The discussion focuses on the torsional resistance of a hollow shaft compared to a solid shaft, specifically when the hollow shaft's internal diameter is two-thirds of its external diameter. The key equations referenced include T/J = G * angle of twist/length and the relationship between torsional resistance and polar moment of inertia. It is established that the torsional resistance decreases when transitioning from a hollow to a solid shaft due to the dependence on the polar moment of inertia rather than the cross-sectional area. The participants clarify the importance of the polar moment of inertia in calculating torsional resistance.
PREREQUISITESMechanical engineers, materials scientists, and students studying torsional mechanics will benefit from this discussion, particularly those involved in the design and analysis of shafts in mechanical systems.
What does your textbook say?praveenpandiyan said:sorry. J represent torsional constant. its the resistance to torsion. I am i correct ? ..or how can i use area here to calculate variation in resistance. bit confued :(
Don't thank me so soon. I was wrong about it. The shear strain in the shaft is rdθ/dz. If you use this to determine the shear stress, and then the torsional moment, you find that it's the polar moment of inertia that is the thing that comes into play (as you said), not the cross sectional area (as I had said). So your were right in the first place. Senior Moment. Sorry about that.praveenpandiyan said:well .torsion for solid shaft , i have torsion eqn T/J=G*tete/L=shear stess/R
but i found finally its torsional stiffness k=T/twist that provide solution. if not i need to do some ground work myself .thanks chester
It seems well covered here: http://www.engineeringtoolbox.com/torsion-shafts-d_947.htmlpraveenpandiyan said:ok. i get that . so my area of solid shaft = .55*A(hollow ).. but resistance depends on polar moment of inertia right? .
j(solid)=pi/32(D)4 .if I am not wrong .. then does my shaft resistance decreasce?.