Abstract
A new method for local strain measurement of soft materials like wood is proposed. Norway spruce samples were subjected to radial compression in an encapsulated split-Hopkinson device (ESHD). High speed photography was used at two magnifications for image based analysis. The strain estimation was made from high magnification images showing compression on local, fiber level for 1–2 growth rings and from low magnification images showing compression on sample level, for 5–8 growth rings. Strain gauges on the ESHD bars give stress and average strain for comparison. Image analysis based on PIV technique gives local and average strain propagation as a function of time. Wood is an inhomogeneous material and thus, local strain is a more proper measure of the response of the material. The high magnification captures differences between earlywood and latewood while the low magnification gives the strain distribution over the whole sample. Both magnifications are important in order to understand the response of the wood material to the sudden compression. A way to estimate the stress field was developed. The results showed similarity to the strain gauge measurement results.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Uhmeier A, Salmén L (1996) Influence of strain rate and temperature on the radial compression behavior of wet spruce. J Eng Mater Technol Trans ASME 118(3):289–294
Widehammar S (2004) Stress–strain relationships for spruce wood: influence of strain rate, moisture content and loading direction. Exp Mech 44(1):44–48
Gama BA (2004) Hopkinson bar experimental technique: a critical review. Appl Mech Rev 57(4):223–250
Davies RM (1948) A critical study of the Hopkinson pressure bar. Philos Trans R Soc Lond Sect B 240(821):375–457
Kolsky H (1949) An investigation of the mechanical properties of materials at very high rates of loading. Proc Phys Soc Lond Sect B 62(II-B):676–700
Widehammar S (2002) A method for dispersive split Hopkinson pressure bar analysis applied to high strain rate testing of spruce wood. Dissertation, Department of Materials Science, Uppsala University
Siviour CR (2009) A measurement of wave propagation in the split Hopkinson pressure bar. Meas Sci Technol 20(6):065702
Gilat A, Schmidt T, Walker A (2009) Full field strain measurement in compression and tensile split Hopkinson bar experiments. Exp Mech 49:291–302
Saari V, Björkqvist T, Engberg BA, Saarenrinne P (2009) Strain distribution in annual rings under compression by high speed photography. In: Proceedings of international mechanical pulping conference, 31st May–4th June 2009, Mid-Sweden University, Sunsvall
Allais L, Bornert M, Bretheau T, Caldemaison D (1994) Experimental characterization of the local strain field in a heterogeneous elastoplastic material. Acta Metallurgica Et Materialia 42(11):3865–3880
Sutton M, Orteau J, Schreier H (2009) Image correlation for shape, motion and deformation measurements. Springer, New York
Zink A, Davidson R, Hanna R (1995) Strain measurement in wood using a digital image correlation technique. Wood Fibre Sci 27:346–359
Vessby J, Serrano E, Enquist B (2010) Contact-free measurement and numerical and analytical evaluation of the strain distribution in a wood-FRP lap-joint. Mater Struct 43:1085–1095
Valla A, Konnerth D, Keunecke D, Niemz P, Muller U, Gindl W (2011) Comparison of two optical methods for contactless, full field and highly sensitive in-plane deformation measurements using the example of plywood. Wood Sci Technol 45:755–765
Thuvander F, Sjödahl M, Berglund L (2000) Measurement of crack tip strain field in wood using a digital image correlation technique. J Mater Sci 35:755–765
Raffel M, Willert CE, Wereley ST, Kompenhans J (2007) Particle image velocimetry, a practical guide, 2nd edn. Springer, Heidelberg/New York
Holmgren S-E, Svensson BA, Grandin PA, Lundberg B (2008) An encapsulated split Hopkinson pressure bar for testing of wood at elevated strain rate, temperature, and pressure. Exp Tech 32(5):44–50
Product-manual for Davis 8.0. LaVision GmbH, Göttingren, Germany (2012)
Keunecke D, Sonderegger W, Pereteanu K, Lüthi T, Niemz P (2007) Determination of Young’s shear moduli of common yew and Norway spruce by means of ultrasonic waves. Wood Sci Technol 41:309–327
Kolsky H (1963) Stress waves in solids. Dover Publications, New York
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2014 The Society for Experimental Mechanics, Inc.
About this paper
Cite this paper
Moilanen, C.S., Saarenrinne, P., Engberg, B.A., Björkqvist, T. (2014). Image Based Local Strain Measurement of Wood. In: Jin, H., Sciammarella, C., Yoshida, S., Lamberti, L. (eds) Advancement of Optical Methods in Experimental Mechanics, Volume 3. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-00768-7_44
Download citation
DOI: https://doi.org/10.1007/978-3-319-00768-7_44
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-00767-0
Online ISBN: 978-3-319-00768-7
eBook Packages: EngineeringEngineering (R0)