Erosion-resistant Mechanism Of Desert Scorpion And A New Evaluating Model

Friction is one of the most common phenomenon in nature.The relative motion or trend of relative motion will generate,when two objects that have contacts with each other under the external force.The tangential motion resistance will produce between the contact surfaces,which is called the friction.Wear is the progressive loss of material surface due to the effect of friction force,causing the failure of materials,which is the three main failure forms of mechanical parts(fracture,corrosion and wear).According to incomplete statistics,80%mechanical failures were caused by abrasion in the world,resulting in a third of the one-time energy loss.The annually economic loss in the United States caused by the wear accounted for about 4%of its gross national product(GNP),while this figure was more than 100 billion Chinese Yuan in our country each year.Erosion wear is one of the most important branch of the wear,it widely appears in the steam turbine,pipelines,centrifugal compressor,centrifugal fan,cyclone separator,gas drilling pipe,throttle manifold,radome,helicopter rotor and other mechanical products,which has become an important failure mode for the device.Currently,the researchers mainly choose wear-resisting material,surface modification or heat treatment technology to improve surface erosion-resistance.However,these methods do not achieve the ideal effect.Therefore,seeking a kind of excellent erosion-resistant technologies has become a popular topic in material science.This paper chose the desert scorpion(Mesobuthus eupeus)as biological prototypes to analyzed the characteristics of scorpions' living environment,surface morphological structure and micro-mechanical property by the microscopic analysis method,while the rainforest scorpion(Heterometrus petersii)was selected as reference object to compare the difference between them.The results show that the scorpion's back has groove caused by connection of internode membrane.Compared with rainforest scorpion,the convex hull with different density and diameter is distributed over the surface of the desert scorpion,especially on the side of the back where the convex hull is most intense.In addition,there are three ridges In the middle of the back which are composed of convex hull.Although rainforest scorpion is larger than desert scorpion,its convex hull structure is smaller than desert scorpion and there are multi-scaled polygon structures among different convex hulls.Compared the micro-hardness of the two kinds of scorpions,it can easily find that the desert scorpion carapace is harder than the rainforest scorpion overall.Particularly,in the position of the convex hull the hardness is much higher than other positions,especially on it ridges.Finally,the friction coefficient test to two scorpions has been carried on and the results show that friction coefficient between desert scorpion and sand is higher than rainforest scorpion,they are 1.483 and 1.115 respectively.With the development of bionic technology,there are many problems need to be solved.Among them,the two problems are very important,one is the scarcity of bionic model,and another is how to prove that biological model has erosion resistance.In this paper,combined with the conventional evaluation method for erosion,a new evaluation model is established to tackle the problems.It can not only evaluate the erosion-resistance of among different creatures,but also can prove that the creatures has erosion resistance performance through comparing other creatures which are entitled to erosion-resistant properties.This model on the basis of the metal samples,first of all,compared the erosion rates under different impact angle through the erosion test.Secondly,comparing and summarizing the speed change between the target surface and sand particles before and after collision,and find the relationship between impact angle and speed changes of particles.Particle velocity analysis shows that the values of vp0-vp1 are different under the different impact angle.Meanwhile,according to the analysis of the mechanics and stress distribution,a kind of boundary conditions has set up based on the friction.It is the value ofvp0-vp1 must less than the value of the boundary conditions.Combined with the classical theory of erosion wear,a new evaluation model is designed.To explore the erosion-resistance of scorpions,the erosion resistance online testing system is chosen to record the videos that the sand particles collide on the carapace.Then analyzes the speed of change before and after the collision,and the erosion-resistant properties of desert scorpions can be demonstrate by employing the evaluation methods mentioned above.Finally,illustrates the curvature of the scorpion structure and convex hull structure can change the impact angle,and the convex hull can also resist the collision,reducing the erosion area on the surface of the target material and improving surface erosion resistance.After extraction of morphology,structure and size of desert scorpion,some bionic samples are designed and fabricated based on the previous studies using two kinds of materials produce the bionic samples(rubber and Stainless steel).Then,after using the cutting equipment and grinding machine to the post-processing of samples,the erosion tests are carried on by employing homemade jet erosion test system.In this paper,different erosion test are designed for different bionic samples,which make the subsequent comparison of results more directly.In contrast,the groove-structure sample is selected as reference which has better erosion-resistant properties based on the previous research.The results showed that the single convex hull structure is appropriate to the surface made of rubber because comparing with the groove-structure sample,the erosion-resistance of the bionic surface increase by about 31.9%.The coupling structure of the groove and convex hull is applicable to the surface made of metal,due to the fact that comparing with grooved-structure sample,the erosion-resistance of coupling bionic sample increase by 50%.New erosion test make better use of the structure characteristics of curvature,which makes erosion resistance of target surface increased by 43.6%.