The Optimization module provides a variety of settings that allow you to configure a bead optimization task. The configuration settings depend on whether you are configuring an optimization task for a condition-based bead optimization (default) or for a general bead optimization. The following topics are covered:
A condition-based bead optimization is based upon a special bending hypothesis and uses special filters to generate beads along the bending trajectories. You use the optimization task editor to customize various aspects of a condition-based bead optimization. To locate the editor, select Task
Editoptimization task name from the main menu bar. To specify a condition-based bead optimization, select the Advanced tab and choose Condition-based optimization.
The following topics are covered:
To configure basic settings:
In the optimization task editor, click the Basic tab.
Choose whether to respect boundary conditions that have been applied to the model.
It is recommended that you freeze regions to which boundary conditions are applied because you do not want these regions to be moved during the optimization. Freezing these regions stabilizes the optimization and often leads to a significantly lower number of iterations.
By default, the Optimization module freezes boundary conditions for the whole model. If desired, click 
and select the region in which the boundary conditions should be frozen.
To configure advanced options:
In the optimization task editor, click the Advanced tab.
Toggle on Growth direction opposite to shell normal to reverse the direction of the nodal displacement that forms the bead.
By default, the direction in which the nodes are moved to form the bead is determined from the stress state of the model at the start of the optimization—the first cycle. Alternatively, you can specify that the optimization determines the direction in which the nodes are moved after every design cycle.
By default, an internally computed value will be used for the bead width. Alternatively, you can specify the absolute value of the width of the bead.
Specify the number of iterations the bead optimization will perform. The number of iterations modifies the step size of the optimization. The default value is 2.
Specify the following Penalty Conditions:
Minimum stress ratio
Enter the value of the minimum von Mises stress ratio to prevent Abaqus/CAE from optimizing regions with very low stresses. Abaqus/CAE does not apply bead optimization in the regions where the von Mises stress is less than the value computed from the specified ratio multiplied by the highest von Mises stress in the design area (0.0 < Minimum stress ratio < 1.0). The default value is 0.001.
Maximum membrane stress ratio
Enter the value of the maximum membrane stress ratio to prevent Abaqus/CAE from optimizing regions in a predominately membrane, or inplane, stress state (the introduction of a bead in a region under a predominately membrane stress state may make the structure softer).
Abaqus/CAE does not apply bead optimization in regions where the membrane stress is greater than the constant value computed from the maximum bending stress in the original model divided by the specified ratio (0.0 < Maximum membrane stress ratio). The default value is 1.0.
Specify the following Mesh Smoothing Parameters:
Curve smooth
Enter the relative value of the radius defining a region of high curvature.
The introduction of a bead during the optimization can squeeze nodes together and result in small elements. For even higher degrees of curvature and large bead heights, the nodes can begin to overlap causing the analysis to fail. To prevent the collapse of the mesh, Abaqus/CAE can modify how it moves nodes while creating a bead in a region of high curvature. High curvature is defined as the radius calculated by multiplying the Curve smooth value and the average element edge length in the design area. High values of Curve smooth and, hence, a large radius encompassing many elements, can be computationaly expensive. The default value is five times the average element length.
Node smooth
By default, the value for Node smooth is 0.25 × bead width. Alternatively, you can specify the absolute minimum in-plane distance between neighboring nodes during the creation of a bead. Values between 0.0 and 0.5 × bead width are allowed.
Node smoothing is applied to prevent sudden changes in displacement of neighboring nodes, especially near the boundary between the design area and the rest of the model or where active design variable constraints are restraining the displacement of nodes.
A general bead optimization is a flexible, sensitivity-based optimization that allows you to apply a range of constraints and objective functions to your model. The sensitivity-based algorithm does not implement a bead filter; therefore, the optimization may not generate a distinct bead pattern. You use the optimization task editor to customize various aspects of a bead optimization. To locate the editor, select TaskEditoptimization task name from the main menu bar. To specify a general bead optimization, select the Advanced tab and choose General optimization (sensitivity-based).
The following topics are covered:
To configure basic settings:
In the optimization task editor, click the Basic tab.
Choose whether to respect boundary conditions that have been applied to the model.
It is recommended that you freeze regions to which boundary conditions are applied because you do not want these regions to be moved during the optimization. Freezing these regions stabilizes the optimization and often leads to a significantly lower number of iterations.
By default, the Optimization module freezes boundary conditions for the whole model. If desired, click and select the region in which the boundary conditions should be frozen.
To configure node settings:
In the optimization task editor, click the Nodal Move tab.
Select the Nodal update strategy.
This setting controls the rate at which the Optimization module updates the shell thickness of design elements during the optimization using the method of moving asymptotes. In most cases you should accept the default setting (Conservative). However, if the design responses are very sensitive and you have problems fulfilling the constraints, you may need a more aggressive rate that requires more optimization iterations. Selecting an aggressive rate may lead to unstable optimization or prevent the optimization from converging on a solution.
Enter the Nodal move limit.
This setting limits the nodal displacement per iteration relative to the maximum displacement prescribed (0.0 < Nodal move limit < 1.0). The default value is 0.1. If you encounter a difficult optimization problem that is slow to converge, you can reduce the size of each optimization iteration by reducing the Nodal move limit.
Note: You prescribe the maximum displacement of a node by specifying the height of the stiffening bead when you create a bead optimization constraint.
To configure the perturbation settings:
In the optimization task editor, click the Perturbation tab.
Enter the number of eigenmodes to track. The default value is five, which means that the Optimization module tracks the five lowest eigenfrequencies.
In some cases many local low frequency eigenmodes appear during the optimization iterations, which leads to a high number of modes to track and degrades performance. You can avoid tracking a high number of modes by choosing the lower bound of the eigenfrequencies to be 25% of the eigenfrequency of interest in the first optimization iteration.
Mode tracking is not required if your design response will use the Kreisselmaier-Steinhauser formulation to evaluate the eigenfrequencies. Your Abaqus model must include an output request for at least the number of eigenfrequencies you are tracking.
Select the region over which the Optimization module should track the eigenmodes. Selecting a region other than the whole model may result in increased performance.
To configure advanced options:
In the optimization task editor, click the Advanced tab.
Specify the Filter Radius of the Sigmund filter, which smoothes the resulting optimization solution. Changing this value may help you to avoid known problems from fluctuations in sensitivity values. The following options allow you to specify the filter radius for a general bead optimization:
Relative to average edge length
Enter the relative filter radius. Abaqus/CAE computes the filter radius as the value specified multiplied by the average element length in the design area (the region that will be optimized). The default value is four. A value of zero turns off the filter; the resulting bead optimization may generate an unsmooth result that is numerically optimal but not a realistic physical solution.
Absolute value
Enter the absolute value of the radius.
For the sensitivity calculation, choose whether the optimization should consider only the nodes in the region that will be optimized (default) or all the nodes in the model.
Enter the Bead perturbation. Abaqus/CAE uses this value to compute a semianalytical sensitivity analysis using a finite difference on the element matrices. The finite difference is computed as the perturbation value specified multiplied by the average element edge length. The default value is 0.0001, which is suitable for most bead optimization problems.