David Dureisseix

An Overview of Mechanisms and Patterns with Origami

Origami (paperfolding) has greatly progressed since its first usage for design of cult objects in Japan, and entertainment in Europe and the USA. It has now entered into artistic areas using many other materials than paper, and has been used as an inspiration for scientific and engineering realizations. This article is intended to illustrate several aspects of origami that are relevant to engineering structures, namely: geometry, pattern generation, strength of material, and mechanisms. It does not provide an exhaustive list of applications nor an in-depth chronology of development of origami patterns, but exemplifies the relationships of origami to other disciplines, with selected examples.

Design and Analysis of a Foldable/Unfoldable Corrugated Architectural Curved Envelop

Origami and paperfolding techniques may inspire the design of structures that have the ability to be folded and unfolded: their geometry can be changed from an extended, servicing state to a compact one, and back-forth. In traditional origami, folds are introduced in a sheet of paper (a developable surface) for transforming its shape, with artistic, or decorative intent; in recent times the ideas behind origami techniques were transferred in various design disciplines to build developable foldable/unfoldable structures, mostly in aerospace industry (Miura, 1985, “Method of Packaging and Deployment of Large Membranes in Space,” Inst. Space Astronaut. Sci. Rep., 618 , pp. 1–9; Ikema , 2009, “Deformation Analysis of a Joint Structure Designed for Space Suit With the Aid of an Origami Technology,” 27th International Symposium on Space Technology and Science (ISTS)). The geometrical arrangement of folds allows a folding mechanism of great efficiency and is often derived from the buckling patterns of simple geometries, like a plane or a cylinder (e.g., Miura-ori and Yoshimura folding pattern) (Wu , 2007, “Optimization of Crush Characteristics of the Cylindrical Origami Structure,” Int. J. Veh. Des., 43 , pp. 66–81; Hunt and Ario, 2005, “Twist Buckling and the Foldable Cylinder: An Exercise in Origami,” Int. J. Non-Linear Mech., 40 (6), pp. 833–843). Here, we interest ourselves to the conception of foldable/unfoldable structures for civil engineering and architecture. In those disciplines, the need for folding efficiency comes along with the need for structural efficiency (stiffness); for this purpose, we will explore nondevelopable foldable/unfoldable structures: those structures exhibit potential stiffness because, when unfolded, they cannot be flattened to a plane (nondevelopability). In this paper, we propose a classification for foldable/unfoldable surfaces that comprehend non fully developable (and also non fully foldable) surfaces and a method for the description of folding motion. Then, we propose innovative geometrical configurations for those structures by generalizing the Miura-ori folding pattern to nondevelopable surfaces that, once unfolded, exhibit curvature.

Distributed Nonsmooth Contact Domain Decomposition (NSCDD): Algorithmic Structure and Scalability

Numerical simulations of the dynamics of discrete structures in presence of numerous impacts with frictional contacts leads to CPU-intensive large time computations. To deal with these problems, numerical tools have been developed, such as the nonsmooth contact domain decomposition (NSCDD). We present further a distributed version of its algorithm with parallel detection of fine contacts and discuss two possible communication schemes to solve the interface problem. Those improvements allow to study scalability and numerical performances of the method for 2D and 3D granular media.

An Experimental Study and Model Determination of the Mechanical Stiffness of Paper Folds

Over the past few decades, folding paper has extended beyond the origami deployable applications to reach the engineering field. Nevertheless, mechanical information about paper behavior is still lacking, especially during folding/unfolding. This article proposes an approach to characterize the paper fold behavior in order to extract the material data that will be needed for the simulation of folding and to go a step further the single kinematics of origami mechanisms. The model developed herein from simple experiments for the fold behavior relies on a macroscopic local hinge with a nonlinear torsional spring. Though validated with only straight folds, the model is still applicable in the case of curved folds thanks to the locality principle of the mechanical behavior. The influence of both the folding angle and the fold length is extracted automatically from a set of experimental values exhibiting a deterministic behavior and a variability due to the folding process. The goal is also to propose a methodology that may extend the simple case of the paper crease, or even the case of thin material sheets, and may be adapted to other identification problems.

A mortar-based mesh interface for hybrid finite element/lumped parameter gear dynamic models - Applications to thin-rimmed geared systems.

An original hybrid gear model is introduced, which combines lumped parameter and finite elements along with a specific interface aimed at coupling mismatched discrete models. A mortar-based interface is presented, which eliminates the numerical errors induced by direct collocations between the tooth contact and gear body models. It is shown that the proposed interface can capture the instant contact conditions in the profile and lead directions for both spur and helical gears. A number of quasi-static and dynamic simulation results are presented, which illustrate the potential and practical interest of the methodology. It is observed that thin rims are more influential in the case of helical gears and that the overall dynamic tooth loads seem largely uncoupled from the local contact conditions on the teeth.

Prediction of the intramembranous tissue formation during perisprosthetic healing with uncertainties. Part 2. Global clinical healing due to combination of random sources

This work proposes to examine the variability of the bone tissue healing process in the early period after the implantation surgery. The first part took into account the effect of variability of individual biochemical factors on the solid phase fraction, which is an indicator of the quality of the primary fixation and condition of its long-term behaviour. The next issue, addressed in this second part, is the effect of cumulative sources of uncertainties on the same problem of a canine implant. This paper is concerned with the ability to increase the number of random parameters to assess the coupled influence of those variabilities on the tissue healing. To avoid an excessive increase in the complexity of the numerical modelling and further, to maintain efficiency in computational cost, a collocation-based polynomial chaos expansion approach is implemented. A progressive set of simulations with an increasing number of sources of uncertainty is performed. This information is helpful for future implant design and decision process for the implantation surgical act.

Fast Solution of Transient Elastohydrodynamic Line Contact Problems Using the Trajectory Piecewise Linear Approach

In order to obtain a fast solution scheme, the trajectory piecewise linear (TPWL) method is applied to the transient elastohydrodynamic (EHD) line contact problem for the first time. TPWL approximates the nonlinearity of a dynamical system by a weighted superposition of reduced linearized systems along specified trajectories. The method is compared to another reduced order model (ROM), based on Galerkin projection, Newton–Raphson scheme and an approximation of the nonlinear reduced system functions. The TPWL model provides further speed-up compared to the Newton–Raphson based method at a high accuracy.

Domain decomposition with discrete element simulations using shared-memory parallel computing for railways applications

Numerical simulation with discrete elements leads to several issues for large-scale problems and long loading times, as for the granular dynamic simulations of the ballasted railway behaviour. To reduce computational costs, we study the use of two strategies: domain decomposition methods and shared-memory parallelisation with OpenMP. An example of a maintenance process, the tamping, on a portion of railway track with seven sleepers, is simulated. La simulation numérique par éléments discrets présente des difficultés pour l’étude de problèmes de grande taille et en temps de sollicitation long, comme la dynamique des milieux granulaires pour le ballast ferroviaire. Afin de résoudre ce problème à moindre coût, on propose d’allier deux stratégies: la décomposition de domaine (DDM) et le calcul parallèle (en mémoire partagée avec OpenMP). Un exemple traitant d’un procédé de maintenance ferroviaire, le bourrage, sur une portion de voie ballastée de 7 blochets de long est étudié.

FFT-Based Methods for Solving a Rough Adhesive Contact: Description and Convergence Study

The contact problem of a semi-infinite elastic body with a rigid rough surface with adhesive forces is modeled using a boundary element method (BEM). An original theoretical framework for this problem is presented. Four original BEM algorithms are studied, for both prescribed normal pressure and prescribed penetration, in primal and dual forms. They are all based on a conjugate gradient iterative solver. For each case, the solver is finely tuned to tackle the current problem. Using fast Fourier transforms (FFT) speeds up the computation of the matrix–vector multiplications. A new way of computing the coefficients of the conjugate gradient solver which reduces the number of FFTs at each step is presented. The stability and efficiency of the different methods are compared, showing a great sensitivity to the Tabor coefficient and to the contact area ratio. The most stable algorithm proved to be reliable for very large-scale computations through a participation to M. Mueser’s Contact Mechanics Challenge.

Transient Thermal Elastohydrodynamic Modeling of Cam–Follower Systems: Understanding Performance

ABSTRACT This article deals with the lubrication of cam–follower contacts in automobile racing applications. Time-dependent thermal elastohydrodynamic line contact simulations are performed to analyze the contact performance achieved with a shear-thinning lubricant under highly dynamic conditions. Comparisons between different simulations are used to quantify the respective influence of shear thinning, thermal softening, and transient effects on friction and film thickness. Furthermore, this article highlights the formation and transport of a transient dimple responsible for an increase in lift close to the conditions where reversals of entrainment occur. Temperature distributions across the film thickness and pressure variations are reported to discuss the underlying phenomena.