李允中臺灣大學:生物產業機電工程學研究所王聖讓Wang, Sheng-JangSheng-JangWang2010-05-052018-07-102010-05-052018-07-102009U0001-1908200914513900http://ntur.lib.ntu.edu.tw//handle/246246/180291水果經採收後在室溫中容易造成軟化喪失商業價值，若要長期存放勢必需要儲藏在較低溫的環境下，以保持其物理性質，利用彈性性質建立水果品質非破壞檢測指標是工程重要的研究課題。本論文探討珍珠拔品種番石榴在儲藏時彈性性質的改變，以ASABE標準平板壓縮試驗及敲擊試驗，檢測在5°C、10°C、15°C與室溫四種溫度下，儲藏期間果實的敲擊振動共振頻率、振動阻尼比和彈性模數的變化，並以COMSOL軟體模擬珍珠拔共振時的振形與共振頻率，再利用巢狀試驗設計來分析儲藏溫度與時間對以上彈性性質的影響。軟體模擬則先將由雷射掃描器掃出的果實外型匯入程式中，再以敲擊試驗測得的彈性模數作為其材料特性，利用COMSOL的三維結構模組計算樣本的振動特徵頻率，並由文獻中彈性球體的振形來判斷共振頻率。模擬的結果除了可以得到與敲擊試驗所得實驗值相近的S20共振頻率，還能找出實驗不易觀察到的S30與 S40共振頻率。實驗結果顯示珍珠拔敲擊振動的共振頻率與平板壓縮及敲擊兩種方法所測得的彈性模數皆隨著儲藏天數的增加而降低，且三者的趨勢相近。敲擊試驗所計算出的振動阻尼比則會隨著儲藏時間上升，並且上升的速率隨儲藏溫度降低而變為緩慢。將此振動阻尼比以巢狀試驗設計分析顯示儲藏溫度及時間的影響皆為顯著，相較於敲擊振動的共振頻率，振動阻尼比的變化較能不受樣本個體差異的影響，更適合做為珍珠拔物理性質的非破壞檢測的指標。Since harvested fruit easily softens and loses its market value at room temperature, a low-temperature environment is required to preserve the fruit’s firmness if a longer shelf life is desired. Thus using elastic property to establish a nondestructive quality evaluation index is one of the important research issues of biological engineering. This study aims at investigating the variations of the elastic properties of stored “Jen-Ju Bar” a most popular variety of guava in Taiwan. The ASABE standard parallel plate compression test and the impulse response test were used to measure the variation of impulse vibrating resonant frequencies, vibrating damping ratios and elastic moduli of the fruit stored at 5°C, 10°C, 15°C and room temperature. Besides, COMSOL Multiphysics was used to simulate the fruit’s vibration modes and resonant frequencies during resonating. Nested experimental design was adopted to analyze the effects of storage duration and temperature on the above elastic properties. Model geometries of fruits for finite elements simulation were constructed using surface topology scanning. Then, the elastic moduli measured in the impulse response test were taken for the material properties. The 3-D structural mode was then used to calculate the samples’ vibrating eigenfrequencies, and the resonant frequencies were determined based on the vibration modes of elastic sphere in literature. The results of the simulation showed that the resonant frequencies of S20 mode resembled the values measured by impulse response test; in addition, the resonant frequencies of S30 mode and S40 mode, rarely observed in experiments, were found. The results of the experiments showed that the impulse vibrating resonant frequencies and the elastic moduli measured by parallel plate compression test and the impulse response test decreased as the storage duration lengthened, and these three showed a similar trend. Vibrating damping ratios measured by impulse response test increased as the storage duration lengthened, with a slower rate of rising at a low storage temperature than at a high storage temperature. The nested experimental design analyses of vibrating damping ratios showed significant effects of both storage temperature and duration. Compared with impulse vibrating resonant frequency, the variation of vibrating damping ratio was less affected by individual sample differences, thus more appropriate for a nondestructive index to evaluate the physical properties of “Jen-Ju Bar”.致謝 i要 iiBSTRACT iii錄 v目錄 viii目錄 xi一章 前言與研究目的 1.1前言 1.2 研究目的 2二章 文獻探討 3.1 珍珠拔種番石榴 3.1.1 珍珠拔果實的呼吸形式 3.1.2 珍珠拔果實的後熟行為及組成分變化 3.1.3 珍珠拔果實的低溫儲藏 4.2 振動特性應用於農產品檢測 5.2.1 連續振動檢測 5.2.2 敲擊檢測的頻域主頻率分析 5.2.3 敲擊檢測的頻域主頻帶分析 7.2.4 敲擊檢測的阻尼比分析 8.3 有限元素分析應用於水果品質檢測 9.4 訊號處理 10三章 理論分析 12.1 頻譜分析原理 12.2 頻譜圖轉換 13.3 彈性球體振動理論 13.3.1 均質彈性球體的彈性模數 15.3.2 均質彈性球體的振形 16.4 振動阻尼比(Damping ratio) 19四章 實驗設備與方法 21.1 實驗流程 22.2 珍珠拔的物理性質 23.2.1 平均重量量測法 23.2.2 體積量測方法 23.3 低溫儲藏設備 23.4 敲擊實驗 24.4.1 振動訊號的感測 25.4.2 訊號擷取與分析 27.5 平板壓縮試驗 30.6 模擬方法 33.6.1 模擬軟體 33.6.2 三維雷射掃描器 34.6.3 模擬設定 35五章 結果與討論 37.1 平板壓縮試驗結果 37.2 敲擊振動試驗結果 40.2.1 振動的共振頻率與阻尼比 40.2.2 計算彈性模數 46.3 珍珠拔果實大小不同所造成的影響 49.4 平板壓縮試驗與敲擊試驗測得之彈性模數關係 51.5 軟體模擬結果 55.6 巢狀試驗設計分析結果 60.7 珍珠拔的劣化情形 62六章 結論 63考文獻 64錄 69application/pdf2237485 bytesapplication/pdfen-US低溫儲藏共振頻率阻尼比彈性模數Low-temperature storage,Resonant frequencyDamping ratioElastic modulusthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/180291/1/ntu-98-R96631011-1.pdf