Study of Fatigue Crack Initiation and the Propagation Mechanism Induced by Pores in a Powder Metallurgy Nickel-Based FGH96 Superalloy.

Thermally induced pores (TIPs) are generally the source of fatigue crack initiation in the powder metallurgy (PM) Ni-based FGH96 superalloy. The effect of TIPs on fatigue crack initiation on the surface of the FGH96 superalloy was detected using scanning electron microscopy (SEM). The cause of fatigue crack deflection was studied using electron backscatter diffraction (EBSD) analysis.

Semantic segmentation of defects based on DCNN and its application on fatigue lifetime prediction for SLM Ti-6Al-4V alloy.

Inevitable defects have an important impact on the fatigue lifetime of additive manufacturing materials. Therefore, it is critical to thoroughly characterize the characteristics of the defects, which requires effective semantic segmentation of the imaged defects. In this paper, a defect dataset for SLM Ti-6Al-4V alloy was obtained by synchrotron radiation computed tomography.

Assessment of Mechanical Properties for Three-Dimensional Needled Composites: A Geometric Partitioning Strategy Dealing with Mesoscopic Needling Damage.

A geometric partitioning strategy was proposed to evaluate the mechanical properties of three-dimensional needled composites. The microstructure of the composite was divided to accurately characterize the mesoscopic damage in the needling regions and the macroscopic damage in the un-needling regions, to balance the computational accuracy and efficiency. The general method of cells (GMC) models along with the damage criteria were established for different material phases in the needling regions, while the continuum damage mechanics (CDM) model was adopted to portray the damage evolution in the un-needling regions.

A Concise Binomial Model for Nonlinear Creep-Fatigue Crack Growth Behavior at Elevated Temperatures.

The creep-fatigue crack growth problem remains challenging since materials exhibit different linear and nonlinear behaviors depending on the environmental and loading conditions. In this paper, we systematically carried out a series of creep-fatigue crack growth experiments to evaluate the influence from temperature, stress ratio, and dwell time for the nickel-based superalloy GH4720Li. A transition from coupled fatigue-dominated fracture to creep-dominated fracture was observed with the increase of dwell time at 600 °C, while only the creep-dominated fracture existed at 700 °C, regardless of the dwell time.

The Location Monitoring of Fatigue Crack Damage by Using the Spectral Area Extracted from FBG Spectra.

In this paper, a new damage feature, spectral area, was extracted to effectively detect crack location by studying the deformation mechanism of fiber Bragg grating (FBG) reflection spectra. In order to verify the robustness and reliability of spectral area to detect crack location, the following work was carried out: Firstly, the strain information was extracted by extended finite element method (XFEM) with fatigue crack propagation. The transmission matrix method (TMM) was used to simulate FBG reflection spectra using numerical results.

Advanced Simulation Tools Applied to Materials Development and Design Predictions.

This thematic issue on advanced simulation tools applied to materials development and design predictions gathers selected extended papers related to power generation systems, presented at the XIX International Colloquium on Mechanical Fatigue of Metals (ICMFM XIX) organized at University of Porto, Portugal, in 2018. Guest editors express special thanks to all contributors for the success of this special issue-authors, reviewers, and journal staff.