initial commit

tube.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""\
+Tube
+"""
+from __future__ import absolute_import, division, print_function, unicode_literals
+from math import sqrt
+
+__author__ = "Daniel Weschke"
+__copyright__ = "Copyright 2019 Daniel Weschke"
+__credits__ = ["Daniel Weschke"]
+__license__ = "MIT"
+__version__ = "2019.02.07"
+__maintainer__ = "Daniel Weschke"
+__email__ = "daniel.weschke@directbox.de"
+__status__ = "Production"  # "Prototype", "Development", "Production"
+
+VERSION = """\
+%(prog)s version {version} {copyright}
+
+For Unicode characters check the file encoding that the console is using.
+Windows user may execute the command "chcp 65001".""".format(
+  version=__version__, copyright=__copyright__)
+
+EPILOG = """\
+"""
+
+def critical_buckling_stress(r, nu, E, t):
+  """\
+  Critical buckling stress of a thin tube loaded with external pressure p.
+
+  r   mean radius (r_a + r_i)/2
+  nu  Poisson's ratio
+  E   Young's modulus
+  t   thickness
+  """
+  return (E/(4*(1-nu**2))*(t/r)**3)
+
+def allowable_stress(sigma, S):
+  """\
+  Allowable stress.
+
+  sigma  stress
+  S      safety factor, elastic buckling stress state S = 3
+  """
+  return sigma/S
+
+def main():
+  """\
+  Main function
+  """
+  import argparse
+
+  parser = argparse.ArgumentParser(
+    description=__doc__, prefix_chars='-', epilog=EPILOG,
+    #usage="%(prog)s [OPTION]... NAME",
+    formatter_class=argparse.RawTextHelpFormatter,
+  )
+  parser.add_argument('-v', '--verbose', action="store_true", help="Verbose output")
+  parser.add_argument('-V', '--version', action='version', version=VERSION)
+  parser.add_argument('-D', '--debug', dest='debug', action='store_true', help=argparse.SUPPRESS)
+  subparsers = parser.add_subparsers(help='', dest='case')
+
+  parser_a = subparsers.add_parser(
+    'buckling', help="critical buckling stress", prefix_chars='-',
+    description="Critical buckling stress of a thin tube loaded with external pressure p.")
+  parser_a.add_argument('NU', type=float, help='Poisson\'s ratio')
+  parser_a.add_argument('R', type=float, help='mean radius')
+  parser_a.add_argument('E', type=float, help='Young\'s modulus')
+  parser_a.add_argument('T', type=float, help='thickness')
+  parser_a.add_argument('S', nargs='?', type=float, default=3., help='safety factor [default for elastic stress state: 3]')
+
+  args = parser.parse_args()
+
+  if args.debug:
+    print(args)
+
+  if args.case == 'buckling':
+    p_crit = critical_buckling_stress(args.R, args.NU, args.E, args.T)
+    print("p_crit =", p_crit)
+    print("p_allow =", allowable_stress(p_crit, args.S))
+
+  return 0
+
+if __name__ == "__main__":
+  import sys
+  sys.exit(main())