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Hammarberg, S., Kajberg, J., Larsson, S. & Jonsén, P. (2020). Ultra high strength steel sandwich for lightweight applications. SN Applied Sciences, 2(6), Article ID 1040.
Open this publication in new window or tab >>Ultra high strength steel sandwich for lightweight applications
2020 (English)In: SN Applied Sciences, E-ISSN 2523-3971, Vol. 2, no 6, article id 1040Article in journal (Refereed) Published
Abstract [en]

Methods for reducing weight of structural elements are important for a sustainable society. Over the recent years ultra high strength steel (UHSS) has been a successful material for designing light and strong components. Sandwich panels are interesting structural components to further explore areas where the benefits of UHSS can be utilized. The specific properties of sandwich panels make them suitable for stiffness applications and various cores have been studied extensively. In the present work, bidirectionally corrugated UHSS cores are studied experimentally and numerically. A UHSS core is manufactured by cold rolling and bonded to the skins by welding. Stiffness is evaluated experimentally in three-point bending. The tests are virtually reproduced using the finite element method. Precise discretization of the core requires large amounts of computational power, prolonging lead times for sandwich component development, which in the present work is addressed by homogenization, using an equivalent material formulation. Input data for the equivalent models is obtained by characterizing representative volume elements of the periodic cores under periodic boundary conditions. The homogenized panel reduces the number of finite elements and thus the computational time while maintaining accuracy. Numerical results are validated and agree well with experimental testing. Important findings from experimental and simulation results show that the suggested panels provide superior specific bending stiffness as compared to solid panels. This work shows that lightweight UHSS sandwiches with excellent stiffness properties can be manufactured and modeled efficiently. The concept of manufacturing a UHSS sandwich panel expands the usability of UHSS to new areas.

Place, publisher, year, edition, pages
Springer Nature, 2020
Keywords
UHSS, Sandwich, Lightweight, Modeling, Bidirectional core, Representative volume element (RVE)
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-78844 (URN)10.1007/s42452-020-2773-5 (DOI)
Note

Validerad;2020;Nivå 2;2020-05-14 (alebob)

Available from: 2020-05-11 Created: 2020-05-11 Last updated: 2020-05-14Bibliographically approved
Suarez, L., Jonsén, P. & Hammarberg, S. (2019). A combined modeling approach to capture the physical interactions between pulp, charge and structure in a tumbling. In: : . Paper presented at VI International Conference on Particle-based Methods, Fundamentals and Applications (PARTICLES 2019), 28-30 October, 2019, Barcelona, Spain. International Center for Numerical Methods in Engineering (CIMNE)
Open this publication in new window or tab >>A combined modeling approach to capture the physical interactions between pulp, charge and structure in a tumbling
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
International Center for Numerical Methods in Engineering (CIMNE), 2019
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-78045 (URN)
Conference
VI International Conference on Particle-based Methods, Fundamentals and Applications (PARTICLES 2019), 28-30 October, 2019, Barcelona, Spain
Available from: 2020-03-13 Created: 2020-03-13 Last updated: 2020-04-28Bibliographically approved
Jonsén, P., Hammarberg, S., Pålsson, B. & Lindkvist, G. (2019). Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Engineering, 130, 76-84
Open this publication in new window or tab >>Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills
2019 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, p. 76-84Article in journal (Refereed) Published
Abstract [en]

Modelling of wet grinding in tumbling mills is an interesting challenge. A key factor is that the pulp fluid and its simultaneous interactions with both the charge and the mill structure have to be handled in a computationally efficient way. In this work, the pulp fluid is modelled with a Lagrange based method based on the particle finite element method (PFEM) that gives the opportunity to model free surface flow. This method gives robustness and stability to the fluid model and is efficient as it gives possibility to use larger time steps. The PFEM solver can be coupled to other solvers as in this case both the finite element method (FEM) solver for the mill structure and the DEM solver for the ball charge. The combined PFEM-DEM-FEM model presented here can predict charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. All cases presented here are numerically modelled and validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill equipped with a torque meter and charge movements captured from high-speed video. Numerical results are in good agreement with experimental torque measurements and the PFEM solver also improves on efficiency and robustness for solving charge movements in wet tumbling mill systems.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Grinding, Modelling, Simulation, Validation
National Category
Applied Mechanics Metallurgy and Metallic Materials
Research subject
Solid Mechanics; Mineral Processing
Identifiers
urn:nbn:se:ltu:diva-71226 (URN)10.1016/j.mineng.2018.10.013 (DOI)000452937000010 ()2-s2.0-85054850385 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-16 (svasva)

Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2019-02-01Bibliographically approved
Hammarberg, S. (2018). A Study on Structural Cores for Lightweight Steel Sandwiches. (Licentiate dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>A Study on Structural Cores for Lightweight Steel Sandwiches
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Lightweight materials and structures are essential building blocks for a future with sustainable transportation and automotive industries. Incorporating lightweight materials and structures in today's vehicles, reduces weight and energy consumption while maintaining, or even improving, necessary mechanical properties and behaviors. Due to this, the environmental footprint can be reduced through the incorporation of lightweight structures and materials. 

Awareness of the negative effects caused by pollution from emissions is ever increasing. Legislation, forced by authorities, drives industries to find better solutions with regard to the environmental impact. For the automotive industry, this implies more effective vehicles with respect to energy consumption. This can be achieved by introducing new, and improve current, methods of turning power into motion. An additional approach is reducing weight of the body in white (BIW) while maintaining crash worthiness to assure passenger safety. In addition to the structural integrity of the BIW, passenger safety is further increased through electrical systems integrated into the modern vehicle. Besides these safety systems, customers are also able to choose from a long list of gadgets to be fitted to the vehicle. As a result, the curb weight of vehicles are increasing, partly due to customer demands. In order to mitigate the increasing weights the BIW must be optimized with respect to weight, while maintaining its structural integrity and crash worthiness. To achieve this, new and innovative materials, geometries and structures are required, where the right material is used in the right place, resulting in a lightweight structure which can replace current configurations. 

A variety of approaches are available for achieving lightweight, one of them being the press-hardening method, in which a heated blank is formed and quenched in the same process step. The result of the process is a component with greatly enhanced properties as compared to those of mild steel. Due to the properties of press hardened components they can be used to reduce the weight of the body-in-white. The process also allows for manufacturing of components with tailored properties, allowing the right material properties in the right place. 

The present work aims to investigate, develop and in the end bring forth two types of light weight sandwiches; one intended for crash applications (Type I) and another for stiffness applications (Type II). Type I, based on press hardened boron steel, consists of a perforated core in between two face plates. To evaluate Type I's ability to absorb energy for crash applications a hat profile geometry is utilized. The hat profile is numerically subjected to loading from which the required energy to deform it can be found. These results are compared to those from a reference test, consisting of a hat profile based on solid steel and with an equivalent weight to that of the Type I hat profile. The aim is to minimize the weight of the core while maximizing the energy absorption. Type II consists of a bidirectional corrugated steel plate, placed in between two face plates. The geometry of the bidirectional core requires a large amount of finite elements for discretization causing a small time step and long simulation times. In order to reduce computational time a homogenization approach is suggested where the aim is to be able to predict stiffness of a planar sandwich at a reduced computational cost. 

The numerical results from Type I show that it is possible to obtain a higher energy absorption per unit weight by introducing perforated cores in sandwich panels. Typically, energy absorption of such a panels were 20% higher as compared to a solid hat profile of equivalent weight, making it an attractive choice for reducing weight while maintaining performance. However, these results are awaiting experimental validation. The results from Type II show that it is possible, by introducing a homogenization procedure, to predict stiffness at a reduced computational cost. Validation by experiments were carried out as a sandwich panel was subjected to a three point bend in the laboratory. Numerical and experimental results agreed quite well, showing the possibilities of incorporating such panels into larger structure for stiffness applications.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
Lightweight, Sandwich, Steel, Energy absorption, Homogenization, Finite element
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-67944 (URN)978-91-7790-074-0 (ISBN)978-91-7790-075-7 (ISBN)
Presentation
2018-04-26, E231, Luleå tekniska universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-03-20 Created: 2018-03-19 Last updated: 2018-11-07Bibliographically approved
Hammarberg, S., Larsson, S. & Jonsén, P. (2014). Modelling of interaction between suspension and structure in a tumbling mill (ed.). In: (Ed.), Eugenio Oñate; Xavier Oliver; Antonio Huerta (Ed.), 11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI): . Paper presented at World Congress on Computational Mechanics (WCCM XI) : 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) 20/07/2014 - 25/07/2014 (pp. 7383-7393). Barcelona, 6
Open this publication in new window or tab >>Modelling of interaction between suspension and structure in a tumbling mill
2014 (English)In: 11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) / [ed] Eugenio Oñate; Xavier Oliver; Antonio Huerta, Barcelona, 2014, Vol. 6, p. 7383-7393Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Barcelona: , 2014
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-32610 (URN)729a123b-4ccb-40bd-956b-75ff8921afe9 (Local ID)978-84-942844-7-2 (ISBN)729a123b-4ccb-40bd-956b-75ff8921afe9 (Archive number)729a123b-4ccb-40bd-956b-75ff8921afe9 (OAI)
Conference
World Congress on Computational Mechanics (WCCM XI) : 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) 20/07/2014 - 25/07/2014
Note
Godkänd; 2014; 20140813 (parj)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-04-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7895-1058

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