Question 1: Why study the natural frequency? Why do modal analysis? Modal analysis is actually to get the modal parameters of the structure, including natural frequency, damping, vibration mode and other parameters. In order to obtain these parameters, modal analysis is generally needed. There are two methods for modal analysis, one is analytical method, which is solved by CAE software, and the other is experimental method. Experimental methods can generally be used to verify the correctness of analytical methods, thus modifying the finite element model.

Question 2: Why do you want to carry out free mode analysis on the structure? Free mode is an inherent property of free vibration of structures, which is only related to the structure itself and has nothing to do with external excitation. The actual structural vibration appears in the form of superposition of its modal formation or its one or more orders. Through free mode analysis, we can determine the dynamic characteristics of the structure, that is, whether the state of each part of the structure is good or bad during vibration, so as to carry out fault diagnosis and optimal design.

Question 3: Hello everyone! Why do you have to do modal analysis before using ansys to do spectral analysis? Thank you. Generally, modal superposition method is used in ANSYS spectrum analysis, and modal analysis is needed in advance, otherwise there is no way to do it.

As for the result of your random response, it should be very small at 20 Hz, and then increase sharply around 890 Hz with the increase of frequency, then decrease gradually after reaching the maximum value, and then increase again, and it may still be in an increasing state at 1000 Hz. However, this process has a lot to do with the actual structure, except that there is a maximum value near 890 Hz, and everything else is uncertain.

Question 4: Why do you want to do multi-degree-of-freedom complex modal analysis? Generally, the frequency of the load is relatively low, so we only need to consider whether it will vibrate with the previous low-order modes. To be precise, it is necessary to analyze the natural frequency (mode) close to the load frequency.

In structural vibration, the proportion of high-order modal energy is too low, which has little effect on the whole structural vibration. Modal analysis is usually done for the first seven orders.

Modal analysis is a modern method to study the dynamic characteristics of structures and an application of system identification method in the field of engineering vibration. Modal is the inherent vibration characteristic of mechanical structure, and each modal has a specific natural frequency, damping ratio and modal shape.

Question 5: Why should modal analysis be done in radar structural design? Modal analysis is the most basic analysis.

Question 6: What are the uses of modal analysis? The ultimate goal of modal analysis research institute is to identify the modal parameters of the system, and provide a basis for the analysis of vibration characteristics of structural systems, the diagnosis and prediction of vibration faults and the optimal design of structural dynamic characteristics.

Question 7: Should modal analysis be constrained? Free mode without adding constraints. The difference of modal parameters between the two structures can be observed through the free mode. Free mode is an inherent property of free vibration of structures, which is only related to the structure itself and has nothing to do with external excitation. However, if we want to pay attention to the modal parameters of the structure in the working state, we must carry out constrained modal analysis, that is, add constraints to the structure according to the actual working state. For modal analysis with prestress, static analysis should be carried out first, and then modal analysis should be carried out on the basis of retaining the results of static analysis. For example, the greater the tension on the steel string, the higher the natural frequency (guitar, erhu, etc. ).

Question 8: Since the constrained mode can better reflect the actual working conditions, why do you want to conduct free mode analysis? What's the role? Usually, we like to do free mode analysis experiments in schools and research institutes, which can be compared with the simulation results of ansys software. Can do a lot of theoretical work, but also gave birth to a lot of papers.

Free mode analysis in engineering is relatively rare and of little significance. In addition, it is difficult to determine the boundary conditions of some structural members, and there is no way to do constrained modes. I have to fool my boss with the free model.

Question: Is it necessary to calculate the static state before calculating the modal in ansys modal analysis? If you want to consider the prestress of the structure, you need to do static calculation first, and there is a special follow-up setting to consider the prestress for modal calculation.

If prestress is not considered, it seems unnecessary.

You can try. It's simple. Modal calculation has no load, but remember to add constraints.

Question 10: Why does modal analysis only need to know that the frequency of the first few general loads is relatively low, and only need to consider whether it will vibrate with the first few low-order modes? To be precise, it is necessary to analyze the natural frequency (mode) close to the load frequency.