scholarly journals Flexural Strength Reduction in Cemented Carbides

2015 ◽  
Vol 128 (2B) ◽  
pp. B-23-B-26 ◽  
Author(s):  
M. Petrovic ◽  
A. Voloder
Keyword(s):  
Flexural Strength ◽  
Strength Reduction ◽  
Cemented Carbides

scholarly journals TENSILE, COMPRESSIVE AND FLEXURAL STRENGTH REDUCTION OF TIMBER IN FIRE

2009 ◽  
Vol 1 (3) ◽  
pp. 148-156 ◽  
Author(s):  
Zoja Bednarek ◽  
Mečislavas Griškevičius ◽  
Gintas Šaučiuvėnas
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Reduction Rate ◽  
Strength Reduction ◽  
Timber Structures ◽  
Static Tests ◽  
Reduction Coefficient ◽  
Temperature Ranges ◽  
In Fire ◽  
Linear Expression

The present research was dedicated to investigation into the strength of timber structures under fire conditions. Two kinds of timber specimens including oak and pine were used. The carried out investigation covered static tests on tensile strength, compressive strength along the grain, compressive strength perpendicular to the grain and flexural strength. The specimens were tested under the temperatures of 50°C, 100°C, 150°C, 200°C and 230°C. The obtained results show that pine specimens have better properties over the entire temperature range in case of tests on tensile and flexural strength. Also, as for these types of strength, oak specimens show a higher strength reduction rate than those of pine specimens, whereas oak specimens have better properties over the entire temperature ranges in case of compressive strength perpendicular to the grain. Based on statistical analysis, a linear expression of the strength reduction coefficient was proposed.

Microwave Irradiation of Candidal Adhesion and Biofilm on Polymethylmethacrylate Resin

2014 ◽  
Vol 905 ◽  
pp. 73-77
Author(s):  
Reiyal Goveas ◽  
Theerathavaj Srithavaj ◽  
Amornrat Wonglamsam ◽  
Boonyanit Thaweboon ◽  
Sroisiri Thaweboon
Keyword(s):  
Flexural Strength ◽  
Microwave Irradiation ◽  
Biofilm Formation ◽  
Strength Reduction ◽  
Maximum Effect ◽  
Phase Study ◽  
Significant Difference ◽  
Candidal Species ◽  
Pmma Resin ◽  
One Way Anova

This 3 phase study examined (1) the effect of microwave irradiation on the adhesion and (2) biofilm formation of 4 candidal species on heat polymerized polymethyl methacrylate (PMMA) specimens. Lastly, (3) the flexural strength of heat polymerized PMMA was tested.C.albicans(ATCC 10231),C. glabrata(ATCC 22019),C. krusei(ATCC 6258) andC.parapsilosis(ATCC 90030) were used. The flexural strength of the PMMA resin after microwave irradiation was tested in accordance with ISO 20795-1 specifications. A one-way ANOVA statistical analysis was used for all the results.The maximum effect of 94% to 98% reduction in adhesion and biofilm counts was seen with microwave irradiation at 850 W and 1000 W for 120 sec. There was no significant difference between the control and irradiated specimens in terms of flexural strength. Reduction of candida adhesion and biofilm on PMMA resin can be achieved with microwave irradiation.

scholarly journals Changes in the Flexural Strength of Ice under Radiation Decay

1990 ◽  
Vol 21 (4-5) ◽  
pp. 341-354 ◽  
Author(s):  
T. D. Prowse ◽  
M. N. Demuth ◽  
H. A. M. Chew
Keyword(s):  
Flexural Strength ◽  
Radiation Energy ◽  
Theoretical Models ◽  
Experimental Methods ◽  
Ice Cover ◽  
Strength Reduction ◽  
Flexural Testing ◽  
Northern Rivers ◽  
Series Of Experiments ◽  
Radiation Decay

The strength of an ice cover significantly affects the timing and severity of breakup on northern rivers. During the pre-breakup period, thermal and radiative warming is known to significantly decrease such strength. Although reductions in strength with temperature are reasonably well known, there is a dearth of data concerning strength changes due to internal radiative melt. In the spring of 1989, near Floral, Saskatchewan, Canada, a detailed series of experiments were conducted to determine changes in flexural strength, porosity and optical properties of the ice cover. The test data strongly support existing theoretical models of strength reduction due to porosity development in columnar grained ice. Experimental methods and results with respect to flexural testing, porosity determinations and radiation energy balance are discussed.

Ultrafine WC-Ni-SiCw Cemented Carbides Fabricated by Spark Plasma Sintering

2012 ◽  
Vol 512-515 ◽  
pp. 924-927
Author(s):  
Hui Yong Rong ◽  
Zhi Jian Peng ◽  
Xiao Yong Ren ◽  
Ying Peng ◽  
Cheng Biao Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Flexural Strength ◽  
Spark Plasma Sintering ◽  
Cemented Carbides ◽  
Plasma Sintering ◽  
Mean Grain Size ◽  
Spark Plasma ◽  
The Mean ◽  
Inhomogeneous Microstructure

Ultrafine WC-Ni cemented carbides with addition of SiC whisker (SiCw) were fabricated by spark plasma sintering. The microstructure and mechanical properties of the fabricated cemented carbides were investigated. It was found that the addition of SiC whisker had no obvious influence on the phase compositions of the cemented carbides, but the mean grain size of the cemented carbides decreased as the addition fraction of SiC whisker increased. The fabricated WC-Ni cemented carbides presented the highest hardness when 0.75 wt% SiC whisker was added. However, the addition of SiC whisker was detrimental to the flexural strength of the cemented carbides because of the formation of inhomogeneous microstructure in the WC-Ni cemented carbides.

Microstructural Aspects of Stress Corrosion of Cementitious Materials

1986 ◽  
Vol 85 ◽  
Author(s):  
U. Schneider ◽  
E. Nagele ◽  
N. Dujardin
Keyword(s):  
Corrosion Resistance ◽  
Flexural Strength ◽  
Stress Corrosion ◽  
Cement Mortar ◽  
Cementitious Materials ◽  
Strength Reduction ◽  
Time Dependent ◽  
Hardened Cement ◽  
Chemical Attack ◽  
Comprehensive Study

ABSTRACTStress corrosion phenomena, i.e. significant effects of mechanical stresses on the corrosion resistance of materials, have been reported for a large variety of materials, including metals, oxides and halides. Recently it has been shown [1,2] that cementitious materials are also sensitive to stress corrosion. The time dependent decrease in the flexural strength of chemically stressed concrete and mortar depends significantly on the mechanical stress acting simultaneously with the chemical attack.For cementitious materials a comprehensive study of the stress corrosion phenomena has been started. In this paper the latest results from the current research program are presented and the interrelations between the microstructure of hardened cement mortar and the strength reduction caused by stress corrosion, are briefly discussed.

Out-of-Flatness Effect on Flexural Strength of Steel Bridge Girders

2019 ◽  
Vol 2673 (3) ◽  
pp. 561-573
Author(s):  
Mahdi Asadnia ◽  
W. M. Kim Roddis
Keyword(s):  
Flexural Strength ◽  
Limit State ◽  
Local Buckling ◽  
Strength Reduction ◽  
Material Behavior ◽  
Bridge Girders ◽  
Maximum Effect ◽  
Highway Bridge ◽  
Bottom Flange ◽  
Steel Bridge

This numerical study determines the effects of out-of-flatness on flexural strength at the onset of yielding in continuous I-shaped and tub (box) steel highway bridge girders. This moment at onset of yielding is the strength limit state for flexural design of steel highway bridge girders, according to the AASHTO standard. Finite element analysis is used to obtain values of flexural strength reduction for girders with various magnitudes of out-of-flatness, covering a range of continuous I-shaped and tub (box) cross sections and spans. Straight girders were used since the evaluated behavior is local buckling. Models are built with co-existing out-of-flatness imperfections in both webs and flanges. The imperfection pattern is set to be compatible with the first buckling mode of the built-up cross section to match the case having the theoretical maximum effect on local buckling. ANSYS heat analysis was used to create appropriate residual stress pattern in the models. Models are laterally supported to ensure the local buckling limit state is the governing failure mode. Both Grade 50 steel and Grade 100 steel plate are considered with elastic-perfectly plastic material behavior. Large deflection theory is used to iteratively capture the secondary moments due to out-of-flatness. Maximum strength reduction implicitly allowed in accordance with the most restrictive value of out-of-flatness for continuous two-span unstiffened I-shaped plate girders by the American Welding Society D1.5 Bridge Welding Code is obtained. Strength-based out-of-flatness criteria for the bottom flange of steel tub girders are proposed as functions of bottom flange slenderness.

scholarly journals Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5599
Author(s):  
Kyong Ku Yun ◽  
Seunghak Choi ◽  
Taeho Ha ◽  
Mohammad Shakhawat Hossain ◽  
Seungyeon Han
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Steel Fiber ◽  
Strength Reduction ◽  
Strength Development ◽  
Fiber Reinforced ◽  
Cast Concrete ◽  
Long Term Performance ◽  
Term Performance

This study analyzed the effect of accelerating agents, such as aluminate, cement mineral, and alkali-free accelerators, on the long-term performance of steel-fiber-reinforced shotcrete. The shotcrete performance was studied based on the type and amount of steel fiber added. Performance tests were performed to identify the accelerator providing better long-term performance to the steel-fiber-reinforced shotcrete. Changes in strength and flexural performance over time were investigated. The compressive strength and flexural strength tests on 1-, 3-, 6-, 12-, and 24-month-old test specimens were performed, wherein 37 kg of steel fiber was added to the cement mineral and aluminate mixes, and 40 kg of steel fiber was added to the alkali-free mix. The 1-month compressive strength result of all the test variables satisfied the Korea Expressway Corporation standard. The compressive strength of the cast concrete and shotcrete specimens increased with age, demonstrating a strength reduction, particularly in the 24-month-old shotcrete specimens. Thus, the shotcrete performance may deteriorate in the long-term. In the 24-month-old specimen, substantial flexural strength reduction was observed, particularly in the aluminate and alkali-free specimens. The relative strength of the specimens was compared with that of the cast concrete mold specimens. The results suggest the use of alkali-free accelerators, considering the long-term performance of tunnels and safety of workers. Moreover, increasing the steel fiber performance rather than the amount of low-performance steel fiber must be considered.

Performance of carbon nanotubes in mortar using different surfactants

2017 ◽  
Vol 44 (8) ◽  
pp. 619-625 ◽  
Author(s):  
M. Elkashef ◽  
M.N. Abou-Zeid
Keyword(s):  
Carbon Nanotubes ◽  
Raman Spectroscopy ◽  
Compressive Strength ◽  
Sodium Dodecyl Sulfate ◽  
Flexural Strength ◽  
Sodium Dodecyl ◽  
Strength Reduction ◽  
Degree Of Dispersion ◽  
Ultrasonication Time ◽  
Triton X

The performance of carbon nanotubes (CNTs) in cement-based composites relies to a great extent on its degree of dispersion. In this work, the performance of two commonly used surfactants; sodium dodecyl sulfate (SDS) and Triton X-100, is being compared. The effect of surfactant-to-CNT ratio on dispersion efficiency is studied using ultraviolet-visible (UV-Vis) spectrometry, to determine the optimum surfactant dosage. For the optimum ultrasonication energy, Raman spectroscopy is used to assess the degree of imperfections on CNTs. CNTs-reinforced mortar specimens prepared using Triton X-100 and SDS are tested for compressive and flexural strength. Triton X-100 is shown to exhibit better dispersion efficiency than SDS, leading to greater improvement in flexural and compressive strength. An ultrasonication time of 60 min (19.4 kJ/mL) is shown to be sufficient to achieve proper dispersion, however notable degradation of CNTs was noted beyond 30 min (9.7 kJ/mL) of dispersion leading to a strength reduction.

scholarly journals The Influence of Concrete Strength on the Effect of Synthetic Fibres on Fire Resistance

2017 ◽  
Vol 62 (1) ◽  
pp. 136-142 ◽  
Author(s):  
Éva Lublóy
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Pore Structure ◽  
Fire Resistance ◽  
Concrete Strength ◽  
Small Diameter ◽  
Concrete Surface ◽  
Strength Reduction ◽  
Fibre Reinforcement ◽  
Polypropylene Fibres

Numerous studies have verified that increased concrete strength reduces its resistance to fire, leads to a higher degree of strength reduction and higher chances of spalling of concrete surfaces.The risks of spalling of concrete surfaces can be reduced by adding synthetic polypropylene fibres. Numerous experiments have shown that the risk of spalling of the concrete surface is significantly lower when using short, small diameter fibres of polypropylene synthetic, because the pore structure created by the burning of fibres reduces the risk of cracking.However, the question arises whether other types of fibres of greater diameter and length are still able to prevent spalling of concrete surfaces without drastically reducing the strength and if so, in what range of concrete strength it is true.The experiments are aimed to determine the effects of micro and macro synthetic fibres on the post-fire residual compressive strength, flexural strength and porosity of concrete.Nine kinds of mixture were prepared and tested. Three of them are without fibers (reference concretes) with diverse strength, three with synthetic micro-fibres with diverse strength and three with synthetic macro-fibres of diverse strength. The experiment was conducted with three concretes with different strength. Each type had a reference concrete without fibre reinforcement, one with micro- and one with macro-fibres.

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