Brushed 304 Stainless Steel Round Tubes Hardness: Rockwell B70 (Medium) Temper Rating: Softened Heat Treatable: No Specifications Met: ASTM A213. ASTM A269 These tubes have a polished surface with minimal grain lines. From cookware to chemical-processing equipment. 304 stainless steel is a good all-around choice for a wide range of applications. It maintains its corrosion resistance in temperatures up to 1500 degree F. One of the most widely used types of steel, low-carbon steel is weldable, machinable, and can be surface hardened by heat treating. It is suitable for a variety of applications, such as structural and power transmission components. Warning: Physical, mechanical, and chemical properties are not guaranteed and are intended only as a basis for comparison. Metric Square TubesA \"Unpolished Yield Strength: 34.000 psi Hardness: Soft (Rockwell B67) Material is Grade S235 carbon steel. Length tolerance is plusminus 2\". Consider the structure shown in Fig. 1. A hollow tube with circular cross-section of length L = 0.5 m is attached to a rigid wall. A force F = 8 kN is applied axially to the tube (through the centroid). Using a design factor of n_D = 2, which metric stainless steel tube would you purchase from McMaster-Carr (McMaster.com), if (1) 10 mm lessthanorequalto OD lessthanorequalto 20 mm and (2) cost must be minimized? What is the implied safety factor? Hand in: Dimensions and product U of the tube you selected. Include your calculations. Safety factor. Consider the structure shown in Fig 2. A hollow tube with square cross-section of length L = 0.5 m is attached to a rigid wall. A force F = 20 kN is applied axially to the beam (through the centroid). Using a design factor of n_D = 2, which general purpose low-carbon steel metric square tube would you purchase from McMaster-Carr (McMaster.com)? What is the resulting safety factor? Hand in: Dimensions and product # of the square bar you selected. Include your calculations Safety factor.
solution:
for Q1
1)for round hollow tube tensile stress is given by
F=8 KN
Sallowable=F/A=F*4/(pi*(OD^2-ID^2))
Sallowable=Sy/nd=24000/2=12000 psi or 82740018 N/m2
putting value we get that
OD^2-ID^2=1.231074*10^-4 m2
from chart for this difference value,only two choice can be recommended and those are
i)OD=20 mm and ID=16 mm(its price in betwwen 33 to 76.56 dollar)
ii)OD=15 mm and ID=9 mm(its price is in between 44.55 to 103.36 dollar)
looking at this two choices first choice is better so we choose first
hence dimension of tube selected are
OD=20 mm and ID=16 mm
where factor of safety is given by
Sallowable=F/A=F*4/(pi*(OD^2-ID^2))=70735530.26 N/m2
Sy=165480037 N/m2 or 24000 psi
factor of safety=nf=Sy/Sallowable=2.3394
2)for Q 2
1)for round hollow square tube tensile stress is given by
F=20 KN
Sallowable=F/A=F/(D^2-d^2)
Sallowable=Sy/nd=34000/2=17000 psi or 117215026 N/m2
putting value we get that
D^2-d^2=1.7062*10^-4 m2
from chart for this difference value,only one choice can be recommended and those are
i)D=25 mm and thickness 2 mm and d=21 mm(its price in betwwen 10.45 to 26.14 dollar)
looking at this choice is better so we choose it
hence dimension of tube selected are
D=25 mm and d=21 mm
where factor of safety is given by
Sallowable=F/A=F/(D^2-d^2)=108695652.2 N/m2
Sy=234430052 N/m2 or 34000 psi
factor of safety=nf=Sy/Sallowable=2.1567
in this way we have solve both of them and decide its dimension for minimzed cost and its implied factor of safety as above.
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