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1

Comparison and study of mechanical and physical properties of metakaolin reinforced gypsum composite

Moradi Hossein, Azima Saba, Ebrahimi-Kahrizsangi Reza

Composites Theory and Practice

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2023

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R. 23, nr 3

129--135

EN

This study investigated the effect of creating a composite of gypsum with metakaolin as well as the physical and mechanical behavior of the produced composites. For this purpose, gypsum composites were prepared with 2.9, 4.8, 6.5, and 9 wt.% metakaolin in 100 g of gypsum and a constant content of water. To determine the mechanical properties of the composites, the compressive strength test was used and the porosity, water absorption percentage, and bulk density of the composites were obtained using the Archimedes method. The results showed that the porosity was reduced by adding up to 7 wt.% metakaolin to the gypsum specimens, it increases the compressive strength by 41% and also raises the Young’s modulus of gypsum by 121%. Scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) was employed for the microstructural evaluations. The EDS-SEM observations showed the presence of Al and Si elements in the fracture zones. The presence of metakaolin elements at one point increases resistance in that area. Metakaolin-reinforced gypsum composites can be used in boards and panels.

2

Mechanical properties of CFST short columns with different void ratios

Song Junxi, Han Zhuowei, Wang Dawei, Lu Xiaorui

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

587--596

EN

In order to study the mechanical behavior of concrete-filled steel tube(CFST) short column with different void ratios under a certain eccentricity. A fiber model of concrete-filled steel tube section with different void heights was established. Compared with existing model test data, the axial force and flexural moment strength models of concrete-filled steel tube columns with different void ratios were established. The results show that, in the case of different void ratios, the cross-section strength envelope shows an overall contraction tendency with the increase of void ratio, and each line is basically parallel. A model for calculating the coefficient of axial load degradation was established. The Han’s flexural moment strength model of the flexural component was revised, and the strength model of concrete-filled steel tube column under eccentric compression considering void ratio was established, which provides a theoretical basis and method for the safety assessment during the operation of concrete-filled steel tube arch bridges.

3

Mechanical behavior and constitutive model of lining concrete in triaxial compression infiltration process under pore water pressure

Xue Weipei, Jing Wei, Wang Zhongjian, Zhang Hanwen, Lin Jian

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e20, 2023

EN

Underground concrete structures are affected by groundwater, the effects of which are different from those of stress environments experienced by ground engineering concrete structures. This study experimentally and theoretically investigates the mechanical behavior, permeability evolution, and deformation failure mechanism of lining concrete under pore water pressure. Results show that an increase in pore water pressure promoted the coupling of seepage and stress fields in concrete. This caused the microcracks to propagate further, which led to a decrease in concrete strength and elastic modulus. Through triaxial compression infiltration, the concrete successively underwent initial compaction, linear elastic deformation, and nonlinear deformation after yielding. Accordingly, its permeability exhibited three trends: gradual decrease, stable development, and a sharp increase. The change in permeability was closely related to the number of pores and the development of microcracks in concrete. The concept of primary pore strain was proposed according to the characteristics of deformation and failure. Moreover, a triaxial compression infiltration constitutive model was derived for concrete based on the principle of effective stress. This model considers the influence of pore water pressure and the initial compaction characteristics. This study can be used to guide the design of lining concrete structures in underground engineering.

4

Investigation of the mechanical and hygrothermal behavior of coffee ground wastes valorized as a building material: analysis of mix designs performance and sorption curve linearization effect

Hamdaoui Mohamed Ali, Benzaama Mohammed-Hichem, El Mendili Yassine, Chateigner Daniel, Gascoin Stéphanie

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e57, 2023

EN

Coffee ground wastes (CGW) are by-products from the coffee-making processes. In this study, we propose to valorize them in construction materials at large scale. In particular, we investigate the mechanical and hygrothermal performances of earthen cob construction with incorporation of various amounts of CGW. Our results indicate that adding coffee grounds to cob enhances its hygrothermal performances as well as its compressive strength. An interesting enhancement of the lightened earth thermal characteristics as well as a good control of the hydric load in the air while maintaining acceptable mechanical properties is observed. Numerical analysis is used to evaluate the hygrothermal behavior of cob specimens to better understand their energy performances. A simplification of the simulation methods using a linearization of the sorption curve is incorporated to reduce calculation times and optimize outputs. The method is validated using experimental data, which shows a promising improvement compared to previous approaches. The proposed method can be faithfully applied to the study of hygrothermal behavior of biomaterials, which is strongly related to the building energy performance and the investigation of their durability in a fast and effcient way.

5

Experimental and numerical investigation of an arch-beam joint for an arch bridge

Yang Yan, Lin Benqing, Zhang Wei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e101, 2023

EN

In this paper, the stress analysis of the most critical beam-arch joint of Yuehu Bridge is conducted, despite the variation in the specific structure of each tied arch bridge. To achieve this, two specimens with different scale ratios were designed. The smaller specimen was used to consider the effect of bridge deck and loading to failure. The experimental results indicate that both specimens did not exhibit significant deformation under the design load, and the measuring point’s stress was located in the elastic section. This implies that the original bridge structure design is rational. However, the arch rib steel plate of the 1/8 scale specimen buckled when subjected to 1.8 times the design load. To validate the experimental results, a finite element model that considers the elastoplastic behavior of the material was established and compared with the experimental results. The comparison shows that the finite element model can predict the mechanical behavior of the structure effectively, thus confirming the rationality of the structure design. Additionally, the study also analyzed the buckling problem of tied arch bridges, which is another critical issue. The in-plane and out-of-plane buckling of fixed and hinged parabolic arches under uniform axial compression were investigated. The results demonstrate that the boundary conditions, rise-span ratio, and bridge deck width significantly affect the buckling performance. Overall, this study provides essential insights into the stress and buckling behavior of tied arch bridges, which can guide the design and construction of such structures in the future.

6

Crack evolution and acoustic emission characteristics of rock specimens containing random joints under uniaxial compression

Ma Wenqiang, Wang Jiuting, Li Xiaoxiao, Wang Tongxu

Acta Geophysica

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2021

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Vol. 69, no. 6

2427--2441

EN

Joints greatly affect the mechanical behavior and crack evolution of jointed rock masses. In this paper, numerical specimens containing pre-existing random joints are constructed based on a combination of the fat-joint and smooth-joint models in the particle flow code in two dimensions (PFC2D). Then, uniaxial compression of these specimens is carried out to reveal the influence of joint length or number on the mechanical behavior, crack development, acoustic emission (AE) event attributes and failure characteristics. The results suggest that a univariant increase in random joint length or number leads to a nonlinear decrease in the uniaxial compressive strength (UCS) and a linear decrease in the elastic modulus, while the fracture behavior of the specimens shows a transformation from brittle to ductile in this process. With increasing joint length or number, the cracks and AE events generated in the joints significantly increase and exceed those generated in the intact rock. Tension cracks play a dominant role in the development of cracks within intact rock, while shear cracks dominate the crack evolution of random joints. More cracks appear in the jointed rock specimens at the elastic deformation stage as the joint length or number increases. The variation in the joint length or number strongly influences the mechanical behavior, crack evolution and failure pattern of the randomly jointed rock specimen.

7

Experimental evaluation of Al-Zn-Al2O3 composite on piston analysis by CAE tools

Krishnan B. Radha, Ramesh M.

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

212--217

EN

Today’s automotive designers and material specialists regard lighter vehicles for less fuel consumption (economy and ecology) and higher safety to passengers. Metal matrix composites have been a large area of interest. Aluminium composite is potentially applied in automotive and aerospace industries, because it has a superior strength to weight ratio and is a light weight metal with high temperature resistance. Composites containing hard oxides and ceramics (such as alumina) are preferred for high wear resistance along with increased hardness. In thiswork, alumina and zinc are reinforced in Al-LM25 alloy through stir casting process, where alumina is varied 6% and 12% in Al-5%Zn. Various mechanical analyses were conducted and the effect of wear with different percentage of alumina reinforcement was studied. The resulting properties are imported in a piston, modelled using solidworks, and analysed in ANSYS work bench. Imparting this new material for pistons could introduce deep design and improvements in engine operation of a vehicle.

8

Experimental and numerical study of bead welding behavior of HDPE pipe under uniaxial loading

Belaziz Azzeddine, Mazari Mohamed

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

183--191

EN

The present paper is devoted to the experimental study of the mechanical behavior of high-density polyethylene structure subjected to traction andwelded by means of butt-welding process. We were based ourselves on experimental testswhich have been carried out to characterize the material studied, introducing the ductility or fragility of the beadwelded section, and understood the effect of crosshead speeds on the mechanical behavior of the weld bead. The experimental results of the welded specimens are compared with those corresponding to the base material. In this study, two crosshead speeds of 10 and 50 mm/min were applied to make the comparison.

9

Thermal damage of CFRP laminate in fiber laser cutting process and its impact on the mechanical behavior and strain distribution

Li Maojun, Gan Guocui, Zhang Yi, Yang Xujing

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1511--1522

EN

Fiber laser cutting is a promising alternative to the conventional methods in machining CFRP with high efficiency, while the influence of machined quality on strain distribution and mechanical behavior of CFRP laminates is yet not fully understand. The aim of this paper is to study the effect of laser cutting parameters on thermal defects and related mechanical performance. DIC technique was successfully employed to assess full-field strain distribution under tensile loading. The relationship between strain distribution and failure evolution/mode was also investigated. Results showed that various thermal defects including matrix recession, resin decomposition, fiber burrs and delamination were observed on entry and exit surfaces, while microcracks, cavities and striations were prevalent on machined surface. Tensile strength of CFRP laminate with open hole was highly related to applied laser processing parameters. DIC technique indicated that the crack propagation and failure mode were in good agreement with the high level of strains developed around the hole. Matrix-fiber interface cracking, fiber breakage and splitting were the main failure modes at test cessation.

10

Experimental validation of a novel thin-walled beam prototype

Silva H. M., Meireles J. F., Wojewoda J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 1

7--23

EN

In this paper, an experimental validation of a novel beam prototype is performed. Tensile tests, both until rupture and on the elastic domain were done in order to determine the material properties. They were used then in Finite Element Analysis model built in ANSYS Mechanical APDL. Three experimental tests were done to the prototype, and, in order to minimize errors, the average value of the three tests determined, and compared with results obtained from the numerical model. It was shown that it was possible to manufacture the beam by the presented manufacturing methodology. An acceptable correlation between the numerical an experimental results was found.

11

Structural optimization of internally reinforced beams subjected to uncoupled and coupled bending and torsion loadings for industrial applications

Silva H. M., Meireles J. F.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 3

731--753

EN

In this work, novel types of internally reinforced hollow-box beams were structurally optimized using a Finite Element Updating code built in MATLAB. In total, 24 different beams were optimized under uncoupled bending and torsion loads. A new objective function was defined in order to consider the balance between mass and deflection on relevant nodal points. New formulae were developed in order to assess the efficiency of the code and of the structures. The efficiency of the code is determined by comparing the Finite Element results of the optimized solutions using ANSYS with the initial solutions. It was concluded that the optimization algorithm, built in Sequential Quadratic Programming (SQP) allowed to improve the effective mechanical behavior under bending in 8500%, showing a much better behavior than under torsion loadings. Therefore, the developed algorithm is effective in optimizing the novel FEM models under the studied conditions.

12

Numerical study on the mechanical behaviour of hollow-box beams subjected to static loading

Silva H. M., Meireles J. F.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 4

871--884

EN

Novel types of internally reinforced thin-walled beams are subjected to a feasibility analysis in terms of their effective mechanical behaviour. The novel beams are subjected to bending and torsion uncoupled loadings and are analysed in terms of their stiffness behaviour in static analysis. The models were built using the commercial Finite Element Method (FEM) software ANSYS Mechanical APDL. The feasibility of the models was determined by the comparison of the stiffness behaviour of the novel beams with simple hollow-box beams, having the same mass and dimensions, with the exception of the thickness. An efficiency parameter is used in order to determine the feasibility of the studied geometries. It is found that the novel geometries represent a great improvement under bending loading, better than under torsion loading. Nevertheless, for bending and torsion combined loadings, if bending loads are predominant, the beams can still be interesting for some applications, in particular those with mobile parts.

13

Comparative effectiveness of the mechanical behaviour of sandwich beams under uncoupled bending and torsion loadings

Silva H. M., Meireles J. F.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 4

855--869

EN

Sandwich geometries, mainly panels and beams, are widely used in several transportation industries, namely aerospace, aeronautic and automotive. Sandwich geometries are known for their advantages in structural applications: high specific stiffness, low weight, and possibility of design optimization prior to manufacturing. This study aims to know the influence of the number of reinforcements (ribs), and of the thickness on the mechanical behaviour of sandwich beams subjected to bending and torsion uncoupled loadings. In this study, four geometries are compared: simple web-core beam, corrugated core, honeycomb core, and joined honeycomb core. The last three are asymmetric, due to the use of odd number of ribs. The influence of the geometry on the results is discussed by means of a parameter that establishes a relation between the stiffness behaviour and the mass of the object. It is shown that all relations are non-linear, despite the elastic nature of the analysis in both the FEM software and in the practical application.

14

Microstructure and Mechanical Behavior of Mg-0.5Si-xSn Alloys

Fu X., Yang Y., Ma Q. Y., Peng X., Xu T.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

179--184

EN

Mg-0.5Si-xSn (x=0.95, 2.9, 5.02wt.%) alloys were cast and extruded at 593K (320 ºC) with an extrusion ratio of 25. The microstructure and mechanical properties of as-cast and extruded test alloys were investigated by OM, SEM, XRD and tensile tests. The experimental results indicate that the microstructure of the Mg-0.5Si-xSn alloys consists of primary α-Mg dendrites and an interdendritic eutectic containing α-Mg, Mg2Si and Mg2Sn. There is no coarse primary Mg2Si phase in the test alloys due to low Si content. With the increase in the Sn content, the Mg2Si phase was refined. The shape of Mg2Si phase was changed from branch to short bar, and the size of them were reduced. The ultimate tensile strength and yield strength of Mg-0.52Si-2.9Sn alloy at the temperature of 473K (200 ºC) reach 133MPa and 112MPa respectively. Refined eutectic Mg2Si phase and dispersed Mg2Sn phase with good elevated temperature stability are beneficial to improve the elevated temperature performance of the alloys. However, with the excess addition of Sn, large block-like Mg2Sn appears around the grain boundary leading to lower mechanical properties.

15

Study of Specific Conditions to Control the Mechanical Behaviour of Dorlastan® Core Spun Yarn

Helali H., Babay D. A., Msahli S., Cheikhrouhou M.

Fibres & Textiles in Eastern Europe

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2013

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Vol. 21, no. 3 (99)

55--60

EN

The mechanical properties of yarns play a phenomenal role in the quality of the end product. Studying these properties requires a specific test following international standards. As for elastic core spun yarn, knowledge of the mechanical behaviour is not obvious due to the absence of the specific condition. The aim of this study was to determine appropriate conditions to control the tenacity, elongation at break and elastic recovery of Dorlastan® core spun yarns of different linear densities (counts) (100, 50, 33.33 & 25 tex) and various elastane drafts. The results obtained show that the initial tension necessary to straighten elastic core spun yarns and eliminate their curling increases while the Dorlastan draft increases and, respectively, the Dorlastan ratios decreases. Furthermore we noted a decrease in tenacity and breaking elongation with a decrease in the dorlastan draft and, respectively, with an increase in Dorlastan ratios. On the other hand, we observed the decreasing trend of elastic recovery while the Dorlastan draft increases.

PL

Celem badań było określenie warunków dla kontroli wytrzymałości właściwej, wydłużenia przy zerwaniu, odprężenia elastycznego przędz rdzeniowych typu Dorlastan o różnych masach liniowych (100, 50, 33.33 i 25 tex) i współczynniku rozciągu przędzy elastomerowej. Badania wykazały, że jeżeli naprężenie wstępne wymagane dla wyprostowania elastycznego rdzenia przędzy i eliminacji spętlenia wzrasta kiedy współczynnik rozciągu dla przędz typu Dorlastan wzrasta. Następnie zaobserwowano, zmniejszenie wytrzymałości właściwej i wydłużenia przy zerwaniu ze zmniejszeniem współczynnika rozciągu. Z drugiej strony obserwujemy zmniejszenie tendencji elastycznego odprężenia gdy współczynnik rozciągu wzrasta.

16

Strain-rate sensitivity of porcine and ovine corneas

Elsheikh A., Kassem W., Jones S.W.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 2

25-36

EN

Knowledge of strain-rate sensitivity of corneal tissue is important for improving the understanding of the tissue's response to mechanical actions and the accurate numerical simulation of corneal biomechanical behaviour under the effects of disease and surgery. In the study, fresh and well-preserved porcine and ovine corneal buttons were subjected to uniaxial tension loads with seven different strain rates ranging between 0.8 and 420% per minute. All specimens exhibited increased stiffness (as measured by the tangent modulus) with higher strain rates. However, clear differences in their behaviour were observed. While ovine corneas showed gradual, consistent and mostly statistically significant increases in stiffness with all elevations in strain rate, porcine corneas' response was significant over only a limited range of low strain rates. The effect of strain rate on the material's stress-strain behaviour was considered in the formation of three sets of constitutive models including: (i) a model based on a simple exponential stress-strain relationship, (ii) the Ogden model that considers the tissue's hyperelasticity but not anisotropy, and (iii) a third model by Holzapfel, Gasser and Ogden that considers both hyperelasticity and anisotropy. The three models are introduced to enable consideration of the strain rate effects in simulations employing finite element programs with varying capabilities or in modelling applications in corneal biomechanics which may or may not require consideration of mechanical anisotropy.