In this work more than 2500 published experimental data on hardness and indentation fracture toughness of cemented carbides during the last 40 years have been collected. The significant number of ...samples displays the influence of microstructure, chemical composition, and processing on the hardness - toughness relationship of cemented carbides. Selected two-dimensional plots are presented and discussed as an example of visualization of the available experimental information. This collected record can serve as an initial reference set for the cemented carbide community using all available shared knowledge organized in one well-structured database.
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•2500 published experimental data on hardness and indentation fracture toughness of cemented carbides•Shared knowledge of cemented carbides during last 40 years organized in structured database•Microstructure, chemical composition and processing influence on the Hv-KIC of cemented carbides•Selected two-dimensional Hv-KIC plots for visualization of the available experimental information
The fatigue/fracture behaviour of bi-material Aluminium/CFRP (Carbon-Fibre Reinforced Polymer) bonded joints was addressed in this work using the modified Paris law. Five types of tests were employed ...to cover appropriately the entire mode I – mode II range. Data reduction schemes based on equivalent crack length concept were developed for all types of tests. Following this methodology, the compliance versus number of cycles relation becomes sufficient to perform post-processing fatigue data analysis. The coefficients of the modified Paris law for each type of test were obtained by fitting a power law to the crack growth rate versus the ratio of total strain energy release rate and its critical value. The objective was to obtain relations representative of the evolution of those coefficients as function of mode ratio. These relations were subsequently input in a cohesive zone model at the local level, i.e., at each integration point. It was verified that the compliance versus number of cycles curves and the fatigue lives predicted numerically are in agreement with the experimental values.
•Mixed-mode I + II fracture parameters of thermally treated granite were measured.•The effect of high temperature on the mixed-mode fracture parameters were discussed.•GMTS criterion was applied to ...discuss the evolution of the fracture parameters.
The destruction and fracture failure of heat-treated rock structures have been major issues in the underground engineering, such as disposal of highly radioactive nuclear waste, deep mining and exploitation of geothermal resources. Although several literatures have focused on studying the mode I fracture toughness and mode I fracture characteristics of heat-treated rocks, studies of the thermal effect on the mixed-mode fracture toughness and mixed-mode fracture characteristics are rare. Additionally, there is a lack of systematic study to analyse the fracture characteristics of heated rocks on theoretic aspects. In this paper, lots of mixed-mode I + II fracture tests were conducted on a heat-treated granite using straight-through notch Brazilian disc specimens. A total of six specimen groups (25, 100, 200, 400, 600 and 800 °C) and four loading mixities (Mode I loading, mode II loading and two mixed-mode loadings) are selected to apply the fracture tests. The results show that temperature treatment can both significantly affect the brittleness and the mixed-mode fracture toughness of the granite, but the fracture initiation angle is not sensitive to high temperature. The mode I fracture toughness and mixed-mode fracture toughness develop similar trend with increasing treatment temperature. The theoretical fracture models can be effectively applied to predict variations of the mixed-mode fracture parameters. This research also indicates that fracture parameters at high temperature are likely to be predicted by the well-known fracture criterion by only taking the rock physical and mechanical parameters at natural temperature. This work could provide a reference to the research on the mechanical properties and fracture failure of rocks during restoring of post-fire rock structures or hydraulic fracturing of hot dry rocks.
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•The notched three-point bend specimens are tested by the modified Hopkinson bar setup to study the initiation and propagation fracture toughness of AA7475-T7351 aluminium alloy under ...dynamic conditions.•The fracture behaviour of AA7475-T7351 aluminium alloy at 9 different loading rates and 7 different temperatures (-150 °C to 200 °C) are studied.•The temperature sensitivity and loading rate sensitivity of the T-L direction are higher compared to L-T direction samples.•The material models are proposed for the initiation and propagation fracture toughnesses of AA7475-T7351.
The fracture behaviour of the aluminium alloy AA7475-T7351 at different loading rates and temperatures (-150 °C to 200 °C) is investigated here. The three-point bend experiments are conducted at Zwick/Roell-50 UTM (crosshead speed up to 100 mm/min), MTS-250 machine (crosshead speed upto 1000 mm/min) and modified Hopkinson pressure bar (striker velocity 11–19 m/s) to understand the initiation and propagation fracture toughness of AA7475-T7351 aluminium alloy along the rolling (L-T) and transverse (T-L) directions. The digital image correlation (DIC) technique is used to obtain the load point displacement (LPD) and crack mouth opening displacement (CMOD) and the same is used to calculate the stress intensity factor (SIF). The fracture surface is studied using a digital stereo microscope (DVM6) and scanning electron microscope (SEM). The fracture toughness of AA7475-T7351 is found to depend on the loading rates and temperatures and found to vary between 50 and 66 MPm1/2 along the L-T direction, whereas the corresponding value along the T-L direction is comparatively less.
Toughening mechanism of the double network (DN) hydrogel has garnered significant attention in recent years. To interpret this mechanism effectively, studying the fracture toughness of DN gels ...becomes essential. In DN gels, the apparent fracture toughness is initially decomposed into two components: the dissipated fracture toughness and the intrinsic fracture toughness. However, further decomposition of these two components and understanding the relationships between them remain areas of ongoing investigation. In this study, we propose a fracture model aimed at elucidating the relationships between the components of apparent fracture toughness. By partitioning the area under the uniaxial tensile curve of the DN gel into five regions, we decompose the apparent fracture toughness into four components. The expressions for these components are derived, and we employ four quantities to characterize the toughening mechanism of the DN gel. The proposed fracture model quantitatively demonstrates that the fracture toughness of the DN gel is enhanced through the presence of two interpenetrating networks. Through tearing tests conducted on both as-prepared and swelling gel samples, the proposed fracture model is validated and exhibits good agreement with experimental results. This study introduces a method based on uniaxial tensile tests to interpret the toughening mechanism of DN gel, thereby facilitating the synthesis and design of future soft materials.
A novel refractory multi-principal element alloy with high strength and toughness matching characteristics was successfully prepared by mixing TA15 alloy with AlNbTiVZr high-entropy alloy. The ...effects of the composition ratio of the high-entropy alloy on the microstructure evolution and its influence on properties were investigated in this study. The tensile strength of the 70 wt % AlNbTiVZr HEA/Ti multi-principal element alloy is 1.18 times more than that of TA15 alloy, which has a value of 1068.0 ± 2.1 MPa. The increase in strength is mainly due to the production of equiaxed fine grains and the development of a robust and resilient body-centered cubic (BCC) phase in the alloy following the introduction of the high-entropy alloy. The attainment of the acceptable tensile strain is the result of the combined influence of the BCC matrix phase and the dispersed second-phase particles. The exceptional mechanical capabilities of the 70 wt % AlNbTiVZr/Ti multi-principal element alloy undeniably enhance its potential for use as a structural component in aerospace load-bearing constructions.
•The refinement of the microstructure in the alloy is led by inhibiting the grain boundary migration process.•The microstructure evolution and the strengthening mechanism of phase transformation is analyzed quantitatively.•The transformation of the fracture mode by the addition of high-entropy alloy AlNbTiVZr added in TA15 alloy is revealed.
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A tungsten carbide ceramic containing 5 vol% silicon carbide was hot pressed to full density at 1820 °C. A small amount of transient liquid phase based on W-C-Si-O facilitated oxide ...removal in the reducing environment and favoured the development of a bimodal microstructure containing sub-micrometric grains with square or rod-like morphologies. These microstructural features led to outstanding mechanical properties from room to elevated temperatures. For the first time, WC-materials were characterized up to 1500 °C exhibiting flexural strength over 1 GPa in the whole temperature range and fracture toughness from 7 to 15 MPa⋅√m.
Lu2Si2O7 nanostructured environmental barrier coating was prepared using as–synthetic Lu2Si2O7 feedstock via atmospheric plasma spraying. The structure and mechanical performances of Lu2Si2O7 ...coatings were characterized in detail. Results indicate that nanostructured Lu2Si2O7 coating exhibits a bi-modal microstructure, lamella structure and unmelted particles. The phase components of nanostructured Lu2Si2O7 coatings consist of β-Lu2Si2O7 and a small number of X2-Lu2SiO5. Furthermore, the nanohardness and elastic modulus of Lu2Si2O7 coatings have the characterization of bi-modal properties via Weibull analysis, i.e., the large Weibull modulus and the small Weibull modulus represent molten lamella structure and unmelted particles, respectively. Meanwhile, the fracture toughness of nanostructured Lu2Si2O7 coatings is superior to conventional Lu2Si2O7 coatings, and the adhesion strength of Lu2Si2O7 coatings is about 22.6 MPa by pull-extend test. Results of research are helpful for the design and preparation of advanced thermal spray coating.
•Nanostructured Lu2Si2O7 coating exhibits a typical bi-modal microstructure.•The adhesion strength of Lu2Si2O7 coatings is about 22.6 MPa.•The fracture toughness of nanostructured Lu2Si2O7 coatings is superior to conventional Lu2Si2O7 coatings.
This study aims to systematically investigate the influence of boron (0–3.0 wt % B) on microstructure and abrasive wear characteristics of high chromium based multi-component white cast iron (Hi-Cr ...MWCI).
As result, the microstructure is mainly composed of martensite matrix and carborides such as M7(C, B)3, M2(C, B), M23(C, B)6. At low load, B can increase the wear resistance of Hi-Cr MWCI owing to the higher volume fraction of M2(C, B). However, it reduces the wear resistance of material due to low the fracture toughness of primary M7C3 or M7(C, B)3 at high load. Therefore it can be concluded that B addition can improve the abrasive wear resistance of Hi-Cr MWCI at low load, but, the opposite tendency will occur at high load.
•Boron can increase the volume fraction and size of carboride.•The shape and stoichiometry of M2(C,B) carboride is altered from fishbone-like to plate-like by 3.0 wt % B.•Boron addition reduce fracture toughness of M7(C,B)3 carboride but its hardness is improved.•The abrasive wear rate is influenced by the matrix and volume fraction of M2(C,B) carboride at low load.•The abrasive wear rate is strongly influenced by the fracture toughness of M7(C,B)3 carboride at high load.
Barre granite exhibits strong anisotropy due to its pre-existing microcracks induced by long-term tectonic loading. The quantification of rock anisotropy in fracture properties such as mode-I ...fracture toughness under a wide range of loading rates is critical to a variety of rock engineering applications. To quantify fracture toughness of Barre granite, notched semi-circular bend (NSCB) fracture tests are conducted statically with an MTS hydraulic servo-control testing machine and dynamically with a split Hopkinson pressure bar (SHPB) system. Barre granite samples are prepared based on the three principal directions, resulting in six orientation sample groups. For dynamic tests, pulse shaping technique is used to achieve dynamic force balance. The finite element method is then implemented to formulate equations relating the failure load to the mode-I fracture toughness using an orthotropic elastic material model. For samples in the same orientation group, the fracture toughness shows clear loading rate dependence, with the fracture toughness increasing with the loading rate. The fracture toughness anisotropy is characterized by the ratio of the largest fracture toughness over the smallest one at a given loading rate. The mode-I fracture toughness anisotropy exhibits a pronounced rate dependence, being strong under static loading while diminishing as the loading rate increases. The mode-I fracture toughness anisotropy may be understood by considering the preferentially oriented microcracks, which will be fully explored in the future.
► Used the ISRM standard to investigate the dynamic fracture toughness of Barre granite. ► Shaped the loading pulse in SHPB tests to achieve dynamic force balance. ► Developed formulas to determine rock fracture toughness for orthotropic elastic material. ► Quantified both static and dynamic fracture toughness anisotropy of Barre granite. ► Demonstrated rate dependence of the fracture toughness anisotropy of Barre granite.
