Study on Simple Method to Measure the Dynamic Fracture Toughness of Ductile Material

韧性材料动态断裂韧性简易测量方法的研究

• 批准号: 63550077
• 负责人: KISHIMOTO Kikuo
• 金额: $ 1.28万
• 依托单位: TOKYO INSTITUTE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1988
• 资助国家: 日本
• 起止时间: 1988 至 1989
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63550077/
• 关键词: Impact Fracture Toughness; J-integral; Dynamic Stress Intensity Factor; Plastic Zone Correction; Three-point-bend; One-point-bend; Simple Formula; 衝撃破壊靭値; 落重式衝撃試験; 曲げ試験; J[D4^]D4積分

In determining the impact fracture toughness, the dynamic stress intensity factor is computed if the plastic zone is limited in size compared with crack and specimen dimensions. on the other hand, the J-integral which is the inertia enhanced version of Rice's J-integral has to be evaluated if the specimen exhibits considerable plasticity prior to fracture. The time variation of the dynamic fracture mechanics parameter K_I(t) or J-integral under impact loading may be computed by the finite element method. However, this method requires a large computer time and is not convenient to use in material testing, The purpose of the present project is to develop a simple method to determine the impact fracture toughness of ductile materials. The main results are summarized as follows:(1) The J-integral can be computed by the conventional finite element method with about 5% errors without considering the singularity of the area integral. The singular area integral can be evaluated analytically by fitting the near-tip field with a function which is transformable into a line integral.(2) Simple formulae of J-integral for the three-point and one-point bend specimens have been derived by applying a plastic zone correction to the formulae of the dynamic stress intensity factors. A reasonable accuracy is obtained by the present method as compared with the elastic/viscoplastic finite element computation and the CPU-time is within 1% of the finite element method.(3) The impact fracture toughness test has been conducted. Methods to detect the initiation of crack have been examined. For relatively brittle materials the electric potential method is useful. However, it is impossible to detect crack initiation by this method if the specimen was fractured with a considerable amount of plastic deformation. Further investigation is needed for such ductile materials.

在确定冲击断裂韧性时，如果塑性区的尺寸与裂纹和试件尺寸相比是有限的，则计算动态应力强度因子。另一方面，如果试件在断裂前表现出相当大的塑性，则必须评估J积分，它是赖斯J积分的惯性增强版本。动态断裂力学参数K_i(T)或J积分在冲击载荷作用下的时间变化可用有限元方法计算。然而，这种方法需要大量的计算机时间，不便于在材料试验中使用，本项目的目的是开发一种测定延性材料冲击断裂韧度的简单方法。主要研究结果如下：(1)在不考虑面积积分奇异性的情况下，用常规有限元方法计算J积分，误差约为5%。奇异面积积分可以通过用函数拟合近端场来解析计算，该函数可转换为线积分。(2)通过对动应力强度因子公式进行塑性区修正，导出了三点和一点弯曲试件的J积分的简单公式。与弹粘塑性有限元计算相比，本方法具有较高的计算精度，计算时间仅为有限元计算的1%以内。(3)进行了冲击断裂韧度试验。对裂纹萌生的检测方法进行了研究。对于相对易碎的材料，电位法是有用的。然而，如果试件断裂时有相当大的塑性变形，这种方法是不可能检测到裂纹萌生的。对于这种延性材料还需要进一步的研究。

项目成果

K.Kishimoto et al: "A Simple Formula for the Dynamic Seress Intansity Factor of an Impacted Freely Supported Bend Specimer" JSME International Journal Ser I. 33. 51-56 (1990)

K.Kishimoto 等人：“A Simple Formula for the Dynamic Seress Intansity Factor of an Impacted Freely Supported Bend Specimer” JSME International Journal Ser I. 33. 51-56 (1990)

Kikuo KISHIMOTO, Noriyasu TAKEUCHI, Shigeru AOKI and Masaru SAKATA: "Study on the Accuracy of J-integral Calculation by Finite Element Method" Dynamic Fracture Mechanics For the 1990's, ASME, PVP-160, (1989) 111-116.

Kikuo KISHIMOTO、Noriyasu TAKEUCHI、Shigeru AOKI 和 Masaru SAKATA：“有限元法 J 积分计算精度的研究”动态断裂力学，1990 年代，ASME，PVP-160，(1989) 111-116。

Kikuo KISHIMOTO, Yousuke FUJINO, Shigeru AOKI and Masaru SAKATA: "A Simple Formula for the Dynamic Stress Intensity Factor of an Impacted Freely-Supported Bend Specimen" JSME International Journal Series I, 33, (1990) 51-56.

Kikuo KISHIMOTO、Yousuke FUJINO、Shigeru AOKI 和 Masaru SAKATA：“冲击自由支撑弯曲样本动态应力强度因子的简单公式”JSME 国际期刊系列 I，33，(1990) 51-56。

K.Kishimoto et al.: "A Simple Formula for the Dynamic Seress Intensity Factore of an Impacted Freely Supported Bend Spectmen" JSME Internationd Journal Ser.I. 33. 51-56 (1990)

K.Kishimoto 等人：“A Simple Formula for the Dynamic Seress Intensity Factore of an Impacted Freely Supported Bend Spectmen” JSME 国际期刊 Ser.I。

K.Kishimoto et al: "Dynamic Fraeaure Mechanic Paramcter Estimation for Three-Point Bail Specimen in Large Scale Yielding" Impact Loading and Dynamic Behaviour of Materials. 1. 127-136 (1988)

K.Kishimoto 等人：“大规模屈服中三点保释样本的动态 Fraeaure Mechanic Paramcter Estimation”冲击载荷和材料的动态行为。