Alternating Slant Mode of the Crack Propagation in Ductile Flat Plates

2011 ◽  
Author(s):  
Liang Xue
Keyword(s):  
Crack Propagation ◽  
Influencing Factors ◽  
Crack Pattern ◽  
The Other ◽  
Ductile Crack ◽  
Flat Plates ◽  
Material Parameters ◽  
Relevant Material ◽  
Numerical Examination ◽  
Plate Plane

Cracks in flat plates are often found to be about 45° to the plate plane for some metals and alloys. There are two identical 45° directions to the plate plane and the choice of crack direction seems to be random. Experiments have shown that, for large flat panels, the long ductile crack propagation exhibits a regular alternating pattern, i.e. the crack switches to the other direction after propagates some distance regularly. In this paper, a numerical examination of the details of the formation of the alternating crack pattern is presented. Relevant material parameters and their influencing factors to the alternating behavior of cracks are discussed.

Investigation on Polymer Adsorption and Retention in a Polymer Flooded Reservoir

2013 ◽  
Vol 734-737 ◽  
pp. 1200-1203
Author(s):  
Shu Qiang Liu ◽  
Ji Cheng Zhang ◽  
Jin Cheng Xu
Keyword(s):  
Polymer Solution ◽  
Influencing Factors ◽  
Polymer Adsorption ◽  
Solution Concentration ◽  
Injection Rate ◽  
The Other ◽  
Injection Time ◽  
Factors Affecting ◽  
Dynamic Factors ◽  
Polymer Retention

During polymer flooding, certain amount of polymer would be lost. Polymer retention causes sweep volume expanding on one side, it also causes polymer loss on the other. Therefore, it is a very important topic to study the influencing factors of polymer retention. There are many factors affecting polymer retention process. This paper mainly studied the influence from dynamic factors such as polymer solution concentration, injection rate, injection time, injected pv number. This paper investigated the influence of these factors on polymer retention process, and optimized these factors to minimize polymer loss in reservoir.

Modeling of Crack Propagation Behavior of High Density Polyethylene by Using Crack Layer Theory: Parametric Study

2015 ◽  
Author(s):  
Jung-Wook Wee ◽  
Byoung-Ho Choi
Keyword(s):  
Crack Propagation ◽  
Parametric Study ◽  
High Density Polyethylene ◽  
Creep Condition ◽  
Growth Behavior ◽  
High Density ◽  
Crack Growth Behavior ◽  
Material Parameters ◽  
Input Parameters ◽  
Crack Layer

Creep and fatigue slow crack propagation of engineering thermoplastics display continuous or discontinuous manner depending on the test condition. It could be simulated accurately by use of crack layer theory with theoretical backgrounds. But many input parameters complexify the use of CL theory. Thus the investigation on the effect of material parameters on the CL growth is necessary for the comprehensive understanding. In this paper, a parametric study of CL growth simulation of single edge notched tension specimen in creep condition was performed. Several material parameters were varied so that the effect of input parameters on the CL growth behavior could be understood. Total lifetime is used to figure out the effect of the parameters quantitatively. This study would be beneficial to understand the effect of material parameters on the slow crack growth behavior of high density polyethylene.

On the Motion of Granular Materials Due to Shear

2000 ◽  
Author(s):  
Mehrdad Massoudi ◽  
Tran X. Phuoc
Keyword(s):  
Finite Difference ◽  
Granular Materials ◽  
Continuum Model ◽  
Theory Model ◽  
Governing Equations ◽  
Flat Plates ◽  
Material Parameters ◽  
Finite Difference Technique ◽  
Linear Differential ◽  
The Continuum

Abstract In this paper we study the flow of granular materials between two horisontal flat plates where the top plate is moving with a constant speed. The constitutive relation used for the stress is based on the continuum model proposed by Rajagopal and Massoudi (1990), where the material parameters are derived using the kinetic theory model proposed by Boyle and Massoudi (1990). The governing equations are non-dimensionalized and the resulting system of non-linear differential equations is solved numerically using finite difference technique.

Design of crack arrestors for ultra high grade gas transmission pipelines: simulation of crack initiation, propagation and arrest

2011 ◽  
Vol 2 (2) ◽  
pp. 307-319
Author(s):  
F. Van den Abeele ◽  
M. Di Biagio ◽  
L. Amlung
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Large Scale ◽  
Large Diameter ◽  
Pipe Material ◽  
High Grade ◽  
Gas Pipelines ◽  
Ductile Crack ◽  
Reinforced Plastics ◽  
Four Point Bending

One of the major challenges in the design of ultra high grade (X100) gas pipelines is the identification of areliable crack propagation strategy. Recent research results have shown that the newly developed highstrength and large diameter gas pipelines, when operated at severe conditions, may not be able to arrest arunning ductile crack through pipe material properties. Hence, the use of crack arrestors is required in thedesign of safe and reliable pipeline systems.A conventional crack arrestor can be a high toughness pipe insert, or a local joint with higher wall thickness.According to experimental results of full-scale burst tests, composite crack arrestors are one of the mostpromising technologies. Such crack arrestors are made of fibre reinforced plastics which provide the pipewith an additional hoop constraint. In this paper, numerical tools to simulate crack initiation, propagationand arrest in composite crack arrestors are introduced.First, the in-use behaviour of composite crack arrestors is evaluated by means of large scale tensile testsand four point bending experiments. The ability of different stress based orthotropic failure measures topredict the onset of material degradation is compared. Then, computational fracture mechanics is applied tosimulate ductile crack propagation in high pressure gas pipelines, and the corresponding crack growth inthe composite arrestor. The combination of numerical simulation and experimental research allows derivingdesign guidelines for composite crack arrestors.

Comparison of Two Ductile Crack Propagation Models of GTN and CZM for Pipe Steel Fracture

2018 ◽  
Author(s):  
Junqiang Wang ◽  
Haitao Wang ◽  
Nan Lin ◽  
Honglian Ma ◽  
Jinlong Wang
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Pipe Steel ◽  
Damage Model ◽  
Crack Tip ◽  
Ductile Crack ◽  
Constraint Effect ◽  
Propagation Models ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

The ductile crack propagation behavior of pressure equipment has always been the focus of structural integrity assessment. It is very important to find an effective three-dimensional (3D) damage model, which overcomes the geometric discontinuity and crack tip singularity caused by cracking. The cohesive force model (CZM), which is combined with the extended finite element method (XFEM), can solve element self-reconfiguration near the crack tip and track the crack direction. Based on the theory of void nucleation, growth and coalescence, the Gurson-Tvergaard-Needleman (GTN) damage model is used to study the fracture behavior of metallic materials, and agrees well with the experimental results. Two 3D crack propagation models are used to compare crack propagation behavior of pipe steel from the crack tip shape, fracture critical value of CTOA and CTOD, constraint effect, calculation accuracy, efficiency and mesh dependence etc. The results show that the GTN model has excellent applicability in the analysis of crack tip CTOD/CTOA, constraint effect, tunneling crack and so on, and its accuracy is high. However, the mesh of crack growth region needs to be extremely refined, and the element size is required to be 0.1–0.3mm and the calculation amount is large. The CZM model combined with XFEM has the advantages of high computational efficiency and free crack growth path, and the advantages are obvious in simulating the shear crack, combination crack and fatigue crack propagation. But, the crack tip shape and thickness effect of ductile tearing specimen can not be simulated, and the CTOA value of local crack tip is not accurate.

scholarly journals Pengembangan Kedelai di Sawah Irigasi Pantura Jawa Barat

2016 ◽  
Vol 16 (1) ◽  
pp. 9
Author(s):  
Wayan Sudana
Keyword(s):  
Influencing Factors ◽  
Coastal Region ◽  
The Other ◽  
Farm Income ◽  
Good Seed ◽  
Rural Employment ◽  
Seed Availability ◽  
The Government ◽  
Area Expansion ◽  
Further Development

<p><strong>English</strong><br />Soybean consumption has grown rapidly, but its production increased at a much lower rate, and as a result its demand can only be met by import. On the other hand, the irrigated land most suitable for soybean development is still in a large potential. To utilize the resource, the government made a special effort through intensification and area expansion program as well. The irrigated lowland at West Java northern coastal region is one of strategic opportunities to boost soybean production based on location, accessibility and land suitability. Soybean is usually produced in the second dry season (July-September), and it is expected to increase farm income, to create rural employment opportunity especially for landless farmer. Some influencing factors for further development are among others good seed availability, irrigation and competition of labor used.</p><p> </p><p><strong>Indonesian</strong><br />Pertumbuhan konsumsi kedelai dari tahun ke tahun terus mengalami peningkatan, sehingga mengakibatkan ketidakseimbangan pertumbuhan konsumsi dan produksi kedelai dalam negeri. Untuk menutupi kekurangan konsumsi dalam negeri terpaksa dilakukan impor. Di lain pihak potensi lahan yang cocok untuk pengembangan kedelai ini masih cukup besar. Untuk memanfaatkan potensi sumberdaya lahan ini pemerintah berusaha melalui berbagai upaya khusus baik melalui intensifikasi maupun ekstensifikasi. Sawah irigasi teknis di Pantura Jawa Barat merupakan salahsatu peluang pengembangan kedelai yang sangat strategis bila dilihat dari letak, aksessibilitas dan kesesuaian bio-fisik lahan. Pengembangan kedelai di lahan ini pada MK II (Juli - September) disamping dapat meningkatkan penerimaan usahatani juga membuka peluang kesempatan kerja bagi buruhtani di pedesaan. Untuk pengembangan selanjutnya faktor yang perlu diperhatikan untuk menunjang keberhasilan program ini antara lain kelembagaan penyediaan benih bermutu, pengaturan air serta persaingan penggunaan tenaga kerja.</p>

scholarly journals Analysing and Comparing Warrantless Tax Inspections and Searches

2019 ◽  
Vol 22 ◽  
pp. 1-33
Author(s):  
Fareed Moosa
Keyword(s):  
Comparative Analysis ◽  
South African ◽  
Information Gathering ◽  
Third Parties ◽  
The Other ◽  
Tax Administration ◽  
Practical Operation ◽  
Effective Administration ◽  
The One ◽  
Relevant Material

Sections 45 and 63 of the Tax Administration Act 28 of 2011 (TAA) confer drastic information gathering powers on officials of the South African Revenue Service (SARS). On the one hand, section 45 permits warrantless routine (non-targeted) and non-routine (targeted) inspections by a SARS official in respect of records, books of accounts and documents found at premises where a taxpayer is reasonably believed to be conducting a trade or enterprise. The purpose of such inspection is to determine whether there has been compliance with specific obligations by the taxpayer. Section 63, on the other hand, permits, on the grounds of urgency and expediency in exceptional circumstances only, warrantless non-routine (targeted) searches by a senior SARS official of a taxpayer and of third parties associated with a taxpayer, as well as searches of a taxpayer's premises and those of third parties. In addition, section 63 permits the seizure of relevant material found at premises searched. All searches and seizures must occur for the purposes of the efficient and effective administration of tax Acts generally. A comparative analysis of sections 45 and 63 of the TAA reveals the existence of key differences in the substance and practical operation of their provisions. This article distils these differences through an in-depth discussion of the nature and extent of the powers of inspection and search conferred by these provisions, as well as by conceptualising the terms “inspection” and “search” for the purposes of sections 45 and 63 respectively.    

Ductile Crack Propagation Simulation of a Cylinder With a Through-Wall Circumferential Flaw Under Excessive Cyclic Torsion Loading

2014 ◽  
Author(s):  
Kiminobu Hojo ◽  
Daigo Watanabe ◽  
Shinichi Kawabata ◽  
Yasufumi Ametani
Keyword(s):  
Cyclic Loading ◽  
Crack Growth ◽  
Rotation Angle ◽  
Fe Analysis ◽  
The Other ◽  
J Integral ◽  
Ductile Crack ◽  
Elastic Plastic ◽  
Cyclic Torsion ◽  
Ductile Crack Growth

A lot of applications of elastic plastic FE analysis to flawed structural fracture behaviors of mode I have been investigated. On the other hand the analysis method has not been established for the case of the excessive cyclic torsion loading with mode II or III fracture. The authors tried simulating the fracture behavior of a cylinder-shaped specimen with a through-walled circumferential flaw subjected to excessive monotonic or cyclic loading by using elastic plastic FE analysis. Chaboche constitutive equation of the used FE code Abaqus was applied to estimate the elastic plastic cyclic behavior. As a result in the case of monotonic loading without crack extension, the relation of torque-rotation angle of the experiment was estimated well by the simulation. Also J-integral by the Abaqus’ function agreed with a simplified J-equation using the calculated torque-rotation angle relation. On the other hand under load controlled cyclic loading associated with ductile crack growth, the calculated torque-rotation angle relation did not agree with the experimental one because of high sensitivity of the used stress-strain curve. J-integral from Abaqus code did not increase regardless of the accumulated crack growth and plastic zone. Several simplified ΔJ calculations tried to explain the experimental ductile crack growth and it seemed that da/dN-ΔJ relation follows the Paris’ law. From these examinations an estimation procedure of the structures under excessive cyclic loading was proposed.

LOW CYCLE FATIGUE BEHAVIOR OF Zn-22Al ALLOY IN SUPERPLASTIC REGION AND NON-SUPERPLASTIC REGION

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5477-5482 ◽  
Author(s):  
ATSUMICHI KUSHIBE ◽  
TSUTOMU TANAKA ◽  
YORINOBU TAKIGAWA ◽  
KENJI HIGASHI
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Crack Tip ◽  
The Other ◽  
Al Alloy ◽  
Cycle Fatigue ◽  
Secondary Cracks

The crack propagation properties for ultrafine-grained Zn -22 wt % Al alloy during low cycle fatigue (LCF) in the superplastic region and the non-superplastic region were investigated and compared with the corresponding results for several other materials. With the Zn - 22 wt % Al alloy, it was possible to conduct LCF tests even at high strain amplitudes of more than ±5%, and the alloy appeared to exhibit a longer LCF lifetime than the other materials examined. The fatigue life is higher in the superplastic region than in the non-superplastic region. The rate of fatigue crack propagation in the superplastic region is lower than that in the other materials in the high J-integral range. In addition, the formation of cavities and crack branching were observed around a crack tip in the supereplastic region. We therefore conclude that the formation of cavities and secondary cracks as a result of the relaxation of stress concentration around the crack tip results in a reduction in the rate of fatigue crack propagation and results in a longer fatigue lifetime.

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