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Characterization & Modeling of Materials in Glass-To-Metal Seals: Part I

Chambers, Robert S.; Emery, John M.; Tandon, Rajan; Antoun, Bonnie R.; Stavig, Mark E.; Newton, Clay S.

To support higher fidelity modeling of residual stresses in glass-to-metal (GTM) seals and to demonstrate the accuracy of finite element analysis predictions, characterization and validation data have been collected for Sandia’s commonly used compression seal materials. The temperature dependence of the storage moduli, the shear relaxation modulus master curve and structural relaxation of the Schott 8061 glass were measured and stress-strain curves were generated for SS304L VAR in small strain regimes typical of GTM seal applications spanning temperatures from 20 to 500 C. Material models were calibrated and finite element predictions are being compared to measured data to assess the accuracy of predictions.

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TYPE SAND Report YEAR 2013
DOIOSTI

Ductile failure X-prize

Boyce, Brad L.; Foulk, James W.; Littlewood, David J.; Mota, Alejandro; Ostien, Jakob T.; Silling, Stewart; Spencer, Benjamin W.; Wellman, Gerald W.; Bishop, Joseph E.; Brown, Arthur; Cordova, Theresa E.; Cox, James; Crenshaw, Thomas B.; Dion, Kristin; Emery, John M.

Fracture or tearing of ductile metals is a pervasive engineering concern, yet accurate prediction of the critical conditions of fracture remains elusive. Sandia National Laboratories has been developing and implementing several new modeling methodologies to address problems in fracture, including both new physical models and new numerical schemes. The present study provides a double-blind quantitative assessment of several computational capabilities including tearing parameters embedded in a conventional finite element code, localization elements, extended finite elements (XFEM), and peridynamics. For this assessment, each of four teams reported blind predictions for three challenge problems spanning crack initiation and crack propagation. After predictions had been reported, the predictions were compared to experimentally observed behavior. The metal alloys for these three problems were aluminum alloy 2024-T3 and precipitation hardened stainless steel PH13-8Mo H950. The predictive accuracies of the various methods are demonstrated, and the potential sources of error are discussed.

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TYPE SAND Report YEAR 2011
DOIOSTI

Towards mesh independent simulation of ductile fracture

Emery, John M.; Foulk, James W.; Wellman, Gerald W.; Veilleux, Michael G.; Fang, H.E.

Recent work at Sandia National Laboratories has focused on preparing strong predictive models for the simulation of ductile failure in metals. The focus of this talk is on the development of engineering-ready models that use a phenomenological approach to represent the ductile fracture processes. As such, an empirical tearing parameter that accounts for mean stress effects along the crack front is presented. A critical value of the tearing parameter is used in finite element calculations as the criterion for crack growth. Regularization is achieved with three different methods and the results are compared. In the first method, upon reaching the critical tearing, the stress within a solid element is decayed by uniformly shrinking the yield surface over a user specified amount of strain. This yields mesh-size dependent results. As a second method for regularization, cohesive surface elements are inserted using an automatic remeshing technique. In the third method, strain-localization elements are inserted with the automated remeshing.

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TYPE Conference YEAR 2010
OSTI

Computational assessment of brittle fracture in glass-to-metal seals

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

Gullerud, Arne S.; Emery, John M.; Jamison, Ryan D.

Glass-to-metal seals are widely used in engineering applications, but are often plagued by cracking and loss of hermeticity despite design efforts to avoid these problems. Standard computational approaches typically rely on under-refined meshes and rule-of-thumb approaches that are not always effective. This paper investigates improvements to current practice in glass-to-metal seal design. First, material models with more extensive temperature dependence are used to enhance the accuracy of residual stress prediction. Second, a Weibull-statistics approach is adopted for the prediction of the likelihood of failure. These approaches are then applied to a simplified seal geometry. The paper demonstrates that the application of these methods, especially the Weibull-statistics approach, have difficulties that need to be addressed before this proposed set of approaches can be effectively used for seal design. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. Copyright © 2010 by ASME.

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TYPE Conference YEAR 2010
OSTIScopus
Results 101–125 of 128
Results 101–125 of 128