PSI - Issue 5

Mikhail Tashkinov et al. / Procedia Structural Integrity 5 (2017) 577–583 Mikhail Tashkinov et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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example, in Fletcher (2000). The graph of the dependence of the constants values on the optimization step for the two methods is shown on Fig. 5a, 5b. It can be observed that the L-M algorithm converges faster than the Newton method (5 iterations against 8). Also, initial constants values can have a significant effect on the convergence rate of the algorithm. Thus, the operation of the L-M algorithm with the zero vector of the initial parameters is shown on Fig. 4c.

а

b

c

Fig. 4. The values of the constants depending on the step of the optimization algorithm: (a) the L-M method; (B) Newton's method; (C) the L-M method with the zero vector of the initial parameters.

4. Conclusions

This work presents the algorithm for the refinement of the constants of a quasi-isotropic layer of a composite material on the basis of a computational-experimental approach using built-in fiber-optic strain sensors and finite element modeling. An example of numerical implementation of the algorithm for solving a test problem is given. The possibility of application of non-destructive monitoring tools for finding the parameters of mechanical models is shown, which, therefore, makes it possible to predict the behavior and failure of materials and composite structures with greater accuracy. The analysis of material constants can be performed on samples of materials that are used in structures. For example, this can be useful when studying the influence of certain technological processes on the properties of the material. It should be noted that, within the framework of this methodology, the readings of fiber optic strain sensors should be considered reliable with the necessary accuracy to serve as a "standard" of strain values. There are many works devoted to the measurement of deformations with embedded and attached on the composite structures FBG sensors with a description of the technical and methodological issues, some results are contained in the work of Anoshkin et al. (2016), Di Sante and Bastianini (2015), Majumder et al. (2008). This area of research is actively developing at the moment, and it can be argued that the latest achievements will contribute to the development of FBG sensors as an increasingly reliable tool for independent non-destructive monitoring. The proposed method can be generalized for transversely isotropic and anisotropic materials. In this case, it is necessary to register a greater number of components of the strain tensor at control points, so various forms os arrangement of the fiber optic lines can be organized, which allow obtaining strain values in different directions (Chow (2005), Jin et al. (1999)).

Acknowledgements

The research was performed at the Perm National Research Polytechnic University, with the support of the Russian Science Foundation (project №15 -19-00243).

References

Anoshkin, A.N., Voronkov, A.A., Kosheleva, N.A., Matveenko, V.P., Serovaev, G.S., Spaskova, E.M., Shardakov, I.N., Shipunov, G.S., 2016.