André Pineau

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The size and the character (low and large angle, special boundaries, tilt and twist boundaries, twins) of the grain boundaries (GBs) in polycrystalline materials influence their strength and their fracture toughness. Recent studies devoted to nanocrystalline (NC) materials have shown a deviation from the Hall-Petch law. Special GBs formed by Σ3 twins in(More)
The micro-mechanisms of crack initiation and propagation identified for DA 718, as well as the competition between initiation site types and locations, cannot be accurately accounted for by current certified methods used to establish aircraft engine disks life,essentially phenomenological. Once identified, these micro-mechanisms have been modelized by(More)
Critical cleavage stress values and carbide sizes obtained in a recent work by Lee et al. [1] are recalculated using 2D and 3D FE simulations and new constitutive law, instead of small scale yielding assumption and likely improper choice for the behavior of SA 508 steel. A new model based on the weakest link concept with the determined carbide size(More)
This study deals with the evaluation of local approach to assess the mechanical integrity of cracked components submitted to cyclic and steady load at elevated temperature. In this approach, a fracture criteeon based on calculated intergranular damage ahead of the crack tip is introduce to simulate both crack initiation and crack propagation in 316 L type(More)
Tensile tests on axisymmetrically notched specimens were performed at various temperatures in the ductile-brittle transition region to study the initiation of fracture. Fracture toughness tests on CT specimens were also carried out in the same region to investigate the critical values of stable crack growth occurring before unstable cleavage fracture.(More)
Fracture toughness tests have been carried out on two A1 alloys (7075 and 7475) containing different amounts of Fe and Si. These materials were tested in T3. T6 and T7 conditions. alone six orientations (LT. LS. TL. TS, SL and ST). Large variations in the fracture toughness (20-60 MP~G were measured. Mechanical tests on notched specimens were also performed(More)
The development of Generation IV fission nuclear reactors and fusion nuclear reactors requires materials able to resist to high temperature (650°C) creep, but also to creep-fatigue. Martensitic 9-12%Cr steels are candidate materials for these applications. Recent studies on commercial P91 steel showed that cyclic loadings coupled to hightemperature creep(More)
Car manufacturers are very much concerned with thermal fatigue damage that may cause Diesel engine to fail after a few thousand cycles on the test bench and under severe operating conditions. The alternative heating and cooling of the operative Diesel engine generates fatigue cracks, initiating from the fire deck of the cast aluminum cylinder head, which(More)
In the framework of Generation IV nuclear reactors and for fusion reactors, oxide dispersion strengthened (ODS) steels and advanced generations of 9-12%Cr martensitic steels are widely investigated [1-4]. Several components in these concepts will be subjected to mechanical loadings (creep, creep-fatigue,...) at high temperatures, between 550°C and 650°C. A(More)
Girth welds of modern line pipe steel, such as X100, issued from a pulsed automatic gas metal arc welding, were tested to check their performance in artic temperature conditions. It is shown that an impact specimen at –20 °C with a notch placed in the middle of the fusion line could break at low energy (<40 J). The brittle zone is located in the(More)