Retrospective Evaluation and Framework Development of Bone Anisotropic Material Behavior Compared with Elastic, Elastic-Plastic, and Hyper-Elastic Properties

The main motivation for studying damage in bone tissue is to better understand how damage develops in the bone tissue and how it progresses. Such knowledge may help in the surgical aspects of joint replacement, fracture fixation or establishing the fracture tolerance of bones to prevent injury. Currently, there are no standards that create a realistic bone model with anisotropic material properties, although several protocols have been suggested. This study seeks to retrospectively evaluate the damage of bone tissue with respect to patient demography including age, gender, race, body mass index (BMI), height, and weight, and their role in causing fracture. Investigators believe that properties derived from CT imaging data to estimate the material properties of bone tissue provides more realistic models. Quantifying and associating damage with in vivo conditions will provide the required information to develop mathematical equations and procedures to predict the premature failure and potentially mitigate problems before they begin. Creating a realistic model for bone tissue can predict the premature failure(s), provide preliminary results before getting the surgery, and optimize the design of orthopaedic implants. A comparison was performed between the proposed model and previous efforts, where they used elastic, hyper- elastic, or elastic-plastic properties. Results showed that there was a significant difference between the anisotropic material properties of bone when compared with unrealistic previous methods. The results showed that the density is 50% higher in male subjects than female subjects. Additionally, the results showed that the density is 47.91% higher in Black subjects than Mixed subjects, 53.27% higher than Caucasian subjects and 57.41% higher than Asian. In general, race should be considered during modeling implants or suggesting therapeutic techniques.

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.

Verification of Stress Transformation in Anisotropic Material Additively Manufactured by Fused Deposition Modeling (FDM)

The widespread use of Additive Manufacturing (AM) has been extensively progressed in the past decade due to the convenience provided by AM in rapid and reliable part production. Fused Deposition Modeling (FDM) has witnessed even faster growth of application as its equipment is environmentally-friendly and easily adaptable. This increased use of FDM to manufacture prototypes and finished parts is accompanied by concerns that 3D printed parts do not perform the same as relatively homogeneous parts produced by molding or machining. As the interface between two faces of bonded material may be modeled by stress elements, in theory by modeling 3D printed layers subjected to tension at varying angles as transformed stress elements, the stress required to break the layer bonds can be determined. To evaluate such a relationship, in this study, the stresses calculated from stress transformation were compared with the behavior of 3D printed specimens subjected to tensile loads.

Faserschonende Carbonfaserproduktion durch innovatives Galetten-Oberflächen-Design - CarboGerd

While carbon fibres can easily absorb forces in the fibre direction, they are extremely sensitive to transverse stress due to their anisotropic material behaviour. During the manufacturing process, unavoidable transverse stresses are induced in the fibre by the drive and deflection godets, which can damage or destroy individual filaments of the roving. The demand for a surface that is gentle on the fibre is offset by the static friction required between the fibre and the godet in order to drive the fibre. The aim of the CarboGerd research project is therefore to develop and validate an optimal godet coating for fibre-protecting and quality-assuring carbon fibre production. For this purpose, both typical coatings (ceramic, Topocrom coatings) and unconventional solutions (elastomer, PACVD coatings) are being tribologically investigated on a laboratory scale and validated on a prototype system.

TOPOLOGY OPTIMIZATION OF PLATE STRUCTURES WITH ANISOTROPIC MATERIALS

This work presents a topology optimization method for the design of structures composed exclusively of rectangular plates made of a predetermined, generally anisotropic material. The geometry projection method is employed to map the highlevel geometry and material properties to a fixed grid for the analysis, thus circumventing the need to re-mesh upon each design iteration. We also impose an overlap constraint in the optimization that reduces waste material when fabricating structures by cutting and joining rectangular plates. We demonstrate our method with a numerical example comparing optimal cantilever beam designs obtained using isotropic- and orthotropic-material plates. For this example, we maximize the stiffness of the structure for a fixed amount of material, and we impose a constraint to reduce overlaps between plates. The examples demonstrate the importance of considering material anisotropy in the design of plate structures. Moreover, it is demonstrated that an optimally stiff design for plates made of an isotropic material can exhibit poor performance if the plates are naively replaced with an anisotropic material.