scholarly journals Sandwich panel with in-plane honeycombs in different Poisson's ratio under low to medium impact loads

2021 ◽  
Vol 60 (1) ◽  
pp. 145-157
Author(s):  
Yi Luo ◽  
Ke Yuan ◽  
Lumin Shen ◽  
Jiefu Liu
Keyword(s):  
Poisson’S Ratio ◽  
Sandwich Panel ◽  
Impact Force ◽  
Impact Resistance ◽  
Poisson's Ratio ◽  
Compression Performance ◽  
Post Impact ◽  
Local Impact ◽  
Collapse Behavior ◽  
The Impact

Abstract In this study, a series of in-plane hexagonal honeycombs with different Poisson's ratio induced by topological diversity are studied, considering re-entrant, semi-re-entrant and convex cells, respectively. The crushing strength of honeycomb in terms of Poisson's ratio is firstly presented. In the previous research, we have studied the compression performance of honeycomb with different negative Poisson's ratio. In this study, a comparative study on the local impact resistance of different sandwich panels is conducted by considering a spherical projectile with low to medium impact speed. Some critical criteria (i.e. local indentation profile, global deflection, impact force and energy absorption) are adopted to analyze the impact resistance. Finally, an influential mechanism of Poisson's ratio on the local impact resistance of sandwich panel is studied by considering the variation of core strength and post-impact collapse behavior.

scholarly journals Investigation on the Debonding Failure Model of Anchored Polyurea Coating under a High-Velocity Water Flow and Its Application

2019 ◽  
Vol 11 (5) ◽  
pp. 1261 ◽  
Author(s):  
Bingqi Li ◽  
Zhenyu Zhang ◽  
Xiaogang Wang ◽  
Xiaonan Liu
Keyword(s):  
Elastic Modulus ◽  
High Velocity ◽  
Poisson’S Ratio ◽  
Impact Resistance ◽  
Engineering Application ◽  
Poisson's Ratio ◽  
Zone Model ◽  
Failure Model ◽  
Flood Discharge ◽  
The Impact

The debonding failure of a polymer-based coating seriously affects the safe operation of buildings under the action of a high-velocity flood discharge flow. In order to achieve a healthy and sustainable operation of hydropower stations, the debonding failure between polyurea coating and concrete was described by the cohesive zone model, and a debonding failure model was proposed and verified. The results obtained from the model were basically consistent with the test results. Accordingly, the influence of the performance of different anchoring types, the material mechanics of polyurea-based coating and the bonding on debonding behavior were analyzed, and engineering application research was also carried out. The impact resistances of polyurea-based coating under different anchoring conditions are obtained, which provide a reference for the anti-shock and wear-resistant design of flood discharge infrastructure. The elastic modulus and Poisson’s ratio of the polyurea-based material have a significant influence on the impact resistance of polyurea-based coatings. When the elastic modulus and Poisson’s ratio of a polyurea-based material are 25 MPa and 0.45, respectively, the impact resistance is optimal. The greater the fracture energy of the bonding material, the better the impact resistance. The engineering application results show that the seepage prevention and anti-wear characteristics of flood discharge infrastructure all meet the engineering requirements.

scholarly journals Study on the Impact Resistance of Metal Flexible Net to Rock fall

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Gaosheng Wang ◽  
Yunhou Sun ◽  
Ao Zhang ◽  
Lei Zheng ◽  
Yuzheng Lv ◽  
...  
Keyword(s):  
Finite Element ◽  
Impact Force ◽  
Impact Resistance ◽  
Time History ◽  
Rock Fall ◽  
Fe Model ◽  
Element Analysis ◽  
Inclination Angles ◽  
Fall Protection ◽  
The Impact

Based on experiments and finite element analysis, the impact resistance of metal flexible net was studied, which can provide reference for the application of metal flexible net in rock fall protection. The oblique (30 degrees) impact experiment of metal flexible net was carried out, the corresponding finite element (FE) to the experiment was established, and the FE model was verified by simulation results to the experimental tests from three aspects: the deformation characteristics of metal flexible net, the time history curves of impact force on supporting ropes, and the maximum instantaneous impact force on supporting ropes. The FE models of metal flexible nets with inclination angles of 0, 15, 30, 45, 60, and 75 degrees were established, and the impact resistance of metal flexible nets with different inclination angles was analyzed. The research shows that the metal flexible net with proper inclination can bounce the impact rock fall out of the safe area and prevent rock fall falling on the metal flexible net, thus realizing the self-cleaning function. When the inclination angle of the metal flexible net is 15, 30, and 45 degrees, respectively, the bounce effect after impact is better, the remaining height is improved, the protection width is improved obviously, and the impact force is reduced. Herein, the impact force of rock fall decreases most obviously at 45 degrees inclination, and the protective performance is relatively good.

scholarly journals 4D Printing of NiTi Auxetic Structure with Improved Ballistic Performance

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 745
Author(s):  
Hany Hassanin ◽  
Alessandro Abena ◽  
Mahmoud Ahmed Elsayed ◽  
Khamis Essa
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Analytical Model ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
4D Printing ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio ◽  
The Impact ◽  
Auxetic Structure

Auxetic structures have attracted attention in energy absorption applications owing to their improved shear modulus and enhanced resistance to indentation. On the other hand, four-dimensional (4D) printing is an emerging technology that is capable of 3D printing smart materials with additional functionality. This paper introduces the development of a NiTi negative-Poisson’s-ratio structure with superelasticity/shape memory capabilities for improved ballistic applications. An analytical model was initially used to optimize the geometrical parameters of a re-entrant auxetic structure. It was found that the re-entrant auxetic structure with a cell angle of −30° produced the highest Poisson’s ratio of −2.089. The 4D printing process using a powder bed fusion system was used to fabricate the optimized NiTi auxetic structure. The measured negative Poisson’s ratio of the fabricated auxetic structure was found in agreement with both the analytical model and the finite element simulation. A finite element model was developed to simulate the dynamic response of the optimized auxetic NiTi structure subjected to different projectile speeds. Three stages of the impact process describing the penetration of the top plate, auxetic structure, and bottom plate have been identified. The results show that the optimized auxetic structures affect the dynamic response of the projectile by getting denser toward the impact location. This helped to improve the energy absorbed per unit mass of the NiTi auxetic structure to about two times higher than that of the solid NiTi plate and five times higher than that of the solid conventional steel plate.

scholarly journals High Partial Auxeticity Induced by Nanochannels in [111]-Direction in a Simple Model with Yukawa Interactions

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2550 ◽  
Author(s):  
Konstantin Tretiakov ◽  
Paweł Pigłowski ◽  
Jakub Narojczyk ◽  
Mikołaj Bilski ◽  
Krzysztof Wojciechowski
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Poisson’S Ratio ◽  
Yukawa Potential ◽  
Poisson's Ratio ◽  
Debye Screening Length ◽  
Debye Screening ◽  
Screening Length ◽  
Narrow Channels ◽  
The Impact

Computer simulations using Monte Carlo method in the isobaric-isothermal ensemble were used to investigate the impact of nanoinclusions in the form of very narrow channels in the [ 111 ] -direction on elastic properties of crystals, whose particles interact via Yukawa potential. The studies were performed for several selected values of Debye screening length ( ( κ σ ) − 1 ). It has been observed that introduction of the nanoinclusions into the system reduces the negative value of Poisson’s ratio towards [ 110 ] [ 1 1 ¯ 0 ] , maintaining practically constant values of Poisson’s ratio in the directions [ 100 ] and [ 111 ] . These studies also show that concentration of particles forming the nanoinclusions in the system has a significant effect on the value of Poisson’s ratio in the [ 110 ] [ 1 1 ¯ 0 ] -direction. A strong (more than fourfold) decrease of Poisson’s ratio in this direction was observed, from − 0.147 ( 3 ) (system without inclusions) to − 0.614 ( 14 ) (system with nanoinclusions) at κ σ = 10 when the inclusion particles constituted about 10 percent of all particles. The research also showed an increase in the degree of auxeticity in the system with increasing concentration of nanoinclusion particles for all the screening lengths considered.

Saint-Venant End Effects for Materials With Negative Poisson’s Ratios

1992 ◽  
Vol 59 (4) ◽  
pp. 744-746 ◽  
Author(s):  
R. S. Lakes
Keyword(s):  
Circular Cylinder ◽  
Elastic Material ◽  
Poisson’S Ratio ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
End Effects ◽  
Slow Decay ◽  
Negative Poisson's Ratio

In this paper we analyze Saint-Venant end effects for materials with negative Poisson ’s ratios. We present an example of slow decay of stress arising from selfequilibrated stress at the end of a circular cylinder of elastic material with a negative Poisson’s ratio. By contrast, a sandwich panel containing rigid face sheets and a compliant core exhibits no anomalous effects for negative Poisson’s ratio, but exhibits slow stress decay for core Poisson’s ratio approaching 0.5. In sandwich panels with stiff but not perfectly rigid face sheets, slow decay of stress is known to occur; a negative Poisson’s ratio results in end stress decay, which is faster than it would be otherwise.

scholarly journals Study of Passive Protective Net Protecting the Rockfall Caused by Open-Pit Blasting on High and Steep Slope

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhiyu Zhang ◽  
Qingyun Qian ◽  
Jianguo Wang ◽  
Haoshan Liu ◽  
Ke Liang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Impact Force ◽  
Impact Resistance ◽  
Steep Slope ◽  
Interaction Time ◽  
Open Pit ◽  
Buffer Time ◽  
The Impact ◽  
Impulse Force ◽  
High And Steep Slope

In order to prevent rockfall caused by open-pit blasting on the high and steep slope and ensure that the passive protective net structure has sufficient impact resistance, the mechanism of blasting flyrock causing rockfall is analyzed by using ANSYS/AUTODYN to establish the model of rockfall and passive protective net; at the same time, the influences of protective net size, rockfall kinetic energy, and rockfall size to the protective effect were also studied. The results show that under the condition of the same rockfall kinetic energy and rockfall size, the larger the size of the protective net, the longer the buffer time, and the impact force that net can sustain is greater; by assuming the protective net size and rockfall size to be a constant, the greater the rockfall kinetic energy, the less the interaction time between rock and net, and the greater the impulse force that net can suffer; similarly, by keeping the protective net size and the kinetic energy of rockfall to be a constant, it is found that the larger the size of the rockfall, the larger the interaction area and longer interaction time with the net, and the less net will be disrupted; the protective net used in the mine can intercept the rockfall caused by flyrock in blasting process effectively and ensure the safety of villager at the foot of the mountain.

Impact Resistance of SM Joints Formed With ICA

2002 ◽  
Vol 124 (4) ◽  
pp. 374-378 ◽  
Author(s):  
C. M. Lawrence Wu ◽  
Robert K. Y. Li ◽  
N. H. Yeung
Keyword(s):  
Impact Damage ◽  
Impact Resistance ◽  
High Energy ◽  
Bending Test ◽  
Conductive Adhesives ◽  
Energy Impact ◽  
Split Hopkinson ◽  
Post Impact ◽  
Impact Bending ◽  
The Impact

Isotropic conductive adhesives (ICA) have been considered as replacement materials for lead-tin solder alloys. In this paper, the post-impact shear strength of ICA surface mount (SM) joints was obtained experimentally and compared with that of SM lead-tin joints. The dynamic impact energy was provided in the form of three-point bending on the PCB using equipment called the split Hopkinson bar. Strain rates of over 4000/s were used for the impact bending test. The action of impact bending was used to simulate the effect on the PCB and the interconnection as a result of high energy impact on an electronic equipment. Shear test was then performed to examine the change in strength of the ICA joints as a result of impact damage. It was found that the SM ICA joints failed due to impact at a strain rate just over 4000/s. Microstructural examination carried out using a scanning electron microscope revealed that the interface between the ICA and copper pad on the PCB was the weakest region of the joint.

scholarly journals Numerical Investigation on Dynamic Response of RC T-Beams Strengthened with CFRP under Impact Loading

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 890
Author(s):  
Huiling Zhao ◽  
Xiangqing Kong ◽  
Ying Fu ◽  
Yihan Gu ◽  
Xuezhi Wang
Keyword(s):  
Numerical Simulation ◽  
Impact Force ◽  
Reaction Force ◽  
Impact Resistance ◽  
Structural Response ◽  
Element Model ◽  
Strengthening Effect ◽  
Strengthened Beam ◽  
Simulation Results ◽  
The Impact

To precisely evaluate the retrofitting effectiveness of Carbon Fiber Reinforced Plastic (CFRP) sheets on the impact response of reinforced concrete (RC) T-beams, a non-linear finite element model was developed to simulate the structural response of T-beams with CFRP under impact loads. The numerical model was firstly verified by comparing the numerical simulation results with the experimental data, i.e., impact force, reaction force, and mid-span displacement. The strengthening effect of CFRP was analyzed from the section damage evaluation. Then the impact force, mid-span displacement, and failure mode of CFRP-strengthened RC T-beams were studied in comparison with those of un-strengthened T-beams. In addition, the influence of the impact resistance of T-beams strengthened with FRP was investigated in terms of CFRP strengthening mode, CFRP strengthening sizes, CFRP layers and FRP material types. The numerical simulation results indicate that the overall stiffness of the T-beams was improved significantly due to external CFRP strips. Compared with the un-strengthened beam, the maximum mid-span displacement of the CFRP-strengthened beam was reduced by 7.9%. Additionally, the sectional damage factors of the whole span of the CFRP-strengthened beam were reduced to less than 0.3, indicating that the impact resistance of the T-beams was effectively enhanced.

Foreign Object Damage Behavior of a SiC Fibrous Ceramic Composite

2017 ◽  
Author(s):  
Nesredin Kedir ◽  
D. Calvin Faucett ◽  
Luis Sanchez ◽  
Sung R. Choi
Keyword(s):  
Ceramic Composite ◽  
Impact Force ◽  
Impact Damage ◽  
Incidence Angle ◽  
Fibrous Composite ◽  
Normal Incidence ◽  
Foreign Object ◽  
Foreign Object Damage ◽  
Post Impact ◽  
The Impact

The response of a SiC fibrous ceramic composite to foreign object damage was determined at ambient temperature and velocities ranging from 40 to 150 m/s. Target specimens were impacted, at a normal incidence angle and in a partially supported configuration, using 1.59 mm-diameter hardened steel ball projectiles. Qualitative analysis of the damage morphologies of targets and projectiles were made via scanning electron microscopy (SEM). In addition, the extent of impact damage was characterized by determining the post-impact strength of each target specimen as a function of impact velocity. Relative to the as-received strength, the fibrous composite showed limited strength degradation due to impact with the maximum reduction of 17 % occurring at 150 m/s. A quasi-static analysis of the impact force prediction was also made based on the principle of energy conservation and the results were verified via experimental data.

Design Considerations for Materials with Negative Poisson’s Ratios

1993 ◽  
Vol 115 (4) ◽  
pp. 696-700 ◽  
Author(s):  
R. S. Lakes
Keyword(s):  
Stress Concentration ◽  
Poisson’S Ratio ◽  
Sandwich Panel ◽  
Poisson's Ratio ◽  
Design Considerations ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

This article presents a study of the implications of negative Poisson’s ratios in the design of components subjected to stress. When the Poisson’s ratio becomes negative, stress concentration factors are reduced in some situations and unchanged or increased in others. Stress decay according to Saint Venant’s principle can occur more or less rapidly as the Poisson’s ratio decreases. Several design examples are presented, including a core for a curved sandwich panel and a flexible impact buffer.

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