Numerical studies on the self-heating phenomenon of elastomers based on finite thermoviscoelasticity

Abstract

Due to their typical material characteristics, elastomer components are used in almost all areas of engineering. In many cases, these components are subject to large cyclic deformations which result in hysteresis and dissipation-induced self-heating. Further they are exposed to varying ambient temperatures. Increased component temperatures can lead to the loss of a function or to total failure. Therefore, it is important to understand the causes and influences of critical temperatures and to identify them early in the development process under the condition of efficient applicability. In addition to the calculation time and accuracy, this also includes the experimental effort required to identify the material parameters and perform validation measurements. Within this work, the phenomenon of dissipative heating in elastomers is investigated in a numerical study using a modified model of the finite thermoviscoelasticity. For this purpose, a sufficiently simple material model was formulated and implemented under the assumption of the quasi-incompressible material behaviour. Based on this, the type and the characteristic features of the self-heating effect are specifically considered, and its dependence on thermal and mechanical initial and boundary conditions is studied. Thus, a new suitable parameter is introduced, which is particularly useful to identify critical loads. Analogously, the identification of dissipation-sensitive temperature ranges is presented. The utility of the general steadystate equilibrium condition as initial condition is also shown. Furthermore, the influence of the material properties on the steadystate equilibrium is demonstrated for the first time through parameter studies. Based on these findings, recommendations for modelling, calculation and experimental parameterisation are proposed.

Numerical studies on the heat dissipation process in elastomers under rotating loading direction

“…The assigned mechanical properties are for carbon black filled natural rubber. The mechanical properties are listed in Table 1 and are taken from [16] except for the value of the relaxation time. The relaxation time is assigned a value of 0.8 s. The chosen relaxation time is calculated using the standard Williams-Landel-Ferry (WLF) equation with the temperature set to 298 K. Other parameters of WLF equation are taken from [16] and are listed in Table 2.…”

“…Good agreement was found to occur between experiments and simulations of the force displacement hysteresis. Furthermore, in a recently published paper by Schröder et al [16], numerical studies were conducted to investigate the influence of the loading amplitude, loading frequency and the material parameters on the self-heating phenomena in elastomers.…”

“…( 12), initially the value of the internal variable is zero and increases with time due to viscous dissipation. An equilibrium state is reached when reaches the value = i (t) and the stress is only calculated with the equilibrium part ( (t) = ∞ (t) ) [16]. With partial integration of Eq.…”

“…where C 1 , C 2 are standard parameters and t is the glass transition temperature. The values of these parameters are taken from [16] and are listed in Table 2.…”

Advanced Characterisation of Soft Polymers under Cyclic Loading in Context of Engine Mounts

“…However, in addition to suitable material models, this also requires suitable methods and equipment for material characterisation, as the publication by Hartmann [ 34 ] describes. This section, therefore, focuses on the viscoelastic material characterisation, which, in the context of dissipative self-heating, has a significant influence on the valency, progress and stability of the resulting temperature field, which is examined in more detail within the study published by Schröder et al [ 35 ]. The present study presents a method for experimental identification of viscoelastic parameters, which can be transferred to complex geometries and multi-axial deformation states and velocities.…”