Tóm tắt luận án Tiến sĩ chuyên ngành Cơ học: Đánh giá và mô phỏng các hệ số đàn hồi đa tinh thể hỗn độn

Mục tiêu nghiên cứu của đề tài "Đánh giá và mô phỏng các hệ số đàn hồi đa tinh thể hỗn độn" là tìm ra các đánh giá tốt hơn các đánh giá đã có, đưa ra được các kết quả so sánh đánh giá giải tích và PTHH cụ thể. Mời các bạn cùng tham khảo.
Nội dung trích xuất từ tài liệu:
Tóm tắt luận án Tiến sĩ chuyên ngành Cơ học: Đánh giá và mô phỏng các hệ số đàn hồi đa tinh thể hỗn độn MINISTRY OF EDUCATION VIETNAM ACADEMY OF ANDTRAINING SCIENCE AND TECHNOLOGYGRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY --------------------------- VUONG THI MY HANH ESTIMATES AND SIMULATIONS FOR THE ELASTIC MODULI OF RANDOM POLYCRYSTALS Major: Mechanics of Solid Code: 9440107 SUMARY OF DOCTORAL THESIS IN MECHANICS HA NOI - 2020The thesis has been completed at: Graduate University Science andTechnology -Vietnam Academy of Science and Technology. Supervisor 1: Prof. DrSc. Pham Duc Chinh Supervisor 2 : Dr. Le Hoai Chau Reviewer 1: Prof. Dr. Pham Chi Vinh Reviewer 2: Assoc. Prof. Dr. La Duc Viet Reviewer 3: Assoc. Prof. Dr. Tran Bao Viet Thesis is defended at Graduate University Scienc and Technology-Vietnam Academy of Science and Technology at ...: ..., on ... / ... / 2020 Hardcopy of the thesis be found at: - Library of Graduate University Science and Technology - Vietnam national library 1 PREFACE1. Reason of choosing the thesisa. Objective reason Polycrystalline materials are being used extensively in allareas of human life. The study of elastic coefficients for thismaterial yields many analytical results: Voigt, Ruess, Hill,Hashin-Strikman, Pham Duc Chinh ... However, the finiteelement method (FEM) results are not surffice for comparison.The question is: are these estimates the best, how to calculate bythe FEM, how the FEM results compared to these estimates ...b. Subjective reason Homogenization of materials is a long-term research field ofsupervisor Pham Duc Chinh and Material Mechanics team withmany published results. The PhD candidate completed themasters thesis on homogenization of thermal conductivity forisotropic composite materials. Therefore, author has selectedthe topic Estimates and simulation for the elastic moduli ofrandom polycrystals as the research thesis.2. Aim, research method of the thesisa. Aim: to find better estimates, compare results of analyticmethod and FEM.b. Method: using energy principles and applying analytical andnumerical methods simultaneously.3. Research subject and scope of the thesisa. Subject: macroscopic elastic moduli of random polycrystals.b. Scope: For estimates, thesis considers d- dimensionalpolyscrystals; For simulation, thesis only considers 2Dpolyscrystals with hexagonal shape of. 24. New contributions of the thesisa. Theory: Generalized polarization fields, estimates andspecific calculation results for elastic moduli of d-dimensionalpolyscrystals are new and better than the previous estimates.b. Numerical simulation: Large-scale FEM results for elasticmoduli of 2D square, orthorhombic and tetragonal polycrystalsfor comparisons with the bounds are new.5. Thesis layoutChapter 1 presents the development history and researchmethods of the previous authors. Chapter 2 constructs generalestimates for macroscopic elastic moduli. Chapter 3 appliesChapter 2 results to 2D and 3D polycrystals; calculates andcompares thesis estimates with V-R, HS, PĐC, SC estimates.Chapter 4 applies FEM to simulate values of 2D polycrystalmacroscopic elastic moduli, compares with analytical results. CHAPTER 1: OVERVIEW1.1. Overview of polycrystaline materials Polycrystalline materials are aggregates of large numbers ofindividual crystals bonded perfectly together. Figure 1.2: Random polycrystalline materials model1.2. Research history of macroscopic elastic moduli1.2.1. Outline the process of developing research fieldCommon approach is using energy priciples, statistical isotropyand symmetric cell hypotheses have been applied to narrow thebounds of estimates from the first order to the second order and 3the third order ones. Experimental data shows that the values ofmacroscopic properties concentrate within higher order bounds.Therefore, third-order estimates are the best ones for themacroscopic properties of polycrystals as well as composites.1.2.2. Typical estimatesa. Voigt- Ruess- Hill estimate (first order)k eff ,  eff : macroscopic bulk and shear elastic moduli;kV , V , kR , R : Voigt, Reuss estimates; Cijkl , Sijkl (i, j, k , l  1, d )  are the stiffness and compliant elastic tensors of α- orientationcrystal, respectively: 1  1   1   kV  Ciijj ; V  2  Cijij  Ciijj  (1.1) d2 d d 2 d ...