Title: Simulation of Glass Cutting with an Impinging Hot Air Jet
By: Dr. Shahani
Thermal cutting of glass sheet due to an impinging hot air jet is simulated and analyzed. Induced thermal stresses due to the moving heat source can be used to stably initiate and attract a crack toward the jet axis. Relative motion between the jet and glass sheet then can be used to cut the glass sheet. This paper presents a theoretical study of this process for straight cuts. Process sinulation is accomplished by analyzing the coupled temperature and stress fields together with the fracture mechanics criteria for the crack growth.
A finite element remeshing technique is employed for the analysis and singular elements are uesd around the crack tip for a more precise computing of the stress intensity factor. It is shown that a certain minimum air temperature for a given nozzle velocity and a certain maximum air jet velocity for a given temperature are required for continuous cutting. The results of the simulation show a good agreement with the published results in the literature. However a variating nature is detected for the distance between the crack tip and the air jet nozzle from a starting value to the steady-state one.
Title: Measuring of crack length in metals by time-flight diffraction technique (TOFD)
By: Dr. Honarvar
Time-of-flight diffraction (TOFD) is an ultrasonic testing technique which has received much attention in recent years. Although, not largely used in NDT applicaations, it is predicted that it will find a special place among NDT techniques in the future. TOFD is based on the measurement of the time-of-flight of waves diffracted from the tips of a crack. In this report, the mathematical model of TOFD and the instruments and procedures for carriyng out the TOFD experiments are decribed. Moreover, advantages & disadvantages of TOFD are reviewed and the standards dealing with TOFD are cited. Steel blocks with implanted defects were manufactured. These defects are crack-like cuts made by a precise wire-cut machine. The blocks were inspected by TOFD technique and the results indicate the capability of TOFD in accurate and measurerment of the depth through-wall thickness of the cracks. Application of TOFD include the inspection of welds in structuers, boiles , and passure vessels.
Title: Design and manufacturing of a multi-function testing machine: multiaxial fatigue strength and combind periodic axial, bending, torsional loadings
By: Mohamadi Shoja Eng.
This testing machine is capable of performing fatigve test under the most general loading condition. While specimen is rotating, it maybe subjected to any combination of the following loading:
1-Pure bending with or without periodic bending excitation
2-Axial loading with or without periodic axial excitation