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Larsson, Per-LennartORCID iD iconorcid.org/0000-0001-6232-8819
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Publications (10 of 112) Show all publications
Larsson, P.-L. (2019). Determination of residual stresses utilizing the the variation of hardness at elastic-plastic indentation. Journal of Testing and Evaluation, 47(4), 3174-3184
Open this publication in new window or tab >>Determination of residual stresses utilizing the the variation of hardness at elastic-plastic indentation
2019 (English)In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, ISSN 0090-3973, Vol. 47, no 4, p. 3174-3184Article in journal (Refereed) Published
Abstract [en]

Material hardness is independent of residual stresses at predominantly plastic deformation in the region of contact between an indenter and the material. This is an important fact, as such a situation is relevant for most metals and alloys. It has, however, been established that when elastic and plastic deformations are of equal magnitude, this independence is lost. This fact complicates residual stress determination in such a situation, pertinent to materials such as ceramics and polymers, but it also provides additional important information for performing such a task in an accurate manner. Presently, a relevant formula for taking advantage of this information is presented. The formula is based on previous results pertinent to indentation analyses of stress-free materials. The predictions are compared to finite element results from previous studies describing cone indentation of materials with residual stresses. The analysis is restricted to classical elastoplasticity.

Place, publisher, year, edition, pages
West Conshohocken, Pennsylvania USA: , 2019
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-258410 (URN)10.1520/JTE20170525 (DOI)000483199800050 ()2-s2.0-85065673202 (Scopus ID)
Note

QC 20190926

Available from: 2019-09-10 Created: 2019-09-10 Last updated: 2019-09-26Bibliographically approved
Fadil, H., Jelagin, D., Larsson, P.-L. & Partl, M. (2019). Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests. International Journal on Road Materials and Pavement Design
Open this publication in new window or tab >>Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests
2019 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed) Published
Abstract [en]

Reliable determination of material properties is a key component for modelling and performance prediction of asphalt pavements. This paper deals with the potential use of instrumented indentation tests for viscoelastic characterisation of asphalt mortar as a new alternative to existing techniques. The main focus lies on the potential of indentation tests for multi-scale measurement of the shear relaxation modulus. A three-dimensional finite element model of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model indentation tests performed at different material scales. The asphalt mortar is modelled as an idealised fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen mastic matrix. Based on the obtained numerical results the scale-dependency of the shear relaxation modulus measured with the indentation test is investigated. It is shown that the measurement scale is effectively controlled by the size of the indenter-specimen contact area, while the effect of indentation depth is minimal. The minimum contact area size required for obtaining representative properties, measured at the mortar scale, is determined. The viscoelastic parameters obtained from the indentation model are compared to those obtained using a representative volume element (RVE) for the asphalt mortar. In this way, the paper provides a new impulse for linking the mortar and asphalt scales in the multiscale modelling of asphalt mixtures. Feasibility of the proposed testing technique is further evaluated experimentally. Viscoelastic indentation tests are performed on asphalt mastics and mortar at two different sizes of contact areas. Experimental results indicate that indentation tests allow reliable characterisation of mortars relaxation modulus on both macro-scale as well as on individual component level.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2019
Keywords
indentation testing, asphalt mortar, bitumen-filler mastics, multiscale, viscoelasticity, FEM
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-255414 (URN)10.1080/14680629.2019.1628434 (DOI)000473928500001 ()
Note

QC 20190815

Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-15Bibliographically approved
Larsson, P.-L. (2019). On Plowing Frictional Behavior during Scratch Testing: A Comparison between Experimental and Theoretical/Numerical Results. Crystals, 9(1), Article ID 33.
Open this publication in new window or tab >>On Plowing Frictional Behavior during Scratch Testing: A Comparison between Experimental and Theoretical/Numerical Results
2019 (English)In: Crystals, ISSN 2073-4352, Vol. 9, no 1, article id 33Article in journal (Refereed) Published
Abstract [en]

Scratch testing is a contact mechanics based nondestructive testing method that, if correctly evaluated, can give a lot of information about the material and tribological behavior of a material. In contrast to the situation with another contact-based method, indentation testing, wear characteristics can also be investigated, for example. In order to get results of practical importance from a scratch test, it is necessary to have evaluation formulae available. Indeed, such formulae exist for scratch testing but can be substantially influenced by frictional effects. For this reason, closed-form analytical relations have been suggested for the purpose of accounting for such effects during scratching and in particular the plowing frictional effect. As a major benefit, these relations can also be of assistance during material characterization through scratch testing. However, the proposed existing relations are based solely on theoretical/numerical analyses and, remembering that the scratch test of course is an experimental approach, verification by experiments is a necessity. Such a task is performed in the present study and it is shown that, based on standard contact global properties, the relations are accurate for most polymeric materials but could also be used for some metallic ones.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
scratch testing, frictional behavior, plowing friction, mechanical analysis, polymeric materials
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-245955 (URN)10.3390/cryst9010033 (DOI)000458578100033 ()
Funder
Swedish Research Council, 621-2005-5803
Note

QC 20190313

Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-03-13Bibliographically approved
Shariati, H., Saadati, M., Bouterf, A., Weddfelt, K., Larsson, P.-L. & Hild, F. (2019). On the Inelastic Mechanical Behavior of Granite: Study Based on Quasi-oedometric and Indentation Tests. Rock Mechanics and Rock Engineering, 52(3), 645-657
Open this publication in new window or tab >>On the Inelastic Mechanical Behavior of Granite: Study Based on Quasi-oedometric and Indentation Tests
Show others...
2019 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, no 3, p. 645-657Article in journal (Refereed) Published
Abstract [en]

The inelastic behavior of Bohus granite is investigated based on experimental and numerical results. The yield surface and related dilation angle are determined based on quasi-oedometric tests performed in an earlier work. It is shown how to obtain the yield surface and dilation angle from this test for hydrostatic pressure levels up to 750MPa. In the constitutive modeling, a Drucker-Prager law is employed together with a variable dilation angle. The constitutive model is first applied to simulate the quasi-oedometric test and the stress and strain fields are obtained. Furthermore, the validation of the model is investigated by simulation of the spherical indentation test. The results are compared with corresponding experimental data and a good agreement is found.

Place, publisher, year, edition, pages
SPRINGER WIEN, 2019
Keywords
Quasi-static indentation, Granite, Inelastic behavior, Tomography
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-248087 (URN)10.1007/s00603-018-1646-3 (DOI)000460704000001 ()2-s2.0-85056638291 (Scopus ID)
Note

QC 20190429

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-04-29Bibliographically approved
Larsson, P.-L. (2019). Principal Stress Ratio Effect at Residual Stress Determination Utilizing the Variation of Indentation Hardness. Lubricants, 7(6), Article ID 50.
Open this publication in new window or tab >>Principal Stress Ratio Effect at Residual Stress Determination Utilizing the Variation of Indentation Hardness
2019 (English)In: Lubricants, ISSN 2075-4442, Vol. 7, no 6, article id 50Article in journal (Refereed) Published
Abstract [en]

The determination of residual stresses is an important issue when it comes to material failure analysis. The variation of global indentation properties, due to the presence of residual stresses, can serve as a guideline for the size and direction of such stresses. One of these global indentation properties, the material hardness, is unfortunately invariant of residual stresses when metals and alloys are at issue. In this situation, one has to rely on the size of the indentation contact area for residual stress determination. For other materials such as ceramics and polymers, where elastic deformations are of greater importance at indentation, such invariance is no longer present. Here, this variation is investigated based on finite element simulations. The aim is then to determine how the indentation hardness is influenced by the principal residual stress ratio and also discuss if such an influence is sufficient in order to determine the size and direction of such stresses in an experimental situation. It should be emphasized that this work does not suggest a new approach to residual stress determination (by indentation testing) but investigates the applicability of previously derived methods to a situation where the surface stress field is not simplified as equi-biaxial or uniaxial. For simplicity, but not out of necessity, only cone indentation of elastic-perfectly plastic materials is considered.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
residual stress determination, hardness, correlation of indentation properties, principal stress influence, relative contact area
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-255575 (URN)10.3390/lubricants7060050 (DOI)000475511800007 ()2-s2.0-85068233582 (Scopus ID)
Note

QC 20190801

Available from: 2019-08-01 Created: 2019-08-01 Last updated: 2019-08-01Bibliographically approved
Larsson, P.-L. (2019). Representative Stress Correlation of Global Scratch Quantities at Scratch Testing: Experimental Verification. Crystals, 9(3), Article ID 154.
Open this publication in new window or tab >>Representative Stress Correlation of Global Scratch Quantities at Scratch Testing: Experimental Verification
2019 (English)In: Crystals, ISSN 2073-4352, Vol. 9, no 3, article id 154Article in journal (Refereed) Published
Abstract [en]

Evaluation and correlation of global quantities, i.e., normal and tangential hardness, at scratch testing in the context of a representative stress description was investigated. In particular, verification based on experimental results is at issue. It has been shown previously that within the framework of classical von Mises elasto-plasticity and quasi-static conditions, correlation can be achieved by using a combination of stresses at different levels of plastic strains to define representative quantities at scratching, accounting for the difference in mechanical behavior at elasto-plastic and rigid plastic scratching. However, verification from experimental results is required, which has been attempted in this study. Predictions based on previous theoretical results were compared with experimental findings for polymeric materials, as well as for different metals. Good agreement was found between the two sets of results, particularly so for the case of polymers modelled by von Mises elasto-plasticity. Accordingly, these results are of direct practical, accurate, and novel relevance for semi-crystalline polymers where viscoelastic effects are negligible.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
scratch testing, contact behavior of global properties, normal hardness, tangential hardness, polymeric materials, metals
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-251354 (URN)10.3390/cryst9030154 (DOI)000464477500003 ()2-s2.0-85064600960 (Scopus ID)
Note

QC 20190516

Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-05-23Bibliographically approved
Staf, H., Olsson, E., Lindskog, P. & Larsson, P.-L. (2018). Determination of the Frictional Behavior at Compaction of Powder Materials Consisting of Spray-Dried Granules. Journal of materials engineering and performance (Print), 27(3), 1308-1317
Open this publication in new window or tab >>Determination of the Frictional Behavior at Compaction of Powder Materials Consisting of Spray-Dried Granules
2018 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 27, no 3, p. 1308-1317Article in journal (Refereed) Published
Abstract [en]

The frictional behavior during powder compaction and ejection is studied using an instrumented die with eight radial sensors. The average friction over the total powder pillar is used to determine a local friction coefficient at each sensor. By comparing forces at compaction with forces at ejection, it can be shown that the Coulomb's friction coefficient can be described as a function of normal pressure. Also stick phenomena has been investigated in order to assess its influence on the determination of the local friction coefficient.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Coulomb friction, cutting inserts, die friction, FEM, finite element simulations, granular powder, powder compaction, reverse engineering, stick, wall friction, WC-Co powder
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-224684 (URN)10.1007/s11665-018-3205-1 (DOI)000426701000041 ()2-s2.0-85042867461 (Scopus ID)
Note

QC 20180326

Available from: 2018-03-26 Created: 2018-03-26 Last updated: 2018-03-26Bibliographically approved
Fadil, H., Jelagin, D. & Larsson, P.-L. (2018). On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests. Experimental mechanics, 58(2), 301-314
Open this publication in new window or tab >>On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests
2018 (English)In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 58, no 2, p. 301-314Article in journal (Refereed) Published
Abstract [en]

In the present paper, a methodology for complete characterization of linear isotropic viscoelastic material with spherical instrumented indentation test is proposed. The developed method allows for measuring two independent viscoelastic functions, shear relaxation modulus and time-dependent Poisson's ratio, from the indentation test data obtained at non-decreasing loading, but otherwise arbitrary. Finite element modelling (FEM) is relied upon for validating the proposed methodology and for quantifying the influence of experimental variables on the measurements accuracy. Spherical indentation experiments are performed on several viscoelastic materials: polyoxymethylene, bitumen and bitumen-filler mastics. The viscoelastic material functions obtained with the indentation tests are compared with the corresponding results from the standard mechanical tests. Numerical and experimental results presented indicate that the methodology proposed allows mitigating the machine compliance and loading rate effects on the accuracy of the viscoelastic indentation tests.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Indentation, Viscoelasticity, Mechanics of materials, FEM, Bitumen, Bitumen-filler mastics
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-222406 (URN)10.1007/s11340-017-0342-7 (DOI)000423584800008 ()2-s2.0-85030833837 (Scopus ID)
Note

QC 20180228

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-05-24Bibliographically approved
Saadati, M., Forquin, P., Weddfelt, K., Larsson, P.-L. & Hild, F. (2018). On the Mechanical Behavior of Granite Material With Particular Emphasis on the Influence From Pre-Existing Cracks and Defects. Journal of Testing and Evaluation, 46(1), 33-45
Open this publication in new window or tab >>On the Mechanical Behavior of Granite Material With Particular Emphasis on the Influence From Pre-Existing Cracks and Defects
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2018 (English)In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 46, no 1, p. 33-45Article in journal (Refereed) Published
Abstract [en]

In this investigation, experiments were carried out in order to determine the mechanical properties of Bohus granite considering the influence from pre-existing cracks and defects. The experimental investigation aimed at a complete material characterization, for the purpose of mechanical analyses using advanced constitutive models, based on a variety of tests. In doing so, direct tensile and compression tests were performed to evaluate the stiffness and strength; quasi-oedometric tests were carried out in order to obtain the deviatoric and volumetric behavior of the material at different levels of hydrostatic pressure (up to 860 MPa); three-point bend tests were performed to evaluate the quasi-static strength of the rock and its distribution. Weibull statistics was then employed to describe the strength distribution. The intact specimens indicated a rather low scatter in the mechanical properties such as Young's modulus and tensile strength. However, specimens with large initial defects behaved differently. The failure mechanism in these specimens was not as brittle as the intact ones. The crack was opened on the tensile surface of such specimens during the three-point bend test at an early stage during loading, as demonstrated by digital image correlation results.

Place, publisher, year, edition, pages
AMER SOC TESTING MATERIALS, 2018
Keywords
granite, constitutive characterization, pre-existing cracks, quasi-oedometric, three-point bending, digital image correlation (DIC)
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-225332 (URN)10.1520/JTE20160072 (DOI)000425663000005 ()2-s2.0-85033563714 (Scopus ID)
Note

QC 20180403

Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2019-06-20Bibliographically approved
Staf, H., Nyrot, E. F. & Larsson, P.-L. (2018). On the usage of a neutron source to determine the density distribution in compacted cemented carbide powder compounds. Powder Metallurgy, 61(5), 389-394
Open this publication in new window or tab >>On the usage of a neutron source to determine the density distribution in compacted cemented carbide powder compounds
2018 (English)In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 61, no 5, p. 389-394Article in journal (Refereed) Published
Abstract [en]

Density variations in pressed powder materials are of substantial importance and will affect shrinkage and geometry after sintering. It is therefore important to accurately measure this quantity in green bodies. This is emphasised by the fact that the density variation can be used for determining material properties in constitutive mechanical models of compaction. An obvious method to determine the density variation is X-ray tomography. For cemented carbides this is not a possible alternative due to the very high X-ray absorption of tungsten making the samples impossible to penetrate. Neutron radiation has a much higher penetration and this suggests that a neutron source could be used for density distribution determination in such materials. This was investigated currently showing promising results when compared with finite element predictions. It is clear that this approach must be improved to be able to use neutron radiation as a tool for density determination. Improvements are suggested.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
Keywords
Powder compaction, sintering, density distribution, neutron radiation, finite element method
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-239099 (URN)10.1080/00325899.2018.1505807 (DOI)000448465700005 ()2-s2.0-85052092698 (Scopus ID)
Note

QC 20181121

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2018-11-21Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6232-8819

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