Joint Configuration Research Articles

Development and Performance Analysis of a Seam Welding Machine for Thin Plate Applications

Resistance Seam Welding (RSEW) is a welding process that uses rotating wheel-shaped electrodes to produce a continuous weld along the seam of the workpiece. RSEW is used for welding metal sheets and utilizes electrical resistance as its heat source. The welding technique applicable to RSEW is the lap joint configuration. In this study, steel plates with thickness variations of 0.15mm, 0.2mm, and 0.3mm were welded using a current of 20 amperes and a welding speed of 3.125 mm/s. The thickness of the welded plates can affect the welding outcome. For the welding process, a current of 20 amperes was used on specimens with lap joint configurations. The specimens were subjected to tensile testing using a tensile testing machine with a capacity of 30 tons. The test specimens included three types of steel plates with varying thicknesses of 0.15 mm, 0.2 mm, and 0.3 mm. The results of the tensile tests indicated that, with the same welding parameters, the tensile strength decreased as the material thickness increased.

Understanding the interplay of Zn vapours and formation of intermetallic compounds during remote laser welding of Zn-coated steel to aluminium in a zero-gap lap joint configuration

Remote laser welding (RLW) of Zn-coated steel to aluminium is challenged by: (1) Zn vaporisation causing spatters and poor seam surface when welding in a zero-gap lap joint configuration; and (2) brittle intermetallic compounds (IMCs) at the weld interface, leading to cracks and poor weld integrity. This paper aims to study the impact of Zn coating during the RLW of Zn-coated steel to aluminium in a nominal zero part-to-part gap lap configuration. The combination of metallurgical and mechanical analysis with an in-process monitoring approach, using a high-speed camera, allowed the study of the interplay between Zn formation/out-gassing, molten pool dynamics and formation of IMCs. Findings revealed that the presence of a Zn coating results in an un-even connection area between steel and aluminium, with localised lack of fusion. A significant 72% joint efficiency compared to parent aluminium was achieved when Zn is removed, opposed to 65% when Zn is present.

Investigation on indirect laser welding of copper to aluminum

Laser beam welding of aluminum (Al) to copper (Cu) is challenging due to the formation of intermetallic compounds that are brittle and have high resistivities. However, the Cu/Al phase diagram shows a region were solubility of Cu in Al is present and, on the other hand, a region with the formation of a eutectic phase between α-Al and Al2Cu is present as well. Targeting this area turned to be advantageous for solid state welding, as shown for probeless Friction-Stir-Spot-Welding realizing ductile joints between Al and Cu.In this paper an approach based on indirect laser welding of Cu with Al will be presented and discussed. A green laser was used in order to join Cu to Al in lap joint configuration. The laser beam irradiates the Cu surface, whereby the formation of a common melt pool between Cu and Al is avoided. The heat input and the temperature gradient are assumed to support diffusion at the interface between Cu and Al forming a near eutectic layer. Indeed, a melting layer is formed at the interface between Cu and Al supporting joint formation based on a firmly bonding between both materials. The solidified layer presents a copper rich area towards the copper sheet with plate-like structures of Al2Cu, a region with α-Al crystals on the aluminum side and a eutectic layer of lamellar Al2Cu and α-Al in between. The described morphology is very similar to investigations on probeless Friction-Stir-Spot-Welding, whereas a very low pressure is adopted in indirect laser welding and Al-oxide layer seems not to act as a barrier for joint formation.

Joint Configuration Optimization and GPU Allocation for Multi-Tenant Real-Time Video Analytics on Resource-Constrained Edge

Joint Configuration Optimization and GPU Allocation for Multi-Tenant Real-Time Video Analytics on Resource-Constrained Edge

Strong column-weak beam relationship of 3D steel joints with tubular columns: Assessment, Validation and Design proposal

The study of moment connections in steel structures subjected to cyclic loads has been extensively studied, providing a great number of requirements, including the strong column-weak beam relationship, to guarantee a satisfactory cyclic performance. However, investigations on the cyclic performance of moment connections considering the bidirectional and axial load effects simultaneously with tubular columns are limited. This study aims to assess and validate the strong column-weak beam relationship of 3D steel moment connections using reduced order models. The simplified model (reduced order model) approach was employed to extend the range of beam and column elements sizes and reduce the experimental and computational costs. These models were calibrated from full-scale experimental studies. A great number of configurations with different beam and column sizes without loss of reliability and structural representativeness of the studied phenomenon were studied. A total of 13640 simplified models were developed. Results show a cyclic behavior controlled by the strong column-weak beam relationship to modify the joint's failure mechanism. The increasing of strong column-weak beam relationship and the biaxial effect caused degradation of the strength and stiffness as well as in dissipated energy. An optimal strong column-weak beam relationship was obtained for all joint configurations analyzed. Finally, a robust design procedure is proposed, ensuring the cyclic behavior of end-plate moment connection with built-up box column including biaxial effect and axial load. Therefore, the use of this type of moment connection can be used in special and intermediate moment frames designed according to Seismic provisions.

Test on seismic behaviors of stainless steel bolted extended end-plate beam-column joints

This study conducted tests on the seismic behavior of austenitic stainless steel bolted extended end-plate beam-column joints, which have been few reported. Considering the influence of material type, end-plate thickness, bolt diameter, panel zone thickness, and loading scheme, 11 stainless steel joints and two carbon steel joints were designed and tested. Material properties, joint failure modes, moment-rotation curves, bolt load distributions, and joint component yield sequences were reported in detail. Experimental research showed that the beam-column joints in austenitic stainless steel experienced four failure modes, i.e. plastic hinge at the beam end, fracture failure of weld between the beam flange and end-plate, bolt rupture failure, and composite failure. All the tested joints had good seismic behavior, with rotation capacity greater than 0.03 rad. The influence of joint configurations on the seismic behavior were analyzed. The results indicated that the end-plate thickness, end-plate stiffener, and bolt diameter had a substantial impact on the joint seismic behavior, while the thickness of column web in panel zone, material properties, and loading scheme had a comparatively small effect. The initial rotational stiffness and moment resistance(yield moment) of joint obtained from the experiment were compared with the predictions of the EN1993-1-8, Design Guide 16, and JGJ 82-2011. Comparisons indicated that the EN1993-1-8 overestimated the initial rotational stiffness; Both the EN1993-1-8 and JGJ 82-2011 underestimated the moment resistance, while the predictions from the Design Guide 16 were significantly higher than the moment resistance and closer to the ultimate moment.

Study on the effectiveness of single-bolt double-lap joints for integrating the damping system with building structure during cyclic load

Purpose Nowadays, in building structures, dampers are connected to the building structure to reduce the damages caused by seismicity in addition to enhancing structural stability, and to connect dampers with the structure, joints are used. In this paper, three different configurations of double-lap joints were designed, developed and tested. Design/methodology/approach This paper aims to analyze three different categories of double-lap single-bolted joints that are used in connecting dampers with concrete and steel frame structures. These joints were designed and tested using computational, numerical and experimental methods. The studies were conducted to examine the reactions of the joints during loading conditions and to select the best joints for the structures that allow easy maintenance of the dampers and also withstand structural deformation when the damper is active during seismicity. Also, a computational analysis was performed on the designed joints integrated with the M25 concrete beam column junction. In this investigation, experimental study was carried out in addition to numerical and computational methods during cyclic load. Findings It was observed from the result that during deformation the double-base multiplate lap joint was suitable for buildings because the deformations on the joint base was negligible when compared with other joints. From the computational analysis, it was revealed that the three double joints while integrated with the beam column junction of M25 grade concrete structure, the damages induced by the double-base multiplate joint was negligible when compared with other two joints used in this study. Originality/value To prevent the collapse of the building during seismicity, dampers are used and further connecting the damper with the building structures, joints are used. In this paper, three double-lap joints in different design configuration were studied using computational, numerical and experimental techniques.

Peridynamic Analysis of Tubular Joints of the Offshore Jacket Structure

Abstract Peridynamic theory is the reformulation of classical mechanics mathematical theory compatible with cracks while performing structural analysis. The present study models the tubular joints having T, Y, K, and X configurations in the peridynamic framework by implementing peridynamic shell governing equations. The linear response of the structure is validated by comparing the magnitude of deformations under static loading and the displacement variation at the subsequent load steps varying in a sinusoidal and irregular manner with the abaqus results. The crack initiation location at the stress-concentrated region and the crack growth path leading to fracture under linearly increasing loads for the considered tubular joints can be inferred from this approach. A comparative study is performed among the joint configurations based on the linear displacement variation and critical loads for the unstable deformation due to damaged material points at the joint intersection. In the present paper, apart from validating the implementation of novel theory in the offshore structure, the drawbacks and intricacies of the classical approach for studying crack initiation and growth in complex tubular joint structures are resolved by the peridynamic approach.

Experimental study on the mechanical properties of longitudinal joints of shield tunnels under large deformation conditions

Known to be the weakest part of the shield tunnel lining rings, the longitudinal joints render the lining rings prone to large deformation and related diverse defects under nonuniform pressure loading, thereby seriously compromising the safety, serviceability and durability of the tunnel structure. In light of the paucity of studies regarding the performance of joints under large deformation, this paper presents a series of experiments examining the damage mechanism of longitudinal joints under large deformation and investigating the effects of the bolt strength, initial joint configuration, and loading level on the mechanical properties of longitudinal joints. Moreover, a finite element model was developed for the joint, capable of simulating large deformation and bolt yielding. Results show that the specimen’s failure is characterized by concrete cracking and spalling at the compression side of the joint, and/or the thread stripping or fracture failure of the bolts. Besides, an increase in bolt strength can increase the bending capacity of the joint. The discontinuous joint configuration determines the compression height of the joint section cannot be continuously changed, which results in an abrupt change in structural stiffness and a four-stage change in bolt strain. Changes in the loading level not only affect the joint’s bending capacity to some extent, but also alter how cracks develop near the joint. Furthermore, the relationship between the joint opening angle and the segmental rotation angle proves the rigid body deformation characteristics of the segment before the bolts yielded. With the segmental rotation angle increased, the maximum joint opening width and mid-span deflection increased linearly, but the compression height decreased meantime. In addition, the relationship between the bolt strain and the segmental rotation angle exhibited a two-stage linearity after the bolt began to be stressed.

Effect of reducing heat input on autogenous TIG welding of Ti–6Al–4V alloy

3 mm-thick Ti–6Al–4V alloy plates were welded in butt joint configuration through autogenous TIG welding method using a trailing gas shielding arrangement. After attaining full penetrated weld joint with appropriate heat input, subsequent experiments were conducted by reducing the heat input, which was obtained through combination of higher welding current and scan speed. An in-depth microstructural analysis of the weld joint executed under different heat input conditions shows a strong correlation with the microhardness, tensile strength, and flexural strength of the weld joint. A significant improvement in the mechanical properties of the weld joint was perceived for employing lower heat input. Alteration in the primary-α, primary-β, and martensite-α phases, due to the variation in heat input, amended the mechanical properties of the weld joint under lower heat input condition. With the reduction of heat input from 0.406 to 0.232 kJ/mm, the tensile and flexural strengths of the weld joint increased from 1020 to 1070 MPa, and from 1015 to 1950 MPa, respectively. The tensile strength of the joint reached up to 98% of the base material at minimum heat input (0.232 kJ/mm). The experimental results show the potential of TIG welding for joining Ti–6Al–4V alloy under low heat input condition.

Development of a design space for dissimilar materials joining in aerospace applications

Abstract This research paper presents an application of the integrated process and product design (IPPD) approach for selecting the best joint configuration for dissimilar material joining in the early product design phase. The proposed methodology integrates the multi-criteria decision making (MCDM) approach with quality function deployment (QFD) to identify the key criteria for joint selection, including load-carrying capacity, size, cost per joint, ease of manufacturing, time consumption and deformation. Three types of joints (rivet, weld and adhesive) and two hybrid joints (adhesive-weld and adhesive-rivet) are considered for three dissimilar material configurations: carbon fiber-reinforced plastic (CFRP) aluminum, CFRP steel, and aluminum-steel. QFD is utilised to transform job requirements into design criteria, and in the second phase, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is employed to choose the optimal joint configuration based on the weighted criteria acquired in the previous phase. The selected joint configuration is then validated through experimental study. The findings demonstrate that the proposed IPPD approach with QFD-TOPSIS techniques is highly effective for selecting mechanical joints for dissimilar material joining in the early design phase. The study concludes that the adhesive-rivet hybrid joint is the optimal solution among all alternatives. The proposed methodology can ultimately lead to improved product reliability and performance, as well as reduced development time and cost.

Geometry effect on the static strength of curved composite bonded joints

In this work, the behavior of composite curved adhesive joints under pressure (p) is analyzed; such joint configuration has applications in aircraft fuselages. The chosen substrates were Carbon-Fiber Reinforced Polymer (CFRP) and three substrate thicknesses (tP) were studied. In addition, three different curvature radii (R), and eight overlap lengths (LO) were evaluated, while only one adhesive type was used. An internal pressure of 1 MPa was considered in all cases. The analyses were performed using the finite element method (FEM) and cohesive zone modelling (CZM). The increase in LO causes a linear increase in the peak peel stresses (σyy), affecting the thinner joints more; these peak stresses were located in the joint's knee region. Pmax was also found influenced by tP and LO, being again the effect more noticeable on the thinnest substrate; however, for LO≥40 mm the effect was negligible. As tP increased, Pmax had no significant improvement for LO≥20 mm. Although increasing R causes a slight reduction in the peak stresses, the stresses along the bond line were more uniform. Although R had no significant effect on Pmax, it increases joint compliance. In conclusion, the chosen adhesive allowed to successfully explore the different geometric parameters where the thinner joints with the largest R showed the best performance.

Analysis of renewable energy consumption and economy considering the joint optimal allocation of “renewable energy + energy storage + synchronous condenser”

As renewable energy becomes increasingly dominant in the energy mix, the power system is evolving towards high proportions of renewable energy installations and power electronics-based equipment. This transition introduces significant challenges to the grid’s safe and stable operation. On the one hand, renewable energy generation equipment inherently provides weak voltage support, necessitating improvements in the voltage support capacity at renewable energy grid points. This situation leads to frequent curtailments and power limitations. On the other hand, the output of renewable energy is characterized by its volatility and randomness, resulting in substantial power curtailment. The joint intelligent control and optimization technology of “renewable energy + energy storage + synchronous condenser” can effectively enhance the deliverable capacity limits of renewable energy, boost its utilization rates, and meet the demands for renewable energy transmission and consumption. Initially, the paper discusses the mechanism by which distributed synchronous condensers improve the short-circuit ratio based on the MRSCR (Multiple Renewable Energy Station Short-Circuits Ratio) index. Subsequently, with the minimum total cost of system operation as the optimization objective, a time-series production simulation optimization model is established. A corresponding optimization method, considering the joint configuration of “renewable energy + energy storage + synchronous condenser,” is proposed. Finally, the effectiveness of the proposed method is verified through common calculations using BPA, SCCP, and the production simulation model, considering a real-world example involving large-scale renewable and thermal energy transmission through an AC/DC system. The study reveals that the joint intelligent control and optimization technology can enhance both the sending and absorbing capacities of renewable energy while yielding favorable economic benefits.

Earthquake wonders: High school investigation in mortise tenon structures

Frequent global earthquakes lead to catastrophic property damage and casualties due to building collapses. However, the 1976 Tangshan Earthquake showcased an exception: the Forbidden City, constructed with wooden materials and featuring mortise-tenon structures, remained unscathed among surrounding destruction. This study investigates the earthquake-resilient attributes of wooden mortise-tenon joints utilizing economical high school equipment. An innovative low-cost sensor system, featuring custom instrumented hammer, is developed and validated. Calibration of the hammer's impact force employs correlation with acceleration data from a standardized scale weight during impact. The system's reliability is tested by comparing resonance frequencies from Finite Element modal analysis and experimental data for a cantilever beam. Impact hammer tests assess frequency response and damping across buildings with various joint configurations. Mortise-tenon joints display augmented frictional damping due to internal displacement. Through simulated vibration acceleration responses, a crucial finding emerges---integration of mortise-tenon joints translates to an impressive 11.0% reduction in earthquake vibrations. This research underscores the potential of accessible high school devices in advancing seismic engineering insights.

Effect of joint configurations on joint strength of different thickness AA6061-T6 friction stir welded blank

This paper presents a comparative study of the mechanical properties and microstructures of three friction stir welded joint configurations, namely square butt (SB), scarf (SC), and double butt lap (DBL) of the aluminium alloy 6061-T6. The experiment was conducted on two aluminium plates of different thicknesses, 2.0 mm on the advancing side and 1.5 mm on the retreating side, at constant welding parameters, such as welding speed, spindle rotation, tool tilt angle, and tool profile. The study compared the joints at different rolling angles, i.e. 0/0, 90/90, 0/90, and 90/0°. Tensile tests were conducted on the joints, and the ultimate tensile strength (UTS) was found to be 6–11% higher in the DBL joint configuration compared to the SC and SB joint configurations. The Vickers hardness values of the SC and DBL joints were also found to be higher than those of the SB joint configuration. The formation of the ‘S’ line was observed to influence the tensile test, hardness, and grain size, which in turn are determined by the shape of the faying surface.

Hybrid joint interface in composite fan blade subjected to bird strike loading

An aircraft engine’s fan blades are one of the most important parts of the engine. Bird strikes on fan blades have always been an issue, as bird parts can strike other parts of the engine, potentially causing more damage. It is impossible to avoid being struck by a bird entirely. However, finite element analysis can be used to optimize the design of blade so that the overall impact of a bird on a jet engine is reduced. Even though current composite blades can withstand the impact of a bird strike, some delamination failures have been observed on the blade’s trailing edge side, probably due to vibration bending modes. Instead of the single fiber composite blade that is currently in use, this research proposes using two fibers (Carbon and Glass). For this to be possible, two fiber joints must be designed properly at different locations on the blade. At crucial joint locations, the minimum inter-laminar strain level was used as the design criteria. Blade deformation is simulated using coupon and sub-element level finite element analysis (FEA) models with appropriate boundary conditions with in-built hybrid joints inside. The first stage of this project involved using the Ansys Parametric Design Language (APDL) and linear static analysis to create coupon models for combinations of joint positions. In the present work, dynamic bird strike analysis on sub-element level models was performed with various joint location combinations. The best joint configurations based on static and dynamic analysis results will be suggested for use in the composite blade to prevent delamination.

Automated fatigue crack detection of orthotropic steel decks using an improved mask region-based convolutional neural network approach

Orthotropic steel decks (OSD) are widely used in the bridge industry, but they are susceptible to fatigue cracking due to various factors such as weld defects, overload traffic, and complicated welded joint configurations. Traditional crack detection methods rely mainly on visual inspection, which is time-consuming and prone to errors. Recently, many crack detection methods based on machine vision have been introduced. However, accurately and effectively detecting fatigue cracks of OSD remains challenging due to the indistinct nature of these cracks compared to the background and their susceptibility to various types of noise. To address these problems, this research proposes an improved Mask Region-based Convolutional Neural Network (Mask R-CNN). The proposed model enhances the feature extraction ability of the original Mask R-CNN by introducing a Convolutional Block Attention Module (CBAM) and Path Augmentation Feature Pyramid Network (PAFPN) into the backbone network. Additionally, a morphological closing operation is performed on the extracted fatigue cracks to address the problem of disjoint cracks. On the basis of crack mask closure, the pixel-wise quantization of cracks was achieved using relevant OpenCV functions. Evaluation on a crack dataset of OSD shows that the proposed model outperforms other methods with precision, recall, average precision (AP), and F1 score of 83.98%, 84.44%, 77.9%, and 84.21%, respectively. In conclusion, the experiment validates that the proposed model can effectively detect, segment, and quantify fatigue cracks of OSD.

A dovetail core design for joints in composite sandwich structures

The increase in the size of composite sandwich structures requires the introduction of core splices to join various segments. In this study, a novel core splice joint configuration is studied and proposed for composite sandwich structures of thick aluminum-based honeycomb core and facesheets made from carbon fibers and epoxy matrix. Experimental and numerical efforts investigate the impact of dovetail joints with different tenon angles on the auxiliary behavior of composite sandwich structures. The results are compared to conventional or straight-core splices without dovetail features. The core-splice interaction with the complete mechanical behavior of the system was assessed by subjecting the fabricated specimens to combinations of bending and shear forces. Additionally, 3D-finite element models compared normal and shear stresses in the splice material and the core/splice interface among the dovetail configurations considered. The study shows that depending on the dovetail joint detail, an ultimate strength increase between 13 and 51% is achieved compared to the strength from currently used straight joints. In terms of toughness, the dovetail specimens show a 2% to 35% higher toughness compared to the standard straight joints.

Intelligent Control of Robots with Minimal Power Consumption in Pick-and-Place Operations

In many industries, such as assembling, welding, packaging, quality control, loading, and wrapping, a specific operation is requested, which is to pick processed objects in a given area of the workspace and hold them there for a rather long time compared with picking. The current study aims to minimize the power consumed by robots in pick-and-place applications with long-term placing and short-term picking operations. The main contribution of the paper is in the development of an approach that ensures the low power required by the robot by selecting the best robot joint configuration for object placement and providing intelligent control of robot joints for object-picking. The proposed and tested methodology is based on the mutual solution of the forward kinematics, inverse kinematics, inverse statics, and reinforcement learning problems in robotics. An appropriate neural-network-based controller is designed. In this work, model development, simulation, and experimental stages are described. As a result, several MATLAB/Simulink™ models and simulation methods are designed for efficient robot control and an appropriate neural-network-based controller is developed. The experiment conducted on the IRB1600 robot demonstrates that up to 18% of the consumed power may be saved thanks to an optimally chosen joint configuration.

Non-linear component-based modelling strategy for beam-to-column steel-concrete composite joints under seismic loads

This paper proposes and validates a computationally efficient, non-linear numerical macro-modelling strategy to predict and assess the global and local response of steel-concrete composite joints, when subjected to seismic loads. The reference numerical model takes the form of a component-based strategy in which each component can be efficiently characterized in resistance and stiffness terms, and each constituent material has a typical non-linear behaviour with hysteresis (Takeda model for concrete, Pivot model the T-stub components and kinematic model for all the other steel members). The major advantage is the possibility to adapt the same unified modelling strategy to different configurations of steel-concrete composite joints, which may differ for geometrical and mechanical configurations of constituent members, position of joint (i.e., interior or exterior), connection type (welded or bolted), etc. As shown, due to the presented modelling approach, even under simplified assumptions, a rather close agreement is generally found between the present numerical predictions and the cyclic response of a selection of three different steel-concrete composite joints of literature, which have been investigated on full-scale experimental configurations. Most importantly, the contribution of steel members and the concrete slab can be efficiently taken into account, and allow to develop the typical mechanisms in which the slab itself is involved for the complex performance of composite frames under seismic events.