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denis-greek [22]
3 years ago
9

Find the True statement

Engineering
2 answers:
dmitriy555 [2]3 years ago
6 0

Answer:

Option A is correct ( Stress relaxation is time- and temperature-dependent).

Explanation:

Luda [366]3 years ago
6 0

Answer:

Option A is correct.

The only completely true statement in all of the available options is that "Stress relaxation is time- and temperature-dependent"

Explanation:

Stress relaxation is the constant decrease of stress with time in a material which is exposed to a constant strain at a constant temperature.

It is similar in concept to vaccination; in that, the material is being prepared to be able to undergo a particular amount of stress at a specific temperature in order to make the stress levels in the material lower than it usually should be.

It is evident that stress relaxation, (the extent), in a material completely depends on the amount of time that the constant strain is applied and the temperature at which this whole process occurs.

Polymers always have a melting temperature.

While it is true that almost all materials can melt. For Polymers, it is not necessarily true that the melting takes place at a constant temperature. In very complex Polymers, melting occurs over an appreciable range of temperature, not sharply as in some simple polymers.

Hence, polymers don't always have a melting temperature, some polymers melt over a range of temperature. So, this statement isn't completely true.

Polyethylene becomes weaker if H is replaced with other radicals inside branches.

This also is a statement that isn't always true. Replacing the H in some of the branches of polyethylene with radicals such as the carboxylic group, the hydroxyl group etc., have been shown to seriously strengthen the polyethylene. Polymers formed by replacing the H with ion-Like radicals are known as ionomers.

These groups have a polarity, hence, they are drawn together by their charges, come together in microdomains, toughening and strengthening the polyethylene without taking its ability to be cast to permanent shapes away.

This statement isn't always true too.

Crazing indicates cracks inside the polymer.

This is also false. Crazing doesn't indicate cracks in materials. What it does is that Crazing precedes the cracks.

Crazing is a phenomenon that entails the formation of microvoids in a material in response to excessive tensile stress being applied to the material. The microvoids (which forms in a plane normal to the tensile stress that caused them) often leads to cracks or fracture later.

So, Crazing doesn't indicate cracks, rather, it precedes them in most cases.

Hope this Helps!!!

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A 20-mm-diameter steel bar is to be used as a torsion spring. If the torsional stress in the bar is not to exceed 110 MPa when o
ch4aika [34]

Answer:

1.887 m

Explanation:

(15 *pi)/180

= 0.2618 rad

Polar moment

= Pi*d⁴/32

= (22/7*20⁴)/32

= 15707.96

Torque on shaft

= ((22/7)*20³*110)/16

= 172857.14

= 172.8nm

Shear modulus

G = 79.3

L = Gjθ/T

= 79.3x10⁹x(1.571*10^-8)x0.2618/172.8

= 1.887 m

The length of the bar is therefore 1.887 meters

5 0
3 years ago
On-site oil storage containers must be marked "Used Oil."<br><br> True. <br><br> False.
Scrat [10]

Answer:

How must used oil storage containers be marked? Containers and aboveground tanks used to store used oil at generator facilities must be labeled or marked clearly with the words “Used Oil" (40 CFR Section 279.22(c)).

Explanation:

i think it will help you

7 0
3 years ago
Which of the following statements is true of a mature technology?
hoa [83]

Answer:

I think it is( More expensive than immature technologies) I took engineering class and this question is still quite tricky.

Explanation:

8 0
3 years ago
(a) What is the distinction between hypoeutectoid and hypereutectoid steels? (b) In a hypoeutectoid steel, both eutectoid and pr
Gnoma [55]

Answer:

See explanation below

Explanation:

Hypo-eutectoid steel has less than 0,8% of C in its composition.

It is composed by pearlite and α-ferrite, whereas Hyper-eutectoid steel has between 0.8% and 2% of C, composed by pearlite and cementite.

Ferrite has a higher tensile strength than cementite but cementite is harder.

Considering that hypoeutectoid steel contains ferrite at grain boundaries and pearlite inside grains whereas hypereutectoid steel contains a higher amount of cementite, the following properties are obtainable:

Hypo-eutectoid steel has higher yield strength than Hyper-eutectoid steel

Hypo-eutectoid steel is more ductile than Hyper-eutectoid steel

Hyper-eutectoid steel is harder than Hyper-eutectoid steel

Hypo-eutectoid steel has more tensile strength than Hyper-eutectoid steel.

When making a knife or axe blade, I would choose Hyper-eutectoid steel alloy because

1. It is harder

2. It has low cost

3. It is lighter

When making a die to press powders or stamp a softer metals, I will choose hypo-eutectoid steel alloy because

1. It is ductile

2. It has high tensile strength

3. It is durable

7 0
3 years ago
Read 2 more answers
A microscope illuminator uses a transformer to step down the 120 V AC of the wall outlet to power a 12.0 V,50 W microscope bulb.
Anna35 [415]

Answer:2.88 ohms

Explanation:

R= V^2 / P

12^2/50

144/50

2.88 ohms

5 0
1 year ago
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