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27 votes

Why doesn't epoxy stick to silicone?

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 ...
niels nielsen's user avatar
24 votes
Accepted

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

The photo you have is not for the standard jigsaw blade. Standard blades teeth point upward and cut upward for the obvious reasons: less wobble, more control, center of force near the handle. This is ...
kamran's user avatar
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16 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

If you think what happens as each tooth cuts material then the blade is put into tension as it cuts, this means that the blade is likely to stay straight, but any unevenness between the teeth side to ...
Solar Mike's user avatar
  • 15.8k
11 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

To enlarge slightly upon Solar Mike's response, a jigsaw that cuts on the upstroke tends to yank the saw shoe down into firm contact with the workpiece. This guarantees that the cut angle will match ...
niels nielsen's user avatar
11 votes

Why does corrosion take place at certain stressed regions?

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 ...
NMech's user avatar
  • 24.3k
9 votes

Why doesn't epoxy stick to silicone?

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 ...
Stian's user avatar
  • 191
7 votes
Accepted

How do the constraints imposed on a material increase the stiffness?

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 ...
Wasabi's user avatar
  • 13.1k
6 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

To expand on Solar Mike's answer and to help explain part of niels nielsen's answer, the saw blade is normally designed to essentially squeeze the material between the teeth and the shoe. This ...
computercarguy's user avatar
6 votes
Accepted

Why do they vacuum pump the carbon fiber fabric?

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 ...
fred_dot_u's user avatar
  • 7,122
5 votes
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Beginners material science for handling a load

Material Properties For the linear-elastic analysis you describe, the key pieces of material information are the elastic modulus (E) to calculate deflection and the yield stress (Fy) to check if the ...
CableStay's user avatar
  • 2,760
5 votes

Influence of design on corrosion control

A is worse because the item holds water. Holding water resuults in corrosion, certainly near the surface. C sheds water so it will normally be dry. Accumulation of impurities seems a needlessly ...
Tiger Guy's user avatar
  • 6,901
4 votes

How effective are screen protectors?

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 ...
Jim Clark's user avatar
  • 496
4 votes

Is it possible to determine how the steel was made, having its microstructure (for example, to distinguish forging from rolled products)?

Steels are usually considered "as cast" or wrought. The microphotograph is overetched and either high magnification or coarse grained , likely had a heat-treatment. Cast or wrought would be ...
blacksmith37's user avatar
  • 6,134
4 votes
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Why does corrosion take place at certain stressed regions?

In the real world ,I don't believe I have seen CORROSION at STRESSED areas. Corrosion may be accelerated at STRAINED areas; the strains introduce energy to the microstructure which may promote ...
blacksmith37's user avatar
  • 6,134
4 votes
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What does time temperature specifically give us?

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 ...
blacksmith37's user avatar
  • 6,134
4 votes
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Heat Deflection VS Coefficient of Thermal Expansion?

CTE characterizes dimensional change, with no load. It corresponds to a relatively fundamental physical principle, making it easy to use in a design calculation Heat Deflection test characterizes the ...
Pete W's user avatar
  • 1,561
4 votes

What is the significance of brittle materials and why do we use them?

Below is a list of the general advantages and disadvantages of cast irons. For applications where ductility is not a major concern, the reasons for the popularity of cast iron can be summarized by the ...
r13's user avatar
  • 8,174
4 votes

How the choice of etchant can affect the severity of hydrogen embrittlement during pickling and passivation?

The primary cause of hydrogen cracking is a susceptible matrix . Typically a carbon or low alloy steel that is hard ( > HRC 25) untempered is the primary problem. The martensitic chrome steels were ...
blacksmith37's user avatar
  • 6,134
3 votes

How does a pressure vessel fail when the interal pressure exceeds the yield stress of the material?

A rupturing pressure vessel consists of an interplay between rupture of the walls, that causes a reduction in pressure via venting, while rupture of the walls also weakens the ability of the structure ...
MeEngineerTrustMe's user avatar
3 votes
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What is the relationship between the strain in different directions?

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 $\nu \ge 0$, $\epsilon_{transverse}$ ($x$- ...
realityChemist's user avatar
3 votes
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Why carbon ceramic brakes

Well mass and high-temperature behavior are really the key benefits with carbon/ceramic brakes. High temperature: Their high temperature properties make them more dependable during heavy use as they ...
Jollerprutt's user avatar
3 votes
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Injection moulding

cell phone housings and trim, Lego blocks and all other similar types of plastic toys, camera housings, plates, bowls, and dishes of plastic as well as plastic knives, forks and spoons, automobile ...
niels nielsen's user avatar
3 votes

Stress strain curve stress and resilience

Strain is determined as $\epsilon = (l - l_o)/l_o$. The 0.2% offset strain is the point where $\epsilon = 0.002$. The 0.2% offset stress is determined by using a line that has the same slope as the ...
Jeffrey J Weimer's user avatar
3 votes

What is meant by Material Toughness being the Ability to Absorb Energy Before Fracture?

Usually the method to measure the toughness is either the Charpy or Izod Test. They are very similar and the main difference are the boundary condition of each one (Charpy fixed both ends, Izod: ...
NMech's user avatar
  • 24.3k
3 votes
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Examples of Materials with a Coefficient of Kinetic Friction Very Close to or Equal to Coefficient of Static Friction?

Steel/Teflon - $\mu_s = \mu_k = 0.27$ Glass/Teflon - $\mu_s = \mu_k = 0.1$ Ice/Ice - $\mu_s = \mu_k = 0.01$ See table here.
r13's user avatar
  • 8,174
3 votes
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What is the most accurate mathematical model of a cantilever beam's bending?

Your question is quite broad. Accuracy depends a lot on the context, so I'll caveat my response by noting that the below is valid only for completely linear-elastic materials (no plastic behaviour ...
Andorrax's user avatar
  • 144
3 votes

Which has more density: 100 °C steam or 100 °C dry air?

There's an air of 'lmgtfy' about this question... Wolfram Alpha is a great resource for quickly finding information like this. You can see that the steam is significantly less dense than the air, at ...
Jonathan R Swift's user avatar
2 votes

Why would the flexural modulus be different than the elastic modulus?

Unlike many other isotropic materials, the polymers do not demonstrate the same deformation characteristics for tension and compression, evident by the stress-strain curves shown below. Therefore, a ...
r13's user avatar
  • 8,174
2 votes

Why do they vacuum pump the carbon fiber fabric?

There are two reasons: One is to remove trapped air bubbles and two to pack the fibres as densely as possible within the structure or weave of the fibre pattern wanted.
Solar Mike's user avatar
  • 15.8k
2 votes
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Calculating tensile strength for aluminium

I confirm that in your case the yield stress is an adapted limit value. However, there is a unit error in your computation. You forgot to convert the area in m2 which means that the results is not 362 ...
ClariB's user avatar
  • 174

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