OptiStruct is a proven, modern structural solver with comprehensive, accurate and scalable solutions for linear and nonlinear
analyses across statics and dynamics, vibrations, acoustics, fatigue, heat transfer, and multiphysics disciplines.
Elements are a fundamental part of any finite element analysis, since they completely represent (to an acceptable
approximation), the geometry and variation in displacement based on the deformation of the structure.
The different material types provided by OptiStruct are: isotropic, orthotropic, and anisotropic materials. The material property definition cards are used to
define the properties for each of the materials used in a structural model.
High Performance Computing leverages computing power, in standalone or cluster form, with highly efficient software,
message passing interfaces, memory handling capabilities to allow solutions to improve scalability and minimize run
times.
Contact is an integral aspect of the analysis and optimization techniques that is utilized to understand, model, predict,
and optimize the behavior of physical structures and processes.
OptiStruct and AcuSolve are fully-integrated to perform a Direct Coupled Fluid-Structure Interaction (DC-FSI) Analysis based on a
partitioned staggered approach.
Uniaxial Fatigue Analysis, using S-N (stress-life) and E-N (strain-life) approaches for predicting the life (number
of loading cycles) of a structure under cyclical loading may be performed by using OptiStruct.
Multiaxial Fatigue Analysis, using S-N (stress-life), E-N (strain-life), and Dang Van Criterion (Factor
of Safety) approaches for predicting the life (number of loading cycles) of a structure under cyclical
loading may be performed by using OptiStruct.
Seam Weld Fatigue analysis is available to facilitate Fatigue analysis for seam welded structures. It allows you to
simulate the Fatigue failure at the seam weld joints to assess the corresponding fatigue failure characteristics like
Damage and Life.
When there is no underlying random vibration but there are a sufficient number of simultaneously occurring sine tones,
it can be considered random vibration.
Sine-sweep on random vibration is a superposition of swept sinusoidal vibration on random vibration. It is considered
as a series of single sine tones on top of random vibration.
Aeroelastic Analysis is the study of the deflection of flexible aircraft structures under aerodynamic loads, wherein
the deformation of aircraft structures in turn affect the airflow.
OptiStruct provides industry-leading capabilities and solutions for Powertrain applications. This section aims to highlight OptiStruct features for various applications in the Powertrain industry. Each section consists of a short introduction, followed
by the typical Objectives in the field for the corresponding analysis type.
This section provides an overview of the capabilities of OptiStruct for the electronics industry. Example problems pertaining to the electronics industry are covered and common solution
sequences (analysis techniques) are demonstrated.
OptiStruct generates output depending on various default settings and options. Additionally,
the output variables are available in a variety of output
formats, ranging from ASCII (for example, PCH) to binary files (for example,
H3D).
A semi-automated design interpretation software, facilitating the recovery of a modified geometry resulting from a
structural optimization, for further use in the design process and FEA reanalysis.
The OptiStruct Example Guide is a collection of solved examples for various solution sequences and optimization types and provides
you with examples of the real-world applications and capabilities of OptiStruct.
Cycle counting is used to extract discrete simple "equivalent" constant amplitude
cycles from a random loading sequence.
Note: For Random Response Fatigue and Sine-Sweep Fatigue, the traditional rainflow
counting method mentioned in this section is not conducted. Instead, the concept
of stress range and number of cycles is inherently taken into account as part of
the fatigue calculation. For more information, refer to Random Response Fatigue Analysis and Sine Sweep Fatigue Analysis.
One way to understand "cycle counting" is as a changing stress-strain versus time
signal. Cycle counting will count the number of stress-strain hysteresis loops and
keep track of their range/mean or maximum/minimum values.
Rainflow cycle counting is the most widely used cycle counting method. It requires
that the stress time history be rearranged so that it contains only the peaks and
valleys and it starts either with the highest peak or the lowest valley (whichever
is greater in absolute magnitude). Then, three consecutive stress points (1, 2, and
3) will define two consecutive ranges as and |. A cycle from 1 to 2 is only extracted if . Once a cycle is extracted, the two points forming
the cycle are discarded and the remaining points are connected to each other. This
procedure is repeated until the remaining data points are exhausted.
Simple Load
History:
Since this load history is continuous, it is converted into a load
history consisting of peaks and valleys only.
It is clear that point 4 is the peak stress in the load
history, and it will be moved to the front during rearrangement (Figure 3). After rearrangement, the
peaks and valleys are renumbered for convenience.
Next, pick the first three stress values (1, 2, and 3) and
determine if a cycle is present.
If represents the stress value, point then:(1)
(2)
As you can see from Figure 3, ; therefore, no cycle is extracted from
point 1 to 2. Now consider the next three points (2, 3, and 4).(3)
(4)
, hence a cycle is extracted from point 2
to 3. Now that a cycle has been extracted, the two points are deleted
from the graph.
The same process is applied to the remaining points:(5)
(6)
In this case, , so another cycle is extracted from
point 1 to 4. After these two points are also discarded, only point 5
remains; therefore, the rainflow counting process is completed.
Two cycles (2→3 and 1→4) have been extracted from this load
history. One of the main reasons for choosing the highest peak/valley
and rearranging the load history is to guarantee that the largest cycle
is always extracted (in this case, it is 1→4). If you observe the load
history prior to rearrangement, and conduct the same rainflow counting
process on it, then clearly, the 1→4 cycle is not extracted.
Complex Load
History
The rainflow counting process is the same regardless of the
number of load history points. However, depending on the location of the
highest peak/valley used for rearrangement, it may not be obvious how
the rearrangement process is conducted. Figure 7 shows just the
rearrangement process for a more complex load history. The subsequent
rainflow counting is just an extrapolation of the process mentioned in
the simple example above, and is not repeated here.
Since this load history is continuous, it is converted into
a load history consisting of peaks and valleys only:
Clearly, load point 11 is the highest valued load and
therefore, the load history is now rearranged and renumbered.
The load history is rearranged such that all points
including and after the highest load are moved to the beginning of the
load history and are removed from the end of the load
history.
Parameters affecting rainflow cycle counting may be
defined on a FATPARM Bulk Data Entry. The appropriate
FATPARM Bulk Data Entry may be referenced from a
fatigue subcase definition through the FATPARM
Subcase Information Entry.