Joint Structure Research Articles

Effects of structural parameters on the load distribution unevenness in CFRP hybrid bonded‐bolted joint

AbstractCarbon Fiber Reinforced Polymer (CFRP) Hybrid Bonded/Bolted (HBB) joint structures are distinguished for their superior jointing performance among current mechanical joint systems, making them a favored option for mechanical joints. These structures are characterized by many structural parameters, with the relationship between these parameters and jointing performance being notably complex. Additionally, the laminate's brittleness and the uneven distribution of bolt loads in multi‐bolt joint structures impair the overall jointing performance. To investigate the impact of structural parameters on the uneven load distribution within CFRP HBB joint structures and improve their jointing performance, a finite element analysis (FEA) model grounded in 3D Hashin failure criterion is developed. Validation of the model with experimental data confirmed the uneven load distribution among bolts in multi‐bolt joints. The study elucidated the influence of changes in structural parameters (overlap length, bolt‐hole spacing, and clearance fit) on the uneven load distribution and the connection strength of CFRP HBB joint structures. A negative correlation is found between the unevenness of load distribution and connection strength, offering insights for enhancing and researching connection strength in CFRP HBB joint structures.Highlights Developed a FEA model based on the 3D Hashin failure criterion for CFRP Bonded‐Bolted joints. Identified key factors affecting HBB joint load distribution and jointing performance. Evaluated the impact of overlap length, bolt‐hole spacing, and clearance fit on CFRP joints. Suggested design optimizations for enhancing the performance of HBB joints.

Analysis of the anisotropic mechanical properties of structural adhesive joints with curing-induced pre-deformations

In modern lightweight construction, multi-material design has become increasingly important. An increasing number of structures are being adhered because adhesive joining technology can be used regardless of the material of the bonded partners. Owing to the dissimilar coefficients of thermal expansion, thermally induced relative displacements of the adherend occur during heat curing. Following these pre-deformations, changes in the mechanical properties of adhesive joints were observed. In this study, thick adherend shear specimens were used to induce defined relative displacements in the shear plane during the curing process. Quasi-static tests showed a directional dependence in the pre-deformation. This anisotropic behaviour was investigated in detail. Results showed that shear band formation occurred in the adhesive owing to the load during the cooling of joined structures. The restructuring of the polymer structure leads to changes in the mechanical properties.

Evaluation of Structural Transition Joints Cu-Al-AlMg3 Used in Galvanizer Hangers

The paper deals with the evaluation of the quality of Cu-Al-AlMg3 structural transition joints (STJ) made by explosion welding proposed for the renovation of galvanizer hangers. The three-layer joint consisted of electrolytic copper with a thickness of 25 mm, 2 mm of aluminium represented by the AW1050 alloy, and 25 mm of the EN AW 575 aluminium alloy. Light microscopy analysis confirmed the wavy pattern of both interfaces of the welded joint and significant plastic deformation in close proximity to the waves. Microhardness measurement revealed a partial strain hardening of the AW5754 copper-aluminium alloy near the interface and a significant increase in microhardness in the vortex zone of waves, reaching a value of up to 863 HV 0.025. Microcracks were also observed in these places. The intermetallic phase Al2Cu was identified in the vortex zones by XRD analysis. As a continuous layer of intermetallic phase was not observed in the interface of the welded joint, it is possible to consider the used welding parameters as appropriate. A semi-quantitative EDX analysis revealed a diversity of chemical composition in the vortex zones, which does not correspond to the phase composition based on the equilibrium binary Al-Cu diagram due to non-equilibrium conditions in the formation of the welded joint interface. The bond strength of three-layer welded joint evaluated by the strength test ranged from 151 to 171 MPa, which represented approximately a two-fold increase in comparison to the ultimate tensile strength of alloy AW1050, while the failure occurred in all samples at the AW1050-AW5754 alloy interface.

Kinetic Recovery of the Patient with Gonarthrosis

Osteoarthritis of the knee, also known as gonarthrosis, is indeed a common and growing concern, particularly as factors like increased life expectancy and rising obesity rates contribute to its prevalence. A few key points to highlight from the statistics you've provided: About 13% of women and 10% of men over the age of 60 are diagnosed with gonarthrosis; The prevalence significantly rises in people over the age of 70, where it affects 40% of this population. This reflects the impact of aging on joint degeneration; Gonarthrosis is more common in women than men. While exact reasons aren't fully clear, hormonal factors, differences in joint anatomy, and possibly physical activity differences may play a role in this disparity; Despite radiographic evidence of osteoarthritis, only a portion of individuals’ experience symptoms. This emphasizes that structural joint changes don't always equate to pain or functional limitations; One study suggests that only 15% of patients with radiographic evidence of gonarthrosis have symptoms, indicating that many individuals may have osteoarthritis without knowing it; The overall incidence of symptomatic gonarthrosis is about 240 cases per 100,000 people per year, making it a significant public health issue. [4]

Evaluating the water resistance performance of coal seam floor rock mass using VW–NC model

The rock mass of coal seam floor plays a crucial role in blocking the uplift and runoff of the underlying confined water in the course of mining under water pressure. Accurately assessing its water resistance performance, which is influenced by numerous factors, is important for preventing accidents caused by inrushing water. This study focuses on a coal mine in the Ningwu coalfield in North China. We establish an evaluation system for the water resistance performance of coal seam floor rock mass, using indices including rock mass thickness, lithological combination characteristics, rock mass quality, structure complexity and bedding plane count. A variable weight–normal cloud (VW–NC) model is formulated to quantitatively evaluate the water resistance performance of the coal seam floor rock mass. Comparative analysis with actual mining conditions and other models reveals that the VW-NC model provides the most precise and accurate results. The study finds that the primary influencing factors on the water resistance performance are weak structural planes, including faults, joints, and bedding planes. The proportions of strong, relatively strong, relatively weak, and weak zones in research area are 20.41%, 59.88%, 12.38%, and 7.33%, respectively.

Predicting fatigue crack initiation life in typical joints of offshore observation tower structures

ABSTRACT Tubular structures are widely used in steel constructions, such as offshore platforms, because of their superior mechanical qualities, efficient use of materials, lightweight and aesthetically pleasing appearance. The most common failure mode of offshore tubular joints is fatigue damage brought on by cyclic loading during the course of their service life, like wind, wave and equipment vibration. In this paper, the finite element model of the TK-type tubular joint at the stress concentration position is established by analyzing the load and response of the observation tower. The continuum damage mechanics method has been used to evaluate the fatigue crack initiation position and life of the tubular joint, and the crack initiation life of the key nodes has been predicted, which provides theoretical support for ensuring the service safety of the offshore observation tower.

Transverse impact performance and finite element analysis of three‐dimensional woven tubular composite with different structures

AbstractIn this study, experiments combined with finite element analysis (FEA) were used to investigate the damage mechanism of transverse low‐velocity impacts on three‐dimensional woven tubular composites (3DWTC) with different structures. The damage morphology after impact was observed using three‐dimensional microscopy and scanning electron microscopy (SEM). Three mesoscale models were constructed based on the authentic structure of the 3DWTC. Additionally, the effects of the structure type on the impact resistance, stress distribution, and damage morphology of 3DWTC were studied. The impact resistance of the shallow cross‐linked (SCL) structure is the strongest, according to the data. The structure that resists impacts the least is the through orthogonal (TO) structure. The greater the straightness of the warps in the structure, the density of the weft, the volume fraction, the greater the cooperative load‐bearing capacity of the warps and wefts, and the greater the speed of stress propagation. The wefts and inner warps are subjected to tensile forces at the point of impact. The outer warps are subjected to compression. The stresses are distributed in a cross‐shaped pattern. The straightened warp and weft parts of the TO serve a key structural role in load‐bearing. The warps of the SCL and the shallow‐crossed curved joint (SCCJ) structure serve a key structural role in the load‐bearing capacity.Highlights The impact resistance of 3DWTCs was investigated. The tensile state, stress propagation rate of 3DWTC were analyzed using the mesoscale model. The main load‐bearing components are revealed. The differences in damage morphology of 3DWTCs are analyzed.

A machine learning assisted preliminary design methodology for bolted composite joints in large structures

Abstract Damage initiation hotspots around features, such as bolts and ply drops, must be investigated during the preliminary design phase of large composite structures, such as composite airframes. A global-local modelling approach is commonly employed to perform this investigation, whereby a global low-fidelity model is used to drive high-fidelity local models around the features of interest. However, this methodology is slow, repetitive and expert-dependent. In this investigation, we address these issues by applying machine learning techniques to this global-local modelling framework and demonstrate the time-saving benefit when predicting damage initiation of bolted composite joints. Feature engineering of model inputs and outputs, and appropriate customisation of machine learning methods enables damage initiation prediction. Special consideration is given to the boundary conditions that must be varied to simulate the response of the bolted composite joints. Results show over three orders of magnitude time-saving benefit and satisfactory accuracy of the proposed methodology. This indicates its potential to be developed further into a rapid design and optimisation tool.

Modified Use of the Component Method to Get More Realistic Force Distribution in Joints of Steel Structures

According to the EN 1993-1-8 Standard, the moment resistance of end-plated connections can be calculated with the use of the component method. In this, a pair-of-force defines the moment resistance. The magnitude and the location of the compression force can be accurately identified. The tension force part is usually the resultant of parallel forces appearing in line with the bolt rows. Following the rules of manual calculation and using a mechanical finite element model, where each component is modelled with spring elements, in some—easily identifiable—cases, leads to different force distribution. The simplifications defined in the Standard provide a longer arm for the same force, and because of this, larger moment resistance at the expense of safety. In this work, an alternative calculation method will be presented that provides the same force values in each bolt row, as the mechanical model of the connection, without constructing the finite element model.

Study on Low-Temperature Deposition of Diamond-like Carbon Film on the Surface of Bionic Joint Thread and Its Properties

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening treatments such as quenching and nitriding, making it prone to thread gluing or excessive wear. In this paper, the feasibility of diamond-like film deposition on the surface of a bionic drill pipe thread was studied. A tungsten transition film was used to improve the thickness of the film and the interfacial bond strength between the film and the substrate. The test results show that the total thickness of the DLC film is about 3~5 μm, the roughness is less than 2 μm, the hardness of the film reaches 24.4 GPa, the friction coefficient is 0.04, and the critical load is 56 N. SEM and EDS analyses show that the tungsten film and the bionic joint thread form a metallurgical structure. The morphology of the diamond-like carbon film is uniform and dense, and there is no obvious stratification between the substrate material. The joint with a diamond-like coating treatment has a longer service life than joints receiving conventional high-temperature nitriding treatment.

Impact of Structural Severity on Outcomes in Knee Osteoarthritis: An Analysis of Data from Phase 2 and Phase 3 Lorecivivint Clinical Trials.

Developing knee osteoarthritis (OA) treatments is challenging due to assessing pain and joint structure outcomes within a highly heterogeneous disease. Lorecivivint (LOR), an intra-articular (IA) CLK/DYRK inhibitor, modulates Wnt and inflammatory pathways. This review analysis of LOR 0.07 mg trial data aims to describe the potential impact of baseline joint structure on OA pain response. Two Phase 2 and two Phase 3 trials enrolled knee OA patients with Kellgren-Lawrence (KL) Grades 2-3 and Pain Numeric Rating Scale (NRS [0-10]) ≥4 to ≤ 8 in target knee. Cumulative frequency distribution plots by KL grade summarized the percentages of patients with medial joint space width (medial JSW) < 3 mm. Osteoarthritis Research Society International Joint Space Narrowing grades and treatment responses in trials capturing Pain NRS were similarly summarized. Pain outcome changes were estimated using baseline adjusted ANCOVA. Compared with phase 2 trials, the phase 3 trials had an increased proportion of patients with baseline medial JSW < 3 mm. LOR demonstrated beneficial treatment effects vs placebo in KL 2 subgroups, which were found to have higher proportions of baseline medial JSW > 3 mm, apart from one Phase 3 trial with advanced structural knee OA. Baseline medial JSWs were heterogeneous across trials despite KL inclusion criteria. LOR demonstrated greater symptomatic improvements in patients with less structurally advanced disease, indicative of an association between OA structural damage and pain. Early treatment interventions may improve outcomes and provide insight for future OA trial inclusion criteria development. OA-02, NCT02536833; OA-04, NCT03122860; OA-10, NCT04385303; OA-11, NCT03928184.

WrapToR composite truss joints: Concept introduction and coaxial joint analysis and demonstration

This study focuses on the development of coaxial continuously wound joint structures for Wrapped Tow Reinforced (WrapToR) trusses, which are carbon fibre composite lattice beams fabricated through a unique winding process. WrapToR truss beams have shown very high levels of performance as beam-like structures, but their usefulness can be greatly extended by using them as members within hierarchical space frames, which can be made into more geometrically complex and generally useful structures. However, the key challenge lies in creating effective joint structures able to connect together multiple WrapToR beams of different sizes and orientations. This paper addresses this challenge by presenting a modified WrapToR winding process which enables three-dimensional winding of arbitrary space frame joints, with an initial focus here on a proof of concept coaxial joint. This includes the design and manufacturing of a coaxial joint demonstrator and the development of a finite element analysis tool to predict its mechanical performance. A cantilevered beam structure combining this joint with two different sizes of WrapToR truss is built and tested, showing high levels of bending rigidity and good agreement with numerical prediction. Following this, the analysis tool is used to explore the achievable design space for coaxial WrapToR joints.

Electrical energy and overpressure characterization of aeronautical fasteners submitted to a lightning current waveform

Understanding and controlling sparking in fasteners and jointed structures is crucial for flight safety, particularly in fuel tanks. This study investigates the relationship between dissipated electrical energy and pressure buildup within fastener cavities during lightning strikes. Experiments were performed on fasteners installed in aluminum and Carbon Fiber Reinforced Polymer (CFRP) samples, with lightning current waveforms ranging from 1 kA to 10 kA. A sensitivity analysis evaluated the influence of key parameters, such as current peak, clearance fit, sample material, polarity, and fastener coating on pressure rise and energy dissipation. Electrical energy up to 80J and pressure levels reaching 600 bar– unprecedented compared to prior studies – were observed. The pressure-energy relationship showed an approximately linear trend, while pressure exhibited a non-linear dependence on clearance fit. Fastener coating and sample material were found to significantly influence the results, with pressure variations reaching up to a factor of 10 in some cases.

Temporomandibular Joint Ankylosis In True Hemifacial Hyperplasia With Infiltrative Lipomatosis - A Case Report

Congenital infiltrative lipomatosis of the face is a benign condition in which mature adipocytes invade adjacent tissues causing diffuse fatty infiltration into the surrounding soft tissue and hyperplasia of the adjacent bone on the affected side. This case report of a 37-year-old female with congenital facial asymmetry and diffuse swelling on the right side of the face suggests true hemifacial hyperplasia, which is supported by both clinical and radiographic data which showed severe involvement of underlying bony structures of the temporomandibular joint, sphenoid, temporal, zygoma, right maxilla, mandible, associated dentition and adjacent soft tissues. It also revealed lipomatous enlargement with right temporomandibular joint ankylosis reported with multiple etiological factors and marked trismus, for which functional rehabilitation was achieved following surgical intervention

Experimental and numerical investigation of novel triangular headed one-sided bolted T-stub connections

The reliable one-sided bolts constitute a vital component of fully bolted joints in demountable steel structures. In this study, an innovative triangular headed one-sided bolt (THOB) based on the traditional hexagon headed bolt (HHB) was proposed, and the tensile performance of T-stubs using the THOBs has been investigated through experimental and numerical approaches. Monotonic tensile tests were performed on 25 THOB bolted T-stubs to analyze the failure modes and load-carrying performance of the specimens. The test results disclosed that, beyond the three typical failure modes stipulated in the Eurocode 3, the specimens exhibited a characteristic failure mode, namely, limit groove pull-off failure. Finite element models, validated by the test results, were employed for the parametric analysis to compare the load-carrying performance of THOB bolted T-stubs with that of HHB bolted T-stubs. The finite element analysis results indicated that the average ratio of the plastic load-carrying capacity of THOB bolted T-stubs to HHB bolted T-stubs was close to 0.88. Furthermore, the load-carrying capacity of THOB bolted T-stubs was evaluated using existing specifications for comparison with the experimental and numerical results, and Eurocode 3 calculations for the plastic load-carrying capacities of THOB bolted T-stubs demonstrated a commendable level of precision. Finally design recommendations were put forward based on the test and finite element analysis results.

Shear tests and meso-scale simulation of cold joint structures in rock-filled concrete: Considering the mutual contact effects between component materials

To realistically reflect the shear performance of the rock-filled concrete (RFC) between layers, this study relies on an RFC dam project in Guizhou Province. Test blocks, measuring 5 m × 4 m × 2 m with cold joints, were cast on site and subjected to shear tests. Additionally, a three-dimensional four-phase meso-model was developed, considering the mutual contact effects between component materials. The mechanical response and damage mechanism of the interlayer were analyzed using the cohesive zone model. The results confirm that the cohesive zone model effectively simulates interlayer cold joint structures. The damage modes of the RFC interlayer include cold joint debonding damage (Mode I) and plastic extrusion damage of self-compacting concrete (Mode II). As the exposed height of the rocks increases, the damage mode shifts from Mode I to Mode II, and higher normal stresses intensify Mode II damage. Meanwhile, the paths of crack extension depend on the distribution of shear-resistant rocks, with weak interfacial transition zones serving as “bridges’’ for crack propagation. The interlayer shear strength is positively correlated with the average exposed height of rocks and normal stresses, with the former having a more significant impact. Finally, the accuracy of the proposed shear strength prediction model for the RFC interlayer was validated by comparing it with results from other studies, providing useful references for meso-numerical modeling of RFC.

A prospective randomized-controlled non-blinded comparative study of the JAK inhibitor (baricitinib) with TNF-α inhibitors and conventional DMARDs in a sample of Egyptian rheumatoid arthritis patients.

To evaluate the efficacy of baricitinib compared to TNF-α Inhibitors and conventional DMARDs (cDMARDs) in patients with RA. Our study included 334 RA patients classified into 3 groups: the first receiving baricitinib, the second receiving TNF-α Inhibitors, and the third receiving cDMARDs. Patients were evaluated at baseline, week 12, and week 24 using TJC, SJC, VAS, DAS28, CDAI, and HAQ-DI. Larsen score was measured at baseline and 24weeks. The response to therapy was assessed at weeks 12 and 24 using ACR 20, ACR 50, and ACR 70 response criteria. Emerging treatment side effects were monitored. Patients receiving baricitinib showed significant improvement regarding all outcome measures at weeks 12 and 24. In addition, baricitinib was comparable to TNF Inhibitors in all outcome measures except the ACR 70 at week 12, which was higher in the baricitinib group. Furthermore, baricitinib group showed significantly better outcome measures and response to therapy in comparison to cDMARDs group. The most common side effects in the baricitinib group were infection, GIT, and CVS complications. The most common side effects in the TNF inhibitors group were infection and skin complications. The cDMARDs had the least side effects, mostly GIT complications. Baricitinib is an effective drug for treating RA refractory to cDMARDs, improving disease activity measures and functional status and reducing the progression of structural joint damage. It has a comparable efficacy and safety profile to TNF Inhibitors. Multicenter studies are recommended to support our results. Key Points • Baricitinib is an effective therapeutic choice for rheumatoid arthritis refractory to cDMARDs. • Patients treated with baricitinib showed improvement in all outcome measures and functional status. • Bricitinib delayed the progression of radiographic joint damage more effectively than cDMARDs. • The efficacy and safety of baricitinib for treating rheumatoid arthritis is comparable to that of TNF inhibitors.

Experimental Investigation on the Important Factors on Structural Adhesive Joint Strength of Fiber-Reinforced Epoxy Composites

The static strength of fiber-reinforced epoxy composite structural adhesive lap joints was examined experimentally. Surface roughness and geometrical control parameters (adherent and adhesive kinds) were assessed for their effects. To examine load, elongation, and strength at failure, tensile tests were conducted. Cyanoacrylate glue outperformed SHCP 268 resin, and glass fiber-reinforced epoxy composites outperformed sisal fiber-reinforced epoxy composites. The study offers information on how to maximize adhesive bonding for lightweight multi-material design construction.

Experimental study on seismic performance of glulam structural columns with anchored connections

In current timber structures, the low initial stiffness, and weak bending resistance of the connections result in significant structural deformation and failures. To improve the mechanical capabilities of timber structural joints, a novel timber-component anchorage system with robust bending resistance was introduced. Thirteen scaled-down specimens of glulam columns with anchored connections were meticulously fabricated for testing, scaled at a ratio of 1/2. Cyclic loading tests were conducted, considering three types of the volume compression percentage of confined wood perpendicular to the grain; and five axial-load levels. Subsequently, various seismic performance aspects of glulam columns with anchored connections were examined, including the failure mode, hysteresis behavior, envelope curve, strength degradation, stiffness degradation, energy dissipation capacity, and critical points. During the analysis, the influence of the P–Δ effect on the results was discussed and a damage-based hysteretic model was presented. Finally, a comparison of the mechanical performance for various types of timber structural joints was conducted. The findings revealed that the failure mode of the anchored glulam columns occurred as cracking perpendicular to the grain, and the anchored columns exhibited superior bending resistance and overall seismic performance.

Mechanical Strength of Additive Manufactured and Standard Polymeric Components Joined Through Structural Adhesives.

The main aim of this work is to evaluate the mechanical properties of additive manufactured polymeric parts joined with standard plastic parts through structural adhesives. The primary advantage of this technique is its ability to significantly increase the size of the final assembly by using additive manufacturing (AM) for complex joints and inexpensive, reliable extruded plastic parts for load-bearing components. This hybrid assembly combines the flexibility and shape adaptability of AM with the structural strength and cost-effectiveness of extruded polymer parts, resulting in a final design that performs comparably to the base material. The materials used in the paper are rigid acrylic adhesive and toughened acrylic, both applicable with almost no surface preparation and fast curing. The 3D-printed parts are produced in ABS, while the standard parts are in PVC. First, the work is devoted to estimating the performance of the adhesives using pin-collar joints and a combined numerical and experimental methodology. The second section presents and discusses the results of two more realistic applications of adhesive bonding to hybrid complex joints. For the pin-collar joints, the results show failure mostly in the adhesive, with an average shear stress of 11.5 MPa and 5.22 MPa and a stiffness of 4449 N/mm and 3649 N/mm for the rigid and toughened adhesives, respectively. The results of the adhesive bonding of structural joints show that the adhesive is always capable of providing the load-carrying capacity required to achieve the strength of traditionally manufactured polymeric parts. The paper shows that adhesives are a feasible way to expand the potential of 3D-printed equipment to obtain larger hybrid parts partially realized with traditional technology, especially with inexpensive off-the-shelf bars and sections.