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Beam General Section Types. Fluid Section Types: Gases. Fluid Section Types: Liquids. Fluid Section Types: Open Channels. Boundary conditions. User-defined mechanical material laws. User-defined thermal material laws. User-defined nonlinear equations. This is a description of CalculiX CrunchiX. If you have any problems using the program, this document should solve them. If not, send us an E-mail dhondt tonline.

The next sections contain some useful information on how to use CalculiX in parallel, hints about units and golden rules you should always keep in mind before starting an analysis. Section five contains a simple example problems to wet your appetite. Section six is a theoretical section giving some background on the analysis types, elements, materials etc.

Then, an overview is given of all the available keywords in alphabetical order, followed by detailed instructions on the format of the input deck.

If CalculiX does not run because your input deck has problems, this is the section to look at. Then, there is a section on the user subroutines and a short overview of the program structure. The CalculiX distribution contains a large set of test examples ccx 2.

If you try to solve a new kind of problem you havent dealt with in the past, check these examples. You can also use them to check whether you installed CalculiX correctly if you do so with the compare script and if you experience problems with some of the examples, please check the comments at the start of the corresponding input deck.

Finally, the Users Manual ends with some references used while writing the code. This manual is not a textbook on finite elements. Indeed, a working knowledge of the Finite Element Method is assumed. For people not familiar with the Finite Element Method, I recommend the book by Zienkiewicz and Taylor [78] for engineering oriented students and the publications by Hughes [32] and Dhondt [18] for mathematically minded readers. Nowadays most computers have one socket with several cores, allowing for the calculations to be performed in a parallel way.

In CalculiX one can. No special compilation flag is needed. Notice that older GNU-compiler versions e. This should not be a problem with the actual compiler version. Default is 1. If both are set, the latter takes precedence. Notice that if a material user subroutine Sections 8. These include this list is possibly not exhaustive :. Calculate the magnetic intensity by use of the Biot-Savart law in parallel.

If the openmp flag is not used, these lines are interpreted by the compiler as comment lines and no parallellization takes place. Notice that this parallellization only pays off for rather big systems, lets say , degrees of freedom for CFD-calculations or 1,, degrees of freedom for mechanical frequency calculations.

Examples: For some reason the function sysconf does not work on your computer system and leads to a segmentation fault. You can prevent using the. You can make maximum use of parallelization e. An important issue which frequently raises questions concerns units. Finite element programs do not know any units. The user has to take care of that. In fact, there is only one golden rule: the user must make sure that the numbers he provides have consistent units.

The number of units one can freely choose depends on the application. For thermomechanical problems you can choose four units, e. If these are chosen, everything else is fixed. If you choose SI units for these quantities, i. However, you can also choose other quantities as the independent ones. A popular system at my company is mm for length, N for force, s for time and K for temperature. Finally, a couple of additional examples. Applying the finite element method to real-life problems is not always a piece of cake.

Especially achieving convergence for nonlinear applications large deformation, nonlinear material behavior, contact can be quite tricky. However, adhering to a couple of simple rules can make life a lot easier.

According to my experience, the following guidelines are quite helpful: 1. Check the quality of your mesh in CalculiX GraphiX or by using any other good preprocessor. If the linear version doesnt run, the nonlinear problem wont run either. The linear version allows you to check easily whether the boundary conditions are correct no unrestrained rigid body modes , the loading is the one you meant to apply etc. Furthermore, you get a feeling what the solution should look like.

The standard shape functions for quadratic elements are very good. Most finite element programs use these standard functions. For linear elements this is not the case: linear elements exhibit all kind of weird behavior such as shear locking and volumetric locking.

Therefore, most finite element programs modify the standard shape functions for linear elements to alleviate these problems.

However, there is no standard way of doing this, so each vendor has created his own modifications without necessarily publishing them. This leads to a larger variation in the results if you use linear elements. Since CalculiX uses the standard shape functions for linear elements too, the results must be considered with care.

That way you get the expanded form of these elements in the. You can easily verify whether the thicknesses you specified are correct. Furthermore, you get the 3D stress distribution.

If the former is incorrect, so will the latter be. If you include contact in your calculations and you are using quadratic elements, use the face-to-face penalty contact method.

In general, for contact between faces the face-to-face penalty method will converge much better than the node-to-face method. The memory needed to run a problem depends on the largest node and element numbers the computational time, though, does not. So if you notice large gaps in the numbering, get rid of them and you will need less memory. In some problems you can save memory by choosing an iterative solution method. The iterative scaling method cf. If you experience problems you can: 1.

In particular, the convergence information for nonlinear calculations may indicate the source of your problem. This file contains information on the number of iterations needed in each increment to obtain convergence 3.

This file is a synopsis of the screen output: it gives you a very fast overview of the number of contact elements, the residual force and the largest change in solution in each iteration no matter whether convergent or not. Figure 1: Geometry and boundary conditions of the beam problem 4. This generates a file with the name ResultsForLastIterations.

This generates a file with the name contactelements. By reading this file in CalculiX GraphiX you can visualize all contact elements in each iteration and maybe find the source of your problems. Running CalculiX you will get information on which fields are allocated, reallocated or freed at which line in the code default is 0. In this section, a cantilever beam loaded by point forces at its free end is analyzed.

The geometry, loading and boundary conditions of the cantilever beam are shown in Figure 1. The size of the beam is 1x1x8 m3 , the loading consists of a point force of 9 N and the beam is completely fixed in all directions on the left end.

Let us take 1 m and 1 MN as units of length and force, respectively. Assume that the beam geometry was generated and meshed with CalculiX GraphiX cgx resulting in the mesh in Figure 2. For reasons of clarity, only element labels are displayed. A CalculiX input deck basically consists of a model definition section describing the geometry and boundary conditions of the problem and one or more. Most keyword cards are either model definition cards i. A few can be both.

This has no effect on the output and only serves for identification. Notice that data on the same line are separated by commas and must not exceed a record length of columns. A keyword card can be repeated as often as needed.

Defining the topology means listing for each element its type, which nodes belong to the element and in what order. The element type is a parameter on the keyword card. In the beam case node brick elements with reduced integration have been used, abbreviated as C3D20R.

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