Heeralal Gargama | IIT Kharagpur (original) (raw)

Papers by Heeralal Gargama

—Traditional Failure Mode and Effects Analysis (FMEA) has shown its effectiveness in defining, id... more —Traditional Failure Mode and Effects Analysis (FMEA) has shown its effectiveness in defining, identifying, and eliminating known and/or potential failures or problems in products , process, designs, and services to help ensure the safety and reliability of systems applied in a wide range of industries. However , its approach to prioritize failure modes through a crisp risk priority number (RPN) has been highly controversial. This paper proposes two models for prioritizing failures modes, specifically intended to overcome such limitations of traditional FMEA. The first proposed model treats the three risk factors as fuzzy linguistic variables, and employs alpha level sets to provide a fuzzy RPN. The second model employs an approach based on the degree of match and fuzzy rule-base. This second model considers the diversity and uncertainty in the opinions of FMEA team members, and converts the assessed information into a convex normalized fuzzy number. The degree of match (DM) is used thereafter to estimate the matching between the assessed information and the fuzzy number characterizing the linguistic terms. The proposed models are suitably supplemented by illustrative examples. Index Terms—Degree of match, failure modes and effects analysis , fuzzy weighted geometric mean, risk priority number.

The present paper reports, novel outcome comprising experimental results on electromagnetic inter... more The present paper reports, novel outcome comprising experimental results on electromagnetic interference (EMI) shielding and radar signal absorption characteristics of a polymer-metal composite (PMC) based on polyvinylidene fluoride (PVDF) dispersed with varying concentration of nanocrystalline iron (n-Fe). The PVDF/n-Fe composites, prepared using mechanical blending followed by hot-molding process at an optimum pressure and temperature, exhibited better filler dispersion. The relevant parameters, i.e.; microwave permittivity, permeability, shielding effectiveness (SE) and loss factors, has been calculated using scattering parameters measured in X-band (8.2–12.4 GHz) by waveguide method. The theoretical EMI SE has also been evaluated by transmission line model, assuming a single layer PMC absorbing structure backed by perfect electrical conductor, using measured material parameters as the input for meaningful comparison with the experimental results. The results so obtained, confirmed an improved shielding and absorption properties of PVDF/n-Fe composites vis-à-vis its counterpart reported in literature. The findings in this work, suggest potential futuristic applications of PMC in shielding and absorption of electromagnetic waves.

J. Appl. Phys. 117, 224903 (2015)

In this paper, the composites of polyvinylidene fluoride (PVDF)/nickel (Ni) prepared through sim... more In this paper, the composites of polyvinylidene fluoride (PVDF)/nickel (Ni) prepared through
simple blending and hot-molding process have been investigated for dielectric, electromagnetic
shielding, and radar absorbing properties. In order to study complex permittivity of the composites
in 40 Hz–20MHz frequency range, impedance spectroscopy (IS) technique is used. Besides, the
complex permittivity and permeability in addition to shielding effectiveness (SE), reflection coefficient
(backed by air), and loss factor are calculated using scattering parameters measured in
X-band (8.2–12.4 GHz) by waveguide method. Further, in X-band, a theoretical analysis of single
layer absorbing structure backed by perfect electrical conductor is then performed. A flanged
coaxial holder has also been designed, fabricated, calibrated, and tested for electromagnetic interference
SE measurement in the broad frequency range (50 MHz–18 GHz). The IS results indicate
large enhancement in dielectric constant as a function of Ni loading in the polymer-metal composite
(PMC) phase. This result has been explained using interfacial polarization and percolation
theory. The frequency dependent response of ac conductivity has been analyzed by fitting the experimental
data to the “Johnscher’s universal dielectric response law” model. The results obtained
for SE (in X-band over broad frequency range) and reflection coefficient indicate that PVDF/Ni
composites give better electromagnetic interference shielding and radar absorption properties at filler
concentration (fcon)fc in the PMC, whereas at fc<fcon, the charge storage mechanism dominates
in the insulator regime of the composite phase. Therefore, the range of PMC compositions
below and above percolation threshold has been observed to have different variety of applications.

International Proceedings of Economics Development and Research 75: 91-95. Singapore: IACSIT Press. (2014)

The deterministic design approaches for designing electromagnetic interference (EMI) shielding s... more The deterministic design approaches for designing electromagnetic interference (EMI) shielding
structures lacks the incorporation of the uncertainty involved in the design variables and/or problem
parameters. The ignorance of such uncertainties in the optimized design solution provides variation in the
expected shielding effectiveness (SE). In this paper a reliability-based design optimization (RBDO) study for
designing electromagnetic (EM) shielding structures is presented. The uncertainty in the variables has been
dealt by employing probabilistic sufficiency factor (PSF), which is a factor of safety relative to a target
probability of failure. In the RBDO, computational burden on the evaluation of PSF at each design point have
been reduced by evaluating PSFs only at the selected design points from the given design space.
Subsequently artificial neural network (ANN) is trained to approximate the PSF as a function of design
variables. The approach is applied to design a three-layered shielding structure for the SE requirement of 80
dB in 8–12.5 GHz frequency range.

International Journal of Performability Engineering Vol. 10, No. 3, May 2014, pp. 251-262.

This paper presents a reliability based design study of multilayered composites for electromagnet... more This paper presents a reliability based design study of multilayered composites for electromagnetic interference shielding applications. In this study, uncertainties in the design and external variables affecting the shielding effectiveness (SE) are modeled based on probability distributions. Monte Carlo simulation is employed at each design point generated via Latin hypercube sampling approach to evaluate the probability of failure from the limit state function. Subsequently, a response surface approximation is employed to approximate the probability of failure in terms of design variables. This approximated polynomial is used to compute the probabilistic constraint in the design optimization. The design problems so formulated are solved using the real-coded genetic algorithm. The plane wave SE theory approach based on transmission line modeling for the multilayer shields in arbitrary polarized and incident direction of electromagnetic wave is adopted for SE calculation. The proposed approach is illustrated through examples by considering the military and commercial shielding requirements.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science December 2014 vol. 228 no. 18 3471-3481

The conventional approaches for electromagnetic shielding structures’ design, lack the incorporat... more The conventional approaches for electromagnetic shielding structures’ design, lack the incorporation of uncertainty in
the design variables/parameters. In this paper, a reliability-based design optimization approach for designing electromagnetic
shielding structure is proposed. The uncertainties/variability in the design variables/parameters are dealt with using
the probabilistic sufficiency factor, which is a factor of safety relative to a target probability of failure. Estimation of
probabilistic sufficiency factor requires performance function evaluation at every design point, which is extremely
computationally intensive. The computational burden is reduced greatly by evaluating design responses only at the
selected design points from the whole design space and employing artificial neural networks to approximate probabilistic
sufficiency factor as a function of design variables. Subsequently, the trained artificial neural networks are used for the
probabilistic sufficiency factor evaluation in the reliability-based design optimization, where optimization part is processed
with the real-coded genetic algorithm. The proposed reliability-based design optimization approach is applied to
design a three-layered shielding structure for a shielding effectiveness requirement of 40 dB, used in many industrial/
commercial applications, and for 80 dB used in the military applications.

Journal of Electromagnetic Waves and Applications, Volume 28, Issue 6, 2014, Feb 27, 2014

This article, presents a reliability-based design optimization (RBDO) study for designing electro... more This article, presents a reliability-based design optimization (RBDO) study for designing electromagnetic shielding structures. The existing deterministic design approaches do not integrate the uncertainty involved in the design variables or problem parameters of such shielding structures thereby, the ignorance of uncertainty provides variation in the expected shielding effectiveness (SE) in the optimized design solution. The application of RBDO allows determining the best design solution, while explicitly considering the inevitable effects of uncertainty in the design variables and problem parameters. The proposed approach employs a nested optimization approach for solving the RBDO formulation for the shielding structure under uncertainty. The real-coded genetic algorithm is being used to handle deterministic constraints (outer loop) whereas hybrid mean-value method is employed to evaluate probabilistic constraints in the RBDO formulation (inner loops). The approach is illustrated with an example considering three-layered shielding structures’ design for the SE requirement of ~80 dB in 8–12.5 GHz frequency range.

During early design and development stages, every engineering system has to meet its specific rel... more During early design and development stages, every engineering system has to meet its specific reliability goals. The target reliability of the system is achieved through application of an effective reliability apportionment technique to its subsystems. There are various traditional methods exist to perform the reliability allocation based on engineering factors that are assessed in a subjective manner. The conventional reliability allocation approach requires the assessment of factors like complexity, cost, and maintenance. This may not be realistic in real applications if they are assessed in a crisp manner by the domain experts of their varied expertise and background.

In this paper, we treat allocation factors as fuzzy numbers, which are evaluated in fuzzy linguistic terms. As a result, fuzzy proportionality factor scales are proposed for the subsystems. In order to accomplish fuzzy division to evaluate the fuzzy proportionality factor, an approximation method based on linear programming for trapezoidal fuzzy numbers is also proposed in this paper. For the evaluation of weighting factors from fuzzy proportionality factors, centroid method of defuzzification is being employed. The allocated reliability of each subsystem is computed with the help of weighting factor thereafter. An example is provided to illustrate the potential application of the proposed fuzzy based reliability allocation approach.

This paper proposes a reliability-based design optimization approach to handle variability/uncert... more This paper proposes a reliability-based design optimization approach to handle variability/uncertainties involved in the design variables/parameters of microwave absorber. The proposed approach uses hybrid genetic algorithm for optimization and Monte Carlo simulation with Latin hypercube sampling technique for probabilistic analysis to identify the optimal design of absorbing structure under probabilistic constraints. The proposed approach is illustrated with examples considering broadband absorbing coatings in the frequency range of 0.2–2, 2–8, and 0.5–8 GHz, respectively.

In this paper, we propose an approach for designing and quantitatively assessing the performance ... more In this paper, we propose an approach for designing and quantitatively assessing the performance of the multilayered radar-absorbing structure. In our proposed approach, a five layered radarabsorbing materials design is optimized from the predefined materials database. But to determine the optimal choice of the material and thickness of each layer, a combined binary and real-coded genetic algorithm (GA) is used to handle the integer and real variables involved in such designs. Further, the proposed approach employs the Latin hypercube sampling with Monte Carlo Simulation to carry out the performance based reliability analysis of the design. Absorber synthesized results are compared with the published work using other algorithms. The outcomes of our approach show that the combined GA works quite well, and most prominently the reliability analysis provides the decision maker a means to select among the several design alternatives available before him.

Proceedings of the International Conference on Soft Computing for Problem Solving (SocProS 2011) December 20-22, 2011, Series: Advances in Intelligent sand Soft Computing Vol 131, Mar 11, 2012

The increased deployment of various electrical and electronic equipments/devices for the commerci... more The increased deployment of various electrical and electronic equipments/devices for the commercial, industrial, and military systems has created a number of sources and receptors of electromagnetic interference that can degrade the system performance or affect safety operation of intelligence/secrecy between the various services. To avoid the interference problems from the adverse effects of electromagnetic waves, there is a greater need for shielding of these equipments/devices. In this paper, a design approach to meet the military requirement shielding for multi-layer electromagnetic shield is described. This design problem is solved by using shielding effectiveness theory based on transmission line modeling and real-coded genetic algorithm with simulated binary crossover and parameter-based mutation. Further, it is shown that by using Monte Carlo simulation, the performance of electromagnetic shielding under the uncertain operating conditions can be evaluated in terms of reliability.

We report optimized design of multilayered electromagnetic shield using real coded genetic algori... more We report optimized design of multilayered electromagnetic shield using real coded genetic algorithm. It is observed that the shielding effectiveness in multilayer design is higher than single layered counterpart of equal thickness. An effort has been made to develop alternative approach to achieve specific objective of identifying the design characteristics of each layer in the multilayered shielding configuration. The proposed approach incorporates interrelated factors, such as, absorption and reflection in the design optimization as per specific shielding requirements. The design problem has been solved using shielding effectiveness theory based on transmission line (TL) modeling and real-coded genetic algorithm (GA) with simulated binary crossover (SBX) and parameter-based mutation. The advantage of real-coded GA lies in efficient solution for electromagnetic interference (EMI) shielding design due to its strength in solving constraint optimization problems of continuous variables with many parameters without any gradient information. Additionally, the role of material parameters, such as permittivity and permeability on reflection characteristics and shielding effectiveness has also been investigated and optimized using the proposed models and real-coded GA. Theoretical optimization of electromagnetic parameters has been carried out for SE ~40 dB for many industrial/commercial applications and SE ~80 dB for military applications.

Traditional Failure Mode and Effects Analysis (FMEA) has shown its effectiveness in defining, ide... more Traditional Failure Mode and Effects Analysis (FMEA) has shown its effectiveness in defining, identifying, and eliminating known and/or potential failures or problems in products, process, designs, and services to help ensure the safety and reliability of systems applied in a wide range of industries. However, its approach to prioritize failure modes through a crisp risk priority number (RPN) has been highly controversial. This paper proposes two models for prioritizing failures modes, specifically intended to overcome such limitations of traditional FMEA. The first proposed model treats the three risk factors as fuzzy linguistic variables, and employs alpha level sets to provide a fuzzy RPN. The second model employs an approach based on the degree of match and fuzzy rule-base. This second model considers the diversity and uncertainty in the opinions of FMEA team members, and converts the assessed information into a convex normalized fuzzy number. The degree of match (DM) is used thereafter to estimate the matching between the assessed information and the fuzzy number characterizing the linguistic terms. The proposed models are suitably supplemented by illustrative examples.

J. Appl. Phys. 117, 224903 (2015)

International Proceedings of Economics Development and Research 75: 91-95. Singapore: IACSIT Press. (2014)

International Journal of Performability Engineering Vol. 10, No. 3, May 2014, pp. 251-262.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science December 2014 vol. 228 no. 18 3471-3481

Journal of Electromagnetic Waves and Applications, Volume 28, Issue 6, 2014, Feb 27, 2014

Proceedings of the International Conference on Soft Computing for Problem Solving (SocProS 2011) December 20-22, 2011, Series: Advances in Intelligent sand Soft Computing Vol 131, Mar 11, 2012