Solidification of thermoviscoelastic melts. Part I: Formulation of model problem

The solidification of a molten layer of amorphous thermoplastic between cooled parallel plates is used to model the mechanics of part shrinkage and warpage and the buildup of residual stresses in the injection molding process. Flow effects are neglected, and a thermorheologically simple thermoviscoelastic material model is assumed. The equilibrium thermomechanical properties of the material and the shift function can be temperature- and pressure-dependent. The model allows material to be added to fill the space created by the packing pressure applied during solidification; therefore, this model can be used to assess packing-pressure effects in injection molding. The model also accounts for freeze-off effects in which the cavity pressure is controlled by the solidification process and must therefore be determined as a part of the solution.

[1]  H. Leaderman.  CHAPTER 1 – VISCOELASTICITY PHENOMENA IN AMORPHOUS HIGH POLYMERIC SYSTEMS , 1958 .

[2]  Calculation of Residual Thermal Stresses in Injection Molded Amorphous Polymers by the Finite Element Method , 1976 .

[3]  G. Adam,et al.  On the Temperature Dependence of Cooperative Relaxation Properties in Glass‐Forming Liquids , 1965 .

[4]  A. Isayev,et al.  Volumetric effects in the injection molding of polymers , 1985 .

[5]  R. Landel,et al.  Equations of state and constitutive equations , 1986 .

[6]  The effect of a temperature gradient on residual stresses and distortion in injection moldings , 1984 .

[7]  R. G. Treuting,et al.  A Mechanical Determination of Biaxial Residual Stress in Sheet Materials , 1951 .

[8]  L. Struik.  Orientation effects and cooling stresses in amorphous polymers , 1978 .

[9]  Marcel Crochet,et al.  Thermoviscoelastic Calculation of Residual Stresses and Residual Shapes of Injection Molded Parts** , 1992 .

[10]  Vijay K. Stokes,et al.  Solidification of thermoviscoelastic melts. Part 4: Effects of boundary conditions on shrinkage and residual stresses , 1995 .

[11]  H. G. Landau,et al.  Thermal Stress in a Viscoelastic-Plastic Plate With Temperature-Dependent Yield Stress , 1960 .

[12]  J. M. Caruthers,et al.  A predictive model for the effects of thermal history on the mechanical behavior of amorphous polymers , 1990 .

[13]  E. Sternberg,et al.  On Transient Thermal Stresses in Viscoelastic Materials With Temperature-Dependent Properties , 1961 .

[14]  A. J. Staverman,et al.  Time‐Temperature Dependence of Linear Viscoelastic Behavior , 1952 .

[15]  F. Schwarzl,et al.  Thermal contraction and volume relaxation of amorphous polymers , 1984 .

[16]  J. R. White,et al.  Effect of injection pressure and crazing on internal stresses in injection-moulded polystyrene , 1980 .

[17]  T. G. Rogers,et al.  Solution of Viscoelastic Stress Analysis Problems Using Measured Creep or Relaxation Functions , 1963 .