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The stiffness of leaf springs was calculated using the master leaf method and the finite element method. A finite element model of the leaf spring system, incorporating structural components such as the spring seat, was developed. This model takes into account nonlinear factors present in the actual working conditions of the leaf springs, such as large deformations, frictional contact, and hinge rotation. The study analyzed how various factors affect the stiffness of the leaf springs. It was found that the stiffness of the leaf spring system increases with the rise in the friction coefficient between the leaves, and initially increases and then decreases as the preload force is augmented. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to improve the mechanical properties of 3D concept designs by combining the design capability of a generative adversarial network with finite element analysis. This approach offers an innovative perspective on the conditioning of generative models while improving design properties and automation. A new design and evaluation framework has been developed for GAN models to generate 3D models with improved mechanical properties. The framework is an iterative process that includes dataset generation, GAN training, and finite element analysis. A "joint" component used in the aerospace industry is considered to demonstrate the proposed method's effectiveness. Over six iterations, an increase of 20% is recorded in the average safety factor of the designs, and the variety of designs produced is narrowed in the desired direction. These findings suggest that the direct generation of structural components with generative models can expand the potential of deep learning in engineering design. Another innovative aspect of this study is that it provides a new option for the conditioning of data-dependent generative design models. [ABSTRACT FROM AUTHOR]

Beams in two configurations; uniform and nonuniform, are common structural components utilized for several engineering applications. Thus, the studies dealing with their behavior under dynamic and vibrations have been increased. In this research, the transverse vibration phenomena of pre-twisted beams were experimentally and theoretically studied by investigating the effect of twisting angles on the first three transverse natural frequencies. In the present experimental part, the pre-twisted beams are manufactured using a 3D printer, and the fundamental frequencies of manufactured pre-twisted beams are measured by a suitable rig. In the theoretical work, the finite element method is used to simulate the transverse vibration behavior of the pre-twisted beams. The accuracy of the simulation process is checked by comparison of the first natural frequencies calculated by the finite element method (using ANSYS Workbench Software) with those measured experimentally. The results show that there is an excellent agreement between the experimental results and finite element outputs. For the clamped-free pre-twisted beam, there is no critical twisting angle. The critical twisting angle is equal to the mode number for simply – simply and clamped simple pre-twisted beam. While there is more than one value of critical twisting angle for the clamped-clamped pre-twisted beam. [ABSTRACT FROM AUTHOR]

A large-scale radio astronomical telescope is a typical complex coupled system, consisting of a feed cabin, cables, and supporting structures. The system is extremely sensitive to wind loads, especially the feed cabin, which has high requirements for vibration displacement during operation, and excessive vibration may affect normal operation. To investigate the wind-induced vibration characteristics of such coupled systems, this study takes the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) as an example to conduct research. First, a refined finite element model of FAST is established, and a dynamic analysis using simulated random wind loads is conducted. The influence of the cable boundary on the time–frequency domain responses of the feed cabin is particularly considered. Then, the gust response factor (GRF) for different structural components within the coupled system is calculated. Finally, the evolution law of the GRF under various wind speeds and directions is revealed by parametric analysis. The parameter analysis only considers the wind directions ranging from 0° to 60°, because FAST is a symmetric structure. The results indicate that obvious differences are observed in both the rotational and translational displacements of the feed cabin under northward wind, especially the results along the east–west axis. When the supporting towers are considered, there is no change in the power spectral density (PSD) of the feed cabin in the low-frequency range. However, in the high-frequency range, taking the supporting towers into account leads to an increase in PSD and a resonance near the first-order natural frequency of the supporting tower. The GRF based on the dynamic response exhibits substantial deviations compared to those obtained from design codes, highlighting the need for an independent analysis when determining GRF for such coupled systems. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to describe the creation and use of a fatigue analysis program written in VBA, designed for the preliminary sizing of metallic structural components used in aerospace applications, subjected to one or multiple fatigue loading cases. The VBA programing language was chosen because of its direct control over the most common spreadsheet computational program, Microsoft Excel. Metal fatigue analysis is an important type of analyses for modern structures. Fatigue failure accounts for around 80-90 percent of common structural failures, and therefore, a quick and reliable analysis is necessary so as to evaluate the structure’s bearing capacity to fatigue load. Due to the nature of the fatigue load and the importance of the structural component, such an analysis can be very time consuming, starting from the finite element model preparation and going through the actual analysis; thus, there is a need for a tool that can evaluate the stress data from the numerical simulation and give reliable information about the behavior of the structural component. [ABSTRACT FROM AUTHOR]

This paper presents a technical-economical optimization by maximizing the ratio between the critical buckling pressure (technical characteristic) and the production cost (economic characteristic) of stiffened cylindrical shells, a basic concept of value analysis. Critical buckling load values were determined using both the Finite Element Method (FEM) and analytical calculations to validate the accuracy of the results obtained. The maximum difference between the analytical and numerical results was 10%. Technicaleconomic optimization was carried out using the design of experiments method with MINITAB 19 and allowed to select the optimal input parameters, stiffener dimensional ratio 0.10, shell wall thickness 2.50 mm, and distance between circumferential stiffeners 400 mm, and identify the main factors that impact the output response. For the optimal constructive configuration, the ratio between the critical buckling load and the production cost of the stiffened cylindrical shells was maximized by 199%. [ABSTRACT FROM AUTHOR]

This investigation aimed to comprehensively investigate the integrity and failure characteristics of deteriorated polymeric components produced through Fused Filament Fabrication (FFF) technology. The primary focus was to examine the performance of flawed 3D-printed samples, which were purposely designed and 3D-printed to incorporate a range of crack types and geometric features that were initially designed through CAD. This study adopted two main approaches to deal with the cracks by producing the flaws through design and laser processes. These specimens were subjected to destructive testing to gain valuable insights into the FFF-printed components' performance and failure characteristics under the tensile mode, a significant concern in engineering applications. A Finite Element Analysis (FEA) was employed on the flawed and intact specimens to compare and correlate the experimental results with the simulation results. This study reveals the tested samples' structural response and failure mechanisms under tensile loading conditions. Exceptionally, it was found that the faulty 3D-printed parts made by the laser process demonstrated less resistance to failure due to disturbing the 3D-printed extruded filament streams. In contrast, the flaws initially produced solely by the 3D printing process showed better resistance to mechanical failure due to the crack-bridging effect. It was observed that there were reductions of 11% and 32% in the failure load of the 3D-printed cracked sample and the laser-cracked samples, respectively, in comparison with the intact one. Additionally, the stress intensity factor showed a decrease of 20% in the laser-cracked sample compared to the 3D-printed one. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One of the major engineering tasks is to evaluate the structural behavior when one of the components has failed. In such cases it is necessary to carry out fail-safe analysis to evaluate if the structure can be used safely in loading conditions. Thus, fail-safe analysis is a vital and important task to properly validate the mechanical structure. The implementation of the fail-safe analysis using the finite element method is usually done by eliminating the given component from the finite element model and carrying out the given analysis. But when due to finite element modeling issues such an approach cannot be carried out without causing singularities in the model, another approach should be used to perform the fail-safe analysis. One such method, presented in this paper, is the zero stiffness method, which applies near-zero stiffness to the structural component that is removed from the finite element model. The zero stiffness method is used by applying close to zero values to the material and element properties, and thus reducing the load that is in the given structural component. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fracture-involved large strain behaviors of amorphous glassy polymers are concerned. • A physically-based constitutive model coupled with phase field method is established. • A unified craze-initiation criterion is proposed within the constitutive model. • The fracture phase field method is utilized in a user-friendly way via Abaqus/Explicit. • The numerical method has been validated by the experiments from the literature. To promote the application of amorphous glassy polymers in structural components, a reliable prediction of the deformation and the potential fracturing behaviors is in demand. This work aims to provide a simple and feasible computational method to analyze the large strain behaviors, including elasticity, viscoplasticity, and the subsequent fracture, of amorphous glassy polymers. This is achieved by incorporating a physically-based constitutive model coupled with the fracture phase field method into the commercial finite element software Abaqus/Explicit. Inside the constitutive model, shear-yielding, crazing, and disentangling are considered as the underlying mechanisms for viscoplastic deformation and damage initiation. It is noteworthy that a unified craze-initiation criterion with a clear physical meaning is proposed, distinguishing this work from the previous in the literature. Moreover, a relatively user-friendly numerical implementation is suggested by exploiting the built-in features of Abaqus/Explicit. Taking the typical amorphous glassy polymers for example, i.e., polycarbonate (PC) and poly-methyl-methacrylate (PMMA), various experiments from the literature have been simulated. The proposed approach has been validated, since an acceptable agreement between the simulated and experimental results is realized. [ABSTRACT FROM AUTHOR]

Foldable structures have been of great interest due to their ability to reduce in size from deployed to folded state, enabling easier storage in scenarios with space constraints such as aerospace and medical applications. Hexagonal structural components have been of interest, due to their ability to tessellate, or cover without gap, 2D and 3D surfaces. However, the study on effective folding strategies for hexagon-based structures and the hexagon geometry itself is limited. Here, we report a strategy of snap-folding hexagonal rings, to result in folded states with only 10.6% the initial area of a single ring. Motivated by this significant packing, we utilize a combination of experiments and finite element analysis to study effective folding strategies and packing abilities of various 2D and 3D hexagonal ring assemblies, with structures that can be folded to 1.5% and 0.4% of their initial area and volume, respectively. The effect of geometric parameters of hexagonal rings on the mechanical stability of their assemblies is investigated. Additionally, the instabilities of rings can be utilized to facilitate the automatic deployment of folded ring assemblies under small perturbations. Furthermore, an assembly with rigid functional panels is explored to demonstrate the functionality and design space for hexagonal ring assemblies. With such significant demonstrated area and volume changes upon snap-folding, it is anticipated that hexagonal ring assemblies could inspire future aerospace or biomedical designs, where reconfiguration and large packing are required. [ABSTRACT FROM AUTHOR]

This paper presents a finite-element-based computational model to evaluate the thermal behaviour of composite slabs with a steel deck submitted to standard fire exposure. This computational model is used to estimate the temperatures in the slab components that contribute to the fire resistance according to the load-bearing criterion defined in the standards. The numerical results are validated with experimental results, and a parametric study of the effect of the thickness of the concrete on the temperatures of the slab components is presented. Composite slabs with normal or lightweight concrete and different steel deck geometries (trapezoidal and re-entrant) were considered in the simulations. In addition, the numerical temperatures are compared with those obtained using the simplified method provided by the standards. The results of the simulations show that the temperatures predicted by the simplified method led, in most cases, to an unsafe design of the composite slab. Based on the numerical results, a new analytical method, alternative to the simplified method, is defined in order to accurately determine the temperatures at the slab components and, thus, the bending resistance of the composite slabs under fire conditions. [ABSTRACT FROM AUTHOR]

Thin-walled stiffened panels are fundamental structural components that form the primary structure of the ship hull. The effectiveness of the stiffener configuration design needs to be assessed because members are unavoidably subjected to various load types during operations. In this situation, assessment is required to quantify the responses and determine the relationship between the structural resistance and input parameters. The aim of this work was to obtain structural resistance data on the stiffened side hull of a medium-sized tanker with various model configurations by using finite element analysis with different loading parameters, i.e., load type and angle, as the main inputs. The results indicate that stiffener configurations subjected to loads at the center and random positions influence the effectiveness in reducing the deformation. The results show that the stiffener is more effective when the location of the force is very close to the stiffener. Therefore, higher strength can be obtained with a design in which the area that is not supported by the stiffener is minimized. [ABSTRACT FROM AUTHOR]

Mode I fracture of plate specimens with sharp V-shaped notches is studied analytically and numerically. Within computations, elastic-perfectly plastic constitutive behaviour is assumed. The crack initiation from the tip of the V-shaped notch is described with the help of a modified Leonov–Panasyuk–Dugdale model using an additional parameter, namely, the diameter of the plasticity zone. Under small-scale yielding conditions in the presence of a singularity of the stress field in the vicinity of the V-shaped notch tip, a coupled fracture criterion is proposed. A strain-based fracture criterion is formulated at the real notch tip, and a force-based criterion operating with averaged normal stresses is considered at the fictitious crack tip. The diagrams of quasi-brittle fracture of specimens from structured material are constructed. The propagation of the plastic zone in the notched plates under quasi-static loading is simulated numerically. The plastic zone size in the vicinity of the V-shaped notch tip is assessed; in the limiting case, the V-notch degenerates into an edge crack. The generalized stress intensity factor for a crack growing from a sharp V-shaped notch is obtained by the finite element method. It is shown that under small-scale yielding, the analytical predictions of the critical load agree with the numerical results for a wide range of opening angles. [ABSTRACT FROM AUTHOR]

In the preliminary stage of the industrial design, the structural analysis of the components made of composite materials is generally difficult to carry out for aircraft structures having complex three-dimensional geometry. More importantly, in the case of composite structures, the lay-up process creates a particular distribution of the material properties that is challenging to simulate in a virtual environment. This research work is, therefore, focused on the use of the finite element method for the numerical analysis and the structural redesign of the bulkhead and flap aircraft components. In particular, the numerical results obtained in this work are the stress and strain fields of these mechanical components. The redesign and the structural optimization of these two mechanical components are performed employing a simple numerical procedure. For this purpose, the quality of the stress and strain fields obtained by performing numerical experiments is evaluated considering failure criteria suitable for composite structures. Subsequently, the analysis developed in this study is used for determining the performance of the material as well as the number and orientation of the plies selected for the composite components. The verification process performed in this work, on the other hand, consisted of a comparative analysis with the same aerospace components made of isotropic and anisotropic materials. The numerical results found are compared with the experimental results available for the aerospace components that are geometrically and functionally similar to the bulkhead. In general, a good agreement is found in the comparison between the numerical and experimental results. [ABSTRACT FROM AUTHOR]

The article discusses the mesh creation techniques for models of discs of axial-flow microturbines. A universal method of optimization of such devices, in terms of their strength improvement, has been proposed. The research focused on microturbines that can operate in combination with ORC systems, especially the ones whose discs have many structural components such as pins or chamfers. Calculations were done using the commercial software ANSYS Workbench. Both tetrahedral and hexahedral grids were used in the analysed models. The calculation time needed for the grid preparation was regarded as an important parameter. Therefore, the reference model was created using the disc slice method. The results obtained for the models that included the full complex geometry of the disc were compared with the results obtained for the reference model. The mesh size coefficient was defined. It enabled to simplify the strength optimisation method for discs of axial-flow microturbine and also made it more universal. After carrying out all analyses and computations, it was possible to develop a scheme of conduct during the optimization of the aforementioned expansion devices. [ABSTRACT FROM AUTHOR]

Offshore wind turbines (OWTs) are deployed in harsh environments often characterized by highly stochastic loads and resistance properties, thus necessitating the need for structural reliability assessment (SRA) to account for such uncertainties systematically. In this work, the SRA of an OWT jacket-type support structure is conducted, applying two stochastic methods to predict the safety level of the structure considering various design constraints. The first method refers to a commercial finite element analysis (FEA) package (DesignXplorer© from ANSYS) which employs direct simulations and the six sigma analysis function applying Latin hypercube sampling (LHS) to predict the probability of failure. The second method develops a non-intrusive formulation which maps the response of the structure through a finite number of simulations to develop a response surface, and then employs first-order reliability methods (FORM) to evaluate the reliability index and, subsequently, the probability of failure. In this analysis, five design constraints were considered: stress, fatigue, deformation, buckling, and vibration. The two methods were applied to a baseline 10-MW OWT jacket-type support structure to identify critical components. The results revealed that, for the inherent stochastic conditions, the structural components can safely withstand such conditions, as the reliability index values were found acceptable when compared with allowable values from design standards. The reliability assessment results revealed that the fatigue performance is the design-driving criterion for structural components of OWT support structures. While there was good agreement in the safety index values predicted by both methods, a limitation of the direct simulation method is in its requirement for a prohibitively large number of simulations to estimate the very low probabilities of failure in the deformation and buckling constraint cases. This limitation can be overcome through the non-intrusive formulation presented in this work. [ABSTRACT FROM AUTHOR]

In the last period of time, lattice structures have been developed as a new type of lightweight material. Significant amount of work has been done to investigate the applications and properties of lattice cells. In many fields of activity, lattice cells are widely used as support structures leading to minimal support material usage. This paper presents a method to design lattice structure of a bracket based on the modal analysis and topology optimization. Traditional design approaches do not make the most of new manufacturing methods, like additive manufacturing, which are removing design constraints and opening up new possibilities. The optimal shape of a part is often organic and counterintuitive, so designing it requires a different approach. Topology optimization allows for specifying where supports and loads are located on a volume of material and lets the software find the best shape. Designers can easily perform lightweight structures, extract CAD shapes and quickly verify the optimized design. In this study, it is optimized the distribution of orthotropic lattice materials inside the shape of the bracket, having as objective to maximize the first natural frequency and a response constraint to keep 40% of the bracket mass. Numerical results demonstrate remarkable structural properties of conforming lattice structures obtained. [ABSTRACT FROM AUTHOR]

Geotechnical design of piled-raft foundation is typically performed using simplified semi-empirical equations that do not consider the interaction between structural components and supporting soil and the effect of bending moment on the differential settlement of piled-raft. In this study, the settlements and rotations computed using an analytical and linear and nonlinear finite element methods were compared. First, a piled-raft foundation for supporting a 130 m-tall wind turbine was designed using simplified analytical method and then a nonlinear finite element model was created in ABAQUS and analyzed. In the finite element modeling, the stress-strain behavior of the soil was represented by linear elastic (LE) and nonlinear elastoplastic Drucker-Prager (DP) models. The interfaces between structural components and soil were modeled as two bodies in the contact that allows slipping and separation at the interfaces. The results showed that the vertical and the horizontal displacements from the analytical procedure were significantly higher than that of the nonlinear finite element method. At the same time, the differential settlement and rotation were lower than that of ABAQUS. The parametric study conducted by varying the wind speed and undrained shear strength of the soil indicates that the difference between the predicted responses decreases when the load is large and/or soil is soft. From the finite element analyses, it was observed that the separation and slip between the soil and pile were negligible. It was also found that the piles contributed more in reducing vertical settlement, raft contributed more in reducing horizontal displacement, and only piles were contributing to reduce differential settlement. [ABSTRACT FROM AUTHOR]

In this paper, a new steel yielding damper in the beam-to-column connections relying on the combination of slit damper and T-stub called T-SSD is proposed, with an aim to increase energy dissipation capacity and stiffness as well as to reduce seismic damage on the structure. Different patterns of connections are considered in the analysis. Nonlinear finite element method is employed to deal with realistic modeling of the specimens and to capture all the main seismic behavioral aspects including the strength, the stiffness, the energy dissipation, ductility, von-Mises stress and equivalent plastic strain distributions of models. A parametric study on the geometry of slit dampers is also performed to determine the best geometrical configurations in terms of mechanical performance. According to the results, the models with T-SSD systems possess satisfactory hysteretic performances. Yielding and local buckling of the T-SSDs under seismic events serve as the primary source of energy dissipation, while the other structural components remain essentially elastic. Strength and energy dissipation capacities were essentially improved by changing the slits configuration. The T-SSD connections can supply the highest initial stiffness, bearing capacity, ductility, and energy dissipation increases by 63%, 94%, 80%, and 35%, respectively, with respect to the T-stub connection. The presence of shear tab in connections could typically result in increased initial stiffness by as much as 25% in comparison with counterpart without shear tab. Theoretical equations estimate the initial stiffness and bearing capacity of the connections 15% more than and 50% less than those of the numerical results, respectively. • In this study, a new yielding damper in the beam-to-column connections called T-shaped slit damper or T-SSD is proposed. • A comparison of performance characteristics of models is presented. • The T-SSD connections can supply the highest initial stiffness and bearing capacity increases by 63% and 94%, respectively. • The highest energy dissipation due to the use of T-SSD connections can be 35% than that of the T-stub connection. • The ductility benefits up to 80% in the T-SSD connection with respect to the T-stub connection. [ABSTRACT FROM AUTHOR]

The columns and the supporting foundations are invariably subjected to the interacting axial force, V, shear force, H and moment, M. It is quite common to consider the interaction of these forces in design of structural components, but the available standards and literature usually ignore the effect of interaction in case of foundations on slopes. Further, very little information is available about seismic capacity of foundations located on slopes. This article presents a numerical study on evaluation of the V–H–M capacity envelopes of strip foundations placed on top and face of slopes and subjected to earthquake action, with an objective of enabling a direct comparison with the capacity of the supported columns. Nonlinear 2D finite element limit analyses are performed for this purpose. Modified 'Probe' analyses are carried out for two representative c-ϕ soil slopes to develop the V–H–M capacity envelopes. The computed capacity envelopes are compared with their counterparts on flat ground. The characteristic features of the capacity envelopes are identified and explained considering the failure patterns under different combinations of V, H and M. A comparison of the capacity envelopes of counterpart foundations on flat ground and of columns is presented to highlight the relative hierarchy of strength of columns and foundations of a typical building on slope. [ABSTRACT FROM AUTHOR]

In the paper, an underwater fishing robot for aquatic products is developed. The finite element analysis method is used to optimize the thickness of the pressure hull of underwater robot, which can prevent hull pressure from being damaged to ensure the normal operation of the underwater vehicle. As an important structural component of underwater fishing machinery, the pressure hull should not only meet the requirements of stability but also require its strength within the allowable range under underwater pressure. The optimized pressure hull structure is more in line with the functional requirements of underwater fishing robots, the weight of the robot overall is reduced, the materials and costs of that are saved, and the reliable reference data for practical forestry engineering applications are provided. [ABSTRACT FROM AUTHOR]

Shear links (SLs) are effective energy dissipation devices for seismic damage mitigation and resilience improvement of bridges or bridge bents. This study is to assess the influences of the SLs on controlling seismic damage or response of tall reinforced concrete (RC) bridge bents. Therefore, two tall RC bridge bent models with and without SLs are designed and tested using the shaking table. The dynamic characteristics and seismic responses are separately presented for both test models under the white noise and three input motions. Both finite element models are conceived to replicate the test results. These results demonstrate that the SLs decrease the maximum curvature and reinforced strain at the column bottom due to the SLs dissipating the seismic energy. The tall RC bridge bent model without SLs suffers seismic damage under the input motions of 0.30 g, whereas the tall RC bridge bent model with SLs undergoes seismic damage until the input motions of 0.50 g. Compared to the tall RC bridge bent model without SLs, the maximum displacements of the tall RC bridge bent model with SLs reduce because the SLs enhance the stiffness of bridge bents, leading to the displacement spectra values reduction for the S-Wave and E-Wave. Both finite element models successfully reproduce the typical test results of the tall RC bridge bent models with and without SLs and track the response variations caused by the SLs. Therefore, the effects of the SLs on controlling seismic damage and improving the seismic resilience of tall RC bridge bents are verified using shaking table tests and numerical simulations. • Tests on the tall RC bridge bents with and without SLs were conducted. • Beneficial effects of SLs on seismic responses of tall RC bridge bents were assessed. • Effects of SLs on mitigating seismic damage of tall RC bridge bents were verified. • Numerical models could detect the response variations caused by SLs. [ABSTRACT FROM AUTHOR]

• We present a new meta model for the relationship between strain data and crack size. • A bootstrap particle filtering is deployed to update the crack forecast algorithm. • The experimental test validates the proposed forecast and updating algorithm. • The sensitivity analyses examine the effect of limited data on the crack forecast. This paper presents an enhanced neural network-bootstrap particle filtering algorithm to construct the complex relationship between the normalized strain relaxation indicators and the crack front profiles based on numerical simulation and experimental validation. The metamodel of normalized strain relaxation indicators and the crack front profile in welded plate joints under bending cyclic loadings is built based on the optimal regression neural network and finite element analysis. To overcome the uncertainties caused by the limited strain measurement, crack measurement, and different non-destructive techniques, this study further proposes new crack-related weight functions and combines a bootstrap particle filtering approach with an interpolation method to finely tune the metamodel and the crack prediction algorithm. As validated by the experimental results, the intelligent crack sizing approach demonstrates a potential solution for crack size monitoring through affordable strain gauges in the broad framework of digitally twinning the next-generation infrastructure. [ABSTRACT FROM AUTHOR]

Objective: For occupant protection, it is important to understand how a car's deceleration time history in crashes can be designed using efficient of energy absorption by a car body's structure. In a previous paper, the authors proposed an energy derivative method to determine each structural component's contribution to the longitudinal deceleration of a car passenger compartment in crashes. In this study, this method was extended to 2 dimensions in order to analyze various crash test conditions. The contribution of each structure estimated from the energy derivative method was compared to that from a conventional finite element (FE) analysis method using cross-sectional forces.Method: A 2-dimensional energy derivative method was established. A simple FE model with a structural column connected to a rigid body was used to confirm the validity of this method and to compare with the result of cross-sectional forces determined using conventional analysis. Applying this method to a full-width frontal impact simulation of a car FE model, the contribution and the cross-sectional forces of the front rails were compared. In addition, this method was applied to a pedestrian headform FE simulation in order to determine the influence of the structural and inertia forces of the hood structures on the deceleration of the headform undergoing planar motion.Result: In an oblique impact of the simple column and rigid body model, the sum of the contributions of each part agrees with the rigid body deceleration, which indicates the validity of the 2-dimensional energy derivative method. Using the energy derivative method, it was observed that each part of the column contributes to the deceleration of the rigid body by collapsing in the sequence from front to rear, whereas the cross-sectional force at the rear of the column cannot detect the continuous collapse. In the full-width impact of a car, the contributions of the front rails estimated in the energy derivative method was smaller than that using the cross-sectional forces at the rear end of the front rails due to the deformation of the passenger compartment. For a pedestrian headform impact, the inertial and structural forces of the hood contributed to peaks of the headform deceleration in the initial and latter phases, respectively.Conclusions: Using the 2-dimensional energy derivative method, it is possible to analyze an oblique impact or a pedestrian headform impact with large rotations. This method has advantages compared to the conventional approach using cross-sectional forces because the contribution of each component to system deceleration can be determined. [ABSTRACT FROM AUTHOR]

Material nonlinearity analyses are widely used to determine the safety of structural components or engineering structures. Although advanced computer hardware technology has considerably improved the computational performance of such analyses, large and complex emerging structures and expensive computational process still attract the attention of researchers toward finding more efficient and accurate numerical solution methods. This paper combines an inelasticity-separated (IS) concept with the finite-element method (FEM) to establish a novel and efficient framework (IS-FEM) for structures with material nonlinear behavior that only occurs within certain small local domains. The IS concept presented in this paper begins by decomposing the strain on a nonlinear material into its linear-elastic and inelastic components and runs through the whole framework. Based on the principle of virtual work, a novel governing equation for structures with an IS form is derived by treating the decomposed inelastic strain as additional degrees of freedom. Moreover, the changing stiffness matrix in the classical FEM is expressed as the sum of the invariant global linear elastic stiffness matrix and another changing inelastic stiffness matrix with a small rank, and it represents the material nonlinearity of local domains so that the efficient solution method can be applied to perform nonlinear analyses via the mathematical Sherman–-Morrison–Woodbury (SMW) formula. Because the unchanging global stiffness matrix is used throughout the whole nonlinear analysis and the computational effort only focuses on a small dimension matrix that represents the local inelastic behavior, the efficiency of the proposed IS-FEM is improved greatly. The proposed method is validated against the results of classical FEM via three separate numerical examples and its value and potential for use in any material nonlinearity analyses are also demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents the development of a formulation, based on Positional Finite Element Method, to describe the viscoelastic mechanical behavior of space trusses. The numerical method used was chosen due to its efficiency in the applications concerning nonlinear numerical analyses. The formulation describes the positional variation over time under constant stress state (creep). The objective is to provide a way to quantify the creep behavior for space truss structures and thus contribute to the encouragement of GFRP usage in such structural components. Time-dependent behavior of such materials is one the most important factors for their use in design of structures, demanding studies about the deformations expected within the operational life of the structural systems. To perform this study, the proposed methodology considers a standard solid rheological model to describe stress-strain time-dependent law. This model is implemented in the formulation for quantify the total strain energy. The effects of the model parameters in the mechanical response of the structure with accentuated geometric nonlinearity were presented. In this analysis, it was possible to identify the influence of the elastic and the viscous moduli on the creep response. Model calibration was performed using test data obtained from literature and a GFRP transmission line tower cross-arm was simulated to predict the evolution of displacements under real operational loads. From the results, it was possible to observe a fast evolution of displacements due to the creep effect in the first 7,500 h. This increase was close to 0.6% in relation to the displacement obtained in the elastic behavior. The presented methodology provided a simple and efficient way to quantify the creep phenomenon in viscoelastic GFRP composites truss structures, as can be seen in the developed analyses. [ABSTRACT FROM AUTHOR]

The single-degree-of-freedom (SDOF) analysis with elastic-plastic resistance is often used for design of protective structures subjected to blast loads. Several documents such as UFC 3-340-02 present design charts for the maximum responses of the elasticplastic SDOF system. The SDOF design charts are available for far-field detonations but seldom for near-field detonations of high explosive in free air, noting that the focus of security design is the near-field. Further, the assumption of uniformly distributed load for the SDOF analysis may not be appropriate for the near-field detonations where blast pressure distribution varies significantly with distance and angle of incidence. In this paper, to resolve these issues, updated SDOF design charts including the response to the nearfield detonations are suggested based on numerical calculations. These generated charts are verified with comparison to UFC 3-340- 02 predictions and finite element analysis results of steel components. The recommendations and limitations for the utility of the SDOF design charts for blast assessment of steel components are provided with an emphasis on the near-field detonations. [ABSTRACT FROM AUTHOR]

This article presents the application of finite-element fuzzy model updating to the DLR AIRMOD structure. The proposed approach is initially demonstrated on a simulated mass-spring system with three degrees of freedom. Considering the effect of the assembly process on variability measurements, modal tests were carried out for the repeatedly disassembled and reassembled DLR AIRMOD structure. The histograms of the measured data attributed to the uncertainty of the structural components in terms of mass and stiffness are utilised to obtain the membership functions of the chosen fuzzy outputs and to determine the updated membership functions of the uncertain input parameters represented by fuzzy variables. In this regard, a fuzzy parameter is introduced to represent a set of interval parameters through the membership function, and a meta model (kriging, in this work) is used to speed up the updating. The use of non-probabilistic models, i.e. interval and fuzzy models, for updating models with uncertainties is often more practical when the large quantities of test data that are necessary for probabilistic model updating are unavailable. [ABSTRACT FROM AUTHOR]

A unified elastoplastic model was proposed to describe the relation among load, displacement, and uniaxial constitutive parameters of ductile materials according to the von Mises energy equivalence principle at a special location or energy center in the deformed region of a structural component (SC). Two pairs of parameters were considered in the model: one was related to the volume of deformed region and the other to the Mises equivalent strain at the energy center. In addition, they are easily determined by finite element analysis (FEA). For eight kinds of SCs under proportional loading, the load–displacement behaviors of various materials predicted by the unified model were highly consistent with the results of FEA. [ABSTRACT FROM AUTHOR]

A novel hot stamping technique known as ‘Solution Heat treatment, Forming and in-die Quenching (HFQ ® )’ was employed to manufacture lightweight structural components from AA6082 tailor-welded blanks (TWBs) of different thickness combinations: 1.5–1.5 and 2.0–1.0 mm. A finite element (FE) model was built to study the deformation characteristics during the hot stamping process. The FE model was successfully validated by comparing simulation results with experimental ones. Subsequently, the verified simulation results were analysed through a novel multi-objective FE platform known as ‘Knowledge-Based Cloud – Finite Element (KBC-FE)’. KBC-FE operates in a cloud environment and offers various advanced unique functions via functional modules. The ‘formability’ module was implemented in the current study to predict the limiting dome height and failure mode during the hot stamping process. Good agreements were achieved between the predicted and experimental results, from which studies were extended to predict the forming features of 2.0–1.5 mm TWBs. The ‘formability’ module has successfully captured the complex nature of a hot stamping process, featuring a non-isothermal and non-linear loading path. The formability of TWBs was found to be dependent on forming speed and blank thickness, out of which the latter has a dominant effect. [ABSTRACT FROM AUTHOR]

The potential drop (PD) crack growth measurement technique is sensitive to strain accumulation which is often erroneously interpreted as crack extension. When testing ductile materials these errors can be significant, but in many cases the optimum method of minimising or suppressing them remains unknown because it is extremely difficult to measure them experimentally in isolation from other sources of error, such non-ideal crack morphology. In this work a novel method of assessing the influence of strain on PD, using a sequentially coupled structural-electrical finite element (FE) model, has been developed. By comparing the FE predictions with experimental data it has been demonstrated that the proposed FE technique is extremely effective at predicting trends in PD due to strain. It has been used to identify optimum PD configurations for compact tension, C(T), and single edge notched tension, SEN(T), fracture mechanics specimens and it has been demonstrated that the PD configuration often recommended for C(T) specimens can be subject to large errors due to strain accumulation. In addition, the FE technique has been employed to assess the significance of strain after the initiation of stable tearing for a monotonically loaded C(T) specimen. The proposed FE technique provides a powerful tool for optimising the measurement of crack initiation and growth in applications where large strains are present, e.g. J-R curve and creep crack growth testing. [ABSTRACT FROM AUTHOR]

Many failures of structural components are attributed to fatigue due to repeated loading and unloading conditions. The crack growth due to fatigue, represents a critical issue for the integrity and capacity of structural components. Apart from the loading conditions, the shape of the structural components plays an important role in their service life. In this study, extended finite element and level set methods are integrated into a probabilistic shape design optimization framework aiming to improve the service life of structural components under fatigue. In this context, the relation between the geometry of the structural components and their service life is investigated. The effect of uncertain material properties as well as the crack tip initialization, described by random variables is also examined. Comparisons between optimized shapes obtained for various targeted fatigue life values are addressed, while the location of the initial imperfection along with its orientation are found to have a significant effect on the optimal shapes for the components studied. [ABSTRACT FROM AUTHOR]

• A probabilistic framework of creep life assessment for components at elevated temperature is provided. • Effect of standard derivation of material parameters on creep reliability assessment is discussed. • Comparisons between probabilistic and deterministic creep design methods are conducted. Current creep life assessment methods of components at elevated temperatures are mainly based on deterministic analysis strategies, which could not achieve the goal of probabilistic evaluation on creep failure. Based on this, a probabilistic framework of creep life assessment for components at elevated temperatures was provided. A method of determining distribution characteristics of material parameters was provided by randomly selecting a group of results at each stress level. Monte Carlo simulation was combined with finite element analysis technology to capture the distribution characteristic of creep rupture life of one typical structural component. Effect of standard derivation of material parameters on creep reliability assessment was discussed. Comparisons between probabilistic and deterministic creep design methods were made. Results indicated that the probabilistic analysis strategy can calculate the specific value of failure probability at various loading conditions, not two values of failure probability (i.e. 100% and 0%) by deterministic analysis strategy. The effect of standard derivation on mean values of effective stress and creep rupture life of the component is dependent on distribution characteristics of material parameters and related variables. A small standard derivation reduces the data scatter of effective stress and creep rupture life of the component. [ABSTRACT FROM AUTHOR]

Bone encompasses a complex arrangement of materials at different length scales, which endows it with a range of mechanical, chemical, and biological capabilities. Changes in the microstructure and characteristics of the material, as well as the accumulation of microcracks, affect the bone fracture properties. In this study, two-dimensional finite element models of the microstructure of cortical bone were considered. The eXtended Finite Element Method (XFEM) developed by Abaqus software was used for the analysis of the microcrack propagation in the model as well as for local sensitivity analysis. The stress–strain behavior obtained for the different introduced models was substantially different, confirming the importance of bone tissue microstructure for its failure behavior. Considering the role of interfaces, the results highlighted the effect of cement lines on the crack deflection path and global fracture behavior of the bone microstructure. Furthermore, bone micromorphology and areal fraction of cortical bone tissue components such as osteons, cement lines, and pores affected the bone fracture behavior; specifically, pores altered the crack propagation path since increasing porosity reduced the maximum stress needed to start crack propagation. Therefore, cement line structure, mineralization, and areal fraction are important parameters in bone fracture. The parameter-wise sensitivity analysis demonstrated that areal fraction and strain energy release rate had the greatest and the lowest effect on ultimate strength, respectively. Furthermore, the component-wise sensitivity analysis revealed that for the areal fraction parameter, pores had the greatest effect on ultimate strength, whereas for the other parameters such as elastic modulus and strain energy release rate, cement lines had the most important effect on the ultimate strength. In conclusion, the finding of the current study can help to predict the fracture mechanisms in bone by taking the morphological and material properties of its microstructure into account. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGMs) are increasingly being used in high-temperature structural components. The time-dependent C -integral, C ( t ), is a significant parameter in characterizing the crack tip stress field from the small-scale to the extensive steady-state creep stages. In this paper, the creep crack behavior of FGMs with a crack parallel to the material property gradients was studied by using the finite element method. It was proven that C ( t ) remained valid for FGMs. An engineering method was proposed to estimate C ( t ) in the small scale and transition creep stages and estimate the crack tip stress field. Finite element results verified that the method could estimate C ( t ) in the small scale and transition creep stages and estimate the crack tip stress field. For cases with creep properties that increased in the crack growth direction, the effect of constraint on the estimated crack tip stress field had to be considered. The constraint parameter of Q was significantly affected by the creep property gradients. The method was independent of the gradient variation law of material properties. [ABSTRACT FROM AUTHOR]

Bent pipes are widely used in many high-end industries as a structural component. Consequently, pipe roll bending has become an attractive manufacturing technology for forming lightweight products. For industrial applications, bent pipes should be accurately shaped into 2D or 3D shapes without defects. In this study, the behavior of pipes with rectangular cross-sections under roll bending was considered in order to improve product quality. When a pipe product is bent with a large curvature, the pipe cross-section shrinks under the bending moment. In order to minimize defects and improve product quality, this paper proposes double-stage forming to regulate the shrinking load, which causes the axial wrinkles and poor strength, as structural members. In double-stage forming, the bending radius at the pre-bending stage is assumed to be a key parameter to avoid cross-section distortion. In order to determine the pre-bending radius, material behavior was analyzed to figure out the reason for the cross-section shrinkage. The bending stresses on the cross-section of the pipe material subject to bending moments bring about the distribution of inward forces, which induce shrinkage moments on the cross-section. The main idea in this paper is that the cross-section distortion can be minimized by regulating the pre-bending radius at the first stage. The proposed process design was evaluated through nonlinear finite element simulation using a commercial program and experiments. [ABSTRACT FROM AUTHOR]

Automotive laminated glass is normally comprised of two soda-lime glass sheets bonded with one plastic interlayer, polyvinyl butyral (PVB). Glass-ply cracking is the principal damage pattern in PVB laminated glass under low-velocity impact. The purpose of this work is to numerically investigate the glass-ply cracking mechanism in the framework of cohesive zone modelling. Toward this end, the glass-ply cracking is modelled via an extrinsic cohesive model. Besides, a laminated glass model is proposed, in which brick elements are adopted and an intrinsic cohesive formulation is employed to model the adhesion between glass and PVB. The nonlinear characteristic of PVB is described by using a Mooney–Rivlin constitutive model. Then, the glass-ply cracking behaviours of a laminated glass beam under drop-weight impact are simulated. The proposed approach is qualitatively validated by comparing the simulation results with the experimental observations. In the simulation, the propagations of stress waves of the laminated glass beam during the crack process are illustrated, and the glass-ply cracking mechanism is revealed. Finally, the effects of the PVB film and the adhesion on glass-ply cracking are investigated. [ABSTRACT FROM AUTHOR]

Scientists and engineers agree that solving complex problems requires integrating traditional physics-based modeling techniques with state-of-the-art deep learning (DL) methods. This paper aims to integrate physics knowledge into a convolutional neural network (CNN) to boost learning within a feasible solution space in a specific domain. Our proposed method uses deep neural networks in the form of (CNNs) augmented with custom loss functions which uses physics rules to bypass the need for Finite Element Analysis and predict high-resolution stress distributions on damaged steel plates with variable loading and boundary conditions. We embedded physics constraints into the loss function to enforce the model training, precisely capturing stress concentrations around the tips of various structural damage configurations. The CNN was designed and trained to use the geometry, boundary conditions, and load as input and predict the stress contours. The proposed framework's performance is compared to Finite-Element simulations using partial differential equation (PDE) solver. The trained DL model can predict the stress distributions of damaged steel plates with a mean absolute error of 0.22% percent and an absolute peak error of 1.5% for the Von Mises stress distribution • The model predicts stress distribution in damaged structural components. • Construct deep neural networks (DNN), which once trained allow to bypass FEA. • The model can predict the stress distributions with MAE of 0.22%. • The model can predict the stress distributions with absolute peak error of 1.5%. [ABSTRACT FROM AUTHOR]

A model for multiaxial high-cycle fatigue life evaluation of notched structural components is proposed, which considers the impact of the stress field on fatigue life by utilizing the Theory of Critical Distances (TCD) and Finite Element Method (FEM). The maximum shear stress range plane is defined as the critical plane, and the damage parameters are the maximum effective shear stress amplitude and the maximum effective normal stress, which are obtained by averaging the stress in the hemisphere volume around the maximum stress point. To validate the accuracy of the model, multiaxial fatigue tests are carried out for both smooth and notched specimens of Aluminum–Silicon alloy. The results indicate that the evaluated life and experimental life have a good agreement. [ABSTRACT FROM AUTHOR]

This paper describes the validation of a Monte-Carlo simulation and finite element analysis of a practical application (mechanical component) using the fatigue testing techniques. Fatigue testing techniques investigate how the component structure reacts to stress over a long period of time and during different levels of its operations. The importance of implementing the Monte Carlo techniques in fatigue life analysis is motivated by the growing evolution of statistical methods for defining fracture and fatigue of mechanical components. The practical application was simulated with a Monte Carlo method and the statistical analysis was realized using the Weibull 9 software. Fatigue life prediction was simulated using finite element analysis with Ansys 15 software. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic response of lightweight acceleration-sensitive non-structural components (NSCs) mounted on irregular reinforced concrete (RC) primary structures (P-structures) using non-linear dynamic finite element (FE) analysis. The aim of this paper is to study the influence of NSC to P-structure vibration period ratio, peak ground acceleration, NSC to P-structure height ratio, and P-structure torsional behaviour on the seismic response of the NSCs. Representative constitutive models were used to simulate the behaviour of the RC P-structures. The NSCs were modelled as vertical cantilevers fixed at their bases with masses on the free ends and varying lengths so as to match the frequencies of the P-structures. Full dynamic interaction is considered between the NSCs and P-structures. A set of 21 natural and artificial earthquake records were used to evaluate the seismic response of the NSCs. The numerical results indicate that the behaviour of the NSCs is significantly influenced by the investigated parameters. Comparison between the FE results and Eurocode (EC8) predictions suggests that EC8 underestimates the response of NSCs mounted on the flexible sides of irregular RC P-structures when the fundamental periods and heights of the NSCs match those of the P-structures. The perceived cause of this discrepancy is that EC8 does not take into account the amplification in the dynamic response of NSCs induced by the torsional behaviour of RC P-structures. [ABSTRACT FROM AUTHOR]

In the paper, the verification of the limit load solutions proposed by EPRI procedures for single edge notched plate under tension (SEN(T)) is presented. For the concept of limit load of the component containing a crack, the force (or torque or pressure) which causes a full plasticity of the uncracked ligament of the structural component must be understood. It should be noted that the value of the limit load is determined under the assumption of elastic–perfectly plastic material. Numerical calculations presented in the paper (FEM) and analysis of the obtained FEM results were used to recalculate existing limit load formulas proposed by EPRI procedures for plane strain and plane stress states. On the basis of numerical calculations and verifications of the present solutions (EPRI solutions), in the paper new analytical formulas for better estimating the limit load value for SEN(T) specimen are presented. The measurable effect of the paper is a catalog of the numerical solutions and their approximation, which may be useful in engineering analysis. [ABSTRACT FROM AUTHOR]

Abstract: The topic of this paper is the fire safety analysis of 3D frame structures such as industrial halls. Cold-formed thin plated elements are used as structural components. The building, which is submitted to a full-scale fire test, is introduced. A blind prediction analysis is performed using the finite element model SAFIR. The thermal response of the structural elements under both a standard fire and a natural fire corresponding to a fire load density of 625MJ/m2 and an opening factor 0.009m1/2 is predicted. As expected, the temperature of the cold-formed sections follows more or less the gas temperature in the fire compartment due to the thin plates. The results of the predicted mechanical response are presented, giving a resistance of 27min (standard fire) and 54min (natural fire). The model is validated based on the results of the full-scale fire test, demonstrating a fire resistance of 62min. Comparison with a simple 2.5D model is made and proved to provide results sufficiently accurate to make it applicable for daily design practice. [Copyright &y& Elsevier]

Abstract: In this paper, the efficiency of the connections of a hybrid steel–concrete girder is evaluated using the finite element approach. The structural components of the connections and their interactions are fully modeled, and the material nonlinearity considering damage and failure is included in the analysis. The FE model is verified by comparison with the experiment. The parametric study is conducted to investigate the behavior of three different connection types. The moment strength, stiffness, and rotation capacities of various connections are examined. The non-dimensional efficiency factor F eff is proposed in order to evaluate the structural efficiency of the connections. The performance of the various connections is evaluated, and efficient connection details are recommended. [Copyright &y& Elsevier]