عنوان

Viscoelastic modeling of injection molding of thermoplastics

شماره

TLpq303812876

زبان متن نوشتاري يا گفتاري و مانند آن

انگلیسی

عنوان اصلي

Viscoelastic modeling of injection molding of thermoplastics

نام عام مواد

[Thesis]

نام نخستين پديدآور

N. M. H. Famili

نام ناشر، پخش کننده و غيره

The University of Akron

تاریخ نشرو بخش و غیره

1990

نام خاص و کميت اثر

305

جزئيات پايان نامه و نوع درجه آن

Ph.D.

کسي که مدرک را اعطا کرده

The University of Akron

امتياز متن

1990

متن يادداشت

Numerical and experimental investigations of two-dimensional, nonisothermal injection of an amorphous viscoelastic melt (polystyrene) were performed. The numerical investigation was initiated by simulation of nonisothermal extrusion into a slit die. It was expanded by the modeling of nonisothermal flow of viscoelastic melt during filling of a center-gated disk and a strip cavity and the relaxation of the stresses during the cooling stage after the cessation of the flow into the strip cavity. These simulations were performed employing Leonov's viscoelastic constitutive equation. Time and spatial development of velocity, shear rate, shear and normal stresses and birefringence was calculated and the thickness of the thermal boundary layer was analyzed. In particular, the thickness of this layer was determined based on the gapwise position of the birefringence maximum and the glass transition temperature. It was found, that the layer calculated based on the birefringence maximum is thicker than the one based on Tg. The viability of the numerical simulations were checked employing a set of experimental procedures based on the rheo-optical characteristics of the polymer. In these studies the dynamic field was related to the birefringence through linear stress-optical law. In the first series of experiments, on-line birefringence was measured for various combinations of wall and melt temperatures at different flow rates. It was found that due to the mirage effect caused by the unsteady thermal diffusivity field during the flow, the experiments could not be performed at low wall temperatures. In these series of experiments, although various qualitative analyses were performed, no quantitative comparison with the theory was obtained. In the second series of experiments, residual birefringence in the part after the nonisothermal flow and relaxation was measured. It was assumed that the residual thermal stresses could be removed without affecting the flow stresses, by a slow annealing at the glass transition temperature. At low wall temperature good agreements between the experiments and the predicted results were obtained. At the wall temperature close to the glass transition temperature the experimental and the predicted results did not compare well indicating a more complex relationship between the thermal and flow residual stresses.

موضوع مستند نشده

Applied sciences

موضوع مستند نشده

Industrial engineering

موضوع مستند نشده

Materials science

موضوع مستند نشده

Materials science

موضوع مستند نشده

Plastics

مستند نام اشخاص تاييد نشده

N. M. H. Famili

نام الکترونيکي

فرمت انتشار

p

نوع ماده

[Thesis]

کد کاربرگه

276903

سطح دسترسي

a

تكميل شده

Y