Time-dependent Mechanics and Damage

Investigating the role of short overheating on the mechanical performance during creep and fatigue, through the use of experiments, phase fields simulation, and dislocations dynamics simulations.

What are we trying to achieve ?

Depending of a rate of a sollicitation, such as a mechanical or a thermal sollicitation , the mechanical performances can change.

We try to better understand the time dependency of the inelastic phenomena to improve the predicting capabilities of the modeling approaches.

Here a the grants we obtain to work on this subject:

Abstract

As the US Air Force fleet continues to age, a greater portion of its budget will be required to ensure safe and effective operations beyond the design service life. In fact, for various military vehicles and platforms, the recommended service life for safe operation is projected to increase by a factor of 1.5 to 5 AFRL, 2014. The high demand for safety and cost reduction culminates in the case of materials systems operating under extreme environments such as turbine blades made of Ni-based single crystal superalloys. Turbine blades are used in the hot section of the engine and are, therefore, subjected to multiaxial high-temperature viscoplastic deformations, namely, creep and dwellfatigue, due to both their complex geometry and their advanced design, e.g., internal cooling channels aimed to increase the exhaust-gas temperature during in-service operations.

Abstract

The underlying hypothesis of this project is that the lattice misfit between phases in Nickel-based superalloys under certain non-isothermal loadings plays an essential role in enhancing creep performance at elevated temperatures. The project, therefore, rests on the transformative paradigm that ?hotter can be longer? depending on how the coherency stresses evolve. To test this hypothesis, the lattice misfit evolution will be tracked in new temperature/stress regimes by in situ X-ray diffraction under synchrotron radiation. In situ results will be used to correlate, at the macroscale, the non-isothermal mechanical responses. Furthermore, discrete dislocation dynamics simulations will be carried out to gain further insight into dislocation/precipitate interactions depending on the microstructural state and lattice misfit. These simulations will help identify and quantify competing mechanisms, e.g., climb/glide and self-interaction/precipitate hardening effects, which will qualitatively help explain experimental results.

  • ONR : Unraveling High-Temperature Creep-fatigue-oxidation in Metals (PI : J.B. le Graverend ; $445,861 ; Juin 2020-Juin 2023)
Abstract

The underlying hypothesis of this project is that the lattice misfit between phases in Nickel-based superalloys under certain non-isothermal loadings plays an essential role in enhancing creep performance at elevated temperatures. The project, therefore, rests on the transformative paradigm that ?hotter can be longer? depending on how the coherency stresses evolve. To test this hypothesis, the lattice misfit evolution will be tracked in new temperature/stress regimes by in situ X-ray diffraction under synchrotron radiation. In situ results will be used to correlate, at the macroscale, the non-isothermal mechanical responses. Furthermore, discrete dislocation dynamics simulations will be carried out to gain further insight into dislocation/precipitate interactions depending on the microstructural state and lattice misfit. These simulations will help identify and quantify competing mechanisms, e.g., climb/glide and self-interaction/precipitate hardening effects, which will qualitatively help explain experimental results.

Where can that be used?

This kind of research has a direct application : by knowing more precisely the behavior of materials, we can more precisely estimate their life expentency, thus improving safety of those who use it, like power plants, planes, spaceships, etc.

Who is involved?

Jean-Briac le Graverend (PI)
Amine Benzergah (Co-PI)

Harikrishnan Rajendran (Alumni)
Pawan Chaugule (Alumni)
Seugjun Lee (Alumni)
Adrien Cassagne (Ph.D.)

Othman Benafan (NASA) has provided the materials HTSMA
GE has provided the materials René N4 and René N5
Zéline Hervier (Turbomeca SAFRAN) has provided the materials MC2

Who is funding?

Air Force Office of Scientific Research

Office of Naval Research

National Science Fondation

Publications and Conferences

Published papers :

  • Phase transformation and viscoplasticity coupling in polycrystalline nickel-titanium-hafnium high-temperature shape memory alloys
    P. Chaugule, O. Benafan, J.B. le Graverend*
    Acta Materialia↗, December 2021
  • Mechanical Twinning in Ni-based Single Crystal Superalloys during Multiaxial Creep at 1050°C
    J.-B. le Graverend*, F. Pettimari-Sturmel, J. Cormier, M. Hantcherli, P. Villechaise, J. Drouin
    Materials Science and Engineering A↗, Avril 2018
  • Ex-situ X-ray Tomography Characterization of Porosity During High-Temperature Creep in a Ni-based Single-Crystal Superalloy: Toward Understanding What Damage is
    J.-B. le Graverend*, J. Adrien, J. Cormier
    Materials Science and Engineering A↗, Mai 2017
  • Strengthening behavior in non-isothermal monotonic and cyclic loading in a Ni-based single crystal superalloy
    J.-B. le Graverend*, J. Cormier, S. Kruch, F. Gallerneau, J. Mendez
    International Journal of Fatigue↗, October 2016
  • Creep of a nickel-based single crystal superalloy during very high temperature jumps followed by synchrotron X-ray diffraction
    J.-B. le Graverend*, A. Jacques, J. Cormier, O. Ferry, T. Schenk, J. Mendez
    Acta Materialia↗, February 2015
  • Highly non-linear creep life induced by a short close γ’-solvus overheating and a prior microstructure degradation on a nickel-based single crystal superall
    J.-B. le Graverend*, J. Cormier, F. Gallerneau, S. Kruch, J. Mendez
    Materials & Design↗, December 2013
  • In situ measurement of the γ/γ’ lattice mismatch evolution of a nickel-base single-crystal superalloy during non-isothermal very high temperature creep experiments
    J.-B. le Graverend*, L. Dirand, A. Jacques, J. Cormier, O. Ferry, T. Schenk, F. Gallerneau, S. Kruch, J.Mendez
    Metallurgical & Materials Transaction A↗, September 2012

Conferences :

  • Creep 2015, Toulouse, France, May 31-June 4, 2015
    Multiaxial Thermo-mechanical loading at high temperature on a Ni-based single-crystal superalloy.
    J.-B. le Graverend (Sp), V. Bonnand, J. Cormier, D. Pacou, J. Mendez
  • TMS 2015, Orlando (FL), USA, March 15-19, 2015
    Porosity evolution during high temperature creep tests in a single crystal superalloy by 3D X-ray computed tomography.
    J.-B. le Graverend (Sp), J. Adrien, J. Cormier, F. Gallerneau, S. Kruch, J. Mendez.