Compressive Behavior of a Polyurea Elastomer

2014 ◽  
Vol 900 ◽  
pp. 7-10
Author(s):  
Fabrizia Ghezzo ◽  
Xi Geng Miao ◽  
Chun Lin Ji ◽  
Ruo Peng Liu
Keyword(s):  
Material Behavior ◽  
Loading Conditions ◽  
Test Results ◽  
Metallic Structures ◽  
Compression Load ◽  
Existing Structures ◽  
The Past ◽  
Severe Shock ◽  
The Impact ◽  
Impact Events

The application of elastomeric coatings for improving the ability of already existing structures to dissipate the energy released by impact events has been investigated by many researchers in the past decade and is today an area of considerable interest. In recent years, polyurea has been successfully applied as a coating material for enhancing the impact protection of buildings and it has also demonstrated a considerable improvement of the survivability of metallic and non-metallic structures subjected to severe shock and impact loading conditions. Given its remarkable properties in terms of impact energy mitigation, life endurance and corrosion resistance, this material is currently of interest for its application in many fields of engineering. This paper presents and discusses the results of the mechanical characterization conducted on a polyurea elastomer fabricated following two different procedures and subjected to varying strain rates of compression load. The tests were conducted to verify the sensitivity of the material behavior to the varying loading conditions and to verify how the fabrication of the material in the laboratory can influence the test results.

Distribution of Brain Strain in the Cerebrum for Laboratory Impacts to Ice Hockey Goaltender Masks

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
J. Michio Clark ◽  
Andrew Post ◽  
T. Blaine Hoshizaki ◽  
Michael D. Gilchrist
Keyword(s):  
Brain Regions ◽  
Ice Hockey ◽  
Tissue Response ◽  
Loading Conditions ◽  
Impact Site ◽  
Trauma Model ◽  
The University ◽  
The Impact ◽  
Impact Events ◽  
The Brain

Concussions are among the most common injuries sustained by goaltenders. Concussive injuries are characterized by impairment to neurological function which can affect many different brain regions. Understanding how different impact loading conditions (event type and impact site) affect the brain tissue response may help identify what kind of impacts create a high risk of injury to specific brain regions. The purpose of this study was to examine the influence of different impact conditions on the distribution of brain strain for ice hockey goaltender impacts. An instrumented headform was fitted with an ice hockey goaltender mask and impacted under a protocol which was developed using video analysis of real world ice hockey goaltender concussions for three different impact events (collision, puck, and fall). The resulting kinematic response served as input into the University College Dublin Brain Trauma Model (UCDBTM), which calculated maximum principal strain (MPS) in the cerebrum. Strain subsets were then determined and analyzed. Resulting peak strains (0.124–0.328) were found to be within the range for concussion reported in the literature. The results demonstrated that falls and collisions produced larger strain subsets in the cerebrum than puck impacts which is likely a reflection of longer impact duration for falls and collisions than puck impacts. For each impact event, impact site was also found to produce strain subsets of varying size and configuration. The results of this study suggest that the location and number of brain regions which can be damaged depend on the loading conditions of the impact.

scholarly journals Impact of the Loading Conditions and the Building Directions on the Mechanical Behavior of Biomedical β-Titanium Alloy Produced In Situ by Laser-Based Powder Bed Fusion

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 509
Author(s):  
Housseme Ben Boubaker ◽  
Pascal Laheurte ◽  
Gael Le Coz ◽  
Seyyed-Saeid Biriaie ◽  
Paul Didier ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Electron Backscatter Diffraction ◽  
Material Behavior ◽  
Powder Bed Fusion ◽  
Loading Conditions ◽  
Compression Tests ◽  
Powder Bed ◽  
X Ray ◽  
The Impact

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of β-Ti42Nb alloy. Compression tests are performed under two strain rates (1 s−1 and 10 s−1) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45∘ exhibit higher flow stress than those produced with a building direction of 90∘, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV0.1. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.

Numerical Investigation of a Ship Collision With Waterway Embankments

2010 ◽  
Author(s):  
Gang Qiu ◽  
Ju¨rgen Grabe
Keyword(s):  
Reaction Force ◽  
Fe Model ◽  
Test Results ◽  
Bridge Abutments ◽  
Inland Waterways ◽  
Existing Structures ◽  
Stopping Distance ◽  
Parametric Studies ◽  
Collision Force ◽  
The Impact

During the last century there has been an increase in frequency of ships colliding with waterway embankments of inland waterways. The increasing occurrence of shipping accidents threatens the safety of freights and the serviceability of existing structures, such as tunnel and bridge abutments which are located near embankments. It is necessary to develop a method enabling prediction of the collision force and the stopping distance of a collision ship. In the related project “Hochdonn” of BAW (Federal Waterways Engineering and Research Institute, Germany) collision experiments were performed to analyze the impact mechanisms in grounding problems. A 3D FE model using a Coupled Eulerian Lagrangian approach is used to recalculate the collision experiment of BAW with the test ship “Gerda”. The stopping distance and the reaction force that are indicated by the numerical simulation match the field test results very closely. In addition two parametric studies are undertaken to quantify the influences on the collision process from the initial velocity as well as the bow type of the ship.

A Fully Nonlinear RANS-VOF Numerical Wavetank Applied in the Analysis of Green Water on FPSO in Waves

2014 ◽  
Author(s):  
Anders Östman ◽  
Csaba Pakozdi ◽  
Lucia Sileo ◽  
Carl-Trygve Stansberg ◽  
Daniel Fonseca de Carvalho e Silva
Keyword(s):  
Model Test ◽  
Parametric Design ◽  
Green Water ◽  
Test Results ◽  
Wave Impact ◽  
Measured Time ◽  
Time Histories ◽  
Practical Tool ◽  
The Impact ◽  
Impact Events

This paper presents numerical simulations of Green Water events and wave impact on a FPSO. The simulations are performed at model scale and the results are compared against experimental model test results. The commercial Star-CCM+ CFD software is used in the simulations. The incoming waves are modeled using 5th order Stokes theory, as implemented in the CFD software. Both fixed and free floating FPSO are considered. The moving FPSO are modeled using Chimera overset mesh technology. The vessels is free to move in heave and pitch at 180 (head sea), roll and heave at 270 (beam sea), while roll, pitch and heave is released at 225 (quartering sea). The computed water height on the deck and the relative wave height in vicinity the vessel are compared against model test results at several positions. Also the impact force on load cells blocks located at the deck of the vessel is computed and compared against model test results. The comparison of the time histories of the water elevation and load histories are in reasonable agreement with the measured time series. The number of grid cells range from 7M for the simulations at head sea, where flow is assumed to be symmetric, to 21M for the simulations at quartering sea. Total wall clock simulation time was about 10days for the most computationally demanding cases, which are the quartering sea simulations. This includes simulation of 12 wave periods with the ship fixed, and thereafter 8 wave periods of the free floating vessel. The computations show that CFD tools can be used as a research tool when studying the physics of green water and wave impact events. However, due to time CPU demanding simulations, this type of CFD analysis are not yet a practical tool for parametric design studies and deck structure optimizations. This work is a part of the research project “Green Water and Wave Impact on FPSO” carried out for and in cooperation with PETROBRAS.

Fluorescent potentiometric dyes for membrane-potential imaging

1994 ◽  
Vol 52 ◽  
pp. 166-167
Author(s):  
Leslie M. Loew
Keyword(s):  
Membrane Potential ◽  
Single Cells ◽  
Quantitative Imaging ◽  
Optical Recording ◽  
Biological Processes ◽  
Major Focus ◽  
The Past ◽  
Excitable Systems ◽  
Major Application ◽  
The Impact

A major application of potentiometric dyes has been the multisite optical recording of electrical activity in excitable systems. After being championed by L.B. Cohen and his colleagues for the past 20 years, the impact of this technology is rapidly being felt and is spreading to an increasing number of neuroscience laboratories. A second class of experiments involves using dyes to image membrane potential distributions in single cells by digital imaging microscopy - a major focus of this lab. These studies usually do not require the temporal resolution of multisite optical recording, being primarily focussed on slow cell biological processes, and therefore can achieve much higher spatial resolution. We have developed 2 methods for quantitative imaging of membrane potential. One method uses dual wavelength imaging of membrane-staining dyes and the other uses quantitative 3D imaging of a fluorescent lipophilic cation; the dyes used in each case were synthesized for this purpose in this laboratory.

Perceived Burden of Informal Caregivers of a Chronically Ill Older Family Member

GeroPsych ◽  
2011 ◽  
Vol 24 (3) ◽  
pp. 143-154 ◽  
Author(s):  
Elmar Gräßel ◽  
Raffaela Adabbo
Keyword(s):  
Family Member ◽  
Informal Caregiver ◽  
Chronically Ill ◽  
Stress Model ◽  
The Past ◽  
Perceived Burden ◽  
Hypothetical Construct ◽  
Care Situation ◽  
The Impact ◽  
Further Development

The burden of caregivers has been intensively researched for the past 30 years and has resulted in a multitude of individual findings. This review illustrates the significance of the hypothetical construct of perceived burden for the further development and design of the homecare situation. Following explanations regarding the term informal caregiver, we derive the construct burden from its conceptual association with the transactional stress model of Lazarus and Folkman. Once the extent and characteristics of burden have been set forth, we then present the impact of perceived burden as the care situation. The question of predictors of burden will lead into the last section from which implications can be derived for homecare and relief of caregivers.

Soziale Disziplinierung im flexiblen Kapitalismus

2004 ◽  
Vol 34 (136) ◽  
pp. 339-356
Author(s):  
Tobias Wölfle ◽  
Oliver Schöller
Keyword(s):  
Social Welfare ◽  
Second Step ◽  
Social Rights ◽  
Federal Law ◽  
Capitalist Development ◽  
The Core ◽  
The Past ◽  
The Impact ◽  
Municipal Level

Under the term “Hilfe zur Arbeit” (aid for work) the federal law of social welfare subsumes all kinds of labour disciplining instruments. First, the paper shows the historical connection of welfare and labour disciplining mechanisms in the context of different periods within capitalist development. In a second step, against the background of historical experiences, we will analyse the trends of “Hilfe zur Arbeit” during the past two decades. It will be shown that by the rise of unemployment, the impact of labour disciplining aspects of “Hilfe zur Arbeit” has increased both on the federal and on the municipal level. For this reason the leverage of the liberal paradigm would take place even in the core of social rights.

Regulatory and sustainability initiatives lead to improved polyaminopolyamide epichlorohydrin (PAE) wet-strength resins and paper products

TAPPI Journal ◽  
2018 ◽  
Vol 17 (09) ◽  
pp. 519-532 ◽  
Author(s):  
Mark Crisp ◽  
Richard Riehle
Keyword(s):  
Health And Safety ◽  
Cost Effective ◽  
Worker Safety ◽  
Regulatory Requirements ◽  
Wet Strength ◽  
The Past ◽  
Consumer Safety ◽  
Federal Institute ◽  
Sustainability Initiatives ◽  
The Impact

Polyaminopolyamide-epichlorohydrin (PAE) resins are the predominant commercial products used to manufacture wet-strengthened paper products for grades requiring wet-strength permanence. Since their development in the late 1950s, the first generation (G1) resins have proven to be one of the most cost-effective technologies available to provide wet strength to paper. Throughout the past three decades, regulatory directives and sustainability initiatives from various organizations have driven the development of cleaner and safer PAE resins and paper products. Early efforts in this area focused on improving worker safety and reducing the impact of PAE resins on the environment. These efforts led to the development of resins containing significantly reduced levels of 1,3-dichloro-2-propanol (1,3-DCP) and 3-monochloropropane-1,2-diol (3-MCPD), potentially carcinogenic byproducts formed during the manufacturing process of PAE resins. As the levels of these byproducts decreased, the environmental, health, and safety (EH&S) profile of PAE resins and paper products improved. Recent initiatives from major retailers are focusing on product ingredient transparency and quality, thus encouraging the development of safer product formulations while maintaining performance. PAE resin research over the past 20 years has been directed toward regulatory requirements to improve consumer safety and minimize exposure to potentially carcinogenic materials found in various paper products. One of the best known regulatory requirements is the recommendations of the German Federal Institute for Risk Assessment (BfR), which defines the levels of 1,3-DCP and 3-MCPD that can be extracted by water from various food contact grades of paper. These criteria led to the development of third generation (G3) products that contain very low levels of 1,3-DCP (typically <10 parts per million in the as-received/delivered resin). This paper outlines the PAE resin chemical contributors to adsorbable organic halogens and 3-MCPD in paper and provides recommendations for the use of each PAE resin product generation (G1, G1.5, G2, G2.5, and G3).

Overseas Development Administration. A Guide to Social Analysis for Projects in Developing Countries. London: HMSO. 1995. viii+248 pages. Hardbound. £18.95.

1996 ◽  
Vol 35 (2) ◽  
pp. 189-190
Author(s):  
Mir Annice Mahmood
Keyword(s):  
Developing Countries ◽  
Social Change ◽  
Practical Experience ◽  
Development Projects ◽  
Social Analysis ◽  
Economic Perspective ◽  
Human Environment ◽  
The Past ◽  
The Impact ◽  
Overseas Development

This book, hereinafter referred to as the Guide, has been developed for those social analysts (e.g., anthropologists, sociologists, and human geographers) who have had little or no practical experience in applying their knowledge as development practitioners. In the past, development projects would be analysed from a narrow financial and economic perspective. But with the evolution of thinking on development, this narrow financial and economic aspect has now been broadened to include the impact on society as the very meaning of development has now come to symbolise social change. Thus, development is not restricted only to plans and figures; the human environment in its entirety is now considered for analysis while designing and implementing development projects.

The Impact of War on Population Health

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Turkan Ahmet
Keyword(s):  
Health Care ◽  
Health Status ◽  
Health Care Services ◽  
Negative Effects ◽  
The Past ◽  
Care Services ◽  
Physical Environments ◽  
The Social ◽  
Personal Experiences ◽  
The Impact

The past few decades of ongoing war in Iraq has had a dramatic impact on the health of Iraq’s population. Wars are known to have negative effects on the social and physical environments of individuals, as well as limit their access to the available health care services. This paper explores the personal experiences of my family members, who were exposed to war, as well as includes information that has been reviewed form many academic sources. The data aided in providing recommendations and developing strategies, on both local and international levels, to improve the health status of the populations exposed to war.

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