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Made available in DSpace on 2022-04-28T19:47:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Hysteresis is a nonlinear phenomenon present in many structures, such as those assembled by bolted joints. Despite a large number of recent findings related to identification techniques for these systems, the problem is still challenging and open to contributions. To fill the gap concerning the proposition of identification algorithms based on closed-form solutions, this work introduces the use of the harmonic balance method to identify a stochastic Bouc–Wen model for predicting the nonlinear behavior of bolted structures. A piecewise smooth procedure is applied on the hysteretic restoring force to become possible to derive an analytical approximation of the response based on the Fourier series. Firstly, the analytical approximation is used to calibrate deterministic Bouc–Wen parameters by minimizing the error between the Fourier amplitudes of the numerical model and those extracted from experimental data using the cross-entropy optimization method. Since the experimental data investigated here contain variability due to the measurement process (aleatoric uncertainties), the deterministic parameters are then used as a priori conditions to update their probability density functions via the Bayesian inference. Having the model parameters as random variables, the stochastic Bouc–Wen model is obtained. This methodology was illustrated in a bolted structure benchmark. The results indicate that the method proposed can identify an accurate stochastic Bouc–Wen model for predicting the dynamics of bolted structures, even taking into account data variability. Department of Mechanical Engineering São Paulo State University (UNESP), Avenida Brasil 56, SP Department of Mechanical Engineering São Paulo State University (UNESP), Avenida Brasil 56, SP FAPESP: 2016/21973–5 FAPESP: 2017/15512–8 FAPESP: 2019/19684-3 FAPESP: 2020/07449-7 CNPq: 306526/2019-0

A series of experiments were carried out for developing a paint coating removal method for high-strength bolted joints in steel bridges. The paint-coated bolted joint specimens were heated to the target temperature of 200 °C by using a sheet-type ceramic heater. The maximum temperature of specimens could be controlled within 10% of the target value. The paint coating was easily removed by using general tools after heating. The behaviour of bolts with thermal expansion and shrinkage was monitored by strain gauges attached to the bolts during heating. It was estimated that the axial forces of the bolts were reduced by 2.6% of the initially installed axial forces, on average.

This article is Part II of the paper containing a description and results of the experimental studies of the deformations, friction processes and structural damping that occur in the foundation bolted joints of propulsion plant components and auxiliary machinery installed on sea-going ships. Part I of this research work presents an analysis of the rigid mountings of machines and devices to the foundations on steel or resin chocks, and explains the need to carry out relevant research in this area. It also presents the description and results of experimental studies carried out for a foundation bolted joint with a conventionally used steel chock. Part II (this article) contains a description and results of similar studies carried out for a foundation bolted joint with a modern chock – cast from epoxy resin compound (EPY), specially developed for this purpose. Then, a comparative analysis of the results obtained for both bolted joints in question was made and the foundation chocks of the poured-in-place resin compound were demonstrated to better fulfill their technical tasks than the steel chocks traditionally used for this purpose.

With the development of spread-tow, thin-ply technology, ultra-thin composite laminates could be produced. Composite bolted joints are commonly used on aircraft’s load-bearing structures and are considered the main cause of stress concentration. The aim of this research is to investigate the bolted joint behavior of composite laminates that combine thin-plies and conventional thick-plies in a predetermined stacking sequence. The impact of thin-ply placement within the stack on bearing strength, including the onset of damages, is examined. The work involves mechanical tests and fractographic activities to understand the damage mechanisms of the plies and their interactions, and its reflections on the bearing load capacity of the joint for double-lap bolted joints. The results showed an improvement in the bearing strength of up to 19% by inserting the thin-plies inside the laminate. The visual examination of the specimens showed a bearing damage mode for all the tested specimens. The computed tomography scans showed damage mechanisms that mostly occurred with the normal plies, rather than breaking the thin-plies. For the specimens of traditional plies, delaminations were noticed at most of the interfaces. For the one with a block of thin-plies in the middle, all the delaminations were forced to the surface layers with an extra large size. Forspecimens with distributed thin-plies, a higher number of smaller delaminations was recognized.

© 2019 Elsevier Ltd High strength steels (HSS) offer a unique opportunity to reduce the weight of civil and off-shore structures and heavy-duty machinery. Such equipment is subjected to continuous cyclic loading and therefore fatigue failure often happens where concentrations of stresses are present, the latter most of the time being caused by connection details. Previous studies have demonstrated that an increase in yield strength does not lead to a proportional increase in fatigue resistance, particularly in welded connections. In that regard, the utilisation of bolted joints is often proposed as an alternative to welded joints. The hole-making procedure is an essential factor in the assessment of the fatigue resistance of bolted joints, since different hole-making techniques yield different surface qualities and residual stresses, which consequently impact the final fatigue limit. This work addresses the effect of the main mechanical (punching, drilling and waterjet) and thermal (plasma and laser) cutting techniques on the fatigue performance of HSS plates containing holes. A series of fatigue tests with moderately thick plates made of S500MC were carried out using different hole-making techniques. The surface, geometry and residual damage of every hole-making procedure were studied by means of optical evaluation, hardness tests and roughness evaluation, and large differences were observed: drilling was found to produce the most geometrically accurate hole and the smoothest surface finish; while laser and waterjet cutting displayed the best fatigue performance. The results of this research can provide an estimation of the applicability of each hole-making process to this particular HSS grade. ispartof: Journal of Constructional Steel Research vol:158 pages:1-14 status: published

Bolted joints are the primary structures for the load transfer of large-scale structures. It is vital to monitor the process of bolt cracking for enduring structural safety. In this paper, a structural health monitoring technique based on the embedding eddy current sensing film has been proposed to quantify the crack parameters of bolt cracking. Two configurations of the sensing film containing one-dimensional circumferential coil array and two-dimensional coil array are designed and verified to have the ability to identify three crack parameters: the crack angle, the crack depth, and the crack location in the axial direction of the bolt. The finite element method has been employed not only to verify the capacity of the sensing film, but also to investigate the interaction between the crack and the eddy current/magnetic field. It has been demonstrated that as the crack propagates, the variations of the induced voltage of the sensing coils are influenced by both eddy current effect and magnetic flux leakage, which play different roles in the different periods of the crack propagation. Experiments have been performed to verify the effectiveness and feasibility of the sensing film to quantify three crack parameters in the process of the bolt cracking.

Problematic. When designing bolted joints (BJ), it is necessary, to carry out verification strength calculations. In this case, it is advisable to use express analysis: calculations using simple formulas of sufficient accuracy. One of the main strength calculations of BJ is the calculation of the gap section weakened by the hole. For BJ plates made of layered fibre-reinforced polymers (FRP), the problem has not yet been solved.Research objective. To verify the accuracy of two well-known express analysis formulas for stress concentration factors (SCF) at the contact of the hole with the bolt, using contrasting examples of materials and schemes for reinforcing FRP plates.Realization technique. Numerical calculations were carried out using the finite element method (contact problem) for a BJ plate made of layered FRP. A 3D orthotropy of each monolayer was assumed. Two simple express analysis formulas were tested. The results are tabulated. The illustrations are provided.The results of research. Numerical estimates are obtained that characterize the degree of influence of material characteristics and reinforcement patterns in a layered FRP plate and the accuracy of the formulas considered.Conclusions. A change in the material and the reinforcement scheme of the layered FRP leads to a significant change in the SCF values of the bolt-loaded hole in the section of the plate weakened by the hole, and the considered express analysis formulas have insufficient accuracy for contrast cases of materials and plate reinforcement schemes. More research is needed., Проблематика. При проектировании болтовых соединений (БС) необходимо, в частности, проводить проверочные прочностные расчеты. При этом желательно применять экспресс-анализ: расчеты по простым формулам достаточной точности. Один из основных прочностных расчетов БС – расчет на разрыв сечения, ослабленного отверстием. Для БС пластин из слоистых полимерных композиционных материалов (ПКМ) проблема еще не решена.Цель исследования. Провести проверку точности двух известных формул экспресс-анализа величины коэффициентов концентрации напряжений (ККН) при контакте отверстия с болтом, на контрастных примерах материалов и схем армирования пластины из ПКМ.Методика реализации. Были проведены численные расчеты с применением метода конечных элементов (контактная задача) для БС пластины из слоистого ПКМ. Предполагалась 3D-ортотропия каждого монослоя. Проверялись две простые формулы экспресс-анализа. Результаты сведены в таблицу. Приведены иллюстрации.Результаты исследования. Получены числовые оценки, характеризующие степень влияния характеристик материала и схемы армирования в пластине из слоистого ПКМ и точность рассмотренных формул.Выводы. Изменение материала и схемы армирования слоистого ПКМ приводит к существенному изменению значений ККН у нагруженного болтом отверстия в ослабленном отверстием сечении пластины, а рассмотренные формулы экспресс-анализа имеют недостаточную точность для контрастных случаев материалов и схем армирования пластины. Необходимы дополнительные исследования., Проблематика. При проектуванні болтових з'єднань (БЗ) необхідно, зокрема, проводити їхні перевірочні розрахунки на міцність. При цьому бажано застосовувати експрес-аналіз: розрахунки по простих формулах достатньої точності. Один з основних розрахунків БЗ на міцність - розрахунок на розрив перетину, ослабленого отвором. Для БЗ пластин із шаруватих полімерних композиційних матеріалів (ПКМ) проблема ще не вирішена.Ціль дослідження. Провести перевірку точності двох відомих формул експрес-розрахунку величини коефіцієнтів концентрації напружень (ККН) при контакті отвору з болтом, на контрастних прикладах матеріалів і схем армування пластини із ПКМ.Методика реалізації. Були проведені чисельні розрахунки із застосуванням методу скінченних елементів (контактна задача) для БЗ пластини із шаруватого ПКМ. Передбачалася 3D-ортотропія кожного моношару. Перевірялися дві прості формули експрес-аналізу. Результати зведені в таблицю. Наведені ілюстрації.Результати дослідження. Отримано числові оцінки, що характеризують ступінь впливу характеристик матеріалу й схеми армування в пластині із шаруватого ПКМ і точність розглянутих формул.Висновки. Зміна матеріалу й схеми армування шаруватого ПКМ призводить до істотної зміни значень ККН у навантаженого болтом отвору в ослабленому отвором перетині пластини, а розглянуті формули експрес-аналізу мають недостатню точність для контрастних випадків матеріалів і схем армування пластини. Необхідні додаткові дослідження.

In a bolted joint, the preload level resulting from the tightening torque represents a very important parameter governing the stresses distributions involving the joint under the real loading conditions. This paper deals with the development of a Finite Element (FE) model for the investigation of the effects of some selected preload levels on the stress-strain states affecting both bolt and plate in a single lap joint. The aim of this FE model is to support the design phase of strain gauges instrumented bolt to evaluate experimentally the rate of tensile load applied to the joint that the bolt absorbs with different preloads. The test article consists of two steel plates, a steel bolt and an aluminum nut. The results herein presented showed firstly that, without bolt preload, the tensile load applied to the joint is completely transferred to the bolt and that the load transferred to the bolt almost linearly decreases as the preload increases. Moreover, at a selected preload level, the transversal and longitudinal stresses (with respect to the load direction) increase as the tensile load increases, while the stress along the plate thickness direction decreases, reaching negative values. On the other hand, at a selected tensile load level, the transversal and longitudinal stresses as well as the stress along the thickness direction decrease as the preload level increases. Predicting the mechanical behaviour of the only bolted joint, if the same bolt model will be used to simulate the mechanical behaviour in a hybrid single-lap joint, possible imperfections of the model will have to certainly be linked to the modelling of the adhesive.

The paper deals with the influence of the geometric (joint clearance) and mechanical parameters (bolt preload, axial force applied to the joint) on the stiffness and strength of the single-bolt, single-shear laminated composite joints using epoxy resin and carbon fibers reinforcement. In the first part of the paper, the finite element model is presented, using three-dimensional elements for studding the influence of the geometric and mechanical parameters on the stiffness of the joint. In the second part, the microscopic failure of the constituent layers using the Hashin failure criterion for composite materials is presented, as well as the influence of the studied parameters on the occurrence of the first lamina failure and the progressive failure phenomenon from the microscopic to the macroscopic level of the joint.

three-dimensional finite element model has been developed to study the temperature effects on stiffness in linear-elastic range of the bolted metal-composite joints. In this study a quasi - symmetric lay - up for CFRP / vinyl ester epoxy laminate is used in conjunction with aluminum alloy (AA 7075 T6), having different thermal expansion coefficients. This generates an uneven load - deformation characteristics and three - dimensional stress field around the hole in single - lap single - bolt joints. The finite element model (FEM) was developed in commercial software PATRAN and the analysis including geometric and full nonlinearity frictional based contact has been performed using NASTRAN SOL 400 solver. The numerical model was calibrated using comparisons of the experimental measurements for surface strains and axial stiffness. The ability of the model to capture the three - dimensional effects such as secondary bending and through - thickness variation of stresses and strains in the presence of temperature variations is highlighted. The numerical and experimental results concluded that the thermal expansion material properties have a strong effect on the stiffness and linear behavior of the single - lap, single - bolt hybrid metal - composite joints.

Hybrid bolted joints, where carbon fiber reinforced polymers and metallic plates are clamped using bolts, are widely used in aircraft structures. During operation, aircraft experience extreme temperatures that can adversely affect the response of an hybrid joint. On account of the lack of understanding on this aspect, we analyzed a representative carbon-aluminum single lap shear bolted joint using a 3D numerical model. A parametric study varying the temperature, friction coefficient, bolt clamping force, bolt-hole clearance, and thickness of the metallic plate, provided insight into their effect on the stiffness stages of the mechanical response of the joint, as well as the contact evolution among the different elements. Bolt-hole clearance was one of the parameters that most influenced the joint stiffness and bolt bending. Temperature excursions induced sliding between plates and significantly altered the clamping load of the bolt, i.e., a 40% reduction and an 18% increase for a negative and positive thermal jumps, respectively. This clamping load variation entails undesirable bolt loosening or even yielding. Therefore, this work sheds light on the detrimental effects of temperature on hybrid joints, thus providing background for a safer structural design. This work has been accomplished within the framework of an ongoing EU H2020 Clean Sky 2 Project INNOHYBOX (Innovative solutions for metallic ribs or fittings introduced in a composite box to optimally deal with thermo-mechanical effects). This project has received funding from the Clean Sky 2 Joint Undertaking (JU) under grant agreement No. 785433. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union.

Monitoring and control of tension in bolted joints is a difficult task that has received long-time attention. A newly proposed technique is to hammer-impact the bolts and estimate the tension based on the vibration response. This present work conducts a thorough experimental investigation of two different bolted structures to identify the potentials of the technique, particularly examining damping ratios and nonlinearity by appropriate signal processing. The applicability of the method is checked by conducting tests with a real multi-bolt structure. For larger tension, the squared first bending natural frequency of a bolt increases approximately linearly with bolt tension. This study investigates the sensitivity of that feature with respect to impact force, i.e. the nonlinearity in the bolt’s frequency response. The damping ratio is estimated and observed to decrease with tension, and is overall reproducible for the tested impact forces, though with significant variation for small bolt tension. A time–frequency analysis provides insights into the variations observed in the measured linear damping ratios and natural frequencies. The time-dependent damping ratios generally depend on acceleration amplitude, especially for small amplitudes and small bolt tension. In contrast, the instantaneous natural frequencies are found to be practically independent of amplitude. The absence of significant nonlinearity is encouraging for the potential of a hammer impact-based technique for estimating bolt tension.

Four different local reinforcement schemes used in composite bolted joints were studied. In numerical study, a set of 3-D failure criteria was used and the progressive failure analysis was implemented via user-defined subroutine vectorized user-material (VUMAT), which was programmed by the commercial finite element (FE) software ABAQUS. In the experiment, test specimens were manufactured with different local reinforcement schemes, and the mechanical performances of these specimens were tested under tensile loads. Failure modes of these specimens were observed and mechanical performances of test specimens with local reinforcement were studied. It was found that the numerical results agreed well with the experiment. It was also found that local reinforcement schemes influenced the mechanical performances of bolted joints obviously and that the tensile strength of composite bolted joints could be improved significantly by burying laminate slices.

This paper focuses on an experimental investigation of the mechanical behavior of bolted joints. A new test apparatus to measure friction hysteresis was designed to provide a reliable experimental database for the calibration of contact models. This apparatus uses a piezoelectric actuator to provide the contact interfaces with stable oscillatory relative displacement. The friction force and the bolt preload were continuously measured during the test, using a load cell and a force washer, respectively. The relative motion between the interfaces was measured using a single laser vibrometer. The influence of the bolt preload and excitation amplitude on friction hysteresis was investigated. A numerical model was developed to extract the tangential contact stiffness from the measured data.

Fiber-reinforced polymer (FRP) structures, due to their low mass, are valuable alternatives to traditional steel or concrete structures in seismic areas. However, to resist seismic actions, FRP structures must be able to dissipate a significant amount of inelastic energy. Since FRP materials are brittle, this dissipation must occur in the joints. Monotonic tension and cyclic tension-compression experiments were thus performed on adhesive and bolted double-lap joints composed of pultruded glass fiber-reinforced polymer (GFRP) profiles; a flexible adhesive was used in the adhesive joints. A significant amount of energy was dissipated in the adhesive joints at lower and medium displacement rates through viscoelastic friction and damage in the adhesive, while almost no energy dissipation occurred at the highest rate. The energy in the bolted joints was dissipated by progressive crushing and shear-out failures in the inner laminates. Although the dimensions and monotonic strength of the adhesive and the bolted joints were similar, the former dissipated significantly more energy at the two lower applied displacement rates. The obtained results can contribute to the seismic design of inelastic joints in FRP structures. (c) 2020 The Authors. Published by Elsevier Ltd.

The joint efficiency of mechanical joints in fiber-reinforced composite materials can be increased significantly by embedding metal plies in the composite layup, as in the case of fiber metal laminates. In this work, a novel finite element-based framework is presented for predicting the static progressive failure behavior of fiber metal laminate bolted joints. Motivated from experimental observations, the proposed framework accounts not only for damage in the fiber-reinforced composite plies, but also for different types of damage of the metallic inlays. For this purpose, user-defined continuum-damage constitutive models are formulated and employed in the general-purpose FE software Abaqus/Implicit for the fiber-reinforced polymer plies and the embedded metallic inlays. Accordingly, the interaction between different failure modes and the influence of the bolt’s washer on the damage evolution is considered to increase the predictive quality. To demonstrate the applicability and validity of the developments, predictive simulations are carried out and compared to conducted experimental measurements on different fiber metal laminate grades (GFRP/stainless steel and CFRP/titanium) with a wide range of metal volume content, reaching from 0% (pure composite material) to 50%.

A three-dimensional progressive damage model has been developed to capture the onset and initial propagation of damage within a three-dimensional woven composite in a single-bolt, double-shear joint. Reinforced with a three-dimensional woven ply to ply interlock IM7 carbon fiber preform impregnated with toughened epoxy resin and manufactured using a resin transfer molding process, the composite represents a unique material currently used in select aerospace structures. The modeled joint is commonly found in many aerospace structures and, when combined with the progressive damage response of this three-dimensional woven composite, the material response can be reliably predicted with a three-dimensional non-linear finite element model. This model is constructed using an orthotropic material assumption far from the bearing area and a voxelized mesoscale model with an as-molded geometry representing matrix and impregnated tow phases. The well-established Hashin failure criteria and the Matzenmiller–Lubliner–Taylor damage model were implemented with the unique morphology of three-dimensional woven composites. The onset of damage and trends seen in the model were found to be in agreement with previous experimental findings.

The case of a bolted flange joint that is part of a model steam generator (SG) for sodium-cooled fast reactor (SFR) is studied to establish the statistical nature of the time to failure due to relaxation of gasket stress. Continued relaxation over a period of time lowers the gasket stresses to a critical sealing limit, causing failure due to leakage, one of the key modes of failure of bolted joints. An analytical model based on deformation compatibility is used to predict gasket load relaxation with time, which includes flexibility and creep behavior of joint members. A corresponding structural analysis was carried out to validate the analytical model. A probabilistic approach is taken to quantify the effect of uncertainties associated with the design variables on the failure of joint using the analytical model. In order to obtain probability of joint failure, Monte-Carlo sampling method was used for statistical trials. Further, sensitivity analysis was carried out to identify the critical design parameters. � 2015 Elsevier Ltd.

This paper aims to model the progressive damage of multi-bolted joints connecting structural elements made up of FRP (fiber- reinforced polymers) composite laminates and comprising different fiber materials (namely, based on basalt, carbon and glass), as well as different stacking sequences. Differences in failure mode and ultimate-load values are numerically investigated. A numerical home-made finite element model has been conceived, implemented, and validated by means of available experimental data. The numerical model is based on an incremental displacement-based approach and on a plane-stress bi-dimensional for- mulation. The stress analysis has been performed by accounting for micro-structural stress-strain localization mechanisms, and describing the progressive damage process by implementing a failure criterion operating at the constituents’ scale (namely, the Huang's criterion). Proposed results have highlighted that bolted joints based on basalt-FRP laminates and defined by a double- bolted configuration exhibited bearing failure loads comparable to those computed for glass-FRP and carbon-FRP laminates. In the case of single-bolted joints, the use of carbon-FRP laminates allowed to obtain the best mechanical properties, although joints based on basalt-FRP laminates numerically-experienced mechanical response and strength features always comparable with those of glass-FRP.

International audience; Predictive simulations of assembled structures raises some computational challenges for usual industrial structures. It is indeed necessary to deal with non-linear phenomena, such as contact or friction, and to consider sources of uncertainties mainly responsible for the deviation between the effective behaviour of the structure and results from deterministic simulations. Each of these two features of assembled structures requires intensive computational resources and the significant number of joints of actual structures increases even more the computational cost. In order to address such problems, this work aims to provide a pragmatic approach to robustly characterize the vibrational behaviour of light assembled structures considering the variability of the parameters of the joints. All the uncertainties of the whole problem are assumed to be associated to the joint interfaces. First, a nominal model of a joint consistent with the studied structure is identified using experimental data. Then a stochastic model of a joint is defined by considering the mechanical design variables of the nominal model as random variables. Based on an approximation of the maximum likelihood principle, the parameters of this stochastic model of joint are identified. A straightforward non-intrusive strategy referred to as the Stochastic Model Reduction (SMR) approach is used in the identification procedure of the stochastic model of the joint. The ease of implementation and the efficiency of the SMR approach justify this choice. The proposed approach is applied to an academic structure which is representative of light assembled structures: a three beam bolted frame. A stochastic model of joint characterized by its stiffness is thus implemented for each elementary joint of this frame. It allows us to characterize the variability of the vibrational behaviour of the frame taking into account the variability of each joint. Finally the comparison of the predicted stochastic response with the experimental behaviour of the structure shows that the proposed approach allows to tackle the variability of the actual structure. The proposed approach has been developped in the purpose of industrial applications. Based on a pragmatic modeling of the joint, a non-intrusive numerical tool and a stochastic modeling, the whole strategy could be indeed easily implemented on more complex industrial assemblies.

Ataş, Akın (Balıkesir Author), Cohesive zone elements are implemented in 3-D finite element models in order to develop a strength prediction method for single-bolted joints in CFRP composite laminates. The motivation for using the CZEs is to avoid experimental correlation factors by directly simulating the subcritical damage mechanisms, which initiate and grow before the catastrophic failure of the joints. The CZEs, placed in the experimentally determined damage locations, receive shear loads and the corresponding shear stresses cause stress concentration relief around the hole boundary. Therefore, a simple maximum stress failure criterion is used to predict the final failure of the joints when the stress level at the 0 degrees layers reaches the ultimate compressive strength. It is shown that the effect of various joint geometries and laminate lay-ups on the joint strength can be accurately accounted for by the method developed.

In this paper, a numerical home-made finite element model for the failure analysis of bolted joints between fiber-reinforced composite laminates is presented. The model is based on an incremental displacementbased approach, it is hinged on the laminate theory and on a progressive material degradation governed by the failure of composite constituents. The model has been applied to a pin-plate system comprising a monodirectional fiber-reinforced laminated plate, and numerical results in terms of the bearing failure load have been successfully compared with available experimental data. Aim of this paper is to evaluate the effectiveness of Rotem’s and Huang’s failure criteria in predicting the pin-bearing failure of bolted joints. The selected criteria act at different material scale: the former operating at the laminate level, while the latter at the constituent’s scale. Proposed results seems to suggest that failure criteria accounting for micro-structural stress-strain localization mechanisms (for instance, Huang’s criterion) give a more accurate estimate in terms of pin-bearing failure load.

The paper presents experimental and numerical analysis of elastic waves propagation in bolted connection of two steel plates. Numerical calculations were carried out using finite element method in two stages. In the first stage, static behavior of the joint during bolts compression was analyzed. Results of static analysis were used to formulate contact conditions for dynamic models. The analysis of wave propagation was taken for four types of bolt connection model. Finally, experimental tests by using a laser vibrometer and piezoelectric actuator were made in order to validate finite element models.

In this study, stress analysis and strength prediction were performed for carbon/epoxy laminates with holes in specific orientations using experimental and numerical techniques. The interaction between the holes was studied with reference to their positions and load direction. The maximum laminate stress at the edge of the holes was identified for different hole orientations. The critical region was determined by considering the maximum stress location at the hole edges. Linear and non-linear behavior around the hole edge was investigated by strain gauge measurements for different hole orientations. Final failure load was predicted for specimens with specific hole orientations by using the point stress criteria (PSC) method. Furthermore, the extended PSC (EPSC) method was proposed to predict the failure load for the specimens with specific hole orientations. The EPSC method was verified by experimental study. © 2019 Elsevier Ltd, This study is funded by Defense Industry Undersecretariat (SSM) under Researcher Training Program for Defense Industry (SAYP). Appendix A

As a demountable structure, the structure with design for deconstruction (DfD) is considered as a key contribution on the promotion of current construction sustainability by directly reusing valuable components from old structures. As a preliminary study, this paper investigated the cyclic behavior of bolted joints consisting of three reinforced concrete blocks bolted by steel bolts under axial compressive, focusing on the damage and failure modes, resistance mechanism and stiffness development of the joints. Results showed that the number of steel bolts, the tightening process of the bolts and concrete compressive strength all had a significant effect on the overall performance and capacity of the joints. The failure mode of most of tested joints was considered as fracture of stirrups and steel bolts in the tested joints. According to the investigation of this study, several recommendations on the design of the joints were provided.

An experimental failure analysis has been carried out to determine the effects of thermal condition and tightening torque on the failure load and failure behavior of single lap double serial fastener glass fiber/epoxy composite joints. 40, 50, 60, 70, and 80 degrees C temperatures were exposed to the specimens during tensile tests. It was seen that, the load-carrying capacity of the joint is decreased gradually by increasing temperature level. In proportion to the room temperature, the maximum decrease of failure loads occurs at 70 degrees C and 80 degrees C with the rate of nearly 55% and 70% respectively, because of the heat damage to the resin matrix. Besides thermal effects, 0 and 6 Nm tightening torques were applied to observe how clamping forces affect the joint strength. The results proved that, tightening torque is effective not only at room temperature, but also at elevated temperatures and contributes to the joint strength. (c) 2012 Elsevier Ltd. All rights reserved.

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research.

This article, in order to improve the assembly of the high-pressure spool, presents an assembly variation identification method achieved by response surface method (RSM)-based model updating using IV-optimal designs. The method involves screening out non-relevant assembly parameters using IV-optimal designs and the preload of the joints is chosen as the input features and modal frequency is the only response feature. Emphasis is placed on the construction of response surface models including the interactions between the bolted joints by which the non-linear relationship between the assembly variation caused by the changes of preload and the output frequency variation is established. By achieving an optimal process of selected variables in the model, assembly variation can be identified. With a case study of the laboratory bolted disks as an example, the proposed method is verified and it gives enough accuracy in variation identification. It has been observed that the first-order response surface models considering the interactions between the bolted joints based on the IV-optimal criterion are adequate for assembly purposes.

Ataş, Akın (Balikesir Author), The stress state around the middle (skin) plate hole of double-lap single bolted joints are investigated under an initial clamping force. Two different materials are considered for the middle plate: a quasi-isotropic carbon fiber reinforced plastic (CFRP) composite laminate and an aluminum alloy 7075-T6 plate. The outer (splice) plates are aluminum alloy 7075-T6 for both cases. The noncommercial FE code ANSYS v12.0 is used for the analyses [1] Linear solid brick elements are used to model the aluminum plates and the composite laminate. One element per layer approach is employed in through-the-thickness direction to model the laminated composite plate. The bolt and the washer are modeled as a single linear elastic deformable solid body. Surface-to-surface contact elements are used to define the contact behavior between the joint members including the effect of friction. Comparison of the stress results show that the clamping force has a significantly different effect for composite and aluminum plates. Initial clamping force introduces beneficial compressive stresses for aluminum plate whereas both tensile and compressive stresses occur for the composite laminate. The stress analysis results are used to explain the phenomena behind the different clamping force responses. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11, Balikesir University Turkish Council of Higher Education

Dynamic analysis of structures with large number of joints is computationally intensive due to non-linear nature and large degrees-of-freedom of the problem. This paper demonstrates that reduced order models provide a good approximation that is computationally much more efficient. Dynamic analysis of bolted lap joints under multiharmonic shear loading has been carried out using both detailed, non-linear, finite element models and reduced-order models. Micro-slip in bolted joints and the resulting energy dissipation is modeled using the Columb friction model. The models are subjected to both harmonic and multi-harmonic excitation, with frequencies above and below the natural frequency of the system. Reduced-order models are obtained by applying Proper Orthogonal Decomposition to the results of full solution. The reduced models are able to calculate both the slip and the energy dissipated without significant loss of accuracy.

This paper presents quasi-static and dynamic modelling of bolted composite structures using the explicit finite element code PAM-CRASH. User controlled point link (PLINK) elements were investigated for modelling the bolted composite joints used in the structures. Simulation results were compared with quasi-static and dynamic structural testing reported previously. Two loading configurations were considered. It was shown that the PLINK element modelling approach agreed well with the experimental results for both loading configurations and for one case offered significant improvements over other simplified bolt modelling methods. A stacked shell modelling approach was used to model the interlaminar delamination damage present in the ball-loaded impact mode. The overall response of the structure was significantly improved by the addition of these energy absorbing interfaces.

International audience; This work aims at investigating the influence of temperature on the strength and the failure mechanisms of carbon fiber fabrics reinforced PPS laminates. Four different tests were carried out at two temperatures (room temperature and 120 °C): tensile, open-hole tensile, single-bolt double lap joint and single-bolt single lap joint. Around its glass transition temperature, temperature contributes to enhance the viscoplastic behavior of the PPS resin but also to degrade the fibers/matrix interface. However, it has no relevant influence on both stiffness (−5%) and strength of notched (−3%) and unnotched (−7%) carbon fiber-reinforced PPS composites. For bolted joint tests, temperature shifts the failure mode from a brittle failure to a progressive failure resulting in a lower strength of the joints: −14% for double lap joints and −21% for single lap joints.

This paper is concerned with the study of bolted joints undergoing fretting damage. The analysis has been prompted by an investigation into failures of wheel-hub assemblies in earth moving equipment. In such applications, premature failures of the wheels initiating at the wheel-hub connection is observed in service. Fretting fatigue and wear induced by flexural loading at the wheel-hub bolted joints are often deemed to be responsible for damage initiation and crack propagation. Ad hoc analytical formulations have been developed and implemented by the authors in order to capture the mechanisms which govern these phenomena. In this article we present a semi-analytical boundary element modelling technique, which combined with contact asymptotic techniques (BEM/CA) can be employed to assess the strength of bolted connections subjected to flexural loadings.

Dynamic experiments were conducted on an all-FRP composite pedestrian bridge. The structure was excited by impact and human-induced vibrations. The peak-picking method and stochastic subspace identification method were used to extract structural dynamic characteristics without knowing the input excitation. Both methods proved to be applicable as output-only methods in situ and in real time. Better results were obtained from ambient excitation than from impact excitation. The joint types used in the truss structure - bolted joints in one span and adhesively bonded joints in the other span - markedly influenced the dynamic behavior of the two spans. The lowest natural frequency resulted from the first lateral mode and was 26-28% smaller for the bolted span than for the bonded span. The bolted span, however, exhibited higher damping ratios than the bonded span due to friction in the bolted joints. The resulting natural frequencies for the tested structure were of the same order of magnitude as for other FRP bridges. © 2006 Elsevier Ltd. All rights reserved.

International audience; Bolted joints are frequently subjected to self-loosening (gradual loss of clamping force) causing multiple failures, especially leaking and breaking of mechanical systems. Such physical phenomena would occur whatever the considered coating (Ag, MoS 2 , Zn-Ni and others). To enlighten this phenomenon, which remains rather misunderstood due to the confined nature of bolted joint contacts, a coupled experimental-numerical approach is adopted on a bolted joint with silver coating. Indeed, from tribological expert assessments of disassembled joints without loosening , a local view of nut/screw threads contacts is proposed, using discrete element method. This method becomes essential in tribology since it offers the ability to model the dynamic behavior of a contact interface. The model is based on a Non-Smooth Contacts Dynamics approach. The case of third body formed in contacts during tightening process, which has been ignored so far, is placed at the focus of self-loosening phenomenon.

In this study, a failure analysis was carried out to determine bearing strengths of mechanically fastened joints with single bolt in glass—epoxy laminated composite plates. Two different geometrical parameters that were the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D) were investigated. For that reason, E/D ratio was selected from 1 to 5, whereas W/D ratio was chosen from 2 to 5. Tensile tests were subjected to composite bolted joints for four different ply orientations such as angle-ply [0/30]s, [0/45]s, [0/60]s, and cross-ply [0/90]s. The major focus of this study was to observe the failure mechanisms of bolted joints under various preload moments as 0, 2.5, and 5 Nm. The experimental results showed that the magnitudes of bearing strengths in bolted joints were strictly influenced from increasing value of applied preload moments, changing of W/D and E/D ratios, and also ply orientations of laminated composite plates.

Gaskets play an important role in the sealing performance of bolted flange joints, and their behaviour is complex due to nonlinear material properties combined with permanent deformation. The variation of contact stresses due to the rotation of the flange and the material properties of the gasket play important roles in achieving a leak proof joint. In this paper, a three-dimensional finite element analysis (FEA) of bolted flange joints has been carried out by taking experimentally obtained loading and unloading characteristics of the gaskets. Analysis shows that the distribution of contact stress has a more dominant effect on sealing performance than the limit on flange rotation specified by ASME. � 2007 Elsevier Ltd. All rights reserved.

The main contribution of this work is to introduce analytical models able to create simple design charts that would allow designers to quickly determine the strength of quasi-brittle structures containing circular holes. Cohesive Zone Models are an excellent tool to model quasi-brittle structures with holes in which a large failure process zone is confined in a plane. Also, the CZM is able to predict the effect of the structure size on its strength. Moreover, it is one of the few models (or the only model) that takes into account the material cohesive law explicitly. Therefore, most of the presented models in this work are based on the cohesive zone model., La principal contribució d'aquest treball és la dʼintroduïr un model analític capaç de generar diagrames de disseny que permeten obtenir la resistència nominal dʼestructures quasi-fràgils que continguin forats. Els models de zona cohesiva permeten predir la resistencia dʼestructures amb forats formades de materials quasi-fràgils amb una gran zona de procés de fallada confinada en un pla. Aquests models també són capaços de predir lʼefecte de la mida de lʼestructura en la resistència nominal. A mès els models de zona cohesiva són un dels pocs (o els únics) que consideren dʼuna manera explítica la llei cohesiva en la seva formulació. Per aquestes raons, la majoria de resultats presentats es basen en els models de zona cohesiva.

International audience; Damping plays an important role in bolted joints of assembled structures due to their significant capacity to dissipate energy. The underlying mechanisms of these dissipative phenomena are generally poorly understood and result from contact and friction effects within the joint interfaces. In order to provide useful virtual prototyping tools for reducing response levels, accurate model-based estimation of modal damping is required. The present study employs an energetic method to calculate the loss factor associated with the localized dissipative interfaces of a global linear structure. The current method is based on the concept of the dissipated energy in the interfaces for which the closed-form expression of the loss factor is the ratio between dissipated energy and maximal potential energy, over a cycle of periodic vibration. The aim of this work is to investigate the advantages and drawbacks of this methodology for particular conditions such as: modal projection , localized damping level and model density. Simulated academic examples, where accurate estimations of the exact solutions are available, will be used to illustrate the methodology and to explore the potential difficulties that may arise in more complex industrial applications.

The development of an enhanced analytical approach to predict the secondary bending of single-lap composite bolted joints is presented. The enhanced accounts for the estimation of secondary bending as a function of geometrical parameters, material properties, and stacking sequence. The model is validated through comparison of the predicted load-displacement curve with experimental tests and literature data. The model accuracy was validated for different values of bolt torque, friction coefficient, geometrical parameters, and material properties. The method has been also used in a parametric study to analyse the influence of the main joint parameters on the load-displacement curve. The model is a valuable preliminary design tool for analysing the influence of the joint parameters on the stiffness of single-lap composite joints including the effect of secondary bending. The authors are indebted for the financial support of this work to the Ministry of Science and Innovation of Spain (projects TRA2010-19573 and DPI2010-15123)

Today more and more light weight structures are used for moved components in automotive, aviation and general industry. Often assemblies of these structures are realized by friction-based connections. Therefore precise information about the friction coefficients are necessary, because in light weight design no simple approximation of the loading capacity with significant over-dimensioning is possible. Furthermore, the short-time tribology of mechanical contacts plays an important role during tightening of bolted joints, especially when using light metals and coated surfaces. Still today, the tightening method of torque controlled screw assembly is the most used. For this tightening method the friction coefficients have to be well-known for an efficient design of the bolted joint. Up to now analytical calculations do not consider any local deviation of friction behavior in component systems, only average values are taken. This is the reason why in modern engineering processes extended friction laws are necessary. A suitable formulation should take contact pressure and sliding velocity into account. Based on this, the contribution shows experimental examples for main uncertainties of frictional behavior during tightening with different material combinations (results from assembly test stand).

This paper presents the numerical study of double-lap bolted joint behavior. This type of joint is mainly used in aeronautical structures to transfer the given loads (by both adhesion and by deformation-shearing). Recent articles, based on experimental fatigue tests conducted by AIRBUS, have shown the beneficial effects of preloading on the fatigue life of these joints. Finite element analyses were performed using ABAQUS® to study the behavior of a double-lap single-bolted joint with different plate thicknesses (joint thickness = 0.5d, 1d, 1.5d, 2d 2.5d, 3d, 3.5d and 4d, where d is the bolt diameter). The numerical model provides several important results. In the case of static loads, elasto-plastic constitutive laws of the bolt and the plate materials allowed the process to be simulated on the basis of tension tests. Mechanical aspects of this type of assembly are numerically identified; from the initial state of adhesion to the state of plastic deformation of parts in contact including the stage of generalized slippage. We note that the fracture load increases slightly when the bolted joint is preloaded while the failure area remains the same. In the case of large plate thickness, the connection is subjected to significant bending stresses and this involves strong local plasticization associated with the loss of preload. In the case of cyclic loading, we consider a numerical model based on the simulation of one loading/unloading cycle. A noticeable decrease in initial preload is observed for certain configurations, in particular those with the largest plate thickness. This phenomenon is related to the effect of strain hardening of the bolt during the first loading cycles. Some experimental work by AIRBUS has shown that the fatigue life of assemblies is dependent on the material plate thicknesses. An extension to the case of a multiple-bolted joint (three rows of three bolts) is finally discussed and highlights the evolution of the rate of load transmission with respect to the applied load.

This chapter discusses experimental and numerical investigation of dynamically loaded bolted joints in carbon fibre/epoxy laminates. Bolted joint testing at loading rates between 1 mm/s and 10 m/s found that joints loaded at or above 1 m/s exhibited significant rate sensitivity. Changes in failure mode, failure load and total energy absorption were found for some joint geometries. Increased loading rate led to increased bearing damage in most joint geometries tested. Finite element modelling techniques applicable to dynamically loaded bolted joints are presented. Modelling results predicted the failure behaviour very well and enhanced the understanding of the failure progression.

An investigation is presented into the behaviour of carbon fibre composite joints subjected to dynamic loading rates in the range of 0.1 m/s to 10 m/s. The research is focused on the response of single fastener joints and more complex structural arrangements involving multiple fasteners and complex loads. Fasteners play a crucial role in the joining of aerospace components due to their ease of installation and inspection and their resistance to creep and environmental degradation. A consequence of the operating environment of aircraft is that many critical load cases involve impact and crash. These loading events are characterised by high loading rates, high kinetic energy and possibly loads well above the static design case. The properties of composite materials change with loading rate, so it is likely that the behaviour of bolted composite joints may also vary significantly. Dynamic behaviour of bolted joints is an area of research that has been given little attention to date. The few available papers on the topic are limited to the investigation of ideal bearing loads and include some contradictory results. The research developed a detailed understanding of the behaviour of bolted joints in composite structures through a combined numerical and experimental investigation. A set of quasi-static and dynamic single fastener joint tests was conducted to develop an understanding of the complex failure mechanisms present in bolted composite joints. Simple structural tests were developed to investigate the interaction of multiple bolts in a joint. High speed camera footage, full-field strain measurement and CT scanning techniques were all used to develop an understanding of the changes in the failure process with increased loading rate. Finite element analyses used implicit and explicit dynamic algorithms to model the tests. The finite element analysis contributed to the understanding of the experimental results as well as providing a predictive tool to minimise the need for further testing. A method of incorporating detailed information about bolt failure into large scale structural models was investigated and developed. The original contributions of this thesis involve novel dynamic joint testing including dynamic pull-through and structural tests. CT Scanning was utilised in a novel way to investigate the complex failure modes within a bolted joint. Novel finite element techniques were developed for modelling bolted joints at both a detailed level and a simplified level for structural analyses. These contributions significantly improve the current understanding of bolted joint failure, both quasi-statically and dynamically, and will allow for more efficient design of bolted composite structures for crash and impact loads.

For a reliable design of bolted joints, it is necessary to evaluate the actual fraction of the external load transmitted through the bolt. The stiffness of the bolt and the member of the joint decide the fractions of external load shared by the bolt and the member. Bolt stiffness can be evaluated simply by assuming the load flow to be uniform across the thickness and the deformation is homogeneous. Then, bolt may be modeled as a tension member and the stiffness can be easily evaluated. But, the evaluation of the member stiffness is difficult because of the heterogeneous deformation. In the present work, joint materials are assumed to be isotropic and homogeneous, and linear elastic axisymmetric finite element analysis was performed to evaluate the member stiffness. Uniform displacement and uniform pressure assumptions are employed in idealizing the boundary conditions. Wide ranges of bolt sizes, joint thicknesses, and material properties are considered in the analysis to evaluate characteristic behavior of member stiffness. Empirical formulas for the member stiffness evaluation are proposed using dimensionless parameters. The results obtained are compared with the results available in the literature. Copyright � 2009 by ASME.