180 research outputs found
Mechanical Behavior and Microstructural Development of Low-Carbon Steel and Microcomposite Steel Reinforcement Bars Deformed under Quasi-Static and Dynamic Shear Loading
Reinforcement bars of microcomposite (MC) steel, composed of lath martensite and minor amounts of retained austenite, possess improved strength and corrosion characteristics over low-carbon (LC) steel rebar; however, their performance under shear loading has not previously been investigated at the microstructural level. In this study, LC and MC steel cylinders were compression tested, and specimens machined into a forced-shear geometry were subjected to quasi-static and dynamic shear loading to determine their shear behavior as a function of the strain and strain rate. The as-received and sheared microstructures were examined using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Higher-resolution microstructural examinations were performed using transmission electron microscopy (TEM). The influence of the starting microstructure on the shear behavior was found to depend strongly on the strain rate; the MC steel exhibited not only greater strain-rate sensitivity than the LC steel but also a greater resistance to shear localization with load. In both steels, despite differences in the starting microstructure, post-mortem observations were consistent with a continuous mechanism operating within adiabatic shear bands (ASBs), in which subgrains rotated into highly misoriented grains containing a high density of dislocations
Dynamic recrystallization : classical concepts and new aspects.
International audienc
INFLUENCE OF FLOW RULE AND INERTIA ON VOID GROWTH IN A RATE SENSITIVE MATERIAL
La déformation d'une cavité ellipsoïdale de révolution dans une matrice infinie soumise à une sollicitation dynamique est étudiée. On montre l'effet stabilisant sur la croissance de l'endommagement de la vitesse de traction et des effets d'inertie dans le domaine dynamique ([MATH]).The growth and deformation of a spheroidal void in an infinite viscous matrix is addressed. In the case of a linearly viscous (newtonian) matrix ([MATH]), an exact solution is obtained. On the basis of this solution the case of a power law viscoplastic matrix ([MATH]) is dealt with by a variational approach. Finally, the Galerkine method is used to take into account inertia effects. This work shows the anisotropy of damage and the stabilizing effect of the remote strain rate [MATH] for a material exhibiting the linear flow rule [MATH] as well as the stabilizing effect of the inertia forces
Recristallisation Continue au Cours de la DĂ©formation Ă Chaud d'un Aluminium 1200
La recristallisation dynamique continue se manifeste par la transformation progressive des sous-grains en grains. Une étude microstructurale effectuée par diffraction des électrons rétrodiffusés a permis de la mettre en évidence lors de la déformation par compression uniaxiale (0,7 Tf, 10-2 s-1) d'un aluminium 1200 (99,3 %).Continuous dynamic recrystallization is characterized by the progressive transformation of the subgrains into grains. This process was investigated by electron back scattered diffraction during uniaxial compression (0,7 Tf, 10-2 s-1) of a 1200 aluminium (99,3 %)
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