Liquefaction Potential Assessment of Brahmaputra Sand Based on Regular and Irregular Excitations Using Stress-Controlled Cyclic Triaxial Test

Shiv Shankar Kumar,Arindam Dey,A. Murali Krishna 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4

The response of saturated soil during earthquakes is governed by many factors such as frequency content, strain, stress, excess pore-water pressure and strength variations within the soil mass. This paper highlights the effect of strains on the stiffness modulus and its degradation at the liquefied condition of cohesionless soil. Cyclic triaxial (CT) tests, in stress-controlled manner, were carried out on saturated sandy soil specimens made at different relative density (Dr = 30% − 90%) and effective stress (σ'c = 50 − 200 kPa). The reconstituted specimens were subjected to regular and irregular stress histories. Representative strong motions with varying PGA were chosen, and the corresponding irregular stress histories were used. Additionally, regular stress histories constituted from different cyclic stress amplitudes were also used. The responses of the saturated specimen were obtained in terms of the excess pore-water pressure generation and strain accumulation with elapsed time. In comparison to the standard frequencyand duration parameters (namely the predominant period and significant durations), it is observed that the responses are more influenced by Arias intensity and specific energy density of the strong motion. Based on the increase in pore-water pressure, reduction in shear modulus and increase in shear strain within the specimens, the complete manifestation of liquefaction is divided in four zones, namely the no liquefaction zone, quasi-liquefaction zone, zone marking the onset of liquefaction and the completely liquefied zone. The criteria for the onset of liquefaction of Brahmaputra sand involving shear strain, peak ground acceleration and cyclic stress ratio are provided.

In-plane Shear Behavior of Corrugated Cellular Solids and Validation of an Open-cell Corrugated Cellular Solid

최정호,Krishna Shankar,최변부,이정환 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

The objective in here is to compare the design of a corrugated wire mesh laminate (CWML) with an open-cell mockup by using a uniaxial shear test. This paper depicts the fabrication of CWML specimens by using a transient liquid phase (TLP) skill at low temperatures and a design of a shear testing frame, and then applying uniaxial shear loading. The material used in the fabrication is a 316 stainless steel woven wire mesh with a 0.22-mm wire diameter and 0.95-mm aperture. Tin-alloy (95%Sn-5%Ag) is used as the bonding material in the TLP method, and the designed shear frames are glued with epoxy. The fabricated samples are tested under a uniaxial condition to determine their shear behaviors. Finite element software is employed to model the CWML and study its reaction to mechanical shear loading. The results of the numerical simulation are confirmed by experimental results for the shear loading behavior. Finally, the CWML is concluded to be of an open-cell foam type, and the results of the numerical model show a reasonably linear match to the experimental results on a log-log scale.

Mechanical behavior and numerical analysis of corrugated wire mesh laminates

최정호,Krishna Shankar,Murat Tahtali 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1

The objective is to show a possibility of corrugated wire mesh laminate (CWML) structure for bone application. CWML is a part of open-cell structures with low density and high strength built with bonded mesh layers. Specimens of CWML made of 316 stainless steel woven meshes with 0.22 mm wire diameter and 0.95 mm mesh aperture, bonded by transit liquid phase (TLP) at low temperatures, were fabricated and tested under quasi-static conditions to determine their compressive behavior with varying numbers of layers of the sample. The finite element software was used to model the CWML and studied their response to mechanical loading. Then, the numerical model was confirmed by the tested sample. Consequently, CWML specimens were reasonably matched with the human tibia bone ranged over apparent density from 0.05 to 0.08 g/cm3 in Young’s modulus and from 0.05 to 0.11 g/cm3 in compressive yield strength. The CWML model can have the potential for bone application.

주름형 와이어 판재의 제작법과 Cancellous Bone에 대한 적용 가능성

최정호(Jeongho Choi),Krishna Shankar 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3

The objective is to validate a new structure of corrugated wire mesh laminates(CWML) to find a possibility for the bone application. Previously, Fabrication of the CWML was shown a disadvantage such as time and financial consuming, because the skill for the manufacturing of the CWML specimens was based on the technique with transit liquid phase(TLP) at high temperature. Thus, this paper suggests a new method to make CWML at low temperature, quasi-static compression test, and comparison fot the bone expectation reported by Cater-Hayes. Applied material is 316 stainless steel wire meshes having three different sizes such as 0.14mm wire diameter related with 0.57 aperture. And bonding material is tin alloy with Argon environment. Consequently, it is shown the CWML model is reasonably matched with Cater-Hayes probability in both the relative elastic modulus and the relative compressive yield strength. The CWML model may have a possibility for the bone replacement but it needs to do more deeply studying in biomedical investigation for a long time.

열처리로 제조된 물결모양 와이어 철망 층 구조의 압축강도

최정호(J. H. Choi),이정환(J. H. Lee),Krishna Shankar,Murat Tahtali,Andrew Neely 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5

The objective in this paper presents an attempt to understand and characterize the behavior of corrugated wire mesh laminates (CWML) under transverse compression loading. Specimens of the CWML are made of stainless steel type 316 woven metal and crossed points in the mesh are bonded with eutectic at low temperature. Experimental testing is conducted on several samples of single layer, two layer, and four layer wire mesh laminates under transverse compression The load deflection behaviors of the single and multi layer laminates observed in the tests are analyzed. Therefore, it does provide significant insight into aspects that influence the deformation behavior of CWML.

Focused Review on Cu–Ni–Sn Spinodal Alloys: From Casting to Additive Manufacturing

Bipin Sankar,Chaitanya Vinay,Jithin Vishnu,Karthik V. Shankar,G. P. Gokul Krishna,V. Govind,A. J. Jayakrishna 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5

The present review article evaluates the research and progress status of Cu–Ni–Sn-based spinodal alloys focussed on themethods and technologies implemented to enhance the properties of cast Cu–Ni–Sn alloys in industrial applications, particularlyin components such as bearings, bushings, propellers, and impellers that find extensive demand in the marineand automotive industry. The review introduces the limitations of employing copper-beryllium alloys in the industry anddiscusses how Cu–Ni–Sn alloys represent a potential alternative. Subsequently, a comprehensive overview of spinodaldecomposition is provided, considering the thermodynamic aspects and the Cu–Ni–Sn ternary phase diagram. The processingof Cu–Ni–Sn alloys via traditional casting is explored with an overview of various casting techniques and ensuingmicrostructure-property relationships. The two significant limitations, segregation during solidification and discontinuousprecipitation, are highlighted. Strategies to overcome these limitations, such as precipitation hardening, spinodal decomposition,thermo-mechanical processing, and composition design (with the effect of varying elemental additions), are furtherelaborated. The review summarises novel processing routes encompassing mechanical alloying, rapid solidification, powdermetallurgy, and spray deposition for developing spinodal Cu–Ni–Sn alloys. Finally, the progress in fabricating Cu–Ni–Snspinodal alloys using additive manufacturing techniques such as selective laser melting is highlighted. There are publishedreview papers on the wrought processing of Cu–Ni–Sn alloys, so this area has not been covered here. Overall, this reviewarticle is intended to streamline an overview of the characteristics and gradual developments from cast Cu–Ni–Sn spinodalalloys to additive manufacturing-based Cu–Ni–Sn spinodal alloys.