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To investigate the relation between the Poisson's ratio of a re‐entrant honeycomb structure by varying the micropolar material constants such as micropolar Young's modulus E_m, micropolar Poisson's ratio V_m, characteristic length l, coupling factor N, and micropolar elastic constants in accordance with the micropolar elastic restrictions, a 2‐D triangular finite element formulation including an extra degree of freedom was derived on the basis of Eringen's micropolar elasticity theory by using a linear triangular element. The effects on the structural Poisson's ratio of the honeycomb structure are studied in detail.

The purpose of this paper is to present results of an investigation, where the elastic tensor based on the engineering constants of sinterized Nylon 12 is characterized and is modeled considering a transversely isotropic behavior as a function of apparent density (relative mass density).

The ultrasound propagation velocity measurement through the material in specific directions by means of the pulse transmission method was used, relating the elastic tensor elements to the phase velocity magnitude through Christoffel's equation. In addition conventional uniaxial tensile tests were carried out to validate the used technique. Laser sintering of Nylon 12 powder (Duraform PA) has been performed at different laser energy densities, fabricating cube‐shaped coupons as well as dogbone flat coupons, using an SLS 125 former DTM machine.

Correlations for each one of the Young moduli, Shear constants and Poisson's ratios, presenting an exponential behavior as a function of the sintering degree, were generated. In addition, as the apparent density reaches a maximum value of 977 kg/m³ at an energy density of 0.032 J/mm², the material behaves in an almost isotropic form, presenting average values for the Young modulus, Shear modulus and Poisson's ratio corresponding to 2,310 MPa, 803 MPa and 0.408, respectively.

The research is limited only to one type of material within the elastic range. Validation of the Young modulus measured along one direction only is performed using a tensile test machine, due to the difficulties in evaluating Poisson's ratios and Shear moduli using conventional tests.

The results presented can be applied to virtual design and evaluating processes such as finite element analysis.

The paper incorporates detailed information regarding the complete elastic characteristics of Nylon 12, including additional measurements of the Shear moduli and Poisson's ratios not studied previously.

Based on Eringen’s micropolar elasticity theory (MET), a two‐dimensional finite element formulation including one extra degree of freedom is derived by using a linear triangular element, and a corresponding computer program is also developed. By varying the technical constants such as micropolar Young’s modulus E_m, micropolar Poisson’s ratio ν_m, characteristic length l, coupling factor N, and micropolar elastic constants in accordance with the micropolar elastic restrictions, their effects on the Poisson’s ratio of the rectangular plate are studied in detail.

This paper aims to evaluate the material properties and dimensional accuracy of a MakerBot Replicator 2 desktop 3D printer.

A design of experiments (DOE) test protocol was applied to determine the effect of the following variables on the material properties of 3D printed part: layer height, per cent infill and print orientation using a MakerBot Replicator 2 printer. Classical laminate plate theory was used to compare results from the DOE experiments with theoretically predicted elastic moduli for the tensile samples. Dimensional accuracy of test samples was also investigated.

DOE results suggest that per cent infill has a significant effect on the longitudinal elastic modulus and ultimate strength of the test specimens, whereas print orientation and layer thickness fail to achieve significance. Dimensional analysis of test specimens shows that the test specimen varied significantly (p < 0.05) from the nominal print dimensions.

Although desktop 3D printers are an attractive manufacturing option to quickly produce functional components, this study suggests that users must be aware of this manufacturing process’ inherent limitations, especially for components requiring high geometric tolerance or specific material properties. Therefore, higher quality 3D printers and more detailed investigation into the MakerBot MakerWare printing settings are recommended if consistent material properties or geometries are required.

Three-dimensional (3D) printing is a rapidly expanding manufacturing method. Initially, 3D printing was used for prototyping, but now this method is being used to create functional final products. In recent years, desktop 3D printers have become commercially available to academics and hobbyists as a means of rapid component manufacturing. Although these desktop printers are able to facilitate reduced manufacturing times, material costs and labor costs, relatively little literature exists to quantify the physical properties of the printed material as well as the dimensional consistency of the printing processes.

The purpose of this paper is to evaluate the second‐ and third‐order elastic constants (SOEC and TOEC) and then velocities and attenuation of ultrasonic waves along unique direction in hexagonal II‐VI group semiconductors, cadmium chalcogenides (CdS, CdSe and CdTe) compounds at room temperature and obtained the ultrasonic behaviour and mechanical properties of these compounds.

Lennard‐Jones potential approach is applied to evaluate the SOEC and TOEC.

The value of ultrasonic attenuation of CdSe is smallest in comparison to other chosen materials. So, CdSe is more ductile and more pure than others. Thus, the mechanical properties of CdSe are better than those of CdS and CdTe, because CdSe has high‐elastic constants and low‐ultrasonic attenuation.

Obtained results, together with other well‐known physical properties, may expand future prospects for the industrial applications and study of these semiconductor materials.

Distributions of stress and strain in composite and cellular materials can differ significantly from the predictions of classical elasticity. For example, concentration of stress and strain around holes and cracks is consistently less than classical predictions. Generalized continuum theories such as micropolar (Cosserat) elasticity offer improved predictive power. In this article Saint‐Venant end effects for self equilibrated external forces in micropolar solids are investigated in two dimensions. A two dimensional finite element analysis is used which takes into account the extra degrees of freedom, to treat the problem of localized end loads acting upon a strip. The rate of decay of strain energy becomes slower in a two dimensional strip as the micropolar characteristic length l is increased (for l sufficiently less than the strip width). For the strip geometry a Cosserat solid exhibits slower stress decay than a classical solid.

The objective of this paper is to construct a continuous model for the thermo‐visco‐elastic contact of a nominal flat, non‐smooth, punch and a smooth surface of a rigid half‐space. The considered model aims at studying the normal approach as a function of the applied loads and temperatures. The proposed model assumes the punch surface material to behave according to the linear Kelvin‐Voigt visco‐elastic material. The punch surface, which is known to be fractal in nature, is modeled in this work using a deterministic Cantor structure. An asymptotic power low, deduced using approximate iterative relations, is used to express the punch surface approach as a function of the remote forces and bulk temperatures when the approach of the punch surface and the half space is in the order of the size of the surface roughness. The results obtained using this model, which admits closed form solution, are displayed graphically for selected values of the system parameters; the fractal surface roughness and various material properties. The obtained results showed good agreement with published experimental results.

The maintenance of aircraft structure with lower cost is one of the prime concerns to regulatory authorities. The carbon fiber-reinforced polymer (CFRP) patches are widely used to repair the cracked structure. The demands and application of CFRP compel its price to increase in the near future. A distinct perspective of repairing the cracked aluminum panel with the hybrid composite patch is presented in this paper. The purpose of this paper is to propose an alternative patch material in the form of a hybrid composite patch which can provide economical repair solution.

The patch hybridization is performed by preparing the hybrid composite from tows of carbon fiber and glass fiber. Rule of hybrid mixture and modified Halpin–Tsai’s equation are used to evaluate the elastic constant. The stress intensity factor and interfacial stresses are determined using finite element analysis. The debonding initiation load is evaluated after testing under mode-I loading condition.

The hybrid composite patch has rendered the adequate performance for reduction of stress intensity in the cracked panel and control of interfacial stresses in the adhesive layer. The repair efficiency and repair durability of the composite patch repair was ensured by incorporation of the hybrid composite patch.

The studies involving patch hybridization for the application of composite patch repair are presently lacking. The influence of the patch stiffness, methodology to prepare the hybrid composite patch and effects of hybridization on the performance of composite patch repair is presented in this paper.

The numerical simulation of metal forming processes follows a highly non‐linear analysis where general aspects such as elastoplasticity, finite deformation and contact mechanics are combined. Approximated solutions obtained by finite element techniques require strong computational effort, that contradicts the need of interactive industrial applications. The first part of the work deals with the description of the main elements of the formulation, with attention to mathematical modelling and the approximating algorithms in the incremental iterative frame of non‐linear analysis, ending with the results obtained in hot rolling simulation. The second part is dedicated to computational efficiency analysis and the presentation of the related methods and results obtained in this work.

The great magnitude differences between the integral tunnel and its structure details make it impossible to numerically model and analyze the global and local seismic behavior of large-scale shield tunnels using a unified spatial scale, even with the help of supercomputers. The paper aims to present a combined equivalent & multi-scale simulation method, by which the tunnel's major mechanical properties under seismic loads can be represented by the equivalent model, and the seismic responses of the interested details can be studied efficiently by the coupled multi-scale model.

The nominal orthotropic material constants of the equivalent tunnel model are inversely determined by fitting the modal characteristics of the equivalent model with the corresponding segmental lining model. The critical sections are selected by comprehensive analyzing of the integral compression/extension and bending loads in the equivalent lining under the seismic shaking and the coupled multi-scale model containing the details of interest is solved by the mixed time explicit integration algorithm.

The combined equivalent & multi-scale simulation method is an effective and efficient way for seismic analyses of large-scale tunnels. The response of each flexible joint is related to its polar location on the lining ring, and the mixed time integration method can speed-up the calculation process for hybrid FE model with great differences in element sizes.

The orthotropic equivalent assumption is, to the best of the authors’ knowledge, for the first time, used in the 3D simulation of the shield tunnel lining, representing the rigidity discrepancies caused by the structural property.