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ABSTRACT
In this study, the embedded rod tool was used to conduct Friction Stir Spot Welding (FSSW), and numerical modeling was established to simulate this process, based on the experimental records of downward force and plunge depth. In this modeling, the relative speed between the workpiece and the tool was predicted by experimental and numerical methods. To verify this model, the friction coefficient for the Al alloy self-mated pair was obtained in the FSSW of the Al alloy, by comparing the measured and computed temperatures. Furthermore, the friction coefficient of Al alloy/steel was obtained in the same method and results. For the FSSW of the Al alloy on steel, the numerical and experimental results showed that higher tool speed leads to a higher plastic flow speed and temperature. When the temperature at the faying surface was higher than 460°C, good bonding was obtained on the surfaces between the Al alloy and the steel.
Nomenclature
| = | Interaction of the flow stress, MPa | |
| A | = | Material constant, s−1 |
| α | = | Material constant, MPa−1 |
| n | = | Material constant |
| Z | = | Zener-Hollomon parameter |
| r | = | Radial coordinate |
| = | Circumference coordinate | |
| z | = | Axial coordinate |
| vr | = | Plastic flow speed in the r, mm/s |
| vθ | = | Plastic flow speed in the θ, mm/s |
| vz | = | Plastic flow speed in the z, mm/s |
| μ | = | Non-Newtonian viscosity |
| = | Density, kg/cm3 | |
| T | = | Temperature, K |
| t | = | Time, s |
| Cp | = | Specific heat, J/kg-K |
| k | = | Thermal conductivity, W/m-K |
| Φ | = | Heat generation rate per unit volume due to the plastic deformation, W/cm3 |
| fi | = | Shear stress at the interface, MPa |
| = | Slip ratio between the tool and the workpiece | |
| = | Shear yield stress of the workpiece at the interface, MPa | |
| μf | = | Friction coefficient |
| pN | = | Pressure under the shoulder, MPa |
| = | Tool rotational speed, rpm | |
| JW | = | A portion of the heat source input into the workpiece |
| kT | = | Thermal conductivity of the tool, W/m-K |
| ht | = | Heat transfer coefficient from top, W/m2-K |
| Ta | = | Room temperature, K |
| hb | = | Heat transfer coefficient from bottom, W/m2-K |
Acknowledgments
The authors would like to thank all reviewers who reviewed this paper. Furthermore, the authors would like to express their appreciation to the Ministry of Science and Technology, Taiwan (MOST-104-2221-E-110-024) for funding support.
Disclosure statement
No potential conflict of interest was reported by the author(s).