HIGH-FREQUENCY ACOUSTIC EMISSION MEASUREMENT IN CHARPY IMPACT TESTING COMBINED WITH BARKHAUSEN NOISE ANALYSIS AND RESIDUAL STRESS LEVEL MEASUREMENT.

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dc.contributor.advisorBalogh, Gabor
dc.contributor.authorOrynbassar, Beibarys
dc.contributor.departmentDE--Műszaki Kar
dc.date.accessioned2026-06-02T12:22:31Z
dc.date.available2026-06-02T12:22:31Z
dc.date.created2026-04-28
dc.description.abstractAccurately evaluating internal residual stresses in ferromagnetic materials is critical for ensuring structural integrity. Conventional stress measurement techniques, such as X-ray diffraction and the hole-drilling method, are inherently limited as they are either purely static or semi-destructive. Those methods can be expensive or destroy the structural integrity of the material. This thesis proposes a novel, non-destructive hybrid methodology that integrates high-frequency Acoustic Emission (AE) and dynamic Barkhausen Noise (BHN) analysis during instrumented Charpy impact testing to evaluate residual stress dynamically. To systematically investigate this, a controlled heat treatment was applied to steel specimens, heated up to 900 degrees Celsius and cooled accordingly (furnace-cooled, air-cooled, and water-quenched) to induce distinct microstructures and residual stress profiles. A customized LabVIEW data acquisition (DAQ) architecture, which is triggered by an optical gate, was developed to synchronously capture the microsecond-scale acoustic and magnetic responses. High-pass Fast Fourier Transform (FFT) filtering (cutoff at 1000 Hz) was successfully applied to eliminate baseline electromagnetic interference and isolate high-frequency acoustic fracture waves. The digital signal processing revealed several significant findings. Cross-correlation analysis proved a strict temporal synchronization between the acoustic shockwave of crack propagation and the magnetic domain wall shifts, achieving coefficients up to |R| = 0.988. Furthermore, the study identified a "Shannon Entropy Paradox," demonstrating that high-energy ductile tearing yields mathematically low-entropy acoustic bursts, whereas low-energy brittle shattering produces highly chaotic, high-entropy signals. Finally, by capturing the dynamic magneto-elastic response (for example the Villari effect), a linear regression model was established, proving that Peak Acoustic Emission can reliably predict the dynamic Peak Barkhausen Noise spike. These experimental findings were successfully validated against theoretical ANSYS Explicit Dynamics simulations across varying temperature profiles (-80 degrees, -20 degrees and 22 degrees). Ultimately, the integration of dynamic AE and BHN signals provides a powerful diagnostic tool capable of differentiating pre-existing residual stress states and monitoring structural embrittlement in real-time.
dc.description.courseMechanical Engineeringen
dc.description.degreeBSc/BA
dc.format.extent57
dc.identifier.urihttps://hdl.handle.net/2437/407701
dc.language.isoen
dc.rights.infoHozzáférhető a 2022 decemberi felsőoktatási törvénymódosítás értelmében.
dc.subjectAcoustic Emission
dc.subjectBarkhausen Noise
dc.subjectResidual Stress
dc.subjectMeasurement of Residual Stress
dc.subjectStress
dc.subject.dspaceEngineering Sciences::Engineering
dc.titleHIGH-FREQUENCY ACOUSTIC EMISSION MEASUREMENT IN CHARPY IMPACT TESTING COMBINED WITH BARKHAUSEN NOISE ANALYSIS AND RESIDUAL STRESS LEVEL MEASUREMENT.
dc.title.translatedNagyfrekvenciás akusztikus emisszió mérése Charpy-féle ütvevizsgálat során, összekapcsolva Barkhausen-zaj analízissel és maradó feszültségszint méréssel
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