Influence Factors and Uncertainty Evaluation for Measuring Results of Percentage Elongation after Fracture of DC03 Cold Rolled Steel Plates

Through the measurement of percentage elongation after fracture of DC03 cold rolled steel plates, the influence of measuring positions of gauge length after fracture on the measuring results of percentage elongation after fracture was analyzed. The difference between two methods of manual measurement and automatic extensometer measurement was also analyzed. Finally the measurement uncertainty of percentage elongation after fracture A_{50 mm} and A_{80 mm} obtained by manual measurement was evaluated. The results show that:the larger the original gauge length was, the smaller the measured percentage elongation after fracture was; the smaller the original gauge length range was, the larger the measured percentage elongation after fracture was; the measuring results of the percentage elongation after fracture obtained by automatic extensometer were less than those obtained by manual measurement; when the coverage factor k was 2, the percentage elongation after fracture of DC03 cold rolled steel plates obtained by manual measurement was A_{50 mm}=49.0%±2.0%, A_{80 mm}=40.5%±2.0%.