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1

Study on tensile fracture failure of a steel plate with a surface crack

Chong Zhewen, Tao Jing, Xie Yuehui, Wu Dongrong, Li Tao

Journal of Theoretical and Applied Mechanics

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2023

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Vol. 61 nr 2

343--354

EN

In order to study the effect of different surface crack parameters on the fracture failure of steel plate, the model was established by FEM. The results showed that the edge surface crack has the greatest influence on the fracture failure of the steel plate, and for non-edge surface cracks, the central surface crack has the greatest influence on the fracture failure of the steel plate. The larger the a/t and the smaller the a/c, the easier the steel plate fracture failure occurs. The a/c has a certain influence on the variation law of K and the position where Kmax appears.

2

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

Kim Jong-Gwan

Journal of Sustainable Mining

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2020

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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.

3

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

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2017

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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.

4

Stiffness behavior of hybrid laminated composites with surface crack

Güneş A., Şahin Ö. A.

Archives of Materials Science and Engineering

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2016

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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.

5

Effect of surface crack depth on hybrid laminated composites

Güneş A., Şahin Ö. S.

Archives of Materials Science and Engineering

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2016

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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.

6

Indentation theory on orthotropic materials subjected to a frictional moving punch

Zhou Y. T., Lee K. Y., Jang Y. H.

Archives of Mechanics

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2014

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Vol. 66, nr 2

71--94

EN

The present article establishes a general theory of frictional moving contact of orthotropic materials indented by a moving rigid punch with various punch profiles. The punch moves to the right or left at a constant speed with the shear stress arising inside the contact region. The motion should be subsonic. By using Galilean transformation and Fourier transform, a singular integral equation of the second kind is obtained, solution of which has a non-square-root or unconventional singularity. Numerical results are presented to show the influences of relative moving velocity and the friction coefficient on surface in-plane stress for each case of the four types of punches, which demonstrates that the surface crack initiation and propagation in load transfer components more likely occur at the trailing edge. The present theory provides a basis for explaining the surface damage mechanism of orthotropic materials under an indentation loading and for exploiting the physics behind the different punch profiles.

7

Slab FEM simulation of hot bar rolling

Aksenov S., Fabik R., Kliber J., Kotas M.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 8

458-460

EN

It is proposed that three dimensional problem of shape rolling be simplified by solving in approximately by the finite element method. A computer software that has been developed on slab method basis to model the deformation of metal during shape rolling eliminates having to conduct multiply costly and time consuming commercial trials and allows innovations to be introduced more quickly. In the given work, computer modelling was carried out to analyse behaviour of potential defect during hot rod rolling. A development of methods and working procedures aimed to avoid the occurrence of surface defects on rods requires to know the origin of the defects and characteristics of their behaviour in the course of rolling. The full-scale experiments designed to measure such characteristics are expansive and complicated, so mathematic simulation is an optimal way of solving such problems. With respect to extreme times necessary for the calculation, it was not realistic to model all 18 passes by complete 3D simulation. Use of the SPLEN finite element code based on FSEM principles has allowed to execute simulation of all 18 passes for rather short time.

PL

Zaproponowano rozwiązanie trójwymiarowego zagadnienia walcowania kształtowego przez zastosowanie uproszczonego, przybliżonego rozwiązania metodą elementów skończonych (MES). Oprogramowanie komputerowe, które zostało opracowane na podstawie metody slab dla modelu odkształcenia metalu w czasie walcowania kształtowego, umożliwia wyeliminowanie kosztownych, i czasochłonnych prób przemysłowych oraz pozwała na to, że innowacyjne rozwiązania będą wprowadzone zdecydowanie szybciej. W przedstawionej pracy, symułacja numeryczna była prowadzona w cełu analizy zachowania się potencjalnych defektów powstających na powierzchni prętów w czasie walcowania na gorąco. Opracowane metody i procedury pracy, zmierzające do ograniczenia występowania defektów powierzchniowych na prętach, wymagają rozpoznania źródła defektów oraz charakterystyki ich zachowania się w czasie procesu walcowania. Eksperymenty w skali rzeczywistej, zaprojektowane w celu zmierzenia tego typu charakterystyk, są bardzo rozbudowane i skomplikowane, więc numeryczna symulacja stanowi optymalną drogę do rozwiązania tego typu problemów. Przy całkowitej symulacji 3D tego procesu, z wykorzystaniem maksymalnego czasu dla niezbędnych obliczeń, nie uzyskano rzeczywistego odwzorowania wszystkich 18 przepustów. Stąd, opierając sę na założeniach FSEM, zastosowano kod SPLEN elementu skończonego, co pozwoliło na wykonanie symulacji wszystkich 18 przepustów w zdecydowanie krótszym czasie.

8

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

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2008

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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.

9

Interaction of surface and internal cracks in railhead

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

Computer Assisted Mechanics and Engineering Sciences

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2007

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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.

10

Determination of crack propagation angle for surface crack subjected to lubricated contact conditions

Zafošnik B., Mishuris G., Ren Z., Flašker J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2005

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z. 82

219-226

EN

The paper describes the role of different terms in asymptotic expansion of the stress field around surface crack tip under lubricated contact conditions. The maximum tangential stress (MTS) crack propagation criterion is modified to account for the influence of internal pressure along the crack surfaces due to trapped fluid. The developed model is used to simulate surface crack growth on a gear tooth flank. Comparison with experimental results shows that the modified MTS criterion predicts the kink angle more accurately than the original criterion.