重组竹横向准脆性断裂的断裂参数

谢鹏; 刘问; 胡雨村; 孟鑫淼; 张涵政

doi:10.13801/j.cnki.fhclxb.20191127.001

重组竹横向准脆性断裂的断裂参数

doi: 10.13801/j.cnki.fhclxb.20191127.001

谢鹏¹,
刘问^{1, 2, ,},
胡雨村^{1, 2},
孟鑫淼^{1, 2},
张涵政¹

1.
北京林业大学　水土保持学院，北京 100083
2.
水土保持国家林业局重点实验室，北京 100083

基金项目: 科技部国家重点研发计划（2017YFC0703502）

详细信息

通讯作者:
刘问，博士，副教授，硕士生导师，研究方向为断裂力学、竹木结构　E-mail: liuwen@bjfu.edu.cn

中图分类号: TB332
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- 被引次数: 0
出版历程
- 收稿日期: 2019-08-04
- 录用日期: 2019-10-05
- 网络出版日期: 2019-11-28
- 刊出日期: 2020-06-15

Fracture parameters of bamboo scrimber’s transverse quasi-brittle fracture

XIE Peng¹,
LIU Wen^{1, 2
, ,},
HU Yucun^{1, 2},
MENG Xinmiao^{1, 2},
ZHANG Hanzheng¹

1.
School of Water and Soil Conservation, Beijing Forestry University, Beijing 100083, China
2.
Key Laboratory of State Forestry Administration of Water and Soil Conservation, Beijing 100083, China

摘要

摘要: 重组竹是一种可再生的绿色建筑结构复合材料，具有结构致密均匀、力学性能高强稳定、尺寸因需而定、原材料利用率高等特点，在工程应用方面前景广阔。为研究重组竹横向准脆性断裂的断裂参数，对不同尺寸重组竹单边缺口(SEN)试样进行三点弯曲断裂试验，基于边界效应模型（BEM），引入平均粒径G这一重要的细观结构参量，建立重组竹细观结构与宏观力学性能之间的关系，由试验得到的峰值荷载P_max计算重组竹横向准脆性断裂的断裂参数，包括抗拉强度f_t和断裂韧度K_IC。经正态分布分析得到重组竹断裂参数均值μ_f和μ_K，且在具有96%可靠性范围几乎覆盖了全部试验离散点，结果如下：f_t=μ_f=216.36 MPa，K_IC=μ_K=16.76 MPa·m^1/2。并利用实验室常规尺寸试样预测重组竹断裂参数，与试验结果之间的误差仅为3.17%。此外，随着重组竹试样缝高比α的增加，其断裂参数先增大后减小。
- 重组竹 /
- 断裂参数 /
- 准脆性断裂 /
- 边界效应模型 /
- 尺寸效应
Abstract: As a renewable and green composite material for buildings, bamboo scrimber has the advantages of densified and uniform micro-structure, high strength, variable size and shape and high utilization rate of raw materials. Therefore, bamboo scrimber has a broad prospect in civil engineering. In order to study the quasi-brittle fracture of bamboo scrimber in the transverse direction, three-point-bending tests were carried out on single-edge-notch (SEN) bamboo scrimber samples with different sizes. Based on the boundary effect model (BEM) in fracture mechanics, a quantified relation between the micro-structure and the mechanical properties of bamboo scrimber was established by introducing an important micro-structure parameter—average grain size G. Its transverse fracture parameters including tensile strength f_t and fracture toughness K_IC were calculated by the peak loads P_max obtained from the tests. Then, the normal distribution was adopted to obtain μ_f and μ_K, the mean value of the fracture parameters as well as to cover the experimental scatters with 96% reliability, with the result as follows: f_t=μ_f=216.36 MPa, K_IC=μ_K=16.76 MPa·m^1/2. The fracture parameters can be predicted by normal-size samples in the laboratory, and the error between the predicted and tested results is only 3.17%. The fracture parameters tend to increase first and then decrease with the increase of crack length to sample height ratio.
- bamboo scrimber /
- fracture parameter /
- quasi-brittle fracture /
- boundary effect model /
- size effect

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图 1 三点弯曲试验示意图

Figure 1. Schematic diagram of three-point bending test

下载: 全尺寸图片幻灯片

图 2 不同高度几何相似重组竹SEN试样示意图

No.1-6 refers to the sample groups with different heights：No.1：S-10-2.5-0.3; No.2：S-20-2.5-0.3; No.3：S-30-2.5-0.3; No.4：S-50-2.5-0.3; No.5：S-100-2.5-0.3; No.6：S-150-2.5-0.3.

Figure 2. Schematic diagram of bamboo scrimbers’ SEN samples with different heights which are geometrically similar

下载: 全尺寸图片幻灯片

图 3 相同高度不同缝高比重组竹SEN试样示意图

Figure 3. Schematic diagram of bamboo scrimbers’ SEN samples with the same height and different crack length to sample height ratios

下载: 全尺寸图片幻灯片

图 4 重组竹破坏断面

Figure 4. Fracture failure surface of bamboo scrimber

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图 5 重组竹边界效应模型（BEM）断裂模式一般关系曲线

Figure 5. General boundary effect model (BEM) relation curves for fracture failure pattern of bamboo scrimber

下载: 全尺寸图片幻灯片

图 6 选择的各组重组竹三点弯曲试验荷载-挠度曲线

Figure 6. Selective load-deflection curves of bamboo scrimber by 3-point-bending test

下载: 全尺寸图片幻灯片

图 7 重组竹试样S20-2.5-0.3-7的断裂破坏

Figure 7. Fracture failure of bamboo scrimbers’ samples S20-2.5-0.3-7

下载: 全尺寸图片幻灯片

图 8 重组竹荷载-挠度曲线示意图

Figure 8. Schematic diagram of bamboo scrimbers’ load-deflection curve

下载: 全尺寸图片幻灯片

图 9 重组竹名义强度σ_n在虚拟裂纹Δa_fic上的分布

Figure 9. Bamboo scrimbers’ constant normal strength σ_n distributes over fictitious crack Δa_fic

下载: 全尺寸图片幻灯片

图 10 重组竹抗拉强度f_t和断裂韧度K_IC的三种分布模型分析结果

Figure 10. Three distribution models’ analysis results of bamboo scrimbers’ tensile strength f_t and fracture toughness K_IC

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图 11 基于正态分布的重组竹P_max-A_e和σ_n-a_e曲线关系预测

Figure 11. Bamboo scrimbers’ P_max-A_e and σ_n-a_e relation prediction based on normal distribution

下载: 全尺寸图片幻灯片

图 12 重组竹常规尺寸（W=50 mm）试件预测断裂参数

Figure 12. Fracture parameters of bamboo scrimber with conventional size(W=50 mm)

下载: 全尺寸图片幻灯片

图 13 不同缝高比重组竹SEN试样的正态分布

Figure 13. Normal distribution of bamboo scrimbers’ SEN samples with different crack length to sample height ratios

下载: 全尺寸图片幻灯片

表 1 10组不同W、 S/W和α的重组竹单边缺口（SEN）试样

Table 1. Ten groups of bamboo scrimbers’ single-edge-notch (SEN) samples with different W, S/W and α

Group class	Group No.	W/mm	B/mm	S/mm	L/mm	S/W	a₀/mm	a₀/W
Different height W with the same span-height ratio S/W and α(a₀/W)	S-10-2.5-0.3	10	21	25	75	2.5	3	0.3
	S-20-2.5-0.3	20	21	50	100	2.5	6	0.3
	S-30-2.5-0.3	30	21	75	125	2.5	9	0.3
	S-50-2.5-0.3	50	21	125	225	2.5	15	0.3
	S-100-2.5-0.3	100	21	250	330	2.5	30	0.3
	S-150-2.5-0.3	150	21	375	475	2.5	45	0.3
Different α(a₀/W) with the same span-height ratio S/W and height W	S-50-4-0.1	50	21	200	280	4	5	0.1
	S-50-4-0.2	50	21	200	280	4	10	0.2
	S-50-4-0.3	50	21	200	280	4	15	0.3
	S-50-4-0.4	50	21	200	280	4	20	0.4
Notes: There are three numbers in the Group No. First refers to the specimen height W, the second and the third refer to span-height ratio S/W and α.

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表 2 重组竹断裂性能统计描述

Table 2. Statistical description of fracture performance of bamboo scrimber

Property	Tensile strength f_t	Property	Fracture toughness K_IC
Sample number	86	Sample number	86
Average vaule/MPa	216.36	Average vaule/(MPa·m^1/2)	16.76
Standard deviation	26.09	Standard deviation	2.021
Median/MPa	213.24	Median/(MPa·m^1/2)	16.52
Minimum value/MPa	167.05	Minimum value/(MPa·m^1/2)	12.94
Maximum value/MPa	267.93	Maximum value/(MPa·m^1/2)	20.75
Skewness	0.73	Skewness	0.73
Kurtosis	–0.947	Kurtosis	–0.947

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