Sharif Digital Repository

Residual stresses are one of the influencing factors on fatigue life. These stresses may cause cracking and failure of the element even in the absence of any applied stress or any external load. For this reason they are very important, and their measurement is crucial. The methods for measuring the residual stress in spite of their name often measure the strain and by analyzing the measured strain, determine the residue stress of the element. The important problem about residual stresses is that their values in the element often remain unknown and usually no simple and non destructive method for measuring is available. Usually finite element analyzing is used for modeling the production... 

In present research, a cohesive based finite element model has been introduced to estimate median crack depth during mechanical machining on optical glasses. Development of the machining numerical model has been initiated by investigating the indentation process. Experimental results of this step have been calibrated primary numerical model which has been used in the scratch process. Due to differences between the scratch mechanism and indentation one, mathematical bases fracture formulas and cohesive relations have been developed. After extracting primary result, using them in the scratch model and developing the primary model, ultimately numerical model has been evolved to an abstract...