Identification of fracture toughness for flat and tempered flat soda-lime glass by means of indentation technique

In this thesis, green coloured flat glass, green coloured tempered flat glass, white coloured tempered flat glass and white coloured flat glass fracture toughness calculations are performed and suitable formulas of Vickers indentation method are searched for tempered flat glass and flat glass. Purpose of the thesis is explained and brief information about literature survey is given in the first p art of this thesis. General information about literature review of glass is given in the second part of the thesis. Fracture mechanics is defined in the third part of the thesis. In the fourth part of this study, experimental studies, progression of experi mental studies and procedure used during experimental studies are defined. Besides, calculations for fracture toughness of glasses are explained in the fourth stage of the thesis. In the fifth and last part of this thesis, experimental test results are com pared and it's determined that which formula is appropriate for white coloured tempered flat glass, which one is suitable for white colured flat glass, which formula is proper for green coloured tempered flat glass and which one is fitting with green colou red flat glass. It is mentioned about advantages of indentation method and purpose of the thesis are given in the first part of the thesis. Fracture toughness of soda - lime and tempered soda - lime glasses have been calculated according to formulas of Vickers indentation methods which are Palmqvist, Half - Penny and Curve Fitting Technique and suitable Vickers indentation method with formulas has been defined for the purpose of the thesis. Basic information about molecular structure and characteristics of glass are indicated in the second stage of the thesis. Classification of glasses literature research about physical, mechanical, chemical and thermal properties of glasses are given in this thesis. Silica glasses which are investigated within the scope of this t hesis are type of oxide glasses and most commonly used glasss type. The composition of silica glasses are depend on eutectic position in the phase diagram of Na2O - CaO - SiO2. Generally, soda - lime glasses contain %22 Na2O, %5Cao and %73 SiO2. The main physic al characteristics of glass is viscosity because viscosity creates the glass melting temperature condition; influence the annealing temperature, processing, refining of glassrs and rate of crystallization. From the chemical properties side, soda - lime glass es are inert as a general rule and soda - lime glasses don't decompose in water and water - based neutral solutions provided that temperature of solution is not high. Glasses don't let permanent deformation due to its molecular structure. Resistivity of glass against compressive stress is very high while resistivity of glass against tensile stress is very low and surface properties of glass determine the mechanical strentgh of glasses.Strength of glasses has been using in daily life is changing between 30 Mpa t o xxii 100 Mpa. Glasses are material type which thermal conductivity is low. Thermal expansion of glasses are varying according to glass kind. Vibration of glasses and thermal expansion coefficient decrease as well as percentage of glass forming oxide increases in glasses. In the third section of this thesis, general information about fracture mechanics is given. Firstly, fracture types are described and then, two fracture mechanics approaches LEFM ( Elastic Fracture Mechanics) and EPFM (Elastic Plastic Fracture Mechanics) are explained. Linear elastic fracture mechanics approach is usually used for brittle materials like glasses that's why, linear elastic fracture mechanics is stated in detail in this thesis. Lastly, materials' fracture toughness experiments whi ch has been commonly used to determine materials' fracture toughness are described as a summary and indentation method is expressed in the scope of thesis. Fracture means breaking into two or more pieces of a solid body under the load. Fracture composes of two phases: Crack generation and crack progression. There are two main type of cracks: Brittle and ductile fracture. Fracture mechanics is a type of science examining cracking in terms of micro and macro. Fracture mechanics is a qualitative approach which defines fracture strength depending on the stress analysis, applied load and structural geometry of defected components. First study about fracture mechanics has come up from Griffith in 1920. There are two differentmethodologies which are Linear Elastic Fracture Mechanics and Elastic - Plastic Fracture Mechanics. Linear elastic fracture is developed to describe crack dimension and fracture under elastic conditions. Linear elastic fracture mechanics has been generally using to define fracture of for the bri ttle materials like ceramics and glasses. Linear elastic fracture mechanics does not work for the ductile materials and elasto - plasto fracture mechanics approach has been using instead. SENB, CT and DCB methods are commonly used for fracture toughness test s. Indentation method has been using for determination of fracture toughness as an alternative way because of its being quick and simple way. In the fourth stage of this thesis, experimental studies are described. Green coloured tempered flat glass samples , white coloured tempered flat glass samples, green coloured flat glass samples and white coloured flat glass sa mples were produced in ŞİŞECAM Trakya Cam Sanayi A.Ş., Trakya plant. Glass samples were exposed to loads which weights are 0,2 kg, 0,3 kg, 0,5 kg, 1 kg, 2 kg, 3 kg, 5 kg and dimension of the marks are measured via optical microscope. It is mentioned abou t experimental test results in the fifth stage of this thesis. Load to crack length change, load to Vickers hardness change, load to elasticity modulus change investigated and calculations are made for fracture toughness formulas. Formulas are classified i nto three main categories: Palmqvist technique, Half - Penny technique and Cuve Fitting technique. Calculations were made by using selected formula between these 3 techniques. c/a is accepted as a reference value in order to specify the proper model and corr ect model is decided by using c/a rate. c/a rate can be used for flat glasses together with formulas of Half - Penny model while c/a rate can be used for tempered flat glasses together with formulas of Palmqvist model. Usability of Curve Fitting method formu las are investigated for both tempered flat glasses and flat glasses. MINITAB programme was used for statistical analysis of formulas. Lastly, comparisons of experimental test results are executed in the sixth stage of this thesis. Statistical analysis is done according to experimental test results and it's tried xxiii to find out suitable tchnique for tempered white flat glasses, white flat glasses, green flat glasses a nd green tempered flat glasses. At the end of this thesis, it's indicated that calculated frac ture toughness of the glass samples are too close to the fracture toughness of glasses given in the literature if fracture toughness of glass samples are computed by using determined formula which is selected from determined fracture .