Restspänningar i riktad plåt
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
In this project residual stresses after roll levelling have been investigated. Three parameterswere varied to find out their impact on the stresses. The parameters were intermesh ofthe rollers, initial stresses due to uncoiling and kinematic hardening. Elastic strain energydensity was used as reference parameter.To calculate the stresses finite element method (FEM) simulations were made. The geometricmodel is mostly similar to SSABs’s pre-roll straightening machine FS4 in Borlänge,Sweden. It got three lower rollers and two upper with an extra end roller to ensure a horizontalfinish. In the simulations, the plate consists of shell elements and the rollers are rigidbodies. The material constants were the same as for SSABs’s high strength steel Strenx960.In simulations including kinematic hardening material model was approximated to linearhardening. The other simulations had a stress-strain curve from a tension test. The stressesdue to uncoiling, which were used as initial condition in the simulations, were calculatedby the analytical model Residual stresses in steel sheets due to coiling and uncoiling: aclosed-form analytical solution by W.M. Quach, J.G. Teng and K.F. Chung.Over all eight simulations were made. Two with kinematic hardening and intermesh of3 mm and 7 mm. Two with only intermesh of 3 mm and 7 mm but without kinematic hardeningor initial stresses. Four simulations had initial stress from uncoiling with a radiusof curvature set to 0.3 m or 0.75 m. For each curvature there were simulations with 3 mmand 7 mm intermesh.Based on the simulation results and the three investigated parameters as input arguments,a function for the elastic strain energy density could be created by a regression analysis.The result shows that it is primarily the initial stresses that causes high strain energy butthe intermesh is also of importance. The kinematic hardening on its own has no meaningbut combined with big deformations, i.e. big roll intermesh, it can have some effects. Howeverthe material model for kinematic hardening did not give a trustful result. To improvethe analysis the material model needs some progress and more simulations must be doneto increase the amount of data.
Place, publisher, year, edition, pages
2016. , 53 p.
Teknik, Restspänningar, inre spänningar, riktning, avhaspling, coiling
IdentifiersURN: urn:nbn:se:ltu:diva-49891Local ID: 73478955-3543-419e-a8e4-1c84fde5b2a8OAI: oai:DiVA.org:ltu-49891DiVA: diva2:1023239
Subject / course
Student thesis, at least 30 credits
Mechanical Engineering, master's level
Validerat; 20160615 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved