1.6 Mechanical Properties, Wear and Corrosioin
How a material's characteristics an shape affect stiffiness, elasticity and strength
How a material's characteristics an shape affect stiffiness, elasticity and strength
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| Sprache | Deutsch |
| Kategorie | Medizin |
| Stufe | Grundschule |
| Erstellt / Aktualisiert | 04.02.2013 / 05.07.2019 |
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When is a material said to behave elastically?
if after being deformed by a load, it returns to its original shape when unloaded
When is a material said to behave plastically
if after being deformed it does not return to its origianl shape
Define elastic limit.
If a material has been stressed to such an extent that it will not return to its original shape and dimension upon removal of the load, then it is said to have exceeded its elastic limit - this is alsno known as plastic deformation
Do a sphere and a cube of the same material have the same elastic modulus?
Yes:
the stress/strain ration does not change. This ration, therefore, is dependent on the material and not on the shape of the structure
Which scientist is associated with elastic modulus?
Thomas Young
denoted by the letter E. It is constant for each material and is thus a measure of the material's ability to maintain shape under external loads.
Stress = load / cross-sectional area
Strain = change in length / origina length
Modulus = Stress / Strain
Two bars of the same material 500mm in length have diameters of 5mm and 7mm respectively.
Which is the easier to bend?
Calculate the "I" value for a beam of 35mm in length.
5mm depth and 15mm width.
Is it easier to bend than a beam of the same length with a width of 10mm and depth of 8mm?
Yes
I1 = (15mm * (5mm)3) / 12 = 156
I2 = (10mm * (8mm)3) / 12 = 426
Define tribology.
Tribology is the study of friction, lubrication and wear
Explain three-body wear.
This is a form of abrasive wear and is caused when a hard partickle or third body becomes trapped between two articalting surfaces.
It can dramtically increse the normal rate of wear of these surfaces.
What type of loading can lead to fatigue war?
occurs after a large number of loading cycles, even though the load is less than that expected to prodce failure in a single load application
When is galvanic corrosion likely to occour?
When two dissimilar metals are touching or in close proximity in a conductive environment or electrolyte
In order for crevice corrosion to be initiated, two dissimilar metals must be present (True / False?).
False:
There is no need for two dissimilar metals to be present to initiate it.
The small relative motion between two touching surfaces is called.
Fretting
is a form of wear which is the result of small relative motion between two touching surfaces which produce depris.
Give another name for creep.
cold-flow
Which factor has the greatest effect on the rate of creep?
Temperature has a pfofound effect on creep.
