scholarly journals Comparison of Field and Laboratory Result of Fiber Reinforced Shotcrete Application

2021 ◽  
Author(s):  
Gökhan Külekçi
Keyword(s):  
Energy Absorption ◽  
Synthetic Fiber ◽  
Laboratory Result ◽  
Ambient Conditions ◽  
Laboratory Environment ◽  
Synthetic Fibers ◽  
Freeze Thaw ◽  
Polyester Fibers ◽  
Main Components ◽  
Very High

Synthetic fibers, which have become one of the main components of shotcrete, have been studied by many researchers in the laboratory environment. Unfortunately, the results obtained as a result of these researches are not suitable for underground chimneys due to the differences in ambient conditions and application differences. In this study, it is aimed to compare the results of the experiment samples prepared and kept in the laboratory with the mechanical properties of the shotcrete applied in underground conditions. For this purpose, keeping the slump and cement proportions constant, 35 cubic samples were prepared using 2 and 6 kg synthetic fiber for 1 m3 in the laboratory, and 30 cylinder samples and 6 plate samples were prepared for underground. While mechanical experiments were carried out on prepared cube and cylinder samples, the EFNARC plate test and freeze-thaw test were carried out on plate samples. It was observed that the set accelerator made a significant increase in resistance at the end of the 28 days and that the resistance of the samples prepared with polyester fibers in the laboratory environment were very high. As a result of the EFNARC panel tests performed, it was determined that the energy absorption of synthetic fibers increased with fiber amount. Thanks to this study, the energy absorption of the synthetic fiber used has been measured, and the reliability and practicality of the experiments carried out in the laboratory have been increased by evaluating the field conditions and laboratory conditions.

Microbeam polarization infrared spectroscopy: single fiber discrimination

1995 ◽  
Vol 53 ◽  
pp. 494-495
Author(s):  
Liling Cho ◽  
David L. Wetzel
Keyword(s):  
Infrared Spectroscopy ◽  
Phase Measurement ◽  
Single Fiber ◽  
Synthetic Fiber ◽  
Liquid Crystal Phase ◽  
Synthetic Fibers ◽  
Polyester Fibers ◽  
Fixed Reference ◽  
Ft Ir ◽  
Ir Microspectroscopy

FT-IR microspectroscopy of single fiber can produce useful information to distinguish among synthetic fibers. Certain fibers can be readily discriminated on the basis of spectra obtained by this technique. Polarization infrared spectroscopy has been used to measure macromolecular properties such as precipitate crystallinity, polymer film draw ratio, and liquid crystal phase. Measurement of IR dichroism requires light polarized both parallel and perpendicular to a fixed reference direction of the sample. Dichroism may be used to compare and discriminate between different polyester fibers and possibly to establish new groups within a subclass. Four fundamental bands (872, 973,1505 and 1579 cm-1) and two overtone bands (1960 and 3435 cm-1) were chosen because they were relatively free from overlapping bands, and they were weak enough not to be over-absorbing in the spectra of thick, unflattened fibers. During industrial production, the process of drawing can impart many useful properties to a synthetic fiber. When this occurs, molecular chains may become oriented in the long direction of the fiber.

Effects of Heat Shrinkage on Structure and Property of Silk/Synthetic Fiber Textured Composite Filaments

2011 ◽  
Vol 175-176 ◽  
pp. 280-283
Author(s):  
Xiao Ying Zhang ◽  
Bao Zhong Wang ◽  
Min Zhang ◽  
Zhi Juan Pan
Keyword(s):  
The Self ◽  
Synthetic Fiber ◽  
Structure And Properties ◽  
Synthetic Fibers ◽  
Structure And Property ◽  
Polyester Fibers ◽  
Yarn Count ◽  
Composite Filament ◽  
Processing Device

The textured yarn was respectively prepared with pure silk, silk/polyester POY composite filament, silk/polyester FDY composite filament by the self-made processing device. The effects of heat shrinkage of polyester fibers on the structure and properties of the textured filaments were investigated. The results revealed that silk/POY composite filament contained higher heat shrinkage. Synthetic fibers produced crimps with larger amplitude and smaller bandwidth, and the textured filaments presented a larger yarn count, resulting in the notable crimped deformation.

scholarly journals Portable DC Supply Based on SiC Power Devices for High-Voltage Marx Generator

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 313
Author(s):  
Jacek Rąbkowski ◽  
Andrzej Łasica ◽  
Mariusz Zdanowski ◽  
Grzegorz Wrona ◽  
Jacek Starzyński
Keyword(s):  
High Voltage ◽  
Specific Area ◽  
Input Voltage ◽  
Marx Generator ◽  
Power Devices ◽  
Laboratory Setup ◽  
High Voltage Gain ◽  
Main Components ◽  
Two Stages ◽  
Very High

The paper describes major issues related to the design of a portable SiC-based DC supply developed for evaluation of a high-voltage Marx generator. This generator is developed to be a part of an electromagnetic cannon providing very high voltage and current pulses aiming at the destruction of electronics equipment in a specific area. The portable DC supply offers a very high voltage gain: input voltage is 24 V, while the generator requires supply voltages up to 50 kV. Thus, the system contains two stages designed on the basis of SiC power devices operating with frequencies up to 100 kHz. At first, the input voltage is boosted up to 400 V by a non-isolated double-boost converter, and then a resonant DC-DC converter with a special transformer elevates the voltage to the required level. In the paper, the main components of the laboratory setup are presented, and experimental results of the DC supply and whole system are also shown.

Thermal failure mechanism of fiber ropes when bent over sheaves

2018 ◽  
Vol 89 (7) ◽  
pp. 1215-1223
Author(s):  
Fanggang Ning ◽  
Xiaoru Li ◽  
Nick O Hear ◽  
Rong Zhou ◽  
Chuan Shi ◽  
...  
Keyword(s):  
Failure Mechanism ◽  
Thermal Damage ◽  
Synthetic Fiber ◽  
Heat Accumulation ◽  
Thermal Failure ◽  
Synthetic Fibers ◽  
Test Conditions ◽  
Bending Process ◽  
Higher Temperature ◽  
Bending Failure

Thermal damage is an important failure mechanism that affects the bending failure of fiber ropes. This is relevant because synthetic fibers often have a relatively low melting point and low thermal conductivity. In cyclic bending over sheave (CBOS), the heat generated by friction and deformation is not conducted rapidly to the external environment, and the temperature of the rope core increases quickly. This higher temperature greatly reduces the mechanical properties of the fiber, thus accelerating the final rope failure. In this paper, evidence of thermal damage in the bending process of a braided synthetic fiber rope is given. The test conditions inducing thermal damage are discussed, including stress level, bending frequency and diameter ratio. The reasons for the heat generation and the dynamic process of heat accumulation inside the rope during CBOS are also discussed. This study aims to provide theoretical and experimental guidance for the design and use of fiber rope.

scholarly journals Degradation of Mechanical Behavior of Sandstone under Freeze-Thaw Conditions with Different Low Temperatures

2021 ◽  
Vol 11 (22) ◽  
pp. 10653
Author(s):  
Jingwei Gao ◽  
Chao Xu ◽  
Yan Xi ◽  
Lifeng Fan
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Energy Absorption ◽  
Uniaxial Compressive Strength ◽  
Dynamic Strength ◽  
Freezing Temperature ◽  
P Wave ◽  
Freeze Thaw ◽  
P Wave Velocity

This study investigated the effects of freezing temperature under freeze-thaw cycling conditions on the mechanical behavior of sandstone. First, the sandstone specimens were subjected to 10-time freeze-thaw cycling treatments at different freezing temperatures (−20, −40, −50, and −60 °C). Subsequently, a series of density, ultrasonic wave, and static and dynamic mechanical behavior tests were carried out. Finally, the effects of freezing temperature on the density, P-wave velocity, stress–strain curves, static and dynamic uniaxial compressive strength, static elastic modulus, and dynamic energy absorption of sandstone were discussed. The results show that the density slightly decreases as temperature decreases, approximately by 1.0% at −60 °C compared with that at 20 °C. The P-wave velocity, static and dynamic uniaxial compressive strength, static elastic modulus, and dynamic energy absorption obviously decrease. As freezing temperature decreases from 20 to −60 °C, the static uniaxial compressive strength, static elastic modulus, dynamic strength, and dynamic energy absorption of sandstone decrease by 16.8%, 21.2%, 30.8%, and 30.7%, respectively. The dynamic mechanical behavior is more sensitive to the freezing temperature during freeze-thawing cycling compared with the static mechanical behavior. In addition, a higher strain rate can induce a higher dynamic strength and energy absorption.

Influence of Fibre Treatment and Matrix Modification on Mechanical Properties of Flax Fibre Reinforced Mortars after Freeze/Thaw Cycles

2022 ◽  
Author(s):  
Bojan Poletanovic ◽  
Katalin Kopecsko ◽  
Ildikó Merta
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Linseed Oil ◽  
Absorption Capacity ◽  
Flax Fibre ◽  
Energy Absorption Capacity ◽  
Freeze Thaw ◽  
Flax Fibres ◽  
Matrix Modification ◽  
Compressive And Flexural Strengths

The aim of this study was to examine the influence of flax fibre protection with the linseed oil and a matrix modification with cement substitution with metakaolin (in 10wt% and 15wt%) on the mechanical properties of cement-based mortars under severe environmental conditions of freeze/thaw cycles. Cement-based mortars (with the dimension of 40x40x160 mm3) were reinforced by 10mm long discrete flax fibres (Linumusitatissimum) and exposed to 51 freeze/thaw cycles under laboratory condition. Their compressive and flexural strengths, as well as specific energy absorption capacity were measured after freeze/thaw cycles and compared to the results of mortars cured for same time in water. Under freeze/thaw cycles mortars reinforced with linseed oil-treated fibres showed the same range of degradation of the compressive and flexural strengths, however, a more pronounced degradation of energy absorption capacity compared to non-treated fibre reinforced mortars was observed. The matrix modification, by partial cement substitution with metakaolin showed optimistic results under freeze/thaw cycles. The compressive strength when cement was partially substituted with metakaolin (in both dosages) increased whereas the flexural strength was slightly lower in case of 10wt% substitution and markedly lower under higher (15wt%) cement substitution. The most relevant is that the decrease of the energy absorption capacity of the fibre reinforced mortar was completely prevented when cement was substituted with metakaolin. It is shown that the energy absorption of the non-treated fibre reinforced mortars increases by 27% when cement was substituted with metakaolin (both 10wt% and 15wt%).

The influence of natural and synthetic fibers on mixed mode I/II fracture behavior of cement concrete materials

2019 ◽  
Vol 46 (12) ◽  
pp. 1081-1089 ◽  
Author(s):  
Hossein Karimzadeh ◽  
Ali Razmi ◽  
Reza Imaninasab ◽  
Afshin Esminejad
Keyword(s):  
Fracture Toughness ◽  
Reinforced Concrete ◽  
Mixed Mode ◽  
Fiber Reinforced Concrete ◽  
Bending Test ◽  
Synthetic Fiber ◽  
Mode I ◽  
Fiber Reinforced ◽  
Synthetic Fibers ◽  
Natural And Synthetic

This paper evaluated mixed mode I/II fracture toughness of fiber-reinforced concrete using cracked semi-circular bend (SCB) specimens subjected to three-point bending test. Additionally, a comparison was made between the experimental results and the estimations made by different theoretical criteria. Natural and synthetic fibers at various concentrations were used in this study. After producing cracks in SCB specimens at different inclination angles to induce different mixed mode loading conditions (from pure mode I to II), the fracture toughness of SCB specimens was determined. Furthermore, the compressive, splitting tensile, and flexural strength of natural and synthetic fiber-reinforced concrete were measured after 7 and 28 days of curing. While there is an increase in the aforementioned strengths with fiber content increase, 0.3% was found to be the optimum percentage regarding fracture toughness for both fibers. Also, the comparison between the experimental and theoretical results showed that generalized maximum tangential stress criterion estimated the experimental data satisfactorily.

scholarly journals Dynamic Characteristics of Sandstone under Coupled Static-Dynamic Loads after Freeze-Thaw Cycles

2020 ◽  
Vol 10 (10) ◽  
pp. 3351
Author(s):  
Bo Ke ◽  
Jian Zhang ◽  
Hongwei Deng ◽  
Xiangru Yang
Keyword(s):  
Energy Absorption ◽  
Dynamic Characteristics ◽  
Shear Failure ◽  
Strain Curve ◽  
Peak Stress ◽  
Peak Strain ◽  
Compression Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Freeze Thaw

The effect of temperature fluctuation on rocks needs to be considered in many civil engineering applications. Up to date the dynamic characteristics of rock under freeze-thaw cycles are still not quite clearly understood. In this study, the dynamic mechanical properties of sandstone under pre-compression stress and freeze-thaw cycles were investigated. At the same number of freeze-thaw cycles, with increasing axial pre-compression stress, the dynamic Young’s modulus and peak stress first increase and then decrease, whereas the dynamic peak strain first decreases and then increases. At the same pre-compression stress, with increasing number of freeze-thaw cycles, the peak stress decreases while the peak strain increases, and the peak strain and peak stress show an inverse correlation before or after the pre-compression stress reaches the densification load of the static stress–strain curve. The peak stress and strain both increase under the static load near the yielding stage threshold of the static stress–strain curve. The failure mode is mainly shear failure, and with increasing axial pre-compression stress, the degree of shear failure increases, the energy absorption rate of the specimen increases first and then decreases. With increasing number of freeze-thaw cycles, the number of fragments increases and the size diminishes, and the energy absorption rates of the sandstone increase.

Inheritance of Grain Yield and Other Quantitative Traits in Maize

1977 ◽  
Vol 13 (3) ◽  
pp. 253-256 ◽  
Author(s):  
B. S. Dhillon ◽  
Joginder Singh
Keyword(s):  
Grain Yield ◽  
Combining Ability ◽  
Narrow Sense Heritability ◽  
Environmental Interactions ◽  
Grain Moisture ◽  
Maize Varieties ◽  
Combining Ability Analysis ◽  
Main Components ◽  
Very High

SUMMARYCombining ability analysis was carried out on diallel crosses of 20 yellow maize varieties in four environments. General combining ability variance (σ2g) was of greater importance than specific combining ability (σ2s) in the inheritance of all traits except grain yield and ear length, where the reverse was true. Interaction components (σ2ge, σ2se) were greater than the respective main components (σ2g, σ2s) for grain yield. The study brought out the prominent role of genotype-environmental interactions. Heritability in the broad sense was very high for all traits except grain yield and grain moisture, and narrow sense heritability was also high for all traits except grain yield and ear length.

Influence of Montmorillonite Treated with Cetyl Trimethyl Ammonium Bromide Addition in Epoxy-Kenaf Composites

2015 ◽  
Vol 754-755 ◽  
pp. 235-239
Author(s):  
A. Zuliahani ◽  
H.D. Rozman ◽  
Abdul Rahman Rozyanty
Keyword(s):  
Cetyl Trimethyl Ammonium Bromide ◽  
Natural Fiber ◽  
Environmental Concern ◽  
Low Cost ◽  
Natural Fibers ◽  
Synthetic Fiber ◽  
Ammonium Bromide ◽  
Synthetic Fibers ◽  
Cetyl Trimethyl Ammonium ◽  
Kenaf Composites

The use of natural fiber as reinforcement in polymer composites has gained importance recently due to environmental concern and its abundance availability from agricultural crops and wood industry [1]. Many advantages offered by natural fibers over synthetic fibers include low density, greater deformability, low cost per unit volume, recyclability and biodegradability [2-3]. In addition, the mechanical properties of natural fibers such as flax, hemp, jute, sisal and kenaf are comparable with glass fiber in respect of strength and modulus [4]. Hence, many studies have been carried out to replace the synthetic fiber for composite preparation.

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