Ratio axial stretch

In film blowing, a tubular film is extruded upwards. It is blown upwards, with air introduced below the die, into a larger tubular film which is then picked up by a pair of nip rolls that seals the bubble (Fig. 3.11 Han, 2007). An external stream of chilled air cools and solidifies the film at a certain point called the freeze line, where the temperature of the film is equal to the melting temperature. A feature of this process is that the film is stretched biaxially, improving mechanical properties. Tangential circumferential stretching depends on blow-np ratio, i.e. the ratio between the tubular film diameter after air introduction and the initial tabular film diameter. This parameter is determined by the pressure level within the bubble. Axial stretching depends... 

The derivatives of with respect to t and Z, evaluated at the center line r = R = 0 are called the (axial) velocity and the (axial) stretch ratio they will here be denoted by v and 1. In the material description these quantities are considered functions of Z and t, i.e.. 

In stretch blow molding, there are two ratios that multiply together to provide the blow up ratio BUR. In extrusion blow molding, there is only the hoop ratio (that is the blow-up ratio). In stretch blow molding there is the hoop that is multiplied by the axial ratio. Thus, BUR = Hoop ratio x axial ratio. 

The aodal ratio is also very important as this provides vertical strength, material distribution, improved barrier, and allows for raw material savings. Usually, the axial ratio should be at least 1.7 with greater than 2 preferred. The aodal ratio is defined as the axial length (Ai) where the actual axial stretch is initiated in the preform measured to the inside bottom of the bottle to be produced divided by the axial length (A2) of the preform as it is measured from the point where stretching is initiated to the inside bottom of the preform. 

Results confirm that truncated conical shapes are formed under plane strain conditions while truncated pyramidal shapes are obtained under bi-axial stretching in the corners and plane-strain conditions in the side walls. It is worth noting that the experimental values of fracture strains for the pyramids are not placed on the equal bi-axial strain ratio line with slope +1 in the principal strain space. In fact, although the onset of failure is located at corners of the pyramids, the values of fracture strains are somewhat deviating towards the plane strain direction. This also explains the existence of different values of fracture strains plotted at various locations of the first quadrant of the principal strain space. 

Each of fee aforementioned materials also has its own stretch ratios. In order to understand stretch blow molding it is necessary to understand the terms orientation temperature, blow pressure, blow-up ratio, axial ratio, hoop ratio, and stretch ratios. 

Note that the ratio of the ratio of the hoop stress (pR/h) to the axial stress (pR/lh) is only 2. From the data in this question the hoop stress will be 8.12 MN/m. A plastic cylinder or pipe is an interesting situation in that it is an example of creep under biaxial stresses. The material is being stretched in the hoop direction by a stress of 8.12 MN/m but the strain in this direction is restricted by the perpendicular axial stress of 0.5(8.12) MN/m. Reference to any solid mechanics text will show that this situation is normally dealt with by calculating an equivalent stress, Og. For a cylinder under pressure Og is given by 0.5hoop stress. This would permit the above question to be solved using the method outlined earlier. 

It is also well known that there exist different extinction modes in the presence of radiative heat loss (RHL) from the stretched premixed flame (e.g.. Refs. [8-13]). When RHL is included, the radiative flames can behave differently from the adiabatic ones, both qualitatively and quantitatively. Figure 6.3.1 shows the computed maximum flame temperature as a function of the stretch rate xfor lean counterflow methane/air flames of equivalence ratio (j) = 0.455, with and without RHL. The stretch rate in this case is defined as the negative maximum of the local axial-velocity gradient ahead of the thermal mixing layer. For the lean methane/air flames,... 

The Poisson ratio can be best described as the material s ability to contract in one direction when stretched in another. If we take one direction as axial and another as transverse, then... 

As discussed in Section 5.4, the colloidal spheres can be stretched to form nonspherical colloids such as ellipsoidal colloids by Ar" laser irradiation. The array of the ellipsoidal colloids is obtained by exposing the colloidal sphere array to a polarized Ar laser beam for 10 min. The films with elliptical pores can be obtained from the array of the ellipsoidal colloids after the same annealing treatment. Figure 5.25 shows the SEM images of the array of the ellipsoidal colloids and the corresponding porous film formed from the structure inversion. The average axial ratio of the colloids and pores are 1.46 and 1.25. The smaller axial ratio for the pores could be attributed to the stress relaxation occurring in the structure inversion process. 

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