Research Of Wear-resistance On Roller With Biomimetical Non-smooth Concave Surface

The friction and wear phenomenon exists in all machines and devices in the industry,which brings the increasing of product costs and loss of large energy, shortage of facilityusing life. Industry roller as an important component in metallurgy equipments is oftendiscarded as useless with friction and wear of the contact surfaces. A great number ofeconomic loss arises for many steel rolling enterprises. The reduction of the friction andwear of rollers has become a difficult technology problem in steel rolling industry atpresent. In order to solve this problem, this paper presents a new way based onengineering biomimetical principles to improve wear resistance and heat-resistantperformance of the industry rollers from a view point of reconstructing surfacemorphology by laser texturing techniques. A serial experiments including principle,model, computer simulation and field experiments are carried out to approve thereliability of this new means.On the principle of engineering biomimetics, some typical organisms surfaces, forexample, seashell, tooth and dung bettle, and so on, similar to industry rollers wearinterfaces were taken as compared wear ways between roller and selected non-smoothorganisms surfaces. The concave shape with diameter 150～350 μm and distributingdensity 2～8/ 2 was chosen as processing parameters of principle test rollers of 55and W9Cr4V steel sheets. Test model rollers surfaces with non-smooth concaves wereprocessed by Laser texturing Technology. Laser processing parameters with possiblesame frequency, focus, pulse etc. were chosen in order to obtain similar hardnesssurfaces.As one important test index, wear loss was taken to be detected by using partialpolynomial regression plan, and three test factors of temperature Z(3300℃,500℃),running time Z4(180s,300s), rotate speed Z5(400r/min,600r/min),non-smoothconcave unit size Z1(150 μ m,200 μ m,250 μ m,300 μ m)and unit distributingdensity Z(2250 μ m,350 μ m)were selected to investigate the effects on the surfacewear loss of 55 steel samples. According to their importance sort to test results, thefactors are Z3, Z4, Z1, Z5, Z2, respectively. The effect from mutual action betweenconcave unit size and its distributing density was not obvious. The regressionequation of test factors to wear mass loss is:y? = ?0.0118z1 +0.0046z2+0.0248z3+0.0147z4+0.0052z5?3.796Friction and wear principle tests of W9Cr4V samples with surface non-smoothconcaves were carried out to probe wear resistance mechanism at 300～500℃ . Theresults show that wear resistant of test samples becomes better with increasingtemperature, and wear loss increasing smaller at below 200, increasing faster atexceed 200℃ . Different concave diameter and density distributing had differenteffect on wear losses of the test samples. When the test loading 30N, rotate speed600 r/min, running time 180s were adopted, the larger the non-smooth concavediameter, the better the wear resistance.Main wear-resistance mechanism of the non-smooth concave surface includes asfellowings:Non-smooth concaves on the sample surface are helpful for changing motiondirectction of the scraps from slipping to rolling;Protrusion near to the concavesare also helpful to reduce micro-vibration for tangential force that can shortencontact time and area in normal direction, and Concave protrusions formed'shadow-effect' act on underlaying loads, passivating scraps and absorbing energy;the interspace formed by the concaves can much more air that make up of a seriesof "air bubbles" apt to reduce resistance and friction.Laser proccessing makescrystal grains fine more obvious, hardness more higher apt to improve wearresistance performances of the surfaces of the non-smooth sample. The hardnessvalues of different areas on the concave surface exist obvious different, and the softparts may absorb more flexibility engery than the hard ones,and those make itpossess of more smaller friction resistance for the concave surface.Three dimensional finite element model of roller and sheet rolling process was firstbuilt according to roller and flattening sheet rolling wear characteristics by usingANSYS/LS-DYNA software. Simulation results showed that comparing withsmooth surface roll sample, the non-smooth roller surface with concaves possessedhad higher Von Mises stress value in favor of enforcing rolling sheet fluidity. Onthe other hand, although stress concentration arises at concave circumjacent area,their values were generally smaller than the limit of strenghteness of the rollers. Itwas these factors that were in favor of improving wear resistance capability of therollers.To obtain the laws of effect from surface concave size and density on wearresistance of test rollers at the term of rolling course, the shear stresses on contactareas were analyzed. Experimental data showed that: (1) In the same concavediameter condition, the longer the distance among concaves was, the smaller theshear stress value at contact points was;(2) In the same distance condition, thebigger the concave diameter was, the smaller the shear stress value at contactpoints was;(3) The two conclusions mentioned above were identical withprinciple test results. According to the optimized principle test results, a fieldexperiments were arranged in two rolling mills in Changcun city and Tonghua cityof Jilin province. Ten rollers with different concave size and distributing densitywere applied in product lines to comparing with the smooth ones, and the resultsshowed that the first group non-smooth roller life were about two times as long asthat of the smooth group.Biologic Non-smooth Theory and Technology (BNTT) and its applications inengineering were summarized and presented outlook in this work. These contentsincluded: (1) to establish mathematical models of the typical wear resistant surfacesand their computer dynamic simulation;(2) to establish a dynamics equationbetween biologic wear resistance non-smooth surfaces roughness parameters andwear mechanism;(3) to summarize and abstract biomimetics principles, appraisedmodels in industry areas, and to put forward a serial optimized design methods andtheory;(4) to improve rapid fabricating techniques and product effectiveness forbiologic non-smooth wear resistant surfaces, to enlarge application areas in otherindustry aspects.