As conducting an impact hammer testing during experimental modal analysis, the multiple impact phenomenon must be avoided. It is generally recognized that the multiple impact phenomenon is induced by the tester’s improper operation and can be avoided through more careful operation. This study theoretically and numerically investigates the whole process of the dynamical interaction between the hammer tip and the impacted structure and discovers the intrinsically physical mechanism of the multiple impact phenomenon. The determination of the interacting process comes down to solve two sets of governing differential equations alternately, and the effectiveness of the theoretical analysis is validated by numerical simulations. Four dimensionless parameters governing the interacting process are recognized in the theoretical framework. The critical stiffness ratio for a given impacted location and the critical impacted location for a given stiffness ratio are analytically determined. These results can guide impact hammer testing to avoid the occurrence of multiple impact by suggesting the hammer tip and impacted locations.

在实验模态分析期间进行冲击锤测试时，必须避免多重冲击现象。人们普遍认为，多重冲击现象是由于测试仪操作不当引起的，可以通过更加小心的操作来避免。本研究从理论上和数值上研究了锤头与被撞击结构之间动力相互作用的全过程，并发现了多重撞击现象的内在物理机制。相互作用过程的确定归结为交替求解两组控制微分方程，数值模拟验证了理论分析的有效性。在理论框架中识别出控制相互作用过程的四个无量纲参数。通过分析确定给定冲击位置的临界刚度比和给定刚度比的临界冲击位置。这些结果可以通过建议锤头和冲击位置来指导冲击锤测试以避免多次冲击的发生。