| When the soil-engaging components of agricultural machinery work in sticky and heavy soil,it directly leads to lower working efficiency and increase fuel consumption because of serious soil adhesion.In addition,wear and tear of soil-engaging component due to soil adhesion reduces its service life and increases economic costs.Procambarus clarkii,through its own continuous evolution,are able to freely dig holes in heavy red soil.Therefore,it requires the exoskeleton of Procambarus clarkii not only reduces adhesion and resistance,but also has a wear-resistant function when interact with wet-slurry soil,thereby better adapting to the harsh soil internal environment.The study of the adhesion-reduction,drag-reduction and wear-resistance mechanism of Procambarus clarkii can provide bionics basis for the design of new soil-engaging component of agricultural implements,and then it can achieve the adhesion-reduction and resistance-reduction in heavy soil.According to the research method of bionic engineering,Procambarus clarkii living in Yunnan heavy soil was selected as a biological prototype in this study.The bio-coupling characteristics of its ability to realize the function of adhesion reduction,drag reduction and wear resistance were investigated.Based on this study,biomimetic convex hull structure was performed optimization and coupling design.Finally,drag-reduction performance of bionic sub-soiling shovel head with bionic microtrichi convex hull structure and the wear-resistance of non-smooth surface sample with microtrichi convex hull structure was evaluated.The study is conducted specifically from the following aspects:(1)To make a quantifiable geometric analysis on the exoskeleton contour curve of Procambarus clarkii,reverse engineering technology was adopted.The three-dimensional model on the claws,cephalothorax,and abdomen of Procambarus clarkii was established using white light three-dimensional scanner.The Imageware software was used to obtain the point cloud data of the section profile curve of the 3D model.The Matlab software was utilized to establish the mathematical equations,and the second derivative and curvature of the curve were calculated to analyze the irregularity of the curve and curvature variation.The results show that the surface of the thoracic exoskeleton of cephalothorax had the noticeable groove structure and its cross-sectional profile curve was convex and concave.Moreover,the curve curvature changed greatly.Therefore,the contact area between the exoskeleton and the soil was decreased,which was beneficial to reduce soil adhesion and friction.The cephalothorax was a large contact area with the soil and withstands much soil loads.It was of great research value in respects of adhesion reduction,drag reduction,and wear resistance.(2)The composition,microscopic morphology and nano-mechanical properties of the exoskeleton on cephalothorax of Procambarus clarkii were analyzed The composition,phase,surface microstructure,and section microstructure of the exoskeleton of cephalothorax on Procambarus clarkii were observed and analyzed using X-ray fluorescence spectrometry,X-ray diffractometry,electron microscopy,and transmission electron microscopy.The nano-scale morphological features on its surface were observed using an atomic force microscope.Nanomechanical properties of the exoskeleton on cephalothorax were measured using a nanoindentation instrument.The results showed that the exoskeleton of cephalothorax is hard,in which the calcium content is 36.39%,and it presents a large amount of amorphous minerals.Tiny convex bulges present on its surface.It had bristles on one side of the convex hull,showing a non-smooth surface.Nano-scale grooves were distributed on the non-smooth surface,forming micro-nanostructures.The exoskeleton cephalothorax of Procambarus clarkii was divided into the epicuticle,exocuticle,and endocuticle.The outer layer of the epicuticle presented a very thin layer of wax.The calcium deposition layer near the epicuticle was covered with pores in the function of bearing the load.The exocuticle and endocuticle were composed of spiral splint layers.Spiral splint layer had a honeycomb structure and played a role in buffering and shock absorption.The nanohardness and elastic modulus of the exoskeleton on cephalothorax was heteropical,and the average values are 0.503 Gpa and 18.019 Gpa,respectively.The coupling of the chemical composition,the surface microcosmic morphology of the special structure of the epidermis of the cephalothorax of the Procambarus clarkii makes the exoskeletons on cephalothorax with the function in adhesion reduction,drag reduction,and wear resistance.(3)After decalcification and deproteinization of the cephalothorax on exoskeleton of Procambarus clarkii,the cross-section structure of the exoskeleton was observed using electron microscopy.The friction coefficient of the cephalothorax on exoskeleton was measured by a friction-wear tester.The results indicated that the calcium salt presents a needle cluster-like gradient distribution in the spiral splint layer.The friction coefficient was the minimum when the friction behavior is just started,which is less than 0.1.As the friction behavior continues,the friction factor gradually increased and showed a sudden variation.The uneven distribution of calcium salts and the unique structure of the epidermis coupled together to make the friction coefficient of exoskeleton on cephalothorax sudden change in a certain interval.(4)According to the convex and bristly composite structure of the cephalothorax on exoskeleton of the Procambarus clarkii,three bionic microtrichi convex hull structures were designed.The biomimetic method was applied to the sub-soiling shovel head to design the bionic single microtrichi convex hull sub-soiling shovel,bionic double microtrichi convex hull sub-soiling shovel,and bionic three microtrichi convex hull sub-soiling shovel.Soil bin test was performed to verify its drag reduction performance.The test results showed that when the soil moisture content is 20.62%,the drag resistance of bionic three microtrichi convex hull sub-soiling shovel head was better than the bionic convex hull sub-soiling shovel heads and the ordinary sub-soiling shovel heads,and the drag reduction effect was best.(5)The friction-wear test platform was designed and the tests were performed to verify the wear resistance of the non-smooth surfaces of the three bionic microtrichi convex hull structures.The test results showed that the wear resistance of non-smooth surface of bionic double microtrichi convex hull was better than that of the non-smooth surface and the smooth surface of bionic convex hull and the wear quality was the least under the same experimental conditions.The conclusions obtained can serve as a basis for the bionic design of the soil-engaging component of agricultural machinery.Therefore,soil-engaging component have the characteristics of adhesion-reduction,drag-reduction and wear-resistance while working in heavy and sticky soil,which meets requirements of the energy saving and consumption reduction in modern agricultural production. |
PDF Full Text Request