Clauß Felix, Epple Niklas, Ahrens Mark Alexander, Niederleithinger Ernst, Mark Peter
Lehrstuhl für Massivbau, Fakultät für Bau- und Umweltingenieurwissenschaften, Ruhr-Universität Bochum, Universitätstraße 150, 44801 Bochum, Germany.
Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany.
Sensors (Basel). 2020 Jul 20;20(14):4023. doi: 10.3390/s20144023.
Due to the high sensitivity of coda waves to the smallest structural alterations such as strain, humidity or temperature changes, ultrasonic waves are a valid means to examine entire structures employing networks of ultrasonic transducers. In order to substantiate this ex ante assessment, the viability of measuring ultrasonic waves as a valid point of reference and inference for structural changes is to be further scrutinized in this work. In order to investigate the influence of mechanical strain on ultrasonic signals, a four-point bending test was carried out on a reinforced concrete beam at Ruhr University Bochum. Thus, measurements collected from a network of selected transducer pairings arranged across the central, shear-free segment of the test specimen, were correlated to their respective strain fields. Detected ultrasonic signals were evaluated employing Coda Wave Interferometry. Such analysis comprised the initial non-cracked state as well as later stages with incremental crack depth and quantity. It was to ascertain that the test specimen can in fact be qualitatively compartmentalized into areas of compression and tension identified via Relative Velocity Changes presented in Attribute Maps. However, since results did not entail a zero crossing, i.e., neither positive nor negative values were to be calculated, only relative changes in this work displayed staggered over the height of the object under test, are discussed. Under the given methodological premises, additional information is currently required to make quantitative assertions regarding this correlation of ultrasonic and strain results. This holds true for the comparability of the ultrasonic and strain results for both non-cracked and even the cracked state.
由于尾波对诸如应变、湿度或温度变化等最小结构变化具有高度敏感性，超声波是利用超声换能器网络检测整个结构的有效手段。为了证实这一事先评估，在本工作中要进一步仔细研究将测量超声波作为结构变化的有效参考点和推断依据的可行性。为了研究机械应变对超声信号的影响，在波鸿鲁尔大学对一根钢筋混凝土梁进行了四点弯曲试验。因此，从布置在试样中央无剪切段的选定换能器对网络收集的测量数据，与它们各自的应变场相关联。利用尾波干涉测量法对检测到的超声信号进行评估。这种分析包括初始无裂纹状态以及裂纹深度和数量增加的后期阶段。目的是确定试样实际上可以通过属性图中呈现的相对速度变化定性地划分为压缩区和拉伸区。然而，由于结果没有出现过零点，即无需计算正值或负值，在本工作中仅讨论在被测物体高度上呈现交错的相对变化。在给定的方法前提下，目前需要额外信息才能对超声结果与应变结果的这种相关性做出定量断言。这对于非裂纹状态甚至裂纹状态下超声结果与应变结果的可比性均适用。
