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The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Annealing Work
With the exception of several of the higher types of alloy s...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

The Modern Hardening Room
A hardening room of today means a very different place from ...

Chromium
Chromium when alloyed with steel, has the characteristic func...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Drop Forging Dies
The kind of steel used in the die of course influences the he...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...



Fatigue Tests






Category: COMPOSITION AND PROPERTIES OF STEEL

It has been known for fifty years that a beam or rod would fail
at a relatively low stress if only repeated often enough. It has
been found, however, that each material possesses a limiting stress,
or endurance limit, within which it is safe, no matter how often
the loading occurs. That limiting stress for all steels so far
investigated causes fracture below 10 million reversals. In other
words, a steel which will not break before 10,000,000 reversals
can confidently be expected to endure 100,000,000, and doubtless
into the billions.

About the only way to test one piece such a large number of times
is to fashion it into a beam, load it, and then turn the beam in
its supports. Thus the stress in the outer fibers of the bar varies
from a maximum stretch through zero to a maximum compression, and
back again. A simple machine of this sort is shown in Fig. 10,
where B and E are bearings, A the test piece, turned slightly
down in the center, C and D ball bearings supporting a load
W. K is a pulley for driving the machine and N is a counter.





Next: Hardness Testing

Previous: Impact Tests



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