Griffith's theory of fracture Coursework Example | Topics and Well Written Essays - 1000 words

Griffiths theory of fracture - Coursework ExampleCeramics and Metals have different atomic coordinate and ionic bonding. Ceramic materials have both ionic and covalent bonds. dome bond is the one that keeps them brittle. Ionic bond is lose and no definite direction.The positive and negative ions are arranged and are held together by friendship created by each separate of different charge. When stress is applied, ions slide past each other then goes to different directions ions of the same charge bumps and trying to fight off each other causing the atoms to spread. The material then breaks. In coats, the atomic structure consist more than positively charged ions on a draw of negatively charge electrons. The electrons allows the positive charge ions to slide and roll past each other without breaking the bond when a certain stress is applied. This causes the metal to be tough. 2) Glass in general has a low tensile strength. This lies entirely with the fact that glass is a solid lacking crystalline structure or namely amorphous solid. Amorphous solid has a moving structure of tinges and are not compact, this results to having a low tensile strength than of other solids. However, there are methods of somehow improving glasss tensile strength, strengthening them. One is by soaking the glass into a bath of potassium nitrate solution on an about 400 to 450 degrees Celsius having. Potassium nitrate has larger molecule structure than of a common sodium nitrate molecule in the surface of the glass. The process will now replace the sodium nitrate on a glass by the potassium nitrate in the bath solution, leaving the glass having a thick forge and a hard wedge. This is called chemical strengthening. Another one is called heat strengthening where a glass surface is heated for about 1100-1500 degrees Fahrenheit then suddenly cooled. After suddenly cooling, the glass molecules compresses, thus having a thick and compressed layer than before. 3) Griffiths equation ste ps directly not to the strength of a material but the fracture in it and how hard can it withstand a force before it collapses. Fracture is the propagation of a crack or a flaw across loaded or force-applied segment. Toughness is the shoes of a material to withstand fracture. Now glass has literally low escapeance to fracture than steel has. In Griffiths equation, you would get stress over test or Youngs modulus of a material first then that you will determine its toughness. A glass generally has only 50-90 GPa. Its ability to resist fracture is very low compared of steel which has a stress over strain ratio of around 190 to 210 GPa. This makes steel as a more preferable material than glass. 4) Elastic deformation by definition is reversible. Meaning, the material will return to its original state when stressed and bending stress is no longer applied. Uniform plastic deformation is an irreversible deformation where the material strains orderedly upon stress. The material will no t return to its original state sort of it cracks or ruptures when certain stress is strong enough for the material to withstand. Local plastic deformation or also known as necking differs from uniform plastic deformation by means of the strain applied. It is a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material. The localised portion of the material where there is a decrease in local area became the basis for neck. 5) In surface elasticity the polymer chains of an elastomer coils at random at a relaxed state. On extension, the chains are stretched out, and their conformational entropy is reduced. This is the reason why a rubber material, when suddenly relaxed from extension, snaps back. This is the basis in an elasticity modulus of a material. The material is highly elastic when its stiffness and extension are balanced together. Stiffness is an extensive property of a material to resist deformation. The high the stiffness can be the high the materials extensions. 6) Thermosetting resin has a composition