6012

5621

كارشناسي ارشد

ساخت و توليد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1389

نه،149ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمود فرزين، مهدي صالحي

فرشيد احمدي

23/3/90

محمدرضا فروزان، حميدرضا سليمي جزي

مهندسي مكانيك

ID5621

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

155 Optimization of HVOF WC Co Coating Thickness by FEM Simulations Mehdi Rezaei m rezaei me@gmail com 2011 16 03 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Mahmood Farzin Email farzin@cc iut ac irAbstractThe purpose of this study that is carried out for the first time is to determine optimal thickness of WC Cospray coating by HVOF High Velocity Oxy Fuel method on the surface of steel pinch roll roller by utilizingfinite element method The pinch roll was considered in this research is located at the end of the hot roll lineof Mobarakeh Steel Company The task of pinch roll is to get and guide sheets toward the mandrel Pinch rollconsists of two rollers that the up roller is movable and the down roller is fixed and its surface is parallel tothe direction of sheet The working environment of these components is acidic and they work in temperatureand humid ambient The surface of these rollers is worn and destroyed due to impact and movement of sheeton it Because of micro level deformation on the surface of pinch roll roller surface was necessary to bemeshed by micron size element thus computational modeling would be complex and difficult At the first therelevant finite element model was optimized After studying various techniques eventually a two dimensional model was considered in which the sheet and pinch roll were supposed to be deformable withmicron element size meshed surface Also in order to optimize and reduce the time and cost of solving onlya 60 degrees sector of pinch roll was modeled and a mass scale 100 applied for the pinch roll Then thecritical condition of pinch roll was determined The Results showed that working condition of the pinch rollat the initial impact is worse than other working times Also hard and thin sheets due to the higher speed atthe hit movement to pinch roll make the condition more critical Surface damage created on the pinch rollroller in the real state was well shown by the finite element model Finally by defining two materials for theroller coating was deposited on the pinch roll in finite element models and the distribution of stress anddeformation were obtained Carbide Tungsten Cobalt WC Co coating was used that by HVOF method wassprayed on the surface of pinch roll In this condition the yield stress of coating was 1500 MPa and itsporosity was less than one percent This cermet is extremely wear resistance and it is used for machiningapplications The connection between the coating and substrate in thermal spraying methods mostly is madeby mechanical locks which have rather low strength Maximum shear stress happens in the interface andsince it is more than adhesion strength lead to delamination and failed coating on the substrate surface Analyses showed although coating greatly improves the surface properties the initial impact of sheet to theroller can cause deformation and failure of coating as well as shear stress generated in the interface would bemuch more than strength adhesion coating to substrate Among the various modes studied the best thicknessof coating was about 600 microns that causes minimum shear stress distribution both in the surface coatingand in the interface of coating substrate Key wordsPinch roll HVOF Finite Element Method Shear stress coating interface of coating substrate

محمود فرزين، مهدي صالحي

فرشيد احمدي

محمدرضا فروزان، حميدرضا سليمي جزي