ASGRO® Fracture Mechanics and Fatigue Crack Growth Analysis Software

NASA JSC Team Royce Forman

Dr. V. Shivakumar Dr. Sambi Mettu Joachim Beek

Leonard Williams Feng Yeh

Southwest Research Institute Team Dr. Craig McClung

Joe Cardinal

Source of Acquisition NASA Johnson Space Center

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gl NASA Fracture Control " i Requirements

• NASA Technical Standard NASA-STO-5007 • Establishes requirements for fracture control of all

NASA manned spaceflight systems and payloads on manned spaceflight systems

• Mandatory for m"anned systems; optional for unmanned systems

• Fracture control process includes non-destructive evaluation as well as analyses of fracture-critical parts

• Fracture mechanics & fatigue crack analysis software package NASGRO meets the analysis requirements

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II NASGRO® Reduces Risk c ii!

• Fracture mechanics & fatigue crack analysis software • Provides optimal design of fracture-resistant structures

¢ Determines safe stresses for a specified lifetime

• Provides specification of fracture control plans at the design stage ¢ Determines safe lifetime for a specified design

¢ Determines required inspection intervals (if any) to maintain safety

• If damage is discovered ... ¢ Determines safe remaining life (if any)

¢ Determines required inspection intervals (if any) to maintain safety

• Accurately simulates crack growth and failure in real structures ¢ Calculate fatigue crack growth rate and remaining life

¢ Calculate conditions (loads, crack sizes) that cause failure

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" NASGRO® Components:

Crack growth module ~ z

• Calculate fatigue crack growth or component life, critical crack sizes, or stress intensity factors for a library of 50+ different crack configurations

• Multiple crack growth equations

• Elastic-plastic crack growth analysis

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" en NASGRO® Components:

• z Material property module

• Store, retrieve, and curve-fit fatigue crack growth and fracture data

• NASA database: • 476 different metallic materials • 3000 sets of fatigue crack growth data • 6000 fracture toughness data points • Statistically-derived crack growth equations for all materials

• Users can create their own database ~..,JtI!l!l 1\ilrtl!!!l1 _Iolx l

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II Typical NASGRO® analysis: en ,.=1 Crack growth or component life calculation

• Problem: • Actual crack or flaw is reported in component

• Hypothetical flaw: assume worst-case scenario based on applied loading, component geometry, and crack location

• Analysis input: • Crack and component geometry

• Component material

• Load type and spectrum

• Analysis results: • Fatigue crack growth rate and remaining life

• Conditions (loads, crack sizes) that cause failure

• Safe stresses to attain a specified lifetime

• Component inspection intervals for safe operation

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I NASGRO Sample Application: I " Orbiter feedline flowliner crack analysis 2:

• Objective: To determine the service life of the Shuttle Orbiter flowliners containing cracks by using a fracture-based assessment to account for crack propagation

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• Problem: Flowliner crack geometry not easily represented by any of 50+ standard cracks in NASGRO crack library 3.5"

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NASGRO Sample Application: Orbiter feedline flowliner crack analysis

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• CAD-like drawing tools to custom­build crack model

• Computational core to calculate crack driving force K

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I NASGRO Sample Application: I II Orbiter feed line flowliner crack analysis

• NASBEM results used in concert with other tools (e.g. NASTRAN structural analysis code) to determine:

• crack growth between flowliner holes as function of flight service history

• flowliner service life

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Summary and Challenges for the Future

• NASGRO® reduces the risk of fracture

• NASGRO is used extensively around the world • Standard code for analysis of space hardware for NASA and its

international partners

• Supported and used by 000, FAA, and private industry in aircraft, rotorcraft, turbine engines, and many others

• Spaceflight systems for future space missions will use innovative materials and methods of construction • New materials will require testing and characterisation for their

properties for use in fracture analyses

• New systems, components, configurations, and manufacturing techniques will need to be certified for flight

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