Tension behaviour of HNBR and FKM elastomers for a wide range of temperatures

Ilseng, Arne; Skallerud, Bjørn; Clausen, Arild Holm

doi:10.1016/j.polymertesting.2015.11.017

Cited by 34 publications

(20 citation statements)

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“…It is therefore essential to obtain precise 23 data at large deformations from experiments in order to 24 analyse such complex load cases successfully. 25 Several studies have been conducted addressing the 26 performance of polymeric materials at elevated tem- with cameras for subsequent DIC analysis, is that such 57 materials are susceptible to volume change during plas-58 tic deformation. Hence, the transverse strains have to 59 be measured in order to calculate the true stress.…”

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confidence: 99%

Experimental set-up for determination of the large-strain tensile behaviour of polymers at low temperatures

et al. 2016

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In this study, we present a method to determine the large-strain tensile behaviour of polymers at low temperatures using a purpose-built temperature chamber made of polycarbonate (PC). This chamber allows for several cameras during testing. In our case, two digital cameras were utilized to monitor the two perpendicular surfaces of the test sample. Subsequently, the pictures were analysed with digital image correlation (DIC) software to determine the strain field on the surface of the specimen. In addition, a thermal camera was used to monitor self-heating during loading. It is demonstrated that the PC chamber does not influence the stress-strain curve as determined by DIC. Applying this set-up, a semi-crystalline cross-linked low-density polyethylene (XLPE) under quasi-static tensile loading has been successfully analysed using DIC at four different temperatures (25 • C, 0 • C, −15 • C, −30 • C). At the lower temperatures, the conventional method of applying a spray-paint speckle failed due to embrittlement and cracking of the spray-paint speckle when the tensile specimen deformed. An alternative method was developed utilising white grease with a black powder added as contrast. The results show a strong increase in both the Young's modulus and the flow stress for decreasing temperatures within the experimental range. We also observe that although the XLPE material is practically incompressible at room temperature, the volumetric strains reach a value of about 0.1 at the lower temperatures.

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confidence: 99%

Experimental set-up for determination of the large-strain tensile behaviour of polymers at low temperatures

et al. 2016

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“…For the creep test, only a slight volume increase can be observed. As the deviatoric behaviour of the material has been found to be viscous and cycle dependent [4] the deformation in this stage is likely to be dominated by the hydrostatic stresses, meaning that the measured axial stress dened in Equation 5 yields a good approximation to the hydrostatic stress response of the tested materials. In the following results, the measured axial stress is therefore denoted as the hydrostatic stress.…”

Section: Resultsmentioning

confidence: 99%

“…Constitutive models commonly applied to predict the visco-hyperelastic response of elastomers in nite element simulations assume a nearly isochoric behaviour independent of loading mode [1,2,3]. Based on available experimental data in uniaxial tension (UT) [4] and conned axial compression (CAC) [5], there are clear indications that this approach can be inaccurate for certain elastomers. It appears that the materials can exhibit a considerable increase of volume in UT, £ arne.ilseng@ntnu.no while the response in CAC is much stier with respect to volume change, yet there is a nite bulk modulus also in this loading case.…”

Section: Introductionmentioning

confidence: 99%

An experimental and numerical study on the volume change of particle-filled elastomers in various loading modes

Ilseng

Skallerud

Clausen

2017

Mechanics of Materials

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Laboratory tests show that there is a pronounced dierence in the volumetric response between uniaxial tension and conned axial compression loading for commercial particle-lled hydrogenated nitrile butadiene rubber (HNBR) and uoroelastomer (FKM) compounds. In uniaxial tension (UT), a volume increase of 5 and 20 % for the HNBR and FKM respectively was present for a hydrostatic stress of less than 6 MPa, in addition, both compounds showed a clear hysteresis loop in the hydrostatic stress -volume ratio space. For conned axial compression (CAC) tests, on the other hand, the materials reached a 6-7 % volume change for a hydrostatic stress of 140 MPa, and an elastic behaviour was seen. This loading mode dependence of the volumetric response has severe implications for the constitutive representation of the materials. It is demonstrated that existing elastomer models, whereof many assume incompressible volumetric response, are unable to capture the behaviour in both loading modes. To gain an increased understanding of the macroscopically obtained results, a tension in situ scanning electron microscopy study was performed.Matrix-particle debonding was observed to occur at the external surface of the materials, rendering a possible explanation for the loading mode dependent volumetric behaviour. Finite element simulations of a single-particle model, incorporating a cylinder of matrix material with a spherical particle in its centre, showed that the observed debonding can explain the experimental response of the materials in a qualitative manner.

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“…43.5 MPa at TR = 0.25, whereas the leg with no groove showed a gradual increase, with its highest value of 32.5 MPa at TR = 1.50. Using the stress-strain curve suggested in the literature [25], the approximate stress of the 40%-deformed FKM material was experimentally reported to be about 1.5-2.0 MPa at constant volume assumption. Referring to the suggested equations in another literature [1], it was reported that when elastomeric seals were compressed by 40%, the contact pressure of the axially and radially restrained grooves would exponentially increase by about 20-25 times greater than those of the unrestrained geometry.…”

Section: Contact Pressure and Gap Distance Under Axial Compressionmentioning

confidence: 99%

Contact Pressure and Strain Energy Density of Hyperelastic U-shaped Monolithic Seals under Axial and Radial Compressions in an Insulating Joint: A Numerical Study

2017

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Abstract:In insulation joints, elastomeric U-shaped monolithic seals (UMSs) are replacing O-ring systems because of their enhanced sealing capabilities for the oil and gas industries. UMSs are compressed axially during assembly and radially when pressurized in operation. The reliability of UMSs due to the displacement imposed during assembly and the internal pressure in operation is influenced by the axial compression ratio, thickness ratio (TR), and geometric complexity. In this study, the hyperelastic behavior of elastomeric UMSs under axial and radial compressions is investigated using axisymmetric finite-element analysis. Twelve examples of UMSs with three geometric restraints (open grooves on both sides (type 1), an open groove on one side only (type 2), and no groove (type 3)) and four thickness ratios (TR = 0.25, 0.50, 1.00, and 1.50) are evaluated. To analyze nonlinear elastomeric materials, neo-Hookean constitutive equations are applied and the UMSs are considered as being a nearly incompressible hyperelastic material with a Poisson's ratio of 0.499. The failure and detachment risks of UMSs are analyzed in terms of the equivalent stress, gap distance, contact pressure, and strain energy density. It is advantageous that the smaller the TR, the smaller the stress distribution. However, the generation of broader detachment regions is observed. Type 1 symmetrically shows the lowest stress distribution and the smallest detachment region, whereas type 3 symmetrically shows the highest values. Type 3 (TR = 0.25) shows the broadest detachment region in the arc-length range from −15.7 to 15.7 mm, whereas the largest gap of 0.7 mm is observed in type 2 (TR = 0.5). For all types, the detachment region disappears completely at TR = 1.0 or higher, which implies that full sealing is occurring. The average contact pressure increases exponentially during axial compression (in assembly) and linearly during radial compression (in operation). The largest contact pressure of 31.5 MPa is observed in type 3 (TR = 1.5), while the lowest is observed in type 1 (TR = 0.25). As for the strain energy density, type 3 at TR = 0.25 shows the largest increase in the strain energy density with 1.75 MJ/m 3 , while type 1 shows the most stable values of all cases. In conclusion, the lowest risk of failure of a nonlinear hyperelastic UMS was investigated numerically with minor equivalent stress and detachment region with higher contact pressure, which can be taken into account to ensure the reliability of the UMS.

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Tension behaviour of HNBR and FKM elastomers for a wide range of temperatures

Cited by 34 publications

References 20 publications

Experimental set-up for determination of the large-strain tensile behaviour of polymers at low temperatures

Experimental set-up for determination of the large-strain tensile behaviour of polymers at low temperatures

An experimental and numerical study on the volume change of particle-filled elastomers in various loading modes

Contact Pressure and Strain Energy Density of Hyperelastic U-shaped Monolithic Seals under Axial and Radial Compressions in an Insulating Joint: A Numerical Study

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