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Lagerblad, U., Wentzel, H. & Kulachenko, A. (2019). Dynamic response identification based on state estimation and operational modal analysis. Mechanical systems and signal processing, 129, 37-53
Open this publication in new window or tab >>Dynamic response identification based on state estimation and operational modal analysis
2019 (English)In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 129, p. 37-53Article in journal (Refereed) Published
Abstract [en]

This paper presents and experimentally validates an augmented Kalman filter extended with a fixed-lag smoother for solving joint state and input estimation problems. Sparse acceleration measurements from a truck side skirt excited by road-induced vibrations from a vibration test track are analysed. The system model is obtained experimentally from an operational modal analysis, reducing modelling errors and avoiding the need for a finite element model and it serves itself as a numerical model. The motion of the truck component is estimated and the results are compared to those of a joint input-state estimation filtering algorithm, in addition to the actual measured motion. Both algorithms are tuned according to a novel process based on minimal a priori information concerning the system states and inputs. The focus of this work is to assess the robustness, performance, and tuning of the algorithms. Two sensor configurations are studied: one where the number of response measurement sensors is high compared to the number of estimated motions and participating modes, and another where the number of response measurements is reduced. Both algorithms perform very well within the first configuration. With a reduced number of response measurements, the fixed-lag smoother is superior to the joint input-state filter in capturing the individual motion of each position on the side skirt.

Place, publisher, year, edition, pages
Academic Press, 2019
Keywords
Experimental validation, Fixed-lag smoother, Joint input-state estimation, Structural dynamics, Automobile testing, Kalman filters, Modal analysis, State estimation, Trucks, Augmented kalman filters, Experimental validations, Filtering algorithm, Fixed lag smoothers, Operational modal analysis, Priori information, Response measurement, Sensor configurations, Vibration analysis
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-252481 (URN)10.1016/j.ymssp.2019.04.019 (DOI)000474682300003 ()2-s2.0-85064436392 (Scopus ID)
Note

QC 20190712

Available from: 2019-07-12 Created: 2019-07-12 Last updated: 2019-07-30Bibliographically approved
Motamedian, H. R., Halilovic, A. & Kulachenko, A. (2019). Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines. Paper presented at ARK JD, 1969, TAPPI, V52, P335. Cellulose (London), 26(6), 4099-4124
Open this publication in new window or tab >>Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines
2019 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 6, p. 4099-4124Article in journal (Refereed) Published
Abstract [en]

Refining (i.e., mechanical beating of pulp) is a common procedure that is used in paper-making to improve the mechanical properties of the final product. The improvements caused by refining are mainly attributed to increased density and to a better bonding between fibers. In this work, we study how various mechanisms that can be triggered by refining affect the tensile behavior of the sheets. Consequently, we use direct numerical simulations of fiber networks. We relate our finding to the experimental measurements that we conducted on handsheets. We have found that fibrillar fines with size distributions below the resolution of modern state-of-the art pulp characterization tools have a substantial contribution to the increased strength and stiffness of the sheets.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Refining, Beating, PFI, Strength, Stiffness, Fines, Densification, Fiber network, Simulation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-251332 (URN)10.1007/s10570-019-02349-5 (DOI)000464849500033 ()2-s2.0-85062974803 (Scopus ID)
Conference
ARK JD, 1969, TAPPI, V52, P335
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved
Motamedian, H. R. & Kulachenko, A. (2019). Simulating the hygroexpansion of paper using a 3D beam network model and concurrent multiscale approach. International Journal of Solids and Structures, 161, 23-41
Open this publication in new window or tab >>Simulating the hygroexpansion of paper using a 3D beam network model and concurrent multiscale approach
2019 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 161, p. 23-41Article in journal (Refereed) Published
Abstract [en]

A number of problems associated with dimensional stability of paper products have to do with hygroexpansion in response to changes in humidity or moisture content. The main underlying mechanism of hygroexpansion in paper is the effect of the change of fiber cross-sections transferred through fiber bonds. In fact, the transverse expansion of fibers can be an order of magnitude greater than the longitudinal expansion. Addressing such problems using modeling on the microscale is associated with large computational costs since both the bonds and the fibers need to be resolved. We present a method for modeling the hygro or thermal expansion of interconnected fiber networks modeled with beam elements and connected through beam-to-beam contact. Being a line structure, beams can only support point wise contact, which poses a challenge for modeling the force transfer induced by the deformation of the cross-sections at the contact point. The idea of implementing the stress transfer is to use a concurrent multiscale approach in which the bond level is resolved in detail using the configuration of the fibers and the computed strains are passed over to the beam elements. We verify and prove the applicability of this approach by comparing it with continuum models. We demonstrate the advantage of using this approach in terms of its tremendous saving in time. The use of beam models for modeling the hygro- or thermal expansion of fiber networks enables considering relevant sizes in the problems involving dimensional stability, in particular those associated with embedded inhomogeneities. We will show the applicability of the model by providing insights into published experimental observations on the hygroexpansion properties of paper products. Finally, we will demonstrate that the use of a 2D model to simulate the inter-fiber bonds in a network, not only leads to underestimation of out-of-plane deformations, but also to overestimation of the contribution of the transverse deformation of fibers to the in-plane dimensional change of the network.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Fiber network, Hygroexpansion, Shrinkage, Drying, Moisture, Paper, Multiscale, Simulation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-245122 (URN)10.1016/j.ijsolstr.2018.11.006 (DOI)000458590500003 ()2-s2.0-85057017030 (Scopus ID)
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-03-15Bibliographically approved
Mansour, R., Kulachenko, A., Chen, W. & Olsson, M. (2019). Stochastic constitutive model of isotropic thin fiber networks based on stochastic volume elements. Materials, 12(3), Article ID 538.
Open this publication in new window or tab >>Stochastic constitutive model of isotropic thin fiber networks based on stochastic volume elements
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 3, article id 538Article in journal (Refereed) Published
Abstract [en]

Thin fiber networks are widely represented in nature and can be found in man-made materials such as paper and packaging. The strength of such materials is an intricate subject due to inherited randomness and size-dependencies. Direct fiber-level numerical simulations can provide insights into the role of the constitutive components of such networks, their morphology, and arrangements on the strength of the products made of them. However, direct mechanical simulation of randomly generated large and thin fiber networks is characterized by overwhelming computational costs. Herein, a stochastic constitutive model for predicting the random mechanical response of isotropic thin fiber networks of arbitrary size is presented. The model is based on stochastic volume elements (SVEs) with SVE size-specific deterministic and stochastic constitutive law parameters. The randomness in the network is described by the spatial fields of the uniaxial strain and strength to failure, formulated using multivariate kernel functions and approximate univariate probability density functions. The proposed stochastic continuum approach shows good agreement when compared to direct numerical simulation with respect to mechanical response. Furthermore, strain localization patterns matched the one observed in direct simulations, which suggests an accurate prediction of the failure location. This work demonstrates that the proposed stochastic constitutive model can be used to predict the response of random isotropic fiber networks of arbitrary size.

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
Mechanical failure, Multi-scale modeling, Plastic softening, Stochastic volume element (SVE), Strain localization, Thin fiber networks, Constitutive models, Failure (mechanical), Fibers, Forecasting, Numerical models, Packaging materials, Probability density function, Random processes, Stochastic systems, Mechanical failures, Strain localizations, Thin fibers, Volume elements, Stochastic models
National Category
Mathematics
Identifiers
urn:nbn:se:kth:diva-248188 (URN)10.3390/ma12030538 (DOI)000460768000207 ()2-s2.0-85061487661 (Scopus ID)
Note

QC 20190412

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-05-20Bibliographically approved
Srinivasa, P. & Kulachenko, A. (2018). A three-dimensional numerical model for large strain compression of nanofibrillar cellulose foams. Nordic Pulp & Paper Research Journal, 33(2), 256-270
Open this publication in new window or tab >>A three-dimensional numerical model for large strain compression of nanofibrillar cellulose foams
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 2, p. 256-270Article in journal (Refereed) Published
Abstract [en]

We investigate the suitability of three-dimensional Voronoi structures in representing a large strain macroscopic compressive response of nanofibrillar cellulose foams and understanding the connection between the features of the response and details of the microstructure. We utilise Lloyd's algorithm to generate centroidal tessellations to relax the Voronoi structures and have reduced polydispersity. We begin by validating these structures against simulations of structures recreated from microtomography scans. We show that by controlling the cell face curvature, it is possible to match the compressive response for a 96.02% porous structure. For the structures of higher porosity (98.41%), the compressive response can only be matched up to strain levels of 0.4 with the densification stresses being overestimated. We then ascertain the representative volume element (RVE) size based on the measures of relative elastic modulus and relative yield strength. The effects of cell face curvature and partially closed cells on the elastic modulus and plateau stress is then estimated. Finally, the large strain response is compared against the two-dimensional Voronoi model and available experimental data for NFC foams. The results show that compared to the two-dimensional model, the three-dimensional analysis provides a stiffer response at a given porosity due to earlier self-contact.

Place, publisher, year, edition, pages
AB SVENSK PAPPERSTIDNING, 2018
Keywords
large strain compression, meso-scale modelling, nanofibrillar cellulose foams, scaling laws, tomography, Voronoi tessellations
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-240031 (URN)10.1515/npprj-2018-3023 (DOI)000450922400011 ()2-s2.0-85050085405 (Scopus ID)
Note

QC 20181210

Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2018-12-10Bibliographically approved
Borodulina, S., Motamedian, H. R. & Kulachenko, A. (2018). Effect of fiber and bond strength variations on the tensile stiffness and strength of fiber networks. International Journal of Solids and Structures, 154, 19-32
Open this publication in new window or tab >>Effect of fiber and bond strength variations on the tensile stiffness and strength of fiber networks
2018 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 154, p. 19-32Article in journal (Refereed) Published
Abstract [en]

As fiber and bond characterization tools become more sophisticated, the information from the fiber scale becomes richer. This information is used for benchmarking of different types of fibers by the paper and packaging industries. In this work, we have addressed a question about the effect of variability in the fiber and fiber bond properties on the average stiffness and strength of fiber networks. We used a fiber scale numerical model and reconstruction algorithm to address this question. The approach was verified using the experimental sheets having fiber data acquired by a fiber morphology analyzer and corrected by microtomographic analysis of fibers in these sheets. We concluded, among other things, that it is sufficient to account for the average bond strength value with an acceptable number of samples to describe dry network strength, as long as the bond strength distribution remains symmetric. We also found that using the length-weighted average for fiber shape factor and fiber length data neglects the important contribution from the distribution in these properties on the mechanical properties of the sheets.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Fibers, Bonds, Stress-strain curve, Paper strength, Network simulation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-239751 (URN)10.1016/j.ijsolstr.2016.12.013 (DOI)000450376100003 ()2-s2.0-85010766651 (Scopus ID)
Note

QC 20190110

Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-18Bibliographically approved
Lagerblad, U., Wentzel, H. & Kulachenko, A. (2018). Fatigue damage prediction based on strain field estimates using a smoothed Kalman filter and sparse measurements. In: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics: . Paper presented at 28th International Conference on Noise and Vibration Engineering, ISMA 2018 and 7th International Conference on Uncertainty in Structural Dynamics, USD 2018, 17 September 2018 through 19 September 2018 (pp. 2805-2817). KU Leuven - Departement Werktuigkunde
Open this publication in new window or tab >>Fatigue damage prediction based on strain field estimates using a smoothed Kalman filter and sparse measurements
2018 (English)In: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics, KU Leuven - Departement Werktuigkunde , 2018, p. 2805-2817Conference paper, Published paper (Refereed)
Abstract [en]

In this work, we address the problem of fatigue damage prediction in a truck component excited by road induced vibrations. The damage is computed from strains estimated from sparse measurements of the dynamic response. Two different fixed-lag smoothing algorithm are employed, an augmented Kalman filter extended with a fixed-lag smoother and a smoothed joint input-state estimation algorithm. The system is described with a finite element model, and due to the complexity of reproducing the system by the model, the resulting representation may contain a number of discrepancies. Nevertheless, both smoothing algorithms succeed in capturing the dynamic behaviour of the component, although the estimated strains are affected more by the large model error than the estimated acceleration are. Furthermore, it is shown that the proposed methodology of strain estimation and fatigue damage calculations correlate well with the observed failure of a component when tested in a full-scale fatigue test of a truck chassis- International Conference on Uncertainty in Structural Dynamics.

Place, publisher, year, edition, pages
KU Leuven - Departement Werktuigkunde, 2018
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-246514 (URN)2-s2.0-85060378508 (Scopus ID)9789073802995 (ISBN)
Conference
28th International Conference on Noise and Vibration Engineering, ISMA 2018 and 7th International Conference on Uncertainty in Structural Dynamics, USD 2018, 17 September 2018 through 19 September 2018
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-03-26Bibliographically approved
Alimadadi, M., Lindström, S. B. & Kulachenko, A. (2018). Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks. Soft Matter, 14(44), 8945-8955
Open this publication in new window or tab >>Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks
2018 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, no 44, p. 8945-8955Article in journal (Refereed) Published
Abstract [en]

High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, we are able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-239757 (URN)10.1039/c7sm02561k (DOI)000450442300008 ()30398491 (PubMedID)2-s2.0-85056540966 (Scopus ID)
Note

QC 20190110

Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Motamedian, H. R. & Kulachenko, A. (2018). Rotational Constraint between Beams in 3-D Space. Mechanical Sciences, 9(2), 373-387
Open this publication in new window or tab >>Rotational Constraint between Beams in 3-D Space
2018 (English)In: Mechanical Sciences, ISSN 2191-9151, E-ISSN 2191-916X, Vol. 9, no 2, p. 373-387Article in journal (Refereed) Published
Abstract [en]

In this paper, we develop two alternative formulations for the rotational constraint between the tangents to connected beams with large deformations in 3-D space. Such a formulation is useful for modeling bonded/welded connections between beams. The first formulation is derived by consistently linearizing the variation of the strain energy and by assuming linear shape functions for the beam elements. This formulation can be used with both the Lagrange multiplier and the penalty stiffness method. The second non-consistent formulation assumes that the contact normal is independent of the nodal displacements at each iteration, and is updated consistently between iterations. In other words, we ignore the contribution due to the change of the contact normal in the linearization of the contact gap function. This assumption yields simpler equations and requires no specific assumption regarding the shape functions for the underlying beam elements. However, it is limited to the penalty method. We demonstrate the performance of the presented formulations in solving problems using implicit time integration. We also present a case showing the implications of ignoring this rotational constraint in modeling a network of beams.

Place, publisher, year, edition, pages
COPERNICUS GESELLSCHAFT MBH, 2018
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-239765 (URN)10.5194/ms-9-373-2018 (DOI)000450293500001 ()2-s2.0-85056869890 (Scopus ID)
Note

QC 20190109

Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
Lagerblad, U., Wentzel, H. & Kulachenko, A. (2016). A fixed-lag smoother for solving input force and support motion identification problems in structural dynamics.
Open this publication in new window or tab >>A fixed-lag smoother for solving input force and support motion identification problems in structural dynamics
2016 (English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work, the problem of joint input and state estimation based on measured response in a dynamic system is addressed.A fixed-lag smoother for support motion or input force estimation in linear structural dynamics is proposed. The unknown inputs are estimated in conjunction with the states in an augmented state description of the system. A fixed-lag smoother maximizes the use of information available in the measurements by allowing a small time lag in the estimation, leading to a recursive non-causal filter. This type of filter has not previously been implemented in the field of structural dynamics. The filter is capable of handling any combination of measured displacement, velocity and acceleration; furthermore are both measurement noise and model errors accounted for and simulated as stochastic processes. In this study, estimations are based on sparse noisy measurements of system displacement and model errors are simulated through the use of deliberately incorrect model descriptions. The proposed algorithm is verified by numerical simulations and the qualities of the estimations are compared to those of the augmented Kalman filter.It is shown that with this filter, significant improvements of the input estimations are achieved, especially of inputs located far away from measurement sensors. The improvement consists of noise reduction, phase correction and by a more accurate division of the individual contribution of multiple inputs.

Publisher
p. 26
Keywords
Joint input-state estimation, Fixed-lag smoother, Force identification, Structural dynamics
National Category
Other Mechanical Engineering
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-193052 (URN)
Note

QC 20160928

Available from: 2016-09-27 Created: 2016-09-27 Last updated: 2016-09-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3611-2250

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