Wyniki wyszukiwania - BazTech

1

Possibilities to modify the properties of the AW7075 aluminum alloy for the automotive industry

Jasiński Robert, Chruścielski Grzegorz

Combustion Engines

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2024

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R. 63, nr 2

9--14

EN

The paper investigated the AW7075 aluminum alloy that is used in the automotive industry. The alloy is widely used, among others, in the production of heads and engine blocks. The possibility of obtaining various properties of the alloy (material states) by appropriate heat treatment (saturation and aging) was demonstrated. The results of strength, hardness, abrasion, and fracture toughness tests of the alloy in the T73, RRA, and HTPP aging treatments, in comparison with the T651 reference state, are presented. The need to select the appropriate parameters of heat treatment in relation to the load conditions of the structural element, especially in elements with notches, was indicated. Depending on the state of the AW7075 alloy, the results prove the wide and diverse possibilities of its use and should be used consciously in the design and production processes of modern automotive drivetrain components.

2

Analysis of the cracking mechanisms in pre-cracked sandstone under radial compression by moment tensor analysis of acoustic emissions

Wang Guozhu, Luo Xulin, Song Lei, Wang Yu, Han Mouwang, Song Zhaocun, Wu Linjun, Wang Zukun

Archives of Civil Engineering

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2022

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Vol. 68, nr 3

447--468

EN

Rock masses, especially those with different pre-existing cracks, are prone to instability and failure under tensile loading, resulting in different degrees of engineering disasters. Therefore, to better understand the effect of pre-existing cracks with different dip angles on the tensile instability failure behaviour of rocks, the mechanism of crack initiation, propagation and coalescence in precracked sandstone under radial compression loading is investigated through numerical simulations. The temporal and spatial evolution of acoustic emission (AE) events is investigated by the moment tensor (MT), and the fracture mode of micro-cracks is determined. The results show that the pre-existing cracks weaken the specimens. The strength, crack initiation points and macro-failure modes of the specimens differ significantly depending on the dip angle of the pre-existing crack. For different dip angles of the pre-existing cracks, all the micro-cracks at the crack initiation point are tensile cracks, which are dominant during the whole loading process, and mixed cracks are mainly generated near the upper and lower loading ends after the peak stress. Of the total number of events, more than 75% are tensile cracks; approximately 15% are shear mode cracks; and the remainder consist of mixed mode cracks. The study reveals the instability and failure mechanism of pre-cracked rock, which is of great significance to ensure the long-term stability of rock mass engineering.

3

Visualization and quantification of aggregate and fiber in self-compacting concrete using computed tomography for wedge splitting test

Rajeshwari B. Raja, Sivakumar M. V. N., Praneeth P. Harsha

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

617--632

EN

Wedge splitting test gained popularity as a stable and simple method to predict the fracture mechanism properties of concrete specimens. The present research focuses on understanding the behavior of self-compacting concrete specimens made with and without steel fibers tested using wedge splitting test, later scanned under high resolution computed tomography. The contribution of hooked end steel fiber and coarse aggregates in fiber reinforced specimens was compared without steel fiber reinforced concrete specimens using high resolution computed tomography. As fracture takes place across the plane perpendicular to the splitting force, i.e. along the depth of specimens. High resolution computed tomography technique was adopted in visualizing the changes taking place across the matrix, coarse aggregate and steel fibers, along with the specimen’s depth. Datasets of the images, obtained from computed tomography, after images analysis and volume reconstruction, revealed a higher coarse aggregate and steel fiber participation in the failure region of without and with fibers specimens. Computed tomography investigation indicated a total of 23 coarse aggregate and 64 steel fibers participated in resisting the failure, during wedge splitting test of without and with fibers specimens. Therefore, high resolution computed tomography can be used in understanding, quantifying the participation of coarse aggregate and steel fiber in the failure plane, under fracture loads.

4

Microstructure characterization of 7055-T6, 6061-T6511 and 7A52-T6 Al alloys subjected to ballistic impact against heavy tungsten alloy projectile

Khan M. A., Wang Y., Malik A., Nazeer F., Yasin G., Khan W. Q., Ahmad T., Zhang H.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1484--1496

EN

A spray formed 7055 Al alloy, and traditional formed 6061 Al and 7A52 Al alloy were subjected to extrusion. Later 7055Al and 7A52 treated with T6 and 6061 Al treated with T6511 heat treatment. To investigate the microstructure evolution by optical microscopy (OM), scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) and X-rays diffraction pattern (XRD) analysis were employed to observe the variation in mechanical properties and damages patterns of single layered aluminum alloys impacted by heavy tungsten alloy (WHA) projectile. During impact a substantial increase in temperature inside the target material caused melting on crater wall. The hard metastable intermetallic compound and pores were produced on penetration path owing to diffusion of projectile particles and rapid melt re-solidification. These compounds enhance the hardness (600-650 HV0.1/10) in the middle deformed channels of 7055 Al alloy target. In addition, small size pores, whirl-pool and white adiabatic shear bands were observed in 7A52 and 6061 Al alloys, respectively. The variation in hardness and microstructure of Al alloys target was limited within the 2 mm area from the perforation path. 7055-T6 Al alloy has demonstrated better ballistic protection in terms of strength, mass efficiency (N), depth of penetration (DOP) and penetration path diameter in comparison of other Al alloys.

5

Badania wpływu kształtu ścian murowanych z elementów silikatowych poddanych ścinaniu

Jasiński R.

Materiały Budowlane

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2017

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nr 4

21--26

PL

Artykuł ten rozpoczyna cykl publikacji dotyczących zagadnień badawczych związanych ze ścinaniem. Omówione zostaną w nim wyniki badań niezbrojonych ścian bez otworów różnych kształtów, wykonanych z silikatowych elementów murowych, a w kolejnej publikacji – z autoklawizowanego betonu komórkowego. Prezentując wyniki badań, skoncentrowano się na wpływie kształtu na wartości naprężeń rysujących i niszczących, kącie odkształcenia i deformacji postaciowej oraz początkowej sztywności oraz sztywności w chwili zarysowania.

EN

This article begins a series of publications on research issues related to the shear. We will discuss the results of the study of unarmed walls without holes of various shapes, made of calcium silicate masonry units in the following issue – of autoclaved aerated concrete. Presenting the results of the study one focused on the influence of the shape on the values of the cracking and ultimate stresses, the strain and deformation angles, the initial and cracking stiffness.

6

Models of damage mechanism of glidcop Cu-Al2O3 micro and nanomaterials

Besterci M., Sülleiová K., Ballóková B., Velgosová O.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 69, nr 2

79--85

EN

Purpose:of this paper was to analyze the fracture mechanism before and after ECAP in the Glidcop AL-60 grade (with 1.1 wt. % of Al2O3) system and to propose damage and/or fracture mechanisms models by means of the method “in situ tensile test in SEM”. Design/methodology/approach: The method of “in-situ tensile testing in SEM” was used for investigations of fracture mechanisms because it enables to observe and document deformation processes directly, thank to which the initiation and development of plastic deformation and fracture can be reliably described. Analyses of microstructure and fracture surfaces were carried out by means of the scanning electrone microscope JEM 100 C. Findings: The deformation and fracture mechanisms of Glidcop AL-60 grade with 1.1 wt. % of Al2O3 phase (1.62 vol. % of Al2O3) were analyzed before and after ECAP (Equal Channel Angular Pressing). Before ECAP it was shown that the deformation process causes increasing of pores and formation of cracks. Decohesion of small Al2O3 particles and clusters occurs and the final fracture path is influenced by coalescence of cracks originated in such. The principal crack propagates towards the sample exterior surface. After ECAP initial cracks were formed in the middle of the specimen first of all in the triple junctions of nanograins and together with decohesion of Al2O3 particles and clusters at small strains lead to the failure. Research limitations/implications: To develop more complex knowledge about the objective material further studies are necessary to focus also on the other factors which besides the secondary phase amount can influence the failure mechanism, e.g. strain rate, temperature and others. Complex analysis allows better understanding of material behavior at different conditions and possibilities of application of products from these materials will be thereby improved. Practical implications: This article completes knowledge about damage/fracture mechanisms and processes of the material with 1.1 wt. % of Al2O3 phase. Some materials with the different volume fraction of a secondary phase have been studied. This concrete one with 1.1% clarifies the fracture process of Glidcop AL-60 material not only after mechanical alloying process but also after ECAP treatment. An effect of the ECAP process on the final material was crucial because not only microstructure but also failure mechanism have been changed. Originality/value: Based on the experimental observations original models of damage and/or fracture mechanisms were proposed.

7

Wpływ anizotropii po walcowaniu na odporność na pękanie materiału AW 7075-T651

Chruścielski G.

Postępy Nauki i Techniki

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2012

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Nr 12

19-27

PL

W pracy przedstawiono wyniki badań własności mechanicznych i odporności na pękanie w płaskim stanie odkształcenia w kierunku zgodnym i poprzecznym do kierunku walcowania dla stopu aluminium AW 7075 T651. Stwierdzono, że odporność na pękanie przy płaszczyźnie pęknięcia X/Y (prostopadłej do kierunku walcowania) jest wyższa o około 20% niż przy płaszczyźnie pęknięcia Y/X (zgodnej z kierunkiem walcowania). Przedstawiono wyniki badań elektronomikroskopowych powierzchni pękania w obu przypadkach. Na podstawie fraktografi wykazano, że pękanie w kierunku X/Y, przebiegające w poprzek granic, propaguje przy udziale licznych uskoków i jest mniej stabilne, co przyczynia się do większej odporności na pękanie. Potwierdzono również mechanizm pękania poprzez łączenie się mikropor, powstałych w strukturze materiału w miejscach wydzieleń faz międzymetalicznych.

EN

The work presents results of researches of mechanical properties and fracture toughness along and across rolling direction for aluminium alloy AW 7075 T651. It is confirmedthat in case of fracture on direction X-Y (perpendiculary to rolling direction) fracture toughness is 20% higher than in case of fracture on direction Y-X (situated along rolling direction). The results of seM and teM resarches of fracture surface are also presented. Based on fractography it is showed that fracture in X-Y direction that runs across grain boundaries has many leaps and is unstable what causes increasing of fracture toughness of material. Mechanism of microvoids coalescence close to particles of the second phases was also observed.

8

Carbonation cracking of reinforced AAC panel

Matsushita F., Aono Y., Shibata S.

Cement Wapno Beton

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2011

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nr spec.

81-85

EN

Carbonation cracking and its mechanism of AAC have not been reported at all. One of the possible mechanisms of carbonation cracking caused by carbonation shrinkage is investigated. Carbonation shrinkage at the occurrence of cracking was approximately 0.12% both for field study and accelerated carbonation, while carbonation degree was approximately 50% and 35%, respectively. Tensile stress in AAC was calculated to reach tensile strain capacity (0.04-0.05%) at the occurrence of cracking both for field study and accelerated carbonation data. In other words, the proposed mechanism of carbonation cracking was certified.

9

Mechanical properties dependency of the pearlite content of ductile irons

Gonzaga R. A., Martinez Landa P., Perez A., Villaneuva P.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 2

150-158

EN

Purpose: In this work, it is pretended to make a comparison of different pearlite contents in pieces with similar shape and dimensions and to analyze the variation of mechanical properties as pearlite content increases. The three pieces used had form of stair made of ductile cast iron. Design/methodology/approach: The present study was based on an adequate balance of alloying elements. None heat treatment was used to obtain different pearlite contents in the microstructures. Many specimens taken from the cast were mechanized to be polished and swabbed with nital to analyze the microstructure. To study the mechanical properties these casts present many tests were done such as Charpy impact test, done at different temperatures. Fracture toughness and tensile strength tests were done, as well. Findings: This study gave evidences that heat treatments are not necessary to obtain different pearlite content in the microstructure. Good mechanical properties are obtained by an appropriate balance of alloying elements. Research limitations/implications: They are that of natural sources. Besides, high and precision technology must be applied to get the present results better. Practical implications: Cast iron productions are focussed straight on machine building and automotive industries and constructions. The low cost production of ductile cast iron, its mechanical properties and low cost transformations are the tempting for application. Originality/value: The whole experimental work and the appropriate results obtained as consequences of the analysis carried out are novel, although applied methods are well known. Values presented in tables are given as new results of our experiments. This work is of great importance for the development of new economical methods for ductile iron production. This study is directed to researchers and metallurgy centres.

10

Rola wodoru w procesie pękania spoin - nowe spojrzenie

Tasak E., Ziewiec A., Adamiec J.

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2008

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R. 52, nr 5

138-138

PL

Przeprowadzono analizę charakteru pękania spoin w stalach mikrostopowych, w stalach bainitycznych niskostopowych oraz w połączeniach różnoimiennych stali T91 z 10CrMo9-10. Ustalono, że wodór wywołuje również powstawanie pęknięć gorących w procesie krzepnięcia spoin. Przeprowadzone badania pozwoliły opracować mechanizm pękania spoin na gorąco oraz dalszego ich rozwoju jako pęknięć zimnych zwłocznych. Zweryfikowano również opisywany w literaturze mechanizm powstawania pęknięć typu "chewron" wykazując, że początkiem pęknięć zimnych typu "chewron" są pęknięcia gorące, w których "magazynowany" jest wodór wywołujący po ostudzeniu spoin pęknięcia zwłoczne.

EN

It has been analysed the nature of weld metal cracking in micro-alloyed steels, bainitic low-alloy steels and in dissimilar joints of T91 with 10CrMo9-10 steels. It has been found that hydrogen induces also hot cracking during the weld solidification process. The authors' investigations enabled to develop the weld metal hot cracking mechanism as well as that of their further growth as delayed cold fractures. The mechanism of chewron type cracking described in the scientific literature has been also verified, pointing out that the chewron type cracks are initiated from hot cracks in which hydrogen is "stored" and induces the delayed fractures after cooling down the welds.

11

Analiza rozwoju małych pęknięć zmęczeniowych od otworu oraz mikromechanizm pękania platerowanej blachy stopu aluminium 2024-T3

Kocańda D., Hutsaylyuk V., Hlado V.

Biuletyn Wojskowej Akademii Technicznej

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2007

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Vol. 56, nr 4

37-53

PL

Zbadano powstawanie i rozwój małych pęknięć zmęczeniowych propagujących od otworu w obustronnie platerowanej blasze lotniczego stopu aluminium 2024-T3 przy stałoamplitudowym jednostronnym zginaniu (R=0,1). Badania początkowego okresu rozwoju pęknięć przeprowadzone za pomocą mikroskopu SEM pozwoliły ustalić miejsce inicjacji pęknięcia i mikromechanizm pękania blachy aluminiowej. Rozwój pęknięć na powierzchni próbek wyciętych z blachy rejestrowano metodą replik. Wykazano duży rozrzut prędkości pękania w przedziale rozwoju małych powierzchniowych pęknięć, który w blachach o grubości 3 mm sięga do 0,5 mm.

EN

The paper deals with mechanism of small crack initiation and growth from a central hole for 2024-T3 Alclad aluminium alloy sheet under cyclic constant amplitude bending (R=0,1). It was established for 3-mm-thick sheet that surface short cracks do not exceed the length of 0,5 mm. Fatigue lifetime that corresponds to this crack length covers 20-25% of total lives of the specimens. The range of crack length was estimated for mechanistically small crack too. The microfacture analysis, made by using SEM microscope, revelated that in cladded sheet the crack source is located beneath a thin Alclad layer at the border with the matrix material. The quasi-cleavage mechanism of cracking was found in the spot of crack initiation as well as in the vicinity of the crack source and in the Alclad layer. This microfracture analysis revealed a complex shape of a crack head in a thin sheet as well.

12

Inżynieria skalna zabytkowych elementów kamiennych

Pinińska J.

Prace Naukowe Instytutu Geotechniki i Hydrotechniki Politechniki Wrocławskiej. Konferencje

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2005

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Vol. 75, nr 41

451-462

PL

Na podstawie analizy zachowania wybranych kamiennych obiektów zabytkowych w klimacie umiarkowanym (Polska) oraz subtropikalnym (Górny Egipt) przedstawiono mechanizmy ich deterioracji w środowisku wód powierzchniowych (elementy mostowe), silnie zurbanizowanym środowisku miejskim (elewacje budynków), zurbanizowanego środowiska chronionego (Cmentarz Powązkowski), pustynnym (Egipt) w rejonie Depresji Fayum oraz Doliny Nilu (Świątynie Maadi Town oraz Hatszepsut). Podano przykłady procesów deterioracji (starzenia) się materiału kamiennego oraz elementy laboratoryjnej oceny stanu deterioracji. Całość analiz oparta jest na prowadzonych od roku 1990 badaniach Zakładu Geomechaniki Uniwersytetu Warszawskiego.

EN

The presented process of deterioration of stone monuments in moderate and subtropical climate conditions are supported by studies undertaken accordingly in Poland and Egypt. Described are cases of some laboratory testing of deterioration process of architectural stone elements. Scientific studies concerned monuments subjected to various environmental conditions like bridge supports under impact of surface waters, front elevations of buildings within densely urbanized area, protected graveyard monuments in the Powązki Cemetery in Warszawa, and the monuments in Hatszepsut and Maadi Town in Egypt subjected to strong impact of seasonal changes of semi-desert conditions at the peripheries of the Nile Valley. All the materials come from the researches carried on since 1990 in the Rock Mechanics Laboratory, Warsaw University.

13

Damage behaviour of high speed textile reinforced composite rotors

Hufenbach W., Langkamp A., Kostka P., Bohm R.

Kompozyty

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2005

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R. 5, nr 2

23-28

EN

Textile reinforced plastics with their excellent light weight characteristics, good resistance to chemicals and their wide scope of design-ability - e.g. possibility of creating a load-adapted thermo-mechanical anisotropic property profile - offer a new range of performance for advanced high-speed rotors. For the load adapted design of variable axial composites for those applications, material adapted calculation methods and optimisation tasks with modified physically based failure criteria and anisotropic, fracture mode specific damage models are developed. The calculation and optimization of the textile reinforcement for complexly loaded composite rotors is performed using extended analytical and numerical calculation methods, which realistically simulate the mechanically or the hygro-thermally induced material strains for the individual textile reinforcement. A linear elastic approach can be applied for the stress strain analysis until the first fracture occurs. After initiation of the first failure, non linear deformation behaviour caused by different damage phenomena of the textile reinforced composite has to be considered within the calculation. In the present work a phenomenological plane stress damage mechanics based model for textile reinforced composites is presented. Damage variables are introduced to describe the evolution of the damage state and as a subsequence the degradation of the material stiffness.

PL

Tworzywa ze wzmocnieniem tekstylnym ze względu na niski ciężar właściwy, odporność na działanie substancji chemicznych oraz możliwość projektowania ich właściwości w szerokim zakresie - na przykład dopasowania anizotropii mechanicznej i termicznej do występujących obciążeń - oferują nowy zakres parametrów eksploatacyjnych nowoczesnych szybkoobrotowych wirników. Zostały opracowane metody umożliwiające projektowanie wirników wykonanych z wieloosiowo wzmocnionych kompozytów z uwzględnieniem stanu obciążenia. Obejmują one fizykalnie uzasadnione kryteria uszkodzeniowe oraz modele procesu niszczenia uwzględniające anizotropię materiału i rodzaj uszkodzenia. Obliczenia i optymalizacja parametrów wzmocnienia tekstylnego wirników poddanych złożonym stanom obciążenia zostały przeprowadzone z użyciem zaawansowanych metod analitycznych i numerycznych, które pozwalają na realistyczną symulację odkształceń wywołanych obciążeniami mechanicznymi lub higrotermicznymi dla określonych rodzajów wzmocnienia. Teoria liniowo-elastyczna może być zastosowana do analizy naprężeń i odkształceń tylko do momentu, w którym zostaje zapoczątkowana degradacja materiału. Zjawiska składające się na proces niszczenia powodują, że w obliczeniach dotyczących odpowiadającego mu zakresu obciążeń stosowane są zależności nieliniowe. Artykuł przedstawia fenomenologiczny model mechaniki pękania kompozytu wzmocnionego tekstylnie dla płaskiego stanu naprężenia. Wprowadzono specjalne zmienne opisujące przebieg procesu niszczenia i towarzyszący mu spadek sztywności.