scholarly journals The flexural strength of bonded ice

2021 ◽  
Vol 15 (6) ◽  
pp. 2957-2967
Author(s):  
Andrii Murdza ◽  
Arttu Polojärvi ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Flexural Strength ◽  
Bond Strength ◽  
Compressive Stress ◽  
Parent Material ◽  
Bending Tests ◽  
Four Point Bending ◽  
Ice Surfaces

Abstract. The flexural strength of ice surfaces bonded by freezing, termed freeze bond, was studied by performing four-point bending tests of bonded freshwater S2 columnar-grained ice samples in the laboratory. The samples were prepared by milling the surfaces of two ice pieces, wetting two of the surfaces with water of varying salinity, bringing these surfaces together, and then letting them freeze under a compressive stress of about 4 kPa. The salinity of the water used for wetting the surfaces to generate the bond varied from 0 to 35 ppt (parts per thousand). Freezing occurred in air under temperatures varying from −25 to −3 ∘C over periods that varied from 0.5 to ∼ 100 h. Results show that an increase in bond salinity or temperature leads to a decrease in bond strength. The trend for the bond strength as a function of salinity is similar to that presented in Timco and O'Brien (1994) for saline ice. No freezing occurs at −3 ∘C once the salinity of the water used to generate the bond exceeds ∼ 25 ppt. The strength of the saline ice bonds levels off (i.e., saturates) within 6–12 h of freezing; bonds formed from freshwater reach strengths that are comparable or higher than that of the parent material in less than 0.5 h.

scholarly journals The flexural strength of bonded ice

2020 ◽  
Author(s):  
Andrii Murdza ◽  
Arttu Polojärvi ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Flexural Strength ◽  
Bond Strength ◽  
Compressive Stress ◽  
Fresh Water ◽  
Parent Material ◽  
Bending Tests ◽  
Four Point Bending ◽  
Ice Surfaces

Abstract. The flexural strength of ice surfaces bonded by freezing, termed freeze-bond, was studied by performing four-point-bending tests of bonded freshwater S2 columnar-grained ice samples in the laboratory. The samples were prepared by milling the surfaces of two ice pieces, wetting two of the surfaces with water of varying salinity, bringing these surfaces together, and then letting them freeze under a compressive stress of about 4 kPa. The salinity of the water used for wetting the surfaces to generate the bond varied from 0 to 35 ppt. Freezing occurred in air under temperatures varying from −25 to −3 °C over periods that varied from 0.5 h to ~100 hours. Results show that an increase in bond salinity or temperature leads to a decrease in bond strength. The trend for the bond strength as a function of salinity is similar to that presented in Timco and O'Brien (1994) for saline ice. No freezing occurs at −3 °C once the salinity of the water used to generate the bond exceeds ~25 ppt. The strength of the saline ice bonds levels off (i.e., saturates) within 6–12 hours of freezing; bonds formed from fresh water reach strengths that are comparable or higher than that of the parent material in less than 0.5 hours.

Delayed Photoactivation of Dual-cure Composites: Effect on Cuspal Flexure, Depth-of-cure, and Mechanical Properties

2019 ◽  
Vol 44 (2) ◽  
pp. E97-E104 ◽  
Author(s):  
KO Hughes ◽  
KJ Powell ◽  
AE Hill ◽  
D Tantbirojn ◽  
A Versluis
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Flexural Strength ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Degree Of Cure ◽  
Bending Tests ◽  
Depth Of Cure ◽  
Four Point Bending ◽  
Tooth Surfaces

SUMMARY Objectives: This study tested whether delayed photoactivation could reduce shrinkage stresses in dual-cure composites and how it affected the depth-of-cure and mechanical properties. Methods and Materials: Two dual-cure composites (ACTIVA and Bulk EZ) were subjected to two polymerization protocols: photoactivation at 45 seconds (immediate) or 165 seconds (2 minutes delayed) after extrusion. Typodont premolars with standardized preparations were restored with the composites, and cuspal flexure caused by polymerization shrinkage was determined with three-dimensional scanning of the external tooth surfaces before restoration (baseline) and at 10 minutes and one hour after photoactivation. Bond integrity (intact interface) was verified with dye penetration. Depth-of-cure was determined by measuring Vickers hardness through the depth at 1-mm increments. Elastic modulus and maximum stress were determined by four-point bending tests (n=10). Results were analyzed with two- or three-way analysis of variance and pairwise comparisons (Bonferroni; α=0.05). Results: Delayed photoactivation significantly reduced cuspal flexure for both composites at 10 minutes and one hour (p≤0.003). Interface was >99% intact in every group. Depth-of-cure, elastic modulus, and flexural strength were not significantly different between the immediate and delayed photoactivation (p>0.05). The hardness of ACTIVA reduced significantly with depth (p<0.001), whereas the hardness of Bulk EZ was constant throughout the depth (p=0.942). Conclusions: Delayed photoactivation of dual-cure restorative composites can reduce shrinkage stresses without negatively affecting the degree-of-cure or mechanical properties (elastic modulus and flexural strength).

scholarly journals Reliability of Different Bending Test Methods for Dental Press Ceramics

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5162
Author(s):  
Daisuke Miura ◽  
Yoshiki Ishida ◽  
Taira Miyasaka ◽  
Harumi Aoki ◽  
Akikazu Shinya
Keyword(s):  
Flexural Strength ◽  
Testing Machine ◽  
Test Methods ◽  
Bending Test ◽  
Biaxial Bending ◽  
Bending Tests ◽  
Four Point Bending ◽  
Biaxial Tests ◽  
Biaxial Flexural Strength ◽  
Flexural Tests

Objective: This study investigates the reliability of different flexural tests such as three-point-bending, four-point bending, and biaxial tests, in strengthening the dental pressed ceramics (DPCs) frequently used in clinical applications. Methods: The correlations between the three types of bending tests for DPCs were investigated. Plate-shaped specimens for the three-point and four-point bending tests and a disc-shaped specimen for the biaxial bending test were prepared. Each bending test was conducted using a universal testing machine. Results: The results for six DPCs showed that the flexural strength in descending order were the three-point flexural strength, biaxial flexural strength, and four-point flexural strength, respectively. Then, a regression analysis showed a strong correlation between each of the three test methods, with the combination of four-point and biaxial flexural strength showing the highest values. The biaxial flexural strength was not significantly different in the Weibull coefficient (m) compared to the other tests, with the narrowest range considering the 95% interval. The biaxial bending test was found to be suitable for materials with small plastic deformation from the yield point to the breaking point, such as DPCs.

scholarly journals Properties of Calcium Sulfoaluminate Cement Mortar Modified by Hydroxyethyl Methyl Celluloses with Different Degrees of Substitution

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2136
Author(s):  
Shaokang Zhang ◽  
Ru Wang ◽  
Linglin Xu ◽  
Andreas Hecker ◽  
Horst-Michael Ludwig ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Bond Strength ◽  
Cement Mortar ◽  
Retention Rate ◽  
Methyl Cellulose ◽  
Tensile Bond Strength ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Cement Mortars

This paper studies the influence of hydroxyethyl methyl cellulose (HEMC) on the properties of calcium sulfoaluminate (CSA) cement mortar. In order to explore the applicability of different HEMCs in CSA cement mortars, HEMCs with higher and lower molar substitution (MS)/degree of substitution (DS) and polyacrylamide (PAAm) modification were used. At the same time, two kinds of CSA cements with different contents of ye’elimite were selected. Properties of cement mortar in fresh and hardened states were investigated, including the fluidity, consistency and water-retention rate of fresh mortar and the compressive strength, flexural strength, tensile bond strength and dry shrinkage rate of hardened mortar. The porosity and pore size distribution were also analyzed by mercury intrusion porosimetry (MIP). Results show that HEMCs improve the fresh state properties and tensile bond strength of both types of CSA cement mortars. However, the compressive strength of CSA cement mortars is greatly decreased by the addition of HEMCs, and the flexural strength is decreased slightly. The MIP measurement shows that HEMCs increase the amount of micron-level pores and the porosity. The HEMCs with different MS/DS have different effects on the improvement of tensile bond strength in different CSA cement mortars. PAAm modification can improve the tensile bond strength of HEMC-modified CSA cement mortar.

Comparison of results obtained by static 3- and 4-point bending and flexural vibration tests on solid wood, MDF, and 5-plywood

Holzforschung ◽  
2013 ◽  
Vol 67 (8) ◽  
pp. 941-948 ◽  
Author(s):  
Hiroshi Yoshihara
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Medium Density Fiberboard ◽  
Flexural Vibration ◽  
Solid Wood ◽  
Bending Tests ◽  
Four Point Bending ◽  
Flexural Vibration Test ◽  
The Difference ◽  
Vibration Tests

Abstract The flexural Young’s modulus of western hemlock, medium-density fiberboard, and 5-plywood (made of lauan) has been determined by conducting three- and four-point bending tests with various span lengths and by flexural vibration test. The Young’s modulus was significantly influenced by the deflection measurement method. In particular, the Young’s modulus was not reliable based on the difference between the deflections at two specific points in the specimen, although this test is standardized according to ISO 3349-1975 and JIS Z2101-2009.

Long-Term Reliability Assessment of Bioceramics for Artificial Joints Using Microdamage Monitoring by AE

2006 ◽  
Vol 309-311 ◽  
pp. 1191-1194
Author(s):  
Shuichi Wakayama ◽  
Teppei Kawakami ◽  
Junji Ikeda
Keyword(s):  
Critical Stress ◽  
Reliability Assessment ◽  
Physiological Saline ◽  
Bending Test ◽  
Unstable Fracture ◽  
Artificial Joints ◽  
Bending Tests ◽  
Four Point Bending

Microfracture process during bending tests of alumina ceramics used for artificial joints was evaluated by acoustic emission (AE) technique. Four-point bending tests were carried out in air, refined water, physiological saline and simulated body fluid. AE behavior during bending test inhibited the rapid increasing point of AE events and energy prior to the final unstable fracture. It was understood that the bending stress at the increasing point corresponds to the critical stress for maincrack formation. The critical stress was affected by water in environments more strongly than fracture strength. Consequently, it was suggested that the characterization of maincrack formation is essential for the long-term reliability assessment of load-bearing bioceramics.

scholarly journals Flow Mechanism and Strength Characteristics of Textile Reinforced Concrete Mixed with Colloidal Nano-SiO2

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Ping Xu ◽  
Rui Shi ◽  
Chao Wang ◽  
Yuhao Cui ◽  
Minxia Zhang
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Flexural Strength ◽  
Silica Fume ◽  
Inhibitory Effect ◽  
Equal Mass ◽  
Textile Reinforced Concrete ◽  
Nano Sio2 ◽  
Four Point Bending ◽  
Concrete Filling

In order to develop textile reinforced concrete (TRC) with good flowability and strength, colloidal nano-SiO2 (CNS) is adopted to improve the performance of TRC. The flowability, compressive strength, flexural strength, and four-point bending tests of TRC matrix with CNS are carried out, and the changes of internal micromorphological characteristics of TRC matrix are analyzed by combining with scanning electron microscopy. The results show that the CNS has an inhibitory effect on the flowability of TRC matrix, and the greater the amount of admixture is, the smaller the slump expansion of TRC matrix is. The compressive strength and flexural strength of TRC matrix show a trend of increasing and then decreasing as the amount of CNS increases, and the compressive strength reaches the maximum at each age (7 d, 14 d, 28 d) when CNS and silica fume replace 5% cement by 1 : 4 equal mass. The flexural strength reaches the maximum at each age (7 d, 14 d, 28 d) when 5% cement is replaced by CNS and silica fume with 3 : 7 equal mass. The flexural strength increases with the increase of CNS admixture. It is found by electron microscope scanning that the incorporation of CNS consumes more Ca(OH)2, refines the Ca(OH)2 crystal size, and generates more C-S-H gels. These C-S-H gels are distributed in a net-like pattern inside the concrete, filling the internal pores, effectively densifying the interfacial transition zone between the cementitious material and the aggregates, and optimizing the internal structure.

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