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The orientation relationships between the compression twins and their matrices in magnesium were investigated using EBSD technique. Schmid factor analyses were applied to determine the orientation dependency of compression twins and the condition for double twinning. Results show that thin compression twin bands of f10 1 11g type lose easily their exact twin relation of 56 h11 2 20i to $40 h11 2 20i due to the instability of twin orientation and immobility of twin boundaries. And the basal orientation with TD-rotation tends to induce tension twinning in compression twins.

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This paper shows the experimental and the theoretically predicted results of the sensitivity characteristics of the arc sensor in a dynamic state during gas metal arc welding. First, a mathematical model of the sensor for theoretical prediction was introduced, and then the rationality of the model was confirmed by a series of corresponding experiments. Finally, simulation analyses were made in order to clarify how the welding system and welding conditions affect the sensitivity characteristics of the arc sensor. It is shown that the frequency of torch height variation (the sensor's input) significantly affects the sensitivities of the welding current and the welding voltage (the sensor's outputs). The current sensitivity is highest when the frequency of torch height variation is ∼5 Hz, but the voltage sensitivity simply increases with the increase of torch height variation frequency. It is also clarified that a decrease in the welding loop's inductance and/or the equivalent output resistance of the welding power source improves the sensor's current sensitivity but decreases voltage sensitivity. Decreasing the electrical resistance, but with an increase in electric field intensity of the arc column, or using a shorter setting electrode extension are useful ways of increasing the current and voltage sensitivities of the sensor.