Shortening Droplet Contact Time over a Wider Impact Velocity Range by Molding Flexible Nanohairs and Substrates

2021 ◽  
Author(s):  
Han-Xiong Huang ◽  
Hui-Long Huang
Keyword(s):  
Impact Velocity ◽  
Contact Time ◽  
Velocity Range

scholarly journals Cratering for Impact of Hypervelocity Projectiles into Granite Targets within a Velocity Range of 1.91–3.99 km/s: Experiments and Analysis

2020 ◽  
Vol 10 (4) ◽  
pp. 1393
Author(s):  
Xiaofeng Wang ◽  
Jingbo Liu ◽  
Biao Wu ◽  
Defeng Kong ◽  
Jiarong Huang ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Scaling Law ◽  
Density Ratio ◽  
Hypervelocity Impact ◽  
Experimental Results ◽  
Tungsten Alloy ◽  
Regression Equations ◽  
Velocity Range ◽  
Predicted Values ◽  
The Impact

To understand and analyze crater damage of rocks under hypervelocity impact, the hypervelocity impact cratering of 15 shots of hemispherical-nosed cylindrical projectiles into granite targets was studied within the impact velocity range of 1.91–3.99 km/s. The mass of each projectile was 40 g, and the length–diameter ratio was 2. Three types of metal material were adopted for the projectiles, including titanium alloy with a density of 4.44 g/cm3, steel alloy with a density of 7.81 g/cm3, and tungsten alloy with a density of 17.78 g/cm3. The projectile–target density ratio (ρp/ρt) ranged from 1.71 to 6.86. The depth–diameter ratios (H/D) of the craters yielded from the experiments were between 0.14 and 0.24. The effects of ρp/ρt and the impact velocity on the morphologies of the crater were evaluated. According to the experimental results, H/D of craters is negatively correlated with the impact velocity, whereas the correlation between H/D and ρp/ρt is weak positive. The crater parameters were expressed as power law relations of impact parameters by using scaling law analysis. The multiple regression analysis was utilized to obtain the coefficients and the exponents of the relation equations. The predicted values of the regression equations were close to the experimental results.

Numerical Study on the Equivalent Target for Deep Penetration

2011 ◽  
Vol 109 ◽  
pp. 32-36
Author(s):  
Shu You Wang ◽  
Jian Bing Men ◽  
Jian Wei Jiang
Keyword(s):  
Impact Velocity ◽  
Numerical Study ◽  
Boundary Effect ◽  
Diameter Ratio ◽  
Boundary Effects ◽  
Deep Penetration ◽  
Finite Element Code ◽  
Velocity Range ◽  
Depth Limit ◽  
Penetration Effect

The influence of radial and axial boundary effect on penetration effect are calculated, numerical simulation are executed to compute the kinetic projectile against deep hard target by finite element code, the boundary effects were achieved for different velocity range. Result shows that the minimal Dt/Dp (diameter ratio of target to projectile) for impact velocity 600m/s is 17.5, while the minimal Dt/Dp for impact velocity 900m/s is 20. Furthermore, the depth of equivalent target to substitute semi-infinite target is twice of penetration depth limit for impact velocity 300m/s, and 1.6 times respectively, for impact velocity 600m/s, 900m/s.

scholarly journals Realistic Reference for Evaluation of Vehicle Safety Focusing on Pedestrian Head Protection Observed From Kinematic Reconstruction of Real-World Collisions

2021 ◽  
Vol 9 ◽  
Author(s):  
Guibing Li ◽  
Jinming Liu ◽  
Kui Li ◽  
Hui Zhao ◽  
Liangliang Shi ◽  
...  
Keyword(s):  
Head Injury ◽  
Impact Velocity ◽  
Real World ◽  
Contact Time ◽  
Injury Risk ◽  
Safety Performance ◽  
Contact Boundary ◽  
Vehicle Safety ◽  
Pedestrian Protection ◽  
Vehicle Impact

Head-to-vehicle contact boundary condition and criteria and corresponding thresholds of head injuries are crucial in evaluation of vehicle safety performance for pedestrian protection, which need a constantly updated understanding of pedestrian head kinematic response and injury risk in real-world collisions. Thus, the purpose of the current study is to investigate the characteristics of pedestrian head-to-vehicle contact boundary condition and pedestrian AIS3+ (Abbreviated Injury Scale) head injury risk as functions of kinematic-based criteria, including HIC (Head Injury Criterion), HIP (Head Impact Power), GAMBIT (Generalized Acceleration Model for Brain Injury Threshold), RIC (Rotational Injury Criterion), and BrIC (Brain Injury Criteria), in real-world collisions. To achieve this, 57 vehicle-to-pedestrian collision cases were employed, and a multi-body modeling approach was applied to reconstruct pedestrian kinematics in these real-world collisions. The results show that head-to-windscreen contacts are dominant in pedestrian collisions of the analysis sample and that head WAD (Wrap Around Distance) floats from 1.5 to 2.3 m, with a mean value of 1.84 m; 80% of cases have a head linear contact velocity below 45 km/h or an angular contact velocity less than 40 rad/s; pedestrian head linear contact velocity is on average 83 ± 23% of the vehicle impact velocity, while the head angular contact velocity (in rad/s) is on average 75 ± 25% of the vehicle impact velocity in km/h; 77% of cases have a head contact time in the range 50–140 ms, and negative and positive linear correlations are observed for the relationships between pedestrian head contact time and WAD/height ratio and vehicle impact velocity, respectively; 70% of cases have a head contact angle floating from 40° to 70°, with an average value of 53°; the pedestrian head contact angles on windscreens (average = 48°) are significantly lower than those on bonnets (average = 60°); the predicted thresholds of HIC, HIP, GAMBIT, RIC, BrIC2011, and BrIC2013 for a 50% probability of AIS3+ head injury risk are 1,300, 60 kW, 0.74, 1,470 × 104, 0.56, and 0.57, respectively. The findings of the current work could provide realistic reference for evaluation of vehicle safety performance focusing on pedestrian protection.

The Dynamic Impact Behaviors of NiTi Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 1933-1936 ◽  
Author(s):  
Ren Bo Xu ◽  
Li Shan Cui ◽  
Yan Jun Zheng
Keyword(s):  
Impact Velocity ◽  
Contact Force ◽  
Contact Time ◽  
Phase State ◽  
Niti Alloy ◽  
Parent Phase ◽  
Dynamic Impact ◽  
Increasing Temperature ◽  
Maximum Contact ◽  
Maximum Contact Force

The contact force during impact of a NiTi alloy was studied in this paper. The contact force and contact time during impact between a spherical impactor and the specimen at different impact velocity and temperature were measured in real time. The maximum contact force and contact time of the NiTi alloy in the martensite state increased and decreased respectively with increasing temperature. The maximum contact force of the NiTi alloy in the parent phase state showed a plateau with increasing impact velocity of the impactor.

Numerical Analysis on Impact Load of Elasto-Plastic Spherical Impact

2011 ◽  
Vol 189-193 ◽  
pp. 1840-1843
Author(s):  
Chang Long Du ◽  
Yu Liu ◽  
Jian Ping Li
Keyword(s):  
Impact Velocity ◽  
Contact Time ◽  
Impact Load ◽  
Contact Stiffness ◽  
Impact Loads ◽  
Elastic Impact ◽  
Impact Simulation ◽  
Negative Exponential ◽  
The Impact ◽  
Exponential Relation

The spherical impact is a common phenomenon in mechanical engineering. The elasto-plastic impact is more complicate than the elastic impact. The elasto-plastic impact loads are investigated for the different contact stiffness and the different impact velocity by the nonlinear finite element method. The accuracy and reliability of the finite elements model are verified by comparing the numerical results of the elastic impact with the Hertz results. The elasto-plastic impact simulation shows that the impact loads have a negative exponential relation with the contact stiffness as well as a linear relation with the impact velocity. The contact time decrease with the increase of the contact stiffness and the impact velocity. The comparison between the influence of the contact stiffness and the impact velocity indicates that the impact velocity has a significant influence on the impact load and the contact stiffness has a big influence on the contact time.

Porous Barriers Efficiency Research under the Compact Elements High-Speed Loading (Part Two)

2020 ◽  
Vol 303 ◽  
pp. 1-7
Author(s):  
E.N. Kramshonkov ◽  
A.V. Krainov ◽  
Evgeny N. Pashkov
Keyword(s):  
Numerical Simulation ◽  
Impact Velocity ◽  
High Speed ◽  
Equal Mass ◽  
Tungsten Alloy ◽  
Shock Interaction ◽  
Initial Speed ◽  
Velocity Range ◽  
High Speed Impact ◽  
Porous Barriers

The paper discusses the results of the numerical simulation of high-speed impact effect of compact projectiles made of steel and tungsten alloy with steel obstacles of equal mass. The obstacles have different initial porosity of the material. Conducted the final evaluation of the penetration speed of the projectile depending on the porosity of the obstacle and the initial speed of the shock interaction. The initial impact velocity range from 1 to 16 [km/s]. The destruction, melting and evaporation of the interacting bodies are taken into account. The analysis of porosity influence evaluation of obstacles material revealed that the protective advantage of porous obstacles disclose at the higher impact velocities, greater than 1.5 [km/s] for steel strikers and 2 [km/s] for projectiles of tungsten alloy. The more impact velocity the more protective effect of porous obstacles.

Second Paper: Extrusion of Steel and Titanium

1967 ◽  
Vol 182 (1) ◽  
pp. 188-202 ◽  
Author(s):  
E. R. Austin ◽  
R. Davies ◽  
F. Bakhtar
Keyword(s):  
Impact Velocity ◽  
High Impact ◽  
Velocity Range ◽  
Backward Extrusion ◽  
Forward Extrusion ◽  
High Speeds ◽  
Extruded Product ◽  
Work Of Deformation ◽  
The Impact ◽  
Very High

This paper describes the results of forward and backward extrusion tests on steel and titanium specimens at very high impact speeds, using reductions in area of 44 to 86 per cent. The specimens were in all cases of 1-in diameter, 1.5 in long. For the cold forward extrusion of steel, impact speeds over the range 68-310 ft/s were used. Comparison of mean extrusion and work of deformation at these high speeds was made with the values arising at very low speed. Extrusion pressures were minimal in the impact velocity range 40-80 ft/s. Tests using steel billets preheated to temperatures between 300 and 600°C showed no great advantage in preheating above 400°C. This degree of preheating showed considerable advantages over the cold process, in that extrusion pressures were much reduced, product quality was improved, and higher extrusion ratios could be obtained. Limited backward extrusion tests at 66 ft/s proved the feasibility of the process. Gold forward extrusion of titanium at 65 and 167 ft/s was successful only at the relatively low reductions in area of 44 and 61 per cent. At higher degrees of deformation, the extruded product broke into small pieces.

The measurement of initial impact velocity and contact time

1971 ◽  
Vol 4 (1) ◽  
pp. 160-163 ◽  
Author(s):  
A Bokor ◽  
H G Leventhall
Keyword(s):  
Impact Velocity ◽  
Contact Time
Sign in / Sign up

Export Citation Format

Share Document