What is Stiffness: Definition and 171 Discussions

The problem is attached.

OK. First of all, I'm novice at Physics so this question may be weird. Above, there are 2 expressions for strain-stress relations. Let's assume that all components in the matrix are variables, not zero, not E, nor not G in the first picture. The first one is written in 2D matrix form, whereas...

Hi everyone, I'm french, so sorry for my bad english. I have a problem to compute the damping as a function of frequency. In fact, I plot the transfer function between the input (which is a force applied bu a hammer) and the output (which is an acceleration). Therefore, I can analyse the mode...

http://i.imgur.com/UNrCRD0.png How can I calculate k1,travel2 & k2,travel2 in this system? I know that k_series = k1*k2/(k1+k2) but that is the extend of my knowledge.

Homework Statement Hi, I need some help analysing this frame. First of all i bellive its hard, if not impossible, to get as detailed results by hand calculations as my softwear CSI Sap2000. Becourse of shear and axial deformation. Is it possible to obtain the stiffness matrix of this frame at...

Hi, There is a rattling noise in one of the automobile passenger car gearboxes that we designed. After few experiments and observations, it was found that the noise is because of incorrect clutch stiffness and hysteresis behavior. I have got some fundamental questions about both: 1. Clutch...

How to derive the formula to find the bending stiffness of an isotropic tapered tube which is cantilevered with a point load applied at the free end?

I am a BSc product design student. This is one of my assignments and I have never done physics in my life. Can anyone help? I do not understand at all!

Homework Statement 1. A structure with weight of 100 kN and which has a natural period of 1 second. Compute the stiffness of the structure. The structure has 5% critical damping. The structure when at rest is subjected to a half sine wave loading having a magnitude of 10kN and lasting 2...

Hi all, I'm wondering if anyone knows of a way to obtain elasticity properties (Ex, Ey, Ez, Gxy, Gxz, Gyz, vxy, vxz, vyz) from the terms of a 6x6 anisotropic stiffness or compliance matrix. I'm looking for a closed form solution, preferably. I would think that there should be a closed form...

Hi all, I'm looking for physical and mathematical explanations for a phenomenon I've noticed when working with rotated material properties relative to an XYZ coordinate system. For certain rotations (~40 to ~50 degrees) about a single axis the S12, S13, or S23 components of the compliance...

Hello. I need help with the following problem: I don't know where to start. I know that the frame can be split up into one symmetric part and one symmetric+assymetric part but i forgot the theory and rules on translation and axis etc. I hope someone can help as I have to hand in the...

Hello, Looking for some advice on increasing bending stiffness of a mild steel 1" x 0.065" round tube. This is for a motorcycle frame and clearance is an issue. There is a fuel tank above and the engine below this top tube (two running parallel) that I wanted to reinforce against bending...

I am going through Shigley's Mechanical Design book and have a quick question on fasteners. Sometimes when calculating the spring rate for a member, you have to multiply the rate by 2, why is this? For instance in this problem http://imgur.com/2ug9AaR When the spring rate is calculated for...

Dear all, I am writing my finite element code for linear elasticity analysis with linear tetrahedral elements. I am not new to the finite element method and my code already works well with element types of triangles, quadrangles in 2D and hexahedrons in 3D but I don't get the correct result...

This problem has a lot of calculations from the beginning so i have skipped to the part i am stuck with and tried to include relevant information, apologies if i have missed anything. Assume all working is correct as i was given the answers. After carrying out the stiffness matrix method I am...

I'm creating a computer implementation to solve planar trusses. And I'm not sure how to check if the truss is solvable or not. Can you help me with that? In my implementation, the trusses are created randomly (needs to be this way), so i get a lot of unstable or indeterminate trusses. I want...

Looking at the Einstein equation, stresses can cause a deformation of space time. This link here https://twitter.com/anilananth/status/339030628181868544 gives a value for the elastic modulus ("stiffness") of spacetime. I think that the value of 10^24GPa must be related to Einstein's...

Hi, When I discuss about gears NVH, the term contact stiffness(Cɣ) comes across very often. It is given with a nominal mean value with its upper and lower fluctuation. I can thus understand that the stiffness varies from the start of mesh till end of mesh reaching the mean value at it's pitch...

Hello every body, I am simulating a 1 dof spring-mass model in ansys workbench. I need to change the stiffness of spring at every substep based on an "if condition". It means that, in every substep, if a specified condition is satisfied, the stiffness will be changed to a defined value. Also...

Hi all. It's been a few years since I've posted here, but it's remained a great go-to resource for me. Any time I have dealt with mechanical vibrations, the fundamental frequency was based on a constant stiffness. However, I have never encountered the subject of finding the fundamental...

Question: Part 1: Below about 80 K the heat capacity at constant volume for hydrogen gas (H2) is 3/2k per molecule, but at higher temperatures the heat capacity increases to 5/2k per molecule due to contributions from rotational energy states. Use these observations to estimate the distance...

Homework Statement Suppose a spring with forces F=k*z. Find the equivalent stiffness of a horizontal spring, where the spring and its horizontal equivalent is separated by theta degrees. The horizontal equivalent presumably will have a force F(x)=k(x)*x Homework Equations F =...

1.How do i derive the stiffness matrix for a beam with nodal linkage? ie the shear force at the first node is 0 but the usual shear and moment resistance is present for the second node. I thouth about solving the problem by just putting the first row of the stiffness matrix as 0 . Am i...

Hi, This is a sample problem from logan finite element method. I have attached the problem and solution given in the book. As per the problem i first derived the stiffness matrix and den putting the boundary conditions started solving for the forces. I am stuck as three forces are unknown but...

Hello, My question is simple, but it does confuse me. I need to know the exact difference between Initial stiffness,post limit stiffness, and secant stiffness in details please Please clarify this on graph if possible Thank you

Hello, I am conducting FE modelling on specimen of steel surrounded by concrete, and i obtain curve which have stiffness similar to experiment(all assume linear behaviour for all materials) but the start of curve is not convenient displacement -0.0071033 0.0123265 0.0310888...

Homework Statement Homework Equations 1-Stiffness matrix? 2-When i am doing the deformation,should i consider stress stiffenning or just solve the problem as is The Attempt at a Solution I tried to form the necessary stiffness matrix but couldn't understand how should i...

Homework Statement A scheme of springs and dampers is given. What is equivalent stiffness and damping? Homework Equations For stiffness in series: keq=ka*kb/(ka+kb) For stiffness in parallel: keq=ka+kb For dampers similarly. The Attempt at a Solution To me it looks like k1 and k2 are in...

Hello, I just have simple question regarding shear stiffness for elevated water tank, this tank is elevated on a column and this column is fix in the base my question is which formula should i use to calculate k k=3EI/L3 OR 12EI/L3 i know the the first for fix pin case and the second...

I am trying to design a spring given the following measurements: Spring Stiffness is 400N/m or 295 ft lbs Outer Diameter of spring is 0.25 in Free Length is 3 cm or 1.18 in Load is max: 5lbs I am having trouble with: Calculating the Spring Diamter so as the spring is not over damped...

Merely a question concerning elementary calculation of stiffness: I have two rectangular and solid bars made of the same homogeneous material: Bar A is 0.85 cm high and 0.5 cm wide, whereas bar B is 1.0 cm high and 0.425 cm wide – and as both bars have the same cross-section area (of 0.425...

Howdy, If I have the following configuration of nodes: 2---4--6 | \ | /| | \ | / | | \| / | | \/ | 1---3--5 What should the dimensions of my FEM stiffness be? Thanks

I need to find the stiffness matrix of a beam element from the basic priciples. I am not allowed to use Lagrange's polynomial or other methods. Need to find the stiffness matrix from basic principles ie to find at each node k11 and so on.. I have attached a screenshot of the problem. When i...

HiAs I am reading through my textbook on the stiffness for two clamped members, As I am reading about the rotschers pressure cone , there is a sentence that say: "in this book we use alpha(half apex angle) = 30 deg except in cases in which the material is insufficient to allow the frusta to...

What led to relativity is the thought experiment where two people are attached, one to a coil and one to a magnet. It is described at the end of this page . http://www.physics.ucla.edu/demoweb/demomanual/modern_physics/special_relativity/special_relativity.html My question is in the...

stiffness of a single interatomic "spring" PLEASE HELP One mole of tungsten (6 1023 atoms) has a mass of 184 grams, and its density is 19.3 grams per cubic centimeter, so the center-to-center distance between atoms is 2.51 10-10 m. You have a long thin bar of tungsten, 2.5 m long, with a square...

Hallo Engineers, I am a little bit confused here and i need some guidance. Can any of you educate me on how to calculate the Bending and Torsional stiffness of a Hat/Omega stringer attached on a plate to form a fuselage panel?..You can also recommend to me a book where it is clearly described...

Homework Statement I have the following practice problem which is presented as follows: What is the size of the global stiffness matrix K (i.e., Kuu) for the 2-D problem? http://imgur.com/KZec3 (Unsolved) http://imgur.com/piv1J (Solved) Homework Equations The Attempt at a...

As per Maxwell reciprocal theorem, it is valid only for elastic materials and structures indergoing small displacements.That is k12 = k21, kij = kji hence stiffness matrix is symmetric. Howbver, I just have been going through MY OWN written programs for geometric non linear problems and I...

AFAIK, the wood used for aircraft structures should have a specific stiffness, that is specific Young's modulus and bending strength, somewhat higher than aluminium (see attached image). If that is the case, why wood aircrafts are generally more subject to aeroelastic effects compared to...

I'm researching CNTs and am currently describing Graphene as I lead from carbon atoms to nano-tubes. I've come across this: "The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses...

Homework Statement a machine of mass 100 tonne generates a simple harmonic disturbing force when operating at a speed of 200rpm. to protect the floor and surrounding machinery it is proposed tp mount the machine on helical springs so that the transmissibility ratio is reduced to 0.1 Q1...

Homework Statement a machine of mass 100 tonne generates a simple harmonic disturbing force when operating at a speed of 200rpm. to protect the floor and surrounding machinery it is proposed tp mount the machine on helical springs so that the transmissibility ratio is reduced to 0.1 Q1...

Homework Statement What happens to the frequency of oscillation if stiffness increases and why? Homework Equations ? The Attempt at a Solution Frequency increases but trying to figure out why.

stiffness and damping coeficients of a VW Golf Hi! I need information about the VW Golf IV 1.6 16V(2003). I need to estimate and calculate the transfer function of the quarter model car so i need the coeficients of stiffness (K) (N/m) and damping (C) (Ns/m) of the front suspension, its...

I am thinking about building a projector screen out of MDF. Here Down Under the available sizes are: http://www.misterplywood.com.au/products/mdf. Building such a screen will be easier than the normal frame with stretched fabric type, but I am concerned about its long-term flatness. So I thought...

Hi, For an undamped mass, spring system subject to a harmonic force, the equation is: ma+kx=Fsin(ωt) where a=d^2/dx^2 After solving the diff eqns, the steady state amplitude is: X=(F/m)/(ω^2-ω0^2) where ω is the frequency and ω0 is the natural frequency =sqrt(k/m) according to the...

My main question is why we derive the structure matrix for a beam like the attached first picture; we assume the beam on the left on point B has no deflection? While i check this by computer analsysis program and it has an effect. Please explain in details The second question is the...

Guys when i study earthquake , they told me that the column stiffness is 12EI/L3 if column is fixed -fixed and 3EI/L3 if column is pin -fixed, so how they get this, i try to study stiffness Matrix and it gives you big matrix for frames not Only one factor like 12EI/L3 please explain