Historically, fatigue tests are performed by rotating bending, i.e. cylindrical specimens are rotated while a load stresses them with a fixed direction in time: this way an alternating cycle from zero is easily obtained. Generally the specimens have a rather small diameter (maximum 10 mm) and it was discovered that, for specimens of larger size, […]
This example is taken from the book Computational Structural Engineering We have the planar frame shown in figure 11.22 through the related beam-type finite element model. From a first linear buckling analysis we find that Fcr = 10512 N. Clearly the element that becomes unstable is the diagonal A, as we can see from figure […]
Every now and then every Structural Engineer has to asses fasteners against thread ripping, especially when non standard screws are used. In fact, in general, handbooks give the tightening torque for every nominal diameter and the load that the bolt can whithstand, assuming that both the screw and the nutscrew are made of steel.In Chapter […]
This simulation was done more for fun rather than being really useful to some design activity. Nonetheless it shows how powerful simulations can be. In this case the material properties used to simulate the tensile test shown in a previous news are here implemented into a Charpy Test coupon (U-shape notch) and the simulation is […]
Introducing the plastic behaviour of a material in a Finite Element Model is not straightforward, but it is not impossible. In the book “Computational Structural Engineering” at Chapter 13 many hints and tips&tricks are given to succesfully introduce into the model the required material data, from a bilinear (simpler) behaviour up to the full stress-strain […]
In general to discriminate if a composite structure can withstand the loads to which it has been designed, the first ply failure approach is followed; this means that when a ply in the laminate reaches its failure point, i.e. has a Failure Index equal to 1.0, then the whole structure is considered failed. Fibers, especially […]
In general the application of a preload inside a member in a Finite Element Model is done by the code by applying MPC equations to the nodes laying on the surface where the preload is to be applied; for example in a bolt modelled with solid elements, the shank will be split at the surface […]
At the times when low computational power and low memory capacity were available, the Superelement technique (more precisely defined as “substructuring“) was used to solve models with a high number of DOFs, while still staying within the limits imposed by the hardware. The method consists in dividing the complete structure to be analysed into substructures; […]
As well known, it is generally a good practice, in a finite element analysis, to perform several iterations of calculation of the same structure in order to determine what is the best mesh density to obtain reliable results. In our days the necessity to try and reduce the commitment of the calculation resources is less […]
I think I am not exaggerating if I say that worldwide the FEA community recognizes that the “best” element type for 3D structures is the hexahedron element (the so-called brick element), especially in its linear formulation (linear shape functions – 8 nodes per element), where with “best” I mean the optimal compromise between model size […]
My generation of Structural Engineers (graduated in the early ’90s of last century) in the mechanical field were post-pioneers in computation with Finite Elements. I say this because they found themselves operating in an industrial environment that was not at all ready to include in the design cycle a phase whose usefulness entrepreneurs struggled to […]
Fatigue assessments are never an easy task, but they are not impossible. FE results on one side give a bunch of information that might confuse and on the other pose questions on both the notch sensitivity and dimensional coefficients. In Chapter 10 of the book “Computational Structural Engineering” the reader is guided through all those […]
In Chapter 17 of the book “Computational Structural Engineering” a very deep analysis of a “simple” bolted connection is presented: influence of preload and friction are discussed and failure is simulated. Finally, a comparison between the implicit and explicit approaches (which are discussed in Chapter 14) is also presented.https://www.cgcae.com/wp-content/uploads/2024/10/Boltfailure.mp4
Here is one case where axisymmetric elements can give great results in very short times, even when dealing with hyperelastic materials! In this case an O-Ring is stretched into its position (this phase is not reported here, but maybe in a future post it will) and then the outer tube is pushed to assemble the […]
