In a static perturbation step the response is always linear, and the results of the step are not considered in subsequent steps. The base state is the current state of the model at the end of the last general analysis step. If the static perturbation step is the first step in the simulation, the base state is the initial conditions defined in the simulation scenario. For a video that describes the fundamentals of static perturbation, see Static Perturbation Step in FEA for 3DEXPERIENCE. Contact in Static Perturbation StepsTwo approaches are available for handling contact in a static perturbation analysis. By default, the open/closed status of each contact constraint is assumed to remain as it is in the base state. Points in contact (that is, points with a “closed” status) are assumed to be sticking if friction is present. When a velocity differential is imposed by the motion of the reference frame or the transport velocity, slipping conditions are assumed regardless of the friction coefficient. By freezing the contact status, contact contributions (and the overall governing equations) are imposed as linear in the solution variables and result in a purely linear static perturbation analysis. Alternatively, in the special case for simulations that include only small-sliding, frictionless contact, you can activate the LCP solution technique to improve performance. The static LCP perturbation procedure treats contact in a nonlinear manner by allowing for contact status changes from applied perturbation loads and boundary conditions. Therefore, the actual set of points in contact (that might differ from the base state) and their normal contact pressure values are computed during the perturbation analysis. Loading and OutputDuring a linear perturbation analysis step, define loads, boundary conditions, predefined temperatures, and fields as the magnitudes of the load perturbations only. Solution variable results are output as changes relative to the previous step (the value of the variable in the base state is not included). However, for a static LCP perturbation procedure, Abaqus reports all contact output quantities (such as contact stresses, contact strains, and contact forces) as total values. This is in response to the cumulative effect of base state loads (and boundary conditions) and perturbation loads (and boundary conditions). Similarly, the contact status corresponds to the state (open or closed) at the end of the perturbation analysis, which can be different from the contact status at the base state. Matrix StorageUsually it is not necessary to specify the matrix storage and solution scheme. Abaqus automatically chooses whether to use a symmetric or unsymmetric matrix storage and solution scheme based on the model and step definition that you use. For example, in problems where every friction coefficient is less than or equal to 0.2, Abaqus invokes the symmetric matrix storage and solution scheme. Alternatively, in problems where any friction coefficient is greater than 0.2, Abaqus uses the unsymmetric matrix storage and solution scheme. However, in cases where you judge that the default value is not the best choice, you might be able to improve computational efficiency by overriding the default selection. | ||||||