delete_bad_elements Module

defines:

• model = delete_bad_shells(model, max_theta=175., max_skew=70., max_aspect_ratio=100.,

  max_taper_ratio=4.0)

• eids_to_delete = get_bad_shells(model, xyz_cid0, nid_map, max_theta=175., max_skew=70.,

  max_aspect_ratio=100., max_taper_ratio=4.0)

pyNastran.bdf.mesh_utils.delete_bad_elements.delete_bad_shells(model: BDF, min_theta: float = 0.1, max_theta: float = 175.0, max_skew: float = 70.0, max_aspect_ratio: float = 100.0, max_taper_ratio: float = 4.0, max_warping: float = 90.0) → BDF

Removes bad CQUAD4/CTRIA3 elements

Parameters:

modelBDF ()

this should be equivalenced

min_thetafloat; default=0.1

the maximum interior angle (degrees)

max_thetafloat; default=175.

the maximum interior angle (degrees)

max_skewfloat; default=70.

the maximum skew angle (degrees)

max_aspect_ratiofloat; default=100.

the max aspect ratio

taper_ratiofloat; default=4.0

the taper ratio; applies to CQUAD4s only

max_warping: float: default=20.0

the maximum warp angle (degrees)

pyNastran.bdf.mesh_utils.delete_bad_elements.element_quality(model, nids=None, xyz_cid0=None, nid_map=None)

Gets various measures of element quality

Parameters:

modelBDF()

a cross-referenced model

nids(nnodes, ) int ndarray; default=None

the nodes of the model in sorted order includes GRID, SPOINT, & EPOINTs

xyz_cid0(nnodes, 3) float ndarray; default=None

the associated global xyz locations

nid_mapdict[nid]->index; default=None

a mapper dictionary

Returns:

qualitydict[name](nelements, ) float ndarray

Various quality metrics names : min_interior_angle, max_interior_angle, dideal_theta,

max_skew_angle, max_aspect_ratio, area_ratio, taper_ratio, min_edge_length

valuesThe result is np.nan if element type does not define

the parameter. For example, CELAS1 doesn’t have an aspect ratio.

Notes

• pulled from nastran_io.py

pyNastran.bdf.mesh_utils.delete_bad_elements.get_bad_shells(model: BDF, xyz_cid0, nid_map, min_theta: float = 0.1, max_theta: float = 175.0, max_skew: float = 70.0, max_aspect_ratio: float = 100.0, max_taper_ratio: float = 4.0, max_warping: float = 60.0) → list[int]

Get the bad shell elements

Parameters:

modelBDF()

the model object

xyz_cid0(N, 3) float ndarray

the xyz coordinates in cid=0

nid_mapdict[nid]index

nidint

the node id

indexint

the index of the node id in xyz_cid0

min_thetafloat; default=0.1

the maximum interior angle (degrees)

max_thetafloat; default=175.

the maximum interior angle (degrees)

max_skewfloat; default=70.

the maximum skew angle (degrees)

max_aspect_ratiofloat; default=100.

the max aspect ratio

taper_ratiofloat; default=4.0

the taper ratio; applies to CQUAD4s only

max_warping: float: default=60.0

the maximum warp angle (degrees)

Returns:

eids_failedlist[int]

element ids that fail the criteria

shells with a edge length=0.0 are automatically added

pyNastran.bdf.mesh_utils.delete_bad_elements.get_min_max_theta(faces, all_node_ids, nid_map, xyz_cid0)

get the min/max thetas for CTETRA, CPENTA, CHEXA, CPYRAM

pyNastran.bdf.mesh_utils.delete_bad_elements.get_node_map(model)

gets an nid->inid mapper

pyNastran.bdf.mesh_utils.delete_bad_elements.quad_quality(element, p1, p2, p3, p4)

gets the quality metrics for a quad

pyNastran.bdf.mesh_utils.delete_bad_elements.quad_quality_nastran(p1: ndarray, p2: ndarray, p3: ndarray, p4: ndarray) → tuple[float, float, float]

Compute CQUAD4 quality metrics using NX Nastran GEOMCHECK definitions.

Parameters:

p1, p2, p3, p4(3,) float ndarray

Corner node coordinates in order.

Returns:

skewfloat

Skew angle in radians (NX: angle between midpoint-joining vectors). Ideal = pi/2. Nastran fails if skew < 30 deg.

taperfloat

Taper ratio (NX: (A_max - Q) / Q). Ideal = 0.0. Nastran fails if taper > 0.5.

warpfloat

Surface warping factor (NX: HH / (D_AC + D_BD)). Ideal = 0.0. Nastran fails if warp > 0.05.

Notes

These formulas match NX Nastran User’s Guide Ch. 15 “User Controlled Element Checks” (Simcenter Nastran 2506).

The existing quad_quality function uses Altair/HyperMesh definitions which differ for taper (average deviation) and warp (angle-based).

pyNastran.bdf.mesh_utils.delete_bad_elements.tri_quality(p1, p2, p3)

gets the quality metrics for a tri

area, max_skew, aspect_ratio, min_theta, max_theta, dideal_theta, min_edge_length