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.

Design and Testing of a Crashworthy Landing Gear

2015 ◽  
Author(s):  
Tae-Uk Kim ◽  
JeongWoo Shin ◽  
Sang Wook Lee
Keyword(s):  
High Speed ◽  
Shock Absorber ◽  
Landing Gear ◽  
Collapse Mechanism ◽  
Gear Design ◽  
Helicopter Landing ◽  
Drop Tests ◽  
The Military ◽  
Secondary Hazards ◽  
Design And Testing

The development of a crashworthy landing gear is presented based on the civil regulations and the military specifications. For this, two representative crashworthy requirements are applied to helicopter landing gear design; the nose gear is designed to collapse in a controlled manner so that it does not penetrate the cabin and cause secondary hazards, and the main gear has to absorb energy as much as possible in crash case to decelerate the aircraft. To satisfy the requirements, the collapse mechanism triggered by shear-pin failure and the shock absorber using blow-off valve are implemented in the nose and main gear, respectively. The crash performance of landing gear is demonstrated by drop tests. In the tests, performance data such as ground reaction loads and shock absorber stroke are measured and crash behaviors are recorded by high-speed camera. The test data shows a good agreement with the prediction by simulation model, which proves the validity of the design and analysis.

Design and Testing of a Crashworthy Landing Gear

2017 ◽  
Vol 3 (4) ◽  
Author(s):  
Tae-Uk Kim ◽  
JeongWoo Shin ◽  
Sang Wook Lee
Keyword(s):  
High Speed ◽  
Shock Absorber ◽  
Landing Gear ◽  
Collapse Mechanism ◽  
Gear Design ◽  
Helicopter Landing ◽  
Drop Tests ◽  
The Military ◽  
Secondary Hazards ◽  
Design And Testing

The development of a crashworthy landing gear is presented based on the civil regulations and the military specifications. For this, two representative crashworthy requirements are applied to helicopter landing gear design: the nose gear is designed to collapse in a controlled manner so that it does not penetrate the cabin and cause secondary hazards, and the main gear has to absorb energy as much as possible in crash case to decelerate the aircraft. To satisfy the requirements, the collapse mechanism triggered by shear-pin failure and the shock absorber using blow-off valve (BOV) is implemented in the nose and main gear, respectively. The crash performance of landing gear is demonstrated by drop tests. In the tests, performance data such as ground reaction loads and shock absorber stroke are measured and crash behaviors are recorded by high-speed camera. The test data show a good agreement with the prediction by simulation model, which proves the validity of the design and analysis.

scholarly journals Numerical Model Study of Prototype Drop Tests on Cube and Cubipod® Concrete Armor Units Using the Combined Finite–Discrete Element Method

2021 ◽  
Vol 9 (5) ◽  
pp. 460
Author(s):  
Giulio Scaravaglione ◽  
John-Paul Latham ◽  
Jiansheng Xiang
Keyword(s):  
Discrete Element Method ◽  
Validation Study ◽  
Free Fall ◽  
Discrete Element ◽  
Drop Test ◽  
Modeling Methodology ◽  
Model Study ◽  
Drop Tests ◽  
Rubble Mound Breakwaters ◽  
Element Method

This paper aims to evaluate the structural strength of unreinforced concrete armor units (CAU), named Cubipod®, used on rubble-mound breakwaters and coastal structures, through a numerical methodology using the combined finite–discrete element method (FDEM). A numerical modeling methodology is developed to reproduce the results of an experimental examination published by Medina et al. (2011) of a free-fall drop test performed on a 15 t conventional Cubic block and a 16 t Cubipod® unit. The field results of the Cube drop tests were used to calibrate the model. The numerically simulated response to the Cubipod® test is then discussed in the context of a validation study. The calibration process and validation study provide insights into the sensitivity of breakage to tensile strength and collision angle, as well as a better understanding of the crushing and cracking damage of this unit under drop test impact conditions.

A novel retractable landing gear of a light amphibious airplane design, synthesis, analysis, and implementation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sinchai Chinvorarat ◽  
Pumyos Vallikul
Keyword(s):  
Impact Load ◽  
Landing Gear ◽  
Drop Test ◽  
Drop Height ◽  
Core Element ◽  
Design Synthesis ◽  
Content Type ◽  
And Performance ◽  
Correct Path ◽  
The Impact

Purpose The purpose of this paper is to present a novel retractable main landing gear for a light amphibious airplane, while the design, synthesis and analysis are given in details for constructing the main landing gear. Design/methodology/approach The constraint three-position synthesis has given the correct path of all linkages that suitably fit the landing gear into the compartment. The additional lock-link is introduced into the design to ensure the securement of the mechanism while landing. Having the telescopic gas-oil shock strut as a core element to absorb the impact load, it enhances the ability and efficiency to withstand higher impact than others type of light amphibious airplane. Findings By kinematics bifurcation analysis, the optimized value of the unlock spring stiffness at 90 N/m can be found to tremendously reduce the extended-retracted linear actuator force from 500 N to 150 N at the beginning of the retraction sequence. This could limit the size and weight of the landing gear actuator of the light amphibious airplane. Practical implications The drop test of the landing gear to comply with the ASTM f-2245 (Standard Specification for Design and Performance of a Light Sport Airplane) reveals that the novel landing gear can withstand the impact load at the drop height determined by the standard. The maximum impact loading 4.8 G occurs at the drop height of 300 mm, and there is no sign of any detrimental or failure of the landing gear or the structure of the light amphibious airplane. The impact settling time response reaches the 2% of steady-state value in approximately 1.2 s that ensure the safety and stability of the amphibious airplane if it subjects to an accidentally hard landing. Originality/value This paper presents unique applications of a retractable main landing gear of a light amphibious airplane. The proposed landing gear functions properly and complies with the drop test standard, ensuring the safety and reliability of the airplane and exploiting the airworthiness certification process.

Effects of Lumbar Spine Assemblies and Body-Borne Equipment Mass on Anthropomorphic Test Device Responses During Drop Tests

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Daniel Aggromito ◽  
Mark Jaffrey ◽  
Allen Chhor ◽  
Bernard Chen ◽  
Wenyi Yan
Keyword(s):  
Lumbar Spine ◽  
Federal Aviation Administration ◽  
Relative Displacement ◽  
Drop Tower ◽  
Test Device ◽  
Hybrid Iii ◽  
Drop Tests ◽  
Occupant Injury ◽  
Maximum Relative Displacement ◽  
The Impact

When simulating or conducting land mine blast tests on armored vehicles to assess potential occupant injury, the preference is to use the Hybrid III anthropomorphic test device (ATD). In land blast events, neither the effect of body-borne equipment (BBE) on the ATD response nor the dynamic response index (DRI) is well understood. An experimental study was carried out using a drop tower test rig, with a rigid seat mounted on a carriage table undergoing average accelerations of 161 g and 232 g over 3 ms. A key aspect of the work looked at the various lumbar spine assemblies available for a Hybrid III ATD. These can result in different load cell orientations for the ATD which in turn can affect the load measurement in the vertical and horizontal planes. Thirty-two tests were carried out using two BBE mass conditions and three variations of ATDs. The latter were the Hybrid III with the curved (conventional) spine, the Hybrid III with the pedestrian (straight) spine, and the Federal Aviation Administration (FAA) Hybrid III which also has a straight spine. The results showed that the straight lumbar spine assemblies produced similar ATD responses in drop tower tests using a rigid seat. In contrast, the curved lumbar spine assembly generated a lower pelvis acceleration and a higher lumbar load than the straight lumbar spine assemblies. The maximum relative displacement of the lumbar spine occurred after the peak loading event, suggesting that the DRI is not suitable for assessing injury when the impact duration is short and an ATD is seated on a rigid seat on a drop tower. The peak vertical lumbar loads did not change with increasing BBE mass because the equipment mass effects did not become a factor during the peak loading event.

Research on Stiffness and Damping Characteristics of Fixed Oily Porous Materials Joint Interface

2011 ◽  
Vol 422 ◽  
pp. 575-579
Author(s):  
Chong Nian Qu ◽  
Liang Sheng Wu ◽  
Jian Feng Ma ◽  
Yi Chuan Xiao
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Parallel Plate ◽  
Joint Interface ◽  
Force Model ◽  
Equivalent Stiffness ◽  
Contact State ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
Damping Model

In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

scholarly journals Simulation Study of a Composite Landig Gear of Ultralight and Very Light Aircraft

2021 ◽  
Author(s):  
Paulina Zenowicz
Keyword(s):  
Simulation Study ◽  
Computer Aided Design ◽  
Landing Gear ◽  
Design Tool ◽  
Drop Test ◽  
Environment Design ◽  
Element Analysis ◽  
Computer Methods ◽  
The One ◽  
Aided Design

There is a need to design new, lighter aircraft structures, which has a direct impact on the safety and costs of aircraft maintenance. One of basic parts of an aircraft is ites landing gear, whose main functions are to enable taxiing, safe landing, take-off, and to assist the remainder of ground operations. Landing gear failures are usually related to metallurgy, processing, environment, design, and causes of overload. These are conditions that can be prevented using modern methods to calculate the strength of such a landing gear in various conditions. The paper presents stages of a simulation study of the fixed three-wheeled spring landing gear for an ultralight aircraft. Analysis of forces acting on the landing gear during drop test and their implementation by numerical computer methods allowed for the creation of a model in the CAD (Computer-Aided Design) tool and its FEA (Finite Element Analysis). These results were compared between a modeled classic spring landing gear and the one made of composite materials. The further goal of the research will be to build a drop test stand for a small landing gear used in airplanes and drones. This method has a significant impact on simplifying the design of the landing gear, its modeling, and optimization.

Nonlinear Transient Analysis of Aircraft Landing Gear Brake Whirl and Squeal

1995 ◽  
Author(s):  
Matt H. Travis
Keyword(s):  
Finite Element ◽  
Transient Analysis ◽  
Landing Gear ◽  
Friction Modeling ◽  
Explicit Integration ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
Nonlinear Transient ◽  
Element Approach ◽  
Stiffness And Damping

Abstract The feasibility of computing non-linear transient finite element simulations of aircraft landing gear brake whirl and squeal is demonstrated and discussed. Methodology to conduct the high frequency brake transient analysis is developed using an explicit integration finite element approach. Results indicate the approach has the capability to simulate brake dynamic behavior in dynamometer and aircraft landing gear installations — thus enabling evaluation of modifications to braking systems that lead to more stable and robust designs. A simple multi-disk brake model is developed and described. Modeling techniques for including the dynamometer road wheel and runway in the simulations are given. Issues such as piston housing hydraulic fluid stiffness and damping effects, and parametric friction modeling are discussed.

Reliability of SAC 105 and SAC1205N under Drop Tests

2016 ◽  
Vol 2016 (1) ◽  
pp. 000106-000110
Author(s):  
Jia-Shen Lan ◽  
Stuwart Fan ◽  
Louie Huang ◽  
Mei-Ling Wu
Keyword(s):  
Fatigue Life ◽  
Solder Joint ◽  
Simulation Model ◽  
Drop Test ◽  
Test Execution ◽  
Fine Pitch ◽  
Mechanical Shocks ◽  
Drop Tests ◽  
Solder Joint Fatigue ◽  
Package Reliability

Abstract In this paper, the solder joint failure and the solder joint fatigue life in the Thin-profile Fine-pitch Ball Grid Array (TFBGA) Package was investigated by performing the drop test, and implementing a simulation model. Owing to the need to meet the increasing demands for functionality, microelectronic package reliability can be compromised and has become the key issue when executing drop tests. During impact in drop test, the deformation of PCB due to bending and mechanical shocks can cause solder joint crack. While this is a well-known issue, observing the solder joint responses during the test execution can be a challenge. Therefore, in this work, a simulation model approach has been developed to investigate the stress and strain of the solder joint during the drop test. In this research, the JEDEC Condition B drop test was simulated, characterized by 1500G peak acceleration and 0.5 ms duration. The drop test simulation model was successful in predicting the solder joint fatigue life with different solder joint materials, such as SAC105 and SAC1205N, while also facilitating result comparison to identify the most optimal structure.

Study on mechanical properties of high damping viscoelastic dampers

2019 ◽  
Vol 22 (14) ◽  
pp. 2925-2936 ◽  
Author(s):  
Yun Chen ◽  
Chao Chen ◽  
Qianqian Ma ◽  
Huanjun Jiang ◽  
Zhiwei Wan
Keyword(s):  
Mechanical Properties ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Hysteretic Behavior ◽  
Loading Frequency ◽  
Equivalent Stiffness ◽  
Viscoelastic Dampers ◽  
Wide Range ◽  
High Damping Rubber ◽  
Stiffness And Damping

The mechanical properties of the viscoelastic damper made of high damping rubber produced in China are investigated in order to provide the basis for its application. At first, the test on material properties of high damping rubber is conducted. The Mooney–Rivlin model, the Yeoh model and the Prony series are applied for simulating the nonlinear behavior of the high damping rubber with the aid of software ABAQUS. Then, three viscoelastic dampers with different sizes are tested under cyclic loading. The effects of strain amplitude and loading frequency on hysteretic behavior of dampers are analyzed. Viscoelastic dampers possess large deformation capability, stable energy-dissipation capacity and good fatigue-resisting property. The effect of strain amplitude is much more significant than loading frequency. The hysteretic behavior of the dampers is simulated by the Bouc–Wen model and the model of the equivalent stiffness and damping, respectively. The prediction results by using the Bouc–Wen model are in good agreement with the experimental results, which indicates that the Bouc–Wen model is applicable to simulate the mechanical properties of high damping viscoelastic dampers with a wide range of shear strain. As to the model of equivalent stiffness and damping, it has the advantages of clear concept and simple calculation. However, the good accuracy of prediction can be obtained only when the shear strain is not greater than 60%.

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