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Hallbäck, Nils
Publications (10 of 22) Show all publications
Sadek, M., Bergström, J., Hallbäck, N. & Burman, C. (2018). 20 kHz 3-point bending fatigue of automotive steels. In: MATEC Web of Conferences: . Paper presented at 12th International Fatigue Congress, FATIGUE 2018, 27 May 2018 through 1 June 2018 (pp. 1-7). EDP Sciences, 165, Article ID 22020.
Open this publication in new window or tab >>20 kHz 3-point bending fatigue of automotive steels
2018 (English)In: MATEC Web of Conferences, EDP Sciences, 2018, Vol. 165, p. 1-7, article id 22020Conference paper, Published paper (Refereed)
Abstract [en]

The 20 kHz load frequency enables fatigue tests for very high cycle fatigue life, 109-1013 cycles, within conveniently short time. In automotive applications, many components are subjected to flexural loading and hence bending fatigue is an important test mode. Ultrasound fatigue test instruments have been used successfully in several assessments of fatigue strength and more commonly in uniaxial loading. Here, a 3-point bending fatigue test rig operating in resonance at 20 kHz load frequency has been designed to test plane specimens at R=0.1 loading. The test rig design and stress calculations are presented. Testing for fatigue strength was conducted using the staircase method with 15 specimens of each steel grade, specimens reaching 108 cycles were considered run-outs giving fatigue strength at 108 cycles. Additional 15 specimens of each grade were tested for S-N curves with the upper limit above 109 cycles. Two different common automotive steels, 38MnSiV5, a micro-alloyed ferritic-pearlitic steel, and 16MnCr5, a carburizing martensitic steel, were tested. The fatigue strengths achieved from the staircase testing are 340 and 419 MPa stress amplitudes for the 38MnSiV5 and 16MnCr5 steels, respectively. The S-N curves of the steels appear to be quite flat in the tested life range 107 - 109.

Place, publisher, year, edition, pages
EDP Sciences, 2018
Keywords
Automotive steels, Carburized steel, Ferritic-pearlitic steel, Three-point bending, VHCF, Binary alloys, Chromium alloys, Fatigue of materials, Fatigue testing, Ferrite, Ferritic steel, Pearlite, Silicon alloys, Stairs, Steel metallography, Steel testing, Pearlitic steels, Three point bending, Manganese alloys
National Category
Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:kau:diva-68076 (URN)10.1051/matecconf/201816522020 (DOI)000478990600218 ()2-s2.0-85048089977 (Scopus ID)
Conference
12th International Fatigue Congress, FATIGUE 2018, 27 May 2018 through 1 June 2018
Available from: 2018-06-26 Created: 2018-06-26 Last updated: 2019-08-29Bibliographically approved
Tofique, M. W. & Hallbäck, N. (2018). Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branches. European journal of mechanics. A, Solids, 69, 168-178
Open this publication in new window or tab >>Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branches
2018 (English)In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 69, p. 168-178Article in journal (Refereed) Published
Abstract [en]

This paper presents the development of the distributed dislocation dipole technique (DDDT) for the analysis of straight, kinked and branched cracks where parts of the cracks may close during loading. The method has been developed for plane problems. Crack cases in which closure occurs are analyzed by reformulating the Buecicner's principle, taking into account the contact stresses at the contacting portions of the crack surfaces. Stress intensity factors corresponding to opening and the in-plane sliding mode of deformation at the crack tips are computed. Several test cases involving straight, kinked and/or branched cracks where parts of the cracks undergoes crack surface closure when subjected to the outer loading are analyzed. The results obtained from the DDDT are compared to those obtained from a Finite Element Method (FEM) analysis of the same crack cases. This comparison shows that the computation of stress intensity factors for the cases involving crack surface closure are less accurate than those for fully open crack cases. However, for the cases under consideration, the stress intensity factors were still computed with a maximum difference of approximately 2 per cent compared to the FEM calculations if Jacobi polynomial expansions of at least the twelfth order were used to represent the crack surface opening and sliding displacements. In most cases under consideration, sixth order Jacobi polynomial expansions were sufficient to obtain results within that margin of deviation.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Applied Mechanics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kau:diva-67306 (URN)10.1016/j.euromechsol.2017.12.004 (DOI)000430767100014 ()
Available from: 2018-05-11 Created: 2018-05-11 Last updated: 2018-07-09Bibliographically approved
Hämäläinen, P., Hallbäck, N., Gåård, A. & Lestelius, M. (2017). On the determination of transverse shear properties of paper using the short span compression test. Mechanics of materials (Print), 107, 22-30
Open this publication in new window or tab >>On the determination of transverse shear properties of paper using the short span compression test
2017 (English)In: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 107, p. 22-30Article in journal (Refereed) Published
Abstract [en]

The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko-Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young's modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko-Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Paper, Pulp and Fiber Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-63022 (URN)10.1016/j.mechmat.2017.01.012 (DOI)000397366100002 ()
Projects
VIPP
Funder
Knowledge Foundation
Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2019-07-09Bibliographically approved
Sadek, M., Bergström, J., Hallbäck, N. & Burman, C. (2016). Computation of and testing crack growth at 20 kHz load frequency. In: F. Iacoviello, L. Susmel, D. Firrao, G. Ferro, (Ed.), 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21): . Paper presented at 21st European Conference on Fracture (ECF), JUN 20-24, 2016, Catania, ITALY (pp. 1164-1172). Elsevier
Open this publication in new window or tab >>Computation of and testing crack growth at 20 kHz load frequency
2016 (English)In: 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21) / [ed] F. Iacoviello, L. Susmel, D. Firrao, G. Ferro,, Elsevier, 2016, p. 1164-1172Conference paper, Published paper (Refereed)
Abstract [en]

Fatigue properties are evaluated in a large span of fatigue lives ranging from a few load cycles to more than 1013 load cycles. If the interest is focused on fatigue lives above 10(7) load cycles, we speak of the very high cycle fatigue (VHCF) range. For evaluation of properties in the VHCF range one often needs to use higher load frequencies to be able to perform testing within a reasonable time. Therefore, the influence of load frequency on fatigue strength and fatigue crack growth is an important issue, both from testing and design perspectives. Within an EU-RFCS research project on the frequency influence on high strength steel fatigue properties the present study has been conducted on fatigue crack growth testing to determine threshold values and crack growth material parameters. The testing was analyzed by FE-computation to determine geometry factors for AK-determination. The testing was performed in a 20 kHz ultrasound resonance instrument. In such a system the whole load train needs to be designed to run at a resonance frequency of 20 kHz, and it implies that the specimen needs to be designed and computations performed by dynamic computational methods. As the crack grows the dynamic response of the specimen will change, and hence calculation to obtain the geometry factor is made with a progressing crack length. A uniaxial tensile load at 20 kHz frequency is applied to a single edged notched side-grooved flat specimen. The specimen dimensions are calculated in order to have a resonance frequency of 20 kHz, which is the frequency used for the experiments. Dynamic FEM computation, with a 3D-model and a quarter symmetry was used with one of the symmetry planes parallel to and in the crack growth line. To avoid crack surface interpenetration during the simulations a rigid thin sheet was introduced and used as a counter-face to the crack surface. The solution obtained was then combined with the breathing crack model proposed by Chati et. al. (1997) in order to solve for the irregularities observed when crack surface interpenetration occurs. Finally, the whole load train was considered. Thus, also the computed frequencies were very close to frequencies observed in experiments. The computation of stress intensities was made for varying crack lengths in a series of simulations. The geometry factor relation was determined and used in 20 kHz crack growth testing to control the actual stress intensity at the advancing crack tip. Comparison of computations and experimental results were made.

Place, publisher, year, edition, pages
Elsevier, 2016
Series
Procedia Structural Integrity, ISSN 2452-3216 ; 2
Keywords
Crack growth, High frequency, Dynamic analysis, steel, threshold testing
National Category
Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:kau:diva-62609 (URN)10.1016/j.prostr.2016.06.149 (DOI)000387976801029 ()
Conference
21st European Conference on Fracture (ECF), JUN 20-24, 2016, Catania, ITALY
Available from: 2017-08-10 Created: 2017-08-10 Last updated: 2019-10-21Bibliographically approved
Hämäläinen, P., Hallbäck, N. & Barbier, C. (2016). Development and evaluation of a high-speed creping simulator for tissue. Nordic Pulp & Paper Research Journal, 31(3), 448-458
Open this publication in new window or tab >>Development and evaluation of a high-speed creping simulator for tissue
2016 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 3, p. 448-458Article in journal (Refereed) Published
Abstract [en]

An innovative creping simulator for tissue has been developed to meet the requirements set by both industrial needs, such as speed and process step duration, and research ambitions, such as flexibility for modifications and efficient operation. Some of these factors can be difficult to achieve with the previously introduced simulators. Lower speeds and much longer process step times can jeopardize results when, for instance, the drying time of chemicals is longer and the speed of creping is slower than in a tissue mill. The newly developed simulator has been used to investigate the effects of paper grammage, creping angle, temperature of dryer, speed and the horizontal force experienced during tissue creping. Results show good agreement with results of industrial-scale tissue production, with the exception of shrinkage which was greater. It was observed that the grammage influences the final thickness and the shrinkage of creped sheets, and that creping speed affects the creping frequency, thickness and shrinkage. The temperature of the surface of a sled mimicking the Yankee cylinder was shown to influence creping frequency and thickness. The horizontal friction force during creping appears to increase if drying temperature is lowered.

Place, publisher, year, edition, pages
AB SVENSK PAPPERSTIDNING, 2016
Keywords
Creping, Test methods, Tissue, Adhesives, Low weight papers, Adhesion, Yankee dryer
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-65094 (URN)000387976000005 ()
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2019-10-28Bibliographically approved
Tofique, M. W., Bergström, J., Burman, C., Hallbäck, N. & Gåård, A. (2016). Fatigue strength, crack initiation, and localized plastic fatigue damage in VHCF of duplex stainless steels. Steel Research International, 87(7), 899-910
Open this publication in new window or tab >>Fatigue strength, crack initiation, and localized plastic fatigue damage in VHCF of duplex stainless steels
Show others...
2016 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 7, p. 899-910Article in journal (Refereed) Published
Abstract [en]

The fatigue strength of two-duplex stainless steel grades, 2304 SRG and LDX 2101, with austenitic–ferritic microstructure is tested using ultrasonic fatigue testing equipment operating at 20 kHz. The testing is conducted in tension-compression mode with the load ratio R=-1. The fatigue strength is evaluated at 107, 108, and 109 load cycles and the estimates of fatigue strength are higher for the LDX 2101 grade. The fatigue crack initiation mechanisms are analyzed using a scanning electron microscope. The fatigue cracks, in all cases, appear to initiate due to accumulation of plastic fatigue damage at the surface. In the 2304 SRG grade, accumulation of fatigue damage occurs at the external surface of fatigued specimens in the form of extrusions at the grain/phase boundaries and in the form of individual slip lines in the austenite phase. Meanwhile, in the LDX 2101 grade accumulation of plastic fatigue damage in the form of extrusions and intrusions occurs mainly within the ferrite grain. When the crack is microstructurally short, the crack growth appears to be crystallographic in nature and the crack appears to change its direction propagating from one grain into another.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2016
Keywords
duplex stainless steel; ultrasonic fatigue testing; plastic fatigue damage; very high cycle fatigue; crystallographic crack growth
National Category
Metallurgy and Metallic Materials
Research subject
Materials Engineering; Mechanical Engineering
Identifiers
urn:nbn:se:kau:diva-38693 (URN)10.1002/srin.201500263 (DOI)000385610500010 ()
Projects
Very High Cycle Fatigue of Stainless Steels - an unknown life
Funder
Knowledge Foundation
Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2017-12-06Bibliographically approved
Hallbäck, N. & Tofique, M. W. (2014). Development of a distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half-plane. International Journal of Solids and Structures, 51, 2878-2892
Open this publication in new window or tab >>Development of a distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half-plane
2014 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, p. 2878-2892Article in journal (Refereed) Published
Abstract [en]

A distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half plane has been developed. The dipole density distribution is represented with a weighted Jacobi polynomial expansion where the weight function captures the asymptotic behaviour at each end of the crack. To allow for opening and sliding at crack kinking and branching the dipole density representation contains conditional extra terms which fulfil the asymptotic behaviour at each endpoint. Several test cases involving straight, kinked and branched cracks have been analysed, and the results suggest that the accuracy of the method is within 1% provided that Jacobi polynomial expansions up to at least the sixth order are used. Adopting even higher order Jacobi polynomials yields improved accuracy. The method is compared to a simplified procedure suggested in the literature where stress singularities associated with corners at kinking or branching are neglected in the representation for the dipole density distribution. The comparison suggests that both procedures work, but that the current procedure is superior, in as much as the same accuracy is reached using substantially lower order polynomial expansions.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Cracks, Dislocation dipoles, stress intensity factors, Singular integral equations
National Category
Other Mechanical Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-34744 (URN)10.1016/j.ijsolstr.2014.04.011 (DOI)000338005200013 ()
Projects
Very high cycle fatigue of stainless steels- an unknown life
Funder
Knowledge Foundation
Available from: 2014-12-09 Created: 2014-12-09 Last updated: 2017-12-06Bibliographically approved
Tofique, M. W., Bergström, J., Hallbäck, N. & Burman, C. (2014). Fatigue initiation and strength of duplex stainless steel strip specimens in the very high cycle fatigue regime. In: Very high cycle fatigue 6 (VHCF6): . Paper presented at 6th International conference on very high cycle fatigue (VHCF6), Chengdu, China.
Open this publication in new window or tab >>Fatigue initiation and strength of duplex stainless steel strip specimens in the very high cycle fatigue regime
2014 (English)In: Very high cycle fatigue 6 (VHCF6), 2014Conference paper, Published paper (Refereed)
Abstract [en]

Fatigue studies of cold-rolled duplex stainless strip steel were performed in the very high cycle fatigue life region. The duplex austenitic-ferritic microstructure gives this grade a combination of high mechanical strength and high corrosion resistance. Fatigue properties of thin steel strips are particular due to cold rolling introducing a very fine microstructure. Crack initiation and fatigue strength are controlled by steel microstructure and alloying. The initiation and growth of the very short initial fatigue crack in very high cycle fatigue are unclear and subject to different descriptions. Fatigue test data of thin strip specimens at very high fatigue lives are scarce due to testing difficulties. For practical reasons testing must be performed at ultrasound test frequencies which involves fixturing problems. A test setup including the load chain ultrasonic horn, fixture and specimen was designed for resonance with a horse-shoe design of a screw fixture. The design of the horse-shoe fixture and the specimens along with FEM calculation of eigenfrequency are presented. Fatigue testing was performed at 20 kHz in R=-1 conditions up to fatigue life of 107 to 5*109 cycles. Fatigue strength was tested and crack initiation was studied on the fracture surface using FEG-SEM at the initiation site.

Keywords
Very high cycle fatigue, initiation, ultrasonic fatigue testing, strip specimen
National Category
Other Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-34633 (URN)
Conference
6th International conference on very high cycle fatigue (VHCF6), Chengdu, China
Projects
Very high cycle fatigue of stainless steels - an unknown life
Funder
Knowledge Foundation
Available from: 2014-11-21 Created: 2014-11-21 Last updated: 2019-11-28Bibliographically approved
Hallbäck, N., Korin, C., Barbier, C. & Nygårds, M. (2014). Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board. Packaging technology & science, 27(9), 701-712
Open this publication in new window or tab >>Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board
2014 (English)In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 27, no 9, p. 701-712Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Wiley Online Library, 2014
National Category
Engineering and Technology Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kau:diva-33788 (URN)10.1002/pts.2060 (DOI)000341142400003 ()
Available from: 2014-09-22 Created: 2014-09-22 Last updated: 2017-12-05Bibliographically approved
Korin, C., Seppänen, R., Vähä-Nissi, M. & Hallbäck, N. (2012). Influence of surface treatments on the mechanical strength of hotmelt adhesive joints made of cartonboards. Journal of Adhesion Science and Technology, 26(20-21), 2339-2356
Open this publication in new window or tab >>Influence of surface treatments on the mechanical strength of hotmelt adhesive joints made of cartonboards
2012 (English)In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 26, no 20-21, p. 2339-2356Article in journal (Refereed) Published
Abstract [en]

The influence of surface treatments including pigment coating, surface sizing and calendering on the mechanical strength of hotmelt adhesive joints in pilot made cartonboards was studied. The mechanical strength of the joints was investigated using the Y-peel test device at 23 degrees C and 50% relative humidity. Some of the samples were investigated with respect to the failure mode by scanning electron microscopy. The surfaces were characterized in terms of surface roughness, surface chemical composition, and adhesion behaviour. A strong adhesive bond displayed fibre tear. In addition to fibre tear, interfacial failure, i.e., failure between the cartonboard and the adhesive, was the main reason for fracture in the bonded assembly. The most important factor controlling the integrity of adhesive joints seemed to be the real contact area. The adhesive joints showed significantly higher strength when the hotmelt adhesive was first applied onto the rougher cartonboard of the assembly and then the smoother cartonboard was pressed on the adhesive than vice versa. The surface roughness of cartonboards mainly depended on whether the surface was pigment coated or not. Calendering displayed only a minor effect. No clear influence of surface chemical composition of the cartonboards on the adhesive joint strength was found due to the fact that changes in surface chemistry in this study also led to changes in surface roughness. The strongest adhesive joint was created between two medium-rough and surface-sized cartonboards.

Keywords
Cartonboard, hotmelt adhesive, mechanical strength, Y-peel test, surface treatment, surface roughness, surface chemistry
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-4970 (URN)10.1163/156856111X599490 (DOI)000308362700004 ()
Available from: 2009-11-25 Created: 2009-11-25 Last updated: 2017-12-12Bibliographically approved
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