Effect of strain rate on crack propagation and fracture toughness of the concrete at mode I and mixed mode I/II

IF 5.6 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics Pub Date : 2025-08-30 DOI:10.1016/j.tafmec.2025.105210

Huidong Cao , Jianfeng Zhao , Ali Arab , Tianyang Du , Shiqi Liu , Chunwei Zhang

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引用次数: 0

Abstract

Although the fracture toughness of concrete materials has been widely studied at different loading rates, the concrete crack propagation and the failure process, which are of great significance to understand the failure mechanism concrete, have been rarely studied. This study conducts the fracture tests at different loading-rate on Semi-circular bending (SCB) specimens with different pre-notched angles by universal testing machine and Split Hopkinson Pressure Bar (SHPB). Digital Image Correlation (DIC) technology is applied to analyze the fracture process of concrete SCB specimens in detail. A new method has been proposed to determine the coordinated time between the SHPB signal and the history of DIC, thereby determining the crack initiation and termination of concrete. The failure on the concrete surface is mainly interfacial transition zone (ITZ) failure, while inside the concrete, the combined failure of aggregates, mortar, and ITZ constitutes the overall fracture at low loading rate. The results show that the peak load of the specimen and its variability increase with loading rate and pre-notched angle, with variability being more sensitive to pre-notched angle. Additionally, as the loading rate increases, the crack propagation speed also increases. The excessively high loading rates should not be used to achieve the expected fracture mode (mode I and mixed mode I/II), and it will overestimate the real value of the fracture toughness. For specimens with β = 0° and 45°,

\dot{K}

_eff should not exceed 212.44

GPa ∙ m^{1 / 2} / s

and 226.63

GPa ∙ m^{1 / 2} / s

for the specimens in the test, respectively. In addition, by inverting the maximum tangential stress (MTS) criterion, the dynamic tensile strength of pre-notched concrete SCB specimens has been determined. This innovative and effective method solves the previously unresolved challenge of calculating dynamic tensile strength in pre-notched SCB specimens. When the loading rates are 3.95 m/s and 4.79 m/s, the tensile strengths of the concrete are 11.63 MPa and 23.45 MPa respectively, and the strain rates are 10.78 s⁻¹ and 88.65 s⁻¹ respectively.

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应变速率对I型和I/II混合模态混凝土裂纹扩展和断裂韧性的影响

虽然对混凝土材料在不同加载速率下的断裂韧性进行了广泛的研究，但对混凝土裂缝扩展和破坏过程的研究却很少，而这对了解混凝土的破坏机制具有重要意义。采用万能试验机和分离式霍普金森压杆（SHPB）对具有不同预缺口角度的半圆弯曲试件进行了不同加载速率下的断裂试验。应用数字图像相关（DIC）技术对混凝土SCB试件的断裂过程进行了详细分析。提出了一种确定SHPB信号与DIC历史之间协调时间的新方法，从而确定混凝土裂缝的起裂和终止。混凝土表面的破坏主要是界面过渡区破坏，而混凝土内部则是集料、砂浆和界面过渡区共同破坏，形成低加载速率下的整体断裂。结果表明：试件的峰值荷载及其变异性随加载速率和预缺口角的增大而增大，且变异性对预缺口角更为敏感；此外，随着加载速率的增加，裂纹扩展速度也随之增加。过高的加载率不能达到预期的断裂模式（I型和I/II混合模式），会高估断裂韧性的真实值。对于β = 0°和45°的试样，试验试样的K≤212.44 GPa∙m1/2/s和226.63 GPa∙m1/2/s。此外，通过反求最大切向应力（MTS）准则，确定了预缺口混凝土SCB试件的动抗拉强度。这种创新和有效的方法解决了以前未解决的计算预缺口SCB试件动态抗拉强度的挑战。加载速率为3.95 m/s和4.79 m/s时，混凝土抗拉强度分别为11.63 MPa和23.45 MPa，应变速率分别为10.78 s−1和88.65 s−1。

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来源期刊

Theoretical and Applied Fracture Mechanics 工程技术-工程：机械

CiteScore

8.40

自引率

18.90%

发文量

435

审稿时长

37 days

期刊介绍： Theoretical and Applied Fracture Mechanics'' aims & scopes have been re-designed to cover both the theoretical, applied, and numerical aspects associated with those cracking related phenomena taking place, at a micro-, meso-, and macroscopic level, in materials/components/structures of any kind. The journal aims to cover the cracking/mechanical behaviour of materials/components/structures in those situations involving both time-independent and time-dependent system of external forces/moments (such as, for instance, quasi-static, impulsive, impact, blasting, creep, contact, and fatigue loading). Since, under the above circumstances, the mechanical behaviour of cracked materials/components/structures is also affected by the environmental conditions, the journal would consider also those theoretical/experimental research works investigating the effect of external variables such as, for instance, the effect of corrosive environments as well as of high/low-temperature.