Fracture Toughness and Subcritical Crack Growth in CVD Diamond

1995 ◽  
Vol 383 ◽  
Author(s):  
A. Kant ◽  
M. D. Drory ◽  
R. O. Ritchie
Keyword(s):  
Fracture Toughness ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Chemical Vapor ◽  
Cyclic Fatigue ◽  
Cvd Diamond ◽  
Compact Tension ◽  
Fatigue Properties ◽  
Free Standing

ABSTRACTThe fracture toughness, stress corrosion and cyclic fatigue properties of polycrystalline chemical vapor deposited (CVD) diamond have been investigated on thick (˜100 to 300 μm) free-standing films. Specifically, the fracture toughness, Kc, of diamond was determined using indentation methods and for the first time by the tensile testing of pre-notched fracture-mechanics type compact-tension samples. Measured Kc values were found to be between 5 and 7 MPa-m1/2 by either method and to be apparently independent of grain size and shape. Studies on subcritical crack growth (i.e., at stress intensities less than Kc) indicated that CVD diamond is essentially immune to stress-corrosion cracking under sustained loads in room air, water and acid environments. Corresponding experiments to examine susceptibility to cyclic fatigue are currently being performed using indentation-precracked cantilever beams cycled in three-point bending.

Subcritical Crack Growth in Single-crystal Silicon Using Micromachined Specimens

2002 ◽  
Vol 17 (3) ◽  
pp. 683-692 ◽  
Author(s):  
A. M. Fitzgerald ◽  
R. S. Iyer ◽  
R.H. Dauskardt ◽  
T. W. Kenny
Keyword(s):  
Fracture Toughness ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Single Crystal Silicon ◽  
High Ratio ◽  
Growth Exponent ◽  
Humid Air ◽  
Crystal Silicon ◽  
High Crack

A micromachined specimen with a test section only 150-μm thick was developed for investigating subcritical crack growth in silicon. Crack growth rates in the range 10−4–10−10 m/s were measured as a function of applied stress intensity (v–K curves) during tests in humid air and dry nitrogen lasting up to 24 h. The fracture toughness, KIc of {110} silicon was also measured at 1.15 ± 0.08 MPa m1/2. While some evidence MPa-m1/2 of subcritical crack growth appeared to occur in the region 0.9 KIc < K > 0.98 KIc, the extremely high crack growth exponent (n 100) and the high ratio of the apparent stress corrosion threshold, KIscc, to the fracture toughness, KIscc/KIc > 0.9, suggests that no clear evidence exists for a stress corrosion process in silicon exposed to humid air.

Microstructural Effects on the Hardness, Elastic Modulus and Fracture Toughness of CVD Diamond

1997 ◽  
Vol 505 ◽  
Author(s):  
A. Kant ◽  
M. D. Drory ◽  
N. R. Moody ◽  
W. J. MoberlyChan ◽  
J. W. Ager ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Measurement Techniques ◽  
Impurity Content ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Cvd Diamond ◽  
Free Standing ◽  
Microstructural Effects ◽  
Grain Bridging

ABSTRACTThe hardness, elastic modulus, and fracture toughness of chemical vapor deposited (CVD) polycrystalline diamond have been investigated on several thick (∼100 μm) free-standing films with regard to the grain size, impurity content and failure mechanisms. Micro-hardness measurements using Vickers indentation, in conjunction with Young's modulus measurement techniques such as nano-indentation, were employed to estimate the indentation fracture toughness. The toughness of CVD diamond was increased through the addition of non-diamond carbon, which promoted intergranular fracture and enhanced the toughness by grain bridging.

Controlling Subcritical Crack Growth at Epoxy/Glass Interfaces

2002 ◽  
Vol 124 (4) ◽  
pp. 328-333 ◽  
Author(s):  
John E. Ritter ◽  
G. S. Jacome ◽  
J. R. Pelch ◽  
T. P. Russell ◽  
T. J. Lardner
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Fatigue Resistance ◽  
Subcritical Crack Growth ◽  
Cyclic Fatigue ◽  
Distilled Water ◽  
Silane Coupling Agents ◽  
Bonding Density ◽  
Low Humidity ◽  
Static And Cyclic Loading

The resistance of silane bonded epoxy/glass interfaces to subcritical crack growth was studied as a function of the density of primary bonds between the silane and epoxy using the double-cleavage drilled compression test (DCDC). The silane coupling agents propyltriethoxysilane (PES), 3-aminopropyltriethoxysilane (3-APES) and various mixtures of 3-APES and PES were used to systematically control the bonding density since 3-APES can form primary bonds with both the glass and the epoxy, while PES forms primary bonds only with the glass. The resistance of these interfaces to crack growth was tested under both static and cyclic loading in high and low humidity test environments. These tests allowed the separation of the effects on crack growth due to stress corrosion and cyclic fatigue. Experimental results showed that the density of primary bonding between the silane layer and the epoxy controls the cyclic fatigue resistance of the silanized interfaces. Additionally, for 3-APES bonded epoxy/glass interfaces cyclic fatigue crack growth predominates at both high and low humidities but for PES bonded interfaces, crack growth by stress corrosion dominates at high humidity and by cyclic fatigue at low humidities. For a 50% 3-APES/50% PES bonded interface, stress corrosion effects are somewhat greater than cyclic fatigue effects at high humidities but at low humidities the two effects are comparable. When testing the interfaces for durability, PES bonded interfaces showed spontaneous delamination when aged in distilled water for 36h at 94°C. On the other hand, 3-APES and mixtures of 3-APES bonded interfaces did not show any detrimental effect of the cyclic fatigue resistance when aged in distilled water at temperatures up to 98°C.

scholarly journals Contributions of stress corrosion and cyclic fatigue to subcritical crack growth in a dental glass-ceramic

2014 ◽  
Vol 30 (8) ◽  
pp. 884-890 ◽  
Author(s):  
Gaurav V. Joshi ◽  
Yuanyuan Duan ◽  
Alvaro Della Bona ◽  
Thomas J. Hill ◽  
Kenneth St. John ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Glass Ceramic ◽  
Subcritical Crack Growth ◽  
Cyclic Fatigue

The Fracture Toughness of Hardened Tool Steels

1987 ◽  
Vol 109 (4) ◽  
pp. 314-318 ◽  
Author(s):  
D. F. Watt ◽  
Pamela Nadin ◽  
S. B. Biner
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Slow Crack Growth ◽  
Crack Opening ◽  
Compact Tension ◽  
Testing Procedure ◽  
Tool Steels ◽  
Opening Displacement ◽  
Tempering Temperature ◽  
Toughness Testing

This report details the development of a three-stage fracture toughness testing procedure used to study the effect of tempering temperature on toughness in 01 tool steel. Modified compact tension specimens were used in which the fatigue precracking stage in the ASTM E-399 Procedure was replaced by stable precracking, followed by a slow crack growth. The specimen geometry has been designed to provide a region where slow crack growth can be achieved in brittle materials. Three parameters, load, crack opening displacement, and time have been monitored during the testing procedure and a combination of heat tinting and a compliance equation have been used to identify the position of the crack front. Significant KIC results have been obtained using a modified ASTM fracture toughness equation. An inverse relationship between KIC and hardness has been measured.

scholarly journals Interaction of Cyclic Loading (Low-Cyclic Fatigue) with Stress Corrosion Cracking (SCC) Growth Rate

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Rehmat Bashir ◽  
He Xue ◽  
Rui Guo ◽  
Yueqi Bi ◽  
Muhammad Usman
Keyword(s):  
Growth Rate ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Cyclic Fatigue ◽  
Joint Effect ◽  
Corrosion Cracking

The structural integrity analysis of nuclear power plants (NPPs) is an essential procedure since the age of NPPs is increasing constantly while the number of new NPPs is still limited. Low-cyclic fatigue (LCF) and stress corrosion cracking (SSC) are the two main causes of failure in light-water reactors (LWRs). In the last few decades, many types of research studies have been conducted on these two phenomena separately, but the joint effect of these two mechanisms on the same crack has not been discussed yet though these two loads exist simultaneously in the LWRs. SCC is mainly a combination of the loading, the corrosive medium, and the susceptibility of materials while the LCF depends upon the elements such as compression, moisture, contact, and weld. As it is an attempt to combine SCC and LCF, this research focuses on the joint effect of SCC and LCF loading on crack propagation. The simulations are carried out using extended finite element method (XFEM) separately, for the SCC and LCF, on an identical crack. In the case of SCC, da/dt(mm/sec) is converted into da/dNScc (mm/cycle), and results are combined at the end. It has been observed that the separately calculated results for SCC da/dNScc and LCF da/dNm of crack growth rate are different from those of joint/overall effect,  da/dNom. By applying different SCC loads, the overall crack growth is measured as SCC load becomes the main cause of failure in LWRs in some cases particularly in the presence of residual stresses.

scholarly journals Cyclical fatigue of annealed and of thermally tempered soda-lime-silica glass

2018 ◽  
Vol 165 ◽  
pp. 18003
Author(s):  
Jens Schneider ◽  
Jonas Hilcken
Keyword(s):  
Crack Growth ◽  
Silica Glass ◽  
Subcritical Crack Growth ◽  
Soda Lime ◽  
Cyclic Fatigue ◽  
Growth Exponent ◽  
Static Fatigue ◽  
Strength Increase ◽  
Soda Lime Silica Glass ◽  
Number Of Cycles

We present experimental and theoretical investigations on the cyclic fatigue of annealed and of thermally tempered soda-lime-silica glass. Static fatigue due to subcritical crack growth at micro cracks significantly decreases the macroscopic strength of soda-lime-silica glass and causes a time-dependent strength reduction. A subsequent thermal tempering process is typically used to induce residual surface compression stresses, which inhibit the crack growth of surface cracks, and corresponding bulk tension stresses. From the experimental results we show that the existing models for static fatigue used in linear elastic fracture mechanics can be used for the lifetime prediction of cyclically loaded annealed glass and thermally tempered glass, although the (static) crack growth exponent slightly decreases in cyclic loading. The equivalent duration of tensile stress at the crack tip of a micro crack governs the crack growths and not the number of cycles. The threshold for subcritical crack growth determined from the cyclic experiments was found to be in good agreement with data from literature. But unlike in strength tests with singular and quasi-static re-loading, it could be found that periodic loading with load free intervals does not lead to a strength increase by crack healing effects. Based on the results, an engineering design concept for cyclically loaded glass is presented.

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