Convergence Extraction 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.

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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What’s New and Improved in StressCheck Professional Webinar Slides (2023)

brent — Wed, 15 Feb 2023 15:54:08 +0000

This 2-hour webinar provided demonstrations of the "latest and greatest" enhancements in StressCheck v11.1, and a look toward future development activities happening in the next StressCheck release in Summer 2023. Some highlights of the webinar included:

Overview of recent features and enhancements already implemented in StressCheck Professional
Demonstration of key features and enhancements available in StressCheck v11.1
Overview of current development activities and future plans for StressCheck Professional
Demonstration of key features and enhancements expected with the next release of StressCheck
Open discussion and Q&A

To view the webinar recording, click here.

StressCheck Demo: Thermo-Mechanical Analysis with Temperature-Dependent Material Properties

brent — Wed, 18 Jan 2023 19:10:09 +0000

Abstract: A thermo-mechanical (Heat Transfer -> Elasticity) analysis is performed for a Handbook model of two Inconel 718 connected pipes connected by a thin fin (\Handbook\Tutorial\ConnectedPipes.scw). The parametric Handbook model contains formula-based, temperature-dependent coefficients of thermal conductivity (when the theory is Heat Transfer) as well as formula-based, temperature-dependent linear isotropic material properties (when the theory is Elasticity). The goals of the thermo-mechanical analysis are to:

Compute the linear (coefficient of thermal conductivity for a reference temperature T=200 °F) and material nonlinear (coefficient of thermal conductivity is allowed to be temperature-dependent) temperature distributions via steady-state conduction heat transfer
Apply the temperature distribution computed from the material nonlinear solution as a thermal load for all elements using a reference temperature of 0 °F
Solve a linear elastic solution using the thermal load, symmetry/rigid body constraints, and temperature-dependent linear isotropic properties
Extract the local stresses at the intersection of the fin and the pipes.

For the steady-state conduction heat transfer analysis, the following boundary conditions are assigned:

Cooling of the external pipe surfaces is by convection via parameters "Hc" (convective film coefficient) and "Tc"(convective temperature).
The left pipe inside temperature is given by parameter "To", and the right pipe inside temperature is given by parameter "Tp".

For the linear elastic analysis, the following boundary conditions are assigned:

Thermal loading of the connecting pipes + fin is defined by importing the temperatures from the material nonlinear steady state conduction heat transfer solution.
Double-symmetry conditions are used to model 1/4 of the connecting pipes + fin.
A nodal constraint in the global X direction restricts rigid body translation.

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 TLAP Scaling for Nonlinear Events

brent — Tue, 18 Oct 2022 15:46:42 +0000

Abstract: demonstration of limit load analysis through parameter-based TLAP load scaling and incremental theory of plasticity (ITP). The parametric TLAP scaling option for ITP Nonlinear Events is available as of StressCheck v11.1. For more details, refer to Total Load at a Point (TLAP) Implementation and Nonlinear Events Overview.

StressCheck Tutorial: Mixed (Hexa/Penta) Boundary Layer Automesh Refinement

brent — Thu, 06 Oct 2022 13:52:58 +0000

Abstract: demonstration of the enhanced Boundary Layer automesh method for generation of mixed (tetra/penta/hexa) element layers around holes, blends, fillets and other regions of interest, with or without the "shrink-to-fit" option. The mixed Boundary Layer automesh method is available as of StressCheck v11.1. For more details, refer to MeshSim Automesh Generation Methods.