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首页> 外文会议>Annual Symposium on Quantitative Nondestructive Evaluation; 19980719-24; Snowbird,UT(US) >MEASUREMENTS OF LONGITUDINAL-WAVE VELOCITY IN IIW-TYPE CALIBRATION BLOCKS
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MEASUREMENTS OF LONGITUDINAL-WAVE VELOCITY IN IIW-TYPE CALIBRATION BLOCKS

机译：IIW型标定块中的纵波速度测量

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The velocity measurements presented in Figures 4 and 5 now allow us to address the feasibility of achieving two of the proposed tolerances stated in the European draft. It is clear that all of the blocks, with the possible exception of block 'A', would be acceptable reference blocks based on the criterion that the blocks have longitudinal-wave speeds of 5920 ±30 m/s. The PEO measurements all fall within this acceptable range, with the exception of block 'A', as do the mean values of the FAST measurements. However, with the estimated uncertainty of the FAST measurements being ±80 m/s, little confidence may be placed in any conclusions based only on these measurements. The situation is further complicated by the fact that different operators used different transducers when making the FAST measurements, i.e. the measurement process did not remain constant. Further statistical analysis is needed to estimate the individual systematic errors due to the different operators and different transducers. Determination of the longitudinal-wave velocity to within a ±0.1% (± 6 m/s) tolerance is not practical or reasonable when conventional NDT-type transducers and signal analysis techniques such as the FAST method are implemented. As seen in Figure 4, the variance between the minimum and maximum velocities measured on each of the blocks exceeds the proposed tolerance of ±6 m/s. Uncertainties in these types of measurements are estimated to be on the order of ±80 m/s, where the majority of this overall uncertainty is due to systematic errors like diffraction and wear plate effects, which currently cannot be corrected for. If only random errors are considered, then the uncertainty due to imprecision reduces to ±17 m/s, which is still three times as great as the proposed ±6 m/s, implying that the measurement process itself is unable to reach uncertainties of ±6 m/s. However, the 0.1% tolerance on longitudinal-wave velocity measurements seems viable when the Pulse Echo Overlap method is used. The effects of systematic errors due to bond thickness and diffraction can be reduced through theoretical corrections. The major drawback of this measurement technique is the extensive amount of time and technical expertise needed to make the measurement properly. While it has been proven to work very well in the laboratory environment, it is not economical or practical to require field inspectors to implement it in a practical environment.
机译：现在，图4和5中显示的速度测量值使我们能够解决实现欧洲草案中提出的两个建议公差的可行性。显然，基于块的纵向波速为5920±30 m / s的标准，所有块（可能有块“ A”除外）都是可接受的参考块。除块“ A”外，所有PEO测量值均在此可接受范围内，FAST测量值的平均值也是如此。但是，由于FAST测量的估计不确定度为±80 m / s，因此仅基于这些测量的任何结论都无法置信。由于不同的操作者在进行FAST测量时使用了不同的换能器，即测量过程没有保持恒定，这一事实使情况更加复杂。需要进一步的统计分析来估计由于不同的操作员和不同的传感器而引起的各个系统误差。当使用常规的NDT型传感器和信号分析技术（例如FAST方法）时，将纵波速度确定在±0.1％（±6 m / s）的公差范围内是不切实际或不合理的。如图4所示，在每个块上测得的最小和最大速度之间的方差超过了建议的±6 m / s的公差。这些类型的测量不确定度估计为±80 m / s，其中大部分总体不确定性是由于系统误差（例如衍射和耐磨板效应）造成的，目前尚无法对其进行校正。如果仅考虑随机误差，则由于不精确引起的不确定性降低到±17 m / s，仍然是建议的±6 m / s的三倍，这意味着测量过程本身无法达到±的不确定性。 6 m / s。但是，使用脉冲回波重叠法时，纵波速度测量的0.1％公差似乎是可行的。通过理论校正可以减少由于键合厚度和衍射引起的系统误差的影响。这种测量技术的主要缺点是正确进行测量需要大量的时间和专业技术。尽管已经证明它在实验室环境中可以很好地工作，但是要求现场检查人员在实际环境中实施它既不经济也不实用。

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