3D Solids Research Articles

Subsurface stress evolution under orthotropic wear and frictional contact conditions

This work presents a computational framework to study the evolution of the subsurface stresses in 3D solids under orthotropic frictional contact and wear conditions. The formulation is based on the influence coefficients methodology to relate the discrete elastic response (i.e., displacements and stresses) to the sampled excitation (i.e., surface contact tractions). The proposed methodology is validated by solving several benchmark problems and is applied to analyze how the subsurface stress distribution (i.e. maximum value and its location) – and its evolution – caused by orthotropic wear conditions are clearly affected not only by the considered wear problems (i.e., sliding wear or fretting wear) but also by the friction coefficient values and the sliding direction angle — relative to the tribological axes. Several numerical examples are presented to show the importance of these last two aspects when orthotropic wear conditions are considered. In other case, we could over- or underestimate the maximum values of the subsurface stresses during the wear process.

S-version finite element strategy for accurately evaluating local stress in the vicinity of dynamically propagating crack front in 3D solid

Developing a numerical method to accurately simulate the brittle crack propagation phenomenon is crucial for ensuring the safety of large-scale steel structures. Although recent studies have demonstrated that using the local fracture stress criterion as the fracture condition is effective, the most critical issue is that the methods for evaluating local stress in the vicinity of the dynamically propagating crack front have not been established. To address this, this paper proposes a strategy for analysing a dynamically propagating crack in 3D solids on the basis of the s-version finite element method (s-method). In the proposed strategy, the local mesh is defined in the vicinity of the crack front as an ideal structured mesh aligned with both the crack front direction and crack propagation direction to accurately simulate the local stress field. The dynamically propagating crack front was modelled by a combination of the nodal force release method and local mesh update. The proposed strategy was verified by evaluating the accuracies of the local stress in stationary and dynamically propagating circular crack problems as well as those of the stress intensity factor. The results demonstrate that the proposed strategy provides unprecedented accuracy and efficiency of local stress evaluation in problems of dynamic crack propagation in a 3D solid without requiring any complicated remeshing procedures. Therefore, the proposed strategy has potential as the basis of a numeral framework for analysing dynamic brittle crack propagation problems dominated by the local fracture stress criterion.

Analisis Sambungan Balok-Kolom Beton Bertulang Dengan Pemodelan Numerik Berbasis Metode Elemen Hingga

A Damage to the reinforced concrete beam-column connection system had found in buildings such as residential buildings, houses of worship, and so on. This was caused by an incidental changed in the position of the beam elevation at the beam-column connection. The research had modelled the reinforced concrete beam-column connection with variations beam elevation, successively: h; 2h; and 3h where h was the height of the column. Modeling used 3D frame idealization and 3D solids element. The idealization of 3D frames had used to evaluate the capacity of the beam-column due to the beam elevation changed. T. The results showed that due to beam elevation chnaged had significant increased in the moment and shear capacity. The percentage increased in moment and shear respectively were 15%, 35%, and 45% of the control beam-column. The most severe cracks were occurred when the beam elevation was at 1.00hb. The percentage of beam-column connection stress concentration is 8,74% (CM); 9.80% (0.25hb); 11.09%(0,50hb); 12.13%(0.75hb); and 13.41% (1.00hb) for the ratio of horizontal and vertical stresses (S11/S22) on concrete frames. The percentage of stress concentration in steel reinforcement is 4.15% (CM); 4.47%(0.25hb); 5.25%(0,50hb); 4.56%(0.75hb); and 4.57%(1.00hb) for the comparison of von Mises and horizontal stresses (SVM/S11)

3D-TSV: The 3D trajectory-based stress visualizer

In this paper, we present novel algorithms for visualizing the three mutually orthogonal principal stress directions in 3D solids under load and we discuss the efficient integration of these algorithms into the 3D Trajectory-based Stress Visualizer (3D-TSV), a visual analysis tool for the exploration of the principal stress directions of 3D stress field. In the design of 3D-TSV, several perceptual problems have been solved. We present a novel algorithm for generating a space-filling and evenly spaced set of stress lines. The algorithm obtains a more regular appearance by considering the locations of lines, and enables the extraction of a level-of-detail representation with adjustable sparseness of the trajectories along a certain stress direction. A new combined visualization of two principal directions via oriented ribbons enables to convey ambiguities in the orientation of the principal stress directions. Additional depth cues have been added to improve the perception of the spatial relationships between trajectories. 3D-TSV provides a modular and generic implementation of key algorithms required for a trajectory-based visual analysis of principal stress directions, including the automatic seeding of space-filling stress lines, their extraction using numerical schemes, their mapping to an effective renderable representation, and rendering options to convey structures with special mechanical properties. 3D-TSV is accessible to end users via a C++- and OpenGL-based rendering frontend that is seamlessly connected to a MatLab-based extraction backend. The code (BSD license) of 3D-TSV as well as scripts to make ANSYS and ABAQUS simulation results accessible to the 3D-TSV backend are publicly available.

Modes and modal analysis of three-dimensional (3D) structures based on the smoothed finite element methods (S-FEMs) using automatically generatable tetrahedral meshes

The smoothed finite element methods (S-FEMs) have been found capable of producing softer models whose “stiffness” is closer to the true continuous model. This paper explores, for the first time, this unique feature of S-FEMs to develop a complete formulism and procedure to study free vibration and forced vibration of solid structures, via (1) solving eigenvalue problems that produces vibration modes of a given structure; (2) using model superimposition techniques and the Lanczos algorithm to obtain transient dynamic solution for structures subjected to arbitrary dynamics forces. The present S-FEM modeling takes the advantageous of the so-called softening effects achieved by establishing proper types of smoothing domains based on edges and faces of the mesh known as ES/FS-FEM, so as to obtain accurate modes for both free and forced vibration analysis. For easy automation in creating 3D solids, we use only the automatically generatable tetrahedral mesh, while to ensure excellent stress solution using the ES/FS-FEM models. A 3D code has been developed in the framework of S-FEMs, and applied to solve a number of 3D solid structures. The results are compared with those from the commercial finite element analysis software ABAQUS in terms of accuracy and convergence.

Modeling of geometric correspondences and transformations via geometry constructions language

Geometric correspondences and transformations can be applied in solutions to numerous problems of geometric modeling, mainly in order to create models of curves and surfaces. Among the tools of CAD systems, the geometric transformations are presented in the form of a limited set of editing tools, array tools, tools providing formation of 3D solids and surfaces through motion. In practice, this set of tools restricts application of the wide capabilities of geometric transformations and correspondences. In this regard, it is proposed to model the geometric transformations and correspondences via the geometry construction language. The elements of the geometric transformation theory are analyzed. The geometric transformations are proposed to be created on par with other objects of the geometric model. The commands of the geometry constructions language enabling construction of the transformation objects are considered, their application is discussed. Solutions to practical problems of surface modeling via the geometry constructions language with the use of geometric transformation are demonstrated on examples. The proposed approach allows us to facilitate modeling of curves and surfaces in CAD systems, if said curves and surfaces can be acquired through geometric transformation or correspondence that can be defined via a certain constructive algorithm.

Three-dimensional dynamic and quasi-static crack growth by a hybrid XFEM-peridynamics approach

This paper aims at presenting a hybrid computational strategy and its detailed implementation for simulation of crack propagation problems in three-dimensional (3D) solids. The key idea of the hybrid approach lies in the combination of extended finite element method (XFEM) and bond-based peridynamics (PD), which takes excellent features of the high computation efficiency by the XFEM and the flexibility by the PD in dealing with crack growth problems. The PD theory is restricted to the region where crack tips are located and cracks grow, while the XFEM theory is applied in the rest of the specimen. One of the merits of this integrated approach allows cracks to grow naturally without any fracture criteria, and it thus enhances the computation efficiency as compared to the pure PD. It additionally removes most of the problems due to the surface effects typical of nonlocal methods. Explicit integration scheme and implicit solving scheme are used for crack propagation problems under dynamic and quasi-static loading conditions. Numerical examples with 3D dynamic and quasi-static crack propagation cases are considered to show the accuracy and performance of the developed method. Reproducing the shape of the experimentally observed crack is demonstrated. For dynamic crack propagation, we additionally explore the change of the crack propagation speed during the cracking process, and the crack propagation speeds from the present method match well with the reference solutions.

A computationally efficient methodology to simulate hybrid bolted joints including thermal effects

Carbon-aluminum bolted assemblies are difficult to simulate because of the complex phenomenology involved (contact, friction, preload and thermal expansion). Therefore, accurate but computationally feasible methodologies are necessary. We propose two simplified methodologies, one based on continuum shell elements and the other on conventional shells, and compare them with a full 3D solids model. The two cases explored are a single-lap shear coupon with one bolt, and a hybrid wingbox subcomponent with 46 bolts. The effect of temperature jumps on the bolt preloads are explored. Results show that the continuum shell model presents the best tradeoff between accuracy and computational cost.

Amorphous Bi2Se3 structural, electronic, and topological nature from first principles

Crystalline ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ is one of the most explored three-dimensional (3D) topological insulators with a $0.3\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ energy gap making it promising for applications. Its amorphous counterpart could bring to light new possibilities for large scale synthesis and applications. Using ab initio molecular dynamics simulations, we have studied realistic amorphous ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ phases generated by different processes of melting, quenching, and annealing. Extensive structural and electronic characterizations show that the melting process induces an energy gap decrease ruled by growth of the defective local environments. This behavior dictates a weak stability of the topological phase to disorder, characterized by the spin Bott index. Interestingly, we identify the occurrence of topologically trivial surface states in amorphous ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ that show a strong resemblance to standard helical topological states. Our results and methods advance the search of topological phases in 3D amorphous solids.

Isogeometric analysis of 3D solids in boundary representation for problems in nonlinear solid mechanics and structural dynamics

AbstractThis contribution presents an isogeometric approach in three dimensions for nonlinear problems in solid mechanics and structural dynamics. The proposed approach aligns with the boundary representation modeling technique in CAD. Isogeometric analysis is combined with the parameterization of the scaled boundary finite element method. In this way, the boundary description of 3D solids in CAD can be directly utilized for the analysis in an isogeometric framework. The approximation of the solution on the boundary is based on bi‐variate NURBS. We also approximate the interior of the solid with uni‐variate B‐splines to facilitate the solution of nonlinear problems. The nonlinear case is extended to three dimensions in this present work. The method is further extended to dynamic problems. The mass and damping matrices are derived using the same basis functions. The solution of the entire solid is obtained with the Galerkin method. We study several nonlinear and dynamic problems with simple geometries and arbitrary number of boundaries. Moreover, a fiber reinforced composite serves as demonstration for complex shapes.

A homogenisation approach for shell structures using scaled boundary isogeometric analysis on RVE‐level

AbstractThis contribution deals with a homogenisation approach for shell structures. A coupled multiscale approach also known as FE2 is used, which satisfies the Hill‐Mandel condition. The macroscopic structure is modelled with shell elements. Assuming periodicity of the mesostructure, which fulfils the scale separation requirement, allows the definition of a representative volume element (RVE). Using the RVE, equivalent homogeneous material parameters are obtained in order to define the overall structure. The shell strains obtained on the macroscopic scale are applied to the RVE. To model the mesostructure as 3D solids, the boundary representation from CAD is adopted. Next, Isogeometric analysis (IGA) is used for the solution on the boundary. In order to analyse the interior of the solid, IGA is combined with the scaled boundary finite element method. While the boundary is approximated using NURBS functions, the interior is approximated by B‐Splines, contrary to the use of an analytical solution in classical SBFEM. As a result, nonlinear problems can be covered. Furthermore, this approach facilitates the direct use of CAD models for analysis, which is especially useful for complex geometries on the mesostructure, e.g. for modelling laminar textile structures, such as woven fabrics or laid webs. Star‐shaped domains needed for the analysis are obtained by subdivision of the overall domain. Using NURBS basis functions for the approximation of the boundary can be problematic because the position of the control points, in contrast to the nodes in FEM, does not necessarily equal the physical coordinates. To enforce prescribed boundary conditions in the framework of homogenisation, this leads to difficulties. To overcome this problem a transition element is utilized to couple the shell kinematics on the macrostructure with the 3D solid on the mesostructure. This results in a method able to use complex geometries from CAD models as representative volume elements for shell structures.

A Universal Force Field for Materials, Periodic GFN-FF: Implementation and Examination.

In this study, the adaption of the recently published molecular GFN-FF for periodic boundary conditions (pGFN-FF) is described through the use of neighbor lists combined with appropriate charge sums to handle any dimensionality from 1D polymers to 2D surfaces and 3D solids. Numerical integration over the Brillouin zone for the calculation of π bond orders of periodic fragments is also included. Aside from adapting the GFN-FF method to handle periodicity, improvements to the method are proposed in regard to the calculation of topological charges through the inclusion of a screened Coulomb term that leads to more physical charges and avoids a number of pathological cases. Short-range damping of three-body dispersion is also included to avoid collapse of some structures. Analytic second derivatives are also formulated with respect to both Cartesian and strain variables, including prescreening of terms to accelerate the dispersion/coordination number contribution to the Hessian. The modified pGFN-FF scheme is then applied to a wide range of different materials in order to examine how well this universal model performs.

TU20. APPLICATION OF REGULARISED STRUCTURAL EQUATION MODELLING TO A BIOPSYCHOSOCIAL MEDIATION MODEL

This article presents three-dimensional (3D) analysis of generally anisotropic elastic, piezoelectric, piezomagnetic, and magneto-electro-elastic solids by boundary element method (BEM). The associated Green's functions of displacements and tractions in both complex and real forms together with their first derivatives are derived completely in the first time by using Radon–Stroh formalism. Like the Stroh formalism for two-dimensional problems, the solutions for the solids with these different material types all bear exactly the same mathematical forms distinguished by the contents and dimensions of the related matrices and vectors. This feature provides a big advantage for computer programming. To emphasize the development of 3D-BEM, the system of algebraic equations to calculate the nodal displacements and nodal tractions along the boundary of 3D solids is formulated. The relations for calculating strains and stresses at the boundary nodes as well as at the interior points are also derived. After the employment of Green's functions to the newly formulated 3D-BEM, we found that the 3D-BEM with complex form solution is computationally more efficient than that with real form solution, although the opposite performance was observed for a single point calculation of Green's function. To verify the correctness of our solutions, numerical examples of a cube with or without through hole are presented as illustrations of our successful implementation in the BEM.

Fast projection ray algorithm for 3D solid space segmentation

Spatial volume element segmentation of 3D solids has a wide range of applications, but its computation is generally time-consuming. Therefore, a fast projection ray algorithm for spatial segmentation of 3D solids is proposed, which is based on a 3D to 2D projection strategy and uses a ray intersection with the 3D body surface for acceleration. The experimental results show that the algorithm can accelerate up to 20,000 times faster than the traditional octree, and can complete the segmentation of millions of spatial volume elements within seconds.

An isogeometric formulation with a three-variable high order shear deformation theory for free vibration analysis of FG porous plates reinforced by graphene platelets

We present a generalized three-variable high order shear deformation theory (THSDT) using isogeometric analysis (IGA) to analyze free vibration of functionally graded porous (FGP) plates reinforced by graphene platelets (GPLs) in this work. It is named as FGP-GPLs for a short. The proposed theory only has got three degrees of freedom (DOFs) per node as the same way of numerically solutions in three-dimensional (3D) solids. THSDT fulfills the classical plate theory (CPT), the first-order shear deformation theory (FSDT) and even the higher-order shear deformation theory (HSDT). IGA is chosen to analyze because of its noteworthy advantages in numerical computational sides of plate problems. In addition, the displacement field of THSDT needs the high continuity in approximated formulation with high-order derivatives for a weak form of fourth order equation. According to IGA formulation based on the generalized THSDT, the shear locking phenomenon is free. The variables of THSDT are less than HSDTs which contain five DOFs per node. The influences of weight fractions, the coefficient porosity, dispersion patterns of GPLs and distribution types of porosity on structure’s natural frequencies are studied through some numerical examples. In order to prove the reliability and accuracy of present method, the numerical results are compared to available published works.
 Keywords:
 FG-porous plate; graphene platelet reinforcements; three-variable high order shear deformation theory (THSDT); isogeometric analysis; free vibration.

Transition metal nitroprussides: Crystal and electronic structure, and related properties

The nitroprusside ion forms 3D, 2D, 1D, 0D and Ionic solids with monovalent and divalent transition metals, which show interesting physical properties among them, spin crossover behavior and ability for the separation and storage of small molecules. • Coordination chemistry of transition metal nitroprussides. • Electronic structure of transition metal nitroprussides. • Structural diversity of transition metal nitroprussides. • Functional properties of transition metal nitroprussides. • Thermal and environmental stability of transition metal nitroprussides. This review summarizes the state of the art on the structural features, thermal and environmental stability, physical properties and potential applications of transition metal nitroprussides, for their 3D, 2D, 1D and 0D structures. The nitroprusside ion, [Fe(CN) 5 NO] 2− , forms insoluble solids with monovalent and divalent transition metals. The crystal structure for the coordination polymers obtained with divalent metals shows a marked dependence on the used preparative route, metal nature and hydration degree, which was the origin of many incongruities in studies published a few decades ago. Nowadays, the structural features and related properties for the immense majority of the solids formed with such metal ions are known and discussed in this review. The preparation of transition metal nitroprussides using co-ligands with different coordination capability to modulate the dimensionality and related properties of the resulting solids has been on the spotlight of research during the last few years, particularly those related to atypical magnetic behavior. This subject is also herein summarized, revealing the large diversity of hybrid inorganic–organic frameworks that can be obtained with some of their physical properties only recently revealed, among them, the thermal-induced spin transition in ferrous nitroprussides containing monodentate and bridging organic ligands acting as pillar or pseudo-pillars in 2D and 3D hybrid materials. This contribution also includes a general overview of the use of spectroscopic tools such as XPS, XAS, Mössbauer, UV–vis-NIR, IR and Raman, to access electronic and structural characteristics of this family of materials. We also carried out a critical analysis of those research areas that, in our opinion, require further studies, representing opportunities to make important scientific contributions on new knowledge on this family of materials. This is the first general review on transition metal nitroprussides.

Diseño de una cabina de pulido para el área de pintura de la empresa privada METALMEIDA CIA. LTDA.

The objective of this project is to carry out the design of a polishing booth for the private company METALMEIDA CIA. LTDA. The function of a polishing booth is to aspirate the air contaminated with dust particles from the various tasks, which include: polishing, grinding and sanding of the casings of food machines and elements in general. For the execution of the mentioned project, a field investigation is carried out with the purpose of establishing the technical conditions both for the design, for the construction and for the functionality of the cabin. Based on an analysis and study, the optimal measurements for the design of the polishing booth were determined, the construction materials were also established, including: 50x50x2 square tube and 2400x1200x1 mm thick galvanized steel tol. The fan used to extract contaminated air from the cabin is of the axial type, due to technical features such as: high flow rates and low pressures. The polishing booth was designed using 3D solids software, with which a static analysis of the metal structure was carried out to determine the area with the greatest displacement, due to the load of the galvanized tol and the extractor. axial that are fastened in the upper part of the cabin, in addition the maximum value of the elastic limit was determined and finally the safety factor of the present design was obtained.

Is the surface fluid during premelting? A study of the surface shear resistance of solid Gallium

Melting of 3D solids is often preceded by a premelting of their surface, a distinct process which begins at a temperature lower than TM (bulk melting temperature). Premelting is usually investigated by non-contact techniques like diffraction or elipsometry, revealing how the surface layer becomes progressively disordered with temperature. Although this disordered surface layer is called a “quasiliquid”, in most cases (except for ice) there is no way of telling whether it is a fluid or a disordered solid. One significant difference between these two states is in their resistance to shear, which should decrease if the surface becomes fluid. To address this question, we developed a mechanical method to measure the effective shear resistance of a metal surface. This property was not measured before. We applied this method to the surface of polycrystalline Gallium, and found that the surface shear resistance vanishes abruptly near the onset of premelting, about 9K below TM. This result confirms that the quasiliquid on the surface of Ga is a fluid.

Three dimensional nonlinear BEM formulations for the mechanical analysis of nonhomogeneous reinforced structural systems

This study presents a coupling formulation for the mechanical modelling of nonhomogeneous reinforced 3D structural systems. The coupling of dissimilar reinforced materials and components provides efficient designs. Particularly, it enables high stiffness and low weight mechanical components, which are largely desired in several engineering applications. In the present study, the Boundary Element Method (BEM) mechanically represents 3D solids through elastic and viscoelastic approaches. The 1D truss BEM elements represent the reinforcements, which allow for elastoplastic behaviour. The sub-region BEM technique models the nonhomogeneous systems whereas connection 1DBEM elements allow for crossing reinforcements along materials interfaces. Bond-slip behaviour has been accounted in the formulation by a nonlinear scheme without special link elements. Different bond-slip laws can be accounted, which enables the mechanical modelling of different adherence behaviours. The proposed formulations are applied in the mechanical analysis of four complex 3D applications. The results achieved by the proposed formulations are compared against the responses of equivalent numerical methods and experimental results available in the literature. The proposed formulations lead to accurate and stable results. Besides, the applications complexity demonstrates it.

Critical phase-transition temperature for freezing stress in thermo-sensitive photopolymers used for visualizing stress fields in solids

Quantitative visualization of the hidden full-field stresses in three-dimensional (3D) solids is crucial for solving various engineering problems; however, it is challenging to achieve using the conventional experimental techniques. Frozen stress technique is an effective method to characterize internal stress fields. However, difficulties in fabricating the complex 3D models impede the extension of this method. The method combining additive manufacturing or 3D printing, printable transparent photopolymers, and frozen stress techniques provides a new approach to overcome these challenges. However, the effects of continuous temperature rise and loading during the frozen stress tests on the stress birefringence of the thermo–sensitive photopolymers have not been studied thoroughly. In this study, the stress birefringence characteristics of the photopolymers were examined using 3D printed transparent disk models and frozen stress tests under various temperatures and radial loads. A reflection polariscope system incorporated with a high-temperature loading chamber was designed to freeze and capture the stress fringes in the printed model. The thermo–optic curve, stability of full-field fringes, and elasticity and plasticity of the photopolymer under high temperatures and remaining loads were investigated. The effects of high temperatures and remaining loads on the stability of the fringe orders were analyzed. The linear relationship between the fringes and stresses in the material was verified using the fringe orders in the central points of the disk models. The critical temperatures that discriminate between the three different thermo–stress states, i.e., glassy state, transition state, and freezing state, were discussed. Our results indicate that the lowest critical temperature for freezing stresses in the tested photopolymer is 80 °C.