## 3 Data Analysis of Similarity Calculation Method for Infield and Outfield Environmental Tests
### Verification of Similarity Calculation Method for Infield and Outfield Tests
The fitting effect of the derived curve is better than that of the four-point interpolation curve, which is close to that of the outfield fitting curve. In other words, the fitting effect of the derived curve is closer to that of the outfield curve. The curve fitting of the infield and outfield tests was optimized by the goodness of fit. The optimized curve does not pass most of the corresponding experimental points. In the process of interpolation, the interpolation curve must pass through the sampling point in the outfield, and at this time, the curve may be quite different from the corresponding data at other temperatures, so the goodness of fit of the curve is relatively low. For samples from the same material, the low-temperature elastic response of the infield and outfield environments obeys the performance law of the same material. By taking the samples  
Figure 11: Derivation curve and fitting curve of polynomial fitting. (**a**) Material A springback derivation (**b**) Material A elongation derivation (**c**) Material B springback derivation (**d**) Material B elongation derivation. Figure 14: _Cont_. Figure 13: Derivation curve and fitting curve of exponential fitting. (**a**) Material A springback derivation (**b**) Material A elongation derivation (**c**) Material B springback derivation (**d**) Material B elongation derivation. The goodness of fit of the derived curve obtained by the similarity calculation method under the three fitting forms is compared with that of the corresponding outfield fitting curves. The results are shown in Figure 15.  
From Figure 15, it can be found that for the three fitting methods and two materials, the goodness of fit of the derived curve obtained by the similarity calculation method is close to that of the corresponding outfield fitting curve. For any kind of material, when its performance in the environmental test chamber is similar to that in the outfield environment (as shown in Figure 9), that is, when the main influencing factor of the material's performance in the outfield environment is the same as that in the infield environment, and there are similar performance changes, this method can be applied. This similarity calculation method of the translation and scaling transformation can be used for different materials and multiple fitting methods, with good feasibility and generalizability. Through the verification of the outfield point data, this study obtains an effective similarity calculation method based on the translation and scaling transformation of the similar curve. Based on the known curve of the infield low-temperature steady-state response of the aircraft rubber sealing materials, two temperature sampling points in  
Figure 14: Derivation curve and fitting curve of Fourier fitting. (**a**) Material A springback Derivation (**b**) Material A elongation Derivation (**c**) Material B springback derivation (**d**) Material B elongation derivation. Figure 15: Goodness of fit of derived curve and fitting curve. the outfield which are far away from each other are taken to obtain the outfield low-temperature performance of the material and judge whether there is any difference in the infield and outfield performance of the material. Based on the similarity of the infield and outfield properties of the material, the curve is obtained by the curve translation and scaling transformation. This method has fewer sampling points in the outfield tests with good curve fitting results. Hence, it can be applied to different kinds of materials and methods due to its good feasibility and generalization ability. In the design and research of the key components of the aircraft, the outfield performance of the material can be easily derived using the similarity calculation method proposed here. This method can also be used as a basic technical support and reference in the selection of the low temperature materials for the key components of aircraft and the design of low temperature environment simulation tests.