Hollow component

A manufacturing method predominately used by the thermoplastic industry for the manufacture of hollow components, also used for thermosetting rubber. The polymer is forced against the inside of the mould surface by gas pressure applied either by a hollow needle or by the decomposition of a blowing agent. 

The most spectacular application example to date is perhaps the Aberfeldy footbridge over the river Tay in Scotland (see Fig. 11.4). This bridge is 113-m long, has a deck width of 2.2 m, and a main span of 113 m [4]. The entire deck structure, hand rails, and A-frame towers are pultruded composites, and the cable stays are Kevlar ropes. The deck structure is assembled from a modular system of pultruded 6-m long, hollow components, which consist of 70 percent by weight of E glass and 30 percent pigmented isophtalic polyester resin. 

Moulding processes for solid, hollow components and containers include the following conventional processes ... 

Different materials can be used for bladders, giving larger, equal, or smaller diameter than the largest diameter of the hollow component. These can be fixed (polyolefins) or flexible (silicones) and an auxiliary core can be used to pre-drape the reinforcement. It is possible to match the possible variations to each specific molding project. IKV tested a number of options in transparent (polymethyl methacrylate) molds, looking also at lost core systems, in which the bladder or core remains in the hollow molding, and possibilities of automation. 

Gas injection, in which after introduction of some polymer into the mold, a charge of inert gas is introduced to force the polymer to the extremities of the mold and so produce a hollow component in the areas penetrated by the gas. 

The manufacture of hollow components can be done with the aid of different processing procedures depending on the component geometry. Here, the aforementioned mold concepts and mold requirements for vacuum and pressure-assisted processes can also retain their validity. New mold requirements arise for the manufacture of the hollow space in the component. 

The autofrettage process, which can be described as a self-shrinking process, provides beneficial compressive hoop stresses at the bore of hollow component, for example, a tube. 

The autofrettage process, which can be described as a self-shrinking process, provides beneficial compressive hoop stresses at the bore of hollow component, for example, a tube, and prolongs their fatigue lifetime, where fatigue life refers to the number of the allowed design cycles by the code or the number of cycles to initiate first cracks. 

In general, hollow components with apertures smaller in diameter than the body are made by blow moulding (either extrusion or injection blow moulding) although it is possible, in the case of objects having a circular cross-section at some point, for them to be injection moulded in two halves and then joined by spin welding (see Fig. 2). Such a method is sometimes used if particularly good control of wall thickness is necessary. 

No. 4,732,478, discloses a streamlined wheel for bicycles which comprises two hollow half shells which are joined to create a rim for support of a tire. Imao et al, U.S. Pat. No. 4,729,605, and Viellard, U.S. Pat. No. 4,741,578, discloses spokes and wheel components useful in composite wheels. 

Transfer matrix calculations of the adsorbate chemical potential have been done for up to four sites (ontop, bridge, hollow, etc.) or four states per unit cell, and for 2-, 3-, and 4-body interactions up to fifth neighbor on primitive lattices. Here the various states can correspond to quite different physical systems. Thus a 3-state, 1-site system may be a two-component adsorbate, e.g., atoms and their diatomic molecules on the surface, for which the occupations on a site are no particles, an atom, or a molecule. On the other hand, the three states could correspond to a molecular species with two bond orientations, perpendicular and tilted, with respect to the surface. An -state system could also be an ( - 1) layer system with ontop stacking. The construction of the transfer matrices and associated numerical procedures are essentially the same for these systems, and such calculations are done routinely [33]. If there are two or more non-reacting (but interacting) species on the surface then the partial coverages depend on the chemical potentials specified for each species. 

The initial configuration is set up by building the field 0(r) for a unit cell first on a small cubic lattice, A = 3 or 5, analogously to a two-component, AB, molecular crystal. The value of the field 0(r) = at the point r = (f, 7, k)h on the lattice is set to 1 if, in the molecular crystal, an atom A is in this place if there is an atom B, 0, is set to —1 if there is an empty place, j is set to 0. Fig. 2 shows the initial configuration used to build the field 0(r) for the simple cubic-phase unit cell. Filled black circles represent atoms of type A and hollow circles represent atoms of type B. In this case all sites are occupied by atoms A or B. 

A snap can be characterized by the geometry of its spring component. The most common snaps are the cantilever type, the hollow-cylinder type (as in the lids of pill bottles) and the distortion type (Fig. 4-15). These snaps include those in any shape that is deformed or deflected to pass over interference. The shapes of the mating parts in a hollow cylinder snap is the same, but the shapes of the mating parts in a distortion snap are different, by definition. These classifications are rather nominal, because the cantilever category is used loosely to include any leaf-spring components, and the cylinder type is used also to include noncircular section tubes. 

Process used provides different control capabilities. As an example closed molding (injection, compression, etc.) provides fine detail on all surfaces. Open molding (blow molding, thermoforming, spray-up, etc.) provides detail only on the one side in contact with the mold, leaving the second side free-formed. Continuous production (extrusion and pultrusion) yields products of continuous length. Hollow (rotational or blow) produces hollow products. These processes can be used creatively to make different types of products. For example, two molded or thermo-formed components can be bonded together to form a hollow product, or they can be blow molded. 

Fig. 12 Expandable microwave vessel. Components I Luer-lock cap 2 piston 3 hollow bore 4 reaction chamber 5 frit 6 product outlet 7 Luer-lock cap...

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