Process Modeling

Lesson Objectives When you finish this lesson you will understand: The various modeling techniques listed below Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords Electro-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-Al Transition 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 x 0 at t 0 = Temp at n*x 0 at n 2 *t 0 Temp at 1mm, 0.1 sec = Temp at 10 mm, 10 sec Okuda, 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 n 2 times, the new temperature distribution becomes similar to the original one”

n=6 n 2 = 36 8 * 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 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) *optimum weld time for the experimental thickness = weld time for new thickness Fong & Tsang “Law of Thermal Similarity” Senior Project, OSU, 2000

Thick/thin and multi-sheet welding Combination 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 2 Bouncing 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 prediction in brown fits well to the experimental data in black.