Design calculation of the wing section. Design and design calculations of the mechanization of the tail part of the wing Fig. 5.2 Equivalent wing

Roof 21.10.2023

Roof

Simple shield (Fig. 7.6). Its longitudinal set consists of spar 1, front 3 and tail 4 stringers. The transverse set consists of a system of split ribs 2.
On the underside, the casing is attached to the frame with rivets. Sometimes, to give the shield greater rigidity, sheathing is also installed on the upper side.

The main power element of the shield is the spar, located near the center of pressure. Under the influence of a load, the spar acts as a multi-support beam supported on the lift rods. The spar is usually made from a standard profile.

Ribs are made by stamping from sheet material. Fastening to the spar is carried out with rivets on the flanged wall or using an angle plate. The tails of the ribs are attached to the tail stringer, which is usually made by stamping from sheet material.

The shield is mounted on the wing using a ramrod. Hinges made of special profile 5 are riveted into the front edge. The same hinges are also present on the rear wing spar.

The shield is controlled by moving the rod along its axis, on which the lift rods are hinged. Moving it in one direction causes the shield to deflect, and in the other direction – cleaning.

Less common are simple flaps, the mounting of which on the wing is carried out using two or more fork-type units. In Fig. Figure 7.7 shows the attachment of a simple shield on three such units. The flap is controlled by a lift, the force of which is applied to a lever mounted on the flap in the cross section of the linkage unit.

In the retracted position, the simple flap is secured with locks to prevent it from being sucked out in flight.

The spar of a simple shield with a ramrod fastening is loaded by the reactions of the ribs, but since the latter are located relatively often, the spar can be considered loaded by distributed forces. The magnitude of the linear load of the spar (Fig. 7.8) will be the magnitude of the linear load of the cleaning rod

Rice. 7.6. Simple shield design

Rice. 7.7. Hanging a simple shield on fork-type units

The spar is a multi-support beam, the supports of which are lift rods. Diagrams of bending moments and shearing forces are constructed using the three-moment theorem.

By composing an equation of three moments for each intermediate support and then solving these equations together, the values of the support moments are obtained. Then the support reactions are calculated.

After determining the support moments and reactions, diagrams of shearing forces and bending moments along the spar are constructed (Fig. 7.9). The size of the cross-section of the spar is determined by the magnitude of shear forces and bending moments.

Rice. 7.10. Leading edge hinges

The ramrod on which the shield is hung works for shearing. Load on one shear plane (Fig. 7.10)

Then the diameter of the cleaning rod

where tв is the destructive shear stress of the ramrod material.

Tander rods work on compression. The traction force is determined by the found reactions of the flap spar:

where is the angle between the thunder rod and the normal to the shield.

Retractable shield. Structurally, the retractable shield (Fig. 7.11) is more complicated than simple. Its longitudinal set consists of one or two spars, front and tail stringers. The transverse set consists of a series of split ribs.
The casing is attached to the frame on the underside. For relatively large shields, stringers are sometimes installed to support the casing. Retractable shields also have an upper covering, with the help of which closed circuits are formed that can absorb torque. The cross-section of the side members of the shield can be I-beam, channel or Z-shaped. For small-sized shields, the spar can be made of one profile. Ribs are made by stamping from sheet metal. They are attached to the side members in the same way as with a simple shield. The front and tail stringers of the shield can be bent or made of special profiles.

Rice. 7.11. Retractable shield design

The air load from the lower skin is transferred to the ribs, causing them to bend.
From the ribs the load is transferred to the spars. The spar is a beam supported on the shield hinge units and loaded with a distributed load under the influence of which it bends. From the side members the load is transferred to the units that attach the flap to the wing. The bending moment is perceived by the side members together with the adjacent skin. The shearing force is perceived by the walls of the side members, and the torque is perceived by closed contours formed by the skin and the walls of the side members.

There are several schemes for mounting a retractable shield on the wing. The most widespread is the mounting scheme on monorails (Fig. 7.12). On monorails attached to the wing, the shield is mounted on carriages. The carriages attached to the shield have rollers that roll along the internal and external surfaces of one of the monorail shelves.
To prevent lateral displacement of these rollers, side rollers or special stops are installed on the outer carriages. For small-sized shields, instead of carriages with rollers, sliders can be installed, which slide along the monorails when the shield moves. Small shields are hung on two monorails, large ones – on several. When the shield is pulled back, it simultaneously tilts down. The shield can be moved using one rod, but it is better to move the shield using two control rods, the forces of which are applied to the brackets attached to the shield spar.

The control rods should be placed in the cross sections of the outer hitch units or close to them, so as not to load the shield with bending from the forces in the rods.

There are also other schemes for mounting a retractable shield on the wing. So, in Fig. Figure 7.13 shows a diagram of hanging a retractable shield on a four-link mechanism. Each shield is suspended on two or more such mechanisms.

In the retracted position, the retractable shield is secured with locks to prevent it from being sucked out in flight.

In order to construct diagrams of shear forces, bending and torque moments for a retractable flap, it is necessary to first determine the support reactions. Let's consider constructing diagrams for a retractable shield with the most common mounting scheme - mounting on monorails. The shield supports are carriage rollers and control rods. The reactions of rollers 1 and 2 (Fig. 7.14) pass through point 3 of the intersection of normals to the surface of the monorail at the points of contact of the rollers (friction forces in the rollers can be neglected). The force in the control rod is determined from the equation of moments relative to point 3:

Rice. 7.14. Determination of reaction forces of a retractable flap

Let's consider constructing diagrams for a panel that has one control rod. The force T and the load of the shield are used to determine its support reactions at the points of 3 sections of the hinge. First, reactions are determined, normal planes of the shield and from the distributed load tsh and force Tsinb (Fig. 7.15, a), and then reactions parallel to the plane of the shield and from the force Tcosb are determined (Fig. 7.15, b). Based on the reactions Rn and Rt, the total reactions at points 3 are determined (see Fig. 7.14): RA and RB.

Based on the reactions found, the forces acting on the rollers are determined (Fig. 7.14, b). Then diagrams are constructed in two planes (Fig. 7.15, c and d).

Rice. 7.15. Diagrams of Q, M and Mkr for a retractable panel

To construct a diagram of torques, it is necessary to determine the position of the stiffness axis. If the shield is made according to a single-spar design, then in the design calculation it is assumed that the stiffness axis coincides with the spar axis; if the shield is completed
according to the two-spar scheme, the position of the rigidity axis is determined in exactly the same way as in a two-spar wing. When counting
linear torque linear load tsh is multiplied by the arm d - the distance from the center of pressure to the center of rigidity. The concentrated torques on the supports and in the section where the force T is applied are found as the product of the reaction forces on the arms dR and the force T on the arm dT (see Fig. 7.14, a). Then a torque diagram is constructed (see Fig. 7.15, d).

If the retractable flap is hung on several monorails and is controlled using two control rods, then the force T, determined in the cross-section of the application of the resulting force P, is distributed among the rods according to the lever rule, and then the support moments and reactions are found using the three-moment theorem. Otherwise, the calculation of such a shield is no different from the above calculation of a shield hung on two monorails.

Based on the found values of Q, M and Mcr, the cross-sections of the power elements of the retractable shield are selected.

Rice. 7.16. Scheme of mounting a retractable flap on rails installed outside the wing contours

Flaps. The design of rotary and slotted flaps and their canopy on the wing is similar to the design of the aileron and its canopy. Single-slot retractable flaps and the last links of multi-slot retractable flaps are also no different in design from the aileron. Retractable flaps are most often mounted on monorails.

With a large size and low construction height, it is not possible to place monorails in the wing contours. In this case, the rails are located outside the wing contours in fairings on its lower surface. One of such schemes is shown in Fig. 7.16. A straight rail 2 is installed on the beam 1, along which the carriage 3, hinged to the flap, moves. The second point of attachment of the flap is lever 4. When the control drive is turned on, carriage 3 moves backward, causing the flap to roll back, and the deflection angle is provided by lever 3 and rotation of the flap relative to the carriage. The entire linkage mechanism is covered by a fairing 5.

On swept wings, to ensure the extension of the flap along the flow, it is necessary either to make the monorails twisted, or to attach the carriages to the flap on pins. To eliminate the possibility of flaps jamming, twisted rails must be made with very high precision, which significantly complicates their production. More often, a hitch with a carriage mounted on the flap using a pivot is used. The diagram of such a carriage is shown in Fig. 7.17. Carriage 2, moving along monorail 1, is mounted on pivot 5 by a vertical eccentric shaft 4. The eccentric shaft allows you to adjust the distance between the carriages, which simplifies the mounting of the flap. After attaching the flap, the eccentric shaft is locked with a locking screw 3. The king pin 5 is mounted on roller bearings 7 on two supports. The front support 6 is located on the spar of the flap 6, the rear support is on a stamped unit 8 installed between two ribs of the flap 11. The kingpin is connected to the rear unit through a thrust bearing 9, closed with a threaded cover 10.

Rice. 7.17. Installing the carriage on the king pin

To simplify the installation of flaps and eliminate misalignment, fasten the carriages
on pins can also be used when the flap is hung on monorails installed in planes perpendicular to the axis of the cylinder or cone, along the surface of which it moves when deflected, i.e. and when twisted monorails are not needed.

Rice. 7.18. Scheme of hanging a retractable flap on remote brackets

The retractable flap can also be hung on external brackets (Fig. 7.18). In this case, the axis of rotation of the flap is outside the contours of the wing. Such remote brackets, although they are covered by fairings, create additional resistance, but structurally this mounting scheme is simpler than mounting on monorails.

In Fig. Figure 7.19 shows the design of a double-slot flap with a deflector.

Rice. 7.19. Double-slot retractable flap

The loads acting on the flap are determined similarly to the loads on the flap. With a multi-slot flap, the load is distributed between its parts in accordance with the recommendations of the standards.

Taking into account the features of the flap hinge, diagrams of Q, M and Mkr are constructed, and then its design calculation is performed. For a multi-slot flap, diagrams Q, M and Mkr are constructed for each part of it.

Questions:

1. Schemes of shields.

2. Design of a simple shield.

3. Hangment of a simple shield on fork-type units.

4. Retractable shield design.

5. Double-slot retractable flap.

Diagrams of Q, M and Mkr for a retractable panel.

Aerodynamic forces act on the flap in flight. The magnitude and distribution of the load are determined based on the results of purging in the wind tunnel with the flap in the non-deflected and deflected position. Due to their smallness, the gravity forces of the flap structure are neglected.

In the absence of purge results, use the load distribution along the span and chord of the flap shown in Fig. 7.2. The load distribution along the chord is taken along the trapezoid, and the height of the load ordinate at the leading edge is equal to , and at the trailing edge is equal. The load distribution along the span is proportional to the chords.

Fig.7.2 Load distribution

Let us determine the value of the velocity pressure for the flap:

, (7.1) where is the air density, kg/m 3 ;

Maximum aircraft speed, m/s;

and the value according to the formula:

(7.2)Dad.

Let us determine the distribution of the load on the flap along the span:

N/m (7.3)

where is the flap chord.

The spanwise load will have a constant value N/m.

Due to the fact that the aileron and flap are similar, both in their shape and in the calculation method, further calculations are carried out similarly to the aileron. Since the loads on the flap are several times smaller, the parameters of the longitudinal-transverse set and flap skin are taken to be the same as those of the aileron.

The width of the flanges along the length of the beam for the flap spar is taken as .

Top and bottom flange values 0.96 mm (8 layers)

Spar wall thickness 0.96 mm (8 layers)

We take the thickness of the skin equal to 1 mm.

Conclusion

In this work, calculations were made of the spars (front, rear), struts, attachment points for the struts to the wing, the main elements of the longitudinal-transverse set of the aircraft wing: power ribs, aileron, flap, differential rocker, control rods, attachment points. Structural and technological solutions were selected for ribs, wing tip, aileron and flap brackets, rocker, and skin. The wing tip was made removable for servicing the rocker and control rods. The wing skin was assumed to be smooth. All elements were selected not only from the conditions of minimum weight and maximum strength, but also ease of manufacture and efficiency.

Also in this work, service hatches were provided for draining and filling fuel, replacing the fuel tank, as well as to ensure ease of assembly and repair of the wing

Since there are structural similarities between flaps, rudders and ailerons, the process for selecting parameters is the same for them. Moreover, in terms of design, flaps and deflectors are made primarily using a single-spar design, and this simplifies the approach to their design.

However, some design features of flaps should be paid attention to.

Spars, in addition to standard loading, can be additionally loaded by concentrated forces from deflector supports applied directly to the chords. In such cases, the support brackets of the deflectors tend to be spaced some distance along the length of the spar, at least a distance equal to the pitch of the ribs.

In the case of small deflector sizes, spars are abandoned altogether, compensating for them by strengthening (thickening) the skin and reducing the pitch of the ribs.

In all cases, the skin plays a very important role in the design of flaps and deflectors, providing not only the necessary strength, but also the required rigidity. When determining its thickness from the condition of working under shear from torsion, the magnitude of the torque can be determined by the formula:

Where q is the distributed load along the span of the flap or deflector itself, respectively; x c is the coordinate of the center of rigidity of the flap or deflector; - coordinate of the center of pressure of the flap or deflector; z is the estimated linear length of the flap.

The center of mass for common flap profiles of a single-spar design (the flap itself or the deflector) is located at approximately 25% of the chord; for double-spar designs, it is shifted to 30% of the chord.

The position of the pressure centers of flaps deflected by 30 ... 35° is almost constant and is located at 38 ... 40% of the flap chord and 50% of the deflector chord.

The linear length of the flap z is taken equal to half the greatest distance between the supports of the flap or deflector section.

Sheathing with a thickness of less than 0.6 mm, as well as walls of ribs and spars thinner than 0.8 mm, is not used.

It is useful to accompany the choice of skin parameters by adjusting the parameters of the flap structural-power scheme. In this case, you can try to agree on a number of requirements - the thickness and modulus of elasticity of the skin, the pitch of the ribs and the amount of permissible operational deflection. Such coordination of parameters is achieved, for example, using graphs similar to Fig. 6, representing the change in deflections of aluminum cladding with a thickness of 0.8 or 1.2 mm depending on the specific pressure p and the distance between the ribs.

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The availability of extensive experimental and statistical data of this kind contributes to a significant simplification of design developments. In any case, even a limited amount of experimental material made it possible to establish that, from the point of view of reducing skin deformations, it is more advantageous to reduce the distance between the ribs rather than between the stringers.

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Design calculation of the wing section. Design and design calculations of the mechanization of the tail part of the wing Fig. 5.2 Equivalent wing

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