# Mechanical Structure Design and Experimental Study of Gamma-ray Monitor for Small Satellite Payload
## 6 Conclusions  
The mechanical design of small satellite GRM payload is completed, comparing with the traditional gamma-ray detector, the novel GRM has the advantages of compact structure, vibration resistance, small size, light weight and no need for high pressure. The finite element model was established by using ABAQUS, and the overload analysis, modal analysis, sinusoidal vibration and random vibration response analysis were completed, and the relevant ground vibration tests were carried out. The conclusions are as follows:  
Figure 14: Performance test before and after mechanical vibration test: (**a**) Performance test site. (**b**) Result of performance test.  
From the static strain cloud diagram, it can be found that the maximum displacement occurs at the center of the beryllium sheet of 15.48 \(\upmu\)m, the maximum deformation is in the elastic deformation stage of the material, and the calculation result of the safety margin is dozens of times the specified standard.The sinusoidal characteristic sweep frequency test shows that the frequency of the first order main mode of the structure is 436.25 Hz, which is greater than the 100 Hz specified in the spacecraft. Through the sinusoidal characteristic frequency sweep before and after the mechanical vibration test, it is concluded that the first order frequency change in X, Y and Z directions of the structure is not more than the 5% specified for the spacecraft, which shows that the structure is not damaged under the mechanical vibration test. From the results discussed above, the stiffness and strength of the structure designed in this paper meet the mission requirements.
2. The empirical value of 0.03 adopted in the finite element calculation is deviated from the actual value. The finite element model is modified using the damping value calculated from the vibration test and half-power bandwidth method. The modified calculation results are in high agreement with the experimental values, which provides a damping reference value for the subsequent finite element calculation.
3. The comparison between modal analysis and sinusoidal characteristic sweep frequency test shows that the first order frequency error in each direction is within the allowable error range of 10% in the engineering analysis. The first order frequency is 420.25 Hz, which meets the requirement that the product must be greater than 100 Hz.  
Conceptualization, S.X. and X.L.; methodology, H.X. and S.Y.; software, P.G., H.X. and S.Y.; validation, P.G., H.X. and S.Y.; formal analysis, P.G., H.X. and S.Y.; investigation, P.G.; resources, D.Z.; data curation, Z.A.; writing--original draft preparation, P.G.; writing--review and editing, H.X.; visualization, H.X. and P.G.; supervision, Z.A.; project administration, D.Z.; funding acquisition, S.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Development of the Gamma-ray Transient Monitor (GTM) Payload for the Earth-moon space DRO exploratory research Program (XDA30050100) of the Institute of High Energy Physics, CAS[PERSON]  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.