Verification of a mathematical model of dynamic loading in the quasistatic statement for a helicopter tubular skid landing gear by the results of drop tests

2012 ◽  
Vol 55 (3) ◽  
pp. 230-232
Author(s):  
S. A. Mikhailov ◽  
D. V. Nedel’ko ◽  
L. V. Korotkov ◽  
S. A. Alimov
Keyword(s):  
Mathematical Model ◽  
Dynamic Loading ◽  
Landing Gear ◽  
Drop Tests ◽  
Skid Landing Gear

METHODOLOGY OF DROP TESTS OF HELICOPTER SKID LANDING GEAR

2012 ◽  
Vol 43 (6) ◽  
pp. 835-849
Author(s):  
Sergey Aleksandrovich Alimov ◽  
Vyacheslav Dmitrievich Limonchikov ◽  
Sergey Anatolyevich Mikhailov ◽  
Dmitry Valeryevich Nedelko ◽  
Sergey Vasilyevich Saltykov
Keyword(s):  
Landing Gear ◽  
Drop Tests ◽  
Skid Landing Gear

Longitudinal Instability in Braked Landing Gear

1981 ◽  
Vol 103 (3) ◽  
pp. 259-265 ◽  
Author(s):  
R. R. Allen ◽  
R. C. O’Massey
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Analytical Methods ◽  
Design Guidelines ◽  
Landing Gear ◽  
Nonlinear Mathematical Model ◽  
Nonlinear Characteristics ◽  
Aircraft Landing ◽  
Design Variables ◽  
Aircraft Landing Gear

An instability in the form of a self-excited, bounded longitudinal oscillation may occur in aircraft landing gear when one or more wheels lock due to excessive braking. The instability usually appears at ground speeds below 40 knots (20 m/s) and results from interaction between structural elasticity and the nonlinear characteristics of tire-runway friction. A nonlinear mathematical model is developed to study the dynamics of this divergence in a braked, dual tire landing gear. Analytical methods are presented to determine critical ground speeds in terms of runway friction characteristics and to predict the amplitude of steady-state oscillations. The effect of design variables on longitudinal stability is evaluated and design guidelines are presented which insure reduction of the severity of this divergent dynamic behavior.

NONLINEAR IMPACT DYNAMIC ANALYSIS AND COMPARISON WITH EXPERIMENTAL DATA FOR THE SKID GEAR

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1403-1408 ◽  
Author(s):  
DONG-HYUN KIM ◽  
YU-SUNG KIM
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Landing Gear ◽  
Gear System ◽  
Dynamic Responses ◽  
Test Results ◽  
Dimensional Finite Element ◽  
Nonlinear Transient ◽  
Skid Landing Gear ◽  
Three Dimensional Finite Element

In this study, nonlinear crash analyses have been conducted for the skid landing gear of helicopter. The realistic configuration of skid landing gear system is considered. Detailed three-dimensional finite element model with variable thickness and material nonlinearity is constructed for required impact design conditions. Advanced computational approach is used to conduct nonlinear transient impact dynamic analyses for different collision models. Characteristics of impact dynamic responses due to the ground crash are practically investigated in detail. It is also shown that the exact consideration of friction effect is very important to accurately predict the crash behavior of the skid type landing gear system. Finally, two typical landing conditions are analyzed and correlated with drop test results.

Nonlinear Grey-box Identification of a Landing Gear based on Drop Test Data

2020 ◽  
Author(s):  
Elias Dias Rossi Lopes ◽  
Helon Vicente Hultmann Ayala
Keyword(s):  
Control Design ◽  
Simulated Data ◽  
Federal Aviation Administration ◽  
Landing Gear ◽  
Drop Test ◽  
Equivalent Stiffness ◽  
Gear Design ◽  
Drop Tests ◽  
Adequate Evaluation ◽  
Stiffness And Damping

In many aircraft applications, especially on an antiskid control design, it is important to understand and consider the gear walk phenomenon, which is characterized by the deflection on the landing gear structure due the high braking force acting at the tire contact with the ground. This phenomenon is observed on drop tests, and its prediction on landing gear design depends on an adequate evaluation of the equivalent stiffness and damping of the structure, which is difficult, since they depend on the mechanism configuration. In this paper, it is presented a grey-box identification methodology for estimating these parameters of the landing gear, based on simulated data of a drop test. As the drop tests are mandatory obligatory for certificating modern aircraft according to e.g. Federal Aviation Regulations (FARs) by the Federal Aviation Administration (FAA), we hope to introduce a method based on measurements that are available at the design phase. The method will be useful to decrease men/hour costs and increase reliability by enabling better and more accurate anti-skid design.

scholarly journals Experimental Snap Loading of Synthetic Ropes

2005 ◽  
Vol 12 (3) ◽  
pp. 163-175 ◽  
Author(s):  
C.M. Hennessey ◽  
N.J. Pearson ◽  
R.H. Plaut
Keyword(s):  
Mathematical Model ◽  
Drop Tower ◽  
Drop Height ◽  
Dynamic Tests ◽  
Drop Weight ◽  
Tensile Forces ◽  
Drop Tests ◽  
Height Drop

Large tensile forces, known as snap loads, can occur when a slack rope becomes taut. Such forces may damage the rope or masses connected to it. Experiments are described in which one end of a rope is attached to the top of a drop tower and the bottom end is attached to a weight. The weight is raised to a certain height and then released. The force at the top of the rope and the acceleration of the weight are recorded during the first snap load that occurs. Repeated drop tests are performed on each rope. The effects of the type of rope, drop height, drop weight, whether the rope has been subjected to static precycling, and the number of previous dynamic tests are examined. A mathematical model is proposed for the rope force as a function of the displacement and velocity of the weight.

scholarly journals Dynamic Processes of Loader Cranes Manipulators with Excessive Backlashes and Elastic Damping in Their Hinges

2019 ◽  
Vol 64 (1) ◽  
pp. 7-14
Author(s):  
Alexander V. Lagerev ◽  
Igor A. Lagerev
Keyword(s):  
Mathematical Model ◽  
Dynamic Loading ◽  
Structural Design ◽  
Impact Load ◽  
Dynamic Processes ◽  
Effective Solution ◽  
Complete Elimination ◽  
Quantitative Characteristics ◽  
Motion Parameters ◽  
Oscillatory Processes

This research is aimed at developing a mathematical model and the methodology for computer simulation of hydraulically driven manipulators of mobile cranes having excessive backlashes in cylindrical joints. The authors proposed a structural design and considered the mechanism of reducing the additional impact load in the hinges by means of elastic damping of oscillatory processes. This method allows estimating the degree of influence of the backlash and stiffness of the elastic damper on the change in the quantitative characteristics of the dynamic loading of the manipulators metalwork and the motion parameters of the transported load. While in operation, the excessive backlashes may cause an increase in the level of dynamic loading of manipulators up to 2 times or more. However, the rational choice of the elastic dampers stiffness allows an effective solution to this problem to the point of complete elimination of the additional impact load.

INFLUENCE OF DYNAMIC LOADING ON THE CHARACTERISTICS OF POLYMER IMPACT DAMPERS

2020 ◽  
Author(s):  
Vladimir Altuhov ◽  
Aleksey Boldyrev ◽  
Pavel Zhirov
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Ambient Temperature ◽  
Dynamic Loading ◽  
Loading Rate ◽  
Rolling Stock ◽  
Wear Factor ◽  
Shock Absorbers ◽  
Draft Gear ◽  
Freight Car

The article is devoted to the study of the influence of dynamic loading on the characteristics of polymer elements of shock absorbers of the rolling stock of railways and to the description of the creation of a mathematical model of their work. The results of mathematical modeling are further used to solve problems of the longitudinal dynamics of rolling stock. In the study, the initial loading rate varied, the ambient temperature and the influence of the wear factor remained unchanged. For the operating speeds of a freight car, a mathematical model of the PMKP-110 draft gear was determined.

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