Viscoelastic material characterization and modeling for polyethylene

1990 ◽  
Vol 30 (10) ◽  
pp. 577-586 ◽  
Author(s):  
C. F. Popelar ◽  
C. H. Popelar ◽  
V. H. Kenner
Keyword(s):  
Viscoelastic Material ◽  
Material Characterization ◽  
Viscoelastic Material Characterization

scholarly journals Viscoelastic Material Characterization: A Realistic Approach to Stress Analysis

2021 ◽  
pp. 119-128
Author(s):  
Amor Zapanta ◽  
Jefferson Talledo
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Material Characterization ◽  
Time History ◽  
Thermal Conditions ◽  
Slow Cool ◽  
Test Sample ◽  
Compound Material ◽  
Semiconductor Packages ◽  
Viscoelastic Material Characterization

This paper presents an advanced method in materials characterization for the mold compound material in semiconductor packages to build models that can technically explain the actual warpage or stress observations under different thermal conditions and time history. In the study, the mold compound material characterization was conducted using Dynamic Mechanical Analyzer (DMA) followed by curve fitting to obtain parameters for the computer modeling input requirement. Thermo-mechanical modeling using viscoelastic material properties was conducted on a bi-material test sample model. Results showed that the new characterized viscoelastic material properties exhibited dependence on time and temperature. Slow cool down from post mold cure (PMC) to room temperature resulted in lower warpage or stress. This observed rate dependent response was explained using viscoelastic material properties in contrast to the usual linear elastic material simplification. Thus, a realistic result from stress or warpage analysis could be achieved using viscoelastic material characterization.

Uniaxial Wave Propagation in a Viscoelastic Material Using Measured Material Properties

1968 ◽  
Vol 35 (3) ◽  
pp. 449-453 ◽  
Author(s):  
W. G. Knauss
Keyword(s):  
Wave Propagation ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Material Characterization ◽  
Wave Speed ◽  
Initial Temperature ◽  
Initial Step ◽  
Shift Factor ◽  
Temperature Dependent ◽  
The Difference

The dynamic response of a long viscoelastic bar due to a step displacement at the end is considered. Neglecting geometric dispersion, the effect of realistic viscoelastic material properties is studied theoretically. The solution is obtained in the form of a Fourier sine integral, the convergence of which is studied numerically by piecewise integration to produce an alternating series. It is found that the initial step wave propagates with a high velocity corresponding to the glassy modulus of the material and its amplitude decays with time and distance along the rod. From a practical viewpoint the wave front may decay to immeasurable proportions and any measurable disturbance appears to travel thereafter, with a velocity which is smaller than the glassy wave speed. The effect of initial temperature is discussed. It is shown for thermorheologically simple materials that both the time and spatial variable are scaled by the same temperature dependent (shift) factor. As a consequence, the difference of wave propagation in hard and viscoelastic polymers is illustrated. It is also shown that limited material characterization is sufficient for certain dynamic problems. Comparison of the exact solution with two approximations is made.

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