| 管俊峰,胡晓智,李庆斌,吴智敏.边界效应与尺寸效应模型的本质区别及相关设计应用[J].水利学报,2017,48(8):955-967 |
| 边界效应与尺寸效应模型的本质区别及相关设计应用 |
| Essential difference and design application of boundary effect model and size effect model |
| 投稿时间：2016-12-29 |
| DOI：10.13243/j.cnki.slxb.20161175 |
| 中文关键词: 边界效应 尺寸效应 三点弯曲 骨料最大粒径 断裂韧度 拉伸强度 |
| 英文关键词: boundary effect size effect three-point-bend maximum aggregate size fracture toughness tensile strength |
| 基金项目:国家自然科学基金重点项目（51339003）；国家自然科学基金项目（51779095）；郑州市科技攻关项目（153PKJGG111） |
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| 全文下载次数: 2026 |
| 中文摘要: |
| 本文研究了边界效应模型（BEM）与尺寸效应模型（SEM）的本质区别及设计应用功能。研究发现：对于SEM，不同缝高比α的试件须应用4个不同的多参数经验方程，且SEM仅限于试验数据拟合功能。BEM仅有唯一解析解，一方面，可由试验数据拟合确定材料参数——断裂韧度KIC和拉伸强度ft；另一方面，可由已确定的KIC和ft建立描述结构破坏的完整设计曲线。基于BEM，进一步分析了试件到结构变化（尺寸高度W从25到25000 mm），对材料3种破坏模式（ft强度控制、KIC韧度控制、准脆性断裂）的本质影响规律。理论研究表明：对于裂缝非常长和尺寸非常大的结构，已满足线弹性断裂条件，因而无须采用尺寸效应模型。尺寸效应的研究仅可应用于裂缝尖端靠近前边界或者后边界的情况，尺寸效应仅为边界效应的特例。最后，基于W依次为40、93、215和500 mm，α依次为0、0.02、0.075、0.15和0.3的混凝土三点弯曲梁的断裂试验成果，采用BEM系统分析了不同试验数据的组合情况对材料参数KIC和ft确定的影响规律。试验结果分析表明：当试验数据满足一定数量后，从整体数据中任意删去1组或2组数据，采用BEM确定的KIC和ft变化较小而基本一致。由不同尺寸W而相同缝高比α的几何相似试件，或不同缝高比α而相同尺寸W试件的峰值荷载Pmax，都可确定出材料参数KIC和ft。本文所提BEM为解决由小尺寸试件确定无尺寸效应的材料参数，及由材料参数预测实际结构破坏等问题提供了新的思路。 |
| 英文摘要: |
| A comparative study of the essential difference, design, and application of boundary effect mod-el (BEM) and size effect model (SEM) was conducted. SEM applies the four different multi-parameter em-pirical equations to the different ratio of initial crack length and specimen depth α. SEM is limited to a da-ta-fitting function. BEM model involves the use of a unique analytical solution. On one hand,BEM can de-termine the material parameters-fracture toughness KIC and tensile strength ft through the fitting of experimen-tal data. On the other hand, it can establish a complete designed curve that describes the overall fracture of structure based on the identified KIC and ft. The effect on three fracture controlled model (ft-controlled, KIC-controlled and quasi-brittle fracture) were systematically calculated and analyzed from specimen to struc-ture (size W=25-25000mm). The results show that linear elastic fracture mechanics (LEFM) applies for very long crack and very large structures, and there is no further need for size effect study. The size ef-fect model is only relevant when the crack tip is close to either the front or back boundaries. The so-called "size effect" is only a special case of boundary effect. Based on the results of fracture tests (the specimen size W is 40, 93, 215 and 500 mm, and the ratio of initial crack length and specimen depth α is 0, 0.02, 0.075, 0.15 and 0.3), the different combination conditions of tested data that BEM systemati-cally studied are adopted to determine the influence law of KIC and ft. The results are shown that, values are basically consistent to KIC and ft, which have been determined by BEM, when the test data reaches a certain amount and one or two groups of data are removed from the overall data, either the specimens have the different W with same α=a0/W, or the same W but different α=a0/W. The studied results of this paper gave a new ideal to solve the problem that the material parameters cannot be accurately obtained us-ing small size specimen,as well as the problem on predicting the actual structure fracture by using the ma-terial parameters. |
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