The fractional dimension of matrix surface combines the influence of intensity to layer of electric arc spray

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The union between layer of electric arc spray and matrix is a kind of mechanical union completely almost, appearance of coarse matrix surface form is the important parameter that affects its to combine strength. The data makes clear, the combinative strength of thermal spraying layer and matrix depends on the surface roughness of matrix surface. In fact, exterior surface roughness is worth the physical quantity that is sunken degree of protruding of surface of a token only, cannot reflect exact form appearance of the surface. If gush is arenaceous thick when changing the face, partial matrix surface can form surface roughness value to cannot be mirrorred " hook " state body appearance, this kind " hook " the power that can produce mechanical lock to decide between coating and matrix, this force can affect the combinative strength of coating matrix greatly. Because this need seeks a kind of parameter that can describe exterior form appearance well and truly. 70 time, american mathematician Mandellbrot built the geometry that divide dimension, advanced the idea of fractional dimension first. Of this one concept build offerred efficient way to describe complex exterior form appearance. Feature of the form appearance that at present a few scholars of domestic had begun to consider to bead is worn in tribology with fractional dimension theory, grain [1] , and the idea that fractional dimension has not introduced in analysing appearance of form of surface of gush arenaceous pretreatment. The description that provides representative Hausdorff dimension to be able to apply to random graph most [2] . Arenaceous to gush the exterior form appearance that after random process is handled, this forms, using Hausdorff dimension to describe is appropriate. The article applied this one concept to measure the cent dimension of surface of the matrix below arenaceous angle of a few kinds of different gush, measured its at the same time the combinative strength of the surface roughness below corresponding condition and layer of electric arc spray. The result makes clear, the fractional thinking of matrix surface can be clearer accurate description is thick the appearance of matrix surface form after changing, evaluate exterior form appearance and union of layer of electric arc spray with fractional dimension intensity impact is more measurable. The test 　 of the preparation of 1 test specimen and strength of union of layer of electric arc spray is below same gush arenaceous atmospheric pressure use different point of view to undertake gush sand preparation to test specimen. Gush is arenaceous adoption device produces Sha Bei Ke to control arenaceous machine of gush sending form for Shanghai, gush arenaceous test specimen secures the fixture that designs in proper motion to go up, this clamping apparatus can adjust the included angle between arenaceous face of gush arenaceous direction and gush well and truly neatly, namely gush arenaceous angle. Gush arenaceous condition is as follows: Test specimen material is 20 steel; Arenaceous type is corundum of 25 eye palm; Gush arenaceous time is 10 S; Gush arenaceous distance is 150 Mm; Gush arenaceous atmospheric pressure is 0.

7MPa; Gush arenaceous angle is 30 ° , 45 ° , 60 ° , 75 ° , 80 ° , 90 ° . Gush sand preparation undertook to surface of drawing test specimen below such condition, the preparation below each angle 5 test specimen, use a test to combine the change of intensity. Parameter of electric arc spray: 160 A of voltage 32 V, electric current, baric 0.

7Material of silk of MPa, spray is the FeCrAl silk of φ 2 Mm. Tensile test presses national level GB8642, 88 undertake. The test sees a picture as a result 1. Graph the combines intensity and point of view concern plan of 1 coating shows a result 1 times to make clear, the prime cause that causes change of coating structure intensity is different gush the appearance of matrix surface form that arenaceous angle causes is different. Gush arenaceous angle from 30 ° ～ strength of tie of the coat in process of 90 ° change increases first, achieve when 45 ° the biggest, show downtrend next. The exterior form appearance to analyse matrix further combines the influence of intensity to coating, the test of the test that made exterior surface roughness to test specimen respectively and fractional dimension is analysed. The surface roughness test of surface of 2 test specimen analyses 　 in afore-mentioned gush arenaceous condition falls to undertake exterior gush sand preparation to test specimen, the typical form appearance below arenaceous angle of 4 kinds of gush sees a picture 2. By the graph 2 can see, gush is arenaceous the mark that makes is wide reduce along with the accretion of gush arenaceous angle. Not fathomless, it is when gush arenaceous point of view is older, the energy of arenaceous bead uses generation plasticity to be out of shape, and when gush arenaceous angle is lesser, its kinetic energy still is used up besides be used at making the surface produces plasticity to be out of shape at surface layer of cutting base metal. Should notice to appear when gush of 45 ° horn is arenaceous particularly " hook " state body appearance. (　 of ° of A) θ =30 (　 of ° of B) θ =45 (　 of ° of C) θ =60 (° of D) θ =90 pursues the typical form appearance of surface of the test specimen below arenaceous angle of 2 each gush (the test specimen that × 67) 　 takes the gush below every kinds of condition to make 3, use a test its surface is average surface roughness. The test of surface roughness is finished on analyzer of appearance of Talysurf50-120 surface form. The average surface roughness below each angle sees a picture 3. Graph the test of exterior surface roughness below arenaceous angle of 3 each gush makes clear as a result, gush arenaceous point of view is not old to the surface roughness influence of matrix surface. The average protruding sunken rate that curve of exterior surface roughness can reflect place to check the surface only, can not mirror graph 2b place to show " hook " the appearance of complex surface form such as shape, is this is planted " hook " ability produces mechanical Suo Dingli, increase the combinative strength between coating and matrix thereby. Nextpage3 gush is arenaceous the analysis of a dimension of mark of appearance of form of surface of test specimen of analysis of test of exterior mark dimension is to pass the test system of image analyzer and computer composition to finish. Test flow sketch map sees a picture 4. Graph analysis of dimension of mark of surface of 4 test specimen checks flow chart above all, optics of park of section of gush arenaceous test specimen microscope falls, through image the analysis extracts its interface curve, read in the curve the computer. The computer can differentiate automatically enclothe curvilinear reseau and can the reseau number that curve of differentiate, record carries and corresponding reseau width, see a picture 5. Graph basis of graph of appearance of 5 surfaces form the concept of Hausdorff dimension, in type of 　 of R -D (1) of μ of N(r)= of the following relation existing between the curvilinear reseau number through enclothing it and reseau width, the curve when N(r) is R for reseau width carries the reseau number that covers it; R is reseau width; D is fractional dimension of the curve; μ is coefficient. Type (1) both sides takes natural logarithm to get LnN(r)=ln μ respectively - 　 of Dlnr (2) changes reseau width continuously, attainable a series of reseau number and corresponding reseau width. The D that undertakes to data linear returns to processing to get is fractional dimension of the curve namely. Because gush arenaceous surface has random sex, considering to 30 different position all are taken to analyse a test to every test specimen when its mark dimension so, with eliminating the error that brings by random sex. Graph 6 for gush arenaceous angle parts is 30 ° , 45 ° , 60 ° and the relation curve between the LnN(r) when 90 ° and L N R. (° of A) θ =30, d=1.

050 　 (° of B) θ =45, d=1.

060 　 (° of C) θ =60, d=1.

055 　 (° of D) θ =90, d=1.

014 graphs the relation graph between the relation of the LnN(r) below arenaceous angle of 6 each gush and Lnr and Lnr 6 make clear, the LnN(r) that measures below each angle and Lnr all show linear concern. What can decide below these angle gush sand preparation is obtained from this is thick the mask that turn a table has fractional dimension feature. Linear slope, namely thick the limits of the fractional dimension that changes the face is 1.

014 ～ 1.

080. Fractional dimension sees a picture along with the change of angle 7. Graph the fractional dimension result below 7 each angle still makes clear, gush arenaceous angle from 30 ° ～ 90 ° change in the process, value of its mark dimension is shown first rise to show downtrend next, maximum was obtained when 45 ° . The combines strength change of the change of dimension of this kind of mark and coating of electric arc gush shows same trend, see a picture 1. The dependence of this combinative strength that confirmed layer of electric arc spray as a result and dimension of mark of appearance of matrix surface form. And to it the change of the matrix surface surface roughness below corresponding each gush arenaceous angle is not big (3) seeing a picture, cannot explain coating combines intensity to follow the change of gush arenaceous angle quite. 　 of 4 conclusion 　 (when arenaceous pretreatment of gush of 1) matrix surface, change gush arenaceous angle is changeable the fractional dimension value of its form appearance, below the craft condition of the article, value of dimension of the mark when 45 ° horn is the greatest. (2) gush arenaceous point of view is not old to influence of surface roughness of base metal surface. (The fractional dimension of the combinative strength value of layer of spray of 3) electric arc and base metal surface shows same metabolic trend. Accordingly, fractional dimension compares exterior surface roughness more the influence that appearance of well and truly form of evaluation matrix surface combines strength to layer of electric arc spray, namely fractional thinking is older, coat tie strength is higher. CNC Milling CNC Machining