Wyniki wyszukiwania - BazTech

1

Non-associated superelasticity in rotating frame formulation

Vieille B., Boubakar M. L., Lexcellent C.

Journal of Theoretical and Applied Mechanics

|

2003

|

Vol. 41 nr 3

676-691

EN

In order to describe and predict the superelastic finite strains behaviour of Shape Memory Alloys, a kinematic description with directors is proposed. Compatible with either isotropic behaviours, it allows a direct extension from the small pertubation formalism. Particularly, a general framework is proposed for the description of the Shape Memory Alloys superelastic behaviour under 3D proportional loadings.

PL

W pracy przedstawiono metodę przewidywania i opisu stanu skończonych supersprężystych odkształceń określających zachowanie się stopów z pamięcią kształtu. Metodę oparto na reprezentacji kinematycznej stanu otrzymanej za pomocą wektorów kierunkowych. Metoda ta, jako spójna dla materiałów izotropowych i anizotropowych, umożliwia wnioskowanie wprost z formalizmu techniki perturbacyjnej bazującej na małym parametrze. W szczególności, zaproponowano ogólne podejście do opisu supersprężystego zachowania się stopów z pamięcią kształtu poddanych proporcjonalnym obciążeniom przestrzennym.

2

Deformation behaviour of TiNi shape memory alloy undergoing R-phase reorientation in torsion-tension (compression) tests

Raniecki B., Miyazaki S., Tanaka K., Dietrich L., Lexcellent C.

Archives of Mechanics

|

1999

|

Vol. 51, nr 6

745-784

EN

The deformation behaviour associated with the R-phase reorientation is investigated in a Ti-51.0 at%Ni polycrystalline shape memory alloy under the torsion-tension (compression) stress state, and special theoretical framework is developed to describe the observed alloy performance. The limit condition to start the reorientation process, represented as a surface on the axial stress-shear stress plane, is determined for the proportional loading path. The result is well described, not by the Huber-Mises condition (the J2-theory) but by the model (the J3-theory), by taking into account the third invariant of stress deviator through the concept of the shape function. The values of the shape function are determined experimentally. The basic experimental features of the deformation in the R-phase, such as the flow rule, the ratios of the reorientation strain rates and the dimensionless ratio of the reorientation work, are compared with the predictions of theories that neglect the effects of pressure, compressibility of reorientation strains and effects of induced anisotropy. The J3-theory turns out to be more realistic than the J2-theory.

3

Mechanical characterization of the interface between a shape memory alloy fiber and a resin epoxy matrix

Thiebaud F., Gabry B., Lexcellent C.

Engineering Transactions

|

1998

|

Vol. 46, iss.3/4

290-314

EN

The aim of this paper is to characterize the interface between a shape memory alloy wire (SMA) and a epoxy resin matrix. Herę we present the effect of various surface treatments applied to SMA NiTi wires on the ąuality of the interface fiber/matrbc. First, the use of the fiber pull-out test allows to separate the different treatments into two families: on the one hand, decohesion of the wire; on the other hand, rupture of the wire before debonding. The data given by the pull-out tests are not sufficient to differenciate the surface treatments which cause the breaking of the wire rather than the interfacial debonding of the fiber/matrbc. In order to complete our research, a topographical study is carried out on different wires. It allows us to extract the parameters which characterize the vertical distribution of roughness and its morphology. The analysis of these experimental results leads to the choice of the surface treatment which will guarantee higher interfacial stresses. Among all the wires studied, we choose the prestrained wire. The quantitative aspect of this study allows us to know better the evolution of the different parameters of roughness, and thus to guide our research works to an optimal surface treatment of the wire.