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Occurrence of Dynamic Shear Bands in AISI 4340 Steel under Impact Loads

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World Journal of Mechanics 2013年第2期3卷 139-145页

作者： Gbadebo Owolabi Daniel Odoh Akindele Odeshi Horace Whitworth Department of Mechanical Engineering Howard University Washington DC USA Department of Mechanical Engineering University of Saskatchewan Saskatoon Canada

In this study, occurrence of adiabatic shear bands in AISI 4340 steel under high velocity impact loads is investigated using finite element analysis and experimental tests. The cylindrical steel specimen subjected to impact load was divided into different sections separated by nodes using finite element method in ABAQUS environment with boundary conditions specified. The material properties were assumed to be lower at the section where the adiabatic shear bands are expected to initialize. The finite element model was used to determine the maximum flow stress, the strain hardening, the thermal softening, and the critical strain for the formation of adiabatic shear bands. Experimental results show that deformed bands were formed at low strain rates and there was a minimum strain rate required for formation of transformed band in the alloy. The experimental results also show that cracks were initiated and propagated along transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by strain-rates. The simulation results obtained were compared with experimental results obtained for the AISI 4340 steel under high strain-rate loading in compression using split impact Hopkinson bars. A good agreement between the experimental and simulation results was obtained.

关键词： Adiabatic Shear Band Finite Element Model Strain Hardening Thermal softening Johnson-Cook Model AISI 4340 Steel

Modelling of Non-coaxial Viscoplastic Deformation in Geodynamics

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Journal of Civil Engineering and Architecture 2014年第8期8卷 1017-1025页

作者： Hans B. Muhlhaus Louise Olsen-Kettle Jingyu Shi Louis Moresi School of Earth Sciences The University of Queensland Brisbane 4072 Australia School of Mathematical Sciences Monash University Clayton 3800 Australia School of Geosciences Monash University Clayton 3800 Australia

The formation of shear bands for time and length scales appropriate for deformation processes in the upper Lithosphere is investigated in plane strain finite element simulations under predominantly uniaxial extension and compression, respectively. The direction of gravity is assumed orthogonal to the extension/compression axis. Mathematically, the formation of shear zones may be explained as a consequence of changes in the type of the governing model equations. Such changes or bifurcations depend strongly on the details of the constitutive relationships such as strain softening, thermal or chemical effects, associated or non-associated--coaxial or non-coaxial flow rules. Here we focus on strain softening and coaxial and non-coaxial flow rules. In the simulations, we consider an initially rectangular domain with the dimensions Lo, Ho in the horizontal, vertical directions, respectively. The domain is extended or compressed by prescribing a uniform, horizontal velocity field along one of the vertical boundaries while keeping the opposite boundary fixed. An important global descriptor of the deformation process is the relationship between the horizontal stress resultant （average horizontal stress） and the strain ln（L/Lo）, where L is the deformed length of the domain. The main goal of this paper is to investigate key factors influencing the phenomenology of the localization process such as flow rule, coaxial, non-coaxial and strain softening. Different origins of the mesh sensitivity of deformations involving localization are also investigated.

关键词： Shearing band non-coaxiality softening viscous plastic materials

Study on Harnessing of Roadway with Badly Damaged Surrounding Rock

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International Journal of Mining Science and Technology 1998年第1期19卷 38-44页

作者：吕家立颜志平

This paper, based on the strain softening character of rock, and the de formation feature of roadway with badly damaged surrounding rock and adopting the ideal elastoplastic softening model, derives the formula for calculating the supporting resistance for the roadway. It is pointed out that controlling the rheid speed of the rock in the plastic softening area is critical and that the combined supporting, i. e. combining surrounding rock internal rein forcement with external supporting f is the reasonahle supporting to this kiud of roadways. The theory and practice introduced in this paper are of universal significance for harnessing the roadway with badly damaged surrounding rock.

关键词： roadway with badly damaged surrounding rock ideal elastoplastic softening model internal reinforcement external supporting boundary structure effect

1-MCP Improved Diverse Sensorial, Biochemical and Physical Apple Traits during Cold Storage Based on Cultivar

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Agricultural Sciences 2017年第1期8卷 77-96页

作者： B. Pashazadeh H. Hajnajari F. Shavakhi Post Harvest Group Sabzevar Branch Islamic Azad University Sabzevar Iran Temperate Fruit Research Center Horticulture Science Research Institute Agricultural Research Education and Extension Organization (AREEO) Karaj Iran Agricultural Engineering Research Institute Agricultural Research Education and Extension Organization (AREEO) Karaj Iran

Apple cultivars’ storability could be strengthened through known techniques of cold storage, advanced industries of control atmosphere or other routine usages like fruit pre-cooling followed by immersion in CA++ solution, depending on genetic potential of the plant material. At the end of pomology and cold storage assessments of 93 apple cultivars, two high yielding native 'Dirras-e Mashhad' and 'Wealthy' were treated by single and combined 1-MCP and ethylene nano-absorbent (ENA) to assess eventual improvements in cold storage span, fruit eating quality and role of cultivar. For this purpose, directs effects and interactions between all sources of variance were studied. Ethylene emission and CO2 amounts were measured. The results showed that reduced weight loss and flesh firmness, were registered in the treated samples of both cultivars compared with the control. Using of 1-MCP affected significantly (p 0.05) on these characteristics. The native apple 'Dirras-e Mashhad' showed higher pH value than 'Wealthy' under the combined treatment (ENA+1-MCP). Genetic source revealed significant difference through lower 'Wealthy' storability. Ethylene emission increased to 53.64 ppm/Kg·hr after 5th month, which resulted in significant difference at p > 0.01 level related to the initial value of 3.26 ppm/Kg·hr. The combined treatment (ENA+1-MCP) affected significantly (p < 0.05) most of the fruit characteristics in both of the cultivars. The treatments demonstrated different results by cultivar.

关键词： 1-MCP Ethylene Nano Absorbent Flesh softening Storage Life

Damage smoothing effects in a delocalized rate sensitivity model for metals

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Theoretical & Applied Mechanics Letters 2012年第5期2卷 18-22页

作者： K.Enakoutsa K.N.Solanki F.R.Ahad Y.Tjiptowidjojo D.J.Bammann Center for Advanced Vehicular Systems Mississippi State University School of Engineering of Matter Transport and EnergyArizona State University

It has been long time established that application of damage delocalization method to softening constitutive models yields numerical results that are independent of the size of the finite element. However, the prediction of real-world large and small scale problems using the delocalization method remains in its infancy. One of the drawbacks encountered is that the predicted load versus displacement curve suddenly drops, as a result of excessive smoothing of the damage. The present paper studies this unwanted effect for a delocalized plasticity/damage model for metallic materials. We use some theoretical arguments to explain the failure of the delocalized model considered, following which a simple remedy is proposed to deal with it. Future works involve the numerical implementation of the new version reproduce real-world problems.

关键词： Bammann-Chiesa-Johnson model damage smoothing Fourier transform softening

Study on Nanofiltration Process for Offshore Oil Fields Seawater Injection Operations

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Study on Nanofiltration Process for Offshore Oil Fields Seaw...

Elastic Modulus Effect Related with Nonlinear Internal Friction

The 12th Asian Pacific Confederation of Chemical Engineering Congress

作者： Shang Yanwu Wang Duo Cheng Huaigang Gao Xueli Shang Minghua Zheng Yamei Xu Jia Gao Congjie College of Chemistry and Chemical Engineering,Ocean University of China,Qingdao 266100,China

For offshore oil fields,seawater is the most sufficient opdon for water injection *** the incompatibility between oil fields formation waters and seawater causes severe scaling problems in the reservoirs,typically is ... 详细信息

关键词： nanofiltration(NF) water injection softening integrated membrane process

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Chinese Physics Letters 1992年第1期9卷 26-29页

作者： TAN Qi Laboratory of Internal Friction and Defects in Solids University of Science and Technology of ChinaHefei 230026

The behavior of elastic modulus related with strain amplitude is *** was found that modulus behaves softening when internal friction exhibits normal amplitude-dependent effects,while increases slightly with the appearance of anomalously amplitude-dependent *** the decrease of frequency of measurement,the variation of modulus with amplitude becomes small.A trial for obtaining information from amplitude internal friction peak was made on the basis of Debye equations.

关键词： friction softening modulus

CENTRIFUGAL TEST STUDY ON THE BEHAVIOR OF SOFT CLAY AT SEA BOTTOM UNDER THE ACTION OF WAVE FORCE

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Transactions of Tianjin University 1999年第2期5卷 104-108页

作者：闫澍旺李飒邓卫东天津大学建筑工程学院重庆交通部高速公路研究所 410184

The importance of studying the behavior of the soil at the sea bottom under the action of wave force has arisen with the development of offshore *** this paper,the behavior of the soft clay under the action of wave forces is studied by performing centrifugal *** soil profile and the wave characters were simulated in the centrifugal model cell according to the typical environmental conditions of the oil fields in the Bohai *** results show that the soft clay layer will be seriously softened near the upper surface under the maximum wave height and slightly affected in the deeper layer,and that no liquefaction was recorded in the silty sand sublayer during the *** is proven that the centrifugal test is a valid technique for simulating the interaction between soil and wave.

关键词： wave soft clay softening centrifugal model test

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如何选择合适的型砂添加剂

铸造 2017年第8期66卷 908-908页

作者：刘金城

各种类型的添加剂简化为三种类型：氧化铁（Iron oxides）粉、燃（烧）尽型添加剂（（Bum-out additives）,和工程型砂添加剂（Engineered additives）氧化铁粉已经应用多年,通常是红色氧化铁粉、黑色氧化铁粉,有时是混合颜色的。氧化... 详细信息

各种类型的添加剂简化为三种类型：氧化铁（Iron oxides）粉、燃（烧）尽型添加剂（（Bum-out additives）,和工程型砂添加剂（Engineered additives）氧化铁粉已经应用多年,通常是红色氧化铁粉、黑色氧化铁粉,有时是混合颜色的。氧化铁起到一层培融物的作用,促进型砂软化（softening of the sand）,在砂芯和铸型出现裂纹之前可以吸收较多的热应力。作为富氧物质,

关键词：氧化铁粉 additives 砂芯 softening 富氧铸造过程热应力芯砂铸件凝固过程粘砂