聲發(fā)射技術(shù)在木材受力破壞過程檢測中的應(yīng)用

利用聲發(fā)射測試和力學(xué)實(shí)驗(yàn)相結(jié)合的方法，研究了東北常見的闊葉材樹種山楊在動(dòng)態(tài)載荷下的聲發(fā)射演變過程；結(jié)合木材粘彈性特點(diǎn)，通過聲發(fā)射參數(shù)分析研究該樹種在不同受力階段試件的聲發(fā)射特點(diǎn)。最后得出以下結(jié)論：（1）徑向紋理不通直的試件比通直的聲發(fā)射撞擊數(shù)要多，而且增加的趨勢較快，但是在試件斷裂前，聲發(fā)射撞擊數(shù)相差不大。（2）在試件斷裂前，振鈴計(jì)數(shù)和能量的變化小，局部極值出現(xiàn)在試件斷裂附近，試件斷裂后出現(xiàn)更多地局部極值；載荷急劇下降的點(diǎn)有振鈴計(jì)數(shù)的急劇降低和能量的急劇升高與之對應(yīng)。（3）隨著時(shí)間和載荷的變化，聲發(fā)射幅值參數(shù)值和撞擊總數(shù)增加快慢可以體現(xiàn)材料在受力條件下的完全彈性、粘彈性和粘性三種狀態(tài)。（4）聲發(fā)射信號的聲發(fā)射率和上升時(shí)間可以預(yù)測材料開始斷裂進(jìn)入危險(xiǎn)期的和材料大量纖維斷裂進(jìn)入嚴(yán)重危險(xiǎn)期的兩個(gè)“臨界點(diǎn)”。
關(guān)鍵詞：無損檢測，臨界點(diǎn)，聲發(fā)射，動(dòng)態(tài)載荷，參數(shù)分析

Application of acoustic emission technology in damage process
?testing of wood under the dynamic loads
SUN Jian-ping?? WANG Feng-hu
（Key Laboratory of Bio-based Material Science and Technology of Ministry of Education,
?Northeast Forestry University? Harbin 150040）

Abstract: The acoustic emission (AE) evolution process of David poplar (Poulus davidiana) samples was investigated by combining the two methods of mechanics testing and acoustic emission technique when the samples were imposed to the dynamic load. By analysis of AE parameters and the elastic-viscosity of wood, the AE characterization under different loads was explored. The results are: (1) Samples without straight radial grain have more hits and increasing faster than samples with straight radial grain, but before fracture hits count is not much different. (2) Before fracture ring count and energy have a little change and local maximum appears near fracture; After fracture there are much more local maximums and rapid drop of load is corresponded with rapid drop of ring count and rapid rise of energy. (3) With the time and load changing, the increase speed of AE cumulative hits and AE cumulative energy can exactly identify complete elasticity, elastic-viscosity and complete viscosity of wood, which of the three stages are the most important feature of wood under load. (4) The AE rate and rising time can be employed to predict two “critical points” of wood fracture damage. The first point means the material is in the state of slight danger and the second point means the material is in the state of serious danger.
Keywords: Non-destructive testing; Critical point; Acoustic emission; Dynamic loads; Parameter analysis