AutoCAD Inventor :: Different Results Between Frame Analysis And FEA
Jan 27, 2013
I am trying to run a simulation on a 4 layer part that has two base layers of I-beams, a frame I made in the frame generator (below) and a solid sheet on top. I am having some issues with the FEA side and was curios to see if the frame analysis tool would yield the same results as the stress analysis simulation. For the frame generator I saw 4 times the amount of deflection despite using (what I believe) are similar loading and constraints, however now I am unsure if I can trust to run an FEA simulation with a frame generated component. The frame is made up of 2 inch steel box beam with a 0.25 inch wall thickness. For the frame analysis package, I have applied a pressure that equates to a 70 kN load across four different sections of the frame. Supports have been placed under all four corners, with 1 being fixed and the other 3 free to move. For the FEA simulation, I applied a similar pressure by creating 2 inch wide plates and applying the same pressure at the same four points. There are also 2 inch square pads under the four corners of the frame with one edge of one pad being fixed and the bottom of the pads having a frictionless constraint. There are separation contacts between both the pressure plates on top of the frame and the frame as well as between the pads and the frame.
with the frame generator is that all the segments of the frame are bonded together (under contacts) which makes sense since they are welded together. However when I put a sheet on top of the frame, there are 3 contact points created between each beam on the frame and the sheet (one on the face of the frame that is in contact with the sheet and the other two on the rounds of the frame and the sheet, even though the rounds are not actually in contact with the sheet). Either way, I am seeing deflections of less than 0.1 mm when a 70 kN load is applied which I know is not right and just want to know if using a frame generated component is not possible with an FEA simulation.
I have a stress analysis result that doesn't make sense to me. I have a flat plate, that is loaded with 100psi equally throughout the surface. I have an array of bolt holes that are 120mm x 109mm spacing. When I do the simulation and look at deflection, I see more movement on the ends. I expected the movement to be consistent eveywhere?
Is this an Inventor issue, or are my expectations in error?
On a side bar, is there a better way to constrain holes than on their edges? I would think that would give errors on the stress levels due to the point (line) contact.
Inventor 2011 Pro 64 bit Windows XP Pro 64 bit Dell Precision PWS390 Intel Core 2 CPU 6700 @2.66GHz 7.93 GHz Ram ATI FireGL V7200
I have created a report from a frame analysis of an arrangement of I-Beam steelwork. I need to check that I have placed the nodes in the right order and this is reflected in the results of the report. I have the parent and child nodes connected at the ends of the beams as shown on the attached screen shot. I'm interested to know if the order in which I have selected the nods makes any difference to the results. There a 3 node connection points at each corner section.
Having an assembly, modeled in the frame generator, then with some additional parts (ribs, plates, etc) added to the assembly as parts and constrained with assembly constraints.. which is the best way to do a frame analysis with the frame analysis enviroment for considering the all structure (frame generators parts + the additional enforcing parts) ?
The assembly look like for example, to this (modeled in autocad).
When I go to Environments>Frame Analysis, I used to get a menu for Constraints, Loads and other settings (similar to the Stress Analyisis menu). I don't get that now. I can right-click on an existing simulation and add constraints and loads, but I would really like to get the menu back.
I can go to tools>Customize, Toolbars tab and Frame Analysis Panel is there. I can click Show and it will show the panel but it stays up all the time. Not what I want.
I have tried resetting the menu, repair installing Inventor and Reinstalling Inventor, but still not joy. How do I get this back to the original setting so that it comes up when I select Frame Analysis?
I understand that in a normal part to apply a load to a face is to make it a UDL (uniformly distributed load) by default. To apply a point load, I was told to create a small sketch and use it to split a face to create, in effect, a small face on which to apply a load, effectively making it a point load.
Now in the frame analysis environment, there is clearly an option for 'force' and one for 'continuous force' which the description clearly describes as a uniformly distributed load. However, when I run the simulation (on a 2m long 100mm x 50mm x 4mm Rectangular hollow beam) with a normal load in the middle of the beam (1m offset); the maximum moment comes out at 500000 Nmm or 500 Nm. By my reckoning the moment should be 1000 Nm as the basic formula for a moment from a point load is M = F*D (Moment = Force * Distance). However, to get 500 Nm, it looks like Inventor is using M = (F*x^2)/2 where x is the midspan of the beam (in this case 1m). .is a normal load in frame analysis the same as a UDL? If so..how to I make it a point load?
There are also some errors stating instability of type 2 at various nodes, I've used both Pinned and Floating constraints at either end of the beam.
I have a question regarding adding a force constraint in the Inventor frame analysis environment. When I add the fixed constraint to the beam the orientation indicator is incorrect - the square indicator being not parallel to the base of the beam. I would like to know why this is and as I am relatively new to frame analysis if I am doing something wrong. I have attached a screen shot of the placement of the constraint on the beam.
Autodesk Inventor Professional 2013 SP2 64-Bit Edition Windows 7 HP Z400, Intel Xeon W3550 3.07GHz 12.0GB RAM, ATI FirePro V4800 (FireGL)
I am trying to run a Frame analysis on a beam structure. I wanted a specific yield stress for the components that make up the beam. So I created a new material and changed the yield stress and change my beam components to that new material. However when I run the simulation the yield stress is not what I made it. Is this allowed?
I am busy constructing my own Structural Shapes Library in Inventor 1012.During the Authoring and Publishing step I mapped Cross Section Properties (Ixx, Iyy, Torsional Section Modulus, Torsional Rigidity Modulus etc) to set parameters in my iPart table.
I have noticed that once this part is then used in Frame Generator to create a simple beam and then analyzed with the Frame Analysis tool, the analysis tool uses the geometry of the part to calculate these properties.
Is there a way that I can force Inventor to use the properties in the iPart Tables? I am worried that any errors in creating the cross section geometry will be carried into the Cross Section Properties calculated by Inventor.
I created a structural shape profile for use in a project. It is square tube with radiused corners, very similar to "ANSI/AISC (Rolled Steel) Structural Tubing Square" in the content center, but mine is 1 inch square with 0.065 inch walls.
I've made a chassis out of my custom tubing. When I run a frame analysis on it, I get an error/warning stating that the torsional section modulus is zero, because I didn't fill in the value when I generated the frame. How do I calculate that value?
I've attached the tube that I used to make the structural shape.
I created an extruded aluminium profile (attached file: Item Profile 8 80x80) which I published into the Content Center. When using this profile in a frame design, and using the Trim To Frame command, the profiles are trimmed at a weird angle (attached pdf file).
I come across this problem from time to time and generally either just ignore it, if the detail is destined for in house manufacture, or alter it in autocad if it's destined for exterior suppliers.
Our guard frames are manufactured from extruded aluminum section (made by a company called palletti) I have when needed created a new frame generator frame member for each new x-section that we wish to use. I then draw a 2d sketch for the base frame skeleton and then a 3d sketch for all the frame work above. This I then use in an assembly to create the framework. This framework assembly then goes into a second assembly where the framework is then adorned with all the accoutrements that make up a guard frame that we can then order as an assembled frame, panels feet, hinges et al.
When placing the views for the detailing of the second assembly sometimes the view will show the wrong length for one or some of the frame members.
;note how the left and right views are different and how some of the frame members are elongated on the lh view.
I'm guessing its because of the home grown frame members but all seems to work well other wise and this only happens infrequently.
HP z210 16Gb ATI FirePro5800 Autodesk Produst design Suite 2012
I'm developing a program which runs several simulations and obtains the results automatically.
I'm using the dynamic simulation API created in Inventor 2013. For that I use the GetResultValues(ByRef values() as Double) method of the class DSResult.
I used the method inside the VBA of inventor and worked well. But when I wrote the program in Visual Basic Express 2010, the method doesn't return anything.
I share an excerpt of the
Dim odoc As AssemblyDocument odoc=invApp.Documents.Open(testPath, True) Dim dsman As Inventor.SimulationManager = odoc.ComponentDefinition.SimulationManager Dim dssim As Inventor.DynamicSimulation = dsman.DynamicSimulations.Item(1) Dim oJoints As Inventor.DSJoints = dssim.DSJoints oJoint = oJoints.Item(1)
[code]....
The method GetResultValues(values) should modify 'values' to a time,value vector.
It works well inside Inventor, but doesn't in the program in VB, although it runs the simulations and does everything else right.
I'm running several dynamic simulations via the API. Then I am getting the results to write in a text file. I want to know the force in a joint so I get the vector of values via
Dim oResults As DSResults Dim oResult As DSResult Dim value() as Double Call oResult.GetResultValues(value())
this vector is a time, force vector but when I verify mi data against the Output Graphe all the decimal points from the force information are gone.
Example:
In Output Grapher
Time (s)Force(N) 0.0118955.66 0.0219500.88
In the vector from API
0.01 1895566 0.02 1950088
is there a way to correct this? I'm getting many force and movement info, so I don't know which ones are reliable.
I have purchased the Autodesk Product Design Suite Premium. It comes with the Frame Generator but does not seem to have the Frame Analysis with it. Is that provided in other Suites or should I have it??
I have an 8" OD/5.523" ID steel tube. A 5.5" OD/4.957"ID tube is placed inside. The 8" and 5.5" tubes are placed over a 4.9375"OD shaft. So basically you have a hollow shaft attached to a drive shaft, with a filler tube placed between them to fill the gap. Two 1-1/2" UNC bolts are placed in matching1.531" diameter holes in every component (thru bolted) with a nut. Tightening the nut will tend to flatten the pipes, taking up the clearance between then and creating a contact pressure on the drive shaft. I have having trouble getting all of the contacts correct since the components are not in contact at the beginning of the simulation due to the radial clearances.
Two axial bolt loads of 129,000 lbs will be placed on the tubes. I have used a sliding/no separation contact between the bolt and nut. Then I put a fixed constraint on the bottom face of the nut (not in contact with the tube) and put a 129,000 force on the top of each bolt head to simulate the axial load created by the bolt preload. What type of contact should I use between the tubes that have radial clearance?
I have attached the tubes and drive shaft. The 1-1/2" bolts and nuts (both heavy hex) were found in the library.
I am trying to properly stress test a steel aircraft fuselage. I can easily model the estimated weight of the pilot, copilot, etc as loads on the airframe. However, when it comes to simulating a high-G situation, (a load factor of around 7.5 times the force of gravity), I am not sure what to do. On one hand, I can simply multiply the loads on the airframe by the load factor and see if the frame can take it. In most cases, it performs very poorly, (safety factor less than 1). However, if I model all the loads under normal conditions, (normal pilot weight, etc.), then add a gravity load equal to 7.5 G, the airframe performs well. Yet I am not sure if the loads on the airframe, (such as pilot weight), are being adjusted along with the increased gravitational load.
My question is, what is the best way to accurately simulate real world loading for high-G situations?
I am doing an eigen frequency analysis of a structure in the range of 0 to 1500 Hz. For my structure I am getting about 6 modes as expected.
For the final results I will mass normalize to convert to an energy based on the relative "displacements" However, each of the "displacements" for the 6 eigenfrequencies are the same?
I know this can not be right as it would mean that all have the same energy which is impossible.
I am trying to determine how to properley constrain the assembly below, so that the compression of the rubber gasket will be properly indicated.
Currently I am seeing the deflection of the shelf in the downward direction, but I do not see any indication of stress in the gasket behind.Currently the gasket is "bonded" to the steel tube the screws are bonded to the shelf bracket and the steel tube.
I put in "work axis" at the center line of the shelf bracket and the CL of the gasket, but I can't find a way to constrain to a work axis.The file is too large to upload here...
and it says I don't have enough memory! How can this be? Its not that complicated of an assembly. I have done bigger. I excluded all the part I'm not using and they are all basic plate and tube parts. There are less than 20 parts in the assembly.
