Wyniki wyszukiwania - BazTech

1

Badanie właściwości mechanicznych stali S355JR o różnych typach budowy mikrostruktury

Lipiec Sebastian

Stal, Metale & Nowe Technologie

|

2023

|

nr 1-2

36--40

PL

W artykule analizowana jest stal S355JR o różnych typach budowy mikrostruktury: poddana normalizacji, ze strukturą ferrytyczno-perlityczną (FP), oraz po wygrzewaniu austenityzującym, następnie chłodzona z dużą prędkością poprzez hartowanie w oleju, ze strukturą ferrytyczno-bainityczną (FB).

XX

An important aspect in the engineering design process is to know the true material characteristics of steels used in specific microstructures. These steels, depending on, among other things, heat treatment or working conditions and regimes, are characterised by a different microstructure. It is important to know the levels of both strength, ductility and fracture toughness of steels with different microstructure. This paper presents the results of an experimental study of S355JR steel with two types of microstructure: ferritic-perlitic and ferritic-bainitic. The basic strength and ductility characteristics of the steel determined by uniaxial tensile test and the results of fracture toughness tests are presented.

2

Stiffness of MCE mixtures based on cement dusty by-products and recycled aggregate

Skotnicki Łukasz, Kuźniewski Jarosław

Roads and Bridges - Drogi i Mosty

|

2023

|

Vol. 22, no. 4

579--592

EN

This paper presents the possibilities of reusing recycled materials in road pavement constructions. This study analyses the effects of reclaimed asphalt pavement (RAP) and cement dusty by-products (UCPP) on the stiffness of mineral-cement-emulsion (MCE) mixtures. Asphalt waste can be used as a secondary raw material for the preparation of cement-stabilised mixtures in cold recycling technology. The use of MCE mixtures in road pavement construction is one way of disposing of construction waste. Testing of MCE mixtures with UCPP was aimed at confirming the applicability of these materials for cold recycled pavement structure layers. The purpose was to evaluate the effect of the innovative UCPP binding agent on the mechanical properties of MCE mixtures. The stiffness of the mixtures in question was analysed. Tests were carried out for fine- and coarse-grained mixtures. The stiffness modulus in indirect tension test on cylindrical specimens (IT-CY) was carried out according to EN 12697-26. Indirect tensile strength (ITS) testing was carried out according to EN 12697-23. The use of innovative binders has made it possible to reduce the stiffness of individual MCE mixtures compared to reference mixtures containing conventional cement, while still maintaining adequate durability. The relationships developed between IT-CY stiffness and ITS strength will allow the design and execution of MCE mixtures in road pavements to be optimised. The use of UCPP changed the mechanical properties of MCE mixtures by reducing their stiffness. This will contribute to the cracking resistance of the base and sub-base layers and increase their fatigue life. The innovative material was used in the experimental section and it is being monitored.

PL

W artykule przedstawiono możliwości powtórnego zastosowania materiałów pochodzących z recyklingu w konstrukcjach nawierzchni drogowych. W pracy analizowano wpływ destruktu asfaltowego i ubocznych cementowych produktów pylastych (UCPP) na sztywność mieszanek mineralno-cementowo-emulsyjnych (MCE). Destrukt asfaltowy może być wykorzystany jako surowiec wtórny do przygotowania mieszanek stabilizowanych cementem w technologii recyklingu na zimno. Zastosowanie w nawierzchniach drogowych mieszanek MCE jest jednym ze sposobów utylizacji odpadów budowlanych. Badania mieszanek MCE z UCPP miały na celu potwierdzenie możliwości zastosowania tych materiałów do warstw konstrukcji nawierzchni, poddanych recyklingowi na zimno. Istotą była ocena wpływu innowacyjnego środka wiążącego UCPP na właściwości mechaniczne mieszanek MCE. Analizowano sztywność przedmiotowych mieszanek. Badania wykonano dla mieszanek: drobnoziarnistej i gruboziarnistej. Badania sztywności w pośrednim rozciąganiu (IT-CY) wykonano wg normy PN-EN 12697-26. Badanie wytrzymałości na rozciąganie pośrednie (ITS) wykonano wg PN-EN 12697-23. Zastosowanie innowacyjnych spoiw pozwoliło na redukcję sztywności poszczególnych mieszanek MCE w porównaniu do mieszanek referencyjnych, zawierających klasyczny cement, przy zachowaniu ich odpowiedniej trwałości. Opracowane zależności pomiędzy sztywnością IT-CY a wytrzymałością ITS pozwolą na optymalizację procesu projektowania i wykonywania mieszanek MCE w nawierzchniach drogowych. Stosowanie UCPP zmieniło właściwości mechaniczne mieszanek MCE, ograniczając ich sztywność. Przyczyni się to do zwiększenia odporności na pękanie podbudowy i zwiększenie jej trwałości zmęczeniowej. Innowacyjny materiał został wykorzystany na odcinku doświadczalnym i jest monitorowany.

3

Cracking resistance of recycled mineral-cement-emulsion mixtures

Skotnicki Łukasz, Kuźniewski Jarosław

Roads and Bridges - Drogi i Mosty

|

2023

|

Vol. 22, no. 1

19--39

EN

Recycling enables reduction in usage of natural resources in road construction, positively affecting its environmental aspects. Construction materials obtained through recycling include mineral-cement-emulsion (MCE) mixtures, which are used in road pavements as base courses. MCE mixture consists of aggregate, added aggregate that improves gradation, bituminous emulsion and cement. Aggregate may be substituted with reclaimed asphalt material obtained from deteriorated pavements. Use of cement in pavement structure generates cracks that propagate upwards through the upper layers. When innovative binders are used instead of pure cement, the number of cracks may be reduced, improving the life of the entire pavement structure. The article presents selected problems pertaining to MCE mixtures produced using an innovative cement-based binder incorporating cement by-pass dust (CBPD). The performed laboratory tests encompassed fatigue life and fracture toughness. The innovative cement-based binders displayed significant influence on the obtained results. Used in combination with reclaimed asphalt pavement material, they reduced cracking in MCE mixtures, improving their fatigue life.

PL

Recykling pozwala na ograniczenie użycia w budownictwie drogowym surowców naturalnych, pozytywnie wpływając na aspekty ochrony środowiska. Do materiałów budowlanych powstających dzięki recyklingowi zalicza się mieszanka mineralno-cemen- towo-emulsyjna (MCE), która jest stosowana do warstw podbudowy konstrukcji nawierzchni drogowych. MCE składa się z kruszywa, kruszywa doziarniającego oraz emulsji asfaltowej i cementu jako spoiw. Kruszywo można zastąpić destruktem asfaltowym ze zdegradowanych nawierzchni drogowych. Zastosowanie cementu w warstwach podbudowy generuje pojawienie się spękań propagujących w kierunku górnych warstw nawierzchni drogowej. Poprzez zastosowanie innowacyjnych spoiw zamiast cementu można zredukować liczbę spękań, a tym samym pozytywnie wpłynąć na trwałość całej konstrukcji nawierzchni. W artykule przedstawiono wybrane zagadnienia dotyczące zastosowania w mieszankach MCE innowacyjnego spoiwa cementowego, wykorzystującego uboczne produkty pylaste pochodzące z cementowni (UCPP). Badania laboratoryjne prowadzone były w zakresie analiz trwałości zmęczeniowej i odporności na pękanie. Innowacyjne spoiwa cementowe wykazały istotny wpływ na rezultaty badań. W połączeniu z destruktem asfaltowym zapewniły redukcję zjawiska pękania w mieszankach typu MCE, co poprawiło ich trwałość zmęczeniową.

4

Analiza wybranych własności mechanicznych i tribologicznych medycznego stopu Ti24Nb4Zr8Sn

Dąbrowski Robert, Sułowski Maciej

Inżynieria Materiałowa

|

2023

|

Vol. 44, nr 5

11--15

PL

W artykule zaprezentowano wyniki badań twardości, odporności na pękanie oraz odporności na zużycie ścierne stopu Ti24Nb4Zr8Sn po obróbce cieplnej, tj. przesycaniu z temp. 850°C i starzeniu w 350, 450 i 600°C. Wykazano, że w stanie przesyconym, gdy w mikrostrukturze jest obecna jedynie faza β, stop charakteryzuje się najmniejszą twardością i największą odpornością na pękanie. Zastosowanie zabiegu starzenia, skutkujące wydzielaniem fazy α z przesyconej fazy β, silnie zmniejsza jego odporność na pękanie. Badany stop wykazuje istotnie różną odporność na zużycie ścierne i różny współczynnik tarcia, zależnie od mikrostruktury i twardości. Minimalną wartość współczynnika tarcia odnotowano po starzeniu w temp. 450°C, w której dochodzi do wydzielania w mikrostrukturze fazy α o dużej dyspersji, tj. przy maksymalnej twardości stopu.

EN

The article presents the results of hardness, fracture toughness and abrasive wear resistance tests of the Ti24Nb4Zr8Sn alloy. These results were obtained after its heat treatment, i.e. solution from 850°C and aging at 350, 450 and 600°C. It has been shown that in the supersaturated state, when only the β phase is present in the microstructure, the alloy is characterized by the lowest hardness and the highest fracture toughness. The application of the aging treatment, resulting in the separation of the α phase from the supersaturated β phase, strongly reduces its fracture toughness. The tested alloy shows significantly different resistance to abrasive wear and a different friction coefficient, depending on the microstructure and hardness. The minimum value of the friction coefficient was noted after aging at 450°C, at which the α phase with high dispersion was precipitated in the microstructure, i.e. at the maximum hardness of the alloy.

5

Influence of hydrogen blended gas transmission under transient flow on L485ME steel grade fracture toughness

Uilhoorn Ferdinand, Witek Maciej

Gaz, Woda i Technika Sanitarna

|

2023

|

Nr 12

2--9

EN

In the present study, the L485ME low-alloy steel grade, widely used in the last few decades in the natural gas transmission pipelines, subjected to hydrogen was investigated with respect to material degradation. A fracture toughness parameter such as the calculated conditional stress intensity factor was compared to the threshold stress intensity factor for the plane strain hydrogen-assisted cracking derived from the experimental data. Based on macroscopic and microscopic evaluation and measurements, the hydrogen-assisted crack size propagation in steel specimens was compared to the subcritical crack growth. The hydrogen content in the tube wall for the base metal and heat-affected zone was estimated, whereas the pressure and temperature conditions in the pipeline were calculated from a non-isothermal transient gas flow model. The results were used to estimate the fracture toughness of the pipe wall material exposed to the hydrogen-blended natural gas.

PL

W niniejszej pracy została przebadana, pod kątem degradacji materiału na skutek działania wodoru, stal niskostopowa gatunku L485ME, szeroko stosowana w ostatnich dziesięcioleciach do budowy rurociągów przesyłowych gazu ziemnego. Parametr odporności na kruche pękanie, taki jak obliczeniowy warunkowy współczynnik intensywności naprężeń, porównano z granicznym współczynnikiem intensywności naprężeń dla wydłużenia płaskiego, który wyznaczono z danych doświadczalnych dla pękania wywołanego wodorem. Na podstawie oceny oraz pomiarów makroskopowych i mikroskopowych, porównano wspomaganą wodorem propagację wielkości podkrytycznego wzrostu pęknięć w próbkach stalowych. Oszacowana została zawartość wodoru w ściance rury dla metalu podstawowego oraz strefy wpływu ciepła. W oparciu o nieizotermiczny model przepływu gazu w stanie nieustalonym, obliczono warunki ciśnienia i temperatury w rurociągu. Uzyskane wyniki wykorzystano do oszacowania odporności na pękanie materiału ścianki rury poddanego działaniu gazu ziemnego z dodatkiem wodoru.

6

An approach to coupling the gas flow dynamics and thermodynamics of hydrogen solubility in L485ME steel grade for estimation of fracture toughness

Witek Maciej, Uilhoorn Ferdinand

Archives of Thermodynamics

|

2023

|

Vol. 44, no 4

381--403

EN

The paper presents the problem of coupling the gas flow dynamics in pipelines with the thermodynamics of hydrogen solubility in steel for the estimation of the fracture toughness. In particular, the influence of hydrogen blended natural gas transmission on hydrogen solubility and, consequently, on fracture toughness is investigated with a focus on the L485ME low-alloy steel grade. Hydraulic simulations are conducted to obtain the pressure and temperature conditions in the pipeline. The hydrogen content is calculated from Sievert’s law and, as a consequence, the fracture toughness of the base metal and heat-affected zone is estimated. Experimental data is used to define hydrogen-assisted crack size propagation in steel as well as to a plane strain fracture toughness. The simulations are conducted for a real natural gas transmission system and compared against the threshold stress intensity factor. The results showed that the computed fracture toughness for the heat-affected zone significantly decreases for all natural gas and hydrogen blends. The applied methodology allows for identification of the hydrogen-induced embrittlement susceptibility of pipelines constructed from thermomechanically rolled tubes worldwide most commonly used for gas transmission networks in the last few decades.

7

Manufacture of Toughened Al2O3-Based Composites by the Combination of RBAO and SPS Processes

Rocha-Rangel Enrique, Calles-Arriaga Carlos A., López-Hernández Juan, Rodríguez-García José A.

Archives of Metallurgy and Materials

|

2023

|

Vol. 68, iss. 1

249--255

EN

The effect of additions of silver or titanium (0.5 or 3 vol.%) microparticles on the microstructure, as well as some physical properties of Al2O3-based composites, were studied. The processing method for the manufacturing of alumina-based composites was a combination of RBAO and SPS processes. After the SPS process, bodies with almost full density were obtained. Observations by optical microscopy show a very fine and homogenous microstructure in all samples. Concerning mechanical properties, the addition of metals on alumina increases its fracture toughness significantly (112% for the sample with additions of silver, while the composite with additions of titanium fracture toughness increases by 72%). In terms of optical properties, both silver and titanium improve the absorbance in the visible range.

8

Effect of crack angle and concrete strength on the dynamic fracture behavior of rock-based layered material containing a pre-existing crack

Guo Tengfei, Liu Kewei, Li Xiang, Jin Peng, Yang Jiacai, Zhang Aimin, Zou Liansong

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 3

art. no. e198, 2023

EN

Dynamic fracture behavior of rock-based layered material containing a pre-existing crack was investigated, which is crucial to evaluate the stability of rock-based systems. Dynamic tests on semi-circular bend (SCB) samples were conducted with a split-Hopkinson Pressure Bar (SHPB) system and the cracking process was collected using digital image correlation (DIC). An MTS Insight 30 electromechanical test equipment was adopted to perform static fracture experiment for comparison. Different typical fracture modes were classified: interfacial fracture, combined mode of tensile–shear fracture, and combined mode of compression–shear fracture. Regardless of static load or dynamic load, the fracture mode is controlled by crack dip angle, and the peak load is proportional to crack dip angle. The increase in concrete strength makes a strengthening impact on the bearing capacity of SCB sample, which can prevent the propagation of secondary cracks in the concrete. Both static and dynamic fracture toughness are significantly affected by dip angle. The difference between static and dynamic fracture toughness of mixed-mode reduces initially and subsequently increases with an increase in dip angle. Furthermore, comparing with static fracture toughness, dynamic fracture toughness substantially depends stronger on dip angle. The dip angle and concrete strength have an obvious effect on the fracture resistance.

9

A novel model for determining the strength and fracture parameters of Q235 steel using double symmetrical edges notched specimens

Han Ruicong, Meng Wei, Guan Junfeng, Hao Ying, Yao Xianhua, Li Lielie, He Shuanghua

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 2

art. no. e75, 2023

EN

A fracture model has been established for simultaneously determining the strength and fracture parameters of materials without size effect using double symmetrical edges notched specimens of metal. The specific method is presented for determining yield strength and fracture toughness using experimental yield loads of the small specimens in laboratory. The formula of nominal stress of double symmetrical edges notched specimen under uniaxial tension considering plastic zone is derived. The influence of different plastic zones size on calculating the fracture and strength parameters has been analyzed. The complete fracture failure curves of the metal material are obtained. The theoretical minimum size of metal specimen satisfying the conditions of linear elastic fracture mechanics is given. The normal method is used to analyze the dispersion of small-size double symmetrical edges notched specimens of hot-rolled carbon steel to predict the fracture properties of large-size specimens. A novel approach has been provided for the rational determination of realistic material parameters and the prediction of load carrying capacity of large-size structures by experimental fracture tests for small-size specimens.

10

Study on mechanical characteristics of rock type I fracture and anchorage strengthening mechanism

Zhang Wei, Zhao Tongbin, Guo Weiyao, Xing Minglu

Journal of Theoretical and Applied Mechanics

|

2022

|

Vol. 60 nr 3

423--434

EN

Engineering rocks are easily affected by excavation unloading and are in uniaxial compres- sion or tension, forming a typical I-type tension crack. Anchor rods are often used for on-site support to ensure safety and reliability of the project. The study of propagation and pen- etration of type I tension cracks and quantitative evaluation of rock anchoring effects are of great significance for exploring mechanical properties of rock fracture and revealing the mechanism of rock failure. In this paper, combined with speckle light measurement, a rock fracture toughness test of different anchoring positions and pre-tightening forces is carried out, the deformation evolution law of the crack tip and the fracture mechanics characteris- tics of the anchored rock are obtained, and the anchoring strengthening mechanism of the rock is discussed based on the theory of the net stress intensity factor. The research shows that the rock fracture process is divided into four stages: elastic deformation, steady crack propagation, crack instability propagation and residual deformation. After anchoring, the time of crack instability growth can be prolonged by 172% and the final residual deformation can be increased by 148%. Compared with the unanchored rock, the fracture toughness of rock initiation and instability increased by 83% and 124% respectively, and increased with growth of the pre-tightening force, which shows that the bolt increases the critical value of rock initiation and instability to achieve the toughening effect. After the rock is anchored, the time required for the crack to propagate to the same length increases by 55%, and the lateral deformation area is reduced by 46%, indicating that the lateral closing force of the bolt inhibits crack propagation and delays the instability of the rock matrix.

11

Wpływ temperatury starzenia na mikrostrukturę i wybrane właściwości mechaniczne stopu Ti24Nb4Zr8Sn

Dąbrowski Robert

Inżynieria Materiałowa

|

2022

|

Vol. 43, nr 5

9--15

PL

Celem pracy była ocena mikrostruktury i wybranych własności mechanicznych stopu Ti24Nb4Zr8Sn w stanie po przesycaniu, tj. oziębianiu w wodzie z wybranej temperaturze wygrzewania (800°C) i starzeniu w zakresie temp. 350–600°C. Wyniki badań wskazały na obecność w mikrostrukturze stopu fazy β w stanie przesyconym oraz wydzieleń fazy α, począwszy od temperatury starzenia 400°C. Twardość próbek stopu wyznaczono w stanie po przesycaniu oraz w całym zakresie temperatur starzenia. W stanie przesyconym (oziębionym w wodzie od 800°C) odnotowano minimalną twardość stopu, tj. 236 HV, której odpowiadała największa odporność na pękanie (KV = 109,5 J). Wraz ze wzrostem temperatury starzenia w zakresie 350–600°C obserwowano spadek odporności na pękanie stopu. Wykazano, że w stanie po przesycaniu oraz przesycaniu i starzeniu przełomy próbek są quasi-kruche, o różnym udziale objętościowym przełomu międzykrystalicznego i transkrystalicznego.

EN

The aim of the study was to evaluate the microstructure and selected mechanical properties of the Ti24Nb4Zr8Sn alloy in the state after supersaturation, i.e. cooling in water from the selected annealing temperature (800°C) and ageing in the temperature range 350–600°C. The test results indicated the presence of the β phase in the supersaturated state in the alloy microstructure and the α phase precipitates – starting from the ageing temperature of 400°C. The hardness of the alloy samples was determined in the state after supersaturation and throughout the entire ageing temperature range. In the supersaturated state (cooled in water from 800°C), the minimum hardness of the alloy was recorded, i.e. 236 HV, which corresponds to the highest impact energy (KV = 109.5 J). A decrease in the fracture toughness of the alloy was observed with the increase in the ageing temperature in the range of 350–600°C. It has been shown that in the state after supersaturation, supersaturation and ageing, the fractures of the samples are quasi-brittle with a different volume fracture of the intercrystalline and transcrystalline fracture.

12

Simulation of the effect laminate sequence on delamination mode-I with elastic couplings

Alhussein Mustafa Abd, Ameer Zuhair Abdul, Hamzah Ahmed Fadhil

Diagnostyka

|

2022

|

Vol. 23, No. 2

no. art. 2022211

EN

A numerical study using the ANSYS 19.R3 environment is discussed in this research. This environment depends on the Virtual Crack Closure Technique (VCCT) method to test a double cantilever beam (DCB) according to the ASTM D5528 standard. Four kinds of laminate stacking sequences were considered. According to the results, the distribution of the strain energy release rates obtained along the delamination front in bending-extension and extension-twisting coupling had a good affinity with bending-extension coupling. At the same time, critical fracture toughness values were estimated to be around 87.9% of critical fracture toughness values bending-extension coupling. These results are proof of the bending-extension and extensiontwisting coupling success while testing the proximity to bending-extension coupling results of the DCB beam. These findings are compatible with the standard ASTM D5288. Therefore, the bending-extension and extension-twisting coupling provide a good indication of the delamination resistance during buckling tests of the composite.

13

Effect of Cooling Rate on Mechanical Properties of New Multicomponent Fe-Based Amorphous Alloy During Annealing Process

Rezaei-Shahreza Parisa, Redaei Hossein, Moosavi Parisa, Hasani Saeed, Seifoddini Amir, Jeż Bartłomiej, Nabiałek Marcin

Archives of Metallurgy and Materials

|

2022

|

Vol. 67, iss. 1

251--254

EN

Fe-based bulk metallic glasses (BMGs) have been extensively investigated due to their ultrahigh strength and elastic moduli as well as desire magnetic properties. However, these BMGs have few applications in industrial productions because of their brittleness at room temperature. This study is focused on the effect of cooling rate on the mechanical properties (especially toughness) in the Fe41Co7Cr15Mo14Y2C15B6 BMG. For this aim, two samples with the mentioned composition were fabricated in a water-cooled copper mold with a diameter of 2 mm, and in a graphite mold with a diameter of 3 mm. The formation of crystalline phases of Fe23(B,C)6, α-Fe and Mo3Co3C based on XRD patterns was observed after the partial crystallization process. To determine the toughness of the as-cast and annealed samples, the indentation technique was used. These results revealed that the maximum hardness and toughness were depicted in the sample casted in the water-cooled copper mold and annealed up to 928°C. The reason of it can be attributed to the formation of crystalline clusters in the amorphous matrix of the samples casted in the graphite mold, so that this decrease in the cooling rate causes to changing the chemical composition of the amorphous matrix.

14

Experimental investigation on mode II fracture performance of old-new concrete

Liu Shuang, Shi Zhenwu, Jiang Tao, Wang Huili

Archives of Civil Engineering

|

2022

|

Vol. 68, nr 3

469--480

EN

The old-new concrete interface is the weakest part in the composite structure, and there are a large number of microcracks on the interface. In order to study the mode II fracture performance of the bonding surface of old-new concrete, the effect of planting rebar and basalt fiber is investigated. Nine Z-shaped old-new concrete composite specimens with initial cracks are made. Nine shear fracture load-displacement curves are obtained, and the failure process and interface fracture are discussed. On this basis, the mode II fracture toughness and fracture energy are obtained. The regression equations for fracture toughness and fracture energy are deduced with analysis of variance (ANOVA). The results show that fracture toughness and fracture energy increase with the increase of planting rebar number and basalt fiber content. With the increase of the planting rebar number, mode II fracture toughness and fracture energy increase more significantly. Planting rebar is the major factor for mode II fracture performance.

15

Fracture toughness, wear, and microstructure properties of aluminum/titanium/steel multi-laminated composites produced by cross-accumulative roll-bonding process

Wang Yaping, Tayyebi Moslem, Assari Amirhossein

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 1

art. no. e49, 2022

EN

For more than a decade many researchers have been developing new ways to produce laminated composites. In this paper, aluminum/titanium/steel multi-laminated composites were fabricated by the cross accumulative roll bonding (CARB) process, and effects of different rolling passes on microstructure, and mechanical properties were investigated. As the number of rolling passes increased, in spite of having no voids and cracks, more instabilities were observed on titanium and steel layers. With regard to mechanical properties, by increasing the rolling passes, the values of ultimate and yield strength, as well as elongation fell, because of the non-uniform distribution of hard layers within the aluminum matrix. Based on scanning electron microscopy (SEM) images, both ductile and cleavage modes of fracture were observed on fracture surfaces. Furthermore, with an increase in the number of rolling passes, the values of fracture toughness pertaining to the crack initiation declined on account of the increased probability of delamination. Plus, the trend of the R-curves was mainly downward due to the growing number of interfaces within the matrix by increasing the number of passes; nonetheless, the upward trend of these curves may be attributed to the ductile Al matrix in which the path of cracks can be bridged. Also, based on the results of wear tests, different wear mechanisms such as adhesion, abrasion, and delamination were observed, and with an increase in the number of rolling passes, the amount of weight loss showed a decline which was due to the rise of hardness concerning the strain-hardened layers.

16

Experimental Determination of the Mode I Fracture Toughness in FRP Laminates with Hybrid Delamination Interfaces

Rzeczkowski Jakub, Samborski Sylwester, Prokopek Katarzyna

Advances in Science and Technology. Research Journal

|

2022

|

Vol. 16, no 5

129--135

EN

This paper aims at experimental research of the effect of hybrid interface (carbon/glass fibers) on delamination resistance in unidirectional fiber reinforced polymer (FRP) composite laminates under the mode I opening load conditions. Three group of laminates exhibiting different combinations of reinforcing materials at delamination plane were tested. Critical strain energy release rates were determined by using the double cantilever beam (DCB) tests in accordance with the ASTM D5528 Standard. Values of the GIC were calculated by using classical data reduction schemes and they were compared with values obtained by using an alternative compliance based beam method (CBBM). For precise detection of delamination onset all tests were additionally supported by registration of the acoustic emission (AE) signal. Contribution of mixed-modes were evaluated by using numerical finite element analysis. Obtained outcomes revealed, that differences in the mode I c-SERR values obtained by using four different methods were insignificant. Moreover, the greatest value of the GIC was determined for laminates with hybrid interface and it was equal 0.24 N/mm.

17

Analysis of deformation and forms of destruction of coating-substrate systems

Chronowska-Przywara Kinga

Tribologia

|

2021

|

nr 4

7--14

EN

The paper presents the results of fracture testing of a coating-substrate system subjected to a concentrated contact load and during a scratch test. A diamond indenter with rounding radii in the range 20-500 µm was used under the tests. Systems with CrN coatings in the range of 1 to 5 µm applied to austenitic steel X5CrNi18-10 were analysed. In the paper, the effect of coating thickness on deformation and fracture of the coating and substrate in the load range of 1 and 3 N is analysed. Cohesion and adhesion sites of the coating to the substrate were determined. Optical profilometer images, scanning microscope images, and Micro Combi Tester images – CSM Instruments were used to analyse Lc1, Lc2, and crack locations. It was observed that, as the indenter radius increases, cracks in the coating-substrate system develop at increasing loads. Average critical forces are also higher with indenters of 200–500 µm. In the case of indentation only, with the indenter’s radius of 500 um, it is 750 Nm for the thinnest 1 µm coating and 1750 Nm for the 5.2 µm coating.

PL

W artykule przedstawiono wyniki badań pękania układu powłoka–podłoże poddanych obciążeniu działającym w styku skoncentrowanym oraz podczas testu zarysowania. Do badań użyto diamentowego wgłębnika o promieniach zaokrąglenia z zakresu 20–500 µm. Analizowano układy z powłokami CrN w zakresie od 1 do 5 µm nałożone na stal austenityczną X5CrNi18-10. W artykule analizowano wpływ grubości powłok na deformacje i pękanie powłoki i podłoża w zakresie obciążenia 1 i 3 N. Wyznaczono miejsca kohezji i adhezji powłoki do podłoża. Do analizy Lc1, Lc2 oraz lokalizacji pęknięć użyto obrazów z profilometru optycznego, zdjęć z mikroskopu skaningowego i zdjęć z Micro Combi Testera – CSM Instruments. W wyniku przeprowadzonych badań zauważono, że wraz ze wzrostem promieniem zaokrąglenia wgłębnika, pęknięcia układu powłoka–podłoże powstają przy coraz większych obciążeniach. Średnie wartości sił krytycznych również jest większe przy stosowaniu wgłębników 200–500 µm. W przypadku samej indentacji przy promieniu wgłębnika 500 µm wynosi 1 µm, 750 Nm, natomiast dla powłoki 5,2 µm 1750 Nm.

18

Analiza porównawcza własności dwóch niekonwencjonalnych superwytrzymałych stali typu maraging do zaawansowanych zastosowań konstrukcyjnych

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

|

2021

|

nr 1-2

32--36

PL

W artykule analizowano własności i mikrostrukturę dwóch wytapianych próżniowo niekonwencjonalnych stali typu maraging: wysokokobaltowej (0,23C-11,5Ni-13,4Co-1,5Mo) i bezkobaltowej (19Ni-4Mo-1Ti). Obie stale miały granicę plastyczności wynoszącą powyżej 1600 MPa i odporność na pękanie (K1C) wyższą od 70 MPa·m1/2. Bardzo wysokie wartości wytrzymałości i odporności na pękanie uzyskane dla badanych stali umożliwiają wykorzystywanie ich do wielu zaawansowanych zastosowań konstrukcyjnych.

EN

The article analyses the properties and microstructure of two unconventional vacuum melted maraging steels: high-cobalt (0.23C-11.5Ni- -13.4Co-1.5Mo) and cobalt-free (19Ni-4Mo-1Ti). Both steels had the yield strength of above 1600 MPa and the fracture toughness (K1C) of over 70 MPa·m1/2. The very high strength and fracture toughness values obtained for the tested steels make them suitable for many advanced structural applications.

19

Experimental and numerical investigation on specimen geometry effect on the ctod value for VL-E36 shipbuilding steel

Kowalski Jakub

Polish Maritime Research

|

2021

|

nr 3

110--116

EN

There are special cases in the marine industry, where additional material tests, such as the fracture toughness test, must be performed. Additional fracture toughness tests, such as CTOD (Crack Tip Opening Displacement), are typically performed on three-point bend specimens. The dimension that defines all the specimen dimensions is the thickness of the material to be tested. It is recommended by classification societies (e.g. DNVGL) to test specimens that are twice as high as the material thickness. The width determines the length and, therefore, the weight of the specimen which, for a 100 mm plate is over 140 kg. Current ASTM E1820, BS7448-1 and ISO 12135 testing standards also allow for proportions other than those recommended. This results in a much smaller test piece. Reducing the specimen size allows the testing machine to achieve lower forces than a specimen with a width to thickness ratio of two. This paper presents the effect of changing the specimen geometry on CTOD test results. Research was performed for specimens with a height to thickness ratio of one and two. Abaqus software was used for numerical calculations. The numerical results were, at selected points, verified experimentally.

20

Improvement of fracture toughness in dense ATZ composites prepared from zirconia powders with different yttria content

Grabowy Marek, Delikhovskyi Yurii, Wilk Agnieszka, Pędzich Zbigniew

Composites Theory and Practice

|

2021

|

R. 21, nr 4

161--168

EN

Alumina toughened zirconia (ATZ) composites with 2.3 vol.% Al2O3 (ATZ-B) and 12.3 vol.% Al2O3 (ATZ-10) were fabricated. The used starting zirconia powders were prepared as a mixture of powders with different yttria content. The alumina additive was commercially available Al2O3 powder. The specific preparation method and optimized sintering conditions allowed us to achieve ATZ products with exceptional properties. These properties were compared with 3Y-TZP sintered samples prepared from commercial powder (Tosoh). The structural and mechanical properties of the investigated ATZ composites were systematically studied. The microstructures were observed by scanning electron microscopy (SEM) on polished and thermally etched surfaces, then the micrographs were binarized and subjected to stereological analysis. Dense (> 99% of relative density), uniform and pore-free microstructures with homogeneously distributed Al2O3 inclusions without any visible agglomerates were obtained. The Vickers hardness and Young’s modulus were enhanced according to the rule of mixtures for the composites. The mechanical behaviour was especially oriented towards increasing the fracture toughness. The K1c parameter reached the extraordinary value of 12.MPa⋅m1/2 for ATZ-B and 9.8 MPa⋅m1/2 for ATZ-10. Comparatively, K1c of the 3Y-TZP reference material was 5.1 MPa⋅m1/2. The mechanisms contributing to the increase in K1c were identified to explain the reason for such a large improvement in the fracture toughness. The investigations were particularly focused on crack propagation analysis. The identified mechanisms include crack path deviation and mixed transgranular-intragranular crack migration (crack bridging), crack propagation through the Al2O3 grains and frequent changes in the fracture propagation directions of a high angle (close to even 90°). Nevertheless, the occurrence of t→m (tetragonal to monoclinic) transformation of the ZrO2 phase was considered to be the main toughening factor. Due to the specific method of preparation, leading to an intensification of yttrium diffusion during sintering, the final microstructure revealed very small grains of a tetragonal zirconia phase. These grains exhibited high transformability, which was the main reason for the distinctin crease in fracture toughness.