Mechanical Fatigue Testing Under Thermal Gradient and Manufacturing Variabilities in Nickel-Based Superalloy Parts with Air-Cooling Holes

Abstract

Background: As aerospace cast parts move to more complex geometries, the impact of process variabilities must be evaluated more precisely to provide new, less empirical acceptation criteria. However, experimental lifetime assessment with Thermal Gradient Mechanical Fatigue (TGMF) are still complicated to reproduce in a laboratory environment. Objective : This paper investigates the impact of geometrical variability on thermo-mechanical fatigue life of Nickel-based superalloy single crystal parts. Methods : To this end, hollow specimens with cooling holes drilled in their centre have been produced with parametrized variations of the wall thickness and have been characterized by Xray tomography. An experimental fatigue setup operating at 1100 • C, with a thermal gradient of 50 • C across the wall, has been developed to assess the life of each specimen. Results : Experimental lifetime assessment were conducted on a sample of specimens containing geometrical defects. Optical observations during the tests have permitted to study crack initiation and propagation in the vicinity of the cooling hole, an area of high thermal and stress gradients where damage localize. Axial strains (in the loading direction) were also gathered and TGMF on Cooling Holes compared to prove the impact of process variabilities on mechanical behaviour. Conclusions : Significant mechanical differences are observed during the tests which can related to the geometrical variations of the specimens and their interaction with the shaped hole. Tests results will be further used to calibrate a creep-fatigue model for lifetime predictions.

Multimodal data augmentation for digital twining assisted by artificial intelligence in mechanics of materials

“…N = 6 in order to have s tol = 0.99. In this example, μ is a vector of 3 angles related to the single crystal CMSX4-PLUS of the specimen as presented in Aublet et al (2022). This parameter is augmented randomly using angle variations below 12 o .…”

“…With the development of non-destructive testing (NDT) in the manufacturing industry, we can expect a growing activity on image-based DTs (Seon et al, 2020;Launay et al, 2021a) for accurate descriptions of as-manufactured geometries and microstructural properties of structural components. Such data are crucial for lifetime predictions (Aublet et al, 2022). Unfortunately, image-based DTs in material science are so complex and time-consuming, so in practice, this task does not scale with the frequency of quality inspection in manufacturing.…”

“…In the second example, we give a detailed description of the considered multimodal data for an academic example and for a mechanical component undergoing cyclic loading at high temperature for its lifetime characterization. The ambient spaces related to the multimodal data in this article are realistic regarding manufactured parts of the aeronautics industry (Aublet et al, 2022).…”

Research on low‐cycle fatigue behavior of Ni‐based single crystal superalloy with shaped film cooling holes at high temperature

“…To address the problem of blade fracture failure caused by FCHs, numerous studies have been conducted on the influence of drilling surface quality 5,6 , holes configuration 7,8 , and crystal orientation 9,10 of the FCHs on their fatigue behavior, including low-/high-cycle fatigue and fatigue-creep behavior. The initial surface integrity assessment of FCHs under different drilling processes has great impact on fatigue life of structural components.…”