An approach to adhesive bond characterisation using guided acoustic waves in multi-layered plates.

The markers (and dashed lines) in figure 7 indicate the points of the specific mode curves, where the modal distance HT <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="italic">d</mi><mi mathvariant="normal">norm</mi></msub></math> ht is minimal. This behaviour is most obvious in figure 2 at HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="italic">f</mi><mo>=</mo><mn>0.1</mn><mspace width="0.1667em" /><mtext>MHz</mtext></math> ht and HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="italic">k</mi><mo>=</mo><mn>0.4</mn><mspace width="0.1667em" /><mtext>rad</mtext><mspace width="0.19em" /><msup><mi mathvariant="normal">mm</mi><mo>-</mo><mn>1</mn></msup></math> ht . Graph HT <math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><mtable displaystyle="true"><mtr><mtd><msub><mrow><mi mathvariant="italic">d</mi><mo stretchy="false">˜</mo></mrow><mi mathvariant="normal">norm</mi></msub><mo>=</mo><mstyle displaystyle="true"><mfrac><mrow><msub><mi mathvariant="italic">d</mi><mi mathvariant="normal">norm</mi><mo mathvariant="normal">,</mo><mi mathvariant="normal">meas</mi></msub></mrow><mrow><msub><mi mathvariant="italic">d</mi><mi mathvariant="normal">norm</mi><mo mathvariant="normal">,</mo><mi mathvariant="normal">sim</mi></msub></mrow></mfrac></mstyle></mtd></mtr></mtable></math> ht (5) Figure 7 shows the first mode repulsion region of the examined specimen (see section 3.1). [Extracted from the article]