Computer program, CRAB, uses finite-element method to calculate creep behavior and predict steady-state stresses in an arbitrary body of revolution subjected to a time-dependent axisymmetric load. Creep strains follow a time hardening law and a Prandtl-Reuss stress-strain relationship

Adams, R.

Greenbaum, G.

English

NASA Technical Reports Server

February 1971
	 Brief 71-10037 
ICY C
AEC-NASA TECH BRIEF 
TES
	 Space Nuclear Svsten is 01/ice 
AEC-NASA Tech Briefs announce new technology derived from the research and development program of the U.S. 
AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial application. Tech Briefs are 
available on a subscription basis from the National Technical Information Service, Springfield, Virginia 22151. Requests 
for individual copies or questions relating to the Tech Brief program may be directed to the Technology Utilization 
Office, NASA, Code KT, Washington, D.C. 20546. 
Computer Program for Predicting Creep Behavior

of Bodies of Revolution 
The problem: 
To predict the creep strains and steady-state stresses 
in an arbitrary body of revolution subjected to a 
time-dependent axisymmetric load. The creep strains 
are assumed to follow a time hardening law, and a 
Prandtl- Reuss stress-strain relationship. 
The solution: 
A computer program called CRAB, which uses the 
finite-element method to calculate the creep behavior 
of bodies of revolution. 
How it's done: 
The body is modeled by a system of discrete, tri-
angular-cross-section, circular-ring elements inter-
connected along circumferential nodal circles. The 
equations of equilibrium for the body are derived 
from the principle of minimum potential energy. 
The creep behavior of the body is obtained by use 
of an incremental approach. The method involves 
starting with the elastic solution of the problem (i.e., 
at time equal to zero) and calculating the creep strains 
for a small time increment. These creep strains are 
treated as initial strains to determine the new stress 
distribution at the end of the time increment. The 
procedure is repeated until either the final time is 
reached or the stress distribution is not changed (i.e., 
a steady-state condition is reached). Once a steady-
state condition is encountered, the program extrap-
olates the creep strains either to the final time or to 
the time at which the loading is to be changed. For
the latter case, the additional stresses caused by the 
load increment are calculated and the creep solution 
technique is again repeated. 
The program can solve problems which require up 
to 360 nodal points and 525 elements to model the 
structure. The time increments at which the creep 
solution is obtained are automatically calculated 
within the program. Displacements, stresses, and 
creep strains are computed for every time step; how-
ever, the user has the option of specifying at which 
time steps the output data are to be printed. 
Notes: 
1. This program is written in FORTRAN IV for use 
on the CDC 6600 computer. 
2. The program would be useful to designers and 
industrial users of pressure vessels. 
Inquiries should be made to: 
COSMIC 
Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B7 1-10037 
Patent status: 
No patent action is contemplated by AEC or NASA. 
Source: G. Greenbaum and R. Adams of

TRW Systems
under contract to

AEC -NASA Space Nuclear Systems Office 
(NUC-1 1104) 
Category 09 
Is
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000037 2020-03-17T02:18:53+00:00Z


Computer program for predicting creep behavior of bodies of revolution

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server