Assessment of NCHRP Report 350 Test Conditions

2002 ◽  
Vol 1797 (1) ◽  
pp. 38-43 ◽  
Author(s):  
King K. Mak ◽  
Roger P. Bligh
Keyword(s):  
Policy Decision ◽  
Impact Angle ◽  
Impact Speed ◽  
Current Test ◽  
Test Conditions ◽  
Level 3 ◽  
Current Impact ◽  
Areas Of Interest ◽  
The Impact ◽  
Test Impact

The appropriateness of test conditions specified in NCHRP Report 350 was assessed. The assessment focused on the basic Test Level 3 and addressed two areas of interest: the effects of higher speed limit on impact speed and the appropriateness of 25° for the impact angle. The following conclusions and recommendations were drawn on the basis of the results of the analysis: ( a) the current test impact speed of 100 km/h (62.2 mph) should be maintained, ( b) the current impact angle of 25° for Test 11 of length-of-need sections of permanent longitudinal barriers should be maintained, ( c) the test impact angle should be reduced from 25° to 20° for Test 11 of length-of-need sections of temporary longitudinal barriers, and ( d) the test impact angle should be reduced from 25° to 20° for Test 21 of barrier transition sections. However, the selection of impact conditions is more a policy decision than a technical issue to be resolved in the update of NCHRP Report 350 guidelines.

Numerical Investigation of the Damage Evolution in Vibration Assisted Nano Impact Machining by Loose Abrasives With Different Operating Parameters

2018 ◽  
Author(s):  
Nick H. Duong ◽  
J. Ma ◽  
Shuting Lei
Keyword(s):  
Material Removal ◽  
Frictional Coefficient ◽  
Material Model ◽  
Impact Angle ◽  
Ductile Material ◽  
Nanoscale Material ◽  
Impact Speed ◽  
Atomic Force ◽  
Afm Probe ◽  
The Impact

In this paper, the commercial FEM software package Abaqus is employed to model a novel nanomachining process, in which an atomic force microscope (AFM) is used as a platform and the nano abrasives injected in slurry between the workpiece and the vibrating AFM probe impact the workpiece and result in nanoscale material removal. Diamond particles are used as loose abrasives. The ductile material model is used to describe the behavior of the silicon workpiece. The effects of impact speed, impact angle, and the frictional coefficient between the workpiece and abrasives on material removal mechanism are investigated. It is found that the impact speed, impact angle, and frictional coefficient between the silicon workpiece and nanoabrasives have big influence on material removal volume in this novel nanomachining process.

A study on the frontal oblique collision-induced derailment mechanism in subway vehicles

2019 ◽  
Vol 234 (6) ◽  
pp. 584-595
Author(s):  
Shuguang Yao ◽  
Huifen Zhu ◽  
Mingyang Liu ◽  
Zhixiang Li ◽  
Ping Xu ◽  
...  
Keyword(s):  
Lateral Displacement ◽  
Element Model ◽  
Vertical Displacement ◽  
Rigid Wall ◽  
Impact Angle ◽  
Oblique Impact ◽  
Oblique Collision ◽  
Impact Speed ◽  
Vertical Displacements ◽  
The Impact

Oblique collisions can more easily lead to train derailment and cause heavy casualties. In this paper, a fine finite-element model of a subway head vehicle–rigid wall frontal oblique collision was established and validated by a single wheelset derailment simulation. Furthermore, the derailment mechanisms and patterns under an oblique impact angle of 6.34°–40° and at an impact speed of 8–40 km/h were studied via simulation. The results indicated that three types of derailment, such as roll-over derailment, climb/roll-over derailment and wheel-lift derailment, have occurred. When the impact speed was set to 25 km/h, a climb/roll-over derailment occurred under the impact angle of greater than 40°; a roll-over derailment occurred under the impact angle of 20°–40°; and the vehicle would not derail when the impact angle was less than 15°. When the impact angle was 6.34°, the vehicle was in danger of wheel-lift derailment with the largest wheel vertical displacement of 26.83 mm and lateral displacement of 12.52 mm under the impact speed of 40 km/h, but it was safe with the largest displacement of no more than 18 mm and lateral displacement of 8.39 mm if the impact speed was less than 40 km/h. It is shown that the derailment patterns are more sensitive to the impact angle. Therefore, both the lateral and vertical displacements should be considered when studying the oblique collision-induced derailment mechanisms and patterns.

Enhanced MASH TL-3 Short-Radius System: Promising Design to Accommodate Flat Terrain and Ditches

2018 ◽  
Vol 2672 (39) ◽  
pp. 155-165
Author(s):  
Akram Y. Abu-Odeh ◽  
Roger P. Bligh ◽  
Christopher Lindsey ◽  
Wade Odell
Keyword(s):  
Impact Angle ◽  
Roadside Safety ◽  
Flat Terrain ◽  
Crash Testing ◽  
Geometrical Constraints ◽  
Level 3 ◽  
Curved Section ◽  
National Cooperative ◽  
The Impact ◽  
Crash Tests

A challenging guardrail installation situation presents itself when two roadways intersect. Combining the guardrails from intersecting roadway results in what is commonly known as a short radius or T-intersection. It is difficult if not physically impossible to provide the required tensile capacity to the geometrical constraints of the curved section. Researchers and practitioners in the roadside safety area have been investigating the short-radius issue for many years. Investigators conducted numerous crash tests for different short-radius guardrail designs, yet none of those designs passed the National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 3 (TL-3) criteria. In 2009, the crash testing guidelines were updated in the Manual for Assessing Safety Hardware (MASH). MASH guidelines increased the impact severity for TL-3 tests over those in NCHRP 350. This paper presents a MASH TL-3 short-radius design that was successfully crash tested for both a flat terrain and a 3H:1V sloped terrain behind the installation. The impact conditions adopted from the MASH terminal/crash cushion matrix were MASH 3-33, 3-32, 3-31, and 3-35 for the flat terrain. Additionally, a slightly modified design that was installed in front of a 3H:1V slope was successfully evaluated using MASH 3-33 and 3-32 test conditions. These tests used a 25° impact angle since it was shown to be more critical for installation during simulation of the system.

scholarly journals Neck Moment Characterization of Restrained Child Occupant at Realistic Nontest Standard Higher Impact Speed of 32.2 km/h

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
S. Shasthri ◽  
V. Kausalyah ◽  
Qasim H. Shah ◽  
Kassim A. Abdullah ◽  
Moumen M. Idres ◽  
...  
Keyword(s):  
Interactive Effect ◽  
Impact Angle ◽  
Side Impact ◽  
Impact Speed ◽  
Child Restraint ◽  
Child Restraint System ◽  
Impact Angles ◽  
Child Occupant ◽  
The Impact

The effects of bullet vehicle crash impact angle, child restraint system design, and restraint harness slack at side impact speed of 32.2 km/h (20 mph) on moments sustained at the neck by a three-year-old child are investigated. Mathematical models are built using the response surface method based on simulation results whereby good fitness is achieved. The singular and cross interactive effect of each predictor on the neck moment are analyzed. The number of significant parameters affecting the neck moment is shown to be the largest for wide impact angles (ϕ≥60°) and the impact angle parameter is largely revealed to be the most sensitive. An ideal safe range for low neck moment has been established to be within ϕ angles 45° and 65°. It is further shown that the nature of all parameters effect on the neck moment is highly dependent on the impact angle range.

FEM Investigation of Phase Transformation in Vibration Assisted Nano Impact Machining by Loose Abrasives (VANILA)

2018 ◽  
Author(s):  
Nick H. Duong ◽  
J. Ma ◽  
Muhammad P. Jahan ◽  
Shuting Lei ◽  
Murali Sundaram
Keyword(s):  
Phase Transformation ◽  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Numerical Study ◽  
Impact Angle ◽  
Machining Parameters ◽  
Phase Volume ◽  
Impact Speed ◽  
Afm Probe ◽  
The Impact

In this paper, a numerical study of a nanomachining process, Vibration Assisted Nano Impact machining by Loose Abrasives (VANILA), has been conducted. In the VANILA process, an atomic force microscope (AFM) is used as a platform and the nano abrasives (diamond particles) are injected in slurry between the silicon workpiece and the vibrating AFM probe. The vibration of the AFM probe generates kinetic energy for the abrasives to impact the silicon workpiece and result in nanoscale material removal. In addition, silicon usually experiences phase transformation when subject to high pressure at nano-scale. The commercial Finite Element Method (FEM) software package Abaqus is employed to simulate the phase transformation experienced by the silicon workpiece in this VANILA process under different machining parameters such as impact speed, impact angle and coefficient of friction between the nano-abrasive and silicon workpiece. It is found that the machining parameters (impact speed, impact angle, and coefficient of friction) have substantial influence on the phase transformation of silicon workpiece in the nanomachining VANILA. Phase volumes for Si-VII, Si-VIII, and Si-X increase as the impact speed increases from 100 m/s to 200 m/s. Phase volume of Si-X increases as the friction coefficient increases. For Si-VII and Si-VIII, the phase volumes decrease as friction coefficient increases from 0.05, 0.3 and 0.5. In addition, the phase volumes for Si-VII, Si-VIII, and Si-X usually increase as the impact angles increases from 20° to 90°. However, for impact speed of 150 m/s and frictional coefficient of 0.05, the Si-VII phase volume increases first as impact angle increases from 20° to 70° and then decreases as the impact angle increases from 70° to 90°.

scholarly journals Gravelling Test for Rail Windshield

2019 ◽  
Vol 26 (1) ◽  
pp. 7-15
Author(s):  
Adam Bilar ◽  
Paweł Boguszewicz ◽  
Witold Perkowski
Keyword(s):  
Test Piece ◽  
High Speed ◽  
Impact Test ◽  
Impact Angle ◽  
Point Of View ◽  
Test Results ◽  
Average Deviation ◽  
Test Conditions ◽  
The Impact ◽  
Standard Concept

Abstract During preliminary tests of locomotive windshield resistance to gravelling, according to the applicable standard PN-EN 15152:2007, carried out in the Institute of Aviation, the problem of the projectile overturning after leaving the cannon barrel was detected. Three tests recorded with a high-speed camera are presented in this article. This problem was found to be due to the incorrect projectile geometry. In order to stabilise the trajectory of the projectile, four types of projectiles were made using military experience. All of them meet relevant test conditions from the point of view of the test piece (locomotive windshield). The best projectile modification was obtained in the tests with an average deviation of the expected impact angle of 11° compared to 75° for a projectile made exactly according to the guidelines of the standard. Each of 22 modified projectiles hit the test piece with the tip, while out of the 12 original projectiles only 4 hit the test piece with the tip. The impact test results confirm that it is possible to perform a gravelling test according to the standard concept, but it seems necessary to clarify the standard requirements and to modify the projectile shape. The article contains a proposal for the projectile modification and highlights inaccuracies in the standard concerning the gravelling test.

FEM Investigation of the Effects of Impact Speed and Angle of Impacts of Abrasive in the Vibration Assisted Nano Impact Machining by Loose Abrasives

2017 ◽  
Author(s):  
Nick H. Duong ◽  
J. Ma ◽  
Shuting Lei
Keyword(s):  
Frictional Coefficient ◽  
Impact Angle ◽  
The Novel ◽  
Abrasive Machining ◽  
Nanoscale Material ◽  
Impact Speed ◽  
Atomic Force ◽  
Hard And Brittle Materials ◽  
Afm Probe ◽  
The Impact

In this paper, the commercial FEM software package Abaqus is employed to model the novel nanomachining process, Vibration Assisted Nano Impact machining by Loose Abrasives (VANILA), which combines the principles of vibration-assisted abrasive machining and tip-based nanomachining to conduct nano abrasive machining of hard and brittle materials. In this novel nanomachining process, an atomic force microscope (AFM) is used as a platform and the nano abrasives injected in slurry between the workpiece and the vibrating AFM probe impact the workpiece and result in nanoscale material removal. Diamond particles are used as the loose abrasives. The effects of impact speed, angle of impacts, and the frictional coefficient between the workpiece and abrasives are investigated using Abaqus. It is found that the impact speed, impact angle, and frictional coefficient between the silicon workpiece and nanoabrasives have big influence on the nanocavity’s size and depth.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

scholarly journals Patient-Centered Medical Home Knowledge and Attitudes of Residents and Faculty: Certification Is Just the First Step

2015 ◽  
Vol 7 (4) ◽  
pp. 580-588 ◽  
Author(s):  
Fadya El Rayess ◽  
Roberta Goldman ◽  
Christopher Furey ◽  
Rabin Chandran ◽  
Arnold R. Goldberg ◽  
...  
Keyword(s):  
Primary Care ◽  
Situated Learning ◽  
Medical Home ◽  
Patient Centered Medical Home ◽  
Patient Centered ◽  
Individual Interviews ◽  
Knowledge And Attitudes ◽  
Positive Attitudes ◽  
Level 3 ◽  
The Impact

ABSTRACT Background The patient-centered medical home (PCMH) is an accepted framework for delivering high-quality primary care, prompting many residencies to transform their practices into PCMHs. Few studies have assessed the impact of these changes on residents' and faculty members' PCMH attitudes, knowledge, and skills. The family medicine program at Brown University achieved Level 3 PCMH accreditation in 2010, with training relying primarily on situated learning through immersion in PCMH practice, supplemented by didactics and a few focused clinical activities. Objective To assess PCMH knowledge and attitudes after Level 3 PCMH accreditation and to identify additional educational needs. Methods We used a qualitative approach, with semistructured, individual interviews with 12 of the program's 13 postgraduate year 3 residents and 17 of 19 core faculty. Questions assessed PCMH knowledge, attitudes, and preparedness for practicing, teaching, and leading within a PCMH. Interviews were analyzed using the immersion/crystallization method. Results Residents and faculty generally had positive attitudes toward PCMH. However, many expressed concerns that they lacked specific PCMH knowledge, and felt inadequately prepared to implement PCMH principles into their future practice or teaching. Some exceptions were faculty and resident leaders who were actively involved in the PCMH transformation. Barriers included lack of time and central roles in PCMH activities. Conclusions Practicing in a certified PCMH training program, with passive PCMH roles and supplemental didactics, appears inadequate in preparing residents and faculty for practice or teaching in a PCMH. Purposeful curricular design and evaluation, with faculty development, may be needed to prepare the future leaders of primary care.

scholarly journals The impact of non-pharmaceutical interventions on COVID-19 epidemic growth in the 37 OECD member states

2021 ◽  
Author(s):  
Francisco Pozo-Martin ◽  
Heide Weishaar ◽  
Florin Cristea ◽  
Johanna Hanefeld ◽  
Thurid Bahr ◽  
...  
Keyword(s):  
Growth Rate ◽  
Early Phase ◽  
Policy Decision ◽  
Multilevel Modelling ◽  
Daily Growth ◽  
Public Places ◽  
Member States ◽  
Unit Increase ◽  
Policy Decision Making ◽  
The Impact

AbstractWe estimated the impact of a comprehensive set of non-pharmeceutical interventions on the COVID-19 epidemic growth rate across the 37 member states of the Organisation for Economic Co-operation and Development during the early phase of the COVID-19 pandemic and between October and December 2020. For this task, we conducted a data-driven, longitudinal analysis using a multilevel modelling approach with both maximum likelihood and Bayesian estimation. We found that during the early phase of the epidemic: implementing restrictions on gatherings of more than 100 people, between 11 and 100 people, and 10 people or less was associated with a respective average reduction of 2.58%, 2.78% and 2.81% in the daily growth rate in weekly confirmed cases; requiring closing for some sectors or for all but essential workplaces with an average reduction of 1.51% and 1.78%; requiring closing of some school levels or all school levels with an average reduction of 1.12% or 1.65%; recommending mask wearing with an average reduction of 0.45%, requiring mask wearing country-wide in specific public spaces or in specific geographical areas within the country with an average reduction of 0.44%, requiring mask-wearing country-wide in all public places or all public places where social distancing is not possible with an average reduction of 0.96%; and number of tests per thousand population with an average reduction of 0.02% per unit increase. Between October and December 2020 work closing requirements and testing policy were significant predictors of the epidemic growth rate. These findings provide evidence to support policy decision-making regarding which NPIs to implement to control the spread of the COVID-19 pandemic.

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