<p>Probability theory has extensive applications across modern scientific disciplines, yet its connection to continuum damage mechanics remains largely unexplored. In this study, we present and validate two scalar damage models whose degradation laws are generated by probability laws via two complementary constructions. Specifically, an exponential law arises under both a cumulative distribution function (CDF) route and a probability-density-function-driven (PDF) route, whereas a Cauchy-type law is naturally obtained from the PDF-driven construction. In the CDF route, the damage potential is defined from the survival function by the normalized integral <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\tilde{\phi }(\phi )=\int _{0}^{\phi }(1-F(\gamma s))\text{ d }s\)</EquationSource> </InlineEquation>, while the PDF route uses <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\tilde{\phi }(\phi )=\frac{G}{\ell } \int _{0}^{\phi /\phi _0} f(s)\text{ d }s\)</EquationSource> </InlineEquation> with <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(F'=f\)</EquationSource> </InlineEquation>; the latter guarantees small-<InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\phi \)</EquationSource> </InlineEquation> linearization (<InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\tilde{\phi }(\phi )\approx \phi \)</EquationSource> </InlineEquation> as <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\phi \rightarrow 0\)</EquationSource> </InlineEquation>) and exact energy saturation (<InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\tilde{\phi }(\infty )=G/\ell \)</EquationSource> </InlineEquation>) without introducing new fields or altering benchmarks. Both models inherit thermodynamic admissibility from a common variational construction; we supply a closed-form proof of positive dissipation and irreversibility. Model parameters are calibrated from uniaxial data by matching the critical energy-release rate and the peak stress, after which no further tuning is required. Spatial regularity is achieved with an integral non-local formulation: the driving strain energy is averaged over a characteristic length so that mesh-objectivity and crack-band width are enforced without adding gradient terms to the energy. The models are implemented in an in-house finite-element code and benchmarked against phase-field on (i) a 2-D single-edge-notch tension/shear specimen, (ii) a notched plate with a hole, and (iii) an asymmetric notched three-point bending test. Both models predict crack paths and peak loads comparable to those by a phase-field method while reducing CPU time by nearly 35%. A final application to a three-point-bend beam with non-planar crack growth confirms their effectiveness and versatility.</p>

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Thermodynamically consistent damage models derived from cumulative distribution functions, with FEM implementations

  • Huilong Ren

摘要

Probability theory has extensive applications across modern scientific disciplines, yet its connection to continuum damage mechanics remains largely unexplored. In this study, we present and validate two scalar damage models whose degradation laws are generated by probability laws via two complementary constructions. Specifically, an exponential law arises under both a cumulative distribution function (CDF) route and a probability-density-function-driven (PDF) route, whereas a Cauchy-type law is naturally obtained from the PDF-driven construction. In the CDF route, the damage potential is defined from the survival function by the normalized integral \(\tilde{\phi }(\phi )=\int _{0}^{\phi }(1-F(\gamma s))\text{ d }s\) , while the PDF route uses \(\tilde{\phi }(\phi )=\frac{G}{\ell } \int _{0}^{\phi /\phi _0} f(s)\text{ d }s\) with \(F'=f\) ; the latter guarantees small- \(\phi \) linearization ( \(\tilde{\phi }(\phi )\approx \phi \) as \(\phi \rightarrow 0\) ) and exact energy saturation ( \(\tilde{\phi }(\infty )=G/\ell \) ) without introducing new fields or altering benchmarks. Both models inherit thermodynamic admissibility from a common variational construction; we supply a closed-form proof of positive dissipation and irreversibility. Model parameters are calibrated from uniaxial data by matching the critical energy-release rate and the peak stress, after which no further tuning is required. Spatial regularity is achieved with an integral non-local formulation: the driving strain energy is averaged over a characteristic length so that mesh-objectivity and crack-band width are enforced without adding gradient terms to the energy. The models are implemented in an in-house finite-element code and benchmarked against phase-field on (i) a 2-D single-edge-notch tension/shear specimen, (ii) a notched plate with a hole, and (iii) an asymmetric notched three-point bending test. Both models predict crack paths and peak loads comparable to those by a phase-field method while reducing CPU time by nearly 35%. A final application to a three-point-bend beam with non-planar crack growth confirms their effectiveness and versatility.