Identification of the parameters of the quadratic model of the elastic anisotropic material

Рассмотрена модель упругости второго порядка для ортотропного материала. Проведенный анализ показывает, что квадратичная часть предложенной модели содержит тринадцать упругих постоянных, из которых девять являются линейно независимыми. Параметры модели определены по данным экспериментов с композитными пластинами. Модель позволяет описывать наблюдаемые в экспериментах нелинейные зависимости между напряжениями и деформациями в процессах растяжения, сжатия и сдвига, а также разносопротивляемость анизотропных материалов. A second-order elasticity model for an orthotropic material is considered. The analysis shows that the quadratic part of the proposed model contains thirteen elastic constants, nine of which are linearly independent. The parameters of the model are determined from the data of experiments with composite plates. The model allows one to describe experimentally observed nonlinear dependences of stresses and strains in the processes of tension, compression, and shear, as well as the difference in resistance of anisotropic materials.

Numerical and Experimental Study of Five-Layer Non-Symmetrical Paperboard Panel Stiffness

This paper concerns the analysis of five-layer corrugated paperboard subjected to a four-point bending test. The segment of paperboard was tested to determine the bending stiffness. The investigations were conducted experimentally and numerically. The non-damaging tests of bending were carried out in an elastic range of samples. The detailed layers of paperboard were modelled as an orthotropic material. The simulation of flexure was based on a finite element method using Ansys® software. Several material properties and thicknesses of papers in the samples were taken into account to analyse the influence on general stiffness. Two different discrete models based on two geometries of paperboard were considered in this study to validate the experimental stiffness. The present analysis shows the possibility of numerical modelling to achieve a good correlation with experimental results. Moreover, the results of numerical estimations indicate that modelling of the perfect structure gives a lower bending stiffness and some corrections of geometry should be implemented. The discrepancy in stiffness between both methods ranged from 3.04 to 32.88% depending on the analysed variant.

Modelling the stiffness of plastic springs manufactured via additive manufacturing

The helical spring is one of the most used components in mechanisms but there is little research on the application of 3D printing, also called Additive Manufacturing, to springs. Therefore, the objective of this paper is to derive a model for the stiffness of 3D printed springs. The equation assumes that springs are made of orthotropic material and with a rectangular wire cross-section, that is, die springs. A second version of the equation has also been postulated that accounts for the misalignment of the deposited tracks with respect to the direction of the coils due to the coil pitch. The two models are compared to various springs printed with PLA and ULTEM 9085 and are found to accurately predict the stiffness of real, 3D printed springs. These equations allow the design and manufacturing of helical die springs for applications with few load cycles and that require chemical and radiation resistance, such as in space. The equations are also the first step in the development of models for new kinds of springs, such as linear conical springs or hollow wire die springs.

Evaluation of the Relation Between Preload Values and Pullout Force of the Cortical Screw Used in Bone Fracture

This study aims to examine the relation between pullout strength and preload values of the cortical screw used in bone fracture fixation. The research question is that "Does the pullout strength of the cortical screw used in the bone fracture fixation change with the preload values of the screw change?". To perform this purpose, the finite element method was selected due to its ease to evaluate and calculate the stresses on the whole model. Models of a cortical screw, partial plate and bone were created using the SolidWorks program. The material properties of the bone were selected orthotropic material type. The bone fixed on the distal and proximal ends. The pullout forces were applied at the bottom of the plate. The screw has been loaded ranges from 100 N - 700 N as preload. The pullout forces were determined 200-400-600 N as in the literature. The results show that the pullout strength of the screw was changed when the preloaded values higher than 400 N. However, it was seen that the pullout strength does not substantially change when the preload values were lower than 400 N. In conclusion, the pullout strength of the screw altered when the preload values of the screw was changed.