Plot Extraction Archives - ESRD

ASIP 2024 Training – Case Studies in Fracture Mechanics Analysis Using StressCheck v12.0

brent — Tue, 10 Dec 2024 17:01:20 +0000

Abstract: this 3-hour training course, originally presented at the ASIP 2024 conference in Austin, TX, explored the following topics:

DEMO: FEA analysis of an aircraft stiffened lug detail
- How a “Single Corner Crack in Lug” solution compares with FEA results?
LEARN: Strategies for efficiently meshing 3D fracture mechanics problems
- Mixed meshing vs. all-tetrahedral meshing along 3D crack fronts
- Automatically-generated vs. manually-input element layers around 3D crack fronts
- No refinements vs. geometrically graded refinements at 3D crack tip intersections
- 100% automesh vs. “seeding" an automesh with hand-meshed nodes/elements
REVIEW: Sample 3D and plane strain fracture mechanics case studies
- “Selected Stress Intensity Factor Cases”, DTD Handbook Section 11.3
Summary & resources
- SC v12.0 training options

StressCheck Tutorial: 3D Splice Joint Hierarchic Modeling with Free/Fused Auto Contact

brent — Wed, 04 Dec 2024 22:32:27 +0000

In this StressCheck v12.0 tutorial, hierarchic modeling of a 3D fastened splice joint is performed via the new Assembly Meshing/Auto Contact feature. The Auto Contact method allows the user to manually toggle between "Contact" (default), "Bonded" or "Free" options, enriching the range of possibilities when performing hierarchic modeling of 3D fastened assemblies.

In the first simulation, traditional multi-body contact (i.e. the "Contact" option) is automatically generated for all matched surfaces during Assembly Meshing, and each plate/fastener body is solved independently for pressures/stresses.
In the second simulation, the existing Auto Contact constraints on the top/bottom surfaces of the middle plate are set to the "Free" option and the existing Auto Contact constraints between the middle plate and associated fastener shank surfaces are set to the "Fused" option.
- This means the middle plate/fasteners are solved as one continuous body, thereby reducing the model hierarchy from six (6) independent bodies to three (3) independent bodies.
Upper and lower plate bore stresses for each multi-body contact simulation are then compared.

StressCheck Tutorial: Comparing Pre- and Post-Repair Configurations via Fused Auto Contact

brent — Wed, 04 Dec 2024 22:04:11 +0000

In this StressCheck v12.0 tutorial, solutions of pre-repaired and post-repaired model configurations will be performed using Assembly Meshing/Auto Contact in combination with Parts & Solution Configurations.

In the pre-repaired configuration, a 3D panel with a circular cutout under axial loading will be analyzed for detailed stresses.
In the post-repaired configuration, a circular tapered doubler patch will be bonded over the circular cutout (via the "Fused" Auto Contact option now available in StressCheck v12.0) and analyzed for detail stresses.
Direct and meaningful comparisons will be made between the pre-repaired and post-repaired configuration stress distributions.

StressCheck Tutorial: New Assembly Meshing/Auto Contact Features in StressCheck v12.0

brent — Wed, 11 Sep 2024 20:11:43 +0000

A new and powerful assembly automeshing/automatic contact detection feature is now available with the release of StressCheck v12.0. Before automeshing an assembly of close-contacting solid bodies, users may enable the "Assembly Meshing" option to enforce element face matching between neighboring surfaces (to within a user-specified tolerance). Once the solid bodies have been automeshed, StressCheck will automatically create contact zones between matched neighboring element faces and assign contact pairs via the new Auto Contact constraint method to the current constraint ID (if existing, otherwise StressCheck will use "AUTO_CONT" as the constraint ID). Individual contact pairs generated via the Auto Contact method may specified as Contact (the default, traditional multi-body contact), Fused (if element face matching was 100% successful, matched element faces are bonded) or Free (matched element faces are free). Note that if individual contact pairs are specified as Contact, and a parameter is not used for the Contact Constant, the Contact Constant value is computed from the assigned material property data and will be updated if one or more of the material properties are modified. This tutorial revisits a previous 3D multi-body contact example and utilizes assembly automeshing/automatic contact detection to significantly reduce the amount of setup time for multi-body contact analysis. The tutorial also demonstrates how refining the automesh (or updating a parameter value which triggers a re-mesh) will result in the re-generation of the contact zones/contact pairs.

StressCheck Tutorial: New Mesh Seeding Features in StressCheck v12.0

brent — Wed, 11 Sep 2024 19:41:16 +0000

A new and powerful mesh seeding feature is now available with the release of StressCheck v12.0. Before automeshing a solid body, users may associate manually generated nodes and/or manually meshed elements with that solid body. During the automeshing process, these nodes and/or elements will be incorporated in the resulting mesh. If users require refinement of the seeded mesh, h-Discretization methods are supported. Note that the automesh must be re-generated after h-Discretizing the seeded mesh. This tutorial revisits the example from the Getting Started Guide and utilizes seeded hand-meshed elements in the region of interest. The hand-meshed elements are then h-Discretized and the automesh is updated.

Experimental Validation of DTA Modeling of Bonded Wing Skin Repairs

brent — Thu, 07 Dec 2023 16:41:37 +0000

Abstract: This presentation is a follow-up to ESRD’s 2022 ASIP presentation titled “DTA of Bonded Repairs on the Wing Skin of the C-130 Using Finite Elements.” That presentation explored a robust method for finite element analysis of bonded skin repairs from the perspective of both static strength and fatigue crack growth. The proposed analysis methodology was presented in a comparative sense, examining a number of criteria in the skin in an undamaged state, a damaged state and a repaired state, in order to allow the analyst to make an assessment of repair effectiveness without detailed knowledge of either the exact boundary conditions of the problem, or of the intricacies of the model itself. One of the criteria for a patch to be deemed effective is that the fatigue life of the skin be at or above that of the pristine configuration. Given the sparse nature of research on the topic of crack growth under bonded repair patches, ESRD partnered with AP/ES to conduct an experimental program to investigate in detail how a small initial flaw propagates in the aluminum skin under a titanium repair up through failure. Experiments were performed alongside blind predictions of life and crack morphology using ESRD’s research tool, CPAT. Additionally, statistical analysis was performed to assess confidence in the predictions. Given the aleatory uncertainty associated with the available crack growth data for the specimen material, it was important that predictions of fatigue life be accompanied by a confidence level when comparing them with experimental outcomes. Because most of the crack propagation occurred under the repair, a marker band spectrum was used during the test and the crack-cycle data was constructed from fractographic examination. The experimental program covered three specimen configurations: (1) Undamaged skin with a surface crack or a corner crack at a hole; (2) Skin with a grindout (to remove hypothetical corrosion damage) and either a surface crack at the bottom of the grindout or a corner crack at a hole located at the center of the grindout; (3) Same as configuration (2) but including a bonded titanium repair. Experimental and predicted results will be presented. Originally presented as a technical paper at the 2023 ASIP conference in Denver, CO.

ASIP 2023 Training – Enhancements in StressCheck v12.0 for DaDT Analysis of 3D Fastened Connections

brent — Thu, 07 Dec 2023 15:55:57 +0000

Abstract: this 2-hour training course, originally presented at the ASIP 2023 conference in Denver, CO, explored the following topics:

StressCheck’s FEA technology implementation for the modeling, meshing and analysis of arbitrarily shaped 3D crack geometries, with and without the local effects of multi-body contact.
Strategies for automatic meshing of 3D cracks with high-aspect ratio, 3D-solid pentahedral and hexahedral elements to support high-quality SIF extractions at any location on the crack front.
New StressCheck 12.0 method to support multi-body contact assembly meshing, auto-detection of contact regions, and automatic assignment of contact pairs for 3D solid bodies.

StressCheck Demo: 2D Splice Joint Case Study

brent — Fri, 02 Jun 2023 16:15:21 +0000

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StressCheck Demo: Computing 2D and 3D Stress Concentrations for an Infinite Plate with Hole in Tension

brent — Wed, 24 May 2023 15:23:34 +0000

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StressCheck Tutorial: Importation and Assignment of Point Displacements & Rotations via the Fit-Auto Method

brent — Fri, 17 Mar 2023 15:58:28 +0000

Abstract: demonstration of 1) how to format an ASCII file containing nine (9) columns of tabular point displacement/rotation data (X, Y, Z, Ux, Uy, Uz, Rx, Ry, Rz) for importation into StressCheck, and 2) how to assign the imported point constraint data to the surfaces of an imported solid (via the Fit-Auto constraint method) for a global-local analysis. For more details, consult Point Displacements/Rotations Implementation.