Abrasion regimes in fluvial bedrock incision

Geology ◽  
2021 ◽  
Author(s):  
Alexander R. Beer ◽  
Michael P. Lamb
Keyword(s):  
Impact Energy ◽  
Fragment Size ◽  
Bedrock Rivers ◽  
Rock Fragments ◽  
River Incision ◽  
Energy Scaling ◽  
Wide Range ◽  
Bedrock Erosion ◽  
Impact Energies ◽  
The Impact

River incision into bedrock drives landscape evolution and couples surface changes to climate and tectonics in uplands. Mechanistic bedrock erosion modeling has focused on plucking—the hydraulic removal of large loosened rock fragments—and on abrasion—the slower fracturing-driven removal of rock due to impacts of transported sediment—which produces sand- or silt-sized fragments at the mineral grain scale (i.e., wear). An abrasion subregime (macro-abrasion) has been hypothesized to exist under high impact energies typical of cobble or boulder transport in mountain rivers, in which larger bedrock fragments can be generated. We conducted dry impact abrasion experiments across a wide range of impact energies and found that gravel-sized fragments were generated when the impact energy divided by squared impactor diameter exceeded 1 kJ/m2. However, the total abraded volume followed the same kinetic-energy scaling regardless of fragment size, holding over 13 orders of magnitude in impact energy and supporting a general abrasion law. Application to natural bedrock rivers shows that many of them likely can generate large fragments, especially in steep mountain streams and during large floods, transporting boulders in excess of 0.6 m diameter. In this regime, even single impacts can cause changes in riverbed topography that may drive morphodynamic feedbacks.

scholarly journals Breakage Susceptibility of Wheat and Triticale Seeds Related to Moisture Content and Impact Energy

2012 ◽  
Vol 45 (3) ◽  
pp. 5-13
Author(s):  
F. Shahbazi ◽  
A Dowlatshah ◽  
S. Valizadeh
Keyword(s):  
Moisture Content ◽  
Impact Energy ◽  
Mechanical Damage ◽  
Moisture Contents ◽  
Seed Damage ◽  
Significant Difference ◽  
Impact Energies ◽  
The Impact ◽  
Content Range ◽  
Wheat Seeds

Abstract Mechanical damage of seeds due to harvest, handling and other process is an important factor that affects the quality and quantity of seeds. Seed damage result in lower grain value, storability problem, and reduced seed germination and seedling vigor and subsequent yield of crops. The objective of this research was to determine the effects of moisture content and impact energy on the breakage susceptibility of wheat and triticale seeds. The experiments were conducted at five moisture contents of 7.5, 12, 17, 22 and 27% w.b. and at the impact energies of 0.05 and 0.1 J. The percentage of breakage of both wheat and triticale seeds increased as impact energy increased. The analysis of variance showed that there was a significant difference between breakage susceptibility of wheat and triticale seeds at the 1% probability level. Triticale seeds had more breakage than wheat seeds. For both wheat and triticale seeds as the moisture content of the seeds increased, the amount of the percentage breakage of seeds decreased as a polynomial. The average values of percentage breakage of wheat seeds decreased from 43.81 to 19.88% as the moisture content increased from 7.5 to 27%. Over this same moisture content range the percentage breakage of triticale seeds varied from 81.34 to 37.77%. Below the moisture contents of 17% for the wheat and 22% for the triticale the percentage breakage of seeds increased dramatically.

scholarly journals Dropped Object Impact Analysis Considering Frequency and Consequence for LNG-FPSO Topside Module

2021 ◽  
Vol 11 (16) ◽  
pp. 7753
Author(s):  
Kwangkook Lee ◽  
Hyunsu Ryu
Keyword(s):  
Impact Energy ◽  
Impact Analysis ◽  
Quantitative Risk Assessment ◽  
Production Area ◽  
The Difference ◽  
Offshore Industry ◽  
Impact Energies ◽  
The Impact ◽  
External Loads ◽  
Specific Orientation

Recently, quantitative risk assessment (QRA) has been widely used as a decision-making tool in the offshore industry. This study focused on analyzing dropped objects in the design of a modern offshore platform. A modified QRA procedure was developed for assessing production module protection against accidental external loads. Frequency and consequence analyses were performed using the developed QRA procedure. An exceedance curve was plotted, and a high-risk management item was derived through this process. In particular, simulations and experiments were used to verify the difference between the potential and impact energies according to drop orientation. When the object dropped in a specific orientation, the impact energy was confirmed to be up to 4.7 times greater than the potential energy. To reflect the QRA results in structural design, the proposed procedure should be used to calculate the maximum impact energy. The proposed procedure provides a step-by-step guide to assess the damage capacity of a production area as well as the damage frequency and consequences.

scholarly journals Increasing the Performance of a Fiber-Reinforced Concrete for Protective Facilities

Fibers ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 64
Author(s):  
Roman Fediuk ◽  
Mugahed Amran ◽  
Sergey Klyuev ◽  
Aleksandr Klyuev
Keyword(s):  
Reinforced Concrete ◽  
Impact Strength ◽  
Impact Energy ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Secondary Cracks ◽  
Wide Range ◽  
Long Time ◽  
The Impact ◽  
Hardening Coefficient

The use of fiber in cement materials is a promising and effective replacement for bar reinforcement. A wide range of fiber-reinforced concretes based on composite binders with increased impact strength characteristics have been developed. The synthesized composites included the composite binder made of Portland cement, silica, and carbonate additives. Basalt and steel were used as fibers. The nature of the influence of the composition and manufacturing technology of cement composites on the dynamic hardening coefficient has been established, while the growth of these indicators is achieved by creating a denser interfacial transition zone between the cement paste, aggregate, and fiber as a result of improving the homogeneity of the concrete mixture and controlling the consistency. Workability indicators (slump flow up to 730 mm; spreading time up to a diameter of 50 cm is up to 3 s) allow them to be classified as self-compacting concrete mixtures. An increase in the values of the impact strength coefficient by a factor of 5.5, the dynamic hardening coefficient by almost 70% as a result of interfacial interaction between fibers and binder matrix in the concrete composite, as well as absorption of impact energy by fiber, was revealed. The formula describing the effect of the loading rate on the coefficient of dynamic hardening of fiber-reinforced concrete has been refined. The fracture processes of the obtained materials have been established: after the initiation of primary cracks, the structure of the composite absorbs impact energy for a long time, while in the inelastic range (the onset of cracking and peak loads), a large number of secondary cracks appear.

Study in Simulated Heat-Affected Zone of Ship Steel

2011 ◽  
Vol 228-229 ◽  
pp. 1196-1200
Author(s):  
Wen Yan Liu ◽  
Ji Bin Liu ◽  
Cong Mao Zhu ◽  
Hui Wang
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Physical Simulation ◽  
Wide Range ◽  
Lath Bainite ◽  
Quench Hardening ◽  
Impact Energies ◽  
The Impact ◽  
Cct Diagrams

The experiments were carried out upon the determination of simulated heat-affected zone continuous cooling transformation (SH-CCT) diagrams, the characteristics of microstructure and Vickers hardness of SH-CCT specimens, and impact toughness in simulated coarse grain heat-affected zone (CGHAZ) of ship steels under different heat input based on physical simulation. The SH-CCT diagram reveals that bainite is always obtained in a wide range of cooling rates. When the maximum cooling rate reaches 100 °C/s (t8/5=3 seconds), the maximum fraction of martensite (8%) is obtained and the microstructures mainly consist of lath bainite and the hardness is only 255 HV. This demonstrates that the steel has a low quench-hardening tendency and excellent resistance to cold cracking. There are no obvious hardening and softening phenomena in simulated CGHAZ. Test results of impact toughness under different heat input in simulated CGHAZ show that the impact energies reach over 30 J at -40 °C when t8/5 is less than 20 s, meeting the stipulated requirements of ship steel (≥22 J at -40 °C) but no great allowance. Thus, to meet the requirement of properties during welding, it is proposed to choose t8/5 ranging from 5 to 20 s, correspondently the line energies ranging from 14 to 37 KJ/cm for 30 mm thick plate.

Impact Toughness of 0.3 Mass% Carbon Tempered Martensitic Steels Evaluated by Instrumented Charpy Test

2014 ◽  
Vol 783-786 ◽  
pp. 1033-1038
Author(s):  
Shigeto Takebayashi ◽  
Kohsaku Ushioda ◽  
Naoki Yoshinaga ◽  
Shigenobu Ogata
Keyword(s):  
Impact Toughness ◽  
Temperature Dependence ◽  
Impact Energy ◽  
Charpy Impact ◽  
Waveform Analysis ◽  
Charpy Impact Energy ◽  
Martensitic Steels ◽  
Tempering Temperature ◽  
Wide Range ◽  
The Impact

The effect of tempering temperature on the impact toughness of 0.3 mass% carbon martensitic steels with prior austenite grain (PAG) size of about 6 μm and 30 μm were investigated. Instrumented Charpy impact test (ICIT) method was used to evaluate the impact toughness. The tempering temperature of 723K gives the largest difference in the Charpy impact energy at room temperature (RT) between the specimens with two different PAG sizes. Investigation of the test temperature dependence of Charpy impact energy in the 723K tempered steels shows a steep transition at around 200 K for the 6 μm PAG specimen, while it shows a continuous slow transition in a wide range of temperature for the 60 μm PAG specimen. ICIT waveform analysis shows that the fracture propagation energy in stead of the fracture initiation energy mainly controls the temperature dependence of the impact energy. The carbide size distribution in these two specimens was investigated by SEM and TEM. The 60 μm PAG specimen shows the distribution of coarser carbides than does the 6 μm PAG specimen, which seems to be the main reason for the observed difference between them in the Charpy impact energy and the other properties of impact fracture.

scholarly journals The Effect of Sorbitol and Conservation Period on The in Vitro Evolution of Solanum Tuberosum L. Plantlets

2012 ◽  
Vol 45 (3) ◽  
pp. 79-86
Author(s):  
Iustina Brînduşa Ciobanu ◽  
Dana Constantinovici
Keyword(s):  
Moisture Content ◽  
Impact Energy ◽  
Solanum Tuberosum L ◽  
Mechanical Damage ◽  
Moisture Contents ◽  
Significant Difference ◽  
Impact Energies ◽  
The Impact ◽  
Wheat Seeds

Abstract Mechanical damage of seeds due to harvest, handling and other process is an important factor that affects the quality and quantity of seeds. Seed damage result in lower grain value, storability problem, and reduced seed germination and seedling vigor and subsequent yield of crops. The objective of this research was to determine the effects of moisture content and impact energy on the breakage susceptibility of wheat and triticale seeds. The experiments were conducted at five moisture contents of 7.5, 12, 17, 22 and 27% w.b. and at the impact energies of 0.05 and 0.1 J. The percentage of breakage of both wheat and triticale seeds increased as impact energy increased. The analysis of variance showed that there was a significant difference between breakage susceptibility of wheat and triticale seeds at the 1% probability level. Triticale seeds had more breakage than wheat seeds. For both wheat and triticale seeds as the moisture content of the seeds increased, the amount of the percentage breakage of seeds decreased as a polynomial. The average values of percentage breakage of wheat seeds decreased from 43.81 to 19.88% as the moisture content increased from 7.5 to 27%. Over this same moisture content range the percentage breakage of triticale seeds varied from 81.34 to 37.77%. Below the moisture contents of 17% for the wheat and 22% for the triticale the percentage breakage of seeds increased dramatically.

${\rm C}^+_{60}$ IONS IN COLLISIONS WITH CRYSTALLINE SURFACES: KINEMATICS AND DYNAMICS

1996 ◽  
Vol 10 (01) ◽  
pp. 11-57 ◽  
Author(s):  
TH. LILL ◽  
H.-G. BUSMANN ◽  
F. LACHER ◽  
I.V. HERTEL
Keyword(s):  
Molecular Dynamics ◽  
Kinetic Energy ◽  
Impact Energy ◽  
Tangential Component ◽  
Measured Velocity ◽  
Surface Molecules ◽  
Molecular Dynamics Calculations ◽  
Impact Energies ◽  
Impact Angles ◽  
The Impact

Collisions of [Formula: see text] ions with surfaces of highly oriented pyrolytic graphite (HOPG), diamond (111) and heteroepitaxial fullerite films on mica in the impact energy range between 100 and 1500 eV are studied by mass, energy, and angle resolved time-of-flight mass spectrometry. For the graphite and diamond surfaces, highly inelastic scattering has been observed. The analysis of the velocity dependence of the scattered ions reveals that the normal and tangential component of the ion velocity have different significance for the collision dynamics. The normal component of the velocity appears to determine the amount of energy transferred into vibrational and deformational energy of the projectile and target. The final kinetic energy is independent of the impact energy for impact angles of ≈20° and impact energies between 140 and 450 eV. This observation can be explained by the existence of an upper bound of the final kinetic energy that is defined by the amount of energy stored in the deformed molecule without being deposited or destroyed. The tangential component is partially transformed into rotational energy of the [Formula: see text] in the collision with the surface, as may be explained by a simple rolling ball model. In contrast, scattering from heteroepitaxial fullerite films is nearly elastic for impact energies up to 230 eV and impact angles of about 20°. Additionally, the velocity distributions reveal a low velocity component. Its relative intensity increases with increasing impact energy and remains the only feature in the velocity distribution for impact energies higher than 290 eV. This component is due to sputtering of surface molecules. The angular dependent intensities of the fast ions exhibit a rich structure. This can be attributed to rainbow scattering, as confirmed by classical trajectory and molecular dynamics calculations with different levels of sophistication. These calculations also show that linear collision sequences along the closed packed rows of the fullerite surface may be generated as the result of the [Formula: see text] impact. A detailed study of these collision sequences by molecular dynamics calculations reveals that rainbow effects might be possible when these sequences are defocused due to thermal motion of the surface molecules. The contribution of this process to the measured velocity and angular distributions is discussed.

Experimental and numerical behaviors of GFRP laminates under low velocity impact

2020 ◽  
Vol 54 (21) ◽  
pp. 2999-3007
Author(s):  
Hüseyin E Yalkın ◽  
Ramazan Karakuzu ◽  
Tuba Alpyıldız
Keyword(s):  
Contact Force ◽  
Impact Energy ◽  
Damage Mechanics ◽  
Matrix Material ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
Wide Range ◽  
The Impact

The aim of the study is to investigate the behavior of laminated composites under low velocity impact both experimentally and numerically. With this aim, the effects of wide range impact energy values between 10 J and 60 J were evaluated experimentally and numerically for the laminate of [±45/(0/90)2]S oriented unidirectional E-glass as reinforcing material and epoxy resin for matrix material. Different impactor velocities were used to maintain the impact energy values and experimental impact tests were generated with drop weight impact testing machine at room temperature. Numerical simulations were performed using LS-DYNA finite element analysis software with a continuum damage mechanics-based material model MAT058. Contact force between impactor and laminate, and transverse deflection at the center of laminate results were obtained as a function of time and used to plot contact force–time curves, contact force–deflection curves and absorbed energy-impact energy curves. Also, delamination area was examined. Finally, numerical results were compared with experimental results and a good correlation between them was observed.

The flexural behaviors of the impacted composite single-lap adhesive joints

2015 ◽  
Vol 22 (5) ◽  
Author(s):  
Emin Ergun ◽  
Hasan Çallioğlu
Keyword(s):  
Experimental Study ◽  
Impact Energy ◽  
Energy Levels ◽  
Composite Plates ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Single Lap Joints ◽  
Impact Tests ◽  
Impact Energies ◽  
The Impact

AbstractThis experimental study deals with the flexural behaviors of composite single-lap adhesive joints after impact tests. Increasing impact energies are applied at the center of the composite plates having three different overlap lengths. It is shown that the overlap lengths and impact energy levels affect considerably the impact responses of the composite single-lap joints. It is also shown that the bending stiffness of the composite increases with increasing overlap length. For this reason, after the impact tests, how these effects influence the flexural behaviors of the impacted composite lap joints was also investigated. The flexural loads of the impacted and non-impacted composite single-lap joints were determined and compared with each other. It is shown that the residual flexural loads after impact increase with increasing overlap lengths but decrease with increasing impact energy.

scholarly journals Design of Bionic Buffering and Vibration Reduction Foot for Legged Robots

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qian Cong ◽  
Xiaojie Shi ◽  
Ju Wang ◽  
Yu Xiong ◽  
Bo Su ◽  
...  
Keyword(s):  
Impact Energy ◽  
Vibration Reduction ◽  
Legged Robots ◽  
Normal Operation ◽  
Natural Vibration Frequency ◽  
Strong Impact ◽  
Legged Robot ◽  
Wide Range ◽  
Unique Shape ◽  
The Impact

When legged robots walk on rugged roads, they would suffer from strong impact from the ground. The impact would cause the legged robots to vibrate, which would affect their normal operation. Therefore, it is necessary to take measures to absorb impact energy and reduce vibration. As an important part of a goat’s foot, the hoof capsule can effectively buffer the impact from the ground in the goat’s running and jumping. The structure of the hoof capsules and its principle of buffering and vibration reduction were studied. Inspired by the unique shape and internal structure of the hoof capsules, a bionic foot was designed. Experimental results displayed that the bionic foot could effectively use friction to consume impact energy and ensured the stability of legged robot walking. In addition, the bionic foot had a lower natural vibration frequency, which was beneficial to a wide range of vibration reduction. This work brings a new solution to the legged robot to deal with the ground impact, which helps it adapt to a variety of complex terrain.

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