Femap Consistent Units, *Note, it will not scale results, on

  • Femap Consistent Units, *Note, it will not scale results, only the model. The load is to be distributed evenly across all of the rails down the length of the deck. It doesn’t matter which system you go with but be sure you are consistent throughout your analysis. A good choice of units is usually based on an appropriate length scale for your problem—for example, use units of mm or inches for handheld objects. Dimensional Analysis: Regularly perform dimensional analysis on your equations and inputs. To measure the acceleration of the spring/mass system we have fixed an accelerometer onto the block. Nastran does not have the understanding of units and all input has to be in a consistent unit set. Using these units, you can verify that the mass is in tonne, but is not important as it is static analysis in this case. 2) Examples of consistent unit systems include using meters Think of a shaker table having ten little spring/mass units attached onto its surface. Units of your results depend of your input units. SI (meters, kilograms, seconds, Kelvin, Amperes) is generally recommended due to its widespread use and reduced conversion errors. I have group off multible beam properties in mm. Looking at the help section, it says that the inputted value isn't G's In FEMAP, you will then input the material props (Model>Material) in a second step. It sounds obvious but one might be surprised how a digit or two can get slipped in among friends. e. Femap Nastran Patran Abaqus Dyna. . Download PDF Using Consistent Engineering Units in Finite Element Analysis Depending on the modelling software used for Finite Element Analysis (FEA), the modelling process often requires a very high level understanding of engineering units. Verify that force, elastic moduli, acceleration, mass density and dimensions represent a consistent set of units. This web tool performs the dimensional analysis and unit conversions required to help you define your engineering problem using a consistent system of units. SI Units The easiest set of consistent units is the SI system of metres (meters), kilograms and seconds. You always can recalculate all model units by using Tools->Convert units - change base factors like lenght or time and Femap will recalculate all derived units, positions of points, nodes, curve lenghts etc. pdf But if you have limited time and are starting a new […] For water, and using the mm/tonnes/s consistent set of units in this model, this simplifies to: Note that “!z” is the Femap variable that represents the depth of water in the equation. But to answer your question, a consistent set of imperial units if you like to use inches is: inches, pounds force, slinches (pound is never a real mass, and is not consistent with F=ma for your other chosen units) and inch/sec2 for gravity/acceleration. The table below shows the input and output units for a few of the most common unit systems. Hello, Version 11. Download this PDF for a discussion of how to recognise and overcome analysis singularities. I'm aware that Abaqus has no units settings, but in this case since the part is required to be modelled in Creo I cannot stay "consistent" 9 or rather, accurate, in Abacus when my instructions are given in mm, and Abacus converts the units of the imported parts from mm to inches and interprets all my inputs in inches. The problem is that I am not getting expected results Please note that the library is currently being updated to insure that the thermal unit values are correct in using consistent units of mW, even though the file header references Watts and will be renamed in the upcoming v12. 4. This document discusses the importance of using consistent engineering units in finite element analysis. If u r providing material specification on ur own the no need to convert units just use geometry in mm. esp does not have consistent units and will cause problems if used as-is. Search consistent unit system table from Abaqus. Learn why getting units right is essential, explore a helpful unit table, and discover expert tips to avoid common pitfalls in your simulations. Hi all! I have a question regarding the selection of suitable units for the calculation of a thermal-mechanical analysis. The key points are: 1) FEA requires a consistent set of engineering units across all model properties to produce a valid analysis. they "go on" about using consistent units, that if you model in mm then your acceleration should be in mm/sec^2 and density should be tonne/mm^3 (1000kg/mm^3) so that the force units sort themselves out The below table shows examples of consistent unit measure selection for different disciplines. Inorder to have the stress in Mpa what should be the unit of: -Specific Heat -Conductivity -Mass Density If the units of force is N and the distances are in mm. Or at least it will when you do thermal analyses. Hi All, When I load materials from the built-in FEMAP database "mat_eng_in-lbf-psi-degF-BTU. These are the two unit systems Ian works in the most. The calculator will also take units of any system and convert them into your system. For example if you use N as force and mm as lenght unit, you get stress results in MPa (N/mm2). I must be missing conversion units somewhere but for the life of me can't figure it out. It provides examples of consistent unit systems using SI units as well as imperial units. One rigid element stretches from one adherend to a node at the center of the gap, while the second rigid element stretches from the other adherend to a coincident node also at the center of the gap. It provides examples of commonly used consistent unit systems including SI units of meters, kilograms, and seconds as well as alternatives using millimeters and Newtons or imperial This post and the pdf doc provide a practical explanation of consistent units in FEA. txt) or read online for free. 18 years ago Hello Marco, Here are responses to your questions - I do not recommend that you input your acceleration in units of g^2/Hz. Along the way, we will share with you some of our time saving techniques. The PDF provides details and a units conversion table. esp" for a thermal analysis, the conductivity and specific heat values don't make sense to me. Depending on the modelling software you use for your Finite Element Analysis (FEA), your modelling process often requires an understanding of consistent units ("coherent units"). Although this procedure may uncover modeling errors, it is not an exhaustive investigation of modeling details, nor does it address the issue of whether the structure . pdf), Text File (. Consistent Units in FEA. The below table shows examples of consistent unit measure selection for different disciplines. pdf - Free download as PDF File (. 1 release. Many FEA modellers/solvers do not show units within the software – the analyst must use consistent units with these. WHAT THIS HANDBOOK COVERS This note is intended for new engineers interested in modeling composites and experienced engineers who would like to get acquainted with the FEMAP interface. The method uses a gap the thickness of the adhesive, two rigid elements, and three zero- length spring elements between coincident nodes. Regards, Joe Expand Post LikeLikedUnlike Reply Blas_Molero (Partner) The document discusses the importance of using consistent engineering units in finite element analysis (FEA). Choosing a Consistent System: Select a base unit system (SI, Imperial/US Customary, CGS) at the beginning and stick to it. Now that we’ve covered the basic operating principles and can recognize the relationship between Base Units and Derived Units, and we understand the importance of Consistent Units, let’s explore some of the advantages, disadvantages, and differences between the two most commonly used unit systems. So, the forces result in daN -> (10 N EnDuraSim-Engineering-Units. You would be responsible for setting correct unit systems. Students also viewed Related documents Preview text UNITS FEMAP/NASTRAN are unitless systems Download 0 0 FEMAP do not manage any unit system, is the only user responsibility to have a coherent system of units between length, area, force, stress, etc. As discussed there, we can choose any set of units for the base physical quantities, and then the values for all physical FEMAP- Beam properties units mm --> m Hello everyone. These derive other units that are commonly used by designers/engineers/analysts, such as Newtons, Joules, Watts, Pascals, and used to quantify measures such as density, acceleration, velocity, viscosity, specific heat and many more. If you want to use 'mm' then units will be Force-Distance-mass-time => N-mm-metric tonne (10^3kg)-s If you want to use 'm' then units will be Force-Distance-mass-time => N-m-kg-s Units in FEA Finite element software requires the use of a consistent set of units. , or Best regards Peter Kaderasz Expand Post LikeLikedUnlike Reply Jakub Hello, this is my first thread. Therefore if you are working in SI units, the acceleration should be defined in (m/sec^2)^2/Hz. Apr 4, 2008 · The geometry was created in Pro/Engineer (units: mm-N-s). Elastic and mass properties are in consistent units ° The weight of your structure can be checked by summing the mass of the model and multiplying it by gravity (for US units of lbf, inch and seconds, it would be 386 in/s2) FEA model with a sufficient mesh density to capture the frequencies of interest (see below) I am posting this motivated by another thread (thread727-136030: Consistent Units for Thermo-Mech Analysis), that made clear how many mistakes people make when using units. 81m/sec^2)^2 A good check to make is to always request accel response for your base drive node, it should match your input ASD if you are consistent with units. The script will change the current femap model between in-lbf and mm-ton. Im working the model in millimeters [mm], the mass in kilogram [kg] for Mass elements, and the Stiffnes Modulus (E) in [daN/mm2] for material and the density in [kg/mm3]. This is Does anyone know how to reconcile the units on density when using FEMAP and using lbf, inches, secs as the base units (this allows for psi to be inputed for stresses)? The Nastran Techs say to divide by the density, which is in units of lbf/in^3 by 386. At the top of each spring is a mass block. Section 4 is intended to be a working document containing a "cookbook" procedure to facilitate the model checking process and help ensure a consistent level of quality. An example--if one uses mm as a length basis and N as a force, then the appropriate mass basis for consistency is Mg (1000 Kg). Hello!, I have answered a question in the FEMAP FORUM about how to mesh with 3-D solid elements a complex assembly, here the requirement was to have at least 3 elements in the AIR VOLUME GAP betwee… Convert Model Units Script Author: Ian Rivard Description: This script was inspired by the FEMCI page on Unit Consistency. Our spring/mass systems are then tuned to range in eigenvalues or natural modes from 1 to 10 Hz in 1 Hz increments. I have created the mass element at the CG, and connected it to the rails using RBE3 elements. pdf But if you have limited time and are starting a new […] This document explains why the use of consistent units is essential to understand in Femap, Nastran, Patran and many other FEA packages The unit system in some FEA software is user defined. As I suspect you already know you have to keep the units consistent when you enter them accounting for the fact that linear distances are in millimeters. 4 (converting ft and gravity), yet when I Consistent units are critical in FEA modelling with Abaqus. This post and the pdf doc provide a practical explanation of consistent units in FEA. As points of reference, the mass density and Young's Modulus of steel are provided in each system of units units (particularly in thermal and fluids analysis) typically requires arduous conversion to maintain a consistent set of units for analysis. Using FEMAP 9. Elastic and mass properties are in consistent units ° The weight of your structure can be checked by summing the mass of the model and multiplying it by gravity (for US units of lbf, inch and seconds, it would be 386 in/s2) FEA model with a sufficient mesh density to capture the frequencies of interest (see below) The point is I think the unit converter enbedded in FEMAP is wrong, because it doesnt convert density from kg/m^3 to t/mm^3 (it uses the factor 1e-9, not 1e-12). I want to calculate the normal modes of a structure. implementing the analytical checks described in Section 3. 1 Femap I need to model a flat deck structure, supported at the ends, with 6 rails that is loaded from an ideal load, ie a mass at the CG. Force Units, Pressure, Density, Mass, Length, MPa, Stress, Tonnes, Newtons, slugs, pounds, inc Selected as Best LikeLikedUnlike Reply kadpeter 9 years ago Hello Jakub, Femap doesn't use any units. You may need m or feet for large objects. Thanks WTMASS is a parameter used to adjust for inconsistent units. To set units u can use tool>convert units>load & can choose any system from library provide. This means (to answer SolidDNA's post) that tonne/mm^3 is the correct unit for mass density. I am using Nastran and Femap both allow for the use of the PShell property card for honeycomb composites. See earlier post, f. BEST PRACTICE FEM Konsistente Einheitensysteme FEM consistent system of units Definition of a consistent system of units (required for LS-DYNA): 1 force unit = 1 mass unit * 1 acceleration unit 1 acceleration unit = 1 length unit / (1 time unit)^2 1 density unit = 1 mass unit / (1 length unit)^3 The following table provides examples of consistent systems of units. We will be working with solid geometry and tetrahedral meshes as we But with Femap charting, you then scale the acceleration results back into g^2/hz by dividing by (9. It also includes efficient, state-of-the-art analytical tools for conducting Nastran modal-based response dynamics simulation. Ensure that each term has consistent units. "Carlton Matthew" wrote: > >"Marco" wrote: >> >>Hello, >>I usually work with SI units for my analyses. My first question is what do you put for a value to similate gravity. If you are working in N, mm, and seconds, then the rest of the consistent units should be as follows: E - MPa It will take your base units of choice (length, mass, time, and temperature) and give you consistent derived units (force, stress, energy, and power). Table 1: unit system definition examples To complicate even more the situation, it is habit in certain industry sectors, like aerospace, to make large usage of inconsistent imperial unit measure system. This presentation will walk through the standard analysis workflow from geometry to stress results and take a look at some of the common pitfalls. EnDuraSim_Consistent_Units. However, units conversion of any sort is best minimised, to avoid becoming responsible for losing the next Mars Climate Orbiter! 3. Jul 10, 2025 · Originally established in 1994, FEMCI serves as a mechanism to distribute information on the finite element analysis (FEA) and structural analysis techniques necessary for a complete and accurate structural analysis of spacecraft and spacecraft components. Femap® with NXTM Nastran® Structural Analysis Toolkit software features an advanced post-processing capability for general purpose Nastran analyses. LikeLikedUnlike Reply chrisstandring 7 years ago @ChipFricke, I believe the file mat_eng_mm-N-tonne-degC-Watts. The answer is simple: BE CONSISTENT. This section of the tutorial deals with how Classical Plate Theory can be used to define a plate element which reasonably replicates the behavior of a Honeycomb Core Composite. And now, when i modeling example ship model in metric system, is there some simple way to change the beam properties units in metric system? We utilize Femap, NX Nastran, Fibersim, Simcenter 3D, and HyperSizer in our analysis work and provide these programs, training, and support as a Value-Added Reseller for Siemens PLM and HyperSizer. Create a new load definition by opening the Model section in the Model Info tree and right clicking Loads. In this technical seminar, we want to get back to the basics and talk about why it’s not always so basic. 3, I know to apply a acceleration constant you input your valuel within Model-Load-Body and you add your density to the material card. As it is shown in the table below, the user must always enter all the input data (lengths, forces, accelerations or other boundary conditions) in accordance with a certain System of Units, and, of course, the results obtained will also be consistent with the System of Units chosen. ocz5, nnwrb, l0ap, cgvng, a5pz, adyfm, y8qz, vim4o, ogiul, qou9lv,