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9

The basic difference between implicit and explicit dynamics solutions is that an explicit solution takes account of the finite propagation speed (at the speed of sound) of dynamic effects through the material. To do that, you need a mesh which is fine enough to represent the spatial effects (e.g. a "stress wave" propagating through the structure), and time-...


3

In linear static formulation of FE problem the equations do not include time, so the time you enter is not used. If, however, you are doing an implicit time dependent analysis, the time and time-steps are used to advance the solution in time. Note that each step is still a static solution of the system. If there is a material non-linearity then the ...


3

"Statics" usually is defined as meaning that the acceleration of the structure is too small to cause significant inertia forces, i.e. the "mass $\times$ acceleration" terms in the equations of motion can be ignored. However the response of the structure may still change with time when the acceleration is negligible, if the material behaviour is nonlinear ...


3

These look like some sort of tensile test on a ductile material which is loaded until it breaks. In the experiment, it looks like the test rig has some "slack" which gets taken up when the load reaches about 25 kN. There may be some flexibility in the test rig that makes the slope of the elastic deformation different from the theoretical model of a ...


3

Without knowing more about your problem the first thing that you need to do is make sure that you are using the right geometry and elements. To use that representation you need to use: 2D geometry Mesh it as shells Assign a plain stress assumption


3

From a theoretical standpoint, the displacement gradient is equivalent to strain (assuming a structural problem). Numerically, you can obtain the derivate of a quantity through multiplication with the derivative of the shape functions, which is often referred to as the B matrix: du = B u


2

It really depends on two things: What do you hope to get out of the analysis? How much discretization do you need to integrate the equations? For the first item, if you need 100 snapshots of stresses during the rolling process, then try the step time divided by 100 as your initial and maximum time increment. If all you need is the final deformed state of ...


2

The STRI3 element is a shell element has 3 integration points according to the ABAQUS manual. Forget 3D coordinates (global X,Y,Z) for the moment. Just think of the shell's local 2D coordinate system in x,y. Take the isoparametric representation of any triangle as having coordinates (0,0), (1,0) and (0,1) as shown below: The integration points in ($\xi$, $\...


2

Maybe it is correct, maybe it isn't. Suppose you "corrode away" a small radius that was causing a stress concentration, and it becomes a bigger radius. Quite likely the maximum stress in the structure (at that concentration) will decrease because of the corrosion. For example an "average" stress of 1.0 and a stress concentration of 10.0 might become an "...


2

The strength of the steel has not changed unless there is some factor you have not mentioned. You can get a good estimate of the remaining strength of the structure by putting in the minimum remaining thickness of the various sections into the program. This technique is accepted by AGA ( American Gas Association) , and I think ASME or ANSI, for determining ...


2

The tail end of the curve is probably not a massive issue as that is well into the region which would normally be considered failure in any case and FE systems often don't really look at failure mode in detail. Of more concern is the elastic region where the FEM results suggest it is a lot stiffer than it is in the experiment. The experimental curve also ...


2

just guessing you might be seeking ascii human readable reporting, you can put in the inp file, (after your first *STEP line.) *EL PRINT,ELSET=setname E S this will dump the data into your ".dat" file. This is primarily useful if you want data for a small element set (like one particular element). If you need the whole model data do yourself a ...


2

In Abaqus, there are two primary analysis methods used for solving structural problems, namely Abaqus/Standard and Abaqus/Explicit (includes dynamic Explicit). Abaqus/Standard has static implicit and dynamic implicit and is suitable for solving smooth nonlinear problems. However, the solution of these problems may converge with difficulty, because of the ...


2

Static analysis is an ideal scenario, no real event is actually static- either quasi-static or dynamic. It is based on the assumption that all loads are applied slowly and gradually until they reach their full magnitudes. So when you have some (pseudo) time steps, what you are basically doing is discretizing the steps of load application.


1

If the model is a three dimensional object, restrain exactly 6 degrees of freedom, so it can not translate or rotate, but it can deform in any way without creating reaction forces at the restraints. If the elements in the model have rotation degrees of freedom, this is easy: you just restrain all 6 degrees of freedom at one grid point. This link shows some ...


1

I'm unsure about the magnitude of the change, but providing tension by preloading an object definitely alters the natural frequency. It is commonly adopted to avoid resonance from external disruptions. I have seen the idea adopted with shafts, but in a single lap joint like your example I can't imagine the affect is very big, as you observed. When ...


1

Well, two categories of questions come to mind straight away: 1) what values were used for the FEM? Are they based on the actual material tested? What was the source of those values and the confidence level? 2) what accuracy were the primary results measured to? Change in length for example - how was it measured? A plastic ruler or a digital vernier with 3 ...


1

plane stress, plane strain, and generalized plane strain are three different things. In each case you need to specify the appropriate element type ( plane stress is default ). Generalized plane strain introduces an additional issue. You must create and assign a reference point to the section. It is the reference point assignment that causes generalized ...


1

In general, how you use ABAQUS depends on what you are looking to observe. Are you hoping to simply observe stress or deflection as a function of time? Are you trying to simulate damage or failure? These considerations matter at a basic level. On a simple level, there are several steps in creating an ABAQUS file from CAE. 1. Creating the geometry of a part....


1

in many cases where this type error is detected during job submission a node set is created to identify the offending nodes. open the odb in the visualization module, go into display group manager, look for node sets with names like "ERROR...." or "WARNING...".


1

There can be thousands of causes for your error. You need to give many more informations to be able to make a guess. Like: discretization, solving methods for the DEQs, grid topology, boundary conditions etc.


1

By default Abaqus decides time increments adaptively. The initial time increment is typically a guess. If the guess is too large to solve the equations for the first time increment, it guesses smaller and repeats the process. If the guess could be larger and the equations still solve well, it increases the guess. If your simulations run in a reasonable ...


1

I have only done this sort of optimization using non-commercial software. Rather than trying to fit "the FRF" (i.e. the complete shape of all your measured response functions) I would start by estimating the frequencies and mode shapes from the measured FRFs and fitting just those parameters. In fact a good first attempt would be just to fit the frequencies,...


1

In a 2d abaqus analysis you can only rotate the material orientation in-plane, in other words you can not "transform" the material 3- direction into the plane of the analysis. (Which seems to be what you are asking in #3) The only solution to this problem is to "manually" transform the material definition, i.e. reordering the values on the *Elastic,...


1

(1) In Abaqus/CAE the stress at each integration point is given by the field variable $S$. Note that in Abaqus, like many or even most FE solvers, the stress computed is the Cauchy (true) stress. So, for a material with local material directions given by the Global basis: $\sigma_{x}=S_{11}$, $\sigma_{y}=S_{22}$, etc. You will need to make sure that stresses ...


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