and damping properties. For example, the interaction of dislocations and point defects in carbon steels are studied. Also the material damage accumulated during a thermal shock treatment can be determined for refractory materials. This can be an advantage in understanding the physical properties of certain materials. Finally, the technique can be used to check the quality of systems. In this case, a reference piece is required to obtain a reference frequency spectrum. Engine blocks for example can be tested by tapping them and comparing the recorded signal with a pre-recorded signal of a reference engine block. By using simple cluster analysis algorithms or principal component analysis, sample's pattern recognition is also achievable with a set of pre-recorded signals. Experimental correlations Rectangular bar Young's modulus with E the Young's modulus m the mass ff the flexural frequency b the width L the length t the thickness T the correction factor The correction factor can only be used if L/t ≥ 20! Shear modulus with Note that we assume that b≥t G the shear modulus ft the torsional frequency m the mass b the width L the length t the thickness R the correction factor Cylindrical rod Young's modulus with E the Young's modulus m the mass ff the flexural frequency d the diameter L the length T the correction factorThe correction factor can only be used if L/d ≥ 20!Shear modulus with ft the torsional frequency m the mass d the diameter L the length Poisson ratio If the Young's modulus and shear modulus are known, the Poisson's ratio can be calculated according to: Damping coefficient The induced vibration signal (in the time domain) is fitted as a sum of exponentially damped sinusoidal functions according to: with f the natural frequency δ = kt the logarithmic decrement In this case, the damping parameter Q−1 can be defined as: with W the energy of the system Extended IET applications: the Resonalyser Method Isotropic versus orthotropic material behaviour Isotropic elastic properties can be found by IET using the above described empirical formulas for the Young’s modulus E, the shear modulus G and Poisson’s ratio v. For isotropic materials the relation between strains and stresses in any point of flat sheets is given by the flexibility matrix [S] in the following expression: In this expression, ε1 and ε2 are normal strains in the 1- and 2-direction and Υ12 is the shear strain. σ1 and