scholarly journals Experimental Investigation on the Impact Dynamics of Saturated Granular Flows on Rigid Barriers

2021 ◽  
Vol 27 (1) ◽  
pp. 127-138
Author(s):  
Nicoletta Sanvitale ◽  
Elisabeth Bowman ◽  
Miguel Angel Cabrera
Keyword(s):  
Particle Size ◽  
High Speed ◽  
Impact Load ◽  
Granular Flows ◽  
Normal Pressure ◽  
Impact Behavior ◽  
Small Scale ◽  
Rigid Barrier ◽  
Fluid Saturation ◽  
The Impact

ABSTRACT Debris flows involve the high-speed downslope motion of rocks, soil, and water. Their high flow velocity and high potential for impact loading make them one of the most hazardous types of gravitational mass flows. This study focused on the roles of particle size grading and degree of fluid saturation on impact behavior of fluid-saturated granular flows on a model rigid barrier in a small-scale flume. The use of a transparent debris-flow model and plane laser-induced fluorescence allowed the motion of particles and fluid within the medium to be examined and tracked using image processing. In this study, experiments were conducted on flows consisting of two uniform and one well-graded particle size gradings at three different fluid contents. The evolution of the velocity profiles, impact load, bed normal pressure, and fluid pore pressure for the different flows were measured and analyzed in order to gain a quantitative comparison of their behavior before, during, and after impact.

Towards rational use of baffle arrays on sloped and horizontal terrain for filtering boulders

2020 ◽  
Author(s):  
George Robert Goodwin ◽  
Clarence E. Choi ◽  
Chan-Young Yune
Keyword(s):  
Horizontal Plane ◽  
Impact Load ◽  
Granular Flows ◽  
Rigid Barrier ◽  
Optimum Configuration ◽  
Granular Assembly ◽  
Sloping Terrain ◽  
The Impact ◽  
Current Guidelines ◽  
Array Of Baffles

Baffle arrays are used to filter boulders from granular flows, such that the impact load exerted on barriers is reduced. However, current guidelines provide limited recommendations on baffle design. In this study, a calibrated Discrete Element Method modelled boulders entrained in a bulk granular assembly interacting with baffles and a terminal rigid barrier. Different baffle spacings relative to the boulder diameter (1 < s/δ < 4) were considered. A ratio of s/δ=1 is recommended for reducing the impact load by up to 80%, whilst s/δ = 4 renders an array of baffles inadequate for filtration. The optimum configuration is a staggered array with three rows of baffles on a horizontal plane in front of a barrier. This layout reduces the peak discharge by up to four times more than a similar array on sloping terrain, compared to channels without baffles. Furthermore, the transition from sloping terrain to a horizontal plane works together with the array of baffles to dissipate flow kinetic energy. On the horizontal plane, baffles attenuate the flow velocity more as the Froude number Fr increases, implying that baffles should be used if high Fr are anticipated. Finally, guidance is provided on estimating load attenuation from boulder filtration.

Froude characterization for unsteady single-surge dry granular flows: impact pressure and runup height

2019 ◽  
Vol 56 (12) ◽  
pp. 1968-1978 ◽  
Author(s):  
C.W.W. Ng ◽  
C.E. Choi ◽  
G.R. Goodwin
Keyword(s):  
Impact Load ◽  
Granular Flows ◽  
Maximum Flow ◽  
Impact Pressure ◽  
Flow Depth ◽  
Rigid Barrier ◽  
Runup Height ◽  
The Impact ◽  
Dem Model

The impact and pileup mechanisms of unsteady granular flows impacting a rigid barrier are governed by the Froude conditions (Fr). Velocity and depth vary along the length of the flow. There is currently no widely accepted approach for characterizing Fr for impact and runup problems. In this study, a discrete element method (DEM) model was calibrated against a physical flume test. Eighty-six simulations were performed using the DEM model to investigate the equivalent Fr governing pileup height and impact pressure for unsteady single-surge dry granular flows against a rigid barrier. Fr and the grain diameter were varied. Results reveal that Fr within the frontmost 5% of a flow governs both pileup height and impact pressure. Thus, taking frontal velocity and maximum flow depth within the frontmost region is crucial for properly characterizing the runup height and impact load. Consistent characterization of Fr is possible near the longitudinal centre of a flow; the frontmost Fr can then be extrapolated from calibration curves. Results imply that existing studies that predict impact pressure based on nonfrontal Fr values may underestimate impact pressure by a factor of up to 2.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

Diamond-Like Carbon Coating—It'S Application for Polymeric Substrates

1991 ◽  
Vol 239 ◽  
Author(s):  
Fred M. Kimock ◽  
Alex J. Hsieh ◽  
Peter G. Dehmer ◽  
Pearl W. Yip
Keyword(s):  
High Speed ◽  
Protective Coatings ◽  
Ion Beam ◽  
Chemical Exposure ◽  
Optical Systems ◽  
Impact Behavior ◽  
Organic Liquids ◽  
Diamond Like Carbon ◽  
Dlc Coating ◽  
The Impact

ABSTRACTWe report on a recently commercialized Diamond-Like Carbon (DLC) coating that has been deposited on polycarbonate at near room temperature, via a unique ion beam system. Aspects of high speed impact behavior, chemical resistance, abrasion resistance, and thermal stability of the coating are examined. Results of scanning electron microscopy studies indicate that adhesion of the DLC coating is very good; no delamination of the coating was found on ballistically tested specimens. The well-bonded DLC coating did not cause the impact performance of polycarbonate to become brittle. Chemical exposure test results show that the DLC coating is capable of protecting polycarbonate from chemical attack by aggressive organic liquids. These ion beam deposited DLC coatings have considerable potential as protective coatings for optical systems.

scholarly journals Experimental and Numerical Impact Analysis of Automotive Bumper Brackets Made of 2D Triaxially Braided CFRP Composites

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3554
Author(s):  
Robert Böhm ◽  
Andreas Hornig ◽  
Tony Weber ◽  
Bernd Grüber ◽  
Maik Gude
Keyword(s):  
High Speed ◽  
Impact Analysis ◽  
Damage Model ◽  
Drop Tower ◽  
Structural Deformation ◽  
Impact Behavior ◽  
Speed Test ◽  
Damage Models ◽  
The Impact ◽  
Carbon Fiber Epoxy

The impact behavior of carbon fiber epoxy bumper brackets reinforced with 2D biaxial and 2D triaxial braids was experimentally and numerically analyzed. For this purpose, a phenomenological damage model was modified and implemented as a user material in ABAQUS. It was hypothesized that all input parameters could be determined from a suitable high-speed test program. Therefore, novel impact test device was designed, developed and integrated into a drop tower. Drop tower tests with different impactor masses and impact velocities at different bumper bracket configurations were conducted to compare the numerically predicted deformation and damage behavior with experimental evidence. Good correlations between simulations and tests were found, both for the global structural deformation, including fracture, and local damage entities in the impact zone. It was proven that the developed phenomenological damage models can be fully applied for present-day industrial problems.

scholarly journals Finite Element Analysis of Impact Energy on Spur Gear

2018 ◽  
Vol 225 ◽  
pp. 06011 ◽  
Author(s):  
Ismail Ali Bin Abdul Aziz ◽  
Daing Mohamad Nafiz Bin Daing Idris ◽  
Mohd Hasnun Arif Bin Hassan ◽  
Mohamad Firdaus Bin Basrawi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Impact Energy ◽  
High Speed ◽  
Impact Test ◽  
Impact Load ◽  
Gear Tooth ◽  
Test Equipment ◽  
Element Analysis ◽  
The Impact

In high-speed gear drive and power transmission, system impact failure mode always occurs due to the sudden impact and shock loading during the system in running. Therefore, study on the amount of impact energy that can be absorbed by a gear is vital. Impact test equipment has been designed and modelled for the purpose to study the impact energy on gear tooth. This paper mainly focused on Finite Element Analysis (FEA) of impact energy that occurred during simulation involving the impact test equipment modelling. The simulation was conducted using Abaqus software on critical parts of the test equipment to simulate the impact event and generate impact data for analysis. The load cell in the model was assumed to be free fall at a certain height which gives impact load to the test gear. Three different type of material for the test gear were set up in this simulation. Results from the simulation show that each material possesses different impact energy characteristic. Impact energy values increased along with the height of load drop. AISI 1040 were found to be the toughest material at 3.0m drop that could withstand up to 44.87N.m of impact energy. These data will be used to validate data in physical experiments in further study.

Effects of Obstacle’s Curvature on Shock Waves in Gravity-Driven Experimental Flows Impacting a Circular Cylinder or a Wall

2020 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Dieter Rickenmann
Keyword(s):  
Shock Wave ◽  
Circular Cylinder ◽  
Pressure Sensors ◽  
Granular Flows ◽  
Impact Pressure ◽  
Small Scale ◽  
Cylinder Surface ◽  
Seismic Signals ◽  
Dynamic Impact ◽  
The Impact

&lt;p&gt;Geophysical granular &amp;#64258;ows such as rock and snow avalanches, flow-like landslides, debris flows, and pyroclastic &amp;#64258;ows are driven by gravity and often impact on engineering structures located in gullies and slopes as they flow down, generating dynamic impact pressures and causing a major threat to infrastructures. It is necessary to understand the physical mechanism of such granular flows impacting obstacles to improve the design of protective structures and the hazard assessment related to such structures. In this study, the small-scale laboratory experiments were performed to investigate the dynamic impact caused by granular flow around a circular cylinder with variable radius of curvatures and the dynamic impact against a flat wall. Pressure sensors were used to measure the impact pressure of granular flows at both the upstream cylinder surface and at the bottom of the channel. Accelerometers were mounted on the underside of channel to record the seismic signals generated by the granular flows before and during the impact with the obstacle. Flow velocities and flow depths were determined by using high-precision cameras. The results show that a bow shock wave is generated upstream of the cylinder, causing dynamic pressures on both the obstacle and the bottom of the channel. The dimensionless standoff distance of the granular shock wave decreases nonlinearly or almost exponentially with increasing Froude number (Fr) in the range of 5.5 to 11.0. The dimensionless pinch-off distance and dimensionless run-up height grow linearly with increasing Fr, and they were significantly influenced by the radius of curvature of the structure at the stagnation point (RCSSP). The dimensionless impact pressure on the structure surface is sensitive to the RCSSP, while the differences decrease as Fr increases; Seismic signals generated at the underside of the channel and at the top of the cylinder were also recorded to assist in analyzing the effects of RCSSP.&lt;/p&gt;

The Structural Impact Characteristics of Indonesian Railway Vehicle

2004 ◽  
Vol 261-263 ◽  
pp. 337-344 ◽  
Author(s):  
Ign Wiratmaja Puja ◽  
T. Hardono ◽  
Khalid ◽  
M.F. Adziman
Keyword(s):  
Impact Energy ◽  
Impact Load ◽  
Rigid Wall ◽  
Impact Behavior ◽  
Railway Vehicle ◽  
Railway Transportation ◽  
Passenger Cars ◽  
Vehicle Structure ◽  
Structural Impact ◽  
The Impact

The Indonesian railway transportation has adventages in term of capacity, efficiency, trafic, and safety compared to the other types of land transportations. At present, the Indonesian Railway Company has 519 locomotives, and 1643 passenger cars, that transport about 184 million man-trip each year[1,2]. Unfortunately, the rate of train collisions in Indonesian railway system was very high. In the last ten years, 2352 train accidents have happened which claimed 997 lives and left 2638 people injured. The record shows that 110 of those accidents were train to train collisions[1]. This paper consider the structural impact behavior of Indonesian passenger railway car subject to collision forces. This characteristic is very important parameter for passenger protection during the course of collision[3-5]. The vehicle structure should be able to absorb the huge impact energy or impact force to ensure the passenger safety[6-9]. The impact energy of cars-train is evaluated using the principle of multibody dynamics[10,11]. The vehicle structure under impact load is analyzed using the finite element method. The principal of symmetry is adopted, so the collision scene could be simulated as collision between the vehicle with a rigid wall. The analysis result shows that the structure is collapse at the passenger area (saloon) which is in agreement with the real collision. Modification is proposed to protect the passenger area by introducing crush zone area and impact energy absorber.

scholarly journals Influence of Voids Ratio on Impact Behavior of Circular Ferrocement Slabs

2019 ◽  
Vol 5 (1) ◽  
pp. 117
Author(s):  
Muyasser M. Jomaah ◽  
Muna Zead Baraa
Keyword(s):  
Impact Energy ◽  
Structural Strength ◽  
Impact Load ◽  
Low Cost ◽  
Load Test ◽  
Wire Mesh ◽  
Impact Behavior ◽  
Experimental Program ◽  
Test Results ◽  
The Impact

The objective of using materials is to fully utilize the properties of these materials in order to obtain the best performance of the structure. The merits of material are based on many factors like, workability, structural strength, durability and low cost. Ferrocement is an excellent construction system. This paper studies the behavior of ferrocement circular slabs under impact load. The experimental program include testing four sime fixed supported ferrocement circular slabs of 800mm diameter and 50mm thickness. The Influence of the use of styropor voids was investigated in different ratios (24% and 48%) and a number of wire mesh layers four and six layers. Impact load test results revealed that increasing number of wire mesh from 4 to 6 led to an increase in the impact energy for first crack by (41.991% ,37.62%) respectively when using voids ratio by (24% and 48%) respectively and impact energy for full perforation by (21.7% and 9.94%) respectively when using voids ratio by (24% and 48%) respectively. Ferrocement circular slabs are used in construction fields such as roofs, tanks, manholes, etc.

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