Department of Mechanical Engineering

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This article presents the results of a study on the corrosion characteristics of the single and dual particle reinforced aluminum alloy 6063 based composites. The reinforcements of silicon carbide and zircon sand were utilized to fabricate the composites by stir casting technique. The influence of reinforcement and their weight percentage on the hardness variations was investigated. The electrochemical tests in sodium chloride solution were conducted to study the corrosion performance of reinforced composites and base alloy. From the corrosion analysis, it was observed that the single particle reinforcement offered better solution on enhancing the corrosion resistance of base aluminum alloy in comparison with dual particle reinforced composites. In the single particle reinforced composites, addition of zircon sand exhibited increased corrosion resistance, when compared to silicon carbide reinforced composites. The governing mechanism behind increased corrosion resistance was found to be the absence of galvanic coupling between the elemental compounds and the corrosive media at particle–matrix interface. The scanning electron microscopy of composites was performed to analyze corrosion mechanism and correlated well with the corrosion behavior. © 2016, © IMechE 2016.

World University root node

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications

Influence of single and dual particle reinforcements on the corrosion behavior of aluminum alloy based composites

The dissimilar joint between aluminium alloy 6063 and aluminium has been made using the friction stir welding process. Three input parameters: Tool rotational speed, feed rate and dwell time have been varied and their effect of the mechanical properties has been studied. Obtained weld joints have been characterized for tensile properties, hardness, and corrosion behavior. Effort has been made to study the in process force acting on the joint and establishing its dependence on the welding parameter. The use of full factorial design methodology brings out the contribution of input parameters and their effect on the output mechanical properties. © 2018 Newswood Limited. . All rights reserved.

Lecture Notes in Engineering and Computer Science

Friction stir welding of dissimilar AA6063/Al joint

This paper addresses the dynamic control of a 2PRP-2PPR vertical planar parallel manipulator. This proposed manipulator can be used for the purpose of lower limb rehabilitation applications (in specific sitting/lying type of lower limb rehabilitation applications). The kinematic and dynamic model of the proposed manipulator are derived and discussed. An augmented PID control along with an uncertainty estimator is proposed for the motion control of the manipulator. The proposed system performance along with the motion controller is demonstrated numerically for the application of lower limb rehabilitation therapies using a clinically recorded gait data. The robustness of the controller and its parameter sensitivity are analysed through different operating conditions and their results are presented. Note: P—stands for Prismatic/translation joint and R—stands for Rotary/revolute joint. © Springer International Publishing AG 2017.

Mechanisms and Machine Science

Augmented PID control of a 2PPR-2PRP planar parallel manipulator for lower limb rehabilitation applications

In present research work, the modified Granjon implant test was performed to evaluate the susceptibility of AISI 8620 and AISI 304 steels toward the hydrogen-assisted cracking. To measure the diffusible hydrogen level (HD) in deposited metal, glycerin method was employed. Shielded metal arc welding process with basic type electrode was used to deposit the metal. The hydrogen was intentionally introduced for the plate of the material AISI 304 by using an oil of grade Society of Automotive Engineers 10, which is of very low viscosity. The heat-affected zone susceptibility was quantified by finding the lower critical stress for a measured hydrogen content. © 2017, Springer Science+Business Media New York and ASM International.

Metallography, Microstructure, and Analysis

Study on Hydrogen-Assisted Cracking in High-Strength Steels by Using the Granjon Implant Test

In Very High Temperature Reactor (VHTR), The Nb-V modified 9Cr-1Mo (P91) creep strength enhanced ferritic (CSEF) steel is currently considered as a candidate material for reactor internals and reactor pressure vessels (RPVs). After the welding of P91 steel, the inhomogeneous microstructure of weldment is a serious issue because it promotes the well-known Type IV cracking in P91 weldments. The present research work is focused on how the microstructure evolve in various zone of P91 pipe weldment during the sub-critical post weld heat treatment (PWHT) and normalized and tempered (N&T) heat treatment. The effect of PWHT and N&T heat treatment are also considered on tensile properties and hardness variation of P91 weldments. To characterize the sample scanning electron microscope (SEM), X-ray diffraction (XRD) and optical micrograph was used. It was observed that the N&T heat treatment provides the homogeneous microstructure compared to PWHT. The superior mechanical properties was also measured in N&T condition compared to PWHT. Study of fracture surface morphology of tensile tested specimen in different heat treatment condition is also presented. © 2017 Elsevier B.V.

Materials Science and Engineering A

Effect of normalization and tempering on microstructure and mechanical properties of V-groove and narrow-groove P91 pipe weldments

The effect of weld groove design and heat treatment on microstructure evolution and Charpy toughness of P91 pipe weldments was studied. The P91 pipe weldments were subjected to subcritical post weld heat treatment (760 °C-2 h) and normalizing/tempering conditions (normalized-1040 °C/40 min, air cooled; tempered 760 °C/2 h, air cooled) were employed. The influence of subsequent PWHT and N&T treatment on the microstructure of various zone of P91 pipe weldments were also investigated. The present investigation also described the effect of PWHT and N&T treatment on hardness, grain size, precipitate size, inter-particle spacing and fraction area of precipitates present in each zone of P91 pipe weldments. The result indicated great impact of heat treatment on the Charpy toughness and microstructure evolution of P91 weldments. The N&T treatment was found to be more effective heat treatment compared to subsequent PWHT. Charpy toughness value was found to be higher for narrow-groove design as compared to conventional V-groove design. © 2017, The Korean Institute of Metals and Materials and Springer Science+Business Media B.V.

Metals and Materials International

Microstructure characterization and charpy toughness of P91 weldment for as-welded, post-weld heat treatment and normalizing &amp; tempering heat treatment

The high-temperature Cr-Mo creep strength-enhanced ferritic (CSEF) steels are mainly used in nuclear and thermal power plants. In the present investigation, a systematic study on fracture surface morphologies of tensile and impact tested specimens and mechanical properties of cast and forged (C&F) P92 steel was performed for various heat treatment conditions. The heat treatment was carried out in normalizing temperature range of 950-1150 °C and then tempered to a fixed tempering temperature of 760 °C. The effect of varying normalizing temperatures before and after tempering on microstructure evolution, tensile properties, Vicker’s hardness and Charpy toughness was studied. The normalizing temperature before and after tempering was having a noticeable effect on mechanical properties of as-received P92 steel. The fracture surface of impact and tensile tested samples was also studied for various normalizing temperatures with or without tempering. Fracture surface morphology was affected by the presence of secondary phase carbide particles. The fraction area of cleavage facets on the tensile fracture surface was found to be increased with an increase in the normalizing temperature. The fractured tensile specimens were characterized by transgranular ductile dimples, tear ridges and transgranular cleavage facets for various heat treatments. The fracture mode of impact tested samples was more complex. It showed both quasi-cleavage facets and ductile dimple tearing for various normalizing temperatures. © 2017, ASM International.

Journal of Materials Engineering and Performance

Effect of Normalizing Temperature on Fracture Characteristic of Tensile and Impact Tested Creep Strength-Enhanced Ferritic P92 Steel

Over the past years, the alloy development has led to the development of new steels such as P91 (X10CrMoVNb9-1), P911 (X11CrMoWVNb9-1-1), and P92 (9Cr–0.5Mo–1.8W–V–Nb). The topic of the present research work was selected to concentrate on the dissimilar welding of P911 and P92 steels by using manual metal arc welding (MMAW) to work on the weldability with pre and post weld heat treatments. The welding procedure for components of 9–12% Cr steels was related to three main aspects: the materials, the process used for welding and the type of components used to weld these steels. MMAW process was applied to produce the dissimilar joint of the P911 and P92 steel by using E-911 electrode. Normalizing and tempering (N&T) and post-weld heat treatment (PWHT) were applied to the welded plates of thickness 12 mm and they were tested using tensile test, hardness test, Charpy toughness test, and microstructural investigations. During the room temperature tensile tests, serrations were also observed. PWHT of weldments resulted in a negligible increase in ultimate tensile strength and yield strength while a significant change was measured after N&T. The N&T condition resulted in minimum hardness gradient and maximum homogenization of microstructure across the dissimilar weldments. The room temperature Charpy toughness value was also found to be maximum for N&T treatment. © 2017 The Indian Institute of Metals - IIM

Transactions of the Indian Institute of Metals

Microstructure Evolution and Mechanical Properties of Dissimilar Welded Joint of P911 and P92 Steel for Subsequent PWHT and N&amp;T Treatment

The paper presents a Hamiltonian approach for extracting the dynamic instability parameters of homogeneously deforming dielectric elastomer actuators subjected to an unequal biaxial prestress, and driven by a suddenly applied electric load. The approach relies on setting up the balance between the kinetic, strain, and electrostatic energy at the point of maximum overshoot in an oscillation cycle. The equation of the stagnation curve, obtained by invoking aforestated statement of energy-balance, is operated upon by the condition of instability to determine the instability parameters. The underlying principles of the approach are elucidated by considering the Ogden family of hyperelastic material models. The approach is however portrayed generically, and hence, can be extended to the other hyperelastic material models of interest. The estimates of the dynamic instability parameters are corroborated by examining the saddle-node bifurcation points in the time-history response obtained by integrating the equation of motion. A parametric study is conducted to bring out the effect of unequal biaxial prestress, and the trends of variation of the critical electric field and the thickness-stretch on the onset of dynamic instability are presented. A quantitative comparison with the static instability parameters reveals that the dynamic instability gets triggered for electric fields that are lower than those corresponding to the static instability. In contrast, the maximum stretch experienced by the actuator at the dynamic instability is significantly higher than that at the static instability. The crucial inferences can find their potential use in the design of DEAs subjected to a transient motion. © 2017 IOP Publishing Ltd.

Smart Materials and Structures

Dynamic instability of dielectric elastomer actuators subjected to unequal biaxial prestress

In this work we have fabricated vertically grown novel rod type nanostructures of zinc oxide on a silicon substrate which are decorated with metals (Al, Ag, Au, and Au-Pd) using sputtering technique. These structures have been utilized in remediation of industrial dyes through solar light photo-catalysis with enhanced efficacy. The obtained structures have been thoroughly characterized using x-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), and Fourier transform infrared spectroscopy (FTIR) analysis etc. The decorating elements have been compared for the photo-catalytic performance relative to the pristine zinc oxide structures and they are found to act as electron sink for the electrons generated by redox reaction on the surface of the ZnO nanostructure. This is attributed as a main reason for increasing the photocatalytic yield by the decorated structures. Approximately 20-45 % (maximum in case of Au-Pd and minimum in case of Ag) enhancement in dye degradation (concentration basis) was achieved by decoration of metals in comparison with undecorated ZnO nanorod. A theoretical model comprising of governing equations associated with the mechanism of the catalysis process was developed for proper understanding of the experimental data. © 2017 IOP Publishing Ltd.