Elastic spring-back

The press temperature influences the possible press time and therefore the capacity of the production line. The minimal press time has to guarantee that the bond strength of the still hot board can withstand the internal steam pressure as well as the elastic spring back of the board when the press opens or when the board leaves the continuous press. 

Two important phenomena limit the speed of compaction and, therefore, the capacity of any pressure agglomeration equipment compressed residual gas (air) in the pores and elastic spring-back. Both cause different, equipment specific cracking and a weakening or, sometimes, total destruction of the products (see also [B.12b B.42 B.56] and Sections 8.4.1 through 8.4.3). 

Fig. 5.9 (Chapter 5) depicts in its entirety the force or pressure diagram of a typical cycle of high-pressure agglomeration as a function of time. The effect of the two phenomena that are responsible for most problems associated with this technology, expansion of compressed air and/or elastic spring back, are shown to occur after having reached and take some time. The more important changes caused by these phenomena, however, are an increase in volume and porosity (Fig. 5.9) and the potential lowering of the product s structural integrity. In the best case, they will (only) lead to reduced strength, which may be corrected by a suitable post-treatment (e.g., coating.

In spite of all these provisions and the development and maintenance of conditions for optimal deaeration and avoiding elastic spring back, the small remaining expansion may still damage the compact when it is ejected from the die. It is always a good... 

Ploughing (in Grinding), Fig. 3 Cross section of a single grain scratch to define chipping and ploughing ratio as well as elastic spring back... 

The application of an external force, although this may involve risks related to the elastic spring-back and/or cracking of the particles. 

One of the fascinating properties of the elastomeric materials is their rubber-like elasticity— that is, they have the ability to be deformed to quite large deformations and then elastically spring back to their original form. This results from crosslinks in the polymer that provide a force to restore the chains to their undeformed conformations. Elastomeric behavior was probably first observed in natural rubber however, the past several decades have brought about the synthesis of a large number of elastomers with a wide variety of properties. Typical stress-strain characteristics of elastomeric materials are displayed in Figure 15.1, curve C. Their moduli of elasticity are quite small, and, they vary with strain because the stress-strain curve is nonlinear. 

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