scholarly journals Fracture Statistics for Inorganically-Bound Core Materials

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2306 ◽  
Author(s):  
Philipp Lechner ◽  
Jens Stahl ◽  
Florian Ettemeyer ◽  
Benjamin Himmel ◽  
Bianca Tananau-Blumenschein ◽  
...  
Keyword(s):  
Distribution Function ◽  
Fracture Stress ◽  
Brittle Materials ◽  
Weibull Model ◽  
Strength Distribution ◽  
Fracture Characteristics ◽  
Weibull Parameters ◽  
Four Point Bending ◽  
Volume Dependence ◽  
Bending Fracture

In this article, we study the fracture characteristics of inorganically-bound foundry cores. It will be shown that the fracture stress of inorganic cores follows Weibull’s strength distribution function for brittle materials. Using three-point and four-point-bending experiments, the volume dependence of the bending fracture stress is analyzed and a Weibull model fitted. Furthermore, the fracture stress of arbitrary bending experiments can be calculated based on the Weibull parameters found.

Macroscopic Fracture Behaviour of CrN Hard Coatings Evaluated by X-Ray Diffraction Coupled with Four-Point Bending

2013 ◽  
Vol 768-769 ◽  
pp. 272-279
Author(s):  
Mario Stefenelli ◽  
Angelika Riedl ◽  
Juraj Todt ◽  
Matthias Bartosik ◽  
Rostislav Daniel ◽  
...  
Keyword(s):  
Fracture Stress ◽  
Fracture Behavior ◽  
Fracture Behaviour ◽  
Hard Coatings ◽  
Relevant Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Four Point Bending ◽  
Macroscopic Fracture ◽  
Crn Coatings

Fracture behavior of hard nanocrystalline coatings decisively influences the lifetime and performance of coated tools. In this work, residual stresses in as-deposited and annealed CrN coatings deposited at 350 °C using bias voltages of −40 V and −120 V were evaluated using synchrotron X-ray diffraction coupled with four-point bending. The stress development during the bending experiments was used to analyse fracture properties of the coatings. The results indicate that an annealing at 550 °C does not deteriorate the fracture behavior of the coatings prepared using −40 V bias. In the case of −120 V bias coatings, the residual stress relaxation after the thermal treatment is accompanied by a fracture strain decrease and a fracture stress increase. The as-deposited and annealed CrN coatings deposited using −120 V bias exhibit significantly large fracture strains in comparison with −40 V samples. Finally the results document that the fracture stress may not be the only relevant parameter when comparing different coating systems. Also the strain at fracture can be considered as significant indicator of the coating fracture response. Methodologically, the results indicate that in-situ X-ray diffraction coupled with four point bending can be effectively used to evaluate macroscopic fracture behaviour of hard coatings.

scholarly journals Influence of Surface Treatment on Strength Distribution of Vita VMK 68 Dental Porcelains

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Serkan Nohut ◽  
Ahmet Tasdemir ◽  
Suleyman Aykut Korkmaz
Keyword(s):  
Distribution Function ◽  
Weibull Distribution ◽  
Statistical Model ◽  
Surface Treatment ◽  
Goodness Of Fit ◽  
Strength Distribution ◽  
Surface Treatments ◽  
Bending Test ◽  
Dental Ceramics ◽  
Weibull Distribution Function

Weibull distribution function is the most commonly used statistical model for the investigation of mechanical properties of dental ceramics and design process with dental ceramics. However, it is still unclear whether the Weibull distribution function is the most appropriate function for fitting the strength data of dental ceramics with different surface treatments. In this paper, three-point bending test results of feldspathic body porcelain (Vita VMK 68) specimens with four different surface treatments are analysed. According to goodness-of-fit tests (Anderson-Darling test, Kolmogorov-Smirnov test, and Akaike information criterion), it is shown that the type of surface treatment has an important influence on deviation of strength distribution from perfect Weibull statistics. It is concluded that estimation of the most suitable statistical model for Vita VMK 68 is not only a material-dependent but also a process-dependent (machining of the specimens) procedure.

Analysis of Flexure Strength Data of Ceramics

1983 ◽  
Vol 105 (3) ◽  
pp. 219-223 ◽  
Author(s):  
S. G. Seshadri ◽  
M. Srinivasan
Keyword(s):  
Strength Distribution ◽  
Service Performance ◽  
Parameter Estimates ◽  
Reliability Data ◽  
Flexure Strength ◽  
Statistical Strength ◽  
Strength Data ◽  
Weibull Parameters ◽  
Surface Flaws ◽  
Test Population

A method to obtain the two and three Weibull parameters from the statistical strength distribution of ceramics, when either surface flaws or volumetric flaws govern fracture, is outlined. The advantages of obtaining confidence in the parameter estimates are given realizing the flaw severity variations within a test population. The inadequacy of testing a very limited number of specimens to gather reliability data to assess service performance is discussed.

Stress Concentrations for Filled and Unfilled Closely Spaced Cylindrical Defects

1985 ◽  
Vol 107 (4) ◽  
pp. 271-276 ◽  
Author(s):  
T. Ihara ◽  
M. C. Shaw
Keyword(s):  
Brittle Fracture ◽  
Tensile Stress ◽  
Young’S Modulus ◽  
Fracture Stress ◽  
Brittle Materials ◽  
Critical Value ◽  
Stress Concentrations ◽  
High Quality ◽  
Close Spacing ◽  
The Matrix

All real materials contain defects which significantly reduce the fracture stress of brittle materials. It has been proposed by Griffith [3] that brittle fracture occurs when the maximum intensified tensile stress on the surface of a defect reaches a critical value. It has recently been found [1] that for many brittle materials of high quality, the nature and density of the defects are such that they may be modelled by isolated cylindrical voids. This study considers the stress intensification consequences of the close spacing of cylindrical defects that are filled with a material having a Young’s modulus different than that of the matrix.

scholarly journals Change in bending fracture stress of silica based glass reinforced by electron beam irradiation

2003 ◽  
Vol 15 (1/2) ◽  
pp. 6-9
Author(s):  
Atsushi KADOWAKI ◽  
Naoki YAMAGUCHI ◽  
Kousuke TAKAHASHI ◽  
Yoshitake NISHI ◽  
Akira TONEGAWA ◽  
...  
Keyword(s):  
Electron Beam ◽  
Fracture Stress ◽  
Electron Beam Irradiation ◽  
Beam Irradiation ◽  
Bending Fracture

scholarly journals INSTRUMENTATION OF FOUR-POINT BENDING TEST DURING 4D COMPUTED TOMOGRAPHY

2018 ◽  
Vol 18 ◽  
pp. 20 ◽  
Author(s):  
Daniel Kytýř ◽  
Tomáš Fíla ◽  
Petr Koudelka ◽  
Ivana Kumpová ◽  
Michal Vopálenský ◽  
...  
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Process Zone ◽  
Brittle Materials ◽  
Time Lapse ◽  
Bending Test ◽  
Ct Scanner ◽  
X Ray ◽  
Four Point Bending ◽  
4D Computed Tomography

High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading.

scholarly journals Mechanical Behavior of Undoped n-Type GaAs under the Indentation of Berkovich and Flat-Tip Indenters

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1192 ◽  
Author(s):  
Lixia Xu ◽  
Lingqi Kong ◽  
Hongwei Zhao ◽  
Shunbo Wang ◽  
Sihan Liu ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Brittle Materials ◽  
Wing Shape ◽  
Gaas Surface ◽  
Surface Material ◽  
Berkovich Indenter ◽  
Fracture Characteristics ◽  
Slip Bands ◽  
Mechanical Machining ◽  
Depth Curves

In this research, the mechanical behavior of undoped n-type GaAs was investigated by nanoindentation experiments using two types of indenters—Berkovich and flat-tip—with force applied up to 1000 mN. From the measured force-depth curves, an obvious pop-in phenomenon occurred at force of 150 mN with the flat-tip indenter representing elastic–plastic transition. The Young’s modulus and hardness of GaAs were calculated to be 60–115 GPa and 6–10 GPa, respectively, under Berkovich indenter. Based on the observation of indent imprints, the fracture characteristics of GaAs were also discussed. A recovery of crack by the next indentation was observed at 1000 mN with Berkovich indenter. In the case of flat-tip indentation, however, surface material sank into a wing shape from 400 mN. In this sinking region, a density of fork-shaped sinking, slip lines, and crossed pits contributed to the slip bands, and converging crossed twinning deformations inside the GaAs material were generated. Since cracks and destructions on GaAs surface took place more easily under the flat-tip indentation than that of Berkovich, a machining tool with a sharp tip is recommended for the mechanical machining of brittle materials like GaAs.

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