Calculate Factor of Safety for Steel Hanger w/ 550 MPa Strength

[walleye3]

Homework Statement

What is the factor of safety of a steel hanger having an ultimate strength of 550.00 MPa and supporting a load of 64000.000N. The steel hanger in question has a cross sectional area of 7.400cm squared

Homework Equations

The Attempt at a Solution

i understand the equation is ulitamate stress divided by allowable stress but the cross sectional area gives me problems. please show me a the steps i should take to find the factor of safety




well i went load/ area > 64000N/7.4cm squared = 8648.65 Pa


550 MPa = 550000kPa/8.648kPa (ultimate stress/allowable stress) =63594.11
63.59 as my answer is that correct ? if not please show me where i went wrong

 

[rock.freak667]

Given the load and the area, how do you find the working stress i.e. stress due to the load?

 

[walleye3]

Load divided by area ...right ? , when it gives me cross sectional area do I need to do anything mathematically with it or do I plug that number in ?

 

[rock.freak667]

Load divided by area ...right ? , when it gives me cross sectional area do I need to do anything mathematically with it or do I plug that number in ?

Well you have the formula

stress = load/area

And you are given both. You want to get the value of stress.

 

[walleye3]

well i went load/ area > 64000N/7.4cm squared = 8648.65 Pa


550 MPa = 550000kPa/8.648kPa (ultimate stress/allowable stress) =63594.11
63.59 as my answer is that correct ? if not please show me where i went wrong

 

[CWatters]

Check the units. cm² ?

 

[walleye3]

oh , i need metres squared

 

[walleye3]

Load/Area= 64000N/0.074m= 864864.8649 Pa > 864.864 kPa
F/S = Ultimate stress/ Allowable Stress = 550 MPa/ 864.864 kPa > 550000 kPa/ 864.864kPa = 635.938


is (635.938 ) my answer ? (factor of safety) ??

 

[rock.freak667]

Load/Area= 64000N/0.074m= 864864.8649 Pa > 864.864 kPa
F/S = Ultimate stress/ Allowable Stress = 550 MPa/ 864.864 kPa > 550000 kPa/ 864.864kPa = 635.938


is (635.938 ) my answer ? (factor of safety) ??

1 cm² = 0.0001 m²

 

[Chestermiller]

1.0 cm²= ?? m²

 

[walleye3]

1 cm = 0.01 m ...

 

[walleye3]

okay thank you... i see my mistake

 

[walleye3]

64000 N/ 0.00074m2 = 86486486.49 Pa > 86486.48649 kPa
F/S Ultimate stress/Allowable Stress = 550 MPa/86486.48649 > 550000kPa /86486.48649= 6.359

 

[CWatters]

Allowable / Actual