检索结果-南通市图书馆

penetration resistance of Skirt-Tip with Rough Base for Suction Caissons in Clay

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2020年第6期34卷 784-794页

作者： WU Yu-qi LI Da-yong YANG Qing State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China College of Civil Engineering Fuzhou UniversityFuzhou 350108China College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590China

Suction caissons can readily penetrate into the seabed under the combination of the self-weight and suction resulted from the encased water being increasingly pumped out. During suction-assisted penetration, the equivalent overburden at the skirt-tip level outside the caisson is generally higher than that inside because the vertical stress within the soil plug is reduced by the exerted suction. This may result in a uniform shear stress developing over the base of the skirt-tip as the soil below the skirt-tip tends to move into the caisson, which leads to an asymmetric failure wedge existing below the base of the skirt-tip. Besides, different adhesion factors along the inside(αi) and outside(αo) of the skirt wall will cause asymmetric plastic zones inside and outside the caisson. Accordingly, an asymmetric failure mechanism is therefore proposed to calculate the penetration resistance of the skirt-tip. The proposed failure mechanism is the first to consider the effect of different adhesion factors(αi) and(αo) on the failure mechanism at the skirt-tip, and involves the contribution from the weighted average of equivalent overburdens inside and outside caisson at the skirt-tip level. The required suction pressure can be obtained in terms of force equilibrium of the caisson in a vertical direction. Finally, the asymmetric failure mechanism at the skirt-tip is validated with the FE calculations. By comparing with the measured data, the predictions of the required suction pressure are found to be in good agreement with the experimental results.

关键词： suction caisson required suction pressure penetration resistance skirt-tip rough base clay

Undue Hardness/Modulus Ratio Claims instead of Physical penetration resistance and Applications with Mollusk Shells

在线全文

学校读者我要写书评

暂无评论

Advances in Materials Physics and Chemistry 2021年第2期11卷 45-57页

作者： Gerd Kaupp University of Oldenburg Oldenburg Germany

The Nanoindentation is a precise technique for the elucidation of mechanical properties. But such elucidation requires physically based interpretation of the loading curves that is widely still not practiced. The use of indentation hardness H and indentation modulus Er is unphysical and cannot detect the most important phase-transitions under load that very often occur. The claim that H versus E plots relate linearly for all different materials is neither empirically found nor correctly deduced. It is most dangerous by producing incorrect materials properties and misleading. The use of H/E (that is also called “elasticity index”) in complicated formulas for brittle parameter, yield strength, toughness, and so-called “true hardness” is also in error. The use of H/E cannot reveal the true qualities of materials without considering phase-transitions under load that require the correct exponent 3/2 on h for the loading curves (instead of disproved 2). This is exemplified with the physical data of different mollusk shells that experience phase-transitions, a new bionics model, and different contributions for their strengthening. The data are compared to the ones of aragonite and calcite and vaterite.

关键词： Nanoindentation H/E Ratio Challenge Phase-Transitions penetration resistance Mollusk Shells Aragonite Calcite Bionics

Design and comparative analysis of self-propelling drill bit applied to deep-sea stratum drilling robot

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第10期24卷 925-936页

作者： Peihao ZHANG Xingshuang LIN Hao WANG Jiawang CHEN Zhenwei TIAN Zixin WENG Ziqiang REN Peng ZHOU Ocean College Zhejiang UniversityZhoushan 316021China Hainan Institute Zhejiang UniversitySanya 572025China The Engineering Research Center of Oceanic Sensing Technology and Equipment Ministry of EducationZhoushan 316000China

Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration.resistance at the front end is the main source of resistance to the robot’s motion in the strata.Since there is no continuous and strong downward drilling force as in conventional drilling rigs,robot movement relies heavily on the drill bit to reduce the drilling resistance.In this study we propose a self-propelling drill bit that can discharge soil debris to provide propulsive force and reduce the resistance.The key parameter of the drill bit design,the spiral blade lead angle,was determined by theoretical analysis of the drill bit’s soil discharging effect.To verify the structural advantages of the self-propelling drill bit in reducing resistance,a comparative analysis with a conventional conical drill bit was conducted.The drilling process of both bits was simulated using finite element simulation at various rotation speeds,the penetration force and torque data of both drill bits were obtained,and tests prepared accordingly in subsea soil were conducted.The simulations and tests verified that the penetration force of the self-propelling drill bit was lower than that of the conventional conical drill bit.The self-propelling drill bit can reduce the resistance effectively,and may play an important role in the stratum movement of drilling robots.

关键词： Subsea stratum investigation Stratum drilling robot Self-propelling drill bit penetration resistance

Extracellular and intracellular infection of Botryosphaeria dothidea and resistance mechanism in apple cells

在线全文

学校读者我要写书评

暂无评论

Horticultural Plant Journal 2023年第2期9卷 209-223页

作者： Li Xin Rui Zhang Xianpu Wang Xiuxia Liu Yicheng Wang Peiran Qi Lishuang Wang Shujing Wu Xuesen Chen State Key Laboratory of Crop Biology College of Horticultural Science and EngineeringShandong Agricultural UniversityTai’anShandong 271018China

Apple ring rot,which is caused by Botryosphaeria dothidea,severely affects apple production.The mechanisms employed in apple cells against B.dothidea remain unknown.In this research,the pathogen infection mode and the relationship between cell death and disease resistance in‘Fuji’/B.dothidea interaction pathosystem were investigated.By using transmission electron microscopy(TEM),our research showed that the pathogen infects apple cells both intracellularly and extracellularly.However,compared with that in immature fruit,the incidence of hyphae in the interior of mature apple fruit cells increased dramatically,suggesting that cell wall-mediated penetration resistance could be important in apple resistance against B.dothidea.TEM ultrastructural characterization identified the nuclear morphology of programmed cell death induction in both apple fruit and callus cells under B.dothidea infection.Overexpression of MdVDAC2(MDP0000271281),which encodes an outer-membrane localized anion channel protein in mitochondria,significantly promoted cell death under B.dothidea infection and simultaneously inhibited pathogen infection,suggesting that cell death represents a disease resistance mechanism in apple against B.dothidea infection.Furthermore,BdCatalase(KAF4307763),a cytochromeP450 family protein BdCYP52A4(KAF4300696),and subtilisin-domain containing proteinswere identified fromB.dothidea-secreted proteins,which suggested the potential involvement of active oxygen species and phytoalexins in combating B.dothidea infection and triggering or dampening apple resistance.Collectively,our research suggested that cell wall-mediated penetration resistance,programmed cell death machinery and microbial effector-interrelated signaling were among strategies recruited in apple to combat B.dothidea.The current research laid the foundation for further investigations into resistance mechanisms in apple.

关键词： Apple Apple ring rot Botryosphaeria dothidea penetration resistance MdVDAC2 Programmed cell death

Pile Running in Layered Soils

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2023年第5期37卷 829-841页

作者： ZHAO Huan WANG Le SUN Li-qiang TIAN Ying-hui Oliver REUL CHEN Quan-zhen State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300072China Department of Infrastructure Engineering The University of MelbourneParkvilleVictoria 3010Australia Department of Geotechnical Engineering University of KasselKassel 34109Germany

This paper presents a case study on incidents of offshore pile running in layered soils.The study provides a detailed description of the seabed soil data,pile driving records,and field surveillance video observations.Three-dimensional large deformation finite element(LDFE)analyses were conducted to retrospectively analyze the incidents,considering the remoulding of seabed soil and degradation of the pile-soil interface in the LDFE modeling.By comparing the field observations with the LDFE analysis,the mechanism of pile running was discussed,with a focus on investigating the pile penetration resistance in each layer.The study revealed that pile running in layered soils primarily resulted from a significant reduction in pile base resistance when transitioning from a strong layer to an adjacent weak layer.To further investigate the pile running mechanism in layered soils,a parametric study on the strength variation of adjacent soil layers and its influence on pile base resistance was conducted.Lastly,a simplified prediction model of pile base resistance,suitable for assessing the risk of pile running in layered soils,was proposed.

关键词： pile running coupled Eulerian−Lagrangian method layered soil penetration resistance pile−soil interaction

Application of biocementation technique using Bacillus sphaericus for stabilization of soil surface and dust storm control

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2022年第5期14卷 537-549页

作者： Davood NAMDAR-KHOJASTEH Masoud BAZGIR Seyed Abdollah HASHEMI BABAHEIDARI Akwasi B ASUMADU-SAKYI Department of Soil Science Faculty of AgricultureShahed UniversityTehran ***Iran Department of Soil and Water Engineering Faculty of AgricultureIlam UniversityIlam ***Iran Department of Plant Protection Faculty of AgricultureShahed UniversityTehran ***Iran International Laboratory for Air Quality and Health School of ChemistryPhysics and Mechanical EngineeringQueensland University of TechnologyBrisbaneQueensland 4000Australia

Dust emission and wind erosion are widespread phenomena in arid and semi-arid regions,which have far-reaching harmful effects to the environment.This study aimed to use microbial induced carbonate precipitation(MICP)method with Bacillus sphaericus to reduce soil losses that occur in a dust-producing area due to wind erosion in the Ilam Province,Iran.Soil samples at the 0-30 cm depth were used and sterilized in an autoclave for 2 h at 121℃ and 103 kPa.Approximately 3 kg soils were weighed and poured in the 35 cm×35 cm×3 cm trays.Different treatments included two levels of B.sphaericus(0.0 and 0.5 OD),three levels of suspension volume(123,264,and 369 mL),two levels of urea-chloride cementation solution(0.0 and 0.5 M),and two levels of bacterial spray(once and twice spray).After 28 d,soil properties such as soil mass loss,penetration resistance,and aggregate stability were measured.The results showed a low soil mass loss(1 g)in F_(14)formulation(twice bacterial spray+264 mL suspension volume+without cementation solution)and a high soil mass loss(246 g)in F_(5) formulation(without bacteria+264 mL suspension volume+0.5 M cementation solution).The highest(42.55%)and the lowest(19.47%)aggregate stabilities were observed in F_(16)and F_(7)formulations,respectively,and the highest penetration resistance(3.328 kg/cm^(2))was observed in F_(18) formulation.According to the final results,we recommended the formulation with twice bacterial spray,0.5 M cementation solution,and 269 mL suspension volume as the best combination for soil surface stabilization.Furthermore,this method is environmentally friendly because it has no adverse effects on soil,water,and plants,thus,it would be an efficient approach to stabilize soil surface.

关键词： soil stabilization microbial cementation calcium carbonate bacteria penetration resistance

penetration Tests of Multi-Bucket Foundation in Sand for Offshore Wind Turbines

在线全文

学校读者我要写书评

暂无评论

Journal of Ocean University of China 2023年第4期22卷 949-960页

作者： ZHANG Puyang QI Xin ZHANG Chao LE Conghuan DING Hongyan State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China

Suction foundations are generally installed with negative pressures to overcome the resistance of soils and complete the penetration,but excessive negative pressures are also avoided to cause seepage damages.In this paper,the model test method was used to analyze the movement characteristics of multi-bucket foundations in the process of sinking in sand,and the common calculation methods of sinking resistances are verified.The critical negative pressure corresponding to the seepage failure of foundation was determined under the action of increasing negative pressure step by step and the characteristics of soil failure were studied.The calculation formula of critical suction in sand was verified in application,and according to the test results,the value of seepage coefficient was modified,which provides an example for the study of suction foundation in sand soils.

关键词： multi-bucket foundation penetration test penetration resistance critical suction seepage failure

Numerical study on the resistance of rigid projectiles penetrating into semi-infinite concrete targets

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2021年第3期37卷 482-493,I0003页

作者： Huawei Yang Jie Zhang Zhiyong Wang Zhihua Wang Q.M.Li College of Management Science and Engineering Shanxi University of Finance and EconomicsTaiyuan 030006China Institute of Applied Mechanics College of Mechanical and Vehicle EngineeringTaiyuan University of TechnologyTaiyuan 030024China Shanxi Key Laboratory of Material Strength and Structural Impact Taiyuan University of TechnologyTaiyuan 030024China Department of Mechanical Aerospace and Civil EngineeringSchool of EngineeringThe University of ManchesterManchester M139PLUK

A study on the resistance of rigid projectiles penetrating into semi-infinite concrete targets is performed in this paper.Experimental data are analyzed to examine the penetration resistance during various stages of the penetration process.A numerical tool using AUTODYN hydrocode is applied in the study.The numerical results on both deceleration-time history and depth of penetration of projectiles are in good agreement with experimental data,which demonstrate the feasibility of the numerical model in these conditions.Based on the numerical model with a two-staged pre-drilled hole,the rigid projectile penetration in tunneling stage is studied for concrete targets with different strengths in a wide range of impact velocities.The results show that the penetration in tunnel stage can be divided into two different cases in terms of initial impact velocity.In the first case,when the impact velocity is approximately less than 600 m/s,the deceleration depends on initial impact velocity.In the second case,when the impact velocity is greater than 600 m/s,the effect of target inertia becomes apparent,which agrees with commonly used concrete penetration resistance equations based on cavity expansion model.

关键词： Rigid projectile penetration resistance Entrance phase Inertial term Concrete target

Structure, Mechanical Behavior and Puncture resistance of Grass Carp Scales

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2017年第2期14卷 356-368页

作者： Peng Liu Deju Zhu Junwen Wang Tinh Quoc Bui College of Civil Engineering Hunan University Changsha 410082 China College of Civil Engineering Tongji University Shanghai 200092 China Department of Civil and Environmental Engineering Tokyo Institute of Technology Tokyo 108-233 Japan

This work is conducted to investigate the hierarchical structure, mechanical behavior and fracture resistance of grass carp scales with different water contents （hydrated and dehydrated） and load conditions （uniaxial, biaxial and punch tests）. The whole cross-section of scales is investigated, and it is found that the bony layer displays discontinuity and partly embeds in collagen layer. Four different locations are considered under both tensile and punch tests. The results of the uniaxial tensile test show a correlation between the failure mode and the distribution of surface morphology on scales. The biaxial test results show that there are minor differences in the tensile strength and the Young＇ modulus compared with those of the uniaxial tests, but the ultimate strain is about 20% - 50%. Puncture tests are also conducted with different size of needles and different hardness silicon rubbers as substrate. The results show that the puncture force and deformation are dependent on the size of needle and the hardness of substrate. The failure pattern of scales is related to the water content. Radial cracks occur in the bony layer of hydrated scale, and the collagen fibers twist around the puncture site. However, the shear failure occurs in the bony layer of dehydrated scale.

关键词： grass carp scale mechanical behavior biaxial test penetration resistance