Analytical Modeling of Strain Rate Distribution During Friction Stir Processing

Abstract

Friction Stir Processing (FSP) is becoming an acceptable technique for modifying the grain structure of sheet metals. One of the most important issues that hinder the widespread use of FSP is the lack of accurate models that can predict the resulting microstructure in terms of process parameters. Most of the work that has been done in the FSP field is experimental, and limited modeling activities have been conducted. In this work, an analytical model is presented that can predict the strain rate distribution and the deformation zone in the friction stir processed zone as a function of process parameters. In the model, the velocity fields within the processed zone are determined by incorporating the effects of both the shoulder and the pin of the tool on the material flow. This is achieved by introducing state variables and weight functions. The model also accounts for different interfacial conditions between the tool and the material. The effects of different process parameters and conditions on the velocity fields and strain rate distributions are discussed. The results clearly show that the model can successfully predict the shape of the deformation zone and that the predicted strain rate values are in good agreement with results reported in the literature.

A review of microstructural changes occurring during FSW in aluminium alloys and their modelling

“…The overall velocity field is consequently written as a summation of weight velocity functions imposed respectively by shoulder ( ( ) ) and pin ( ( ) ). This model follows the approach originally proposed by Darras and Khraisheh (2008). The CA approach is initially based on an original microstructure.…”

Sustainable and green manufacturing and materials design through computations

“…Darras and Khraisheh predicted the velocity fields and effective strain rate using the analytical models incorporating the effects of shoulder and pin on the material flow. 77 The influence of welding speed and rotational speed on the velocity and strain-rate distribution were also studied. In Buffa et al's study, the effect of varying pin geometries and welding speeds on the material flow and grain size is studied through a thermo-mechanically coupled, rigid-viscoplastic, 3D finite element analysis.…”

CAFE modeling, neural network modeling, and experimental investigation of friction stir welding

“…The temperature and strain rate values obtained from the above described models are used as input to the cellular automata cells integrated to each integration point of finite elements containing initial grain size of base metal obtained from experiments. The initial grain size will be converted into final grain size as per equation ( 5) in each CA cells and from equation (6), the average element level grain size can be evaluated. For the same FSW conditions, the grain size was measured experimentally in the weld region and compared for validation.…”

“…The strains and strain rates developed along the welding directions were predicted. Darras and Khraisheh 6 predicted the velocity fields and effective strain rate using the analytical models incorporating the effects of shoulder and pin on the material flow. The influence of welding speed and rotational speed on the velocity and strain-rate distribution were also studied.…”