PSI - Issue 5

Abdelouahid El Amri et al. / Procedia Structural Integrity 5 (2017) 363–368 Abdelouahid El Amri / Structural Integrity Procedia 00 (2017) 000 – 000

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constrained materials. Greater temperatures produce melting, with large mobility and easy rearrangement of matter that, after solidification, establish new solid bonds, what is used locally in welding and globally in casting. fig.3 shows that , the damage mechanism for a specimen in the current study is highly liked with that occurs at superplastic forming which is void nucleation and growth at the interface of the second phase and the matrix particularly at the grain boundary , and shows also , the cyclic behavior of a material under thermomechanical uniaxial deformations it is fundamental to predict the fatigue life of the components, using the criterions that define the uniaxial fatigue. A material fractures when it becomes suddenly disjoined; i.e. when the stress in a material is increased there is a point when it cannot keep bonded and breaks apart. The failure behavior can be measured by the ultimate stress, the ductility or ultimate strain, and the toughness or ultimate deformation energy. The numerical study it is focused on the stress-strain cyclic deformation under a uniaxial loading, proportional or non-proportional. Modeling the mechanical behavior of a material under uniaxial elastoplastic strain becomes fundamental to predict the fatigue life of the components, using the uniaxial fatigue criteria . Fig . 4 represents a plot from ABAQUS, showing the von Mises stress in Pascal [Pa] and the effective plastic strain (PEEQ), at displacement 3mm.

Figure . 4 : Von- Mises at displacement 3mm.

Figure.5 : Temperature variation under different values of displacement

The total elongation in a tensile specimen can be considered to be comprised of two parts, local elongation in the region that fractures, and uniform elongation in the remainder of the specimen. Uniform elongation is related to the yield-tensile ratio, tending to decrease with increasing ratios as shown in Fig.5 . In the design of steel structures it is assumed that members have the capability to rotate and deflect adequately before fracture. In a beam with a moment gradient, if the yield strength is less than the tensile strength, the plastic region of a beam can extend over some length of the beam as the bending moment at the critical section increases above the plastic moment by virtue of strain hardening. On the other hand, if the yield strength and tensile strength are equal (yield-tensile ratio of 1.0), there can be no extension of the plastic region because the tension flange can rapidly reach its ultimate strain and rupture as the plastic moment is reached to the maximum (plastic zones). The annealing temperature (i.e., with increasing the mean grain size), the strength of the material decreased. As the annealing temperature increases, the grains gradually grew to attain more equiaxed microstructures. Small