Defining Cracks - Revision history

Nairnj: /* References */

2026-03-29T17:17:17Z

References

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	<ref name="cutting">J. A. Nairn. Numerical simulation of orthogonal cutting using the material point method. Engineering Fracture Mechanics, 149:262–275, 2015.</ref>		<ref name="cutting">J. A. Nairn. Numerical simulation of orthogonal cutting using the material point method. Engineering Fracture Mechanics, 149:262–275, 2015.</ref>

			<ref name="icracks">J. A. Nairn and Y. E. Aimene, "Modeling Multiple Crack Propagation in the Material Point Method by J-Integral Methods Accounting for Other Cracks Intersecting the J Contour," ''Engineering Fracture Mechanics'', '''322''', 111143 (2025). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/InteractingCracks.pdf See PDF])</ref>


	</references>		</references>

Nairnj: /* Interacting Cracks */

2026-03-29T17:17:02Z

Interacting Cracks

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	The key change in CRAMP<ref name="CRAMP"/> compared to conventional MPM is that each node can have more then one velocity field to separately track particle motion above and below cracks. When only a single crack is near a node, that node may have velocity fields. When MPM extrapolates particle velocities to the grid, it traces a line from each particle to the node. If the line does not cross any crack, it adds to velocity field [0] on that node. If it crosses the single crack, it adds to velocity field [1]. The left side of the figure on the right show a single blue crack. The particles labeled [0] are on the same side of the crack as the indicated node and extrapolate to velocity field [0] on that node. The particles labeled [1] are on the opposite of the crack and extrapolate to velocity field [1] on that node.		The key change in CRAMP<ref name="CRAMP"/> compared to conventional MPM is that each node can have more then one velocity field to separately track particle motion above and below cracks. When only a single crack is near a node, that node may have velocity fields. When MPM extrapolates particle velocities to the grid, it traces a line from each particle to the node. If the line does not cross any crack, it adds to velocity field [0] on that node. If it crosses the single crack, it adds to velocity field [1]. The left side of the figure on the right show a single blue crack. The particles labeled [0] are on the same side of the crack as the indicated node and extrapolate to velocity field [0] on that node. The particles labeled [1] are on the opposite of the crack and extrapolate to velocity field [1] on that node.

	The right side of the figure shows extension of CRAMP to handle two interacting cracks. When two cracks are near a node, that node may have up to four velocity fields, which are determined by tracing lines from particles to the node. Field [0] is from particles on the same side of both cracks. Field [1] is from particles on the opposite side of the first crack (here the blue crack). Field [2] is from particles on the opposite side of the second crack (the red crack). Field [3] is from particles that are on the opposite side of both cracks.		The right side of the figure shows extension of CRAMP to handle two interacting cracks.<ref name="icracks"/> When two cracks are near a node, that node may have up to four velocity fields, which are determined by tracing lines from particles to the node. Field [0] is from particles on the same side of both cracks. Field [1] is from particles on the opposite side of the first crack (here the blue crack). Field [2] is from particles on the opposite side of the second crack (the red crack). Field [3] is from particles that are on the opposite side of both cracks.

	The extension to three interacting and explicit cracks is not handled. In other words, MPM models cannot explicitly resolve three cracks that are all near a single node (''i.e.'', within the same background cell). If three crack are found, the simulation will continue and a warning will appear in the output file. The results near those three interacting cracks may not be accurate. Note that although three cracks in the same cell are not handled, an MPM model can handle any number of cracks as long as no more then two are near any given node. Despite this limitation, CRAMP does handle two cracks in the same cell, which is an improvement over typical finite element methods (''e.g.'', XFEM) that are limited to just a single crack in any element.		The extension to three interacting and explicit cracks is not handled. In other words, MPM models cannot explicitly resolve three cracks that are all near a single node (''i.e.'', within the same background cell). If three crack are found, the simulation will continue and a warning will appear in the output file. The results near those three interacting cracks may not be accurate. Note that although three cracks in the same cell are not handled, an MPM model can handle any number of cracks as long as no more then two are near any given node. Despite this limitation, CRAMP does handle two cracks in the same cell, which is an improvement over typical finite element methods (''e.g.'', XFEM) that are limited to just a single crack in any element.

Nairnj: /* References */

2026-03-29T17:13:44Z

References

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	<ref name="RCurve">J. A. Nairn, "Analytical and Numerical Modeling of R Curves for Cracks with Bridging Zones," <i>Int. J. Fracture</i>, <b>155</b>, 167-181 (2009). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/JBridging.pdf See PDF])</ref>		<ref name="RCurve">J. A. Nairn, "Analytical and Numerical Modeling of R Curves for Cracks with Bridging Zones," <i>Int. J. Fracture</i>, <b>155</b>, 167-181 (2009). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/JBridging.pdf See PDF])</ref>

	<ref name="mixedmode">J. A. Nairn and Y. E. Aimene, "A re-evaluation of mixed-mode cohesive zone modeling based on strength concepts instead of traction laws", ~~submitted~~ (2021).</ref>		<ref name="mixedmode">J. A. Nairn and Y. E. Aimene, "A re-evaluation of mixed-mode cohesive zone modeling based on strength concepts instead of traction laws", ''Engineering Fracture Mechanics'', '''248''', 107704 (2021). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/StrengthCZM.pdf See PDF])</ref>

	<ref name="wood">J. A. Nairn, "Material Point Method Simulations of Transverse Fracture in Wood with Realistic Morphologies," <i>Holzforschung</i>, <b>61</b>, 375-381 (2007). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FractureSim.pdf See PDF])</ref>		<ref name="wood">J. A. Nairn, "Material Point Method Simulations of Transverse Fracture in Wood with Realistic Morphologies," <i>Holzforschung</i>, <b>61</b>, 375-381 (2007). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FractureSim.pdf See PDF])</ref>

Nairnj at 23:21, 26 April 2024

2024-04-26T23:21:45Z

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	This section explains how to add explicit cracks to an MPM ~~simulation~~.		This section explains how to add explicit cracks to both 2D and 3D MPM simulations.

	== Introduction ==		== Introduction ==

Nairnj: /* Introduction */

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Introduction

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	The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/>, use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>		The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/>, use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>

	The remainder of this page explains how to define cracks in 2D problems only. As separate page explains how to define crack in [[3D ~~Crack~~\|3D problems]].		The remainder of this page explains how to define cracks in 2D problems only. As separate page explains how to define crack in [[3D Cracks\|3D problems]].

	== Crack Definition Commands ==		== Crack Definition Commands ==

Nairnj: /* Introduction */

2024-04-26T21:50:22Z

Introduction

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	The extension of MPM to model explicit cracks is called CRAMP for '''CRA'''cks in the '''M'''aterial '''P'''oint Method. The commands is this section are used to define the explicit cracks (and there can be any number of them). In addition, whenever a simulation has cracks you can use [[Crack Settings\|crack settings commands]] to customize the features of the crack physics, set various [[Common Material Properties\|material fracture properties]] to control crack propagation, or add [[Traction Laws\|traction laws]] to model cohesive zones.		The extension of MPM to model explicit cracks is called CRAMP for '''CRA'''cks in the '''M'''aterial '''P'''oint Method. The commands is this section are used to define the explicit cracks (and there can be any number of them). In addition, whenever a simulation has cracks you can use [[Crack Settings\|crack settings commands]] to customize the features of the crack physics, set various [[Common Material Properties\|material fracture properties]] to control crack propagation, or add [[Traction Laws\|traction laws]] to model cohesive zones.

	The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/> ~~(although only available in [[OSParticulas]])~~, use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>		The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/>, use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>

	The remainder of this page ~~is limited~~ to cracks in 2D problems. ~~See~~ [[3D ~~Cracks~~]] ~~for information on creating and using cracks in 3D calculations~~.		The remainder of this page explains how to define cracks in 2D problems only. As separate page explains how to define crack in [[3D Crack\|3D problems]].

	== Crack Definition Commands ==		== Crack Definition Commands ==

Nairnj at 04:23, 29 January 2022

2022-01-29T04:23:15Z

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	The remainder of this page is limited to cracks in 2D problems. See [[3D Cracks]] for information on creating and using cracks in 3D calculations.		The remainder of this page is limited to cracks in 2D problems. See [[3D Cracks]] for information on creating and using cracks in 3D calculations.

	== Crack Definition ~~Commmands~~ ==		== Crack Definition Commands ==

	[[File:OneCrack.png\|right]]		[[File:OneCrack.png\|right]]

Nairnj: /* Introduction */

2022-01-29T04:20:26Z

Introduction

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	The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/> (although only available in [[OSParticulas]]), use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>		The development of CRAMP is described first in a paper by Nairn (2003)<ref name='CRAMP'/> (and its development was done using [[NairnMPM]]). Some other papers discuss calculation of J integral and stress intensity factor,<ref name="GuoJ"/>, propose energy balance propagation,<ref name="EB"/> handle cracks in 3D<ref name="Guo3D"/> (although only available in [[OSParticulas]]), use cracks to model imperfect interfaces,<ref name="IIC"/>, use traction laws with cracks,<ref name="RCurve"/>, and define a new approach to mixed-mode cohesive zone modeling.<ref name="mixedmode"/> Some applications of using cracks in MPM include wood fracture,<ref name="wood"/> use of cracks to model glue bonds in oriented strand board,<ref name="OSB"/> simulation of dynamic fracture,<ref name="BardF"/> simulation of crack growth with fiber bridging.<ref name="MDF"/>, and simulation of cutting.<ref name="cutting"/>

			The remainder of this page is limited to cracks in 2D problems. See [[3D Cracks]] for information on creating and using cracks in 3D calculations.

	== Crack Definition Commmands ==		== Crack Definition Commmands ==

Nairnj: /* Growing the Crack */

2021-03-15T19:23:43Z

Growing the Crack

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	</ol>		</ol>

	<li><tt>(tract)</tt> - this optional parameter can assign a [[Traction Laws\|traction law]] to all new crack particles created by the growing action by setting it to the [[Material Command Block\|material ID]] for a traction law material. To set a traction law material but no crack tip material in <tt>(mat)</tt> in scripted files, you can set<tt>(mat)</tt> to "0" (or actually to any invalid material ID). In <tt>XML</tt> files, you assign a [[Traction Laws\|traction law]] using a [[Material Command Block#Referencing Materials in XML Files\|<tt>mat='n'</tt> or <tt>matnam='name'</tt> attribute]] on the command. (See notes [[#Notes\|2 and 3]]).		<li><tt>(tract)</tt> - this optional parameter can assign a [[Traction Laws\|traction law]] to all new crack particles created by the growing action by setting it to the [[Material Command Block\|material ID]] for a traction law material. To set a traction law material but no crack tip material in <tt>(mat)</tt> in scripted files, you can set<tt>(mat)</tt> to "0" (or actually to any invalid material ID). In <tt>XML</tt> files, you assign a [[Traction Laws\|traction law]] using a [[Material Command Block#Referencing Materials in XML Files\|<tt>mat='n'</tt> or a <tt>matnam='name'</tt> attribute]] on the command. (See notes [[#Notes\|2 and 3]]).
	</ul>		</ul>

Nairnj: /* Crack Definition Commmands */

2021-02-01T21:55:22Z

Crack Definition Commmands

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	* [[#Growing the Crack\|<tt>GrowCrack</tt>, <tt>GrowCrackLine</tt>, and <tt>GrowCrackArc</tt> commands]] - these commands extend the crack (the corresponding <tt>XML</tt> commands are <tt><pt></tt>, <tt><Line></tt>, and <tt><Circle></tt>).		* [[#Growing the Crack\|<tt>GrowCrack</tt>, <tt>GrowCrackLine</tt>, and <tt>GrowCrackArc</tt> commands]] - these commands extend the crack (the corresponding <tt>XML</tt> commands are <tt><pt></tt>, <tt><Line></tt>, and <tt><Circle></tt>).
	* [[#Crack Thickness\|<tt>CrackThickness</tt> command]] - this commands sets the crack thickness (the corresponding <tt>XML</tt> command is <tt><Thickness></tt>).		* [[#Crack Thickness\|<tt>CrackThickness</tt> command]] - this commands sets the crack thickness (the corresponding <tt>XML</tt> command is <tt><Thickness></tt>).
	* <tt>CustomTractionProp command</tt> - this command selects a [[Traction Laws\|traction law]] to be ~~insert~~ whenever this crack propagates. This command is only needed to override [[Crack Propagation Commands#Traction Law in Wake of Propagation\|default methods for inserting traction laws]]. See the [[#Starting the Crack\|<tt><CrackList></tt> element]] to set custom traction propagation material in <tt>XML</tt> files.		* <tt>CustomTractionProp command</tt> - this command selects a [[Traction Laws\|traction law]] to be inserted whenever this crack propagates. This command is only needed to override [[Crack Propagation Commands#Traction Law in Wake of Propagation\|default methods for inserting traction laws]]. See the [[#Starting the Crack\|<tt><CrackList></tt> element]] to set custom traction propagation material in <tt>XML</tt> files.

	=== Starting the Crack ===		=== Starting the Crack ===