Isotropic Damage Mechanics - Revision history

Nairnj: /* Damage Metric */

2026-03-29T17:59:06Z

Damage Metric

← Older revision		Revision as of 17:59, 29 March 2026
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	== Damage Metric ==		== Damage Metric ==

	The standard approach in isotropic damage mechanics to initiate and evolve damage according is to use a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials, although it can be more stable to other damage mechanics methods (but stability ~~alone~~ is not enough to justify its use).		The standard approach in isotropic damage mechanics to initiate and evolve damage according is to use a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials, although it can be more stable than other damage mechanics methods (but stability is not enough to justify its use).

	=== Stress Metric ===		=== Stress Metric ===

Nairnj: /* Constitutive Law */

2023-11-18T17:50:09Z

Constitutive Law

← Older revision		Revision as of 17:50, 18 November 2023
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	== Constitutive Law ==		== Constitutive Law ==

	This [[Material Models\|MPM ~~Material~~]] is an isotropic, elastic material, but once it initiates damage, it evolves using isotopic damage mechanics methods. The constitutive law for this material is		This [[Material Models#Softening Materials\|MPM softening material]] is an isotropic, elastic material, but once it initiates damage, it evolves using isotopic damage mechanics methods. The constitutive law for this material is

Nairnj: /* Damage Metric */

2023-11-18T00:21:36Z

Damage Metric

← Older revision		Revision as of 00:21, 18 November 2023
Line 10:		Line 10:
	== Damage Metric ==		== Damage Metric ==

	The standard approach in isotropic damage mechanics to initiate and evolve damage according is to use a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials.		The standard approach in isotropic damage mechanics to initiate and evolve damage according is to use a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials, although it can be more stable to other damage mechanics methods (but stability alone is not enough to justify its use).

	=== Stress Metric ===		=== Stress Metric ===

Nairnj: /* Damage Metric */

2023-11-18T00:20:40Z

Damage Metric

← Older revision		Revision as of 00:20, 18 November 2023
Line 10:		Line 10:
	== Damage Metric ==		== Damage Metric ==

	The standard approach in isotropic damage mechanics is to evolve damage according to a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials.		The standard approach in isotropic damage mechanics to initiate and evolve damage according is to use a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials.

	=== Stress Metric ===		=== Stress Metric ===

Nairnj: /* Material Properties */

2023-11-17T23:26:18Z

Material Properties

← Older revision		Revision as of 23:26, 17 November 2023
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	\| ([[Common Material Properties\|other]]) \|\| Properties common to all materials \|\| varies \|\| varies		\| ([[Common Material Properties\|other]]) \|\| Properties common to all materials \|\| varies \|\| varies
	\|}		\|}

			If needed, you can set [[Setting Forces and Fluxes#Initial Particle Damage\|set initial damage parameter]] for particles using [[Particle-Based Boundary Conditions\|particle boundary conditions]].

	== History Variables ==		== History Variables ==

Nairnj: /* History Variables */

2023-11-17T01:10:03Z

History Variables

← Older revision		Revision as of 01:10, 17 November 2023
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	== History Variables ==		== History Variables ==

	This material stores allocates all history variables used by its parent [[Isotropic Softening Material\|IsoSoftening]] material, but only ~~some of them~~ are used:		This material stores allocates all history variables used by its parent [[Isotropic Softening Material\|IsoSoftening]] material, but only the following ones are used:

	# The current damage state with the following possible values:		# The current damage state with the following possible values:

Nairnj: /* Mixed-Mode Metric */

2023-11-17T00:45:18Z

Mixed-Mode Metric

← Older revision		Revision as of 00:45, 17 November 2023
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	<math>\Phi(\mathbf{\sigma},D) = d\bigl(\bar{\mathbf{\sigma}},F_I(D),F_{II}(D)\bigr)</math>		<math>\Phi(\mathbf{\sigma},D) = d\bigl(\bar{\mathbf{\sigma}},F_I(D),F_{II}(D)\bigr)</math>

	where <math>d()</math> represent a calculation of as signed distance from the current principal stress state <math>\bar{\mathbf{\sigma}}</math> to the principal stress failure surface defined by current tensile and shear strengths (<math>F_I(D)</math> and <math>F_{II}(D)</math>). The sign is negative when stress is inside the failure surface and positive when it is outside.		where <math>d()</math> represent a calculation of signed distance from the current principal stress state <math>\bar{\mathbf{\sigma}}</math> to the principal stress failure surface defined by current tensile and shear strengths (<math>F_I(D)</math> and <math>F_{II}(D)</math>). The sign is negative when stress is inside the failure surface and positive when it is outside.

	=== Strength Models ===		=== Strength Models ===

Nairnj: /* Damage Metric */

2023-11-17T00:42:44Z

Damage Metric

← Older revision		Revision as of 00:42, 17 November 2023
Line 10:		Line 10:
	== Damage Metric ==		== Damage Metric ==

	The standard approach in isotropic damage mechanics is to evolve damage according to a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch ~~using~~ [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials.		The standard approach in isotropic damage mechanics is to evolve damage according to a scalar metric. Once that is in place, material modeling can simply apply one-dimensional damage mechanics methods. Unfortunately, real-life damage is not one dimensional and it is likely the entire concept of isotropic damage mechanics is misguided. A better approach to extending 1D damage mechanics to 3D is to switch to [[Isotropic Softening Material\|anisotropic damage mechanics]]. Anisotropic damage mechanics replaces the scalar metric from 1D methods with evolution determined by 3 components of traction on a crack surface. Isotropic damage mechanics is made available here mostly for comparison purposes. It is likely not a realistic approach to modeling damage in materials.

	=== Stress Metric ===		=== Stress Metric ===

Nairnj: /* Constitutive Law */

2023-11-17T00:41:33Z

Constitutive Law

← Older revision		Revision as of 00:41, 17 November 2023
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	<math>\mathbf{\sigma} = (1-D) \mathbf{C}( \mathbf{\varepsilon}- \mathbf{\varepsilon}_{res})</math>		<math>\mathbf{\sigma} = (1-D) \mathbf{C}( \mathbf{\varepsilon}- \mathbf{\varepsilon}_{res})</math>

	where ~~'''~~C~~'''~~ is stiffness tensor for the underlying isotropic material, ''D'' is a scalar damage parameter, and <math>\mathbf{\varepsilon}_{res}</math> is any residual strain (such as thermal or solvent induced strains).		where <math>\mathbf{C}</math> is stiffness tensor for the underlying isotropic material, ''D'' is a scalar damage parameter, and <math>\mathbf{\varepsilon}_{res}</math> is any residual strain (such as thermal or solvent induced strains).

	== Damage Metric ==		== Damage Metric ==

Nairnj: /* Material Properties */

2023-01-30T22:49:02Z

Material Properties

← Older revision		Revision as of 22:49, 30 January 2023
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	\| SofteningII \|\| Attach a [[Softening Laws\|softening law]] (by name or ID) for propagation of shear damage, but only used when metric=2. Once attached, enter all required properties for that law by prefacing each property with "II-". <math>F_{II}(D)</math> is tauc times this softening law. \|\| none \|\| Linear		\| SofteningII \|\| Attach a [[Softening Laws\|softening law]] (by name or ID) for propagation of shear damage, but only used when metric=2. Once attached, enter all required properties for that law by prefacing each property with "II-". <math>F_{II}(D)</math> is tauc times this softening law. \|\| none \|\| Linear
	\|-		\|-
	\| coefVariation ~~\|\| This property assigns a coefficient of variation to failure properties. The property that is affected is determined by the~~ <tt>~~coefVariationMode~~<~~/tt~~> parameter. Each particle's relative property is set at the start of the simulation to have the same Gaussian distribution of values about their means, but will have no spatial correlations. A better approach to stochastic modeling would use Gaussian random fields with spatial correlation (see below). \|\| ~~none~~ \|~~\| 0~~		\| coefVariation<br>wShape<br>wV0<br>statDistributionMode \|\| See the corresponding properties defined for an [[Isotropic Softening Material#Material Properties\|Isotropic softening material]]. \|\| \|\|
	\|-
	\| coefVariationMode \|\| The options are 1 = vary only strength, 2 = vary only toughness, and 3 = vary strength and toughness. Note that strength, toughness, and critical crack opening displacement (COD) are interrelated. Option 1 means COD will increase to keep toughness constant; 2 means COD will decrease to keep strength constant; 3 means COD will remain constant. \|\| ~~none~~ \|\| 1
	\|-		\|-
	\| ([[Common Material Properties\|other]]) \|\| Properties common to all materials \|\| varies \|\| varies		\| ([[Common Material Properties\|other]]) \|\| Properties common to all materials \|\| varies \|\| varies
	\|}		\|}

	An alternative to randomly varying strength or toughness using coefVariation and coefVariationMode properties is to set the relative values using a [[PropertyRamp Custom Task]]. For example, a BMP image of a Gaussian random field could assign relative strengths or toughnesses with random variations that include spatial correlations.

	== History Variables ==		== History Variables ==