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Bilgisayar yardımıyla süper alaşım malzeme verileri ve tasarım kriterleri kütüphanesi oluşturulması

Başlık çevirisi mevcut değil.

  1. Tez No: 75153
  2. Yazar: M.ÇAĞLAYAN TAŞÇIOĞLU
  3. Danışmanlar: DOÇ. DR. MEHMET DEMİRKOL
  4. Tez Türü: Yüksek Lisans
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 103

Özet

ÖZET Yüksek sıcaklıklarda uzun çalışma sürelerinde, gerilme altında çalışmak zorunda olan çelik ve çelik alaşımlarından tasarlanan makina parçalarında bilinen içyapı davranışları geçerliliğini yitirir. Hızla gelişen günümüz teknolojisinde yüksek sıcaklıklarda olumsuz çevre şartları altında oksidasyona ve korozyona maruz kalarak, boyut toleransları içinde kalmak zorunda olan ve plastik şekil değişime uğrayarak çalışmak zorunda kalan malzemelerin geliştirilmesine olan ihtiyaç hızla artmaktadır. Temeli krom ve nikele dayanan ve bu amaç için geliştirilmiş süperalaşımların mekanik özellikleri ancak uzun süreler de gerçekleştirilen deneyler sonucunda belirlenebilmektedir. Bu tez çalışmasında değişik ticari ve araştırma kuruluşları tarafından yaygın kullanılan demir, kobalt ve nikel esaslı süperalaşımlara ait, değişik ısıl işlem yöntemleri, üretim yöntemleri, şekillendirme usulleri, vb. şartları altında elde edilen mekanik deney verilerinin bir çatı altında toplanması amaçlanmıştır. Bu amaca yönelik olarak, pratikte en çok uygulama alanı bulan 14 süperalaşım seçilerek mekanik özelliklerine ait ortak deney türleri tespit edilmiş ve bu verilerin, yazılan bilgisayar programı içinde geniş bir yelpaze etrafında derlenmesi amaçlanmıştır. Programa Inconel 718 süperalaşımına ait değişik kaynaklardan toplanan bütün veriler yüklenmesi ve programın kapsamı içinde olan diğer süperalaşımlara ait temel mekanik veriler ve genel bilgiler kullanıma hazır hale getirilmesi amaçlanmıştır. Visual Basic programlama dili ile yazılan ve Windows ortamında çalışan süperalaşım malzeme kütüphanesi programı, ele alınan alaşımlar için teorik ve pratik bilgileri içeren bir paket program halinde geliştirilmiştir. Program veritabanına yüklenen, gerilme-kırılma ömrü, kırılma dayanımı-kırılma ömrü grafik verileri kullanarak Larson Miller Parametresi yardımıyla malzeme seçimi hesabı yapabilmeyi de hedeflemektedir. Program, güncelliğini koruyabilmesi için kullanıcılara elde edilecek yeni deney verilerine ait grafik ve tabloları kütüphane veritabanına interaktif olarak esnek biçimde yerleştirebilme imkanı vermeyi amaçlayan modülleri sunmayı hedeflemiştir. Bunun için programın kapsamı, çok malzeme grubu içermesinin yerine daha az sayıda malzeme ile bu malzemelere ait elde edilmiş bütün verilerin girilmesiyle sınırlandırılması ile kısıtlanması amaçlanmıştır.

Özet (Çeviri)

SUMMARY SUPERALLOYS MATERIAL LIBRARY AND DESIGN PRINCIPALS SOFTWARE The need for high temperature materials has raised considerably during last fifty years. The increased demand of energy can be met mostly by wing thermal sources and in this case, the requirement of big thermodynamically efficiency has prime importance. In order to satisfy high thermomechanical efficiency, there is an absolute requirement of working at elevated temperatures, as high as possible. Therefore, in design of machine elements, which are primed to work at temperatures absolutely requires appropriate materials to withstand the loading conditions properly [1,2,3]. Typical applications exposed to high temperatures can be given as steam power plant parts for high temperatures around 500°C, jet engine parts at 800°C and some petroleum refinery parts at 1000°C [4,5,6]. The long term exposure of temperature above ambient temperature can be alter the mechanical properties of materials with the aid of several strengthening and softening mechanisms as seen in Figurel [7]. vauuva p Recovery - - >? h»i“W\\\, Recrystalllzatlon - ?, \> >.\ ». \ \ v\\\\ Grain Boundary ^Migration ' ^ S of toning Processes! Illlll/ 1)111 / Intercrystalllne f, //?'///-- ' 'Transcrystalllne 1E£I^ 7777777777777 /Grain Boundary ////////////// ( '/SUB///*. Fracture Mode ^f^///A\\\wH\N Fig 1. The mechanism effecting hot strength and ductility of materials [7] XIThe time dependent plastic deformation of materials under strain at elevated temperatures is called creep, and the creep properties of materials should be taken into account, if long term durability of machine element is expected. Therefore, one of the most critical factors determining the integrity of elevated temperature components is their creep behavior. Due to thermal activation, materials can slowly and continuously deform even under constant load or stress and eventually fail. As a consequence of such deformation, unacceptable dimensional changes and distortions as well as final rupture of the component may occur. Depending on the component, the final failure may be limited either by deformation or by fracture. Local creep processes at the tip of a pre-existing defect or stress concentration, can also lead to local crack growth and eventual failure [1,8,91. Creep resistant alloys have been designed and developed for high temperature applications by introducing some mechanisms which reduce the effectiveness of creep deformation mechanisms. Creep properties of materials are generally determined by means of a test in which a constant uniaxial load or stress is applied to specimen and resulting strain is recorded as a function of time. Some tests, called as stress rupture tests, which considers only rupture time at a specified temperature and constant stress. Test periods are generally chosen between 1000-10000 hours. Because the components of power plants and process industry are designed to operate for times in excess of 100.000 hours, extrapolation of laboratory creep and rupture data to actual service conditions is unavoidable. Even if long-time data are available for selected heats of material, heat-to-heat variations in properties make it necessary to estimate the long-time behavior for other heats. Greater difficulty is encountered in estimating the remaining creep lives of in service components, decisions have to be mad based on very short-time laboratory tests (usually less than 1000 hr). The need for extrapolation techniques that permit estimation of the long-term creep and rupture strength of materials based on short-duration tests is thus a very real and important one in design [10,1 1]. In order to overcome this difficulty Larson-Miller introduced the concept of a time- temperature parameter in the form of[12] P(cr)=T(C+logtr) (1) For a given material, a plot of stress versus the parameter (P) resulted in a single envelope curve. C is the Larson-Miller Constant which is usually assumed to be 20, is if ten based logarithm is considered. Another use of Larson Miller Parameter is that it can be expressed in terms of minimum creep rate, instead of rupture time, according to expression, P(cr)=T(C-ln£ss) (2) C is usually assumed to be 46, if natural base logarithm is taken. A Typical Larson Miller Master Curve for Inconel 718 is shown in Figure 2 [13]. xnMaster Curve for Larson-Miller Parameter for ln-71 8 STRESS MPa 61.? 51.0 Y 50.049( 48.983 0 10 20 30 40 50 60 LARSON-MILLER PARAMETER P=T(lnt+4ö) (K-h) xlOOO 48.749* 48.21 3* 46.929( 45.630Î 44.202Î 43.545İ 42.08H 40.968< 40.470: 240 344.75 448.175 482.65 51 7 125 620.55 689.5 896.35 965.3 1 034.25 1103.2 1 1 37.6^ Source :CalcuIated by C.T reft.Processing and thermal History - Fig 2. Larson-Miller Master Curve for Inconel 718 [13,14]. Materials which must be used at elevated temperatures must have creep resistance; fatigue resistance; thermal shock resistance; good fracture properties and, with a ductile to brittle transition, this temperature should be as low a possible; oxidation and hot corrosion resistance; high stress to rupture values; ease of fabrication and joining; impact and erosion resistance; thermal properties, etc. Alloys used at elevated temperatures must also withstand the deteriorating effect of the service atmosphere. In additional, these materials must also posses sufficient strength for the design conditions have satisfactory stability to withstand damaging metallurgical structural changes at operating temperature. From the standpoint of resisting oxidation and high temperature corrosion, the most important alloying element is chromium. Corrosion-resistant steels, stainless steels, nickel-chromium alloys, cobalt-chromium contain significant amounts of chromium, are used extensively in high temperature applications. The term of ”Superalloy“ was first used shortly after Word War II to describe a group of alloys developed for use in turbosuperchargers and aircraft turbine engines which required high performance at elevated temperatures. These alloys usually consist of various formulations made up from the following elements: iron, nickel, cobalt, chromium, as well as lesser amounts of tungsten, molybdenum, tantalum, niobium, titanium and aluminum. The most important properties of the superalloys are long time strength at temperatures above 650 °C and resistance to hot corrosion and erosion [7]. xmMany types of alloys fall under the broad coverage of superalloys. These include iron base alloys, with chromium and nickel: complex iron-nickel-chromium-cobalt composition: cobalt base alloys, carbide strengthened; nickel base alloys, solid solution strengthened and, precipitation or dispersion strengthened. The superalloys are used in both the wrought and the cast forms [7]. These type of materials must be available in a wide variety of forms: bars, castings, extrusions, forgings, sheet, tubing's and thus have to be processed economically by number of production routes including powder metallurgy [15,16]. Technical advance in the processing of superalloys can be summarized as; vacuum melting, electro slag refining, directional solidification, superplastic forging, hot isostatic pressing of powders, dispersion strengthening. The importance of these processing developments with respect to rupture strength is shown in Figure 3 which demonstrates how the performance and temperature capability of gas turbine blades, which can be regarded as one of the best example to reveal high temperature problem, have been improved [7]. Rupture strength. 207 MNm”' SOOHrs 900 O a> 800 a E |2 700 1940 Rene' 120 1950 1960 1970 First hardware to test 1990 Fig. 3. Progress in turbine blade materials [7] It has been showed that the latest precision casting technique, based on directionally solidification, which imparts significantly improved ductility and thermal shock resistance to obtain better high temperature creep resistance. This controlled solidification technique has been used to produce both columnar grain and alloy single crystal gas turbine components. The benefits are; superior thermal shock resistance, longer cyclic strain life, longer creep life, better intermediate temperature ductility and, good thin-wall properties [17]. In order to increase their popularity the elevated, temperature properties for superalloys must be exhibited in a simple way similar to low temperature metal and metal alloys. A number of commercially produced alloys, mechanical and physical properties of which are obtained by their producers' long term tests, need to be presented in a collected model. In this study, the mechanical properties data of superalloys were investigated and collected after a short introduction to high temperature problem and creep phenomena. A computer program including manufacturing processes, mechanical xivproperties at room and elevated temperatures, physical and chemical properties of selected superalloys was prepared. The superalloys covered by the study are as following: ? Iron base superalloys: A-286, 16-25-6, ? Nickel base superalloys: Inconel 718, Inconel X-750, MAR M200, Inconel 901, Waspaloy, IN- 100, Rene 41, Udimet 700 and TD-Nickel ? Cobalt base superalloys: X-40, S-816, Vitallium The software allows to find necessary information about the superalloys and contains a wide variety of experimental data in tabular and graphical form. Test data were collected into the superalloy database program through the combined efforts of the Data and Publications Panel of the ASTM-ASME-MPC Joint Committee on Effect of Temperature on the Properties of Metals and the Defense Metals Information Center, Metal Alloy Producers' printed and unprinted data sheets, Air Force and other Government of U.S. Agency Technical Reports and Reports issued by several Information Centers [13,14]. The designer who wants to reach the superalloys' data should easily handle, understand and use the Supperalloy Design Package without faced any logical and technical problem. The database software was developed by a Windows developer programming language, which is called Visual Basic. Superalloy Design Package Program aims to offer: ? general information about superalloys: ? theoretical information about creep problem, ? application potentials, ? exhibition of selected superalloys on graphic screen, ? solving creep problems with the aid of stress, temperature, rupture time, and, creep rate data of the superalloys, ? easy updating facility, ? enable to customize present data. It was protected by a security controller. It is restricted by a password which just only one superuser knows. Other users want to modify it must apply to the superuser. The follow chart of the Superalloy Library Program is outlined below: 1. General information (text base): It introduces to the package (using editing, sources), creep, superalloys, selected materails, abbreviations of the terms, typical applications. A brief description of each alloy has been provided, including a listing of major procurement specifications, ranges of chemical composition, typical applications, and information on processing and heat treatment. 2. Selection of an alloy which is partially loaded or full loaded a. Loading full data from database: it enables to activate and print all information, physical, mechanical, fabrication techniques Connects you to add or edit new graphics xvb. Loading partial data from database: It enables long-term life prediction for a given specific superalloy from database. It calculates one of design or work stress and rupture time or prediction rupture life at a specific temperature on a selected material. It enables to see basic properties for a design. It appears a new form for adding new graphics as real as loaded before. 3. Drop to design mode for selecting the best material: a. It is expected you to enter design conditions: stress, rupture time and temperature. b. Calculates the optimum solution according to Larson-Miller parametric extrapolation technique. c. Compares all superalloys loaded results in a table and shows unit cost. d. Print out facility of the results if necessary 4. Development the database while in use: it gives permission to add either text information to text database or test data to graphic database 5. Security mode: It enables to secure the software against unauthorized usage The database software uses approximately 7MB under Windows 95 and requires Pentium 120 processor, 16 MB temporary memory. xvi

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