PSI - Issue 31

R. Balokhonov et al. / Procedia Structural Integrity 31 (2021) 58–63 R. Balokhonov et al. / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction Due to their high strength-to-weight ratio, durability, wear resistance and microhardness, metal-matrix composites and coatings are widely used in aerospace, construction, power and engineering industries, for example, to protect spacecraft from orbital debris (Pramanik and Basak (2018); Huang et al. (2020)). Aluminum, boron and silicon carbides, and alumina are the most commonly used materials for making composites. There are different techniques to fabricate composite materials and coatings: solid-state sintering (Balokhonov et al. (2020)), cold spray deposition (Peat et al. (2017)), selective laser melting (Muvvala et al. (2017)) and others. Due to the difference between the thermal expansion coefficients of the matrix, particle and coating materials, residual stresses arise during cooling of composite layers (Baragetti et al. (2019); Wang et al. (2020)). Problems associated with the influence of residual stresses on the material strength are still debatable. Due to complex hierarchically organized structure, the deformation behavior of composite materials is not always possible to predict within the framework of conventional single-scale approaches. Microstructural inhomogeneity is due to the presence of curvilinear interfaces between the matrix and particles, as well as the difference in their mechanical and thermal properties (elastic moduli, characteristics of plasticity and strength, coefficients of thermal expansion). Composites and coated materials are studied both experimentally and theoretically (Yilmaz et al. (2019); Balokhonov et al. (2019)). Experiments are rather expensive and time-consuming. Simulation is necessary tool in engineering failure analysis (Booker et al. (2019)). Advantage of numerical simulation is the possibility of varying one parameter, with the others being the same, as well as studying the stress concentration evolution in the bulk of the material and during deformation (Baragetti et al. (2019); Eremin et al. (2020); Pastorcic et al. (2019)). Power of modern computers makes it possible to carry out calculations considering the material microstructure explicitly with a high degree of accuracy (Balokhonov et al. (2020); Romanova et al. (2020)). Theoretical studies of the composite deformation are mainly aimed at the development of numerical-analytical models for homogeneous single-layer and multilayer coatings of various thicknesses with plane interfaces, for example (Yilmaz, (2019)). Two- and three-phase composites with particles of ideal round (Pitchai et al. (2020)), rectangular (Dongfeng et al. (2018)), and hexagonal shapes (Pachaury et al. (2019)) are modeled considering the microstructure explicitly. Taking into account the complex irregular and experimentally observed shape (Balokhonov et al. (2020); Choudhary et al. (2020)) of strengthening particles in the numerical calculations is important for reliable describing the stress concentration, plastic strain localization and cracking. 2. Plane-stress simulation of deformation and fracture Deformation and fracture of the composite RVE (Fig.1 a) comprising aluminum matrix and boron carbide particle of irregular experimentally observed shape (Fig.1 b, c) is taken into account explicitly as initial data of the plane-stress dynamic boundary-value problem. Two types of problems are solved numerically by ABAQUS/Explicit and compared to each other for investigating the influence of thermal residual stresses on the strength of composites Case1 – cooling followed by composite tension, Case2 – composite tension from the initial undeformed state. At the step of cooling the temperature is of the same value throughout the computational domain and linearly decreases from the recrystallization to room temperatures. The Duhamel – Neumann’s relations are solved, for which an additional contribution into the cubic part of the stress tensor is included into consideration – in calculating the cubic strain a term responsible for thermal expansion is added 1 ( ) 2 ( ) 3 p ij kk ij ij kk ij ij K T σ ε α δ μ ε ε δ ε = − Δ + − −      (1) is the Kronecker delta, K and µ are the bulk and shear moduli, α is the thermal expansion coefficient, T Δ is the temperature drop, the dot denotes time derivative and the comma means summation. ij σ ij ε p ij ε ij δ where , and are the stress, strain and plastic strain tensors,