This study is concerned with the mixed initial boundary value problem for a dipolar body in the context of the thermoelastic theory proposed by Green and Naghdi. For the solutions of this problem we ...prove a result of Hölder’s-type stability on the supply terms. We impose middle restrictions on the thermoelastic coefficients, which are common in continuum mechanics. For the same conditions we propose a continuous dependence result with regard to the initial data.
Additive manufacturing has multiple advantages over conventional fabrication techniques, such as the geometrical freedom and, to a great extent, the omission of tooling equipment. Hence, futuristic ...designs and non‐standard topology‐optimized structures can be fabricated without causing noteworthy extra cost, since the geometrical complexity is, exaggeratedly spoken, for free. The manufacturing time and the amount of required raw material are the key criteria, which determine the expenses. What at first glance appears as an engineer's dream, introduces its complexity in the description of the material's characteristics and their volatility to the manufacturing conditions. Within this study, the main properties (i.e., surface hardness, tensile, and compression strength, as well as fracture toughness) and their anisotropic and inhomogeneous nature are addressed. Detailed overviews of the progress to date for aluminum, iron, titanium, cobalt, and nickel based raw materials are provided. Furthermore, an overview about the state‐of‐the‐art in the medical sector is included, comprising the areas of utilization and several trail studies.
Powder‐Bed‐Fusion techniques are future orientated manufacturing processes, which allow the fabrication of custom designed components and fully unleash their potential when only low quantities are required. One of the current challenges is the prediction of the material properties, which are anisotropic due to the layer wise generation of the components with numerous tiny weld‐tracks.
The thorough description of the peculiarities of additively manufactured (AM) structures represents a current challenge for aspiring freeform fabrication methods, such as selective laser melting ...(SLM). These methods have an immense advantage in the fast fabrication (no special tooling or moulds required) of components, geometrical flexibility in their design, and efficiency when only small quantities are required. However, designs demand precise knowledge of the material properties, which in the case of additively manufactured structures are anisotropic and, under certain circumstances, inhomogeneous in nature. Furthermore, these characteristics are highly dependent on the fabrication settings. In this study, the anisotropic tensile properties of selective laser-melted stainless steel (1.4404, 316L) are investigated: the Young's modulus ranged from 148 to 227 GPa, the ultimate tensile strength from 512 to 699 MPa, and the breaking elongation ranged, respectively, from 12% to 43%. The results were compared to related studies in order to classify the influence of the fabrication settings. Furthermore, the influence of the chosen raw material was addressed by comparing deviations on the directional dependencies reasoned from differing microstructural developments during manufacture. Stainless steel was found to possess its maximum strength at a 45° layer versus loading offset, which is precisely where AlSi10Mg was previously reported to be at its weakest.
Contemporary researchers have specified that natural flax fiber is comparable with synthetic fibers due to its unique physical and mechanical characteristics which have been recognized for decades. ...Flax fiber-reinforced composites have the potential for wide usage in sport and maritime industries, and as automotive accessories. In addition, this composite is in the development stages for future applications in the aeronautical industry. However, designing the flax composite parts is a challenging task due to the great variability in fiber properties. This is caused by many factors, including the plant origin and growth conditions, plant age, location in the stem, fibers extraction method, and the fact that there is often a non-uniform cross section of the fibers. Furthermore, the water and moisture absorption tendency of the flax fibers and their composites and the consequent detrimental effects on their mechanical performance are also major drawbacks. Fibers may soften and swell with absorbed water molecules, which could affect the performance of this bio-composite. Flax fibers’ moisture absorption propensity may lead to a deterioration of the fiber–matrix interface, weakening the interfacial strength and ultimately degrading the quality of the composite. This review represents a brief summary of the main findings of research into flax fiber reinforced composites, focusing on the challenges of its water and moisture absorption behavior on their performance.
Models considering (a) unit cell with a single fiber and (b) larger number of fibers.
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This review article is intended to highlight and categorize the most important and novel studies ...conducted to explore the mechanical behavior of nano-composites reinforced with carbon nanotubes (CNTs). The existing articles cover the mechanical performance of reinforced composites, both theoretically and experimentally, which allows an accurate estimate of the mechanical performance of these nano-structures. It was addressed that the predictive methods can be categorized as: models based on unit cells with a single fiber, models considering a unit cell with a larger number of fibers, and how the fibers are modeled: as a 1D, 2D, or 3D configuration. Furthermore, we review two different experimental methods (destructive and non-destructive) in order to highlight more investigations in this particular field of research. The presented review article includes: (i) a brief outline to CNT reinforced composites; (ii) a review of investigation on analytical, numerical, and experimental modeling; and (iii) a comprehensive conclusion regarding the argued investigations and some thoughts on the potential development.
Abstract The current investigation deals with the deformation of a non-homogeneous thermoelastic half space under hydrostatic initial stress for the Green–Naghdi model III. The medium is supposed to ...be rotating with a constant angular velocity. The non-homogeneous properties of the material are along the x -direction. At the first instance, the problem has been solved analytically to obtain stress and displacement components. Further, the numerical values of these expressions are evaluated using a computer program for a particular medium. The numerical values obtained are then presented graphically to show the effect of initial stress parameter and non-homogeneity parameter on the quantities.
Abstract In this study it is approached a linear model for the mixture of two Cosserat bodies having pores. It is formulated the mixed problem with initial and boundary data in this context. The main ...goal is to show that the coefficients that realize the coupling of the elastic effect with the one due to voids can vary, without the mixture being essentially affected. In a more precise formulation, this means that a small variation of the coefficients in the constitutive equations of the two continua causes only a small variation of the solutions of the corresponding mixed problems, that is, the continuous dependence of the solutions in relation to these coefficients is ensured. The considered mixture model is consistent because all estimates, specific to continuous dependence, are made based on rigorous mathematical relationships.
The paper aims to study, using the finite element method, the elastic behavior of a cylinder made by a material with micropolar structure, containing (as the results of the processing or introduced ...intentionally) voids. To study such a type of problem, a theoretical model of a continuous solid body with voids in the material is presented, after which, in order to determine the effect that these voids have, a model with finite elements is made, using Lagrange’s equations. This model can be applied to any type of elastic solid with voids. In the paper study the elastic response of a hollow cylinder made by a material with voids. Finally, comparative results are obtained to show the influence of voids on the elastic behavior of the body in some classic cases. These results are compared with the values obtained in the literature by experimental methods. It is found that a small percentage of voids can lead to significant variations on the mechanical properties.
We consider a thermoelastic Cosserat body with dual-phase lag. In order to formulate a dual-phase-lag model, an equation is introduced, of the time differential type, to characterize the thermal ...effects and the coupling with the deformation from an elastic point of view. We associate with this model a mixed problem with initial data and conditions to the limit. We then obtain some qualitative estimates on the solutions of this mixed problem, without resorting to restrictive conditions on the thermoelastic coefficients. In order to obtain the uniqueness of the solution, we appeal to a Lagrange-type identity, easily obtained in the given context, and to a law of conservation, previously demonstrated. Then, we establish an inequality which is of the Gronwall’s type, that is useful for proving the continuous dependence of the solutions in relation to initial values and loads, which is another important result of our study.
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