Weld Sensitivity Analysis in FEMFAT Weld

Weld Sensitivity Analysis

in FEMFAT Weld

Axel Werkhausen

1

© ECS / Disclosure or duplication without consent is prohibited

Content

• Introduction

• FEMFAT WELD

• R1MS Concept

• WELD Database

• Sensitivity Databases and –Factors

• Work Flow

• Example Front Cradle

• Summary


Introduction

• Scatter in weld geometry cannot be avoided

• Fatigue life will be influenced by variations of weld geometry

• If a welding joint is critical depends on:

– the loading situation

– which geometry parameter varies

– the range of variation

• Most important geometry parameters:

– gap dimension

– weld thickness (a)

– degree of weld penetration (h = d/t)

– weld seam inclination angle (a)


Sensitivity Databases

• FE-analysis of Radaj-models for three different parameter

variations following the quality classes B, C and D of DIN 5817:


Joint Types for Sensitivity Analysis

Good

quality

Standard

quality

Poor

quality

Weld climb angle a 150° 110° 90°

Weld reinforcement 2.5 mm 3.25 mm 4.5 mm

Plate offset 1 mm 1.5 mm 2.5 mm

Degree of penetration h 100% 100% 70%

• Butt Joint

• Overlap Joint

Good

quality

Standard

quality

Poor

quality


Weld thickness a 10 mm 10 mm 5.3 mm

Gap dimension 0 mm 1.67 mm 5 mm

Degree of penetration h 100% 100% -14%


Joint Types for Sensitivity Analysis

• T-Joint 90°

• Y-Joint

Good

quality

Standard

quality

Poor

quality


Weld thickness a 15 mm 10 mm 7 mm



Good

quality

Standard

quality

Poor

quality


Weld thickness a 8.2 mm 9 mm 10 mm




Sensitivity Databases

• WELD Databases for two qualities of every geometry parameter:

Database name Geometry

parameter Quality

weld50_sensitivity_standard.dbs All Moderate (C)

weld50_sensitivity_gap_small.dbs Gap Better (B)

weld50_sensitivity_gap_big.dbs Gap Poorer (D)

weld50_sensitivity_penetration_degree_big.dbs h Better (B)

weld50_sensitivity_penetration_degree_small.dbs h Poorer (D)

weld50_sensitivity_seam_thickness_big.dbs a Better (B)

weld50_sensitivity_seam_thickness_small.dbs a Poorer (D)

weld50_sensitivity_inclination_angle_big.dbs a Better (B)

weld50_sensitivity_inclination_angle_small.dbs a Poorer (D)


Workflow

• Analysis of a welded component using

Damages D or Safety Factors S

• Start of Sensitivity Analysis by selecting the appropriate job file

• Visualization of both damage/safety and the sensitivity factors

Three additional

analysis runs will

be performed


Sensitivity Factor

• Special analysis results will be available:

Damage D Safety factor S Remarks

Result 1 Sensitivity factor

Result 2 Ratio of poorest to standard

quality

Result 3 Ratio of the best to the standard

quality

Result 4 DOriginal SOriginal Result of original analysis

Result 5 F1 * DOriginal F1 * SOriginal Anticipated damage/safety for

reduction in parameter

Result 6 F2 * DOriginal F2 * SOriginal Anticipated damage/safety for

increase in parameter

small

bigsmall

sensD

DDF

big

smallbig

sensS

SSF

dardsD

DF

tan

small1

dardsS

SF

tan

small1

dardsD

DF

tan

big

2 dardsS

SF

tan

big

2


FEMFAT Weld Sensitivity Analysis Weld Geometry Definition

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Parameter:

• Degree of Weld Penetration – h

• Seam Thickness – a

• Seam Inclination Angle – a

• Weld Gap

Problem:

In reality variations in the weld geometry parameter are observed

coming from the manufacturing process!

a

a

h d/t

We

ld g

ap

Example: T-Joint 90°

FEMFAT Weld Sensitivity Analysis helps assessing the influence of variations in

weld geometry parameters on fatigue results.


FEMFAT Weld Sensitivity Analysis Weld Geometry Definition

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Parameter –

T-Joint 90°

Better Quality

(Quality class B)

Standard Quality

(Quality class C)

Worse Quality

(Quality class D)

Degree of weld penetration - h 100% 50% 0%

Seam thickness - a 1.5 t t 0.7 t

Seam inclination angle - a 110° 100° 90°

Weld gap (at 3mm thickness) 0mm 0.5mm 1.5mm

h d/t

We

ld g

ap

Determination of notch factors for weld database (total 9 databases)

a

a

Example: T-Joint 90°

Computation of Sensitivity Factor

different quality classes for geometry parameters

different fatigue results


FEMFAT Weld Sensitivity Analysis Workflow

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1.) Standard FEMFAT Analysis A standard weld evaluation (damage or safety analysis) must be performed using FEMFAT

BASIC, Channel or TransMAX.

2.) Start of Sensitivity Analysis

using Templates The sensitivity analysis is started by

selecting the appropriate job file from

the template folder.


FEMFAT Weld Sensitivity Analysis Template Job Files

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3.) Sensitivity Analysis Routine - The settings from the last FEMFAT analysis are used.

- A group containing all weld nodes is formed for the sensitivity analysis.

- Three computations per geometry parameter are performed for this group (one for each

quality).

4.) Computation of Sensitivity Factors The fatigue results from Point 3.) are used to calculate the sensitivity factors using the

FEMFAT Result Manager.

All the necessary steps from Points 3.) & 4.) are carried out by FEMFAT automatically

using the template job files!


FEMFAT Weld Sensitivity Analysis Results

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If one geometry parameter (‘weld thickness’, ‘degree of penetration’, ‘weld climb angle’) is

analyzed:

0 = no sensitivity

1 = very sensitive

<0 = Improvement



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If only the geometry parameter ‘gap dimension‘ is analyzed:

0 = no sensitivity

1 = very sensitive

<0 = Improvement



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If all geometry parameters are analyzed:

0 = no sensitivity

1 = very sensitive

<0 = Improvement


FEMFAT Weld Sensitivity Analysis Example

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Weld Sensitivity Analysis of Subframe in FEMFAT BASIC (Endurance Safety)

2 Types of Weld Seams:

- T – joint 90°

- Lap joint

Comparison of the Sensitivity

Factors for weld geometry

parameters ‘Gap Dimension’ and

‘Degree of Weld Penetration’.



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Endurance Safety [-]

Better Quality Standard Quality Worse Quality

1.24 (N6836)

Results for varying Geometry Parameter ‘Gap Dimension‘

16.047.1

24.147.1

small

bigsmall

sensS

SSF

Little Sensitivity to

Variation in Gap

Dimension!

1.47 (N6836) 1.38 (N6836)



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Endurance Safety [-]

Better Quality Standard Quality Worse Quality

Results for varying Geometry Parameter ‘Degree of Weld Penetration‘

84.088.3

63.088.3

big

smallbig

sensS

SSF

High Sensitivity to

Variation in Degree

of Weld Penetration

3.88 (N6836) 0.63 (N6836) 1.38 (N6836)


Example: Front Cradle

• Investigations of a passenger car front cradle

Author: ECS/Hofwimmer 21 Date: Sept. 10th 2012

Sensitivity Factor Analysis (variation of gap between sheets)

Standard Damage Analysis


Assessment of measured geometry variations

Author: ECS/Hofwimmer 22 Date: Sept. 10th 2012

Damage[-]

Bad

Moderate

Good

Penetration Degree

Dam

ag

e [

-]


Summary

• Variations in weld geometry according production tolerances always occurs and influences the fatigue life

• Damage analysis of welded joints and components using simple shell

models and SN curve informations from a database according the R1MS

concept can be done with FEMFAT WELD.

• Submodel analysis according Radaj of three qualitiy standards has been

performed for different joint types. => WELD Databases for different

qualities.

• Introduction of new sensitivity paramters to describe the influence of

parameter variations on the fatigue behavior.

• Now it is possible to identify, which geometry parameter has to be

observed during production process, depending on the loading situation.

• If informations of the real geometry are available, the corresponding

fatigue life can be estimated without addtional submodel analysis.

Weld Sensitivity Analysis in FEMFAT Weld

Technology

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