木材干縮力平衡測試系統(tǒng)的研制1)

劉建霞　王喜明　慕厚春　吳向文

(內(nèi)蒙古農(nóng)業(yè)大學(xué)，呼和浩特，010018)

?

木材干縮力平衡測試系統(tǒng)的研制1)

劉建霞王喜明慕厚春吳向文

(內(nèi)蒙古農(nóng)業(yè)大學(xué)，呼和浩特，010018)

為了同步測試木材在干燥過程中的干縮力、質(zhì)量變化和干縮量，研制了木材干縮力測試系統(tǒng)。系統(tǒng)利用了木材干燥過程中水分散失導(dǎo)致外部干縮力變化的關(guān)系，設(shè)計(jì)了基于溫濕度試驗(yàn)箱的一體化控溫控濕力學(xué)測試系統(tǒng)，更好地研究和探索了木材在干燥過程中的干縮力、質(zhì)量變化和干縮量之間的關(guān)系。測試結(jié)果表明：用此設(shè)備可實(shí)時(shí)檢測干縮力、質(zhì)量變化和干縮量的平衡情況，初步調(diào)控了木材干縮不均導(dǎo)致干燥過程中的開裂、翹曲變形等缺陷。

木材；干縮力；干縮量；力學(xué)測試系統(tǒng)

The integrated mechanics testing system was developed to synchronously determine the stress and shrinkage of drying, and the quality changes of specimens during the drying process. The system was reconstructed from the temperature and humidity chamber, and developed in view of the relation of the overall drying stress and moisture loss in the process of drying. The new testing system was benefit to explore the relationship between drying stress, drying shrinkage and quality changes. By testing, the system could measure the drying stress, shrinkage and quality changes synchronously, and regulate and control the drying defects including checks and warps deformation by the shrinkage heterogeneity.

木材干縮直接影響木材的干燥質(zhì)量，木材在干燥過程中因水分散失發(fā)生尺寸上的減小而產(chǎn)生干縮力。木材在干燥的過程中，表層的水分首先蒸發(fā)，當(dāng)其質(zhì)量變化降至纖維飽和點(diǎn)以下時(shí)，表層開始產(chǎn)生收縮；而相鄰內(nèi)層的質(zhì)量仍高于纖維飽和點(diǎn)未收縮。在干燥前期，外層受拉應(yīng)力，內(nèi)層受壓應(yīng)力；隨著干燥的進(jìn)行，外層逐漸由受拉應(yīng)力變?yōu)槭軌簯?yīng)力，而內(nèi)層則變?yōu)槭芾瓚?yīng)力。這種應(yīng)力直接導(dǎo)致初期端裂、表裂和后期內(nèi)裂，影響木材和木制品的尺寸、形狀和結(jié)構(gòu)的穩(wěn)定性[1-4]。因此，準(zhǔn)確、快速、智能地測量干燥過程中木材的干縮對于提高木材科研水平和木材干燥生產(chǎn)質(zhì)量、效率具有重要意義。了解木材的干縮力與質(zhì)量變化、干縮量之間的關(guān)系，對研究木材干燥工藝、木材的合理加工和利用意義重大。……