If i use impact testing machine for applying load for Fatigue crack growth in mild steel, then still i can use Paris Law for crack growth. As i think the load applied is still of constant amplitude and will apply it to the the test piece again and again and the load applied is still fatigue as it will vary as ....hit and remove load...and measure the crack growth.
If i am wrong, please correct me. If there is any related document please also mention that.
Thanks
To answer your question, you might consider the following:
- What stress state / stress field(s) will an impact load produce in your specimen?
- How does that compare to a tensile / compressive (and/or bending) load applied on the edge of the specimen, as is usual for a fatigue test?
- In particular, will your impact loading produce a uni-axial or a bi-axial stress field?
- Impacts do not produce a uniform stress field. What does this mean for the stress around the crack-tip? Will the crack have to grow through an area which already contains a stress gradient, before being disturbed by the presence of the crack?
- Cracks tend to grow perpendicular to the principal stress direction, what will that be for your impact loading?
To better answer your question, it is necessary to know more about the dynamics of the test load. In my opinion, fatigue assessments cannot be reliably undertaken without a full understanding of the actual dynamics of the component under test. This is particularly relevant when dynamic amplification is associated with resonance. This property both adds to the stress range in fatigue assessments and the number of cycles applicable to a Miner’s Rule summation. Paris" law will not be particularly helpful without this basic information.
you can new device interaction between the energy of impact toughness and low cycle fatigue
@Eric Ancich Sir !
After studying Miner’s Rule summation, it is good for assessing the remaining life of component when it is subjected to particular stress level. My study is to use Charpy v-notch test equipment and apply low amplitude load again and again, having a stress of ratio R=0, to mild steel specimen having a notch made according to ASTM standard for three point bending. Plot a-N curve and then from there measure C and M and then Plot log da/dn vs log dk......which is Paris law .
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