mass Module

All mass elements are defined in this file. This includes:

• CMASS1

• CMASS2

• CMASS3

• CMASS4

• CONM1

• CONM2

All mass elements are PointMassElement and Element objects.

class pyNastran.bdf.cards.elements.mass.CMASS1(eid: int, pid: int, nids: List[int], c1: int = 0, c2: int = 0, comment: str = '')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

Defines a scalar mass element.

1	2	3	4	5	6	7
CMASS1	EID	PID	G1	C1	G2	C2

Creates a CMASS1 card

Parameters

eidint

element id

pidint

property id (PMASS)

nidsList[int, int]

node ids

c1 / c2int; default=0

DOF for nid1 / nid2

commentstr; default=’’

a comment for the card

Centroid()

Centroid is assumed to be c=(g1+g2)/2. If g2 is blank, then the centroid is the location of g1.

G1()

G2()

Mass()

Pid()

Gets the Property ID of an element

Returns

pidint

the Property ID

classmethod _init_from_empty()

_properties = ['node_ids']

classmethod add_card(card, comment='')

Adds a CMASS1 card from BDF.add_card(...)

Parameters

cardBDFCard()

a BDFCard object

commentstr; default=’’

a comment for the card

center_of_mass()

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

property node_ids

raw_fields()

safe_cross_reference(model: BDF, xref_errors)

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

type = 'CMASS1'

uncross_reference() → None

Removes cross-reference links

write_card(size: int = 8, is_double: bool = False) → str

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.mass.CMASS2(eid, mass, nids, c1, c2, comment='')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

Defines a scalar mass element without reference to a property entry.

1	2	3	4	5	6	7
CMASS2	EID	M	G1	C1	G2	C2

Creates a CMASS2 card

Parameters

eidint

element id

massfloat

mass

nidsList[int, int]

node ids

c1 / c2int; default=None

DOF for nid1 / nid2

commentstr; default=’’

a comment for the card

Centroid()

Centroid is assumed to be c=(g1+g2)/2. If g2 is blank, then the centroid is the location of g1.

G1()

G2()

Mass()

classmethod _init_from_empty()

_properties = ['node_ids']

classmethod add_card(card, comment='')

Adds a CMASS2 card from BDF.add_card(...)

Parameters

cardBDFCard()

a BDFCard object

commentstr; default=’’

a comment for the card

center_of_mass()

cp_name_map = {'M': 'mass'}

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

classmethod export_to_hdf5(h5_file, model, eids)

exports the masses in a vectorized way

property node_ids

raw_fields()

repr_fields()

Gets the fields in their simplified form

Returns

fieldsList[varies]

the fields that define the card

safe_cross_reference(model: BDF, xref_errors)

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

type = 'CMASS2'

uncross_reference() → None

Removes cross-reference links

validate()

card checking method that should be overwritten

write_card(size: int = 8, is_double: bool = False) → str

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.mass.CMASS3(eid, pid, nids, comment='')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

Defines a scalar mass element that is connected only to scalar points.

1	2	3	4	5
CMASS3	EID	PID	S1	S2

Creates a CMASS3 card

Parameters

eidint

element id

pidint

property id (PMASS)

nidsList[int, int]

SPOINT ids

commentstr; default=’’

a comment for the card

Centroid()

Mass()

S1()

S2()

classmethod _init_from_empty()

_properties = ['node_ids']

classmethod add_card(card, comment='')

Adds a CMASS3 card from BDF.add_card(...)

Parameters

cardBDFCard()

a BDFCard object

commentstr; default=’’

a comment for the card

center_of_mass()

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

property node_ids

raw_fields()

type = 'CMASS3'

uncross_reference() → None

Removes cross-reference links

write_card(size: int = 8, is_double: bool = False) → str

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.mass.CMASS4(eid, mass, nids, comment='')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

Defines a scalar mass element that is connected only to scalar points, without reference to a property entry

1	2	3	4	5
CMASS4	EID	M	S1	S2

Creates a CMASS4 card

Parameters

eidint

element id

massfloat

SPOINT mass

nidsList[int, int]

SPOINT ids

commentstr; default=’’

a comment for the card

Centroid()

Mass()

S1()

S2()

classmethod _init_from_empty()

_properties = ['node_ids']

classmethod add_card(card, icard=0, comment='')

center_of_mass()

cp_name_map = {'M': 'mass'}

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

property node_ids

raw_fields()

safe_cross_reference(model: BDF, xref_errors)

type = 'CMASS4'

uncross_reference() → None

Removes cross-reference links

write_card(size: int = 8, is_double: bool = False) → str

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.mass.CONM1(eid, nid, mass_matrix, cid=0, comment='')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

Concentrated Mass Element Connection, General Form Defines a 6 x 6 symmetric mass matrix at a geometric grid point

1	2	3	4	5	6	7	8	9
CONM1	EID	G	CID	M11	M21	M22	M31	M32
	M33	M41	M42	M43	M44	M51	M52	M53
	M54	M55	M61	M62	M63	M64	M65	M66

Creates a CONM1 card

Parameters

eidint

element id

nidint

the node to put the mass matrix

mass_matrix(6, 6) float ndarray

the 6x6 mass matrix, M

cidint; default=0

the coordinate system for the mass matrix

commentstr; default=’’

a comment for the card

::

[M] = [M11 M21 M31 M41 M51 M61]

[ M22 M32 M42 M52 M62] [ M33 M43 M53 M63] [ M44 M54 M64] [ Sym M55 M65] [ M66]

static Centroid()

Cid()

static Mass()

MassMatrix()

Nid()

_finalize_hdf5(encoding)

hdf5 helper function

classmethod _init_from_empty()

_properties = ['node_ids']

classmethod add_card(card, comment='')

Adds a CONM2 card from BDF.add_card(...)

Parameters

cardBDFCard()

a BDFCard object

commentstr; default=’’

a comment for the card

center_of_mass()

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

property node_ids

raw_fields()

repr_fields()

Gets the fields in their simplified form

Returns

fieldsList[varies]

the fields that define the card

safe_cross_reference(model: BDF, xref_errors)

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

type = 'CONM1'

uncross_reference() → None

Removes cross-reference links

update_by_cp_name(name, value)

write_card(size: int = 8, is_double: bool = False) → str

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.mass.CONM2(eid, nid, mass, cid=0, X=None, I=None, comment='')

Bases: pyNastran.bdf.cards.elements.mass.PointMassElement

1	2	3	4	5	6	7	8
CONM2	EID	NID	CID	MASS	X1	X2	X3
	I11	I21	I22	I31	I32	I33
CONM2	501274	11064		132.274

Creates a CONM2 card

Parameters

eidint

element id

nidint

node id

massfloat

the mass of the CONM2

cidint; default=0

coordinate frame of the offset (-1=absolute coordinates)

X(3, ) List[float]; default=None -> [0., 0., 0.]

xyz offset vector relative to nid

I(6, ) List[float]; default=None -> [0., 0., 0., 0., 0., 0.]

mass moment of inertia matrix about the CG I11, I21, I22, I31, I32, I33 = I

commentstr; default=’’

a comment for the card

Centroid()

This method seems way more complicated than it needs to be thanks to all these little caveats that don’t seem to be supported.

Centroid_no_xref(model: BDF) → np.ndarray

This method seems way more complicated than it needs to be thanks to all these little caveats that don’t seem to be supported.

Cid()

I = None

Mass moments of inertia measured at the mass center of gravity in the coordinate system defined by field 4. If CID = -1, the basic coordinate system is implied. (Real) I11, I21, I22, I31, I32, I33 = I

Inertia()

Returns the 3x3 inertia matrix .. warning:: doesnt handle offsets or coordinate systems

Mass()

Nid()

X = None

Offset distances from the grid point to the center of gravity of the mass in the coordinate system defined in field 4, unless CID = -1, in which case X1, X2, X3 are the coordinates, not offsets, of the center of gravity of the mass in the basic coordinate system. (Real)

classmethod add_card(card, comment='')

Adds a CONM2 card from BDF.add_card(...)

Parameters

cardBDFCard()

a BDFCard object

commentstr; default=’’

a comment for the card

center_of_mass() → numpy.ndarray

centroid_mass_inertia() → Tuple[numpy.ndarray, float, numpy.ndarray]

cid = None

Coordinate system identification number. For CID of -1; see X1, X2, X3 below. (Integer > -1; Default = 0)

cross_reference(model: BDF) → None

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

eid = None

Element identification number. (0 < Integer < 100,000,000)

classmethod export_to_hdf5(h5_file, model, eids)

exports the elements in a vectorized way

mass = None

Mass value. (Real)

nid = None

Grid point identification number. (Integer > 0)

property node_ids

offset(xyz_nid)

raw_fields()

repr_fields()

Gets the fields in their simplified form

Returns

fieldsList[varies]

the fields that define the card

safe_cross_reference(model: BDF, xref_errors)

Cross links the card so referenced cards can be extracted directly

Parameters

modelBDF()

the BDF object

type = 'CONM2'

uncross_reference() → None

Removes cross-reference links

update_by_cp_name(name, value)

validate()

card checking method that should be overwritten

write_card(size: int = 8, is_double: bool = False) → str

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)

class pyNastran.bdf.cards.elements.mass.PointMassElement

Bases: pyNastran.bdf.cards.base_card.Element

dummy init

repr_fields() → List[Union[int, float, str, None]]

Gets the fields in their simplified form

Returns

fieldsList[varies]

the fields that define the card

write_card(size: int = 8, is_double: bool = False) → str

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: bool = False) → str

pyNastran.bdf.cards.elements.mass.is_positive_semi_definite(A, tol=1e-08)

is the 3x3 matrix positive within tolerance