-situ measurements, it was determined that the temperature on the inner surface of the enclosure was lower than the specified value.