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Licensed Unlicensed Requires Authentication Published by De Gruyter April 7, 2017

Influence of strain rate, temperature and fatigue on the radial compression behaviour of Norway spruce

Carolina Moilanen, Tomas Björkqvist, Markus Ovaska, Juha Koivisto, Amandine Miksic, Birgitta A. Engberg, Lauri I. Salminen, Pentti Saarenrinne and Mikko Alava
From the journal Holzforschung

Abstract

A dynamic elastoplastic compression model of Norway spruce for virtual computer optimization of mechanical pulping processes was developed. The empirical wood behaviour was fitted to a Voigt-Kelvin material model, which is based on quasi static compression and high strain rate compression tests (QSCT and HSRT, respectively) of wood at room temperature and at high temperature (80–100°C). The effect of wood fatigue was also included in the model. Wood compression stress-strain curves have an initial linear elastic region, a plateau region and a densification region. The latter was not reached in the HSRT. Earlywood (EW) and latewood (LW) contributions were considered separately. In the radial direction, the wood structure is layered and can well be modelled by serially loaded layers. The EW model was a two part linear model and the LW was modelled by a linear model, both with a strain rate dependent term. The model corresponds well to the measured values and this is the first compression model for EW and LW that is based on experiments under conditions close to those used in mechanical pulping.

Acknowledgements

The Academy of Finland is acknowledged for the funding of the project Woodmat (decision number 140462), in which this research has been conducted. The Swedish Knowledge Foundation and the member companies of the E2MP-Research Profile at Mid Sweden University are also acknowledged for supporting this research. M. Ovaska, A. Miksic and M. Alava are supported by the Academy of Finland through its Centres of Excellence Program (2012–2017 under project no. 251748). The authors are also grateful for the assistance with the high strain rate material testing by Max Lundström and Staffan Nyström in the Mid Sweden University Material’s Lab.

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Received: 2016-9-8
Accepted: 2017-3-1
Published Online: 2017-4-7
Published in Print: 2017-6-27

©2017 Walter de Gruyter GmbH, Berlin/Boston

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