PREETAM C MOHAPATRA | Intel Corporation (original) (raw)

Papers by PREETAM C MOHAPATRA

International Journal of Adhesion and Adhesives, 2021

Abstract While strain-hardening mechanisms for many metals are well understood, polymers in gener... more Abstract While strain-hardening mechanisms for many metals are well understood, polymers in general, and adhesives in particular, have received less attention. Thin adhesive joints are difficult to characterize, for instance, where the constraint of relatively rigid adherends can mask plastic response. The aim of this work was to quantify adhesive plastic strain hardening and evaluate the effectiveness of a nonlinear hardening model. The plastic response of two structural epoxy adhesives was shown to be dominated by kinematic hardening. A numeric model was developed to describe the shear stress-strain response of scarf and lap shear joints. Experimental adhesive joint responses were compared with linear and nonlinear hardening models. A nonlinear kinematic hardening model described the shear stress-strain response within 3% for a toughened adhesive. Agreement with a second adhesive, using a nonlinear combined hardening model, was within 2%.

Journal of Adhesion Science and Technology, 2019

Piezoelectric materials are widely referred to as "smart" materials because they can transduce me... more Piezoelectric materials are widely referred to as "smart" materials because they can transduce mechanical pressure acting on them to electrical signals and vice versa. They are extensively utilized in harvesting mechanical energy from vibrations, human motion, mechanical loads, etc., and converting them into electrical energy for low power devices. Piezoelectric transduction offers high scalability, simple device designs, and high-power densities compared to electro-magnetic/static and triboelectric transducers. This review aims to give a holistic overview of recent developments in piezoelectric nanostructured materials, polymers, polymer nanocomposites, and piezoelectric films for implementation in energy harvesting. The progress in fabrication techniques, morphology, piezoelectric properties, energy harvesting performance, and underpinning fundamental mechanisms for each class of materials, including polymer nanocomposites using conducting, non-conducting, and hybrid fillers are discussed. The emergent application horizon of piezoelectric energy harvesters particularly for wireless devices and self-powered sensors is highlighted, and the current challenges and future prospects are critically discussed.

While strain-hardening mechanisms for many metals are well understood, polymers in general, and a... more While strain-hardening mechanisms for many metals are well understood, polymers in general, and adhesives in particular, have received less attention. Thin adhesive joints are difficult to characterize, for instance, where the constraint of relatively rigid adherends can mask plastic response. The aim of this work was to quantify adhesive plastic strain hardening and evaluate the effectiveness of a nonlinear hardening model. The plastic response of two structural epoxy adhesives was shown to be dominated by kinematic hardening. A numeric model was developed to describe the shear stress-strain response of scarf and lap shear joints. Experimental adhesive joint responses were compared with linear and nonlinear hardening models. A nonlinear kinematic hardening model described the shear stress-strain response within 3% for a toughened adhesive. Agreement with a second adhesive , using a nonlinear combined hardening model, was within 2%.

International Journal of Engineering Research and Development, 2017

Electrostatic actuation is one of the most prevalent methods of excitation and measurement in mic... more Electrostatic actuation is one of the most prevalent methods of excitation and measurement in micron to Nano scale resonators. Heretofore, in the dynamical behavior analyses of these systems, the resonating beam has been assumed to be perfect conductor which is obviously an approximation. In this paper, effect of electrical resistivity on the vibrational response of these systems including natural frequency and damping, is investigated. The governing coupled nonlinear partial differential equations of motion are extracted and a finite element formulationby developinga new electromechanical element is presented. Calculated natural frequencies are compared with experimental measurements and a closer agreement is achieved in comparison with previousfindings. Results indicate there is a jump in frequency and damping of the system at a critical resistivity. As system size is decreased and applied voltage approaches toward pull-in voltage, electrical resistivity fully dominates the response nature of the system.

Society of the Advancement of Material and Process Engineering, 2017

Cohesive failure is preferred over adhesive failure in bonded joints. Cohesive failure can be def... more Cohesive failure is preferred over adhesive failure in bonded joints. Cohesive failure can be defined in terms of mechanical properties of adhesive, while adhesive failure is a property of adhesion strength between two bonding surfaces. Although the benefits of bonding apply to both metallic and non-metallic materials, the use of bonding has proven particularly attractive for fiber-reinforced composites due to the complications involved with bolted attachment of composites. Bonding of composite parts is challenging since the interface (adhesive) failure or adherend failure should be avoided. The present work considers cohesive, adhesive and adherend failure in shear, so that the effect of bond quality on mode II crack growth can be better understood. Failure modes for weak bonds were observed to be adhesive failure in static and fatigue loading. Strong bonds showed cohesive failure for fatigue loading. However, in static loading, strong bonds with a tough adhesive had a cohesive-adherend mixed failure mode and strong bonds with the standard adhesive had a cohesive-adhesive mixed failure. The fracture toughness for strong bonds in comparison to weak bonds, increased by 100 % for a tough adhesive and 50 % for a standard adhesive. The fatigue crack growth rate for weak bonds increased with a decrease in adhesive toughness.

Society for the Advancement of Material and Process Engineering -North America, 2018

With increasing demand for bonded structures in industrial applications, there is a need for accu... more With increasing demand for bonded structures in industrial applications, there is a need for accurate characterization of adhesives. Adhesives have been observed to behave differently in tension and shear. Their properties also vary between bulk resins and thin films in a bonded structure. An important aspect of structural adhesives is the ability to demonstrate toughness beyond their yield point. This makes the study of adhesive yield criteria important for design. Usually, the yield surface of materials is studied by loading in biaxial stress space. However, adhesives in a bonded structure can only be loaded perpendicular to the bond surface and in shear. A circular tension-shear mixed mode Arcan fixture has been used to study yielding of thin film metals, polymers and composites. This article describes the design of an Arcan fixture and test specimen to achieve reduced stress concentrations, increased stress uniformity, a higher shear to peel stress ratio and the ability to test a bond in compression-shear. Adhesive strain measurements using a noncontact Digital Image Correlation technique are also discussed.

Society for the Advancement of Material and Process Engineering, 2016

Structural adhesives, used in aerospace, are designed to perform according to specific mechanical... more Structural adhesives, used in aerospace, are designed to perform according to specific mechanical loading requirements. Tough adhesives are capable of sustaining large strain in both tension and shear. However, failure stress, failure strain and modes of failure are different for various shear configurations. The focus of this work was to study and compare failure mechanisms under static loading. An elastic-plastic yield criterion and a hydrostatic pressure sensitive yield criterion were compared. The effects of both normal and shear stress on the performance of bulk adhesives as well as on thin film adhesive joints were evaluated. The hydrostatic criterion was 15% better in predicting shear stress than the elastic plastic yield criterion in case of thick adherend lap shear joints and 4% better for lap shear joints and bulk shear specimens.

CAMX Conference Proceedings , 2014

This project considered two adhesives; a ductile and brittle adhesive, to compare their effect on... more This project considered two adhesives; a ductile and brittle adhesive, to compare their effect on joint strength. The optimal thickness of both the adhesives was determined by varying the bondline thickness between aluminum adherends. The ductile adhesive was more sensitive to bondline thickness than the brittle adhesive. The failure mode was cohesive for bondline thicknesses of less than 0.2 mm and transitioned to adhesive failure for bondline thicknesses over 0.6 mm. The joint profile was tailored to study the effect of bondline thickness variation. A convex and concave profile were compared to consider the effect of free edge thickness. A tapered profile was used to consider manufacturing misalignment. The ductile adhesive was stronger with the concave profile and the brittle adhesive was stronger with the convex profile, while misalignment lowered the strength of both adhesives. The failure mode for the tailored profiles was a mix of cohesive and adhesive failure, even though their maximum thickness was less than 0.6 mm. Finite element analysis (FEA), using a maximum plastic shear strain criterion, was used to describe the experimental results. The model correctly described the effect of adhesive thickness and bondline profile for the ductile adhesive, but was less successful in predicting the trends of the brittle adhesive. The results suggest that failure criteria for bonded joints may be adhesive dependent.

Abstract- MEMS have been popular these days due to its multifarious utilities and diverse applica... more Abstract- MEMS have been popular these days due to its multifarious utilities and diverse application. Radio frequency technology is one of such potential areas where MEMS has proved its worth. Though RF MEMS being a little newer than other MEMS technologies has progressed tremendously and holds rein of communication engineering which is the most important sector for chip industries. In this article various applications of RF MEMS and related switching devices has been focused. Above all, the best possible effort has been given to realize a state of art of RF MEMS related issues from multiple angles of design, application, manufacturing, marketing and industry

Abstract-Nanorobotics being a promising research and development era has gained acute attention ... more Abstract-Nanorobotics being a promising research and
development era has gained acute attention and response from
Govt. as well as industries. For long term future application;
the characterization and manufacturing techniques of Nano
robots is yet to be much more developed. Apart from
biomedical applications its potential use in defense,
automotive &aerospace, automation of production
industry,molecular chemistry, material science research and
electronics-communication engineering could be estimated to
visualize its tremendous accuracy, precession, smaller size,
lesser weight, accessibility and efficiency. The Smaller the
size the larger are the specific surface area and energy
efficiency. This is the prime concept behind all micro or
nanotechnology devices. Even though the nanobots have not
yet been deployed in any commercial application with
currently available science and technology; the ongoing
intensity of research & development work tends to a brighter
future where we expect number of miracles with such tiny
nanomachines. In this context a productive discussion has
been carried out concerned with the future application as well
as past-present research scenario of nanorobotics. A numerous
examples have been cited about the work conducted by
individual scientists, engineers and different organizations.
This review work expects a positive attention from its future
readers towards nanorobotics; one of the marvelous sub-areas
of nanotechnology.

International Journal of Adhesion and Adhesives, 2021

Abstract While strain-hardening mechanisms for many metals are well understood, polymers in gener... more Abstract While strain-hardening mechanisms for many metals are well understood, polymers in general, and adhesives in particular, have received less attention. Thin adhesive joints are difficult to characterize, for instance, where the constraint of relatively rigid adherends can mask plastic response. The aim of this work was to quantify adhesive plastic strain hardening and evaluate the effectiveness of a nonlinear hardening model. The plastic response of two structural epoxy adhesives was shown to be dominated by kinematic hardening. A numeric model was developed to describe the shear stress-strain response of scarf and lap shear joints. Experimental adhesive joint responses were compared with linear and nonlinear hardening models. A nonlinear kinematic hardening model described the shear stress-strain response within 3% for a toughened adhesive. Agreement with a second adhesive, using a nonlinear combined hardening model, was within 2%.

Journal of Adhesion Science and Technology, 2019

Piezoelectric materials are widely referred to as "smart" materials because they can transduce me... more Piezoelectric materials are widely referred to as "smart" materials because they can transduce mechanical pressure acting on them to electrical signals and vice versa. They are extensively utilized in harvesting mechanical energy from vibrations, human motion, mechanical loads, etc., and converting them into electrical energy for low power devices. Piezoelectric transduction offers high scalability, simple device designs, and high-power densities compared to electro-magnetic/static and triboelectric transducers. This review aims to give a holistic overview of recent developments in piezoelectric nanostructured materials, polymers, polymer nanocomposites, and piezoelectric films for implementation in energy harvesting. The progress in fabrication techniques, morphology, piezoelectric properties, energy harvesting performance, and underpinning fundamental mechanisms for each class of materials, including polymer nanocomposites using conducting, non-conducting, and hybrid fillers are discussed. The emergent application horizon of piezoelectric energy harvesters particularly for wireless devices and self-powered sensors is highlighted, and the current challenges and future prospects are critically discussed.

While strain-hardening mechanisms for many metals are well understood, polymers in general, and a... more While strain-hardening mechanisms for many metals are well understood, polymers in general, and adhesives in particular, have received less attention. Thin adhesive joints are difficult to characterize, for instance, where the constraint of relatively rigid adherends can mask plastic response. The aim of this work was to quantify adhesive plastic strain hardening and evaluate the effectiveness of a nonlinear hardening model. The plastic response of two structural epoxy adhesives was shown to be dominated by kinematic hardening. A numeric model was developed to describe the shear stress-strain response of scarf and lap shear joints. Experimental adhesive joint responses were compared with linear and nonlinear hardening models. A nonlinear kinematic hardening model described the shear stress-strain response within 3% for a toughened adhesive. Agreement with a second adhesive , using a nonlinear combined hardening model, was within 2%.

International Journal of Engineering Research and Development, 2017

Electrostatic actuation is one of the most prevalent methods of excitation and measurement in mic... more Electrostatic actuation is one of the most prevalent methods of excitation and measurement in micron to Nano scale resonators. Heretofore, in the dynamical behavior analyses of these systems, the resonating beam has been assumed to be perfect conductor which is obviously an approximation. In this paper, effect of electrical resistivity on the vibrational response of these systems including natural frequency and damping, is investigated. The governing coupled nonlinear partial differential equations of motion are extracted and a finite element formulationby developinga new electromechanical element is presented. Calculated natural frequencies are compared with experimental measurements and a closer agreement is achieved in comparison with previousfindings. Results indicate there is a jump in frequency and damping of the system at a critical resistivity. As system size is decreased and applied voltage approaches toward pull-in voltage, electrical resistivity fully dominates the response nature of the system.

Society of the Advancement of Material and Process Engineering, 2017

Cohesive failure is preferred over adhesive failure in bonded joints. Cohesive failure can be def... more Cohesive failure is preferred over adhesive failure in bonded joints. Cohesive failure can be defined in terms of mechanical properties of adhesive, while adhesive failure is a property of adhesion strength between two bonding surfaces. Although the benefits of bonding apply to both metallic and non-metallic materials, the use of bonding has proven particularly attractive for fiber-reinforced composites due to the complications involved with bolted attachment of composites. Bonding of composite parts is challenging since the interface (adhesive) failure or adherend failure should be avoided. The present work considers cohesive, adhesive and adherend failure in shear, so that the effect of bond quality on mode II crack growth can be better understood. Failure modes for weak bonds were observed to be adhesive failure in static and fatigue loading. Strong bonds showed cohesive failure for fatigue loading. However, in static loading, strong bonds with a tough adhesive had a cohesive-adherend mixed failure mode and strong bonds with the standard adhesive had a cohesive-adhesive mixed failure. The fracture toughness for strong bonds in comparison to weak bonds, increased by 100 % for a tough adhesive and 50 % for a standard adhesive. The fatigue crack growth rate for weak bonds increased with a decrease in adhesive toughness.

Society for the Advancement of Material and Process Engineering -North America, 2018

With increasing demand for bonded structures in industrial applications, there is a need for accu... more With increasing demand for bonded structures in industrial applications, there is a need for accurate characterization of adhesives. Adhesives have been observed to behave differently in tension and shear. Their properties also vary between bulk resins and thin films in a bonded structure. An important aspect of structural adhesives is the ability to demonstrate toughness beyond their yield point. This makes the study of adhesive yield criteria important for design. Usually, the yield surface of materials is studied by loading in biaxial stress space. However, adhesives in a bonded structure can only be loaded perpendicular to the bond surface and in shear. A circular tension-shear mixed mode Arcan fixture has been used to study yielding of thin film metals, polymers and composites. This article describes the design of an Arcan fixture and test specimen to achieve reduced stress concentrations, increased stress uniformity, a higher shear to peel stress ratio and the ability to test a bond in compression-shear. Adhesive strain measurements using a noncontact Digital Image Correlation technique are also discussed.

Society for the Advancement of Material and Process Engineering, 2016

Structural adhesives, used in aerospace, are designed to perform according to specific mechanical... more Structural adhesives, used in aerospace, are designed to perform according to specific mechanical loading requirements. Tough adhesives are capable of sustaining large strain in both tension and shear. However, failure stress, failure strain and modes of failure are different for various shear configurations. The focus of this work was to study and compare failure mechanisms under static loading. An elastic-plastic yield criterion and a hydrostatic pressure sensitive yield criterion were compared. The effects of both normal and shear stress on the performance of bulk adhesives as well as on thin film adhesive joints were evaluated. The hydrostatic criterion was 15% better in predicting shear stress than the elastic plastic yield criterion in case of thick adherend lap shear joints and 4% better for lap shear joints and bulk shear specimens.

CAMX Conference Proceedings , 2014

This project considered two adhesives; a ductile and brittle adhesive, to compare their effect on... more This project considered two adhesives; a ductile and brittle adhesive, to compare their effect on joint strength. The optimal thickness of both the adhesives was determined by varying the bondline thickness between aluminum adherends. The ductile adhesive was more sensitive to bondline thickness than the brittle adhesive. The failure mode was cohesive for bondline thicknesses of less than 0.2 mm and transitioned to adhesive failure for bondline thicknesses over 0.6 mm. The joint profile was tailored to study the effect of bondline thickness variation. A convex and concave profile were compared to consider the effect of free edge thickness. A tapered profile was used to consider manufacturing misalignment. The ductile adhesive was stronger with the concave profile and the brittle adhesive was stronger with the convex profile, while misalignment lowered the strength of both adhesives. The failure mode for the tailored profiles was a mix of cohesive and adhesive failure, even though their maximum thickness was less than 0.6 mm. Finite element analysis (FEA), using a maximum plastic shear strain criterion, was used to describe the experimental results. The model correctly described the effect of adhesive thickness and bondline profile for the ductile adhesive, but was less successful in predicting the trends of the brittle adhesive. The results suggest that failure criteria for bonded joints may be adhesive dependent.

Abstract- MEMS have been popular these days due to its multifarious utilities and diverse applica... more Abstract- MEMS have been popular these days due to its multifarious utilities and diverse application. Radio frequency technology is one of such potential areas where MEMS has proved its worth. Though RF MEMS being a little newer than other MEMS technologies has progressed tremendously and holds rein of communication engineering which is the most important sector for chip industries. In this article various applications of RF MEMS and related switching devices has been focused. Above all, the best possible effort has been given to realize a state of art of RF MEMS related issues from multiple angles of design, application, manufacturing, marketing and industry

Abstract-Nanorobotics being a promising research and development era has gained acute attention ... more Abstract-Nanorobotics being a promising research and
development era has gained acute attention and response from
Govt. as well as industries. For long term future application;
the characterization and manufacturing techniques of Nano
robots is yet to be much more developed. Apart from
biomedical applications its potential use in defense,
automotive &aerospace, automation of production
industry,molecular chemistry, material science research and
electronics-communication engineering could be estimated to
visualize its tremendous accuracy, precession, smaller size,
lesser weight, accessibility and efficiency. The Smaller the
size the larger are the specific surface area and energy
efficiency. This is the prime concept behind all micro or
nanotechnology devices. Even though the nanobots have not
yet been deployed in any commercial application with
currently available science and technology; the ongoing
intensity of research & development work tends to a brighter
future where we expect number of miracles with such tiny
nanomachines. In this context a productive discussion has
been carried out concerned with the future application as well
as past-present research scenario of nanorobotics. A numerous
examples have been cited about the work conducted by
individual scientists, engineers and different organizations.
This review work expects a positive attention from its future
readers towards nanorobotics; one of the marvelous sub-areas
of nanotechnology.