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1

Engineering point of view: There are ropes that do have significant bending stiffness (and, as a consequence, compression hardness). E.g. steel wire ropes. This is almost never an advantage - such ropes tend to self-tangle easier (but making intentional knots is harder), tend to break at small bending radius (making most knots unusable) and tend to retain ...


2

"$E$", "$K$", and "hardness", all indicate stiffness but are measured and used in different manners. $E$ - Elastic modulus is defined as the slope of the tangent line to the stress-strain (elastic) curve. It is a material-specific quantity that measures the resistance to being deformed elastically when stress is applied to it, ...


1

Check out this link, it might help. Should we use Hooke's Law (that linearly relates stresses to strains) if the stiffness of body is changing during deformation? Now, the stiffness equation i.e. K = EA/L is only used for axial loading conditions. It is derived by dividing the load applied by max deflection. However, for bending cases, the bending stiffness ...


2

(Spring) Stiffness $K$ is a property of a structure which includes geometric and material effects. On the other hand, Young's Modulus $E$ is a property of the material. Bottom line is that given the same material (i.e. same Young's modulus), changing the cross-section A or the length L could result in different deformation. So: for a given structure K is ...


3

Having low stiffness is part of the specification of a rope. It would be far cheaper to obtain the same tensile strength with a solid rod. Creating and manipulating multiple strands is expensive. It is designed to use multiple thin strands to achieve this lack of stiffness. The question of how thin strands, with their small moment of area, achieve this lack ...


2

It won't just keep itself straight You know a steel beam held at one end won't just keep itself straight either right? It also bends under it's own weight when supported by one end. Just because you can't perceive something with eyes doesn't mean it's not there. It just means your eyes aren't precise enough. The fact that the rope has a radius of curvature ...


1

They design the jumping rope this way. if it would have any moment strength or compression strength it woul act as a soft "column" at the strat where half of the cord is bent up to reach the Jumper's harness. Thus it could send the jumper into an unpredictable dangerous arc, as opposed to let them fall straight down into hopefully a clear vertical ...


17

TL;DR: The bending and compression (buckling) stiffness is so small because the second moment of area of the fibres is small. Bending stiffness It does have a bending stiffness however it is really really small. More precisely it has a really really small second moment of area per fibre. (see the numerical example below to understand why many more ...


3

The standard is that The cylinder part should be hatched but not the rib. So something like the following.


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