scholarly journals Parametric Study on the Free-Fall Water Entry of a Sphere by Using the RANS Method

2019 ◽  
Vol 7 (5) ◽  
pp. 122
Author(s):  
Pengyao Yu ◽  
Cong Shen ◽  
Chunbo Zhen ◽  
Haoyun Tang ◽  
Tianlin Wang
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Free Fall ◽  
Water Entry ◽  
Time Step ◽  
Measuring Device ◽  
Mesh Density ◽  
The Impact ◽  
Peak Value ◽  
Rans Method

Motivated by the application of water-entry problems in the air-drop deployment of a spherical oceanographic measuring device, the free-fall water entry of a sphere was numerically investigated by using the transient Reynolds-averaged Navier–Stokes (RANS) method. A convergence study was carried out, which accounts for the mesh density and time-step independence. The present model was validated by the comparison of non-dimensional impact force with previous experimental and numerical results. Effects of parameters, such as impact velocity, radius, and mass of the sphere on the impact force and the acceleration of the sphere, are discussed. It is found that the peak value of the non-dimensional impact force is independent of the impact velocity and the radius of the sphere, while it depends on the mass of the sphere. By fitting the relationship between the peak value of the non-dimensional impact force and the non-dimensional mass, simplified formulas for the prediction of peak values of the impact force and the acceleration were achieved, which will be useful in the design of the spherical oceanographic measuring device.

scholarly journals Experimental and Numerical Simulation Studies of RC Beams under the Actions of Equal Energy Impact Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xiwu Zhou ◽  
Xiangyu Wang ◽  
Runcheng Zhang ◽  
Wen Zhang
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Impact Testing ◽  
Rc Beams ◽  
Finite Element Software ◽  
Equal Energy ◽  
Drop Weight ◽  
Weight Impact ◽  
The Impact ◽  
Peak Value

In this study, two groups of RC beams were subjected to low-speed drop weight impact test by using the domestic advanced ultrahigh heavy-duty drop weight impact testing machine system. The main aspects studied are the influence of the combination of different impact velocity and mass on the dynamic response and local and global damage change of RC beam under the same impact energy. Next, the numerical model considering material strain rate is established using ABAQUS finite element software to verify and expand the experimental results. The results show the following: (1) under the condition of equal energy, the peak value of impact force measured in this experiment increases with the increase of impact velocity, yet the mid span displacement and rebar strain first increase and then decrease. In addition, when the impact velocity is 2.25 m/s and the impact mass is 400 kg, the beam has the most serious damage; (2) compared with the mass, the impact velocity has more obvious effects on the peak value of cumulative impact force, mid span displacement, and rebar strain; (3) with the decrease of the impact velocity (the increase of the mass), the local damage of the beam is gradually weakened and the overall damage is gradually exacerbated. The failure mode of the beam is transformed from local punching shear failure to overall static failure type.

scholarly journals Impact Force of Free-fall Lifeboats at Water Entry

1994 ◽  
Vol 90 (0) ◽  
pp. 165-173
Author(s):  
Kazuo HITOMI ◽  
Osamu MIYATA
Keyword(s):  
Impact Force ◽  
Free Fall ◽  
Water Entry

Water Entry of a Wedge by Hydroelastic Orthotropic Plate Theory

1999 ◽  
Vol 43 (03) ◽  
pp. 180-193 ◽  
Author(s):  
Odd M. Faltinsen
Keyword(s):  
Impact Velocity ◽  
Cross Sections ◽  
Orthotropic Plate ◽  
Plate Theory ◽  
Three Dimensional ◽  
Water Entry ◽  
Natural Period ◽  
Cross Sectional ◽  
Flow Effects ◽  
The Impact

Water entry of a hull with wedge-shaped cross sections is analyzed. The stiffened platings between two transverse girders on each side of the keel are separately modeled. Orthotropic plate theory is used. The effect of structural vibrations on the fluid flow is incorporated by solving the two-dimensional Laplace equation in the cross-sectional fluid domain by a generalized Wagner's theory. The coupling with the plate theory provides three-dimensional flow effects. The theory is validated by comparison with full-scale experiments and drop tests. The importance of global ship accelerations is pointed out. Hydrodynamic and structural error sources are discussed. Systematic studies on the importance of hydroelasticity as a function of deadrise angle and impact velocity are presented. This can be related to the ratio between the wetting time of the structure and the greatest wet natural period of the stiffened plating. This ratio is proportional to the deadrise angle and inversely proportional to the impact velocity. A small ratio-means that hydroelasticity is important and a large ratio means that hydroelasticity is not important.

Study on Corner Contact Shock of Gear Transmission by ADAMS Software

2015 ◽  
Vol 778 ◽  
pp. 205-211
Author(s):  
Li He ◽  
Jin Yuan Tang
Keyword(s):  
Penetration Depth ◽  
Impact Velocity ◽  
Impact Force ◽  
Ansys Software ◽  
New Approach ◽  
Adams Software ◽  
Simulation Results ◽  
The Impact ◽  
The Relationship ◽  
Key Parameter

Solving gear meshing impact force problems by using ADAMS software is studied.A pair of tooth meshing model is established based on UG, modal neutral file is generated by using ANSYS software, calculating gear meshing impact after Importing ADAMS. The relationship between the impact velocity and the impact force by taking reasonable key parameter about penetration depth in ADAMS simulation.A new approach for studying gear meshing impact is proposed here, and the simulation results show that ADAMS software is a very useful tool for solving gear corner contact shock problems outside the normal path of action line.

Numerical Analysis of Impact Velocity on the Responses of Adhesively Bonded Steel Butt Joint with Material Properties

2013 ◽  
Vol 644 ◽  
pp. 193-196 ◽  
Author(s):  
Min You ◽  
Kai Liu ◽  
Hai Zhou Yu ◽  
Ling Wu ◽  
Mei Li
Keyword(s):  
Impact Velocity ◽  
Material Properties ◽  
Impact Test ◽  
Failure Time ◽  
Butt Joint ◽  
The Finite Element Method ◽  
Adhesively Bonded ◽  
Izod Impact ◽  
The Impact ◽  
Peak Value

The effect of the impact velocity on the responses of the adhesively bonded steel butt joint during Izod impact test and the failure procedure is studied using the finite element method software ABAQUS. The results obtained show that the failure time of the element becomes little shorter when the impact velocity increased from 3.2 m/s to 10.2 m/s. The peak value of the Seqv in element 1 increases first and then decreased when the impact velocity reached 4.2 m/s. When the impact velocity is higher than 6.2 m/s, the peak value of the Seqv increased again as the impact velocity increased until 10.2 m/s. It is recommended that the impact velocity of 3.2 m/s or 5.2 m/s is suitable for Izod impact test for the adhesively bonded steel butt joint.

A comparative study on the behaviour of free-fall lifeboat launching from a skid and from a hook

2000 ◽  
Vol 214 (2) ◽  
pp. 359-370 ◽  
Author(s):  
M Reaz H Khondoker ◽  
M Arai
Keyword(s):  
Numerical Simulation ◽  
Dynamic Response ◽  
Comparative Study ◽  
Impact Force ◽  
Free Fall ◽  
Water Entry ◽  
Hydrodynamic Forces ◽  
Response Criteria ◽  
Risk Of Injury ◽  
Tremendous Impact

There are two commonly used launching methods of free-fall lifeboats: from a skid and from a hook. A free-fall lifeboat, whether it is released from a skid or from a hook, experiences tremendous impact when it enters the water. This impact force, together with other hydrostatic and hydrodynamic forces and moments, affects the motions and accelerations of the boat considerably. In this paper, a comparative study on the behaviours of the skid and hook launching of free-fall lifeboats has been presented. Numerical simulation for different launching methods has been used as a tool to obtain trajectories of the lifeboat for different launching conditions. Also polar diagrams of accelerations are drawn using the data computed for the same conditions. Dynamic response criteria have been used in order to evaluate the risk of injury to the occupants during water entry of the lifeboat.

Numerical Analysis of Impact Loads on Subsea Structures During Water Entry in Presence of Waves

2020 ◽  
Author(s):  
Gustavo Garcia Momm ◽  
Ivan Fábio Mota de Menezes
Keyword(s):  
Constant Velocity ◽  
Oil And Gas ◽  
Free Fall ◽  
Water Entry ◽  
Gas Production ◽  
Rigid Bodies ◽  
Bottom Surface ◽  
Impact Loads ◽  
Flat Bottom ◽  
The Impact

Abstract Subsea structures employed on offshore oil and gas production systems are likely to be subject to severe loads during deployment. Lowering these structures through the wave zone is a critical operation and the prediction of the loads associated is complex as it involves accelerations of these bodies induced by the vessel motion and the sea surface displacements. This work presents a numerical approach to assessment of the effect of waves on the impact loads that subsea structures are subject to during water entry. A 2D one degree of freedom model using the SPH method was developed to estimate slamming loads on rigid bodies during water entry considering both calm and wavy surfaces. Initially the model was employed to simulate the water entry of wedge considering both free fall and constant velocity cases, obtaining loads profile similar to experiments and numerical simulations from the literature. Later, the constant velocity model was configured to a flat bottom surface rigid body in order to represent a subsea manifold. A regular waves generator provided different wavelength, height and phase enabling slamming load assessment in various situations.

scholarly journals Impact of rockfalls on protection measures: an experimental approach

2015 ◽  
Vol 15 (4) ◽  
pp. 885-893 ◽  
Author(s):  
J. K. Yuan ◽  
Y. R. Li ◽  
R. Q. Huang ◽  
X. J. Pei
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Incident Angle ◽  
Drop Height ◽  
Current Standard ◽  
Protection Measures ◽  
Buffer Material ◽  
Cushion Layer ◽  
Study Laboratory ◽  
The Impact

Abstract. The determination of rockfall impact force is crucial in designing protection measures. In the present study, laboratory tests are carried out by testing the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway, and cushion layer on the protection measures to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall and the length of the platform on the slideway. A great drop height and/or a short platform produces a fast impact velocity. Spherical rockfalls experience a greater impact velocity than cubes and elongated cuboids. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the lower the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by not taking into consideration the rockfall shape, platform, and cushion layer.

Incline Impact: A Case Study

2021 ◽  
Vol 9 (1) ◽  
pp. 327-333
Author(s):  
S. Malasri ◽  
◽  
T. Podesta ◽  
R. Moats ◽  
T. Waddell ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Impact Test ◽  
Free Fall ◽  
Rolling Friction ◽  
Shock Test ◽  
Platform Location ◽  
Christian Brothers ◽  
Impact Tester ◽  
The Impact

An incline impact test can be used as a shock test in lieu of a drop test in several test protocols, including ISTA Procedure 1A [1]. Some test protocols, such as ISTA Procedure 1E [2], only allow for an incline impact test and horizontal impact test. In this case study, a graph was developed for a 500-lb impact tester at Christian Brothers University (CBU) Packaging Laboratory. It determines sliding platform location on the incline for a given packaged-product weight to meet the impact velocity recommended by the International Safe Transit Association (ISTA). One station of the platform location higher than the station obtained from the graph is recommended to ensure the meeting of ISTA recommended impact velocity. It is well known that weight is not used in impact velocity of a free fall drop. However, this case study shows that weight contributes to impact velocity of an incline impact test. It contributes to the rolling friction. A heavier weight yields a smaller coefficient of rolling friction ( 𝜇𝑘 ), which results in a higher impact velocity. The coefficient of rolling friction for CBU’s incline impact tester can be computed from 𝜇𝑘 = −9 −5𝑤 + 0.1092, where w is the total weight of the sliding platform and packaged product.

Statistical Evolution of Microvoids in Particle-Filled Polymers under Plate Impact

2006 ◽  
Vol 312 ◽  
pp. 111-116 ◽  
Author(s):  
Jian Kang Chen ◽  
Zhu Ping Huang ◽  
Shu Lin Bai
Keyword(s):  
Impact Velocity ◽  
Critical Value ◽  
Strain Wave ◽  
Plate Impact ◽  
Filled Polymers ◽  
One Dimensional ◽  
Adhesive Energy ◽  
The Impact ◽  
Statistical Evolution ◽  
Peak Value

Statistical evolution of microvoids in a particle-filled polymer under plate impact is theoretically studied. Based on the constitutive equations of the material recently obtained by the authors, the velocity of the propagation of one-dimensional strain wave caused by the plate impact is analyzed, and the evolution of the microdamage is calculated. It is shown that the microvoid evolution is influenced by several factors, such as particle size-dispersity, average radius of particles, and the adhesive energy of the interface. The numerical results show that there is a sensitive crest of the impact velocity for microvoid evolution. If the impact velocity reaches the critical value corresponding to the peak value of the crest, the microvoids accumulation will increase rapidly, and it may lead to the dynamic failure of the material.

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