K19
Materials 4

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16:05
conference time (CEST, Berlin)
Evaluation and Validation of Rubber FEA for High Pressure High Temperature Applications Through a Large-Scale O-Ring Test Program
28/10/2021 16:05 conference time (CEST, Berlin)
Room: K
A. Zhong (Halliburton Carrollton Technology Center, USA); Z. Fan (Halliburton, SGP)
A. Zhong (Halliburton Carrollton Technology Center, USA); Z. Fan (Halliburton, SGP)
Despite significant advancements in rubber finite element analysis (FEA), rubber modeling remains to be a challenge, due to incompressibility, large deformation, viscoelasticity, permanent set, and thermal aging. These challenges become more acute for rubber applications in oil and gas industry under high pressure and high temperature (HPHT) conditions. In this work we focus on two specific topics in rubber modeling under HPHT conditions, rubber failure criteria and validation of rubber FEA for a quasi-static loading. Taking advantage of a comprehensive experimental program [1] which studied the extrusion-resistance performance of of four different ISO3601-1 sized O-rings made from a single batch of rubber. The study was conducted at 400°F when subjected to three extrusion gaps, at squeezes of 4%, 10%, and 15%. A total of 160 tests were performed in which the pressures required to extrude the O-rings were measured. Using these data, we evaluated four different rubber failure criteria (strain energy density, maximum principal strain, maximum principal stress and maximum shear stress criteria, respectively) and determined the most applicable failure criterion for these applications. As the physical measurements from the O-ring test program showed that rubber properties have certain degree of variabilities, so the extrusion tests for O-rings with the same nominal size have a statistical distribution. This statistical variability dictates that validation of rubber FEA should be performed in a statistical sense. Our rubber FEA approach is validated through the large-scale O-ring experimental observations. The validated rubber FEA approach has been successfully applied in much more complicated sealing systems, including packer elements for downhole fluid isolations [2]. Reference [1] Zhong, A., Glaesman, C. (2020), O-Ring Extrusions under High Pressure High Temperature Conditions, 198th Technical Meeting of the Rubber Division, ACS Virtual Technical Meeting, October 20-22, 2020 [2] Zhong, A, Dockweiler, D. (2020), Learning Cycle-based Project Management and Its Application, SPE 201515, 2020 SPE Annual Technical Conference and Exhibition, (virtual) October, 2020
Rubber, Failure Criteria, FEA, design
16:25
conference time (CEST, Berlin)
Simulation-based Design and Prediction of Effective Mechanical Properties of Woven, Weft and Warp Knitted Fabrics
28/10/2021 16:25 conference time (CEST, Berlin)
Room: K
D. Neusius, J. Orlik, O. Sivak, K. Steiner (Fraunhofer ITWM, DEU)
D. Neusius, J. Orlik, O. Sivak, K. Steiner (Fraunhofer ITWM, DEU)
Our software tool TexMath is a modular program for simulating mechanical material properties and optimizing textile products as well as multi-scale problems for textile applications. With MeshUp we create periodic textile structures of all kinds (woven fabrics, knitted warp and weft fabrics, spacer textiles) according to the respective machine control with complex weaves/knitting looping diagrams. A graphical user interface is being developed which allows simple usage of MeshUp with industry standards of textile pattern definition. In addition to pattern generation this includes intuitive definition of boundary conditions and keeps all patterns, machines and materials as well as simulation results in a database. With FiberFEM, woven and braided textiles, spacer fabrics, scrims and trusses can be calculated and optimized regarding their effective mechanical material properties. A special feature of FiberFEM is that, in addition to tensile and shear properties, effective bending and torsional properties of textiles can also be determined based on their textile structure and yarn properties. As input variables FiberFEM requires the microstructure description from MeshUp, the fiber cross-section geometry, as well as mechanical fiber properties such as tensile stiffness and friction. As output the effective mechanical textile quantities are calculated. Besides the calculation of the effective mechanical material properties for already existing woven or knitted textiles for technical and medical applications, the approach also offers the potential for the targeted design and optimization of new textiles with a given mechanical property profile. The tool FIFST is specialized for dynamic simulations of stretchable knitted fabrics and teir production. For example, the knitting process can be simulated, the pull-off from the knitting machine, the shrinkage to a relaxed textile and also the further deformation during tightening can be calculated. This means that the design of the knitted fabric can also be adapted to predefined tension profiles and individualized machine control is possible for the production of personalized textiles or product-specific designs. The numerical implementation uses the finite element method with non-linear truss elements, which has been extended for contact problems by an additional internal variable - the sliding of threads at contact nodes. The friction law is implemented with the Euler-Eutelwein model, which was extended by an additional adhesion term. Adhesion thus allows different pre-strains in the respective meshes. The elastic energy is calculated directly from the yarn force-elongation curves. All tools have interfaces to each other and also to GeoDict (optionally to Ansys/Abaqus as IGES-formats) in order to perform further fluid mechanical simulations on the textiles, e.g. to determine their permeability in any elongation state. An interface with FeelMath allows further detailed three-dimensional mechanical simulations at specific yarn or contact points, so that strength and durability can also be investigated.
Textiles, Simulation, FE, Beams, Trusses
16:45
conference time (CEST, Berlin)
Mechanical Modeling of Nonwovens from Polymeric Fibers
28/10/2021 16:45 conference time (CEST, Berlin)
Room: K
Y. Chen, Y. Lin (The Dow Chemical Company, USA)
Y. Chen, Y. Lin (The Dow Chemical Company, USA)
Nonwoven fabrics refer to materials with fibers orientated in a preferential or non-preferred direction within the structure and congregated by mechanical constraints such as bonding or self-entanglement of fibers. Polymeric fiber-based nonwovens are widely used in Health and Hygiene applications such as diapers, feminine napkins, and wipes. The mechanical properties of nonwoven sheets such as strength and strain at break are relevant to those applications. The present study aims to provide a fundamental understanding on the property relationship between individual fibers and nonwoven material with specific bonding patterns using finite element modeling. The investigation focuses on the validation of the prediction response when compared to experimental results and elucidating the deformation of the nonwoven material under tension. The model was validated to accurately predict the mechanical properties of the nonwoven sheet using the structural characteristics and fiber properties as the inputs. Comparative studies were subsequently carried out to study the influence of fiber orientation distribution, fiber dimensions, and the bonding pattern (bonding geometry, bonding density, bonding strength, etc.) on the mechanical properties of the nonwoven material. It was demonstrated that the mechanical strength of the nonwoven is proportional to properties of the fiber with the same bonding pattern and fiber orientation distribution, under the circumstance that the fiber properties do not alter the deformation mechanism of the nonwoven under loading. The outcome of the modeling work also reveals that, among all the parameters, the bonding pattern plays a significant role along with the fiber properties. With the employment of the developed modeling tool, a design of experiments (DOE) can be performed to optimize the bonding pattern and lead to better mechanical properties if the fiber properties are constrained. The study reveals that with manipulation of the bonding pattern for the nonwoven, the strength and strain at failure can be optimized within a factor of 2.
Nonwoven, modeling, mechanical properties, polymeric fiber
17:05
conference time (CEST, Berlin)
Modeling and Experimental Characterization of Adhesive Curing Processes
28/10/2021 17:05 conference time (CEST, Berlin)
Room: K
D. Lindeman, A. Hedegaard (3M Company, USA)
D. Lindeman, A. Hedegaard (3M Company, USA)
Structural adhesives are widely used in many industries, including the automotive, aerospace, and electronics industries. To avoid damage to sensitive components, warpage of the final assembly, surface defects, and/or reduced bond life, the chemical shrinkage and residual stresses associated with the curing process of the adhesive must often be understood. In this presentation a finite element-based method for simulating curing processes is outlined and validated. The method developed uses a transient coupled thermal-structural analysis procedure. Using user-defined subroutines, the conversion rate is calculated as a function of temperature using the measured reaction kinetics of material, and an explicit update procedure is used to calculate the total conversion. The elastic (and, optionally, viscoelastic) properties of the material are then updated as functions of conversion and temperature, and the new stresses and material Jacobian are defined. In addition, at each time step the conversion and temperature-dependent chemical shrinkage and thermal strains are updated. Finally, the heat generation associated with the exothermic reaction is updated, and the equilibrium iteration or time stepping process is continued. The experimental methods required to characterize the conversion and temperature-dependent properties of the material (including density, thermal conductivity, specific heat, heat-of-reaction, reaction kinetics, chemical shrinkage, thermal expansion and elastic or viscoelastic properties) are also discussed. The experimental methods used include Differential Scanning Calorimetry (DSC), Fourier Transform Infrared spectroscopy (FTIR), and Dynamic Mechanical Analysis (DMA). Of particular interest is the use of a DMA testing procedure featuring a multi-wave drive signal that enables the measurement of a frequency-dependent response in a time span that is sufficiently short to assume that the conversion level is constant during the test cycle. This method enables the generation of master curves at multiple iso-conversion levels. In addition, by defining both temperature and conversion-dependent shift factors, a "master curve of master curves" can be constructed (the Time-Temperature-Cure Superposition (TTCS) principle). The experimental methods developed to validate the curing model will also be discussed. In addition, a native Abaqus implementation of the cure modeling procedure will be introduced.
Adhesives, curing, chemical shrinkage, residual stress, finite element analysis
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