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Larsson, Per-LennartORCID iD iconorcid.org/0000-0001-6232-8819
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Publications (10 of 101) Show all publications
Staf, H., Olsson, E., Lindskog, P. & Larsson, P.-L. (2017). On rate-dependence of hardmetal powder pressing of cutting inserts. Powder Metallurgy, 60(1), 7-14.
Open this publication in new window or tab >>On rate-dependence of hardmetal powder pressing of cutting inserts
2017 (English)In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 60, no 1, 7-14 p.Article in journal (Refereed) Published
Abstract [en]

The rate-dependence of hardmetal powder pressing in cutting insert production is investigated experimentally and numerically. In the latter case, the finite element method is relied upon using a continuum mechanics approach. In particular, possible rate-dependency due to creep deformation and rate-dependent friction is discussed with the experimental investigation focusing mainly on dimensional changes during sintering but also pressing forces. The results indicate that rate-dependent frictional effects are the dominating feature and accordingly, it can be argued that for the metal powders investigated here, creep deformations do not have to be accounted for in the constitutive description at the timescales relevant for powder pressing and when the shape after sintering is concerned. For the present powder, the apparent frictional effect decreases at higher pressing rates. Additional details of the friction behavior are studied comparing finite element simulations with experiments.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2017
Keyword
Rate-dependence, powder compaction, friction, creep, WC-Co powder, cutting inserts, material model, finite element simulations
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-205172 (URN)10.1080/00325899.2016.1260904 (DOI)000396619000003 ()2-s2.0-85007143910 (Scopus ID)
Note

QC 20170411

Available from: 2017-04-11 Created: 2017-04-11 Last updated: 2017-06-29Bibliographically approved
Larsson, P.-L. (2017). On the Influence of Elastic Deformation for Residual Stress Determination by Sharp Indentation Testing. Journal of materials engineering and performance (Print), 26(8), 3854-3860.
Open this publication in new window or tab >>On the Influence of Elastic Deformation for Residual Stress Determination by Sharp Indentation Testing
2017 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 26, no 8, 3854-3860 p.Article in journal (Refereed) Published
Abstract [en]

The determination of residual stresses in engineering materials using sharp indentation testing is studied analytically and numerically. The numerical part of the investigation is based on the finite element method. In particular, the effect from elastic deformations on global indentation properties is discussed in detail. This effect is essential when residual stresses are to be determined based on the change of the contact area due to such stresses. However, standard relations for this purpose are founded on the fact that the material hardness is invariant as regards residual (applied) stresses. Presently, this assumption is scrutinized and it is shown that it is only valid at dominating plastic deformation around the contact region. The hardness dependence of residual stresses can, however, be correlated in the same way as in the case of stress-free materials, indicating that the wealth of characterization formulas pertinent to indentation hardness is available also for the purpose of residual field determination. Only cone indentation of elastic-perfectly plastic materials is considered, but the generality of the results is discussed in some detail.

Place, publisher, year, edition, pages
Springer, 2017
Keyword
elastic deformations, hardness values, residual stresses, sharp indentation
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-214345 (URN)10.1007/s11665-017-2816-2 (DOI)000407994400024 ()2-s2.0-85021998112 (Scopus ID)
Note

QC 20170912

Available from: 2017-09-12 Created: 2017-09-12 Last updated: 2017-11-10Bibliographically approved
Weddfelt, K., Saadati, M. & Larsson, P.-L. (2017). On the load capacity and fracture mechanism of hard rocks at indentation loading. International Journal of Rock Mechanics And Mining Sciences, 100, 170-176.
Open this publication in new window or tab >>On the load capacity and fracture mechanism of hard rocks at indentation loading
2017 (English)In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 100, 170-176 p.Article in journal (Refereed) Published
Abstract [en]

The load capacity of selected hard rocks subjected to circular flat punch indentation is investigated. The compacted zone underneath the indenter is assumed to be limited and only responsible for the load transition to the rest of the material. Therefore, the theory of elasticity is used to define the stress state in a semi-infinite medium loaded by a flat punch indenter. The final load capacity is related to the formation of a sub-surface median crack that initiates due to tensile hoop (circumferential) stresses. Therefore the final failure should occur at a force level in which the hoop stress is greater than the tensile strength of the rock. Since the tensile stress is distributed over a volume of material, tensile crack failure can occur at different locations with tensile hoop stress depending on where the most critical flaw is located. Therefore, the initiation of the median crack that should be responsible for the final load capacity is treated as a probabilistic phenomenon. This process is described by Weibull theory which will be used as a failure criterion. It is assumed here that the opening of median crack triggers a final violent rupture, therefore the assumption in Weibull theory, that the final failure occurs as soon as a macroscopic fracture initiates from a microcrack is fulfilled. The effective volume is calculated for a semiinfinite medium loaded by a flat punch indenter. The material properties of Bohus granite obtained from three point bending tests are used as reference values in describing the Weibull size effect. The experimental results for the stamp load capacity of three selected hard rocks are taken from the literature. They are considered similar rocks to the reference material in this paper, which is Bohus granite. The model describes the observed load capacity with a very good accuracy for all three rocks. It is likely that the presently proposed methodology is applicable for other types of semi-brittle materials and indenter shapes.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-220606 (URN)10.1016/j.ijrmms.2017.10.001 (DOI)000418009400017 ()2-s2.0-85033561320 (Scopus ID)
Note

QC 20180115

Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-01-15Bibliographically approved
Larsson, P.-L. & Olsson, E. (2017). Plastic zone size at sharp indentation contact of classical elastic-plastic materials: Behavior at linear strain hardening. Journal of Testing and Evaluation, 45(5).
Open this publication in new window or tab >>Plastic zone size at sharp indentation contact of classical elastic-plastic materials: Behavior at linear strain hardening
2017 (English)In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 45, no 5Article in journal (Refereed) Published
Abstract [en]

The present analysis concerns a finite-element study of sharp (cone) indentation of classical elastic-plastic materials with linear strain hardening and, especially, the details of the behavior of the size of the plastic zone are at issue. It is shown that the plastic zone size parameters are dependent on two parameters: the well-known Johnson parameter and the level of plastic hardening. This dependence includes both geometrical and material properties. The details of the influence from the hardening level have not been explicitly studied previously. The results are compared with previous findings for elastic-ideally plastic materials.

Place, publisher, year, edition, pages
ASTM International, 2017
Keyword
Correlation, Hardness, Indentation testing, Plastic zone, Correlation methods, Finite element method, Hardening, Plastics, Strain hardening, Thermoelectricity, Elastic ideally plastic materials, Elastic-plastic Material, Finite-element study, Plastic hardening, Plastic zone size, Plastic zones, Sharp indentation, Elastoplasticity
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-216562 (URN)10.1520/JTE20160140 (DOI)2-s2.0-85029157162 (Scopus ID)
Note

QC 20171108

Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2017-11-08Bibliographically approved
Olsson, E. & Larsson, P.-L. (2016). A unified model for the contact behaviour between equal and dissimilar elastic-plastic spherical bodies. International Journal of Solids and Structures, 81, 23-32.
Open this publication in new window or tab >>A unified model for the contact behaviour between equal and dissimilar elastic-plastic spherical bodies
2016 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 81, 23-32 p.Article in journal (Refereed) Published
Abstract [en]

A unified method for calculating the contact force and the contact area between two dissimilar elastic-plastic spheres is presented with the aim of simulating granular materials using particle methods. Explicit equations are presented for the case when the plastic behaviour of the spheres is described with three material parameters. This makes the analysis applicable for a wide range of materials. The model is partly based on dimensionless quantities emerging from the Brinell hardness test. Large deformation of the contact is accounted for in the analysis, which allows for accurate contact relations up to indentation depths relevant for powder compaction. The presented model shows excellent agreement with finite element simulations of two spheres in contact and the results found in literature. An implementation of the contact model in Python is provided together with the online version of this paper.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Contact mechanics, Force-displacement relations, Elastic-plastic material, Large deformations, Discrete element method
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-183306 (URN)10.1016/j.ijsolstr.2015.10.004 (DOI)000370089200003 ()2-s2.0-84956688028 (Scopus ID)
Note

QC 20160309

Available from: 2016-03-09 Created: 2016-03-07 Last updated: 2017-11-30Bibliographically approved
Larsson, P.-L. (2016). Correlation of global quantities for material characterization by sharp indentation testing of elastoplastic materials. Journal of Testing and Evaluation, 44(6), 2293-2301.
Open this publication in new window or tab >>Correlation of global quantities for material characterization by sharp indentation testing of elastoplastic materials
2016 (English)In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 44, no 6, 2293-2301 p.Article in journal (Refereed) Published
Abstract [en]

Indentation problems pertinent to sharp indenters were examined. The analysis concerned classical elastic-plastic materials and, especially so, the details of the behavior of global contact quantities, such as mean contact pressure and the size of the contact area, in the transition region where elastic and plastic effects are of equal magnitude. The global contact quantities were correlated accurately using a single parameter, comprising both geometrical and mechanical properties, and presented using closed form expressions directly applicable to material characterization or measurements of residual mechanical fields by sharp indentation tests, but also for situations such as contact in gears or in electronic devices. The derived relations were based on highly accurate previous results from finite element studies of sharp indentation problems.

Place, publisher, year, edition, pages
ASTM International, 2016
Keyword
Elastoplastic materials, Hardness, Indentation correlation, Level II indentation, Relative contact area, Elastoplasticity, Materials testing, Closed-form expression, Contact areas, Elastic-plastic Material, Finite-element study, Material characterizations, Mean contact pressure, Transition regions, Characterization
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-201994 (URN)10.1520/JTE20150011 (DOI)000402374600023 ()2-s2.0-85002252464 (Scopus ID)
Note

QC 20170303

Available from: 2017-03-03 Created: 2017-03-03 Last updated: 2017-06-15Bibliographically approved
Larsson, P. L. & Olsson, E. (2016). Elastic-plastic contact between hard metal particles. In: Key Engineering Materials: (pp. 86-99). .
Open this publication in new window or tab >>Elastic-plastic contact between hard metal particles
2016 (English)In: Key Engineering Materials, 2016, 86-99 p.Conference paper, Published paper (Refereed)
Abstract [en]

In the present study contact between elastic-plastic dissimilar spherical particles are investigated. The investigation is based on analytical and numerical methods and in the latter case in particular the finite element method. The results presented are pertinent to force-displacement relations at contact when elastic and plastic deformations are of equal magnitude. Especially, hard metal particles are considered with a typical application area being analysis of powder compaction.

Keyword
Contact mechanics, Elastic-plastic deformation, Force-displacement relations, Hard metals, Spherical particles
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-186764 (URN)10.4028/www.scientific.net/KEM.681.86 (DOI)2-s2.0-84959543060 (Scopus ID)
Note

QC 20160530

Available from: 2016-05-30 Created: 2016-05-13 Last updated: 2016-05-30Bibliographically approved
Larsson, P.-L. (2016). Plastic Zone Size at Sharp Indentation of Classical Elastic-Plastic Materials: Behavior at Ideally Plastic Hardening. Journal of engineering materials and technology, 138(1).
Open this publication in new window or tab >>Plastic Zone Size at Sharp Indentation of Classical Elastic-Plastic Materials: Behavior at Ideally Plastic Hardening
2016 (English)In: Journal of engineering materials and technology, ISSN 0094-4289, E-ISSN 1528-8889, Vol. 138, no 1Article in journal (Refereed) Published
Abstract [en]

Sharp indentation problems are examined based on finite element methods (FEMs) and self-similarity considerations. The analysis concerns classical elastic-plastic materials with low, or no, strain-hardening and especially the details of the behavior of the size of the plastic zone are at issue. The results are correlated using a single parameter, comprising both geometrical and mechanical properties, and compared with previously presented semi-analytical findings. The numerical analysis is restricted to cone indentation of elastic-ideally plastic materials.

Place, publisher, year, edition, pages
ASME Press, 2016
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-181448 (URN)10.1115/1.4031736 (DOI)000389761500009 ()2-s2.0-84943789324 (Scopus ID)
Note

QC 20160203

Available from: 2016-02-03 Created: 2016-02-02 Last updated: 2017-11-30Bibliographically approved
Saadati, M., Forquin, P., Weddfelt, K., Larsson, P.-L. & Hild, F. (2015). A numerical study of the influence from pre-existing cracks on granite rock fragmentation at percussive drilling. International journal for numerical and analytical methods in geomechanics (Print), 39(5), 558-570.
Open this publication in new window or tab >>A numerical study of the influence from pre-existing cracks on granite rock fragmentation at percussive drilling
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2015 (English)In: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 39, no 5, 558-570 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study is to investigate the effect of pre-existing, or structural, cracks on dynamic fragmentation of granite. Because of the complex behavior of rock materials, a continuum approach is employed relying upon a plasticity model with yield surface locus as a quadratic function of the mean pressure in the principal stress space coupled with an anisotropic damage model. In particular, Bohus granite rock is investigated, and the material parameters are chosen based on previous experiments. The equation of motion is discretized using a finite element approach, and the explicit time integration method is employed. The pre-existing cracks are introduced in the model by considering sets of elements with negligible tensile strength that leads to their immediate failure when loaded in tension even though they still carry compressive loads as crack closure occurs because of compressive stresses. Previously performed edge-on impact tests are reconsidered here to validate the numerical model. Percussive drilling is simulated, and the influence of the presence of pre-existing cracks is studied. The results from the analysis with different crack lengths and orientations are compared in terms of penetration stiffness and fracture pattern. It is shown that pre-existing cracks in all investigated cases facilitate the drilling process.

Keyword
granite, percussive drilling, KST-DFH model, pre-existing cracks, fragmentation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-159908 (URN)10.1002/nag.2331 (DOI)000351068800006 ()2-s2.0-84924022663 (Scopus ID)
Note

QC 20150414

Available from: 2015-02-11 Created: 2015-02-11 Last updated: 2017-12-04Bibliographically approved
Larsson, P.-L. & Olsson, E. (2015). A numerical study of the mechanical behavior at contact between particles of dissimilar elastic-ideally plastic materials. Journal of Physics and Chemistry of Solids, 77, 92-100.
Open this publication in new window or tab >>A numerical study of the mechanical behavior at contact between particles of dissimilar elastic-ideally plastic materials
2015 (English)In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 77, 92-100 p.Article in journal (Refereed) Published
Abstract [en]

In the present study contact between elastic-ideally plastic dissimilar spheres are investigated in detail. The investigation is based on numerical methods and in particular the finite element method. The numerical results presented are discussed with respect to correlation of global contact properties as well as the behavior of local field variables such as contact pressure distribution and the evolution of the effective plastic strain. Large deformation effects are accounted for and discussed in detail. The constitutive behavior is described by classical Mises plasticity. It is shown that correlation of the dissimilar contact problem can be accurately achieved based on the Johnson contact parameter with the representative stress chosen as the yield stress of the softer material.

Keyword
Alloys, Metals, Mechanical properties
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-159349 (URN)10.1016/j.jpcs.2014.08.016 (DOI)000346952600012 ()2-s2.0-84908429060 (Scopus ID)
Note

QC 20150202

Available from: 2015-02-02 Created: 2015-01-29 Last updated: 2017-12-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6232-8819

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