The Mooney-Rivlin constitutive model is often used for the characterization of hyperelastic rubber-like materials. To obtain the material constants for a model, only a uniaxial-tension-data set is usually used. Though it is regularly used for its easiness of processing data in a simple and practical way, the method is considered to be insufficiently accurate. To analyse the shortcoming of the method, a detailed examination was done with the Mooney-Rivlin two-parameter model. This paper discusses the variations related to three basic load curves, i.e., uniaxial, equibiaxial and pure-shear curves. For a visual observation of the fitted-data dispersion, two data-fitting cases were considered. The first one was the data fitting only through uniaxial data while the second one was a combination of uniaxial and pure-shear experimental-data curve fitting. A detailed one-to-one comparison of the curves was done to achieve an accurate estimation of the variations. Keywords: uniaxial tension, equibiaxial loading, pure shear/planar shear loading, curve fitting, Mooney-Rivlin constitutive modelMooney-Rivlinov temeljni model se pogosto uporablja za karakterizacijo gumi podobnih hiperelasti~nih materialov. Za materialne konstante se obi~ajno uporablja set podatkov, dobljenih z enoosnim nateznim preizkusom.^eprav se ta na~in uporablja zaradi enostavnosti in prakti~nosti metode pa ga lahko smatramo kot manj natan~nega. Zato, da bi avtorji tega prispevka ugotovili neskladje, so izvedli natan~no analizo z Mooney-Rivlinovim dvoparametri~nim modelom. V~lanku avtorji obravnavajo variacije, ki se nana{ajo na tri osnovne krivulje obremenjevanja: enoosno, ekvivalentno dvoosno in~isti strig. Vizualno opazovanje raztrosa prilagojenih podatkov so izvedli na osnovi dveh na~inov prilagajanja podatkov. Prvo prilagajanje podatkov so izvedli na osnovi rezultatov enoosnega nateznega preizkusa. V drugem primeru so uporabili kombinacijo obeh: eksperimentalne rezultate enoosnega nateznega preizkusa in~istega striga. Izvedli so natan~no primerjavo krivulj in ocenili odstopanja. Klju~ne besede: enoosni nateg, ekvivalentna biaksialna obremenitev,~isti strig, ravninska stri`na obremenitev, prilagajanje krivulje, Mooney-Rivlinov konstitutivni (temeljni) model

The risk of error in using only uniaxial data for fitting constitutive model curves is emphasized by many hyperelastic material researchers over the years. Unfortunately, despite these indications, often the method is utilized in finding material constants for mathematical models. The reason behind this erroneous practice is the difficulty in obtaining biaxial data. Therefore, as a remedial measure, in this research work we suggest a method of forecasting biaxial data from uniaxial data with a reasonable accuracy. Initially, a set of data is collected through standard uniaxial test. A predefined generalized function is then used to generate a set of values which subsequently used as multiplication factors in order to get biaxial tension data. Eventually, with availability of two data sets, Mooney-Rivlin two parameter model was used for combined data fitting. Material constants were then obtained through least squares approach and thereby theoretical load curves namely uniaxial, equi-biaxial tension and pure shear were drawn. The results of this work suggest a definite improvement related to three curves when compared with only uniaxial test data fitted outcomes. For validation of secondary biaxial data, separate eqi-biaxial test was done and resulting curves were compared. Biaxial primary data curve and forecasted data driven curve show identical data distribution pattern though there is a shift and therefore provide a basis for further research in this direction.

Mooney-Rivlin is the most frequently used model from all models used for mechanical characterization of the hyperelestic materials. Simplicity, applicability in a large rage of strains are the key reasons for regular use of this model. However, depending on the number of parameters, the Mooney model can take several forms. While, nine parameter being the highest order noticed, two parameter model is the most commonly found form in the current research domain. Since two parameter model used repetitively, we investigated the effect of incremental change in two material constant values one at a time, on model curve. As Drucker Stability Criterion is governing the extreme values of material parameters, changes in the model curves are discussed related to it. Resultant effects on stress-strain curves due to change in parameter values were examined and physical effect on the characterization is interpreted accordingly.

Mechanical behavior of a rubber bushing of a stabilizer of a passenger car is studied in this article. An analysis of behavior of the bushing loaded in the axial direction is performed. An identification of the critical points in the bushing body and, especially, in the interface between the bushing and the stabilizer bar for later optimization of the whole system of the stabilizer fixing in the car construction is the aim of this work. An advanced FEM system including such effects as a strongly nonlinear strain/stress relation of material of the bushing (hyperelasticity), large displacements, large deformations, and contact between the bushing and the stabilizer bar was used for the numerical analysis.

This paper deals with an FEM simulation of a multi-purpose tyre. It is focused on the tyre tread pattern lateral stiffness under static conditions. Its behaviour under given radial and lateral loads and its stiffening using connecting bridges are simulated. A tyre is a complex composite composed of different rubber materials and textile or steel reinforcements. Rubber materials are described using hyperelastic models in the analyses. FEM software MSC Marc/Mentat is employed as a calculation tool and its various functionalities are utilized for a description of the tyre models. In the last step, calculated stiffnesses of all the tread patterns were evaluated and compared to each other.