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Qin, Hao
Publications (8 of 8) Show all publications
Lindgren, L.-E., Qin, H. & Wedberg, D. (2017). Improved and simplified dislocation density based plasticity model for AISI 316 L. Mechanics of materials (Print), 108, 68-76
Open this publication in new window or tab >>Improved and simplified dislocation density based plasticity model for AISI 316 L
2017 (English)In: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 108, p. 68-76Article in journal (Refereed) Published
Abstract [en]

A previously published dislocation density based flow stress model has been refined and made more consistent with underlying physical assumptions. The previous model included many temperature dependent parameters that are taken as constant in the current work. The model has also been simplified with respect to dynamic strain aging. Additional contributions to flow stress from the Hall-Petch effect and solute hardening have now been explicitly included in the model. Furthermore, the dynamic recovery part of the model has been improved.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-62446 (URN)10.1016/j.mechmat.2017.03.007 (DOI)000399859100006 ()2-s2.0-85015320929 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-17 (rokbeg)

Available from: 2017-03-13 Created: 2017-03-13 Last updated: 2018-09-13Bibliographically approved
Abiri, O., Qin, H. & Lindgren, L.-E. (2016). Comparison of Multiresolution Continuum Theory and Nonlocal Dame model for use in Simulation of Manufacutring Processes (ed.). International Journal for Multiscale Computational Engineering, 14(1), 81-94
Open this publication in new window or tab >>Comparison of Multiresolution Continuum Theory and Nonlocal Dame model for use in Simulation of Manufacutring Processes
2016 (English)In: International Journal for Multiscale Computational Engineering, ISSN 1543-1649, Vol. 14, no 1, p. 81-94Article in journal (Refereed) Published
Abstract [en]

Modelling and simulation of manufacturing processes may require the capability to account for localization behavior, often associated with damage/fracture. It may be unwanted localization indicating a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying physics, as well as the robustness of the simulation procedure. Two different approaches for achieving mesh-independent solutions are compared in this paper. They are the multiresolution continuum theory (MRCT) and nonlocal damage model. The MRCT theory is a general multilength-scale finite element formulation, while the nonlocal damage model is a specialized method using a weighted averaging of softening internal variables over a spatial neighborhood of the material point. Both approaches result in a converged finite element solution of the localization problem upon mesh refinement. This study compares the accuracy and robustness of their numerical schemes in implicit finite element codes for the plane strain shear deformation test case. Final remarks concerning ease of implementation of the methods in commercial finite element packages are also given.

National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-3403 (URN)10.1615/IntJMultCompEng.2016016322 (DOI)000374274000006 ()2-s2.0-84963719840 (Scopus ID)13b0c7c1-e817-4a05-82b9-e5bdf5fc5bc2 (Local ID)13b0c7c1-e817-4a05-82b9-e5bdf5fc5bc2 (Archive number)13b0c7c1-e817-4a05-82b9-e5bdf5fc5bc2 (OAI)
Note

Validerad; 2016; Nivå 2; 20160418 (oluabi)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-03-29Bibliographically approved
Qin, H. (2016). Multiresolution Continuum Theory and Dislocation Density Based Constitutive Relations (ed.). (Doctoral dissertation). Paper presented at . Luleå tekniska universitet
Open this publication in new window or tab >>Multiresolution Continuum Theory and Dislocation Density Based Constitutive Relations
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In classical description, the mechanical state of a material point depends on the variables defined at this point solely. It can integrate and catch some aspects of the material’s microstructure by conventional homogenization method. The application of the conventional continuum assumption results in a simplified description of the system which makes the large scale simulation of the material more efficient but at the expense of a loss of information at small length scales. Localization is a phenomena where a large degree of deformation occurs in highly concentrated regions. The conventional continuum theory with strain softening can not give the convergent solution as the size of the localization zone is completely determined by the mesh discretization. The multiresolution continuum theory (MRCT) is a higher order continuum theory where additional kinematic variables supplementing the conventional macroscopic displacement field are added to account for deformations at several distinct length scales. The direct inclusion of the length scale parameters in the material’s constitutive equations remedies the convergence problem. In crystalline materials the initiation of plastic flow and subsequent permanent plastic deformation is attributed to the presence and movement of dislocations and also the interactions between the dislocation themselves and different kinds of obstacles, inclusions, second phase particles and grain boundaries etc. Some of these defects can alsolead to damage initiation in the materials. For example, the stresses developed at the dislocation pile-ups contribute to the initiation of the microvoids and microcracks. A dislocation density based damage model has been developed and combined with a physically based flow stress model. They are calibrated and validated for 316L stainless steel at different temperatures and strain rates. These models have been implemented into the macroscopic material description of the MRCT element.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-18468 (URN)8c03605b-d889-4215-b9f9-93be959d9107 (Local ID)978-91-7583-559-4 (ISBN)978-91-7583-560-0 (ISBN)8c03605b-d889-4215-b9f9-93be959d9107 (Archive number)8c03605b-d889-4215-b9f9-93be959d9107 (OAI)
Note

Godkänd; 2016; 20160215 (haoqin); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Hao Qin Ämne: Materialmekanik/Material Mechanics Avhandling: Multiresolution Continuum Theory and Dislocation Density Based Constitutive Relations Opponent: Professor emeritus Kenneth Runesson, Avd för material- och beräkningsmekanik, Institutionen för tillämpad mekanik, Chalmers tekniska högskola, Göteborg. Ordförande: Professor Lars-Erik Lindgren, Avd för material- och solidmekanik, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Tid: Måndag 25 april, 2016 kl 09.30 Plats: E246, Luleå tekniska universitet

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-03-29Bibliographically approved
Qin, H., Lindgren, L.-E., Liu, W. K. & Smith, J. (2015). Implicit finite element formulation of multiresolution continuum theory (ed.). Computer Methods in Applied Mechanics and Engineering, 293, 114-130
Open this publication in new window or tab >>Implicit finite element formulation of multiresolution continuum theory
2015 (English)In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 293, p. 114-130Article in journal (Refereed) Published
Abstract [en]

The multiresolution continuum theory is a higher order continuum theory where additional kinematic variables account for microstructural inhomogeneities at several distinct length scales. This can be particularly important for localization problems. The strength of this theory is that it can account for details in the microstructure of a material without using an extremely fine mesh. The present paper describes the implementation and verification of a 3D elastic–plastic multiresolution element based on an implicit time stepping algorithm. It is implemented in the general purpose finite element program FEAP. The mesh independency associated with the length scale parameter is examined and the convergence rate of the element is also evaluated.

National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-12995 (URN)10.1016/j.cma.2015.04.009 (DOI)000361475900006 ()2-s2.0-84929590164 (Scopus ID)c254f331-c2a8-4a87-812d-b4194f70df20 (Local ID)c254f331-c2a8-4a87-812d-b4194f70df20 (Archive number)c254f331-c2a8-4a87-812d-b4194f70df20 (OAI)
Note

Validerad; 2015; Nivå 2; 20150508 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-03-29Bibliographically approved
Qin, H. & Lindgren, L.-E. (2015). MRCT Element With A Dislocation Based Plasticity Model (ed.). In: (Ed.), E. Oñate; D.R.J. Owen; D. Peric; M. Chiumenti (Ed.), Computational Plasticity XIII: Fundamentals and Applications - Proceedings of the 13th International Conference on Computational Plasticity - Fundamentals and Applications,held in Barcelona, Spain, 1-3 September 2015. Paper presented at International Conference on Computational Plasticity. Fundamentals and Applications : 01/09/2015 - 03/09/2015 (pp. 366-377). Barcelona: International Center for Numerical Methods in Engineering (CIMNE)
Open this publication in new window or tab >>MRCT Element With A Dislocation Based Plasticity Model
2015 (English)In: Computational Plasticity XIII: Fundamentals and Applications - Proceedings of the 13th International Conference on Computational Plasticity - Fundamentals and Applications,held in Barcelona, Spain, 1-3 September 2015 / [ed] E. Oñate; D.R.J. Owen; D. Peric; M. Chiumenti, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2015, p. 366-377Conference paper, Published paper (Refereed)
Abstract [en]

The multiresolution continuum theory (MRCT) [1] has been established to link the material's macroscopic behaviour with its microstructural inhomogeneities. Additional kinematic variables in addition to the conventional macroscopic displacement field are added to account for microstructural deformations at multiple microscales. Metal plasticity is associated with interaction of motion of dislocations and microstructures. A Dislocation density based material model [2] calibrated and validated for AISI 316L at different temperatures and strain rates is used as the macroscopic constitutive equation of the MRCT element. We investigated particularly how the changing property of the microdomain with changing temperature affects the macroscopic behaviours of the material

Place, publisher, year, edition, pages
Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2015
National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-30911 (URN)000380573600035 ()4e77612b-7d77-4737-943d-06b1cff46de7 (Local ID)978-84-944244-6-5 (ISBN)4e77612b-7d77-4737-943d-06b1cff46de7 (Archive number)4e77612b-7d77-4737-943d-06b1cff46de7 (OAI)
Conference
International Conference on Computational Plasticity. Fundamentals and Applications : 01/09/2015 - 03/09/2015
Note

Validerad; 2016; Nivå 1; 2016-10-06 (andbra)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2019-03-29Bibliographically approved
Qin, H. (2014). Multiresolution Continuum Theory Finite Element For Implicit Time Stepping Methods (ed.). (Licentiate dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>Multiresolution Continuum Theory Finite Element For Implicit Time Stepping Methods
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The multiresolution continuum theory is a higher order continuum theory where additional kinematic variables are added to account for the microstructural inhomogeneities at several distinct length scales. This can be particularly important for localization problems. The strength of this theory is that it can account for details in the microstructure of a material without using an extremely fine mesh. The thesis focuses on implementation and verification of a 3D elastic-plastic multiresolution element based on an implicit time stepping algorithm. It is implemented in the general purpose finite element program FEAP. The mesh independence associated with the length scale parameter is examined and the convergence rate of the element is also evaluated.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2014. p. 94
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-18682 (URN)9ccfac04-54f9-40da-a900-816f0dd954ac (Local ID)978-91-7583-117-6 (ISBN)978-91-7583-118-3 (ISBN)9ccfac04-54f9-40da-a900-816f0dd954ac (Archive number)9ccfac04-54f9-40da-a900-816f0dd954ac (OAI)
Note
Godkänd; 2014; 20141110 (haoqin); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Hao Qin Ämne: Materialmekanik/Material Mechanics Uppsats: Multiresolution Continuum Theory Finite Element For Implicit Time Stepping Methods Examinator: Professor Lars-Erik Lindgren, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: PhD, Senior Lecturer Sebastian Skatulla, University of Cape Town, South Africa Tid: Fredag den 12 december 2014 kl 10,15 Plats: A106, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Qin, H., Lindgren, L.-E., Liu, W. & Tang, S. (2013). Multiscale resolution continuum theory for elastic plastic material with damage, an implicit 3D implementation (ed.). In: (Ed.), Computational Plasticity XII: Fundamentals and Applications - Proceedings of the 12th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2013. Paper presented at International Conference on Computational Plasticity. Fundamentals and Applications : 03/09/2013 - 05/09/2013 (pp. 1448-1457). Barcelona
Open this publication in new window or tab >>Multiscale resolution continuum theory for elastic plastic material with damage, an implicit 3D implementation
2013 (English)In: Computational Plasticity XII: Fundamentals and Applications - Proceedings of the 12th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2013, Barcelona, 2013, p. 1448-1457Conference paper, Published paper (Refereed)
Abstract [en]

The multiscale resolution continuum theory (MRCT) [1] is a higher order continuum theory in which additional kinematic variables are added to account for the size effect at several distinct length scales. This remedies the deficiency of the conventional continuum approach when predicting both strain softening and strain hardening materials and resolves the microstructure details without extremely fine mesh in the localization zone, however additional nodal degrees of freedom are needed and the requirement of element size at the length scale somewhat adds to the computational burden. This paper is an extension of the simplified 1D multiscale implementation presented in Complas XI 2011 [14]. A 3D elastic-plastic multiscale element, with one additional subscale in which the damage is applied, is implemented implicitly in the general purpose finite element analysis program FEAP.

Place, publisher, year, edition, pages
Barcelona: , 2013
National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-39275 (URN)df0eb0ee-732c-4f1d-afa3-8e33e12160cb (Local ID)9788494153150 (ISBN)df0eb0ee-732c-4f1d-afa3-8e33e12160cb (Archive number)df0eb0ee-732c-4f1d-afa3-8e33e12160cb (OAI)
Conference
International Conference on Computational Plasticity. Fundamentals and Applications : 03/09/2013 - 05/09/2013
Note

Godkänd; 2013; 20140115 (andbra)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2019-03-29Bibliographically approved
Lindgren, L.-E., Qin, H., Liu, W. K. & Tang, S. (2011). Simplified multiscale resolution theory for elastic material with damage (ed.). In: (Ed.), Computational plasticity XI : fundamentals and applications: proceedings of the XI International Conference on Computational Plasticity - fundamentals and applications held in Barcelona, Spain, 07 - 09 September 2011. Paper presented at International Conference on Computational Plasticity : 07/09/2011 - 09/09/2011 (pp. 576-586). Barcelona: CINME
Open this publication in new window or tab >>Simplified multiscale resolution theory for elastic material with damage
2011 (English)In: Computational plasticity XI : fundamentals and applications: proceedings of the XI International Conference on Computational Plasticity - fundamentals and applications held in Barcelona, Spain, 07 - 09 September 2011, Barcelona: CINME , 2011, p. 576-586Conference paper, Published paper (Refereed)
Abstract [en]

The multiscale resolution continuum theory (MRCT) is a higher order continuum mechanics. A particle is represented by a point that is deformable. This enables the possibility to include the effect of microstructure features in the continuum model on the deformation behavior through additional nodal variables for the higher order scale. This reduces the need for a very fine mesh in order to resolve microstructure details. It is possible to further reduce the computational effort by keeping the additional degree of freedoms to a minimum by tailoring the theory to specific phenomena. The latter is illustrated in a simplified context for an elastic material with damage.

Place, publisher, year, edition, pages
Barcelona: CINME, 2011
National Category
Other Materials Engineering
Research subject
Material Mechanics; Centre - Centre for High Performance Steel (CHS)
Identifiers
urn:nbn:se:ltu:diva-36951 (URN)acb15268-0853-475e-8c80-78fcb3b7a493 (Local ID)9788489925731 (ISBN)acb15268-0853-475e-8c80-78fcb3b7a493 (Archive number)acb15268-0853-475e-8c80-78fcb3b7a493 (OAI)
Conference
International Conference on Computational Plasticity : 07/09/2011 - 09/09/2011
Note

Godkänd; 2011; 20120404 (andbra)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2019-03-29Bibliographically approved
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