Band 10, Heft 1

The article focuses on the influence of differential shrinkage linked by drying at the early-age displacements and strain distribution of a concrete ring specimen. Depending on the gradient of dimension changes through the thickness, tensile stress occurs near the exposed surface where drying is greater and thus results in strain gradients development. An experimental design was carried out on a concrete ring cast in laboratory conditions in order to monitor strains and displacements. Subsequently, a finite element method was used to simulate the ring’s behaviour in drying conditions. The gradient development linked by a non-uniform moisture distribution in the thickness is established by solving the non-linear partial differential drying equation with Mensi’s diffusion law. The stress and displacement analysis was modeled by three nodes curved shell FEM (CSFE-sh) based on strain approximation with the shell theory. Finally, the ring’s behaviour includes both differential shrinkage resulting in the mechanical and physical properties of gradients development in the thickness and the influence of prestressing, in which the tensile creep effects have a great influence. The comparison of experimental results with numerical simulation shows that drying and tensile creep phenomena have the most important influence on the early-age stress development in the walled ring.

With the development of simulation programs, it is necessary to simulate the problems that occur in the human body that are related to mechanical engineering. Whereas blood is a liquid with mechanical properties, the artery is a substance that also contains mechanical properties. Smoking increases blood viscosity, and this viscosity affects the velocity and blood pressure as well as the artery itself. In this research article, the effect of blood viscosity on the aorta will be studied because it is one of the main arteries of the heart and obtains blood flow in the artery. The blood’s kinetic equations were solved using the COMSOL program’s laminar processor, and fluid–structure interaction was utilized to connect the mechanics of motion with the stresses that affect the artery. In addition, the effect of viscosity on the deformation of the artery and its movement was studied, and the result showed that most of the blood does not reach the branches of the artery, where the speed of blood flow was 0.18 m/s at the value of the viscosity of 0.1 Pa s. The increase in viscoelasticity leads to an increase in pressure at the beginning of the carotid artery, which hinders the flow of blood. The velocity of blood flow decreases with the increase in viscosity, and this reduces pressure on the artery walls, as the stress on 0.1 Pa s was equal to 16,705 Pa s (m.124). An artery’s deformation is directly related to the stresses on it, and when the deformation goes down, the artery’s size goes down.

Nowadays, core/shell structures due to very high thermal and electrical conductivity are taken into account in the manufacture of many industrial sensors and catalysis. Ni–Al core/shell structures are known as one of the most practical materials due to their high chemical stabilities at elevated temperatures. Since the evaluation of the mechanical properties of the industrial core/shell catalysts is crucial, identification of the mechanism responsible for their plastic deformation has been a challenging issue. Accordingly, in this study, the mechanical properties and plastic deformation process of Ni–Al core/shell structures were investigated using the molecular dynamics method. The results showed that due to the high-stress concentration in the Ni/Al interface, the crystalline defects including dislocations and stacking faults nucleate from this region. It was also observed that with increasing temperature, yield strength and elastic modulus of the samples decrease. On the other hand, increasing the temperature promotes the heat-activated mechanisms, which reduces the density of dislocations and stacking faults in the material. Consequently, the obstacles in the slip path of the dislocations as well as dislocation locks are reduced, weakening the mechanical properties of the samples.

Concrete shells are widespread in civil engineering constructions. Because of the moldability of concrete, special structures such as domes, bridge caissons, buried or raised reservoirs, and arch dams are built with concrete. In this study, we are particularly interested in the variation of the thickness and the resulting strains during a short-term mechanical loading of a concrete ring in its elastic phase. On the one hand, transverse stresses through the thickness are calculated numerically by implementing a particular family of finite elements (four degrees of freedom per summit node) with a two-dimensional shell model, which accounts for thickness variations and transverse distortions. On the other hand, an experimental device was mounted in order to validate numerical predictions.

This article illustrates the specifications required to accurately design, specify, and install embedded anchor bolts between old and new concrete composite specimens for concrete repair or reinforcing of collapse concrete a research hotspot. The concrete slabs are facing a major challenge with deterioration, especially for reinforcement corrosion caused mainly by severe cycles of various chemical attacks. In this research, the impact of using contact plates between composite specimens was investigated by testing grouped specimens, thereby the models were divided into two groups, which tested under static load. The findings of a series of tests conducted to evaluate the structural behavior of shear connections (by pushout test) by including many parameters; the diameter (8, 12 and 16 mm), bounding between different compressive strength should be changed [normal concert (NC) mixes , ultra-high performance fiber concrete (UHPFC), and self-compacting mortar (SCM)]. Also, the embedded length of bolts was varied from 70, 130, to 190 mm. These parameters were studied individually in two groups. The first group was without contact plate and the second group was with contact plate. Experimental findings were obtained and reported, including the failure modes, maximum resistance, slippage capacity, and load–slip characteristic responses of the connections. Based on the obtained data, a relationship between the studied parameters was investigated. Experimental findings showed that the ultimate strength of rough surface specimens (without contact plate) was about 31% greater than that of smooth surface specimens (with contact plate), and obviously, all pushout specimens failed due to stud shank failure.

Layered composite materials are widely used across a variety of sectors, including the automotive industry, aerospace engineering, offshore, and various mechanical domains, because of their strong yet lightweight structures. Therefore, various emergent theories are available on the deformation of layered beams. The previous research studies are insufficient as they are based on deformation of layered composite and sandwich arches with simply supported (SS) end conditions. Therefore, it is a good opportunity for researchers to investigate the arches using exponential shear deformation and normal deformation theory. The leading hypothesis mainly adds to the research of bending for sandwich and layered composite arches adopting the exponential theory. The present theory does not require any shear correction factor to satisfy zero transverse shear stress condition at the bottom and top fibers of arches. Governing equations and associated end conditions are derived through principle of virtual work. Navier’s techniques used for sandwich and layered composite arches are SS boundary conditions subjected to uniformly distributed load. The results of the current study showed that the exponential normal and shear deformation theories may be used to evaluate static responses for layered composite and sandwich arches. The obtained results from the present theory are validated through the results available in published literature.

In this work, the state -space nonlocal strain gradient theory is used for the vibration analysis of magneto thermo piezoelectric functionally graded material (FGM) nanobeam. An analysis of FGM constituent properties is stated by using the power law relations. The refined higher order beam theory and Hamilton’s principle have been used to obtain the motion equations. Besides, the governing equations of the magneto thermo piezoelectric nanobeam are extracted by developed nonlocal state-space theory. And to solve the wave propagation problems, the analytical wave dispersion method is used. The effect of magnetic potential, temperature gradient, and electric voltage in variant parameters are presented in graph.

In a context where daily and seasonal temperature changes or potential fire exposure can affect the mechanical response of structures strengthened with fiber-reinforced polymer (FRP) composites during their life cycle, the present work studies the bond behavior of FRP laminates glued to concrete substrates under a thermal variation. The problem is tackled computationally by means of a contact algorithm capable of handling both the normal and tangential cohesive responses, accounting for the effect of thermal variations on the interfacial strength and softening parameters, which defines the failure surface and post cracking response of the selected specimen. A parametric investigation is performed systematically to check for the effect of thermo-mechanical adhesive and geometrical properties on the debonding load of the FRP-to-concrete structural system. The computational results are successfully validated against some theoretical predictions from literature, which could serve as potential benchmarks for developing further thermo-mechanical adhesive models, even in a coupled sense, for other reinforcement-to-substrate systems, useful for design purposes in many engineering applications.

Recently, the use of reinforced concrete (RC) structures is becoming very common worldwide. Because of earthquakes or poor design, some of these structures need to be retrofitted. Among different methods of retrofitting a structure, we have utilized a steel cage to support a column under axial load. The numerical modeling of a retrofitted column with a steel cage is carried out by the finite-element method in ABAQUS, and the effectiveness of the number of strips, size of strips, size of angles, RC head, the strips’ thickness, and the steel cage’s mechanical properties are studied on 15 different case studies by the single factorial method. These parameters proved to be very effective on the load distribution of the column because by choosing the optimum case, lower amounts of force are born by the column. By increasing the number of strips, the steel cage would reach 52% of the total load. This value for the size of strips and angles’ size is 48 and 50%, respectively. However, the thickness of the strips does not have a significant effect on the load bearing of the column. In order to fully predict the load distribution of the retrofitted columns, the data of the present study are utilized to propose a predictive model for N c / P FEM and N c / P FEM using artificial neural networks. The model had an error of 1.56 (MAE), and the coefficient of determination was 0.97. This model proved to be so accurate that it could replace time-consuming numerical modeling and tedious experiments.

The investigation related to the serviceability analysis, particularly in terms of crack spacing prediction, has remarkably increased recently. In addition, the prediction of serviceability analysis is highly dependent and influenced by different physical and material factors that contribute to the crack spacing of reinforced concrete (RC) structures. As a result, the cracking phenomenon has not been fully grasped due to these factors’ wide variety and complexity. Recently, soft computing techniques have gained considerable popularity due to their capability of learning and producing generalized solutions and exhibiting desirable performance in terms of time, effort, and cost. However, the literature on crack spacing prediction using various machine learning approaches is limited and insufficient. Therefore, this article is dedicated to estimating the primary crack spacing of RC structures using different machine learning methods. As a part of the study, the findings of these approaches will be computed and compared to the benchmark experimental results. Besides, the results of the developed models will be compared against that of available approaches in the literature to highlight their reliability. Furthermore, a parametric assessment will be conducted to emphasize the most influencing input parameter on the primary crack spacing of RC structures.

If not detected early, the cracks in structural components may ultimately result in the failure of the structure. This issue becomes even more critical when the component under investigation is a prosthesis placed in the human body. This study presents a crack location identification method based on the time domain in a cantilever beam of metallic biomaterials (CBMB). The absolute difference between the central difference approximation of the root mean square (RMS) of displacement of points on the cracked and uncracked beams was applied as a cracked location indicator. Captured time-domain data (displacement) at each node of the cracked and uncracked beams were processed into a central difference approximation of the RMS of displacement. Then, the crack could be detected by a sudden change of the cracked location indicator. The feasibility and effectiveness of the proposed method were validated by numerical simulations. The finite-element simulation of a CBMB with a transverse notch was analyzed in the numerical study. The notch or crack was detected along the beam under a moving load at various locations. A set of simulation experiments and numerical calculations was performed to determine whether the proposed identification method would accurately detect the location of a crack in a cantilever beam under a moving load compared to the location found by an exact solution method. The results showed that the proposed method was not only as able as the analytical method but also robust against noise: it was able to detect a crack precisely under 5% noise.

In this research, flow around two vibrating cylinders in a tandem arrangement is simulated at Reynolds number Re = 200 using the dynamic overset mesh technique in finite volume-based commercial software. This investigation aims to study the combined influences of the spacing between the two identical circular cylinders and their excitation frequency in the flow. The cylinders are excited by a transverse forced vibration in a uniform cross-flow by applying a simple harmonic motion. The gap distance between the vibrating cylinders is chosen to be L / D = 1.5 and 4, and the vibration amplitude is kept constant at A / D = 0.25. The study focuses on three frequency ratios of the cylinders’ excitation frequency to Strouhal shedding frequency of the single stationary cylinder f e / f s = 0.8, 1.0, and 1.2. Simulation results showed that the flow characteristics over the two vibrating circular cylinders differ from that of a single vibrating cylinder. Also, it is observed that the lock-in state (resonance) for the two vibrating cylinders and the vortex wake patterns are highly affected by the gap distance between cylinders and the excitation frequency.

An electric motor mounting bracket is used in electric vehicles, especially hybrid ones using a parallel hybrid configuration. This study aims to analyze the strength and performance of the initial design and topology optimized design. This study uses the finite-element method (FEM) in the bracket design modeling by applying topology optimization. The topology optimization results show a mass reduction of 50% from the initial design mass. In the case of static loading, the results of optimized design 2 have a stress of 142.19 MPa and a safety factor of 3.09. While optimized design 1 has a stress of 313.8 MPa and a safety factor of 1.4. In terms of dynamic loading, the initial design, optimized design 1, and optimized design 2 have the first natural frequency, which is higher than the operating frequency of the electric motor, respectively, 100.49, 69.043, and 74.864 Hz. Optimized design 1 has the lowest natural frequency and the highest amplitude compared to the initial design, and optimized design 2 has lower damping characteristics. The study results conclude that optimized design 2 is superior in static and dynamic loading.

This article provides a new finite-element procedure based on Reddy’s third-order shear deformation plate theory (TSDT) to establish the motion equation of functionally graded porous (FGP) sandwich plates resting on Kerr foundation (KF). Although Reddy’s TSDT is attractive, it cannot be exploited as expected in finite-element analysis due to the difficulties in satisfying the zero shear stress boundary condition. In this study, the proposed element has four nodes, each with seven degrees of freedom (DOF). The performance of this element is confirmed by conducting various examples, showing its accuracy and range of applications. Then, some studies are performed to present the effects of input parameters on the vibration of FGP sandwich plates resting on KF.

Fiberglass-reinforced plastics (FRP) composite materials for ships that are widely used are marine-grade unsaturated polyester resin matrix and combimat fiber, a combination of marine-grade chopped strand mat (CSM) and woven roving (WR) fibers. Although less popular than marine CSM–WR, marine biaxial warp-knitted glass fabrics have the potential to be applied as fiber laminates for ship hull materials. A comparative study of tensile and bending strength between marine CSM–WR composite and marine CSM–biaxial composite had been conducted. All composites met the criteria of the Indonesian Classification Bureau. Specifically, the CSM–biaxial had higher tensile and flexural strength with fewer laminations than the CSM–WR. Laminate type II had the highest average normalized tensile and flexural strength, 186.1 and 319.2 MPa. A layer of biaxial fiberglass had a very significant effect on tensile and flexural strength. Besides its strength, fewer type II laminations can speed up the production process of FRP ship hulls. Furthermore, the CSM–biaxial composite had relatively high normalized flexural strength compared to other references. However, the normalized tensile strength achieved in this study was at an intermediate level compared to other references.

In this study, a closed-form analytical solution is derived to compute the stress formulations for a thick cylindrical pressure vessel made of functionally graded material (FGM) with varying parameters, which are mechanical and thermal boundary conditions. The assumed mechanical boundary condition is the time-dependent pressure acting on the internal surface of the cylinder, while the assumed thermal boundary condition is the transient temperature distribution over the cylinder thickness. The material properties are considered to be graded exponentially in the radial direction, except Poisson’s ratio which is assumed to be constant. The stress and displacement formulations are evaluated using Mathematica software for the uncoupled thermo-mechanical analysis. The results of radial, hoop, and axial stress are plotted at various times for two FGM cylinders, the SS304-Alumina FGM cylinder and the TZM-SIC FGM cylinder, to study the impact of using different materials for the same boundary conditions on the results. The results obtained in this study are beneficial as these contribute to the design and modeling of cylinders that are exposed to time-dependent internal pressure and transient temperature profiles.

With the quick progress of industrialization and urbanization, the construction industry has become one of the largest energy-consuming industries. However, the current prefabricated shear wall focuses on the upgrade of seismic function, with less analysis of the energy efficiency of the overall structure. In this study, a sustainable prefabricated building shear wall that takes into account both energy conservation and stress is first proposed, and then the shear wall is modelled by finite element method (FEM) software. Meanwhile, the force functions of the shear wall model, including concrete strength, axial condensability rate, and aspect rate, and finally the seismic function are verified. The experimental outcomes demonstrate that the maximum difference between the FEM analysis outcomes and the test data is only 10.66%, and the overall difference in the outcomes is relatively small. The larger the aspect rate of the proposed sustainable assembled shear wall model, the better the ductility of the member, and the bigger the axial condensability rate and concrete strength, the lower the ductility of the member. In the seismic function analysis, the maximum layer displacement angles of this shear wall are all less than 1/120, which is in line with the national seismic code. This indicates its good seismic function and provides a methodological reference for the upgrade of the structural function of shear walls.

In this study, four absolute nodal coordinate formulation (ANCF)-based approaches are utilized in order to predict the buckling load of Lee’s frame under concentrated load. The first approach employs the standard two-dimensional shear deformable ANCF beam element based on the general continuum mechanics (GCM). The second approach adopts the standard ANCF beam element modified by the locking alleviation technique known as the strain-split method. The third approach has the standard ANCF beam element with strain energy modified by the enhanced continuum mechanics formulation. The fourth approach utilizes the higher-order ANCF beam element based on the GCM. Two buckling load estimation methods are used, i.e ., by tracing the nonlinear equilibrium path of the load–displacement space using the arc-length method and applying the energy criterion, which requires tracking eigenvalues through the dichotomy scheme. Lee’s frame with different boundary conditions including pinned–pinned, fixed-pinned, pinned-fixed, and fixed–fixed are studied. The complex nonlinear responses in the form of snap-through, snap-back, and looping phenomena during nonlinear postbuckling analysis are simulated. The critical buckling loads and buckling mode shapes obtained through the energy criterion-based buckling method are obtained. After the comparison, higher-order beam element is found to be more accurate, stable, and consistent among the studied approaches.

The research starts with the treatment of the multiscale transmission problem and establishes the electromagnetic solidification transmission coupling mathematical model based on the indirect coupling method. It uses the three-dimensional magnetic field finite element theory to establish a three-dimensional crucible structure continuous casting model built on the electromagnetic solidification transmission coupling mathematical model. This model is used to optimize the parameters of the composite crucible structure and to simulate electromagnetic transmission and braking phenomena. The results show that the L-shaped static magnetic field has a more potent inhibition and a guidance effect on melt circulation. The braking effect of the actual magnetic field on the downward impact is worse. Under the influence of an L-shaped magnetic field, the flow velocity of the melt is better, and the flow state distribution is more smooth and uniform. The computational efficiency test results show that the conversion calculation time of the method designed in this study is 18.03 min. The total calculation time is 680.48 min, which is superior to traditional methods. It proves that this model can accurately analyze the magnetic field coupling problem and at the same time ensure the superiority of its computing efficiency.

During an evacuation, the tsunami lifeboat should be able to withstand the possible external loads that might be occurred, such as collisions, violent crashes, and capsizing events. Special structural reinforcement and improvement, such as a crash absorber, are attached to prevent damage due to the impact load. Therefore, this article focuses on the crushing behaviour of the tsunami lifeboat crash absorber made of the multi-cell glass fibre-reinforced composite panel. The effect of the cross-section geometry design of the cell on the damage mechanism and energy absorption behaviour was investigated. The explicit dynamic finite element method was used to identify the multi-cell configuration’s crashworthiness performance. Experimental studies such as tensile and three-point bending tests were conducted to define the material properties and validation of the FE model. The simulation results showed that the explicit dynamic finite element method has effectively estimated the crash absorber crushing damage. The circular cross-section has shown the most significant crash absorption capability compared to the others, namely the honeycomb, the square, and the triangular cell. Furthermore, the 4CSM laminate type has revealed a lower energy absorption than the 4WRC45 and 4WRC laminates. Otherwise, the study exhibits that the cross-sectional geometry and the laminate type significantly influence the crash absorber performance for improving the tsunami lifeboat crashworthiness.

This article describes a parametric design and fabrication workflow influenced by Frei Otto’s form-finding experiments on soap films. The research investigates minimal surface geometry by combining physical and digital experiments in a computational framework. Operating on mesh topology, various parametric design tools and plug-ins in Rhinoceros/Grasshopper are presented to discuss the translation of minimal surfaces to flat strips suitable for planar fabrication using flexible materials. These tools are tested on a case study to show the automated design and manufacture of double-curved surfaces as double-layered strips running in perpendicular directions that can be affixed at point connections for structural stability. The development of the parametric workflow, material constraints, and stripped fabrication of layers are discussed.

Wind turbines generate clean and renewable energy for the international market. The most ‎‎important aspect of wind turbine maintenance is reducing failures, downtime, and operating and maintenance expenses. ‎This study aims to detect multiple faults exhibited by wind turbine blades; failures such as cracks (tip crack, mid-span crack, and crack ‎near the root) were observed in the blades at different locations. The research suggests a new approach, incorporating vibration signals and machine learning techniques to identify various failures in wind turbine blades. The technology of ranking features such as ReliefF algorithms, chi-squares, and information gains was adopted to discuss a method framework to diagnose several problems in wind turbine blades, such as cracks in different locations. The k-nearest neighbors (KNNs), support vector machines, and random forests are used to classify data based on measured vibration signals. The eight main time-domain features are calculated from the vibration signals. The proposed methodology was validated using four databases. The results showed good classification accuracy in four databases, with at least three non-conventional features in each database’s top nine features of the three classification techniques. The results also showed that when the ReliefF selection algorithm is applied with the KNN classification algorithm, it generates the highest classification accuracy under all failure conditions, and the value is 97%. Finally, the performance of the proposed classification model is compared with other machine learning classification models, and a promising result is obtained. ‎

The properties of epoxy asphalt materials and carbon fiber composites are closely related to temperature, so it is important to study the mechanical properties of these two materials when they are used in track at different temperatures. The parallel analysis method is adopted in this study. The carbon fiber composite is regarded as a continuous elastomer, and its stress and strain components are fully expressed in a matrix form in a three-dimensional coordinate system. Finally, 21 elastic constants are selected. At the same time, the mechanical properties of epoxy asphalt materials in viscoelastic and tensile aspects were studied considering the temperature zone expansion factor. The results show that the maximum degradation of carbon fiber composites in tensile strength occurs at low temperature and dry state, and the degradation rate is 30.8%. In terms of compressive strength, the maximum degradation rate of the material is 21.9% under high temperature and wet conditions. The elongation at break of epoxy asphalt materials showed a trend of first increasing and then decreasing. In the whole working temperature zone, it increased from 311.78 to 354.55% and then decreased to 228.89%. The bond elongation first increases and then decreases. Taking 0℃ as the dividing point, the bond elongation increases from 85.7% at − 20℃ to 256.7% at 0℃ in the temperature zone below 0℃, while it decreases from 256.7% at 0℃ to 80.6% in the temperature zone above 0℃. Therefore, the mechanical properties of the two materials have the characteristics of high temperature sensitivity.

This 3D coupled hygro-elastic model proposes the three-dimensional (3D) equilibrium equations associated with the 3D Fick diffusion equation for spherical shells. The primary unknowns of the problem are the displacements and the moisture content. This coupled 3D exact shell model allows to understand the effects of the moisture field in relation with the elastic field on stresses and deformations in different plates and shells. This model is specifically developed for configurations including functionally graded material (FGM) layers. Four different geometries are analyzed using an orthogonal mixed curvilinear reference system. The main advantage of this reference system for spherical shells is the degeneration of the equations to those for simpler geometries. The solving method is the exponential matrix method in the thickness direction. The closed-form solution is possible because of simply supported sides and harmonic forms for displacements and moisture content. The moisture content amplitudes are directly applied at the top and bottom outer faces through steady-state hypotheses. The final system is based on a set of coupled homogeneous second-order differential equations. The moisture field effects are evaluated for the static analysis in terms of displacement, strain, and stress components. After preliminary validations, used to better understand how to properly define the calculation of the curvature-related terms and FGM properties, four new benchmarks are proposed for several thickness ratios, geometrical data, FGM configurations, and moisture values imposed at the external surfaces. From the results, it is clear the accordance between the uncoupled hygro-elastic model and this new coupled hygro-elastic model when the 3D Fick diffusion law is employed. Both effects connected with the thickness layer and the embedded material are included in the 3D hygro-elastic analyses proposed. The 3D coupled hygro-elastic model is simpler than the uncoupled one because the 3D Fick diffusion law does not have to be separately solved.

This work made a comparison of the effects of selected element formulations (EFs) through nonlinear finite element analysis (NLFEA) and physical configurations in scenario design, particularly target locations. The combined results help in quantifying structural performance, focusing on crashworthiness criteria. The analysis involves nonlinear dynamic finite element methods, using an explicit approach applied to an idealized system. This system models ship-to-ship collisions, specifically the interaction between Ro and Ro and cargo reefer vessels, with one striking the other. Summarizing initial NLFEA results reveals that the chosen EF significantly influences the crashworthiness criteria. Notably, differences in formulations lead to different calculation times. The Belytschko–Tsay (BT) EF is the quickest, followed by the Belytschko–Leviathan (BL), with around a 36% difference. Conversely, formulations such as the Hughes–Liu involve much longer processing times, more than twice that of BT. To address the potential impact of shear locking and hourglassing on calculation accuracy during impact, the fully integrated (FI) version of the EF is used. It mitigates these undesired events. For formulations with the same approach, the FI BT formulation suppresses hourglassing effectively, unlike others that show orthogonal hourglassing increments. To ensure reliability, rules were set to assess hourglassing. The criterion is that the ratio of hourglass energy to internal energy should be ≤10%. All formulations meet this criterion and are suitable as geometric models in NLFEA. Regarding reliability and processing time, analyzing the computation time offers insights. Based on calculations, BL is the fastest, followed by Belytschko–Wong–Chiang, while the FI BT formulation takes more time for the same collision case.

An unavailable semi-analytical non-local 3D solution for functionally graded nanoshells with constant radii of curvature is presented. The small length scale effect is included in Eringen’s nonlocal elasticity theory. The constitutive and equilibrium equations are written in terms of curvilinear orthogonal coordinates systems which are only valid for spherical and cylindrical shells, and rectangular plates. The stresses and displacements are assumed in terms of the Navier method which is applicable for simply supported structures. The derivatives in terms of thickness are approximated by the differential quadrature method (DQM). The thickness domain is discretized by the Chebyshev–Gauss–Lobatto grid distribution. Lagrange interpolation polynomials are considered as the basis function for DQM. The correct free surface boundary condition for out-of-plane stresses is considered. Several problems of isotropic and functionally graded shells subjected to different types of loads are analyzed. The results are compared with other three-dimensional solutions and higher-order theories. It is important to emphasize that the radii of curvature are crucial at nanoscale, so it should be considered in the design of nanodevices.

With the increased emphasis on the use of recyclable bio-based materials and further understanding of the mechanical properties of laminated bamboo, the development of a new generation of low-cost bamboo-based composites for ship structure has generated a significant interest. Laminated bamboo composites comprising Apus bamboo ( Gigantochloa apus ) and Waru fiber at different layer orientations were investigated to obtain the mechanical characteristics. The influence of different laminate directions was studied through several methods of mechanical testing, including impact tests using ASTM D256, bending tests using ASTM D7264, and tensile tests using ASTM D3039. Results showed that material strength properties could be improved by using on-axis direction (0°). The bamboo composites with unidirectional (0°) laminate direction exhibited superior mechanical properties to bidirectional laminate directions (45°/−45° and 0°/90°). The addition of Waru fiber improved the mechanical properties of the currently developed material; that is, bending strength increased by about 3.17–14.18% and tensile strength was in the range of 4.88–20.28%. Only those composites with 0° and 0°/90° layer orientations fulfilled the Indonesian Bureau Classification strength threshold.

A reliability-based approach is presented to investigate the effects of structural and load uncertainties on the reliability estimation of ship hull girders. Structural uncertainties included randomness in material properties, geometric properties, initial geometric imperfections, and corrosion behavior. Load uncertainties included statistical uncertainties, model uncertainties, environmental uncertainties, and uncertainties related to nonlinearity. The hull girder ultimate strength was calculated using Smith’s method, and the probabilistic density function was evaluated by employing Monte Carlo simulations. In the load estimation, the still water bending moment and wave-induced bending moment were calculated using a simplified formula of the International Association of Classification Societies-Common Structural Rules code and then modified with load parameters. The reliability index was estimated using a first-order reliability method considering the operating time, the duration of the ship in the alternate hold loading condition, and the severity of the corrosion rate. As a result, sagging conditions dominated the collapse mode. The reliability indexes were obtained for the observed cases, and the viability of the ship was assessed accordingly.

This research applies a numerical study of topology optimization of laminate composite structures by using a finite element method (FEM). In this methodology, the plies orientation is excluded from the optimization. The geometry-based optimization from frames of a MALE UAV fuselage structure is presented. The minimum strain energy with an optimization constraint of 20% of weight reduction is used in the objective function. Before the primary analysis, benchmark studies of topology optimization without considering orientations from previously published literature are performed. The convergence studies were taken to acquire the appropriate mesh size in the FEM technique, which utilized a four-noded shell element. The finite element analysis and optimization results showed that the structural design of the newly framed composite fuselage MALE UAV meets the structural strength requirements specified in the airworthiness standard STANAG 4671.

The inelastic deformation of a 30 m high-speed craft (HSC) subjected to slamming pressure is the main topic of this research. In this work, the commercial software package ABAQUS FEA is used to predict the structural behavior, especially in the hull area under the chine. Dynamic explicit solver simulations are done to predict plastic deformation. Before the principal analysis of the actual size of the ship hull structure model, the numerical studies were validated against relevant experimental data from the previous open literature. A reassessment of the design guidelines was also done to forecast the slamming load on the HSC structure. Then, with the slamming load pressure increased to the design limit, a parametric analysis was also conducted with two different idealizations of the pressure type: rectangular and triangular. Finally, this study identifies the variables that must be considered when calculating the degree of structural deformation brought on by slamming loads.

Pitting corrosion is the most common, dangerous, and destructive corrosion type in marine and offshore structures. This type of corrosion can reduce the strength of the ship plate, so investigating it using several numerical grounding scenarios is needed to determine the significant degradation of the strength of the structural plate. In this study, a finite element study was used to evaluate the influence of pitting corrosion location on the strength of the bottom plate ship in grounding simulation. This study simulated 14 scenarios using different pitting positions on the bottom plate. Finite element using explicit dynamic simulation in LS Dyna software was employed to evaluate the strength of the bottom plate on the ship. The output parameters, such as reaction force and plate deformation, were assessed to compare the grounding simulation results. The simulation indicates that the location of pitting corrosion will affect stress concentration, crack initiation, reaction force, and penetrating position when the crack nucleates. The result shows the critical position of the pit, which is located near the stress concentration ring (nearly 100 mm from the center of the plates) in the plain plates.

Antiballistics are used as personal protective equipment required by military and police personnel. They have been mentioned frequently in recent decades due to the increasing cases of war. Several studies have reviewed the development of antiballistic technology. However, there needs to be more discussion on and systematic reviews of the current milestones of antiballistic materials, testing, and procedures. In addition, compared to other fields, antiballistic studies are rarely carried out by public researchers because research on weapons is still a sensitive topic. Researchers who want to discuss antiballistics must cooperate with the country's defense and security agencies. This article aims to present a summary on and the development of scientific research on the theoretical concept of impact, the experimental approach for ballistic tests on advanced materials, the idealization of ballistic tests in computational mechanic simulations, and milestones of technical apparatus for ballistic performance measurement, over a period of more than 500 years. Thus, this analysis makes an excellent contribution to the field of antiballistics. This article review is based on hundreds of international journals and websites that are still active and can be accounted for legally. The results show that research related to antiballistics will continue to grow yearly.

Cylindrical shell structures are ubiquitous and essential supporting structures in various engineering applications. The aim of this research work is to provide a comprehensive overview of the behavior of cylindrical shell structures under different loading conditions, including external pressure, axial compression, and bending moment. The study found that the behavior of cylindrical shells was affected by their geometry, including diameter, length, thickness, and imperfections. These factors should be carefully considered in the design and analysis of cylindrical shells. Additionally, stiffeners and sandwich structures can be applied to improve the structural performance of cylindrical shells under different loading conditions. The work also highlighted the latest research trends in the field, such as the use of advanced materials, and numerical simulations to improve the understanding and design of cylindrical shell structures. Overall, this study has provided a valuable resource for engineers and researchers working on cylindrical shell structures, helping them to design and analyze the cylindrical shell structures more efficiently and effectively.

Research on natural convection is exciting in some experimental and numerical cases, especially in rectangular cavities with relatively low heat dissipation and thermal control systems with low cost, reliability, and ease of use. The present study will use the meshless radial basis function method to solve the velocity formulation of the Navier–Stokes equations by varying some nominal Rayleigh numbers of 10 4 , 10 5 , and 10 6 . The numerical accuracy is compared with the previous research. The advantages of the meshless method are that it does not require a structured mesh and does not require inter-nodal connectivity. The results show that the temperature pattern is identical to the previous research. The calculations have been done for three different Rayleigh numbers of 10 4 , 10 5 , and 10 6 for 151 × 151 nodes. The variations of the Ra number will affect the isothermal, velocity contours, and Nusselt number.

The rising demand for liquefied natural gas (LNG)-fueled ships requires the LNG bunkering facility that partially uses a ship-to-ship operation. The bunkering process of LNG fuel may have a greater risk due to LNG volatility. The cryogenic temperature of LNG poses a threat to the personnel and structural embrittlement to ships. Therefore, cryogenic spill protection optimization was introduced concerning the structural strength analysis using finite element (FE) by utilizing cryogenic temperature loads provided by the computational fluid dynamics (CFD) model of an LNG release. This study aims to build a platform for transferring the temperature load profile from CFD to FE software accurately. The CFD model usually uses a structured Cartesian grid, and the FE method adopts an unstructured tetrahedral or hexahedral mesh. As a result, both configurations store results at different positions, and it is not preferred for the load profile to be transferred directly. The error will be greater due to the variance of positions. Random Forest, a machine learning method, has been employed that uses a regression technique to deal with a continuous variable. An accurate load profile for the FE model can be obtained by adopting decision tree learning in Random Forest. The procedure for determining the temperature load profile is presented in this article.

Spar-type floating offshore wind turbine has been massively developed considering its design simplicity and stability to withstand the wave-induced motion. However, the variation of the local sea level and the readiness of supporting production facilities demand the spar design to adapt in a viable way. Considering this, the present article investigated how the slenderness (length over diameter ratio) and the roundness of cross section influence the hydrodynamic characteristics, which are the crucial parameters of floater performances. The OC3-Hywind spar-type floating platform was adapted as the reference model. The length of the reference floater was then varied with a ratio of 1.5, 2, 2.5, and 3 and the diameter was proportionally scaled to obtain constant buoyancy. The number of the sides which indicated the roundness of the cross section was varied to be 4, 6, 8, 10, 12, 14, and infinity (cylindrical shape). The analysis was conducted using potential flow theory in a boundary element method solver through an open-source code NEMOH. Initially, panel convergence was conducted and compared with the experimental results of the reference model to obtain the appropriate simulation settings before being used for the case configuration analysis. Results stated that the roundness effect with sides greater than 16 had little effect on dynamic characteristics. Meanwhile, the spar with the largest diameter was more stable against the translational motion.