Influence of toughness on Weibull modulus of ceramic bending strength

1986 ◽  
Vol 1 (1) ◽  
pp. 120-123 ◽  
Author(s):  
K. Kendall ◽  
N. McN. Alford ◽  
S. R. Tan ◽  
J. D. Birchall
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Crack Length ◽  
Weibull Modulus ◽  
Bending Strength ◽  
Griffith Criterion

It is demonstrated both theoretically and experimentally that fracture toughness does not directly influence the Weibull modulus of ceramic bending strength for materials that obey the Griffith criterion for crack propagation. Weibull modulus remains unchanged as toughness is increased. However, toughness variations with crack length do affect the Weibull modulus. Thus materials that display R-curve behavior or Dugdale character give an increased Weibull modulus and appear more reliable.

scholarly journals Bending strength and reliability of porcelains used in all-ceramic dental restorations

Cerâmica ◽  
2018 ◽  
Vol 64 (372) ◽  
pp. 491-497
Author(s):  
A. A. de Almeida Junior ◽  
G. L. Adabo ◽  
B. R. Galvão ◽  
D. Longhini ◽  
B. G. Simba ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Weibull Modulus ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Weibull Analysis ◽  
Specific Group ◽  
Dental Restorations ◽  
Residual Amorphous Phase ◽  
All Ceramic

Abstract Four dental porcelains for covering zirconia were sintered (fired) at 910-960 °C and characterized, focusing in analyzing reliability, physical and mechanical properties. Samples with relative density close to 99% presented leucite crystallization apart from residual amorphous phase. Hardness between 491±23 and 575±32 HV was different among all ceramics. Fracture toughness between 1.13±0.11 and 1.42±0.25 MPa.m1/2 was statistically different. Bending strength results were not different for three porcelain groups (73±9 to 75±12 MPa), with the exception of one specific group (62±4 MPa). Weibull analysis indicated bending strength between 73 and 75 MPa, Weibull modulus (m) between 5.7 and 7.1, while the ceramic with strength of 60 MPa presented m=13.6. The use of classical theory of fracture mechanics associated to the results of properties obtained in this work indicated the critical failure size in these ceramics lays between 65 and 90 μm and the theoretical fracture energy of porcelains is approximately from 10.5 to 16.3 J/m. It was concluded that the porcelains had different behavior, and it seems that there is no clear relationship among the studied properties.

Microstructure and Mechanical Properties of Sintered Fibrous Monolith Cemented Carbide

2013 ◽  
Vol 815 ◽  
pp. 233-239
Author(s):  
Xue Quan Liu ◽  
Cun Guang Ding ◽  
Chang Hai Li ◽  
Yi Li ◽  
Li Xin Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Crack Propagation ◽  
Fracture Energy ◽  
Bending Strength ◽  
Extrusion Process ◽  
Cemented Carbide ◽  
Cemented Carbides ◽  
Microstructure And Mechanical Properties

A fibrous monolith cemented carbide with WC-6Co as cell and WC-20Co as cell boundaries was produced through hot co-extrusion process in this paper. The density, hardness, bending strength and fracture toughness of the fibrous monolith cemented carbide were tested, and the fracture and crack propagation were observed by metalloscope and SEM. The results showed that the bending strength and fracture toughness of the fibrous monolith cemented carbides was remarkably improved 71.91% and 45.7% respectively, while the hardness was slightly decreased 1% compared with WC-6Co composites. It is the reason that the tougher shell WC-20Co with higher bending strength and fracture toughness can absorb more fracture energy, which can slow down and prevent the crack propagating from brittle core WC-6Co.

scholarly journals Effects of HfC Particles on Crack Initiation and Propagation Behavior of WC/Co Composites

2019 ◽  
Vol 37 (3) ◽  
pp. 628-635
Author(s):  
Xinyu Yan ◽  
Shouren Wang ◽  
Daosheng Wen ◽  
Gaoqi Wang ◽  
Wentao Liu
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Bending Strength ◽  
Crack Tip ◽  
Crack Deflection ◽  
Simulation Software ◽  
Homogeneous Distribution ◽  
The Matrix ◽  
Crack Pinning ◽  
Crack Bifurcation

Tungsten carbide composites were prepared by cold-pressing and hot-pressing sintering; fracture toughness and bending strength of the specimens were tested. The microstructures of HfC/WC/Co composites were observed with the SEM. The mathematical models were established to investigate the relationship between stress intensity factors of crack straight-through, crack deflection, and crack bifurcation with crack length, based on the crack propagation energy release rate. The simulation software ABAQUS was used to verify the four crack propagation methods of crack straight-through, crack deflection, crack bifurcation and crack pinning. The simulation results show that adding appropriate amount of HfC can effectively improve the fracture toughness and bending strength of the composites. The homogeneous distribution of HfC and Co in the matrix has a significant effect on the improvement of the strength and toughness of the composites, and the improvement mechanism is to disperse or transfer the stress at the crack tip to HfC by crack deflection, crack bifurcation, crack pinning, transcrystalline fracture, etc. As a result, the stress concentration at the crack tip in the matrix is reduced, and the toughness of the composites is improved.

Properties of Nanostructured 3Y-TZP Blocks Used for CAD/CAM Dental Restoration

2008 ◽  
Vol 396-398 ◽  
pp. 603-606 ◽  
Author(s):  
Claudinei dos Santos ◽  
Felipe Antunes Santos ◽  
Carlos Nelson Elias
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Weibull Modulus ◽  
Bending Strength ◽  
Dental Restoration ◽  
Tetragonal Zro2 ◽  
All Ceramic ◽  
Cad Cam ◽  
Ceramic Blocks ◽  
Xrd Patterns

Several CAD/CAM systems are available to dental prosthesis laboratories which can be used to fabricate all-ceramic copings and frameworks. The use of these systems presents low demand, due principally the high blocks ceramics cost used for theses systems. Usually, these ceramic blocks are sintered at high temperatures, between 1450 and 15500C, resulting in micrometric ZrO2 microstructure. A considerable innovation in these ceramics systems used in CAD/CAM applications was introduced by the use of nanometric-tetragonal ZrO2 blocks, which are sintered at low sintering temperatures resulting in nanometric grains morphology and improved mechanical properties. The purpose of the present work is to characterize the mechanical properties of nanoparticled zirconium oxide blocks comparing with commercial micrometric ceramic parts. XRD patterns showed that the blocks have only the tetragonal-ZrO2 as crystalline phase. The tetragonal-monoclinic transformation phase was responsible for the excellent mechanical properties. Nanometric blocks presented hardness of 13GPa, fracture toughness of 11MPam1/2 , bending strength of 1020MPa and Weibull modulus, m=14, while micrometric ZrO2 blocks similar hardness, fracture toughness 8.5MPam1/2, bending strength of 850MPa and Weibull modulus of 10.

Understanding the thermal durability of wood-based composites (WBCs) using crack propagation fracture toughness

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sweta Mahapatra ◽  
Arijit Sinha ◽  
John A. Nairn
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Bending Strength ◽  
Oriented Strand Board ◽  
Medium Density Fiberboard ◽  
Strength Properties ◽  
Wood Products ◽  
Trilinear Model ◽  
Different Temperatures

Abstract Wood-based composites (WBCs) are engineered wood products that are commonly used in the building and furniture industries. Most research on their durability has relied on internal bond testing, bending strength properties, or damage observations. An alternative property with potentially more information is fracture toughness. Here, fracture toughness was continuously measured during crack propagation for three different composites—oriented strand board (OSB), medium density fiberboard (MDF), and particleboard (PB). The resulting plots for fracture toughness as a function of crack growth are known as the material’s R curve. To assess the role of temperature on WBC durability, R curve experiments were repeated at 10 different temperatures from 20 to 200 °C. Trends in experimental results could be described by a trilinear model. OSB and MDF toughness initially increased with temperature and then decreased above 80 °C. The toughness of PB, which was made with a different resin, remained constant or decreased slightly until decreasing faster above 140 °C. Both the resin type and composite structure affected the results.

Influence of Porosity on Fracture Toughness and Fracture Behavior of Antibiotic-Loaded PMMA Bone Cement

2021 ◽  
Author(s):  
Sunjung Kim ◽  
Caroline Baril ◽  
Shiva Rudraraju ◽  
Heidi-Lynn Ploeg
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Bone Cement ◽  
Pore Size ◽  
Bending Strength ◽  
Volume Fraction ◽  
Total Joint Replacement ◽  
Experimental Results ◽  
Pmma Bone Cement ◽  
Cement Strength

Abstract Aseptic loosening is the most common reason for long-term revision of total joint replacement (TJR). Infection is the main reason for short-term revision of TJR. In our previous studies, experimental results showed that acrylic bone cement-loaded with antibiotics had a detrimental effect on cement strength such as bending strength, compressive strength, and fracture toughness. This result implied that the mechanical failure of antibiotic loaded bone cement was potentially related to porosity volume fraction. Hence, the objective of this study was to investigate the effect of pore size and distribution on bone cement fracture toughness. The effect of pores was analyzed using the extended Finite Element Method (X-FEM) method to model crack propagation and its modulation by pore sizes and locations. Numerically obtained load-displacement responses were compared to experimental results. We observed that crack propagation is affected by several pore parameters; as expected these include pore size and pore locations (pore-pore interactions) and are related to implicit pore-crack interactions. The experimental and numerical investigations presented in the current study contribute to a better understanding of the effect of pores on bone cement fracture toughness; key insights include the identification of a critical pore size for reduced fracture toughness, and relative insensitivity of crack propagation to stochastically distributed pore locations.

Fractal Properties of Fracture Surfaces: Roughness Indices and Relevant Lengthscales

1994 ◽  
Vol 367 ◽  
Author(s):  
Elisabeth Bouchaud
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Correlation Length ◽  
Crack Velocity ◽  
The Self ◽  
Fracture Surfaces ◽  
Griffith Criterion ◽  
Fractal Properties ◽  
Roughness Index ◽  
Static Fracture

AbstractExperiments aiming at the measurement of the roughness index ζ of “rapid” fracture surfaces are briefly reviewed. For rapid crack propagation, measured values of ζ are close to 0.8, which seems to be a universal exponent. However, it is argued, by re-writing the Griffith criterion for a self-affine crack, that the self-affine correlation length ξ might depend upon the microstructure, and hence on the fracture toughness. More recent experiments are also described, which reveal at smaller lengthscales the existence of a quasi-static fracture regime separated from the previously studied rapid fracture regime by a crossover length which decreases with increasing crack velocity.

Assessing the role of adhesives in durability of laminated veneer lumber (LVL) by fracture mechanics

Holzforschung ◽  
2016 ◽  
Vol 70 (8) ◽  
pp. 763-771 ◽  
Author(s):  
Babak Mirzaei ◽  
Arijit Sinha ◽  
John A. Nairn
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Crack Length ◽  
Mechanical Performance ◽  
Phenol Formaldehyde ◽  
Laminated Veneer Lumber ◽  
Conventional Tests ◽  
Durability Assessment ◽  
Strength And Stiffness

Abstract This study explored the suitability of fracture toughness properties for durability assessment of wood composite panels by observing changes in fracture toughness during crack propagation following cyclic exposure to moisture conditions. The main objective was to develop a new method for ranking the role of adhesives in the durability of wood-based composites. This new approach was compared to conventional mechanical performance tests, such as observing strength and stiffness loss after exposure. Comparing changes in fracture toughness as a function of crack length after moisture cycling shows that this approach can distinguish different adhesive systems on the basis of their durability, while conventional tests fail in this regard. The most and least durable adhesives (polyvinyl acetate and phenol formaldehyde) could be distinguished based on steady-state toughness alone, but this was not the case for the performance of two other adhesives (emulsion polymer isocyanate and phenol resorcinol formaldehyde). Further analysis of experimental R curves (toughness as a function of crack length) based on kinetics of degradation was able to rank all adhesives confidently. Probably, the failure of conventional tests in this context is that they are based on initiation of failure, while the fracture tests require consideration of fracture properties after a significant amount of crack propagation has occurred.

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