Shell

class itasca.structure.Shell

Objects of this type should not be created (instantiated) directly in Python. Use the module functions that return instances of this type.

beta() → float.: Get Shell system beta angle. This is defined as the angle between the element local system x-axis and the material system x-axis. In radians measured counter-clockwise from the element local x-axis.

connectivity(component: int) → bool.: Get the index of the node with component-ID id in the element. A ValueError exception is raised if no node in that element matches.

depth_factor() → float.: Get the depth factor at which stresses have been recovered. The depth equals Ft/2 where t is the Shell element thickness. F values equal to +1.0 or -1.0 correspond to the outer/inner Shell surface. The outer surface is defined by the positive z-direction of the local Shell element system. F values of 0.0 corresponds to the Shell mid-surface. The depth factor can be modified with the \(structure Shell recover stress\) command.

element_type() → str.: Get the name of the finite-element type used by this Shell element. The possible types for Shell elements are ‘cst’, ‘csth’, ‘dkt’, ‘dkt-cst’, and ‘dkt-csth’.

force_nodal() → (vec3,vec3, vec3,vec3, vec3,vec3).: Get the generalized nodal force acting on the Shell at each node. The translational and rotational components of node 1 are given first.

group([slot: str or int]) → str.: Get the Shell group name in a given slot.

group_remove(group_name: str or int[, slot: str or int]) → bool.: Remove from the given group from all group slots of the Shell. One argument of type string, giving the group name, is required. The return value is a bool which is True if the group was removed from any slot, otherwise False.

groups() → {slot: group_name}.: Get a dictionary describing which groups this Shell is part of. The keys of the dictionary are the slot names and the values are the group names.

in_group(group_name: str or int[, slot: str or int]) → bool.: Test if the Shell is part of a given group. If the optional argument slot is given, only that slot is searched. Otherwise, all group slots are searched.

local_system() → Tens3.: Get local coordinate system of this element as a 3x3 tensor.

mark() → bool.: Get the mark flag on the structural element. The structural element logic may modify this flag during command processing and cycling.

nodes() → tuple of Structural element node objects.: Get a tuple containing the structural element nodes attached to this elemment.

pos() → vec3.: Get the position vector of the element, defined as the element centroid.

pressure() → float.: Get the uniform pressure acting on the Shell. A positive value acts in the z-direction of the element local system.

prop_anis() → (membrane: tuple of float, bending: tuple of float).: Get the anisotropic material properties. Material-stiffness coefficients c’11, c’12, c’13, c’22, c’23, c’33 are returned for both the membrane and bending stiffnesses in that order. If the element does not have anisotropic properties, zeros are returned.

prop_ortho() → (membrane: tuple of float, bending: tuple of float).: Get the orthotropic material properties. Material-stiffness coefficients c’11, c’12, c’13, c’22, c’23, c’33 are returned for both the membrane and bending stiffnesses in that order. If the element does not have orthotropic properties, zeros are returned.

prop_type() → str.: Get the material property type. Possible return values are ‘isotropic’, ‘orthotripc’, and ‘anisotropic’.

resultant(location: int) → length 8 tuple of float.: Get stress resultants last calculated for the element at the index \(location\). A \(location\) value of 0 gives the resultant at the element centroid; \(location\) values 1, 2 and 3 give the resultant at the nodes. The components in the return value are: Mx, My, Mxy, Nx, Ny, Nxy, Qx and Qy. Note that stress resultants must be calculated with the \(structure Shell recover\) command. See also the \(resultant_valid\) method.

resultant_valid() → bool.: Get stress resultant validity flag. True indicates that the stress resultant values are valid. False indicates that resultants have not been calculated or that there has been a change since they were last calculated that would invalidate the results.

set_extra(slot: int, value: any) → None.: Set the Shell extra data in the given slot.

set_group(group_name: str or int[, slot: str or int]) → None.: Set the Shell group name in a given slot.

set_mark(bool) → None.: Set the mark flag on the structural element. The structural element logic may modify this flag during command processing and cycling.

set_pressure(float) → None.: Set the uniform pressure acting on the Shell. A positive value acts in the z-direction of the element local system.

set_thermal_expansion(float) → None.: Set the thermal-expansion coefficient for the structural element.

stress(location: int) → stens3.: Get the Shell stresses at the current depth factor at the index \(location\). A \(location\) value of 0 gives the stress at the element centroid; \(location\) values 1, 2 and 3 give the stress at the nodes. Stresses are expressed in the global system. Note that compressive stresses are negative.

stress_max() → float.: Get the maximum stress of the element. This is the maximum principal stress of the fiber stress at depth +1 or -1, which is the combination of membrane and bending resultants.

stress_prin(location: int) → vec3.: Get the resolved principal stress at the current depth factor at the index \(location\). A \(location\) value of 0 gives the stress at the element centroid; \(location\) values 1, 2 and 3 give the stress at the nodes. Returns a vector encoded as (minimum, intermediate, maximum). Note that compressive stresses are negative in FLAC3D.

stress_valid() → bool.: Get the stress validity flag for the element. True indicates that the stresses last calculated at the current depth factor are valid. Galse indicates that stresses have not been calculated, or that there has been a change that invalidates the last stresses calculated.

thermal_expansion() → float.: Get the thermal-expansion coefficient for the structural element.

young() → float.: Get the Youngs modulus of the element. Modifying the value during cycling may be a danger.

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Updated: Oct 31, 2024