The first high-performance seismometer on Mars, deployed by InSight, has been working for nearly two martian years. However, the recorded seismic data are substantially affected by the natural frequencies of the lander. To analyze the effect of natural frequencies of the lander on specific components of the seismic data, we built a simplified finite-element model of the lander to conduct modal analyses. Three natural frequencies were modeled by comparing them with those identified from the observed data. These natural frequencies are nonconstant and temperature dependent, which can be explained as an elastic modulus reduction of the solar panels (35% at most) and/or the property changes of the ground media beneath the lander due to a daily air temperature variation of approximately 100 K on Mars. Compared with previous studies based on empirical models before the launch, our results can quantitatively evaluate natural modes and their temperature dependency. Thus, these analyses are helpful in avoiding the potential interference of natural frequencies and improving the reliability of seismic data applications.
As one of the key components of solid rocket motors (SRMs) and launch vehicles (LVs), the deformation and damage of the composite rocket motor case (CRMC) can directly affect the effectiveness of the SRMs. Therefore, it is particularly important to analyze the damage failure of composite cases. As the analysis remains complex due to the different failure modes of composites at different scales, this paper applies multiscale analysis methods to CRMC damage. A multiscale mechanical model of CRMC is established, and data transfer between the microscale, mesoscale, and macroscale models is achieved using submodel techniques. In this paper, CRMC was finely modeled, and the thickness and carbon fiber angle of each fiber winding layer were accurately described. Additionally, the results of hydrostatic tests and numerical calculations were compared to verify the validity of the modeling method. The stress levels of the material at macroscale, mesoscale, and microscale scales were obtained through numerical calculations, and the microscale damage failure behavior of the material under the internal pressure load of the composite shell was predicted by combining the strength assessment criterion.
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