New FEA Tools for Engineering Analysts
CAD/CAE interoperability tools, new elements, additional material models,
faster solvers, and innovative training techniques make the latest finite
element field worth a closer look.
What's new in the classroom?
Learning FEA software traditionally meant taking classes in college or then
picking up pointers from the smartest designer in the department. Newer
instruction ideas, like Webcasts, still require analysts to take notes and pay
attention to lectures, but they can do so through their own computer. This type
of e-learning enables analysts to learn at their own pace with their own tools.
Webcasts are available as streaming audio/video files that can be stopped and
replayed on demand.
Many colleges and a few companies offer classes over the Web. When they are
available for FEA subjects, their variety is quite diverse. So far only Algor
offers a full range of discussions on finite element topics at no cost to the
user. One recent discussion covered guidelines for selecting the appropriate
solver for the model.
With an Internet connection, analysts can watch at their convenience as
instructors discuss details of specific elements, and other aspects of FEA.
During live Webcasts, viewers can e-mail or call in with questions. This
interactive forum allows instant answers and gets users up and running in the
most efficient manner possible.
Dave Lytle, an instructor with Algor, Inc., leads a discussion on meshing
techniques and guidelines. The company has built a state-of-the-art broadcast
studio for Webcasts and recently implemented technology that lets the instructor
"walk" through finite element models. Here, Lytle points out areas
that might be refined to better capture anticipated stresses.
Finite element technology is changing so fast that analysts who keep their
noses to the grindstone may miss out on many of the recent, useful developments.
For example, an actuator element, just one of several new inventions, simulates
the motion of hydraulic, pneumatic and electric cylinders and solenoids. This
element lets designers analyze complex mechanical events that would have been
nearly impossible even just a few months ago.
What's more, FEA companies consistently improve their solvers in order to
reduce solution times. They have to. The ever-increasing memory and disk space
capacities on todayís computers encourage finite element analysts to work with
larger and larger models.
These trends and developments make it useful to occasionally step back from
the daily grind for a better view of what's cropping up in the industry.
What's new in preprocessing?
Shown here, Algorís InCAD DesignPak captures geometry directly from CAD
solid modelers for linear static stress analysis in Algor. InCAD DesignPak
provides an introductory step into the FEA realm, but provides the flexibility
and extensibility to add additional analysis capabilities by utilizing the same
user interface as all of Algorís product line.
Success using universal files, such as IGES, to transfer geometry from a CAD
solid modeler to FEA software has been so intermittent that companies began
integrating their FEA programs inside CAD programs. This arrangement was
intended to provide CAD/CAE interoperability with entry-level FEA tools for
design engineers who typically desire quick verification of their product
design. Although this software arrangement has solved the problem of geometry
transfers, extending the software for new analysis tasks is often quite
difficult or impossible.
For example, limiting the number of available element types in order to
simplify FEA programs also significantly limits what can be modeled. Engineers
and analysts realized that the lack of other element types, such as beam, truss,
or brick elements, in such a product keep them from analyzing even moderately
complex parts or mechanisms.
Some FEA companies now recognize that a better approach is to reside just
"one window away" from the CAD system while still directly
transferring geometry through memory. Communication with the CAD solid modeler
remains direct, but upgrades and expansions to the analysis program are easy.
InCADPlus from Algor provides an example of a full-featured CAD/CAE
interoperability solution. Like InCAD DesignPak, the software works directly
with CADKEY, Pro/ENGINEER for Windows, Mechanical Desktop, SolidWorks, and Solid
Edge using the same interface regardless of the CAD system or analysis type
involved. However, InCADPlus provides Algorís full range of finite element
modeling capabilities, including the ability to combine multiple element types;
solid FEA brick, tetrahedral or hybrid meshing; and midplane meshing.
Itís also easier on analysts when they are presented with a consistent user
interface regardless of the type of analysis being performed. A consistent user
interface saves users from mastering a different GUI just because the analysis
needs to be changed. In addition, the interface is the same no matter which CAD
package you use.
Another trend is the increasing level of expectations for engineering
software. There was a time when engineers were comfortable working through a
command-line prompt or an unfriendly technical terminal. Engineering software
was almost expected to be difficult.
That is no longer the case. A modern graphic user interface with
user-friendly dialogs and wizards are features analysts now expect in FEA
software. For example, Algorís effort to meet this demand has delivered
additional ease-of-use features such as context-sensitive help, which calls up
relevant written information no matter where you are in the program. In
addition, Algor interfaces with Microsoft Office so users can, for example,
import load curve data from an Excel spreadsheet.
Furthermore, a single consistent interface across low-end, intermediate, and
high-end analysis capabilities means users arenít confused when they add other
capabilities in order to perform different analyses. So whether working on
problems involving heat transfer, electrostatic, linear static stress, linear
vibration, fluid flow, or analyzing mechanical events, users work within the
same FEA interface.
Meshing a model with solid elements makes sense when the part has a
substantial thickness. But meshing a thin-wall part, such as the housing on the
left, with solid elements can often produce a large number of elements and cause
long solution times. Algorís automatic midplane meshing capability can
simplify the problem by generating the midplane surface and, therefore, replace
the solid elements with plate/shell elements, as shown to the right. The
plate/shell model will solve more quickly and encourages more what-if studies.
Another one of our recent developments has been the expanded use of the
20-node brick element in linear static stress problems. The element is modeled
as a standard eight-node brick, but includes mid-side nodes. Although 20-node
brick elements are not new, they have been available mostly in more expensive
nonlinear, FEA programs. Brick elements are generally regarded as more efficient
than tetrahedral elements in that fewer brick elements are necessary to obtain a
similar level of accuracy in a particular model.
The additional nodes allow it to capture bending more accurately than
eight-node elements or tetrahedra. Another way to capture bending involves the
use of a large number of elements. The new element also avoids this latter
tactic. The 20-node element works with isotropic and orthotropic material
models, and can be temperature-dependent, making it applicable to a wide range
of linear material models.
Analysts should need only one library to maintain all known material property
data. Algorís software is delivered with a material library and manager that
enables engineers to quickly access standard material properties or to define
customized material property libraries for use with all analysis types.
Additionally, a piezoelectric material model is available for the new brick
element. In the same way that heat generates stress in a temperature-dependent
element, voltage generates stress in the piezoelectric material model.
New material models are enabling analysts to handle multiphysics applications
more easily. Recently, Algor introduced a new piezoelectric material model that
produces stress results based on voltage loads. An electrostatic analysis can be
used to calculate voltage results, which are then automatically transferred via
the global data input screen in Superdraw III to a linear static stress model.
The final stress results are shown at the right.
Composite elements are available for wider application use than ever before.
These elements are modeled in the same manner as plate/shell elements. The data
input screen for a composite element lets users assign the number of plies that
make up the laminate. Each ply gets assigned a thickness, an orientation angle
that positions the plies with respect to each other, and a material for that
ply. This is accomplished in Algor through a simple three-column spreadsheet
that tracks the user-defined data.
Composite elements have been available for many engineering conditions, such
as vibration analyses and linear static stress. More recently, they have been
extended to model linear critical buckling. This type of analysis uses Euler
approximations to find a buckling load multiplier. The composite element is also
proving useful in simulations of mechanical events, including those involving
Kinematic elements, another recent invention, assist with large models by
transmitting loads, motion, and displacements, but are not considered when
calculating stresses. These elements are ideal for large models with small areas
of engineering concern.
Kinematic elements were used in conjunction with Algorís Mechanical Event
Simulation software to perform motion analysis and simulation of this landing
gear assembly. Flexible elements were defined at the joints to determines
stresses (see inset) while kinematic elements were used on the remainder of the
model to speed processing times.
A more general development, communication links between different analysis
modules, adds even more capability. Integrating different analyses together more
directly lets the user model the multiple physical phenomena affecting parts in
the real world. For instance, the link will let users perform an electrostatic
analysis to determine unknown voltages and then automatically apply the
calculated results to a linear static stress model utilizing the piezoelectric
material model to find the stress from those voltages.
What's new in solvers?
Analysts probably expect to see new elements and features in preprocessors
since that is where they spend most of their analysis time. But some of the
developments they don't see, such as solvers, can be equally impressive.
Recent solver development has focused on sparse matrix and iterative
technology. While aerospace companies have made frequent use of this technology
in the past, a growing number of analysts from all industries are now taking
advantage of the solvers due to the processing speed gains that are possible
when analyzing large models. In the recent past, users would ask themselves: How
can I simplify a model so that it runs faster? But the recent trend is to
analyze the real thing -- a more complete model. This trend has encouraged
increased model size and the need for faster solvers, such as the sparse matrix
and iterative versions.
Sparse solvers are based on the fact that zero terms in the stiffness matrix
do not need to be considered. The iterative solver is often the fastest for
analyzing large solid models, but there is a price for its speed -- it does not
always converge. The iterative technology uses extrapolation techniques so itís
not actually solving for every instance. Therefore, any intermediate results in
a linear static stress analysis are not meaningful.
Because itís important to tell whether or not a solution is converging or
how it is converging, users can watch the progress of the analysis through a
monitor program that generates real-time plots of convergence. This is also
important when simulating moving mechanisms. For example, if a large mechanism
is not converging due to geometry issues, such as widely varying stiffnesses
throughout the model, analysts can switch to the sparse solver, which will
converge. In addition to the sparse solver, analysts can always choose reliable
skyline or banded solvers for more general scenarios. Both of these are stable,
direct solvers that do not have convergence issues that are inherent in the
Iterative solvers are perfect candidates for fluid-flow problems, which
traditionally involve large models where the results are not significantly
changing from one timestep to another. Expect to see big changes in this
analysis arena in the next few months.
One of the most significant changes is the capability to analyze moving
events in a finite element analysis using Mechanical Event Simulation software.
The concept is simple: things move, they collide, and sometimes they break.
However, FEA technology for linear static analysis models only stationary
objects, often requires input of approximated loads, and is unreliable for large
deformations. True-to-life simulations, on the other hand, let users analyze
true events, including those involving small and large-scale motion.
An automatic time-stepping feature in the Mechanical Event Simulation
software makes it possible to simulate actual events. During periods of relative
inactivity in an analysis, for example, a car headed toward a telephone pole,
nothing is happening so the software assigns a large timestep to the event. But
when contact is imminent, the software reduces the timestep to fractions of a
second to capture the detail during the actual impact.
Algorís Mechanical Event Simulation software can be used to simulate the
actual impact of independent objects. For example, engineers at West Coast
Engineering, Ltd., the largest Canadian pole manufacturer, analyzed the impact
of a car into a pole to assess the performance of the transmission pole under
extreme dynamic loading.
Model courtesy of West Coast Engineering, Ltd., British
This kind of automation in software is showing up in other places as well.
Not long ago, engineers measuring the motion characteristics of a mechanism
would manually transfer loads from one program to another. According to more
recent thinking, if the engineer should choose to perform a static stress
analysis instead of the dynamic event, than let the software perform the load
transfers to an FEA program.
This idea has resulted in whatís called an Inertial Load Transfer module.
The capability expands upon recent geometry-transfer techniques that bring over
an entire assembly and turn it into an FEA model comprised mainly of kinematic
elements. After an analysis reveals the motion, the Inertial Load Transfer
module automatically transfers loads to a linear or nonlinear stress analysis
and performs an analysis on one or more parts to get the resulting stresses.
Older systems would require working in a kinematics package on a separate
kinematic model. Results would often be transferred manually, a process that
invites error. In addition, the kinematic model is based on assumed joint
stiffnesses and rigid-body motion, not flexible-body motion.
FEA companies are paying more attention to simplifying the application,
modification, and removal of loads and constraints to models. With this
technology, FEA users can right-click on a model location to apply constraints
or loads, or right-click on an existing one to alter its magnitude. In addition,
this technology is available for all analysis types. Because FEA is an iterative
process with one analysis often leading to another, efforts in this area will
increase the userís overall efficiency by enabling quicker, easier
modification of model properties. That is, the user can quickly review the
results and then change the model and begin another analysis, if necessary.
Right-click application also introduces more types of common loads,
constraints, and ways of connecting parts. These are especially critical for
motion studies, which require engineers to identify where and how links are
jointed. For example, a piston and rod are connected at a joint that should not
translate from side to side, but must rotate about a connection point. Itís
important to define the joint properly to capture the true motion of the
To quickly model such connections, expect to see kinematic pivots, which
enable kinematic elements to rotate in different relationships to each other.
Kinematic pivots are the first of a series of joints that accurately model
movement for analysis using Mechanical Event Simulation.
Also, look for more dynamic postprocessing capabilities, real-time
monitoring, and presentation capabilities. For example, users should be able to
dynamically rotate, pan or zoom in on a model in order to quickly examine von
Mises stresses or other results regardless of where they reside on the model. In
addition, analysts can take advantage of timesaving monitoring capabilities,
which make results available graphically during the analysis of time-dependent
analyses like transient heat transfer and Mechanical Event Simulation. Engineers
do not need to wait for an analysis to finish before evaluating the results to
determine if modifications are necessary.
Once analysts have completed their analyses, the task of presenting the
results remains. Report Wizards generate fully customizable HTML reports of the
FEA model data that can include VRML, AVI, JPG, TIF, PNG, TGA and PCX graphic
files. The reports can be printed or distributed via an Intranet or the
Algorís HTML Report Wizard automatically generates an analysis report that
can be printed or distributed via an Intranet or the Internet. The report
includes detailed model data, graphics and multimedia files and user-specified
information that can be transmitted to a client or supervisor through any web
Users should not be surprised to learn that most ideas for new features come
from them. Many of these new features stemmed from customer feedback. If you
have an idea for a new software feature, contact Algor or the developer of your
FEA software package.