12116

11102

كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1395

يازده، 115ص.: مصور، جدول، عكس(رنگي)، نمودار

ص. ع. به فارسي و انگليسي

محمود فرزين

فرشيد احمدي

واژه نامه

محمد مشايخي، رضا جعفري

1395/11/17

كتابنامه

مكانيك

مهندسي مكانيك

ID11102

چكيده در ساالهاي اخير توجه زيادي به فرايندهاي ميكروفرمينگ و بررسي تفاوت آنها با فرايندهاي ماكروفرمينگ شده است در اين پژوهش فرايند 2 ECAP كه مهمترين فرايند 1 SPD براي توليد ريزساختار ميباشد مورد بررسي قرار گرفته است قالب 3 RS ECAP با قطر 3 ميليمتر ساخته شد و خواص نمونههاي تيتانيومي حاصل از آن با خواص نمونههاي حاصل از فرايند ECAP با قطر 5 42 ميليمتر مقايسه شاد در ابتدا براي همگنساازي سااختار تيتانيوم CP نمونهها به مدت يك سااعت در دماي 111 درجه ساانتيگراد و شارايط عبور گاز ا ا ا ا ا ا آرگون آنيل شادند با توجه به نتايج مطالعات پيشاين اين فرايند در دماي 151 درجه ساانتيگراد و شارايط روانكار تركيبي انجام شاد با ا ا ا توجه به نتايج آزمون ميكروسااختي مشااخص شااد كه اين كوچك سااازي ابعاد موجب افزايش بازده فرايند و بهبود خواص نهايي نمونه ميشااود طبق نتايج ميكروسااختي سااختي تيتانيوم CP پس از 12 مرحله عبور از قالب RS ECAP از 45 511 به 943 ويكرز رساايده اسااات از طرفي نتاايج آزمون نانوساااختي نشاااان داد كه ساااختي تيتانيوم از 7 731 به 4 163 ويكرز و مدول يانگ از 2 312 به 5 112 گيگاپاساكال رسيده است با توجه به افزايش سختي تيتانيوم به مقادير زياد مشخص شد كه استحكام نمونه بسيار بهبود يافته است افزايش استحكام از يك طرف و كاهش مدول يانگ از طرف ديگر تيتانيوم را براي كاربرد ايمپلنت دنداني مناسب مينمايد در ادامه براي بهبود شارايط و افزايش بازده فرايند RS ECAP به كمك نرم افزار آباكوس شابيهساازي شد به كمك شبيهسازي تاثير پارامترهاي خارجي دما سرعت ضريب اصطكاك زاويه برخورد كانال و زاويه انحناي خارجي بر روي مقدار كرنش پالستيك معادل يكنواختي كرنش پالستيك معادل و نيروي فرايند مورد بررسي قرار گرفت كلمات كليدي ميكروفرمينگ ماكروفرمينگ SPD ECAP ميكروسختي آباكوس 1 Equal Channel Angular Extrusion 2 Severe Plastic Deformation 3 Reduced Scale ECAP

006 Effect of size reduction on properties of nanostructure titanium samples obtained by the ECAP process Mehdi Abasi Chermahini mehdi abasi@me iut ac ir Date of Submission 2017 01 10 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mahmoud Farzin Farzin@cc iut ac irAbstractIn recent years much attention has been paid to Micro forming processes and differences between the Micro forming and Macro forming processes ECAP is the most important SPD process for producingmicrostructures In this study ECAP process is investigated Reduced scale ECAP RS ECAP die with adiameter of 3 mm was made and mechanical properties of titanium samples obtained from RS ECAP werecompared with properties of samples obtained from ordinary ECAP with a diameter of 14 5 mm To obtain ahomogenous structure CP Ti was annealed at 800 C for one hour in an argon atmosphere and then air cooled According to the results of previous studies RS ECAP tests were performed at 250 C and acomposite lubricant containing about 50 graphite powder 25 MoS2 and 25 grease was used betweenthe billet and the die walls in order to reduce frictional effects Results of the Micro hardness test showed thatscale reduction increases efficiency and improves the final properties of the sample Micro hardness of CPtitanium increases from 205 5 to 349 Vickers after 10 passes of R S ECAP The Nano hardness test resultsshowed that the hardness of titanium increases from 237 7 to 362 4 Vickers and Young s modulus decreasesfrom 123 1 to 108 5 GPa after 10 passes of Micro ECAP According to the results it was found that thehardness of pure titanium has highly increased that represents noticeable improvement in strength of puretitanium On one hand improvement of strength and on the other hand reduction of Young s modulus oftitanium makes the product suitable for dental implants applications Increasing the strength of ECAP CPtitanium used for implants applications leads to its life increase and its less possibility to be broken Since theYoung s modulus of bone is less than titanium the lower the Young s modulus of titanium implants the lowerthe damage into the jaw bone and therefore it would be less likely to be loosened In the next stage to improveefficiency of the process RS ECAP was simulated using Abaqus software Using these simulations influenceof external parameters such as temperature process speed friction channel angle and the corner angle of dieon equivalent plastic strain uniformity of equivalent plastic strain and process force were studied Accordingto the simulation results in general it can be concluded that for a given small corner angle of die by increasingtemperature increasing friction and reducing the rate equivalent plastic strain will increases Also for a givensmall corner angle of die by decreasing temperature and increasing rate and friction increases the uniformityof equivalent plastic strain For larger corner angle of die friction temperature and rate do not haveconsiderable effect on the amount of equivalent plastic strain and uniformity of equivalent plastic strain Meanwhile by increasing friction reducing process temperature reducing the corner angle of die andincreasing rate increases process force Keywords Micro forming Macro forming RS ECAP Micro hardness Nano hardness Abaqus

محمود فرزين

فرشيد احمدي

محمد مشايخي، رضا جعفري