Stress-strain state of ice cover during aircraft takeoff and landing

2015 ◽  
Vol 56 (5) ◽  
pp. 920-926 ◽  
Author(s):  
A. V. Pogorelova ◽  
V. M. Kozin ◽  
A. A. Matyushina
Author(s):  
В.М. Козин

Рассмотрено влияние физико – механических характеристик льда на напряженно-деформированное состояние (НДС) ледяного покрова при его деформировании изгибно – гравитационными волнами (ИГВ), возбуждаемыми движущейся по льду нагрузкой с резонансной скоростью, т.е. в условиях изгибно-гравитационного резонанса (ИГР). Исследования проведены с целью дальнейшего изучения возможностей резонансного метода разрушения ледяного покрова (РМРЛ), осуществляемого судами на воздушной подушке (СВП). Отмечено, что в определенных ледовых условиях РМРЛ может оказаться эффективнее существующих традиционных технологий разрушения ледяного покрова. Перечислены основные физико-механические свойства льда, влияющие на НДС ледяного покрова в условиях ИГР. Приведены наиболее вероятные диапазоны их изменения. Задача о деформировании ледяного покрова перемещающейся по нему распределенной нагрузкой рассматривается в линейной постановке. Лёд моделируется изотропной пластиной бесконечной протяжённости, поведение которой описывается реологической вязко – упругой моделью Кельвина – Фойгта. Работоспособность полученных зависимостей проверена путем сопоставления результатов численных расчётов прогибов льда с данными натурных экспериментов. Приведены результаты теоретических исследований влияния на НДС ледяного покрова изменения параметров основных физико-механических характеристик льда в пределах их наиболее вероятного диапозона изменения при резонансной скорости движения нагрузки. Сделан вывод, что при расчетах НДС ледяного покрова в условиях ИГР, т.е. при определении толщины ледяного покрова, разрушаемого СВП резонансным методом, следует уточнять только значение модуля Юнга для конкретных ледовых условий. Остальные характеристики льда можно выбирать в соответствии с их осредненными значениями. The influence of the physical and mechanical characteristics of ice on the stress – strain state (SSS) of the ice cover when it is deformed by bending-gravitational waves (IGW) caused by a load moving along the ice at a resonant speed, i.e. under conditions of bending – gravitational resonance (IGR), is considered. The research was conducted in order to further study the possibilities of the resonant method of ice cover destruction (RMRL), carried out by hovercraft (SVP). It is noted that in certain ice conditions, RMRL can be more effective than existing traditional technologies of ice cover destruction. The main physical and mechanical properties of ice that affect the VAT of the ice cover in the conditions of GAMES are listed. The most probable ranges of their changes are given. The problem of ice cover deformation by a distributed load moving along it is considered in a linear formulation. Ice is modeled by an isotropic plate of infinite extent, the behavior of which is described by the rheological viscoelastic Kelvin-Voigt model. The efficiency of the obtained dependences was verified by comparing the results of numerical calculations of ice deflections with the data of field experiments. The results of theoretical studies of the influence of changes in the values of the main physical and mechanical characteristics of ice within their most probable range of changes at the resonant speed of the load movement on the ice cover VAT are presented. It is concluded that when calculating the VAT of ice cover in the conditions of GAMES, i.e. when determining the thickness of the ice cover destroyed by the SVP resonance method, it is necessary to specify only the value of the Young's modulus for specific ice conditions. Other ice characteristics can be selected according to their averaged data.


Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.


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