Numerical simulation of three-dimensional heat transfer and plastic flow during friction stir welding

Abstract

Three-dimensional visco-plastic flow of metals and the temperature fields in friction stir welding have been modeled based on the previous work on thermomechanical processing of metals. The equations of conservation of mass, momentum, and energy were solved in three dimensions using spatially variable thermophysical properties and non-Newtonian viscosity. The framework for the numerical solution of fluid flow and heat transfer was adapted from decades of previous work in fusion welding. Non-Newtonian viscosity for the metal flow was calculated considering strain rate, temperature, and temperature-dependent material properties. The computed profiles of strain rate and viscosity were examined in light of the existing literature on thermomechanical processing. The heat and mass flow during welding was found to be strongly three-dimensional. Significant asymmetry of heat and mass flow, which increased with welding speed and rotational speed, was observed. Convective transport of heat was an important mechanism of heat transfer near the tool surface. The numerically simulated temperature fields, cooling rates, and the geometry of the thermomechanically affected zone agreed well with independently determined experimental values.

Ultrafine-Grained Al-Mg-Sc Alloy via Friction-Stir Processing

“…[39,40] To calculate Z, accurate knowledge of strain rate in the process is very important. Studies related to this have been carried out by many groups [38,[41][42][43][44][45][46] using experimental, analytical, and numerical methods. However, no work reported so far is capable of describing strain rate satisfactorily partly due to simplification and partly due to poor understanding of actual material flow process during FSP.…”

“…A similar correlation between grain size and Z has been shown to exist by many researchers for FSP materials. [38,39] C. Processing Parameters, Heat Input, and Grain Refinement…”

“…[38] The calculated Q total is given in Table II along with shear stress and plunge force corresponding to each tool rotation rate. The heat flux and temperature as a function of tool rotation rate has been shown in Figure 12.…”

Sürtünme Karıştırma Kaynağı Yapılmış Alüminyum Alaşımlarının Isı Akışının Modellemesi ve Pratik Doğrulaması

“…The thermal conductivity and specific heat of AA6061-T6 were taken from reference [17]. which gave the most realistic thermal profile.…”

“…Q is activation energy and equal to 1.45 ×105 J/mol, R is universal gas constant and equal to 8.31451 J/(mol×K). These coefficients are also taken from reference [17]. Shear thinning behavior of the plasticized aluminum is well represented by this equation.…”