Hot answers tagged

13

Every time you bend aluminium below the recrystallisation temperature, the macroscopic grains become smaller: this is known as cold work. The sides of the tab are either stretched or compressed. The effect is the same as the rolling example below. This is indeed a plastic deformation: the tab stays in place and doesn't bend back and stays in place. ...


8

It's a combination of 1, 3, 4, the product development cycle, and the nature of the product. 1 - Damage in materials is a cumulative process, the product of hundreds or thousands of little events (e.g. the tightening and loosening of the belts) or one big event (a crash). So, the product has to be designed to always have a certain damage capacity ...


4

I have seen 'lollipop cutters' used for this purpose, just a single pass into the side (closest to option B). The thickness of the shank means it's not a perfectly square bottomed slot, but was sufficient in the instance in question. The image below shows the cutter type: And the profile in question: The method of adding an undercut radius will certainly ...


2

I think this is more a comment than an answer, but I have too small reputation to comment (poor me!). Summarizing, you are asking: how dynamic loads propagate inside a structure? I would underline that, in my perspective, telling that you are not concerned about vibrations, is a wrong starting point (fatigue crack derives exactly from them); for a ...


2

If, for any reason, the fatigue process becomes time-dependent, then it also becomes frequency-dependent. Under normal conditions, fatigue failure is independent of frequency. But when corrosion or high temperatures, or both, are encountered, the cyclic rate becomes important. The slower the frequency and the higher the temperature, the higher the crack ...


2

It really depends a lot on your model and types of loads but here are some generalities: Shell elements usually require a lot less computational work than solid elements. This means that you can achieve reliable results with much fewer elements and within a fraction of the time. The rule-of-thumb is to use 1-D (Beams) or 2-D (shells) elements as much as ...


1

Compressed air like an air suspension in a car or truck. 100K is not many cycles for a steel spring; springs such as engine valves run many ,many millions of cycles ,normally without failure.


1

Bottom Line is that either can be used successfully if properly applied. The most appropriate has to do with: the application and (e.g. symmetries in geometry vs. irregular shapes and loads) what you are aiming to get out of the analysis. (e.g. just a single value for the entire structure, or looking at more detail at locations with problems). The main ...


1

Simply put this is a textbook example of what not to do. The geometry of the connection, a solid bar to a narrow bolt invites stress concentration at the necking where the bolt enters the rod. The heavy disk will rattle and slowly wear the bolt threads out, allowing play at the connection The play of the disk will cause intense momentum back and forth ...


1

Fatigue is the stress on a material due to cyclic loading. The best comparison is a rubber band. When you pull it over and over it stretches out because the fatigue is causing the elasticity to wear out and it becomes more and more plastic until the band snaps. While technically the the tab is breaking because of plastic deformation, fatigue fracture would ...


1

Steels are relatively unique among metals with a very reliable endurance limit equal to 1/2 of tensile strength. Cast irons definitely do not have this feature. Nickel and cobalt alloys might have it but there is limited data. Fatigue test coupons are smooth with no stress concentration ; not to say that they never contain an inclusion. So fatigue tests ...


1

Yes, to a degree. The endurance limit is normally expressed as a fraction of the yield stress and for steel a typical value is 1/2 (50%). This is is certainly a reasonable assumption for common low alloy, medium carbon steels ie the sort of steels that you might reasonably select for a shaft. In fact for many practical purposes the factor of safety that ...


1

I suspect not, based on a table provided here . It would appear that the relationship is strongly material-dependent and not analytically calculable.


1

per wikipedia: Typical values of the limit for steels are 1/2 the ultimate tensile strength, to a maximum of 290 MPa https://en.wikipedia.org/wiki/Fatigue_limit Whether you want to rely on such a rule of thumb depends on your application.


1

Fatigue is failure cause by cycling loads which do not exceed the yield stress of the material, typically over tens of thousands of cycles. Not to be confused with work hardening which occurs over relatively few cycles at stresses exceeding the yield stress of the material. Fatigue strength is usually defined by the stress at which a material will exhibit ...


1

Almost everyone is partly right. You can fail the ring-pull by simple overload in one 'cycle' or you can accumulate plastic strain in three or four cycles. This wouldn't normally be considered even low-cycle fatigue but I don't know that there's a lower limit on how many cycles Paris' Law can be applied.


Only top voted, non community-wiki answers of a minimum length are eligible