Effect of residual stress distribution in a log on lumber warp due to sawing: a numerical simulation based on the beam t
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Effect of residual stress distribution in a log on lumber warp due to sawing: a numerical simulation based on the beam theory Hiroyuki Yamamoto1 · Miyuki Matsuo‑Ueda1 · Tsubasa Tsunezumi1 · Masato Yoshida1 · Kana Yamashita2 · Yukari Matsumura2 · Yosuke Matsuda2 · Yuji Ikami2 Received: 22 May 2020 / Accepted: 21 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract When a squared lumber such as a beam and/or a bearer is produced from a log, they often show warps. Warp of the sawn lumber is practically not serious when the pith is located at the center of the cross-section, as in the lumber-with-pith, but causes serious problems in the lumber-without-pith. In the present study, a mechanical model was introduced to explain lumber warping based on beam theory, and a numerical simulation using the introduced model examined how the magnitude and type of the residual stress distribution would affect the warps of the lumbers sawn from the four-sided cants with various sizes and shapes in their cross-sections, and how the different sawing patterns would affect the production efficiency of the straight lumber, which is manufactured from the four-sided cant by quartering and subsequent correction sawing. As a result, the following suggestions were obtained. The warp of the sawn lumber is affected by the type and the magnitude of the inherent strain distribution in the log and furthermore by the cross-sectional shape and/ or size of the four-sided cant. Production efficiency of the straight lumbers differs depending on the sawing patterns. In the present study, two types of sawing patterns (a) and (b) were assumed. The sawing pattern (a) gave better production efficiency than the sawing pattern (b) in the sense that straight lumbers are produced with higher volumes as well as with less variation in dimension of the cross-section.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s0022 6-020-01240-y) contains supplementary material, which is available to authorized users. * Hiroyuki Yamamoto [email protected]‑u.ac.jp 1
Department of Forest and Environmental Resources Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464‑8601, Japan
2
Department of Wood Properties and Processing, Forestry and Forest Products Research Institute, 1 Mastunosato, Tsukuba 305‑8687, Japan
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Wood Science and Technology
Introduction When a long-sized lumber, such as a beam or a bearer, is produced from the felled log by using a band saw, it often exhibits bow, crook, twist and/or other warps (Kübler 1987; Archer 1986; Maeglin et al. 1985; Maeglin 1987; Johansson et al. 1994; Perstorper et al. 1995a, b; Yang 2005; Okuyama et al. 2004; Cassens and Serrano 2004; Ormarsson et al. 2009; Johansson and Ormarsson 2009). Warp of the sawn lumber is not serious when the pith is centered on the cross-section of it, as in a lumber-with-pith. However, in a lumber-without-pith, the warp becomes more severe (Ikami et al.
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