## 1 Introduction
In addition, the model is not feasible for predicting the behaviour of complex loading conditions, such as multiaxial loading or cyclic loading, see [27; 28]. The Anand model does not include backstress; therefore, the model is not able to describe kinematic hardening during cyclic loading. This type of behaviour can also be described by a combination of material models. There is a material model for isotropic or kinematic hardening, a model for capturing viscoplastic behaviour (time-dependent, viscosity), and a model for solutions of creep. The Chaboche model with an optional number of parameters can be used to describe kinematic hardening [29]. The Perzyna material model with two parameters can be used to describe time-dependent behaviour [30]. The behaviour during secondary creep can be described using the Norton relation [31]. Commercial software (for example, Ansys 2022 R2, MSC_Marc 2023.1) can combine these material models and can therefore be used to simulate the complex behaviour of the material. The implicit stress integration algorithm is critical in the context of building constitutive models for solders, particularly in the construction of algorithms for temperature-constant deformation. In this special case, the combination of Chaboche-Perzyna-Norton models can be efficiently implemented into an FE code by using the algorithm of [PERSON] et al. [32], which is based on successive substitution with an application of a damped Newton-Raphson method. Temperature influence is usually introduced using exponential and polynomial functions for some parameters. These functions are critical in precisely predicting the behaviour of solder materials at various temperatures [33]. Furthermore, for accurate capturing of the relaxation behaviour, an algorithm suited for a viscoplastic model with the inclusion of a static recovery term must be implemented [34]. The return mapping method is used in this approach, which incorporates common tactics of the elastic predictor and the plastic corrector within the integration algorithm. The primary purpose of this study is to compare the solder alloys of SAC305 and SACX0807 from tensile properties and creep behaviour points of view. Creep and tensile tests were performed at room temperature, whereas axial strain was measured by using the DIC method, which allowed the capture of strain contours. The benefit of DIC was fully used in creep tests, which were conducted on an hourglass-type specimen. Capturing strains on particular cross-sections of the specimen brings more creep curves from a single creep test. This is beneficial for calibrating viscoplastic models, as presented in the numerical study of SAC305 based on the results of the classic mechanical tests [35; 36]. The method of determining the values of material parameters for material models is usually described in the source articles for the given material model. However, these procedures usually do not involve combinations of material models. Another method is to use the Finite Element Model Updating (FEMU) approach. Here, an experiment (or set of experiments) is simulated using the finite element method with a selected material model. The result of the simulation is compared with the result of the experiment, and by gradually changing the values of the material parameters, the difference between them is minimised. Nowadays, there is commercial software (for example, OptiSLang 2022 R2) that allows this method to be used, including a few minimisation algorithms (gradient, evolutionary, simplex, etc.). However, the main novelty of the article is the presentation of a new accelerated technique using the DIC method for the evaluation of the creep properties of metallic materials. The strains captured via the optical method on the curved surface of an hourglass specimen in time are evaluated in the form of creep curves for selected cross-sections corresponding to different nominal stresses. The new approach can help experimenters estimate the Norton exponent and plan classic creep tests.