5
First off, always remember that garbage in = garbage out; so if your data is garbage then your statistics will be garbage.
In this situation your optimal data would be something like Run Hours Until Failure and your entire dataset would have failed already. With this in mind you may want to choose a conservative number from whatever statistic you calculate....
4
If you don't have hard data, making assumptions (preferably "reasonable" ones) is the only option you have. (Maybe that's why engineers used to call their slide rules "guessing sticks...")
You can't ignore the fact that most of the units have not failed so far. A plausible approach to this would be to use the times-to-failure that you know, to fit the ...
4
RPM = revolutions per minute.
In the context of vibration monitoring, 1 x rpm means a vibration frequency that is the same as the rotation speed (one vibration oscillation per revolution of the rotor), 2 x rpm means a frequency 2 x the rpm (two oscillations per revolution), etc.
Because of nonlinear effects in the mechanical system, vibrations can be ...
3
As mentioned, the formula $\tau_{avg}=\frac{V}{A}$ is called average shear stress. In some calculations it might suffice to calculate $\tau_{avg}$ for a widely used cross-section (let's say a standardized beam,e.g. HEA or IPE in Europe), and apply a safety coefficient to come up for shear flow.
The other formula $\tau=\frac{V\cdot Q}{I\cdot t}$ (beam shear ...
3
Brittleness describes the inability of a material to absorb a considerable amount of plastic deformation. Thus, the material fails without a lot of deformation.
Hardening, on the other hand is the process of increasing a material's yield strength $\sigma_y$
The principle used for work/strain hardening has to do with residual strain.
If you stretch e.g. ...
2
this is a classic fatigue fracture, caused by a cyclic/reversed bending load superimposed on a static tension load. The cyclic load is caused by the reversed bending; the neutral axis shows clearly as a straight line running diagonally across the center of the part. the fact that it is a straight line demonstrates that the torsion component was not the ...
2
The statistical tool Weibull as suggested by the previous two responded is the tool of choice for Mean Time To Failure (MTTF) calculations. Based on your comment as capture below, it appears that Weibull Analysis didn’t generate expected results.
Most statisticians that I have worked with recommend a sample size of 30 for most statistical analysis. My ...
answered Aug 30 '15 at 15:27
Mahendra Gunawardena
7,0755 gold badges23 silver badges62 bronze badges
2
Let assume a leak has been reported in the following pump system. As a result there is 1 inch of water on the floor. To identify the failure a root cause analysis (RCA) needs to be performed. To illustrate RCA few unrealistic conditions such as operating temperature range of -40C to 85C have been specified.
Based on the above image the flange consist of 3 ...
2
X-rays are a poor way to test for cracking in a ceramic. A crack in a ceramic part which has not shattered to pieces is a very small feature, of order ~0.001" wide or less, which commonly-used x-ray equipment cannot resolve. Second, a tiny crack in a ceramic part does not present a significant difference in x-ray absorptivity, inelastic scattering, or ...
2
Go directly to the ASTM site. I put "nylon rope" in search and it said there were 154 possibilities.
1
Actually it is.
When a material is loaded the stress state in the material is the same - it does not depend on the orientation that the stresses are analysed.
Mohr's circle is a way of visualising a stress state at different orientations/planes.
At yielding of the material, the stress state is that the maximum shear strength at yielding is equal to the ...
1
Probably ASTM A931 - 18 Standard Test Method for Tension Testing of Wire Ropes and Strand
There are others closely related but not exactly the same.
ASTM F3410 - 19 Standard Test Method for Testing Fiber Rope Used in Water Sports
ISO 3108:2017(en), Steel wire ropes — Test method
1
I think you might be mixing up the intentions of the two analysis tools you you mentioned - Root Cause Analysis and Design of Experiments. Consider thinking of it this way:
Root Cause Analysis is something you do in order to help identify, well, the "Root Cause" of some issue or problem. There are multiple ways to go about doing a root cause analysis in ...
1
At the time of 1994 Northridge earthquake in California, I along with many other engineers inspected several four and five story damaged buildings to assess the urgent safety situation.
We observed many torn base plates of various thickness and sizes up to 2" thickness. The most probable cause was shear rupture under large pendulum motion of the columns.
...
1
Ductile ("able to be drawn out into a thin wire") makes sense as the failure method, because the test is stretching the sample. Malleable ("able to be hammered or pressed into shape without breaking or cracking") doesn't make sense here, since the sample is not under compression! You could describe a three-point bend failure as Malleable, however. When @...
1
This is a typical case of stresses on shells and plates and obviously lends itself to analyzing using polar coordinates.
If your element is a thin shell and is loaded in a way that only membrane stresses are involved there are some formulas in references such as Roark's formulas for stress and strain. Otherwise you may need to use FEM and define your ...
1
This is very similar to the punching shear in column caps.
One would calculate the shear at a distance d/2 away from the rod, with d being the thickness of flange. Hwever if your guid rail or slidin track has prticular constrains you need to consider the impact of that too.
I would apply ultimate stress method and just divid the factored load by the ...
1
Any NATRAN solution should output the margin-of-safety factors if you output the stresses. Whether they are meaningful for any particular analysis is up to the user to decide, of course. For example, they probably are not meaningful for a vibration analysis since the mode amplitudes are arbitrary, but they would be meaningful for a forced response or ...
1
This depends on the alloy type (and specific alloy) and the quality of the material after it's been produced which can change depending on the manufacturing parameters.
The strengths of additive manufactured material are often better than cast when it's done properly, but I have yet to see any that are better than forged/rolled material. I have seen ...
Only top voted, non community-wiki answers of a minimum length are eligible