# Questions tagged [stiffness]

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### What's the most anisotropic material? Is there a dense stiffness matrix?

The stiffness (aka. tangent modulus of the stress) can be represented as a symmetric 6-by-6 matrix, i.e. it has 21 independent components in the most general case. In the linear case, this matrix is ...
790 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 ...
988 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 ...
95 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 ...
159 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 ...
95 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 ...
48 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 $q$ ...
105 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. ...
86 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 $\psi_{n}$, ...
117 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 ...
312 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 ...
181 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, ...
3k 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 ...
737 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 ...
108 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 "...
91 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 ...