`bars` Module

digraph inheritancef8b99e8d07 { bgcolor=transparent; rankdir=LR; size=""; "pyNastran.bdf.cards.base_card.BaseCard" [URL="../pyNastran.bdf.cards.base_card.html#pyNastran.bdf.cards.base_card.BaseCard",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top",tooltip="Defines a series of base methods for every card class"]; "pyNastran.bdf.cards.base_card.Element" [URL="../pyNastran.bdf.cards.base_card.html#pyNastran.bdf.cards.base_card.Element",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top",tooltip="defines the Element class"]; "pyNastran.bdf.cards.base_card.BaseCard" -> "pyNastran.bdf.cards.base_card.Element" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.BAROR" [URL="#pyNastran.bdf.cards.elements.bars.BAROR",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top",tooltip="+-------+---+-----+---+---+-------+-----+-------+------+"]; "pyNastran.bdf.cards.base_card.BaseCard" -> "pyNastran.bdf.cards.elements.bars.BAROR" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.CBAR" [URL="#pyNastran.bdf.cards.elements.bars.CBAR",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top",tooltip="+-------+-----+-----+-----+-----+-----+-----+-----+------+"]; "pyNastran.bdf.cards.elements.bars.LineElement" -> "pyNastran.bdf.cards.elements.bars.CBAR" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.CBARAO" [URL="#pyNastran.bdf.cards.elements.bars.CBARAO",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top",tooltip="Per MSC 2016.1"]; "pyNastran.bdf.cards.base_card.BaseCard" -> "pyNastran.bdf.cards.elements.bars.CBARAO" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.CBEAM3" [URL="#pyNastran.bdf.cards.elements.bars.CBEAM3",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top"]; "pyNastran.bdf.cards.elements.bars.LineElement" -> "pyNastran.bdf.cards.elements.bars.CBEAM3" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.CBEND" [URL="#pyNastran.bdf.cards.elements.bars.CBEND",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top"]; "pyNastran.bdf.cards.elements.bars.LineElement" -> "pyNastran.bdf.cards.elements.bars.CBEND" [arrowsize=0.5,style="setlinewidth(0.5)"]; "pyNastran.bdf.cards.elements.bars.LineElement" [URL="#pyNastran.bdf.cards.elements.bars.LineElement",fillcolor=white,fontname="Vera Sans, DejaVu Sans, Liberation Sans, Arial, Helvetica, sans",fontsize=10,height=0.25,shape=box,style="setlinewidth(0.5),filled",target="_top"]; "pyNastran.bdf.cards.base_card.Element" -> "pyNastran.bdf.cards.elements.bars.LineElement" [arrowsize=0.5,style="setlinewidth(0.5)"]; }

defines:

CBAR
CBARAO
BAROR
CBEAM3
CBEND

class pyNastran.bdf.cards.elements.bars.BAROR(pid, is_g0, g0, x, offt='GGG', comment='')[source]

Bases: BaseCard

1	2	3	4	5	6	7	8	9
BAROR		PID			G0/X1	X2	X3	OFFT
BAROR		39			0.6	2.9	-5.87	GOG

classmethod _init_from_empty()[source]

classmethod add_card(card, comment='')[source]

raw_fields()[source]: Gets the fields of the card in their full form

type = 'BAROR'

write_card(size: int = 8, is_double: bool = False) → str[source]

Writes the card with the specified width and precision

Parameters:

sizeint (default=8): size of the field; {8, 16}
is_doublebool (default=False): is this card double precision

Returns:

msgstr: the string representation of the card

class pyNastran.bdf.cards.elements.bars.CBAR(eid, pid, nids, x, g0, offt='GGG', pa=0, pb=0, wa=None, wb=None, comment='')[source]

Bases: LineElement

1	2	3	4	5	6	7	8	9
CBAR	EID	PID	GA	GB	X1	X2	X3	OFFT
	PA	PB	W1A	W2A	W3A	W1B	W2B	W3B

or

1	2	3	4	5	6	7	8	9
CBAR	EID	PID	GA	GB	G0			OFFT
	PA	PB	W1A	W2A	W3A	W1B	W2B	W3B

1	2	3	4	5	6	7	8	9
CBAR	2	39	7	6	105			GGG
		513	0.0	0.0	-9.	0.0	0.0	-9.

Adds a CBAR card

Parameters:

pidint: property id
midint: material id
nidslist[int, int]: node ids; connected grid points at ends A and B
xlist[float, float, float]: Components of orientation vector, from GA, in the displacement coordinate system at GA (default), or in the basic coordinate system
g0int: Alternate method to supply the orientation vector using grid point G0. Direction of is from GA to G0. is then transferred to End A
offtstr; default=’GGG’: Offset vector interpretation flag
pa / pbint; default=0: Pin Flag at End A/B. Releases the specified DOFs
wa / wblist[float, float, float]: Components of offset vectors from the grid points to the end points of the axis of the shear center
commentstr; default=’’: a comment for the card

Area()[source]: returns the area of the element face

Centroid()[source]

G0()[source]: gets G0

Ga()[source]: gets Ga/G1

Gb()[source]: gets Gb/G2

I1()[source]

I2()[source]

J()[source]: returns the Polar Moment of Inertia, \(J\)

Length()[source]: Gets the length, \(L\), of the element.

\[L = \sqrt{ (n_{x2}-n_{x1})^2+(n_{y2}-n_{y1})^2+(n_{z2}-n_{z1})^2 }\]

Mid()[source]

Nsm()[source]: Placeholder method for the non-structural mass, \(nsm\)

classmethod add_card(card, baror=None, comment='')[source]

Adds a CBAR card from BDF.add_card(...)

Parameters:

cardBDFCard(): a BDFCard object
beamorBAROR() or None: defines the defaults
commentstr; default=’’: a comment for the card

center_of_mass()[source]

cross_reference(model: BDF) → None[source]

Cross links the card so referenced cards can be extracted directly

Parameters:

modelBDF(): the BDF object

classmethod export_to_hdf5(h5_file, model, eids)[source]: exports the elements in a vectorized way

get_axes(model: BDF) → tuple[bool, Any][source]

Gets the axes of a CBAR/CBEAM, while respecting the OFFT flag.

Returns:

is_passed: bool: flag
out: (v, ihat, jhat, khat, wa, wb): data

Notes

pyNastran.bdf.cards.elements.bars.rotate_v_wa_wb() for a description of the OFFT flag.

get_axes_by_nodes(model: BDF, node1: GRID, node2: GRID, xyz1: np.ndarray, xyz2: np.ndarray, log: SimpleLogger) → tuple[bool, Any][source]

Gets the axes of a CBAR/CBEAM, while respecting the OFFT flag.

Notes

pyNastran.bdf.cards.elements.bars.rotate_v_wa_wb() for a description of the OFFT flag.

get_edge_ids()[source]: Return the edge IDs

get_orientation_vector(model: BDF)[source]

Gets the axes of a CBAR/CBEAM, while respecting the OFFT flag.

Notes

pyNastran.bdf.cards.elements.bars.rotate_v_wa_wb() for a description of the OFFT flag.

get_x_g0_defaults()[source]

X and G0 compete for the same fields, so the method exists to make it easier to write the card

Returns:

x_g0varies: g0 : list[int, None, None] x : list[float, float, float]

Notes

Used by CBAR and CBEAM

property node_ids

property nodes

property nodes_ref

raw_fields()[source]: Gets the fields of the card in their full form

repr_fields()[source]: Gets the fields of the card in their reduced form

safe_cross_reference(model: BDF, xref_errors)[source]

type = 'CBAR'

uncross_reference() → None[source]: Removes cross-reference links

update_by_cp_name(cp_name, value)[source]

validate()[source]: card checking method that should be overwritten

write_card(size: int = 8, is_double: bool = False) → str[source]

Writes the card with the specified width and precision

Parameters:

sizeint (default=8): size of the field; {8, 16}
is_doublebool (default=False): is this card double precision

Returns:

msgstr: the string representation of the card

write_card_16(is_double=False)[source]

class pyNastran.bdf.cards.elements.bars.CBARAO(eid, scale, x, comment='')[source]

Bases: BaseCard

Per MSC 2016.1 +——–+——+——-+——+—–+——–+—–+—-+—-+ | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | +========+======+=======+======+=====+========+=====+====+====+ | CBARAO | EID | SCALE | X1 | X2 | X3 | X4 | X5 | X6 | +——–+——+——-+——+—–+——–+—–+—-+—-+ | CBARAO | 1065 | FR | 0.2 | 0.4 | 0.6 | 0.8 | | | +——–+——+——-+——+—–+——–+—–+—-+—-+

Alternate form (not supported): +——–+——+——-+——+—–+——–+—–+—-+—-+ | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | +========+======+=======+======+=====+========+=====+====+====+ | CBARAO | EID | SCALE | NPTS | X1 | DELTAX | | | | +——–+——+——-+——+—–+——–+—–+—-+—-+ | CBARAO | 1065 | FR | 4 | 0.2 | 0.2 | | | | +——–+——+——-+——+—–+——–+—–+—-+—-+

Creates a CBARAO card, which defines additional output locations for the CBAR card.

It also changes the OP2 element type from a CBAR-34 to a CBAR-100. However, it is ignored if there are no PLOAD1s in the model. Furthermore, the type is changed for the whole deck, regardless of whether there are PLOAD1s in the other load cases.

Parameters:

eidint: element id
scalestr: defines what x means LE : x is in absolute coordinates along the bar FR : x is in fractional
xlist[float]: the additional output locations (doesn’t include the end points) len(x) <= 6
commentstr; default=’’: a comment for the card
MSC only

classmethod _init_from_empty()[source]

classmethod add_card(card, comment='')[source]

Adds a CBARAO card from BDF.add_card(...)

Parameters:

cardBDFCard(): a BDFCard object
commentstr; default=’’: a comment for the card

raw_fields()[source]

repr_fields()[source]

Gets the fields in their simplified form

Returns:

fieldslist[varies]: the fields that define the card

type = 'CBARAO'

write_card(size: int = 8, is_double: bool = False) → str[source]

Writes the card with the specified width and precision

Parameters:

sizeint (default=8): size of the field; {8, 16}
is_doublebool (default=False): is this card double precision

Returns:

msgstr: the string representation of the card

class pyNastran.bdf.cards.elements.bars.CBEAM3(eid, pid, nids, x, g0, wa=None, wb=None, wc=None, tw=None, s=None, comment='')[source]

Bases: LineElement

dummy init

Area()[source]: returns the area of the element face

Centroid()[source]

G0()[source]: gets the orientation vector node

Ga()[source]: gets node 1

Gb()[source]: gets node 2

Gc()[source]: gets the node between node 1 and 2

Length()[source]

We’ll fit a 2nd order polynomial to the x, y, and z coefficients. We know GA (t=0), GB(t=1), and GC (t=0.5 assumed). This gives us A, for:

y1 = a1*t^2 = b1*t + c1

where:

yi is for the x, y, and z terms

[xa, xb, xc] = [A][a1, b1, c1].T [ya, yb, yc] = [A][a2, b2, c2].T [za, zb, zc] = [A][a3, b3, c3].T

[a1, b1, c1] = [A^-1][[xa, xb, xc].T A = [0. , 0. , 1. ]

[1. , 1. , 1. ] [0.25, 0.5 , 1. ]

Ainv = [ 2., 2., -4.]: [-3., -1., 4.] [ 1., 0., 0.]

MassPerLength()[source]: Get the mass per unit length, :math:` rac{m}{L}`

Nsm()[source]: Placeholder method for the non-structural mass, \(nsm\)

Volume()[source]

classmethod _init_from_empty()[source]

_integrate(xabc, yabc, zabc)[source]

We integrate:

y = sqrt(x’(t)^2 + y’(t)^2 + z’(t)^2)*dt from 0 to 1 y = sqrt(r)

/where:

x(t) = a*t^2 + b*t + c
x’(t) = 2*a*t + b
x’(t)^2 = 4*(a*t)^2 + 2*a*b*t + b^2

expanding terms:

x’(t)^2 = 4*(a1*t)^2 + 2*a1*b1*t + b1^2
y’(t)^2 = 4*(a2*t)^2 + 2*a2*b2*t + b2^2
z’(t)^2 = 4*(a3*t)^2 + 2*a3*b3*t + b3^2

grouping terms:

a = 4 * (a1 ** 2 + a2 ** 2 + a3 ** 2) * t^2
b = 2 * (a1 * b1 + a2 * b2 + a3 * b3) * t
c = b1 ** 2 + b2 ** 2 + b3 ** 2
y = integrate(sqrt(a*t^2 + b*t + t), t, 0., 1.)

Looking up integral formulas, we get a really complicated integral.

for a = 0 (and rewriting):

y = integrate(sqrt(a*t + b), t, 0., 1.)
y = (2*b/3a + 2*t/3) * sqrt(at + b)

or:

y = (2*c/3b + 2*t/3) * sqrt(b*t + c)

_properties = ['node_ids', 'nodes']: Defines a three-node beam element

classmethod add_card(card, comment='')[source]

Adds a CBEAM3 card from BDF.add_card(...)

Parameters:

cardBDFCard(): a BDFCard object
commentstr; default=’’: a comment for the card

center_of_mass()[source]

cross_reference(model: BDF) → None[source]

Cross links the card so referenced cards can be extracted directly

Parameters:

modelBDF(): the BDF object

get_edge_ids()[source]: Return the edge IDs

get_x_g0_defaults()[source]

X and G0 compete for the same fields, so the method exists to make it easier to write the card

Returns:

x_g0varies: g0 : list[int, None, None] x : list[float, float, float]

Notes

Used by CBAR, CBEAM, and CBEAM3

property node_ids

property nodes

raw_fields()[source]

repr_fields()[source]

Gets the fields in their simplified form

Returns:

fieldslist[varies]: the fields that define the card

safe_cross_reference(model: BDF, xref_errors)[source]

type = 'CBEAM3'

uncross_reference() → None[source]: Removes cross-reference links

write_card(size: int = 8, is_double: bool = False) → str[source]

Writes the card with the specified width and precision

Parameters:

sizeint (default=8): size of the field; {8, 16}
is_doublebool (default=False): is this card double precision

Returns:

msgstr: the string representation of the card

class pyNastran.bdf.cards.elements.bars.CBEND(eid, pid, nids, g0, x, geom, comment='')[source]

Bases: LineElement

Creates a CBEND card

Parameters:

eidint

element id

pidint

property id (PBEND)

nidslist[int, int]

node ids; connected grid points at ends A and B

g0int

???

xlist[float, float, float]

???

geomint

1 : The center of curvature lies on the line AO (or its extension) or vector v. 2 : The tangent of centroid arc at end A is parallel to line AO or vector v.

Point O (or vector v) and the arc must be on the same side of the chord AB.

3The bend radius (RB) is specified on the PBEND entry:: Points A, B, and O (or vector v) define a plane parallel or coincident with the plane of the element arc. Point O (or vector v) lies on the opposite side of line AB from the center of the curvature.
4THETAB is specified on the PBEND entry. Points A, B, and O (or vector v): define a plane parallel or coincident with the plane of the element arc. Point O (or vector v) lies on the opposite side of line AB from the center of curvature.

commentstr; default=’’

a comment for the card

Area()[source]: returns the area of the element face

Centroid()[source]

Ga()[source]

Gb()[source]

Length()[source]: Gets the length, \(L\), of the element.

\[L = \sqrt{ (n_{x2}-n_{x1})^2+(n_{y2}-n_{y1})^2+(n_{z2}-n_{z1})^2 }\]

classmethod _init_from_empty()[source]

_properties = ['node_ids']

classmethod add_card(card, comment='')[source]

Adds a CBEND card from BDF.add_card(...)

Parameters:

cardBDFCard(): a BDFCard object
commentstr; default=’’: a comment for the card

center_of_mass()[source]

cross_reference(model: BDF) → None[source]

Cross links the card so referenced cards can be extracted directly

Parameters:

modelBDF(): the BDF object

get_x_g0_defaults()[source]

property node_ids

property nodes

property nodes_ref

raw_fields()[source]

repr_fields()[source]

Gets the fields in their simplified form

Returns:

fieldslist[varies]: the fields that define the card

safe_cross_reference(model: BDF, xref_errors)[source]

type = 'CBEND'

uncross_reference() → None[source]: Removes cross-reference links

validate()[source]: card checking method that should be overwritten

write_card(size: int = 8, is_double: bool = False) → str[source]

Writes the card with the specified width and precision

Parameters:

sizeint (default=8): size of the field; {8, 16}
is_doublebool (default=False): is this card double precision

Returns:

msgstr: the string representation of the card

class pyNastran.bdf.cards.elements.bars.LineElement[source]

Bases: Element

dummy init

Area()[source]: returns the area of the element face

C()[source]: torsional constant

E()[source]: returns the Young’s Modulus, \(E\)

G()[source]: returns the Shear Modulus, \(G\)

I11()[source]: returns the Moment of Inertia, \(I_{11}\)

I12()[source]: returns the Moment of Inertia, \(I_{12}\)

I22()[source]: returns the Moment of Inertia, \(I_{22}\)

J()[source]: returns the Polar Moment of Inertia, \(J\)

Length()[source]: Gets the length, \(L\), of the element.

\[L = \sqrt{ (n_{x2}-n_{x1})^2+(n_{y2}-n_{y1})^2+(n_{z2}-n_{z1})^2 }\]

Mass()[source]: Get the mass of the element.

\[m = \left( \rho A + nsm \right) L\]

MassPerLength()[source]: Get the mass per unit length, :math:` rac{m}{L}`

Nsm()[source]: Placeholder method for the non-structural mass, \(nsm\)

Nu()[source]: Get Poisson’s Ratio, :math:` u`

Rho()[source]: Get the material density, :math:` ho`

get_edge_ids()[source]: Return the edge IDs

uncross_reference() → None[source]: Removes cross-reference links

pyNastran.bdf.cards.elements.bars.check_offt(element)[source]: B,G,O Note: The character ‘O’ in the table replaces the obsolete character ‘E’ allowed = ‘GGG,BGG,GGO,BGO,GOG,BOG,GOO,BOO,GGE,BGE,GEG,BEG,GEE,BEE,GGB,BGB,GBG,BBG,GBB,BBB,B’

pyNastran.bdf.cards.elements.bars.get_bar_vector(model: BDF, elem, node1: GRID, node2: GRID, xyz1: np.ndarray)[source]: helper method for rotate_v_wa_wb

pyNastran.bdf.cards.elements.bars.get_bar_yz_transform(v: ndarray, ihat: ndarray, eid: int, xyz1: ndarray, xyz2: ndarray, nid1: int, nid2: int, i: ndarray, Li: float) → tuple[ndarray, ndarray][source]

helper method for _get_bar_yz_arrays

Parameters:

vlist[float, float, float]: the projection vector that defines the y-axis (jhat)
ihat(3, ) float ndarray: the normalized x-axis (not including the CBEAM offset)
eidint: the element id
xyz1 / xyz2(3, ) float ndarray: the xyz locations for node 1 / 2
nid1 / nid2int: the node ids for xyz1 / xyz2
i(3, ) float ndarray: the unnormalized x-axis (not including the CBEAM offset)
Lifloat: the length of the CBAR/CBEAM (not including the CBEAM offset)

Returns:

yhat (3, ) float ndarray: the CBAR/CBEAM’s y-axis
zhat (3, ) float ndarray: the CBAR/CBEAM’s z-axis

pyNastran.bdf.cards.elements.bars.init_x_g0(card, eid, x1_default, x2_default, x3_default)[source]: common method to read the x/g0 field for the CBAR, CBEAM, CBEAM3

pyNastran.bdf.cards.elements.bars.init_x_g0_cbeam3(card, eid, x1_default, x2_default, x3_default)[source]: reads the x/g0 field for the CBEAM3

pyNastran.bdf.cards.elements.bars.rotate_v_wa_wb(model: BDF, elem, xyz1: np.ndarray, xyz2: np.ndarray, node1: GRID, node2: GRID, ihat_offset: np.ndarray, i_offset: np.ndarray, eid: int, Li_offset: float, log: SimpleLogger) → tuple[NDArray3float, NDArray3float, NDArray3float, NDArray33float][source]

Rotates v, wa, wb

Parameters:

modelBDF(): BDF : assume the model isn’t xref’d None : use the xref’d values
elemCBAR() / CBEAM(): the CBAR/CBEAM
xyz1 / xyz2(3, ) float ndarray: the xyz locations for node 1 / 2
node1 / node2GRID(): the xyz object for node 1 / 2
ihat_offset(3, ) float ndarray: the normalized x-axis (not including the CBEAM offset)
i_offset(3, ) float ndarray: the unnormalized x-axis (not including the CBEAM offset)
eidint: the element id
Li_offsetfloat: the length of the CBAR/CBEAM (not including the CBEAM offset)
logLog(): a logging object or None

Returns:

vlist[float, float, float]: the projection vector that defines the y-axis (jhat)
walist[float, float, float]: the offset vector at A
wblist[float, float, float]: the offset vector at B
xform(3, 3) float ndarray: a vstack of the [ihat, jhat, khat] axes

Notes

This section details the OFFT flag.

ABC or A-B-C (an example is G-G-G or B-G-G) while the slots are:

A -> orientation; values=[G, B]

B -> End A; values=[G, O]

C -> End B; values=[G, O]

and the values for A,B,C mean:

B -> basic
G -> global
O -> orientation

so for example G-G-G, that’s global for all terms. BOG means basic orientation, orientation end A, global end B

so now we’re left with what does basic/global/orientation mean? - basic -> the global coordinate system defined by cid=0 - global -> the local coordinate system defined by the

CD field on the GRID card, but referenced by the CBAR/CBEAM

orientation -> wa/wb are defined in the xform_offset (yz) frame;
this is likely the easiest frame for a user

bars Module

`bars` Module