This paper presents a mathematical model of nonlinear supersonic flutter of viscoelastic shells. To describe the strain processes in shallow shells, the Boltzmann-Volterra integral model is used. Based on linear integral models in geometrically nonlinear formulations, equations of nonlinear oscillations of shallow shells are derived. The Koltunov-Rzhanitsyn kernel is used as a relaxation kernel. The equations of motion of shallow shells after applying the Bubnov-Galerkin method in axial coordinates are reduced to solve a system of nonlinear integro-differential equations (IDE) with variable coefficients relative to the time function. The IDE solution is found numerically using quadrature formulas.

Finite Element Analysis was carried out to describe the effect of frictional boundary conditions and percentage reduction on deformation modelling (forward extrusion) of Aluminum AA6063 alloy. Curved die profiles of regular polygons (square, hexagonal, heptagonal, and octagonal) were designed using MATLAB R2009b and Autodesk Inventor 2013 to generate the coordinate and the solid CAD model of the die profile respectively form a circular billet. The numerical analysis was performed using DeformTM-3D commercial package with frictional boundary conditions of 0.38 and 0.75 representing the wet and dry condition and varying the percentage reduction of 50%, 70%, and 90%. The results of the temperature distribution, effective stress, effective strain, and strain rate were reported. As the percentage area reduction increases, the extrusion pressure also increases with an increasing frictional condition, and die length. Also, extrusion pressure decreases when the side of the polygon increases from square-shaped section follow by hexagonal shaped-section and least in octagonal shaped-section for both friction factors and percentage area reductions. For a given percentage reduction and cross-sectional area, there is no distinct difference between the predictive loads for the shaped-polygons. When the result of this analysis is compared with the experimental results from the literature, it is evident that DeformTM-3D is an effective tool for finite element analysis of non-isothermal deformation processes.

In this work, the study of the evolutive behaviour of composite steel-concrete sections used in bridge decks was performed. A new method is proposed for the annex of EC3 part 2, in order to study the evolution effective steel area in a composite section, for serviceability and ultimate states. A coherent theoretical framework is presented, based on several relevant codes, namely the new Eurocodes. With this framework, a computer program is developed taking into account several important aspects in the behaviour of steel-concrete composite sections, such as nonlinear stress-strain relationships of the materials, local buckling of steel plates, time-dependent effects in concrete behaviour and load history. Also a new algorithm is proposed in order to compute strain fields at the section level from a known set of internal forces in the section, in nonlinear constitutive relations. Results obtained with the developed computer program are presented for several examples of typical sections found in bridge decks. Those results include moment-curvature plots, evolution of the strain field, evolution of the neutral axis, evolution of the stress in some points of the section. The influence of the concrete ultimate resistance and the staged construction sequence in the behaviour of the section is also evaluated.

The study and determining of fibre-orientation with a two-dimensional (2D) image analysis of cross-sections is a fast and efficient way to get the fibre orientation distribution over a wide specimen area. There are several techniques for measuring fiber-orientation; however, the present study is based on a technique for the sake of obtaining better results . In this work , we utilize second moments technique to determine fibre orientation state by the use of a Scanning Electron Microscope (SEM) images. In order to determine the fiber-orientation state, a second order orientation tensor is employed. A thermoplastic matrix containing 5, 10, 15, 20, 25 and 30% by weight of hemp fiber is molded using an injection molding machine to obtain dumbbell samples. The orientation tensor is determined by employing geometric parameters of fibers on cross-sections.The geometric parameters are calculated by using image analysis, which employs a computational code especially developed to obtain a tensor components.

Immediate aid to survivors of a natural disaster is the keynote to crisis management. Providing temporary access is one of the most important principles of immediate relief. However, in the post-disaster conditions, it is not possible to use road construction machinery, especially in rural areas. Therefore, in this study, the feasibility of using a Rapid Assembly Building (RAB) system for the temporary pavement with the possibility of rapid construction, which follows the natural topography of the place, is investigated. The introduced system consists of a high-density polyurethane (PUR) foam core as well as two continuous layers of high-density polyethylene (HDPE) facings. For this purpose, the mechanical properties of the materials and composite pavement were determined by a series of laboratory tests. Then, the mechanical performance and bearing behaviour of an element of the presented pavement system was numerically modelled under AASHTO loading. Since in the post-disaster situation, it is not possible to establish the subgrade, an uncompacted subgrade is used for modelling. The results show that this system can be used well in post-disaster situations to provide a rapid, safe, yet robust road without any permanent deformation.

The efficacy of stainless-steel micro-particles on friction stir processed aluminium-based matrix composite (ABMC) was studied using tribological, mechanical and structural analysis tools. The stainless-steel powder (17-4PH) of average size 45 – 90 µm was used as the reinforcement particle. The parametric values employed during the fabrication of ABMC- AA7075-T651/17-4PH were the rotational speed of 1500 rpm and travel speed of 20 mm/min while the plunge depth and tilt angles used were respectively 0.3 mm and 3 degrees. Tribological study was carried out under the influence of dry sliding condition with varying loads of 20 N and 50 N using tribometer while the scanning electron microscope (SEM) was used to capture the wear track. Structural analysis was examined with the aid of x-ray diffraction (XRD). The tensile strengths of the fabricated ABMC were also tested and the fracture surfaces were studied using SEM analysis. The results from the study revealed that at higher loading of 50 N, the wear performance was significantly improved for the fabricated aluminium composite- AA7075-T651/17-4PH when compare with lower loading of 20 N. The tensile properties for the ABMC were also improved under the influence of the stainless steel microparticles. There was structural improvement in ABMC wherein the value for crystallite size was lowest while micro-strain, dislocation density, as well as full width at half maximum (FWHM), had the highest values over the FSPed AA7075-T651 and the parent material. The examined fractured surface of the fabricated composite was dominated with fine, network and equiaxed dimples with cup and cone attributes confirming superb interfacial bonding and that the failure mode was ductile.

The cardiac output and stroke volume of a healthy person was estimated using a 3D fluid-structure interaction (FSI) simulation coupled with an echocardiogram Doppler (echo-Doppler) during exercising and resting. The geometry, dimensions, and blood flow through the aortic valve were measured using the echo-Doppler. A 3D FSI simulation was modeled using an arbitrary Lagrangian-Eulerian mesh. The 3D FSI cardiac output and stroke volume results were 15.4% lower than Doppler results when brachial pressures applied with differences between brachial, central, and left ventricular pressures. While without considering these brachial pressures differences, the discrepancy between the FSI cardiac output and stroke volume results with Doppler increased to 22.3% and 26.2%, respectively. Eventually, the comparisons of the 3D FSI results and clinical measurements demonstrated that numerical methods can be a potential computational tool to estimate cardiac output and stroke volume for different heart rates when they coupled with the clinical measurements.

Cracks are one of the main causes of structural failure and they develop in the structures due to various reasons such as fatigue, temperature variation, excessive load, cyclic load, environmental effects, impact loading etc. Thus, structural health monitoring is necessary to avoid risks, damages and failures. So, in order to avoid an extensive failure or accident, the early prognosis of crack in structures is necessary. Visual inspection and some non-destructive testing (NDT) methods for detection of crack are difficult as it requires time, expenses and are quite inefficient. So the alternative methods are motivated to be developed. In this study, vibration analysis, finite element analysis (FEA) and an alternative way which is artificial neural network (ANN) is used to predict, detect and identify the damages in structures. It is found that the theoretical, experimental, finite element analysis and artificial neural network have good accuracy in predicting the crack characteristics.

This paper studies the bending behavior of honeycomb structures by varying their weight through the introduction of glass microspheres. For this purpose, four different types of syntactic foam specimens were manufactured, varying the percentage by volume of glass microspheres between 20%, 30% and 40%. Afterwards, three-point bending tests were performed on each of these groups of specimens based on ASTM D7264/D7264M-15, thus obtaining data that allowed determining mechanical behavior and comparing it with material without glass microspheres. The optimum positive influence of microspheres over specific flexural strength was found at 30% of addition of glass bubbles. Additionally, results of the structures under impact gravity test confirm that 30% is a good proportion for these structures.

The purpose of the study is to improve the performance characteristics of powder pseudo-alloy materials using surface heat treatment. Such materials have unique properties, for example, self-lubrication under dry friction conditions, high thermal conductivity coefficient, and high electroerosion resistance. The disadvantage of powder pseudo-alloys is their relatively low strength. The paper considers the method of surface hardening by high-energy treatment - laser radiation. The paper describes the method of experimental research, describes the method of obtaining powder material, its chemical composition, shows the equipment used. The results of studies of the microstructure and microhardness of the surface layer of steel-copper powder pseudo-alloy after laser heat treatment (LHT) of a continuous-wave fiber laser with a maximum power of 1 kW are given, LHT modes are indicated, the influence of LHT parameters on the characteristics of the hardened layer is evaluated. It is revealed that the partial melting region in which melting occurs in the volumes of the fusible component (copper) in the initial structure and contacting segments of steel matrix is formed in the material in addition to the total melting zone. Then the quenching zone from the solid state follows, in which the maximal hardness up to 1000 HV is attained for best samples in the volume of martensite, which is formed in perlite colonies of the initial steel–copper material.