LifeTime Manual


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Table of Contents

LifeTime Users Manual Rev. 1 v Flexcom Version 7.7

Table of Contents

CHAPTER 1 - INTRODUCTION ................................................... 1Overview..............................................................................1

Operation Mode 1 ................................................................ 2Fatigue Analysis Methods......................................................... 3Operation Mode 2 ................................................................ 4

Manual Organisation ..............................................................5CHAPTER 2 - OPERATION.......................................................... 7

Introduction..........................................................................7LifeTime Inputs .....................................................................8Top Menu Bar......................................................................10

File......................................................................................10Run .....................................................................................10Modules ...............................................................................10View....................................................................................11Help ....................................................................................12

LifeTime - Reference ............................................................13Title - Specify .......................................................................14Seastate File- Specify.............................................................15Mode ...................................................................................16SN Curve Linear - Data........................................................17SN Curve Piecewise Linear ...................................................19


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Table of Contents

LifeTime Users Manual Rev. 1 vi Flexcom Version 7.7

SN Curve Data Pairs ........................................................... 21Stress Spectra Define ......................................................... 22Hot Spots Define................................................................ 24Hot Spots Histogram Data................................................... 25Hot Spots Fatigue Data ....................................................... 27Channels Define................................................................. 29Histogram Output Specify.................................................... 30Bins - Define........................................................................ 31Define Stress Properties ........................................................ 33File Type ............................................................................. 36

Stress Histograms ............................................................... 37CHAPTER 3 - MODE 1 EXAMPLE APPLICATION.........................41

Riser and Environment......................................................... 41LifeTime Analyses ............................................................... 42Base Case Analysis.............................................................. 43Sensitivity Analysis #1 Effect of PDF ................................... 46Sensitivity Analysis #2 Effect of Endurance

Limit ................................................................................. 46Sensitivity Analysis #3 Effect of Thickness

Effects............................................................................... 47

Example Files ..................................................................... 47CHAPTER 4 - MODE 2 EXAMPLE APPLICATION.........................49

Riser and Environment......................................................... 49


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Table of Contents

LifeTime Users Manual Rev. 1 vii Flexcom Version 7.7

LifeTime Mode 2 Analysis......................................................49Example Files......................................................................52


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Chapter 1 - Introduction

LifeTime Users Manual Rev. 1 1 Flexcom Version 7.7

CHAPTER 1 -INTRODUCTIONWelcome to the Users Manual for LifeTime, the Flexcom fatigue postprocessor and general

cycle counting tool. This Introduction provides an overview ofLifeTime, and describes the

content of the Users Manual. This is done in two sections, as follows:

Overview provides an overview of the operation ofLifeTime and explains how you

run Mode 1 and Mode 2 analyses.

Manual Organisation summarises the contents of the remainder of this manual.

OVERVIEW

LifeTime can operate in two ways - in the terminology used in the rest of this manual, we

sayLifeTime has two Modes of Operation, which are identified as Mode 1 and Mode 2.

Mode 1 is the more usual method of running the program, and is used to compute fatigue life

estimates from the results ofFlexcom random sea dynamic analyses. The different methods

used by the program to accomplish this task are detailed later in this section.

In the second mode of operation, LifeTime can be used as a general cycle counting tool.

The input in this case is a random response time history or histories, typicallyFlexcomrandom sea analysis timetrace output. However you can use LifeTime to cycle count any

time history data organised in a format which mimics the Flexcom timetrace output

format. The LifeTime Mode 2 output is simply response histograms.


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Operation Mode 1

The steps in performing a fatigue (Mode 1) analysis with LifeTime are as follows:

Step 1:

Perform a Flexcom random sea analysis for each fatigue seastate.

In setting up each analysis, you request timetrace output of axial force, Y bending

moment and Z bending moment at each location (hot spot) of interest. You can also

optionally request any other timetrace output of interest. It is not necessary for the

Flexcom analyses to generate database output, although they can do so.

Step 2:

Specify the fatigue analysis input data via the LifeTime GUI.

The various GUI menus and the format of the data required in each are described in

detail in the next chapter of the manual, but the actual data to be specified is

summarised here to illustrate the program operation.

Fatigue seastate data:

Here you list the names of the Flexcom random sea analyses, and tabulate the

% occurrences of the corresponding seastates.

Fatigue data:

Here you specify data such as the stress concentration factor and S-N curve to

be used in the fatigue analysis. You also specify (i) the probability density

function (pdf) to use in the fatigue calculations, whether Rayleigh or Dirliks; (ii)

whether to use bending stresses only or combined bending and axial stresses;and (iii) whether to include thickness effects in the calculations and what

threshold thickness to employ. Finally, this input category also includes a list

of the actual fatigue hot spots of interest. Full details are provided in Chapter 2.


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Step 3

Run LifeTime.

When running, the program loops over all seastates and all of the hot spots for which

forces were output in the Flexcom analyses, and calculates fatigue damage using themethods to be described shortly.

LifeTime creates three output files each time you run a Mode 1 analysis. The main analysis

results are output to a file named jobname.lif, where jobname is the name of your

LifeTime analysis. LifeTime also creates a debug output file named jobname.dbg, to

which are routed results of the program intermediate calculations for each individual seastate

(that is, each Flexcom analysis), for checking and interpreting the analysis results. A succinct

summary output file is also created tabulating only the minimum fatigue life at each hot spotfrom each of the three LifeTime methods. This data is in a format suitable for importing

into, say, Excel for subsequent plotting, and so the file is named jobname.plt.

Fatigue Analysis Methods

Three methods are used when you run a LifeTime Mode 1 analysis to calculate fatigue

damage and fatigue life. These are:

Calculating the standard deviation () and mean zero up-crossing period (Tz) of

combined axial and bending stress directly from Flexcom time histories, and then

calculating fatigue damage from these based on an assumption that stress peaks are

distributed according to the Rayleigh probability density function (pdf).

Calculating the spectrum of combined stress from the Flexcom time histories, and

then evaluating the moments of this spectrum. These are then used to compute

fatigue based on an assumption that stress peaks are distributed according to either

the Rayleigh or Dirliks probability pdf.

Calculating damage directly from the Flexcom stress histories using the rainflow

cycle counting technique.


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Because combined stress varies throughout the cross-section, LifeTime actually

applies the above three methods at 8 points, at 45 intervals, around the hot spot

outer surface. So for each hot spot you nominate, a fatigue life estimate is actually

calculated for 8 points around the circumference.

Operation Mode 2

The steps in performing a general cycle counting (Mode 2) analysis with LifeTime are as

follows:

Step 1:

Perform a Flexcom random sea analysis for each fatigue seastate.

In setting up each analysis, you again request timetrace output of the variable(s) of

interest. Obviously for meaningful cycle counting the same variables should be

nominated in all of the Flexcom runs.

Step 2:

Specify the fatigue analysis input data via the LifeTime GUI.

The various GUI menus and format of the data required in each is described in detail

in the next chapter of the manual, but again the actual required data is summarised

here to illustrate the program operation.

Fatigue seastate data:

As for Mode 1, you list the names of the Flexcom random sea analyses and

tabulate the % occurrences of the corresponding seastates.

General data:

Here you specify the variables (or channels) of the Flexcom timetrace output

which you want cycle counted. You also specify the bins or divisions for the

histogram output.


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Step 3:

Run LifeTime as previously.

The main analysis results, histograms in this case, are now output to a file named

jobname.bin. Again, LifeTime also creates a debug output file namedjobname.dbg to which are routed results of the program intermediate calculations

for each individual seastate (Flexcom analysis), for checking and interpreting the

analysis results.

MANUAL ORGANISATION

The following is a list of the chapters which make up this manual, together with a brief

description of the contents of each.

Chapter 1 (this chapter), Introduction, provides a brief introduction to LifeTime

and describes the program modes of operation and the Users Manual contents.

Chapter 2, Operation, describes briefly how to perform a LifeTime analysis. A

Reference section describes the required data inputs in full.

Chapter 3, Mode 1 Example Application, describes in detail an example drilling riser

fatigue analysis with LifeTime.

Chapter 4, Mode 2 Example Application, describes in detail an example cycle

counting (Mode 2) LifeTime analysis.


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Chapter 2 - Operation


CHAPTER 2 -OPERATIONOperation is a detailed guide to the operation of LifeTime. It comprises the following

sections:

Introduction gives an overview of the program operation.

LifeTime Inputs gives a brief overview of the program inputs.

Top Menu Bar describes the options in the LifeTime top menu bar.

Reference describes in detail the data inputs to LifeTime on a menu-by-menu basis.

Stress Histograms discusses LifeTime stress histogram output, and provides insightsinto the significance and use of some of the other input parameters relating to this

type of output.

INTRODUCTION

You run LifeTime by clicking on the LifeTimebutton on the FlexcomModules Sidebar. When

you click on the LifeTimebutton the Working Areachanges to that for LifeTime, as shown

below.


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In addition to the above, there are a number of options on the top menu bar associated with

performing a LifeTime analysis. These top menu bar options are described later. The next

section summarises the LifeTime inputs in the above screen.

LIFETIME INPUTS

As you can see from the picture above, data input to LifeTime is divided into eleven

sections; Title, Seastate File, Mode, Stress Dataand SN Curve, Stress Spectra, Hot Spots, Channels,Histogram Output, Bins, Properties and File Type. The options in each are now briefly

summarised.

Title allows you to specify an optional title for your LifeTime analysis. The Seastate File

section is used to specify the names of the Flexcom analyses that generated the stress data


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for the LifeTime analysis, together with the relative annual occurrences of the

corresponding fatigue seastates. In Chapter 1 this is termed the analysis fatigue seastate data.

The two LifeTime modes of operation were discussed in Chapter 1. TheModesection allows

you to nominate the mode for a particular run. Certain subsequent input sections are specificto one or other mode.

Stress Data is specific to Mode 1 analyses. It allows you to specify the stress concentration

factor (SCF) to be used in your fatigue calculations; whether the analysis is to be based on

combined stress or bending stresses only; and whether or not thickness effects are to be

considered. Further details are in the Reference section to follow.

The Stress Spectrasection is also specific to Mode 1 analyses. You use it to specify a number of

additional parameters relating to stresses, in particular the calculation of stress spectra.

The final section specific to Mode 1 is Hot Spots. Here you identify the locations of interest

(hot spots) in your model for which fatigue life predictions will be calculated. You can also

specify whether or not you want LifeTime to generate a histogram of stress for each hot

spot and if so, at what point on the cross-section circumference.

Channels, which is the first section exclusive to Mode 2, allows you to nominate channels for

cycle counting. Channel in this context refers to an individual variable in a Flexcom

timetrace output file this is the same terminology as used in the Flexcom Reference

Manual in relation to the operation of the TimetracePostprocessor. Histogram Output, also Mode 2

specific, is used to specify the number of channels in the Flexcom timetrace files, a start time

to exclude transient effects from the calculation, and a scale factor used to transform data in

Flexcom units to appropriate units for the histogram output

Bins is used to define bins or divisions for stress histogram output. It is common to both

modes of operation. It is optional if you dont invoke this option LifeTime chooses

suitable divisions.

Propertiesallows you to enter alternative stress properties for sections within your model in

the same manner as you might in the FlexcomMain Analysismodule using the Properties

Stressoption.


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The final section, File Type, is specific to Mode 2 analyses. It allows you to specify the format

of the Flexcom timetrace output files. This may beASCII, Importor Binary.

TOP MENU BAR

There are five options in the LifeTime top menu bar, namelyFile, Run, Modules, Viewand

Help. This is identical to most other Flexcom modules.

File

The menu you get when you invoke the Fileoption is shown below. The first four Filemenu

items are for manipulating files in the standard ways.Exitcloses down Flexcom.

Run

The Analysismenu is used to launch a LifeTime analysis once all the input data has been

specified.

Clicking on LifeTime starts the fatigue analysis run. The fourth icon on the toolbar

performs the same task.

Modules

The Modules menu, shown below, allows you to switch between the various Flexcom

modules. It is functionally identical to theModulesSidebar.


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View

The Viewmenu bar option allows you to examine various files associated with a LifeTime

fatigue analysis run by opening them in the Viewerapplication. Viewer is discussed in more

detail in Chapter 4 of the Flexcom Reference Manual.

Table 2.1 below tabulates the various files produced in a LifeTime analysis.


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Table 2.1. LifeTime GUI and Fatigue Analysis Files.

File Name Description

j o b n am e . l f t

j o b n am e .s e a

j o b n am e . l f k

j o b n am e . v e r

j o b n am e . l i f

j o b n am e .d b g

j o b n am e .p l t

j o b n am e .b i n

GUI data file.

Analysis input file (1) Fatigue seastate data.

Analysis input file (2) Remaining data.

Verification file.

Main output file Mode 1.

Debug output file Modes 1 & 2.

Summary output file Mode 1.

Main output file Mode 2.

Of these eight files, seven can be examined via the Viewer, the only exception being the GUI

data file itself.

Help

The final top menu bar option, Help, is used to display on-line help (Help Topics) or

information about the LifeTime/Flexcom version number and licence details (About

Flexcom).


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LifeTime - Reference


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Title - Specify

Mode: Modes 1 and 2

Purpose: To specify a title for your LifeTime analysis.

Window:

Data Inputs:

Input: Description

Title: A title for the LifeTime run. This entry is optional.


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Seastate File- Specify

Mode: Modes 1 and 2

Purpose: To list the names of the Flexcom random sea analyses on which

LifeTime fatigue calculations or cycle counting is to be based, and to

tabulate the % occurrences of the corresponding seastates.

Window:

Data Inputs:

Input: Description

File Name: The generic name of the Flexcom analysis for a particular fatigue seastate.A file extension is not required.

Percentage

Occurrence:

The percentage occurrence or the actual number of occurrences of this

seastate per annum.


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Mode

Mode: Modes 1 and 2

Purpose: To specify the mode or type of analysis you want LifeTime to perform.

Window:

Data Inputs: None

Notes:

(a) The two LifeTime modes of operation are described in Chapter 1 of this Users

Manual. Mode 1 is the more usual method of running the program, and is used to

compute fatigue life estimates from the results of Flexcom random sea dynamic

analyses. In Mode 2, LifeTime can be used as a general cycle counting tool.


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SN Curve Linear - Data

Mode: Mode 1 only

Purpose: To specify a linear S-N curve.

Window:

Data Inputs:

Input: Description

Curve Name: A unique name for the S-N curve. A valid curve name can consist of up to

256 alphanumeric characters with blank spaces permitted. Curve names are

not case sensitive.

m: The first parameter defining the S-N curve. See Note (a) below.

K: The second parameter defining the S-N curve. See Note (a) below.

Endurance

Limit:

A stress range value below which no fatigue damage occurs, regardless of

the number of cycles. See Note (b) below.

Notes

(a) S-N curves are generally defined in the form KNSm= where Sdenotes stress range,N

the number of cycles to failure at this range, and m and K are constants. Taking

logarithms of both sides and rearranging gives:


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Km

Nm

S log1

log1

log +=

which is the equation of a straight line when logSis plotted against logN. In this case

mis the inverse slope and Kis a function of the line intercept. These are the parameters

input above.

(b) The specification of an Endurance Limitis optional, and if omitted defaults to 0, that is,

no endurance limit.

(c) Use as many lines as you need to completely define a particular SN curve. Simply leave

Column 1 blank for second and subsequent lines. For subsequent SN curves, put the

curve name in Column 1 and specify the force-deflection data in the same way


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SN Curve Piecewise Linear

Mode: Mode 1 only

Purpose: To specify a piecewise linear S-N curve.

Window:

Data Inputs:

Input: Description



not case sensitive.

m: The first parameter defining the S-N curve. See Note (a) below.

K: The second parameter defining the S-N curve. See Note (a) below.

N1: The number of cycles value defining the lower end of the line segment

where these m and K values apply.

N2: The number of cycles value defining the upper end of the line segment

where these m and K values apply.

Notes

(a) A piecewise-linear S-N curve is one which plots as a series of straight line segments

when logS is plotted against logN. In this case mand Kvary between line segments;


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theN1 andN2values above specify the segment of the S-N curve X (number of cycles

to failure) axis where each mand Kcombination apply.

(b) Use as many lines as you need to completely define a particular S-N curve. Simply leave

Column 1 blank for second and subsequent lines. For subsequent curves, put the curve

name in Column 1 and specify the S-N data in the same way.


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SN Curve Data Pairs

Mode: Mode 1 only

Purpose: To specify a S-N curve directly.

Window:

Data Inputs:

Input: Description



not case sensitive.

S: A stress range value.

N: The number of cycles to cause failure at this stress range

Notes:

(a) Use as many lines as you need to completely define a particular S-N curve. Simply leave

Column 1 blank for second and subsequent lines. For subsequent curves, put the curve

name in Column 1 and specify the S-N data in the same way.


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Stress Spectra Define

Mode: Mode 1 only

Purpose: To specify a number of additional parameters relating to stresses in

LifeTime, some (though not all) of which relate to the calculation of

stress spectra.

Window:

Data Inputs:

Input: Description

Scale Factor

for Stress:

This is used to transform stresses in the Flexcom units to units consistent

with the S-N curve data. For Imperial units, a value of6.9444E-06 wouldbe typical to transform lb/ft2 to ksi. For SI units, a value of 1.E-06 would

be typical to transform N/m2 to MPa. In some cases LifeTime is in a

position to decide the appropriate value to use, in which case the default

value of1 is appropriate. See Note (a) below.

Start Time: This input is used to exclude initial transients from the fatigue calculations.

Any data from solution times prior to this start time is ignored in the

LifeTime calculations.

Number of

Ensembles:

The number of ensembles to be used in calculating stress spectra. This

number must be greater than 1, and in fact defaults to 4. The significance

of this input here is the same as in the Flexcom Database Postprocessorand


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Timetrace Postprocessor.

Probability

Density

Function:

A drop-down list which allows you to choose the probability density

function (pdf) to be used in calculating fatigue life estimates from stress

spectra.

Selecting Rayleigh (the default) selects the standard Rayleigh pdf, while

selectingDirlik selects the rainflow range proposed by Dirlik. This latter

option is more appropriate when the stress spectra are broad banded (the

Rayleigh pdf is narrow banded).

Stress

Histogram

Range Index:

An index for calculating equivalent ranges in stress histograms. The entry

is optional, and if omitted, defaults to 1, in which case the equivalent range

for each histogram bin is a simple average of the values of the stresses

enclosing or defining that bin. The section Stress Histograms following

this Reference section discusses stress histograms in more detail, and

provides insights into the significance and use of some of the input

parameters relating to this type ofLifeTime output.

Notes

(a) Flexcom outputs the value you specify for g, the gravitational constant, to every

analysis database. If any of the Flexcom analyses you list in your Seastate File Specify

data generated a database file, then LifeTime retrieves this value and uses it to

determine if you used Imperial or SI units in your data. Specifically, if 109 g ,

then LifeTime decides you employed SI units; if 3332 g , then LifeTime

decides you used Imperial units. In either case, LifeTime automatically determines the

scale factor required to transform stresses to MPa or ksi as appropriate, so you do not

need to specify a Scale Factor for Stress - just let LifeTime determine the appropriate

scale. But if none of your Flexcom analyses generated a database, you should change

from the default value of 1, unless this value is consistent with your S-N curve

specification.


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Hot Spots Define

Mode: Mode 1 only

Purpose: To specify the analysis hot spot sets; locations for which fatigue life

estimates are required.

Window:

Data Inputs:

Input: Description

Set Name: A unique name for the hot spot set. A valid set name can consist of up to

256 alphanumeric characters with blank spaces permitted. Hot spot setnames are not case sensitive.

Elements: The elements in this hot spot set.

Local Node: This drop-down menu offers a choice between three locations on the

specified elements. First node refers to the first specified node of an

element,Midpointis self-explanatory, while Last nodeis the second specified

node of an element.


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Hot Spots Histogram Data

Mode: Mode 1 only

Purpose: To specify histogram options for hot spots.

Window:

Data Inputs:

Input: Description

Set Name: The hot spot set for which you are defining histogram properties.

Stress

Histogram:

This entry is a drop down menu for specifying whether or not you want

LifeTime to generate a histogram of stress for each hot spot within this

hot spot set.

If you choose No Stress Histogram (which is the default), no histogram is

produced for any of the hot spots in the hot spot set, unless it happens to

be the location of the minimum fatigue life predicted by the rainflow cycle

counting method.

Stress Point: This is an optional input to specify the point on the circumference (stress

point) for which a stress histogram is to be produced. This input is invalid

unless you selected Create Stress Histogramin the previous input. If no value


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is input here, a histogram is produced for the stress point at which the

predicted fatigue life is a minimum.

Input a value between 1 and 8 to nominate a stress point. This

corresponds to an angle measured in degrees anti-clockwise from the local

element cross-section y-axis where 1 = 0, 2 = 45, 3 = 90, etc.


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Hot Spots Fatigue Data

Mode: Mode 1 only

Purpose: To specify fatigue data for a hot spot set.

Window:

Data Inputs:

Input: Description

Set Name: The hot spot set to which the fatigue properties are to be assigned.

S-N Curve: The name of a defined S-N curve.

SCF: The stress concentration factor (SCF) to be used in fatigue calculations.

Stress Type: This entry is in fact a drop-down list which you use to nominate the type

of stress to be used in the LifeTime fatigue calculations.

You can choose between bending stresses only, axial stresses only or

combined bending and axial stresses, which is. the default.

Threshold

Thickness:

The threshold thickness for the inclusion of thickness effects. See Notes

(a) and (b) below.

Exponent: The exponent value nused in the calculation of the stress multiplication


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factor when threshold thickness effects are included. Defaults to 4. See

Notes (a) and (b) below.

Notes:

(a) The specification of a threshold thickness allows you to take account of the fact that the

fatigue strength of some structural members can be dependent on material thickness,

fatigue strength decreasing with increasing thickness. If you specify a threshold

thickness, the stresses calculated by LifeTime are further multiplied by a factor f

given by

n

bt

tf

1

=

Here bt is the threshold thickness you specify; and t is the greater of bt and the

actual thickness of the particular location under consideration (this ensures that f is

always greater than or equal to 1). Note that although a single value of bt is input, f is

naturally computed individually for each hot spot, since the structure thickness may

vary from location to location. The exponent value ncan also be specified and defaults

to 4.

(b) The specification of threshold thickness is optional. By default, thickness effects are

ignored unless you explicitly specify a threshold thickness.


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Channels Define

Mode: Mode 2 only

Purpose: To specify channels for cycle counting.

Window:

Data Inputs:

Input: Description

Channel

Number:

The number of the channel for cycle counting. This must be non-zero, and

must be less than or equal to the total number of channels. To count more

than one channel, input one channel number per line.


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Histogram Output Specify

Mode: Mode 2 only

Purpose: To specify parameters relating to Mode 2 output.

Window:

Data Inputs:

Input: Description

Number of

Channels:

The number of individual data values output byFlexcom to the timetrace

output files at each solution time. See Note (a) below.

Start Time: The time (in seconds) at which to start using data from the seastate files. It

is used to exclude initial transients from the fatigue calculations. Any data

from solution times prior to this start time is ignored in the fatigue

calculations.

Scale Factor: This value is used to transform data in the Flexcom units to appropriate

units for the histogram output. The value specified here is applied to all

output channels. This input is optional, and defaults to 1.

Notes

(a) This value must be the same for all of the files listed in the Seastate File Specifymenu.

Likewise, for meaningful cycle counting, the individual channels must be the same in

each of the files. Note however that there is no requirement that the simulation lengths

are the same in all of the analyses. Nor is it necessary that the individual solution time

be the same in all of the Flexcom analyses.


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Bins - Define

Mode: Modes 1 and 2

Purpose: To specify the bins or divisions for histogram output.

Window:

Data Inputs:

Input: Description

Divisions for

Stress

HistogramOutput:

This entry allows you to enter values to specify how values are grouped in

histogram output. This entry is optional for a Mode 1 analysis but required

for a Mode 2 analysis. In a Mode 1 analysis, this input refers to stresshistograms produced by LifeTime. The section Stress Histograms

following this Reference section discusses stress histograms in more

detail, and provides insights into the significance and use of some of the

other input parameters relating to this type ofLifeTime output.

Notes

(a) The following is an example of this Bins Definewindow.


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You can use as many values per line and as many lines as you need to unambiguously

define your histogram. A histogram is assumed to start at 0, so the first value you

specify is the upper stress of the first bin of the histogram.


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Define Stress Properties

Mode: Mode 1 only

Purpose: To assign effective geometric properties to element sets for use in

calculating stresses.

Window:

Data Inputs:

Input: Description

Set Name: The hot spot set to which these stress properties are to be assigned.

Do: The external diameter. This is the value used in calculating bending stress

from bending moment. This entry is optional in certain cases see Notes

(a) and (b) below.

Di: The internal diameter. This input is used only in calculating the thickness

of the pipe if thickness effects are included in the fatigue analysis. If

thickness effects are omitted, the internal diameter value is immaterial. If

thickness effects are included in an analysis, this entry is still optional in

certain cases see Notes (a) and (b) below.

A: The effective cross-sectional area for the pipe, to be used in calculating

axial stress from axial force. This entry is optional in certain cases see

Notes (a) and (b) below.


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Iyy: The second moment of area about the local y-axis for the elements of the

set. This entry is optional in certain cases see Notes (a) and (b) below.

Izz: The second moment of area about the local z-axis for the elements of the

set. This entry is optional in certain cases see Notes (a) and (b) below.

Notes

(a) It may seem curious that in general you need to specify diameter, cross-section area and

moment of inertia values for hot spots although these values have already been input to

Flexcom. The reason is because Flexcom does not echo this data to timetrace output

files, and by default onlyFlexcom timetrace output is required as input to LifeTime.

Flexcom does however output the external and internal diameter for each element to

database output files. So ifFlexcom database output is available, then LifeTime can

read the required structural data from that source, thus eliminating the need for a repeat

specification of this data.

LifeTime reads the name of each Flexcom analysis from the Seastate File Specify data

and opens the appropriate timetrace output files for that analysis. The program also

checks for the existence of a database output file from the analysis. If a database exists,

the program retrieves the external and internal diameter values for each hot spot from

that file, and then uses these values to calculate cross-section areas and moments of

inertia.

(b) There are a number of important points to note with regard to this facility:

Only one database needs to exist, and it can correspond to any analysis in your list.

LifeTime reads database output once only, regardless of how many database files exist.

Once it has retrieved the required structural properties from a database file, the

program does not check for the existence of database output from any subsequent

analysis in the seastate file.

The database file need not contain very much actual results output. The inputs required

byLifeTime are written by default to a header block at the start of the database file at


43/60



the time of the first output to the database. So in fact database output at only one time

is sufficient, and the actual amount of output can be minimised accordingly.

If database output exists but you specify structural properties for some or all hot spot

sets, the values you input in LifeTime take precedence over the values in the database.


44/60



File Type

Mode: Mode 2

Purpose: To specify the format of the Flexcom timetrace output files.

Window:

Data Inputs: None

Notes:

(a) The File Typemay beASCII, Importor Binary, defaulting toASCII.

(b) You should ensure that the timetrace output from each of the Flexcom analyses you

list in your Seastate File Specifydata is consistent with the File Typespecified here.


45/60



STRESS HISTOGRAMS

When you run a LifeTime Mode 1 (fatigue) analysis, the main output file jobname.lif

contains, by default, a histogram of stress at the hot spot with the lowest fatigue life, for thelocation on the cross-section (the stress point) at which this minimum occurs. You have

the option, when inputting data via the Hot Spots Definemenu, of requesting histograms at

other locations as well. A number of data inputs relate to the format of this output, and the

significance of these is now illustrated with reference to an actual LifeTime stress histogram.

The next page shows an example stress histogram from a LifeTime Mode 1 analysis. As you

can see, the histogram is in 5 columns. The first is simply the bin number. The second is the

associated stress range (that is, peak to trough). Note that these are nominal longitudinal

stresses, that is, not including the effect of SCF. The third column is used for output of the

number of cycles in this stress range identified during rainflow cycle counting.

Columns 4 and 5 show details of fatigue life calculations based directly on the histogram data.

A total damage is calculated for each bin based on a representative or equivalent stress for

the bin, the user-specified SCF, and the user-specified S-N curve. By default, this equivalent

stress is simply the average of the stresses enclosing or defining the bin. However you can

change from this default using the input Stress Histogram Range Index in the Stress Spectra

Definemenu. The index value you specify, which we will denote here as n, is used to calculate

an equivalent stress range Sequsing the following relation:

nnn

eqSSn

SSS

1

12

1

1

1

2

)()1(

+

=++

where S1 and S2 are the stresses defining the bin (S2 > S1). This equivalent stress can be

considered a power average of the stress bin. Note that for the defaultn

value of 1,Seq

issimply(S1 + S2).


46/60



St r ess Hi st ogr am f or El ement 205 St r ess Poi nt 5=================================================

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! Bi n # ! Str ess Range ! No. of ! Equi val ent Range ! Damage !! ! ( ks i ) ! Cycl es ! ( ksi ) ! !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

! 1 ! 0. 000- 0. 010 ! 722262 ! 0. 005 ! . 70610E- 09 !! 2 ! 0. 010- 0. 025 ! 734964 ! 0. 018 ! . 23979E- 07 !! 3 ! 0. 025- 0. 050 ! 695252 ! 0. 038 ! . 19164E- 06 !! 4 ! 0. 050- 0. 100 ! 688244 ! 0. 075 ! . 13212E- 05 !! 5 ! 0. 100- 0. 200 ! 699632 ! 0. 150 ! . 93537E- 05 !! 6 ! 0. 200- 0. 300 ! 871474 ! 0. 250 ! . 48702E- 04 !! 7 ! 0. 300- 0. 400 ! 814534 ! 0. 350 ! . 11678E- 03 !! 8 ! 0. 400- 0. 500 ! 568232 ! 0. 450 ! . 16466E- 03 !! 9 ! 0. 500- 0. 600 ! 459608 ! 0. 550 ! . 23359E- 03 !! 10 ! 0. 600- 0. 700 ! 303826 ! 0. 650 ! . 24651E- 03 !! 11 ! 0. 700- 0. 800 ! 281780 ! 0. 750 ! . 34130E- 03 !! 12 ! 0. 800- 0. 900 ! 159724 ! 0. 850 ! . 27466E- 03 !! 13 ! 0. 900- 1. 000 ! 86578 ! 0. 950 ! . 20328E- 03 !! 14 ! 1. 000- 1. 100 ! 55480 ! 1. 050 ! . 17239E- 03 !! 15 ! 1. 100- 1. 200 ! 31390 ! 1. 150 ! . 12584E- 03 !! 16 ! 1. 200- 1. 300 ! 12556 ! 1. 250 ! . 63571E- 04 !

! 17 ! 1. 300- 1. 400 ! 1314 ! 1. 350 ! . 82525E- 05 !! 18 ! 1. 400- 1. 500 ! 1168 ! 1. 450 ! . 89605E- 05 !! 19 ! 1. 500- 1. 600 ! 0 ! 1. 550 ! . 00000E+00 !! 20 ! 1. 600- 1. 700 ! 0 ! 1. 650 ! . 00000E+00 !! 21 ! 1. 700- 1. 800 ! 0 ! 1. 750 ! . 00000E+00 !! 22 ! 1. 800- 1. 900 ! 0 ! 1. 850 ! . 00000E+00 !! 23 ! 1. 900- 2. 000 ! 0 ! 1. 950 ! . 00000E+00 !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Tot al s 7188018 . 20194E- 02

Fat i gue damage di r ect l y f r omhi st ogr am . 20194E- 02Fat i gue l i f e di r ectl y f rom hi stogr am 495. 20 year s

Associ ated wei ght ed mean st r ess val ue 37. 116

This additional fatigue output is provided as a means of checking the adequacy of the

definition of stress bins. If the definition is reasonable, the fatigue life output as calculated

directly from the histogram will agree reasonably well with the value calculated by rainflow

cycle counting. Note that the histogram output also reports a weighted mean stress. This is

simply the sum of the mean stresses at this location from each of the fatigue seastates,

weighted by the percentage occurrence of that seastate.

If you do not define any histogram bins via the Bins Definemenu, LifeTime behaves asfollows. If the program has deduced from Flexcom database output that stresses are in

either ksi or MPa, then a default bin specification with 21 bins is used. The stress ranges

defining these bins are tabulated below. If on the other hand the program is unable to

determine what are the units of stress (for example, because no Flexcom database output is


47/60



available), then no stress histograms are produced, regardless of whether such histograms

have been requested in the specification of hot spots.

Stress RangeBin #ksi MPa

1 0.00-0.10 0.00-0.50

2 0.10-0.20 0.50-1.00

3 0.20-0.30 1.00-1.50

4 0.30-0.40 1.50-2.00

5 0.40-0.50 2.00-2.50

6 0.50-0.75 2.50-4.00

7 0.75-1.00 4.00-6.00

8 1.00-1.20 6.00-8.00

9 1.20-1.40 8.00-10.0

10 1.40-1.60 10.0-12.5

11 1.60-1.80 12.5-15.0

12 1.80-2.00 15.0-20.0

13 2.00-5.00 20.0-30.0

14 5.00-7.50 30.0-45.0

15 7.50-10.0 45.0-60.0

16 10.0-12.5 60.0-80.0

17 12.5-15.0 80.0-100.

18 15.0-20.0 100.-150.

19 20.0-25.0 150.-300.

20 25.0-50.0 300.-500.

21 > 50.0 > 500.

If you do input a stress bins definition, LifeTime actually adds one bin to the end of your

specification, and uses it for all stresses above the maximum value in your data. This is

provided of course that the associated number of such cycles is non-zero. In the example


48/60



histogram above, this final bin is absent, so clearly there are no stress ranges counted above 2

ksi in this case.

Note that LifeTime now also creates a plot of each histogram you request. An example is

shown below. Histogram plots are arbitrarily assigned the same file extension as snapshot

plots.

0 0.5 1 1.5 2 2.5

Stress Range

0

0.2

5

0.5

0.7

5

1

1.2

5

1.5

No.ofCycles

(x1E6)

Stress Histogramfor Element 291, Stress Point 1


49/60

Chapter 3 - Mode 1 Example Application


CHAPTER 3 -MODE 1 EXAMPLE APPLICATIONThis chapter describes an example LifeTime fatigue (Mode 1) analysis of a deepwater

drilling riser, and compares the effect on predicted fatigue life of varying some of the input

variables.

RISER AND ENVIRONMENT

The riser used in this example application is that used in Chapter 2, Example 1 Deepwater

Drilling Riser, of the Flexcom Examples Manual. Further details of the model can be found

in the Example Manual.

To illustrate the operation of LifeTime, twelve random sea analyses of this system are

performed, for the following combinations of significant wave height Hs and mean zero

crossing period Tz.

Combination Hs (ft) Tz (s)

1 2.0 5.0

2 2.0 6.0

3 3.5 6.04 3.5 7.0

5 5.0 9.0

6 6.5 8.0

7 6.5 9.0

8 9.5 9.0

9 9.5 10.0

10 12.5 10.0

11 15.5 12.0

12 18.5 12.0

Each analysis is run for 10900s, this being three hours of simulation plus 100s initially to be

discarded to exclude transients from the fatigue calculations.


50/60



The Flexcom input files for the analyses are included with the Flexcom software. The

names of the files are tabulated later. However there are a number of points to note about

the specification of both the type and the amount of output data in these files:

Force timetrace output only is requested in all twelve dynamic analyses, but this does

not have to be the case you can also request motion and reaction timetraces which

will simply be ignored byLifeTime.

The timetrace specification is the same in all the dynamic runs, although this is not

necessary for a Mode 1 LifeTime analysis.

Database output is requested in one dynamic analysis (the first, named Dynamic

1), but only for a very limited number of output times.

LIFETIME ANALYSES

A total of four LifeTime analyses are reported here to demonstrate the program operation.

The fatigue seastate data (as defined in Chapter 1) is the same in all four runs. This consists

of the names of the twelve riser dynamic analyses and the percentage occurrences of the

associated seastates, which are as follows:

Seastate Analysis Name % Occurrence

1 Dynamic 1 10.50

2 Dynamic 2 17.73

3 Dynamic 3 11.97

4 Dynamic 4 16.81

5 Dynamic 5 8.18

6 Dynamic 6 11.70

7 Dynamic 7 9.16

8 Dynamic 8 5.00

9 Dynamic 9 5.42

10 Dynamic 10 2.81

11 Dynamic 11 0.69

12 Dynamic 12 0.04


51/60



BASE CASE ANALYSIS

The first LifeTime analysis is considered the base case in the sensitivity study which follows

in the other three runs. The combination of options for the base case is as follows:

Rayleigh pdf specified

No endurance limit in S-N curve

No thickness effects

In the LifeTime input data for this analysis, which is included with the software, the

following are noteworthy:

No structure data is input, and no explicit value is specified for the Scale Factor for

Stress input. This is because database output was requested in one of the Flexcom

analyses, so LifeTime will be able to read the required diameters, cross-section areas

etc. from the database file.

Likewise the program will know from the value ofg in this output that Imperial units

are used, and so will automatically use a factor of 6.9444E-06 to generate stresses in

ksi (this fact is echoed to the main output file jobname.lif, which also contains a table

of the actual structure data values read from the database).

The following table presents a summary of the LifeTime results for this case.

Hot Spot Fatigue Life (years)

Element Local Node Statistics Spectrum Rainflow

153 First Node 2175 2118 2170

164 First Node 6264 6075 6193

192 First Node 3558 3442 3380

229 First Node 4089 3988 3983

291 Last Node 608 592 614

For the hot spot with the lowest fatigue life, Element 291, the three methods agree to within

less than 1%. Overall the agreement between the three methods at each hot spot is good.


52/60



The stress histogram for Hot Spot 5 produced by this analysis is shown below. The fatigue

life calculated directly from the histogram is around 611 years, which agrees very closely with

all of the values in the table above.

St r ess Hi st ogr am f or El ement 291 St r ess Poi nt 1=================================================

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! Bi n # ! Str ess Range ! No. of ! Equi val ent Range ! Damage !! ! ( ks i ) ! Cycl es ! ( ksi ) ! !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! 1 ! 0. 000- 0. 010 ! 1327624 ! 0. 005 ! . 12979E- 08 !! 2 ! 0. 010- 0. 025 ! 568435 ! 0. 018 ! . 18546E- 07 !! 3 ! 0. 025- 0. 050 ! 567772 ! 0. 038 ! . 15650E- 06 !! 4 ! 0. 050- 0. 100 ! 624482 ! 0. 075 ! . 11988E- 05 !! 5 ! 0. 100- 0. 200 ! 963766 ! 0. 150 ! . 12885E- 04 !! 6 ! 0. 200- 0. 300 ! 1014924 ! 0. 250 ! . 56718E- 04 !! 7 ! 0. 300- 0. 400 ! 833059 ! 0. 350 ! . 11943E- 03 !

! 8 ! 0. 400- 0. 500 ! 567431 ! 0. 450 ! . 16442E- 03 !! 9 ! 0. 500- 0. 600 ! 386549 ! 0. 550 ! . 19646E- 03 !! 10 ! 0. 600- 0. 700 ! 233633 ! 0. 650 ! . 18956E- 03 !! 11 ! 0. 700- 0. 800 ! 156197 ! 0. 750 ! . 18919E- 03 !! 12 ! 0. 800- 0. 900 ! 99458 ! 0. 850 ! . 17103E- 03 !! 13 ! 0. 900- 1. 000 ! 61522 ! 0. 950 ! . 14445E- 03 !! 14 ! 1. 000- 1. 100 ! 36115 ! 1. 050 ! . 11222E- 03 !! 15 ! 1. 100- 1. 200 ! 20314 ! 1. 150 ! . 81434E- 04 !! 16 ! 1. 200- 1. 300 ! 11818 ! 1. 250 ! . 59836E- 04 !! 17 ! 1. 300- 1. 400 ! 7641 ! 1. 350 ! . 47990E- 04 !! 18 ! 1. 400- 1. 500 ! 5266 ! 1. 450 ! . 40401E- 04 !! 19 ! 1. 500- 1. 600 ! 2280 ! 1. 550 ! . 21080E- 04 !! 20 ! 1. 600- 1. 700 ! 1204 ! 1. 650 ! . 13257E- 04 !! 21 ! 1. 700- 1. 800 ! 302 ! 1. 750 ! . 39231E- 05 !! 22 ! 1. 800- 1. 900 ! 390 ! 1. 850 ! . 59128E- 05 !! 23 ! 1. 900- 2. 000 ! 291 ! 1. 950 ! . 51113E- 05 !

! 24 ! > 2. 000 ! 173 ! ! !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Tot al s 7490646 . 16367E- 02

Fat i gue damage di r ect l y f r omhi st ogr am . 16367E- 02Fat i gue l i f e di r ectl y f rom hi stogr am 610. 99 year s

Associ ated wei ght ed mean st r ess val ue . 642E- 03

The figure below plots fatigue damage as a function of seastate for this hot spot. Seastate 6,

with a Hs of 6.5ft and a Tz of 8s, is the one that causes the most damage. Again all three

methods show close agreement.


53/60



0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

3.00E-04

3.50E-04

4.00E-04

1 2 3 4 5 6 7 8 9 10 11 12

Damage

Seastate

Statistics

Spectra

Rainflow

The same information is presented below except that the vertical axis in this case is the

percentage of the total damage caused by each seastate. Seastate 6 generates over 20% of the

total, although it occurs for less than 12% of the time. The most common environment,

Seastate 2 at nearly 18%, generates just over 3% of the total damage, as it is relatively benign.

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

1 2 3 4 5 6 7 8 9 10 11 12

%

ofTotalDamage

Seastate No.

Statistics

Spectra

Rainflow


54/60



SENSITIVITY ANALYSIS #1 EFFECT OF PDF

The first sensitivity study investigates the effect of using Dirliks pdf rather than the (default)

Rayleigh function. The LifeTime results for this case are shown below:



153 First Node 2175 2179 2170

164 First Node 6264 6268 6192

192 First Node 3558 3566 3380

229 First Node 4089 4131 3983

291 Last Node 608 588 614

The choice of pdf affects only the Spectrum results. The effect is to increase the predicted

fatigue life (but by only about 4%) at all hot spots except the 5th, where there is in fact a small

reduction (less than 1%).

SENSITIVITY ANALYSIS #2 EFFECT OF ENDURANCE LIMIT

In the second sensitivity study, an endurance limit of 0.5ksi is defined in the S-N curve

specification. (This value is somewhat arbitrary and intended for illustration only.) The

LifeTime results for this case are:



153 First Node 2890 2804 2941

164 First Node 15408 14749 17559

192 First Node 5580 5379 5359

229 First Node 7071 6870 6958

291 Last Node 653 635 657

The effect is, as expected, to increase fatigue lives in all cases, by about 7% in the case of the

critical hot spot.


55/60



SENSITIVITY ANALYSIS #3 EFFECT OF THICKNESS EFFECTS

In the final sensitivity study, a non-zero threshold thickness of 0.07ft (0.84) is specified.

This value is chosen as being larger than the thickness at all hot spots in the LifeTime

analysis except the last one, located on Element 291. So the results at all hot spots except this

last one should be unchanged; at the last hot spot the fatigue life should be reduced.

The results from this analysis are:



153 First Node 2175 2118 2170

164 First Node 6264 6075 6193

192 First Node 3558 3442 3380

229 First Node 4089 3988 3983

291 Last Node 591 575 597

As expected, the output at the first four hot spots is unchanged. At the last hot spot the

fatigue life is reduced as expected (by about 3%).

EXAMPLE FILES

All of the analysis input files required to run these examples may be found in the

Examples\LifeTime Examples\Example 1 Mode 1 subdirectory of your Flexcom

installation directory, provided that you installed the examples when you installed Flexcom.

If you did not install the examples, you may do so at any time by running the Setup program.

The actual file names and their contents are as follows.

Static.fl3 Flexcom GUI file Initial static analysis

Drill Ship.res Vessel response (RAO) file

Dynamic 1.fl3 Flexcom GUI file Dynamic analysis (1)


etc. down to ...



56/60



Base Case.lft LifeTime GUI file Base case

Sensitivity 1.lft LifeTime GUI file Sensitivity study (1)




57/60



CHAPTER 4 -MODE 2 EXAMPLE APPLICATIONThis chapter describes an example LifeTime Mode 2 analysis.

RISER AND ENVIRONMENT

The riser and environment data used in this example is exactly the same as used in the Mode

1 example analysis described in Chapter 3, and will not be repeated here. Refer to Chapter 3

for a detailed specification.

LIFETIME MODE 2 ANALYSIS

A single LifeTime Mode 2 analysis is reported here to demonstrate the program operation.

The fatigue seastate datais the same as in all the examples of Chapter 3. The fatigue data is as

follows. Cycles are counted for 1 channel of the Flexcom timetrace output only, namely

local-z bending moment at the last node of Element 291 (the last channel, Channel 16). A

scale factor of 0.000044857 is input. This in fact transforms the Flexcom output (in foot-lb)

to bending stress in ksi (based on an OD of 1.75 ft and a second moment of area of 0.13546

ft4). The histogram produced by this run should be similar to that produced by the Mode 1

analysis of Chapter 3. This Mode 1 histogram is shown on the next page.

The histogram produced by the example Mode 2 analysis is shown on the page after that. In

this case no fatigue calculations are reported. Obviously the number and distribution of

cycles corresponds closely to that produced by the Mode 1 analysis, thus verifying the

operation ofLifeTime in Mode 2. (The slight differences are due to the fact that the Mode 1

combined stresses are based on both local-y and local-z moment.) The two histograms are

plotted in Figure 4.1, showing close agreement.


58/60



St r ess Hi st ogr amf or El ement 291 St r ess Poi nt 1=================================================

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! Bi n # ! St r ess Range ! No. of ! Equi val ent Range ! Damage !! ! ( ks i ) ! Cycl es ! ( ksi ) ! !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! 1 ! 0. 000- 0. 010 ! 1327624 ! 0. 005 ! . 12979E- 08 !! 2 ! 0. 010- 0. 025 ! 568435 ! 0. 018 ! . 18546E- 07 !! 3 ! 0. 025- 0. 050 ! 567772 ! 0. 038 ! . 15650E- 06 !! 4 ! 0. 050- 0. 100 ! 624482 ! 0. 075 ! . 11988E- 05 !! 5 ! 0. 100- 0. 200 ! 963766 ! 0. 150 ! . 12885E- 04 !! 6 ! 0. 200- 0. 300 ! 1014924 ! 0. 250 ! . 56718E- 04 !! 7 ! 0. 300- 0. 400 ! 833059 ! 0. 350 ! . 11943E- 03 !! 8 ! 0. 400- 0. 500 ! 567431 ! 0. 450 ! . 16442E- 03 !! 9 ! 0. 500- 0. 600 ! 386549 ! 0. 550 ! . 19646E- 03 !! 10 ! 0. 600- 0. 700 ! 233633 ! 0. 650 ! . 18956E- 03 !! 11 ! 0. 700- 0. 800 ! 156197 ! 0. 750 ! . 18919E- 03 !! 12 ! 0. 800- 0. 900 ! 99458 ! 0. 850 ! . 17103E- 03 !

! 13 ! 0. 900- 1. 000 ! 61522 ! 0. 950 ! . 14445E- 03 !! 14 ! 1. 000- 1. 100 ! 36115 ! 1. 050 ! . 11222E- 03 !! 15 ! 1. 100- 1. 200 ! 20314 ! 1. 150 ! . 81434E- 04 !! 16 ! 1. 200- 1. 300 ! 11818 ! 1. 250 ! . 59836E- 04 !! 17 ! 1. 300- 1. 400 ! 7641 ! 1. 350 ! . 47990E- 04 !! 18 ! 1. 400- 1. 500 ! 5266 ! 1. 450 ! . 40401E- 04 !! 19 ! 1. 500- 1. 600 ! 2280 ! 1. 550 ! . 21080E- 04 !! 20 ! 1. 600- 1. 700 ! 1204 ! 1. 650 ! . 13257E- 04 !! 21 ! 1. 700- 1. 800 ! 302 ! 1. 750 ! . 39231E- 05 !! 22 ! 1. 800- 1. 900 ! 390 ! 1. 850 ! . 59128E- 05 !! 23 ! 1. 900- 2. 000 ! 291 ! 1. 950 ! . 51113E- 05 !! 24 ! > 2. 000 ! 173 ! ! !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Tot al s 7490646 . 16367E- 02

Fat i gue damage di r ect l y f r om hi st ogr am . 16367E- 02

Fat i gue l i f e di r ectl y f r om hi stogram 610. 99 years

Associ ated wei ght ed mean st r ess val ue . 642E- 03


59/60



Hi st ogr am f or Channel 16=========================

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! Bi n # ! Range ! No. of cycl es !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -! 1 ! 0. 00- 0. 01 ! 1328563 !! 2 ! 0. 01- 0. 03 ! 568478 !! 3 ! 0. 03- 0. 05 ! 568347 !! 4 ! 0. 05- 0. 10 ! 623213 !! 5 ! 0. 10- 0. 20 ! 967352 !! 6 ! 0. 20- 0. 30 ! 1015324 !! 7 ! 0. 30- 0. 40 ! 833274 !! 8 ! 0. 40- 0. 50 ! 565528 !! 9 ! 0. 50- 0. 60 ! 384644 !! 10 ! 0. 60- 0. 70 ! 234730 !! 11 ! 0. 70- 0. 80 ! 156452 !! 12 ! 0. 80- 0. 90 ! 98359 !! 13 ! 0. 90- 1. 00 ! 61544 !! 14 ! 1. 00- 1. 10 ! 35553 !! 15 ! 1. 10- 1. 20 ! 19919 !! 16 ! 1. 20- 1. 30 ! 12082 !! 17 ! 1. 30- 1. 40 ! 7582 !! 18 ! 1. 40- 1. 50 ! 5372 !! 19 ! 1. 50- 1. 60 ! 1968 !! 20 ! 1. 60- 1. 70 ! 1205 !! 21 ! 1. 70- 1. 80 ! 322 !! 22 ! 1. 80- 1. 90 ! 368 !! 23 ! 1. 90- 2. 00 ! 291 !! 24 ! > 2. 00 ! 173 !- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Tot al 7490643

Associ at ed wei ght ed mean val ue 0. 00

0 0.5 1 1.5 2 2.5

Stress range (ksi)

0

0.2

5

0.5

0.7

5

1

1.2

5

1.5

No.ofCycles(x1E6)

Stress Histogramfor Element 291, Stress Point 1Histogramfor Channel 16


60/60


Figure 4.1: Mode 1 and Mode 2 Stress Histograms

EXAMPLE FILES

The files required to run this example analysis are exactly the same as for the analysesdescribed in Chapter 3, except for the actual LifeTime GUI file. For this Mode 2 run, the

LifeTime file is named Mode 2.lft. All of the files required to run the example may be found

in the Examples\LifeTime Examples\Example 1 Mode 1 and Examples\LifeTime

Examples\Example 1 Mode 2 subdirectories of your Flexcom installation directory,

provided that you installed the examples when you installed Flexcom. If you did not install

he examples, you may do so at any time by running the Setup program.

LifeTime Manual

Documents

Transcript of LifeTime Manual