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Process Modeling. Process Modeling. Learning Activities View Slides; Read Notes, Listen to lecture Do on-line workbook. Lesson Objectives When you finish this lesson you will understand: The various modeling techniques listed below. Keywords - PowerPoint PPT Presentation
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Process Modeling
Process Modeling
Lesson ObjectivesWhen you finish this lesson you will understand:• The various modeling techniques listed below
Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. Do on-line
workbook
KeywordsElectro-thermal Modeling, Thermo-mechanical Modeling, Electrode Modeling, Surface Contact Modeling, Solidification Modeling, Process Control Modeling, Law of Thermal Similarity, Machine Characteristics Modeling
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
Resistive Current Path “Breakdown” Model
Liang, “Foundational Study of Contact Behavior..”,OSU Dissertation, 2000
Liang, “Foundational Study of Contact Behavior..”,OSU Dissertation, 2000
IRW Tech Catalog, Rel #2, Jan 1999
Model for Heat Generation - Electrode Face
IRW Tech Catalog, Rel #2, Jan 1999
Alcan A-Nose
Electrode Design - Heat Generation
A Model For Expulsion Prediction
IRW Tech Catalog, Rel #2, Jan 1999
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
IRW Tech Catalog, Rel #2, Jan 1999
Model of stress
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
IRW Tech Catalog, Rel #2, Jan 1999
Model of Heating for Electrode Misalignment
IRW Tech Catalog, Rel #2, Jan 1999
Model of Heating for Electrode Misalignment
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Melting &Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
A heat balance problem is set up when welding Steel to Aluminum Using a Transition Material of Roll Bonded Al to Steel Sheet.
Heat Balance
Steel
Aluminum
Steel-AlTransition
Move to Next Slide to See Nugget Growth
Results and Discussion(nugget development model)
Steel
Al
One CycleTwo CyclesThree CyclesFour CyclesFive CyclesSix CyclesSeven CyclesEight CyclesNine CyclesTen CyclesEleven CyclesTwelve Cycles
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
0.1 Sec
10 sec
Law of Thermal Similarity
Temp at x0 at t0 = Temp at n*x0 at n2*t0
Temp at 1mm, 0.1 sec = Temp at 10 mm, 10 secOkuda, T. Law of Thermal Similarity,Mitsubishi Electric 1973
Law of Thermal Similarity
Okuda, T. Law of Thermal Similarity,Mitsubishi Electric 1973
“For the case where the plate thickness and the diameter of the electrodes are magnified by n times, if we also change the current density by 1/n times (which is current by n times), and heating time by n2 times, the new temperature distribution becomes similar to the original one”
n=6n2 = 368 * 36 = 288
Okuda, T. Law of Thermal Similarity,Mitsubishi Electric 1973
Measurement of melted and partially melted thicknesses using picral etch
Thickness not melted
Melted & solidified weld
nugget
Partially melted zone
Nugget
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Measurement of Heat affected(HAZ) and non-heat affected (N-HAZ) melted
thicknesses using Nital etch
Non-recrystallized thickness (N-HAZ)
Recrystallized thickness (HAZ)
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Law of Thermal Similarity Applied to Stacks of Mild Steel Sheet
Thinnest Outer Sheet
Sum of All Thickness
Optimum Weld Time Example
Optimum weld time for 1.25 sheet welded to itself = 8 cycles
Total thickness welded with this combination = 2.5 mm
Optimum weld time for different thickness combinations can be derived from the following equation:
*optimum weld time for the experimental thickness = weld time for new thickness
2)_exp
_( thicknesserimental
thicknessnew
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Calculate Time Constant for unit thickness 1mm to 1mm
(for 1.25mm – 1.25mm = 8 cycles)
2)_exp
_( thicknesserimental
thicknessnew *optimum weld time for the experimental thickness = weld time for new thickness
cyclescyclesmm
mm58*)
5.2
2( 2
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Thick/thin and multi-sheet welding
Combination 1
2.5 mm sheet welded to 1.25 mm sheet
Combination 2
3 sheets of 1.25 mm thickness each welded together
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Verification – Thin-Thick sheet• Total thickness welded for combination 1 = 3.75 mm• Weld time for combination 1 = (3.75/2.5)2*8 = 18 cycles• Weld time for any single welding pulse can not exceed 8 cycles; cooling times need to be added and pulsed welding done to keep thin sheet from overheating
• Weld schedule = 7 cycles weld + 4 cycles cool + 7 cycles weld (total time = 18 cycles)
Note: weld time reduced from 8 cycles to 7 cycles for each pulse to fit in within the total weld time.
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Verification – Thin-Thick sheet
Weld nugget is evenly distributed in the thick/thin sheets
Thin sheet is not overheated and the nugget is symmetrical with the two outer surfaces
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Verification – 3 Sheet Combination
• Total thickness welded for combination 2 = 3.75 mm • Weld time for combination 1 = (3.75 /2.5)2*8 = 18 cycles
• Weld time for any single welding pulse can not exceed 8 cycles; cooling times need to added and pulsed welding needs to be done
• Weld schedule = 7 cycles weld + 4 cycles cool + 7 cycles weld (total time = 18 cycles)
Note: weld time reduced from 8 cycles to 7 cycles for each pulse to fit in within the total weld time.
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Verification – 3 Sheet Combination
Weld nugget is evenly distributed in the 3 sheet combination as well
Good sized nugget without overheating surfaces
Fong & Tsang “Law of Thermal Similarity”Senior Project, OSU, 2000
Modeling Efforts
• Electrothermal Modeling• Nugget Growth• Electrode Design• Expulsion
• Thermomechanical Modeling• Stress Analysis
• Electrode Modeling • Electrode Life• Electrode Misalignment
• Surface Contact• Solidification• Process Control
• Law of Thermal Similarity• Machine Characteristics
IRW Tech Catalog, Rel #2, Jan 1999
Machine Characteristics - Regions to Model
IRW Tech Catalog, Rel #2, Jan 1999
Mechanical Models to Characterize Machine
Model 2Bouncing Region
Model 3 Welding Region
IRW Tech Catalog, Rel #2, Jan 1999
Ball Test Results to Confirm Bouncing Region Model
After the first bounce, the model predictionin brown fits well to the experimental data in black.