Journal of Engineering Mechanics

Inspired by the origami process, a multicellular tube formed by origami folding based on polygons was designed. First, the accuracy of the finite-element model was verified by experiments; then, under the conditions of the same wall thickness, mass, and energy absorption, comparative studies were carried out between multicellular tubes based on polygonal origami folding (MTPOFs), hollow tubes (HTs), and multicellular tubes (MTs). The results showed that regardless of the same wall thickness or the same mass and energy absorption conditions, MTPOFs have advantages over corresponding MTs and HTs. The crushing force efficiency and specific energy absorption of the square MTPOF were 131.45% and 193.57% higher than those of the square HT with the same wall thickness, respectively. Compared with the hexagonal HT, the crushing force efficiency and specific energy absorption of the hexagonal MTPOF increased by 99.02% and 125.01%, respectively. Under the same energy absorption, the crushing force efficiency of the square MTPOF improved by 78.78% and the specific energy absorption improved by 42.05% compared with the square HT. Ultimately, an investigation was conducted into the energy absorption of the structure concerning variations in wall thickness and the ratio of side length to height $H/a$. As a result, deformation mode diagrams corresponding to different $H/a$ values were obtained.

Abstract

To analyze the effect of temperature on the failure of the interface between reactive powder concrete (RPC) and aggregate, a constitutive model based on the elastoplastic theory to describe both tension and shear failure modes at high temperatures is developed. The influence of damage is incorporated in the developed model. A unified yield function is proposed based on the Mohr-Coulomb criterion to describe plastic behavior at the interface. The evolution of damage is distinguished by different energy dissipation potential functions for tension and shear. Microstructure analysis of the failure surface reveals that the interface degraded with increasing of temperature due to the decomposition of concrete hydrates and the formation of cracks. Comparisons between predictions and experimental data validate accuracy of the proposed model, demonstrating that it can effectively describe the mechanical behavior of cement-aggregate interface at different temperatures.

Practical Applications

In the current study, the authors investigated the mechanical properties of the interface between reactive powder concrete (RPC) and stone materials under high-temperature conditions through experimental and theoretical analysis. The tension and shear constitutive models of the interface at different temperatures are developed based on elastoplastic mechanics model, and the evolution of damage is considered. The developed constitutive models for the tensile and shear behavior of the interface were implemented in user defined subroutine of finite element software ABAQUS, and the predictions exhibited good agreement with experimental results. The developed model can assist engineers in studying the failure of the interface between the matrix and aggregates after a fire incident and analyzing the internal damage of concrete in construction projects. It provides significant assistance in the assessment of building structural fire performance and the analysis of concrete durability.

Abstract

The present study provides the analytical solution for magnetoelastic plane-wave diffraction by a rigid strip in an infinite orthotropic medium. The mathematical formulation of the considered model involves a mixed boundary value problem, which is solved by using the integral equation method. The contour integration technique has been used to establish the closed-form expressions of vertical diffracted displacement and normal stress. The deduced expressions of the vertical diffracted displacement and normal stress are matched with preestablished result through the special cases and serves the validation of the present study. The pattern of the diffracted displacement component in the considered medium, and its varying behavior with various affecting parameters, i.e., magnetoelastic coupling parameter, wave number, phase velocity of the propagating magnetoelastic wave, and distance, are computed numerically and delineated by means of graphical representation for orthotropic and isotropic materials. Moreover, the impact of anisotropy of the infinite medium has been unrevealed through comparative study, which is one of the achievements of the present work.

Practical Applications

The diffraction of longitudinal magnetoelastic plane waves through a rigid strip in an orthotropic material holds significant applications across diverse engineering fields. In nondestructive testing (NDT), the understanding of wave diffraction patterns aids in the detection and characterization of defects or structural changes in orthotropic materials without causing damage. This knowledge is vital for structural health monitoring (SHM), allowing for the timely identification of damage, cracks, or alterations in material properties. Moreover, the insights gained from wave diffraction contribute to the design and optimization of magnetoelastic devices, including sensors, actuators, and transducers, enhancing their performance and sensitivity. In the realm of communication, the propagation of magnetoelastic waves through rigid strips in orthotropic materials is instrumental in designing efficient waveguides and communication devices. Additionally, the study of wave diffraction facilitates the development of magnetostrictive components for applications in robotics, medical devices, and automotive systems. Furthermore, the unique acoustic properties of orthotropic materials, influenced by magnetoelastic wave diffraction, contribute to the design and optimization of acoustic devices such as speakers and ultrasonic transducers.

Architected cellular materials and structures provide the ability to tailor mechanical and functional properties based on design topological aspects. With the progressive advancement of additive manufacturing techniques, challenges and difficulties related to fabricating complex geometries are substantially reduced. Among different architected cellular materials, two types of closed-walls cellular materials, plate-lattices and triply periodic minimal surface (TPMS)–based lattices, provide outstanding mechanical properties. Plate-lattices are well-known for high stiffness, while TPMS lattices provide higher energy absorption capabilities. Herein, the mechanical behavior of the most two promising designs of both families is investigated experimentally and using finite-element analysis (FEA), namely sheet-based diamond TPMS and simple cubic–face-centered cubic–body-centered cubic (SC-FCC-BCC) plate-lattice. Fused deposition modeling (FDM) technology is utilized to fabricate the structures with acrylonitrile butadiene styrene (ABS) at several combinations of relative densities and unit cell sizes. Under quasi-static loading, diamond structures showed higher strength and energy absorption capabilities at various relative densities compared to plate-lattices. Based on experimental results, diamond is found to be 52% stiffer than the plate-lattice at low relative densities. These variations are diminished as relative density increased. ANOVA results, provided as main effects plots, show a significant dependence of mostly all mechanical properties on the three-dimensional (3D) topological design of the samples. Both structures presented outstanding mechanical energy absorption ability, suggesting their utilization in impact loading applications.

Abstract

Based on the method of continuous distribution of dislocations and relevant theories of fracture mechanics, the effect of the distribution of hydrogen atoms at the crack tip (CT) on the emission of dislocations from kinked cracks under far-field uniform tensile stress is studied. The results show that hydrogen atoms can promote the emission and migration of CT dislocation, which leads to the increase of dislocation density (severe dislocation plugging), the increase of energy release rate, and the decrease of elastic zone size (dislocation-free zone) at CT. In addition, the sequence of initiation of grain boundary (GB) microcracks caused by dislocation emission at both ends of the whole crack (horizontal section and kinked section) and the propagation mechanism of a crack in a kinked section are analyzed. The results show that the critical tensile stress of GB microcrack initiation decreases with the increase of hydrogen atom radius $r_h$ and the decrease of hydrogen atom position $x_h$, indicating that hydrogen atoms promote the initiation of GB microcrack initiation. At the same time, the existence of hydrogen atoms not only promotes the initiation of GB microcrack, but also accelerates the expansion of kinked cracks, which may eventually lead to the convergence of the main crack and the microcrack, resulting in the failure and destruction of materials. Therefore, the theoretical research in this paper has made a new understanding of the mechanism of hydrogen fracture of crystal materials.

Practical Applications

In this paper, the effects of hydrogen atoms at CT on dislocation emission at CT, crack initiation at GB, and the size of the dislocation-free zone were studied by establishing a crack dislocation model and using the distributed dislocation method. The results show that the accumulation of hydrogen atoms at the CT promotes the emission of dislocation at the CT, leads to the serious plugging of dislocation near the GB, promotes the initiation of microcracks and the expansion of kinked cracks, and leads to the reduction of the size of the dislocation-free zone at the CT. This work provides new information on the microscopic fracture mechanics of hydrogen on materials. On the one hand, it can better predict and prevent the fracture of materials, so as to improve the safety of engineering structures. On the other hand, it can help explain some microscopic experimental phenomena.

The study of elastic wave scattering is crucial for nondestructive testing, quality assurance, and failure prevention of quasicrystal (QC) structures. In the present paper, the dynamic behavior of an interface crack in one-dimensional (1D) hexagonal piezoelectric quasicrystal (PQC) coating and semiinfinite homogeneous elastic substrate subjected to incident elastic-time harmonic waves is studied. The scattering problem of plane waves is reduced to a set of the Cauchy singular integral equations (SIEs) of the second kind by introducing the dislocation density functions. The SIEs are solved employing excellent properties of the Jacobi Polynomials, and the dynamic stress intensity factors (DSIFs) at the crack tips are obtained. The effects of the different PQC coating, incidence waves, crack size, incidence angle, and coupling coefficients on the DSIFs are displayed graphically. The consequences indicate that the presence of the phason field intensifies the fluctuation of the DSIFs at the crack tips, and the higher the coupling coefficients of the phonon-phason field, the easier the crack propagates. Additionally, the crack propagation can be suppressed by selecting the appropriate PQC coating and incidence angle. This work will benefit the understanding of the dynamic failure of PQC and its application.

In this paper, the field-enriched finite-element method is developed to simulate crack evolution of quasibrittle materials under compression by considering two kinds of fracture criteria: the maximum circumferential stress criterion; and the Mohr–Coulomb criterion. The benchmark of the specimens containing a single flaw is illustrated to verify that the maximum circumferential stress criterion and the Mohr–Coulomb criterion can capture the tensile crack and secondary crack. Moreover, the numerical examples of specimens containing two flaws are illustrated to prove that the field-enriched finite-element method can effectively simulate the crack coalescence in specimens under compression. Finally, specimens containing multiple flaws are illustrated to investigate the crack evolution mechanism under compression as well as the crack coalescence types.