Glossary of terms

• Acceleration of OpenGL
  The implementation of rendering software in hardware which speeds up rendering because the CPU will have to do less. OpenGL has been designed for hardware acceleration but its functionality can also be entirely implemented in software.

• anisotropic permeability
  The reinforcement permeability varies depending on the direction in which the resin flows. This is typically caused by the geometry of the fabric, and useful in applications where high strength is required in a specific direction.

• connector
  A virtual connection between two points that acts like a tube with no volume and no resistance. Can be defined in RTM-Worx using the RTM runner with a high fibre/volume fraction (say 99%) and low permeability (1000 times as low as adjacent surfaces).

• Control panel
  Used in two contexts: (1) the pane at the left side of the RTM-Worx window and (2) the Windows Control panel where you can change settings of your system.

• Control Volume Method (CVM)
  A method to divide a large and complex product into small volumes to which conservation laws (mass, momentum, energy) are applied to obtain a set of equations that describe the flow and can be solved numerically.

• curve
  In RTM-Worx a curve is a line that connects several keypoints. It can have a diameter (runner) and optionally porosity and permeability (RTM runner). Curves are used to define surface boundaries.

• depth clipping
  A method where a plane parallel to the computer screen is used to cut away anything in between the viewer and this plane. This allows you to look inside complex models.

• DXF
  A file format designed by AutoDesk to exchange CAD models between applications and used in AutoCAD™. DXF is an acronym for Drawing eXchange Format.

• easy flow path
  A channel that is formed in between a rigid mould wall and the reinforcement. When the permeability of the reinforcement is low, the resistance of such a channel can be orders of magnitude smaller than the resistance to flow in the reinforcement.

• edge injection
  Injection of the resin along an edge of the mould. In practice typically achieved by making a channel along the edge with a restriction to the mould.

• element
  Smallest entity in which the model is subdivided for the calculation of flow of the resin through the reinforcement (or volumes). Runners are subdivided in line or runner elements, which are straight tubes with two vertices. Surfaces are subdivided into triangles with three vertices. The pressure gradient is constant on an element. Using more and smaller elements increases the accuracy of the calculation, but also the calculation time.

• fibre/volume fraction
  Fraction of the volume that is occupied by the reinforcement. Equal to (1 - porosity).

• Finite Difference Method (FDM)
  An alternative method to discretize the partial differential equations that describe conservation of mass, momentum and energy. The advantage of the FDM is that it is easy to implement, but it is generally limited to rectangular geometry which cannot be multiply connected (e.g. no ribs or stiffeners). It has therefore been used a lot in scientific environments.

• Finite Element Method (FEM)
  This is the method used in RTM-Worx to discretize the partial differential equations that describe conservation of mass, momentum and energy into a linearised set of equations that can be solved numerically. The geometry is subdivided into smaller objects, so-called elements, in which the resin velocity is constant and pressure varies linearly.

• graded mesh
  Subdivision of a surface into triangular elements, where the size of the elements varies gradually from very small to large and vice versa. Graded meshes offer the advantage of the ability to use small elements in the neighbourhood of details in the geometry while the overall number of elements can be limited by using larger elements where possible.

• icon
  Tiny image that is used to indicate file types, programs and button commands.

• isothermal calculation
  Calculation in which it is assumed that the temperature differences are too small to affect the flow kinetics. Without the need to calculate temperatures and reaction kinetics, the calculation can be very fast, and few material data is needed. For RTM and Vacuum Injection, the isothermal calculation delivers a lot of results at very low cost.

• isotropic permeability
  Reinforcement that has a resistance to flow of resin that is equal in all directions. An example is a random mat, and several square weaves (but not all of them, the 45 degree direction can differ from weft and warp, even when weft and warp are identical!).

• keypoint
  The representation of a location in space (with x, y and z coordinates), used in RTM-Worx for the vertices of curves. Keypoints can be assigned properties to turn them into venting or injection ports.

• line element
  A Finite Element on a curve or runner.

• mesh
  The subdivision of the model geometry into elements. Curves and runners are subdivided into line elements, surfaces are subdivided into triangles.

• model
  The complete, but simplified, description of the RTM-process for a product, which includes the geometry, reinforcement properties and resin viscosity.

• multithreaded
  Logical division of an computer program into different tasks that run asynchronously. Synchronisation of - and communication between threads adds little overhead, because threads are part of the same process. A well-designed multithreaded application utilises resources (most notably the CPU) more efficiently. For example: RTM-Worx uses a separate thread to render the plot of the model. This thread has a slightly lower priority compared to the main thread that handles user input, which keeps RTM-Worx responsive, even when almost 100% of the CPU capacity is used to draw the model.

• nodal Control Volume
  The FEM nodes all have a volume associated with them that is composed out of parts of the elements the node is connected to. The flow front is tracked by monitoring the filled fraction of each nodal Control Volume.

• node (FEM)
  Vertices of elements that define the position of the element in 3D space; e.g. a node has x, y and z coordinates. In RTM-Worx, pressures are calculated at the nodes which defines the pressure gradient and resin velocity in each element.

• OpenGL
  A library of subroutines, designed by Silicon Graphics Inc. (SGI), to render 3D realistic images. This library shields application programs from the actual implementation, which can be either in hardware (fast but expensive), or in software (slow but cheap). OpenGL is available on a lot of platforms, including Unix™, Linux, Mac OS™, OS/2™ and Microsoft Windows™. OpenGL has been used a lot in the scientific community, but gains more and more acceptance in the gaming industry (most notably DOOM) which in turn boosts the development of cheap hardware that accelerates OpenGL.

• permeability
  A measure of the resistance of a porous medium to the flow of fluids. Permeability is a reinforcement property, independent of the resin.

• porosity
  Fraction of the total mould volume that can be occupied by the resin. It is related to the fibre/volume fraction Vf as: porosity = 1 - Vf.

• post processing
  The calculations and user actions to view results of the simulation graphically in order to interpret what happened in the mould. See also 'pre-processing'.

• pre-processing
  Actions to be taken before the simulation can be done. Includes entering the geometry, reinforcement and resin properties, and verifying the correctness of the model. The term originates from the classical batch-oriented FEM applications where you had to put all the data in an ASCII file which was then submitted to the FEM application which would read the input file, do a lot of number crunching and produced a lot of output files. In the course of time, specific applications were developed to be able to build the input file interactively (called a pre-processor) or to view the results graphically (called a postprocessor). RTM-Worx integrates all this functionality in one application and a single interface.

• RAM
  Random Access Memory. Your computer needs kind of memory to (temporarily) store application code and data, because the CPU can only execute instructions and fetch/store data that is available in RAM. The contents of RAM are lost when you turn off your computer. RTM-Worx stores the complete model and the simulation results from a single calculation step in RAM. The amount of RAM used by RTM-Worx depends on the complexity of the model and the number of nodes and elements in the mesh.

• registration
  For the RTM-Worx license, you need to register your copy of RTM-Worx after installing it on your system. Because licenses are sold on a per-machine basis, you need to register separately for each computer you want to run RTM-Worx on. RTM-Worx generates a Site Code that is specific to the installation and computer it runs on. You contact us with the Site Code to acquire an accompanying Registration code. This registration code has to be entered in the dialog that also specifies the Site Code. RTM-Worx will run when the Registration code matches with the Site Code until the license expiry date has passed.

• runner
  A curve with a diameter is called a runner and can be used to model tubes (resin delivery) and easy flow paths. The flow in a runner is always assumed to be in the length direction.

• shell element
  A triangular element suitable to model resin flow in a thin-walled section of your product. Locally, the flow is treated two dimensionally. It is assumed that the flow in the third direction, perpendicular to the triangle is negligible compared to the in-plane flow.

• shell link
  Same as a shortcut. See below.

• shortcut
  Introduced with the Windows 95 interface, and also incorporated in Windows NT 4.0, shortcuts are small files that serve as an alias to a file stored elsewhere (like links under Unix). Shortcuts are used for the icons on your desktop and the entries in the Start menu, but you can also create and store shortcuts in any directory on your harddisk. Actually, the Desktop and Start menu are directories too.

• STL
  A file format defined by SLA (for interfacing CAD programs with Stereolithografy equipment) that describes the geometry of an object in 3D space by a list of triangles (no more, no less). RTM-Worx is able to read both the ASCII and binary STL file formats. Most CAD applications can write those files because their structure is so simple. However, the geometry is stored quite inaccurately (single precision) and small details or rounded corners will result in a lot of extremely stretched triangles. We recommended you to remove all details, rounding etc. before generating an STL file to transfer the model to RTM-Worx.

• surface
  Surfaces are used to model thin-walled sections of the product geometry. A surface is a flat or curved plane in space defined by a loop of boundary curves in between keypoints that will also be on the surface boundary. You can assign thickness and reinforcement properties to surfaces to turn them into volumes.

• tag number
  A number, assigned as a property of keypoints, curves or surfaces that can be used to quickly select a set of objects with identical properties. Typically used when RTM-Worx imports a FEM model that uses so-called Element Groups to assign properties. The element group number is assigned as the tag number.

• toolbar
  A rectangular window located below the menu or above the status line with buttons and edit fields that provide quick and easy access to the functionality of RTM-Worx.

• ToolTip
  A small window with a terse description of a button, edit field or other control. It pops up if the mouse cursor is on top of the control (like when you are hesitating because you are trying to think of what it does), but stays away when you move quickly (you know what you are doing and don't need any help). RTM-Worx also uses the ToolTips to display error conditions, valid ranges for numerical input and results of expressions.

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