Patent application EP16382250A (EP), filed 2016-06-02
Publication number: EP3252627A1
Title: SPOT WELD FRACTURE CALCULATION METHOD AND DEVICE FOR HIGH-STRENGTH STEELS
Abstract: [0001]    Spot weld fracture calculation method for high-strength steels, which comprises the steps of entering in a processing unit the at least certain mechanical properties of sheets (1, 2) of steel; modelling said sheets (1, 2) of steel and the at least one spot weld (3) by means of finite elements (61); applying boundary conditions of the at least one load (4) and at least one movement restriction; assigning a mechanical behaviour of the model of finite elements (61); a first calculation step for determining strains, stresses and displacements of the nodes; a second calculation step for determining the J-integral in at least one critical zone; storing J-integral values and judging a possibility of fracture of the at least one spot weld (3), thereby characterizing the maximum force that the welded joins are able to withstand.
IPC codes: B23K  11/    11            A I
G01N   3/    00            A I
G06F  17/    50            A I
Claims: number: 1
text: Spot weld fracture calculation method for high-strength steels,
wherein a first sheet (1) of steel with certain first mechanical properties is joined to at least one second sheet (2) of steel with certain second mechanical properties by means of at least one spot weld (3), wherein the at least one spot weld (3) is subject to at least one load (4),characterized in that it comprises the steps of:
number: 2
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that the first sheet (1) of steel is joined to a second sheet (2) of steel by means of at least one spot weld (3).
number: 3
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that the step of assigning a mechanical behaviour of the model of finite elements (61) comprises a previous step of segmenting the at least one spot weld (3) into at least a first base material (11) of the first sheet (1) of steel, a second base material (21) of the second sheet (2) of steel, a first thermally affected zone (12) of the first sheet (1), a second thermally affected zone (22) of the second sheet (2) and a fusion zone (34).
number: 4
text: Spot weld fracture calculation method for high-strength steels according to Claim 3,characterized in that the step of assigning a mechanical behaviour of the model of finite elements (61) comprises assigning to the first base material (11) of the first sheet (1) the map of material (15) corresponding to the first sheet (11), and to the second base material (21) of the second sheet (2) the map of material (15) corresponding to the second sheet (2).
number: 5
text: Spot weld fracture calculation method for high-strength steels according to Claim 3,characterized in that the step of assigning a mechanical behaviour of the model of finite elements (61) comprises assigning to the first thermally affected zone (12) of the first sheet (1) and to the second thermally affected zone (22) of the second sheet (2) a mechanical behaviour on the basis of a material and of a distance to the centre of the spot weld (3).
number: 6
text: Spot weld fracture calculation method for high-strength steels according to Claim 3,characterized in that the step of assigning a mechanical behaviour of the model of finite elements (61) comprises assigning to the fusion zone (34) a strain-stress curve of the material.
number: 7
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that the step of determining the J-integral in at least one critical zone of the model of finite elements (61) comprises determining a sector of the notch tip (32) of the spot weld (3) included in a critical section on the basis of the at least one applied load (4).
number: 8
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that the step of modelling by means of finite elements (61) comprises establishing a mesh (6) of solid elements.
number: 9
text: Spot weld fracture calculation method for high-strength steels according to Claim 3,characterized in that the step of modelling by means of finite elements (61) comprises establishing a size of at least 0.1 mm in the finite elements (61) of the first thermally affected zone (12) of the first sheet (1), of the second thermally affected zone (22) of the second sheet (2) and of the fusion zone (34).
number: 10
text: Spot weld fracture calculation method for high-strength steels according to Claim 3,characterized in that the step of modelling by means of finite elements (61) comprises establishing a size of at least 1.5 mm in the finite elements (61) of the first base material (11) of the first sheet (1) of steel and of the second base material (21) of the second sheet (2) of steel.
number: 11
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that the step of applying boundary conditions comprises establishing a restriction of movement on the second sheet (2) of steel.
number: 12
text: Spot weld fracture calculation method for high-strength steels according to Claim 1,characterized in that it comprises a step of data output that comprises providing a maximum load force (7) and a displacement evolution (8) during the application of the at least one load (4) of the first sheet (1) of steel joined to the at least one second sheet (2) of steel by means of the at least one spot weld (3).
number: 13
text: Electronic device configured in order to implement the spot weld fracture calculation method for high-strength steels according to Claims 1 to 12.
Office action: search_report, dated 2017-12-06
Rejection reasons: inventive_step_epc_56
Prior art cited: ref_id: EP1742033A1
ref_type: patent
severity: background
ref_id: EP1777509A2
ref_type: patent
severity: background
ref_id: - WORLDAUTOSTEEL: "Automotive Steel Definitions", 20 January 2016 (2016-01-20), XP055314169, Retrieved from the Internet <URL:https://web.archive.org/web/20160120103629/http://www.worldautosteel.org/steel-basics/automotive-steel-definitions> [retrieved on 20161026]
ref_type: npl
severity: background
ref_id: EP1742033A1
ref_type: patent
severity: background
ref_id: EP1777509A2
ref_type: patent
severity: background
ref_id: - S BURGET ET AL: "Characterization and modeling of fracture behavior of spot welded joints in hot-stamped ultra-high strength steels", 11TH LS-DYNA FORUM 2012, 2012, pages 1 - 10, XP055314321, Retrieved from the Internet <URL:https://www.dynamore.de/de/download/papers/ls-dyna-forum-2012/documents/crash-4-3> [retrieved on 20161026]
ref_type: npl
severity: background
ref_id: - DANCETTE S ET AL: "A finite element model for the prediction of Advanced High Strength Steel spot welds fracture", ENGINEERING FRACTURE MECHANICS, PERGAMON PRESS, NEW YORK, NY, GB, vol. 87, 10 March 2012 (2012-03-10), pages 48 - 61, XP028485695, ISSN: 0013-7944, [retrieved on 20120321], DOI: 10.1016/J.ENGFRACMECH.2012.03.004
ref_type: npl
severity: background
ref_id: - UC BOULDER: "FEM Modeling: Mesh, Loads and BCs", 9 September 2015 (2015-09-09), pages 1 - 19, XP055314724, Retrieved from the Internet <URL:http://www.colorado.edu/engineering/CAS/courses.d/IFEM.d/IFEM.Ch07.d/IFEM.Ch07.pdf> [retrieved on 20161027]
ref_type: npl
severity: background
ref_id: EP1742033
ref_type: patent
severity: background
ref_id: EP1777509
ref_type: patent
severity: background
ref_id: - S Burget ET AL, "Characterization and modeling of fracture behavior of spot welded joints in hot-stamped ultra-high strength steels", 11th LS-DYNA Forum 2012, (2012), pages 1 - 10, URL: https://www.dynamore.de/de/download/papers/ls-dyna-forum-2012/documents/crash-4-3, (20161026), XP055314321 [Y] 1-13 * abstract * * figures 1, 2, 5-15 * * sections 2, 5 and 6 *
ref_type: npl
severity: obviousness
ref_id: - DANCETTE S ET AL, "A finite element model for the prediction of Advanced High Strength Steel spot welds fracture", ENGINEERING FRACTURE MECHANICS, PERGAMON PRESS, NEW YORK, NY, GB, vol. 87, doi:10.1016/J.ENGFRACMECH.2012.03.004, ISSN 0013-7944, (20120310), pages 48 - 61, (20120321), XP028485695 [Y] 1-13 * section 2.2.1 * * figure 9 *
ref_type: npl
severity: obviousness
ref_id: - UC Boulder, "FEM Modeling: Mesh, Loads and BCs", (20150909), pages 1 - 19, URL: http://www.colorado.edu/engineering/CAS/courses.d/IFEM.d/IFEM.Ch07.d/IFEM.Ch07.pdf, (20161027), XP055314724 [A] 1,11 * figures 7.5,7.12 *
ref_type: npl
severity: background
Final disposition: pending (2017-12-06)