【摘要】：竹材材性變異性大,快速檢測(cè)竹材的物理力學(xué)性能并對(duì)其進(jìn)行分級(jí)是竹產(chǎn)業(yè)發(fā)展的必然趨勢(shì)。毛竹(Phyllostachys pubescens)是本文的主要研究對(duì)象,比較分析毛竹高度方向上幾何尺寸的變化規(guī)律,對(duì)其進(jìn)行分段研究。通過壓痕法快速檢測(cè)毛竹的壓痕強(qiáng)度,探究壓痕強(qiáng)度與竹材基本密度之間的相關(guān)性,驗(yàn)證能否用壓痕法快速檢測(cè)竹材的密度。分析不同壓痕強(qiáng)度等級(jí)竹材維管束的微觀結(jié)構(gòu)特征和微纖絲角的大小,探討維管束結(jié)構(gòu)和微纖絲角的大小對(duì)竹材物理力學(xué)性能的影響機(jī)制。論文的主要研究結(jié)論如下:(1)以0.9 m及枝下高作為分割點(diǎn),將毛竹分成三段,即:根部(砍伐處-0.9 m)、主干(0.9 m-枝下高)和稍部;并且0.9 m處的徑級(jí)越大,毛竹的鮮重及體積越大。把0.9m處的徑級(jí)作為主要指標(biāo),將0.9 m處的徑級(jí)分成4個(gè)等級(jí)即:低徑級(jí):φ≤10 cm;中徑級(jí):10 cmφ≤12 cm;中高徑級(jí):12 cmφ≤14 cm;高徑級(jí):φ≥14 cm。(2)參照國內(nèi)外標(biāo)準(zhǔn),根據(jù)預(yù)試驗(yàn)的結(jié)果,在方便加工、確保有效測(cè)試次數(shù)、提高工作效率,避免試驗(yàn)過程出現(xiàn)偏心、受力不均等造成的劈裂現(xiàn)象的情況下,最終確定竹環(huán)的長度為20±0.5 mm,壓輥直徑為15 mm,壓頭形狀是“十字型”,壓入位移3 mm,確定竹環(huán)的壓痕強(qiáng)度。(3)毛竹壓痕強(qiáng)度與基本密度呈線性相關(guān)(R~2=0.8794)。毛竹株內(nèi)壓痕強(qiáng)度和基本密度差異性不顯著,毛竹間壓痕強(qiáng)度與基本密度差異性極顯著。因此,用壓痕法快速檢測(cè)鮮竹的壓痕強(qiáng)度是可行的,通過壓痕強(qiáng)度與基本密度的關(guān)系式:y=0.0188x+0.1113可計(jì)算出毛竹的基本密度。參照AITC Grading Handbook for Laminating Lunber中E-rated Grades的分級(jí)方法,將壓痕強(qiáng)度分成四個(gè)等級(jí),根據(jù)每個(gè)等級(jí)壓痕強(qiáng)度范圍,可推測(cè)出毛竹基本密度的范圍,為毛竹的定向利用提供數(shù)據(jù)支持。(4)不同壓痕強(qiáng)度等級(jí)竹材的基本密度與順紋抗壓強(qiáng)度、抗彎彈性模量和抗彎強(qiáng)度都呈正相關(guān),相關(guān)性顯著。壓痕強(qiáng)度與順紋抗壓強(qiáng)度、抗彎強(qiáng)度和抗彎彈性模量呈正相關(guān),相關(guān)性顯著。因此,利用壓痕法快速檢測(cè)鮮竹的力學(xué)性能,并對(duì)其進(jìn)行分級(jí)是合理可行的。(5)維管束面積和纖維鞘面積隨竹材基本密度的增加而增大,最大密度(0.71 g/cm~3)竹材的內(nèi)方纖維鞘面積是最小密度(0.46 g/cm~3)竹材的3倍還多。不同密度竹材的內(nèi)方纖維鞘的長、短軸隨著密度的增加而增大。當(dāng)密度大于0.61 g/cm~3時(shí),隨著密度增加纖維鞘長軸增加緩慢,纖維之間排列的密實(shí)程度也在增加,單根纖維顯得小而密實(shí),毛竹的力學(xué)性能隨之增大。因此竹材維管束纖維鞘內(nèi)的密實(shí)纖維決定著竹材的密度和力學(xué)性能。從竹青到竹黃毛竹微纖絲角的變化規(guī)律不明顯,差異不顯著。毛竹微纖絲角與壓痕強(qiáng)度、抗彎強(qiáng)度和模量有顯著的相關(guān)性。
[Abstract]:The variability of bamboo properties is great. It is an inevitable trend for the development of bamboo industry to quickly detect and classify the physical and mechanical properties of bamboo. Phyllostachys pubescens (Phyllostachys pubescens) is the main research object of this paper. The variation of geometric size in the height direction of Phyllostachys pubescens is compared and analyzed, and the segmented study is carried out. The indentation strength of Phyllostachys pubescens was detected quickly by indentation method, and the correlation between indentation strength and basic density of bamboo was explored to verify whether the indentation method could be used to detect the density of bamboo quickly. The microstructure characteristics and microfibril angle of bamboo vascular bundles with different indentation strength grades were analyzed, and the influence mechanism of vascular bundles structure and microfibrillar angle on the physical and mechanical properties of bamboo was discussed. The main conclusions of this paper are as follows: (1) using 0.9m and subbranch height as the dividing point, Phyllostachys pubescens is divided into three segments: root (cutting site-0.9 m), trunk (0.9m-branch height) and slightly); And the larger the diameter grade at 0.9 m, the larger the fresh weight and volume of Phyllostachys pubescens. Taking the diameter grade at 0.9m as the main index, the diameter grade at 0.9m is divided into four grades: low diameter grade: 蠁 鈮，

本文編號(hào)：2495704