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The cracking of nickel-based single-crystal alloys is associated with the residual stress. In this paper, we employed focused ion beam and digital image correlation (FIB-DIC) technology to characterize the crack-tip residual stress at ultrahigh spatial resolution. The repeatability and accuracy of FIB-DIC were validated by experiments and simulations. A direct correlation between residual stress and hardness was established, which provides a new way to prevent cracking through the visualization and control of residual stress. [ABSTRACT FROM AUTHOR]

The present study was devoted to investigating the stress corrosion behavior of Ni-based single-crystal superalloys using in situ three-dimensional X-ray tomography. The dynamics of a total of 169 cavities were tracked in situ for representative statistics. Our results demonstrated that the growth rate of the cavities under stress corrosion conditions was correlated with their size and spatial distribution, which provides new insights for preventing premature cavity coarsening through the tailoring of the cavity. [ABSTRACT FROM AUTHOR]

An in situ tensile test of the ring-rolled GH4169 alloy is performed to investigate the plastic deformation behavior at the micro level. Slip system activations are identified by slip traces captured by a scanning electron microscope and lattice orientation data acquired by electron backscattered diffraction. Our results demonstrated that the fraction of low-angle grain boundaries gradually increased upon tensile deformation, and the misorientation evolution in the grain interior was severely inhomogeneous. The Schmid factors at the grains of interest are calculated for comparison with the actual activated slip systems. Most of the slip system activation coincides with the Schmid law, as opposed to the initiation of other potential slip systems at some grains. [ABSTRACT FROM AUTHOR]

Due to the limited ability for perfusion, traditional intramembranous ossification (IMO) often fails to recapitulate the natural regeneration process of most long bones and craniofacial bones. Alternatively, endochondral ossification (ECO) strategy has emerged and has been evidenced to circumvent the drawbacks in the routine application of IMO. Here, an injectable, poly(glycerol sebacate)‐co‐poly (ethylene glycol)/polyacrylic acid (PEGS/PAA) hydrogels are successfully developed to induce a hypoxia‐mimicking environment and subsequently recapitulate ECO via in situ iron chelation. With the incorporation of PAA, these hydrogels present remarkable viscoelasticity and high efficacy of iron ion‐chelating after injection, giving rise to the activation of HIF‐1α signaling pathway and suppression of inflammatory responses, and thereby improving chondrogenic differentiation in the early stage and facilitating vascularization in the later stage, which consequently trigger typical ECO. More importantly, through sustained and stable expression of HIF‐1α regulated by PEGS/PAA hydrogels throughout the regeneration, a harmonious chondrogenic/osteogenic balance can be struck and thereby accelerating the progress of ECO compared to the PEGS. The findings provide an efficient strategy to achieve in situ ECO via biomaterial‐based iron ion‐chelating and ensuing hypoxia‐mimicking, representing a novel and promising concept for future application in bone regeneration. [ABSTRACT FROM AUTHOR]

The microporous architecture of biomaterials/scaffolds plays a critical role in cellular behaviors of marrow stromal cells in the field of tissue regeneration, but the role of microporous density in this process and its underlying molecular mechanism are poorly understood. In the present work, a series of three-dimensional (3D) trimodal macro/micro/nano-porous MBG scaffolds (TMSs) with different microporous densities were developed to investigate the influence of microporous density on the attachment, proliferation and osteogenic differentiation of rat bone marrow stromal cells (rBMSCs), and the fundamental molecular mechanism was explored. The results demonstrated that scaffolds with micropores significantly promoted initial cell adhesion, ALP activity and osteogenesis-related gene/protein expressions, especially the one with 20% microporous density (TMS 20). We found that the appropriate microporous density modulated the adsorption of fibronectin (Fn), and in turn facilitated integrin receptor binding affinity, focal adhesion complex formation and subsequent FAK/MAPK signaling pathway activation. Based on these studies, it can be confirmed that microporous density contributes to the regulation of cellular response, which can provide a new insight into the design of future bone substitutes in a 3D environment. [ABSTRACT FROM AUTHOR]

Oscillatory two-phase flow as a common two-phase flow occurs extensively within the engine's thermal management system. However, it is found that the oscillatory two-phase flow patterns at the same location have different flow states caused by the strong turbulence under fast moving speed conditions, making it difficult to propose systematic identification and judgement criteria. Common image processing methods applied to tube flow are unsuitable for the analysis of oscillatory two-phase flow with particularly complex flow patterns. To solve this problem, this paper presents a study aiming to determine common rules from the instantaneous flow patterns by eliminating the random variability and making the oscillatory two-phase flow pattern images more representative. Applying the phase-averaged pre-processing and textural feature method to the instantaneous oscillatory two-phase flow patterns, which are captured by the designed visualized test bench, the lowest identification results based on the Support Vector Machine (SVM) could achieve an accuracy of 92.5%. The results suggest that the study presented in this paper offers an effective method for the analysis and identification of oscillatory two-phase flow patterns. Visualized experimental results in the related fields of two-phase flow will be more comprehensive with objective descriptions and representative flow pattern images. • Use the machine learning method to study the complicated oscillatory two-phase flow. • Apply the phase-averaged and textural feature method to optimize the identification. • The accuracy of identification in transition flow and turbulence flow increased significantly. • Recognition of the flow patterns depending on the Reynolds number was obtained in the range of 92.5%–100%. [ABSTRACT FROM AUTHOR]