Polymer Modulus of Elasticity and Hardness From Impact Data

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Hany A. Sherif ◽  
Fahad A. Almufadi
Keyword(s):  
Modulus Of Elasticity ◽  
Complex Modulus ◽  
Polymeric Materials ◽  
Time Duration ◽  
Simple Method ◽  
Normal Contact ◽  
Adopted Model ◽  
Force Time ◽  
Impact Data ◽  
The Impact

The present paper introduces a simple method to predict the modulus of elasticity and the hardness of polymeric materials that range from soft elastomers to hard plastics. Hertzian elastic impact model is used to define the relationship between the contact time duration and the maximum force of normal contact due to the impact of a hard sphere indenter with the tested polymer sample. It is shown that the adopted model and experimental method can be used as a tool for extracting the magnitude of the complex modulus of elasticity. Moreover, a new impact index is shown to be proportional to the polymer shore hardness. Theoretical and experimental results based on the force–time signals are consistent and show good correlation.

Models for Materials Damping, Loss Factor, and Coefficient of Restitution

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Hany A. Sherif ◽  
Fahad. A. Almufadi
Keyword(s):  
Loss Factor ◽  
Polymeric Materials ◽  
Theoretical Models ◽  
Coefficient Of Restitution ◽  
Complex Model ◽  
Damping Coefficient ◽  
Damping Factor ◽  
Simple Method ◽  
Adopted Model ◽  
The Impact

Common parameters between metallic and polymeric materials are the coefficient of restitution, the damping coefficient, and loss factor. Although the relationship between the coefficient of restitution and the loss factor is quite direct, their dependence on the damping coefficient is not so simple and mainly affected by the adopted model used to describe the material response under impact. In the present study, Kelvin–Voigt linear model and Hunt–Crossley complex model are analyzed to describe how the coefficient of restitution depends on the viscous damping coefficient of impact. The correlation between the theoretical models and the experimental data is also shown. A simple method to predict the impact damping factor of both polymeric and metallic materials from the measured temporal signal of the impact force is demonstrated.

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

scholarly journals Reciprocal hemizygosity analysis reveals that the Saccharomyces cerevisiae CGI121 gene affects lag time duration in synthetic grape must

2021 ◽  
Author(s):  
Runze Li ◽  
Rebecca C Deed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperatures ◽  
Lag Time ◽  
Lag Phase ◽  
Phenotypic Traits ◽  
Time Duration ◽  
Phase Duration ◽  
Grape Must ◽  
The Impact ◽  
Reciprocal Hemizygosity Analysis

Abstract It is standard practice to ferment white wines at low temperatures (10-18 °C). However, low temperatures increase fermentation duration and risk of problem ferments, leading to significant costs. The lag duration at fermentation initiation is heavily impacted by temperature; therefore, identification of Saccharomyces cerevisiae genes influencing fermentation kinetics is of interest for winemaking. We selected 28 S. cerevisiae BY4743 single deletants, from a prior list of open reading frames (ORFs) mapped to quantitative trait loci (QTLs) on chromosomes VII and XIII, influencing the duration of fermentative lag time. Five BY4743 deletants, Δapt1, Δcgi121, Δclb6, Δrps17a, and Δvma21, differed significantly in their fermentative lag duration compared to BY4743 in synthetic grape must (SGM) at 15 °C, over 72 h. Fermentation at 12.5 °C for 528 h confirmed the longer lag times of BY4743 Δcgi121, Δrps17a, and Δvma21. These three candidate ORFs were deleted in S. cerevisiae RM11-1a and S288C to perform single reciprocal hemizygosity analysis (RHA). RHA hybrids and single deletants of RM11-1a and S288C were fermented at 12.5 °C in SGM and lag time measurements confirmed that the S288C allele of CGI121 on chromosome XIII, encoding a component of the EKC/KEOPS complex, increased fermentative lag phase duration. Nucleotide sequences of RM11-1a and S288C CGI121 alleles differed by only one synonymous nucleotide, suggesting that intron splicing, codon bias, or positional effects might be responsible for the impact on lag phase duration. This research demonstrates a new role of CGI121 and highlights the applicability of QTL analysis for investigating complex phenotypic traits in yeast.

scholarly journals Assessing an Atmospheric Correction Algorithm for Time Series of Satellite-Based Water-Leaving Reflectance Using Match-Up Sites in Australian Coastal Waters

2021 ◽  
Vol 13 (10) ◽  
pp. 1927
Author(s):  
Fuqin Li ◽  
David Jupp ◽  
Thomas Schroeder ◽  
Stephen Sagar ◽  
Joshua Sixsmith ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Atmospheric Correction ◽  
Correction Method ◽  
In Situ Measurements ◽  
Landsat 8 ◽  
Correction Algorithm ◽  
Simple Method ◽  
North East ◽  
The Impact

An atmospheric correction algorithm for medium-resolution satellite data over general water surfaces (open/coastal, estuarine and inland waters) has been assessed in Australian coastal waters. In situ measurements at four match-up sites were used with 21 Landsat 8 images acquired between 2014 and 2017. Three aerosol sources (AERONET, MODIS ocean aerosol and climatology) were used to test the impact of the selection of aerosol optical depth (AOD) and Ångström coefficient on the retrieved accuracy. The initial results showed that the satellite-derived water-leaving reflectance can have good agreement with the in situ measurements, provided that the sun glint is handled effectively. Although the AERONET aerosol data performed best, the contemporary satellite-derived aerosol information from MODIS or an aerosol climatology could also be as effective, and should be assessed with further in situ measurements. Two sun glint correction strategies were assessed for their ability to remove the glint bias. The most successful one used the average of two shortwave infrared (SWIR) bands to represent sun glint and subtracted it from each band. Using this sun glint correction method, the mean all-band error of the retrieved water-leaving reflectance at the Lucinda Jetty Coastal Observatory (LJCO) in north east Australia was close to 4% and unbiased over 14 acquisitions. A persistent bias in the other strategy was likely due to the sky radiance being non-uniform for the selected images. In regard to future options for an operational sun glint correction, the simple method may be sufficient for clear skies until a physically based method has been established.

scholarly journals Analysis of the Viscoelastic Sphere Impact against a Viscoelastic Uflyand-Mindlin Plate considering the Extension of Its Middle Surface

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Yury A. Rossikhin ◽  
Marina V. Shitikova ◽  
Phan Thanh Trung
Keyword(s):  
Contact Force ◽  
Middle Surface ◽  
Hertzian Contact ◽  
Mindlin Plate ◽  
Strong Discontinuity ◽  
Time Duration ◽  
Suggested Approach ◽  
Viscoelastic Sphere ◽  
The Impact ◽  
Contact Domain

In the present paper, the problem on impact of a viscoelastic sphere against a viscoelastic plate is considered with due account for the extension of plate’s middle surface and local bearing of sphere and plate’s materials via the Hertz theory. The standard linear solid models with conventional derivatives and with fractional-order derivatives are used as viscoelastic models, respectively, outside and within the contact domain. As a result of impact, transient waves (surfaces of strong discontinuity) are generated in the plate, behind the wave fronts of which up to the boundaries of the contact domain the solution is constructed in terms of one-term ray expansions due to short-time duration of the impact process. The motion of the contact zone occurs under the action of extension forces acting in the plate’s middle surface, transverse force, and the Hertzian contact force. The suggested approach allows one to find the time-dependence of the impactor’s indentation into the target and the Hertzian contact force.

Nitrification preservation in activated sludge during curative bulking chlorination

2003 ◽  
Vol 47 (11) ◽  
pp. 85-92 ◽  
Author(s):  
E. Cotteux ◽  
P. Duchene
Keyword(s):  
Activated Sludge ◽  
Pilot Plant ◽  
Wastewater Treatment Plants ◽  
Oxygen Uptake Rate ◽  
Ammonia Concentration ◽  
Synthetic Wastewater ◽  
Biological Wastewater Treatment ◽  
Simple Method ◽  
Method Of Measurement ◽  
The Impact

The bulking that occurs in biological wastewater treatment plants using activated sludge is very often controlled by the injection of sodium hypochlorite into the return activated sludge (RAS) stream. In the present study undertaken at two pilot plants fed with synthetic wastewater, the impact of the pass frequency of the sludge at the chlorine dosing point on the nitrifying flora is analysed. The pass frequency is one for the pilot plant 1 and two for the pilot plant 2. A dose of chlorine of 4.85 ± 0.05 g/kg/MLVSS per day was applied at both pilots. The preservative effect on nitrifying activity of the lowest concentration of chlorine at the dosing point and therefore of the highest pass frequency was evidenced. Among other tools, a simple method of measurement of the oxygen uptake rate enabled us to monitor the effect of chlorination on nitrification before recording an increase in the ammonia concentration in the bulking.

Steady Magnetohydrodynamic Micropolar Casson Fluid of Brownian Motion Over a Solid Sphere with Thermophoretic and Buoyancy Forces: Numerical Analysis

2020 ◽  
Vol 9 (4) ◽  
pp. 336-345
Author(s):  
Silpi Hazarika ◽  
Sahin Ahmed
Keyword(s):  
Brownian Motion ◽  
Buoyancy Force ◽  
Power Plants ◽  
Thermal Flux ◽  
Solid Sphere ◽  
Casson Fluid ◽  
Similarity Solutions ◽  
Surface Drag ◽  
Adopted Model ◽  
The Impact

The impact of heat transfer in micropolar fluid may be developed due to its various promising applications in engineering, bio-medical sciences, geo-thermal progression, spherical storage tanks, nuclear power plants, automobile sectors etc. Motivated by such significance, the current study is to expound the influences of micropolar Casson fluid flow over a solid sphere with Brownian motion, thermophoretic force and buoyancy force surrounded by porous medium. The adopted model having complex PDE’s are reduced to dimensionless ODE’s by utilizing proper similarity solutions. A numerical approach have been carried out for velocity, micro rotation, temperature and concentration, the solutions are procured by Matlab Bvp4c code and plotted graphs for diverse involved parameters. An adequate result is acquired by an assessment with earlier available work. The effects of key parameters on surface drag coefficient, surface thermal flux and particles concentration flux are examined and displayed in tabular form. Grash of number raises the profiles of thermal flux and concentration flux where the buoyancy force is more dominant. Further, the obtained results indicate that the angular velocity is elevated near the surface of the sphere, and they behaves asymptotically far away from the surface due to the effect of micropolar parameter. Moreover, temperature and molar species concentration are enriched with upper values of micropolar factor. It is perceived that, augmented values of Casson parameter amplifies the velocity outline.

The Impact of Video Speed on the Estimation of Time Duration in Sport

2021 ◽  
pp. 1-11
Author(s):  
Lisa-Marie Schütz ◽  
Geoffrey Schweizer ◽  
Henning Plessner
Keyword(s):  
Real Time ◽  
Time Estimation ◽  
Slow Motion ◽  
Sport Performance ◽  
Time Duration ◽  
Video Presentation ◽  
Sporting Activities ◽  
The Impact ◽  
Estimation Of Time

The authors investigated the impact of video speed on judging the duration of sport performance. In three experiments, they investigated whether the speed of video presentation (slow motion vs. real time) has an influence on the accuracy of time estimation of sporting activities (n1 = 103; n2 = 100; n3 = 106). In all three studies, the time estimation was more accurate in real time than in slow motion, in which time was overestimated. In two studies, the authors initially investigated whether actions in slow motion are perceived to last longer because the distance they cycled or ran is perceived to be longer (n4 = 92; n5 = 106). The results support the hypothesis that the duration of sporting activities is estimated more accurately when they are presented in real time than in slow motion. Sporting officials’ judgments that require accurate time estimation may thus be biased when based on slow-motion displays.

Analysis of Externalities of Economic Activity of the Enterprise

2021 ◽  
Vol 2021 (2) ◽  
pp. 86-94
Author(s):  
Dmytro V. Kozlov
Keyword(s):  
Transaction Costs ◽  
Economic Activity ◽  
Environmental Externalities ◽  
Negative Externalities ◽  
Time Duration ◽  
Marginal Costs ◽  
Positive Externalities ◽  
State And Market ◽  
The Impact

The problems of research of internalities and externalities with the further development of the general classification of externalities of economic activity of the enterprise are defined. The influence of negative and positive externalities on society and enterprise is considered. The concept of negative externalities differs from transaction costs. It is noted that transaction costs can be reflected in cash and can be offset by market inclusion in the price of the products, but this is not possible for externalities. It is emphasized that the purpose of economic activity of any enterprise is to exceed the positive externalities over the negative and achieve the maximum difference between them. The different time duration of the impact of the enterprise on third parties is given. The sign of externalities on the scale of action is emphasized. The externalities of the enterprise are considered in their essence according to the principles of sustainable development, highlighting economic, social and environmental externalities. It is emphasized that economic externalities can arise in the course of the whole business cycle of full-fledged work of all parts of the enterprise. In contrast to economic, social externalities affect people both within the enterprise, that is workers and citizens of the society in which the enterprise operates. And when it comes to environmental externalities, the mediator between the source and recipient of externalities is the environment. Externalities are distinguished according to the means of accounting and the degree of influence on the subject of perception. The necessity of regulation of externalities through internalization and actions of the enterprise with the help of state and market instruments is substantiated. It is emphasized that internalization is the transformation of negative externalities into positive ones in terms of convergence of marginal costs and benefits of the enterprise to marginal social costs and utility.

scholarly journals A Comprehensive Set of Impact Data for Common Aerospace Metals

2017 ◽  
Vol 12 (6) ◽  
Author(s):  
M. R. W. Brake ◽  
P. L. Reu ◽  
D. S. Aragon
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Model Development ◽  
Coefficient Of Restitution ◽  
Image Correlation ◽  
Plastic Behavior ◽  
Data Set ◽  
Force Resolution ◽  
Impact Data ◽  
The Impact

The results of two sets of impact experiments are reported within. To assist with model development using the impact data reported, the materials are mechanically characterized using a series of standard experiments. The first set of impact data comes from a series of coefficient of restitution (COR) experiments, in which a 2 m long pendulum is used to study “in-context” measurements of the coefficient of restitution for eight different materials (6061-T6 aluminum, phosphor bronze alloy 510, Hiperco, nitronic 60A, stainless steel 304, titanium, copper, and annealed copper). The coefficient of restitution is measured via two different techniques: digital image correlation (DIC) and laser Doppler vibrometry (LDV). Due to the strong agreement of the two different methods, only results from the digital image correlation are reported. The coefficient of restitution experiments are in context as the scales of the geometry and impact velocities are representative of common features in the motivating application for this research. Finally, a series of compliance measurements are detailed for the same set of materials. The compliance measurements are conducted using both nano-indentation and micro-indentation machines, providing sub-nm displacement resolution and μN force resolution. Good agreement is seen for load levels spanned by both machines. As the transition from elastic to plastic behavior occurs at contact displacements on the order of 30 nm, this data set provides a unique insight into the transitionary region.

Sign in / Sign up

Export Citation Format

Share Document