Analysis and Research of the High-Cycle Fatigue Fracture Mode Based on Stress Ratio and Residual Stress of Ti-6Al-4V

The content of titanium is about 0.63% in the earth’s crust, and it ranks 10th among all elements. The content of titanium is next to the metal elements of aluminum, iron and magnesium, iron, and magnesium; titanium alloys have low density, high specific strength (the ratio of tensile strength to density), wide working range (−253°C–600°C), and excellent corrosion resistance melting point; the chemical activity of titanium alloy is very high, and it easily reacts with hydrogen, oxygen, and nitrogen, so it is difficult to be smelted and processed, and the processing cost is high. Titanium alloys also have poor thermal conductivity (only 1/5 of iron and 1/15 of aluminum), small deformation coefficient, large friction coefficient, and other characteristics. They are widely used in aircraft fuselage, gas turbine, petrochemical, automotive industry, medical, and other fields for important parts.

Investigation of Laser Treatment as a Method for Fatigue Crack Growth Retardation in Aluminum Alloy 2198-T851

Among the third-generation Al-Li alloys, AA2198 stands out for its lower density, formability and increased stiffness, being suitable for use in aircraft fuselage sheets and other inner structures in order to reduce weight and improve performance. An important topic related to damage tolerant structures is the development of techniques to retard fatigue crack propagation, such as the localized heating by a laser source. The aim of the present work was to find the most suitable parameters for the production of laser heating lines in 2198-T851 alloy sheets in order to reduce the fatigue crack growth rate in this material. Laboratory tests using C(T) specimens under two loading conditions (R = 0.1 and 0.5) provided a useful dataset on the laser heated material. The experimental results indicate a 200 W laser beam power at treatment speeds of 1 and 10 mm/s was sufficient to retard crack growth in the current setup. The more expressive results were obtained for 200 W laser power with a speed of 1 mm/s and cyclic loading with stress ratio R = 0.1.

IR Susceptibility of Supersonic Aircraft according to Omni-directional Detection Angle

Infrared guided weapons act as threats that greatly degrade the survivability of combat aircraft. Infrared weapons detect and track the target aircraft by sensing the infrared signature radiated from the aircraft fuselage. Therefore, in this study, we analyzed the infrared signature and susceptibility of supersonic aircraft according to omni-directional detection angle. Through the numerical analysis, we derived the surface temperature distribution of fuselage and omni-directional infrared signature. Then, we calculated the detection range according to detection angle in consideration of IR sensor’s parameters. Using in-house code, the lethal range was calculated by considering the relative velocity between aircraft and IR missile. As a result, the elevational susceptibility is larger than the azimuthal susceptibility, and it means that the aircraft can be attacked in wider area at the elevational situation.

АНАЛІЗ МОЖЛИВОСТЕЙ РЕАЛІЗАЦІЇ МОДУЛЬНОГО ПРИНЦИПУ СТВОРЕННЯ МОДИФІКАЦІЙ ПОВІТРЯНИХ СУДЕН ТА ЇХ ЕФЕКТИВНОЇ ЕКСПЛУАТАЦІЇ В СИСТЕМІ ВІТЧИЗНЯНИХ АВІАПЕРЕВЕЗЕНЬ

It is known that an aircraft generates income for the operating airline only when it is in the air. Being on the ground, at the airport, airlines incur high costs for aerodrome maintenance of the aircraft. The longer the aircraft is stationary on the ground, the shorter the actual flight time of the aircraft. In this regard, the possibility of implementing one of the promising principles for the creation and effective operation of modifications of aircraft of the transport category - the modular principle - has been analyzed. The prospects for the implementation of modular modifications in domestic airlines in the context of further development of the market economy are considered. Modifications based on the implementation of the modular principle are classified into two types - created in the form of autonomous modules placed in the fuselage during aircraft operation and in the form of a removable modular compartment of the aircraft fuselage. A review and analysis of existing projects of these types of modular constructive and technological solutions, a comparison of their advantages and disadvantages in the technical and economic aspects of the prospects for their feasibility are carried out. The possibility of effective implementation of the modular principle of modifications of aircraft of the transport category was assessed, for which a generalized analysis of domestic and foreign information related to the state of the problem under discussion was carried out, on the basis of which an enlarged block diagram of a comprehensive methodology for analyzing the efficiency of operation of modular modifications in the air transportation system was synthesized in comparison with traditional (existing). The key aspects of the content of the main blocks of the scheme are revealed, including the main provisions of the maintenance and repair of aircraft in modern conditions of their operation, based on foreign experience, as well as the main aspects of the content of the blocks for accounting for weight losses in the design and implementation of traditional and modular modifications of aircraft. The generalized information related to the implementation of the synthesized block diagram, focused on subsequent addition, should form the basis of compliance methods and regulatory documentation in the design and implementation of promising domestic modifications of aircraft of the transport category.

ПРОЕКТУВАННЯ СТУЛКОВОГО ВІДСІКУ ХВОСТОВИХ ВАНТАЖНИХ ЛЮКІВ ЛІТАКІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

The method for determining the main parameters of the tail cargo doors of transport category aircraft is developed. There have been prepared initial data and described the methodology for finding them. An example based on an existing transport aircraft is considered. The basic nomenclature of transported cargoes of the designed aircraft, its dimensions and weight, methods of loading and mooring, additional loading equipment were taken as initial data. As well as such necessary design, operational and regulatory parameters and data as landing gear type, its “kneeling” system, rails of the upper loading equipment for loading and unloading, cargo trajectories during loading and landing, requirements of international regulatory organizations FAR, CS, AP. The principle of determining the dimensions of the cargo compartment, cargo floor and the hitting platforms in the form of ramp with pressure door, ladders is presented, based on the initial data. Taking into account the loading and unloading, landing operations described the dependence of the ramp length on the length of the cargo floor. The correct formation of these parameters is one of the most important tasks, from the solution of which directly depend the operational characteristics of the future transport aircraft. A method for designing cargo door fairings in the transport category aircraft fuselage tail part is also presented. There have been determined the main features of the fairings compartment, its main components and their varieties, depending on the scheme of the cargo door. At the stage of preliminary design, the principles for determining the main parameters of the fairings compartments based on their design purpose are outlined.Also provided information on the fairings compartment structural elements parameters selection: the axes of the fairings hinge, the selection of control cylinders and their installation, the parameters of the open and closed position locks, pressurization and sealing of the fairings compartment. Considered the design features of the fuselage tail section various theories fairings compartment - made in cross-section with one radius (in the shape of a cylinder) and given in cross-section with two radii (double-deck).

Research on Nonlinear Deformation and Stability of an Aircraft Fuselage Composite Section under Transverse Bending

Currently, there is a lack of studies on the strength and stability of reinforced composite shells, taking into account the momentness and nonlinearity of the initial stress-strain state. Most of the known solutions to the shells stability problems are obtained by analytical and numerical methods, as a rule, in the linear approximation, i.e. in the classical formulation. A developed technique is proposed implementing the finite element method for solving the problems of strength and stability of discrete-reinforced cylindrical shells made of the composite material, taking into account the momentness and nonlinearity of their subcritical stress-strain state. The transverse bending stability of the reinforced aircraft fuselage compartment made of composite material has been investigated. The effect of deformation nonlinearity, stiffness of stringer set, shell thickness on critical loads of the shell instability has been determined.

HIGH ENERGY WIDE AREA BLUNT IMPACT OF COMPOSITE AIRCRAFT STRUCTURES—PART A: DESIGN AND ANALYSIS METHODOLOGY OF REPRESENTATIVE SUBSTRUCTURE

Large test structures, common in the aerospace industry, offer a challenge to model, manufacture and test, with high cost associated with computational as well as materials, specimen fabrication, test planning/setup, and instrumentation resources. In this paper, a methodology is presented to demonstrate use of a smaller-sized substructure to produce equivalent response to the original, larger structure. The structure under study is a quarter barrel of typical commercial aircraft fuselage section made of carbon fiber reinforced polymer (CFRP), initially consisting of two circumferential structural members (C-frames and shear ties), and 12 stringers cocured to the skin. Through a series of finite element analyses and a modified specimen design, a substructure representing the quarter barrel was validated for loading conditions generated by high energy wide area blunt impacts (HEWABI) which are potentially caused by accidental contact from moving ground service equipment (GSE). The substructure is made of one circumferential member (C-frame and shear tie), and 6 stringers co-cured to skin and is shown to have similar stiffness and stresses in the region of interest. Finite element analysis (FEA) with progressive damage analysis demonstrates the equivalent response between the substructure and full quarter barrel. This methodology can be used in a wide range of applications, as long as the loading area is distant enough from the modified structure end and the correct boundary conditions/fixtures are defined to represent the omitted portions of the structure of interest.

Robot Motion Planner for Under-Constrained Trajectories With Part-Specific Geometric Variances

Industrial manipulators often interact with large and complex objects for a variety of automation tasks. Finding a feasible path for the robot end-effector that ensures task success is often non-trivial due to considerations such as reachability, singularity avoidance, and collision avoidance. This paper proposes an approach to expand the search space for feasible robot trajectories (and search for an optimal solution) by taking advantage of task redundancy for certain tasks while ensuring task completion. The effort builds on previous work enabling virtual fixture generation for complex shapes given CAD or scan data. The proposed method has been developed into a trajectory planning library on the ROS (Robot Operating System) framework and tested by simulating an interaction of a six-axis industrial robot with an aircraft fuselage. Results show increased coverage of task area with minimal robot base placements.