Explain ANSYS nCode

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FATIGUE EVALUATIONUSING ANSYS NCODE

DESIGNLIFE


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Short overview of fatigue

Introduction to nCode Design Life products

nCode Design Life basic procedure

Main Glyph items

Duty Cycle procedure example

New features for nCode 6.0

OBJECTIVES


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To make it simple, fatigue is a special structural failurestructural failure, dueto crack growth caused by repeated loading cyclesrepeated loading cycles.

Usually loads that result in fatigue failure cause stress levels

that are below the yield stress limit of the material. In other words, a specific load magnitude may not cause failure in anot cause failure in asingle applicationsingle application, but it may result in fatigue failure after severalfatigue failure after several

cyclescycles.

FATIGUE ANALYSIS


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Why perform a fatigue analysis?Why perform a fatigue analysis? Cant the resistance tofatigue be estimated from a stress analysis?

Sometimes it can!Sometimes it can!

Other design factors may contribute to fatigue life. Parts subjected to very simple loading conditions.

But, if the component is subjected to complex loads thatcomplex loads that

vary with timevary with time, a simple stress study can lead to incorrect

results. In this case, a fatigue analysis is recommended.

FATIGUE ANALYSIS


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nCode Design Life is an advanced tool for fatigue evaluation,developed by HBM.

Fully integrated with ANSYS WorkBench 11.0 SP1.

New version (for ANSYS 12.1) to be released this month.

INTRODUCTION TO NCODE DESIGN LIFE PRODUCTS


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Different modules are available, with specific capabilities.

INTRODUCTION TO NCODE DESIGN LIFE PRODUCTS

Package/Module Description

ANSYS nCode DesignLife Standard Base package including Stress-Life, Strain-

Life and Dang Van analyzers

ANSYS nCode DesignLife Modules/add-ons

ANSYS nCode DesignLife

Vibration

Adds ability to do vibration fatigue

analysis. Simulate swept sine and PSD

loadings


Accelerated Testing

Signal processing package complementary

to vibration option. Design accelerated virtual

and physical vibration tests.


Welds

Fatigue life prediction forseam welds and

spot welds.


Parallelization

DesignLife is multi-threaded and licensed

per core with one core included in the base

package.


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What does nCode Design Life and ANSYS Fatigue tools havein common?

They are both postpost--processorsprocessors, reading results from ANSYS.

Some basic featuresbasic features are available in both modules.

nCode Design Life provides some additional advanced

features, unavailable in ANSYS Fatigue Tools:

Several signal treatment toolssignal treatment tools, for load time histories;

More material modelsmaterial models (like Dang Van multiaxial method);

More complex fatigue calculationscomplex fatigue calculations (like vibration analysis and

accumulated damage evaluation); Easier to capture fatigue design intentdesign intent (with workflow templates

and reference files);

More detailed postpost--processingprocessing (like hot-spot identification).

NCODE DESIGN LIFE x ANSYS FATIGUE TOOLS


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nCode Design Life reads the stress results from the ANSYSsimulation.

Loading histories can be defined directly in Design Life.

NCODE DESIGN LIFE BASIC PROCEDURE


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nCode Design Life main screen


Desktop

Reference Files

(*.RST, loading curves...)

Glyph Library


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A GlyphGlyph is a tool that represents a specific stage or operationfrom the fatigue calculation.

For example, there are glyphs for geometry import, material definition,

postprocessing

Each glyph has input and output connections.

Right-clicking a glyph provides advanced properties

configuration. In Design Life, the user can define a fatigue calculation

procedure by assembling some glyphs, creating a workflowcreating a workflow.



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Some Glyph libraries available in nCode Design Life.



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Considering a typical SN fatigue calculation, the followingglyphs are used:

FE Input : FEA results import and load case combination

SN Analysis : material definitions, loading conditions and fatigue solution

advanced properties

Hot Spot Detection : identification of critical points for damage plots

FE Display : result plots

Data Values Display : result tables



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Glyphs are connected, sharing and transferring information. This fatigue map can be savedcan be saved as a Design Life workflow.



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Direct recognitionDirect recognition of ANSYS results files (*.RST); Several cases can be combined in one single results file.

Results from the FEA model can be visualized in the Design

Life interface;

FINITE ELEMENT INPUT


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nCode DesignLife automatically recognizes groupsautomatically recognizes groups, basedon FEA file information.

Parts, materials, element types

User defined groupsUser defined groups can be created, with on-screen

selection of nodes or elements.

FINITE ELEMENT INPUT


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nCode DesignLife allows the definition of several fatiguematerial models, including:

SN curvesSN curves (standard, mean multi-curves, R-ratio multi-curves, Haigh

multi-curves, Bastenaire and temperature multi-curves);

N curvesN curves (standard, mean multi-curves, R-ratio multi-curves andtemperature multi-curves);

Dang VanDang Van multiaxial safety factor;

Spot WeldSpot Weld analysis;

Seam WeldSeam Weld analysis;

MATERIAL MODELS

nCode Design Life comes

with a demo materialdatabase, with 100+

example materials, with

different curves!


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Fatigue curves can be derived from mechanical propertiesderived from mechanical properties. For example, curve based on ultimate tensile stress of the material.

The curves can also be manually specifiedmanually specified.

For example, a list of stress-cycle pairs to define a SN curve.

MATERIAL MODELS


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Time Series Time history is obtained from transient analysis.

Constant Amplitude

Creates a 2 point stress history, by scaling and linear superposition.

Time Step

Combination of static loadcases to generate stress/strain history.

Vibration

Determines the rain flow to be used for further analysis.

Duty Cycle

Evaluates the combined effect of repeating loading events, with

accumulated damage calculation.

These loading conditions can be derived from FEA results,

from static, transient, modal and harmonic analysis.

LOADING CONDITIONS


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The fatigue solver provides some advanced setup optionsadvanced setup options,such as:

Result to be readResult to be read from FEA (stress, strain, displacement );

Method for combinationMethod for combination of stress/strain components (Absolute Max

Principal, Signed von Mises, Signed Shear, Critical Plane);

Mean stress correctionMean stress correction (Goodman, Gerber, Morrow, SWT);

Elastic plastic correctionElastic plastic correction (Hoffmann-Seeger, Neuber);

Duty cycle event processingevent processing (independent, combined);

Calculations on surface nodes onlysurface nodes only;

GroupsGroups to be processed;

Unit systemUnit system of the imported file;

Check forstatic failurestatic failure;

ADVANCED OPTIONS


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The fatigue solver provides results like damage, life, biaxialityratio and dominant stress direction.

Results are available in contour plotscontour plots and data tablesdata tables.

The hotspot glyph identifies the most critical regionsmost critical regions.

POST-PROCESSING FEATURES


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Study of a steel lever, subjected to 4 loading classes. Each class is defined by two loads, shown on the next slide.

SN Fatigue study is performed, with accumulated damage

evaluation (via duty cycle). Frictionless supports are defined on the holes and hub base.

DUTY CYCLE EXAMPLE


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DUTY CYCLE EXAMPLE

! "#

#!$ # % "

$ % ! % "$

% # "

A

B

Tension Force, applied on the hole,

in the X-direction

Remote Force, aligned with holes

axis, at Z = 30mm, in the Y-direction


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Two simulations are performed (max. and min. angles). Each simulation includes 4 loadsteps (one for each class).

DUTY CYCLE EXAMPLE

2 RST files are created.They are renamed for

easier reference, as

MAX.RST and MIN.RST


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Design Life is available on the WorkBench launcher. A working directory is selected, where the RST files are.

DUTY CYCLE EXAMPLE


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Workflow for the fatigue duty cycle calculation.

DUTY CYCLE EXAMPLE

Reads FEA results

Combine files

Material Properties

Loading Definition

Advanced Run Options

Critical Regions

Contour Plots

Data Tables


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RST files are dragged to the FE Input glyph. Since a duty cycle analysis will be performed, those files are

combined in a single one.

Mesh and FEA results can be visualized in this glyph as well.

DUTY CYCLE EXAMPLE


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A demo material will be used, with fatigue behavior derivedfrom mechanical properties (UTS = 400 MPa).

DUTY CYCLE EXAMPLE


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Loading history must be defined as a duty cycle. Each class is a duty cycle event (time step load provider).

Number of cycles (repeats) is defined for each event.

DUTY CYCLE EXAMPLE


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In each event, results can be selected from the global file,defining the loading conditions of this event.

DUTY CYCLE EXAMPLE

Class #1 is defined by the results from

loadstep 1, from both simulations

(MAX.RST and MIN.RST).

! "#


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It is important to check if the run options are properly defined,in the Advanced Edit window.

DUTY CYCLE EXAMPLE


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The solution is ready to run. Diagnostic messages can beobtained during the calculation for debug purposes.

DUTY CYCLE EXAMPLE


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In the results post-processing, damage values can be studied. The hotspot feature identifies the 10 most critical nodes, showing

their location over the geometry.

DUTY CYCLE EXAMPLE


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Fully-integrated with ANSYS 12.1, available in May 2010 Main new features:

Virtual Strain Gage

Glyph for fatigue crack propagation

Better integration with optimization tools like DesignXplorer and

modeFrontier

Named Selections recognition from WorkBench

NEW FEATURES FOR NCODE 6.0


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FOR MORE INFORMATION ABOUT

NCODE DESIGN LIFE,CONTACT OUR TEAM

THANK YOU

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