this gives the data required for chapter 2 i.e design properties of materialsFull description
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thinkiit solution hcverma class xi
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This book gives properties for various materials that are used in mechanical design. The intention is to give general information on each type of material, with typical strength properties. Basic d...
Failure-of-materials-in-mechanical-design-pdf
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Using Al, Al2O3 and SiC, different types of composites have been prepared in this experiment. Green compacts of Al composites were made at a compressing load of 1 ton and 2 ton respectively. These compacts were sintered at two different sintering tem
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Summary of Mechanical Properties of Materials o
Stress = force/area Units are Nm
o
-2
σ
=F/A
or Pa
Strain = extension/original length
ε
=
∆
l/l
Strain has no units (dimensionless) o
Young Modulus= stress/strain Units are Nm
o
-2
E=
σ
/ε
or Pa
Area of circular section
A =
π
d2 / 4
Units are m 2 o
Ceramic materials such as brick and concrete are strong in compression but weak in tension.
o
The strength of a material is represented by its breaking stress or yield stress
o
o
o
Breaking stress (or fracture stress or fracture strength) is the stress at which the material fractures. Yield stress (or yield strength) is the stress above which permanent deformation (plastic in the case of metals) occurs. The compressive strength of a material is the stress at which it will yield (ie undergo permanent deformation) in compression.
o
The stiffness or rigidity of a material is represented by its Young modulus E.
o
i n the elastic region) E is found from the initial gradient of a stress-strain graph (ie in
o
o
o
o
o
o
o
Up to the elastic limit (or yield point) materials will return to their original relaxed state when a mechanical stress is removed. In the case of metals the elastic region region is linear. Beyond the elastic limit permanent deformation and/or fracture occur. The toughness of a material is the energy needed to break the sample (per unit area of fracture surface). An alternative measure measure is the energy used or work work done to break it per per unit volume of material. Toughness is measured by an impact test (energy lost by a swinging hammer in breaking a sample of the material, divided divided by the area of cross section section of the sample). Alternatively it is measured by the area under the stress-strain curve up to the point of fracture. This area represents the work done per unit volume to break the sample. The hardness of a material material is how difficult it is to indent or scratch. Indentation hardness is related to the compressive strength of the material. Metals often have fairly high E values (50 – 400 GPa) and strength fairly high values (typically several hundred hundred MPa). They undergo undergo significant plastic deformation. The area under their stress-strain curves is large, so these materials are tough. Ceramic materials have high E values, often with high strength, but do not undergo permanent deformation. The area under their stress-strain stress-strain curves is small – they are are brittle (opposite of tough). Ceramics like brick and and stone are stronger in compression compression than tension, and their their applications reflect this. Polymers tend to have have low yield points – so are are relatively weak. Thermoplastic polymers polymers show considerable strain strain to failure. The area under their stress-strain stress-strain graphs is often moderate moderate so they are of moderate toughness.
