Fracture mechanics analysis of crack shapes due to cyclic loading in baria–silicate glass

2007 ◽  
Vol 22 (12) ◽  
pp. 3415-3422 ◽  
Author(s):  
K. Suputtamongkol ◽  
K.J. Anusavice ◽  
J.J. Mecholsky
Keyword(s):  
Cyclic Loading ◽  
Fracture Mechanics ◽  
Silicate Glass ◽  
Load Level ◽  
Bending Test ◽  
Repeated Loading ◽  
Aqueous Environment ◽  
Loading Frequency ◽  
Loading Test ◽  
Critical Crack

The objective of this study was to determine the geometric characteristics associated with the critical crack caused by cyclic loading. In an attempt to simulate an intraoral loading condition, the Hertzian cyclic loading of baria–silicate glass was performed using a type 302 stainless steel indenter under an aqueous environment using clinically relevant parameters, i.e., a low loading frequency (∼3 Hz) and a low load level (⩽200 N). The indenter diameter (4.76 mm) approximated the cuspal radii of molar and premolar teeth. Ten bar specimens each were subjected to loading cycles of 0, 103, 104, and 105 cycles. A four-point bending test was used to quantify the severity of the strength reduction caused by the repeated loading test. There was a decrease in fracture stress after 103 cycles that was associated with cone crack formation. No significant additional reduction was found after 105 cycles for specimens tested both in air and in deionized water. Stress-corrosion fatigue accelerated the surface crack propagation rate in baria–silicate glass specimens. Four different crack geometries were identified along with failure mechanisms. Various fracture mechanics approaches were tested against observed crack geometries. The previously unobserved triangular crack geometry was found.

scholarly journals Investigation of the Elastic Modulus of Polymer Sleepers Under a Quasistatic and Cyclic Loading

2019 ◽  
Vol 15 (2) ◽  
pp. 125-133
Author(s):  
Vít Lojda ◽  
Aran van Belkom ◽  
Hana Krejčiříková
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Prestressed Concrete ◽  
Load Level ◽  
Bending Test ◽  
Elastic Behaviour ◽  
Loading Frequency ◽  
Wheel Load ◽  
Four Point Bending ◽  
Four Point Bending Test

AbstractIn ballasted track, the wheel load is transmitted to the subgrade via sleepers commonly made of impregnated wood, prestressed concrete, steel or recently developed polymer sleepers. Mentioned material types of sleepers are characterized by different elastic moduli being a key parameter in any numerical model. Hence, this paper aims to determine the elastic modulus of sleepers subjected to a laboratory four-point bending test. Traffic resembling load level of 60 kN adopted from a typical axle load distributed by the rails to the sleeper was applied in a quasistatic and cyclic loading. The samples included sleepers made of polymers complemented with wood and pre-stressed concrete. The results of this paper are based on the elastic modulus investigation. Main conclusions are focused on the sleeper’s elastic modulus under changing loading frequencies. Wood and prestressed concrete sleepers indicated mainly elastic behaviour resulting in a constant elastic modulus. However, polymer sleepers showed a loading frequency dependent elastic modulus as a result of their viscous elastic behaviour. Moreover, the conclusions of this paper involve E-modulus measurements of impregnated beech sleepers in order to describe their piece by piece elasticity variation due to their natural origin.

Membrane filter properties and application of the filter to undrained cyclic triaxial test of unsaturated materials

2017 ◽  
Vol 54 (8) ◽  
pp. 1196-1202 ◽  
Author(s):  
Hailong Wang ◽  
Junichi Koseki ◽  
Tomoyoshi Nishimura ◽  
Yukika Miyashita
Keyword(s):  
Hydraulic Conductivity ◽  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Membrane Filter ◽  
Water Pressure ◽  
Characteristic Curve ◽  
Loading Frequency ◽  
Loading Test ◽  
Pressure Plate

Properties of the membrane filter recently introduced as an alternative to the ceramic disk are revealed through diffusion and hydraulic conductivity tests. It is shown that diffusion of air through the membrane filter is significantly affected by suction magnitude and that hydraulic conductivity of the membrane filter can easily be affected by the quality of water used in the test. The application of the membrane filter to the soil-water characteristic curve tests (SWCC tests) shows that similar SWCCs can be obtained by employing pressure plate apparatuses with either the ceramic disks or the membrane filter installed, and that repeatability of the SWCC by using the membrane filter pressure plate apparatus is reasonably good. The application of the membrane filter to the undrained cyclic loading test of unsaturated sandy materials shows that the response (the duration to measure the equilibrated pore-water pressure of unsaturated materials) of the membrane filter pedestal in a modified triaxial system may be as short as ∼2 s in certain test conditions, and fairly good pore-water pressure and air pressure measurements can be obtained during undrained cyclic loading with a loading frequency of 0.1 Hz.

Stability threshold for cyclic loading of saturated clay

1989 ◽  
Vol 26 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Guy Lefebvre ◽  
Denis LeBoeuf ◽  
Benoît Demers
Keyword(s):  
Shear Strength ◽  
Cyclic Loading ◽  
Strain Rate ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Repeated Loading ◽  
Loading Test ◽  
Stability Threshold ◽  
The Stability ◽  
Undrained Shear

This paper presents the results of an experimental investigation performed to study the stability threshold under cyclic (repeated) loading, and the postcyclic static strength of a sensitive clay from the Hudson Bay region. The strain rate and structure effects were also studied by carrying out monotonic and cyclic triaxial tests at both slow and rapid strain rates or frequencies, and at confining pressures above and below the apparent preconsolidation pressure. The stability threshold for both structured and normally consolidated Grande Baleine clay is about 60–65% of the original undrained shear strength measured at the same strain rate as that used in the repeated loading test. The undrained shear strength and the failure envelope remain essentially unchanged if the repeated preloading is kept below the threshold. The clay structure remains unaltered by this preloading. Key words: clay, stability threshold, cyclic loading, earthquake, postcyclic strength.

CYCLIC LOADING TEST OF REINFORCED CONCRETE (RC) BEAMS INCORPORATING ALTERNATIVE CEMENTITIOUS MATERIALS

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Isamu Yoshitake ◽  
Shun Inoue ◽  
Kota Motoyoshi
Keyword(s):  
Cyclic Loading ◽  
Cementitious Materials ◽  
Bending Test ◽  
Water Tank ◽  
Rc Beams ◽  
Loading Test ◽  
Cyclic Loading Test ◽  
Slag Powder ◽  
Fatigue Durability ◽  
Furnace Slag

The focus of this study is to examine flexural fatigue durability of RC beams, which were made with various cementitious materials. The cementitious materials tested in this study were blast furnace slag powder, fly-ash, silica-fume, and an artificial admixture of rich SiO2 and Al2O3. Fifteen RC beams for each admixture were prepared in addition to a control mixture (without admixture). The dimensions of the RC beams without stirrups were 160 x 160 x 1200 mm. Three beams for each mixture were soaked into a water-tank until the cyclic loading test. The study conducted static and cyclic four-points bending test. The paper aims to report the effect of the alternative cementitious materials on the fatigue durability of RC beams, which were exposed to the dry and wet environmental conditions.

scholarly journals Factors Affecting the Dependency of Shear Strain of LRB and SHDR: Experimental Study

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 98
Author(s):  
Chao-Yong Shen ◽  
Xiang-Yun Huang ◽  
Yang-Yang Chen ◽  
Yu-Hong Ma
Keyword(s):  
Experimental Study ◽  
Low Temperature ◽  
Shear Strain ◽  
Loading Frequency ◽  
Loading Test ◽  
Characteristic Strength ◽  
Rubber Bearing ◽  
Dominant Feature ◽  
Loading Sequence ◽  
G Value

In this research we conducted a sensitivity experimental study where we explored the dependency of the shear strain on the seismic properties of bearings, namely lead rubber bearing (LRB) and super high damping rubber bearing (SHDR). The factors studied were vertical pressure, temperature, shear modulus of the inner rubber (G value), loading frequency, and loading sequence. Six specimens were adopted, i.e., three LRBs and three SHDR bearings. A series of test plans were designed. The seismic characteristics of the bearings were captured through a cyclic loading test, which included post-yield stiffness, characteristic strength, area of a single cycle of the hysteretic loop, equivalent stiffness, and equivalent damping ratio. A whole analysis of variances was then conducted. At the same time, to explore certain phenomena caused by the factors, an extended discussion was carried out. Test results showed that the temperature is the most dominant feature, whereas the G value is the least contributing factor, with the effect of the loading frequency and the loading sequence found between these two. The increment of the post-yielded stiffness for LRB from 100% to 25% is a significant reduction from a low temperature to high one. The slope of the characteristic strength versus the shear strain for LRB under high temperature is larger than the one under low temperature.

scholarly journals Study of the Mechanical Environment of Chondrocytes in Articular Cartilage Defects Repaired Area under Cyclic Compressive Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Hai-Ying Liu ◽  
Hang-Tian Duan ◽  
Chun-Qiu Zhang ◽  
Wei Wang
Keyword(s):  
Articular Cartilage ◽  
Cyclic Loading ◽  
Response Curve ◽  
Fluid Pressure ◽  
Cartilage Defects ◽  
Loading Frequency ◽  
Liquid Pressure ◽  
Mechanical Environment ◽  
Finite Element Software ◽  
Maximum Value

COMSOL finite element software was used to establish a solid-liquid coupling biphasic model of articular cartilage and a microscopic model of chondrocytes, using modeling to take into account the shape and number of chondrocytes in cartilage lacuna in each layer. The effects of cyclic loading at different frequencies on the micromechanical environment of chondrocytes in different regions of the cartilage were studied. The results showed that low frequency loading can cause stress concentration of superficial chondrocytes. Moreover, along with increased frequency, the maximum value of stress response curve of chondrocytes decreased, while the minimum value increased. When the frequency was greater than 0.2 Hz, the extreme value stress of response curve tended to be constant. Cyclic loading had a large influence on the distribution of liquid pressure in chondrocytes in the middle and deep layers. The concentration of fluid pressure changed alternately from intracellular to peripheral in the middle layer. Both the range of liquid pressure in the upper chondrocytes and the maximum value of liquid pressure in the lower chondrocytes in the same lacunae varied greatly in the deep layer. At the same loading frequency, the elastic modulus of artificial cartilage had little effect on the mechanical environment of chondrocytes.

Fracture Mechanics Based Model for Joints under Cyclic Loading

2006 ◽  
Vol 132 (11) ◽  
pp. 1151-1159 ◽  
Author(s):  
Eric Puntel ◽  
Gabriella Bolzon ◽  
Victor E. Saouma
Keyword(s):  
Cyclic Loading ◽  
Fracture Mechanics
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