## 1 Introduction  
Polyamide 6 (PA6) is a widely used material in many fields of the industry. It serves as the matrix of many composite materials, and it is one of the most significant materials in 3D printing. As this and many other polymeric materials are more and more frequently being used, engineers come across these materials in product design. Finite element simulations are now an essential part of any product's design phase. Different material models (elastic, plastic, viscoelastic, etc.) can simulate the material response of polymeric materials under certain types of loadings. Since this research is aimed to help the design process, the plastic behavior was not investigated. There are many accepted ways to model polymeric materials in the elastic region. The simplest approach is the use of a linear elastic material model, which is generally used to model the small strain behavior of the material. For the modeling of higher deformations in the elastic strain zone, the usage of nonlinear material models is advised (bilinear, multilinear and hyperelastic). The bilinear material model uses two lines, and the multilinear material model uses more than two lines to describe the stress-strain relation. Hyperelastic models (Mooney-Rivlin, Ogden, etc.) have been developed for elastomers. However, these models can also be used to model plastics. In the case of thermoplastics, such as PA6, hyperelastic models do not provide more information than simple linear elastic material models, see in [1]. The reason for the different modeling approaches is the nonlinear elastic relation between the stress and strain values of polymeric materials [2; 3; 4; 5]. Generally, under small strains, the polymers behave linearly, but after a certain strain value, the linearity is lost, and the material starts to behave nonlinearly. The length of this section differs from polymer to polymer [6]. Another aspect, which must be considered is the viscoelastic behavior (linear or nonlinear) in polymeric materials, so the stress-strain behavior of the material is time dependent. In the case of linear viscoelastic materials, there is a linear connection between the stress and strain values at any given time, while nonlinear viscoelastic materials present a nonlinear connection. These materials are often characterized by their stress relaxation and creep behaviors [1; 6; 7; 8; 9; 10; 11]. PA6 is widely used as a structural element; thus, the time dependence of the material was neglected in our investigations because such elements are generally subjected to quasi-static loads. Alongside these properties, the mechanical properties of polymeric materials largely depend on the circumstances, such as the temperature, the testing rate, and the humidity [12; 13; 14]. The material that will be investigated is the PA6, a semicrystalline thermoplastic. Its stress-strain curves in the elastic region begin with a linear section, then transition into nonlinearity as the stresses increase [15; 16]. The water content and the temperature also have a significant effect on the mechanical properties [14; 16; 17; 18]. Testing rate dependence and creep are also present in the material [15; 19]. To avoid measurement inconsistencies, all specimens have to be prepared from the same sheet of plastic, stored under the same conditions, and tested at the same rate. The multilinear and viscoelastic material models are able to accurately model the nonlinear elastic behavior of the material, but the creation of them requires either load case-specific measurement data or, in the case of more complex loading, measurement data from different measurement methods [1; 11; 20; 21; 22]. The linear elastic material model, on the other hand, only requires Young's modulus or the shear modulus and the Poisson's ratio of the material [1]. These data are broadly available, and the creation of the material model is simpler, but the effectiveness of these models is varied [6].