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New Data for Research on the Early Bronze Age in Northern Poland (2350-1600 BC) This paper reports on archived archaeological material and some recent discoveries of stray finds from north-central Poland that can be dated to the Early Bronze Age, mostly from the site of Lachmirowice in the Kuyavia region, including ceramic vessels and a stone tool identified as an arrow shaft straightener. The other objects analysed are two clay tuyeres from Chełmno land (Culm) and three bronze daggers from the region of Greater Poland and Mazovia, which can be connected to the Úněticean metal industry. To improve the quality of the information on the artefacts, we determined their chemistry and technology and combined this with the stylistic and technological trajectories of the era. The results obtained add information about the beginnings of the Bronze Age in northern Poland and help to better understand how the local post-Neolithic communities in this region were being integrated within the Bell Beaker and Úněticean milieu., Archäologisches Korrespondenzblatt, Bd. 51 Nr. 4 (2021): Archäologisches Korrespondenzblatt

Even though the central role of mechanics in cardiovascular system is widely recognized, estimating mechanical deformation and strains in-vivo remains an ongoing practical challenge. Herein, we present a semi-automated framework to estimate strains from four-dimensional (4D) echocardiography images and apply it to the aortic roots of patients with normal trileaflet aortic valves (TAV) and congenital bicuspid aortic valves (BAV). The method is based on fully nonlinear shell-based kinematics, which divides the strains into in-plane (shear and dilatational) and out-of-plane components. The results indicate that, even for size-matched non-aneurysmal aortic roots, BAV patients experience larger regional shear strains in their aortic roots. This elevated strains might be a contributing factor to the higher risk of aneurysm development in BAV patients. The proposed framework is openly available and applicable to any tubular structures.

Celem artykułu jest ekonomiczna analiza motywacji i sposobów działania przemytników oraz migrantów poprzez weryfikację hipotezy stanowiącej, że zwalczanie nielegalnego przemytu migrantów jest niezwykle trudne ze względu na wzajemne korzyści czerpane przez uczestników transakcji zawieranych na rynku usług wspierających migracje. Dodatkowo korzyści te wynikają z systematycznego ograniczania ryzyka nadużycia praw człowieka w trakcie migracji pod wpływem czynników rynkowych i technologicznych. Czynniki ekonomiczne decydują o wysokim poziomie zdolności dostosowawczych rynku przemytu migrantów do stosowanych instrumentów polityki migracyjnej, nie tylko przez elastyczne ceny, ale także przez przerzucanie kosztów na migrantów. W rezultacie zaostrzona polityka migracyjna Unii Europejskiej może doprowadzić do pogorszenia przestrzegania standardów praw człowieka w procesie przemytu migrantów.

A three-dimensional hierarchic finite element-based computational framework is developed for the investigation of inter-laminar stresses and displacements in composite laminates of finite width. As compared to the standard finite elements, hierarchic finite elements allow to change the order of approximation both locally and globally without modifying the underlying finite element mesh leading to very accurate results for relatively coarse meshes. In this paper, both symmetric cross-ply and angle-ply laminates subjected to uniaxial tension are considered as test cases. Tetrahedral elements are used for the discretisation of laminates and uniform or global p-refinement is used to increase the order of approximation. Each ply within laminates is modelled as a linear-elastic, homogenous and orthotropic material. With increasing the order of approximation, the developed computational framework is able to capture the complex profiles of inter-laminar stresses and displacements very accurately. Results are compared with reference results from the literature and found in a very good agreement. The computational model is implemented in our in-house finite element software library Mesh-Oriented Finite Element Method (MoFEM). The computational framework has additional flexibly of high-performance computing and makes use of the state-of-the-art computational libraries including Portable, Extensible Toolkit for Scientific Computation (PETSc) and the Mesh-Oriented datABase (MOAB).

This paper is a summary of the design and workmanship of a Formula Student transmission system vehicle. We conducted simulation research on transmission system damage. Damage occurred during the Formula Student competition, which is why we needed to improve the drivetrain system. The article proposes a variant of the change brackets and carrying out simulation studies on the new construction. For selected models, the transmission system, which is also determined by its impact on strength and reliability, is driven by a four-cylinder engine with a displacement of 0.6 dm3.

No abstract available.

This report contains a brief descriptionof of Moving Weighted Least Squares Approximation implementation in MoFEM. The approach is used for projecting data between different finite element meshes or ct scan data. The performance of the approach is demonstrated on two examples.&nbsp

Thin fluid flow in contact interfaces between solids with rough surfaces is often described by the Reynolds equation, known to overestimate the fluid velocity in fractures compared to fullNavier-Stokesequations (NSE). The resolution of NSE is difficult if a fine surface discretisation is needed and/or if contact is taken into account. We propose a novel approach considering the flow governed by NSE in a single layer of prism elements. Using the hierarchical basis approximation, we can interpolate the velocity profile across the thickness by polynomials of an arbitrary order.

We present an implementation of the finite-element method with hierarchical basis functions of arbitrary order for simulating incompressible steady-state fluid flow governed by Navier-Stokes equations (NSE). To verify the proposed formulation, we solved a problem of the fluid flow around a rigid sphere considering different velocity magnitudes. For a low-Reynolds-number flow the result coincides with the analytical solution for the Stokes flow, while for a higher Reynolds number a vortex is formed behind the sphere. The developed framework can be used to study the fluid flow in contact interfaces between solids with rough surfaces (e.g. in fractures) and compare the effect of the model describing the fluid flow (Reynolds, Stokes, or full NSE) on the transmissivity of these interfaces. The development is undertaken in MoFEM., {"references":["L. Kaczmarczyk, Z. Ullah, K. Lewandowski, X. Meng, X.-Y. Zhou, C. Pearce, I. Athanasiadis, H. Nguyen, C.-A. Chalons-Mouriesse, and E. Miur. Mofem-v0.8.16, November 2018. http://mofem.eng.gla.ac.uk.","M. Ainsworth and J. Coyle. Hierarchic finite element bases on unstructured tetrahedral meshes. International Journal for Numerical Methods in Engineering, 58(14), 2003.","H. Bériot, A. Prinn, and G. Gabard. Efficient implementation of high-order finite elements for helmholtz problems. International Journal for Numerical Methods in Engineering, 106(3), 2016.","F. Fuentes, B. Keith, L. Demkowicz, and S. Nagaraj. Orientation embedded high order shape functions for the exact sequence elements of all shapes. Computers & Mathematics with Applications, 70(4), 2015.","G.K. Batchelor. An introduction to fluid dynamics. Cambridge University Press, 1967.","O.C. Zienkiewicz and R.L. Taylor. The finite element method: the basis, volume 1. Butterworth- Heinemann, 2000.","S.R. Brown, H.W. Stockman, and S.J. Reeves. Applicability of the Reynolds equation for modeling fluid flow between rough surfaces. Geophysical Research Letters, 22(18), 1995."]}

This paper presents a mathematical formulation and numerical modelling framework for brittle crack propagation in heterogeneous elastic solids. Such materials are present in both natural and engineered scenarios. The formulation is developed in the framework of configurational mechanics and solved numerically using the finite-element method. We show the methodology previously established for homogeneous materials without the need for any further assumptions. The proposed model is based on the assumption of maximal dissipation of energy and uses the Griffith criterion; we show that this is sufficient to predict crack propagation in brittle heterogeneous materials, with spatially varying Young’s modulus and fracture energy. Furthermore, we show that the crack path trajectory orientates itself such that it is always subject to Mode-I. The configurational forces and fracture energy release rate are both expressed exclusively in terms of nodal quantities, avoiding the need for post-processing and enabling a fully implicit formulation for modelling the evolving crack front and creation of new crack surfaces. The proposed formulation is verified and validated by comparing numerical results with both analytical solutions and experimental results. Both the predicted crack path and load–displacement response show very good agreement with experiments where the crack path was independent of material heterogeneity for those cases. Finally, the model is successfully used to consider the real and challenging scenario of fracture of an equine bone, with spatially varying material properties obtained from CT scanning.This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.

This paper presents a hierarchic finite element-based computational framework for the multi-scale modelling of composite laminates. Hierarchic finite elements allow changing the approximation order locally or globally without changing the underlying finite element mesh. Both micro- and macro-level structures are discretised with these elements. The macro-level structures of composite laminates are divided into several blocks during the pre-processing stage, and approximation orders are assigned to each block independently. Due to a sharp increase in the interlaminar stresses, higher approximation orders are used in the vicinity of free edges as compared to the rest of the problem domain. This freedom of assigning approximation orders independently to each block provides an efficient and accurate way for modelling composite laminates. The computation framework can either accept the user-defined ply-level homogenised elastic material properties or calculates these directly from the underlying representative volume element consisting of matrix and fibre using the computational homogenisation. The model developed for the computational homogenisation has the flexibility of unified imposition of representative volume element boundary conditions, which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. The computational framework has additional flexibly of high-performance computing and makes use of state-of-the-art computational libraries including Portable, Extensible Toolkit for Scientific Computation (PETSc) and the Mesh-Oriented datABase (MOAB). Symmetric cross-ply, angle-ply and quasi-isotropic laminates subjected to uniaxial loading are used as test cases to demonstrate the correct implementation and computational efficiency of the developed computational framework.

Description of developed mortar contact approach for hierarchical basis function in the regime of small strains and small tangential displacements within MoFEM.

This paper presents a multiscale computational homogenisation approach for the calculation of homogenised structural level mechanical properties of 3D textile/woven based fiber reinforced polymer (FRP) composites. Textile or woven composites, in which interlaced fibres are used as reinforcement, are a class of FRP composites which provide flexibility of design and functionality and are used in many engineering applications, including ships, aircrafts, automobiles, civil structures and prosthetics [1]. The more recently developed 3D-textile composites, consisting of 3D arrangements of yarns in a polymer matrix, allow weaving of near-net-shape and complex structures as compared to the traditional 2D-textile composites. In addition, these 3D-textile composites provide high through-thickness mechanical properties, lower manufacturing cost and improved impact and delamination resistance. The macro or structural level mechanical properties of these composites are rooted in their underlying complicated and heterogeneous micro structures. The heterogeneous microstructure of these composites requires a detailed multiscale computational homogenisation, which results in the macroscopic constitutive behaviour based on their microscopically heterogeneous representative volume elements (RVE). Elliptical cross sections and cubic splines are used respectively to model the cross sections and paths of the yarns within these RVEs. The RVE geometry along with other input parameters, e.g. material properties and boundary conditions, are modelled in CUBIT/Trelis using a parameterised Python script. The multiscale computational homogenisation scheme, with a unified imposition of RVE boundary conditions, is implemented in MoFEM (Mesh Oriented Finite Element Method) [2], which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. MoFEM utilises hierarchic basis functions [3], which permits the use of arbitrary order of approximation leading to accurate results for relatively coarse meshes. The matrix and yarns within the RVEs are modelled by considering isotropic and transversely isotropic materials models respectively. The principal direction of the yarns required for the transversely isotropic material model is calculated using a computationally inexpensive potential flow analysis along these yarns. Furthermore, the computational framework is designed to take advantage of distributed memory high-performance computing. The implementation and performance of the computational tool is demonstrated with a variety of 2.5D and 3D woven based FRP composites including 3D orthogonal interlock, 3D orthogonal layer-to-layer interlock, 3D orthogonal through-the-thickness angle interlock, 2.5D layer-to-layer angle interlock and 2.5D layer-layer angle interlock [4]. Keywords: Fiber reinforced polymer composites, 3D textile/woven composites, Finite element analysis, Multiscale computational homogenization. References: [1] Z. Ullah, Ł. Kaczmarczyk, S. A. Grammatikos, M. C. Evernden and C. J. Pearce (2016). Multi-scale computational homogenisation to predict the long-term durability of composite structures. Computers and Structures, 181 . pp. 21- 31. [3] Ł. Kaczmarczyk, Z. Ullah, K. Lewandowski, X. Meng, X. -Y. Zhou, I. Athanasiadis, I and C. J. Pearce (2017). MoFEM-v0.6.20. Zenodo. http://doi.org/10.5281/zenodo.1053811 [3] M. Ainsworth and J. Coyle (2003). Hierarchic finite element bases on unstructured tetrahedral meshes. International Journal for Numerical Methods in Engineering, 58 (14): 2103–2130, [4] Y. Rahali, M. Assidi, I. Goda, A. Zghal, and J. F. Ganghoffer (2016). Computation of the effective mechanical properties including nonclassical moduli of 2.5 D and 3D interlocks by micromechanical approaches. Composites Part B: Engineering, 98, 194-212.

This presentation encompassesdescription of the unilateral contact problem andoverview ofpast workontied mesh problem on small strain elasticity[1]. Furthermore, author's future work ispresented, thatfocusesonfrictionless unilateral contact of bodies withplanar surfaces. All analyseswere performed withMoFEM. [1] Ullah Z, Kaczmarczyk Ł,Pearce CJ. Three-dimensional mortar contact formulation: an efficient and accurate numerical implementation. In: Proceedings of the 25nd UK conference of the association for computational mechanics in engineering 12 - 13 April 2017, Birmingham:University of Birmingham2017.

A solid-shell element which does not possess rotational degrees of freedom (DOFs) and which is applicable to thin plate/shell problems is considered. The element approximation is constructed in prisms, where displacements on the upper and lower surfaces are approximated in the global coordinate system. In addition, two other fields are defined in the shell natural (local) coordinate system that represent the components of the displacement vector in both the current shell normal direction and the current shell tangent plane. To each field, an arbitrary order of approximation can be defined, and all fields reproduce a complete and conforming polynomial approximation basis for the solid prism element. It is not necessary to augment the formulation with an assumed natural strain (ANS) field or enhanced assumed strain (EAS) field or to use reduced integration, making the element ideally suited for geometrically and physically nonlinear problems., mofem.eng.gla.ac.uk

In this paper the development of efficient computational method for Helmholtz equation is presented. Here we solve the Helmholtz equation in the frequency domain, applying hierarchical finite element approximation with generalized Duffy transformation based on unstructured meshes, where both pressure field and geometry are independently approximated with arbitrary and heterogeneous polynomial order. We demonstrate the implementation and performance of the numerical approach by benchmark problems, especially under pollution effects, which also validate the accuracy and efficiency of an object oriented a priori error estimator through numerical assessments.

This paper presents a method for identification of cell forces. We propose both a local and non-local method. The former assumes rotation free field of surface tractions, while the latter introduces an intrinsic length scale parameter, such that cells can locally apply a moment on the material surface. This paper focuses attention on a numerical aspect of force identification without investigating, at this stage, the true nature of that forces.

SUMMARY This paper presents a computational framework for quasi-static brittle fracture in three-dimensional solids. The paper sets out the theoretical basis for determining the initiation and direction of propagating cracks based on the concept of configurational mechanics, consistent with Griffith's theory. Resolution of the propagating crack by the FEM is achieved by restricting cracks to element faces and adapting the mesh to align it with the predicted crack direction. A local mesh improvement procedure is developed to maximise mesh quality in order to improve both accuracy and solution robustness and to remove the influence of the initial mesh on the direction of propagating cracks. An arc-length control technique is derived to enable the dissipative load path to be traced. A hierarchical hp-refinement strategy is implemented in order to improve both the approximation of displacements and crack geometry. The performance of this modelling approach is demonstrated on two numerical examples that qualitatively illustrate its ability to predict complex crack paths. All problems are three-dimensional, including a torsion problem that results in the accurate prediction of a doubly-curved crack. Copyright © 2013 John Wiley & Sons, Ltd.

Two examples illustrating microstructural size effect and higher-order deformation are considered within the context of second-order computational homogenization. Governing equations and appropriate discretization are briefly reviewed, including the scale transition equations and the enforcement of generalised boundary conditions for the RVE (representative volume element). The first example serves as a means of validation for second-order computational homogenization and highlights the difference in terms of higher-order deformation of the RVE between the first and second-order schemes. The second example (indentation test) focuses on microstructural size effect, whereby the result is shown to be dependent on the intrinsic length of the RVE.

This paper presents a numerical multiscale modelling strategy for simulating fracturing in materials where the fine-scale heterogeneities are fully resolved, with a particular focus on concrete. The fine-scale is modelled using a hybrid-Trefftz stress formulation for modelling propagating cohesive cracks. The very large system of algebraic equations that emerges from detailed resolution of the fine-scale structure requires an efficient iterative solver with a preconditioner that is appropriate for fracturing heterogeneous materials. This paper proposes a two-grid strategy for construction of the preconditioner that utilizes scale transition techniques derived for computational homogenization and represents an adaptation of the work of Miehe and Bayreuther [2] and its extension to fracturing heterogeneous materials. For the coarse scale, this paper investigates both classical C 0 -continuous displacement-based finite elements as well as C 1 -continuous elements. The preconditioned GMRES Krylov iterative solver with dynamic convergence tolerance is integrated with a constrained Newton method with local arc-length control and line searches. The convergence properties and performance of the parallel implementation of the proposed solution strategy is illustrated on two numerical examples.

This paper presents a corotational hybrid-Trefftz formulation for modelling propagating cohesive cracks and captures moderate rotations but small strains. The formulation is characterised by the fact that stresses are approximated within the domain of the element and the stiffness can be expressed via a boundary rather than a domain integral. Thus, compared to their FEM counterpart, hybrid-Trefftz stress elements exhibit faster convergence of the stress fields. Furthermore, the displacements are approximated on element boundaries and the displacement basis is defined independently on each element interface. Thus, the overall bandwidth of the stiffness matrix is very small and computationally efficient to solve. A corotational formulation for hybrid-Trefftz elements is also introduced in order to capture the effect of geometric nonlinearities in the form of moderate rotations. The model’s performance is demonstrated on three examples, illustrating crack propagation and the influence of geometric nonlinearities.

In the analysis of composite materials with heterogeneous microstructures, full resolution of the heterogeneities using classical numerical approaches can be computationally prohibitive. This paper presents a micromechanics-enhanced finite element formulation that accurately captures the mechanical behaviour of heterogeneous materials in a computationally efficient manner. The strategy exploits analytical solutions derived by Eshelby for ellipsoidal inclusions in order to determine the mechanical perturbation fields as a result of the underlying heterogeneities. Approximation functions for these perturbation fields are then incorporated into a finite element formulation to augment those of the macroscopic fields. A significant feature of this approach is that the finite element mesh does not explicitly resolve the heterogeneities and that no additional degrees of freedom are introduced. In this paper, hybrid-Trefftz stress finite elements are utilised and performance of the proposed formulation is demonstrated with numerical examples. The method is restricted here to elastic particulate composites with ellipsoidal inclusions but it has been designed to be extensible to a wider class of materials comprising arbitrary shaped inclusions., 28 pages, 12 figures, 2 tables

This paper presents a formulation for the three-dimensional numerical simulation of mechanically regulated bone adaptation. Attention is focussed on a phenomenologically-based approach to bone remodelling that can be used as a computationally efficient tool to provide insight into the overall response of bone to mechanical loading. A discretisation approach is developed based on a hybrid finite element formulation where displacement, stress and density fields are approximated independently. The paper also discusses a solution algorithm tailored for shared memory multi-core computers. The performance of the model is demonstrated by two numerical examples.

Formulation of the scale transition equations coupling the microscopic and macroscopic variables in the second-order computational homogenization of heterogeneous materials and the enforcement of generalized boundary conditions for the representative volume element (RVE) are considered. The proposed formulation builds on current approaches by allowing any type of RVE boundary conditions (e.g. displacement, traction, periodic) and arbitrary shapes of RVE to be applied in a unified manner. The formulation offers a useful geometric interpretation for the assumptions associated with the microstructural displacement fluctuation field within the RVE, which is here extended to second-order computational homogenization. A unified approach to the enforcement of the boundary conditions has been undertaken using multiple constraint projection matrices. The results of an illustrative shear layer model problem indicate that the displacement and traction RVE boundary conditions provide the upper and lower bounds of the response determined via second-order computational homogenization, and the solution associated with the periodic RVE boundary conditions lies between them.