Impact response characteristics and meso-evolution mechanism of functionally gradient brittle materials with pore hole damage

In current US Military operations, warfighters are frequently subjected to blast events, which can lead to traumatic brain injury (TBI). In response to this recent and increasingly prevalent threat, helmet systems must protect the head against high velocity, short duration overpressures in addition to blunt and ballistic impacts. Understanding the blast impact response characteristics of helmet systems may improve the design and selection process for headborne equipment and contribute to reducing blast-related brain injury.

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Experimental Investigations of Offshore Sand Production Monitoring Based on the Analysis of Vibration in Response to Weak Shocks

Geofluids ◽

10.1155/2021/9953498 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Yichen Li ◽

Gang Liu ◽

Zongwen Jia ◽

Min Qin ◽

Gang Wang ◽

...

Keyword(s):

Pipe Wall ◽

Oil Wells ◽

Impact Response ◽

Sand Production ◽

Time Frequency ◽

Response Characteristics ◽

Sand Particles ◽

Production Monitoring ◽

Offshore Oil ◽

The Impact

Sand production is a problem that is often encountered in unconventional oil and gas exploitation and that is difficult to effectively solve. Accurate online monitoring of sand production is one of the keys to ensuring the safety and long-term production of oil wells as well as efficient production throughout the life cycle of production wells. This paper proposes a method for monitoring sand production in offshore oil wells that is based on the vibration response characteristics of sand-carrying fluid flow impinging on the pipe wall. This method uses acceleration sensors to obtain the weak vibration response characteristics of sand particles impinging on the pipe wall on a two-dimensional time-frequency plane. The time-frequency parameters are further optimized, and the ability to identify weakly excited vibration signals of sand particles in the fluid stream is enhanced. The difference between the impact response of the sand particles and the impact response of the fluid flow to the pipe wall is identified, and corresponding indoor verification experiments are carried out. Under different sand contents, particle sizes, and flow rates (sand content 0-2‰, sand particle size 96-212 μm, and flow velocity 1-3 m/s), the impact response frequency of sand particles to the pipe wall exhibits good consistency. The characteristic frequency band of sand impacting the pipe wall is 30-50 kHz. A statistical method is used to establish the response law of the noise signal of the fluid. Based on this knowledge, a real-time calculation model of sand production in offshore oil wells is constructed, and the effectiveness of this model is verified. Finally, a field test is carried out with a self-developed sand production signal dynamic time-frequency response software system on 4 wells of an oil production platform in the Bohai Sea. This system can effectively distinguish sand-producing wells from non-sand-producing wells. The dynamic time-frequency response, field test results, and actual laboratory results are consistent, verifying the effectiveness of the method proposed in this paper and further providing a theory for improving the effectiveness of the sand production monitoring method under complex multiphase flow conditions. This study also provides technical guidance for the industrial application of sand production monitoring devices in offshore oil wells.

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Effect of Porosity on Dynamic Mechanical Properties and Impact Response Characteristics of High Aluminum Content PTFE/Al Energetic Materials

Materials ◽

10.3390/ma13010140 ◽

2019 ◽

Vol 13 (1) ◽

pp. 140 ◽

Cited By ~ 4

Author(s):

Chunlan Jiang ◽

Shangye Cai ◽

Liang Mao ◽

Zaicheng Wang

Keyword(s):

Mechanical Properties ◽

Energetic Materials ◽

Aluminum Content ◽

Dynamic Compression ◽

Dynamic Mechanical Properties ◽

Impact Response ◽

Dynamic Mechanical ◽

Response Characteristics ◽

High Aluminum Content ◽

High Aluminum

In order to obtain the effect of porosity on the dynamic mechanical properties and impact response characteristics of high aluminum content PTFE/Al energetic materials, PTFE/Al specimens with porosities of 1.2%, 10%, 20%, and 30% were prepared by adding additives. The dynamic compression properties and impact response characteristics of high aluminum content PTFE/Al energetic materials with porosity were studied by using a split Hopkinson pressure bar (SHPB) impact loading experimental system. Based on the one-dimensional viscoplastic hole collapse model, an impact temperature rise analysis model including melting effects was used, and corresponding calculation analysis was performed. The results show that with the increase of porosity, the yield strength and compressive strength of the material will decrease. Under dynamic loading, the reaction duration of PTFE/Al energetic materials with different porosities generally shows a tendency to become shorter as the porosity increases, while the ignition delay time is basically unchanged. In this experiment, the material response has the optimal porosity with the lowest critical strain rate, the optimal porosity for PTFE/Al energetic materials with different porosity and high aluminum content (50/50 mass ratio, size of specimens Φ8 × 5 mm) is 10%. The research results can provide an important reference for the engineering application of PTFE/Al energetic materials.

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Impact response characteristics of a cyclotetramethylene tetranitramine based polymer-bonded explosives under different temperatures

Journal of Applied Physics ◽

10.1063/1.4820248 ◽

2013 ◽

Vol 114 (11) ◽

pp. 114906 ◽

Cited By ~ 3

Author(s):

Dai Xiaogan ◽

Wen Yushi ◽

Huang Hui ◽

Zhang Panjun ◽

Wen Maoping

Keyword(s):

Impact Response ◽

Response Characteristics ◽

Different Temperatures ◽

Polymer Bonded Explosives ◽

Cyclotetramethylene Tetranitramine

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The Impact Response Characteristics Research of the Multilayer Structure, Cantilever-Type Electrothermal Actuator Based on MEMS

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.901.87 ◽

2014 ◽

Vol 901 ◽

pp. 87-92

Author(s):

Ya He Wang ◽

Yue Yue Shen ◽

Chao Lv

Keyword(s):

Multilayer Structure ◽

Fem Simulation ◽

Impact Response ◽

Von Mises Stress ◽

Beam Model ◽

The Finite Element Method ◽

Response Characteristics ◽

Von Mises ◽

Fixed End ◽

The Impact

To study the impact response characteristics of multilayer structure, cantilever-type electrothermal actuators based on MEMS, a composite cantilever-beam model consisting of two layers of materials, SiO2 and Al, is built. By using the engineer mechanics theory, the von mise stress under the impacts in the fuze system can be obtained. Meanwhile, the Finite Element Method (FEM) simulation is made to get the deformation displacement of the fixed end and the von mises stress distribution of the model. Besides, the natural frequency response is studied. The results present the actuators response characteristics of impacts in the fuze system.

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