In the assessment of breathing cracks, it is assumed that both sides of the crack will contact each other along with the vibration, causing the blades to exhibit nonlinear behaviors. Therefore, nonlinear approaches are much more sensitive to the cracks and are also capable of detecting their location and size. Recently, a nonlinearity measure-based damage location method was proposed for the distributed vibration responses of beam-like structures. However, its procedures require collecting the trajectories of the non-destructive status of structures, which introduce substantial difficulties to engineering applications. In this paper, a bicoherence-based nonlinearity measurement method is proposed for identifying the location of breathing cracks in blades. It can evaluate the extent of nonlinearity in the responses of blades under random excitations and avoids using the non-destructive status of structures. The additional nonlinearity in a blade with a breathing crack, based on distributed parameter modeling, is discussed, while the distributed responses on characteristic point were collected to estimate the degree of nonlinearity. A Total Nonlinearity Index (TNLI) was used to establish the damage indicator of the blade, and the crack was identified by finding the maximum components. Validation experiments were conducted to verify the effectiveness of the proposed method, in which a vision measurement system was employed to obtain the distributed vibration responses.

在呼吸裂纹的评估中，假设裂纹的两侧会随着振动相互接触，导致叶片表现出非线性行为。因此，非线性方法对裂纹更加敏感，并且还能够检测它们的位置和大小。最近，针对梁状结构的分布振动响应，提出了一种基于非线性度量的损伤定位方法。然而，它的程序需要收集结构无损状态的轨迹，这给工程应用带来了很大的困难。在本文中，提出了一种基于双相干的非线性测量方法来识别叶片呼吸裂纹的位置。它可以评估随机激励下叶片响应的非线性程度，避免使用结构的非破坏性状态。讨论了基于分布式参数建模的带有呼吸裂纹的叶片中的附加非线性，同时收集特征点的分布式响应以估计非线性程度。总非线性指数（TNLI）用于建立叶片的损伤指标，并通过寻找最大分量来识别裂纹。进行了验证实验以验证所提出方法的有效性，其中采用视觉测量系统来获得分布式振动响应。讨论了基于分布式参数建模的方法，同时收集特征点上的分布式响应来估计非线性程度。总非线性指数（TNLI）用于建立叶片的损伤指标，并通过寻找最大分量来识别裂纹。进行了验证实验以验证所提出方法的有效性，其中采用视觉测量系统来获得分布式振动响应。讨论了基于分布式参数建模的方法，同时收集特征点上的分布式响应来估计非线性程度。总非线性指数（TNLI）用于建立叶片的损伤指标，并通过寻找最大分量来识别裂纹。进行了验证实验以验证所提出方法的有效性，其中采用视觉测量系统来获得分布式振动响应。