In many technical domains, adhesively bonded joints have been employed extensively. These joints perform poorly against peel stresses despite having good shear characteristics. A step-lap joint (SLJ) ...is one of the techniques used to reduce the peel stresses at the edges of the overlap area to avoid damages. In these joints, the butted laminations of each layer are successively offset in succeeding layers in the same direction. Bonded joints are subjected to cyclic loadings in addition to static loads. It is difficult to predict their fatigue life accurately; however, this information must be clarified to explain their failure characteristics. To this end, the fatigue response of an adhesively bonded step-lap joint subjected to tensile loading was investigated with the developed finite-element (FE) model. In the joint, toughened type DP 460 and A2024-T3 aluminium alloys were used for the adhesive layer and adherends, respectively. The cohesive zone model with static and fatigue damages were linked to each other and were used to represent the response of the adhesive layer. The model was implemented using an ABAQUS/Standard user-defined UMAT subroutine. Experiments found in the literature served as a basis for validating the numerical model. The fatigue performance of a step-lap joint for various configurations subjected to tensile loading was examined thoroughly.
The aim of the present study was to compare the cyclic fatigue resistance of Reciproc Blue R25 (VDW, Munich, Germany) with Reciproc R25 (VDW) and WaveOne Gold Primary (Denstply Maillefer, Ballaigues, ...Switzerland).
Fifteen Reciproc Blue R25, 15 Reciproc R25, and 15 WaveOne Gold Primary instruments were collected and tested in a dynamic cyclic fatigue test device, which has an artificial canal with a 60° angle of curvature and a 5-mm radius of curvature. All instruments were operated until fracture occurred, and time to fracture (TF) and the lengths of the fractured fragments were recorded. The mean and standard deviations of TF and fragment length were calculated for each reciprocating system. TF data were subjected to Kruskal-Wallis 1-way analysis of variance and the Dunn test, whereas fractured fragment length data were subjected to 1-way analysis of variance (P < .05).
Reciproc Blue R25 exhibited the highest cyclic fatigue resistance (P < .05). The cyclic fatigue resistance values of WaveOne Gold Primary were significantly higher than those of Reciproc R25 (P < .05). There was no significant difference in the mean length of the fractured fragments among the instruments (P > .05).
Reciproc Blue R25 instruments had significantly higher cyclic fatigue resistance than WaveOne Gold and Reciproc R25 instruments.
•The cyclic fatigue (CF) resistance of novel Reciproc Blue was compared with WaveOne Gold and Reciproc.•Reciproc Blue R25 exhibited the highest CF resistance.•The CF resistance of WaveOne Gold was significantly higher than Reciproc.
Step lap joints are kinds of lap structures, where butted laminations of each layer are consecutively offset in succeeding layers in the same direction. They are mainly designed this way to reduce ...the peel stresses at the edges of the overlap area observed in single lap joints. In their service, lap joints are often subjected to bending loads. However, the performance of a step lap joint under flexural loading has not been studied in the literature yet. For this purpose, 3D advanced finite-element (FE) models of the step lap joints were developed via ABAQUS-Standard. DP 460 and A2024-T3 aluminum alloy were used for the adhesive layer and adherends, respectively. The polymeric adhesive layer was modelled using cohesive zone elements with quadratic nominal stress criteria and power law interaction of the energies to characterize the damage initiation and damage evolution, respectively. A surface-to-surface contact method with a penalty algorithm and a hard contact model was used to characterize the contact between the adherends and the punch. Experimental data were used to validate the numerical model. The effects of the configuration of the step lap joint on its performance in terms of the maximum bending load and the amount of energy absorbed were analyzed in detail. A step lap joint with three steps (three-stepped lap joint) was found to show the best flexural performance, and when the overlap length at the upper and lower steps was increased, the amount of energy absorbed by the joint increased markedly.
The micro cutting process differs significantly from its counter partner — the macro-cutting process — due to the fact that the uncut chip thickness is comparable with the crystal size of the ...workpiece and the cutting edge radius. In this study, the effects of cutting tool geometry including its nose radius and rake angle as well as its frictional behavior against the workpiece on the deformation characteristics of the single crystal were investigated extensively. To this end, a three-dimensional hybrid finite-element smoothed particle hydrodynamics model of micro-cutting of face centered cubic copper was developed, where its behavior was simulated using a crystal-plasticity theory, implemented through a VUMAT Fortran subroutine in ABAQUS/Explicit. The model was verified using the experimentally obtained specific cutting energy, available in the literature. The total shear strain accumulated on all slip systems, the individual contributions of different slip systems, the shear angle, the ploughing force and maximum principal stress were evaluated for the varying parameters mentioned above.
The abrasive water jet (AWJ) cutting technique is one of the promising techniques used in machining of composite materials due to lack of thermal damage, lower tool wear and higher productivity. In ...this study, the AWJ cutting of a cross-ply CFRP laminate was investigated experimentally and numerically. The purpose is to understand the underlying physics of the AWJ cutting of a composite plate, which can be later used to control the process as well as optimizing its parameters. In the performed tests of the plate with a stacking sequence of 0°/90°/0°/90° and having a total thickness value of 0.84 mm, where the pressure of particles and impact angle were varied, different failure characteristics such as fiber pull-out, fiber breakage, fiber debonding, matrix cracking and delamination were noticed. A three-dimensional FE model of the process was developed using ABAQUS finite element software to understand the underlying physics. In the model, the pure water jet particles following the linear Hugoniot form of the Mie-Grüneisen equation of state and highly rigid abrasive particles were modelled using smooth particle hydrodynamics. While the three dimensional Hashin damage model was used to simulate the intra ply damage, cohesive zone elements were used to predict the delamination. The damage characteristics in the composite plate was investigated for different process parameters. When the speed of the AWJ particles increased from 300 m/s to 600 m/s, the amount of delamination decreased from 6.44% to 5.69% at the top interface with no more delamination observed at the middle and bottom interfaces. The delamination performance of 0°/90°/0°/90° orientation was found to be better than those of 0°/90°/90°/0° and 0°/0°/90°/90° orientations. The impact angle of the particles affected the material removal rate in the process significantly. The failure behaviour of the laminate subjected to AWJ and pure water jet cuttings (PWJ) were also compared.
Due to their effective and affordable joining capabilities, resistance spot-welded (RSW) structures are widely used in many industries, including the automotive, aerospace, and manufacturing sectors. ...Because spot-welded structures are frequently subjected to cyclic stress conditions while in service, fatigue failure is a serious concern. It is essential to comprehend and predict their fatigue behavior in order to guarantee the dependability and durability of the relevant engineering products. The analysis of fatigue failure in spot-welded structures is the main topic of this paper, along with the prediction of fatigue life (Nf) and identification of failure mechanisms. Also, the effects of parameters such as the amount of cyclic load applied, the load ratio, and size of the spot-welding on the Nf were investigated. To achieve this, the fatigue performance of spot-welded joints was simulated using the extended finite element method (XFEM). The XFEM method is particularly suited for capturing intricate crack patterns in spot-welded structures because it allows for the modeling of crack propagation without the need for remeshing. It was observed that when the cycling load was decreased by 20%, Nf increased by around 250%. On the other hand, the fatigue life of the structure, and, hence, the crack propagation rate, was significantly affected by the load ratio and diameter of the spot-welding. This paper presents the details of the novel approach to studying spot-weld fatigue characterization using XFEMs to simulate crack propagation.
In this paper, the size effect in unidirectional (UD) laminated glass-fibre reinforced plastic (GFRP) composites subjected to quasi-static bending loading was investigated: the sensitivity of a ...specimen’s mechanical behaviour and failure mechanism to its geometry was studied. Composite beams with different numbers of 0° unidirectional plies were tested and their post-deformation structures were analysed microscopically. In the subsequent simulations, the intraply damage was modelled using continuum damage mechanics, implemented as a user-defined VUMAT subroutine in ABAQUS/Explicit, while cohesive zone elements were employed to characterize the delamination between different plies. It was observed that the flexural failure triggered the multiple delaminations; their location was studied. The influence of the size effect on the bending response of the UD composite beams was analysed in depth. The findings of the current study can be used to design modern structures made of composite materials.
Bonded joints used in wing sections and frames of aircraft structures are mostly exposed to cyclic loadings instead of static ones during their services. Bending types of dynamic loadings are mostly ...encountered. In this study, the fatigue response of a single lap joint (SLJ) exposed to bending loading was studied with the developed advanced finite-element (FE) model. The cohesive zone model describing the behaviour of the adhesive layer used the damage mechanism, where static and fatigue damages were linked to each other; i.e., the total damage was accumulated because of material deterioration and cyclic plastic separation. This enabled us to predict the fatigue characteristics including the finite fatigue life, crack propagation rate using Paris law. The model was implemented via a user-defined UMAT subroutine offered in ABAQUS-Standard. The numerical model was validated by experiments available in the literature. The fatigue performance of an SLJ subjected to bending loading was investigated for different lap joint configurations. A smaller bending load, a thicker adherend or a longer overlap length (OL) led to enhanced fatigue life. For instance, the fatigue life was observed to increase up to 50 times for a 66% increase in OL.
The influence of cutting speed and temperature softening was extensively investigated for conventional cutting process. However, this has not been addressed adequately for micro-cutting, especially ...of the single crystals, where the depth of cut is in the same range or even smaller than the average grain size of a polycrystalline aggregate. To this end, in this study, a three-dimensional finite-element model of orthogonal micro-cutting of b.c.c. β-brass was developed. The behaviour of the single crystal was simulated using an enhanced modelling scheme for a strain-gradient crystal-plasticity theory accounting for the temperature softening, implemented through a VUMAT FORTRAN subroutine in ABAQUS/Explicit. The findings here were compared with those in the literature qualitatively. It was observed that while the cutting speed had limited effects on the chip formation mechanism of the single-crystal workpiece, the temperature softening had noteworthy effects in terms of the cutting force, chip shape, evolving strain gradients and activation of different slip systems.
This paper aims to investigate the crashworthiness performance of thin-walled tubes under quasi-static conditions both experimentally and numerically. Single-cell and multi-cell tubes made of ...aluminum were tested under quasi-static compressive loading. A three-dimensional finite element (FE) model accounting for the damage in the constitutive equations was developed. It was validated through experiments based on the force–displacement behavior and the deformation views of the tubes. The sensitivity of the initial peak force, total energy absorption, specific energy absorption, and crush force efficiency to different model parameters such as the tube height and thickness, velocity of the rigid upper plate, and the type of the constitutive equations used were investigated in detail. It was observed that the element type used (shell/solid) in the FE model and the element size in the thickness direction played an important role in simulating the tests accurately. In addition, surrogate-based optimization of the single-cell tubes (T0) and two different types of multi-cell tubes (T4E, T8E) is performed to maximize crush force efficiency (CFE) and specific energy absorption (SEA). It is found that CFE of the optimum T4E design is 8.5% greater than CFE of the optimum T8E design and 30% greater than CFE of the optimum T0 design. It is also found that SEA of the optimum T4E design is 9.8% greater than SEA of the optimum T8E design and 213% greater than SEA of the optimum T0 design.
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