Bilgisayar yardımıyla plastik malzeme seçimi
Computer aided thermoplastic selection
- Tez No: 21982
- Danışmanlar: DOÇ. DR. SELMA AKKURT
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 167
Özet
ÖZET BİLGİSAYAR YARDIMIYLA PLASTİK MALZEME SEÇİMİ Bilim ve teknikteki gelişmeler sonucu mühendislik malzemeleri sürekli çeşitlenmekte, yepyeni üstün özellikleri olan malzemeler ortaya çıkmaktadır. Bu durumda problem haline gelen malzeme seçiminde bilgi sayarların yardımı kaçınılmaz hale gelmiştir. Bu çalışma plastik malzeme seçimi amacıyla bir veritabanı oluşturulmasını ve bu veritabanında yer alan malzemeler arasından çeşitli şartlara uygun malzemelerin listesinin eldesini amaçlamaktadır. Program malzeme ön seçimi için çok kullanışlıdır. Veritabanı çalışmada belirlenen hedef uyarınca yalnız Türkiye'de kullanılan (üretilen veya ithal edilen) termoplastiklerden oluşturulmuştur. Kayıt sayısı artırılabilir. Ancak yeni kayıtların termoplastik grubuna ait malzemelerden seçimi gereklidir. Çünkü programda malzemelerin birbiriyle karşılaştırıldıkları özellikler ve özel niteliklere göre malzeme listesinin el de edilmesini sağlayan arama kodlara termoplastik malzemeler için belirlenmiştir. Malzemelerin özellikleri ISO 3167 'ye uygun çubuk için belirlenmiştir. Bu özellikler şunlardır: Genel tanıtım, mekanik, darbe, termik, fiziksel, optik, elektriksel ve aleve dayanım özellikleri. Programda 30' un üzerinde plastik ailesi ve bu ailelere ait 400 'ün üzerinde plastik malzemeye yer verilmiştir. Program plastik malzemeler için oluşturulacak veritabanları az. ve malzeme seçim programlarına temel teşkil etmeyi hedeflemektedir. Program çeşitli hardware ve software kısıtlamaları dolayısıyla sınırlıdır. Daha pahalı donanımlarla programın verimi daha da artırılabilir. Bu tür yatırımlar program kullanışlılığını ispatlamadan yapılmamalıdır. Programın gözükmeyeni eksiklerinin sonraki vedsionldrda düzeltilmesi dileğiyle.
Özet (Çeviri)
SUMMARY COMPUTER AIDED THERMOPLASTIC SELECTION Design synthesis involves the planning, manufacturing, presenting; of a product to the market and its development within the market (Fig 1.). İn design synthesis, decreasing redesign cycle number involves correct material selection methods constructing the design. The corre lation between design and material selection methods is shown in Fig. 2 jY]. As the design progresses, the number of materials declines rapidly. The incorrect choice of material selection results in poor- design or overdesign. Material selection methods must be used to pre vent this. The objective of this study is to create a database consisting of thermoplastic of group of plastic materials which can be used with a PC and to construct a material selection programme in conjuction. The program includes the mechanic, impact, physical, optical, thermic, electrical and flame redardant properties of these materials. What is a plastic? A plastic is a synthtic, or man-made material, similar in many ways to natural resins found in trees and other plants. It generally has a high molecular weight. A molecule is the smllest existing par ticle of a chemical compound; it is made up of at least two atoms, an atom being the smallest particle of a chemical element. The molecular weight is the sum of the weights of all the atoms in a molecule. A plastic is solid in its unprocessed and processed states; but, while it is being processed into finished items, it is softened enough through the combined application of heat, pressure and mechanical working to be formed into various shapes such as plastic film, refri gerator containers or bottles. VllThere are two major subdivisions of the large and still growing family of plastics, made on the basis of their behavior toward heat- thermosets and thermoplastics. Thermosets, or thermosetting plastics, generally soften only on ce under heat and do not soften again on subseguent heating. Thermo plastics, on the other hand, can time and again be“softened”by heat ing and made rigid by cooling (just as ice can time and again be“softened”into water by heating and remade into ice by cooling). Redesign Tentative outline design T Definition of reauired ' material prooenies I T Does suitable material exist? Yes -No Yes- Manulacture and tes: prototype Poor material Poor“design I ? Unsatisfactory Satisfactory ! Bad Good Fig. Iterative process in design. [l] vixi -ENSi?.ES3NG SCIENCE STATISTICS DYNAMICS STRESS ANALYSIS FLUIDS HEAT COMPUTER SCIENCE DESIGN METHODS APPROXIMATE ANALYSIS: VIABILITY BETTER ANALYSIS'- PERFORMANCE OPTIMISATION METHODS'- EFFICIENCY DETAILED ANALYSIS: (FINITE ELEMENT ETC) EXACT DIMENSIONS MARKET NEED MBODIMENTv MATERIALS SELECTION ALL MATERIALS ILCWPRECISiONI SUBSET OF MATERIALS i HIGHER PRECISION IBEST AVAILABLE FRCGSICNi -\ PRODUCT MATEPIALS SÇ'g'ÇE. STRUCTURE PROPERTIES PROCESSING JCU- ”G FINISHING ECONOMICS Fig. 2. Design process, much simplified(central column), showing how engineering science and materials science interface with each stage; breadth and precision of materials data required at each stage differ greatly. [2] Polyethylene can be given as an example to thermoplastics: Polyethlene is a thermoplastic material formed through the poly merization ethylene gas. PE varies from type to type according to the particular molecular structure of each type (i.e.. its crystalli- nity, molecular weight, and molecular weight distribution). The molecular structure, in turn, is dependent upon the temperatures, pressures, catalyst types, modifiers, and reactor design used in the manufacture of PE. The material varies in physical properties from hard to soft, rigid to flexible, and tough to weak. It ranges in optical properties from clear to opaque, and glossy to dull. Its flow rates during processing range from extremely high to extremely low. Basically, PE is produced by polymerizing ethylene gas (C H ) with a catalyst in a reactor at some combination of temperature and - IX -pressure. The result is a joining together of the ethylene molecules into long polymer chains. PE was first produced by a high pressure process which until re cently accounted for all but a very small portion of the low and me dium density PE (LDPE, MDPE) produced in the world. In the 1950s, a low pressure process was developed for the pro duction of high density PE (HDPE). Because of the fundamental diffe rences in the high and low pressure processes, the materials made by each are, in a number of very important respects, quite different. More recently, Technology has been developed allowing the use of a low pressure process to produce LDPE, now commonly called linear low desity PE (LLDPE). The molecular structure of these materials falls somewhere between that of HDPE and LDPE. Tough films can be produced at reduced gages, and film applications are expected to be a major market for these products. The possible use of existing low pressure, as well as existing high pressure equipment for production of LLDPE will have a great influence on the industry for years to come.\[4 j Extrusion can be given as an example to processing techniques of thermoplastics: Extrusion is the process of applying heat and pressure to melt the thermoplastic resin and force it through an accurately dimen sioned die to continuously produce shapes in the form of unsupported film and sheeting; pipe and other profiles; film for coating paper, paper board, metal foil, cellophane, plastics films, cloth and other subtrates; or coating around wire or cable. jTSJ Oxygen Index Test can be given as an example to test methods of thermoplastics: The oxygen index test was developed by Eenimore and Martin at the General Electric Research and Development Centre, and adopted as an ASTM Test in 1970 (ASTM D2863). - xThe test's purpose is to measure relative flammability of mate rials by burning them in a controlled environment, and it offers a possibility for ranking polymer flammability. The test atmosphere is an externally controlled mixture of N2 and 0. A specimen, supported in a sample holder, is ignited with the pilot flame. Upon succesful ignition, the pilot flame is removed. In successive test runs, the 0 concentration is reduced to a point where the sample can no longer self-support combustion. The oxygen index is the minimum oxygen concentration in which the material will just self-support combustion for 3 minutes, or burn 3 inches. It should be noted that there is an LOI-dependance on temperature. j~24] How to use the program: There are 10 sections in the main menu of the program. The first three sections are concerned with the database. The first section is for choosing new files. The second section is for making changes in chosen files whereas the third is for viewing the files.. The fourth and eigth sections are related with material selecti on. In the fourth section, a searching code is created in order to view material lists according to a spacific code. The searching code is classified acording to one of the 4 areas consisting of chemical name, production method, production objective, the application of the materials. The lists of the materials according to the searching code in the fifth section. The sixth section is used to view material lists according the quantative properties of the materials. For example the lists of materials whose densities are lower thar 2 gr/cm. In the sevnth section, tables are constructed from the properti es. xi -In the eighth section, graphies are drawn from the properties of the materials in order to compare plastic famlies. In the nineth section, the standart number of the test are given. The tenth section is used to exit the program. - XII
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