Schallemission

Schallemission, widely known in English as acoustic emission (AE), refers to the emission of transient elastic waves produced by the rapid release of energy within a material under stress. The phenomenon arises when microscopic sources such as crack tips, dislocations, or debonding release energy faster than the surrounding medium can equilibrate. The emitted signals propagate as stress waves that can be detected on the surface or embedded in the structure.

Common sources include crack initiation and growth, plastic deformation, frictional sliding at interfaces, phase transformations, and gas release under pressure. AE signals carry information about the location, nature, and severity of the underlying event, making them useful for real-time monitoring of structural integrity.

Measurement involves sensors, typically piezoelectric transducers, placed on the surface or embedded in the component. Data are collected as waveform bursts and analyzed using parameters such as amplitude, energy, duration, counts, rise time, and frequency content. Localization can be achieved by triangulating wave arrival times from multiple sensors, allowing approximate source positioning within the structure.

Applications include nondestructive testing and structural health monitoring in civil engineering, aerospace, marine, and energy sectors. AE is used to monitor weld integrity, pressurized vessels, pipelines, and rotating machinery. It enables detection of active damage before macroscopic failure and can guide maintenance decisions.

Limitations include sensitivity to environmental noise, attenuation with distance and material properties, and the need for expert interpretation to distinguish legitimate events from artifacts. Standards and best practices for sensor selection, data acquisition, and analysis exist in many regions and are commonly grouped under acoustic emission testing.