# Tag Info

## Hot answers tagged mechanical-failure

17

radian is a derived unit, defined as the ratio of arc length to radius. As the ratio of two lengths it is dimensionless.

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. ...

13

According to the ASME Process Piping Code (B31.3) $$p = \frac{2 * t * S * E}{D - 2 * t * Y}$$ where $p$ = internal pressure $t$ = wall thickness $S$ = material's tensile strength $D$ = outer diameter $Y$ = wall thickness coefficient (B31.3-1999, Table 304.1.1) $E$ = material and pipe construction quality factor (B31.3-1999, Table A-1A) Note that this ...

10

I'd be less worried about the shards and more about the structural integrity of the oven. When the bricks crack they lose most of their structural integrity. This may lead to the oven collapsing. It's much safer to line the inside with firebricks. They are solid and more expensive but you can be sure they won't crack under the heat. They will also protect ...

9

The pressure rise is easy enough to calculate from the ideal gas law $$PV=nRT.$$ In your case $V$, $n$, and $R$ are fixed so you can convert this to a simple ratio $$P_2=P_1\frac{T_2}{T_1}.$$ Be careful here to use an absolute temperature scale (usually measured in Kelvin). From the numbers you give, the pressure will rise to about 2.6 atm assuming that ...

8

The intuitive meaning of Saint Venant's principle is that "if two different sets of applied loads are statically equivalent, then the differences between the two stress patterns they create are only significant close to where the loads are applied". This is used very frequently in engineering modelling. For example if a beam is bolted to a support with ...

8

I'm going to run with this assuming the arm looks like the following diagram (I'm ignoring the 11.4 pounds of the bar for now to make the concepts easier to explain - that can be added later by assuming all 11.4 pounds run through the center of the bar.): This is a pretty simple setup. To figure out the loading on the shaft, we have to move the load from ...

8

What would be the difference between a fault tolerant and robust design? The most important difference is that robustness takes into account external factors. A more robust system will function in spite of some conditions that would impair the normal function of a less robust system. More robust systems might be referred to as sturdy, heavy-duty, perhaps ...

7

To add to @alephzero's answer, here's an layman's explanation of Saint-Venant's Principle: far enough away from the load's point of application, equivalent loads can be treated as identical. For instance, the stress profile of a column of area $A$ with a concentrated load $F$ applied at the top is effectively identical to the stress profile of the same ...

5

In the world of plastic piping, the formula is different, because the material doesn't yield. For isotropic plastics, B31.3 shows piping as: $$p = \frac{2St}{D-t}$$ Where D, t and S remain the same as above. However, the allowable strength (S) is given by an applicable ASTM specification, which functions the same as the yield stress - but is not ...

5

This is not an authoritative answer as I don't know the ATEX regulation that well. You have it however right that the ability to form a spark is relevant here. So your next step would be to look at the materials you use. Steel gives sparks on occassion. Most ATEX mechanical tools (hammers, wrenches) are from Bronze or Beryllium, so I would research in that ...

5

Vacuum pressure on a vessel is quite different than positive pressure. Under positive pressure, the shell of the vessel is essentially under a uniform membrane tension due to the shell wanting to expand outward from the pressure. Under vacuum (negative) pressure, the opposite is true, where the shell is in compression. While a cylinder is stronger in this ...

5

The bricks themselves should be fine, at least for one cycle, IF they are heated reasonably slowly. Plenty of people have put bricks in barbecues and bonfires. Remember they were already fired in a kiln when they were made, to fuse the clay particles together so that they wouldn't turn into mud as soon as it rained. The only exception is if the bricks are ...

5

Those figures are about right for the bare minimum wall thickness for the walls of a cylinder however, as you say, this would be inadequate in practice for a number of reasons. Safety concerns dictate that steam pressure vessels are designed with a large factor of safety. You certainly don't want any sort of pressure vessel to be operating anywhere near ...

5

It's difficult to be certain, but I suspect what you have is commonly known as a spring speaker clip. Using those terms in your search engine to find one that has listing for maximum and voltage. My search, done in the US, resulted in primarily US sources, one of which lists a set that can handle 300 volts and 15 amps.

5

The main reason from a designer's point of view is the consequence of a failure. Almost always, something like battery failure or a puncture doesn't cause any collateral damage - you just replace the failed part. (Even a tyre blowout when driving at high speed rarely causes much secondary damage - and that is a rare type of "tyre failure" compared with the ...

4

Summary: Both processes depend on relative solubility of solute between high and low temperature solvent phases. How each process proceeds at sub-microscopic scale is very different. Precipitation hardening is diffusion-limited, while martensite formation is diffusionless. Precipitation hardening is a diffusion-limited process in which (generally ...

4

I know of at least one case where such material was added inside the spring to dampen it. The spring will be resonant at some frequency. If there is enough component of that frequency in whatever is driving the spring, then it could oscillate or "ring". This can be undesirable because it will subject whatever it is connected to to forces at this frequency,...

4

TL/DR As the other answers have stated, radians are dimensionless. Cycles and Turns This is a question that seems to come up often, and from many different quarters; not only from students and lay people, but I have seen plenty of professionals for whom the concept of radians causes difficulty. One way that seems to help some people's intuition is to put ...

4

As a rule of thumb: When brittle materials are subjected to torsion they fail in the plane, where tension is at its highest, i.e. at a 45° angle. Ductile materials on the other hand fail in the plane of maximum shear stress. Take a look at Mohr's Circle for pure shear. Maximum-Shear-Stress Theory states: [...] yielding of the [ductile] material begins ...

3

Without knowing additional details, my attempt at a catch-all answer: Summary: attempt to minimize wear. Millions of cycles is a lot for even low-load contact surfaces. Use components with high hardness and smooth materials. PTFE or UHMWPE backed by metal for full-contact bearings, and AISI 52100 or AISI 440C for ball bearings. There may be an issue with ...

3

A moment has a direction, which you can imagine when you look at the direction of the force and the axis you're calculating the moment from. Depending on which direction you're looking at it from, however, it can be seen as either clockwise or counter-clockwise. To remedy this confusion, we use the right-hand rule to identify whether a moment is positive or ...

3

Yes. In a perfectly elastoplastic material (where the stress-strain relationship is perfectly linear until the yield point and is then constant and equal to the yield point), the material will elastically recover all of its elastic deformation, but the plastic deformation will remain. This is the blue line in the figure below. In (not perfectly) ...

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. ...

3

The basic Euler buckling formula is unrealistic because it implies perfect geometry and perfect alignment of the loads. Therefore a large empirical safety factor is required. It is also a potentially catastrophic failure mode, in the sense that the buckled column supports no load at all, unlike plastic failure in compression for example. There are ...

2

Short answer Orthogonal cutting increases pressure and decreases tool life. Thus isn't used if aim isn't cutting. Lathe operation is a shaping operation, not a cutting operation most of the time. Long answer Orthogonal cutting isn't suitable because Cutting forces act on a smaller area of cutting surface on tool if orthogonal cutting is employed so it ...

2

With a spring and a (accurate) actuator you can create one. One end of the spring is the force applicator the other end is moved by the actuator so the spring compresses a certain amount. Then by Hooke's law you can control the force that the spring applies to your test piece. This works best if the test piece doesn't deform.

2

Engineering bricks (solid) are fired at 1200 degrees in a kiln so don't worry about your complicated mathematics , your pizza oven will never get to that temp.if it did or even if it got much much higher the bricks would just melt together.(They call them clinkers) I am a bricklayer with 47 years experience and a lot of that time was building and repairing ...

2

It appears the spline-like grooves pressed into the shaft's surface are upsets, which are there to derive an interference or press fit between the shaft and the gear. This is intended to fasten the gear onto the shaft so hard that it will not come loose, but if too much torque is applied to the gear by the worm drive, it will shear loose from the shaft and ...

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