PyFlange API documentation

This package has the ambitious goal of providing all the tools engineers need for the design of large bolted flanges such as the flanges used in offshore wind for connecting the turbine tower to the foundation.

Far from achieving its goal, this package currently contains only an implementation of Marc Seidel’s polynomial model for predicting bolt forces and moments due to shell pull.

This package has beend developed within the Bolt and Beoutiful GROW project by KCI, Siemens Gamesa and TNO.

The rest of this documentation will show how to get started and where to find extra documentation.

Installation

Once the Bolt and Beautiful project gets closed, this package will be released to the public with GPLv3 license and will be installable via

pip install pyflange

Until then, the source needs to stay closed and accessible to a limited number of people such as yourself. Therefore you need to install the wheel package after downloading it from GitHub.

cd <path/to/whl/package>
pip install pyflange-0.1.0-py3-none-any.whl

Usage instructions

After installing the package, you can import it in your python code as start using it. First of all, you need to create a FlangeSegment object as shown below.

# Create the bolt object
from pyflange.bolts import StandardMetricBolt
M80 = StandardMetricBolt("M80", "10.9", shank_length=0.270, stud=True)
Nb = 120    # number of bolts

# Define the gap parameters
from pyflange.gap import gap_height_distribution
D = 7.50                        # meters, flange outer diameter
gap_angle = pi/6                # 30 deg gap angle
gap_length = gap_angle * D/2    # outer length of the gap
u_tol = 0.0014                  # flatness tolerance in mm/mm
gap_dist = gap_height_distribution(D, u_tol, gap_length)    # lognormal distribution

# Create the FlangeSegment model
from pyflange.flangesegments import PolynomialLFlangeSegment
fseg = PolyNomialLFlangeSegment(
   a = 0.2325,                # distance between inner face of the flange and center of the bolt hole
   b = 0.1665,                # distance between center of the bolt hole and center-line of the shell
   s = 0.0720,                # shell thickness
   t = 0.2000,                # flange thickness
   R = D/2,                   # shell outer curvature radius
   central_angle = 2*pi/Nb,   # angle subtented by the flange segment arc

   Zg = -14795000 / Nb,    # load applied to the flange segment shell at rest
                           # (normally dead weight of tower + RNA, divided by the number of bolts)

   bolt = M80,             # bolt object created above
   Fv = 2876000,           # design bolt preload, after preload losses

   Do = 0.086,             # bolt hole diameter
   Dw = 0.140,             # washer diameter

   gap_height = gap_dist.ppf(0.95),    # maximum longitudinal gap height, 95% quantile
   gap_angle = gap_angle)              # longitudinal gap length

# Assert if the flange-segment fails with failure mode B.
# If not, an exception will be raised.
fseg.validate(325e6, 315e6)

Notice that a consistent set of units of measurements has been used for inputs, namely: meter for distances, radians for angles and newton for forces. It is not required to always use these units (meter, newton), but you should choose your units and always apply them consistently.

Once you have your fseg object, you can obtain the bolt forces and moments as follows:

Fs = fseg.bolt_axial_force(3500)    # bolt force corresponding to shell pull Z = 3500 N
Ms = fseg.bolt_bending_moment(2000) # bolt bending moment corresponding to shell pull Z = 2000 N

The argumment Z, passed to bolt_axial_force and bolt_bending_moment can also be a numpy array. In that case an array of Fs and Ms value will be returned.

import numpy as np
Z = np.array([2000, 2500, 3000])
Fs = fseg.bolt_axial_force(Z)       # return the numpy array (Fs(2000), Fs(2500), Fs(3000))
Ms = fseg.bolt_bending_moment(Z)    # return the numpy array (Ms(2000), Ms(2500), Ms(3000))

Indices and tables