Fracture, Fatigue and Indentation Behavior of Pyrolytic Carbon for Biomedical Applications

1995 ◽  
Vol 383 ◽  
Author(s):  
R. O. Ritchie ◽  
R. H. Dauskardt ◽  
W. W. Gerberich ◽  
A. Strojny ◽  
E. Lilleodden
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Mechanical Heart Valve ◽  
Pyrolytic Carbon ◽  
Cyclic Fatigue ◽  
Graphite Substrate ◽  
Static Fatigue ◽  
Small Surface ◽  
Biomedical Implant ◽  
Valve Prostheses

ABSTRACTThe fracture, fatigue and indentation properties of pyrolytic carbon, both as a monolithic material and as a coating on a graphite substrate, are described in light of its use for biomedical implant applications, specifically for the manufacture of mechanical heart valve prostheses. From the perspective of determining properties that are important for the prediction of safe structural lifetimes in such prostheses, it is found that by traditional engineering standards, pyrolytic carbon has low damage tolerance, i.e., fracture toughness values between 1 and 3 MPa√m and susceptibility to subcritical crack growth by both cyclic fatigue and stress-corrosion cracking (static fatigue). Subcritical crack-growth rates are evaluated in simulated physiological environments for both through-thickness “long” cracks, and for physically “small” surface cracks, the latter measurements being performed for cracks initiated at hardness indents. The unusual deformation characteristics of indentation in pyrolytic carbon are described based on instrumented microhardness indentation and scanning probe microscopy (AFM/STM) studies.

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.

Subcritical Crack Growth of α/β-Sialon Ceramics in Distilled Water

2008 ◽  
Vol 403 ◽  
pp. 129-132
Author(s):  
Marco Riva ◽  
Rainer Oberacker ◽  
Michael J. Hoffmann ◽  
Theo Fett
Keyword(s):  
High Pressure ◽  
Life Cycle ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Testing Procedure ◽  
Fatigue Tests ◽  
Static Fatigue ◽  
Distilled Water

Environmental-assisted subcritical crack growth on two different /-sialon ceramics is determined in static fatigue tests. The goal of these investigations was to determine the influence of delivering medium of high pressure pumps on their durability (life cycle). Therefore 4-point-bending bars were statically loaded in distilled water and subcritical crack growth was analyzed. The large number of spontaneous failure and survivals made the development of a modified testing procedure necessary in order to obtain a significant database.

The Static Fatigue Limit in the Thermal Activation Approach to Subcritical Crack Growth

1979 ◽  
Vol 62 (9-10) ◽  
pp. 536-537 ◽  
Author(s):  
D. K. SHETTY ◽  
A. R. ROSENFIELD ◽  
W. H. DUCKWORTH ◽  
G. K. BANSAL
Keyword(s):  
Crack Growth ◽  
Fatigue Limit ◽  
Thermal Activation ◽  
Subcritical Crack Growth ◽  
Static Fatigue

Toughness and Subcritical Crack Growth in Nb/Nb3Al Layered Materials

1996 ◽  
Vol 434 ◽  
Author(s):  
D. R. Bloyer ◽  
K. T. Venkateswara Rao ◽  
R. O. Ritchie
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Fatigue Behavior ◽  
Laminated Composite ◽  
Stable Crack Growth ◽  
Cyclic Fatigue ◽  
Fatigue Crack Growth Resistance ◽  
Crack Arrester ◽  
The Matrix ◽  
Particulate Reinforced

AbstractA brittle intermetallic, Nb3Al, reinforced with a ductile metal, Nb, has been used to investigate the resistance curve and cyclic fatigue behavior of a relatively coarse laminated composite. With this system, the toughness of Nb3Al was found to increase from ∼1 MPa√m to well over 20 MPa√m after several millimeters of stable crack growth; this was attributed to extensive crack bridging and plastic deformation within the Nb layers in the crack wake. Cyclic fatigue-crack growth resistance was also improved in the laminate microstructures compared to pure Nb3Al and Nb-particulate reinforced Nb3Al composites with crack arrester orientations in the laminate providing better fatigue resistance than either the matrix or pure Nb.

Subcritical Crack Growth in Cementitious Materials Subject to Chemomechanical Deterioration—Experimental Test Using Specimens of Negative Geometry

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
Weijin Wang ◽  
Teng Tong ◽  
Susheng Tan ◽  
Qiang Yu
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Crack Tip ◽  
Cementitious Materials ◽  
Hardened Cement ◽  
Static Fatigue ◽  
Cement Pastes ◽  
Stable Crack Propagation ◽  
Hardened Cement Pastes ◽  
Physical And Chemical

Knowledge of the subcritical crack growth (SCG) in cement-based materials subject to concurrent physical and chemical attacks is of great importance for understanding and mitigating the chemomechanical deterioration in concrete structural members. In this study, the SCG in hardened cement pastes is investigated experimentally by a novel test approach aided with microcharacterization. In the test, specimens of negative geometry are designed, which enable the use of load control to trigger stable crack propagation in hardened cement pastes. Multiple specimens, cast from the same batch of mixture, are exposed to the same chemical condition and loaded at the same age. With the aid of a high-resolution microscopy system, which is used to trace the crack tip, the average trend and the associated variation of the dependence of crack velocity v on the stress intensity factor K at the crack tip are obtained. Different from static fatigue, three distinctive regions are captured in the K–v curves of specimens experiencing chemomechanical deterioration. With the help of advanced techniques including scanning electron microscopy (SEM), atomic-force microscopy (AFM), and Raman spectroscopy, the microstructure destruction and chemical composition change induced by the imposed chemomechanical attack are characterized at different stages. In addition to the physical insights for deeper understanding of the coupled effect of chemomechanical attack, these experimental results provide important macro- and microscopic benchmarks for the theoretical modeling and numerical investigation in the future studies.

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.

Evaluation of Tensile Static, Dynamic, and Cyclic Fatigue Behavior for A Hiped Silicon Nitride at Elevated Temperatures

1992 ◽  
Vol 287 ◽  
Author(s):  
Chih-Kuang Jack Lin ◽  
Michael G. Jenkins ◽  
Matitison K. Ferber
Keyword(s):  
Silicon Nitride ◽  
Cyclic Loading ◽  
Crack Growth ◽  
Failure Mechanism ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Cyclic Fatigue ◽  
Creep Rupture ◽  
Static Fatigue ◽  
Dynamic Fatigue

ABSTRACTTensile fatigue behavior of a hot-isostatically-pressed (HIPed) silicon nitride was investigated over ranges of constant stresses, constant stress rates, and cyclic loading at 1150-1370°C. At 1150°C, static and dynamic fatigue failures were governed by a slow crack growth mechanism. Creep rupture was the dominant failure mechanism in static fatigue at 1260 and 1370°C. A transition of failure mechanism from slow crack growth to creep rupture appeared at stress rates ≤10−2 MPa/s for dynamic fatigue at 1260 and 1370°C. At 1 150-1370°C, cyclic loading appeared to be less damaging than static loading as cyclic fatigue specimens displayed greater failure times than static fatigue specimens under the same maximum stresses.

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.

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