Hello, should we choose different hammers for different materials? In today's work, I tested the origin frequency response of the automobile air-conditioning box. I chose the nylon hammer, and the first-order mode is about 250Hz, which is inconsistent with the actual situation, and the coherence is very good. Does this mean that the lower-order mode is not excited due to the selection of a harder hammer? Should I choose a rubber hammer to excite lower order modes? Thank you. Looking forward to your reply?
It should be impossible to excite higher-frequency modes without exciting the lower-frequency modes. The impact event excites *all* frequencies up to a cutoff frequency; the stiffer the tip, the higher this cutoff frequency is. The value of a less-stiff tip is concentrating all of the energy of the impact event over the lower frequency range, rather than spreading it out. What do you expect the first natural frequency to be, and why do you expect that?
@@SimcenterTesting Perhaps my colleagues gave me the experience that the mode of the car air-conditioning box is about 200Hz. When choosing a harder nylon hammer, I found that one peak of the FRF curve exceeds 300Hz, so I feel abnormal; May nylon hammers fail to excite low-order modes?
Hello, should we choose different hammers for different materials? In today's work, I tested the origin frequency response of the automobile air-conditioning box. I chose the nylon hammer, and the first-order mode is about 250Hz, which is inconsistent with the actual situation, and the coherence is very good. Does this mean that the lower-order mode is not excited due to the selection of a harder hammer? Should I choose a rubber hammer to excite lower order modes? Thank you. Looking forward to your reply?
It should be impossible to excite higher-frequency modes without exciting the lower-frequency modes. The impact event excites *all* frequencies up to a cutoff frequency; the stiffer the tip, the higher this cutoff frequency is. The value of a less-stiff tip is concentrating all of the energy of the impact event over the lower frequency range, rather than spreading it out. What do you expect the first natural frequency to be, and why do you expect that?
@@SimcenterTesting Perhaps my colleagues gave me the experience that the mode of the car air-conditioning box is about 200Hz. When choosing a harder nylon hammer, I found that one peak of the FRF curve exceeds 300Hz, so I feel abnormal; May nylon hammers fail to excite low-order modes?