Rajesh V. Patil

Bio: Rajesh V. Patil is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Welding & Heat exchanger. The author has an hindex of 3, co-authored 15 publications receiving 29 citations. Previous affiliations of Rajesh V. Patil include Sinhgad Institute of Technology & Sinhgad College of Engineering.

Bending and vibration studies of FG porous sandwich beam with viscoelastic boundary conditions: FE approach

Abstract: Abstract Bending and vibration characteristics of FG porous sandwich beam with viscoelastic boundary conditions are investigated. Complex shear modulus and associated loss factor are considered for the viscoelastic interlayer. The beam is constrained by viscoelastic supports (VES) at either end. Complex stiffness model is adopted for VES. The transverse deflection, natural frequency, loss factors, and mode shapes are obtained by varying VES stiffness. Furthermore, the study is extended to sandwich beams with various (H, O, V, and X) porosity patterns. The results convey that VES contribution in vibration damping is more predominant when the supports are less stiff (more viscous).

Estimation of Orthodontic Force Parameters with Developed Computer Application for En-Masse Retraction of Six Maxillary Anterior Teeth

Abstract: In the current research study, a computer application (desktop software) was developed to determine orthodontic force application points to achieve en-masse retraction of six maxillary anterior teeth. In this type of tooth movement, retraction forces are applied with retraction spring by fixing it anteriorly and posteriorly. Based on other orthodontic force, moment and distance parameters, proper location of retraction spring attachment on anterior and posterior side is needed to ensure accurate application of orthodontic appliances. In this research study, the computer application (desktop software) based on simple trigonometric calculation was developed for the ease of estimation of location of required retraction force. This computer application can be used both in labial orthodontics (LaO) and lingual orthodontics (LiO) if other force, moment, and distance parameters are known. Due to simple user interface of computer application, the task of determination of force application points will be simplified for orthodontists which is desirable.

Coaxial monitoring of the fibre laser lap welding of Zn-coated steel sheets using an auxiliary illuminant

Abstract: In the laser welding process, weld defects are often caused by many factors, such as variations in the laser power, welding speed and gaps between two workpieces. In an auto-welding system, the on-line monitoring of the welding quality is very important in avoiding weld defects. In this paper, an on-line coaxial monitoring system with an auxiliary illuminant was built for the fibre laser welding of galvanised steel; images of the weld pool were taken during the welding process. Profiles of the weld pool and the keyhole were obtained by processing the images using the region-growing algorithm and the Canny algorithm. In this research, we used the on-line monitored weld pool width to monitor the weld surface width. The weld penetration status was divided into the three categories of incompletely penetrated, moderately penetrated and over-penetrated using the value of d (diameter at the bottom of the keyhole)/D (diameter at the top of the keyhole). Thus, the weld width and weld penetration status of fibre laser welding can be monitored on-line.

Active closed-loop vortex-induced vibration control of an elastically mounted circular cylinder at low Reynolds number using feedback rotary oscillations

Abstract: An active rotary oscillation feedback control methodology is adopted to suppress the flow-induced transverse vibration (VIV) of an elastically supported impenetrable circular cylinder in a uniform low Reynolds number flow ( $$\textit{Re} = 100$$ ). The coupled fluid–structure interaction is replicated by applying the moving mesh technique via a user-defined function (UDF) in the main code of a commercial CFD solver. The closed-loop VIV control action is realized by active forced rotational oscillations of the circular cylinder about its axis based on the feedback signal of the lift coefficient. This prevents the occurrence of resonance by shifting the vortex shedding frequency away from the natural oscillator frequency. Three different active closed-loop proportional controllers are implemented, and their superior performance in cylinder VIV suppression is demonstrated against that of a representative open-loop control system with pre-specified rotational oscillations. It is shown that, in comparison with the open-loop system, the selected closed-loop controller achieves a better cylinder VIV response suppression with a much lower control effort along with considerable reductions in the associated lift/drag coefficients. Furthermore, the closed-loop controller is very effective in a wide range of reduced velocities and does not need to find the “lock-on” forcing frequency for proper de-synchronization. Moreover, the imposed feedback cylinder rotary oscillation is found to considerably affect the spatial characteristics of the wake flow structure by changing the 2S-Coalescent wake pattern (C-2S-mode) of an uncontrolled cylinder into the classical von Karman vortex street (2S-mode), very similar to that of a stationary obstacle. Lastly, when the system is in the fully developed condition, the proportional controller can be complemented by a fuzzy logic inference system for intelligent tuning of gain parameter in order to suppress the impulsive upsurge observed in the cylinder force coefficients of the proportional controller at the start of the control action.

Free vibration analysis of a cantilever beam with a slant edge crack

Abstract: As one of major failure modes of mechanical structures subjected to periodic loads, edge cracks due to fatigue can cause catastrophic failures in such structures. Understanding vibration characteristics of a structure with an edge crack is useful for early crack detection and diagnosis. In this work, a new cracked cantilever beam model is presented to study the vibration of a cantilever beam with a slant edge crack, which cannot be modeled by previous methods considering a uniform edge crack along the width of the beam in the literature. An equivalent stiffness model is proposed by dividing the beam into numerous uniform independent thin pieces along its width. The beam is assumed to be an Euler–Bernoulli beam. The crack is assumed to be distributed along the width of the beam as a straight line and a parabola. The methodology proposed in this work can also be extended to model a crack with an arbitrary curve. Effects of crack depths on the nondimensional equivalent stiffness at the crack section of the c...

Parametric investigation of the mechanical behavior of expanding-folding absorbers and their implementation in sandwich panels core

Abstract: Thin-walled energy absorbers are one of the common structures that are used in vehicle body for increasing the crashworthiness and consequently decreasing injuries. Investigated new type of thin-walled aluminum matrix and a thin-walled steel punch energy absorber structure has been investigated in this paper. Energy is absorbed as the matrix expansion followed by simultaneous matrix and punch folding. Present study proposes a sandwich panel based on expanding-folding absorber units to evaluate their crush mechanism. Parametric study has been done using finite element code LS-DYNA while experimental tests have been implemented to validate the FE model. The panels have been tested under three axial quasi-static loading conditions including a rigid half-cylinder and a rigid plate. Parametric study considers the punch angle, matrix thickness and punch thickness. The optimum structure based on energy absorption has then been used as a structural member in the sandwich panel until a panel with high specific energy absorption be introduced. Also it have been seen that all the curves for the expansion section can be estimated using polynomial second order functions, with a high accuracy.

Numerical Modelling and Multi Objective Optimization Analysis of Heavy Vehicle Chassis

Abstract: The primary supporting structure of an automobile and its other vital systems is the chassis. The chassis structure is required to bear high shock, stresses, and vibration, and therefore it should possess adequate strength. The objective of current research is to analyze a heavy motor vehicle chassis using numerical and experimental methods. The CAD design and FE analysis is conducted using the ANSYS software. The design of the chassis is then optimized using Taguchi design of Experiments (DOE); the optimization techniques used are the central composite design (CCD) scheme and optimal space filling (OSF) design. Thereafter, sensitivity plots and response surface plots are generated. These plots allow us to determine the critical range of optimized chassis geometry values. The optimization results obtained from the CCD design scheme show that cross member 1 has a higher effect on the equivalent stresses as compared to cross members 2 and 3. The chassis mass reduction obtained from the CCD scheme is approximately 5.3%. The optimization results obtained from the OSF scheme shows that cross member 2 has a higher effect on equivalent stress as compared to cross members 1 and 3. The chassis mass reduction obtained from optimal space filling design scheme is approximately 4.35%.