Dynamics of structures

Dynamic problems for metamaterials: Review of existing models and ideas for further research

Mechanical mismatches between implanted electronics and biological tissues can lead to inaccurate readings and long-term tissue damage. Here, we show that functionalized multi-walled carbon nanotubes twisted into helical fibre bundles that mimic the hierarchical structure of muscle can monitor multiple disease biomarkers in vivo. The flexible fibre bundles are injectable, have a low bending stiffness and display ultralow stress under compression. As proof-of-concept evidence of the sensing capabilities of these fibre bundles, we show that the fibre bundles enable the spatially resolved and real-time monitoring of H2O2 when implanted in tumours in mice, and that they can be integrated with a wireless transmission system on an adhesive skin patch to monitor calcium ions and glucose in the venous blood of cats for 28 d. The versatility of the helical fibre bundles as chemically functionalized electrochemical sensors makes them suitable for multiple sensing applications in biomedicine and healthcare. Functionalized multi-walled carbon nanotubes twisted into helical fibre bundles that mimic the hierarchical structure of muscle can be used for the long-term monitoring of multiple disease biomarkers in vivo.

Functionalized helical fibre bundles of carbon nanotubes as electrochemical sensors for long-term in vivo monitoring of multiple disease biomarkers

Numerical simulation and experimental validation of the dynamic response of aluminum plates under free air explosions

Thermomechanical postbuckling of shear deformable laminated cylindrical shells with local geometric imperfections

A numerical mesh-free model applied to a strong formulation for simulating elasto-plastic structures with contact is developed in the context of large deformation. This numerical mesh-free model is based on the Asymptotic Numerical Method (ANM) which is used in the meshless collocation framework to extend its application field to elasto-plastic problems with contact. The efficiency of this model is to take into account of large deformations and to avoid the meshing distortion problem. According to (ANM) techniques, the development in Taylor series is performed to obtain a sequence of linear systems to be solved. These linear systems are then discretized by a collocation meshless approach by using the Moving Least Squares (MLS) functions and a continuation method is adopted to evaluate the solution. The unilateral contact problem is identified to boundary conditions which are replaced by force-displacement relations through a regularization technique. The performance of the proposed approach is tested on several elasto-plastic bi-dimensional examples without and with contact. The obtained results are compared to those computed by the Newton–Raphson method.

A numerical mesh-free model for elasto-plastic contact problems

A semi-analytical buckling analysis of imperfect cylindrical shells under axial compression

In this paper a high order implicit algorithm is developed for solving instationary non-linear problems. This generic numerical method combines four mathematical techniques: a time discretization, a homotopy transformation, a perturbation technique and a space discretization. The time integration is performed by classical implicit schemes (Euler implicit for problems with a first order time derivative and Newmark for second order). The time-discretization leads to non-linear equations. In this paper a new technique is proposed to solve iteratively the latter equations. The key points in this approach are, first a high order solver based on perturbation techniques, second the possibility of choosing the iteration operator, which limits the number of matrices to be triangulated. To illustrate the performance of the proposed algorithm two examples are considered: the Korteweg-de Vries equation (KdV) and the non-linear oscillations of a 2D elastic pendulum.

A high order implicit algorithm for solving instationary non-linear problems

Influence of localized imperfections on the buckling of cylindrical shells under axial compression

This work concerns numerical simulations of the frictional contact of two elastic deformable bodies and a novel treatment technique of incompatible contact nodes. These numerical simulations are based on a high order mesh-free method coupling the Moving Least Square (MLS) with the Asymptotic Numerical Method (ANM) and on a regularization technique. The obtained nonlinear problem is solved by using ANM applied on strong formulation in order to avoid numerical integrations. According to ANM, the Taylor series development of unknown variables on nodes of nonlinear contact problem leads to a sequence of linear systems to be solved. These linear systems are then discretized by a collocation mesh-free approach by using the MLS functions and a continuation method is adopted to evaluate the solution. The contact problem is identified to boundary conditions which are replaced by force-displacement relations through a regularization technique. The ability of the proposed approach is tested on some contact elastic deformable bi-dimensional examples. The obtained results are compared to an analytical solution and to a numerical solution obtained by the Newton–Raphson method coupled also with MLS approximation.

Mohammad Jamal

Papers

A numerical mesh-free model for elasto-plastic contact problems

A semi-analytical buckling analysis of imperfect cylindrical shells under axial compression

A high order implicit algorithm for solving instationary non-linear problems

Influence of localized imperfections on the buckling of cylindrical shells under axial compression

High order mesh-free method for frictional contact