A system for determining a trigger amplitude indicating a precursor to a material fracture in a specimen under test includes a microphone converting acoustic emission emitted by the specimen under test into electrical signals. A load is exerted upon the specimen under test and the acoustic emission are emitted when the load causes the specimen under test to undergo deformation prior to the material fracture. A control module is in electrical communication with the microphone and executes instructions to monitor the electrical signals generated by the microphone and filter the electrical signals generated by the microphone. The control module converts the electrical signals generated by the microphone into individual frequency components based on a fast Fourier Transform (FFT). The individual frequency components each include a peak intensity. The control module determines the trigger amplitude based on the peak intensity of the individual frequency components of the FFT.

A system for determining a trigger amplitude indicating a precursor to a material fracture in a specimen under test includes a microphone converting acoustic emission emitted by the specimen under test into electrical signals. A load is exerted upon the specimen under test and the acoustic emission are emitted when the load causes the specimen under test to undergo deformation prior to the material fracture. A control module is in electrical communication with the microphone and executes instructions to monitor the electrical signals generated by the microphone and filter the electrical signals generated by the microphone. The control module converts the electrical signals generated by the microphone into individual frequency components based on a fast Fourier Transform (FFT). The individual frequency components each include a peak intensity. The control module determines the trigger amplitude based on the peak intensity of the individual frequency components of the FFT.

A method of extruding a material including a binder and one or more energetic fillers and using an installation including an extruder including a sheath having at least one extrusion screw present therein, the extruder having at least one acoustic sensor fastened on the sheath, and a monitor system suitable for detecting an anomaly as a function of the acoustic signal picked up by the acoustic sensor, the monitor system being configured to measure variations in the amplitude of the acoustic signal picked up by the acoustic sensor, the method including an extrusion step for extruding the material through the extruder during which the acoustic signal picked up by the sensor is analyzed by the monitor system, and a detection step for detecting variation in the composition of the extruded material from variation in the amplitude of the acoustic signal.

A method of extruding a material including a binder and one or more energetic fillers and using an installation including an extruder including a sheath having at least one extrusion screw present therein, the extruder having at least one acoustic sensor fastened on the sheath, and a monitor system suitable for detecting an anomaly as a function of the acoustic signal picked up by the acoustic sensor, the monitor system being configured to measure variations in the amplitude of the acoustic signal picked up by the acoustic sensor, the method including an extrusion step for extruding the material through the extruder during which the acoustic signal picked up by the sensor is analyzed by the monitor system, and a detection step for detecting variation in the composition of the extruded material from variation in the amplitude of the acoustic signal.

A method is provided including the steps: —first excitation of the object via a multifrequency signal; —detecting a first response signal of the object at one or multiple measuring points at the object; —transforming the first response signal from a time range into a frequency-dependent range; —selecting one or multiple frequencies, based on the frequency-dependent range; —second excitation of the object based on the selected frequencies; —detecting a second response signal of the object at one or multiple measuring points of the object; —ascertaining a mechanical parameter based on the second response signal.

A method is provided including the steps: —first excitation of the object via a multifrequency signal; —detecting a first response signal of the object at one or multiple measuring points at the object; —transforming the first response signal from a time range into a frequency-dependent range; —selecting one or multiple frequencies, based on the frequency-dependent range; —second excitation of the object based on the selected frequencies; —detecting a second response signal of the object at one or multiple measuring points of the object; —ascertaining a mechanical parameter based on the second response signal.

A method for inspecting a fastened structure, the fastened structure having at least one structural member defining a bore therein and a mechanical fastener received in the bore, includes applying acoustic energy to the fastened structure, the acoustic energy being applied over a plurality of frequencies, measuring a response of the fastened structure across at least two frequencies of the plurality of frequencies, and comparing the response of the fastened structure at the at least two frequencies of the plurality of frequencies to predefined values for the at least two frequencies of the plurality of frequencies to determine whether an out-of-tolerance condition is present.

A method for inspecting a fastened structure, the fastened structure having at least one structural member defining a bore therein and a mechanical fastener received in the bore, includes applying acoustic energy to the fastened structure, the acoustic energy being applied over a plurality of frequencies, measuring a response of the fastened structure across at least two frequencies of the plurality of frequencies, and comparing the response of the fastened structure at the at least two frequencies of the plurality of frequencies to predefined values for the at least two frequencies of the plurality of frequencies to determine whether an out-of-tolerance condition is present.

Embodiments include an electromagnetic acoustic transducer (EMAT) system. The EMAT system includes a plurality of magnets and a conductor set. The plurality of magnets has a like pole arrangement and wherein each magnet is in close proximity to one another. The conductor set includes electrically conductive elements. A portion of the conductor set is positioned proximate to the plurality of magnets. The plurality of magnets and the conductor set are positioned proximate to a test object. The EMAT system is configured to perform at least one of generating and receiving an elastic wave. Embodiments also include a method of elastic wave measurement for nondestructive testing and evaluation. The method includes the steps of positioning an EMAT proximate a test object, generating an elastic wave such that the elastic wave propagates about the test object, detecting the elastic wave propagating about the test object, and analyzing difference in elastic wave character between the elastic wave in the generating step and the elastic wave in the detecting step to evaluate the test object.

A sensing system contains a vibration device attached to a stem of an agricultural crop for applying vibration to the agricultural crop, at least one sensor attached to the stem of the agricultural crop for sensing vibration of the agricultural crop caused by the vibration applied to the agricultural product from the vibration device to transmit vibration information relate to the vibration of the agricultural crop and a computing device for identifying one local maximum value among a plurality of local maximum values in a frequency spectrum obtained from the vibration information received from the at least one sensor as a resonance frequency of the vibration of the agricultural crop to determine a growth degree of a fruit of the agricultural crop based on the identified resonance frequency.