NEW EXCITATION (MULTIPLE WIDTH PULSE EXCITATION (MWPE)) METHOD FOR SHM SYSTEMS—PART 1: VISUALIZATION OF TIME- FREQUENCY DOMAIN CHARACTERISTICS

Structural health monitoring (SHM) of additively manufactured polymer parts is challenging due to the very strong attenuation of the surface waves. To excite the part surface at a very wide frequency band in a very short time, Multiple Width Pulse Excitation (MWPE) signal was introduced. MPWE was used to excite the surface of the structure for the implementation of the Surface Response to Excitation (SuRE) method. A cross-shaped polymer part was fabricated additively for the identification of the hidden geometry of the infill. The part had four extensions with identical geometry but different internal designs. Two of the extensions had cross infills and the other two had square infills. For each type of infill, one extension had 1 mm and the other extension had 2 mm thick skin. The part was excited at the middle with WMPE excitation and the dynamic response was monitored at the end of each extension. The Short-Time Fast Fourier Transform (STFFT) was used for the analysis of the signal in the time-frequency domain. The two dimentional sum of the squares of the differences (2DSSD) was used for the classification of the signal. Compressive force and type of infill was identified accurately for all the test cases.