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RUD Flat connector

New size available

RUD has added to complete existing range of flat mining connectors the size 48 x 152

Superior chain link with the “super connector” makes underground conveying better and cheaper:

DOMINATOR – developed flat connector for mining applications cuts down wear – Number 1 in dynamic strength.

If you do not like technical jargon but still appreciate qualified information on further developments, please read on:

flat connector We refer to chain conveyors for underground applications and in particular to the connector elements required by them. RUD has already taken a decisive step in their development with its flat mining connector which has proved successful in worldwide use. But nothing could be more obsolete than yesterday’s technology. And RUD designers have taken full account of the fact that demands on the dynamic strength of flat connectors in mining applications are constantly rising – quite simply because of the higher capacity that can be achieved!
There are various ways of enhancing the fatigue strength of components for a finite period in engineering applications. The most effective technique is work hardening, i.e. the application of residual pressure stresses to surface areas that are in danger of cracking.

DOMINATOR

Higher dynamic strength through RUD work hardening.
The dynamic strength criterion for flat connectors in mining applications is constantly rising as performance is enhanced. Various engineering techniques are available to increase the fatigue strength of components. Work hardening is one of the most effective, i.e. the application of residual pressure stresses to surface areas that are in danger of cracking.

Surface hardening to prevent cracking
Cracks generally originate from notches close to the surface (points which interrupt the flow of energy) that are exposed to normal tension stresses. The simplest solution is to design the component to allow for dynamic load considerations. However, there are requirement-related transitions which have to be “defused” by other methods. For the work hardening of components that are in danger of cracking and hard rolling (crankshafts) are known. At RUD, a residual pressure stress area is generated using a special tool on flat connectors for mining use.

Residual pressure stress area reduces normal tension stress.
By work hardening of the notch base, a residual natural pressure stress area σD is established in the coldforming range. The depth effect is many times higher than when other work hardening methods are used.
A possible crack can only develop or be propagated if an external normal tension stress is applied to the component and develops a particular magnitude. The crack will always run vertical to this normal tension.

The stable residual pressure tension zone σD built up by hardening is superimposed on the normal tension stress σZ applied from the outside and reduces it to the resulting tension σR. Depending on the magnitude of the residual pressure stresses, an incipient crack can be prevented or its occurrence or advance retarded. The main work hardening parameters are determined by the material and geometry.
They are the hardening force, tool shape and nature of the impressions.

Longer service life
The effectiveness of the technique was confirmed and brought to readiness for series production in extensive laboratory and practical tests. In fatigue tests with hardened notch samples and chain connectors, load cycle numbers were achieved which were 100 % or more better than the values for unhardened samples. The load cycle numbers of conventional RUD mining chain connectors have always been twice as high as the values stipulated in DIN 22258.

Load cycle numbers
σo = 250 N/mm2                 σu = 50 N/mm2

pursuant to DIN 22258

min. 40.000

RUD-standard

min. 90.000

RUD-DOMINATOR up to size 38

min. 150.000

Size 42 + 48

min. 100.000

SUMMARY
The technique developed by RUD research and applied to series production is based on a mode of action which is already known in engineering, but has seldom been used previously. The greatly extended service life, as compared with untreated components or treated using other methods, justifies the use of this technique. In addition, this method is an economical alternative to the habitual techniques.