Abstract. The validity of several known failure initiation criteria at reentrant corners in brittle elastic materials is examined and a simple one is proposed. Their predictions, under mode I stress field, are compared to experimental observations carried out on PMMA (polymer) and Alumina-7%Zirconia (ceramic) V-notched specimens. Because all realistic V-notched reentrant corners are blunt, a detailed experimental procedure has been followed, focusing on specimens with different notch tip radii. It is demonstrated that by assuming a sharp V-notch, some failure criteria predict reasonably well the experimental findings, and that corrections are needed in order for these to take into consideration the realistic radius at the notch tip.

Three mixed mode failure initiation criteria at reentrant corners in brittle elastic materials are examined. Prediction of failure load and crack initiation angle are compared to experimental observations carried out on PMMA (polymer) and MACOR (glass ceramic) V-notched specimens. Since the mode mixity ratio influences greatly both the failure load and crack initiation angle, a detailed experimental procedure has been followed, focusing on obtaining a wide range of mode mixity ratios. It is demonstrated that by assuming a sharp V-notch tip some failure criteria predict reasonably well both the crack initiation angle and failure load.

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A model of gas metal arc welding was developed that solves the magnetohydrodynamic equations for the flow and temperature fields of the molten electrode and plasma simultaneously, to form a fully coupled model. A commercial finite-element code was extended to include the effects of radiation, Lorentz forces, Joule heating and thermo-electric effects. The model predicts the shape of the free surfaces of the molten metal as the droplets form, detach, and merge with the weld pool. It also predicts the flow, temperature, and electric field. Material properties and the welding parameters are the input variables in the model. The geometry of the numerical model was constructed to fit an experimental apparatus using an aluminium electrode and an argon shielding gas. Droplet frequency measurements were used to verify the model's predictions. For a typical arc, the temperature of the plasma can range up to 20 000 K, where there is more uncertainty in the thermophysical properties of the plasma, and the properties in this range are highly non-linear. For this range, the material properties of the model were adjusted to obtain a better fit between the numerical and the experimental results. The model and experimental results were comparable.