Friction - Revision history

Nairnj: /* Frictional Heating */

2026-03-29T17:02:28Z

Frictional Heating

← Older revision		Revision as of 17:02, 29 March 2026
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	When doing simulations that include [[Thermal Calculations\|conduction calculations]], you can optionally convert the work of frictional sliding into heat. Two options are available that can be used to activate heat conversion for [[#Friction on Explicit Cracks\|frictional sliding between crack surface]] and/or for [[#Friction in Multimaterial MPM\|friction sliding in multimaterial contact]]. To track the total amount of friction heating, the simulation can choose <tt>Friction Work</tt> in the [[MPM Global Archiving Options\|global archiving options]].		When doing simulations that include [[Thermal Calculations\|conduction calculations]], you can optionally convert the work of frictional sliding into heat. Two options are available that can be used to activate heat conversion for [[#Friction on Explicit Cracks\|frictional sliding between crack surface]] and/or for [[#Friction in Multimaterial MPM\|friction sliding in multimaterial contact]]. To track the total amount of friction heating, the simulation can choose <tt>Friction Work</tt> in the [[MPM Global Archiving Options\|global archiving options]].

	Frictional heating was improved in Fall 2015 (in [[OSParticulas]]) and in January 2016 (in [[NairnMPM]]) to use a second order method.<ref~~>J.A. Nairn and G. S. Smith (2016)~~ "~~Generalized Contact and Improved Friction Heating the Material Point Method," in preparation.<~~/~~ref~~> The new method can be observed to converge faster, especially in simulations with high contact forces and vibrations.		Frictional heating was improved in Fall 2015 (in [[OSParticulas]]) and in January 2016 (in [[NairnMPM]]) to use a second order method.<ref name="gencontact/> The new method can be observed to converge faster, especially in simulations with high contact forces and vibrations.

	== Deprecated Friction Commands ==		== Deprecated Friction Commands ==

Nairnj: /* References */

2026-03-29T17:01:47Z

References

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	== References ==		== References ==
	<references/>		<references>

			<ref name="gencontact">J. A. Nairn, S. G. Bardenhagen, and G. S. Smith, "Generalized contact and improved frictional heating in the material point method.=," ''Computational Particle Mechanics'', '''5''', 285–296 (2018) ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/MPMContactLawsSV.pdf See PDF])</ref>

			</references>

Nairnj at 22:53, 2 January 2021

2021-01-02T22:53:44Z

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	Both [[MPM Input Files#Using Explicit Cracks\|explicit cracks]] and [[Multimaterial MPM\|multimaterial mode MPM]] can model ~~frictional~~ contact between ~~the~~ surfaces.		Both [[MPM Input Files#Using Explicit Cracks\|explicit cracks]] and [[Multimaterial MPM\|multimaterial mode MPM]] can model contact between surfaces using a variety of [[Contact Laws\|contact laws]].
	__TOC__		__TOC__
	== Introduction ==		== Introduction ==

	The contact between materials or between crack surfaces can be modeled ~~as frictional contact, which is done~~ by selecting any of the available [[Contact Laws\|contact laws]]. When ~~frictional~~ contact is activated and the surfaces are in contact, the tangential traction, S, is change to some function of normal force, N, and possibly other parameters of the various [[Contact Laws#Frictional Contact Laws\|contact laws]]. For example, [[Coulomb Friction Law\|Coulomb friction]] will set tangential traction to		The contact between materials or between crack surfaces can be modeled by selecting any of the available [[Contact Laws\|contact laws]]. When contact is activated and the surfaces are in contact, the tangential traction, S, is change to some function of normal force, N, and possibly other parameters of the various [[Contact Laws#Frictional Contact Laws\|contact laws]]. For example, [[Coulomb Friction Law\|Coulomb friction]] will set tangential traction to

Nairnj: /* Introduction */

2021-01-02T21:22:44Z

Introduction

← Older revision		Revision as of 21:22, 2 January 2021
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	== Introduction ==		== Introduction ==

	The contact between materials or between crack surfaces can be modeled as frictional contact, which is done by selecting any of the available [[Contact Laws}contact laws]]. When frictional contact is activated and the surfaces are in contact, the tangential traction, S, is change to some function of normal force, N, and possibly other parameters of the various [[Contact Laws#Frictional Contact Laws\|contact laws]]. For example, [[Coulomb Friction Law\|Coulomb friction]] will set tangential traction to		The contact between materials or between crack surfaces can be modeled as frictional contact, which is done by selecting any of the available [[Contact Laws\|contact laws]]. When frictional contact is activated and the surfaces are in contact, the tangential traction, S, is change to some function of normal force, N, and possibly other parameters of the various [[Contact Laws#Frictional Contact Laws\|contact laws]]. For example, [[Coulomb Friction Law\|Coulomb friction]] will set tangential traction to

Nairnj: /* Notes */

2017-09-15T22:01:41Z

Notes

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	# If you use both <tt>law</tt> and <tt>lawname</tt> attributes in the same <tt>XML</tt> command, the <tt>lawname</tt> is used to select the law.		# If you use both <tt>law</tt> and <tt>lawname</tt> attributes in the same <tt>XML</tt> command, the <tt>lawname</tt> is used to select the law.
	# Note than an <tt>XML</tt> file can [[Material_Command_Block#Referencing_Materials_in_XML_Files\|reference materials by name or number]], but not mix these methods. The <tt>Friction</tt> command should therefore always refer to contact law ~~material~~ by the same method other material commands are using reference materials.		# Note than an <tt>XML</tt> file can [[Material_Command_Block#Referencing_Materials_in_XML_Files\|reference materials by name or number]], but not mix these methods. The [[#Setting Frictional Contact Properties\|<tt>Friction</tt> command]] should therefore always refer to contact law materials by the same method that other material commands are using reference materials (in that same <tt>XML</tt> file).

	== References ==		== References ==
	<references/>		<references/>

Nairnj: /* References */

2017-09-15T22:00:20Z

References

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	The above commands set the default frictional properties for contact between any two materials. Custom friction (or conversion to [[Imperfect Interfaces\|imperfect interface]] contact) was done using a [[Common Material Properties#Contact Properties\|<tt>Friction</tt> or <tt>Interface</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.		The above commands set the default frictional properties for contact between any two materials. Custom friction (or conversion to [[Imperfect Interfaces\|imperfect interface]] contact) was done using a [[Common Material Properties#Contact Properties\|<tt>Friction</tt> or <tt>Interface</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.

			== Notes ==

			# If you use both <tt>law</tt> and <tt>lawname</tt> attributes in the same <tt>XML</tt> command, the <tt>lawname</tt> is used to select the law.
			# Note than an <tt>XML</tt> file can [[Material_Command_Block#Referencing_Materials_in_XML_Files\|reference materials by name or number]], but not mix these methods. The <tt>Friction</tt> command should therefore always refer to contact law material by the same method other material commands are using reference materials.

	== References ==		== References ==
	<references/>		<references/>

Nairnj: /* Friction on Explicit Cracks */

2017-09-15T21:00:56Z

Friction on Explicit Cracks

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	<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>		<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>

	where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws#Frictional Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also be selected by is number (in <tt>(lawnum)</tt>)~~, but if both ID and number are used in the same command, the ID is used to select the law. Note than an <tt>XML</tt> file can~~ [[~~Material_Command_Block~~#~~Referencing_Materials_in_XML_Files~~\|~~reference materials by name or number~~]]~~, but not mix these methods. The <tt>Friction</tt> command should refer to contact law material by the same method other material commands reference materials~~.		where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws#Frictional Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also by selected by number (in <tt>(lawnum)</tt>) or name ([[#Notes\|but not both]]).

	The above commands set the default frictional contact properties for crack surfaces. When a simulation only has only one crack, this setting is enough. For simulations with more than one crack, you can set [[Defining Cracks#Starting the Crack\|different frictional properties]] for each crack, or convert some cracks to [[Imperfect Interfaces#Imperfect Interfaces on Explicit Cracks\|imperfect interfaces]].		The above commands set the default frictional contact properties for crack surfaces. When a simulation only has only one crack, this setting is enough. For simulations with more than one crack, you can set [[Defining Cracks#Starting the Crack\|different frictional properties]] for each crack, or convert some cracks to [[Imperfect Interfaces#Imperfect Interfaces on Explicit Cracks\|imperfect interfaces]].

Nairnj: /* Friction in Multimaterial MPM */

2017-09-15T21:00:06Z

Friction in Multimaterial MPM

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	<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>		<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>

	where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can ~~also~~ be selected by number (in <tt>(lawnum)</tt>), but if both ~~ID and number are used in the same command, the ID is used to select the law~~.		where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can be selected by number (in <tt>(lawnum)</tt>) or name ([[#Notes\|but not both]]).

	The above commands set the default frictional properties for contact between any two materials. When a simulation only has two materials contacting by friction, this setting is enough. For simulations with more than two materials, you can set different frictional properties for each material pair, or even combine material pairs interacting by friction with those connected by an [[Imperfect Interfaces\|imperfect interface]], by using a [[Common Material Properties#Contact Properties\|<tt>Contact</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.		The above commands set the default frictional properties for contact between any two materials. When a simulation only has two materials contacting by friction, this setting is enough. For simulations with more than two materials, you can set different frictional properties for each material pair, or even combine material pairs interacting by friction with those connected by an [[Imperfect Interfaces\|imperfect interface]], by using a [[Common Material Properties#Contact Properties\|<tt>Contact</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.

Nairnj: /* Friction on Explicit Cracks */

2017-09-15T20:56:01Z

Friction on Explicit Cracks

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	In <tt>XML</tt> files, the default frictional contact properties for cracks are defined with a <tt><Friction></tt> command within the [[Crack Settings\|<tt><Cracks></tt> element]] in the <tt><MPMHeader></tt>:		In <tt>XML</tt> files, the default frictional contact properties for cracks are defined with a <tt><Friction></tt> command within the [[Crack Settings\|<tt><Cracks></tt> element]] in the <tt><MPMHeader></tt>:

	<Friction law='(lawnum)' lawname='(lawID)'/>		<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>

	where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws#Frictional Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also be selected by is number (in <tt>(lawnum)</tt>), but if both ID and number are used in the same command, the ID is used to select the law. Note than an <tt>XML</tt> file can [[Material_Command_Block#Referencing_Materials_in_XML_Files\|reference materials by name or number]], but not mix these methods. The <tt>Friction</tt> command should refer to contact law material by the same method other material commands reference materials.		where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws#Frictional Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also be selected by is number (in <tt>(lawnum)</tt>), but if both ID and number are used in the same command, the ID is used to select the law. Note than an <tt>XML</tt> file can [[Material_Command_Block#Referencing_Materials_in_XML_Files\|reference materials by name or number]], but not mix these methods. The <tt>Friction</tt> command should refer to contact law material by the same method other material commands reference materials.

Nairnj: /* Friction in Multimaterial MPM */

2017-09-15T20:54:42Z

Friction in Multimaterial MPM

← Older revision		Revision as of 20:54, 15 September 2017
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	<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>		<Friction law='(lawnum)'/> or <Friction lawname='(lawID)'/>

	where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also be selected by is number (in <tt>(lawnum)</tt>), but if both ID and number are used in the same command, the ID is used to select the law.		where <tt>(lawID)</tt> is the ID of the desired [[Contact Laws\|frictional contact law]]. In <tt>XML</tt> files, the [[Contact Laws\|contact law]] can also be selected by number (in <tt>(lawnum)</tt>), but if both ID and number are used in the same command, the ID is used to select the law.

	The above commands set the default frictional properties for contact between any two materials. When a simulation only has two materials contacting by friction, this setting is enough. For simulations with more than two materials, you can set different frictional properties for each material pair, or even combine material pairs interacting by friction with those connected by an [[Imperfect Interfaces\|imperfect interface]], by using a [[Common Material Properties#Contact Properties\|<tt>Contact</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.		The above commands set the default frictional properties for contact between any two materials. When a simulation only has two materials contacting by friction, this setting is enough. For simulations with more than two materials, you can set different frictional properties for each material pair, or even combine material pairs interacting by friction with those connected by an [[Imperfect Interfaces\|imperfect interface]], by using a [[Common Material Properties#Contact Properties\|<tt>Contact</tt> material property]] for the secondly-defined material of each pair needing different contact mechanics.