Numerical modeling of non-destructjve testjng of composites - PowerPoint PPT Presentation

Numerical modeling of non-destructjve testjng of composites Katerina Beklemysheva, Alexey Ermakov, Alexander Kazakov, Igor B. Petrov, Alexey Vasyukov Moscow Instjtute of Physics and Technology

Composites Low-velocity strike on a polymer composite constructjon  Caused by: hail, debris, maintenance failures, etc.  Internal composite damage – damage is not visible!  Methods and standards for strength tests, developed for metals, are not efgectjve enough for composites.  Non-destructjve testjng devices for composites require a signifjcant amount of tjme and laboratory equipment.

Problem statement Back side notch Separated-combined sensor (two piezoelectric crystals ) Emituer and receiver on the front side

Anisotropic material

Grid-characteristic method  Split by space variables Этап 1 Этап 2 u n +O ( τ 2 ) u n+ 1 =⃗ u n − τ ( A 1 Δ 1 +A 2 Δ 2 )⃗ Итог (2D) ⃗  Hyperbolic equations in plane ( ξ, t)

GCM on unstructured grid  Tetrahedral interpolatjon of a Riemann’s invariant : • linear – fjrst order of approximatjon; • quadratjc – second order of approximatjon; • scheme hybridizatjon depending on a solutjon “smoothness”. N’ B B n+1 AB BC τ O O A A O C C BD n K N CD A AD D D λτ

Borders and contacts External surface Surface between media B’ n+1 τ n B А – real node В – virtual node • External force • Adhesion • External velocity • Sliding • Mixed conditjons • Frictjon • Destructjble adhesion

Verifjcation • SiteScan D-20 с преобразователем RDT2550

A-scan comparison

A-scan comparison

A-scan comparison

Serial calculations Emituer and receiver on the front side

Data representation Green – separated-combined sensor. Purple – combined sensor. X axis – tjme step, Y axis – velocity amplitude, averaged by receiver area: z component for longitudinal wave, x or y – transverse.

Steel plate: Transverse Longitudinal wave wave notch depth Green – separated-combined sensor. Purple – combined sensor. • Increasing notch depth => increasing number of responses. • The initjal signal is visible on the transverse wave data. • Combined sensor is betuer for processing longitudinal wave response, but can’t be used for transverse waves.

Steel plate: Transverse Longitudinal wave wave pulse length Green – separated-combined sensor. Purple – combined sensor. • Increasing pulse length => increasing noise amplitude • The initjal signal becomes visible on longitudinal wave data. • Transverse wave signal from the notch is visible only on low pulse length.

Composite plate: notch depth Purple – combined sensor, blue – separated-combined sensor, across the fjber directjon, green – along. Lefu – transverse wave along fjber directjon, center – across, right – longitudinal wave. • High noise on the longitudinal component

Conclusion • A hybrid grid-characteristjc method of 1-2 order on irregular tetrahedral grid is used. • A carbon fjber polymer matrix of unidirectjonal composite is modeled as a homogeneous orthotropic media with a single distjnguished directjon along the fjber. • A comparison with an isotropic material (steel) was conducted. • One-dimensional graphics, which correspond to A-scans in real devices, were obtained. • The detailed analysis of received data is presented.

Application 1. Analysis of complex NDT cases: detail geometry, delaminatjons, complex destructjon types. 2. Development of diagnostjc methodology, parameters and modes optjmizatjon. 3. Equipment prototyping – research and selectjon of sensor parameters. 4. Assessment of danger from various destructjon types.

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