CAJ | 학술논문

【目的】根据悬臂板一阶弯曲振形给出动态测试木材泊松比的方法，测试西加云杉木材试件径切板顺纹、横纹的泊松比和横切面横纹试件的泊松比；对西加云杉木材试件的测试结果，分析用悬臂板试件测量一阶弯曲频率，代入到悬臂梁的公式推算出弹性模量的精度；同时用低碳钢板的动态测试试验来验证动态测试木材泊松比方法的正确性，为在木建筑、家具、木材加工等行业中对木材力学性能测定研究工作提供借鉴。【方法】根据动力学原理，利用 YD-28A 型四通道动态电阻应变计和 CRAS 振动及动态信号采集分析系统等测试仪器，以敲击方式激励悬臂西加云杉木材、低碳钢试件的自由振动，通过滤波处理保留其基频振动，记录并显示基频振动的横向应变和纵向应变的衰减振波曲线，并从同一时刻的横向应变峰值与纵向应变峰值比值得泊松比。【结果】横向应变振波曲线的正(负)峰值对应于纵向应变振波曲线的负(正)峰值，说明横向应变振波曲线与纵向应变振波曲线的相位差为180°或横向应变与纵向应变是反向的；通过低碳钢板验证试验，从其振波曲线第一通道和第二通道读出峰峰值，计算它们的比值后取平均值，得低碳钢泊松比的测量值μ=0.28，符合其规范值为0.25～0.28的要求；西加云杉木材的径切面顺纹泊松比μLR与径切面横纹泊松比μRL测量值之比为10.6，即径切面顺纹泊松比比径切面横纹泊松比大一个数量级；用悬臂梁公式推算的弹性模量值比实际弹性模量值偏小0.7%。【结论】根据悬臂板的一阶弯曲振形测试泊松比的动态方法是行之有效的，具有快速、简便、精度高的优点；西加云杉试件的径切面顺纹泊松比比径切面横纹泊松比大一个数量级，体现了木材的各向异性；用悬臂板云杉试件测得的一阶固有频率，代入到悬臂梁理论公式推算的弹性模量值具有足够精度。【目的】根據懸臂闆一階彎麯振形給齣動態測試木材泊鬆比的方法，測試西加雲杉木材試件徑切闆順紋、橫紋的泊鬆比和橫切麵橫紋試件的泊鬆比；對西加雲杉木材試件的測試結果，分析用懸臂闆試件測量一階彎麯頻率，代入到懸臂樑的公式推算齣彈性模量的精度；同時用低碳鋼闆的動態測試試驗來驗證動態測試木材泊鬆比方法的正確性，為在木建築、傢具、木材加工等行業中對木材力學性能測定研究工作提供藉鑒。【方法】根據動力學原理，利用 YD-28A 型四通道動態電阻應變計和 CRAS 振動及動態信號採集分析繫統等測試儀器，以敲擊方式激勵懸臂西加雲杉木材、低碳鋼試件的自由振動，通過濾波處理保留其基頻振動，記錄併顯示基頻振動的橫嚮應變和縱嚮應變的衰減振波麯線，併從同一時刻的橫嚮應變峰值與縱嚮應變峰值比值得泊鬆比。【結果】橫嚮應變振波麯線的正(負)峰值對應于縱嚮應變振波麯線的負(正)峰值，說明橫嚮應變振波麯線與縱嚮應變振波麯線的相位差為180°或橫嚮應變與縱嚮應變是反嚮的；通過低碳鋼闆驗證試驗，從其振波麯線第一通道和第二通道讀齣峰峰值，計算它們的比值後取平均值，得低碳鋼泊鬆比的測量值μ=0.28，符閤其規範值為0.25～0.28的要求；西加雲杉木材的徑切麵順紋泊鬆比μLR與徑切麵橫紋泊鬆比μRL測量值之比為10.6，即徑切麵順紋泊鬆比比徑切麵橫紋泊鬆比大一箇數量級；用懸臂樑公式推算的彈性模量值比實際彈性模量值偏小0.7%。【結論】根據懸臂闆的一階彎麯振形測試泊鬆比的動態方法是行之有效的，具有快速、簡便、精度高的優點；西加雲杉試件的徑切麵順紋泊鬆比比徑切麵橫紋泊鬆比大一箇數量級，體現瞭木材的各嚮異性；用懸臂闆雲杉試件測得的一階固有頻率，代入到懸臂樑理論公式推算的彈性模量值具有足夠精度。
【목적】근거현비판일계만곡진형급출동태측시목재박송비적방법，측시서가운삼목재시건경절판순문、횡문적박송비화횡절면횡문시건적박송비；대서가운삼목재시건적측시결과，분석용현비판시건측량일계만곡빈솔，대입도현비량적공식추산출탄성모량적정도；동시용저탄강판적동태측시시험래험증동태측시목재박송비방법적정학성，위재목건축、가구、목재가공등행업중대목재역학성능측정연구공작제공차감。【방법】근거동역학원리，이용 YD-28A 형사통도동태전조응변계화 CRAS 진동급동태신호채집분석계통등측시의기，이고격방식격려현비서가운삼목재、저탄강시건적자유진동，통과려파처리보류기기빈진동，기록병현시기빈진동적횡향응변화종향응변적쇠감진파곡선，병종동일시각적횡향응변봉치여종향응변봉치비치득박송비。【결과】횡향응변진파곡선적정(부)봉치대응우종향응변진파곡선적부(정)봉치，설명횡향응변진파곡선여종향응변진파곡선적상위차위180°혹횡향응변여종향응변시반향적；통과저탄강판험증시험，종기진파곡선제일통도화제이통도독출봉봉치，계산타문적비치후취평균치，득저탄강박송비적측량치μ=0.28，부합기규범치위0.25～0.28적요구；서가운삼목재적경절면순문박송비μLR여경절면횡문박송비μRL측량치지비위10.6，즉경절면순문박송비비경절면횡문박송비대일개수량급；용현비량공식추산적탄성모량치비실제탄성모량치편소0.7%。【결론】근거현비판적일계만곡진형측시박송비적동태방법시행지유효적，구유쾌속、간편、정도고적우점；서가운삼시건적경절면순문박송비비경절면횡문박송비대일개수량급，체현료목재적각향이성；용현비판운삼시건측득적일계고유빈솔，대입도현비량이론공식추산적탄성모량치구유족구정도。
Objective]Based on the first bending mode shape of cantilever slab,this work proposed a method for dynamic testing of lumber Poisson’s ratio. In this paper,this method was used to measure Poisson’s ratio of Sitka Spruce ( Picea sitchensis) lumbers along and across grain on radial section and across grain on transverse section. Based on the testing results,the accuracy is analyzed with testing results of elastic modulus,calculated by substituting the first-order bending frequency,measured with cantilever plate specimen,into cantilever formula. Meanwhile,dynamic testing of mild steel plate was conducted to verify the correctness of the dynamic method of testing for lumber MOE.[Method]Based on the theory of structural dynamics,free vibration of cantilever specimen of Sitka Spruce lumbers and mild steel can be stimulated by knocking,and the fundamental vibration should be reserved by filtering processing. Additionally,decaying curve of oscillatory waves for transverse and longitudinal strain of fundamental vibration should also be recorded and displayed. Besides,Poisson’s ratio can be obtained from the ratio between transverse strain peak and longitudinal strain peak at the same time. [Result]It is seen that the positive ( negative) peak in oscillatory wave curve for transverse strain is corresponding to that for longitudinal strain,meaning that the phase difference,between oscillatory wave curves for transverse strain and longitudinal strain,is 180°,or that transverse strain and longitudinal strain are in reverse. According to verification test of mild steel,the average value should be taken after calculating the ratios between peak-to-peak values read from the first channel and the second channel in oscillatory wave curve. Finally,the measurement of Poisson’s ratio of low-carbon steel should be μ=0. 28 (the standard value is 0. 25 -0. 28). The ratio,between μLR,(Poisson’s ratio of grain at radial section) to μRL(Poisson’s ratio of stripe at radial section) is 10. 6,which means the Poisson’s ratio of grain at radial section is one order higher than that of stripe at radial section. Elastic modulus calculated with cantilever formula is 0. 7% smaller than the actual one.[Conclusion]The dynamic method for Poisson’s ratio measurement with the first-order bending mode shape of cantilever plate is proved to be feasible,efficient and highly accurate;Poisson’s ratio of grain at radial section of Sitka Spruce is one order higher than that of stripe at cross section,which represents the anisotropy of lumber; The elastic modulus is sufficiently accurate by substituting the first-order fixed frequency,measured with the cantilever plate of Sitka Spruce specimen,into cantilever theoretical equation.