Shape memory alloy flexures

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Within the framework of the EuroFusion WPMAG project, an automatic laser-welding line was constructed to produce a 1 km long, empty stainless steel jacket demonstrator for the React & Wind (RW) conductor for EU-DEMO. Four 500 m long C-profiles made of 316L austenitic stainless steel were fabricated from ~8 m long sections using the manual TIG (Tungsten Inert Gas) welding method. A series of experimental investigations was carried out on the welded samples, including ferrite content measurements, microhardne

Accurately modeling the mechanical behavior of materials is crucial for numerous engineering applications. The quality of these models depends directly on the accuracy of the constitutive law that defines the stress–strain relation. However, discovering these constitutive material laws remains a significant challenge, in particular when only material deformation data is available. To address this challenge, unsupervised machine learning methods have been proposed to learn the constitutive law from deformati

A three-dimensional frame-element based approach is presented to simulate cyclic inelastic interactions of local and lateral torsional buckling – collectively termed interactive buckling. The approach integrates a multiaxial fiber-based beam-column element termed the torsional fiber element, capable of representing deformation modes characteristic of inelastic warping and St Venant torsion with a multiaxial constitutive model that represents the effective constitutive response associated with cyclic inelast

Water plays a critical role in chemistry and biochemistry due to its unique properties that arise from its polar nature and the hydrogen-bonding network it forms. Its vibrational motions occur on the few-femtosecond timescale and are pivotal for energy transfer within the hydrogen-bond network. Despite the latter, the real-time observation of these motions has not been achieved so far due to the high time resolution necessary to capture them. Here, we investigate the ground state vibrational dynamics of liq

We present an in-situ Lorentz Transmission Electron Microscopy (LTEM) investigation into the cumulative effects of pulsed laser excitation on the metamagnetic transition in freestanding FeRh thin films. Our experiments demonstrate that repeated ultrafast laser pulses progressively introduce defects and associated residual strains, which promote the ferromagnetic phase and change the nucleation process from a homogeneous to a heterogeneous mechanism. This evolution is marked by a significant 20 K reduction i

Masonry walls are critical structural elements in buildings subjected to seismic actions. Their seismic performance is strongly influenced by the mechanical properties of the masonry units, particularly the vertical and horizontal compressive strengths of the bricks. During an earthquake, damage in unreinforced masonry (URM) walls initiates with cracking at the head and bed joints and can propagate through the bricks, affecting the overall drift capacity. Although current design recommendations recognize th

Begun in 2017 and set to be finished at the end of 2020, the "Bergère 2020" Project is set to renovate the buildings in the Nestlé HQ.With a higher accent brought on Building automation, this thesis views itself as an exploratory journey in the literature and techniques for predictive analysis in the building environment. 3 Indicators are proposed to be able to monitor the performance of the building, and Predictive ANalysis techniques are explored and proven to be promising, with implementation planned for

On application of heat, shape memory polymers (SMPs) are able to revert to a primary shape from a secondary shape induced by mechanical deformation. It may be desirable to induce shape recovery at controlled rates under quasi-isothermal conditions, e. g. in certain biomedical applications in which actuation occurs at body temperature, requiring knowledge of the time dependent response of SMPs. In the present work, the time dependence of isothermal shape recovery has been investigated for two shape memory po

The influence of internal stress anisotropy resulting from anisotropic loading in a roll-to-roll (R2R) process, and polymer substrate anisotropy on the crack onset strain (COS) of thin oxide coatings was analyzed. Experimental data obtained for R2R processed films were compared with data obtained using an isotropic sheet-to-sheet (S2S) process with the same anisotropic substrate. In the R2R case the COS was found to increase by 20% between the transverse direction and the machine direction. In the S2S case

NiTi alloy wires were embedded during the infusion processing of woven carbon fibre reinforced plastic (CFRP) composite plates with the purpose to passively increase their damping. Two types of NiTi wires, having the same diameter of 203 mu m, were considered, one superelastic at room temperature, the other one martensitic. For the first one, a martensitic transformation was induced by applying a pre-strain of 2.5% before embedding the wires. The coexistence of austenite and martensite should provide dampin

This communication presents the modeling and the first demonstration of very large deformation balloon actuators based on pyrotechnics on chip. The gas and pressure generated by the combustion of a solid propellant stored in a micromachined cavity lead to the large deformation of the elastic membrane closing the cavity, forming a balloon with a radius of few millimeters. By combining the experimental data obtained on the mechanical properties of the elastic membrane and volume of gas generated per unit of m

The importance of Fibre Reinforced Polymers (FRPs) as a material used for civil engineering purposes has grown in the last decade. Especially the introduction of pultrusion at an industrial level as a way to produce big batches of FRP made it possible to offer the advantages – like the high strength-to-weight ratio or the good corrosion resistance – at a reasonable cost. One issue when designing with pultruded FRPs are the connections. Up to now, connections between pultruded FRPs have been designed in the

At present, little is known about the response of the martensitic phase in TiNi alloys to heavy ion irradiation. However, previous studies [2,3] of ion and electron irradiation show that these alloys are highly susceptible to disorder and amorphization at damage levels below 1 dpa. This substantially affects their transformation characteristics and their shape memory effect. The present study focuses on the effect of 5 MeV Ni ion irradiation of plastically strained (epsilon-4%) martensitic TiNi thin films,

To gain insight into the physical nature of the coupling between mechanical stress and humidity variations, the behaviour of thin wood strips was studied using specially developed apparatus for creep/recovery and relaxation/blotting-out tests in a controlled humidity environment. The load time and the rate of viscoelastic creep were found to have little influence on mechano-sorptive creep. Moreover, creep trajectory curves for specimens with continuous and interrupted humidity cycles indicated divergence fr

The attachment of the first wall modules of the ITER FEAT fusion reactor is designed using flexible connectors made from titanium alloys. An assessment of the tensile and fatigue performance of two candidate alloys, a classical two phase Ti6Al4V alloy and a monophase alpha alloy Ti5Al2.5Sn, has been carried out using 590 MeV protons for the simulation of the fusion neutrons. The dose deposited was up to 0.3 dpa and the irradiation temperature was between 40 degreesC and 350 degreesC. The unirradiated tensil

The purpose of the present work is to study the relation between the microstructure and the martensitic transformation in a binary NiTi alloy. Moreover, it has been conducted on wires which diameters are between 1.52mm and 50µm in order to demonstrate the possible appearance of a size effect. The transformation temperatures during the martensitic transformation in wires made of Ti-51.14at.% Ni have been studied as a function of the wire's diameter, the temperature and the duration of the heat treatment. The

In the more recent applications of technical polymers, they are frequently submitted to high strain rates. Being viscoelastic by nature, their mechanical properties are rate dependent. It is therefore important to investigate their properties over a wide range of strain rates. The aims of this study are twofold: i) to propose an experimental technique applicable to a large domain of strain rates, included those covering impact tests, and ii) to apply this technique to the study of the rate dependence of the

Reinforced concrete slabs supported on columns fail by punching when a conical plug of concrete perforates the slab above the column. This failure has been mostly investigated experimentally, so what can numerical simulation contribute to understand this phenomenon? To answer this question, a computational simulation tool based on the finite element method is developed. This numerical model is implemented into a computer code in applying the object-oriented programming concept. The requirements that the num

Shape memory alloy flexures

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Microstructure, mechanical properties and residual stress of welded stainless-steel jackets for React & Wind conductor in EU-DEMO

Learning physics-consistent material behavior from dynamic displacements

A torsional fiber element and a multiaxial softening model to simulate cyclic interactive buckling in wide-flanged steel members

Real-Time Tracking of the intramolecular vibrational dynamics of liquid water

Investigating Ultrafast Laser Driven Ferromagnetic Phase Nucleation Kinetics in FeRh using In-situ and Ultrafast Lorentz TEM

Influence of the Horizontal-to-Vertical Compressive Strength Ratio of Hollow Clay Bricks on the In-Plane Lateral Loading Behaviour of Unreinforced Masonry Walls

A Big Data approach to Building Automation and Predictive Maintenance Techniques

Tailoring the time-dependent recovery of shape memory polymers

Influences of roll-to-roll process and polymer substrate anisotropies on the tensile failure of thin oxide films

Passive damping of composites with embedded shape memory alloy wires

Large Deformation Balloon Micro-Actuator Based on Pyrotechnics on Chip

Adhesively bonded lap joints of pultruded GFRP shapes

Nickel ion irradiation of plasitically deformed martensitic titanium nickel thin films

Transient moisture effects on wood creep

Impact of irradiation on the tensile and fatigue properties of two titanium alloys

Transformation martensitique multiple dans un alliage à mémoire de forme Ni-Ti

Approche expérimentale du comportement mécanique des polymères en sollicitation rapide

Numerical analysis of punching failure in reinforced concrete structures