Wyniki wyszukiwania - BazTech

1

Measurement of surface subsidence and ground collapse caused by underground mining in the Boleo Copper District, Mexico

Kim Jong-Gwan

Journal of Sustainable Mining

|

2020

|

Vol. 19, iss. 2

126--134

EN

Subsidence and vertical movements in mines are a challenge in mining operations. To qualify as a controlled mine site, ground movements must be measured regularly during mining operations. Boleo Copper District mine was monitored and the movement during mining operations was measured from Oct. 31, 2018 to March 15, 2019. The evaluation of vertical and horizontal movement was determined in four locations in the mine areas M303, M303S, M303 C, and M305. The exploitation area, which measured approximately 80 £ 90 m2 with a height of 2.4 m, impacted the surface in the form of cracks. These cracks were observed on the topographic surveys and varied during the mining operations from the beginning to the end. The final results indicated that the points with the greatest displacement were those in the central zone of the mine excavation (points #3, 5, and 6) and the displacement trend of the ground was toward this zone. In theory, the subsidence is typically lesser than the thickness of the extracted ore. In this case, the maximum subsidence was 1.15 m and the ore seam thickness was 2.4 m. The maximum possible subsidence is typically 55-65% of the extracted seam thickness; however, because chain pillars are generally left in place, and provide some support, this maximum possible subsidence is rarely reached. In this case, the maximum subsidence was 52% of the seam thickness.

2

Benefits of using amorphous metallic fibers in concrete pavement for long-term performance

Yang J. M., Shin H. O., Yoo D. Y.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 4

750--760

EN

This study aims to examine the implications of amorphous metallic fibers on the mechanical and long-term properties of concrete pavement. Two different amounts of amorphous metallic fibers were incorporated into concrete, and plain concrete without fibers was also adopted as comparison. Test results indicated that the overall mechanical properties of concrete were improved by including the fibers, and the improvement increased when a higher amount of fibers was used. In particular, the equivalent flexural strength and flexural strength ratio were substantially improved by incorporating the amorphous metallic fibers. This may enable the thickness of airfield concrete pavement to decrease. The resistance to surface cracking of concrete pavement by repeated wheel loading was also improved with the addition of amorphous metallic fibers. In addition, by adding 5 kg/m3 and 10 kg/m3 amorphous metallic fibers in concrete pavement, roughly 1.2 times and 3.2 times longer service life was expected, respectively, as compared to their counterpart (plain concrete). Based on a life cycle cost analysis, the use of amorphous metallic fibers in concrete pavement was effective at decreasing the life cycle cost compared to plain concrete pavement, especially for severe traffic conditions.

3

Stiffness behavior of hybrid laminated composites with surface crack

Güneş A., Şahin Ö. A.

Archives of Materials Science and Engineering

|

2016

|

Vol. 80, nr 2

49--52

EN

Purpose: The purpose of this paper investigates to stiffness behavior of hybrid laminated composites with surface crack. Design/methodology/approach: Hybrid laminated composites has 18 layers and 90x25 mm size with two different layers line up. The low velocity impact test of hybrid laminated composites carried on 3 m/sec with a/t=0.4 and a/c=0.4 surface crack parameters. Findings: The results are presented as the change of force-time and force-displacement graphs. As a result of this study, effects of stacking sequence on hybrid composite plates were analysed. Research limitations/implications: The research of stiffness behavior or dynamic response of hybrid laminated composites can contribute to developing new composite materials. Practical implications: These hybrid laminated composites materials could be used for different aviation areas. Originality/value: This paper is based on studies from Selçuk University and all the experiments and results were conducted by me.

4

Effect of surface crack depth on hybrid laminated composites

Güneş A., Şahin Ö. S.

Archives of Materials Science and Engineering

|

2016

|

Vol. 82, nr 1

38--41

EN

Purpose: The purpose of this paper researches to effect of different surface crack depth on hibrid laminated composites under low velocity impact forces. Design/methodology/approach: Hybrid laminated composites have 90x25 mm size and 18 layers with two different stacking sequence. Low velocity impact test of hybrid laminated composites with surface crack have been investigated with different a/t surface crack parameters and 3 m/sec velocity. Findings: The results are presented force-time and energy-time graphs than effects of different crack parameters were observed. As a result of this study, effects of surface crack depth on hybrid composite plates were analysed. Research limitations/implications: The research of dynamic behavior of hybrid laminated composites with surface crack can contribute to literature searches. Practical implications: These hybrid laminated composites materials could be used for different aviation areas. Originality/value: This paper is based on studies from Selçuk University and all the experiments and results were conducted by me.

5

Opracowanie półprzemysłowej technologii chłodzenia natryskowego, w oparciu o symulacje laboratoryjne i próby przemysłowe w celu ograniczenia pęknięć powierzchniowych na wlewkach COS

Marcisz J., Mazur A., Zdonek B., Burian W., Wittchen W.

Prace Instytutu Metalurgii Żelaza

|

2009

|

T. 61, nr 1

53-57

PL

Celem pracy było określenie możliwości uzyskania zmodyfikowanej strukturalnie warstwy przypowierzchniowej o odpowiednich właściwościach plastycznych na skutek dodatkowego chłodzenia wlewków ciągłych podczas ich odlewania przed klatką odginającą oraz opracowanie wytycznych do technologii chłodzenia wlewków po wyjściu z pierwszej klatki odginającej. Na podstawie prób przemysłowych, symulacji numerycznych i prób laboratoryjnych chłodzenia natryskowego opracowano półprzemysłową technologię dodatkowego chłodzenia podczas ciągłego odlewania przed odginaniem pasma w zakresie: rodzaju dysz chłodzących, liczby dysz chłodzących, parametrów mediów chłodzących, odległości dysz f: odścian wlewka dla wytypowanego gatunku stali i parametrów odlewania. Istotnym elementem technologii chłodzenia jest uzyskanie zmodyfikowanej mikrostrukturalnie warstwy o odpowiedniej grubości na obwodzie wylewka. W wyniku realizacji pracy opracowano koncepcję prototypu urządzenia do chłodzenia wlewków przed odginaniem pasma oraz koncepcję urządzenia do dodatkowego chłodzenia wlewków pomiędzy klatkami odginająco-prostującymi II i III. Umiejscowienie dodatkowego chłodzenia w tym miejscu stwarza możliwości uzyskania warstwy o zmodyfikowanej mikrostrukturze o znacznie większej grubości w porównaniu do możliwości układu zainstalowanego przed odginaniem.

EN

The purpose of the work was to determine the possibilities of obtaining the structurally modified surface layer with relevant plastic properties as a result of extra cooling of cast strands during casting upstream of the unbending stand and to develop the guidelines on technology for cooling strands upon leaning the first unbending stand. Based on the industrial tests, numerical simulations and laboratory tests of spray cooling the semi-industrial technology for extra cooling during the continuous casting before band deflection was developed with regard to: type of cooling nozzles, number of cooling nozzles, parameters of cooling media, distance of nozzles from ingot walls for specific steel grade, and casting parameters. The essential element of the cooling technology is to obtain the microstructurally modified layer with relevant thickness at strand circumference. As a result of the work the prototype construction of equipment for cooling of continuous strands before band deflection and the concept of equipment for extra cooling of strands between the deflecting-straightening stands II and III was developed. Locating the extra cooling at this point creates the possibilities to obtain a layer with modified microstructure and much higher thickness as compared to that provided by the system installed before deflection.

6

Opracowanie podstaw technologii chłodzenia natryskowego w celu ograniczenia pęknięć powierzchniowych na wlewkach COS

Marcisz J., Mazur A., Zdonek B., Żak A., Wittchen W.

Prace Instytutu Metalurgii Żelaza

|

2008

|

T. 60, nr 2

53-55

PL

Celem pracy było opracowanie podstaw technologii chłodzenia natryskowego modyfikującego strukturę warstwy przypowierzchniowej wlewków ciągłych, prowadzącego do zmniejszenia ilości i głębokości pęknięć powierzchniowych oraz określenie wytycznych do technologii przemysłowej dla wybranych grup gatunkowych stali i formatów wlewków. Przeprowadzono laboratoryjne próby natryskowego schładzania powierzchni odcinków wlewków ciągłych w celu opracowania parametrów chłodzenia wlewków COS oraz założeń do zaprojektowania i wykonania prototypu urządzenia do schładzania. Wykonano symulację numeryczną ciągłego odlewania z krótkotrwałym schładzaniem i ponownym nagrzewaniem warstwy powierzchniowej wlewków (320x270 mm) dla wytypowanego gatunku stali. Końcowym etapem pracy była przemysłowa próba schładzania powierzchniowego wlewków 320x270 mm na jednej żyle urządzenia COS z zastosowaniem zaprojektowanego i wykonanego w ramach pracy prototypu urządzenia oraz badania strukturalne weryfikujące skuteczność zastosowanego dodatkowego chłodzenia. Wyniki badań metalograficznych przypowierzchniowej warstwy wlewka ciągłego poddanego dodatkowemu chłodzeniu przed klatką ciągnąco-prostującą wykazały, że dla zastosowanego układu dysz chłodzących uzyskano modyfikację warstwy przypowierzchniowej wlewka ciągłego na głębokości max ok. 3 mm. Grubość warstwy zmodyfikowanej jest zgodna z obliczeniami numerycznymi. Zmodyfikowana struktura składa się z rozdrobnionych ziarn ferrytu i kolonii perlitu bez obecności niekorzystnych kolumnowych ziarn austenitu pierwotnego. W zmodyfikowanej warstwie przypowierzchniowej nie występowały mikropęknięcia.

EN

The purpose of the work was to develop the basis for technology for spray cooling to modify the structure of the surface layer of cast strands, leading to reduction in the number and depth of surface cracks and determination of the guidelines for industrial technology for selected groups of steel grades and formats of cast strands. The laboratory tests of spray cooling the surface of cast strand sections were carried out to develop the cast strand cooling parameters and assumptions to design and make the prototype of cooling device. The numerical simulation of continuous casting with short-term cooling followed by heating of the surface layer of cast strands (320x270 mm) was carried out for the designated steel grade. The final stage of the work was the industrial test of surface cooling of 320x270 mm cast strands conducted on one strand of the continuous casting machine using the prototype of the device designed and made as a part of this work and the structural tests to verify the efficiency of the applied additional cooling. The results of metallographic examinations of surface layer of the cast strand subject to additional cooling before the unbending stand showed that for the applied system of cooling nozzles the modification of the cast strand's surface layer was obtained at a maximum depth of approx. 3 mm. Thickness of the modified layer is in conformity with numerical calculations. The modified structure consists of refined ferrite grains and pearlite colonies without the presence of unfavourable columnar grains of original austenite. In the modified surface layer, there were no micro-cracks.

7

Computer and Practical Simulation of the Surface Crack Reducing on the Billet during Bar and Wire Rod Rolling Process

Kotas M., Gajdzica T., Aksenov S., Kliber J.

Hutnik, Wiadomości Hutnicze

|

2008

|

Vol. 75, nr 8

483-486

EN

The processors acting in the car industry make continuously a stress on producers of wires and rods to eliminate the occurrence of surface defects on the semi-finished products. A development of methods and working procedures aimed to avoid the occurrence of surface defects on wires and rods requires to know the origin of the defects and characteristics of their behaviour in the course of rolling. A set of practical tests examined the behaviour of an artificial crack in the course of rolling directly in realistic operation conditions of the continuous small-section rolling mill of rods and wires of Tfinecke żelezarny a.s. A crack was created on billets and, after rolling, detected in final wire or rod. In this relation, the applied way of detection of hot and cold surface defects in the course of production and processing of wires and rods is presented applying facilities working on a base of eddy current checking. Applying the FEM, numeric simulation of a crack behaviour was prepared in the course of deformation of the rolling stock caused by passing between rolls.

PL

Technologowie pracujący w przemyśle samochodowym stale wywierają nacisk na producentów prętów i walcówki, żądając usunięcia defektów powierzchniowych występujących w tych wyrobach. Rozwój metod i technologii wytwarzania w celu zmniejszenia częstości występowania wad powierzchniowych na prętach i walcówce wymaga wiedzy na temat pochodzenia wad i ich zachowywania się w trakcie procesu walcowania. W zakładach Tfinecke źelezarny a.s. badano zachowanie się specjalnie stworzonych pęknięć na powierzchni prętów i walcówki w warunkach rzeczywistego procesu ciągłego walcowania. Pęknięcie było wykonane na wsadzie, a następnie po procesie walcowania, wykrywane na powierzchni końcowego wyrobu. Do wykrywania defektów powierzchniowych, występujących na gorącej bądź zimnej powierzchni wyrobu w trakcie trwania procesu kształtowania, zastosowano urządzenia wykorzystujące metodę prądów wirowych. Stosując MES przeprowadzono numeryczną symulację zachowania się pęknięć podczas odkształcenia, przy przejściu wyrobu pomiędzy walcami.

8

Interaction of surface and internal cracks in railhead

Dhanasekar M., Han J., Qin Q. H.

Computer Assisted Mechanics and Engineering Sciences

|

2007

|

Vol. 14, No. 1

79-89

EN

This paper presents a two-dimensional model for the analysis of interaction between surface and internal cracks in the railheads subjected to wheel loading. The shape of the railhead, the surface crack and the internal crack are modelled as curved cracks defined by the theory of continuous distribution of dislocation in an infinite body. From the boundary conditions along these cracks, a system of singular integral equations is deduced. Influence functions in these singular integral equations are first expanded into the Cauchy kernel multiplying normal functions and later are reduced to a system of linear equations and solved numerically. Stress intensity factors (SIFs) of the surface crack tip are calculated from the numerical solution of distribution function along these cracks directly, eliminating need for any indirect integral method. The method does not require meshing and hence idealisation of the shapes of the cracks, thereby improving accuracy and reducing pre- and post processing efforts. Interaction between the internal crack and the surface crack is examined in detail through several examples.