The Influence of Loading Rate on Direct and Indirect Tensile Strengths: Laboratory and Numerical Methods

To investigate different responses of direct and indirect tensile strengths to loading rate, direct and indirect tension tests were performed on sandstone, rust stone, and granite specimens. Typical load curves indicate that a peak tensile stress frequently appears before the second peak stress, used to calculate the tensile strength in indirect tension tests. As expected, increase in the loading rate increases the tensile strength. In addition, the calculated tensile strengths of the indirect tension tests are frequently higher. Interestingly, the increase ratio of the tensile strength with the increase in the loading rate in indirect tension tests is higher. To verify the above results, crack propagation and stress evolution in direct and indirect tension tests were dynamically monitored using PFC 3D. For direct tension tests, specimens fail at the peak tension point, corresponding to the tensile strength. However, for indirect tension tests, minor cracks, composing of continuous microcracks, form before the peak stress and accompany with the decreased slope of the compression curve. At the peak point, tensile stresses significantly concentrate at the crack tips and further cause large-scale crack propagation. In addition, the initiation stress instead of the peak tensile stress is closer to the tensile strength, obtained from the direct tests for the same loading rate.

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Experimental Investigation on Fracture and Tensile Characteristics of Micro-Surfacing Containing Crumb Rubber

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.385-387.489 ◽

2008 ◽

Vol 385-387 ◽

pp. 489-492 ◽

Cited By ~ 1

Author(s):

Zheng Chen ◽

Shao Peng Wu ◽

Tao Zhang ◽

Ling Pang

Keyword(s):

Tensile Strength ◽

Crumb Rubber ◽

Point Load ◽

Indirect Tensile Strength ◽

Asphalt Emulsion ◽

Mean Values ◽

Modified Asphalt ◽

Tension Tests ◽

Indirect Tension ◽

Indirect Tensile

The major objective of this research was to evaluate the tensile and fracture properties of micro-surfacing, which as a preventive maintenance surface treatment on asphalt pavement, that formed the basis for the ISSA recommendation of an optimum micro-surfacing design incorporating crumb rubber. The research involved a full-factorial experiment with different rubber contents (0, 2 and 5%) and different polymer modified asphalt emulsion contents ranged from 10 to 13% by total weight of crushed aggregate in micro-surfacing. Fracture and indirect tension tests were performed on micro-surfacing beams and Marshall test samples, respectively, at two different test temperatures of 25 and -10°C. The variables studied were indirect tensile strength, peak center-point load carried, and load-point displacement. The results show that higher mean values of indirect tensile strength were obtained corresponding to the highest modified asphalt emulsion content (13%), irrespective of rubber contents, particularly at lower temperatures. A statistical analysis of the test results reveals that there are no significant differences among the means of most of the variables studied corresponding to different rubber contents. However, the differences are significant for different asphalt emulsion contents.

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Tensile strength of sands treated with microbially induced carbonate precipitation

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0230 ◽

2020 ◽

Vol 57 (10) ◽

pp. 1611-1616 ◽

Cited By ~ 1

Author(s):

Ashkan Nafisi ◽

Douglas Mocelin ◽

Brina M. Montoya ◽

Shane Underwood

Keyword(s):

Tensile Strength ◽

Large Earthquake ◽

Carbonate Precipitation ◽

Direct Tension ◽

Sem Images ◽

Cemented Soil ◽

Tension Tests ◽

Deformational Behavior ◽

Microbially Induced Carbonate Precipitation ◽

Sand Type

During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ∼900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition.

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Loading-Rate Dependency of Uniaxial and Indirect Tensile Strength.

Shigen-to-Sozai ◽

10.2473/shigentosozai.109.865 ◽

1993 ◽

Vol 109 (11) ◽

pp. 865-869 ◽

Cited By ~ 8

Author(s):

Seisuke OKUBO ◽

Fengnian JIN ◽

Masao AKIYAMA

Keyword(s):

Tensile Strength ◽

Loading Rate ◽

Indirect Tensile Strength ◽

Rate Dependency ◽

Indirect Tensile

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Mechanical and physical properties of slate from Britannia Cove, Newfoundland

Canadian Journal of Civil Engineering ◽

10.1139/l08-042 ◽

2008 ◽

Vol 35 (7) ◽

pp. 751-755 ◽

Cited By ~ 5

Author(s):

M.R. Alam ◽

A.S.J. Swamidas ◽

J. Gale ◽

K. Munaswamy

Keyword(s):

Fracture Toughness ◽

Physical And Mechanical Properties ◽

Test Results ◽

Direct Tension ◽

Element Analysis ◽

Tension Tests ◽

Strain Fracture ◽

Indirect Tension ◽

American Society ◽

Experimental Values

The experimental investigation described in this study was carried out to determine the physical and mechanical properties (elastic moduli, Poisson’s ratio, compressive and tensile strengths, hardness and plane strain fracture toughness) of slate quarried from Britannia Cove, Bonavista, Newfoundland, Canada. Microscopic observations were carried out to determine layers’ orientation and thickness and the grain boundaries. All tests were carried out according to American Society for Testing and Materials (ASTM) and International Society for Rock Mechanics (ISRM) procedures. The results obtained from this investigation were compared with those obtained from other published results for slate, mined from different parts of the world. It is seen that the present test results are compatible with other published results except for fracture toughness and direct tension tests. In fracture toughness tests, the calculated values using accepted empirical equations were much higher than the numerically computed values using finite element analysis (FEA). For the case of direct and indirect tension tests, the differences between our experimental values and previously published results were quite large.

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MECHANICAL STRENGTH OF SEALED-CURED NEAT CEMENT-PASTE

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2015.62 ◽

2015 ◽

Vol 2 (1) ◽

Author(s):

S. Walker ◽

W. Choi ◽

M. Picornell ◽

R. Mohan ◽

S. Hamoush

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Cement Paste ◽

Concrete Strength ◽

Curing Time ◽

Portland Cement Concrete ◽

Direct Tension ◽

Tension Tests ◽

Water To Cement Ratio ◽

Program Show

The strength of Portland cement concrete is dependent on the strength of the cement paste binding the aggregates together. An understanding of the cement paste is the first step to assess the concrete strength. To this end, a program for strength testing of cement paste was implemented for water to cement ratios of 0.35 and 0.40. The compressive strength was evaluated using two inch cubes and four inch diameter cylinders; while the tensile strength evaluation was based on flexure and direct tension tests. All the specimens were cured in the mold the first day, followed by curing in sealed vacuum bags for the remaining of the time. The total curing time ranged from three, seven, fourteen and twenty-eight days. Three replicate specimens were prepared, cured, and tested for each combination of water to cement ratio, type of specimen, and time of curing. The results of the testing program show that while the compressive strength increases for increasing curing time, the tensile strength shows a consistent decline. These results indicate that the sealed curing forced that further hydration caused “self-desiccation” of the CSH, inducing new cracks or extension of existing cracks that would be responsible for the loss of tensile strength.

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Tensile behaviour identification in Ultra-High Performance Fibre Reinforced Cementitious Composites: indirect tension tests and back analysis of flexural test results

Materials and Structures ◽

10.1617/s11527-020-01576-8 ◽

2020 ◽

Vol 53 (6) ◽

Author(s):

Francesco Lo Monte ◽

Liberato Ferrara

Keyword(s):

High Performance ◽

Tensile Behaviour ◽

Cementitious Composites ◽

Test Results ◽

Direct Tension ◽

Identification Procedure ◽

Horizon 2020 ◽

Tension Tests ◽

Indirect Tension ◽

High Performance Fibre

AbstractWithin the framework of the European Programme Horizon 2020, the Research Project ReSHEALience is currently running with the objective of developing a new approach for the design of structures exposed to extremely aggressive environments, based on Durability Assessment based Design and Life Cycle Analysis. To this aim, new advanced Ultra-High Performance Fibre Reinforced Cementitious Composites with improved durability, called Ultra-High Durability Concretes, are under investigation to characterize their tensile response in both ordinary and very aggressive conditions. In this context, the first step is to develop an effective approach for identifying the main parameters describing the overall behaviour in tension. In the present study, indirect tension tests have been performed via two techniques, based on Double Edge Wedge Splitting and 4-Point Bending Tests. Starting from the test results, a combined experimental-numerical identification procedure has been implemented in order to evaluate the effective material behaviour in direct tension in terms of stress–strain law. In the paper, the mechanical characterization for the reference mix is reported so to describe the identification procedure adopted.

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A New Flattened Cylinder Specimen for Direct Tensile Test of Rock

Sensors ◽

10.3390/s21124157 ◽

2021 ◽

Vol 21 (12) ◽

pp. 4157

Author(s):

Qiuhua Rao ◽

Zelin Liu ◽

Chunde Ma ◽

Wei Yi ◽

Weibin Xie

Keyword(s):

Tensile Strength ◽

Tensile Test ◽

Cylindrical Specimen ◽

Image Correlation ◽

Stress Distributions ◽

Direct Tension ◽

Brazilian Disc ◽

Indirect Tensile ◽

Direct Tensile ◽

Direct Tensile Test

In recent decades, researchers have paid more attention to the indirect tensile test than to the direct tensile test (DTT) of rocks, mainly due to difficulties in the alignment and the stress concentration at the end of an intact cylindrical specimen. In this paper, a new flattened cylinder specimen and a clamp device were designed to obtain the true tensile strength of the rock in DTT. Stress distributions of the specimen with different lengths (l) and cutting thicknesses (t) were analyzed, and damage processes of the specimen were monitored by the Digital Image Correlation (DIC), the fractured sections were also scanned. Different mechanical parameters were also obtained by the DTT of the flattened cylinder specimens and the intact cylinder specimens, as well as the Brazilian disc. Research results show that the tensile strength obtained by DTT is smaller than the Brazilian disc and is slightly greater than the intact cylindrical specimen. The flattened cylinder specimen with 0.20 ≤ 2t/D < 0.68 and 0.10 ≤ l/D ≤ 0.20 is recommended to measure the true tensile strength of rock material in DTT. This new shape of the specimen is promising to be extended in the uniaxial or triaxial direct tension test.

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Numerical analysis of the influence of sample stiffness and plate shape in the Brazilian test

DYNA ◽

10.15446/dyna.v82n194.45526 ◽

2015 ◽

Vol 82 (194) ◽

pp. 79-85 ◽

Cited By ~ 1

Author(s):

Martina Inmaculada Álvarez Fernández ◽

Celestino González Nicieza ◽

Maria Belén Prendes Gero ◽

José Ramón García-Menéndez ◽

Juan Carlos Peñas Espinosa ◽

...

Keyword(s):

Tensile Strength ◽

Tensile Stress ◽

Tensile Tests ◽

Indirect Measurement ◽

Brazilian Test ◽

Stress Fields ◽

Plate Shape ◽

Load Increase ◽

Indirect Tensile ◽

Different Young’S Modulus

Due to the heterogeneity of rocks, their tensile strength is around 10% of their compressive strength, which means that breakage is mainly caused by tensile stress. The measure of tensile stress is very difficult due to rock fragility, so it has usually been measured by indirect measurement methods , including the Brazilian test. However, recent works indicate that the tensile strength values obtained through the Brazilian test must be increased by almost 26%. To understand this divergence, indirect tensile tests have been monitored. The aim is to know the material deformation and load increase by means of stepwise regression. Stress fields in slightly deformed samples are analyzed and modeled (3D finite differences) with loads applied on flat and curved plates and different Young's modulus. Finally, the results are analyzed and compared with strength values reported using Timoshenko theory and Hondros' approximation.

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