Solid Modeling Archives - ESRD

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.

Webinar: Benefits of Mixed Meshing for Multi-Body Contact Applications

brent — Mon, 13 Mar 2023 20:42:18 +0000

[vc_row][vc_column width="1/2"][vc_message message_box_color="peacoc" icon_fontawesome="fa fa-lightbulb-o"]March 13, 2023 @ 1:00 pm EST[/vc_message][vc_column_text]Strategies for incorporating advanced mixed (hexa/penta) automeshing techniques for improved quality and efficiency of 3D multi-body contact applications will be explored.[/vc_column_text][vc_cta h2="" add_button="right" btn_title="WATCH NOW" btn_color="danger" btn_link="url:%23recording|||"]This webinar is now available to watch on-demand.[/vc_cta][/vc_column][vc_column width="1/2"] [caption id="attachment_27442" align="alignnone" width="1166"] 3D Splice Plate problem definition (top right), mixed mesh taking advantage of symmetry (top left) and plate von Mises stresses (bottom).[/caption] [/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

WEBINAR SUMMARY

[/vc_column_text][vc_custom_heading text="In this 3-part, pre-recorded 40-minute webinar we will present how the automeshing enhancements now available in StressCheck v11.1 significantly aid in the rapid generation of penta- and hexa-dominant meshes for use in 3D multi-body contact applications. To realize these concepts in a practical setting, a 3D splice joint assembly will be constructed, analyzed and post-processed, with detailed commentary on each step in the workflow process." font_container="tag:p|text_align:left" use_theme_fonts="yes"][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

WEBINAR HIGHLIGHTS

[/vc_column_text][vc_column_text]Part 1: Model Definition & Parametric Geometry Construction

Problem definition, scope and use of symmetry to reduce model size
Importation of a parameter file (.par)
Construction of 3D parametric solid bodies (boxes, cylinders, cones, etc.)
Boolean union/subtraction operations between 3D solid bodies to define 3D splice joint parts
Copy operations to duplicate child fastener bodies from a single parent fastener body
Body-to-body imprints between all parts for optimization of contacting surfaces

Part 2: Part Definition, Contact Zone Setup, Mixed Mesh Generation, Material Properties & Boundary Conditions

Creation of Parts for efficient bookkeeping and visualization
Generation of the solid mixed meshes for each Part via Global, Boundary Layer and Thin Section automesh methods
Creation of contact zones for Part regions expected to be in contact
Definition and assignment of material properties to each Part
Assignment of boundary conditions (loads and constraints) to each Part
Assignment of contact pairs to allow gap and pressure computations between Part contact zones

Part 3: Solution Setup, Execution and Post-Processing

Linear multi-body contact solution setup and initiating the solver
Evaluation of max contact pressure error, solve time and degrees of freedom solved (DOF)
Plotting the deformation of the 3D splice joint assembly
Plotting of von Mises stresses for each Part in the 3D splice joint assembly
Unaveraged vs. averaged von Mises stresses for each plate Part
Computing the stress resultants to ensure quality load transfer between Parts
Summary and wrap-up

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DTA of Bonded Repairs on the Wing Skin of the C130 Using Finite Elements

brent — Thu, 08 Dec 2022 18:01:39 +0000

Abstract: Current methodologies for the design and application of repairs to damaged sections of aircraft wing skin can be lacking in analytical support, relying instead on accumulated practical experience to determine the effectiveness of a given patch design. These methods are, by their nature, effective, being based on observation, but inefficient, requiring a knowledge base acquired over years of experience. This can make sustainment organizations inflexible and vulnerable to gaps in knowledge between newer members and more seasoned experts. This approach is also problematic in its potential for wasted effort and material, applying repairs that may be more intensive than is required for a given situation. These problems can all be addressed by the introduction of an accessible, robust analysis methodology cast in the form of an Engineering Simulation Application for the verification of a repair’s performance qualities prior to an actual aircraft application. The finite element method is ideally suited to provide an analysis procedure for this type of problems that can be used by analysts with widely varying degrees of expertise both in numerical simulation and bonded repair application. This presentation will outline a proposed methodology for utilizing finite element analysis to assess the effectiveness of a given bonded repair. Originally presented as a technical paper at the 2022 ASIP conference in Phoenix, AZ.

ASIP 2022 Training – Best Practices for the Modeling and Analysis of Bonded Doubler Repairs

brent — Mon, 05 Dec 2022 15:01:02 +0000

Abstract: this 2-hour training course, originally presented at the ASIP 2022 conference in Phoenix, AZ, explored the following topics:

StressCheck’s FEA technology implementation enabling modeling of very thin domains, including adhesive layers with 3D-solid elements.
Best practices and guidelines for modeling and analyzing 3D bonded repair doubler variations (e.g. racetrack/rectangular, circular/elliptical, tapered, metallic, ply-by-ply, homogenized, etc.) for circular cutouts and grindouts.
Performing “what if?” logic-driven studies of a digital 3D bonded repair handbook solution via StressCheck API-powered Engineering Simulation App, in which user-defined input data is passed from Python or Excel VBA to StressCheck Professional to perform scripted “on-the-fly” model adjustments and repair-oriented computations.

StressCheck Tutorial: Parametric Solid Modeling of a 3D Bracket

brent — Fri, 02 Sep 2022 13:42:42 +0000

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StressCheck Tutorial: Computing Part-Thru Crack SIF’s from Geometric Nonlinear Solutions

brent — Tue, 23 Aug 2022 14:12:00 +0000

Abstract: comparison between linear and geometric nonlinear stress intensity factor (SIF) extractions for a fitting section with a part-thru corner crack at a bearing-loaded hole. Note: solving a geometric nonlinear analysis results in normal springs being released in tension (compression-only).

StressCheck Tutorial: Filled vs Open Hole SIF Comparison for 3D Offset Hole

brent — Tue, 16 Nov 2021 16:38:35 +0000

Abstract: comparison of 3D part-thru crack stress intensity factor (SIF) distributions for filled (pin-propped) vs open (bearing-loaded) offset holes. Simultaneous solution and extractions based on Parts and Solution Configurations.

StressCheck Tutorial: Using Cutting Planes for Model Viewing and Live Results Processing

brent — Thu, 21 Oct 2021 15:05:14 +0000

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Helpful Hints and Tips: Advanced StressCheck Automation – Model Setup & Analysis (Python)

brent — Mon, 30 Aug 2021 19:03:02 +0000

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