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The effects of compressibility and strength on penetration of long Rod and jet

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Defence Technology（防务技术） 2018年第2期14卷 99-108页

作者： Weng-jie Song Xiao-wei Chen Pu Chen Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China Centre for Applied Physics and Technology(CAPT) Peking UniversityBeijing 100871China State Key Lab of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The approximate compressible model is adopted to study the effects of strength and compressibility on the penetration by WHA long Rod and copper jet into semi-infinite target in detail. For WHA Rod penetrating PMMA at 2 km/s Rod and target. For WHA Rod penetrating 4340 Steel and 6061-T6 Al at 2 km/s < V < 10 km/s, the effect of strength is strong and the effect of compressibility is negligible at lower impact velocity, whilst the effect of strength is weak and the effect of compressibility becomes stronger at higher impact velocity. For the copper jet penetrating 4030 Steel, 6061-T6 Al and PMMA. the virtual origin model is adopted, and the compressibility and strength are implicitly considered by the linear relation between the penetration velocity and impact velocity. The effects of compressibility and target resistance on penetration efficiency are studied. The results show that the target resistance has a significant effect on the penetration efficiency. Howver PMMA is much more compressible than copper and the huge difference of compressibility has a significant effect on the penetration by hypervelocity copper jet into PMMA.

关键词： Compressibility Strength Long Rod Jet Compressible model Virtual origin model

Streamwise vortex generation by the Rod

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Chinese Journal of Aeronautics 2019年第8期32卷 1903-1911页

作者： Ryszard SZWABA Pawel FLASZYNSKI Piotr DOERFFER Department of Experimental AeRodynamics Institute of Fluid Flow Machinery Polish Academy of Sciences

The technology development related to aeRodynamics is leading to ever increasing loads of wings, airfoils and turbine and compressor blades. The increase in aeRodynamic forces is often leading to flow separation and depreciation of the aeRodynamic performance of flying objects or propulsion systems. Flow control methods are required to avoid these negative effects. In the recent two decades the flow control by means of air-jet vortex generators has been also intensively investigated. In this method a streamwise vortex is intRoduced by an oblique jet. The necessity to supply air by a pipe system may be considered a disadvantage. In order to eliminate this feature, it has been proposed to put out a Rod instead of a jet. It has been shown that the application of a Rod can intRoduce the same effect as a jet, as long as the streamwise vortex generation is concerned and appropriate dimensions are used. The present paper focuses on the influence of Rod vortex generators on a flow pattern downstream. The results presented here concern experimental and numerical investigations and provide guidelines for the design of a new flow control method dedicated mainly to external flows.

关键词： Air-jet vortex generator Boundary layer Flow control Rod vortex generator Streamwise vortices

Laterally pre-compressed SiC tiles against long Rod impact

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Defence Technology（防务技术） 2018年第5期14卷 585-589页

作者： Bo-yang Luo Wei-liang Goh Zhong Chen Jian-ming Yuan Temasek Laboratories Nanyang Technological University School of Materials Science and Engineering Nanyang Technological University

A combined experimental and computational study was carried out to investigate ballistic performance of laterally preload compressed SiC tile against long Rod impact. A 100 x 100 by 20 mm thick SiC tile was pushed into a 5 mm thick steel frame at high temperature of 430 ℃ so that after cool down to room temperature, the lateral preload compressive stress was developed in the SiC tiles. Depth of penetration tests of the SiC tiles with and without pre-stress were performed, where tungsten alloy long Rods at a nominal velocity of 1240 m/s were launched to hit the SiC tiles backed by the steel blocks. Compared with the SiC tiles without any pre-stress, the pre-compressed SiC tiles were found to reduce significantly the residual penetration in the backing block. Simulations were carried out using the LS-dyna hydrocode,taking account of preload stress. The simulations showed that the lateral preload compression strengthened the intact SiC tiles and dwell occurred in the early penetration stage, eRoding the striking long Rod efficiently.

关键词： Pre-compressed SiC tile DOP test WHA long Rod

Observation of two-times self-focusing of femtosecond laser beam in ZnO crystal by two-photon luminescence

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Science Bulletin 2018年第21期63卷 1392-1396页

作者： Xiaorui Wang Honggang Ye Zhicheng Su Dapeng Yu Shijie Xu Department of Physics and Shenzhen Institute of Research and Innovation (HKU-SIRI)The University of Hong KongHong KongChina Department of Physics Southern University of Science and TechnologyShenzhen 518055China Department of Applied Physics Xi'an Jiaotong UniversityXi'an 710049China

By ‘‘seeing" the green two-photon luminescence, two separate focusing points are observed on the propagation axis of a converging femtosecond laser beam in a ZnO single crystal Rod. It is found that the selffocusing effect makes a significant contribution to the formation of the first focusing point, while the second focusing point is caused by self-refocusing. The position of the first focusing point is in good agreement with the value predicted by a model developed by Chin and his co-workers. These experimental findings could be the unprecedented evidence for the self-focusing and refocusing effect of the femtosecond laser filament propagation in nonlinear media.

关键词： Self-focusing Self-refocusing ZnO Rod Two-photon luminescence

Some Interesting Traveling Waves in a Transversely Isotropic Incompressible Hyperelastic Semi-infinite Rod

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Acta Mechanica Solida Sinica 2018年第6期31卷 698-716页

作者： Ran Wang Xuegang Yuan Hongwu Zhang Jie Xu Jing Zhang State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsDalian University of TechnologyDalian 116024China College of Science Dalian Minzu UniversityDalian 116600China College of Mathematics and Information North Minzu UniversityYinchuan 750021China

In this paper,the bounded traveling wave solutions are examined for a system of partial differential equations with certain boundary conditions.Interestingly,this system can be used to describe the axially symmetric motion of a semi-infinite incompressible hyperelastic cylindrical Rod.With the aid of traveling wave transformations,the partial differential equations can be reduced to a traveling wave equation.The implicit analytical expressions determining the traveling waves are derived.Significantly,the influences of material parameters on the qualitative properties are discussed in detail by using the phase portraits of the traveling wave system. Smooth solutions such as the periodic traveling wave solutions and the solitary wave solutions with the peak form are shown.In particular,some interesting singular traveling wave solutions including the solitary cusp wave solutions and the periodic cusp wave solutions with the peak form are obtained.Numerical examples for all these waves are given.

关键词： Semi-infinite cylindrical Rod Planar dynamical system Bound traveling wave Solitary cusp wave

Microstructural observations on the terminal penetration of long Rod projectile

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Defence Technology（防务技术） 2017年第6期13卷 413-421页

作者： Krushna Kumbhar P.Ponguru Senthil A.K.Gogia Armour Design and Development Division Defence Metallurgical Research LaboratoryHyderabad 500058India

Present study focuses on the terminal penetration of tungsten heavy alloy(WHA) long Rod penetrator impacted against armour steel at an impact velocity of 1600 m/s. The residual penetrator and armour steel target recovered after the ballistic test have been characterized using optical microscope, scanning electron microscope(SEM) and electron probe micro analyzer(EPMA). Metallurgical changes in target steel and WHA remnant have been analysed. Large shear stresses and shear localization have resulted in local failure and formation of erosion pRoducts. Severe plastic deformation acts as precursor for formation of adiabatic shear band(ASB) induced cracks in target steel. Recovered WHA penetrator remnant also exhibits severe plastic deformation forming localized shear bands, ASB induced cracks and shock induced cracks.

关键词： Long Rod projectile Terminal penetration Shear localization Adiabatic shear band Tungsten heavy alloy Armour steel

Numerical simulation and analysis of drill Rods vibration during roof bolt hole drilling in underground mines

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International Journal of Mining Science and Technology 2018年第6期28卷 877-884页

作者： Shaowei Liu Mengxiong Fu Housheng Jia Wenbin Li Yafei Luo School of Energy Science and Engineering Henan Polytechnic UniversityJiaozuo 454000China The Safety of Coal PRoduction Collaborative Innovation Center Jiaozuo 454000China

Structural deterioration in the roof in an underground mine can easily cause roof fall, and deterioration is difficult to detect. When drilling holes for roof bolts, there is a relationship between the vibration of the drill Rod and the properties of the rock being drilled. This paper analyzes transverse, longitudinal, and torsional vibrations in the drill Rod by using vibration theory. Characteristic indexes for three kinds of vibration are determined. Using the finite element analysis software ABAQUS, a model for drill Rod vibration during the drilling of roof bolt holes was established based on the geological and mining conditions in the Guyuan Coal Mine, northern China. Results from the model determined that the transverse and the longitudinal vibration decrease as the rock hardness decreases. In descending order, sandstone,sandy mudstone, mudstone, and weak interbeds cause progressively less vibration when being drilled.The ranking for strata that cause decreasing torsional vibration is slightly different, being, in descending order, mudstone, sandstone, sandy mudstone, and weak interbeds. These results provide a theoretical basis for predicting dangerous roof conditions and the presence of weak interbeds to allow for adjusting bolt support schemes.

关键词： Roof bolt holedrilling Drill Rod vibration Vibration radius Vibration point amplitude Negative angular acceleration

Single Rod instrumentation in patients with scoliosis and comorbidities: Indications and outcomes

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World Journal of Orthopedics 2018年第9期9卷 138-148页

作者： Athanasios I Tsirikos Peter R Loughenbury Scottish National Spine Deformity Centre Royal Hospital for Sick Children

AIM To present our results on the use of a single Rod instrumentation correction technique in a small number of patients with major medical co-morbidities.METHODS This study was a prospective single surgeon series. Patients were treated with single Rod hybrid constructs and had a minimum 2-year follow-up. Indications included complex underlying co-morbidities, conversion of growing Rods to definitive fusion, and moderate adolescent idiopathic primarily thoracic scoliosis with severe eczema and low body mass index(BMI).RESULTS We included 99 consecutive patients. Mean age at surgery was 12.8 years(SD 3.5 years). Mean scoliosis correction was 62%(SD 15%) from 73°(SD 22°) to 28°(SD 15°). Mean surgical time was 153 min(SD 34 min), and blood loss was 530 mL(SD 327 mL); 20% BV(SD 13%). Mean clinical and radiological follow-up was 3.2 years(range: 2-12) post-operatively. Complications included Rod failure, which occurred in three of our complex patients with severe syndromic or congenital kyphoscoliosis(3%). Only one of these three patientsrequired revision surgery to address a non-union. Our revision rate was 2%(including a distal junctional kyphosis in a Marfan's syndrome patient).CONCLUSION The single Rod technique has achieved satisfactory deformity correction and a low rate of complications in patients with specific indications and severe underlying medical conditions. In these children with significant co-morbidities, where the risks of scoliosis surgery are significantly increased, this technique has achieved low operative time, blood loss, and associated surgical morbidity.

关键词： Pediatric scoliosis Indications Spinal deformity Surgery Spinal fusion Single Rod technique Outcomes

A three-stage model for the perforation of finite metallic plates by long Rods at high velocities

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Defence Technology（防务技术） 2019年第3期15卷 409-418页

作者： Yu He Liu-yun Xu He-ming Wen Zheng-cao Lu National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics CAEP Mianyang 621900 China CAS Key Laboratory for Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei Anhui 230027 China

A three-stage theoretical model is presented herein to predict the perforation of a thick metallic plate struck normally by a long Rod at high velocities. The model is suggested on the basis of the assumption that the perforation of a thick metallic plate by a long Rod can be divided into three stages:(1) initial penetration;(2) plug formation and (3) plug slipping and separation. Various analytical equations are derived which can be employed to predict the ballistic limit, residual velocity and residual length of the long Rod. It is demonstrated that the present model predictions are in good agreement with available experimental results for the perforation of finite steel targets struck normally by steel as well as tungsten alloy long Rods at high velocities. It is also demonstrated that the dynamic maximum shear stress of a plate material has strong effect on plug formation and plug thickness which, in turn, exerts considerable influence on the residual velocities and lengths of a long Rod at impact velocities just above the ballistic limit.

关键词： Perforation Long Rod Finite metallic plate Ballistic limit Residual velocity Residual length