Detection of fatigue macrocracks in 1100 aluminum from thermomechanical data

Harvey, D. P.; Bonenberger, R.J.

doi:10.1016/s0013-7944(99)00140-x

Cited by 12 publications

(12 citation statements)

References 15 publications

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“…For loading below the fatigue limit, the temperature rise at the same location was observed to be negligible. Similar trends of three phases of temperature rise were observed by Liaw et al ., 4 Wong and Kirby, 5 Starke et al ., 12 Jacobsen et al ., 13 Blotny and Kaleta 14,15 and Harvey and Bonenberger 16 …”

Section: Introductionsupporting

confidence: 82%

Analysis of temperature distribution near the crack tip under constant amplitude loading

Pandey

Chand

2008

Fatigue Fract Eng Mat Struct

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A B S T R A C T An analytical/numerical method has been developed to find the temperature rise near the crack tip under fatigue loading. The cyclic plastic zone ahead of the crack tip is assumed to be the shape of the source of heat generation and some fraction of plastic work done in cyclic plastic zone as heat generation. Plastic work during fatigue load was found by obtaining stress and strain distribution within the plastic zone by Hutchinson, Rice and Rosengren (HRR) crack tip singularity fields applied to small scale yielding on the cyclic stress strain curve. A two-dimensional conduction heat transfer equation, in moving coordinates, was used to obtain temperature distribution around the crack tip. Temperature rise was found to be a function of frequency of loading, applied stress intensity factor and thermal properties of the material. A power-law relation was found between the rise in temperature at a fixed point near the crack tip and range of stress intensity factor.Keywords crack tip; plastic strain energy density; point source; temperature rise. N O M E N C L A T U R Ea = Crack length, m da/dN = Crack growth rate, m/cycle t = Time, s v = Velocity of the crack tip =ȧ(t), ms −1 n = Cyclic strain hardening exponent k = Cyclic strength coefficient, Pa q = Heat generation per unit growth of the crack, Jm −2 q = Rate of heat generation per unit volume, Jm −3 -s E = Modulus of elasticity, Pa I n = Non-dimensional parameter of exponent n K I = K Imax − K Imin = Range of stress intensity factor under mode I loading, MPa (m) 1/2 σ ∞ = Range of remotely applied load, (= σ max -σ min ), Pa F = A function of geometry of the specimen = Frequency of loading, cycle/s σ 0 = Cyclic yield stress ( σ 0 ∼ 2σ 0 ), Pa σ ij = Range of stress ahead of crack tip, i, j = r, θ, z in Polar co-ordinate and x, y and z in Cartesian co-ordinate, Pa. Subscript eq = equivalent ε p ij = Range of plastic strain ahead of crack tip, i, j = r, θ , z in Polar co-ordinate and x, y and z in Cartesian co-ordinate. Subscript

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Section: Introductionsupporting

confidence: 82%

Analysis of temperature distribution near the crack tip under constant amplitude loading

Pandey

Chand

2008

Fatigue Fract Eng Mat Struct

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“…Thermal effects also carry information useful for diagnostics and study of damage kinetics, structural transformations, etc. [18,26].The reliability of data obtained in studying nonstationary thermomechanically coupled dynamic processes in high strain rate (10 2 -10 3 sec -1 ) and very high strain rate (10 3 -10 6 sec -1 ) deformation is strongly dependent on the choice and individualization of constitutive equations. A criterion for choosing a model should be its capability of describing viscosity, dependence of the yield stress on the strain rate, hardening, thermal effects, damage, etc.…”

mentioning

confidence: 99%

“…Thermal effects also carry information useful for diagnostics and study of damage kinetics, structural transformations, etc. [18,26].…”

mentioning

confidence: 99%

Using a split Hopkinson bar to specify the parameters of thermomechanical models of flow under high strain rate deformation

Сенченков

Andrushko

2008

Int Appl Mech

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By way of numerical simulation, a method is developed to determine the parameters of the thermomechanical Bodner-Partom model of flow under high strain rate deformation using a split Hopkinson bar. The classical method is generalized in two directions. To evaluate the kinematic hardening parameters, the wave reflected from the free end of the bar is used. The thermomechanical parameters that are responsible for the stored energy of cold work are calculated from measurements of temperature changes in the specimen Keywords: split Hopkinson bar, Bodner-Partom model, Baushinger effect, temperature change, finite-element method, stored energy of cold workIntroduction. The coupling of mechanical and thermal fields is of theoretical and applied importance. While in service, many structural elements of modern engineering are subjected to cyclic or impulsive loads, which may induce inelastic residual strains and temperature changes, either reversible (thermoelastic) or irreversible (dissipative) [12,13,30]. Monotonic quasistatic, high strain rate, and very high strain rate loading may give rise to local regions of large inelastic strains and high temperature (thermal shear bands) [22,23,25,28], which may lead to failure.On the other hand, thermal effects of deformation represent a number of prominent aspects of material behavior, which are either difficult or impossible to analyze within the framework of purely mechanical models. Among them are stored energy of cold work, dissipation of mechanical energy as heat, etc. A conceptual factor is that a characteristic variable of an adiabatic process is temperature, which can be measured experimentally. Thermal effects also carry information useful for diagnostics and study of damage kinetics, structural transformations, etc. [18,26].The reliability of data obtained in studying nonstationary thermomechanically coupled dynamic processes in high strain rate (10 2 -10 3 sec -1 ) and very high strain rate (10 3 -10 6 sec -1 ) deformation is strongly dependent on the choice and individualization of constitutive equations. A criterion for choosing a model should be its capability of describing viscosity, dependence of the yield stress on the strain rate, hardening, thermal effects, damage, etc.A split Hopkinson bar is widely used to test dynamic properties [15,17,19,20,24]. The equipment developed in [21] to measure temperature in a sample through which a wave propagates allows us to study the effects of thermomechanical coupling.The thermodynamically consistent Bodner-Partom model [9][10][11] was used in [27] to determine, for AMg-6 aluminum alloy, the portion of the inelastic work that does not dissipate as heat and accumulates by hardening ("cold work"). The results obtained there were used for numerical simulation of thermal (temperature) effects in a disk under impulsive radial loading. An analysis revealed that a chief task in studying such effects is to individualize the parameters of a thermodynamic model of flow under high strain rate loading.In the present paper, we carry o...

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“…Thermal effects are also helpful in diagnostics and analysis of damage kinetics, structural changes, etc. [15,22].The major problem in evaluating thermal effects in nonlinear materials is identification of the stored and dissipated fractions of the total plastic energy. Systematic research of these issues originated in the calorimetric tests conducted by Taylor and Quinney [29].…”

mentioning

confidence: 99%

“…Thermal effects are also helpful in diagnostics and analysis of damage kinetics, structural changes, etc. [15,22].…”

mentioning

confidence: 99%

Thermomechanical coupling effects in a materially nonlinear disk under impulsive radial loading

Сенченков

Andrushko

2006

Int Appl Mech

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A thermomechanically generalized Bodner-Partom model is developed. It is used to determine the fraction of plastic work that is not dissipated into heat and is stored in the material and to find a numerical solution to the dynamic thermomechanical problem for a disk under radial impulsive loading and to analyze the change in temperature due to thermomechanical coupling Keywords: stress waves, temperature, cold work, plastic material, disk, impulsive loading, finite-element method Introduction. Deformation, especially at high strain rates, can cause reversible (thermoelastic) and irreversible (dissipative) changes in temperature [24,30,31]. Such processes arouse theoretical and practical interest because of two circumstances. First, high and very high strain rates may give rise to localized regions of large plastic strains and high temperatures (adiabatic shear bands) [20,23,26], which lead to failure. Local thermal phenomena may also occur under monotonic quasistatic tension to large plastic strains (Lüders bands) [21,23]. Second, strain-induced thermal effects reflect some important aspects of the behavior of materials that are either difficult or fundamentally impossible to analyze with purely mechanical models. Of such are stored energy of cold work (SECW), dissipation of mechanical energy into heat, etc. Thermal effects are also helpful in diagnostics and analysis of damage kinetics, structural changes, etc. [15,22].The major problem in evaluating thermal effects in nonlinear materials is identification of the stored and dissipated fractions of the total plastic energy. Systematic research of these issues originated in the calorimetric tests conducted by Taylor and Quinney [29]. Later studies on SECW are reviewed in [8,10,18]. Fundamental results on the kinetics of accumulation and dissipation of plastic energy obtained by microcalorimetric methods are reported in [12,21]. However, most studies on the subject use quasistatic loading. A few publications on dynamic processes [6,19,27] use rather approximate approaches and estimations.In the present paper, we use the thermodynamically generalized Bodner-Partom model [4,10] to evaluate the fraction of plastic work of AMg-6 alloy that is not dissipated into heat, but is stored in the material through hardening and to find a numerical solution to the thermomechanical dynamic problem for a disk under radial impulsive loading and to study the issues of energy accumulation and dissipation and associated temperature changes.1. Thermodynamics. The constitutive equations of nonlinear plastic materials (such as metals) in thermodynamic formulation is based on general Green-Naghdy theory [17] concretized in [4,10].The local balance equations for momentum and energy written in terms of Cartesian coordinates Ox x x 1 2 3 are σ ρ

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Detection of fatigue macrocracks in 1100 aluminum from thermomechanical data

Cited by 12 publications

References 15 publications

Analysis of temperature distribution near the crack tip under constant amplitude loading

Analysis of temperature distribution near the crack tip under constant amplitude loading

Using a split Hopkinson bar to specify the parameters of thermomechanical models of flow under high strain rate deformation

Thermomechanical coupling effects in a materially nonlinear disk under impulsive radial loading

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