The paper shows a method to determine parameters of rheological constitutive models for powder injection moulding.
Numerical simulations are a very important feature of the beginning of any product or technology development. It requires also accurate constitutive models describing material behaviour at large shear rates. The choice of a rheological model and the determination of its parameters should be made from tests generating such conditions.
To identify rheological constitutive model of feedstocks, one generalized constitutive law is applied. The three binders prepared during the course of this research were blends of polypropylene (PP), Polyethylene glycol (PEG) and a Paraffin wax (PW). The powdered metal in the feedstocks was Inconel.
The thermal characterization of binders, polymers and feedstocks included differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Thus, a glass transition, melting and degradation temperatures of each components of the binder were defined by differential scanning calorimeter (DSC). Then, a thermogravimetric analysis (TGA) was conducted under inert atmospheric conditions. The samples were heated over a range of temperature from 25°C to 500°C. These TGA scans allow inspecting the homogeneity of feedstock after mixing.
The rheological properties of the resulting binder formulations and feedstocks were characterized by a capillary rheometer.
Then, comparisons are carried out between the experimental results and those for analytical models. Thus, several were used such as power law, Williams-Landel-Ferry, Arrhenius, Chong and Carreau-Yasuda. In the wake of this comparison, identification of parameters using in models were performed.