الفهرس 
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Abstract
Fatigue being an insidious failure mechanism since it is likely to progress unseen is almost impossible to be completely avoided. It is therefore necessary to live with deterioration of materials and struc¬to incorporate guards against premature fatigue failure In a design it is necessary to characterize fatigue resistance of.constructional materials.
The fatigue load found actually in engineering parts not a simple cyclic tension-compression load, but instead, a mixture between this cyclic load and an impact load resulting from the tolerances and clearances existing in any machine.
B~ impact fatigue we mean that the tension-compression for example, is applied theoretically at zero time or in other words the strain rate is very high.
An experimental apparatus capable of giving both the simple fatigue load and the impact fatigue load was cons¬tructed. This apparatus actuates on the principle of Hopkinson’s bar, which explains the wave propagation of shock waves In cylindrical long bars. Special arrangements are made to fix the specimen so that it can be subjected
to continuous tension-compression loading.
A motor driving a shaft resting on two bearings and carrying a combined flywheel-eccentric arrangement IS used. is eccentric may have any eccentricity from zero to five course change the stress given meter long steel shaft connected to the eccentric means of a connecting-rod. The 2.5 meter long hammer on five wood bearings with plastic sleeves to reduce reflection from the bearings. The load is then transmitted to an intermediate bar holding the specimen.
His specimen is connected from the other side to a short bar carrying four strain gauges. The specimen is To the bars by means of two nuts, one for each bar.
e strain gauges carried by the short fixed bar enable the ’ignal passing through the specimen (and not the reflected to be’ recorded. This signal proportional to the stre~s was then sent to a TS26B Sedeme-type exten¬bridge then filtered in an AF501 band pass The filtered signal was then fed to Tektronix-type oscilloscope, where the wave pattern easily stored and photographed. In the last few years, the use of materials other metals has increased a lot. The development of poly¬for a lighter weight, lower cost or good insulating became familiar.