A Transient Thermal Model for Friction Stir Weld. Part I: The Model

Abstract

Current analytical thermal models for friction stir welding (FSW) are mainly focused on the steady-state condition. To better understand the FSW process, we propose a transient thermal model for FSW, which considers all the periods of FSW. A temperature-dependent apparent friction coefficient solved by the inverse solution method (ISM) is used to estimate the heat generation rate. The physical reasonableness, self-consistency, and relative achievements of this model are discussed, and the relationships between the heat generation, friction coefficient, and temperature are established. The negative feedback mechanism and positive feedback mechanism are proposed for the first time and found to be the dominant factors in controlling the friction coefficient, heat generation, and in turn the temperature. Furthermore, the negative feedback mechanism is found to be the controller of the steady-state level of FSW. The validity of the proposed model is proved by applying it to FSW of the 6061-T651 and 6063-T5 aluminum alloys.

A Transient Thermal Model for Friction Stir Weld. Part II: Effects of Weld Conditions

“…[16] and [11]. These results can be summarized by the following two chains based on the chain rule I with negative feedback mechanism: [29] x ":…”

“…Other parameters can be found in Part I. [29] III. COMPUTED RESULTS A complete FSW process includes plunge, first dwell, weld, second dwell, and cool periods.…”

“…[26] So the shoulder heat generation and the pin heat generation described in Part I [29] may be rewritten as…”

“…By defining a tool friction factor, [29] while experimental results are reported by Liu and Ma. [12] Fig.…”

“…Part I [29] has built a transient thermal model that considers the entire FSW process. It has been proved to be self-consistent, and its calculated results correspond well with the experimental results reported by Liu and Ma [12] and Sato et al [5] In Part II, the model is used to study the relationship between welding conditions, heat generation, temperature, and friction coefficient.…”