Blar i NTNU Open på forfatter "Hopperstad, Odd Sture"
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A combined isotropic, kinematic and distortional hardening model for aluminum and steels under complex strain-path changes
Qin, Jisheng; Holmedal, Bjørn; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2018)In this work, a new model is proposed for predicting stress transients caused by strain path changes. The model is formulated in stress space, where a second order tensor, i.e., the microstructure stress deviator, is used ... -
A Combined Precipitation, Yield Stress, and Work Hardening Model for Al-Mg-Si Alloys Incorporating the Effects of Strain Rate and Temperature
Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore (Journal article; Peer reviewed, 2018)In this study, a combined precipitation, yield strength, and work hardening model for Al-Mg-Si alloys known as NaMo has been further developed to include the effects of strain rate and temperature on the resulting stress–strain ... -
A Lode-dependent Gurson model motivated by unit cell analyses
Dæhli, Lars Edvard; Morin, David; Børvik, Tore; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2017)In this study, the effects of including a dependency on the third deviatoric stress invariant in the void evolution equation of the Gurson model are examined using unit cell calculations and imperfection band analyses. ... -
A microstructure-based yield stress and work-hardening model for textured 6xxx aluminium alloys
Khadyko, Mikhail; Myhr, Ole Runar; Dumoulin, Stephane; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2016)The plastic properties of an aluminium alloy are defined by its microstructure. The most important factors are the presence of alloying elements in the form of solid solution and precipitates of various sizes, and the ... -
A Multi-Scale Approach for Modelling of Fracture in Aluminium Alloys under Impact Loading
Valle, Heidi; Frodal, Bjørn Håkon (Master thesis, 2015)The main objective of this thesis was to investigate the ballistic properties of an isotropic AlMgSi aluminium alloy both experimentally and numerically. Uncoupled and coupled fracture models were calibrated using ... -
A nano-scale material model applied in finite element analysis of aluminium plates under impact loading
Johnsen, Joakim; Holmen, Jens Kristian; Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore (Journal article, 2013)Finite element simulations of AA6070 aluminium plates struck by ogival-nose projectiles are performed. The aluminium plates are 20 mm thick and heat treated to temper O, T4, T6 and T7. A nano-scale material model, consisting ... -
A numerical study on the deformation and fracture modes of steel projectiles during Taylor bar impact tests
Rakvåg, Kristian Gaarder; Børvik, Tore; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2014)A heterogeneous material model based on macro-mechanical observations is proposed for simulation of fracture in steel projectiles during impact. A previous experimental study on the deformation and fracture of steel ... -
A physically-based constitutive model applied to AA6082 aluminium alloy at large strains, high strain rates and elevated temperatures
Vilamosa, Vincent; Clausen, Arild Holm; Børvik, Tore; Holmedal, Bjørn; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2016)This paper presents a physically-based constitutive model applied to an AA6082 aluminium alloy subjected to large strains, high strain rates and elevated temperatures. The model accounts for thermo-elasticity, thermo-vis ... -
A study of the influence of precipitate free zones on the strain localization and failure of the aluminium alloy AA7075-T651
Fourmeau, Marion; Marioara, Calin Daniel; Børvik, Tore; Benallal, Ahmed; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2015)Age-hardened aluminium alloys have various degrees of precipitate-free zones (PFZs) along grain boundaries (GBs). The PFZs are weak zones and their existence promotes combined transgranular and intergranular fracture, thus ... -
A thermo-elasto-viscoplastic constitutive model for polymers
Johnsen, Joakim; Clausen, Arild Holm; Grytten, Frode; Benallal, Ahmed; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2018)In this study, a thermo-elasto-viscoplastic model is developed for a low density cross-linked polyethylene (XLPE) in an attempt to describe the combined effects of temperature and strain rate on the stress-strain response ... -
A through-thickness damage regularisation scheme for shell elements subjected to severe bending and membrane deformations
Costas Pino, Miguel; Morin, David; Hopperstad, Odd Sture; Børvik, Tore; Langseth, Magnus (Journal article; Peer reviewed, 2018)This research work proposes and validates a damage regularisation model for shell elements used in large-scale simulations. The model evaluates the ratio of bending to membrane loading in the elements based on the ... -
Aluminium plates with geometrical defects subjected to low-velocity impact: Experiments and simulations
Espeseth, Vetle; Børvik, Tore; Hopperstad, Odd Sture (Peer reviewed; Journal article, 2022)In this paper, an experimental and numerical program investigating impact in the low-velocity regime ( m/s) on 1.5 mm thick AA6016 aluminium plates in three different heat treatments (T4/T6/T7) is presented. The tests were ... -
Aluminium plates with pre-formed slits subjected to blast loading
Granum, Henrik; Aune, Vegard; Børvik, Tore; Hopperstad, Odd Sture (Chapter, 2018)The dynamic response of thin, perforated aluminium plates subjected to blast loading was studied both experimentally and numerically. Two different blast intensities were used and the plates were pre-cut with four horizontal ... -
Aluminum foam-filled extrusions subjected to oblique loading: experimental and numerical study
Reyes, Aase Gavina Roberg; Hopperstad, Odd Sture; Langseth, Magnus (Journal article; Peer reviewed, 2004)The behavior of empty and foam-filled square thin-walled aluminum columns in alloy AA6060 subjected to quasi-static oblique loading was examined. Previous studies have shown that by introducing a load angle, the energy ... -
An Experimental and Numerical Study of Thermoplastics at Large Deformations
Andersen, Marius (Doctoral thesis at NTNU;2016:191, Doctoral thesis, 2016)This thesis has examined the mechanical behavior of HDPE and PVC at large strains and at low to intermediate strain rates. This examination has been done by analyzing experimental results from uniaxial tension and ... -
An experimental study on the deformation and fracture modes of steel projectiles during impact
Rakvåg, Knut Gaarder; Børvik, Tore; Westermann, Ida; Hopperstad, Odd Sture (Journal article, 2013)Previous investigations of the penetration and perforation of high-strength steel plates struck by hardened steel projectiles have shown that under certain test conditions the projectile may fracture or even fragment upon ... -
An experimental-numerical method to determine the work-hardening of anisotropic ductile materials at large strains
Khadyko, Mikhail; Dumoulin, Stephane; Børvik, Tore; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2014)The determination of work-hardening for ductile materials at large strains is difficult to perform in the framework of usual tensile tests because of the geometrical instability and necking in the specimen at relatively ... -
An explicit integration scheme for hypo-elastic viscoplastic crystal plasticity
Zhang, Kai; Holmedal, Bjørn; Dumoulin, Stephane; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2014)An explicit integration scheme for rate-dependent crystal plasticity (CP) has been developed in this work. Additive decomposition of the velocity gradient tensor into lattice and plastic parts is adopted for describing the ... -
Anisotropic failure modes of high-strength aluminium alloy under various stress states
Fourmeau, Marion; Børvik, Tore; Benallal, A; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2013)The influence of stress state and plastic anisotropy on the fracture behaviour of a rolled AA7075-T651 aluminium plate under quasi-static loading conditions is studied both experimentally and numerically. Material tests ... -
Anisotropic Plasticity and Fracture of Three 6000-Series Aluminum Alloys
Thomesen, Susanne; Hopperstad, Odd Sture; Børvik, Tore (Peer reviewed; Journal article, 2021)The influence of microstructure on plasticity and fracture of three 6000-series aluminum alloys is studied with emphasis on the anisotropy caused by the extrusion process. Tension tests on smooth and notched specimens are ...