Mechanical damage of the horticultural produce during postharvest transportation is an important criteria for fruit sorting and grading. The vibration during transportation has a significant effect on the mechanical damage of the fruit. In this study, the effect of different vibration spectrum shapes on mechanical damage of Huangguan pear (Pyrus bretschneideri Rehd, cv. Huangguan) was investigated. Four acceleration spectrums (spectrum Ⅰ, spectrum Ⅱ, spectrum Ⅲ, and spectrum Ⅳ) with same vibration level and different shapes were evaluated. The power spectral density (PSD) amplitude in the resonant region was in the order of spectrum Ⅰ > spectrum Ⅱ> spectrum Ⅲ > spectrum Ⅳ. The change in appearance, physiological properties (respiratory rate and weight loss), and mechanical properties (firmness and elastic modulus) of the pears were evaluated after vibration. Results showed that vibration resulted in quality deterioration of pear. Compared to the control group, respiratory rate and weight loss of the pears increased while the flesh firmness and elastic modulus of the pears decreased after vibration. The mechanical damage became more serious as stacked position increased. The effect of spectrum shape on the mechanical damage of pear was also obvious. Different degree of mechanical damage was observed under spectrum Ⅰ, spectrum Ⅱ, spectrum Ⅲ, and spectrum Ⅳ vibration. The higher the acceleration PSD in resonant region, the more serious the mechanical damage of pear. In comparison with the control group, pear under spectrum Ⅰ effect showed the most mechanical damage and the pear under spectrum Ⅳ effect had the minimum mechanical damage. Furthermore, $S-G_{rms}$ curves (damage area - vibration level) showed a clockwise rotation from spectrum Ⅰ to Ⅲ vibration. This study reveals the mechanical damage mechanism of pears based on acceleration spectrum shape and provides guidance for postharvest loss reduction using simulated test.

园艺产品在采后运输过程中的机械损伤是水果分选和分级的重要标准。运输过程中的振动对果实的机械损伤有显着影响。在这项研究中，研究了不同振动频谱形状对黄冠梨（Pyrus bretschneideri Rehd, cv. Huangguan）机械损伤的影响。评估了具有相同振动水平和不同形状的四个加速度谱（谱Ⅰ、谱Ⅱ、谱Ⅲ和谱Ⅳ）。谐振区的功率谱密度(PSD)幅值顺序为谱Ⅰ>谱Ⅱ>谱Ⅲ>谱Ⅳ。外观、生理特性（呼吸频率和体重减轻）的变化，振动后评估梨的机械性能（硬度和弹性模量）。结果表明，振动导致梨品质变差。与对照组相比，振动后梨的呼吸频率和重量减轻增加，而梨的果肉硬度和弹性模量降低。随着堆叠位置的增加，机械损伤变得更加严重。光谱形状对梨机械损伤的影响也很明显。在谱Ⅰ、谱Ⅱ、谱Ⅲ、谱Ⅳ振动下观察到不同程度的机械损伤。共振区加速度PSD越高，梨的机械损伤越严重。与对照组相比，光谱Ⅰ作用下的梨机械损伤最大，光谱Ⅳ作用下的梨机械损伤最小。此外，$\mathrm{小号}-G_{r米秒}$曲线(损伤面积-振幅)由谱Ⅰ到谱Ⅲ呈顺时针旋转。该研究基于加速度谱形状揭示了梨的机械损伤机制，并通过模拟试验为减少采后损失提供了指导。