Session: 12-23-02: Symposium on Multiphysics Simulations and Experiments for Solids

Paper Number: 142344

142344 - Fatigue Life Prediction of Elastomers Under Multiaxial Loading 

Background:

Elastomers are highly desirable for sealing applications because of their large strain elastic and incompressible behaviour. For oil and gas industry, elastomers are generally used as sealing elements in various products/tools such as valves, completion packers, blowout preventers (BOP) and rotating control devices (RCD) for pressure control. In all these applications, life of the product or tool is often depending on structural integrity of the elastomeric component which is often subjected to repeated complex multiaxial loads and failure overtime. Conventional fatigue life damage models based upon coupon level material characterization tests cannot predict the failure of elastomeric components under real operating conditions.

 

Method:

In the current work to predict the failure of elastomeric component such as that in annular BOP under real operating conditions, a damage accumulation framework is developed by combining finite element (FE) model of actual product with industry accepted lab-scale material characterization test such as uniaxial tension and small-scale calibration test to mimic the multi-axil failure mode. In this approach, the fatigue life of an elastomeric component is given by N = (ε_failure- ε) ^b /D. Here N is the cycles to failure, ε_failure is the elongation of elastomer obtained from coupon level material characterization test_, ε is the maximum strain obtained from the FE model of the given product under operational loading conditions, D is the damage accumulation per load cycle obtained using the small-scale calibration tests, and b is the material constant.  Finite element model can capture the effect of geometry and loading conditions on the strain distribution, whereas lab-scale and small-scale tests capture fundamental material response of the elastomer. 

 

Results:

The developed methodology was implemented to predict the fatigue life of the sealing element in two different sizes of annular BOP at room and elevated temperature. It was found that at elevated temperature, a small decrease in the elongation limit of elastomer from temperature induced softening results in a significant drop in the fatigue life of the sealing element, from over hundreds of cycles at room temperature to few cycles at elevated temperature.

 

Conclusion:

In this work, a framework is presented to predict the fatigue life of elastomeric components under multiaxial loading. The presented framework is general and can be applied to various products from simple O-rings to big and complex seals used in the Oil & Gas industry.

Presenting Author: Viraj Singh SLB

Presenting Author Biography: Viraj Singh received his PhD in Mechanical Engineering in the year 2014 from the University of Kansas with focus on computational mechanics. He is currently working as Electronics Modeling Lead/Manager in SLB’s Enable Technology Development group and has co-authored over 25 journal/conference papers. His research interests include finite element modeling, constitutive material modeling and design optimization.

Authors:

Viraj Singh SLB
Haitao Zhang SLB
Haoming Li SLB
Chris Nault SLB