含水率與溫度對於柳杉潛變行為之影響

Abstract

本研究針對柳杉小型實木試片之含水率進行調控及測量，進行不同試驗溫度固定載重之短期潛變試驗，比較含水率及溫度分別對於木材短期潛變應變之影響，由試驗結果得，在試驗過程中，水分的變動會使木材出現額外的變形，整體試驗結果，以環境平衡含水率為分界，逐漸趨向於2群，透過等時線分析結果，可得到木材在固定載重之下，其潛變應變受到含水率的影響大於溫度，當木材脫濕時，會造成應變的跳升，於多因子分析結果中，可以印證機械吸附為非時變性的現象。於本研究中將木材因為含水率變化產生的額外應變以獨立的因子進行模擬，將木材的潛變行為總應變分成瞬間應變、潛變應變、機械吸附現象產生之應變3個部分進行疊加擬合，所得出的擬合曲線與以TTSP將短期潛變試驗結果進行平移之潛變主曲線相關度高，可作為木材含水率加入潛變主曲線擬合之參考模式。

In this study, to investigate the effects of moisture content and temperature on the creep behavior of Japanese cedar, a series of short-term creep tests under various conditions has been conducted. According to the short-term creep test results of groups of different temperatures and moisture contents, the changing of moisture contents affected the creep strain more obvious than the changing of temperatures did. Desorption of water would cause the deformation increased. Testing results have been departed into 2 cases and, one of them was the groups that moisture contents of specimens were lower than the equilibrium moisture content of the ambient environment and the other was that moisture contents of specimens were higher than the equilibrium moisture contents of the ambient environment. In addition, the analysis of isochrones indicated the same results as the previous researches that the mechano-sorptive behavior is time-independence. The effect of moisture contents of wood specimens had been considered being added into the model of explaining the creep behavior of wood in this study. Moreover, the total creep strain of wood could be explained using a proposed model separated into 3 parts: instantaneous strain, creep strain, and strain induced by mechano-sorptive behavior. The fitting results demonstrated that the proposed model has high correlation to the creep master curves constructed by time-temperature superposition principle (TTSP). It is possible to use this model to predict to creep behavior of wood under the situation of moisture content changing.