Numerical Investigation of Elastomer Seal Performance

Analytical models for swelling of rubberlike materials are difficult to formulate, and restricted in actual application due to their need for simplifying assumptions. Tests conducted on laboratory size samples of swelling elastomers cannot reproduce actual oil well conditions, and cannot cover all possible variations of testing parameters. However, these laboratory tests do provide useful information about material response of swellable elastomers in various conditions, serving as a basis for analytical and numerical modeling. Properly developed and robust numerical models can be used to predict near-actual performance of elastomeric seals. The current chapter describes the use of numerical (finite element) simulation to investigate swelling elastomer seal behavior in downhole petroleum applications. Variations in sealing (contact) pressure are studied for seal length, seal thickness, compression ratio, water salinity, swelling time, and type of well completion (open-hole or cased-hole). Month-long swelling experiments on samples of two actual elastomers (Chapters 3 and 7) provide input to the numerical model in terms of real material and deformation data. On the basis of these results, petroleum engineers can make informed decisions about the selection of elastomer material and seal geometry appropriate for the well type and conditions encountered. Application developers and researchers can also find this investigation useful in performance analysis and design of swelling elastomer seals.

Elastomeric Seal Stress Analysis Using Photoelastic Experimental Hybrid Method

Stress freezing is an important and powerful procedure in 3-dimensional experimental stress analysis using photoelasticity. The application of the stress freezing technique to extract stress components from loaded engineering structures has, however, declined over the years even though its principles are well established. This is attributed to huge costs arising from energy consumption during the process. In addition, significant time is needed to generate the desired information from isoclinic and isochromatic fringes. To overcome the limitations of stress freezing in photoelasticity and transform it into an economical device for stress analysis in an engineering environment, a new stress freezing cycle that lasts 5 hours is proposed. The proposed technique is used in several applications of elastomeric seals with different cross-sectional profiles to assess its suitability. It was found that reducing the cycle time can lead to huge energy savings without compromising the quality of the fringes. Moreover, the use of isochromatic only to extract stress components leads to a shorter processing time to achieve desirable information since the process of obtaining isoclinic data is involving. In this paper, results of stress analysis from stress frozen elastomeric seals with various cross-sections using the new stress freezing cycle are presented.

A mathematical model for evaluating adhesion contact of an elastomeric seal-on-seal structure

For low impact docking systems (LIDS) developing for rendezvous and docking of spacecraft, the main interface docking seal (MID seal) is one of the key components, and its seal and adhesion performances are crucial for mating LIDS-adapted spacecrafts. An elastomeric seal-on-seal structure is one of the mainstream designs of the MID seal and is generally made of silicone rubbers that can adapt to complex space environments. For the MID seal of seal-on-seal structure, the adhesion performance has been confirmed to have significant effects on the separation reliability of mating spacecrafts. By analyzing the sealing and adhesive mechanisms of the MID seal that is an elastomeric seal-on-seal structure, an adhesive contact model of single rough peak is derived on the grounds of Johnson, Kendall and Roberts (JKR) theory. Utilizing the asperities model and the adhesive contact model of single rough peak, an adhesive contact model of the elastomeric seal-on-seal structure is further proposed. The experiments were performed to verify the adhesion model, and the satisfied consistencies were presented in the comparative studies of the experimental data and the calculated data. Based on the proposed mathematical model, the simulation analyses were performed to disclosure adhesive performances of the MID seal. The influence rules of some parameters on adhesive performances were presented, including material parameters, geometric parameters, and parameters of surface morphology. The research findings are proven to be favorable for the design, machining, assemblage and actual service of the MID seal, and can be also used for other elastomeric seals.

Numerical Approach for the Assessment of Micro-Textured Walls Effects on Rubber Injection Moulding

Micro-surface texturing of elastomeric seals is a validated method to improve the friction and wear characteristics of the seals. In this study, the injection process of high-viscosity elastomeric materials in moulds with wall microprotusions is evaluated. To this end, a novel CFD methodology is developed and implemented in OpenFOAM to address rubber flow behaviour at both microscale and macroscale. The first approach allows analyzing the flow perturbation induced by a particular surface texture and generate results to calculate an equivalent wall shear stress that is introduced into the macroscale case through reduced order modelling. The methodology is applied to simulate rubber injection in textured moulds in an academic case (straight pipe) and a real case (D-ring seal mould). In both cases, it is shown that textured walls do not increase the injection pressure and therefore the manufacturing process is not adversely affected.

Elastomeric door seal analysis under aircraft cabin pressure

Simple strategies are used to physically represent the cabin pressure acting on elastomeric seals for aircraft door applications. The relationships between rubber response, contact problem and air pressure are assumed as the initial step to understand the risks of air leakage during the early stages of a flight cycle. Through the finite element method, the non-linear boundary problem is investigated with the distinct contact response from two types of door interfaces. The options available within the ABAQUS commercial software are explored to model the seal as nearly incompressible, whereby the limitations are compared for each solution. In a qualitative approach, the simulations use the contact pressure distributions to define the pressure load for air leakage investigations on the door corners.