Nasrollahi Amir, Rizzo Piervincenzo
Laboratory for Nondestructive Evaluation and Structural Health Monitoring Studies, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
J Acoust Soc Am. 2018 Oct;144(4):2201. doi: 10.1121/1.5056172.
This article presents a nondestructive evaluation (NDE) method to infer the neutral temperature and the axial stress in thick beams. The method relies on the propagation of highly nonlinear solitary waves generated at one end of a chain of spherical particles in a dry point contact with the beam to be evaluated. The waves are reflected back to the chain and the research hypothesis is that the axial stress, which influences the beam's stiffness, affects the amplitude and speed of the reflected waves. To verify this hypothesis a general finite element model of thermally stressed beams was developed and coupled to a discrete particle model able to predict the propagation of the waves along an L-shaped granular medium. The models were validated experimentally to quantify the repeatability of the setup, the sensitivity of the wave features on the thermal stress, and the independence of the wave features on the neutral temperature of the beam. The hypothesis was proven valid by both the numerical and the experimental results. In the future, these findings may be used to refine a NDE method to assess stress in columns, to infer the neutral temperature of continuous welded rails, and to prevent thermal buckling of critical structures.
本文提出了一种无损评估（NDE）方法，用于推断厚梁中的中性温度和轴向应力。该方法依赖于在与待评估梁进行干点接触的球形颗粒链一端产生的高度非线性孤立波的传播。这些波反射回颗粒链，研究假设是影响梁刚度的轴向应力会影响反射波的幅度和速度。为了验证这一假设，开发了热应力梁的通用有限元模型，并将其与能够预测波沿L形颗粒介质传播的离散颗粒模型耦合。通过实验对模型进行了验证，以量化设置的可重复性、波特征对热应力的敏感性以及波特征对梁中性温度的独立性。数值和实验结果均证明该假设有效。未来，这些发现可用于完善一种无损评估方法，以评估柱中的应力、推断连续焊接钢轨的中性温度，并防止关键结构的热屈曲。
