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Underground Space 2022年第5期7卷 847-861页

作者： Lifeng Fan Han Li Yan Xi Beijing University of Technology Beijing 100124China

Underground thermal engineering such as geothermal exploitation usually involves the response of impact loads due to the drilling operation and blasting load.This study investigated the dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling under natural cooling,water cooling,and liquid nitrogen cooling.Firstly,split Hopkinson pressure bar tests were performed on granite under three different cooling methods to study the dynamic mechanical parameters with thermal cycles.Subsequently,the damage factors were calculated to evaluate the damage on granite and the relationship between damage and stress.Finally,the granite fragments after impact were sieved,and the fractal dimension and average fragment size were introduced to analyze the fragmentation characteristics.The results demonstrate that the degradation of dynamic mechanical properties mainly occurs in the first four thermal cycles;with the increase of damage factor,the stress decreases linearly under the three cooling methods,and the damage caused by liquid nitrogen cooling to granite is the most significant,followed by water cooling.Fragments of granite change from axial splitting failure to a more complex composite failure mode.In addition,with the decrease of the average fragment size,the fractal dimension of the granite gradually increases,resulting in the higher fragmentation degree and the better uniformity of fragmentation.

关键词： Split Hopkinson pressure bar dynamic mechanical properties Fragmentation characteristics Cooling treatment

dynamic mechanical properties and Energy Dissipation Characteristics of Frozen Soil Under Passive Confined Pressure

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Acta Mechanica Solida Sinica 2021年第2期34卷 184-203页

作者： Jinxuan Jia Huaiping Tang Huijian Chen Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Impact compression tests on frozen soil samples with different freezing temperatures and subjected to passive confined pressure were performed using a split Hopkinson pressure bar at different loading strain rates.The three-dimensional stress-strain curves of the frozen soil samples under the corresponding conditions were obtained.The experimental results showed that,when the frozen soil was loaded to its elastic limit,shear failure occurred,the bearing capacity of pore ice was lost,and the thawed soil functioned as the main stress-bearing body.Nevertheless,the capacity of frozen soil to withstand hydrostatic pressure continued to increase.The dynamic mechanical properties of the frozen soil under passive confined pressure were observed to be strongly related to the loading strain rate and freezing temperature.As the loading strain rate increased,the secant modulus,elastic modulus,and strength(including the shear strength)of the frozen soil increased,whereas its Poisson^ratio and coefficient of lateral pressure decreased.As the freezing temperature decreased,the secant modulus,elastic modulus,and shear strength of the frozen soil increased;however,its Poisson5s ratio and coefficient of lateral pressure decreased.When the frozen soil was subjected to impact loading under passive confined pressure,energy dissipation occurred due to plastic deformation,mesoscopic damage evolution,and ice-water phase transition.When shear failure occurred,the absorption energy per unit volume of frozen soil increased as the freezing temperature decreased and the loading strain rate increased.

关键词： Frozen soil Split Hopkinson pressure bar Passive confined pressure dynamic mechanical properties Energy dissipation

Flexural and dynamic mechanical properties of Alkali-Treated Coir/Pineapple Leaf Fibres Reinforced Polylactic Acid Hybrid Biocomposites

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Journal of Bionic Engineering 2021年第6期18卷 1430-1438页

作者： Ramengmawii Siakeng Mohammad Jawaid Mohammad Asim Hassan Fouad Sameer Awad Naheed Saba Suchart Siengchin Department of mechanical and Process Engineering The Sirindhorn International Thai-GermanGraduate School of Engineering(TGGS)King Mongkut’s University of Technology North BangkokBangkok10800Thailand Laboratory of Biocomposite Technology Institute of Tropical Forestry and Forest Products(INTROP)Universiti Putra Malaysia43400 UPMSerdangSelangorMalaysia Applied Medical Science Department Community CollegeKing Saud UniversityP.O.Box 10219Riyadh11433Saudi Arabia Chemistry School of Science and TechnologyUniversity of New EnglandArmidaleNSW2351Australia

Polylactic acid(PLA)possesses good mechanical and biodegradability properties which make it a suitable material for polymer composites whereas brittleness and high costs limit its utilization in various applications.The reinforcement of natural fibres with biopolymers has been formed to be an efficient technique to develop composites having the ability to be fully biodegradable.This study concerns with the incorporation of various percentages of untreated and alkali-treated Coir Fibres(CF)and pineapple leaf fibres(PALF)in PLA biocomposites and characterizations of flexural,morphological and dynamic mechanical properties.Flexural properties showed that the treated C1P1 hybrid composites(C1P1A)displayed highest flexural strength(35.81 MPa)and modulus(5.28 GPa)among all hybrid biocomposites.Scanning Electron Microscopy(SEM)revealed a behaviour of fibre-matrix adhesion in untreated treated biocomposites.SEM observation revealed good dispersion of the fillers in PLA.dynamic mechanical analysis revealed that C1P1A showed highest glass transition temperature(Tg)and storage modulus(E')while untreated C3P7 displayed the least Tg and E'.Overall findings showed that alkali-treated hybrid biocomposites(CF/PALF/PLA)especially C1P1A have improved flexural properties,dynamic and morphological properties over untreated biocomposites.Success of these findings will provide attracting consideration of these hybrid biocomposites for various lightweight uses in a broad selection of industrial applications such as biomedical sectors,automobile,construction,electronics equipment,and hardware tools.

关键词： Coir fibres Pineapple leaf fibres Biocomposites Polylactic acid mechanical properties dynamic mechanical properties

Experimental Study on the dynamic mechanical properties of Reinforced Concrete under Shock Loading

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Acta Mechanica Solida Sinica 2016年第1期29卷 22-30页

作者： Haifeng Liu Jie Fu Jianguo Ning Department of Civil and Hydraulic Engineering Ningxia University State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology

A simple experimental method was introduced to study the mechanical properties of reinforced concrete under shock loading. The one-stage light gas gun was used to test the me- chanical properties of reinforced concrete with different reinforcement ratios under various impact velocities. Three Mn-Cu piezoresistive pressure gauges embedded in the target were used to record the voltage-time signals, from which the stress-strain curves of reinforced concrete were obtained using Lagrangian analysis. Experimental results indicated that the load-bearing capacities of re- inforced concrete increased greatly with the impact velocity and the reinforcement ratio. The peak stress of the shock wave decreased exponentially with the propagation distance.

关键词： reinforced concrete shock loading Lagrangian analysis dynamic mechanical properties

dynamic mechanical properties of Wood Powder /Polypropylene Composites

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Chinese Forestry Science and Technology 2003年第1期2卷 56-59页

作者： Yasunori HATANO Forestry and Forest Products Research Institute Tsukuba Tsukuba Ibaraki Japan

The dynamic mechanical properties of wood powder/polypropylene composites with different wood content treated and untreated with the compatibilizer have been studied. It has been found that addition of wood powders and the compatibilizer can both improve the viscoelasticity of composites. Glass transition temperature (Tg) of appropriate wood powder-filled composites decreased. The value for the storage modulus (G') increased gradually with increasing wood powder content. The addition of the compatibiliz...

关键词： dynamic mechanical properties wood powder/polypropylene composites compatibilizer

EFFECTS OF MOLECULE AGGREGATION STATE OF HINDERED PHENOL ON dynamic mechanical properties OF CHLORINATED POLYETHYLENE

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Chinese Journal of Polymer Science 2004年第1期22卷 7-16页

作者：吴驰飞 Institute of Material Science and Technology East China University of Science and Technology Shanghai 200237 China

Hindered phenol compound 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}- 2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) is a polymorphous material with different physical structures. The initial AO- 80 is highly crystalline, whereas AO-80 obtained by cooling from its molten state is an amorphous material. Annealing treatment below the melting point of AO-80 results in structural development. The mixture of chlorinated polyethylene (CPE) and vitrified AO-80 particles exhibits a dramatic change in the dynamic mechanical properties during heat treatment at 130'C. This change can be attributed to the decomposition of the vitrified AO-80 particles and the hybridization of two constituents. The vitrified AO-80 particles can crystallize again in a CPE matrix by annealing at 100'C, but this crystal is different from that of the initial AO-80 in its microstructure. In addition, the incorporation of CPE chains caused a dramatic increase in the modulus. As a result, the AO-80 crystal particles that contain some CPE chains act as multifunctional cross- links and the CPE/AO-80 hybrid was found to be a new type of elastomer.

关键词： Hindered phenol Polymorphous dynamic mechanical properties Chlorinated polyethylene

dynamic mechanical properties of Functional Additives and Mica Filled EVA Nanocomposites

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Dynamic Mechanical Properties of Functional Additives and Mi...

Theory Research on Analysis of Taylor Impact Experiment for Material dynamic mechanical properties

2007年全国高分子学术论文报告会

作者：华诚张诚沈伟马淳安浙江工业大学绿色化学合成国家重点实验室培育基地浙江工业大学绿色化学合成国家重点实验室培育基地浙江工业大学绿色化学合成国家重点实验室培育基地浙江工业大学绿色化学合成国家重点实验室培育基地

＜正＞dynamic mechanical analysis（DMA）is carried out to explore temperature dependence of viscoelasticity for a series of Poly（ethylene-co-vinylacetate）（EVA）based hybrids,which include several functional additives KT-A（abbr.A）,KT-B（abbr.B）modified EVA and mica filled EVA/A/B blends.Data output from DMA show that all the above additives have a significant effect on viscoelastic properties.With the addition of A,the position of the damping peak shifts to a higher region and the value of the loss tangent （Tan（?））increases dramatically.The laminal mica filled EVA/A/B nano-composites are also prepared by using melt intercalation techniques.The results indicate that the dynamic mechanical properties of the mica filled EVA/A/B nanocomposites can be improved within a certain extent.

关键词： EVA Mica Melt Intercalation dynamic mechanical properties

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dynamic compressive response of porcine muscle measured using a split Hopkinson bar system with a pair of PVDF force transducers

2011爆轰与冲击动力学国际会议

作者： ZHAO Guang-ming (Key lab on safe and effective coal mining sponsored by Anhui province and ministry of education Anhui University of Science and Technology Huainan Anhui 232001 China)

＜正＞By suitable hypothesization and approximation of the Taylor impact process,the present paper has proposed a method to calculate the dynamic yielding strength of the material by turning to the length of the proje... 详细信息

关键词： dynamic mechanical properties Taylor impact Reproducing Kernel Particle Method Impact

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Defence Technology（防务技术） 2023年第10期28卷 298-305页

作者： Yao-ke Wen Liang Xu Ai-jun Chen Fang-dong Dong Bin Qin School of mechanical Engineering Nanjing University of Science and TechnologyNanjing210094China School of Science Nanjing University of Science and TechnologyNanjing210094China Science and Technology on Transient Impact Laboratory Beijing102202China

The classic metallic Split Hopkinson Pressure Bar(SHPB)cannot capture the transmitted signal accurately when measuring soft biological tissue,because of the very low wave impedance and strength of this material.So the dynamic compressive response of porcine muscle has been investigated by using a modified SHPB.The forces on both ends of the sample measured using Polyvinylidene fluor(PVDF)transducers were applied to calculate the stress in the specimen instead of the strain gauge signal on the transmitted bar.Moreover,a circular cardboard disk pulse shaper was applied for generating a suitable incident pulse to achieve stress equilibrium and constant strain rates in the specimens.Then,the dynamic mechanical properties of porcine muscle parallel and perpendicular to the fiber directions were measured,and the stress equilibrium process during loading was analyzed,as well as the inertia-induced extra stress being corrected.Furthermore,quasi-static tests were conducted at two different strain rates to investigate the strain rate dependence using a universal material testing machine.The results show that the stress-strain curves are sensitive to strain rate in the two different loading directions.The compressive stress perpendicular to the fiber direction is stiffer than that parallel to the fiber direction.In addition,a strain rate-dependent constitutive model was developed based on the mechanical response of the muscle at different strain rates and fitted to the experimental data.The results show that the overall fit is good,and the constitutive model could describe the muscle's dynamic mechanical properties.

关键词： PVDF Hopkinson bar Porcine muscle dynamic mechanical properties Constitutive model

Experimental study of the dynamic mechanical responses and failure characteristics of coal under true triaxial confinements

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International Journal of Mining Science and Technology 2023年第6期33卷 761-772页

作者： Zhanguo Ma Pengfei Yan Shixing Cheng Peng Gong Fuzhou Qi Jianguo Wang State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 221116China

Investigations on the dynamic mechanical properties and failure mechanisms of coal under in-situ stress is essential for the prevention of dynamic disasters in deep coal mines.Thus,a modified true triaxial Hopkinson bar was employed to explore the dynamic mechanical behaviors of coal at different confining pressures(0–20 MPa)and strain rates(40–220 s^(-1)).The results show that the dynamic peak stress is positively correlated with lateral static pre-stressσy andσz,but negatively correlated with axial static prestressσx.At approximate strain rates,increasing the lateral static pre-stress facilitates increasing the dynamic peak stress,but the minimum lateral static pre-stress is the primary factor limiting a significant increase in dynamic peak stress of coal.Furthermore,the dynamic differential stress is linearly related to the logarithm of strain rate,and the peak strain varies linearly with strain rate.However,there is no significant correlation between confining pressure and peak strain.Moreover,X-ray CT images and photographic fracture observations of coal samples show the failure patterns under uniaxial and triaxial conditions are splitting failure and shear failure,respectively.The device provides a viable approach for fully comprehending the dynamic mechanical behaviors of rock-like material in complex stress conditions.

关键词： Coal True triaxial SHPB test dynamic mechanical properties Failure characteristics