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Questions tagged [fatigue]

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5
votes
1answer
134 views

Fatigue resistance at filleted corners - Design detail

So, I have a situation where we are putting load on a plate from above, and the plate has a step in it, which was made by milling a bigger block of steel (i.e. there are no layers and everything is ...
1
vote
0answers
22 views

Can you estimate the S-N curve from variable-loading data only, using Miner's rule?

I'm doing some work on fatigue failure. Everything I've read so far assumes that the S-N curve is either on a spec sheet somewhere, or can be empirically determined in laboratory testing with several ...
0
votes
0answers
18 views

Polymers: Creep modulus failure criteria

I am developing a polymer component that is under statical, vibration and temperature loads and is made out of PA66 GF35 (polyamide 6.6 with 35 wt% short glass fiber). The component needs to ...
2
votes
1answer
57 views

Do I use alternating, mean or max/min stresses for Miner's rule?

I am trying to work out fatigue life of a part using Miner's rule, however I am having some trouble working out which stress values to use. I have seen some examples but there seems no rhyme or reason ...
1
vote
4answers
285 views

Is there any link between tensile strength and endurance limit for steel ?

I'm designing a shaft, and i have to choose a material. I deal with cyclic stress in my machine, so i set up an expression for all the possible stresses and combined it with von Mises criteria for ...
0
votes
0answers
21 views

Long term deflection

I've been working with a team of 'designers' that are highly concerned over a potential failure mode of ABS plastic. Their theory is that under a static load well under the yield point of the material ...
0
votes
2answers
74 views

mean fatigue strength

In context of machine design, what is mean fatigue strength? (as I am thinking I am mixing it up with midrange strength) In my class we deal a lot with steels and this is a low strength steel, but I ...
8
votes
2answers
225 views

Why do car-seats have an expiration date?

My wife and I are expecting our first child, and therefore are expecting to purchase a car seats. My wife and I have discovered that car seats have "expiration dates": a car seat, no matter how ...
2
votes
0answers
42 views

How do I implement scientific experiment to derive a equation called Gerber Line? [closed]

How do I implement scientific experiment to derive a equation relevant to subject of stress and fatigue called Gerber Line equation? May you also provide some historical context to that?
1
vote
1answer
39 views

stress wave propogation in metals

Over years of flying small airplanes I have seen fatigue cracks and frayed brackets and connections. I wonder if there is an easy way to search the propagation of stress wave in machinery and ...
5
votes
2answers
1k views

How does the S-N curve (or Wöhler curve) of a material change with frequency?

How a Material fatigues can be characterized by a Wöhler curve where each datapoint corresponds to a failure with the stress on the y-Axis and the number of cycles on the x-axis. An example is the ...
11
votes
3answers
949 views

Why do beverage can tabs break when bent?

Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off. ...