Bulging factor is an
engineering
Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...
term describing the
geometry
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
of out-of
plane deformations of the surface of a crack on a
pressurized fuselage
The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...
structure. It is used in evaluating the damage tolerance of
airframe
The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system.
Airframe design is a field of aeros ...
fuselages.
[United States of America. Federal Aviation Administration. Bulging Factor Solutions for Cracks in Longitudinal Lap Joints of Pressurized Aircraft Fuselages. Springfield, 2004. pp.1-3,10]
The single curved geometry and pressure differential causes a
longitudinal
Longitudinal is a geometric term of location which may refer to:
* Longitude
** Line of longitude, also called a meridian
* Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, ...
crack to bulge out or protrude from the original shape. This change in geometry, or “bulging effect”, significantly increases the
stress intensity factor
In fracture mechanics, the stress intensity factor () is used to predict the Stress (mechanics), stress state ("stress intensity") near the tip of a Fracture, crack or Notch (engineering), notch caused by a remote load or residual stresses. It i ...
at the crack tips. The effects of this
loading condition can trigger different types of failure mechanisms.
For the case of unstiffened shell structures, the bulging factor can be defined as the ratio of stress-intensity (SIF) of a curved shell to the stress-intensity factor of a flat panel:
The representation of this phenomenon becomes rather complex due to the
biaxial
In crystal optics, the index ellipsoid (also known as the optical indicatrix or sometimes as the dielectric ellipsoid) is a geometric construction which concisely represents the refractive indices and associated polarizations ...
and internal pressure load and structural configuration.
References
* Lazghab Tarek, Fayza Ayari, Lotfi Chelbi. Crack growth in cylindrical aluminum shells with inner reinforcing foam layer. Springer, 2006. pp. 151.
Pressure vessels
Fracture mechanics
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