Evaluation of Impulse Attenuation by Football Helmets in the Frequency Domain

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Nicolas Leiva-Molano ◽  
Robert J. Rolley ◽  
Taylor Lee ◽  
Kevin G. McIver ◽  
Goutham Sankaran ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Head Injuries ◽  
Mechanical Impedance ◽  
Design Parameters ◽  
Impact Loads ◽  
Design Standards ◽  
Impact Location ◽  
Dynamic Impedance ◽  
Grading Systems ◽  
Football Helmets

Abstract Design of helmets used in contact sports has been driven by the necessity of preventing severe head injuries. Manufacturing standards and pass or fail grading systems ensure protective headgear built to withstand large impacts, but design standards do no account for impacts resulting in subconcussive episodes and the effects of cumulative impacts on its user. Thus, it is important to explore new design parameters, such as the frequency-domain measures of transmissibility and mechanical impedance that are based on energy absorption from a range of impact loads. Within the experimentally determined frequency range of interest (FROI), transmissibilities above unity were found in the 0–40 Hz range with the magnitude characteristics varying considerably with impact location. A similar variability with location was observed for the mechanical impedance, which ranged from 9 N/m to 50 N/m. Additional research is required to further understand how changes in the components or materials of the components will affect the performance of helmets, and how they may be used to reduce both transmissibility and dynamic impedance.

scholarly journals Calculation features of wall panels with monolithic cement bond of layers in the stages of installation, transportation and maintenance

Vestnik MGSU ◽  
2019 ◽  
pp. 367-375 ◽  
Author(s):  
Elena A. Korol’ ◽  
Marina N. Berlinova
Keyword(s):  
Middle Layer ◽  
Structural Features ◽  
Design Parameters ◽  
Competitive Advantages ◽  
Design Standards ◽  
Wall Panels ◽  
Multilayer Wall ◽  
Current Design ◽  
Infinite Variety ◽  
Construction Practice

Introduction. When building residential, public and administrative buildings of various spatial structural designs (monolithic, precast-monolithic, precast, etc.), it is common practice to design self-sustaining (non-structural) outer walls within a storey. Developing and using new design and fabrication solutions of multilayer industrial-made wall panels in modern construction practice makes actual the issue of improving methods of their calculation in different stages of maintenance and under various sorts and combinations of loads and effects. However, there is an infinite variety of possible loading levels in practice and, therefore, the same variety of design approaches would be required. This is obviously unacceptable for engineering calculations, hence it is necessary to provide a monolithic matrix bond of layers, both technologically and structurally, which can provide a generalized approach to the calculation of multilayer enclosing structures in accordance with current design standards. Materials and methods. The article describes structural features of a multilayer wall panel made of structural concrete with the middle layer of concrete with low thermal conductivity and monolithic bond of layers. These features have an influence on creation of a design model and a calculation procedure in the stages of transportation, installation and maintenance. Results. The article has examined the structures described above in the sense of design parameters that provide their competitive advantages in strength and maintenance as compared with conventional mass-built enclosures. Conclusions. The studies demonstrate that when combining loads of force and non-force character, stresses in the considered structure do not exceed allowable values in all the stages what proves the prospects of using the multilayer panels with monolithic bond of layers for erection of various-purpose frame-panel buildings.

Dynamic Characteristics Analysis of NuScale in Frequency Domain

2021 ◽  
Author(s):  
Jingrui Yang ◽  
Qian Ma ◽  
Lingtong Han ◽  
Peiwei Sun
Keyword(s):  
Frequency Domain ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Dynamic Characteristics ◽  
Water Desalination ◽  
Design Parameters ◽  
Mechanism Analysis ◽  
Secondary Loop ◽  
Calculation Results

Abstract NuScale is a small nuclear reactor that relies on natural circulation. Its modular production and inherent safety can not only be used to generate electricity in some remote areas, but also provide energy for water desalination and regional heating. However, the dynamic characteristics of the NuScale are different from those of the traditional PWRs because of its passive characteristic. Therefore, it is necessary to study and analyze the system dynamic characteristics of NuScale. The NuScale PWR model is established based on MATLAB&Simulink. It includes point-reactor kinetics model with six groups delayed neutrons, coolant system and steam generator system. The model is established based on the conservation equations of mass, energy and momentum. And the correctness of the model is verified by the comparison between the steady-state calculation results and the design parameters. Transient calculation results are verified by mechanism analysis. To evaluate the dynamic characteristics of NuScale, the sine function changes with different frequencies in reactor reactivity and feedwater mass flow rate are introduced. The amplitude and phase responses of reactor power, secondary loop steam pressure, secondary loop mass flow rate, secondary loop steam temperature, and coolant average temperature are recorded. Then the Bode plot can be drawn with amplitude and phase responses in different frequencies. To evaluate the NuScale dynamic characteristics, frequency domain analysis is performed.

Combat Helmet Design Incorporating Multiple Ballistic Threats, Brain Functional Areas and Injury Considerations

2016 ◽  
Author(s):  
Peter Matic ◽  
Alex E. Moser ◽  
Robert N. Saunders
Keyword(s):  
Head Injury ◽  
Diagnostic Criteria ◽  
Computer Aided Design ◽  
Brain Injuries ◽  
Head Injuries ◽  
Design Parameters ◽  
Head Impacts ◽  
Direct Head ◽  
Back Face ◽  
Helmet Design

Combat helmet protection zone parametric design is presented for small arms and explosive device ballistic threat notional spatial distributions. The analysis is conducted using a computer aided design software application developed to evaluate ballistic threats, helmet design parameters, and a standard set of common brain injuries associated with head impacts. The analysis helps to define the helmet trade space, facilitates prototyping, and supports helmet design optimization. Direct head impacts and helmet impacts, with and without helmet back face contact to the head, are tabulated. Head strikes are assumed to produce critical or fatal penetrating injuries. Helmet back face deflections and impact generated projectile-helmet-head motions are determined. Helmet impact obliquity is accounted for by attenuating back face deflection. Head injury estimates for ten common focal and diffuse head injuries are determined from the back face deflections and the head injury criteria. These, in turn, are related to the abbreviated injury score and associated radiographic dimensional diagnostic criteria and loss of consciousness diagnostic criteria from the trauma literature.

scholarly journals Brain injury in sports

2016 ◽  
Vol 124 (3) ◽  
pp. 667-674 ◽  
Author(s):  
John Lloyd ◽  
Frank Conidi
Keyword(s):  
Brain Injuries ◽  
Scientific Evidence ◽  
Head Injuries ◽  
Skull Fracture ◽  
Angular Acceleration ◽  
Linear Acceleration ◽  
Impact Testing ◽  
Common Belief ◽  
Percentage Reduction ◽  
Football Helmets

OBJECT Helmets are used for sports, military, and transportation to protect against impact forces and associated injuries. The common belief among end users is that the helmet protects the whole head, including the brain. However, current consensus among biomechanists and sports neurologists indicates that helmets do not provide significant protection against concussion and brain injuries. In this paper the authors present existing scientific evidence on the mechanisms underlying traumatic head and brain injuries, along with a biomechanical evaluation of 21 current and retired football helmets. METHODS The National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was modified and validated for impact testing of protective headwear to include the measurement of both linear and angular kinematics. From a drop height of 2.0 m onto a flat steel anvil, each football helmet was impacted 5 times in the occipital area. RESULTS Skull fracture risk was determined for each of the current varsity football helmets by calculating the percentage reduction in linear acceleration relative to a 140-g skull fracture threshold. Risk of subdural hematoma was determined by calculating the percentage reduction in angular acceleration relative to the bridging vein failure threshold, computed as a function of impact duration. Ranking the helmets according to their performance under these criteria, the authors determined that the Schutt Vengeance performed the best overall. CONCLUSIONS The study findings demonstrated that not all football helmets provide equal or adequate protection against either focal head injuries or traumatic brain injuries. In fact, some of the most popular helmets on the field ranked among the worst. While protection is improving, none of the current or retired varsity football helmets can provide absolute protection against brain injuries, including concussions and subdural hematomas. To maximize protection against head and brain injuries for football players of all ages, the authors propose thresholds for all sports helmets based on a peak linear acceleration no greater than 90 g and a peak angular acceleration not exceeding 1700 rad/sec2.

Optimization of Complex Dynamic Systems With Respect to Their Behavior in Time and Frequency Domain

2011 ◽  
Author(s):  
Matthias Marx ◽  
Chunsheng Wei ◽  
Dirk So¨ffker
Keyword(s):  
Frequency Domain ◽  
Dynamic Systems ◽  
Power Flow ◽  
Dynamical Behavior ◽  
Magnetic Bearing ◽  
Rotor System ◽  
Active Magnetic Bearing ◽  
Design Parameters ◽  
Powertrain System ◽  
Aging Mechanisms

This paper describes an integrated optimization process of dynamic systems including design parameters and control algorithms. In contrast to known approaches the developed approach is based on an optimization loop including the evaluation of the dynamical behavior of technical systems with respect to the behavior and related properties in time and frequency domain. This includes as well the behavior of the system, the objective function as the formulation of the restrictions to be considered for the dynamical behavior (stationary and instationary). The proposed approach is declared in detail and will be illustrated using two typical technical applications as examples. The first application example is the optimization of the control system of an active magnetic bearing (AMB) rotor system. Hereby the modeling of the AMB rotor system is briefly introduced. An H∞ controller is designed for the control of the system. The performance both in time and frequency domain is optimized in parallel. The algorithm will be explained by simulation examples. The second example is the optimization of the pow-ermanagement system of a fuel cell/supercap-based hybrid electric powertrain. Hereby the modeling of the electric power flow within the powertrain system is demonstrated and its influence on certain system properties like availability, efficiency, and typical aging mechanisms is discussed. The proposed method leads to near-optimal results in a few steps for both of the systems introduced.

Efficient Dynamic Analysis of a Combined Spar System via a Frequency Domain Approach

2005 ◽  
Author(s):  
Pol D. Spanos ◽  
Rupak Ghosh ◽  
Lyle D. Finn ◽  
Fikry Botros ◽  
John Halkyard
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Alternative Methods ◽  
Design Parameters ◽  
Combined System ◽  
Frequency Dependent ◽  
Equivalent Linear ◽  
Frequency Domain Approach

The response of a combined Spar/ risers/mooring lines system is conventionally determined by conducting nonlinear time domain analysis. The system nonlinearity is introduced by the mooring nonlinear force, the friction between the buoyancy-can and the preloaded compliant guide, and the quadratic model of the fluid related damping. Obviously, during the design process, it is important to understand the sensitivity of the Spar responses to various parameters. To a great extent, these objectives cannot be readily achieved by using time domain analysis since, in this context, elements with frequency dependent representation such as the added masses and supplementary damping must be incorporated in the analysis; this may require the use of elaborate convolution techniques. This attribute of the time domain solution combined with the necessity of running a significant number of simulations makes it desirable to develop alternative methods of analysis. In the present paper, a frequency domain approach based on the method of the statistical linearization is used for conducting readily a parametric study of the combined Spar system. This method allows one to account by an equivalent linear damping and an equivalent linear stiffness for the mooring nonlinearity, friction nonlinearity, and the damping nonlinearity of the system. Further, frequency dependent inertia and radiation damping terms in the equations of motion are accommodated. This formulation leads to a mathematical model for the combined system, which involves five-by-five mass, damping and stiffness matrices. In the solution procedure, the equivalent parameters of the linear system are refined in an iterative manner, and by relying on an optimization criterion. This procedure is used to assess the sensitivity of representative Spar system responses to various design parameters. Further, the effect of various design parameters on the combined system response is examined. The environmental loadings considered are of the JONSWAP format of a 100-yr hurricane in the Gulf of Mexico.

scholarly journals Estimation of Length and Order of Polynomial-based Filter Implemented in the Form of Farrow Structure

2016 ◽  
Vol 6 (4) ◽  
pp. 1099-1102
Author(s):  
S. Vukotic ◽  
D. Babic
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
Frequency Domain ◽  
Digital Signal ◽  
Design Parameters ◽  
Basic Design ◽  
Farrow Structure ◽  
Interpolation Filters ◽  
Two Parameters ◽  
Domain Performance

Digital polynomial-based interpolation filters implemented using the Farrow structure are used in Digital Signal Processing (DSP) to calculate the signal between its discrete samples. The two basic design parameters for these filters are number of polynomial-segments defining the finite length of impulse response, and order of polynomials in each polynomial segment. The complexity of the implementation structure and the frequency domain performance depend on these two parameters. This contribution presents estimation formulae for length and polynomial order of polynomial-based filters for various types of requirements including attenuation in stopband, width of transitions band, deviation in passband, weighting in passband/stopband.

Attachment of a crash-tested traffic barrier to a new bridge deck design in aluminium

2021 ◽  
Author(s):  
Charles-Darwin Annan ◽  
Martin Cormier ◽  
Mario Fafard
Keyword(s):  
Plastic Deformation ◽  
Bridge Deck ◽  
Bridge Decks ◽  
Risk Level ◽  
Impact Loads ◽  
Design Standards ◽  
Performance Levels ◽  
Anchorage System ◽  
Current Design ◽  
Advanced Analysis

<p>Traffic barriers are mounted on bridges to provide a physical impassable limit to redirect errant vehicles safely into the roadway. The desired level of performance is determined by the bridge usage and the roadway configuration; higher performance levels are associated with higher risk level for impact and severity of impact. Current design standards require that the designed traffic barrier and anchorage system be tested under real crash conditions to assure crashworthiness, i.e. satisfactory interaction with design vehicles. Certain modifications to an already crash-tested and approved barrier may be permitted if it can be demonstrated by advanced analysis that they would not adversely affect the designed performance of the barrier. This study seeks to evaluate the design of a connector for attaching an already approved traffic barrier on bridge decks made from welded multi-void aluminium extrusions. The attachment design facilitates installation, and is able to absorb vehicular impact loads without any permanent plastic deformation in the aluminium deck panel.</p>

scholarly journals A Numerical Ice Load Prediction Model Based on Ice-Hull Collision Mechanism

2020 ◽  
Vol 10 (2) ◽  
pp. 692
Author(s):  
Meng Zhang ◽  
Karl Garme ◽  
Magnus Burman ◽  
Li Zhou
Keyword(s):  
Failure Modes ◽  
Impact Load ◽  
Infinite Plate ◽  
Design Parameters ◽  
Load Prediction ◽  
Impact Location ◽  
Crushing Force ◽  
Broken Ice ◽  
Level Ice ◽  
Ice Failure

A simplified numerical model is introduced to predict ice impact force acting on the ship hull in level ice condition. The model is based on ice-hull collision mechanisms and the essential ice breaking characteristics. The two critical ice failure modes, localized crushing and bending breaking, are addressed. An energy method is used to estimate the crushing force and the indentation displacement for different geometry schemes of ice-ship interaction. Ice bending breaking scenario is taken as a semi-infinite plate under a distributed load resting on an elastic foundation. An integrated complete ice-hull impact event is introduced with ice failure modes and breaking patterns. Impact location randomness and number of broken ice wedges are considered in order to establish a stochastic model. The analysis is validated by comparison with the model ice test of a shuttle passenger ferry performed in May 2017 for SSPA Sweden AB at Aker Arctic Technology Inc. Good agreement is achieved with appropriate parameter selection assumed from the model test and when ice bending failure is dominant. This model can be used to predict the ice impact load and creates a bridge between design parameters (ice properties and ship geometry) and structure loads.

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