Zirkonyum esaslı kalın camsı metalin frezelenmesinin sonlu elemanlar analizi
Finite element analysis of milling zirconium based bulk metallic glass
- Tez No: 293666
- Danışmanlar: YRD. DOÇ. DR. MUSTAFA BAKKAL
- Tez Türü: Yüksek Lisans
- Konular: Mühendislik Bilimleri, Engineering Sciences
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2010
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Malzeme ve İmalat Bilim Dalı
- Sayfa Sayısı: 137
Özet
Metaller genellikle kristal yapıdadırlar yani atomları uzayda belirli bir düzene göre dizilmişlerdir. Belirli koşullar sağlanırsa atomlar arası bu düzen oluşmayabilir ve böylelikle metalin iç yapısındaki atom dizilişi düzensiz yani metal amorf olabiliir. Bu şekilde elde edilen metallere amorf ya da camsı metal denmektedir. İlk camsı metal Au-Si alaşımının camlaştırılması(camsı metal veya amorf metal) ile 1960 yılında Clement ve arkadaşları tarafından elde edilmiştir. Bu camlaştırma işlemi çok yüksek soğuma hızları (105-106 Ks-1) ile elde edilmiştir. Fakat bu teknik kullanılarak ancak birkaç mikron boyutlarında parça elde edilebilmekteydi ve bu camsı metallerin uygulama alanını kısıtlamaktaydı. Bu kısıtlar ancak Kalın Camsı Metaller (KCM)'in düşük soğuma hızları(
Özet (Çeviri)
Metals are in crystal structure, it means their atoms are arranged in an order in space. If particular conditions are provided, this arrangement of atoms can be prevented and thus, metal atoms come together randomly. As a result structure of metal is not crystal anymore, it is called amorphous. The metals, which are produced in this way, called amorphous metal or metallic glass. The first metallic glass, Au-Si alloy, was obtained by Klement and his friends in 1960. This vitrification process was achieved by high cooling rates, 105-106 Ks-1 . But in these years metallic glasses could be produced in dimensions of only a few microns by using high cooling rates therefore the application field of metallic glasses were limited. These limitations were overcome by obtaining Bulk Metallic Glasses (BMG) in very low cooling rates which were less than 100K/s. In order to achieve these low cooling rates Peker and Johnson used Zr-Ti-Cu-Ni-Be alloys due to their great glass formation ability. As a result of this, bulk metallic glasses were produced by traditional casting processes in 50-100mm dimensions by using very low cooling rates,1 K/s,. The first commercial BMG produced by this technique took the name of Vitreloy.With the production of BMGs it became possible to investigate the mechanical properties of BMGs in very different loading conditions. Thus the unique mechanical properties of BMGs were determined. These properties can be summarized as; high yield strength, wide elastic limit and fracture toughness which can be comparable to crystalline metals.The first quasi-static experiments were carried out by Bruck, and the yield strength of Vitreloy 1(Zr41.2Ti12.8Cu12.5Ni10Be22.5) was determined as 1.9 GPa, and the elastic limit was %2 at room temperature. In addition the widest research about the deformation behavior of bulk metallic glasses were carried out by Lu. Lu investigated the deformation behavior of BMGs in very wide loading conditions and obtained the stress-strain relations at different strain rates and temperatures.In machining processes, in which high strain rates and high temperature occur, it is important to have the knowledge about the static and dynamic behaviors of BMGs at different loading conditions in order to understand the nature of machining processes.As mentioned above in machining processes high temperatures come across, in course of BMG machining if the temperatures are above the crystallization temperature of BMG (445oC), the amorphous structure of BMG will collapse. Losing the amorphous structure means losing the unique mechanical properties mentioned above. Therefore, it is important to determine the optimum cutting parameters and in which parameters that BMG sustain its amorphous structure. On the other hand the experiments, which are used to determine these parameters, are expensive and time consuming. Therefore the ultimate goal is to replace these experimental methods with physics-based models in order to optimize the process parameters and cost.For this purpose, the finite element analysis of slot milling, which is one of the most important step of machining processes, of BMGs are investigated at this work.The alloy used at this work is commercially called Vitreloy 105 and has the chemical composition of Zr52,5Ti5Cu17,9Ni14,6Al10.In the early steps of the study the milling chip of BMG was investigated by finite element method. In machining, that includes fast plastic deformation actually, chips occur due to plastic deformation. In the light of this knowledge, milling chips were collected, mounted, investigated by an optic microscope and modeled by a commercial CAD software. Then the modeled milling chip exported to ANSYS, which is a finite element software, in order to perform an inverse engineering application which is based on plastering of milling chip back to work piece. But due to high strains and remeshing problems this application was resigned.After that it was understood that in order to model the milling of the alloy, the deformation behavior of BMG should be determined to do this Lu?s research was taken as a reference. In conclusion stress-strain data which was used in finite element analysis, was obtained and a constitutive equation for BMG was formed by using numerical methods. After forming the material model, the cutting tool was modeled in 3D by using SolidWorks. Finite element analysis was performed by DEFORM which is used commonly to analyze the manufacturing processes. Consequently the cutting forces obtained from milling experiments of 6.35 diameter Zr based BMG and the cutting forces obtained from finite element analysis were compared to each other.As a result it is seen that the estimated cutting forces by finite element model are so much accordance with experimental results.
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