The propagation of Griffith cracks at high temperatures by mass transport processes

Stevens, R. N.; Dutton, R.

doi:10.1016/0025-5416(71)90076-0

Cited by 83 publications

(15 citation statements)

References 43 publications

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“…When the porosity is of non-equilibrium shape, e.g., crack-like, gradients in chemical potential  due to surface tension will always exist and provide local driving force for crack regression [56]. In the absence of an applied stress (relaxed crack) and for the case of material transport controlled healing reaction steady state crack regression rate may be expressed by pre-exponential factor for surface, grain boundary, or lattice diffusion, respectively, subjected to local microstructure constraints (e.g., grain size, grain boundary width).…”

Section: Thermodynamic Aspectsmentioning

confidence: 99%

Generic principles of crack-healing ceramics

Greil

2012

J Adv Ceram

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Abstract:Ceramic materials able to heal manufacture or damage induced microstructure defects might trigger a change in paradigm for design and application of load bearing ceramics. This work reviews thermodynamic and kinetic aspects governing the regeneration of solid contact able to transfer stress between disrupted crack surfaces in ceramics. Major crack healing processes include perturbation of crack-like pores followed by sintering of isolated pores, as well as reaction with an environmental atmosphere and filling of the crack space with an oxidation product. Since thermally activated solid state reactions require elevated temperatures which may exceed 1000 ℃, processes able to trigger crack healing at lower temperatures are of particular interest for transferring into engineering applications. Generic principles of microstructure modifications able to facilitate crack repair at lower temperatures will be considered: (i) acceleration of material transport by grain boundary decoration and grain size reduction, and (ii) reduction of thermal activation barrier by repair filler activation. Examples demonstrating crack healing capability include oxidation reaction of low energy bonded intercalation metal from nano-laminate MAX phases and catalyzed surface nitridation of polymer derived ceramics containing repair fillers.

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Section: Thermodynamic Aspectsmentioning

confidence: 99%

Generic principles of crack-healing ceramics

Greil

2012

J Adv Ceram

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“…This subsection is concerned with the situation where surface diffusion is so rapid that the crystal creeps negligibly during the time of interest. On the basis of several theoretical studies (Stevens and Dutton, 1971;McCartney, 1976;Gao, 1992Gao, , 1995Sun et al, 1994,' Wang and Suo, 1997), we suggest the following sequence of events in the Newcomb and Tressler experiments. When the fiber is under no stress, the pore has a rounded shape maintained by the surface tension.…”

Section: Energeticsmentioning

confidence: 57%

Mechanism-Based Design for High-Temperature, High-Performance Composites. Book 4

Evans¹,

Leckie²,

Hutchinson³

1997

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The paper describes a phase-sensitive photothermal technique for the determination of the thermal conductance of a crack or interface embedded within a plate of finite thickness. The technique involves sinusoidally-modulated heating at one point on the surface using a focused laser beam and measurement of the phase shift of the thermal wave at some other point. An analysis is presented for the relationship between the phase lag, the modulation frequency, the specimen geometry, and the thermal properties of both the interface and the solid. The technique is demonstrated using a model system comprising two stainless steel disks, with the "interfaces" between them being formed either by simply placing the two disks in contact with each another, or by placing thin layers of polyethylene sheets between the disks. The trends are rationalized on the basis of the thermal properties of the constituents.70:FZ6S(8/12/97)January 13. 1998-3:25 PM/mcf INTRODUCTIONThe present article describes a photothermal technique and the associated analysis for the determination of the thermal conductance of a crack or interface embedded within a plate of finite thickness. The technique is based on periodic heating at a point on one surface, using, for example, a focused laser beam, and measurement of the phase lag of the thermal wave at some other point. In the absence of an interface, the technique can be used to determine the thermal diffusivity of the material. The work is motivated by concurrent studies on the thermal conductance of delamination cracks in fiber-reinforced ceramic matrix composites (CMCs) and its effect on failure in the presence of a temperature gradient. An example of such a crack is shown in Fig. 1. Although the technique is being developed mainly to study CMCs, it can be applied readily to other problems involving interfaces or cracks in multilayered or coated systems.Photothermal techniques have been used extensively to study the thermal properties of materials [1][2][3][4][5][6][7][8][9][10][11][12]. A recent summary of these can be found in [12]. The techniques have been used also as nondestructive tools for detecting sub-surface defects [12][13][14][15][16][17][18]. The focus of the present work is on one specific subgroup of these techniques, notably, that based upon periodic heating and phase lag measurement.The main advantage of the present technique is that it provides quantitative information about the thermal conductance of cracks and interfaces, rather than simply identifying regions where such defects are present. This information is crucial for failure prediction in a broad range of technological systems, including delamination of thermally-loaded CMC structures, multilayered power electronic devices and thermal barrier coatings.In the past, thermal conductances have been measured predominantly by dc techniques [19][20][21][22]. These techniques require a heat flux, q, to flow through the 70:FZ6S(8/12/97)January 13, 1998*3:25 PM/mcf interface as well as through the bulk of the two contacting s...

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“…[27] Since G shows how the stress/strain related free energy of the system changes with L, it affects chemical potential l t of the SAs located at the crack tip. [26] Note that G affects also the characteristic diffusion length l d since G determines the crack opening displacement (COD) at the tip of plastically blunted crack:…”

Section: Plasticmentioning

confidence: 99%

“…[13] Relatively slow propagating SCC cracks in metals are expected to blunt. The plastic opening d in this case provides a natural length scale and arrives in the GALOP model, where d should exceed the groove width w % 5DL* tg (h/2) to enable nonconstrained Mullins grooving ( Figure 5), as well as in the refined version of RGM, where the diffusion length l d was assumed to scale as d. [14] Chemical potential at the crack tip l t can be viewed as the free energy per atom at the tip and represents the thermodynamic stimulus for crack extension: [26] …”

Section: Plasticmentioning

confidence: 99%

“…Equation [9] can be obtained by using the standard thermodynamic definition l = -( ¶F/ ¶n) and calculating the change in the Helmholtz free energy DF = DL1(G -c eff )/Dn of the system ''a sample containing the crack of the length L + loading device'' caused by small crack extension DL under constant stress r. [26] The number of atoms, Dn, which should be removed from the tip to the reference site to produce the extension DL of the crack, the front of which has a unit width, is n % DLh1/x. Dividing DF by Dn yields l t given by Eq.…”

Section: Plasticmentioning

confidence: 99%

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Dissolution Condensation Mechanism of Stress Corrosion Cracking in Liquid Metals: Driving Force and Crack Kinetics

Glickman

2010

Metall Mater Trans A

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Stress corrosion cracking (SCC) in aqueous solution is driven by exothermic reactions of metal oxidation. This stimulus, as well as classical mechanisms of SCC, does not apply to SCC in liquid metals (LMs). In the framework of the dissolution-condensation mechanism (DCM), we analyzed the driving force and crack kinetics for this nonelectrochemical mode of SCC that is loosely called ''liquid metal embrittlement'' (LME). According to DCM, a stress-induced increase in chemical potential at the crack tip acts as the driving force for out-of-the-tip diffusion mass transfer that is fast because diffusion in LMs is very fast and surface energy at the solid-liquid interface is small. In this article, we review two versions of DCM mechanism, discuss the major physics behind them, and develop DCM further. The refined mechanism is applied then to the experimental data on crack velocity V vs stress intensity factor, the activation energy of LME, and alloying effects. It is concluded that DCM provides a good conceptual framework for analysis of a unified kinetic mechanism of LME and may also contribute to SCC in aqueous solutions. CRYSTAL plasticity and strength are environmentally sensitive properties. Along with corrosion and stress corrosion cracking (SCC), complex but well amenable to scientific interpretation electrochemical phenomena, more abstruse nonelectrochemical effects in crystal plasticity were observed for solids of different molecular nature when under simultaneous action of tensile stress and wetting liquids. The most famous among these effects is liquid metal embrittlement (LME), which describes premature failure of metals under simultaneous action of tensile stress and wetting liquid metals. LME creates potential reliability concerns in many technologies, including nuclear energy, welding, soldering, protective coatings, and gas industry. [1][2][3][4][5][6][7][8][9][10] The fact that LME was reported not only for polycrystals but also for single-crystalline [1][2][3][4][5] and amorphous metals [11] suggests that the phenomenon can not be explained in terms of either grain boundary (GB) diffusion/grooving modified by stress or adsorptionenhanced dislocation injection/mobility. LME was reported to most strongly manifest itself in solid metal (SM)-liquid metal (LM) couples, which form simple eutectic phase diagrams without any intermetallics; [9] this suggests that the concept of formation and fracture of brittle surface films does not apply to LME. Figure 1 taken from Reference 5 shows that LME involves subcritical crack growth, the typical feature that distinguishes SCC from crack nucleation-controlled brittle fracture below the ductile-brittle transition temperature in inert atmosphere. Crack kinetics observations have made clear that LME is not a ductile-brittle transition but a special case of time-dependent process of SCC. The subcritical growth under LME starts at an apparent threshold stress intensity K TH that can be as small as~0.1 MPaAEm ½ ; the process of crack extension spans almost all the lifetim...

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The propagation of Griffith cracks at high temperatures by mass transport processes

Cited by 83 publications

References 43 publications

Generic principles of crack-healing ceramics

Generic principles of crack-healing ceramics

Mechanism-Based Design for High-Temperature, High-Performance Composites. Book 4

Dissolution Condensation Mechanism of Stress Corrosion Cracking in Liquid Metals: Driving Force and Crack Kinetics

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