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The load factor, and in particular its sign, depends not only on the forces acting on the aircraft, but also on the orientation of its vertical axis. During straight and level flight, the load factor is +1 if the aircraft is flown "the right way up", [ 2 ] : 90 whereas it becomes −1 if the aircraft is flown "upside-down" (inverted).
Loads imposed on structures are supported by means of forces transmitted through structural elements. These forces can manifest themselves as tension (axial force), compression (axial force), shear , and bending , or flexure (a bending moment is a force multiplied by a distance, or lever arm, hence producing a turning effect or torque ).
The total load on a particular section of a ship's hull is the sum total of all primary, secondary, and tertiary loads imposed on it from all factors. The typical test case for quick calculations is the middle of a hull bottom plate section between stiffeners, close to or at the midsection of the ship, somewhere midways between the keel and the ...
Plane stress typically occurs in thin flat plates that are acted upon only by load forces that are parallel to them. In certain situations, a gently curved thin plate may also be assumed to have plane stress for the purpose of stress analysis. This is the case, for example, of a thin-walled cylinder filled with a fluid under pressure.
For this reason, the useful load fraction calculates a similar number, but it is based on the combined weight of the payload and fuel together in relation to the total weight. Propeller-driven airliners had useful load fractions on the order of 25–35%. Modern jet airliners have considerably higher useful load fractions, on the order of 45–55%.
For two-dimensional, plane strain problems the strain-displacement relations are = ; = [+] ; = Repeated differentiation of these relations, in order to remove the displacements and , gives us the two-dimensional compatibility condition for strains
a simple massless force, [citation needed] an oscillator, [citation needed] or; an inertial force (mass and a massless force). [citation needed] Numerous historical reviews of the moving load problem exist. [1] [2] Several publications deal with similar problems. [3] The fundamental monograph is devoted to massless loads. [4]
The structure has no possible states of self-stress, i.e. internal forces in equilibrium with zero external loads are not possible. Statical indeterminacy, however, is the existence of a non-trivial (non-zero) solution to the homogeneous system of equilibrium equations. It indicates the possibility of self-stress (stress in the absence of an ...