# Homework Help: Mechanical principles assistance.

1. Jan 10, 2012

### studenteng

1. The problem statement, all variables and given/known data

Hello this is my first post.
Im currently studying towards a level three national diploma in engineering operations.
I need some assistance with a mechanical principles problem. ( A crude drawing of the problem has been attached haha)
I need to work out the direct and shear stresses on a pair of bolts with an 18mm diameter. The bolts are installed at a 60 degree angle to the applied load and share the loading equally the pull on the joint they are connected to is 100kn ( both sides). The part of the problem i am struggling with is intergrating the angle into my equations. I can work out shear and direct stresses easily when dealing on flat non angled surfaces, but im struggling a bit with the angle.
Id appreciate a description of the method needed to work out the direct and shear stresses when dealing with an angle, rather than the actual answer as i wont learn anything. Im thinking ill need to use trigonometry to resolve this problem, as im stumped in seeing any other way. Maybe some resoloution of forces? Any help will be greatley appreciated.

2. Relevant equations - 3. The attempt at a solution
I also need to work out the limiting factor of safety for both bolts, which i can do without any assistance.
I work direct stress to be f/a = 110kn /(pi (18x10 to the -3 ) / 4) = Direct stress per bolt. But once again im not sure if this is even right as i havent taken the angle into consideration.
Basically i need some form of assistance.

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2. Jan 10, 2012

### nvn

studenteng: Yes, go ahead and break the applied load into components, using trigonometry. You must list relevant equations yourself, and show your work. And then someone might check your math.

Check your calculation of area of a circle; your area calculation currently looks incorrect. And, the total applied load should not be applied as tensile force.

(1) By the way, always leave a space between a numeric value and its following unit symbol. E.g., 18 mm, not 18mm.

(2) The unit symbol for kilonewton is spelled kN, not kn. Lowercase n means nano. Always use correct capitalization of units.

(3) For exponentiation, use the caret (^) symbol. E.g., 10^-3, not "10 to the -3."

(4) For scientific notation, you can use 18e-3.

3. Jan 11, 2012