scholarly journals Research on the Size Effect of Unstable Fracture Toughness by the Modified Maximum Tangential Stress (MMTS) Criterion

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jian Li ◽  
Zhao-Wen Du ◽  
Zhong-Ping Guo ◽  
De-Chun Ai
Keyword(s):  
Fracture Toughness ◽  
Size Effect ◽  
Tangential Stress ◽  
Maximum Tangential Stress ◽  
Unstable Fracture ◽  
Bending Tests ◽  
Three Point Bending ◽  
Higher Order Terms ◽  
Minimum Height ◽  
Significant Size

This paper investigates the unstable fracture toughness of specimens of different heights using the double-K model for three-point bending tests on notched concrete beams. It is shown that unstable fracture toughness exhibits a significant size effect. The modified maximum tangential stress (MMTS) criterion is used to explain the size effect of unstable fracture toughness. The MMTS criterion considers the higher order terms of the Williams series expansion of the stress field. The results show that the MMTS criterion can reasonably estimate unstable fracture toughness. It is recommended that the minimum height of the specimen be 200 mm when three-point bending tests on notched beams are used to determine unstable fracture toughness.

Fracture behaviors of HVFA-SCC mixed with seawater and sea-sand under three-point bending

2022 ◽  
pp. 136943322110273
Author(s):  
Lingzhu Zhou ◽  
Yu Zheng ◽  
Linsheng Huo ◽  
Yuxiao Ye ◽  
Xiaolu Wang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Unstable Fracture ◽  
Replacement Ratio ◽  
Three Point Bending ◽  
Model Code ◽  
Softening Curve ◽  
Sea Sand ◽  
Fracture Behaviors ◽  
Tensile Softening

This paper aims to study the fracture behaviors of high-volume fly ash-self-compacting concrete (HVFA-SCC) mixed with seawater and sea-sand (SWSS) or freshwater and river sand (FWRS). Three-point bending test were performed on 24 notched beams fabricated with varying in replacement ratio of fly ash (0%, 30%, 50%, and 70%) and the type of water and sand (SWSS and FWRS). The initial and unstable fracture toughness of these test specimens are determined by the double- K fracture model. The effect of fly ash replacement ratio and type of water and sand on the fracture parameters is analyzed and discussed. In addition, the cohesive fracture toughness of all the test specimens is calculated by using Gauss–Chebyshev integral method and the weight function method based on the bilinear tensile softening curve given in CEP-FIP Model Code. A comparison of fracture toughness parameters of determined from the experimental approach and analytical approaches is presented in these SCC specimens. Results show that SCC mixed with SWSS replacing FWRS can improve the unstable fracture toughness and fracture energy, and decrease its brittleness behavior. The cohesive fracture toughness of SWSS-SCC specimens is underestimated by these analytical methods based on the tensile softening curve given in CEP-FIP Model Code.

Fracture Toughness and Cracking Behaviour of SCC Compared to VC

2013 ◽  
Vol 577-578 ◽  
pp. 205-208
Author(s):  
Sara Korte ◽  
Veerle Boel ◽  
Wouter de Corte ◽  
Geert de Schutter
Keyword(s):  
Fracture Toughness ◽  
Fracture Process ◽  
Critical Value ◽  
Fracture Parameter ◽  
Self Compacting Concrete ◽  
Bending Tests ◽  
Three Point Bending ◽  
Notched Specimens ◽  
Subsequent Determination

Vibrated concrete (VC) and self-compacting concrete (SCC) have a substantially different composition, resulting in dissimilar mechanical properties regarding cracking behaviour. The critical value of the mode I stress-intensity factor KICis an appropriate fracture parameter for evaluating fracture toughness and can be obtained from three-point bending tests (3PBT) on small, notched specimens. Subsequent determination of the energy release rate thus allows to examine the crack propagation and fracture process of both concrete types. This paper describes the results of such 3PBTs on samples, made from VC and SCC. Evaluation of the cracking behaviour, derived from these results, reveals remarkable differences.

Multi-Parameter Fracture Mechanics: Crack Approaching a Bi-Material Interface

2018 ◽  
Vol 784 ◽  
pp. 79-84
Author(s):  
Lucie Malíková ◽  
Jan Klusák
Keyword(s):  
Tangential Stress ◽  
Initial Crack ◽  
The Finite Element Method ◽  
Material Interface ◽  
Stress Criterion ◽  
Three Point Bending ◽  
Maximum Tangential Stress Criterion ◽  
Higher Order Terms ◽  
Elastic Mismatch ◽  
Crack Propagation Angle

Fracture behaviour of a crack approaching a bi-material interface is investigated. A three-point bending configuration of a cracked specimen is simulated numerically by means of the finite element method and the interaction between the crack and aggregate is studied. The crack deflection angle is estimated by means of the maximum tangential stress criterion in its classical as well as generalized (multi-parameter) form considering the Williams’ power series with various numbers of the higher-order terms for the tangential stress approximation. The influence of the elastic mismatch and of other parameters on the calculated initial crack propagation angle is discussed.

scholarly journals Study of size effect using digital image correlation

2015 ◽  
Vol 8 (3) ◽  
pp. 323-340 ◽  
Author(s):  
A. H. A. SANTOS ◽  
R. L. S. PITANGUEIRA ◽  
G. O. RIBEIRO ◽  
R. B. CALDAS
Keyword(s):  
Digital Image Correlation ◽  
Size Effect ◽  
Digital Image ◽  
Concrete Beams ◽  
Image Correlation ◽  
Displacement Fields ◽  
Bending Tests ◽  
Three Point Bending ◽  
New Methods ◽  
Dic Technique

Size effect is an important issue in concrete structures bearing in mind that it can influence many aspects of analysis such as strength, brittleness and structural ductility, fracture toughness and fracture energy, among others. Further this, ever more new methods are being developed to evaluate displacement fields in structures. In this paper an experimental evaluation of the size effect is performed applying Digital Image Correlation (DIC) technique to measure displacements on the surface of beams. Three point bending tests were performed on three different size concrete beams with a notch at the midspan. The results allow a better understanding of the size effect and demonstrate the efficiency of Digital Image Correlation to obtain measures of displacements.

Evaluation of size effect on mixed-mode fracture behavior of epoxy/silica nanocomposites

2017 ◽  
Vol 52 (4) ◽  
pp. 239-248 ◽  
Author(s):  
Ahmad Ghasemi-Ghalebahman ◽  
Javad Akbardoost ◽  
Yaser Ghaffari
Keyword(s):  
Fracture Toughness ◽  
Tangential Stress ◽  
Mixed Mode ◽  
Fracture Behavior ◽  
Process Zone ◽  
Maximum Tangential Stress ◽  
Mixed Mode Fracture ◽  
Mode Fracture ◽  
Stress Criterion ◽  
Maximum Tangential Stress Criterion

The aim of this study was to examine the effect of size on the mixed-mode fracture toughness of quasi-brittle nanocomposites with the help of modified maximum tangential stress criterion. The literature reveals that the effect of size on mixed-mode fracture behavior of brittle nanocomposites has not been well investigated previously using modified maximum tangential stress criterion. The studied nanocomposites were made of epoxy resin reinforced with 7 wt%, 20–30 nm nanosilica. The accuracy of the method was assessed by taking into account the high-order terms of Williams series expansion along with finite element over-deterministic method. To investigate the effect of size on fracture toughness, a number of three-point semi-circular bending tests with different radii and four angles of edge–crack orientation were conducted and subjected to mixed-mode loading. The size of fracture process zone and apparent fracture toughness ( Kc) were also evaluated as a function of sample size. Experimental results showed that the proposed approach can accurately predict the fracture behavior of studied nanocomposites.

scholarly journals Study on the Static and Dynamic Fracturing Properties of Marble after Being Damaged Dynamically

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yunqiu Liu ◽  
Anqi Fu ◽  
Binsong Jiang ◽  
Liyuan Yu ◽  
Xiaobing Wang
Keyword(s):  
Fracture Toughness ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Cumulative Damage ◽  
Bending Tests ◽  
Three Point Bending ◽  
Cyclic Impact Loading ◽  
Loading Tests ◽  
Cyclic Impact ◽  
The Impact

A split Hopkinson pressure bar (SHPB) system was first used to perform the cyclic impact loading tests on notched semicircular bend (NSCB) marble specimens. Then, static and dynamic three-point bending tests were conducted on these dynamically damaged specimens, respectively. In the cyclic impact loading tests, the dynamic elastic modulus decreases gradually as the impact number increases, but dynamic cumulative damage exhibits a growing trend. In the static and dynamic three-point bending tests, when dynamic cumulative damage is less than 0.345, the dynamic fracture toughness values are larger than the static fracture toughness values, but the experimental data exhibit the opposite results when dynamic cumulative damage ranges from 0.345 to 0.369. Through the quantitative analysis of fracture surface morphologies, the roughness and area of the fracture surfaces increase with an increasing dynamic cumulative damage. Under the same dynamic cumulative damage of the specimens, both the roughness and area of the surfaces fractured by static three-point bending are larger than those fractured by dynamic three-point bending.

scholarly journals Processing and mechanical characterization of Al2O3/Ni and Al2O3/C0 composites by pressureless sintering of nanocomposite powders

2018 ◽  
Vol 12 (2) ◽  
pp. 123-128 ◽  
Author(s):  
Yildiz Kafkaslioğlu ◽  
Hüseyin Yilmaz ◽  
Yahya Tür
Keyword(s):  
Fracture Toughness ◽  
Metallic Phase ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Bending Tests ◽  
Three Point Bending ◽  
Green Strength ◽  
Nanocomposite Powders ◽  
Hardness Values

Al2O3/Ni and Al2O3/Co nanopowder mixtures (with 3 vol.% of metallic phase) were synthesized by heterogeneous precipitation method. In order to increase the green strength, polypropylene carbonate (PPC) was used as a binder while preparing green compacts. Uniaxially pressed powder mixtures were sintered at 1550?C for 2 h in a reducing atmosphere. The effects of Ni and Co nanophases on the microstructure and mechanical properties of Al2O3 ceramics were studied by X-ray diffraction, scanning electron microscopy, Vickers indentation technique and three-point bending tests. The metallic phase hindered the densification of alumina matrix, yet hardness values of Al2O3, Al2O3/Ni, and Al2O3/Co composites were comparable. Vickers fracture toughness results indicate that the composites have higher fracture toughness, but the characteristic flexural strength and Weibull modulus are higher for the pure Al2O3.

Temperature and Orientation Dependence of Fracture Behavior of Directionally Solidified Duplex-Phase Crystals Composed of Ni3X-Type Intermetallic Compounds

2006 ◽  
Vol 512 ◽  
pp. 67-72 ◽  
Author(s):  
Koji Hagihara ◽  
Naoyuki Yokotani ◽  
Yukichi Umakoshi
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
Lamellar Structure ◽  
Fracture Behavior ◽  
Orientation Dependence ◽  
Directionally Solidified ◽  
Bending Tests ◽  
Three Point Bending ◽  
Controlling Mechanism ◽  
Fracture Behaviors

Fracture behaviors of three directionally solidified (DS) duplex-phase alloys composed of Ni3Nb(D0a)/Ni3Al(L12), Ni6TaAl(D024)/Ni3Al(L12) and Ni3Ti(D024)/Ni3Si(L12) phases, respectively were investigated by three-point bending tests, focusing on temperature and orientation dependence. The temperature-toughness relation showed dissimilar curves depending on alloy. The increasing rate of fracture toughness was the highest in the Ni3Al/Ni3Nb alloy with fine lamellar structure and was the lowest in the Ni3Al/Ni6TaAl alloy with rod-like precipitates. The controlling mechanism for the temperature dependence of fracture behavior of Ni3Al/Ni3Nb alloys was discussed.

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