täristinmenetelmä

täristinmenetelmä, literally the tremor or shaker method, is a vibration-based testing approach used mainly in materials science and structural engineering. It involves exciting a specimen with a controlled dynamic input and analyzing its response to determine mechanical properties or reveal internal flaws. The term is common in Finnish technical literature and denotes methods that rely on induced vibration rather than static loading.

In practice, a sample is mounted on a shaker or struck with a calibrated impulse. Sensors such as accelerometers or strain gauges record the resulting motion. Data are analyzed in the time or frequency domain, often using Fourier transform or modal analysis to extract natural frequencies, damping, and stiffness. By comparing measurements over time or across conditions, engineers infer changes in material condition, including the presence of cracks or delaminations.

Applications include nondestructive evaluation, quality control, and structural health monitoring of metals, composites, ceramics, and assemblies. The method is suited for rapid screening, determining elastic moduli, and detecting flaws without sample destruction.

Advantages include being non-destructive and relatively fast, with potential for in situ testing. Limitations involve sensitivity to boundary conditions and fixture geometry, the need for careful calibration, and reduced reliability for highly heterogeneous or geometrically complex specimens.

History and usage: täristinmenetelmä has been developed and documented in Finnish engineering contexts since the late 20th century and is also used in international vibroacoustic testing traditions. See also nondestructive testing, modal analysis, vibration testing.