This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Dynamic plastic properties, deformation modes, constitutive relations and shock states are described  Experimental observations in the quasi-static, transitional dynamic and shock regimes are presented  Mechanisms associated with inertia, enclosed gas and microscopic strain-rate sensitivity of base material are elucidated  Mesoscopic modelling and its applications are discussed with regard to idealised and realistic cell structures  Macroscopic continuum-based modelling for compression-dominated loading is summarised and commented

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Nondestructive and accurate measurement of residual stress in ceramic coatings is challenging, but it is crucial to the assessment of coatings failure and life. In this study, for the first time, the thermal‐cycle dependent residual stress in an atmosphere plasma sprayed thermal barrier coating system has been nondestructively and accurately measured using photoluminescence piezo‐spectroscopy. Each thermal cycle consists of a 5‐minute heating held at 1150°C and a 3‐minute water quenching. The measurement was performed within a crack‐susceptible zone in the yttria‐stabilized‐zirconia (YSZ) top coat (TC) closely above the thermally grown oxide layer. A YSZ:Eu3+ sublayer was embedded in TC as a stress sensor. It was found that the initial residual stress was compressive, with a mean value of 240 MPa, which rapidly increased to 395 MPa after 5 thermal cycles (12.5% life) and then increased gradually to the peak of 473 MPa after 25 thermal cycles (62.5% life). After 30 thermal cycles (75% life), the mean stress dropped abruptly to 310 MPa and became highly heterogeneous, with gradual reduction toward final spallation. The heterogeneous stress distribution indicates that many microcracks nucleated at different locations and the spallation occurred due to the coalescence of the microcracks.

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This study aims at understanding the constitutive relation and critical condition for the shock compression of cellular solids. A 2D virtual foam is constructed from the cross-section of a closed-cell aluminium foam imaged by micro X-ray computed tomography, which enables the realistic consideration of mesoscale structural effect in numerical modelling. Quasi-static and shock compressions of the 2D foam are simulated. A series of Hugoniot relations between shock speed (and other mechanical quantities) and impact speed are determined from the FE simulations. It is found that the shock speed increases approximately linearly with impact speed, similar to that observed for condensed solids, but the related material constants for cellular solids have different physical implications, whereas the shock strain, stress and energy increase with impact speed nonlinearly, due to shock-enhanced cell compaction and cell-wall deformation. Based on conservation laws in continuum mechanics, other Hugoniot relations are derived from the basic linear one, which agree well with those obtained from FE simulations. It is thus demonstrated that the unique linear Hugoniot relation can be used to characterise the shock constitutive behaviour which is distinct from the quasi-static one. Furthermore, a new analytical method based on the linear Hugoniot relation is proposed to estimate the critical impact speed for shock initiation, which has reasonable agreement with the present FE simulation and previous experimental and numerical results, and outperforms the existing methods.

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There is a demand for more efficient and powerful gas turbines, which are characterized by higher operating temperatures, longer lifetimes, and other features. 1-3 This demand has led to great challenges in the development of advanced thermal protection technologies, among which thermal barrier coatings (TBCs) are regarded as one of those most promising to meet the demand. 4-8 Typically, TBCs consist of the following four layers 5,6 : (i) the superalloy substrate, which is the main load-bearing constituent; (ii) the ceramic top coat (TC), which is usually composed of 6-8 wt.% yttria-stabilized zirconia (YSZ) and acts as a temperature insulator; (iii) an aluminum-containing bond coat (BC) between the substrate and the TC, which is usually composed of MCrAlY (where M is Ni and/or Co) and used for alleviating the thermal expansion mismatch stress between the aforementioned two layers; and (iv) a thermally grown oxide (TGO), which forms between TC and BC when they are exposed to high temperature and provides oxidation resistance. Each of these constituent layers presents marked differences in physical, thermal, and mechanical properties, and all contribute to determine performance and durability. Typically, the TBCs are fabricated using either electron-beam physical vapor deposition