Microstructure, Tensile and Fatigue Behaviour of Resistance Spot Welded Zinc Coated Dual Phase and Interstitial Free Steel

Kaushal Kishore,Pankaj Kumar,Goutam Mukhopadhyay 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

Galvannealed (hot dip galvanized and annealed) dual phase (DP600) steel and interstitial free (IF) steel are two of the widelyused materials in automotive industries owing to their high specific strength, toughness, formability and corrosion resistance. This inevitably requires their joining to form larger components. Resistance spot welding has emerged as the predominantwelding technique for joining of sheet metals in automotive industries. There are complexities regarding microstructuralvariation of the fusion zone and across heat affected zones during spot welding of fundamentally dissimilar steels. This isfurther aggravated by the prospect of zinc redistribution during the welding process. Current study presents the evolution ofmicrostructure in different zones of welding in IF and DP600 steel. Micro-hardness profiles and electron back scattered diffractionstudies were performed. Furthermore, redistribution of elements in different welding zones is studied using electronprobe micro analysis. The effect of welding current and time on the nugget size and the strength of the weld during tensile–shear is determined. It was observed that there was an increase in nugget diameter and maximum load bearing capacity ofthe joint with an increase in heat input, until the occurrence of expulsion. Furthermore, critical nugget diameter for pull-outfailure was determined and existing empirical models were verified for the applicability in this case. None of the existingempirical models could predict the critical nugget diameter correctly and thus a new empirical relationship between sheetthickness and critical nugget diameter for zinc coated dissimilar steels has been proposed. Failure behaviour of the spotweldedsheets were studied under tensile–shear configuration under quasi-static and fatigue mode of loading and it showedsubstantial difference in location of crack initiation and fractographic features. Tensile–shear specimen at optimum weldingparameter failed from the base metal of the IF steel side with dimples on the fracture surface, whereas fatigue specimenfailed from the heat affected zone of the IF steel side with transgranular striations on the fracture surface.

Some Properties of Harmonic Functions Defined by Convolution

Dixit, Kaushal Kishor,Porwal, Saurabh Department of Mathematics 2009 Kyungpook mathematical journal Vol.49 No.4

In this paper, we introduce and study a comprehensive family of harmonic univalent functions which contains various well-known classes of harmonic univalent functions as well as many new ones. Also, we improve some results obtained by Frasin [3] and obtain coefficient bounds, distortion bounds and extreme points, convolution conditions and convex combination are also determined for functions in this family. It is worth mentioning that many of our results are either extensions or new approaches to those corresponding previously known results.

Fatigue Properties of Resistance Spot Welded Dissimilar Interstitial‑Free and High Strength Micro‑Alloyed Steel Sheets

Gorti Janardhan,Kaushal Kishore,Goutam Mukhopadhyay,Krishna Dutta 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

This study aims to investigate the influence of nugget diameter on tensile-shear and fatigue properties of the dissimilar resistancespot-welded joints of interstitial free and high strength niobium microalloyed steel sheets. The spot-weldings are doneat currents of 7 kA and 9 kA at welding time of 300 ms with electrode force of 2.6 kN. Fatigue tests are done at different loadamplitudes, considering the maximum tensile-shear load bearing capacity of the joints. The tests are interrupted before thefinal failure to understand the crack initiation and propagation paths. The study is supplemented by the microstructural anddetailed fractographic analyses. The results indicated that the fatigue strength of the spot-welds increased with a decrease innugget diameter. This could be attributed to the higher microhardness of heat affected zone (HAZ), presence of compressiveresidual stress and lower variation in thickness reduction on the IF steel side, welded at 7 kA. However, the tensile-shearload bearing capacity of the spot-welds increased with increase in the nugget diameter. The failure of the spot-welded jointunder static loading initiates from the HAZ/base metal interface of the IF steel side. Nevertheless, under cyclic loading crackinitiates from the notch root at the interface of two sheets lying in the HAZ of IF steel side. Fractographic investigationsindicate intergranular fracture features in combination with striations, secondary cracks on the IF steel side under cyclicloading. Fracture surfaces of the specimens failed under static loading shows however, shear dimples on the IF steel side.

Neuro-evolutionary based controller design for linear and non-linear systems

Samarth Singh,Kaushal Kishore,S A Akbar 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10

In the present work a Neuro-Evolution based approach has been used to train a neural network for control of some sample systems. This method makes use of Genetic algorithm, here it is generating a population of neural networks and introduces mutation for producing better off-springs for the next generation. The approach is kind of black box optimization and do not require any back propagation for training. It makes use of fitness function to evaluate performance of off-springs, this fitness function is based on a novel reward function which allows for quick and smooth settling of the sample system towards set point. In order to address dynamics of the system’s time sequenced error has been taken as exogenous input for the neural network. The method has been tested on a linear first order system and a system having non linearity.

Partial Sums of Starlike Harmonic Univalent Functions

Porwal, Saurabh,Dixit, Kaushal Kishore Department of Mathematics 2010 Kyungpook mathematical journal Vol.50 No.3

Although, interesting properties on the partial sums of analytic univalent functions have been investigated extensively by several researchers, yet analogous results on partial sums of harmonic univalent functions have not been so far explored. The main purpose of the present paper is to establish some new and interesting results on the ratio of starlike harmonic univalent function to its sequences of partial sums.

New Subclasses of Harmonic Starlike and Convex Functions

Porwal, Saurabh,Dixit, Kaushal Kishore Department of Mathematics 2013 Kyungpook mathematical journal Vol.53 No.3

The purpose of the present paper is to establish some interesting results involving coefficient conditions, extreme points, distortion bounds and covering theorems for the classes $V_H({\beta})$ and $U_H({\beta})$. Further, various inclusion relations are also obtained for these classes. We also discuss a class preserving integral operator and show that these classes are closed under convolution and convex combinations.

Convolution on a Generalized Class of Harmonic Univalent Functions

Porwal, Saurabh,Dixit, Kaushal Kishore Department of Mathematics 2015 Kyungpook mathematical journal Vol.55 No.1

In the present paper, we introduce new subclasses of harmonic univalent functions and establish certain results concerning the convolution of functions for these subclasses. Relevant connections of the results presented here with various known results are briefly indicated.

Heuristic Guided Artificial Potential Field for Avoidance of Small Obstacles

Sagar Dalai,Mahammad Irfan,Samarth Singh,Kaushal Kishore,Dr. S.A Akbar 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10

In this paper, a modified heuristic guided Artificial Potential Field (APF) based algorithm has been proposed to find a practical trajectory for an Autonomous Unmanned Aerial Vehicle (UAV) path planning. The local minima are encountered in the conventional APF algorithm due to the cancellation of attractive and repulsive potential while avoiding unknown obstacles within the desired path, which results in the trapping of the agent before reaching the goal. Consequently, the traditional APF technique is therefore no longer advantageous in such cases. So in this proposed perpendicular approach based on APF helps to avoid such local minima. The advantage of the newly proposed method is the low computing time that lines up with the standard global path planner method. The proposed algorithm is tested and validated against existing general potential field techniques for different simulation scenarios in a 3D simulated environment using ROS and Gazebo supported PX4-SITL. The results have been presented for drone navigation and obstacle avoidance for the different scenarios in a simulated environment.

Prevalence of peste des petits ruminants among sheep and goats in India

Vinayagamurthy Balamurugan,Paramasivam Saravanan,Arnab Sen,Kaushal Kishor Rajak,Gnanavel Venkatesan,Paramanandham Krishnamoorthy,Veerakyathappa Bhanuprakash,Raj Kumar Singh 대한수의학회 2012 JOURNAL OF VETERINARY SCIENCE Vol.13 No.3

This study measured the clinical prevalence of peste des petits ruminants (PPR) among sheep and goats in India between 2003 and 2009 by analyzing clinical samples from suspected cases of PPR that were submitted to the Rinderpest and Allied Disease Laboratory, Division of Virology, IVRI, Mukteswar for PPR diagnosis. PPR outbreaks were confirmed by detecting PPR virus (PPRV)-specific antigen in the clinical samples. Clinical samples (blood, nasal swabs, spleen, lymph node, kidney, liver, intestine, and pooled tissue materials) were taken from a total of 592 sheep and 912 goats in different states of India and screened for the presence of PPRV antigen using a monoclonal antibodybased sandwich ELISA kit. A total of 20, 38, and 11laboratory-confirmed PPR outbreaks occurred among sheep, goat, and combined sheep and goat populations, respectively. Our findings provide evidence of widespread PPR endemicity in India. The underlying reasons could be variations in husbandry practices in different geographical regions, agro-climatic conditions, and livestock migration. Furthermore, decrease in the number of PPR outbreaks over time might be due to the effectiveness of current live PPR vaccines and timely vaccination of target species. Vaccination against PPR has been practiced in India since 2002 to control this disease.