scholarly journals A smart passive MR damper with a hybrid powering system for impact mitigation: An experimental study

2021 ◽  
pp. 1045389X2098808
Author(s):  
S. Jin ◽  
L. Deng ◽  
J. Yang ◽  
S. Sun ◽  
D. Ning ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Mr Damper ◽  
Damping Force ◽  
Softening Effect ◽  
Impact Speed ◽  
Impact Mitigation ◽  
Passive Damper ◽  
Comparison Results ◽  
Wide Range ◽  
The Impact

This paper presents a smart passive MR damper with fast-responsive characteristics for impact mitigation. The hybrid powering system of the MR damper, composed of batteries and self-powering component, enables the damping of the MR damper to be negatively proportional to the impact velocity, which is called rate-dependent softening effect. This effect can keep the damping force as the maximum allowable constant force under different impact speed and thus improve the efficiency of the shock energy mitigation. The structure, prototype and working principle of the new MR damper are presented firstly. Then a vibration platform was used to characterize the dynamic property and the self-powering capability of the new MR damper. The impact mitigation performance of the new MR damper was evaluated using a drop hammer and compared with a passive damper. The comparison results demonstrate that the damping force generated by the new MR damper can be constant over a large range of impact velocity while the passive damper cannot. The special characteristics of the new MR damper can improve its energy dissipation efficiency over a wide range of impact speed and keep occupants and mechanical structures safe.

Design and Experiment of the Magnetorheological Damper with Multiple Poles

2015 ◽  
Vol 764-765 ◽  
pp. 223-227 ◽  
Author(s):  
Yao Jung Shiao ◽  
Mei Ling Jow ◽  
Wen Hwa Kuo ◽  
Quang Anh Nguyen ◽  
Chao Wei Lai
Keyword(s):  
Mr Damper ◽  
Magnetorheological Damper ◽  
Vehicle Body ◽  
Main Function ◽  
Damping Force ◽  
Operation Conditions ◽  
Wide Range ◽  
Complete Procedure ◽  
The Impact ◽  
Multiple Poles

The main function of a suspension system is to isolate and absorb the impact from road surface to vehicle body. To provide good riding comfort, a damper with variable and wide-range damping is highly needed. This paper presents a complete procedure from design, optimization to experiment for a magnetorheological (MR) damper with multiple poles. This new designed damper is entirely different from those conventional single-pole MR dampers, effectively by extending the range of damping force. Magnetic simulation has been done in the paper to provide an optimal structure of the damper which significantly enhances the damping force while avoids magnetic saturation. The new damper was also manufactured and tested. The experimental results show that the provided damping force can be significantly increased with the increase of input current from low to high speeds. Damping force can be varied by 7.41 times. It proves that this new MR damper with high damping force can be controlled adaptively at wide range of operation conditions. It is suitable to be an adaptively variable damping source in semi-active suspension systems.

Numerical Modeling of Hydrodynamic Impact and Local Slamming Effects

2015 ◽  
Author(s):  
Ali Mohtat ◽  
Ravi Challa ◽  
Solomon C. Yim ◽  
Carolyn Q. Judge
Keyword(s):  
Numerical Method ◽  
Impact Velocity ◽  
High Speed ◽  
Impact Behavior ◽  
Analytical Prediction ◽  
Arbitrary Lagrangian Eulerian ◽  
Hydrodynamic Impact ◽  
Ale Formulation ◽  
Wide Range ◽  
The Impact

Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic wedge impacting a water free-surface is investigated. The fluid field is modeled using a finite element (FE) based arbitrary Lagrangian-Eulerian (ALE) formulation and the structure is modeled using a standard Lagrangian FE approximation. Validation of the numerical method against experimental test data and closed form analytical solutions shows that the ALE-FE/FE continuum approach captures the impact behavior accurately. A detailed sensitivity analysis is conducted to study the role of air compressibility, deadrise angle, and impact velocity in estimation of maximum impact pressures. The pressure field is found to be insensitive to air compressibility effect for a wide range of impact velocities and deadrise angles. A semi-analytical prediction model is developed for estimation of maximum impact pressures that correlates deadrise angle, impact velocity, and a nonlinear interaction term that couples hydrodynamic effects between these parameters. The numerical method is also used to examine the intrinsic physics of water impact on a high-speed planing hull with the goal of predicting slamming loads and resulting motions.

Rupture of thin films formed during droplet impact

2009 ◽  
Vol 466 (2116) ◽  
pp. 1229-1245 ◽  
Author(s):  
Rajeev Dhiman ◽  
Sanjeev Chandra
Keyword(s):  
Impact Velocity ◽  
Liquid Films ◽  
Solid Substrate ◽  
Contact Angles ◽  
Droplet Impact ◽  
Film Rupture ◽  
Droplet Spreading ◽  
Spreading Model ◽  
Wide Range ◽  
The Impact

Rupture of liquid films formed during droplet impact on a dry solid surface was studied experimentally. Water droplets (580±70 μm) were photographed as they hit a solid substrate at high velocities (10–30 m s −1 ). Droplet–substrate wettability was varied over a wide range, from hydrophilic to superhydrophobic, by changing the material of the substrate (glass, Plexiglas, wax and alkylketene dimer). Both smooth and rough wax surfaces were tested. Photographs of impact showed that as the impact velocity increased and the film thickness decreased, films became unstable and ruptured internally through the formation of holes. However, the impact velocity at which rupture occurred was found to first decrease and then increase with the liquid–solid contact angle, with wax showing rupture at all impact velocities tested. A thermodynamic stability analysis combined with a droplet spreading model predicted the rupture behaviour by showing that films would be stable at very small or at very large contact angles, but unstable in between. Film rupture was found to be greatly promoted by surface roughness.

scholarly journals Why Impacted Yarns Break at Lower Speed Than Classical Theory Predicts

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
James D. Walker ◽  
Sidney Chocron
Keyword(s):  
Impact Velocity ◽  
Classical Theory ◽  
Impact Speed ◽  
Projectile Impact ◽  
Theoretical Maximum ◽  
Theory Result ◽  
Single Yarn ◽  
The Impact ◽  
Good Agreement ◽  
Minimum Impact

Fabrics are an extremely important element of body armors and other armors. Understanding fabrics requires understanding how yarns deform. Classical theory has shown very good agreement with the deformation of a single yarn when impacted transversely. However, the impact speed at which a yarn breaks based on this classical theory is not correct; it has been experimentally noted that yarns break when impacted at a lower speed. This paper explores the mechanism of yarn breakage. The problem of the transverse strike of a yarn by a flat-faced projectile is analytically solved for early times. It is rigorously demonstrated that when a flat-faced projectile strikes a yarn, the minimum impact speed that breaks the yarn will always be at least 11% less than the classical-theory result. It is further shown that when the yarn in front of the projectile “bounces” off the projectile face due to the impact, the impact speed that breaks the yarn is further reduced. If the yarn bounces elastically off the projectile face at twice the impact velocity (the theoretical maximum), there is a 40% reduction in the projectile impact speed that breaks the yarn.

Validation of the S5P Formaldehyde L2 product using MAX-DOAS network observations

2020 ◽  
Author(s):  
Isabelle De Smedt ◽  
Gaia Pinardi ◽  
Corinne Vigouroux ◽  
Steven Compernolle ◽  
Kai Uwe Eichman ◽  
...  
Keyword(s):  
A Priori ◽  
Retrieval Algorithm ◽  
Comparison Results ◽  
Seasonal And Diurnal Variations ◽  
Wide Range ◽  
Polluted Sites ◽  
German Aerospace ◽  
The Impact

<p>The Sentinel-5 Precursor (S5P) was launched on the 13th of October 2017, with on board the TROPOspheric Monitoring Instrument (TROPOMI). The formaldehyde (HCHO) L2 product is operational since the end of 2018. The prototype of the tropospheric HCHO retrieval algorithm is developed at BIRA-IASB and implemented at the German Aerospace Center (DLR) in the S5P operational processor (De Smedt et al., 2018).</p><p>In this work, we investigate the quality of the HCHO tropospheric column product and its validation within the MPC framework (Mission Performance Center) and the S5PVT NIDFORVAL project (S5P NItrogen Dioxide and FORmaldehyde VALidation). Within NIDFORVAL, the S5P HCHO product has been validated using the full FTIR and MAXDOAS dataset. Validation results have been assessed against reported product uncertainties taking into account the full comparison error budget, showing that the product quality reaches its requirements.</p><p>Here, we focus on satellite-satellite comparison based on the OMI QA4ECV HCHO product and on ground-based validation using MAX-DOAS and Pandora network observations. About 15 HCHO measuring stations are involved, providing data corresponding to a wide range of observation conditions at mid and low latitudes, and covering remote, sub-urban, and urban polluted sites. Comparison results show usually negative biases for large HCHO columns, while a positive offset is observed for the lowest columns. For the MAX-DOAS stations providing vertical profile retrievals, the impact of a priori profiles on the comparison is assessed. The dataset allows to discuss validation results as a function of emission source. Seasonal and diurnal variations are compared. Long term variation are also monitored using the OMI and MAX-DOAS QA4ECV dataset.</p>

Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere

2019 ◽  
Vol 827 ◽  
pp. 349-354
Author(s):  
Kiyohiro Ito ◽  
Fei Gao ◽  
Masayuki Arai
Keyword(s):  
Gas Turbine ◽  
Impact Velocity ◽  
Thermal Barrier Coatings ◽  
High Velocity ◽  
Turbine Blades ◽  
Interfacial Crack ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Wide Range ◽  
The Impact

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.

scholarly journals Numerical Study of the Interaction between Level Ice and Wind Turbine Tower for Estimation of Ice Crushing Loads on Structure

2019 ◽  
Vol 7 (12) ◽  
pp. 439 ◽  
Author(s):  
Ming Song ◽  
Wei Shi ◽  
Zhengru Ren ◽  
Li Zhou
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Numerical Study ◽  
Mesh Size ◽  
Impact Speed ◽  
Wind Turbine Tower ◽  
Comparison Results ◽  
Ice Loads ◽  
Level Ice ◽  
The Impact

In this paper, the interaction between level ice and wind turbine tower is simulated by the explicit nonlinear code LS-DYNA. The isotropic elasto-plastic material model is used for the level ice, in which ice crushing failure is considered. The effects of ice mesh size and ice failure strain on ice forces are investigated. The results indicate that these parameters have a significant effect on the ice crushing loads. To validate and benchmark the numerical simulations, experimental data on level ice-wind turbine tower interactions are used. First, the failure strains of the ice models with different mesh sizes are calibrated using the measured maximum ice force from one test. Next, the calibrated ice models with different mesh sizes are applied for other tests, and the simulated results are compared to corresponding model test data. The effects of the impact speed and the size of wind turbine tower on the comparison between the simulated and measured results are studied. The comparison results show that the numerical simulations can capture the trend of the ice loads with the impact speed and the size of wind turbine tower. When a mesh size of ice model is 1.5 times the ice thickness, the simulations can give more accurate estimations in terms of maximum ice loads for all tests, i.e., good agreement between the simulated and measured results is achieved.

scholarly journals Research on Tunnel Surrounding Rock Failure and Energy Dissipation Based on Cyclic Impact and Shear Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yu Ding ◽  
Zhuoying Tan ◽  
Shuguang Li ◽  
Runke Huo ◽  
Ziliang Liu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Impact Velocity ◽  
Rotation Speed ◽  
Rock Failure ◽  
Surrounding Rock ◽  
Stress Strain ◽  
Impact Speed ◽  
Upper Limit ◽  
Cyclic Impact ◽  
The Impact

Aiming at the cyclic impact deformation and failure of tunnel surrounding rock under shear stress, a self-developed rotation-impact simulation test platform was used to determine the number of failures, stress-strain curves, and energy in the process of cyclic impact failure. The failure process of rock under different impact velocities and shear stresses has been systematically studied. Results show that, under the same impact speed, the shear stress will increase with the increase in the rotation speed, but an upper limit will exist. When the rotation speed reaches this upper limit, the shear stress will no longer increase. The presence of shear stress will reduce the number of impacts required for rock failure. When the impact speed is 7.2 m/s, the number of impacts at the maximum rotation speed is 60% of the static state. When the impact velocity is 16.8 m/s, this value is only 33.3%. At the same impact velocity, the stress-strain curves under different rotation speeds do not change significantly, but with the increase in the rotation speed, the slope of the elastic stage of the stress-strain curve gradually decreases, and the corresponding stress of the rock sample decreases when the maximum strain is reached. With the increase in shear stress, the crushing specific energy required for rock failure gradually decreases. The greater the impact velocity, the more obvious the impact of shear stress on energy dissipation. In the tunnel process, when the surrounding rock is subjected to impact loads from different directions, only the axial strain analysis will have certain safety hazards, and timely support and reinforcement work are required.

scholarly journals Intelligent Control Based on a Neural Network for Aircraft Landing Gear with a Magnetorheological Damper in Different Landing Scenarios

2020 ◽  
Vol 10 (17) ◽  
pp. 5962 ◽  
Author(s):  
Quoc Viet Luong ◽  
Dae-Sung Jang ◽  
Jai-Hyuk Hwang
Keyword(s):  
Neural Network ◽  
Mr Damper ◽  
Landing Gear ◽  
Magnetorheological Damper ◽  
Damping Force ◽  
Hybrid Controller ◽  
Aircraft Landing ◽  
Neural Network Controller ◽  
Passive Damper ◽  
Aircraft Landing Gear

A typical oleo-pneumatic shock-absorbing strut (classic traditional passive damper) in aircraft landing gear has a metering pin extending through the orifice, which can vary the orifice area with the compression and extension of the damper strut. Because the metering pin is designed in a single landing condition, the traditional passive damper cannot adjust its damping force in multiple landing conditions. Magnetorheological (MR) dampers have been receiving significant attention as an alternative to traditional passive dampers. An MR damper, which is a typical semi-active suspension system, can control the damping force created by MR fluid under the magnetic field. Thus, it can be controlled by electric current. This paper adopts a neural network controller trained by two different methods, which are genetic algorithm and policy gradient estimation, for aircraft landing gear with an MR damper that considers different landing scenarios. The controller learns from a large number of trials, and accordingly, the main advantage is that it runs autonomously without requiring system knowledge. Moreover, comparative numerical simulations are executed with a passive damper and adaptive hybrid controller under various aircraft masses and sink speeds for verifying the effectiveness of the proposed controller. The main simulation results show that the proposed controller exhibits comparable performance to the adaptive hybrid controller without any needs for the online estimation of landing conditions.

Design Optimization of a Bi-Fold Magnetorheological Damper Subject to Impact Loads

2017 ◽  
Author(s):  
Muftah Saleh ◽  
Ramin Sedaghati ◽  
Rama Bhat
Keyword(s):  
Magnetic Field ◽  
Design Optimization ◽  
Impact Velocity ◽  
Dynamic Range ◽  
Magnetorheological Damper ◽  
Damping Force ◽  
Mr Fluid ◽  
Bingham Plastic ◽  
Turbulent Condition ◽  
The Impact

Dynamic range (ratio of the maximum on-state damping force to the off-state damping force), is an important index characteristic of the performance of the Magnetorheological Energy Absorbers (MREAs). In high speed impact, the dynamic range may fall into the uncontrollable zone (≤ 1) due to the increase in the off-state damping force which is associated with the transition of the flow from laminar to turbulent condition. Therefore, it is of paramount importance to design optimize the MREA in order to increase its dynamic range while accommodating the geometry, MR fluid flow and magnetic field constraints. In this study, a design optimization problem has been formulated to optimally design a bi-fold MREA to comply with the helicopter crashworthiness specifications for lightweight civilian helicopters. It is required to have a minimum dynamic range of 2 at 5 m/s impact velocity while satisfying the constraints imposed due to the geometry, volume of the device, magnetic field and the flow of the magnetorheological fluid in the MR valve. Meanwhile in order to comply with the helicopter crashworthiness requirement, the MREA device should be designed to generate 15 kN field-off damping force at the design impact velocity if the MREA is to be integrated with skid landing gear systems. The magneto-static analysis of the MREA valve has been conducted analytically using simplified assumptions in order to obtain the relation between induced magnetic flux in the MR fluid gaps in active regions versus the applied current and MREA valve geometrical parameters. Both Bingham plastic models, with and without minor loss factors, have been utilized to derive the dynamic range and the results are compared in terms of the generated off-state damping force, on-state damping force, and dynamic range. The Bingham plastic model with minor loss coefficients was found to be more accurate due to the turbulent condition in the MREA caused by the impact. Finally, the performance of the optimized bi-fold MREA has been evaluated under different impact speeds.

Sign in / Sign up

Export Citation Format

Share Document