On the Use of an Elastic-Plastic Contact Law for the Impact of a Single Flexible Link

1995 ◽  
Vol 117 (4) ◽  
pp. 527-533 ◽  
Author(s):  
A. S. Yigit
Keyword(s):  
Impact Force ◽  
Body Motion ◽  
Model Parameters ◽  
Impact Model ◽  
Flexible Link ◽  
Continuous Transition ◽  
Flexible Links ◽  
Elastic Plastic ◽  
The Impact ◽  
Impact Models

An elastic-plastic contact law is proposed for modeling impact of a single flexible link. This contact law allows continuous transition between contact and noncontact phases and is capable of predicting impact force histories. The impact model parameters can readily be obtained from the material and geometric properties. Excellent agreement with the experimental results has been obtained for both elastic and rigid body motion of the link. The impact force histories are also obtained and compared for perfectly elastic and elastic-plastic impact models. It is shown that a perfectly elastic impact assumption is not realistic for most impacts of flexible links.

scholarly journals Modelling the impact of a new tobacco product: review of Philip Morris International’s Population Health Impact Model as applied to the IQOS heated tobacco product

2018 ◽  
Vol 27 (Suppl 1) ◽  
pp. s82-s86 ◽  
Author(s):  
Wendy B Max ◽  
Hai-Yen Sung ◽  
James Lightwood ◽  
Yingning Wang ◽  
Tingting Yao
Keyword(s):  
Population Health ◽  
New Product ◽  
Health Impact ◽  
Tobacco Product ◽  
Dynamic State ◽  
Model Parameters ◽  
Impact Model ◽  
Tobacco Products ◽  
Philip Morris ◽  
The Impact

ObjectivesWe review the Population Health Impact Model (PHIM) developed by Philip Morris International and used in its application to the US Food and Drug Administration (FDA) to market its heated tobacco product (HTP), IQOS, as a modified-risk tobacco product (MRTP). We assess the model against FDA guidelines for MRTP applications and consider more general criteria for evaluating reduced-risk tobacco products.MethodsIn assessing the PHIM against FDA guidelines, we consider two key components of the model: the assumptions implicit in the model (outcomes included, relative harm of the new product vs cigarettes, tobacco-related diseases considered, whether dual or polyuse of the new product is modelled, and what other tobacco products are included) and data used to estimate and validate model parameters (transition rates between non-smoking, cigarette-only smoking, dual use of cigarettes and MRTP, and MRTP-only use; and starting tobacco use prevalence).ResultsThe PHIM is a dynamic state transition model which models the impact of cigarette and MRTP use on mortality from four tobacco-attributable diseases. The PHIM excludes morbidity, underestimates mortality, excludes tobacco products other than cigarettes, does not include FDA-recommended impacts on non-users and underestimates the impact on other population groups.ConclusionThe PHIM underestimates the health impact of HTP products and cannot be used to justify an MRTP claim. An assessment of the impact of a potential MRTP on population health should include a comprehensive measure of health impacts, consideration of all groups impacted, and documented and justifiable assumptions regarding model parameters.

scholarly journals Using Random Effects to Build Impact Models When the Available Historical Record Is Short

2012 ◽  
Vol 51 (11) ◽  
pp. 1994-2004 ◽  
Author(s):  
Filipe Aires
Keyword(s):  
Random Effects ◽  
Spatial Data ◽  
Spatial Location ◽  
Historical Record ◽  
Impact Model ◽  
Local Conditions ◽  
Real World Application ◽  
Socioeconomic Data ◽  
The Impact ◽  
Impact Models

AbstractThe analysis of the affect of weather and climate on human activities requires the construction of impact models that are able to describe the complex links between weather and socioeconomic data. In practice, one of the biggest challenges is the lack of data, because it is generally difficult to obtain time series that are long enough. As a consequence, derived impact models predict well the historical record but are unable to perform well on real forecasts. To avoid this data-limitation problem, it is possible to train the impact model over a large spatial domain by “pooling” data from multiple locations. This general impact model needs to be spatially corrected to take local conditions into account, however. This is particularly true, for example, in agriculture: it is not efficient to pool all of the spatial data into a single very general impact model, but it is also not efficient to develop one impact model for each spatial location. To solve these aggregation problems, mixed-effects (ME) models have been developed. They are based on the idea that each datum belongs to a particular group, and the ME model takes into account the particularities of each group. In this paper, ME models and, in particular, random-effects (RE) models are tested and are compared with more-traditional methods using a real-world application: the sales of salt for winter road deicing by public service vehicles. It is shown that the performance of RE models is higher than that of more-traditional regression models. The development of impact models should strongly benefit from the use of RE and ME models.

scholarly journals Opinion Impact Models and Opinion Consensus Methods in Ad Hoc Tactical Social Networks

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Demin Li ◽  
Jie Zhou ◽  
Jingjuan Zhu ◽  
Jiacun Wang
Keyword(s):  
Social Networks ◽  
Ad Hoc ◽  
Consensus Methods ◽  
Impact Model ◽  
The Social ◽  
Heterogeneous Social Networks ◽  
The Impact ◽  
The Relationship ◽  
Impact Models ◽  
General Opinion

Ad hoc social networks are special social networks, such as ad hoc tactical social networks, ad hoc firefighter social networks, and ad hoc vehicular social networks. The social networks possess both the properties of ad hoc network and social network. One of the challenge problems in ad hoc social networks is opinion impact and consensus, and the opinion impact plays a key role for information fusion and decision support in ad hoc social networks. In this paper, consider the impact of physical and logical distance on the opinions of individuals or nodes in heterogeneous social networks; we present a general opinion impact model, discuss the local and global opinion impact models in detail, and point out the relationship between the local opinion impact model and the global opinion impact model. For understanding the opinion impact models easily, we use the general opinion impact model to ad hoc tactical social networks and discuss the opinion impact and opinion consensus for ad hoc tactical social networks in the end.

scholarly journals An analytical model to determine the impact force of drone strikes

2021 ◽  
Author(s):  
Florian Franke ◽  
Michael Schwab ◽  
Uli Burger ◽  
Christian Hühne
Keyword(s):  
Load Distribution ◽  
Impact Force ◽  
Analytical Calculation ◽  
Calculation Model ◽  
Material Behavior ◽  
Major Influence ◽  
Impact Model ◽  
Simulation Data ◽  
Input Parameters ◽  
The Impact

AbstractIn addition to the well-known threats of bird and hail strikes, small unmanned aerial vehicles (sUAV) pose a new threat to manned aviation. Determining the severity of collisions between sUAVs and aircraft structures is essential for the safe use and integration of drones in airspace. A generic analytical calculation model needs to be developed to supplement the existing test and simulation data. This paper presents an analytic model for drone collisions with perpendicular and inclined targets. The targets have a rigid or elastic material behavior. The aircraft impact model, which is used for the design of nuclear reactor structures, is transferred and adjusted for sUAV impacts to calculate the impact force. A mass- and a burst load distribution are needed as input parameters. Both distributions are determined for an sUAV design depending on the flight direction. Compared to previous calculations, the new approach is to consider a moving target structure, which produces more realistic results. We compare the calculation results with simulation data from sUAV collisions with a commercial airliner windshield from the literature. The calculations show plausible results and a good agreement with literature data. Subsequently, the influence of the input parameters on the impact force is investigated. We see that spring stiffness, target mass, burst load distribution and damping have minor influence on the overall impact force. The impact velocity, mass distribution and flight orientation on the other hand have a major influence on the impact force. Further tests are needed to validate the impact model.

scholarly journals NUMERICAL MODELLING OF BIRD STRIKE ON A ROTATING ENGINE BLADES BASED ON VARIATIONS OF POROSITY DENSITY

2022 ◽  
Vol 23 (1) ◽  
pp. 412-423
Author(s):  
Sharis-Shazzali Shahimi ◽  
Nur Azam Abdullah ◽  
Ameen Topa ◽  
Meftah Hrairi ◽  
Ahmad Faris Ismail
Keyword(s):  
Numerical Modelling ◽  
Structural Integrity ◽  
Constitutive Relations ◽  
Material Model ◽  
Initial Stresses ◽  
Model Parameters ◽  
Bird Strike ◽  
Elastic Plastic ◽  
Engine Blade ◽  
The Impact

A numerical investigation is conducted on a rotating engine blade subjected to a bird strike impact. The bird strike is numerically modelled as a cylindrical gelatine with hemispherical ends to simulate impact on a rotating engine blade. Numerical modelling of a rotating engine blade has shown that bird strikes can severely damage an engine blade, especially as the engine blade rotates, as the rotation causes initial stresses on the root of the engine blade. This paper presents a numerical modelling of the engine blades subjected to bird strike with porosity implemented on the engine blades to investigate further damage assessment due to this porosity effect. As porosity influences the decibel levels on a propeller blade or engine blade, the damage due to bird strikes can investigate the compromise this effect has on the structural integrity of the engine blades. This paper utilizes a bird strike simulation through an LS-Dyna Pre-post software. The numerical constitutive relations are keyed into the keyword manager where the bird’s SPH density, a 10 ms simulation time, and bird velocity of 100 m/s are all set. The blade rotates counter-clockwise at 200 rad/s with a tetrahedron mesh. The porous regions or voids along the blade are featured as 5 mm diameter voids, each spaced 5 mm apart. The bird is modelled as an Elastic-Plastic-Hydrodynamic material model to analyze the bird’s fluid behavior through a polynomial equation of state. To simulate the fluid structure interaction, the blade is modelled with Johnson-Cook Material model parameters of aluminium where the damage of the impact can be observed. The observations presented are compared to previous study of a bird strike impact on non-porous engine blades. ABSTRAK: Penyelidikan berangka telah dijalankan ke atas bilah enjin berputar tertakluk kepada impak pelanggaran burung. Pelanggaran burung tersebut telah dimodelkan secara berangka sebagai silinder gelatin dengan hujungnya berbentuk hemisfera demi mensimulasikan impaknya ke atas bilah enjin yang berputar. Pemodelan berangka bilah-bilah enjin yang berputar tersebut menunjukkan bahawa pelanggaran burung mampu menyebabkan kerosakan teruk terhadap bilah enjin terutamanya apabila bilah enjin sedang berputar oleh sebab putaran menghasilkan tekanan asal di pangkal bilah enjin. Kajian ini mengetengahkan pemodelan berangka ke atas bilah-bilah enjin tertakluk kepada pelanggaran burung terhadap bilah-bilah enjin yg mempunyai keliangan demi menyelidik dan menilai kerosakan kesan daripada keliangan tersebut. Keliangan juga mempengaruhi tahap-tahap desibel ke atas bilah kipas ataupun bilah enjin, kerosakan hasil serangan burung boleh menterjemah tahap ketahanan struktur integriti bagi bilah-bilah enjin tersebut. Penyelidikan ini mengguna pakai perisian “LS-Dyna Pre-post” untuk simulasi pelanggaran burung. Hubungan konstitutif berangka telah dimasukkan sebagai kata kunci di mana ketumpatan SPH burung, masa simulasi 10ms, dan halaju burung ditetapkan kepada 100 m/s. Bilah tersebut berputar pada 200 rad/s arah lawan jam dengan jejaring tetrahedron. Kawasan berliang atau kosong di sepanjang bilah ditetapkan diameternya kepada 5 mm, dan dijarakkan 5 mm di antara satu sama lain. Burung pula dimodelkan sebagai material “Elastic-Plastic-Hydrodynamic” untuk mengkaji sifat bendalir burung melalui persamaan polinomial. Demi mensimulasi interaksi struktur bendalir, bilah tersebut dimodelkan sebagai parameter aluminium material “Johnson Cook” di mana kerosakan daripada impak tersebut dapat diteliti. Penelitian-penelitian tersebut dibandingkan dengan kajian terdahulu ke atas serangan burung terhadap bilah-bilah enjin tidak berliang.

Elastic/Plastic Contact Mechanics-Based Analysis of Hard Disk Drive Media Damage From Slider Corner Impacts

2007 ◽  
Author(s):  
Raja R. Katta ◽  
Andreas A. Polycarpou ◽  
Jorge V. Hanchi
Keyword(s):  
Thin Film ◽  
Contact Mechanics ◽  
Impact Damage ◽  
Disk Drive ◽  
High Impact ◽  
Impact Model ◽  
Elastic Plastic ◽  
The Impact ◽  
Contact Parameters ◽  
Very High

A contact mechanics-based elastic-plastic impact model which considers slider corner – head disk interaction has been proposed. This model estimates the impact contact parameters accounting for the plastic deformation effects of the realistic thin-film disk media. These properties were utilized for the elastic-plastic impact model to estimate the contact parameters. Very high impact velocities and/or small slider corner radii resulted is extremely high contact depths where the disk substrate mostly dominated the impact and the effect of layers could not be seen. At lower impact velocities and higher corner radii, the impact damage was relatively smaller. The effect of the thin-film layers, which are stiffer than the substrate, was clearly observed.

Some insights into slamming forces: Compressible and incompressible phases

2000 ◽  
Vol 214 (6) ◽  
pp. 881-888 ◽  
Author(s):  
E F Campana ◽  
A Carcaterra ◽  
E Ciappi ◽  
A Iafrati
Keyword(s):  
Impact Force ◽  
Mass Parameter ◽  
Free Fall ◽  
The Body ◽  
Body Motion ◽  
Closed Form Expression ◽  
Surface Evolution ◽  
Entry Velocity ◽  
Wetted Area ◽  
The Impact

In the present paper the slamming force occurring in the free-fall impact of cylindrical bodies over the water surface is analysed in both compressible and incompressible stages. In the compressible phase the hydrodynamic analysis is carried out by the acoustic approximation and a closed-form expression for the impact force is recovered. The incompressible stage is approached through an unsteady boundary element method to compute the free surface evolution and the slamming force on the body. In both cases the hydrodynamic force is coupled to the rigid body motion to update the entry velocity of the body. The combined effect of the increasing wetted area and the reducing entry velocity leads to a maximum in the impact force that depends on the body mass. A parametric investigation shows that in the impact of a wedge section, if the maximum is reached either in the compressible or in the incompressible stages, a similar square root trend characterizes the dependence of this maximum on a non-dimensional mass parameter.

Interaction between dry granular flow and rigid barrier with basal clearance: analytical and physical modelling

2020 ◽  
Vol 57 (2) ◽  
pp. 236-245 ◽  
Author(s):  
Clarence Edward Choi ◽  
Charles Wang Wai Ng ◽  
Haiming Liu ◽  
Yu Wang
Keyword(s):  
Granular Flow ◽  
Impact Force ◽  
Particle Diameter ◽  
Physical Modelling ◽  
Impact Model ◽  
Jump Height ◽  
Rigid Barrier ◽  
Physical Experiments ◽  
Dry Granular Flow ◽  
The Impact

Some types of barriers are designed with a clearance between the bottom of the barrier and the channel bed. This feature allows small discharges to pass, thereby reducing the maintenance required over the service life of the barrier. Aside from the practical function of a clearance, it influences the impact force, jump height, and discharge. In this paper, a series of physical experiments was conducted using a 6 m long flume to model the interaction between dry granular flow and rigid barrier with a basal clearance. The ratio between the clearance and particle diameter Hc/D was varied from 0 to 10. The channel inclination was varied from 15° to 35° to achieve different Froude numbers before impact. A new impact model for predicting impact force exerted on the barrier with a basal clearance is presented and evaluated. Results reveal that Hc ≥ 3D is capable of reducing the impact force and overflow. Findings from this study highlight the importance of considering the effects of basal clearance on the design of multiple-barrier systems.

The Effect of the Impact Model on Vibration Response of Discrete and Continuous Systems

2012 ◽  
Author(s):  
M. R. Brake
Keyword(s):  
Constitutive Model ◽  
Coefficient Of Restitution ◽  
Degree Of Freedom ◽  
Impact Dynamics ◽  
Impact Model ◽  
Single Degree Of Freedom ◽  
Elastic Plastic ◽  
Single Degree ◽  
Contact Models ◽  
The Impact

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, the number of elements required to accurately model the constitutive properties of an impact event is impractical. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In order to understand the effect of the impact model on the system’s dynamics, simulations are conducted to investigate a single degree of freedom, two degrees of freedom, and continuous system each with rigid stops limiting the amplitude of vibration. Five contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps show that simplified contact models can lead to incorrect assessments of the system’s dynamics and stability. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system.

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