There is no old definition.
(new)
These types of dies can be designed for single or for double-action
presses. In (he first case, the blank holder gels its power from a mechanism
located below the bed of the press.
Fig. 11.10 shows a die for
a drawing operation on a single-action press.
The
die in Fig. 11.10 consists of the upper shoe (2) and lower shoe (9), with guide
posts (7). The die ring (3) and ejector (5) are attached to the upper shoe. The
punch (4), the pressure pad (6), and the cushion pin (8) arc attached to the
lower shoe. A workpiccc with a flange that has been previously drawn, is
inserted between the clastic stop pins (10), which are inserted in the pressure
pad. The punch is vented to aid in stripping the workpiccc from the punch.
(Vukota Boljanovic, Sheet Metal Forming Processes and Die Design,page 158)
This type of die performs a single operation
on a part at every stroke of the press. It may be a pierce, blank, form, or
draw operation or a combination of these. A single operation die may or may not
produce the part complete. It may take a series of single operation dies to
produce the part complete. Single operation dies may be used for low quantity
production or if the part is too large. These are typical applications.
The
cost of this type of die is about the same as a progressive die because the
operations or dies needed is the same. Usually, the speed or production rate is
limited or slow because the die is hand fed or roboticaly fed, both of which
require time.
All
of the tools mentioned above can perform various operations such as draw
forming and blanking. The multi-slide tooling is the only one limited to
forming operations. You can also have combination type tools such as a
progressive compound die.
(Jim Szumera,James A. Szumera,The Metal Stamping Process: Your Product from Concept to Customer,page 33)
2) SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS (SHS) (Group: Energy-saving technologie)
There is no old definition.
(new)
(new)
Development
of efficient and energy-saving technologies is of great importance today.
Self-propagating high-tempera hi re synthesis (SHS) or combustion synthesis is
a relatively novel and simple method for making certain advanced ceramic,
composites, and intermetallic compounds (Fig. 2.8). This method has received
considerable attention as an alternative to conventional furnace technology
[61—65J.
The
SHS or combustion synthesis approach uses highly exothermic reactions. Such
reactions typically have high activation energies and generate a substantia)
amount of heat. Once the reactions are initiated, to render self-sustaining
reactions and to form a combustion wave, the
temperature of the combustion can be very high (as 5000 K) and the rate of wave
propagation can be very rapid (as 25cm/s). This process offers an opportunity
to investigate reactions in extreme thermal gradients (as 105 K/cm)
conditions.
Reactions
between particulate materials are an alternative way lo produce various types
of materials considering the extreme simplicity of the process, relatively low
energy requirement, high purity of the products obtained, the possibility to
obtain metastable phases, and the possibility of simultaneous synthesis and
densi-fication. Higher purity of products is the consequence of high
temperature associated with the combustion. Volatile impurities are expelled
as the wave propagates through the sample. The possibility of forming metastable
phases is based on high thermal gradients and rapid cooling rate associated
with the reaction.
Two
approaches are being used in SHS technology. The first approach is the
production of intermediate products, which are then used as raw materials in
further processing; the second one is based on direct
Actually
over 500 compounds have been synthesized bv the SHS method. Some of these
materials are listed in Table 2.6.
(Ruren Xu,Wenqin Pang,Qisheng Huo,Modern Inorganic Synthetic Chemistry,page 24)
3) Silicates (Group: Material)
There is no old definition.
(new)
Silicate
minerals are those minerals that contain |Si04J ' as the fundamental
unit of their chemistry and structure. Any other chemical element may occur in
silicate minerals. |Si04)~l is a tetrahedron containing
the four oxygen atoms in the apices and thcsilicium atom in the center. Up to
all four oxygen atoms may be shared
with other tetrahedrons. The number of shared oxygen atoms and the final space
distribution are used to classify the silicate minerals.
Despite
the lact that silicate minerals may accommodate any chemical element in their
structures, the most common elements found are Al, Mg, Fe, Ca. Na, and K. Al is a common substitute for Si in the silica
tetrahedron. Table I shows the classification of silicates* including their
basic tetrahedral structure and most common minerals.
Transition Zone are largely composed of the
following Ca-, Mg-, Fe-bearing silicate minerals; olivine [(Mg, FeJ2SiO.1l, pyroxene (see above), and garnet |(Ca, Mg, Fe))(Al, Fe, Cr,
Ti)>SiiOi<]. Chemical elements inside parenthesis in the chemical
formulas occupy the same structural site and may vary in proportion one to
another in a replacement process. Whenever valences are different, a conjugate
elemental substitution occurs to compensate charge imbalance. The chemical
element substitutions characterize these minerals as solid solutions. Extreme
chemical compositions are called "end members." Each end member has a
specific name, as for example "diop-side" lor the pyroxene end member
CaMgSi20.
( Muriel Gargaud, Encyclopedia of Astrobiology, 1. cilt,2011,page:1511)
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