I have a strength of material problem with an aluminum rod that has a steel core that has a force placed on it and I have to find the stress in each materialI am only given diameters and the load forceI am also given the yield stress for the aluminum partI was thinking that if I use that yield stress and find the steels yield stress I can find the ratio for the modulus of elasticities and then from there find actual forceBut I think that is an illegal assumption on my partIs this where the elastic perfectly plastic part comes into play?
I'm assuming the force is axial tension or compression of the rodIf so, the problem boils down to two parallel springsImagine the two pieces are disconnected - you have a hollow aluminum tube, and a steel barCompute the stiffness (the spring constant) of each piece using this formula: k EA / L where k is the spring constant, E is the modulus of elasticity, A is the cross-sectional area, and L is the lengthSo, you should end up with k_alum and k_steel, the spring constants for each pieceNow, when you have a force which compresses each spring by the same amountWhy the same amount? Because in reality, the two springs are fused together (one inside the other)When you have two springs in parallel, you have two load paths; two paths through which load can travelHow much load goes through each path depends upon the relative stiffness of each pathThe relative stiffness is simply the fraction of the total stiffnessSo, add the two spring constants together, and find the fraction of the total spring constant that each individual constant contributesThe fraction of the load that travels through that piece is the fraction of that piece's stiffness compared to the total stiffness of all the springs which are in parallel: f_alum (f_total) (k_alum / k_total) f_steel (f_total) (k_steel / k_total) where k_total is of course k_alum + k_steelNow that you know the force transmitted through each piece, simply divide those forces by their respective cross-sectional areas, and you have the stress in each pieceIf the stress in one pieces exceeds its yield stress, then set the stress in that part equal to its yield stress, and redistribute the amount of force required to generate the difference in stress to the other parts (in proportion to their stiffnesses).
first I'd crawl in there and see if the lines are insulated iin the crawlwhat you do t o improve cooling is to shut vents in rooms not being usedWorking the thermostat makes no senseIf you set it for 70 and it's 76 in the room then the air runs full blastIf you set it for 64 and it's 76 in the room then the air runs full blastIn eithecase it runs full blastIt's not like your car where you adjust the fan speed.
