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Yu Qian - One of the best experts on this subject based on the ideXlab platform.
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benefits of high strength Reduced Modulus hsrm concrete railroad ties under center binding support conditions
Construction and Building Materials, 2018Co-Authors: Adam I Zeitouni, Dimitrios C. Rizos, Yu QianAbstract:Abstract Concrete ties, also referred to as sleepers or crossties, have become a promising alternative to timber ties for freight lines in demanding territories with high curvature, high grade, and high axle loads. Concrete ties have also become popular in rail transit systems. High strength (HS) concrete is the material of choice in the fabrication of prestressed concrete railroad ties. The higher strength of the concrete is directly related to higher values of the elastic Modulus, thus increasing the rigidity of the material. The combination of increased strength, rigidity, and the material brittleness may lead to premature cracking and deterioration which has raised major concerns within the rail industry. With experience in frontier concrete material research, researchers at the University of South Carolina (USC) have developed a High Strength Reduced Modulus (HSRM) concrete by introducing weathered granite aggregates into concrete mix designs. A comprehensive study has been conducted at USC to quantify the benefits of using HSRM concrete in railroad ties. Both laboratory experiments and computer simulations at the material, component, and structural levels were performed. HSRM can improve the cracking resistance and fatigue performance and extend the service life of the concrete ties. This paper presents the details of the computer simulations used to quantify the benefits of using the HSRM material in ties subjected to center binding conditions. Three-dimensional nonlinear Finite Element (FE) models have been developed for the HSRM and the “Standard” concrete ties. Nonlinear material models based on concrete damaged plasticity are implemented. The concrete-steel bond interface is also modeled. The numerical models are first validated through comparisons with laboratory testing results of prestressed concrete prisms and commercial prestressed ties, which showed excellent agreement. Results from a parametric study simulating the center binding conditions in a tangent track have shown that the HSRM concrete tie outperforms the Standard concrete tie by: (i) showing smoother stress distribution, (ii) delaying the initiation of cracks, and (iii) failing at higher ultimate loads.
Dimitrios C. Rizos - One of the best experts on this subject based on the ideXlab platform.
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benefits of high strength Reduced Modulus hsrm concrete railroad ties under center binding support conditions
Construction and Building Materials, 2018Co-Authors: Adam I Zeitouni, Dimitrios C. Rizos, Yu QianAbstract:Abstract Concrete ties, also referred to as sleepers or crossties, have become a promising alternative to timber ties for freight lines in demanding territories with high curvature, high grade, and high axle loads. Concrete ties have also become popular in rail transit systems. High strength (HS) concrete is the material of choice in the fabrication of prestressed concrete railroad ties. The higher strength of the concrete is directly related to higher values of the elastic Modulus, thus increasing the rigidity of the material. The combination of increased strength, rigidity, and the material brittleness may lead to premature cracking and deterioration which has raised major concerns within the rail industry. With experience in frontier concrete material research, researchers at the University of South Carolina (USC) have developed a High Strength Reduced Modulus (HSRM) concrete by introducing weathered granite aggregates into concrete mix designs. A comprehensive study has been conducted at USC to quantify the benefits of using HSRM concrete in railroad ties. Both laboratory experiments and computer simulations at the material, component, and structural levels were performed. HSRM can improve the cracking resistance and fatigue performance and extend the service life of the concrete ties. This paper presents the details of the computer simulations used to quantify the benefits of using the HSRM material in ties subjected to center binding conditions. Three-dimensional nonlinear Finite Element (FE) models have been developed for the HSRM and the “Standard” concrete ties. Nonlinear material models based on concrete damaged plasticity are implemented. The concrete-steel bond interface is also modeled. The numerical models are first validated through comparisons with laboratory testing results of prestressed concrete prisms and commercial prestressed ties, which showed excellent agreement. Results from a parametric study simulating the center binding conditions in a tangent track have shown that the HSRM concrete tie outperforms the Standard concrete tie by: (i) showing smoother stress distribution, (ii) delaying the initiation of cracks, and (iii) failing at higher ultimate loads.
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Finite Element Model of High Strength Reduced Modulus High Performance Concrete
2016 Joint Rail Conference, 2016Co-Authors: Albert R. Ortiz, Juan M Caicedo, Dimitrios C. RizosAbstract:High Performance Concrete (HPC) with early strength development is the material of choice in the fabrication of prestressed concrete railroad ties. The higher strength of HPC results in significantly higher values of the Elastic Modulus and increases the brittleness and the rigidity of the material, leading to premature cracking and the deterioration of the railroad ties. A High-Strength Reduced-Modulus High Performance Concrete (HSRM-HPC) material has been developed by the authors and used in the fabrication of prototype concrete ties. Detailed models based on the Finite Element Method of the HSRM-HPC have been developed to simulate the ASTM-C469 tests for elastic Modulus. The HSRM-HPC constituent materials, i.e. aggregates and cement mortar, have been explicitly modeled and assigned properties determined experimentally. Aggregates size and distribution is modeled using a combination of probabilistic distributions consistent with the results of an experimental sieve analysis. Details of the development of each model are discussed. The models are verified with experimental data. Assessment studies have been performed in order to optimize the models with respect to efficiency, the quality of the results and computational times.Copyright © 2016 by ASME
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High-Strength Reduced-Modulus High Performance Concrete (HSRM-HPC) for Prestressed Concrete Tie Applications
2016 Joint Rail Conference, 2016Co-Authors: Dimitrios C. RizosAbstract:A High-Strength Reduced-Modulus High Performance Concrete (HSRM-HPC) for use in prestressed concrete rail ties has been developed by the authors. The HSRM-HPC material was originally considered for highway bridges but was rejected because of the accidental finding of the low Modulus of elasticity. It is shown that the elastic Modulus of the HSRM-HPC is Reduced as much as 50% compared to the conventional HPC of the same strength while preserving all other properties of the conventional HPC. The use of the more flexible HSRM-HPC in concrete ties leads to Reduced stress amplitudes and regularized stress fields at the rail seat area and the middle segment of the tie, which are the two most critical areas of tie failure. This work discusses the development and characterization of the HSRM HPC material, as well as current work on the performance assessment of such ties. The material development, material characterization, and performance assessment is conducted through experimental testing and computer simulations. The benefits of HSRM-HPC ties are quantified and discussed.Copyright © 2016 by ASME
Chunqiang Zhuang - One of the best experts on this subject based on the ideXlab platform.
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approximate linear relation between Reduced Modulus and stiffness in completely amorphous si c n films
Surface & Coatings Technology, 2014Co-Authors: Chunqiang Zhuang, Regina Fuchs, Christoph Schlemper, Lei Zhang, Michael Vogel, Thorsten Staedler, Xin JiangAbstract:Abstract An approximately linear relation between Reduced Modulus (Er) and stiffness (S) was observed based on the characterization of completely amorphous Si–C–N hard films by means of nanoindentation. This linear relation was verified by a series of amorphous Si–C–N films prepared under different experimental conditions. Furthermore the linear relation can be extended to amorphous Si–B–C–N film systems. This finding provides one possible way to evaluate the hardness and Reduced Modulus of a material without involving the contact area.
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Approximate linear relation between Reduced Modulus and stiffness in completely amorphous Si–C–N films
Surface and Coatings Technology, 2014Co-Authors: Chunqiang Zhuang, Regina Fuchs, Christoph Schlemper, Lei Zhang, Michael Vogel, Thorsten Staedler, Xin JiangAbstract:Abstract An approximately linear relation between Reduced Modulus (Er) and stiffness (S) was observed based on the characterization of completely amorphous Si–C–N hard films by means of nanoindentation. This linear relation was verified by a series of amorphous Si–C–N films prepared under different experimental conditions. Furthermore the linear relation can be extended to amorphous Si–B–C–N film systems. This finding provides one possible way to evaluate the hardness and Reduced Modulus of a material without involving the contact area.
Azman Jalar - One of the best experts on this subject based on the ideXlab platform.
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Effect of Blast Wave on Intermetallics Formation, Hardness and Reduced Modulus Properties of Solder Joints
Solid State Phenomena, 2020Co-Authors: Nur Shafiqa Safee, Wan Yusmawati Wan Yusoff, Ariffin Ismail, Norliza Ismail, Maria Abu Bakar, Azman JalarAbstract:Tin-Silver-Copper (SnAgCu) lead-free solder on Electroless Nickel Immersion Gold (ENiG) and Immersion Tin (ImSn) surface finish printed circuit board was subjected to blast test. A variation of intermetallic compounds (IMC) layer, hardness and Reduced Modulus of soldered sample exposed to blast test were intensively investigated using optical microscope and nanoindentation machine. Formation of IMCs due to reaction between solder and substrate during blast test provided deleterious effect of metallurgical bond strength and reliability on the solder joint. Microstructural analysis was evaluated via Infinite Focused Microscope (IFM). The findings of these studies indicate that best surface finished for blast test performance was not necessarily the best surface finish for optimum reliability. ENiG and ImSn surface finish can be advantage or a disadvantage depending on the application, package and reliability requirements. As a result, most component assemblers are using ENiG and ImSn in order to improve solderability as well as the wettability between solder and the substrate and to meet various package requirements.
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Effects of thermal cycling on the mechanical properties of gold wire bonding
2014 IEEE International Conference on Semiconductor Electronics (ICSE2014), 2014Co-Authors: Wan Yusmawati Wan Yusoff, Norinsan Kamil Othman, Azman Jalar, Irman Abdul RahmanAbstract:The mechanical properties of gold wire bonding are subjected to thermal cycling (TC) test has been investigated. Gold wire bonding was experienced to temperature cycle of (−65) °C to 150 °C for 10, 100, and 1000 cycles. In order to determine the mechanical properties of gold wire, nanoindentation test was performed. A constant load nanoindentation test was carried out at the center of the gold wire to investigate hardness and Reduced Modulus. The load-depth curve for the thermal cycled gold wire bond displayed apparent discontinuities during loading as compared to the as-received gold wire bond. The hardness value has increased after the gold wire bond subjected to thermal cycle whilst, the hardness value has decreased with the increment of the TC cycle number. For Reduced Modulus, the values increased with increase of the TC cycle number. The decrease in the hardness value is in line with theoretical grain size coarsening following thermal treatment. These nanoindentation results are important in assessing the strength of gold wire bond after exposure to the thermal cycles.
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The re-evaluation of mechanical properties of wire bonding
2011 International Symposium on Advanced Packaging Materials (APM), 2011Co-Authors: Azman Jalar, Norinsan Kamil Othman, Muhammad Nubli Zulkifli, Shahrum AbdullahAbstract:Wire bonding is the most popular interconnection technique that has been used in microelectronics packaging due to its maturity and cost effectiveness. The technology advances in the era of miniaturization and multifunction have urges the need for the smaller wire bond size to cope with the decrease of bond pad pitches. Ultimately, this will introduces al lot of technology challenges in the characterization and performance of wire bonding micromechanical properties. The conventional tests such as wire pull and ball shear tests provide inadequate information in respect of bonding and metallurgical response of the interconnection. This is because the evaluations of wire bond performance based on conventional tests are more into qualitative results or failure modes rather than detailed quantitative results. Furthermore, the results obtained through wire pull and ball shear tests will change and introduce a lot of variations as the ball bond diameter become smaller. In the present analysis, nanoindentation test was introduced in order to provide more adequate information about the quality of wire bond. Nanoindentation test provides the micromechanical properties in terms of hardness and Reduced Modulus value in the small length scale. This will facilitate the micromechanical properties measurement of the wire bond. In addition, the continuous measurement of stiffness provided from nanoindentation test realizes the qualitative results of materials such as deformation, strain hardening effect and creep behaviour. Wire bonding process was prepared using thermosonic wire bonding technology using 25 μm diameter of gold wire on the Aluminium bond pad. The nanoindentation test was conducted at various locations on the ball bond that has been cross-sectioned diagonally prior to the indentation process. To further investigate the micromechanical properties, the location of indentations was divided into two zones namely Zone 1 and Zone 2. Zone 1 is located at the area near to the intermetallic layer of Au and Al, while Zone 2 is located at deformed ball bond created from the inner chamfer of capillary. The results show that the micromechanical properties of ball bond vary throughout the location of indentations. The hardness and the Reduced Modulus for the indentations that located at the Zone 1 have higher average values compared to that of the indentations that located at the Zone 2. The average value of hardness and Reduced Modulus for the indentations at the Zone 1 are 1.011 GPa and 88.652 GPa, respectively. While the average value of hardness and Reduced Modulus for the indentations at the Zone 2 are 0.853 GPa and 70.652 GPa, respectively. In addition, indentation 1 of Zone 1 that located perpendicular to the effect of deformation created from the end of capillary has the highest value of hardness with value of 1.156 GPa. The value of hardness for the indentations 3 and 4 of Zone 1 has the lowest value of hardness with value of 0.928 GPa and 0.834 GPa, respectively. It is known that the hardness and the Reduced Modulus are related with the yield strength and diffusivity of materials. Thus, the results obtained from nanoindentation test are useful in explaining the strengthening and bondability of ball bond, at least from metallurgical point of view. Therefore, the nanoidentation test is suitable approach to re-evaluate the mechanical properties of wire bonding in addition to the conventional tests.
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Nanoindentation Test for the Stiffness Distribution Analysis of Bonded Au Ball Bonds
Advanced Materials Research, 2010Co-Authors: Norinsan Kamil Othman, Mohd Nubli Zulkifli, Azman Jalar, Shahrum AbdullahAbstract:The Reduced Modulus value for the bonded Au ball bond that have undergone three different time intervals of high temperature storage (HTS) have been obtained by using nanoindentation test. Twelve indentations have been made at three different locations (Au, IMC and Si area) across the bonded ball bonds to evaluate the variation of Reduced Modulus with the location of indentation. It was shown that the Reduced Modulus value for the indentations at IMC area is increased with the increment of HTS time interval. It was also observed that the Reduced Modulus at the Au area was increased with the increment of the HTS exposure time. No particular pattern was noted to describe the changes of Reduced Modulus with the location of the indentations that have been made. It was also found that the average Reduced Modulus for Au obtained through nanoindentation with value of 107 GPa has higher value compared to that of the Young’s Modulus value obtained through actual tensile test with value of 79 GPa.
Xin Jiang - One of the best experts on this subject based on the ideXlab platform.
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approximate linear relation between Reduced Modulus and stiffness in completely amorphous si c n films
Surface & Coatings Technology, 2014Co-Authors: Chunqiang Zhuang, Regina Fuchs, Christoph Schlemper, Lei Zhang, Michael Vogel, Thorsten Staedler, Xin JiangAbstract:Abstract An approximately linear relation between Reduced Modulus (Er) and stiffness (S) was observed based on the characterization of completely amorphous Si–C–N hard films by means of nanoindentation. This linear relation was verified by a series of amorphous Si–C–N films prepared under different experimental conditions. Furthermore the linear relation can be extended to amorphous Si–B–C–N film systems. This finding provides one possible way to evaluate the hardness and Reduced Modulus of a material without involving the contact area.
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Approximate linear relation between Reduced Modulus and stiffness in completely amorphous Si–C–N films
Surface and Coatings Technology, 2014Co-Authors: Chunqiang Zhuang, Regina Fuchs, Christoph Schlemper, Lei Zhang, Michael Vogel, Thorsten Staedler, Xin JiangAbstract:Abstract An approximately linear relation between Reduced Modulus (Er) and stiffness (S) was observed based on the characterization of completely amorphous Si–C–N hard films by means of nanoindentation. This linear relation was verified by a series of amorphous Si–C–N films prepared under different experimental conditions. Furthermore the linear relation can be extended to amorphous Si–B–C–N film systems. This finding provides one possible way to evaluate the hardness and Reduced Modulus of a material without involving the contact area.
