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33 records · Page 2

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NASA NTRS2012

Application of Benchmark Examples to Assess the Single and Mixed-Mode Static Delamination Propagation Capabilities in ANSYS

The application of benchmark examples for the assessment of quasi-static delamination propagation capabilities is demonstrated for ANSYS. The examples are independent of the analysis software used and allow the assessment of the automated delamination propagation in commercial finite element codes based on the virtual crack closure technique (VCCT). The examples selected are based on two-dimensional finite element models of Double Cantilever Beam (DCB), End-Notched Flexure (ENF), Mixed-Mode Bending (MMB) and Single Leg Bending (SLB) specimens. First, the quasi-static benchmark examples were recreated for each specimen using the current implementation of VCCT in ANSYS . Second, the delamination was allowed to propagate under quasi-static loading from its initial location using the automated procedure implemented in the finite element software. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Overall the results are encouraging, but further assessment for three-dimensional solid models is required.

Krueger, Ronald↗

NASA NTRS2018

A Benchmark Example for Delamination Propagation Predictions Based on the Single Leg Bending Specimen Under Quasi-Static and Fatigue Loading

Benchmark examples based on Single Leg Bending (SLB) specimens with equal and unequal bending arm thicknesses were used to assess the performance of delamination prediction capabilities in finite element codes. First, the development of the quasi-static benchmark cases using the Virtual Crack Closure Technique (VCCT) is discussed in detail. Second, based on the quasi-static benchmark results, additional benchmark cases to assess delamination propagation under fatigue loading are created. Third, the application is demonstrated for the commercial finite element code Abaqus Standard 2018. The benchmark cases are compared to results obtained from VCCT-based, automated quasi-static propagation analysis. A comparison with results from automated fatigue propagation analysis was not performed at this point since the current version of Abaqus does not include this capability under variable mixed-mode conditions. In general, good agreement between the results obtained from the quasi-static propagation analysis and the benchmark results were achieved. Overall, the benchmarking procedure proved valuable for analysis verification.

Krueger, Ronald↗

NASA NTRSDate not supplied

A Benchmark Example for Delamination Propagation Predictions Based on the Single Leg Bending Specimen under Quasi-static and Fatigue Loading

Ronald Krueger↗

NASA NTRSDate not supplied

Calculating Mode Mixity in Interlaminar Fracture of Composite Laminates

To accurately predict delamination under mixed-mode loading, cohesive elements must partition the energies dissipated in Mode I and Mode II correctly. The ability of cohesive models to predict mode mixity was evaluated by performing analyses of the single leg bending (SLB) test, which exhibits a variable mode mixity with crack length. Accordingly, two numerical integration methods were developed to compute the energy partitioning: (i) a local calculation of the accumulated work of tractions at each point along the crack path, and (ii) a global J-integral “snapshot” calculation along a contour around the process zone. In the case of a composite laminate with properties characterized by short fracture process zone (FPZ), the results of these two methods correlate well with each other and with a linear elastic fracture mechanics solution. However, FPZscan be long due to fiber bridging or due to the intrinsic toughness of the material. Then, the results of mode-mixity calculations obtained with various methods vary widely from each other. It is argued that the global J-integral calculation is the most accurate interpretation of the energy release rate and mode mixity for either short or long process zones. This solution will provide a more accurate characterization of resistance curves and mode mixity in experimental results, and it will also guide the development of more accurate mixed-mode cohesive laws for tougher materials characterized by strong R-curve responses, such as thermo-plastic composites.

cohesive zone analysis↗

DOE OSTI2021

UNREVIEWED DISPOSAL QUESTION EVALUATION: Disposal of the Perma-Fix Environmental Services Macroencapsulated Debris at the Area 5 Radioactive Waste Management Site, Nevada National Security Site, Nye County, Nevada

This Unreviewed Disposal Question Evaluation (UDQE) assesses whether the Perma-Fix Environmental Services (PERM) Macroencapsulated Debris, Radioactive Lead (Pb) Solids, Cadmium/Mercury/Silver (Cd/Hg/Ag) Containing Batteries from U.S. Department of Energy (DOE) Generators (PERM000000027, Revision 28 [PERM 2021]) is suitable for shallow land burial (SLB) at the Area 5 Radioactive Waste Management Site (RWMS) on the Nevada National Security Site (NNSS). Disposal of the PERM Macroencapsulated Debris, Radioactive Pb Solids, Cd/Hg/Ag Containing Batteries from DOE Generators meets all performance objectives of DOE Manual DOE M 435.1-1, Radioactive Waste Management Manual, Chapter IV, Section P (DOE 1999). The PERM Macroencapsulated Debris, Radioactive Pb Solids, Cd/Hg/Ag Containing Batteries from DOE Generators stream is recommended for acceptance without conditions.