| Forage grass is the basis and premise of animal husbandry development and is rich in nutrients.Among them,alfalfa and king grass can be directly used for livestock such as cattle,horses,sheep,etc.,and can also be modulated into silage to replace concentrate.The level of mechanized harvesting of pasture in China is relatively backward compared with that of European and American countries.Therefore,it is particularly important to study the harvesting,especially cutting technology and equipment of forages such as alfalfa and king grass.Due to the low cutting speed of the reciprocating cutter,it is easy to block when cutting the crop stalk,and the disc cutter requires a higher rotation speed,and the cutter has a short life.In this paper,based on the study of the mechanical properties of alfalfa and king grass,a flexible cutting test bench was developed for forage,and the prototype test was carried out.The results show that cutting speed was moderate,stubble quality was good,and blockage is not easy to occur.Firstly,the mechanical properties of shear,compression,bending and tensile properties of stalks of alfalfa and king grass were studied by universal testing machine.Experiments show that the mechanical properties of stalk are affected by the sampling position.The maximum average shear strength of alfalfa stalk was 6.55 MPa ± 0.79 MPa;the maximum average values of radial pressure and radial compressive strength were 38 N ± 3.56 N,1.3 MPa ± 0.165 Mpa;the maximum mean bending force and flexural modulus of elasticity were 6.84 N ± 1.05 N and38.34 MPa ± 4.46 MPa;The maximum mean values of shear force and shear strength per unit diameter at nodal sites of king grass stalk were 17.28 N/mm ± 1.07 N/mm and 1.79 MPa ± 0.21 MPa,the maximum mean values of axial compressive strength was 3.64 MPa ± 0.83 MPa,and the maximum mean values of compressive modulus of elasticity was 89.32 MPa ± 16.30 MPa;the maximum mean values of bending strength and flexural modulus of elasticity were 2.42 MPa ± 0.88 MPa,1344.71 MPa ± 503.75 MPa respectively.The maximum mean values of shear force and shear strength per unit diameter of nodeless stalk were 26 N/mm ± 2.4 N/mm and 3.92 MPa ± 0.58 MPa;the maximum mean values of axial compressive strength and compressive modulus of elasticity were 6.78 MPa ± 0.81 MPa and 172.45 MPa ± 40.61 MPa;the maximum mean values of bending strength and flexural modulus of elasticity were 3.51 MPa ± 0.61 MPa and 3462.21 MPa ± 841.59 MPa respectively.This provides data support for the design of mechanical devices such as harvesting and modulation processing of alfalfa and king grass.The microstructure of alfalfa was also observed.The results showed that thickness of the thick-walled mechanical tissue in the lower part of alfalfa stalk was about 200 μm to 400μm,diameter of the intercellular cavity was about 8.3 μm,and transverse fiber connection was tight,vascular bundles were numerous;Thickness of the middle stalk was about 50 μm-75 μm,diameter of the intercellular cavity was about 25 μm,and transverse fiber connection was relatively tight,vascular bundle was relatively more;Thickness of the thick-walled mechanical tissue in the higher part of alfalfa stalk was uneven,and thickness of the epidermis was about16 μm-58 μm,diameter of the intercellular cavity was about 40 μm.Vascular bundle was less.Secondly,through the 3D scanner and reverse engineering software Geomagic Studio,the moving blade and fixed blade solid model on self-propelled silage harvester produced by some Germany were reversely reconstructed,the 3D model of blades were obtained and optimized.In addition,a forage stalk cutting blade for chain cutter was designed.Afterwards,it was determined that angle between moving blade and the Cutting direction is 40°,edge angle was30°,angle and the Cutting direction was 17.5°,cutting edge angle was 25.7°,cutting angle between moving blade and fixed one is 22.5°.Then,by consulting relevant literature at home and abroad,a forage material flexible cutting test device was developed based on the study of the mechanical properties of alfalfa and king grass.The test device is mainly composed of forage stalk feeding device,stalk cutting device for forage and data acquisition system,etc.,which can complete operation of feeding,cutting,laying and conveying of forage stalk at one time.The test bench can simulate the actual cutting and harvesting process of forage stalks in the fields,at the same time,test data such as the cutting resistance torque and the flexible cutting drive sprocket rotation speed in the cutting process can be collected in real time,and then calculate the cutting resistance and cutting speed.The cutting inclination can be adjusted on test bench to facilitate the study of the influence of different cutting inclination angles on cutting performance of stalks.Cutting speed of the device is adjustable from 0 m/s to 15 m/s,feeding speed is from 0 m/s to 4 m/s,and the transverse conveying speed is adjustable from 0 m/s to 2 m/s.Finally,the cutting test was carried out on the test bench developed by the alfalfa,king grass and mulberry,and the influence of cutting speed,cutting inclination and cutting speed ratio on the maximum cutting force per unit diameter was analyzed,and the optimal combination was found.The results showed that the cuttings of the alfalfa,king grass and mulberry were flat and the test bench was not prone to blockage.The optimum combination of test is cutting speed of 10 m/s,cutting inclination of 10° cutting speed ratio of 6.9,and the test bench basically meets the design requirements. |
