6 Evaluating Stresses from Measured Strains in Viscoelastic Body Using Numerical Laplace Transformation 59 Fig. 6.3 Input strains Fig. 6.4 Calculation results of through-thickness strains Each result is compared with the values obtained by 3D FEM and computed from the constitutive equations in Laplace domain using numerical Laplace transformation. The calculation results are generally more consistent than the values computed by the numerical Laplace transformation especially near the end of the data. It is shown that in-plane stresses can be obtained by the proposed method. 6.7 Conclusions This study proposes a method for computing stresses from measured values of in-plane strains in viscoelastic body under plane stress condition. Since the relation between a through-thickness strain and in-plane strains is expressed in Laplace domain, Poisson’s ratio can be treated as time- and temperature-dependence. The stresses are computed from the throughthickness strains and in-plane strains by numerical integration. The effectiveness of the proposed method is demonstrated by computing stresses from strains. The values obtained by the proposed method are compared with the values obtained by 3D FEM and computed from the constitutive equations in Laplace domain using numerical Laplace transformation. The calculation results are generally more consistent than the values computed by the numerical Laplace transformation especially near the end of the data. It is shown that in-plane stresses can be obtained by proposed method. In addition, stresses can be calculated by taking Poisson’s ratio into consideration of the time dependency by using the proposed method. In the future, it is necessary to compute stresses from various strains and to examine effectiveness. Acknowledgments This work is supported by JSPS KAKENHI Grant Number JP18K03845.
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