Three-Dimensional Thermal Model of Resistance Spot Welding in Aluminum

1999 ◽  
Author(s):  
A. A. S. Arefin Kabir ◽  
Jamil A. Khan ◽  
Kirk Broach
Keyword(s):  
Contact Resistance ◽  
Phase Change ◽  
Weld Pool ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Work Piece ◽  
Contact Conductance ◽  
Faying Surface ◽  
Surface Contact ◽  
Surface Contact Resistance

Abstract A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.

Deformation and Solidification of Droplet Impact With Variable Thermal Contact Resistance

2003 ◽  
Author(s):  
W. Wang ◽  
H.-H. Qiu ◽  
P. Cheng
Keyword(s):  
Numerical Simulation ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Solidification Process ◽  
Numerical Results ◽  
Thermal Contact Conductance ◽  
Contact Conductance ◽  
Molten Droplet ◽  
Comparison Results

Interfacial thermal contact resistance between the impinging flow of a molten droplet and a substrate, which is qualified by thermal contact conductance, plays an important role in the spreading and solidification of a droplet. In the present study, a simple correlation for the thermal contact conductance in the rapid contact solidification process was developed. With this correlation being directly used in numerical simulation, for the first time, a variable thermal contact resistance was taken into consideration to simulate both the dynamics and phase change responses during a molten droplet impingement. Numerical results were compared with that of the cases when thermal contact resistance was zero or a constant. The changes in spread factor with time and thermal contact conductance indicated that predictions from the computer simulation were sensitive to the values of thermal contact resistance. Experiment was conducted to demonstrate the validity of the present study. Comparison results showed that rather than using a constant average value, better agreement between the experimental and numerical results would be obtained if a variable thermal contact resistance were used in the numerical simulation.

Boron Nitride Particle Filled Paraffin Wax as a Phase-Change Thermal Interface Material

2006 ◽  
Vol 128 (4) ◽  
pp. 319-323 ◽  
Author(s):  
Zongrong Liu ◽  
D. D. L. Chung
Keyword(s):  
Boron Nitride ◽  
Phase Change ◽  
Melting Temperature ◽  
Thermal Contact ◽  
Thermal Interface Material ◽  
Paraffin Wax ◽  
Thermal Contact Conductance ◽  
Thermal Interface ◽  
Contact Conductance ◽  
Increasing Temperature

Wax (predominantly tricosane paraffin wax, with a melting temperature of 48°C) filled with hexagonal boron nitride (BN) particles (5-11μm) was found to be an effective phase-change thermal interface material. The thermal contact conductance, as measured with the interface material between copper surfaces, decreased with increasing temperature from 22to48°C, but increased with increasing temperature from 48to55°C. The melting of the wax enhanced the conductance, due to increased conformability to the mating surfaces. For a given BN volume fraction and a given temperature, the thermal contact conductance increased with increasing contact pressure. However, a pressure above 0.30MPa resulted in no significant increase in the conductance. The conductance increased with BN content up to 6.2vol.%, but decreased upon further increase to 8.6vol.%. The highest conductance above the melting temperature was 18×104W∕m2.°C, as attained for a BN content of 4.0vol.% at 55°C and 0.30MPa. Below the melting temperature, the highest conductance was 19×104W∕m2.°C, as attained for a BN content of 6.2vol.% at 22°C and 0.30MPa.

On the Enhancement of the Thermal Contact Conductance: Effect of Loading History

1999 ◽  
Vol 122 (1) ◽  
pp. 46-49 ◽  
Author(s):  
Y. Z. Li ◽  
C. V. Madhusudana ◽  
E. Leonardi
Keyword(s):  
Heat Flow ◽  
Contact Resistance ◽  
Experimental Work ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Cost Effective ◽  
Thermal Contact Conductance ◽  
Loading History ◽  
Contact Conductance ◽  
Resistance To Heat

A resistance to heat flow exists at the junction of two surfaces. It has long been recognized that there exists a hysteresis effect, that is, the value of thermal contact resistance in the unloading process is less than that in the loading process at the same load. However, little work has been done in utilizing this phenomenon to enhance the thermal contact conductance. The present experimental work investigated the effect of loading history; in particular the number of load cycles and overloading pressure, on the thermal contact conductance. It was found that the value of the thermal contact conductance might be enhanced by up to 51 percent. A cost-effective way of enhancing the contact conductance is suggested. [S0022-1481(00)01601-7]

scholarly journals Tuning thermal contact conductance at graphene–copper interfaceviasurface nanoengineering

Nanoscale ◽  
2015 ◽  
Vol 7 (14) ◽  
pp. 6286-6294 ◽  
Author(s):  
Yang Hong ◽  
Lei Li ◽  
Xiao Cheng Zeng ◽  
Jingchao Zhang
Keyword(s):  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Contact Conductance

By introducing a surface nanoengineering design at sub-nm level, the thermal contact resistance between graphene and copper is reduced by 17% due to enhanced phonon couplings across the interface.

Realizing the nanoscale quantitative thermal mapping of scanning thermal microscopy by resilient tip–surface contact resistance models

2018 ◽  
Vol 3 (5) ◽  
pp. 505-516 ◽  
Author(s):  
Yifan Li ◽  
Nitin Mehra ◽  
Tuo Ji ◽  
Jiahua Zhu
Keyword(s):  
Thermal Properties ◽  
Contact Resistance ◽  
Quantitative Assessment ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Scanning Thermal Microscopy ◽  
Thermal Microscopy ◽  
Substrate Interface ◽  
Surface Contact ◽  
Surface Contact Resistance

Quantitative assessment of thermal properties by scanning thermal microscopy (SThM) is a demanded technology, but still not yet available due to the presence of unpredictable thermal contact resistance (TCR) at the tip/substrate interface.

New Apparatus for Characterizing Electrical Contact Resistance and Thermal Contact Conductance

2011 ◽  
pp. 1003-1008
Author(s):  
Nedeltcho Kandev ◽  
Hugues Fortin ◽  
Sylvain Chénard ◽  
Guillaume Gauvin ◽  
Marie-Hélène Martin ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Thermal Contact ◽  
Electrical Contact ◽  
Thermal Contact Conductance ◽  
Electrical Contact Resistance ◽  
Contact Conductance ◽  
New Apparatus

Thermal Contact Resistance Modeling of Non-Flat, Roughened Surfaces With Non-Metallic Coatings

2000 ◽  
Vol 123 (1) ◽  
pp. 11-23 ◽  
Author(s):  
E. E. Marotta ◽  
L. S. Fletcher ◽  
Thomas A. Dietz
Keyword(s):  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Metallic Coatings ◽  
Thermomechanical Model ◽  
Contact Conductance ◽  
Flat Surfaces ◽  
Resistance Modeling ◽  
Aluminum Substrates

Essentially all models for prediction of thermal contact conductance or thermal contact resistance have assumed optically flat surfaces for simplification. A few thermal constriction models have been developed which incorporate uncoated, optically non-flat surfaces based on the bulk mechanical properties of the material. Investigations have also been conducted which incorporate the thermophysical properties of metallic coatings and their effective surface microhardness to predict the overall thermal contact conductance. However, these studies and subsequent models have also assumed optically flat surfaces; thus, the application of these models to optically non-flat, coated surface conditions is not feasible without modifications. The present investigation develops a thermomechanical model that combines both microscopic and macroscopic thermal resistances for non-flat, roughened, surfaces with non-metallic coatings. The thermomechanical model developed as a result of this study predicts the thermal contact resistance of several non-metallic coatings deposited on metallic aluminum substrates quite well.

New Apparatus for Characterizing Electrical Contact Resistance and Thermal Contact Conductance

2011 ◽  
pp. 1003-1008 ◽  
Author(s):  
Nedeltcho Kandev ◽  
Hugues Fortin ◽  
Sylvain Chénard ◽  
Guillaume Gauvin ◽  
Marie-Hélène Martin ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Thermal Contact ◽  
Electrical Contact ◽  
Thermal Contact Conductance ◽  
Electrical Contact Resistance ◽  
Contact Conductance ◽  
New Apparatus
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