Can you put some units onto your workings out? It would be easier to follow what you are doing (for us and for you).Confusedbiomedeng said:Homework Equations
σ/y=m/I=E/R
I=πD4/64[/B]
y=125/2
The Attempt at a Solution
i)17.5/62.5=M/11984224
0.28x11984224=3355582.72Nmm=M
ii)0.28/200x103=1.4mm=R
Can anyone tell me where I am going wrong ?
in the final answers i have them put in ?? should i put them in throughout the workings??scottdave said:Can you put some units onto your workings out? It would be easier to follow what you are doing (for us and for you).
It would help me to figure out what you were doing.Confusedbiomedeng said:in the final answers i have them put in ?? should i put them in throughout the workings??
So where did the 17.5 come from? I am guessing it is σ. It would be nice to eliminate guessing, when figuring out where you are going wrong.Confusedbiomedeng said:y=125/2
The Attempt at a Solution
i)17.5/62.5=M/11984224
0.28x11984224=3355582.72Nmm=M
ii)0.28/200x103=1.4mm=R
Can anyone tell me where I am going wrong ?
Yes it is stated in the question and I forgot to put it in so 17.5n/mm2 then y is 125/2 because everything is in mm2 so I don't need to change the diameter . I ,I worked out by ∏(1254)/64 but now I'm wondering should the equation for I be ∏(D4)/32?? So sorry for any confusionscottdave said:So where did the 17.5 come from? I am guessing it is σ. It would be nice to eliminate guessing, when figuring out where you are going wrong.
Ok could you just explain why that equation and not M/I =E/R? And so I have the right answer for the allowable bending momentChestermiller said:I confirm you calculation of the bending moment, and I confirm the factor of 64 in the denominator. But the equation for the radius of curvature should be $$R=\frac{Er}{\sigma}$$where r is the radius of the bar.
It's that too. I just found it easier to calculate it the other way.Confusedbiomedeng said:Ok could you just explain why that equation and not M/I =E/R?
The formula for calculating bending moments for a round bar is M = (E * I * y) / R, where E is the modulus of elasticity, I is the moment of inertia, y is the distance from the neutral axis, and R is the radius of the bar.
The modulus of elasticity (E) for a round bar can be found by dividing the stress by the strain. It is typically given in units of N/mm2 (newtons per square millimeter).
The moment of inertia (I) for a round bar is a measure of its resistance to bending. It is calculated by using the formula I = (pi * D^4) / 64, where D is the diameter of the bar.
The distance from the neutral axis (y) for a round bar is the distance from the center of the bar to the point where the bending moment is being calculated. It is typically measured in millimeters (mm).
Calculating bending moments for a round bar is important in determining the maximum stress that the bar can withstand before it will fail due to bending. This information is crucial in the design and analysis of structures and mechanical components that utilize round bars.