Subcritical Crack Growth of α/β-Sialon Ceramics in 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.

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

MATEC Web of Conferences ◽

10.1051/matecconf/201816518003 ◽

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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Stress Corrosion Cracking of En 31 Ball Race Steel Using Fracture Mechanics Methods of Analysis

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1971_013_011_02 ◽

1971 ◽

Vol 13 (2) ◽

pp. 61-64 ◽

Cited By ~ 2

Author(s):

B. G. Cox ◽

E. G. Ellison

Keyword(s):

High Pressure ◽

Stress Intensity ◽

Fracture Mechanics ◽

Ethylene Glycol ◽

Crack Growth ◽

Subcritical Crack Growth ◽

Diesel Oil ◽

Intensity Threshold ◽

Measurement And Analysis ◽

En 31

Subcritical crack growth was studied in an En 31 ball race steel subjected to various fluids, some of which are suitable for possible use in high pressure applications. Using fracture mechanics techniques of measurement and analysis, it was found that Esso Univis P38, Shell Tellus 15, and a 25 per cent glycerine–ethylene glycol mixture caused subcritical crack growth with a corrosion stress intensity threshold approximately half that obtained in air. Diesel oil had no effect. Evidence of blunting of the crack system and some effects of history were found.

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

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.1979.tb19129.x ◽

1979 ◽

Vol 62 (9-10) ◽

pp. 536-537 ◽

Cited By ~ 4

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

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

Journal of Applied Mechanics ◽

10.1115/1.4035523 ◽

2017 ◽

Vol 84 (4) ◽

Cited By ~ 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.

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Simple Mechanical Testing Method to Evaluate Influence of High Pressure Hydrogen Gas

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2018-84187 ◽

2018 ◽

Author(s):

Toshio Ogata

Keyword(s):

Mechanical Properties ◽

High Pressure ◽

Test Piece ◽

Testing Procedure ◽

Fatigue Tests ◽

Pressure Vessels ◽

Hydrogen Gas ◽

Testing Method ◽

Gas Cylinder ◽

Pressure Hydrogen

A simple testing method to evaluate the influence of high pressure hydrogen gas up to 100 MPa on mechanical properties at the temperature between 20 K and up to 800 K had been developed. In this method, instead of using high-pressure gas vessels, high pressure gas was filled into a small hole in the hollow-type test piece from a hydrogen gas cylinder or a compressor for 10 MPa or 100 MPa test. A small inner diameter of the hole enables to evaluate also the reduction of area in the slow strain-rate tensile (SSRT) tests. The temperature of the test piece with the high pressure gas can be changed simply by surrounding coolant or heater between 20 K and 800 K. Lots of test results by this method proved that almost the same results were obtained between this method and the conventional method with high-pressure gas vessels where test piece is installed. The great advantages of this method are not only the less cost for the facilities of high-pressure vessels but also the ability of tests at lower or higher temperatures than those with the vessels. So, this method is proposed to be used world-widely to evaluate the mechanical properties of structural materials for extremely severe environments, such as high-pressure hydrogen applications and also to study the mechanism of the influence of high-pressure hydrogen for design and reliability of those facilities. In this paper, the details of testing procedure of this method and results of tensile and fatigue tests in up to 70 MPa hydrogen gas on several kinds of stainless steels obtained by this method are presented.

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Controlling Subcritical Crack Growth at Epoxy/Glass Interfaces

Journal of Electronic Packaging ◽

10.1115/1.1503064 ◽

2002 ◽

Vol 124 (4) ◽

pp. 328-333 ◽

Cited By ~ 5

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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A Fracture Mechanics-Based Approach to Establish Minimum Pressurization Temperature Envelopes

Volume 7: Operations, Applications and Components ◽

10.1115/pvp2017-65805 ◽

2017 ◽

Author(s):

Phillip E. Prueter ◽

Seetha Ramudu Kummari ◽

David A. Osage

Keyword(s):

High Pressure ◽

Life Cycle ◽

Fracture Mechanics ◽

Brittle Fracture ◽

Crack Growth ◽

Life Cycle Management ◽

Risk Tolerance ◽

Operating Conditions ◽

High Hydrogen ◽

Pressure Hydrogen

Preventing brittle fracture is an essential part of instituting life-cycle management strategies for fixed pressure equipment. Using fracture mechanics principles to establish permissible minimum pressurization temperature (MPT) envelopes for components is one way to mitigate the potential for unstable flaw growth. In the refining industry, heavy-walled, low-alloy hydroprocessing reactors are designed to operate at elevated temperatures and high hydrogen partial pressures. Components that operate in high-pressure hydrogen environments require special treatment and necessitate guidance that falls outside the bounds of current pressure vessel construction codes. This operating environment results in two factors that affect the MPT envelope: long-term temper embrittlement and hydrogen embrittlement. Additionally, hydrogen charging can manifest damage in two ways: fast (brittle) fracture due to a reduction in fracture toughness and slow (subcritical) hydrogen-assisted crack growth. When developing a MPT envelope for a given component, both failure modes need to be considered in addition to residual stress effects from weld overlay or cladding. MPT envelopes provide insight into the permissible pressure-temperature combinations for specific locations and for chosen reference flaw sizes. From a reliability standpoint, understanding the risk of brittle fracture associated with heavy-walled reactors for all operating scenarios is crucial. Furthermore, taking the appropriate life-cycle management steps, such as establishing MPT envelopes, coupling MPT analysis predictions with targeted inspection, optimizing process operating conditions, and developing a flaw acceptance criteria to mitigate the risk of crack propagation and ultimately, brittle fracture is essential. In this study, a fracture-mechanics based methodology is summarized that is fully documented in upcoming Welding Research Council (WRC) Bulletin 562 [1] to determine MPT envelopes for all components (in any service environment) based on fast fracture with supplemental MPT requirements based on slow fracture for equipment that operates in high-pressure hydrogen environments. Finally, a finite element analysis-based case study of a 2-1/4-Cr-1-Mo hydrotreater reactor is summarized and practical life cycle-management guidance is offered based on analysis results. This example highlights how evaluation of start-up and shut-down procedures for heavy-walled reactors has the potential to save significant time and related cost per unit shut-down cycle, while maintaining an acceptable risk tolerance against subcritical crack growth and brittle fracture.

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

MRS Proceedings ◽

10.1557/proc-383-229 ◽

1995 ◽

Vol 383 ◽

Cited By ~ 4

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.

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