four point bending
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2022 ◽  
Vol 2022 ◽  
pp. 1-11
Author(s):  
Songfang Xie ◽  
Mingxing Gao ◽  
Hangtian Li

In order to improve mechanical properties of fly ash/slag concrete with large size cobble as coarse aggregate, this paper analyzes the effect of different factors on the concrete through the flexural strength test. The Monte Carlo simulation is used in the finite element solver of ANSYS to conduct the four-point bending beam test. Three-dimensional and two-dimensional finite element models are established to discuss how the gradation of large size cobbles affects the performance of the concrete by comparing macromechanical experiments. Results show that the gradation of large size cobbles is the main factor affecting the performance of the concrete. Slag generates the least effect on the concrete with cobble as coarse aggregate. When the mixing amount of slag and fly ash is 10%, the concrete presents the best flexural performance. Through the numerical loading test of the two-dimensional model for fly ash/slag concrete with cobble as coarse aggregate, it can be concluded that the change of the concrete follows the law of macromechanical properties.


Author(s):  
Shuliang Wang ◽  
Mengjun Yao ◽  
Yangzhong Jing ◽  
Xujia He ◽  
Mingyu Bao ◽  
...  

Abstract A high-temperature autoclave was used to grow CO2 corrosion-product films on P110SS steel specimens while the surface of the specimens was continuously subjected to tensile stress in a four-point bending jig; the autoclaving times were 6, 18, 36, and 72 h. A scanning electron microscope was used to observe the surface topography of the corrosion-product films formed on the P110SS steels. An X-ray diffraction was used to analyze the phase compositions of the corrosion products. The electrochemical performance of the films was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization curves. The results showed that tensile stress could hinder the formation of corrosion-product films; the integrity and compactness of the films worsened, but the phase compositions of the films did not change. The applied tensile stress resulted in a smaller grain size of the corrosion-product films, and the grain boundaries increased. In addition, owing to the induced tensile stress, the charge transfer resistances decreased, and the corrosion current densities increased for the P110SS steels with corrosion-product films in a 3.5 wt.% NaCl solution saturated with CO2.


Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 582
Author(s):  
Felix Lohse ◽  
Karl Kopelmann ◽  
Henriette Grellmann ◽  
Moniruddoza Ashir ◽  
Thomas Gereke ◽  
...  

Fiber-reinforced rubber composites with integrated shape memory alloy (SMA) actuator wires present a promising approach for the creation of soft and highly elastic structures with adaptive functionalities for usage in aerospace, robotic, or biomedical applications. In this work, the flat-knitting technology is used to develop glass-fiber-reinforced fabrics with tailored properties designed for active bending deformations. During the knitting process, the SMA wires are integrated into the textile and positioned with respect to their actuation task. Then, the fabrics are infiltrated with liquid silicone, thus creating actively deformable composites. For dimensioning such structures, a comprehensive understanding of the interactions of all components is required. Therefore, a simulation model is developed that captures the properties of the rubber matrix, fiber reinforcement, and the SMA actuators and that is capable of simulating the active bending deformations of the specimens. After model calibration with experimental four-point-bending data, the SMA-driven bending deformation is simulated. The model is validated with activation experiments of the actively deformable specimens. The simulation results show good agreement with the experimental tests, thus enabling further investigations into the deformation mechanisms of actively deformable fiber-reinforced rubbers.


Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 474
Author(s):  
Yufan Yan ◽  
Xianjia Meng ◽  
Chuanyong Qu

The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.


Author(s):  
Shintaro Yoshihara ◽  
hideto YANAGIHARA

Abstract We have developed a method to variably induce lattice strains and to quantitatively evaluate the induced magnetic anisotropy. Both tensile and compressive strains were introduced into epitaxial films of cobalt ferrite (CFO) grown on a single crystal MgO(001) substrate using a four-point bending apparatus made of a plastic material fabricated by a 3D printer. The change in magnetic anisotropy due to bending strain can be measured quantitatively by using the conventional magneto-torque meter. The strain-induced magnetic anisotropy increased with the tensile strain and decreased with the compressive strain as expected from a phenomenological magnetoelastic theory. The magnetoelastic constant obtained from the changes in bending strains shows quantitatively good agreement with that of the CFO films with a uniaxial epitaxial strain. This signifies that the magnetoelastic constant can be evaluated by measuring only one film sample with strains applied by using the bending apparatus.


Author(s):  
Silvia Greco ◽  
Luisa Molari

The good mechanical performance of bamboo, coupled with its sustainability, has boosted the idea to use it as a structural material. In some areas of the world it is regularly used in constructions but there are still countries in which there is a lack of knowledge of the mechanical properties of the locally-grown bamboo, which limits the spread of this material. Bamboo is optimized to resist to flexural actions with its peculiar micro structure along the thickness in which the amount of fibers intensifies towards the outer layer and the inner part is composed mostly of parenchyma. The flexural strength depends on the amount of fibers, whereas the flexural ductility is correlated to the parenchyma content. This study focuses on the flexural strength and ductility of six different species of untreated bamboo grown in Italy. A four-point bending test was carried out on bamboo strips in two different loading configurations relating to its microstructure. Deformation data are acquired from two strain gauges in the upper and lower part of the bamboo beam. Difference in shape and size of Italian bamboo species compared to the ones traditionally used results in added complexity when performing the tests. Such difficulties and the found solutions are also described in this work. The main goal is to reveal the flexural behavior of Italian bamboo as a functionally graded material and to expand the knowledge of European bamboo species toward its use as a structural material not only as culm but also as laminated material.


Author(s):  
J. Khatib ◽  
Ali Hussein Jahami ◽  
Mohammed Sonebi ◽  
Adel Elkordi

This research work aimed to study the usage of Bamboo strips as shear reinforcement in reinforced concrete (RC) beams. Four beams were considered in this study. The flexural reinforcement for all beams was the same. As for shear reinforcement, one beam was reinforced with conventional shear reinforcement with spacing (s=180 mm), while the other three beams were reinforced with bamboo strips with three different spacings (s=180 mm, s= 90 mm, and s=60 mm). The beams were subjected to a four-point bending test to plot the load-deflection curve for each beam. Results showed that the beam reinforced with bamboo strips spaced at 180 mm has 30% higher shear capacity than the beam with conventional shear reinforcement at the same spacing. Also, as the spacing of bamboo strips decreased, the shear capacity of beams increased nonlinearly.


2022 ◽  
Vol 1212 (1) ◽  
pp. 012034
Author(s):  
S Maricar ◽  
K Sulendra ◽  
H Listiawaty ◽  
H O Baide

Abstract The development of utilization of low quality wood as construction material is needed to reduce the exploitation of natural forests. However, low quality wood species have disadvantages in terms of mechanical properties. The mechanical properties of Sengon wood are relatively low, so it does not qualify as a structural element. Therefore, the system glulam can be applied to overcome this problem. The system glulam can produce relatively light structural elements with adequate performance. This system has been extensively developed, even at the stage of applying external reinforcement, to improve the performance of structural laminated beams. On that basis, this study aims to determine the flexural strength of laminated beams of Sengon wood as a low quality wood species. In order to achieve this goal, the laminated beam was tested using method four point bending test method. Tests were carried out on long span laminated beams (L = 2750 mm) to observe flexural strength. There are five (5) laminated blocks tested, namely (BLS-1, BLS-2, BLS-3, BLS-4 and BLS-5). Each group has dimensions of 55 mm in width and 155 mm in height. Each specimen consists of six layers of wood boards with a density Falcata 0.3 g / cm3. The thickness of each layer was 26 mm and bonded with resin urea formaldehyde cold setting. Double-sided adhesive laying of 350 gr / m2 at a compressive force of 2 MPa. The analysis result shows that the load-deflection relationship between BS-L consists of linear and nonlinear phases. The load performance characteristics of the two types of laminated beams are expressed as the ratio of the proportional limit load to the maximum load. The ratio value is expressed in the form P eBL-s = 0.7P max BL-S andM eBL-s = 0.7M max BL-S. This form is similar to previous studies with a Pe to Pmax ratio of 0.80.9. In this case, the average flexural strength of the laminated beam is 17 MPa with a maximum strain of 0.004.


Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 277
Author(s):  
Marcin Górecki ◽  
Krzysztof Śledziewski

This paper presents the results of experimental investigations performed on beams with corrugated webs. The aim of the research was to determine the effect of the geometric parameters of the sinusoidal web on the behavior of I-beams subjected to four-point bending. Special attention was paid to the effects of web thickness and wave geometry on the deflection of beams. The obtained failure modes of particular test samples are presented. Reference has also been made to the determined standard load capacities based on Annex D of the EC3 standard. In order to compare the performance of beams with corrugated webs, the results for beams with flat webs of the same thickness of web sheets are also presented.


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