aircraft Stringer
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Stringer

Stringer aircraft. Stringer wing aircraft

 

Stringer - a longitudinal element of the power set of plane which is associated with the ribs and the wing skin or fuselage frames. The main purpose is the thrust of compression and tension. Stringer also accepts local aerodynamic loads, trim secures and enhances its rigidity.

Depending on the location and destination of the local stringers can gain typical, butt, and head-end. By strengthening local refers to the location of the stringers places where the focus the load or on the edges of the cut-outs in the casing. Play-stringers are lining the joints, types provides whole rigidity.

Modern aircraft are distinguished by new stringers made of bent and extruded sections with a pitch of 150-400 mm. In areas where cracks may appear, to increase the survivability of the entire structure, stringers made of strong materials are placed in the cladding, which act as limiters for the distribution of cracks - stoppers. Some power circuits have powerful stringer sets where the side member belts are rather weak. In such cases, the cross-sectional areas of the side members are of the same order of magnitude as the cross-sectional areas of the stringers. Therefore, stringers differ from side members in a weak section. 

The functions are determined by the constructive and power circuit. In the wing of the spar type, the stringers act as reinforcement of the skin to enhance its tangential critical stresses when the wing is operated on bending and torsion. They take part in the transfer of aerodynamic load directly to the ribs. In the monobloc wing, in addition, the stringer set, together with the skin, takes most of the bending moments. Sheathing and stringers at the same time work on decompression and compression, they are subject to regulatory stresses. The weight of the stringer varies depending on the design of about 12% of the total weight of the wing.

In addition, stringers fulfill their role in the fuselage structure according to the scheme. In semi-monococks (stringer fuselages), the load is taken up by the skin, which is supported by a large number of stringers, and in some cases, spars may be included in the set. A similar type of fuselage is used on the Il-96, Tu-154, SSJ. In spar-stringer fuselages in those parts where huge cutouts need to be made, a spar scheme is used, turning into a stringer one, due to the attachment of stringers and lowering the sections of the spars. A striking example is the MiG-15.

Forms section

There are several types of sectional forms stringers:

  • Curved;

  • Pressed;

  • closed;

  • open.

Interrupted profiles have a higher critical compressive stress than the bent shapes of identical sections and equal to the area of ​​the cross member. For this reason, in compressed panels monoblock wing stringers are mainly used in extrusions. Bent shape of the profile used for the stringers, which under main load acting on the wings of the tension. Closed profile with paneling forms a closed loop, ensures that higher voltages than equal in cross-sectional area at the other types.

To reduce the weight and create an equally durable design, stringers are created with a variable span of area in cross section, which are reduced to the end of the wing. The stringer wall thickness typically varies within 0,5-3,0 mm. 

stringer maximum load

More details for aircraft stringer

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