27

There are two reasons why. First, for any glue to stick to something, that something needs to be wettable by the glue. A cured silicone surface is bristling with uncrosslinked silicone units which have extremely low surface energy and hence are very difficult if not impossible to wet by glues like epoxy. This means the cured epoxy exhibits no adhesion to the ...


23

Different gears have different drivers for having holes. One way you can categorize gears is by whether they are used primarily for transferring: motion: transferring angular position and angular velocity (see clockwork) torque: when the gears are used in power transmission Motion Gears that transfer motion don't need to transfer power. So their strength ...


11

UPDATED TL;DR: Cast iron has the advantage, because it has a greater capacity to hold heat, and because of its lower conductivity it releases it more slowly, thus its temperature does not fluctuate as much (thus having a more even and steady heat flow) UPDATE: Answering in terms of the advantage (scroll way down) for the following sections Answer to ...


10

One of the mechanism that affect corrosion is known in the literature as Stress Corrosion Cracking (SCC). The idea is that tensile stressed regions are prone to crack development. Crack development essentially maximizes the area that corrosion can develop. Since corrosion, degrades the properties of the material, this accelerates further the crack ...


9

Silicone is not a single substance, it is a very very wide range of different types of materials with widely varying properties! All materials that have several siloxane monomers in them can reasonably be called silicones. This can take almost any shape; foams, glues, coatings, rubbers, oils, powders, gels. 3D printed solids, even. Some silicones will adhere ...


8

In addition to the other answers such as weight reduction and inertia, there are other possibilities: Often there can be a precision machined hole for timing purposes. A common solution for some / many internal combustion engines to get camshafts timed to the crankshaft. Of course, dial gauges may also be used. Also, there can be threaded holes to help with ...


7

It could be for combination of reasons. lubrication: the holes will both pump and let the lubricant pass through. Reduced angular momentum reduces backlash and adds to gearbox responsiveness. Lighter gears need less shaft support, helping the averall compactness of the gearbox.


6

Steel beams and columns can and have been prestressed by steel tendons in major buildings. Because steel tendons can be applied post-construction many times they are employed in refurbishing bridges and distressed structures. Following is a steel beam with a post-tensioned tendon. If $X$ is the amount of force in the tendon, and $c$ is the distance to the ...


6

Let me see if I understood it correctly: You have a rubber block under a uniaxial load (compression or tension). That block may or may not be constrained on one pair of sides (the load is applied along the block's x-axis and the block can't deform in the y-axis but can in the z-axis, for example). If this is the case, then the 1.33 is easy enough to explain. ...


6

The Load-Displacement (or Load Extension) and stress strain diagrams are two diagrams identical in shape. See below. The main visible difference is the values on axis (which are at first glance neglected). So, it is natural when you first encounter them to question why do you want to learn about a stress and strain diagram which has obscure quantities (as ...


5

Solar Mike's answer is accurate. Carbon fiber has a resin to fiber ratio which provides the optimum strength. This is typically measured by weight. The amount of resin is applied to the fiber prior to enclosing it for vacuum application. Once the vacuum begins, all of the air is removed from the fiber, forcing the resin into the voids, ensuring the ...


5

The point where steel stops behaving in an elastic manner (i.e. return to its original stress) is essentially the yield point. The yield starts for most steels at approximately 0.2% elongation. You might find some authors, that distinguish between the yield point and the Elasticity point, however IMHO for all intents and purposes they might just as well ...


5

Depends on the application, but generally there are two reasons why: reduced weight lowers inertia loads (opposite of a flywheel), but more often less material = lower costs if these are high volume parts.


5

Also someone may have to pick the machine up and carry it. Reducing weight is not just related to the intrinsic function of the machine, its shafts and so on.


5

Mill hardening would refer to work hardening, where cold-rolling the material distorts the grain structure and causes dislocation pile-up and entanglements, which reduce the material's ductility and thereby increase its yield strength.


4

In the food industry not many materials are used because of strict policies. The mostly used ones are definitely stainless steels (AISI304/316 and the even better AISI316/L). The other common material is nylon. For applications where only food contact is required(ie containers mostly) also BOPP or other polyolefins are used but they are not common in food ...


4

When I look on the net I found a surprising result : GD seems to stand for German Din (material specifications). GD Zinc is a zinc die cast alloy with 4 Cu and 1 Al. Equivalent to AG 41A alloy in the US. So one of the components is brass ,the other is an ( ordinary) zinc die cast.


4

peristaltic pumps are available from a variety of sources, not just stenner. you can buy either fixed-rate pumps or variable-rate pumps as either stand-alone units or computer-controlled (RS232, USB, etc.) devices. you can also select the tubing material for compatibility with the chemicals you wish to pump. Finally, note that you can buy motorized pump ...


4

The basic method for hardness measurement is using an indender and a standard force on a material surface and then measuring either the depth or the area of the imprint. However, is happening with almost all hardness scales is that you cannot obtain meaningful results for all types of materials, for a given force and a specific indender. Therefore what you ...


4

One method that I have used for mechanical properties is based on the Ashby selection charts. Software exists to apply this approach. I am not aware whether comparable methods and tools exist for optical properties. You may to best to start with the base success/fail criteria for mechanical properties, graduate to the maximum/minimum selection criteria for ...


4

Pretty standard old technology; A moot point whether prestressed cable or rebar is used. However ; cold drawn cable can be stronger. The problem is civil engineers don't understand the possible problem of hydrogen stress cracking of high strength steels. There have been several TV mockumentaries ( eg. Engineering Disasters) of serious cable failures. ...


4

I would recommend you have your boys wear a helmet while playing. Also cover the landing area with 8 inch deep bed of mulch or some soft material like foam sheets covered by a mat. With all due respect to the enviably beautiful job your husband has done, 5 feet cantilever swing is the ideal unbalanced pendulum, overtime working its way to loosen up the nails ...


4

I don't think of a screen protector as a mono layer, but a lamination. Deformable (softer) materials (possibly above and also) below the rigid layer (this layer also generally provides adhesion). That way point loads become distributed (potentially to the protector and also) to the device. Example: a thin clear sticky low molecular weight polymer (1), an ...


4

You left off a "T" ; it is "time, temperature, transformation". It is a basis to evaluate hardenability of alloy steels. A sample is austenitized, then rapidly cooled to some temperature ,and held at that temperature for a specific time . Then rapidly cooled to room temperature and the microstructure examined . And after one finishes the ...


3

In this case, we say that $\epsilon_{axial}$ ($z$-direction in your diagram) is positive by convention. Then, for a normal material with a Poisson's ratio $\nu \ge 0$, $\epsilon_{transverse}$ ($x$- and $y$-directions in your diagram) will be negative. The fact that the material is isotropic means we have no way of distinctly labeling one direction $x$ and ...


3

The steam pressure in the boiler will be greater than atmospheric, so the steam temperature will be above 100C. A typical ready-built boiler boiler for steam powered models (sold with a pressure test certificate!) would have a maximum working pressure of 4 or 5 bar, which would give steam temperatures around 150C. Many common plastics will start to soften at ...


3

Heat is the transfer of energy from a hotter region to a cooler region. The surface in contact with the earth enjoys the benefit of conductive heating. Being cooler, the energy of the warmer earth will be transferred to the earth-bridge, ostensibly until the energy imbalance is removed. The air-bridge is going to become colder due to the colder air and will ...


3

There is nickel , titanium alloy Nitinol. I don't remember much about it except it has unique mechanical properties.


3

Ashby method as per 'Material Selection in Mechanical Design' by M Ashby (Butterworth Heinemann) is a powerful method to select material according to functional needs. The key point of this method is to build a 'performance index' to classify materials. For example, you could classify materials according to their ratio $\frac{E}{\rho}$ (Young modulus over ...


3

This is an issue as old as the time of roman carriages or earlier. Basically you need to design the joint connecting the two different structures using both smart design anticipating vibrations and concentrated stresses and utilizing impact damping rubber pads, coil springs, or system of links and levers designed to absorb the intense forces of the road ...


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