LSTaSC
General
What is Topology Optimization?
Topology optimization is a structural design optimization technique for distributing material efficiently across the design domain by changing the topology of the design for a given set of loading and boundary conditions such that, the resulting design has better performance targets in terms of improved stiffness, and reduced mass.
In topology optimization, the overall topology of the structure is varied by removing unwanted material from the structure such that the final design is lighter without compromising the performance characteristics.
LSTaSC
LSTaSC is a topology and shape computation tool of LSDYNA suite developed by Livermore Software Technology Corporation.
Figure 1: User Interface of LSTaSC 3.1
In LSTaSC, the goal is to obtain a structure with uniform energy density distribution to suit crashworthiness applications where internal energy absorption of the design parts is important.
Figure 2: Starting design of the beam, optimized form of the beam and the topology evolution with element density contours.
Case
Case
A case in LSTaSC corresponds to the loading and boundary conditions of the structure and the resulting topology from optimization will be in accordance to this load case.
Any number of load cases can be added but a unique name should be provided for each case with input being the LSDYNA keyword file. LSDYNA executable should be selected as the solver command. Any LSDYNA command line options such as memory, no. of CPUs, ... can be entered directly in the command section.
 
Part
Part
The Part dialogue box has options to select the part to be optimized and define few optimization parameters such as mass fraction, minimum variable fraction for element deletion, element neighbor radius and geometry definitions.
Mass fraction is the amount of mass to be retained after optimization process. A mass fraction of 0.25 indicates for example that LSTaSC will try to retain 25% mass of the part. A minimum variable fraction can be specified by the user, elements with design variable values below this limit will be deleted, which is 0.05 for nonlinear problems and 0.001 for linear problems by default. The design variables of all the elements are updated based on field variable (internal energy density) values of the neighboring elements. A virtual sphere with a radius is defined and elements within this radius are considered to be the neighboring elements (refer to LSTaSC User’s manual for more information). The default Neighbor Radius value is 1.0, which means the results from all elements sharing a node with an element are likely to be used.

Method
Method
The termination criteria for the optimization process in terms of maximum number of iterations and optimization convergence tolerance are defined in this panel.

Run
Run
This panel is used to start, stop or to restart the optimization process.

View
View
The view panel is similar to a postprocessor. Various topology histories plots such as change in mass fraction, element fraction, constraint values etc over the iterations are displayed in this panel. The model plots options are used to view d3plot data of iterations.

Figure 01: Final topology
Figure 02: The topologies at different iterations