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Effect of Relative Stress on Post-Peak Uniaxial Compression fracture energy of Concrete

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Journal of Wuhan University of Technology(Materials Science) 2003年第4期18卷 89-92页

作者：王学滨 PANYi-shan LiaoningTechnicalUniversity

fracture energy in strain softening regime was investigated analytically by considering microstructures interaction and *** on gradient-dependent plasticity, the thickness of localized band was determined completely and strictly by characteristic length in relation to average grain *** obtaining the plastic shear displacement of the band,the formula on axial response of concrete was proposed and the analytical post-peak fracture energy was deduced.A comparison between present theoretical results and earlier experimental results was carried out and the analytical result is reasonable and has a plausible foundation as considering the localized failure *** the relative stress leads to increasing the fracture energy *** larger the shear elastic modulus and shear softening modulus,the lower the post-peak fracture energy.A larger fracture energy is caused by a larger thickness of shear band or a larger characteristic length of concrete *** the inclination angle of the shear band and the compressive strength are not concerned with structural size of specimen,the post-peak fracture energy is size independent.

关键词： fracture energy relative stress gradient-dependent plasticity thickness of shear band uniaxial compression characteristic length

fracture energy evaluation on 7075-T651 aluminum alloy welds determined by instrumented impact pendulum

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Transactions of Nonferrous Metals Society of China 2016年第4期26卷 974-983页

作者： R.R.AMBRIZ D.JARAMILLO C.GARCIA F.F.CURIEL Instituto Politécnico Nacional CIITEC-IPN Cerrada de Cecati S/N Col.Sta.Catarina C.P 02250AzcapotzalcaDFMexico Mechanical and Aerospace Engineering Carleton University1125 Colonel By DriveOttawaONK1S 5B6Canada Universidad Autónoma de Coahuila(UAdeC) Facultad de MetalurgiaCarr 57Km 5MonclovaCoahuilaMexico

By using an instrumented impact pendulum, the force versus time curves of 7075-T651 aluminum welds were obtained from standard Charpy-V samples. Considering the force-time curves and constant impact velocity, the fracture energies for different zones were quantified. A fracture energy improvement for the HAZ(33.6 J) was observed in comparison with the weld metal(7.88 J), and base metal(5.37 J and 7.37 J for longitudinal and transverse directions, respectively). This toughness increment was attributed to the microstructural transformation caused by the thermodynamic instability of η′ precipitates during the welding. fracture energy for weld metal was higher than that for base metal, probably due to pores created during solidification. Regarding the dynamic yielding force obtained from the force-time curves, an approximation to the dynamic yield strength for weld, HAZ and base metal was determined. fracture surfaces revealed an intergranular failure for base metal in longitudinal direction, whereas a predominately brittle failure(cleavage) with some insights of ductile characteristics was observed for the transverse direction. In contrast, a ductile failure was observed for weld metal and HAZ.

关键词： 7075-T651 welded joint instrumented Charpy pendulum force-time curve fracture energy dynamic yield strength

A brief discussion on the relationship between apparent stress and slip-weakening law based on the energy partition criteria

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Earthquake Science 2009年第1期22卷 63-67页

作者： Boyan Liu Baoping Shi College of Earth Science Graduate University of Chinese Academy of Sciences Beijing 100049 China

According to the representation theorem of seismic energy radiation, we know that, at any point on the fault, the instantaneous seismic radiation energy, Es, the seismic moment M0, and the apparent stress σa=μEs /M0 （μ is the shear modulus on the fault plane） should be positive values at any time during an earthquake faulting. However, we have noticed that, in recent source parameter inversion scheme for deriving the critical slip-weakening distance, the apparent stress used as a constraint condition on the fault plane could be less than zero or negative value, and the negative part was considered as dissipation energy and incorporated to the fracture energy. Although the mathematical formula in such case has no influence to the final resolution, however, the earthquake dynamic source process violates obviously the basic physical law, which could results in the overestimating of radiated seismic energy. In this study, we have proposed an alternative way to take account of the apparent stress expression based on the earthquake energy partition principle, and at the same time, we have also suggested that an additional constraint regarding to the radiation energy conservation on the fault could be added into the source parameter inversion in order to estimate the critical slip-weakening distance Dc.

关键词： apparent stress seismic radiation energy fracture energy critical slip-weakening distance

Mechanical properties and impact resistance of concrete composites with hybrid steel fibers

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Frontiers of Structural and Civil Engineering 2022年第5期16卷 615-623页

作者： FatihÖZALP Halit Dilşad YILMAZ Burcu AKCAY Department of Civil Engineering Faculty of Engineering and Natural SciencesIstanbul Medeniyet Universityİstanbul 34700Turkey ISTON Istanbul Concrete Elements Factoriesİstanbul 34325Turkey Faculty of Engineering Kocaeli UniversityKocaeli 41000Turkey

The aim of this study is to develop concrete composites that are resistant to armor-piercing projectiles for defense *** reinforcement configurations have been tested,such as short steel fibers,long steel fibers,and steel mesh *** different concrete mix designs were prepared as“Ultra High Performance(UHPFRC),High Performance(HPFRC)and Conventional(CFRC)Fiber Reinforced Concrete”.The content of hybrid steel fibers was approximately 5%in the UHPFRC and HPFRC mixtures,while the steel fiber content was approximately 2.5%in the CFRC *** addition,a plain state of each mixture was *** properties of concrete were determined in experimental *** addition to the fracture energy and impact strength,two important indicators of ballistic performance of concrete are examined,which are the penetration depth and damage *** results of the study show that the depth of penetration in UHPFRC was around 35%less than that in *** was determined that the mixtures of UHPFRC and HPFRC containing 5%by volume of hybrid steel fibers showed superior performance(smaller crater diameter and the less projectile penetration depth)against armor-piercing projectiles in ballistic tests and could be used in defense structures.

关键词： projectile impact depth of penetration fracture energy crater diameter UHPFRC

Effect of Coarse Aggregate Size on and Crack Opening in Normal and Relationship between Stress High Strength Concretes

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Journal of Materials Science & Technology 2005年第5期21卷 691-700页

作者： Jun ZHANG Qian LIU Lin WANG Department of Civil Engineering Tsinghua University Beijing 100084 China

Fine and coarse aggregates play an important role in the fracture of concrete. However, quantitative information available on the effect of the coarse aggregate size on the fracture properties of concrete is still limited. In the present paper, the effect of coarse aggregate size （single grade of 5～10, 10～16, 16～20 and 20～25 mm） on stress-crack opening （σ-w） relation in normal and high strength concretes （compressive strength of 40 and 80 MPa, respectively） was studied. The investigation was based on three-point bending tests implemented by fictitious crack analysis. The result shows that coarse aggregate size and cement matrix strength significantly influence the shape of σ-w curve. For a given total aggregate content, in normal strength concrete, smaller size of aggregate leads to a high tensile strength and a sharp stress drop after the peak stress. The smaller the coarse aggregate, the steeper the σ-w curve. By contrast, in high strength concrete, the effect of aggregate size on σ-w relation almost vanishes. A similar σ-w relation is obtained for the concrete except for the case of 20～25 mm coarse aggregate size. The stress drop after the peak stress is more significant for high strength concrete than that for normal strength concrete. Meanwhile, the smaller the coarse aggregate size, the higher the flexural strength. fracture energy and characteristic length increase with increasing coarse aggregate size in both normal and high strength concretes.

关键词： Aggregate size Stress-crack opening relation fracture energy Bending test

Size effect of fracture characteristics for anisotropic quasi-brittle geomaterials

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International Journal of Mining Science and Technology 2023年第2期33卷 201-213页

作者： Cunbao Li Dongchao Yang Heping Xie Li Ren Jun Wang Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyShenzhen UniversityShenzhen 518060China Shenzhen Key Laboratory of Deep Engineering Sciences and Green energy College of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China MOE Laboratory of Deep Earth Science and Engineering Sichuan UniversityChengdu 610065China

Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture toughness, effective fracture energy and fracture process zone(FPZ) size of geomaterials were first analyzed by systematic size effect fracture experiments. The results showed that the nominal strength and the apparent fracture toughness decreased with increasing bedding plane inclination *** larger the specimen size was, the smaller the nominal strength and the larger the apparent fracture toughness was. When the bedding inclination angle increased from 0° to 90°, the effective fracture energy and the effective FPZ size both first decreased and then increased within two complex variation stages that were bounded by the 45° bedding angle. Regardless of the inherent anisotropy of geomaterials,the nominal strength and apparent fracture toughness can be predicted by the energy-based size effect law, which demonstrates that geomaterials have obvious quasi-brittle characteristics. Theoretical analysis indicated that the true fracture toughness and energy dissipation can be calculated by linear elastic fracture mechanics only when the brittleness number is higher than 10;otherwise, size effect tests should be adopted to determine the fracture parameters.

关键词： Size effect Inherent anisotropy fracture toughness fracture energy Effective FPZ size Quasi-brittle geomaterials

Research on the Bending Impact Resistance and Transverse fracture Characteristics of Bamboo under the Action of Falling Weight

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Journal of Renewable Materials 2023年第1期11卷 473-490页

作者： Hao Jia Benhua Fei Changhua Fang Huanrong Liu Xiubiao Zhang Xinxin Ma Fengbo Sun Department of Biomaterials International Centre for Bamboo and RattanBeijing100102China SFA and Beijing Co-Built Key Laboratory of Bamboo and Rattan Science&Technology State Forestry AdministrationBeijing100102China

Drop weight impact tester was used to accurately measure the bending impact resistance of various parts of Phyllostachys edulis,commonly known as moso bamboo,with a growth cycle of 3–8 *** crystallinity in the bottom(B),middle(M)and top(T)of bamboo at different ages was calculated using peak height analysis in X-ray *** of Spearman correlation analysis was used to represent the correlation between chemical composition and impact *** breaking load(BL),fracture energy(FE)and impact deflection(ID)of 3–8-year-old bamboo were found to be in the range of~670–2120 N,~5.17–15.55 J,and~3.60–~17.76 mm,*** the growth period of bamboo rises,the cellulose crystallinity at the B and T decreases first and then increases,while that for the M increases first and then remains ***,the bending impact performance of bamboo was found to become stable with its growth and *** flexural impact and toughness of the 4-year-old bamboo base material were better than other *** enhancement in the bending impact properties of bamboo at different growth periods was influenced by the lignin content,while the value of FE was mainly positively correlated with ash,cold and hot water extracts and benzyl alcohol *** the content of holocellulose and pentosan,air-dry density and,base density negatively influenced the *** the change in the height of the bamboo,the correlation between its impact mechanical properties and chemical composition gradually *** study provides data support and theoretical basis for the age-appropriate thinning and application of moso bamboo.

关键词： Moso bamboo lifespan bending impact breaking load fracture energy impact deflection chemical composition correlation

Experimental Investigation on fracture Performance of Short Basalt Fiber Bundle Reinforced Concrete

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Structural Durability & Health Monitoring 2022年第4期16卷 291-305页

作者： Jinggan Shao Jiao Ma Renlong Liu Ye Liu Pu Zhang Yi Tang Yunjun Huang School of Water Conservancy and Civil Engineering Zhengzhou UniversityZhengzhou450001China Henan Traffic Engineering Technology Co. Ltd.Zhengzhou450015China Key Laboratory of Deep Underground Science and Engineering(Ministry of Education) College of Architecture and EnvironmentSichuan UniversityChengdu610065China Henan Provincial Communications Planning&Design Institute Co. Ltd.Zhengzhou450015China

In this paper,a notched three-point bending test is used to study the fracture performance of the short basalt fiber bundle reinforced concrete(SBFBRC).To compare and analyze the enhancement effect of different diameters and different content of basalt fiber bundles on the fracture performance of concrete,some groups are set up,and the P-CMOD curves of each group of specimens are measured,and the fracture toughness and fracture energy of each control group are *** fracture toughness and fracture energy are two important fracture performance parameters to study the effect and law of the new basalt fiber bundles on the fracture performance of *** research results show that the diameter and content of the new basalt fiber bundles have a certain effect on the fracture performance of *** the increase of the content of basalt fiber bundles,the peak load,crack initiation toughness,instability toughness and fracture energy of SBFBRC are greatly improved compared with the benchmark *** the fiber bundle diameter is 0.2 mm,the peak load increases by 69.5%compared with the reference *** instability toughness reaches its maximum value at 0.2 mm diameter,which is 59.7%higher than the benchmark.

关键词： Basalt fiber bundle fracture toughness fracture energy fiber concrete

Effect of fly ash replacement level on the fracture behavior of concrete

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Frontiers of Structural and Civil Engineering 2013年第4期7卷 411-418页

作者： Mahdi AREZOUMANDI Jeffery SVOLZ Department of Civil Architectural and Environmental EngineeringMissouri University of Science and TechnologyRolla MO 65409USA

The production of portland cement–the key ingredient in concrete–generates a significant amount of carbon ***,due to its incredible versatility,availability,and relatively low cost,concrete is the most consumed manmade material on the *** method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the *** study presents the results of an experimental investigation that evaluates effect of fly ash replacement level on the fracture energy of *** study includes four mixes with 0%,30%,50%,and 70%fly ash as a cement *** experimental program consisted of 32 fracture beams to study the fracture behavior of *** experimental fracture energies were compared with the fracture energy provisions of different design codes and also different analytical ***,statistical data analyses(parametric and non-parametric)were performed to evaluate whether or not there is any statistically significant difference between the experimental fracture energies of different *** of these statistical tests show that the mix with higher level of fly ash replacement level has higher fracture energy.

关键词： concrete fracture energy fly ash