≪ View Page

Unterschiede

Hier werden die Unterschiede zwischen zwei Versionen angezeigt.

Link zu dieser Vergleichsansicht

Beide Seiten der vorigen RevisionVorhergehende Überarbeitung
Nächste Überarbeitung		Vorhergehende Überarbeitung
en:materialdaten:reine_polymere_uebersicht:rheologische_materialdaten [2025/05/27 12:58] – deppe2en:materialdaten:reine_polymere_uebersicht:rheologische_materialdaten [2026/01/10 20:23] (aktuell) – neelest
Zeile 4: Zeile 4:
 ===== Rheological Data ===== ===== Rheological Data =====
  
-**Path:** Main menu > Material > New polymer... Tab: Rheological data+**Path:** Main menu > Material > New polymer... Tab: Rheological data\\ 
 +{{:materialdaten:reine_polymere_uebersicht:iconmaterialnew-material.ico?nolink&60x60 |}} 
 +\\ 
 +\\ 
 +\\ 
 +**Path:** Main menu > Material > Edit material (file)... Tab: Rheological data\\ 
 +{{:materialdaten:reine_polymere_uebersicht:iconmaterialedit-material.ico?nolink&60x60 |}} 
 +\\ 
 +\\ 
 +\\ 
 +{{ :en:materialdaten:reine_polymere_uebersicht:en_sigma150_dlg_materialdaten_008.png?nolink |}}
  
- +Fluids can be divided into two groups regarding to their flow characteristics:
- +
-**Path:** Main menu > Material > Edit material (file)... Tab: Rheological data +
- +
- +
- +
- +
- +
-**Figure:** Dialog box Rheological data +
- +
-  +
- +
-Fluids can be divided into two groups regarding to their flow characteristics (see figure):+
  
   * Newtonian fluids   * Newtonian fluids
Zeile 24: Zeile 22:
  
 The following law is valid for Newtonian fluids: The following law is valid for Newtonian fluids:
 +
 $$\tau = \eta \cdot \dot{\gamma}$$ $$\tau = \eta \cdot \dot{\gamma}$$
- 
  
 with shear stress τ, viscosity η and shear rate γ̇. This law states that the shear stress and shear rate are proportional to each other, with the viscosity being the proportionality factor. In the case of polymeric fluids, or melts, this flow behavior only occurs at very low shear rates and, in some cases, at very high ones. Deviations are manifested in so-called pseudo plasticity, dilatancy or the presence of a yield point. with shear stress τ, viscosity η and shear rate γ̇. This law states that the shear stress and shear rate are proportional to each other, with the viscosity being the proportionality factor. In the case of polymeric fluids, or melts, this flow behavior only occurs at very low shear rates and, in some cases, at very high ones. Deviations are manifested in so-called pseudo plasticity, dilatancy or the presence of a yield point.
Zeile 31: Zeile 29:
 In the shear rate ranges that prevail in practice, the flow behavior of polymer melts is characterized as pseudo plastic. This describes a flow behavior which deviates from that of Newtonian fluids, where the viscosity is no longer constant but highly dependent on the shear rate. In the shear rate ranges that prevail in practice, the flow behavior of polymer melts is characterized as pseudo plastic. This describes a flow behavior which deviates from that of Newtonian fluids, where the viscosity is no longer constant but highly dependent on the shear rate.
  
 +{{ :en:materialdaten:reine_polymere_uebersicht:en_sigma150_dlg_materialdaten_009.svg?nolink&700 |}}
  
 +The figure shows the basic viscosity profile as a function of the shear rate. Where the shear rate range is not too large, it is possible to describe this behavior by the empirical power law according to OSTWALD and DE WAELE:
  
-**Figure:** Material properties 
- 
-  
- 
-The figure shows the basic viscosity profile as a function of the shear rate. Where the shear rate range is not too large, it is possible to describe this behavior by the empirical power law according to OSTWALD and DE WAELE: 
 $$\eta = K \cdot \dot{\gamma}^{n-1}$$ $$\eta = K \cdot \dot{\gamma}^{n-1}$$
  
- +here n is the exponent of the power law and K the power law coefficient. The simple structure of this equation means that almost all flow problems that can be solved for Newtonian fluids can be treated analytically. A straight line is also obtained for the power law when plotted on a double-logarithmic scale. As can be seen from the figure, a corresponding exponent n must be calculated for different curve segments. The flow coefficient K is described by:
-here n is the exponent of the power law and K the power law coefficient. The simple structure of this equation means that almost all flow problems that can be solved for Newtonian fluids can be treated analytically. A straight line is also obtained for the power law when plotted on a double-logarithmic scale. As can be seen from the figure, a corresponding exponent n must be calculated for different curve segments. +
- +
-A formulation derived from the purely thermally activated process (Arrhenius law) has proved successfully for describing the temperature dependence of the viscosity with the aid of the power law coefficient.+
  
 $$K = K_0,T \cdot e^{-\beta(T - T_0)}$$ $$K = K_0,T \cdot e^{-\beta(T - T_0)}$$
  
 +Constant $K_{0,T}$ corresponds to the viscosity at a shear rate of γ̇ and the reference temperature $T_0 = 0°C$ describes the temperature dependence of the viscosity.
  
-Constant $K_{0,T}$ corresponds to the viscosity at a shear rate of   and the reference temperature $T_0 = 0°C$ describes the temperature dependence of the viscosity.+{{ :en:materialdaten:reine_polymere_uebersicht:en_sigma150_dlg_materialdaten_010.svg?nolink&700 |}}
  
- +{{ :en:materialdaten:reine_polymere_uebersicht:en_sigma150_dlg_materialdaten_011.svg?nolink&700 |}}
- +
-**Figure:** Basic viscosity function profile for a polymer +
- +
- +
- +
-  +
- +
-**Figure:** Approximation of the viscosity function in ranges with straight-line sections+
  
 The CARREAU law supplies a better description over broad areas of the viscosity function. This is particularly true for materials which display a pronounced transition from the Newtonian to the structural-viscosity range: The CARREAU law supplies a better description over broad areas of the viscosity function. This is particularly true for materials which display a pronounced transition from the Newtonian to the structural-viscosity range:
  
 +$$\eta = \frac{A}{\left[1 + (B \cdot \dot{\gamma})^C\right]}$$
  
 where $A$ is the zero viscosity, $B$ the reciprocal transitional shear rate and $C$ the gradient ($C = n-1$). where $A$ is the zero viscosity, $B$ the reciprocal transitional shear rate and $C$ the gradient ($C = n-1$).
  
- +{{ :en:materialdaten:reine_polymere_uebersicht:en_sigma150_dlg_materialdaten_012.svg?nolink&700 |}}
- +
-**Figure:** Determination of the Carreau parameters +
    
 +In addition, there are other approaches that are better suited to certain applications. These are presented in formula form below:
  
   * **Carreau Yasuda-Law:**   * **Carreau Yasuda-Law:**
Zeile 115: Zeile 98:
 T₀ = reference Temperature\\ T₀ = reference Temperature\\
  
-The Carreau law can be used for the correct description of the specific material behavior of polymers over a wide shear rate and temperature range. Given that this law is restricted in its analytically applications, from the shear rates and temperatures which prevail in the process the coefficients of the power law will be calculated in SIGMA. The input mask Rheological data gives three different options for the description of the rheological behavior of the polymer melt. In the Rheological data input mask (see figure), there are three different formulation forms to choose from for describing the rheological behavior of polymer melts. The difference of the laws is that they describe the temperature dependency of the viscosity in different ways. This distinction was introduced in order to ensure a problem-free input independent to the origin of the data (CAMPUS, BAYMAT, VISCOSITY). In case that Carreau-WLF data are taken from the BASF VISCOSITY database it is necessary to select the switch position Carreau-WLF (C1, C2). In the event of that the data are derived from BAYER BAYMAT select the Carreau-WLF (TB, TS) option. In this case SIGMA sets the two constants C1 and C2 on 8.86 and 101.6. Then they cannot be edited any longer.+The Carreau law can be used for the correct description of the specific material behavior of polymers over a wide shear rate and temperature range. Given that this law is restricted in its analytically applications, from the shear rates and temperatures which prevail in the process the coefficients of the power law will be calculated in SIGMA. The input mask Rheological data gives three different options for the description of the rheological behavior of the polymer melt. In the Rheological data input mask, there are three different formulation forms to choose from for describing the rheological behavior of polymer melts. The difference of the laws is that they describe the temperature dependency of the viscosity in different ways. This distinction was introduced in order to ensure a problem-free input independent to the origin of the data (CAMPUS, BAYMAT, VISCOSITY). In case that Carreau-WLF data are taken from the BASF VISCOSITY database it is necessary to select the switch position Carreau-WLF (C1, C2). In the event of that the data are derived from BAYER BAYMAT select the Carreau-WLF (TB, TS) option. In this case SIGMA sets the two constants C1 and C2 on 8.86 and 101.6. Then they cannot be edited any longer.