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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

Investigating the Effect of Photo-Oxidative Degradation on the Ageing Resistance of the Car Mudflaps Manufactured with Post-Production High-Density Polyethylene Wastes

Czarnecka-Komorowska Dorota, Swain Chandra, Kopeć Bogdan, Borowski Jacek, Garbacz Tomasz

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 4

38--47

EN

The paper presents the results of the ageing resistance of automotive mudflaps made of recycled polyethylene blends. The mudflaps were manufactured by a plastic sheet extrusion-calendaring process in Novotech Kostrzyn nad Odrą company. The changes of the mechanical properties in the tensile test and impact toughness test as well as in Shore hardness due to the accelerated aging process were characterized, taking into account the aging sensitivity coefficient (KI), and changes in the structure within the wavenumber range 4000-400 cm-1, taking into account the CI coefficient. The results showed a higher melting point and crystallinity for the recycled HDPE blends during photo-oxidative degradation. Moreover, the results presented decreased tensile strength and ductility, due to macromolecular chain scission caused by oxidation. It was found that the blends of HDPE based on recycled materials are more sensitive to the aging process than virgin HDPE. Finally, it can be concluded that the sensitivity to ageing blends increases with the increase of recycled HDPE content in the HDPE matrix.

7

Mechanical stability of retained austenite in aluminum-containing medium-Mn steel deformed at different temperatures

Kozłowska Aleksandra, Radwański Krzysztof, Matus Krzysztof, Samek Ludovic, Grajcar Adam

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

324--338

EN

The thermal and mechanical stabilities of retained austenite in aluminum-containing medium-Mn 0.16C–4.7Mn–1.6Al–0.2Si sheet steel were investigated. The strain-induced martensitic transformation in Mn TRIP steel was studied at different temperatures. Static tensile tests were carried out at the temperature ranging from − 60 to 200 °C. The tests allowed to study the influence of the temperature on austenite-to-martensite transformation kinetics. The interrupted tensile tests and corresponding X-ray measurements of retained austenite amount were performed to determine the mechanical stability of retained austenite using the Sugimoto model. The microstructure changes were investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Observed results reflected the effects of deformation temperature on the mechanical stability of retained austenite and the corresponding response of this phase to martensitic transformation. It was found that an increase in the deformation temperature resulted in the reduced intensity of the TRIP effect due to the higher mechanical stability of retained austenite. At the highest deformation temperature (200 °C), the evidence of thermally activated processes affecting the mechanical behavior was identified.

8

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.

9

Investigations on tensile and flexural characteristics of fly ash and banana fiber-rein

Gopalan Venkatachalam, Sharma Shashank Kumar, Jangid Anil Kumar, Pragasam Vignesh, Satonkar Nilesh, Chinnaiyan Pandivelan

Engineering Transactions

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2020

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Vol. 68, iss. 1

89--101

EN

Polymer matrix composites (PMCs) generally use the inorganic and non-biodegradable materials as reinforcements. This paper presents a PMC with reinforcement of fly ash and banana fiber. The epoxy resin is used as a matrix. This paper investigates the influences of the percentage of fly ash, the percentage of banana fiber and the size of banana fiber on tensile and flexural behaviors of fly ash and banana fiber reinforced epoxy matrix composite. Taguchi’s orthogonal array is used in the design of the experiments in the sample preparations. Analysis of variance (ANOVA) is employed to find the significance of input parameters on tensile and flexural behaviors.

10

Mechanical behavior around double circular openings in a jointed rock mass under uniaxial compression

Lin Qibin, Cao Ping, Cao Rihong, Lin Hang, Meng Jingjing

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 1

264--281

EN

To better understand the mechanical behavior in a jointed rock mass, a series of uniaxial compression tests were conducted on non-persistently jointed rock specimens with double circular holes. Acoustic emission (AE) and digital image correlation (DIC) techniques were applied to capture micro-crack events and real-time strain field evolution in the specimens. The results indicate that the existence of non-persistent joints has a significant influence on the strength characteristics of the specimens. Specifically, peak strength decreases at first and reaches a minimum at 30° then increases with increase in the joint dip angle. DIC technology has successfully monitored the development of surface strain fields. The fracture evolution process is comprehensively understood. Every sudden change in a strain field is usually accompanied by apparent AE events and stress–strain curves take the form of oscillations. The crack coalescence modes among joints can be summarized as six types and the crack coalescence patterns around holes and joints can be divided into three categories. These results are helpful to understanding further the mechanical properties and fracture mechanism of openings in non-persistently jointed rock masses.

11

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.

12

Vibration Control Devices for Building Structures and Installation Approach: a review

Sarwar Waseem, Sarwar Rehan

Civil and Environmental Engineering Reports

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2019

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Vol. 29, no. 2

74--100

EN

Retrofit and structural design with vibration control devices have been proven repeatedly to be feasible seismic hazard mitigation approach. To control the structural response; supplemental energy dissipation devices have been most commonly used for energy absorption. The passive control system has been successfully incorporated in mid to high rise buildings as an appropriate energy absorbing system to suppress seismic and wind-induced excitation. The considerable theses that are highlighted include vibration control devices, the dynamic behavior of devices; energy dissipation mechanism, devices installation approach and building guidelines for structural analysis and design employing vibration control devices also, design concern that is specific to building with vibration control devices. The following four types of supplemental damping devices have been investigated in this review: metallic devices, friction devices, viscous fluid devices, and viscoelastic devices. Although numerous devices installation techniques available, more precisely, devices installation approaches have been reviewed in this paper, including Analysis and Redesign approach (Lavan A/R), standard placement approach, simplified sequential search algorithm, and Takewaki approach.

13

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.

14

Effect of High-Frequency Electric Resistance Welding (HF-ERW) Parameters on Metallurgical Transformations and Tensile Properties of API X52 Microalloy Steel Welding Joint

Sabzi M., Kianpour-Barjoie A., Ghobeiti-Hasab M., Dezfuli S. M.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1693--1699

EN

This study investigates the effects of frequency, compression force and Vee angle parameters of High-Frequency Electric Resistance Welding (HF-ERW) process on mechanical properties of API X52 microalloy steel welding joint. Therefore, API X52 microalloy steel sheets having thickness of 8 mm was provided to manufacture pipes with the diameter of 16”. with direct weld seams using the HF-ERW method. During the manufacturing process, frequency values of 150, 200 and 250 kHz, compression forces of 2, 4 and 6 mark and Vee angles of 3°, 5°, and 7° were adopted. After changing the welding parameters, from the welded pipes, tensile and Charpy impact test samples prepared to macroscopically evaluate the weld metal flow and examine the effects of these parameters on mechanical properties of the welded joints. According to the results, it was concluded that frequency of 150 kHz, the compression force of 4 mark and Vee angle of 5° yields best mechanical properties in the HF-ERW joint of API X52 microalloy steel.

15

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.

16

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 2

329--351

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.

17

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.

18

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.

19

Crystallization behavior and microstructure of bio glass-ceramic system

Mehdikhani B., Borhani G. H.

International Letters of Chemistry, Physics and Astronomy

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2013

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Vol. 14

58--68

EN

The effects of Al2O3 on the crystallization behavior of glass compositions in the Na2O-CaO-SiO2 system were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Effect of Al2O3 content on the mechanical, density, phase formation and microstructures of Na2O-CaO–P2O5–Al2O3-SiO2 glass ceramics were studied. Thermal parameters of each glass were studied by DTA. The density of the glass ceramic samples was measured by Archimedes’ method. It was found that the glass–ceramic containing 2.0 molar percent Al2O3 had desirable sintering behavior and reached to an acceptable density. Phase investigation and micro structural study were performed by XRD and SEM, respectively.

20

The influence of strain rate on microstructure and mechanical behavior of P/M feal

Śleboda T.

Metallurgy and Foundry Engineering

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2008

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Vol. 34, no. 2

133-138

EN

As part of a broader study of the thermomechanical processing of P/M FeAl alloys, this research is focused on the influence of processing strain rate on the microstructural evolution and mechanical behavior of the processed materials. For the purposes of this study, water atomized FeAl powder was consolidated by hot pressing resulting in fully dense products. The consolidated P/M samples were thermomechanically processed in compression at 800 and 900oC at strain rates of 0.1 s-1 and 10 s-1, to a true strain of 1. The influence of thermomechanical processing parameters on the material flow and microstructural development of investigated alloy was analyzed. Considerable strain rate sensitivity of investigated alloy was observed, specially with reference to microstructural development.

PL

W niniejszej pracy przedstawiono wybrane wyniki badań wpływu prędkości odkształcenia na rozwój mikrostruktury oraz charakter odkształcenia plastycznego stopu z grupy FeAl. W badaniach zastosowano rozpylany wodą proszek stopu. W pełni zagęszczone poprzez prasowanie na gorąco próbki z proszków poddano próbie ściskania w temperaturach 800°C oraz 900°C przy prędkościach odkształcenia równych 0.1 s(-1) oraz 10 s(-1), do wartości odkształcenia rzeczywistego równej 1. W materiałach odkształconych w temperaturze 800°C rozdrobnienie mikrostruktury nastąpiło tylko przy większej prędkości odkształcenia (10 s(-1) ), natomiast w temperaturze 900°C materiał uległ rekrystalizacji niezależnie od prędkości odkształcenia. Badania wykazały stosunkowo dużą czułość stopu na prędkość odkształcenia, szczególnie w odniesieniu do zmian strukturalnych związanych z procesami rekrystalizacji.