Plastic materials formulas

With use of model of an ideal plastic material formulas for calculation of tension of drawing, definition of optimum geometry of the channel of the drawing tool and extent of plastic deformation are received when drawing continuous profiles of not round cross section. 

Poly(vinyl chloride) as previously discussed in Sec. 10.3, Formulas and Key Properties of Plastic Materials, has the following structures ... 

An extensive new Section 10 is devoted to polymers, rubbers, fats, oils, and waxes. A discussion of polymers and rubbers is followed by the formulas and key properties of plastic materials. Eor each member and type of the plastic families there is a tabulation of their physical, electrical, mechanical, and thermal properties and characteristics. A similar treatment is accorded the various types of rubber materials. Chemical resistance and gas permeability constants are also given for rubbers and plastics. The section concludes with various constants of fats, oils, and waxes. 

Today there are between 45 and 50 plastic materials. Physical volume, averaging a 13% per year growth rate for the past ten years, reached an estimated 16 billion pounds in 1968, higher than that of any metal except iron and steel, and approaching the total for non-ferrous metals. The number of formulas, grades, and types of these materials is greatly expanded by the use of plasticizers, fillers, and polymerization alternatives. All of these formulations are presumably different from one another and offer the user a broad material selection to fit his property and cost requirements. 

A new ASME code for calculating high pressure vessels (Sect VIII Div. 3) is based on the formulae to determine the internal pressure pcompi-pi for complete plastic yielding through the full wall with some assumptions, e.g. perfectly elastic-plastic material behavior and the GE-hypothesis [2]. 

To pursue the goal of obtaining a simple formula for the estimation of DB which does not rely on experimental diffusion data, reference Eq. (6-20) for all plastic materials was developed (Brandsch et al. 1999). The theoretical assumptions for this equation are given in Chapter 6. Following the approach treated in Chapter 6 a refined equation for DP resulted ... 

A rule of thumb formula for calculating cooling is given in greater detail in Lesson 7.5. The formula employs variables of the melt temperature, wall temperature, demolding temperature, as well as the plastic material s thermal... 

Reactions (9.46) and (9.47) lead to highly polymeric plastic material which probably has the formula indicated. 

It is an unfortunate fact that many students and indeed design engineers are reluctant to get involved with plastics because they have an image of complicated materials with structures described by complex chemical formulae. In fact it is not necessary to have a detailed knowledge of the structure of plastics in order to make good use of them. Perfectly acceptable designs are achieved provided one is familiar with their perfonnance characteristics in relation to the proposed service conditions. An awareness of the structure of plastics can assist in understanding why they exhibit a time-dependent response to an applied force, why acrylic is transparent and stiff whereas polyethylene is opaque and flexible, etc., but it is not necessary for one to be an expert... 

One way of looking at the fracture characteristics of a ductile material is by measuring the amount of plasticity at a crack tip prior to crack propagation (Fig. 8.84). One test which measures this is the crack-tip opening displacement (CTOD), 5. Wells has found that 6 can be related to the strain energy release rate, G, by the formula ... 

In computing ordinary short-term characteristics of plastics, the standard stress analysis formulas may be used. For predicting creep and stress-rupture behavior, the method will vary according to circumstances. In viscoelastic materials, relaxation data can be used in Eqs. 2-16 to 2-20 to predict creep deformations. In other cases the rate theory may be used. 

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