Multiaxial fatigue life evaluation of tubular adhesively bonded joints (original) (raw)
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International Journal of Adhesion and Adhesives, 2018
Many studies have investigated adhesive tubular joints subjected to axial load. However, previous analytical studies were only limited to the joints with single-layer isotropic or orthotropic materials, and the corresponding mathematical models were highly complicated. Thus, the aim of this article is to develop a simplified but comprehensive model for studying adhesive-bonded tubular This paper is dedicated to the memory of Professor Dr. Michael W. Hyer, whose knowledge has instilled into the first author (SA) and the following generations of SA students. coupler joints subjected to tension. The joint adherends can be made of isotropic, orthotropic, or multilayer composite materials. This study presents the formulation of the mathematical model for stress analysis in coupler joints. Assumptions of an axisymmetric joint with linearly elastic adherends and adhesive materials are employed. A thin adhesive layer is considered such that only the out-ofplane adhesive stresses are concerned and are treated to be uniform through the layer thickness. Using elasticity theory and the newly developed finite-segmented method, stress distributions in both adherends and the adhesive can be evaluated. The influence of fiber angle in the cases of composite adherends and joint geometries are studied. The results provide an excellent guideline in designing adhesive-bonded cylindrical joints with isotropic and composite adherends under axial loads.
Recent research on fatigue of tubular joints
2017
Some of the structural systems used in the agricultural, road and mining industries are subjected to cyclic loading and are therefore prone to fatigue failure under service loads. These structural systems range from trailers, road sign portals, towers, bridges and dragline structures. Recent development has resulted in the production of steel materials that are relatively higher in strength and thin-walled. There has also been an increased use of concrete-filled tubular members in structural systems especially in long span bridge structures and towers. The understanding of tubular joints with concrete-filled chords has therefore become important. This paper therefore outlines recent research that has been carried out to better understand the behaviour of various welded thin-walled tube-plate and tube-tube joints under cyclic loading. The research has also included tests on tubular joints with concrete-filled chords under cyclic loading. The research has focussed on high cycle fatigu...
Static and dynamic strength evaluation of interference fit and adhesively bonded cylindrical joints
International Journal of Adhesion and Adhesives, 2010
The present work aims at defining the anaerobic adhesive residual strength in drive-fit and adhesively bonded cylindrical joints, loaded with a tension-tension fatigue cycle. The final purpose is to evaluate the possibility of reducing the interference level by taking advantage of the adhesive strength. The tested specimens are some shaft hub cylindrical joints made of different materials: the hubs are always made of steel alloy whereas the shafts are made both of steel alloy and of aluminium alloy. Firstly, some coupling and decoupling tests have been performed in order to evaluate the static strength of the joints, calculated as the addition of the interference contribution with the adhesive contribution. Then, the fatigue tests have been carried out in order to evaluate the adhesive residual strength after 10 6 tensiontension fatigue cycles. The fatigue cycles have been related to the static strength of the joint. The mechanical behaviour of steel-steel couplings has been observed to be strongly different from the aluminium-steel ones.
Fatigue behaviour of multiplanar tubular joints
1994
Circular hollow sections are frequently used in structures subjected to fatigue loading such as bridges, offshore structures and cranes. These sections are generally connected by direct welding of the sections to each other. For the design of these welded connections, information is required on the fatigue behavior. Especially for multiplanar connections, insufficient data is available regarding stress concentration factors (SCF's) which affect the fatigue life. Also, there is no standard for determining the fatigue strength of welded tubular joints. This has led to a divergence in the methods being used both experimentally as well as numerically. This publication presents the results of experimental and numerical research on the fatigue strength of welded tubular joints. The research projects aim to provide guidelines and design recommendations on the fatigue strength of welded tubular joints, to be proposed for inclusion in international codes of practice such as Eurocode 3.
Parametric analysis of composite tubular adhesive joints bonded by the bi-adhesive technique
Academia Materials Science, 2024
Adhesive bonding plays a fundamental role in various industries, including aerospace, aeronautics, and automotive sectors. Unlike traditional mechanical joints, adhesive joints offer an efficient approach with fewer components, leading to weight reduction in the final structure. Additionally, these joints facilitate the joining of dissimilar materials while distributing applied loads more uniformly, resulting in better stress distributions compared to conventional joining techniques. Within this context, the integration of adhesive bonds in joggle tubular structures presents a viable alternative to join tubes with identical diameter. The bi-adhesive technique involves using a brittle adhesive in the inner overlap region, and a ductile adhesive at the overlap edges, aiming to improve load transfer. The objective of this study is to conduct a numerical analysis using cohesive zone modelling (CZM) to investigate the tensile behavior of joggle tubular adhesive joints between composite adherends and bonded by the bi-adhesive technique. Initially, the proposed CZM approach is validated against experimental data. Subsequently, the focus is on numerically assessing the tensile strength of the joints and testing different bi-adhesive joint options, aiming to improve the maximum load (Pm), displacement at Pm (dPm), and energy absorbed at failure (Ef). Validation of the cohesive models has been successfully achieved. In conclusion, it was found that, depending on the bi-adhesive conditions, improvements are possible to obtain over single adhesive joints.
Static and Fatigue Characterization of Adhesive T-Joints Involving Different Adherends
Processes
It is very important to understand the damage mechanisms as well as the mechanical response of T-joints involving different materials on the base plate. For this purpose, two configurations were studied. In one, the joint is composed of a base plate and a T-element, both in Al 6063-T5, while in the other one, the aluminum base plate was replaced by a glass fiber composite. Finally, each configuration was divided into two batches, where in one, the elements were bonded with a stiff adhesive (Araldite® AV 4076-1/HY 4076) while in the other, a more ductile adhesive (Araldite® AW 106/HV 953 U) was used. The static and fatigue strength of all configurations was evaluated in bending. In all cases, the damage occurred at the end of the T-element, where a crack appeared and propagated toward the interior of the T-joint. The bending strength is highest for joints involving aluminum and the ductile adhesive, which is 2.8 times higher than the same configuration involving composite base plates...
Journal of Adhesion Science and Technology, 2017
Finite element analysis has been carried in the present research to study individual and combined effect of internal pressure and torsional loading on stress and failure characteristics in case of an adhesively bonded Tubular Single Lap Joints (TSLJ) made of laminated Fiber reinforced polymer (FRP) composite materials. Effect of changing torsional load magnitude on an internally pressurised adhesively bonded TSLJ on interlaminar stresses and onset of different joint fracture modes (adhesion and cohesion failures) has also been studied in the present analysis. Three dimensional stress analysis of the adhesively bonded TSLJ has been carried out through suitable ANSYS Parametric Design Language (APDL) of ANSYS 14.0. Tsai-Wu coupled stress criterion has been used for predicting the onset of joint failures in the TSLJ. It has been observed that stresses (σ r , σ θ , σ z , τ rz) induced within the joint region under pure internal pressure loading are least affected through introduction of a torsional loading in the TSLJ. However, the stresses (τ rθ and τ θz) which are considered to be significant under pure torsional loading get tremendously enhanced due to the varying torsional loading. The interface between the outer tube and adhesive of the TSLJ has been observed to be the most critical bondline interface which is prone to undergo adhesion failure towards the free edges under pure internal loading conditions. However, under pure torsional loading conditions it tends to fracture through adhesion failure towards the clamped edge of the TSLJ. Under combined torsional and internal pressure loading the joint fails towards the clamped edge of the along the critical path which happens to be within the bondline interface, indicating predominance of torsional loading over the pure internal pressure loading. A comparative study based on the magnitude of failure index revealed that torsional loading marginally affects the joint failure as the internal pressure loading improves the compactness of the bonded joint hence improving the resistance of the TSLJ against initiation of joint fractures.
Regularization of torsional stresses in tubular lap bonded joints_IJAA_2014_Spa_Dra.pdf
This paper describes the analytical stress analysis of a tubular single lap joint under torsion with a functionally graded modulus adhesive (FGA). The adhesive technology offers several advantages in structural applications, such as bonding dissimilar materials, but suffers from severe stress concentrations in the bondline which often act as a trigger for fracture phenomena. To overcome these problems, FGA with nanoparticles distributed inside the polymer can be used, as proposed recently in technical literature. The aim of the work is to retrieve which is the optimal stiffness of the adhesive layer to regularize the stresses. The peculiar geometry analyzed permits a straightforward analytical approach since pure torsion on tubes do not cause any bending and no Poisson 0 s effect creates peel stress in the adhesive, therefore only shear stress are to be considered. The work first develops the equations which govern the shear stress distribution in the adhesive and then by forcing the shear stress to be constant is able to find out which is the stiffness profile along the bondline. The axial distribution of the stiffness of the FGA layer along the overlap is provided and the dependence on the elasto-geometrical parameters is discussed. The findings of the paper can be used to tailor the reinforcement distribution, under the hypothesis of a continuously changing adhesive stiffness.
Adhesively Bonded Carbon/Titanium Joints Under In-plane and Bending Loads
T he goal of this research is to optimize the design of single-lap joints made by joining composite material to metals. The single-lap joint under both out-of-plane load and tensile load was examined. It is observed that designing a joint for one kind of load is not always satisfactory because for other load cases, different stresses would govern the design. Local stress peaks were investigated in order to find ways to decrease these peaks. An approach for optimizing the joint was chosen so the stress peaks at each end could be minimized (peel, axial and shear stress). By tapering the titanium adherend inside and outside, the stress distribution in the adhesive can be significantly changed at the tapered end and all three important stresses that governed the design (peel, axial and shear stress) are decreased for a joint under tension and out-of-plane load. For dissimilar adherends, the numerically largest stresses always occur in the adhesive at the edge of the overlap adjacent to the adherend with the lower value of flexural stiffness and the relative difference in these peaks is a function of the relative flexural stiffness of two adherends. Using an outer bead of adhesive decreases the stress peak at composite edge. Thus, two methods are used to reduce adhesive stresses: tapering and addition of adhesive beads. Having completed a finite element stress analysis, the results are used to predict the strength of a given joint. A strain energy based on failure criteria was evaluated, which addressed the problem of stress singularities in the finite element method. Three point bending tests were performed using different bonding configurations to verify the strength of the adhesive joint and to evaluate the failure criterion. Optimization of the parameters of the joint geometry was achieved from the results of this study.