| Macadamia nuts have been successfully cultivated as crops in Australia and the USA and were introduced to China for experimental planting since 1980s. It is rich in fat and protein. It can prevent a variety of cardiovascular and cerebrovascular diseases and has a very good effect on lowering cholesterol. The current production is well over 700000 tones annually in China, but processing technology for Macadamia nuts is undeveloped, especially breaking shell. So there is important significance that carry out research on macadamia nuts shelled.The following work is carried out in this paper.(1) Orthogonal design was-carried out for optimizing technical parameters of breaking Macadamia nut shell. The loading rate, loading directions and moisture content of Macadamia nut shell were selected as factors and intergrated kernel rate of Macadamia nuts was selected as evaluation index in this experiment. Macadamia nuts in different moisture content were selected as test samples, moisture content of which was obtained by hot air drying in 55℃. Experiment of breaking Macadamia nut was carried out in electronic tensile testing machine. The results indicate that moisture content of Macadamia nut shell and loading direction have more significant effect on intergrated kernel rate than loading rate. The most optimal combination of technics parameters is that loading rate, loading direction and moisture content of Macadamia nut shell are 45mm/min, horizontal,6%～9%, respectively. In this case, the highest intergrated kernel rate of Macadamia nut is 93%.(2) The compression test was carried out in the moisture content 6%～9% of Macadamia nut shell and loading rate 45mm/min. Average shelled forces are 1018N,2274N,1173N in hilum, width and horizontal, respectively. The elastic modulus of Macadamia nut shell that was calculated by the Hertz contact stress theory are 32.24Mpa,68.63Mpa,39.65Mpa in hilum, width and horizontal, respectively. The results indicate that Macadamia nut is anisotropic. Compression capability is the strongest in width and the weakest in horizontal. The biggest shelled force are 2016 N in horizontal, therefore the shelled force should not be less than 2500N for ensuring that all nuts are cracked. The loaded force should be in horizontal when Macadamia nut shell was crushed.(3) Accord to Finite element analysis diagram of Macadamia nuts in the three loading directions, it can be known that cracks are easy to emerge and expand in horizontal. It is also horizontal which is most appropriate for breaking Macadamia nut shell. The simulation results are consistent with the results analysis of experiment.(4) The parameters were obtained by experiment. The macadamia nut shell-breaking machine was designed according to parameters.(5) The static analysis of shaft is carried out. The stress of shaft was changed range of 0-87MPa, most of it was under50Mpa. The maximal stress of main shaft focused on the shaft shoulder matched with bearing, it caused a large deformation when installing rotor, the value of deformation was 37.9um. Z-coordinate had the relatively large deformation.(6) Modal of shaft and hammer were analyzed. The first order natural frequency of main shaft was 4542 Hz respectively, it is dramatically higher than the excitation frequency of shaft and has good dynamic characteristics.(7) The design was carried out in the macadamia nut shell-breaking machine.93% of Macadamia nut was breaked and the highest intergrated kernel rate of Macadamia nut is 72%.In summary, to improve the intergrated kernel rate of Macadamia nut, the macadamia nut shell-breaking machine was designed accord to parameters that were obtained by experiment. This macadamia nut shell-breaking machine has good dynamic and static performance and work performance. The research on Macadamia broken shell machine provides technology for Macadamia nut processing, and it will promote the development of the macadamia nut industry. |
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