• Title/Summary/Keyword: Alloy element

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Thermoelastic eigenfrequency of pre-twisted FG-sandwich straight/curved blades with rotational effect

  • Souvik S. Rathore;Vishesh R. Kar;Sanjay
    • Structural Engineering and Mechanics
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    • v.86 no.4
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    • pp.519-533
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    • 2023
  • This work focuses on the dynamic analysis of thermal barrier coated straight and curved turbine blades modelled as functionally graded sandwich panel under thermal environment. The pre- twisted straight/curved blade model is considered to be fixed to the hub and, the complete assembly of the hub and blade are assumed to be rotating. The functionally graded sandwich composite blade is comprised of functionally graded face-sheet material and metal alloy core. The constituents' material properties are assumed to be temperature-dependent, however, the overall properties are evaluated using Voigt's micromechanical scheme in conjunction with the modified power-law functions. The blade model kinematics is based on the equivalent single-layer shear deformation theory. The equations of motion are derived using the extended Hamilton's principle by including the effect of centrifugal forces, and further solved via 2D- isoparametric finite element approximations. The mesh refinement and validation tests are performed to illustrate the stability and accurateness of the present model. In addition, frequency characteristics of the pre-twisted rotating sandwich blades are computed under thermal environment at various sets of parametric conditions such as twist angles, thickness ratios, aspect ratios, layer thickness ratios, volume fractions, rotational velocity and blade curvatures which can be further useful for designing the blade type structures under turbine operating conditions.

Pilot study for investigating behavior of recentering frame connection equipped with friction damper

  • Kim, Young Chan;Hu, Jong Wan
    • Steel and Composite Structures
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    • v.44 no.4
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    • pp.569-586
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    • 2022
  • This study introduces a novel friction damper as a component of a recentering frame connection, to solve the problem of structural repair costs, caused by stiffness deterioration and brittle fracture of the central brace frame (CBF). The proposed damper consists of shape memory alloy (SMA) bars with pretension applied to them to improve the stability. SMAs reduce the residual displacement by virtue of the properties of the materials themselves; in addition, a pretension can be applied to partially improve their energy dissipation capacity. The damper also consists of a friction device equipped with friction bolts for increased energy dissipation. Therefore, a study was conducted on the effects of the friction device as well as the pretension forces on the friction damper. For performance verification, 12 cases were studied and analyzed using ABAQUS program. In addition, the friction and pretension forces were used as variables in each case, and the results were compared. As a result, when the pretension and friction force are increased, the energy dissipation capacity gradually increases by up to about 94% and the recentering capacity decreases by up to about 55%. Therefore, it has been shown that SMA bars with adequate pretension in combination with bolts with adequate frictional force effectively reduce residual deformation and increase damper capacity. Thus, this study has successfully proposed a novel friction damper with excellent performance in terms of recentering and energy dissipation capacity.

Effects of the stiffness of an inclusion on the mechanical behavior of an aluminum alloy plate with a lateral notch

  • Moulgada Abdelmadjid;Zagane Mohammed El Sallah;Murat Yaylaci;Ait Kaci Djafar;Benouis Ali;Baltach Abdelghani;Sevval Ozturk;Mehmet Emin Ozdemir;Ecren Uzun Yaylaci
    • Steel and Composite Structures
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    • v.51 no.1
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    • pp.63-72
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    • 2024
  • This study delves into the interaction dynamics between lateral notches and inclusions, providing valuable insights for more effective engineering of structural components. By employing the finite element method, the research analyzes how inclusions affect the dimensions and contours of the plastic zone under confined plasticity conditions. Several parameters were investigated, including loading influence, the distance between the inclusion and notch tip, inclusion stiffness, and the distribution of Von Mises stress, as well as normal stresses σxx and σyy, and Comparison between different stresses. Examining stress distributions under varying loading conditions reveals a significant intensification, particularly near the crack tip. Moreover, the presence of an inclusion near the notch base reduces both the size and shape of the plastic zone. The distribution of the stresses for different loads knows an increase in intensity, especially near the crack head, which is the most requested by the tensile forces on its upper part, which can cause either the crack's initiation or opening, inducing significant stresses.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF EQUIATOMIC AND NON-EQUIATOMIC TiMoTaNbV HIGH ENTROPY ALLOYS PREPARED USING VACUUM ARC REMELTING

  • SEONGI LEE;KWANGMIN LEE
    • Archives of Metallurgy and Materials
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    • v.65 no.4
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    • pp.1311-1315
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    • 2020
  • This study investigates the microstructures and the mechanical properties of equiatomic Ti20Mo20Ta20Nb20V20 and non-equiatomic Ti40Mo15Ta15Nb15V15 and Ti60Mo10Ta10Nb10V10 HEAs using X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FE-SEM), and micro-Vickers hardness test. The specimens were fabricated using the vacuum arc remelting (VAR) process and homogenized at a temperature of 1300℃ for 4 h in a vacuum atmosphere. The determined thermodynamic parameters, Ω ≥ 1.1, δ ≤ 6.6%, and VEC < 6.87, suggested that the HEAs consisted of BCC solid solutions. XRD patterns of all the HEAs displayed single BCC phases. The difference in the solidification rate led to the micro-segregation associated with the elements Ta and Mo enriched in the dendrite arms and the elements V and Ti in the inter-dendritic regions. The HEA specimens showed a decrease in hardness with higher concentration of Ti element because the intrinsic hardness of Ti is lower as compared to the intrinsic hardness of Nb and Mo.

STRESS ANALYSIS OF SUPPORTING TISSUES AND IMPLANTS ACCORDING TO IMPLANT FIXTURE SHAPES AND IMPLANT-ABUTMENT CONNECTIONS (임플랜트 고정체의 형태와 연결방식에 따른 임플랜트 및 지지조직의 응력분포)

  • Han Sang-Un;Park Ha-Ok;Yang Hong-So
    • The Journal of Korean Academy of Prosthodontics
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    • v.42 no.2
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    • pp.226-237
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    • 2004
  • Purpose: Four finite element models were constructed in the mandible having a single implant fixture connected to the first premolar-shaped superstructure, in order to evaluate how the shape of the fixture and the implant-abutment connection would influence the stress level of the supporting tissues fixtures, and prosthethic components. Material and methods : The superstructures were constructed using UCLA type abutment, ADA type III gold alloy was used to fabricate a crown and then connected to the fixture with an abutment screw. The models BRA, END , FRI, ITI were constructed from the mandible implanted with Branemark, Endopore, Frialit-2, I.T.I. systems respectively. In each model, 150 N of vertical load was placed on the central pit of an occlusal plane and 150 N of $40^{\circ}$ oblique load was placed on the buccal cusp. The displacement and stress distribution in the supporting tissues and the other components were analysed using a 2-dimensional finite element analysis . The maximum stress in each reference area was compared. Results : 1. Under $40^{\circ}$ oblique loading, the maximum stress was larger in the implant, superstructure and supporting tissue, compared to the stress pattern under vertical loading. 2. In the implant, prosthesis and supporting tissue, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 3. In the superstructure and implant/abutment interface, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 4. In the implant fixture, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 5 The stress was more evenly distributed in the bone/implant interface through the FRI of trapezoidal step design. Especially Under $40^{\circ}$ oblique loading, The maximum stress was smallest in the bone/implant interface. 6. In the implant and superstructure and supporting tissue, the maximum stress occured at the crown loading point through the ITI. Conclusion: The stress distribution of the supporting tissue was affected by shape of a fixture and implant-abutment connection. The magnitude of maximum stress was reduced with the internal connection type (FRI) and the morse taper type (ITI) in the implant, prosthesis and supporting tissue. Trapezoidal step design of FRI showed evenly distributed the stress at the bone/implant interface.

Effects of alloy elements on electrochemical characteristics improvement of stainless steel in sea water (해수환경하에서 스테인리스강의 전기화학적 특성 개선을 위한 합금원소의 영향)

  • Lee, Jung-Hyung;Choi, Yong-Won;Jang, Seok-Ki;Kim, Seong-Jong
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.7
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    • pp.890-899
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    • 2014
  • Austenitic stainless steel is widely used in various industries due to its excellent corrosion resistance. However, Cr carbides precipitation along the grain boundaries after heat treatment or welding may develop Cr depleted zone, which acts as a preferential site for intergranular corrosion attack. To resolve this, carbon stabilizing element such as Ti or Nb are added to suppress formation of Cr carbides. However, there are few reports on corrosion characteristics under seawater environment of the stabilized stainless steel. This study investigated the effects of alloying contents on the electrochemical characteristics in seawater of stainless steel containing stabilizing element(Ti and Nb). To achieve this, the changes on the microstructure due to alloying were observed with microscope, and the electrochemical characteristics were determined by measurement of natural potential and potentiodynamic polarization experiments. The microscopic observation revealed that all specimens had inclusions other than the austenite matrix phase due to the addition of alloying elements. Such inclusions are considered to have different electrochemical characteristics from those of the matrix, and thus a clear distinction was found according to the type of stabilizers and the contents. The results of this study suggest that it is important to consider the effects of alloying contents on the electrochemical characteristics in seawater with the addition of Ti or Nb into austenitic stainless steel.

A Study on the Change of Burning Rate of Zirconium-Nickel Delay Elements Depending on the Ambient Temperature (Zr/Ni계 지연제의 주변 온도에 따른 연소속도 변화 연구)

  • Kim, Ho-Sub;Lim, Ho Young;Kang, Yo Han;Kim, Do Hyun;Lee, Geun Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.7
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    • pp.82-89
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    • 2020
  • Among the explosives in ammunition, the delay elements, which are used as a retardant, could be influenced by the ambient temperature in the Republic of Korea, where the highest and lowest average annual temperature difference is clear. On the other hand, there has been no domestic research on this. This study examined the linear burning rates of the zirconium-nickel delay elements depending on the ambient temperature in South Korea. The ambient temperature data of South Korea were obtained from the meteorological administration, which was used to set the experimental conditions. The operational time for the K414 fuze was measured by changing the ambient temperature by 10 ℃ from -40 ℃ to 50 ℃. To convert the delay time into the burning rates, the height of the delay element in the K414 fuze body was used. The results indicated that the characteristics of the burning rates for the zirconium-nickel delay element could be estimated as linear, and both the burning rates and the delay time of the zirconium-nickel delay element were 2.73mm/ms and -4.18ms, respectively. This led to an approximately 80 ms delay time difference in the environment where the highest and lowest average annual temperature difference was above 20 ℃. Therefore, the delay time reflecting the ambient temperature should be considered when the test evaluation criteria of zirconium-nickel delay elements are established.

Study on Material Fracture and Debris Dispersion Behavior via High Velocity Impact (고속충돌에 따른 재료 파괴 및 파편의 분산거동 연구)

  • Sakong, Jae;Woo, Sung-Choong;Kim, Jin-Young;Kim, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.11
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    • pp.1065-1075
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    • 2017
  • In this study, high velocity impact tests along with modeling of material behavior and numerical analyses were conducted to predict the dispersion behavior of the debris resulting from a high velocity impact fracture. For the impact tests, two different materials were employed for both the projectile and the target plate - the first setup employed aluminum alloy while the second employed steel. The projectile impacts the target plate with a velocity of approximately 1 km/s were enforced to generate the impact damages in the aluminum witness plate through the fracture debris. It was confirmed that, depending on the material employed, the debris dispersion behavior as well as the dispersion radii on the witness plate varied. A numerical analysis was conducted for the same impact test conditions. The smoothed particle hydrodynamics (SPH)-finite element (FE) coupled technique was then applied to model the fracture and damage upon the debris. The experimental and numerical results for the diameters of the perforation holes in the target plate and the debris dispersion radii on the witness plate were in agreement within a 5% error. In addition, the impact test using steel was found to be more threatening as proven by the larger debris dispersion radius.

STRESS DISTRIBUTION OF PERIODONTALLY INVOLVED TEETH RESTORED WITH VAR10US POSTS -THREE-DIMENSIONAL FINITE ELEMENT STUDY- (치주 지지가 감소된 소구치에서 포스트가 치근 응력 분포에 미치는 영향에 대한 3차원 유한요소법적 연구)

  • Jeong, Hye-Jin;Yoo, Jae-Heung;Oh, Nam-Sik;Kim, Han-Sung
    • The Journal of Korean Academy of Prosthodontics
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    • v.45 no.5
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    • pp.567-578
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    • 2007
  • Statement of problem: The endodontically treated tooth is generally restored with post and core, owing to the brittle and the loss of large amount of tooth structure. As periodontal treatment was developed, there are many cases that periodontally involved teeth used in prosthetic treatment. Purpose: The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post materials and the amount of remaining alveolar bone height. Material and method: The 3-dimensional finite element models of mandible 1st premolars were divided into six types according to the various amount of remaining alveolar bone and post type. All types were modeled using equal length, diameter and shape of the post. Three types of post and core materials were used: prefabricated titaniumpost and amalgam core, prefabricated stainless steel post and amalgam core, and cast gold post and core. 300 Newton force was applied to functional cusp of mandible 1st premolar. Results: The results were as follows: First, there was no apparent difference in the pattern of stress distribution according to the alveolar bone condition concentrate on the post middle area. Second, there was difference in pattern of stress distribution according to the core materials, gold post and core generated same than amalgam core. Third, there was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. But a cast gold post and core generated the lowest maximum stress value, a stainless steel post generated the highest maximum stress value. Fourth, in the reduced alveolar bone model, maximum stress value is 1.5 times than that of the normal alveolar bone model. Conclusion: Within the limitations of this study, to provide minimal stress to the root with alveolar bone reduced, the post length may be as long as apical seal was not destroyed. To prevent fracture of tooth, it is rational to use gold alloy which material was good for stress distribution for post materials.

Simulation and Experimental Investigation of Reverse Drawing Process for Manufacture of High-Capacity Aluminum Liner (대용량 알루미늄 라이너의 성형을 위한 역 드로잉 공정 해석 및 실험)

  • Lee, Seungyun;Cho, Sungmin;Lee, Sunkyu;Lyu, Geunjun;Kim, Soyoung;Kang, Sunghun
    • Journal of the Korean Institute of Gas
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    • v.20 no.4
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    • pp.78-84
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    • 2016
  • In this work, finite element investigations were carried out to optimize reverse drawing process design for manufacture of high-capacity aluminum liner used in fuel cell vehicle. The tensile tests with aluminum alloy Al6061 annealed at $350^{\circ}C$ were carried out to obtain the flow stresses. In order to estimate more accurate flow stresses after necking, the flow stresses were estimated from the comparison of load vs. displacement curves which were obtained from experimental and simulation results of tensile tests. In case of finite element analyses of reverse drawing processes, it was focused on the effects of process designs such as punch and die designs, blank holding force, drawing ratio and the clearance between the punch and blank holder on the generation of wrinkle and fracture of the blank and partially heated punch. However, it was revealed that experimental results still show the fracture at the end of 2nd drawn cup, although partially heated punch is used. Nevertheless, the drawn cup can be used because the sufficient length of the drawn cup for the next flow forming process and spinning process was obtained.