Desenvolvimento de um equipamento portátil para ensaios de tração em materiais biológicos

Abstract

Among the various types of biological materials, the connective tissues are responsible for binding, supporting and protecting the human body. Of the studies carried out with these tissue types, an evaluation of the mechanical properties of these materials is essential to know their behavior and to base the development of new techniques implants and of lesions’ treatment. One of the simplest and most widely used methods for obtaining mechanical properties is the tensile test. Despite the relative simplicity, it is noted that this type of method generally requires a process of preservation of the specimen until the test is performed, which may lead to changes in its properties. Considering the difficulty of the researchers to perform or test traction soon after a removal of the biological material, the objective of this work is to construct an equipment capable of performing the tests in the places where the withdrawal occurs. The project was divided into mechanical, electronic and measurement’s validation for use in biological materials. The first stage was composed by the idealization of the mechanical structure and the mechanisms of the traction system of the equipment, for that, it was chosen to use aluminum in the composition of most pieces. After the 3D design process and tests in computer simulation programs, the machine was built and integrated into the electronic part. The development of the electronics was done with modules of easy access in the market, enabling rapid prototyping aiming at obtaining results for the validation of the prototype. A comparator watch was used to measure the deformation of the test piece and standard weights were used for the validation of the force measurement during the test. The deformation validation process was performed in 12 groups, varying the following factors: load, speed and position. In this way, the errors and the confidence intervals were calculated. The mean displacement error interval was 0.0132 +/- 0.0064 mm. Meanwhile the interval estimate of the mean of the force measurement error was -0.0004 and 0.0012 kgf. Therefore, because it is a material with anisotropic characteristics and based on works that show the variations of this type of material, it was concluded that the machine meets this application, because the obtained errors are smaller than the smallest variation of these measures.