Presentation at 1st GCEC meeting: Unilateral contact for small strains deformation using mortar method

<p>This presentation encompasses description of the unilateral contact problem and overview of past work on tied mesh problem on small strain elasticity [1]. Furthermore, author's future work is presented, that focuses on frictionless unilateral contact of bodies with planar surfaces. All analyses were performed with MoFEM.</p> <p>[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 Birmingham 2017.</p

Brittle crack propagation intersecting a contact interface within the framework of Arbitrary Lagrangian-Eulerian description of motion

Configurational mechanics provides the theoretical basis for modelling thermodynamically consistent crack propagation in brittle materials. Using the Arbitrary Lagrangian-Eulerian (ALE) formulation, material kinematics that describe crack surface increment are coupled with spatial kinematics that describe elastic body deformation. To include the contact interaction into the model, a mortar-like formulation was exploited. While the crack surface is distant from the contact interface, contact elements act only in the spatial domain. However, once the crack surface is in the proximity of the contact zone, additional considerations are needed. Firstly, mesh cutting and mesh smoothing due to evolution of the crack surface affect the position of nodes in the material domain, requiring reconstruction of contact elements. Secondly, once the crack front reaches the contact interface, contact pressure provides an additional contribution to configurational forces driving the crack propagation. Therefore, topological changes due to crack propagation and evolution of contact surfaces are strongly coupled. Here we present for the first time the solution of this coupled problem using a monolithic approach. Examples are considered demonstrating the robustness of the proposed framework and evaluating the effect of the contact loading on the crack propagation.</div

Data-driven finite element method

The standard approach to mechanical problems requires the solution to the mathematical equations that describe both the conservation laws and the constitutive relationships, where the latter is obtained after fitting experimental data to a certain material model. In this work, we follow an alternative approach, and develop a Data-Driven (DD) framework for mechanical problems. The conservation laws are satisfied by means of the finite element method; instead of a constitutive relationship we can use experimental data directly, thereby avoiding the need for material model parameters. In this paper, the DD approach is applied to a flow problem in porous media. We present the solution algorithm, demonstrate its efficiency with numerical examples, and, finally, study the influence of the noise present in the data on the results. The framework has been implemented in the open-source finite element software MoFEM

Finite-element modelling of triboelectric nanogenerators accounting for surface roughness

Triboelectric nanogenerators (TENG) transform mechanical energy into electrical energy as a result of contact between suitably chosen surfaces. Surface roughness plays a key role in the performance of contactseparation TENG, defining the ratio of real contact area to the apparent one for a given contact force. We develop a novel numerical approach for coupling mechanical contact and electrostatics equations to simulate TENG behaviour using the finite-element library MoFEM. Good qualitative agreement is found between the numerical predictions of the proposed method, available experimental data and approximate analytical models. The developed finite-element framework can be used for further study of the effect of various TENG parameters on the output performance