# Questions tagged [stiffness]

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### Bending stiffness of composite shaft

What is the method to compute the effective bending stiffness "EI" of a composite structure, in this case a shaft (as seen below). The shaft is hollow with outer radius $r_{o}$, inner radius ...
18 views

### Database for stiffness matrix? [closed]

I have searched everywhere for the stiffness matrix of GFRP, but there isn't a single paper or site that experimented the full matrix. Is there any sort of database for the stiffness matrix of many ...
29 views

### How do FE solvers solve the case of panel buckling under pure shear?

How do FE solvers solve the case of panel buckling under pure shear? The main problem is that global matrix of initial stess is singular in that case. One method is to apply some forces that shear is ...
42 views

### Solving for stiffness matrix numerically by a set of measurements

Is it in general possible when you have a mechanical structure (in this case I am referring to the structure in this post) and you want to determine the global stiffness matrix of this structure, to ...
310 views

### FEM - is symmetry a boundary condition?

In FEM is symmetry technically a boundary condition? For example using the FEM on a symmetrically loaded and supported beam. The FEM can be simplified by using symmetry. However, is this symmetry ...
483 views

### Degrees of freedom of an internal hinge in plane beam?

What are the degrees of freedom of an internal hinge in a plane beam? I understand that the bending moment=0, does this mean there is no slope either? Or does it have both degrees of freedom of ...
32 views

### Looking for thin flexible and strong material

I have a project in which I have to use a up to 2.5mm diameter needle with a 90 degree (L shape) angle similar than the one in the following picture: I say similar because there is only the tip of ...
2k views

### Stiffness of a cantilever beam

I am working on calculating the stiffness of a cantilever beam by applying a distributed load. I wanted to ask if the distribution of the load on the beam effects its stiffness. For eg., if I apply a ...
3k views

### How does stiffness/rigidity affect the bending moment of a beam

My question may sound silly as it’s mainly good sense but I may be mixing things up. Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other ...
117 views

### Stiffness of highly compressible materials

A foam which I have performed compression tests on shows results similar to the following hysteresis cycle: (Note that the first bend in the graph is not the yield point; the hysteresis cycle returns ...
544 views

### Determining when bolt will bend

I'm attaching a metal pipe to a metal tube as shown in the below diagram. The bolt is threaded through one wall of the pipe and does not pass through the opposite wall of the pipe, but is tightened to ...
107 views

### Increasing the stiffnes of a structure by adding stiffener, but at the same time reducing main surface thickness

Let's say I'm designing a table surface which has to be stiff, rigid, but at the same time, not too heavy. It is rectangular in shape and ratio of length:width is quite large. It is only supported on ...
56 views

### How to implement a Monte Carlo Simulation for studying uncertainty in dynamic stiffness?

I have a dynamic mechanical system of the form: $$\mathbf{M{\ddot q}+{\Omega_c}G{\dot q}+{Kq}=F(t)}$$ and I need to introduce some uncertainty for the $K$ parameter, which is a symetric matrix of $q$ ...
120 views

### Beam stiffness matrix with sliding end release in arbitrary angle

I know how to get the stiffness matrix of a beam with any type of end releases (hinges and rollers) by applying Guyan reduction (static condensation) to the beam stiffness matrix in local axes. ...
91 views

### What is the deflection of planet-ring Gear Mesh along the pressure line and the position of the Plant gear?

For a Sun-Planet mesh in a planetary gear train, there will be a deflection $\delta_{sn}=\delta_{s}-\delta_{n}$ along the pressure line and the position of the planet will be determined by $\psi_{n}$, ...
128 views

### Asymettric stiffness matrix for a generator-gearbox-turbine system

I need to model the system in figure, where turbine, shaft1 and gear1 are a unique rigid body, while shaft2 can be modeled like a torsional spring. Using as coordinates Theta1, clockwise angular ...
359 views

### How much does the elasticity (Young's Modulus) of concrete and asphalt change with ambient temperature?

I'm assuming here that all materials will have a change in elasticity due to thermal expansion/contraction and a resultant reduction/increase in the strength of the bonds of the atoms leading to a ...
203 views

### Why does a simple pin-ended triangular (arched/curved) beam deflect more due to secondary effects (non-linear analysis)?

I cannot wrap my head around this. I have made two simple models, a triangular (or curved or arched) beam that is pin ended and has a single point load of 1N downwards at it's center, and a flat beam ...
2k views

### Definition of stiffness for structural dynamics: How would you find the stiffness of an unusual beam directly?

I have a structure which is essentially a curved beam (not an arch or anything simple) which I have modeled in microstran/spacegass. It looks something like this: Or for something more simple, ...
4k views

### Convert translational stiffness to rotational stiffness of a screw

I have the formula for the translational stiffness which is : However, what I would like to find is the rotational stiffness. Is there any formulas to convert from one to an other knowing the pitch ...
1k views

### Stiffness of members in a bolted joint

I'm trying to calculate the safety factor against separation of members in a design that looks like this: I know how to find the bolt and cylinder stiffness, but I don't know how to find the ...
116 views

### Elasticity of a drilled plate

If I take a large thin plate and I uniformly drill a very large number of holes (diameter "d") very close together (minimum spacing "s"), what will be the stiffness of this new plate? When I say "...
96 views

### Dominant parameters in the dynamical response of a linear oscillator

I am working with a very simple 3-DOF damped LTI spring-mass system. As an exercise I am altering two parameters simultaneously (stiffness and damping coefficients connecting mass 1 to mass 2) to see ...