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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
© ECS / Disclosure or duplication without consent is prohibited
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)
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Sensitivity Databases
• FE-analysis of Radaj-models for three different parameter
variations following the quality classes B, C and D of DIN 5817:
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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 climb angle a 110° 100° 90°
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%
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Joint Types for Sensitivity Analysis
• T-Joint 90°
• Y-Joint
Good
quality
Standard
quality
Poor
quality
Weld climb angle a 110° 100° 90°
Weld thickness a 15 mm 10 mm 7 mm
Gap dimension 0 mm 1.67 mm 5 mm
Degree of penetration h 100% 50% 0%
Good
quality
Standard
quality
Poor
quality
Weld climb angle a 110° 100° 90°
Weld thickness a 8.2 mm 9 mm 10 mm
Gap dimension 0 mm 1.67 mm 5 mm
Degree of penetration h 100% 80% 5%
© ECS / Disclosure or duplication without consent is prohibited
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)
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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
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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
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FEMFAT Weld Sensitivity Analysis Weld Geometry Definition
10
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.
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FEMFAT Weld Sensitivity Analysis Weld Geometry Definition
11
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
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FEMFAT Weld Sensitivity Analysis Workflow
13
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.
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FEMFAT Weld Sensitivity Analysis Template Job Files
14
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!
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FEMFAT Weld Sensitivity Analysis Results
15
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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FEMFAT Weld Sensitivity Analysis Results
16
If only the geometry parameter ‘gap dimension‘ is analyzed:
0 = no sensitivity
1 = very sensitive
<0 = Improvement
© ECS / Disclosure or duplication without consent is prohibited
FEMFAT Weld Sensitivity Analysis Results
17
If all geometry parameters are analyzed:
0 = no sensitivity
1 = very sensitive
<0 = Improvement
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FEMFAT Weld Sensitivity Analysis Example
18
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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FEMFAT Weld Sensitivity Analysis Example
19
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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FEMFAT Weld Sensitivity Analysis Example
20
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)
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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
© ECS / Disclosure or duplication without consent is prohibited
Assessment of measured geometry variations
Author: ECS/Hofwimmer 22 Date: Sept. 10th 2012
Damage[-]
Bad
Moderate
Good
Penetration Degree
Dam
ag
e [
-]
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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.