Groups of Physical Parameters Influencing the Three Stages Pull-Out Behavior of Glass Multi-filament Yarns Embedded in Micro-concrete

Author(s):  
H. Aljewifi ◽  
B. Fiorio ◽  
J. -L. Gallias
2012 ◽  
Vol 166-169 ◽  
pp. 3254-3257
Author(s):  
Bo Liu ◽  
Li Huang ◽  
Dong Yang Li

Based on the local deformation theory, we study the mechanics behavior of anchorage interface of full-length bonded rock bolt by using a mathematics model (tri-linear model). With pull-out load increasing, the changing process of anchorage interface of full-length bonded bolt is divided into three stages in this paper: elastic stage, plastic softening stage and crack slipping stage. It is found that in the state of elastic, axis force decreases rapidly with bolt depth increasing, and when pull-out load is greater than elastic ultimate load, attenuation degree will slow for the occurring of interface plastic softening and crack slipping in the top of bolt. The result indicates that the continuous change of axis force with bolt depth reflects that the bolt interface bond strength changes with the increase of pulling load.


1990 ◽  
Vol 211 ◽  
Author(s):  
Gilles Chanvillard ◽  
Pierre-Claude Aitcin

AbstractThe pull-out behavior of non-straight steel fibers cannot always be analyzed solely in terms of bonding. Rather, it is necessary to take into account the mechanical anchorage provided by the fiber geometry.It is shown in this paper, that in the case of non-straight steel fibers a strong interaction exists between bonding and anchorage. A micro-mechanical model, based on the dissipation of energy during slipping of the fiber is proposed. In this model, bonding is included on the basis of the Coulomb friction law, without reference to a bond-slip law; mechanical anchorage is modelled from plastic deformation of the fiber.With this model, it is possible to evaluate the significance of some physical parameters such as the water/cement ratio of the matrix, the fiber's geometry and the steel properties. Moreover, this model provides a rational basis for the optimization of the fiber-cementitious matrix interaction from an energy point of view.


2018 ◽  
Vol 7 (1) ◽  
pp. 08
Author(s):  
Farhana Septriana Rahmat ◽  
Srikandi Srikandi ◽  
RTM Sutamihardja

Washing Effects of Chloride Content in Process of Making Carrageenan of Seaweed, Eucheuma cottoniiThis study was conducted experimentally using Completely Randomized Design (CRD) with three (3) of standard treatments and three (3) replications. Stages of treatments included: Extraction of seaweed with three stages: extraction of seaweed with normal washing process, the twice extraction of the seaweed with laundering at the beginning, and four times extraction of the seaweed with the washing at the end. Drying of seaweed extraction, milling of dried seaweed to be come carrageenan, and filtering. Carrageenan screening results conducted to determine the yield, test physical parameters such as viscosity, pH, water content, the gel strength, and ash content. And also test the chemical parameters such as levels of sulphate and chloride levels (as cleaning KCl based). The results showed that the washing process four times in the end give chloride levels (as KCl based cleaning) was lowest with an average of 0,16%, compared to the treatment washing process twice in the beginning with an average of 0,33%. And the manual process of KCl based cleaning with an average of 0,49% therefore the normal process of providing value levels of chloride as KCl based cleaning was the highest. The results of the study concluded that the washing process at the beginning and at the end, affect the chloride levels based cleaning obtained at below 2%. The washing process that can be used for the manufacture of carrageenan of the seaweed (Eucheuma cottonii) were the best in the washing process four times at the end.Keywords: Eucheuma cottonii, leaching, chloride, carrageenan  ABSTRAK Penelitian ini dilaksanakan secara eksperimen dengan menggunakan metode Rancangan Acak Lengkap (RAL) dengan 3 (tiga) taraf perlakuan masing-masing 3 (tiga) kali ulangan. Tahapan kerja meliputi: Ekstraksi rumput laut dengan tiga tahapan yaitu ekstraksi rumput laut dengan proses pencucian normal, ekstraksi rumput laut dengan pencucian di awal sebanyak dua kali, dan ekstraksi rumput laut dengan pencucian di akhir sebanyak empat kali. Pengeringan hasil ekstraksi rumput laut, penggilingan rumput laut kering hingga menjadi karaginan, dan penyaringan. Hasil penyaringan karaginan dilakukan penentuan rendemen, uji parameter fisik seperti viskositas, pH, kadar air, kekuatan gel, dan kadar abu. Serta uji parameter kimia seperti kadar sulfat dan kadar klorida sebagai KCl dry based. Hasil yang diperoleh menunjukkan bahwa perlakuan proses pencucian empat kali di akhir memberikan nilai kadar klorida sebagai KCl dry based terendah dengan rata-rata 0,16%, dibandingkan dengan perlakuan proses pencucian dua kali di awal dengan rata-rata 0,33%, dan proses manual (sebagai KCl dry based) dengan nilai rata-rata 0,49%, jadi proses normal memberikan nilai kadar klorida (sebagai KCl dry based) yang menghasilkan nilai tertinggi. Hasil penelitian disimpulkan bahwa proses pencucian di awal dan di akhir, berpengaruh terhadap kadar klorida dry based yang diperoleh yaitu di bawah 2 %. Proses pencucian yang dapat digunakan untuk pembuatan karaginan dari rumput laut Eucheuma cottonii yang terbaik yaitu proses pencucian empat kali di akhir.Kata kunci :  Eucheuma cottonii, pencucian, klorida, karaginan


1965 ◽  
Vol 5 ◽  
pp. 120-130
Author(s):  
T. S. Galkina

It is necessary to have quantitative estimates of the intensity of lines (both absorption and emission) to obtain the physical parameters of the atmosphere of components.Some years ago at the Crimean observatory we began the spectroscopic investigation of close binary systems of the early spectral type with components WR, Of, O, B to try and obtain more quantitative information from the study of the spectra of the components.


Author(s):  
K. Tsuno ◽  
T. Honda ◽  
Y. Harada ◽  
M. Naruse

Developement of computer technology provides much improvements on electron microscopy, such as simulation of images, reconstruction of images and automatic controll of microscopes (auto-focussing and auto-correction of astigmatism) and design of electron microscope lenses by using a finite element method (FEM). In this investigation, procedures for simulating the optical properties of objective lenses of HREM and the characteristics of the new lens for HREM at 200 kV are described.The process for designing the objective lens is divided into three stages. Stage 1 is the process for estimating the optical properties of the lens. Firstly, calculation by FEM is made for simulating the axial magnetic field distributions Bzc of the lens. Secondly, electron ray trajectory is numerically calculated by using Bzc. And lastly, using Bzc and ray trajectory, spherical and chromatic aberration coefficients Cs and Cc are numerically calculated. Above calculations are repeated by changing the shape of lens until! to find an optimum aberration coefficients.


Author(s):  
S. Mahajan

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.


Author(s):  
E. Bischoff ◽  
O. Sbaizero

Fiber or whisker reinforced ceramics show improved toughness and strength. Bridging by intact fibers in the crack wake and fiber pull-out after failure contribute to the additional toughness. These processes are strongly influenced by the sliding and debonding resistance of the interfacial region. The present study examines the interface in a laminated 0/90 composite consisting of SiC (Nicalon) fibers in a lithium-aluminum-silicate (LAS) glass-ceramic matrix. The material shows systematic changes in sliding resistance upon heat treatment.As-processed samples were annealed in air at 800 °C for 2, 4, 8, 16 and 100 h, and for comparison, in helium at 800 °C for 4 h. TEM specimen preparation of as processed and annealed material was performed with special care by cutting along directions having the fibers normal and parallel to the section plane, ultrasonic drilling, dimpling to 100 pm and final ionthinning. The specimen were lightly coated with Carbon and examined in an analytical TEM operated at 200 kV.


Author(s):  
J.T. Fourie

Contamination in electron microscopes can be a serious problem in STEM or in situations where a number of high resolution micrographs are required of the same area in TEM. In modern instruments the environment around the specimen can be made free of the hydrocarbon molecules, which are responsible for contamination, by means of either ultra-high vacuum or cryo-pumping techniques. However, these techniques are not effective against hydrocarbon molecules adsorbed on the specimen surface before or during its introduction into the microscope. The present paper is concerned with a theory of how certain physical parameters can influence the surface diffusion of these adsorbed molecules into the electron beam where they are deposited in the form of long chain carbon compounds by interaction with the primary electrons.


Author(s):  
Linda Sicko-Goad

Although the use of electron microscopy and its varied methodologies is not usually associated with ecological studies, the types of species specific information that can be generated by these techniques are often quite useful in predicting long-term ecosystem effects. The utility of these techniques is especially apparent when one considers both the size range of particles found in the aquatic environment and the complexity of the phytoplankton assemblages.The size range and character of organisms found in the aquatic environment are dependent upon a variety of physical parameters that include sampling depth, location, and time of year. In the winter months, all the Laurentian Great Lakes are uniformly mixed and homothermous in the range of 1.1 to 1.7°C. During this time phytoplankton productivity is quite low.


Author(s):  
K.L. More ◽  
R.A. Lowden

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.


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