scholarly journals Effects of the impact angle on the coefficient of restitution based on a medium-scale laboratory test

2018 ◽  
Author(s):  
Yanhai Wang ◽  
Wei Jiang ◽  
Shengguo Cheng ◽  
Pengcheng Song ◽  
Cong Mao
Keyword(s):  
Laboratory Test ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Small Scale ◽  
Medium Scale ◽  
Motion Trajectories ◽  
Small Impact ◽  
General Rules ◽  
Highly Correlated ◽  
The Impact

Abstract. The reliability of a computer program simulating rockfall trajectory depends on the ascertainment of reasonable values for the coefficients of restitution, which typically vary with the kinematic parameters and terrain conditions. The effects of the impact angle on the coefficients of restitution have been identified and studied using laboratory experiments. However, the laboratory tests performed to date have largely been limited to a small scale. This paper presents the results of a medium-scale laboratory test on the coefficients of restitution for spherical polyhedrons impacting concrete slabs. The specimens were made of natural limestone, and the motion trajectories were recorded by a 3D motion capture system. The normal coefficient of restitution Rn and the impact angle α are highly correlated. Comparisons between the results of existing tests and our experiments demonstrate that certain general rules regarding the effect of the impact angle hold regardless of the test scales and conditions. Increasing the impact angle will induce reductions in the values of Rn and the energy coefficient of restitution RE, whereas it will have a significant impact on the tangential coefficient of restitution Rt. A small impact angle will likely cause the rebound angle to exceed the impact angle, which typically causes a higher Rn and lower RE. This phenomenon leads to extreme scatter in the measured data under the conditions of a small impact angle and hinders the prediction of the rockfall trajectory.

scholarly journals Effects of the impact angle on the coefficient of restitution in rockfall analysis based on a medium-scale laboratory test

2018 ◽  
Vol 18 (11) ◽  
pp. 3045-3061 ◽  
Author(s):  
Yanhai Wang ◽  
Wei Jiang ◽  
Shengguo Cheng ◽  
Pengcheng Song ◽  
Cong Mao
Keyword(s):  
Kinetic Energy ◽  
Laboratory Test ◽  
Laboratory Tests ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Small Scale ◽  
Lumped Mass ◽  
Mass Model ◽  
Medium Scale ◽  
The Impact

Abstract. The reliability of a computer program simulating rockfall trajectory depends on the ascertainment of reasonable values for the coefficients of restitution, which typically vary with the kinematic parameters and terrain conditions. The effects of the impact angle with respect to the slope on the coefficients of restitution have been identified and studied using small-scale laboratory tests. To investigate whether the existing conclusion based on small-scale laboratory tests is valid when the test scale changes as well as the role of rotation in the effect of the impact angle on the coefficients of restitution, this study performed a medium-scale laboratory test using spherical limestone polyhedrons to impact concrete slabs. Free-fall tests are conducted, and the velocities before and after the impact are obtained by a 3-D motion capture system. The comparison of results between our test and the existing small-scale tests verified that several general laws occur when accounting for the effect of the impact angle, regardless of the test scales and conditions. Increasing the impact angle will induce reductions in the normal coefficient of restitution Rn, the kinematic coefficient of restitution Rv and the kinetic energy coefficient of restitution RE, whereas it will lead to increases in the tangential coefficient of restitution Rt. The rotation plays an important role in the effect of the impact angle. A higher percentage of kinetic energy converted to rotational energy always induces a higher normal coefficient of restitution Rn and a lower tangential coefficient of restitution Rt. As the impact angle decreases, the ratio between the rebound angle β and the impact angle α increases, and the percentage of kinetic energy dissipated in rotation as the collision became higher. Considering that the effect of block shape and the detailed impact orientations are not involved in the present study, the test results are valid for trajectory simulation codes based on a lumped-mass model and can be referenced in the trajectory predication of spherical rocks impacting hard surfaces using a rigid body model.

TurkStream Collapse Test Program

2018 ◽  
Author(s):  
Chris Timms ◽  
Doug Swanek ◽  
Duane DeGeer ◽  
Arjen Meijer ◽  
Ping Liu ◽  
...  
Keyword(s):  
Thermal Ageing ◽  
Full Scale ◽  
The Black Sea ◽  
Small Scale ◽  
Test Program ◽  
Line Pipe ◽  
Medium Scale ◽  
Collapse Resistance ◽  
Full Scale Tests ◽  
The Impact

The TurkStream pipeline project is designed to transport approximately 32 billion cubic meters of natural gas annually from Russia to Turkey under the Black Sea, with more than 85% of the deep-water route being deeper than 2000 m. The offshore section is intended to consist of two parallel lines, each approximately 900 km long. The preliminary stages of the front end engineering design (pre-FEED) phase was managed by INTECSEA. To support the analyses and design of the deepest portions, a full scale collapse test program was performed by C-FER Technologies (C-FER). This collapse test program, which included 62 full-scale collapse and pressure+bend tests, 54 medium-scale ring collapse tests, and hundreds of small-scale tests, was primarily aimed at measuring, quantifying and documenting the increase in pipe strength and collapse resistance resulting from the thermal induction heat treatment effect (thermal ageing) that arises during the pipe coating process. Two grades of 32-inch (813 mm) outside diameter (OD) line-pipe, SAWL450 and SAWL485 with wall thicknesses of 39.0 mm or 37.4 mm, respectively, were supplied from various mills for testing. The collapse test program objectives were as follows: • Determine the collapse resistance of line pipes originating from various pipe mills; • Determine the pressure+bend performance of line pipes originating from various pipe mills; • Measure the effect of thermal ageing on material and collapse testing results, including the impact of multiple thermal cycles; and • Evaluate the results of medium-scale ring collapse tests as compared to full-scale tests. This paper presents selected results of this work, along with some comparisons to predictive equations.

scholarly journals Development of a novel lateral resistance measurement penetrometer for pipe–soil interaction centrifuge model test

2018 ◽  
Vol 14 (11) ◽  
pp. 155014771881564 ◽  
Author(s):  
Yu Zhang ◽  
Zhongtao Wang ◽  
Huafu Pei
Keyword(s):  
Impact Angle ◽  
Resistance Measurement ◽  
Small Scale ◽  
Centrifuge Model Test ◽  
Submarine Landslides ◽  
Centrifuge Tests ◽  
Impact Forces ◽  
Lateral Resistance ◽  
Offshore Pipeline ◽  
The Impact

Offshore pipelines are exposed to potential submarine landslides. It is difficult to measure the impact forces exerted on a pipeline induced by submarine landslides because the upper seabed is very soft and an impact angle exists in practice. Current laboratory experiments are limited on measuring the normal force exerted on pipeline by the slides. This article describes the feasibility and performance of a novel penetrometer, which is designed to measure impact forces of submarine landslides on offshore pipeline including both the normal and frictional forces from variable impact angle in centrifuge test, termed as the lateral resistance measurement penetrometer. The calibration procedure for this particular version is illustrated in detail and the reliability and feasibility of the lateral resistance measurement penetrometer are preliminarily confirmed by an experimental study. Pipe–soil interaction centrifuge tests were subsequently performed on a normally consolidated kaolin sample with 40 g level conducted in Dalian University of Technology drum centrifuge to investigate the effect of incident angles on the impact forces exerted by submarine landslides on a pipeline. The impact forces deduced from the lateral resistance measurement penetrometer are analysed in comparison with published results. The lateral resistance measurement penetrometer is a potentially valuable device to measure the interaction force between submarine landslides and offshore pipeline, cables and other subsea facilities in small-scale centrifuge models.

Evaluation of Elastic-Plastic Rebound Properties of Coal Fly Ash Particles for Use in a Universal Turbine Deposition Model

2015 ◽  
Author(s):  
Steven M. Whitaker ◽  
Jeffrey P. Bons
Keyword(s):  
Experimental Data ◽  
Yield Stress ◽  
Material Properties ◽  
Coal Fly Ash ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Deposition Model ◽  
Mechanics Model ◽  
The Impact ◽  
Impact Models

Three particle impact models have been evaluated to determine their ability to predict particle material properties and restitution coefficients using experimental data for the coefficient of restitution of particles impacting a 410 stainless steel plate. The particles consisted of PMMA and three coal fly ashes: JBPS, Bituminous, and Lignite. Particle speeds ranged from approximately 20 to 120 meters per second, and the nominal impact angle was approximately 85 degrees. Flow temperatures for the ash particulate experiments were set at 295 K and 395 K. The impact models were applied to the experimental data via curve fitting to evaluate the yield stress of the particulate, which was known for the PMMA. For the ash particulate, a linear law of mixtures was used to approximate the modulus of elasticity and Poisson’s ratio for use in the yield stress determination. A Hertzian mechanics model was shown to over-predict the yield stress of the PMMA particulate, indicating that, for known material properties, they would under-predict the coefficient of restitution. A Plastic-JKR model and a finite element based model by Wu et al. showed good agreement between the calculated yield stress and known range of yield stress values for the PMMA particulate, indicating that the model would accurately predict restitution coefficients for particulate with known material properties (or could be used to accurately determine the material properties from experimental coefficient of restitution data). However, some questions remain as to the ability of these models to be used for non-spherical, conglomerate type particulate. A thorough overview of the impact process is provided, and the application of the results of the study to the development of a physics-based universal impact and deposition model is presented.

Impact Erosion of Quartz Crystals by Micro-Particles in Abrasive Waterjet Micro-Machining

2013 ◽  
Vol 797 ◽  
pp. 46-51 ◽  
Author(s):  
H. Qi ◽  
J.M. Fan ◽  
Jun Wang
Keyword(s):  
Material Removal ◽  
Impact Angle ◽  
Machining Process ◽  
Abrasive Waterjet ◽  
Small Scale ◽  
Material Strength ◽  
Micro Machining ◽  
Micro Particles ◽  
Crater Volume ◽  
The Impact

Abrasive waterjet (AWJ) micro-machining is a precision processing technology with some distinct advantages. To understand the machining process, the erosion mechanism is presented and discussed when micro-particle impacting on a quartz crystal specimen. It is found that three types of impressions are formed which are craters, micro-dents and scratches. Small-scale craters including crashed zones and radial cracks are associated with plastic flow and subsurface micro-cracks that decrease the material strength, but cause little material removal, while large-scale craters including conchoidal fractures caused by the propagation of lateral cracks dominate the volume change of the specimen. Micro-dents are produced by the impact of particles possessing small kinetic energies, and scratches are generated by particle sliding or rolling over the target surface and make a negligible contribution to material removal. The crater volume generated by the impact of individual particle is then discussed with respect to particle impacting velocity and impact angle. It shows that an increase in particle impact angle or particle velocity increases the crater volume due to the increased conchoidal fractures during the impact process.

scholarly journals The Volta Basin Water Allocation System: assessing the impact of small-scale reservoir development on the water resources of the Volta basin, West Africa

2009 ◽  
Vol 21 ◽  
pp. 57-62 ◽  
Author(s):  
C. Leemhuis ◽  
G. Jung ◽  
R. Kasei ◽  
J. Liebe
Keyword(s):  
Water Resources ◽  
Water Allocation ◽  
Hydrological Modeling ◽  
Small Scale ◽  
Climate Conditions ◽  
Allocation System ◽  
Medium Scale ◽  
Volta Basin ◽  
Basin Water ◽  
The Impact

Abstract. In the Volta Basin, infrastructure watershed development with respect to the impact of climate conditions is hotly debated due to the lack of adequate tools to model the consequences of such development. There is an ongoing debate on the impact of further development of small and medium scale reservoirs on the water level of Lake Volta, which is essential for hydropower generation at the Akosombo power plant. The GLOWA Volta Project (GVP) has developed a Volta Basin Water Allocation System (VB-WAS), a decision support tool that allows assessing the impact of infrastructure development in the basin on the availability of current and future water resources, given the current or future climate conditions. The simulated historic and future discharge time series of the joint climate-hydrological modeling approach (MM5/WaSiM-ETH) serve as input data for a river basin management model (MIKE BASIN). MIKE BASIN uses a network approach, and allows fast simulations of water allocation and of the consequences of different development scenarios on the available water resources. The impact of the expansion of small and medium scale reservoirs on the stored volume of Lake Volta has been quantified and assessed in comparison with the impact of climate variability on the water resources of the basin.

Some Aspects of the Dynamical Behavior of the Impact Damper

2005 ◽  
Vol 11 (4) ◽  
pp. 459-479 ◽  
Author(s):  
F. Peterka ◽  
B. Blazejczyk-Okolewska
Keyword(s):  
Vibration Amplitude ◽  
Degrees Of Freedom ◽  
Dynamical Behavior ◽  
Coefficient Of Restitution ◽  
Harmonic Force ◽  
Impact Damper ◽  
Motion Trajectories ◽  
The Impact ◽  
Impact Motion ◽  
External Harmonic Force

In this paper we show some aspects of the dynamical behavior of a two-degrees-of-freedom system forced with an external harmonic force, which impacts cause a reduction of the vibration amplitude of the basic system. The purpose of the presented investigations is to determine the coefficient of restitution and the damping coefficient of the fender that ensure the required degree of a reduction in these vibrations. The regions of existence bifurcation diagrams and motion trajectories of different kinds of impact motion are presented and analyzed. The impact damper of vibrations is compared with a linear damper. The investigations have been conducted by means of numerical simulations.

A semi-analytical model for oblique impacts of elastoplastic spheres

2008 ◽  
Vol 465 (2103) ◽  
pp. 937-960 ◽  
Author(s):  
Chuan-Yu Wu ◽  
Colin Thornton ◽  
Long-Yuan Li
Keyword(s):  
Poisson’S Ratio ◽  
Numerical Data ◽  
Impact Angle ◽  
Coefficient Of Restitution ◽  
Rigid Body Dynamics ◽  
Poisson's Ratio ◽  
Published Data ◽  
Element Analysis ◽  
Oblique Impacts ◽  
The Impact

Results of finite-element analysis (FEA) of oblique impacts of elastic and elastic, perfectly plastic spheres with an elastic flat substrate are presented. The FEA results are in excellent agreement with published data available in the literature. A simple model is proposed to predict rebound kinematics of the spheres during oblique impacts. In this model, the oblique impacts are classified into two regimes: (i) persistent sliding impact, in which sliding occurs throughout the impact, the effect of tangential (elastic or plastic) deformation is insignificant and the model reproduces the well-established theoretical solutions based on rigid body dynamics for predicting the rebound kinematics and (ii) non-persistent sliding impact, in which sliding does not occur throughout the impact duration and the rebound kinematics depends upon both Poisson's ratio and the normal coefficient of restitution (i.e. the yield stress of the materials). For non-persistent sliding impacts, the variation of impulse ratio with impact angle is approximated using an empirical equation with four parameters. These parameters are sensitive to the values of Poisson's ratio and the normal coefficient of restitution, but can be obtained by fitting numerical data. Consequently, a complete set of solutions is obtained for the rebound kinematics, including the tangential coefficient of restitution, the rebound velocity at the contact patch and the rebound rotational speed of the sphere during oblique impacts. The accuracy and robustness of this model is demonstrated by comparisons with FEA results and data published in the literature. The model is capable of predicting complete rebound behaviour of spheres for both elastic and elastoplastic oblique impacts.

Can Values of Honesty, Hard Work, Loyalty and Discipline Predict Entrepreneurial Orientation of Muslim Owner Managers?

2015 ◽  
Vol 3 (1) ◽  
pp. 31 ◽  
Author(s):  
Rohani Mohd ◽  
Badrul Hisham Kamaruddin ◽  
Khulida Kirana Yahya ◽  
Elias Sanidas
Keyword(s):  
Entrepreneurial Orientation ◽  
Two Dimensions ◽  
Hard Work ◽  
Small Scale ◽  
Sampling Frame ◽  
Policy Makers ◽  
Learning Institutions ◽  
Innovative Orientation ◽  
The Impact ◽  
True Values

The purpose of the present study is twofold: first, to investigate the true values of Muslim owner managers; second, to examine the impact of these values on entrepreneurial orientations of Muslim small-scale entrepreneurs. 850 Muslim owner managers were selected randomly using the sampling frame provided by MajlisAmanah Rakyat Malaysia (MARA). 162 completed questionnaires were collected and analyzed. For this paper only two dimensions of entrepreneurial orientations were analyzed: proactive orientation and innovative orientation. Interestingly, the findings revealed that Muslim businessmen/women are honest, loyal, disciplined and hard working. Loyalty and honesty are positively related to proactive orientation, while discipline and hard-work are positively related to innovative orientation. The findings provide implications for existing relevant theories, policy makers, practitioners and learning institutions. 

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