Effect of Ultrasound on Mechanical Properties of Walnut

Walnut mechanical properties are an appropriate criterion for designing and adjusting the various parts of harvesting machines that are in contact with walnut. In this research, the aim is to find the effect of ultrasound factors on walnut mechanical properties to reduce walnut rupture force and energy. Walnuts were treated with three ultrasound time duration (5, 10, and 15 min) and three ultrasound bath temperatures (20, 35, and 50 ºC). After the walnuts were treated by ultrasound factors, wet and dried walnut samples were loaded at three loading speeds (0.5, 1.5, 2.5 mm/s) along width and length direction for determination of mechanical properties. Regarding the ANOVA results, the ultrasound time factor had the most effect on the rupture force, energy, and toughness. Results showed walnut ultrasound-treated samples had minimum rupture force and energy. Also, rupture force, required energy, and toughness decreased with increasing ultrasound bath temperature and the ultrasound time duration. The minimum walnut rupture force was obtained at 62.7 N in 25 min ultrasound time duration, 50 ºC bath temperature, 1.5 mm/s loading speed, and width loading direction for wet walnut sample.