scholarly journals Fatigue and fracture mechanical properties of selected concrete for subtle precast structural elements

2020 ◽  
Vol 310 ◽  
pp. 00033
Author(s):  
Stanislav Seitl ◽  
Petr Miarka ◽  
Vlastimil Bílek
Keyword(s):  
Mechanical Properties ◽  
Precast Concrete ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Structural Elements ◽  
Mechanical Fracture ◽  
Fatigue And Fracture ◽  
Natural Aggregates ◽  
Concrete Elements ◽  
Bearing Part

Precast concrete elements used as a civil structure are usually made of a cement-based matrix and natural aggregates (such as sand, gravel, crushed stone, etc.). These structures are usually exposed not only to a static load but also to a cyclic load if they load the bearing part of a bridge (traffic etc.). The knowledge of fatigue and fracture mechanical characteristics is important in designing and modelling new structures. This paper introduces and compares fracture mechanical properties obtained from static and fatigue tests for three kinds of concrete. The focus was set on the bulk density, flexural and compressive cube strength, fracture toughness and fatigue properties (S−N − Wöhler curve). All of these tests are important for a practical application in the design of precast concrete structures. The experimental results were statistically analysed and they showed that the fatigue and mechanical fracture properties improved with improved mechanical parameters of concrete.

scholarly journals Development in mechanical and fatigue properties of AA6061/AL2O3 nanocomposites under stirring temperature (ST)

2021 ◽  
Vol 4 (12(112)) ◽  
pp. 47-52
Author(s):  
Raad Mohammed Abed ◽  
Ali Yousuf Khenyab ◽  
Hussain Jasim M. Alalkawi
Keyword(s):  
Mechanical Properties ◽  
Cost Effective ◽  
Fatigue Tests ◽  
Core Material ◽  
Fatigue Properties ◽  
Uniform Distributions ◽  
Al2o3 Composite ◽  
Structural Applications ◽  
The Matrix ◽  
High Fatigue

Aluminum is expected to remain the core material for many critical applications such as aircraft and automobiles. This is due to the high resistance to different environmental conditions, desired and manageable mechanical properties, as well as high fatigue resistance. Aluminum nanocomposites such as AA6061/Al2O3 can be made in many ways using a liquid metallurgy method. The main challenges for this method in the production of nanocomposites are the difficulties of achieving a uniform distribution of reinforcing materials and possible chemical reactions between the reinforcing material and the matrix. For structural applications exclusive to aerospace sectors. The growing cost-effective nanocomposites mass production technology with essential operational and geometric flexibility is a big challenge all the time. Each method of preparing AA6061/Al2O3 nanocomposites can provide different mechanical properties. In the present study, nine nanocomposites were prepared at three stirring temperatures (800, 850, and 900 °C) with the level of Al2O3 addition of 0, 5, 7, and 9 wt %. The results of tensile, hardness and fatigue tests revealed that the composite including 9 wt % Al2O3 with 850 °C stirring temperatures has the best properties. It was also revealed that the 850 °C stirring temperature (ST) with 9 wt % Al2O3 composite provide an increase in tensile strength, VHN and reduction in ductility by 20 %, 16 % and 36.8 % respectively, compared to zero-nano. Also, the fatigue life at the 90 MPa stress level increased by 17.4 % in comparison with 9 wt % nanocomposite at 800 °C (ST). Uniform distributions were observed for all nine microstructure compositions.

Fatigue Properties of 3D Welded Thin Structures

2020 ◽  
Author(s):  
Seyed M. Allameh ◽  
Avery Lenihan ◽  
Roger Miller ◽  
Hadi Allameh
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Fatigue Testing ◽  
Interfacial Area ◽  
Tensile Tests ◽  
Orientation Dependence ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Mig Welding ◽  
Welded Structures

Abstract Additive manufacturing technology has matured enough to produce real industrial components. A newer method of 3D printing is the deposition of molten metal beads using a MIG weld torch. This involves a 3D printer equipped with a MIG torch layering the metals in desired shapes. It allows the fabrication of components made of MIG weld wires, currently available from various elements including Cu, Al, steel and alloys. Some of these structures made by 3D welding will have applications in critical load bearing conditions. The reliability of such components will be vital in applications where human lives are at stake. Tensile tests are conducted to verify the required strength of the fabricated parts which will undergo monotonic loading; however, fatigue tests are required for cases where cyclic loading will take place. Conventional tensile and fatigue testing requires macro-scale samples. With MIG welding, it is possible to make thin-walled structures. Fatigue testing on samples extracted from thin walls is made possible by microtesting. This study is focused on the mechanical properties of 3D welded structures made from MIG welding wires. Our earlier results showed orientation dependence of mechanical properties in 3D welded structures. They also showed the effect of substrates in expression of the orientation dependence. Welding on metal substrate produces weld beads that are harder at the substrate interfacial area. However, for structures welded on ceramics, the opposite is true. They exhibit a softer substrate interfacial area and a relatively harder top. Our newer results show fatigue properties of structures made by 3D welding. Microsamples measuring 0.2 mm × 0.2 mm × 1.0 mm were extracted from metal beads using a CNC mill along with an EDM. The contours of the samples were machined by milling and the back side was cut by electro discharge machining. Specimens were then polished to the desired size and mounted in the grippers of an E1000 Instron load frame. WaveMatrix® application software from Instron was used to control the machine and to obtain testing data. Fatigue tests were performed, and life cycles were determined for various stress levels up to over 5 million cycles. The preliminary results of tensile tests of these samples show strength levels that are comparable to those of parent metal, in the range of 600–950MPa. Results of fatigue tests show high fatigue lives associated with relatively high stresses. The preliminary results will be presented and the implications of the use of 3D welded rebar in 3D printing of reinforced concrete structures will be discussed.

Fatigue Properties of Al-Li Plates Joined by Friction Stir Welding

2008 ◽  
Vol 385-387 ◽  
pp. 849-852 ◽  
Author(s):  
Pasquale Cavaliere ◽  
Francesco W. Panella ◽  
Antonio Squillace
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Testing Machine ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Control Mode ◽  
Fatigue Properties ◽  
Amplitude Control ◽  
Friction Stir

Al-Li alloys are characterized by a strong anisotropy in mechanical properties and microstructure with respect to the rolling direction. Plates of 2198 Al-Li alloy were friction stir welded by employing maximum rotation speed: 1000 rev/min and welding speed of 80 mm/min, both in parallel and orthogonal directions with respect to the rolling one. The joints mechanical properties were evaluated by means of tensile tests at room temperature. In addition, fatigue tests performed with a resonant electro-mechanical testing machine under constant amplitude control up to 250 Hz loading, were conducted in axial control mode with R(σmin/σmax)=0.33, for all the welding and rotating speed conditions. The fatigue crack propagation experiments were performed by employing single edge notched specimens.With the aim to characterize the weld performances, both the microstructure evolution at jointed cross sections, related to the welding variables, and the fractured surfaces were respectively analyzed by means of optical and scanning electron microscopy.

Three Ways of Sampling and Fatigue Test Results of Steel P92

2014 ◽  
Vol 891-892 ◽  
pp. 273-277
Author(s):  
Josef Volák ◽  
Zbynek Bunda
Keyword(s):  
Mechanical Properties ◽  
Power Plant ◽  
Fatigue Test ◽  
Fatigue Tests ◽  
Energy Industry ◽  
Fatigue Properties ◽  
Test Results ◽  
Steam Turbines ◽  
Standard Samples ◽  
Energy Component

This paper describes the fatigue properties of the steel P92. This material is widely used in the energy industry, especially for pipes and pipe bends of supercritical steam turbines. Steel P92 is alloyed with 2 % of tungsten compared to steel P91. This increases a creep strenght of the material. It is possible to reduce wall thickness of the P92 pipe up to about 20%. Fatigue tests were carried out on standard samples and compared with SFT samples (Small Fatigue Test). Using the device SSam 2 made by company Rolce Royce, it is possible to gently remove a samples from energy component without power plant shutdowns. Consider these correlations, i tis possible to determine mechanical properties of the material from small amount of removed experimental material.

Effect of Fly Ash and Activator on Performance of Steam-Cured Concrete

2010 ◽  
Vol 113-116 ◽  
pp. 1013-1016 ◽  
Author(s):  
Zhi Min He ◽  
You Jun Xie ◽  
Guang Cheng Long ◽  
Jun Zhe Liu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Precast Concrete ◽  
Early Age ◽  
Flexure Strength ◽  
Concrete Elements ◽  
Chemical Activator

In precast concrete elements manufacturing, steam-cured concrete incorporating 30% fly ash encountered the problem of a too low demoulding compressive strength. To resolve it, this paper developed a new steam-cured concrete (AFSC) incorporating fly ash and a chemical activator. Experiments were conducted to investigate the mechanical properties of AFSC. The corresponding mechanism was also discussed by testing the microstructure of concrete. Results indicate that the demoulding compressive strength of AFSC can meet production requirements, and compressive and flexure strength of AFSC at later ages increase well. Compared with that of ordinary steam-cured concrete, AFSC has a higher tensile strength, and the capability of AFSC to resist cracks is enhanced remarkably. At an early age, addition of the chemical activator can distinctly accelerate the extent of hydration of the fly ash cement systems, and thus the microstructure of concrete becomes denser.

Connections in Precast Concrete Elements

2016 ◽  
Vol 691 ◽  
pp. 376-387 ◽  
Author(s):  
Ivan Hollý ◽  
Ivan Harvan
Keyword(s):  
Structural Integrity ◽  
Precast Concrete ◽  
Concrete Structures ◽  
Structural Elements ◽  
Entire Structure ◽  
Engineering Department ◽  
Final Design ◽  
Structural Engineer ◽  
Concrete Elements

The structural integrity of precast concrete structures depends mainly on the connections between the precast structural elements. The purpose of a connection is to transfer loads, restrain movement, and/or to provide stability to a component or an entire structure. Therefore, the design of connections is one of the most important aspects in the design of precast concrete structures. All connections should design with valid codes. Every precasters have developed connection details over the years that suit their particular production and erection preferences. It is common, that the structural engineer to show loads and connection locations and allow the successful manufacturer’s engineering department to provide the final design and details of the connections.

scholarly journals Performance of Isolated Footings Reinforced Randomly by Glass Fiber

2019 ◽  
pp. 1-8
Author(s):  
Elsayed El Kasaby ◽  
Mohammad Farouk A. Bdelmagied
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Fatigue Properties ◽  
Structural Elements ◽  
Fiber Glass ◽  
Forming Process ◽  
Rectangular Shape ◽  
Concrete Crack ◽  
Reinforced Steel ◽  
Positive Effect

Fiber glass reinforced concrete (FGRC) is used form any structural elements due to its high mechanical properties, particularly flexural strength. As the concrete crack forming process accelerates and the probability of sudden fractures increases. There were various methods to eliminate this weakness of concrete. One of most common methods was employed of randomly distributed fiber. In this paper, two types of isolated footings were utilized, square and rectangular shape reinforced by a fiber glass with a length of 18 mm and having a rate of (0.20, 0.30, 0.35, 0.40, 0.50 and 1.00%) of weight, to experimentally investigate the tensile and fatigue properties of footings The results of FGRC were compared with the reinforced steel concrete. The results revealed that FGRC has a positive effect on the tensile and fatigue properties of isolated footing, especially with higher percentage of used fiber glass.

scholarly journals Low Cycle Fatigue Properties of a Low Rare Earth-Containing Me20 Magnesium Alloy

2021 ◽  
Author(s):  
Ke Wang
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Automotive Industry ◽  
Earth Element ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Element Addition

A newly-developed rare earth-containing ME20 magnesium alloy was studied in this thesis. As a potential structural material for applications in automotive industry, low cycle fatigue properties are inevitably required. Strain-controlled low cycle fatigue tests were conducted on this wrought alloy with different specimen orientations. Microstructure, tensile behaviors and low cycle fatigue properties were studied. The effect of different specimen orientations on microstructures and mechanical properties were also discussed. Results show that rare earth element addition in this alloy helped weaken the texture and specimen orientations had little influence over microstructure and fatigue properties of this magnesium alloy.

scholarly journals Effect of Solidification Time on Microstructural, Mechanical and Fatigue Properties of Solution Strengthened Ferritic Ductile Iron

Metals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 24 ◽  
Author(s):  
Thomas Borsato ◽  
Paolo Ferro ◽  
Filippo Berto ◽  
Carlo Carollo
Keyword(s):  
Mechanical Properties ◽  
Ductile Iron ◽  
Fatigue Tests ◽  
Solidification Time ◽  
Fatigue Properties ◽  
Matrix Structure ◽  
Green Sand ◽  
Cast Sample ◽  
Iron Castings ◽  
Scanning Electron

Microstructural, mechanical, and fatigue properties of solution strengthened ferritic ductile iron have been evaluated as functions of different solidification times. Three types of cast samples with increasing thickness have been produced in a green sand automatic molding line. Microstructural analyses have been performed in order to evaluate the graphite nodules parameter and matrix structure. Tensile and fatigue tests have been carried out using specimens taken from specific zones, with increasing solidification time, inside each cast sample. Finally, the fatigue fracture surfaces have been observed using a scanning electron microscope (SEM). The results showed that solidification time has a significant effect on the microstructure and mechanical properties of solution strengthened ferritic ductile iron. In particular, it has been found that with increasing solidification times, the microstructure becomes coarser and the presence of defects increases. Moreover, the lower the cooling rate, the lower the tensile and fatigue properties measured. Since in an overall casting geometry, same thicknesses may be characterized by different microstructures and mechanical properties induced by different solidification times, it is thought that the proposed methodology will be useful in the future to estimate the fatigue strength of cast iron castings through the numerical calculation of the solidification time.

scholarly journals Recycled Aggregates from Construction and Demolition Waste in the Manufacture of Urban Pavements

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6605
Author(s):  
Manuel Contreras-Llanes ◽  
Maximina Romero ◽  
Manuel Jesús Gázquez ◽  
Juan Pedro Bolívar
Keyword(s):  
Precast Concrete ◽  
Breaking Load ◽  
Construction And Demolition Waste ◽  
Recycled Aggregates ◽  
Waste Streams ◽  
Demolition Waste ◽  
Class 1 ◽  
Natural Aggregates ◽  
Precast Elements ◽  
Concrete Elements

Construction and Demolition Waste (CDW) is among the largest waste streams in the world. Therefore, within the Circular Economy concept, there is a growing interest in its reuse. The purpose of this work was to study the use of recycled aggregates (RAs) obtained by a specific separation method from CDW, replacing natural aggregates (NAs) in the manufacture of precast concrete elements, such as kerbstones and paver blocks. The physical and technological properties of precast products formulated with RAs were analysed in accordance with current regulations, comparing them with those of commercial products manufactured with NAs. The results indicated that partial or total substitution of NAs by RAs increased the water absorption and apparent porosity values of the precast elements while reducing the bulk density and compressive strength. However, all units manufactured with RAs showed breaking load values higher than the minimum required by EN 1338 and, in some cases, slightly higher average tensile strength values than the reference material. In addition, some of the compositions including RAs gave rise to pieces that, according to their flexural strength, were classified as class 1 and marked S in accordance with EN 1340. According to abrasion resistance, in most cases, the precast elements are classified as Class 4 and I (≤20 mm). Finally, precast concrete produced from RAs satisfies the tolerance requirements for classification as class 3 (≤1.5 kg m−2). Therefore, it could be suitable for use in high pedestrian or traffic areas.

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