Application of digital image Correlation in Measuring residual stress by center hole drilling

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Application of digital image Correlation in Measuring residual stress by center hole drilling

ارائه دهنده: Provider: Jalal Nouri

اساتید راهنما: Supervisors: Dr.Amir-Hossein Mahmoudi

اساتید مشاور: Advisory Professors: Dr.Hassan Khotanlou

اساتید ممتحن یا داور: Examining professors or referees: Dr.Ali Alavi-nia - Dr.Hashem Mazaheri

زمان و تاریخ ارائه: Time and date of presentation: 2023/03/06

مکان ارائه: Place of presentation: Seminar 3 Department of Mechanics

چکیده: Abstract: The digital image correlation (DIC) method has garnered a lot of attention in the last decade. Many researchers have carried out extensive research in various fields of engineering, e.g., mechanical engineering and in the field of measurement of displacement fields and strain and, consequently, measurement of stress. This method possesses characteristics that have well shown its superiority over other methods of displacement field measurement. Characteristics such as no need for a professional operator, no need for complicated and expensive prerequisites to begin the test, and not being affected by environmental conditions such as temperature, etc. are some of the advantages of this method. Also, the ease of access and affordability of imaging and calculating equipment, as well as the advancement of these two fundamental requirements for the DIC method have increased the power of this method and, as a result, the enthusiasm of researchers to use it. However, the method is not free of defects. One of the important limitations in the DIC method is that the optical axis of the mirror is required to be positioned perpendicular to the surface of the specimen; therefore, this limitation has been expressed as one of the three fundamental principles of the DIC method. Some researchers have explicitly described the results obtained from the method as invalid if the optical axis of the camera is not aligned perpendicular to the surface of the specimen. This limitation has caused the DIC method to be inefficient in laboratory and even industrial cases. In order to measure residual stresses by hole-drilling methods, making errors in drilling—in case of removing the drill and other equipment to capture the image—results into the inefficiency of the DIC method. To measure the displacement field in cases where it is not possible for the camera to be positioned perpendicular to the surface of the specimen, other papers have recommended 3D DIC, which is beyond the scope of the present research. Other papers have also suggested the use of optical devices such as mirrors or prisms; nevertheless, it should be noted that using mirrors to capture perpendicular images is not always practical. In the present research, eliminating the requirement of the optical axis of the camera being perpendicular in the DIC method and also making an arrangement and instructions for measuring residual stresses by the incremental center-hole drilling method in this this way are performed in two dimensions (only with one camera). In this research, mathematical theoretical foundations were established for the DIC method. The experiments also confirmed this claim with acceptable accuracy

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