Study on the Influence of Inertia Effect in Dynamic Splitting Test of Concrete

2019 ◽  
Vol 815 ◽  
pp. 182-187
Author(s):  
Zhen Fu Chen ◽  
Pan Liu

A group of concrete spilitting tensile test was carried out by using the drop test machine Studying on the inertial effect on the dynamic tensile strength of concrete under different working conditions. The result show:with the increase of the drop height and quailty, peak load, loading rate of the concrete are increasing gradually.peak load of the test group is slightly higher than control group, The inertia effect has a certain influence on the dynamic tensile strength of concrete.

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Fanlu Min ◽  
Zhanhu Yao ◽  
Teng Jiang

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1to 10−4 s−1in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates.


Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4599
Author(s):  
Jong-Ju Ahn ◽  
Hyung-Joon Kim ◽  
Eun-Bin Bae ◽  
Won-Tak Cho ◽  
YunJeong Choi ◽  
...  

The purpose of this study was to evaluate the bone regeneration efficacy of an 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-cross-linked collagen membrane for guided bone regeneration (GBR). A non-cross-linked collagen membrane (Control group), and an EDC-cross-linked collagen membrane (Test group) were used in this study. In vitro, mechanical, and degradation testing and cell studies were performed. In the animal study, 36 artificial bone defects were formed in the mandibles of six beagles. Implants were inserted at the time of bone grafting, and membranes were assigned randomly. Eight weeks later, animals were sacrificed, micro-computed tomography was performed, and hematoxylin-eosin stained specimens were prepared. Physical properties (tensile strength and enzymatic degradation rate) were better in the Test group than in the Control group. No inflammation or membrane collapse was observed in either group, and bone volumes (%) in defects around implants were similar in the two groups (p > 0.05). The results of new bone areas (%) analysis also showed similar values in the two groups (p > 0.05). Therefore, it can be concluded that cross-linking the collagen membranes with EDC is the method of enhancing the physical properties (tensile strength and enzymatic degradation) of the collagen membranes without risk of toxicity.


Author(s):  
Rafael Calvão BARBUTO ◽  
Ivana DUVAL-ARAUJO ◽  
Sumara Marques BARRAL ◽  
Raphael Grossi ROCHA ◽  
Cristiane de Souza BECHARA ◽  
...  

Background : The use of alloplastic meshes has been historically contra-indicated in patients with infection. Aim : To evaluate the use of polypropylene meshes in the treatment of abdominal wall defects in rats with peritonitis. Methods : Twenty Wistar female rats were divided into two groups: induction of peritonitis (test group) and without peritonitis (control group). An abdominal wall defect was created in all animals, and polypropylene mesh was applied. The evaluation of the tensile strength of the mesh was carried out using tensiometer and microscopic analysis of the healing area was done. Results : More adhesion of the mesh to the rat abdominal wall was observed in test group. The histopathological analyses showed prevalence of moderate to accentuated granulation tissue in both groups, without significant differences. Conclusion : The use of the mesh coverage on abdominal wall defects of rats with induced peritonitis did not show worse results than its use in healthy animals, nor was its integration to the resident tissue any worse.


2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Weichao Wang ◽  
Mengmeng Wang ◽  
Xiliang Liu

The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals.


2019 ◽  
Vol 48 ◽  
Author(s):  
Juliano PILON ◽  
Ana Rosa COSTA ◽  
Lourenço CORRER-SOBRINHO ◽  
Mário VEDOVELLO FILHO ◽  
Heloísa Cristina VALDRIGHI

Abstract Introduction The orthodontic movement is directly influenced by the ability of orthodontic wires to slide through brackets and tubes. Therefore, the main concern during orthodontic movement corresponds to the frictional forces generated at the bracket-orthodontic wire interface. Objective This study aimed to evaluate the frictional resistance of esthetic orthodontic wires. Material and method Fifty test brackets were obtained and divided into five groups (n = 10) based on the type of rectangular orthodontic wire, as follows: conventional metallic wire (Morelli, Brazil) (G1, control group) and esthetic wires (G2, Ortho Organizer; G3, Tecnident; G4, Trianeiro; and G5, TP Orthodontics). The following materials and conditions were used: 0.019 x 0.025-inch wires, ceramic brackets with edgewise prescription, torque and/or angulation of 0°, and 0.022 x 0.028-inch slots. The specimens were tested for their tensile strength using an Instron universal test machine at a speed of 1.0 mm / min and a load cell of 500N. The tensile strength data were analyzed by one-way analysis of variance (ANOVA) followed by Tukey’s post-hoc test, with a 5% significance level. Result The frictional resistance (N) of the metallic orthodontic wire (8.07 ± 0.43) was significantly higher than that of the esthetic wires: Ortho Organizer (4.01 ± 0.25), Tecnident (3.87 ± 0.31), Trianeiro (4.47 ± 0.26) and TP Orthodontics (4.49 ± 0.30) (p <0.05), with no significant difference between them (p> 0.05). Conclusion To conclude, the esthetic orthodontic wires tested herein showed less frictional resistance as compared to the conventional metallic wire.


2020 ◽  
Vol 14 (01) ◽  
pp. 013-018
Author(s):  
Vivian Santos Torres ◽  
Max José Pimenta Lima ◽  
Heloísa Cristina Valdrighi ◽  
Elisângela de Jesus Campos ◽  
Milton Santamaria-Jr

Abstract Objective This study aimed to evaluate in vitro the effects of whitening dentifrices on enamel color, the shear bond strength of orthodontic brackets and adhesive remnant index (ARI). Materials and Methods Eighty bovine teeth with brackets were randomly divided into four groups (n = 20): control group (GC)–water, test group 1 (GT1)–Colgate Total 12, test group 2 (GT2)–Curaprox Black Is White, and group test 3 (GT3)–Luminous White. All groups were submitted to brushing, simulating 12 months. The specimens were exposed to spectrophotometer color evaluation and to a shear strength test in a universal test machine using a 300 kN load with a crosshead speed of 0.5 mm/min. The ARI was evaluated with a stereoscopic magnifying glass. Statistical Analysis Nonparametric Kruskal–Wallis and Dunn’s tests were used for the color analysis, and Friedman and Nemenyi tests were used to compare the times in the variable. To compare the shear force between the groups, the data were evaluated by one-way analysis of variance and Tukey’s test, and ARI was analyzed using Fisher’s exact test, always with a significance level of 5%. Results In the color analysis, GT3 presented the greatest progression in whitening effect. GT1 had greater shear strength than GT3 did (p ≤ 0.05). For ARI, the score 1 was predominant in the GC and GT1. The GT2 and GT3 groups had scores of 3. Conclusion The whitening dentifrices promoted significant color change over the 12-month brushing time and may have interfered in the resistance to shear bond strength and ARI.


2019 ◽  
Vol 23 (Suppl. 3) ◽  
pp. 815-820
Author(s):  
Shengwei Li ◽  
Cunbao Li ◽  
Wei Yao ◽  
Ru Zhang ◽  
Jing Xie ◽  
...  

To study the effect of wetting-drying cycles on dynamic tensile strength of rock, dynamic indirect tension test of sandstone samples after 0, 1, 3, and 5 wetting-drying cycles was conducted. Tensile failure was observed by digital image correlation. The result shows that failure appears in the center of the samples initially, consistent with tensile strain field results obtained by digital image correlation. An empirical formula was derived to link loading rate and dynamic tensile strength of rock after wetting-drying cycles. As the loading rate increases, tensile strength increases significantly. Tensile strength reduces as the number of wetting-drying cycles increases. These results provide reference data for complex engineering problems such as those that occur in coal mining, tunneling and water conservancy.


Sign in / Sign up

Export Citation Format

Share Document