scholarly journals Correlation between Paris function parameters to crack velocity for Alumina ceramics

2011 ◽  
Vol 8 (2) ◽  
pp. 326-332
Author(s):  
Baghdad Science Journal
Keyword(s):  
Experimental Data ◽  
Crack Growth ◽  
Exponential Function ◽  
Crack Velocity ◽  
Alumina Ceramic ◽  
Velocity Versus ◽  
Rate Theory ◽  
Alumina Ceramics ◽  
Region I ◽  
Different Grain Size

The question about the existence of correlation between the parameters A and m of the Paris function is re-examined theoretically for brittle material such as alumina ceramic (Al2O3) with different grain size. Investigation about existence of the exponential function which fit a good approximation to the majority of experimental data of crack velocity versus stress intensity factor diagram. The rate theory of crack growth was applied for data of alumina ceramics samples in region I and making use of the values of the exponential function parameters the crack growth rate theory parameters were estimated.

Slow crack-growth behavior of alumina ceramics

2000 ◽  
Vol 15 (1) ◽  
pp. 142-147 ◽  
Author(s):  
M. E. Ebrahimi ◽  
J. Chevalier ◽  
G. Fantozzi
Keyword(s):  
Stress Intensity Factor ◽  
Grain Size ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Velocity ◽  
Slow Crack Growth ◽  
Velocity Versus ◽  
Water Molecules ◽  
Alumina Ceramics

The fracture behavior of high-purity alumina ceramics with grain sizes ranging from 2 to 13 μm is studied by means of the double torsion method. Crack-propagation tests conducted in air, water, and silicon oil, for crack velocities from 10−7 to 10−2 m/s, show that slow crack growth is due to stress corrosion by water molecules. An increase of the grain size leads to enhanced crack resistance, which is indicated by a shift of the V–KI (crack velocity versus applied stress intensity factor) plot toward high values of KI. Moreover, the slope of the curve is apparently higher for coarse grain alumina. However, if the R-curve effect is substracted from the experimental results, a unique V–KItip (crack velocity versus stress intensity factor at the crack tip) law is obtained for all alumina ceramics, independently of the grain size. This means that the crack-growth mechanism (stress corrosion by water molecules) is the same and that the apparent change of the V–KI law with grain size is a direct effect of crack bridging.

scholarly journals Comparative study of creep and fatigue crack growth in Poly (Vinyl chloride) pipe

2012 ◽  
Vol 9 (2) ◽  
pp. 359-366
Author(s):  
Baghdad Science Journal
Keyword(s):  
Experimental Data ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Crack Velocity ◽  
Rate Theory

The Rate theory of crack growth in PVC pipe has been studied for creep and fatigue crack propagation. Rate theory function parameters, (RTFP), were estimated theoretically from exponential function parameters, (EFP), to experimental data of crack velocity versus stress intensity factor ,(V-K) diagram, to creep crack propagation . Also (RTFP) were estimated theoretically from (EFP) to experimental data of (V-?K) diagram to fatigue crack propagation. Temperature effect with (RTFP) was discussed. Crack velocity function denoted with stress intensity factor and temperature degrees has been determined to fatigue and creep crack propagation theoretically and comparative results this function with experimental data of (V-K or ?K) diagram .

A four-point bending technique for studying subcritical crack growth in thin films and at interfaces

1997 ◽  
Vol 12 (3) ◽  
pp. 840-845 ◽  
Author(s):  
Qing Ma
Keyword(s):  
Crack Growth ◽  
Growth Velocity ◽  
Crack Velocity ◽  
Subcritical Crack Growth ◽  
Beam Theory ◽  
Velocity Versus ◽  
Displacement Curve ◽  
Load Displacement ◽  
Corrosion Mechanisms ◽  
Crack Growth Velocity

A technique was developed to obtain the subcritical crack growth velocity in a 4-point bending sample by analyzing the load-displacement curve. This was based on the observation that the compliance of a beam increases as the crack grows. Beam theory was used to analyze the general configuration where two cracks propagated in the opposite directions. A simple equation relating the crack velocity to the load and displacement was established, taking advantage of the fact that the compliance was linearly proportional to the crack lengths; thus the absolute crack length was not important. Two methods of obtaining crack velocity as a function of load were demonstrated. First, by analyzing a load-displacement curve, a corresponding velocity curve was obtained. Second, by changing the displacement rate and measuring the corresponding plateau load, a velocity value was calculated for each plateau load. While the former was capable of obtaining the dependence of crack velocity versus load from a single test, the latter was found to be simpler and more consistent. Applications were made to a CVD SiO2 system. In both cases of crack propagation either inside the SiO2 layer or along its interface with a TiN layer, the crack growth velocity changed with the stress intensity at the crack tip exponentially. As a result, a small crack will grow larger under essentially any tensile stresses typically existing in devices, provided that chemical agents facilitating stress corrosion mechanisms are also present.

scholarly journals Modelling the Depth of Jet Penetration in Abrasive Waterjet Contouring of Alumina Ceramics

2004 ◽  
Vol 471-472 ◽  
pp. 462-468
Author(s):  
Jun Wang ◽  
H. Liu ◽  
Chuan Zhen Huang
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Mathematical Models ◽  
Alumina Ceramic ◽  
Abrasive Waterjet ◽  
Alumina Ceramics ◽  
Predictive Capability ◽  
Jet Penetration ◽  
Good Agreement

Predictive mathematical models for the depth of jet penetration are presented for both straight-slit cutting and contouring by an abrasive waterjet (AWJ). The plausibility and predictive capability of the models are assessed and verified by an experimental investigation when cutting an 87% alumina ceramic. It shows that the predictions of the models are in good agreement with the experimental data.

Chraracteristics of Crack Growth of Alumina Ceramics Under Cyclic Loads

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1737-1743
Author(s):  
Yong Hak Huh ◽  
Seong Jae Cho ◽  
Jiho Song
Keyword(s):  
Crack Growth ◽  
Intergranular Fracture ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Alumina Ceramics ◽  
Microstructural Behavior ◽  
Point Bend ◽  
Different Grain Size ◽  
Grain Bridging ◽  
Crack Interface

Characteristics of crack growth under cyclic loading for alumina ceramics have been investigated. Three alumina ceramics with different grain size were fabricated by hot-pressing. Cyclic fatigue tests were carried out using four-point bend specimen. From examination of crack path and microstructural behavior from the tested specimens, grain bridging along the crack interface and intergranular fracture mode at the fracture surface were observed. The crack growth rate curve presented by using the cyclic parameter, [Formula: see text], could be divided into three regions. These regions were closely related to the fraction of intergranular fracture area. Crack closure influencing the cyclic parameter was evaluated as a function of stress ratio.

High-Resolution Measurement of Crack Growth in Micro-Machined Crystal Silicon

1999 ◽  
Vol 605 ◽  
Author(s):  
A.M. Fitzgerald ◽  
R.H. Dauskardt ◽  
T.W. Kenny
Keyword(s):  
Crack Growth ◽  
Crack Velocity ◽  
High Speed ◽  
Continuous Process ◽  
Growth Behavior ◽  
Velocity Versus ◽  
Crack Growth Behavior ◽  
Time Data ◽  
Crystal Silicon ◽  
Discrete Crack

AbstractTime dependent sub-critical cracking associated with environmental species such as moisture may have significant implications for the reliability of MEMS devices made of silicon. However, the existence of such stress corrosion phenomena in silicon remains controversial. Sub-critical crack-growth behavior in brittle materials is commonly characterized using crack velocity versus applied stress intensity curves (v-K curves). Crack velocity is inferred by curve-fitting crack length versus time data taken at low sample rates (<100 Hz) under the assumption that crack growth is a continuous process. However, we have observed discrete crack growth behavior in a micro-machined compression-loaded double cantilever beam. The samples are fabricated from (100) single crystal silicon wafers. A thin film resistor sputtered onto the sample surface using a lithographic technique is used to directly measure crack extension. The crack growth in all samples is characterized by periods of rapid crack growth interspersed with long periods of arrest in which no evidence of sub-critical cracking was observed. High speed data acquisition (up to 100 MHz) was performed and crack velocities as high as 1.7 km/s were accurately measured during these rapid growth periods.

A Method for the Analysis of the Growth of Short Fatigue Cracks

1995 ◽  
Vol 117 (4) ◽  
pp. 408-411 ◽  
Author(s):  
A. J. McEvily ◽  
Y.-S. Shin
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Material Constant ◽  
Plastic Zone Size ◽  
Surface Cracks ◽  
Zone Size ◽  
Short Cracks

A method for the analysis of the fatigue crack growth rate for short cracks has been developed and is applied to the case of fatigue crack growth of short surface cracks in a 1045 carbon steel. The method entails three modifications to standard LEFM procedures. These modifications include the use of a material constant to bridge between smooth and cracked specimen behavior, consideration of the plastic zone size to crack length ratio, and incorporation of the development of crack closure. Comparisons are made between calculations based upon this approach and experimental data.

scholarly journals Effect of Crack Bridging on the Toughening of Ceramic/Graphene Composites

2018 ◽  
Vol 57 (1) ◽  
pp. 54-62 ◽  
Author(s):  
S.V. Bobylev ◽  
A.G. Sheinerman
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Growth ◽  
Crack Deflection ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Crack Bridging ◽  
The Matrix ◽  
Graphene Content ◽  
Graphene Platelets

Abstract A model is proposed describing the effect of crack bridging on the fracture toughness of ceramic/graphene composites. The dependences of the fracture toughness on the graphene content and the sizes of the graphene platelets are calculated in the exemplary case of yttria stabilized zirconia (YSZ)/graphene composites. The calculations predict that if crack bridging prevails over crack deflection during crack growth, the maximum toughening can be achieved in the case of long graphene platelets provided that the latter do not rupture and adhere well to the matrix. The model shows good correlation with the experimental data at low graphene concentrations.

Remaining Lives of Fatigue Crack Growths for Pipes With Subsurface Flaws and Subsurface-to-Surface Flaw Proximity Rules

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Valery Lacroix
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Japan Society ◽  
Rule Based ◽  
Aspect Ratios ◽  
Inner Surface ◽  
American Society

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed into a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the recharacterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rate calculations. In this study, fatigue crack growth calculations were carried out for pipes with subsurface flaws, using the proximity rule provided in the current ASME (American Society of Mechanical Engineers) Section XI and JSME (The Japan Society of Mechanical Engineers) codes and the proposed subsurface-to-surface flaw proximity rule. Different pipe sizes, flaw aspect ratios, and ligament distances from subsurface flaws to inner surface of pipes were taken into account. The results indicate the current proximity rule gives less conservative fatigue lives, when the aspect ratios of the subsurface flaws are small.

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