Este artigo propõe a construção de um instrumento eletrônico denominado luxímetro digital, aliando a simplicidade e o baixo custo, o que o torna mais simples e barato do que aqueles que se encontram no mercado. A sua construção tende a facilitar a difusão e o acesso a este tipo de instrumento de medidas entre professores do ensino médio e instituições de ensino, sendo ideal para constituir um laboratório de ciências.

This paper proposes the construction of an electronic instrument called digital luximeter, combining simplicity and low cost, making it simpler and cheaper than those on the market. Its construction tends to facilitate dissemination and access to this type of measuring instrument between high school teachers and educational institutions, making it ideal to be a science lab.

A method of successive Lagrangian formulation of linear approximation for solving boundary value problems of large deformation in finite elasticity is proposed. Instead of solving the nonlinear problem, by assuming time steps small enough and the reference configuration updated at every step, we can linearize the constitutive equation and reduce it to linear boundary value problems to be solved successively with incremental boundary data. Moreover, nearly incompressible elastic body is considered as an approximation to account for the condition of incompressibility. For the proposed method, numerical computations of pure shear of a square block for Mooney-Rivlin material are considered and the results are compared with the exact solutions. Mathematical subject classification: Primary: 65C20; Secondary: 74B20.