Publications associées à Capsizing due to friction-induced twist in the failure of stopper knots

The strength of surgical knots involves a critical interplay between friction and elastoplasticity

Paul Grandgeorge, Pedro Miguel Nunes Pereira de Almeida Reis, Paul Johanns, Changyeob Baek

Knots are the weakest link in surgical sutures, serving as mechanical ligatures between filaments. Exceeding their safe operational limits can cause fatal complications. The empirical nature of present guidelines calls for a predictive understanding of the ...

AMER ASSOC ADVANCEMENT SCIENCE2023

Mechanics of Physical Knots: From Filaments in Contact to Surgical Suturing

Paul Johanns

In this thesis, we study the mechanics of tight physical knots. Knots are omnipresent in surgery, climbing, and sailing, with disastrous consequences when the filament or the rope fails to perform its function. Even if the importance of mechanical analysis ...

EPFL2023

Exploring the inner workings of the clove hitch knot

Paul Grandgeorge, Pedro Miguel Nunes Pereira de Almeida Reis, Paul Johanns, Tomohiko Sano, Changyeob Baek

We perform a combined experimental and computational investigation of the clove hitch knot. We develop a physical model for the clove hitch by tying an elastic rod onto a rigid cylinder. In the experiments, we characterize the mechanical performance, geome ...

ELSEVIER2022

Onset of sliding across scales: How the contact topography impacts frictional strength

Jean-François Molinari, Fabian Barras, Ramin Aghababaei

When two solids start rubbing together, frictional sliding initiates in the wake of slip fronts propagating along their surfaces in contact. This macroscopic rupture dynamics can be successfully mapped on the elastodynamics of a moving shear crack. However ...

AMER PHYSICAL SOC2021

Finite Element Modeling of Tight Elastic Knots

Paul Grandgeorge, Pedro Miguel Nunes Pereira de Almeida Reis, Paul Johanns, Tomohiko Sano, Changyeob Baek

We present a methodology to simulate the mechanics of knots in elastic rods using geometrically nonlinear, full three-dimensional (3D) finite element analysis. We focus on the mechanical behavior of knots in tight configurations, for which the full 3D defo ...

2020

Variational phase-field continuum model uncovers adhesive wear mechanisms in asperity junctions

Jean-François Molinari, Sylvain Collet

Wear is well known for causing material loss in a sliding interface. Available macroscopic approaches are bound to empirical fitting parameters, which range several orders of magnitude. Major advances in tribology have recently been achieved via Molecular ...

2020

Optimization of multi-directional fiber architecture for resistance and ductility of bolted FRP profile joints

Thomas Keller, Lulu Liu, Xin Wang

In view of the low structural efficiency of bolted joints in pultruded fiber-reinforced polymer (FRP) profiles with mainly unidirectional (UD) fiber architecture, off-axis plies were considered as an effective way to improve bolted joint performance. An ex ...

ELSEVIER SCI LTD2020

Statistical Fatigue Investigation and Failure Prediction of a Healable Composite System

Véronique Michaud, Amaël Maximilien Cohades, Nathan Klaus Hostettler

Fiber reinforced polymers are massively used as an alternative to metals in structural applications. The brittle nature of their matrix, however, makes them more susceptible to crack formation and propagation resulting in costly repair operations and incre ...

2020

Effect of a second layer on the time to failure of compressed riprap as mountain riverbank protection

Anton Schleiss, Mário Jorge Rodrigues Pereira Da Franca, Mona Jafarnejad Chaghooshi, Michael Pfister

Recently, Jafarnejad, Franca, Pfister, and Schleiss [2017. Time-based failure analysis of compressed riverbank riprap. Journal of Hydraulic Research, 55(2), 224–235. doi: 10.1080/00221686.2016.1212940] presented an experimental study on the stability of co ...

Taylor & Francis Ltd2019

Interparticle Friction Leads to Nonmonotonic Flow Curves and Hysteresis in Viscous Suspensions

Matthieu Wyart, Hugo Robin Louis Perrin

Hysteresis is a major feature of the solid-liquid transition in granular materials. This property, by allowing metastable states, can potentially yield catastrophic phenomena such as earthquakes or aerial landslides. The origin of hysteresis in granular fl ...

American Physical Society2019

Measurements of internal cracking in punching test slabs without shear reinforcement

Aurelio Muttoni, Miguel Fernández Ruiz, Jürgen Einpaul

Advancing the knowledge about the punching behaviour of flat slabs has been held back by the fact that only indirect measurements of the internal failure mechanism have typically been available. In this paper, a novel experimental approach for tracking the ...

2018

Experiment and Machine Protection from Fast Losses caused by Crab Cavities in the High Luminosity LHC

Andrea Santamaría García

The High Luminosity Large Hadron Collider (HL-LHC) upgrade aims for a tenfold increase in integrated luminosity compared to the nominal Large Hadron Collider (LHC), and for operation at a leveled luminosity five times higher than the nominal LHC peak lumin ...

EPFL2018

Dynamic behavior of rock during its post failure stage in SHPB tests

Xin Cai, Yang Zou, Yang Zhao

In order to investigate the micro-process and inner mechanism of rock failure under impact loading, the laboratory tests were carried out on an improved split Hopkinson pressure bar (SHPB) system with synchronized measurement devices including a high-speed ...

Elsevier Science Bv2017

The influence of through-thickness reinforcement geometry and pattern on delamination of fiber-reinforced composites: Part II - Modeling

John Botsis, Véronique Michaud, Georgios Pappas

This article reports modeling techniques and results based on experimental Mode I characterization of a layered woven GFRP material with tufting reinforcement. Standard tuft and loop-less geometries are investigated on three different areal patterns to eva ...

Elsevier2017

Tuning knot abundance in semiflexible chains with crowders of different sizes: a Monte Carlo study of DNA chains

Giovanni Dietler

We use stochastic simulation techniques to sample the conformational space of linear semiflexible polymers in a crowded medium and study how the knotting properties depend on the crowder size and concentration. The abundance of physical knots in the chains ...

Royal Society of Chemistry2016

Characterization of Grey Cast Iron-Steel Tribo-system under Starved Lubrication Conditions : Failure, Failure Detection and Laser Surface Texturing

Fatemeh Saeidi

Reducing friction and wear is essential for building efficient systems with low energy consumption and a long lifetime. Surface texturing is one of the methods to reduce friction and wear, especially in oil-lubricated systems. However, there is still a lac ...

EPFL2016

Time-dependent failure analysis of large block size riprap as bank protection in mountain rivers

Mona Jafarnejad Chaghooshi

Erodible river banks need to be safe against the possible scouring during flood events in mountain rivers. The consequences of the bank failure are probably lateral uncontrolled erosion and flooding with disastrous losses in residential areas or damage of ...

EPFL2016

Experimental investigation of kink initiation and kink band formation in unidirectional glass fiber-reinforced polymer specimens

Thomas Keller, Anastasios Vassilopoulos, Wei Sun

The failure mechanism of non-slender glass fiber-reinforced epoxy prismatic specimens subjected to axial compression and different temperatures was investigated. Digital image correlation was used to map and derive the failure modes. The failure mode chang ...

Elsevier2015

Configurable Electric Vehicle (CEV) demonstrator

Alfred Rufer, Rosa Martel Danoary Tsirinomeny

In order to make electric vehicles more and more attractive, it is essential to improve the range flow rate1 under limited charging infrastructures. Therefore, a universal input and high power electric energy conversion will impose new requirements on powe ...

2015

Influence of boundary conditions and size effect on the drift capacity of URM walls

Katrin Beyer, Sarah Petry

In codes the drift capacity of unreinforced masonry (URM) walls is often estimated as a function of the failure mode and the aspect ratio. The empirical relationships are based on results from quasi-static cyclic tests on single URM walls, which were teste ...

Elsevier2014