Nourain Jamal, Ying Yi-bin, Wang Jian-ping, Rao Xiu-qin, Yu Chao-gang
Department of Biosystems Engineering, Institute of Modern Agricultural Equipment and Automation, Zhejiang University, Hangzhou 310029, China.
J Zhejiang Univ Sci B. 2005 Jun;6(6):483-90. doi: 10.1631/jzus.2005.B0483.
The "Huang gua" melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.
对“黄瓜”甜瓜的物理特性进行了测量，包括硬度和静态弹性模量。水果和蔬菜的振动特性由其弹性模量（硬度）、质量和几何形状决定。因此，有可能根据其振动特性来评估水果和蔬菜的硬度。建议通过分析水果的振动响应来无损测量其弹性特性（硬度）。脉冲响应法常用于测量水果的硬度。使用三种类型的球（木质、钢质和橡胶质）对水果进行激励，并通过加速度计检测振动。使用英斯特朗设备测量甜瓜果肉内部、中间和外部的静态弹性模量。采用有限元（FE）技术确定所选测量传感器的最佳激励位置，并分析水果的振型。发现了四种类型的振型（扭转或弯曲振型、第一类、第二类球形振型和呼吸振型）。有限元模拟结果与实验结果吻合良好。硬度与共振频率之间（r2 = 0.91）以及共振频率与刚度因子之间（r2 = 0.74）存在相关性。提出了水果激励和响应测量的最佳位置和合适方向。
