# A New Data Processing Approach for the SHPB Test Based on PSO-TWER
###### Abstract  
This study addresses the challenge of accurately determining the arrival time of stress wave signals in SHPB test data processing. To eliminate human error, we introduce the time-window energy ratio method and evaluate six filters for noise reduction using box fractal dimensions. A mathematical model is established to optimize the stress equilibrium and impact process, which is solved using particle swarm optimization, resulting in the PSO-TWER method. We explore the impact of inertia weight and calculation methods on optimization outcomes, defining a stress equilibrium evaluation index. The results indicate that time-window length significantly affects arrival-time outputs, and the dynamic inertia weight factor enhances optimization convergence. The method accurately determines arrival times and effectively screens test data, providing a robust approach for SHPB test data processing. SHPB; time-window energy ratio; particle swarm optimization algorithm; inertia weight; PSO-TWER +
Footnote †: journal: Medical  
signals of mines. [PERSON] [7] presented an arrival picking method based on the difference between multi-window energy ratios, and the method obtained precise arrival picking points for seismic signals with low signal-to-noise ratios. In SHPB test data, the frequency of electrical signals detected by strain gauges is far lower than for seismic and microseismic signals. In an efficient time domain, except for noise waves, only one or two significant peaks are present in incident, reflected, and transmitted waves. The substantial energy interference caused by the superposition of complex noise is less. In order to facilitate the calculations, the problem of arrival picking can be solved by the stationary time-window energy ratio method. Due to differences in testing equipment, noise often exists in waveform signals, and denoising processing is necessary; the fractal theory can be used to describe the complexity of signals or images. [PERSON] et al. [4] used the fractal geometry theory to analyze the development of horizontal and vertical mining cracks quantitatively during coal mining. [PERSON] et al. [8] analyzed the fractal dimension of fracture images of coal-rock composites after uniaxial loading. [PERSON] et al. studied fracture network photographs using fractal dimensions. [PERSON] et al. [9] analyzed the fractal characteristics of mining fracture networks. [PERSON] et al. [10] described the fractal characteristics of carbonate-based sand and silicate-based sand, and the effect of grain size on the pore size distribution and fractal dimensions was discussed. According to the standards of the SHPB test, a stress equilibrium check must be performed prior to test data processing and show the typical waveform of the stress equilibrium. However, the relevant standards for stress balance need to be clearly defined. The stress equilibrium process is related to the load force in the terminal face of the incident bar and the transmitted bar. Based on these characteristics, [PERSON] [11] defined a threshold in his study; the internal stress of the rock specimen reaches a constant state when the relative stress difference between the two ends of the specimen is less than 5%. [PERSON] [12] proposed the stress equilibrium factor in their study; it is considered that the stress equilibrium state of the specimen is better when the factor is close to 0. The above two methods are also widely recognized and applied; the quality of three-wave selection is closely related to the stress equilibrium state. Therefore, a mathematical model related to the stress equilibrium factor can be constructed based on the length of the time window as the independent variable. The solution of mathematical models often relies on algorithms. [PERSON] introduced several novel, metaphor-free, and parameter-free optimization algorithms for addressing diverse single, multi-, and many-objective optimization challenges across science and engineering [13; 14].