International Journal of Advance Agricultural Research
ISSN: 2053-1265
Vol. 7(3), pp. 78-88, April 2019

Mechanical analysis and parameter design of walnut flexible shell-breaking equipment

Xiaoming Wang1, Changhe Li1*, Ji Che2, Mingzheng Liu1, Lianxing Gao3, Xinping Li4, Xiangdong Liu1 and
Yanbin Zhang1

1School of Mechanical and Automotive Engineering, Qingdao University of Technology, 266520 Qingdao, China.
2Xinjiang jiangning Light Industry Machinery Engineering Technology Co., Ltd. 830006 Urumqi, China.
3College of engineering, Shenyang Agricultural Uinversity, 110866 Shenyang, China.
4College of Agricultural Equipment Engineering, Henan University of Science and Technology, 471003 Luoyang, China.
5Xin Jiang University Institute of Science and Technology, 843000 Aksu, China.

*To whom correspondence should be addressed. E-mail:,

Received 19 February, 2019; Received in revised form 20 March, 2019; Accepted 25 March, 2019.


Flexible-belt, Walnut, Stress analysis, Critical force, Crack extension.

Walnut is a kind of nut with high nutritional value, but there is still a lack of research on using mechanical method to crack the shell. To complement the process of breaking walnut shells with mechanical approaches, a walnut shell-kernel separation device was designed. Based on the flexible-belt shearing extrusion breakage system, conditions for the walnut entering the extrusion space as well as the extruding-in angle (α0) and the extrusion angle (α) of the walnut during breakage were assessed theoretically and empirically. Results show that when 0°<α0≤44°, the walnut can enter the extrusion space. When the upper working belt (that is, the extruding roller) is 23 mm away from the lower working belt, walnut shells crack when α is 20° and break when α is 15°. A mathematical model of extrusion force and shear force on walnut shells by upper and lower working belts was established theoretically. Stiffness at different positions of the walnut shell was analyzed by the theory of elastic mechanics, which contributed the critical force of instability of different positions.Conditions for crack extension after walnut shell breakage were analyzed and calculated by the fracture mechanics theory. The results demonstrated when the mean crack length is 20 mm, the critical external force for crack extension is 19.1 N.

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