Development of the wing structure of a special-purpose aircraft with 12 ton commercial load, also in this work strength calculation of wing elements was made

Contents

Table of contents

Introduction

1. Selection of aircraft prototype by its characteristics

2. Establishment of mass and geometric characteristics of the aircraft, wing layout

3. Purpose of overload and safety factor

4. Determining Wing Loads

4.1. Determination of aerodynamic loads

4.2. Define mass and inertial forces

4.2.1. Determination of distributed forces based on own weight of wing structure

4.2.2. Determination of distributed mass forces from fuel tanks weight

4.2.3. Building Epures from Concentrated Forces

4.3 Calculation of moments acting relative to the conditional axis

4.3.1 Determination of Mz due to aerodynamic forces

4.3.2. Determination of Mz EMI from distributed wing mass forces (Mz EMI and Mz EMI)

4.3.3 Determination of Mz from concentrated forces

4.4 Determination of design values of Mizg and Mkr for assigned wing section

5. Selection of structural-power scheme of the wing, selection of parameters of design section

5.1 Selection of structural-power diagram of the wing

5.2 Selection of wing design section profile

5.3 Selection of section parameters (approximate calculation)

5.3.1 Determination of normal forces acting on wing panel

5.3.2. Determining Skin Thickness

5.3.3 Determination of the pitch of stringers and ribs

5.3.4 Determination of section area of stringers

5.3.5 Determination of cross-sectional area of spars

5.3.6 Determination of spar wall thickness

6. Calculation of wing section for bending

6.1 Calculation Procedure for the First Approach

6.2 Determination of stringer critical voltages

7. Calculation of wing section for shear

7.1 Calculation Procedure

8. Calculation of wing section for torsion

8.1 Determination of wing section stiffness center position

8.2 Determination of tangent force flow from torsion

9. Check of skin and walls of spars for strength and stability

Conclusion

List of sources used

Appendix A

Introduction

The wing is a bearing surface that creates aerodynamic lift that provides flight of the aircraft. The wing also takes part in providing transverse stability and controllability of the aircraft. It can be used to attach engines, landing gear, to accommodate fuel, equipment, weapons and other payloads. The wing shall have high bearing capacity and minimum aerodynamic resistance in the main flight modes, have sufficient strength and rigidity at the lowest weight of the structure, as well as good technological and operational qualities.

From the point of view of construction mechanics, the wing is a cantilevered bar loaded with the above loads, which cause bending and torsion deformations.

The value of active forces, their distribution by span and chord are determined during strength calculation of the wing. The general power operation of the wing as a bar and the operation of its elements in the perception of local air load are separately considered.

The purpose of course design is to develop the wing design of a special-purpose aircraft with a 12 ton commercial load, and strength calculation of wing elements will also be carried out in this work.

The following tasks will be considered during the course project:

selection of aircraft prototype by its characteristics;

determination of the weight and geometric characteristics of the aircraft, necessary for load calculation, according to the selected prototype, wing layout;

assignment of operational overload and safety factor for the specified design case;

determination of loads acting on the wing when the aircraft performs the specified maneuver, construction of symbols;

selection of the type of structural-power scheme of the wing and selection of section parameters;

calculation of wing section for bending;

calculation of wing section for shear;

calculation of wing section for torsion;

check of wing skin and spar walls for strength and stability.

5. Selection of structural-power scheme of the wing, selection of parameters of design section

5.1 Selection of structural-power diagram of the wing

The choice of structural-power scheme of the wing is determined by a number of conditions, namely:

layout of the wing itself - presence of hatches in the skin for maintenance of equipment units located in the wing, presence of fuel tanks inside the wing, niches for LG retraction, etc.

fuselage layout - the presence of sufficient volumes for the central part of the wing in the fuselage (with a single-member wing, minimum volumes are required in the fuselage)

stiffness requirements

The most common are the following structural-power schemes of free-bearing wings:

one-longeron

monoblock or caisson

single-spar with "inner brace"

multilongeron

Single-member circuit The wing of a single-member circuit is essentially (when using rigid skin) a mixed circuit wing: at the root or near the cuts in the skin - a single-member circuit, and at the end of the wing - a monoblock one. The spar is located in this scheme near the maximum thickness of the profile, and its belts perceive (at the root) the full value of normal forces from the bending moment. To receive (together with the spar wall) cutting forces and normal forces from the moment acting in the plane of wing chords, one or two longitudinal walls are installed.

Monoblock and caisson scheme The difference between a monoblock wing and a caisson wing is that in a monoblock wing, normal bending forces are perceived by the skin and its supporting stringers along the entire outline of the wing cross section, and in a caisson wing, normal bending forces are perceived by the skin and stringers only along a portion of the contour, such as a sock or, as usual, a middle portion.

Single-member circuit in internal brace. This scheme is applicable for swept wings with a sweep angle of at least 35 degrees. The internal brace is the support of the spar in the form of the end of the pinched beam, which usually runs perpendicular to the aircraft axis at a distance of 0.3-0.5 (depending on the sweep angle and wing constriction) half-span from the aircraft axis of symmetry .

Multi-member circuit Multi-member circuit for straight and swept wings of modern aircraft is not used. From a constructive point of view, a multi-member circuit seems appropriate for triangular wings of small elongation.

7. Calculation of wing section for shear

The calculation of the wing section for shear is carried out without taking into account the influence of torsion (the transverse force of the Q∑ is considered to be applied in the center of the section stiffness, believing that the spar walls and skin work on the shift).

Conclusion

In this course project, the wing of a special-purpose aircraft with a 12 ton commercial load was calculated.

Values of loads acting on the wing, bending moments relative to the conditional axis were obtained. The structural power scheme of the wing is chosen - caisson (with two spars).

In this work, the parameters of the skin, stingers, spars were selected according to the estimated area in the stretched and compressed zones. The number of stringers in the compressed panel is 28, in the stretched panel - 23. As a result of calculating the wing section for bending, it was revealed that the stress of the stringers in the compressed panel and stretched does not exceed the stress of the total stability loss. Calculations of the wing section for shear and torsion were carried out.

Checking the skin and walls of spars for strength and stability showed that the strength conditions are met.