纯钛塑性变形行为的晶体塑性有限元模拟

硕士学位论文

纯钛塑性变形行为的晶体塑性

有限元模拟

THE FINITE ELEMENT SIMULATION ON PLASTIC BEHAVIOR OF PURE

TITANIUM

黄晓华

2010年7月

国内图书分类号：TG113.12 学校代码：10213国际图书分类号: 669.017.3 密级：公开

工学硕士学位论文

纯钛塑性变形行为的晶体塑性

有限元模拟

硕 士 研 究 生： 黄晓华

导 师： 来忠红 副教授

申 请 学 位： 工学硕士

学 科、专 业： 材 料 学

所 在 单 位： 材料科学与工程学院

答 辩 日 期： 2010年7月

授予学位单位： 哈尔滨工业大学

Classified Index: TG113.12

U.D.C: 669.017.3

Dissertation for the Master Degree in Engineering THE FINITE ELEMENT SIMULATION ON PLASTIC BEHAVIOR OF PURE

TITANIUM

Candidate：Huang Xiaohua

Supervisor：Associate Prof. Lai Zhonghong Academic Degree Applied for：Master of Engineering Speciality：Materials Science

Affiliation：School of Materials Science and Engineering

Date of Defence:July, 2010

Degree-Conferring-Institution:Harbin Institute of Technology

哈尔滨工业大学工学硕士学位论文

摘要

本文采用晶体塑性有限元(Crystal Plasty Finite Element Method，CP-FEM)为基础，结合Voronoi图表技术建立了包含纯钛材料基本参数的单晶体和多晶体塑性变形有限元模型，从细观角度研究了晶体的变形行为。

首先利用晶体塑性有限元方法，建立了纯钛单晶塑性变形模型，对钛单晶体的拉伸变形行为进行了研究，模拟结果表明在边界约束条件下，单晶体拉伸变形的同时发生了取向的旋转，其滑移系的滑移方向会逐步趋向于与拉伸方向平行。

利用建立的单晶体模型研究了晶体初始取向与晶体滑移的宏观力学响关系，结果表明，软位向方向拉伸的拉伸应力小于硬位向方向拉升应力，模拟变形过程符合Schmid定律。

通过Voronoi图表信息建立了TA2多晶体模型，并模拟了拉伸变形，对照真实材料拉伸实验，分析了晶体变形过程的外形、组织形貌及应力应变关系，模拟与实验结果接近。分段表征了TA2多晶体模型变形的应力应变演化过程，描述了多晶体塑性变形弹性阶段、屈服阶段、硬化阶段与颈缩阶段应力应变分布，详细分析了晶粒变形的不均匀性的微观机制，说明了桔皮组织的形成过程。

分析了不同晶粒尺寸对多晶体塑性变形行为的影响，研究结果表明，随着晶粒度减小，晶体屈服强度增大，硬化曲线变陡，结果符合Hall-Petch关

σ=64.9MPa，K=473.3MPa xμm1/2。系，预测TA2纯钛的Hall-Petch常数为

利用设定同取向晶粒建立织构模型的方法研究了初始织构对多晶体变形各向异性及应力应变关系的影响，结果表明随着织构强度的升高，多晶体变形不均匀性增大，多晶体屈服强度升高，硬化曲线变陡。

关键词：TA2纯钛；塑性变形；有限元模拟；晶粒取向；晶粒尺寸；织构

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哈尔滨工业大学工学硕士学位论文

Abstract

Based on Crystal Plasty Finite Element Method (CP-FEM) and Voronoi diagram, the poly-crystal plasticity finite element model of single crystalline and polycrystalline materials of TA2 pure titanium is set up. And the deformation behavior of crystal from the microscopic view was researched by this finite element model.

The tensile deformation behavior of single crystalline was studied firstly and the results show that the rotation of orientation occurred at the same time with the tensile deformation of single crystalline and the slip direction of slip-systems could gradually parallelled with the tensile direction.

Influence of orientation factors during uniaxial tension of single crystal metal is studied using the model of single crystalline. The results show that different orientation factors have contributed to the yield strength and tensile stress during plastic deformation. With the orientation factor reduced, the yield sress of single crystalline becomes lower, which accords with Schmid’s law.

Compare the results of the model of single crystalline with the results of the actual material tensile tests, the change of metallographic structure and the tensile curve from simulation analysis results are well in agreement with that of experment. The relationship between the deformation course、the morphology of microstructures and the stress was analyzed, the evolution of stress and strain of polycrystalline deformation were catalyzed, the stress and strain distributions in elastic stage、plastic stage、hardening stage and the necking stage were described. The inhomogeneity of micro mechanism of plastic deformation of polycrystalline was described in detail. According to the inhomogeneity micro mechanism, the formation mechanism of tangerine peel is investigated.

The influences of the different grain size to the behavior of the plastic deformation of polycrystalline were analyzed. The yield stress increased with the decreasing of the size of crystal grains, the hardening curve began to climb quite steeply and the maximum tensile stress increased. The increasing rule accord with Hall-Petch’s law, the predictive factors of TA2 titanium by simulation are σ=64.9MPa，K=473.3MPa xμm1/2.

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