Mechanical Engineering

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In this work, a three-dimensional thermomechanical finite element model has been developed to simulate the additive manufacturing process of a Ti-6Al-4V hip implant fabricated using the laser powder bed fusion process. The developed numerical model is used to predict the thermal fields, residual stresses, and part deformation during the printing process. To reduce the mass and consequently the weight of the hip implant, topology optimization has been carried out. Furthermore, the additively manufactured Ti-6Al-4V hip implant subjected to realistic loading conditions is analyzed. In the numerical model, new elements are activated for each layer to simulate the recoating of metal powder, and the thermal gradient, residual stress, and deformation associated with the layer are computed. It is observed that the implant geometry significantly influences the quality of the printed part. Topology-optimized geometry shows a notable reduction in residual stress generation and distortions, along with a significant reduction in mass. © IMechE 2022.

World University root node

(SoE) School of Engineering

Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering

Finite element analysis and topology optimization of Ti-6Al-4V hip implant fabricated by laser powder bed fusion process

This study focuses on characterizing the fatigue damage accumulated in nonlinear aeroelastic systems subjected to stochastic inflows through both numerical simulations and wind tunnel experiments. In the mathematical model, nonlinearities are assumed to exist either in the structure (via a cubic hardening nonlinearity in the pitch stiffness), or in the flow (via dynamic stall condition), or simultaneously in both the structural and aerodynamic counterparts. The aerodynamic loads in the attached flow and dynamic stall conditions are estimated using Wagner's formulation and semi-empirical Leishman–Beddoes model, respectively. To augment the findings to in-field flow conditions, the oncoming wind flow is considered to be randomly time-varying in nature. The stochastic input flow fluctuations are modeled using a Karhunen–Loeve Expansion formulation. The response dynamics and the associated fatigue damage of the aeroelastic system, possessing different sources of nonlinearities, are systematically investigated under isolated cases of deterministic and stochastic input flows. Specifically, the pertinent role of stochasticity in the input flow is brought out by presenting the response dynamics and the associated fatigue damage accumulation for different values of noise intensity and time scale of the input flow fluctuation. It is demonstrated that under fluctuating flow conditions, the dynamics intermittently switch between attached flow and the dynamic stall regimes even at low mean flow speeds. The intermittent nature of the response varies as the time scale and intensity of the oncoming flow are varied. The role of torsional stresses as the predominant component dictating the fatigue damage accumulation irrespective of the source of nonlinearity is illustrated. Using the rainflow counting method and Miner's linear damage accumulation theory, it is shown that the accumulated fatigue damage is substantially higher under stochastic flow conditions as compared to deterministic input flows. Importantly, it is observed that different time scales and intensities of the oncoming flow fluctuation play a pivotal role in dictating the fatigue damage in aeroelastic systems. Finally, fatigue damage is observed to be significantly higher for torsionally dominant oscillations in the dynamical stall regime compared to the oscillations at the attached flow regime. The numerical findings are strengthened by drawing comparisons with the preliminary results obtained from wind tunnel experiments performed on a NACA 0012 airfoil undergoing dynamic stall. To the best of our knowledge, this is the first study that systematically bridges the dichotomy between the stall-induced dynamical signatures in stochastic aeroelastic systems and maps the same to the corresponding structural damage. © 2022 Elsevier Ltd

Fulltext

International Journal of Non-Linear Mechanics

Stall-induced fatigue damage in nonlinear aeroelastic systems under stochastic inflow: Numerical and experimental analyses

This paper addresses the joint optimization model of production scheduling, work-in-process (WIP) inventory control and group preventive maintenance (PM) planning in a multi-machine system with multi-components. The objective is to obtain optimum production sequence, PM intervals and grouping of components, which minimize the total expected cost per unit time of the system. A new meta-heuristic named Jaya algorithm and two popular algorithms viz. simulated annealing (SA) and particle swarm optimization (PSO) are applied to optimize the objective function. Initially, the optimum group of components is obtained based on the integer multiples of individual PM intervals. Secondly, the job permutation sequence incorporating group PM intervals is identified with the largest order value (LOV) rule. The shift in optimum PM intervals is realized with an advanced-postpone balancing approach. Computational results reveal that the proposed integrated model along with group PM yields up to 25% cost reductions when compared to the integrated model with individual maintenance as well as 37% savings while no integration is performed. Furthermore, the performance of algorithms is evaluated with large-sized problems. The obtained results show that Jaya and SA yielded comparable results, however, PSO is least productive. Thus, the proposed approach yields better economic performance and brings more improvised solutions as compared to the conventional methods of integrated scheduling and maintenance optimization problems. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Annals of Operations Research

Joint optimization of production scheduling and group preventive maintenance planning in multi-machine systems

This study focuses on characterizing the bifurcation scenario and the underlying synchrony behavior in a nonlinear aeroelastic system under deterministic as well as stochastic inflow conditions. Wind tunnel experiments are carried out for a canonical pitch-plunge aeroelastic system subjected to dynamic stall conditions. The system is observed to undergo a subcritical Hopf bifurcation, giving way to large-amplitude limit cycle oscillations (LCOs) in the stall flutter regime under the deterministic flow conditions. At this condition, we observe intermittent phase synchronization between pitch and plunge modes near the fold point, whereas synchronization via phase trapping is observed near the Hopf point. Repeating the experiments under stochastic inflow conditions, we observe two different aeroelastic responses: low amplitude noise-induced random oscillations (NIROs) and high-amplitude random LCOs (RLCOs) during stall flutter. The present study shows asynchrony between pitch and plunge modes in the NIRO regime. At the onset of RLCOs, asynchrony persists even though the relative phase distribution changes. With further increase in the flow velocity, we observe intermittent phase synchronization in the flutter regime. To the best of the authors' knowledge, this is the first study reporting the experimental evidence of phase synchronization between pitch and plunge modes of an aeroelastic system, which is of great interest to the nonlinear dynamics community. Furthermore, given the ubiquitous presence of stall behavior and stochasticity in a variety of engineering systems, such as wind turbine blades, helicopter blades, and unmanned aerial vehicles, the present findings will be directly beneficial for the efficient design of futuristic aeroelastic systems. © 2022 Author(s).

Chaos

Experimental investigation on the synchronization characteristics of a pitch-plunge aeroelastic system exhibiting stall flutter

The effect of variation of mass flow rate (m f ) and number of collectors (N) on the yearly efficiency of a single slope solar still by incorporating series connected N similar photovoltaic thermal flat plate collectors (NPVTFPCSS) has been investigated, keeping a constant water depth in basin as 0.14 m. The various parameters have been calculated, taking into account all four types of weather conditions for New Delhi using computing code developed in MATLAB-2015a. All equations and required data have been fed to the computing code for evaluating different relevant parameters. It has been concluded that the value of all types of annual efficiencies, except annual electrical efficiency, diminishes with increase in the value of m f at a selected value of N until m f = 0.10 kg/s and then becomes almost constant. Optimal values of N from annual overall exergy efficiency and annual overall thermal efficiency viewpoints have been found as four and ten respectively. © 2022 IWA Publishing. All rights reserved.

Water Supply

An investigation on effect of variation of mass flow rate and number of collectors on yearly efficiency of single slope solar still by incorporating N similar photovoltaic thermal flat plate collectors

This work investigates the effect of ultrafine-grain microstructure on the oxidation behavior of AlCoCrFeNi high entropy alloy (HEA). The ultrafine-grain microstructure is obtained using stationary friction processing performed at two different rotational speeds, 400 and 1800 rpm, for 5 min duration. Processed samples demonstrate high depth of refinement (DOR) and ultrafine grain size (0.43-1 μm) at high rotational speeds along with significant phase transformations from BCC/B2 to FCC microstructure. Further, surface free energy of the ultrafine-grain microstructure is enhanced up to 35%. Oxidation kinetics of the ultrafine-grained sample is decelerated up to 12-48% in a temperature range of 850-1050 °C for a duration of 100 h. Chromia and alumina were the predominant oxides formed in almost all the samples oxidized at elevated temperature. In addition, spinel Co(Cr,Fe)2O4/Fe(Co,Cr)2O4 formation is also detected in the unprocessed oxidized samples. Processed samples rich in grain boundaries (GBs) promote internal oxidation to form Al-rich inner oxides. The enhanced oxidation resistance of the processed samples is attributed to the microstructural refinement and homogenization resulting in the formation of protective chromia followed by Al-rich inner oxides. © 2022 American Chemical Society.

ACS Omega

Enhanced Oxidation Resistance of Ultrafine-Grain Microstructure AlCoCrFeNi High Entropy Alloy

Worker' work-rotation between the workstations of an assembly line is a common task to an assembly line manager, to manage the workload between the assembly line workers. Usually, worker work rotation makes an interruption to a continuous production system. It is a desire of an assembly line manager to avoid the worker's work-rotation, at least between the work breaks. This work aims to protect the manager's interest by predicting the comfortable work-duration time of an assembly line worker for a given work, based on the working condition and the instantaneous physical & mental status of the worker. The comfortable work-duration time can be used during the worker's work assignment to reduce interruptions. Factors, which influence the longevity of workers' comfortable work duration time are identified. IIoT based sensors are proposed here to monitor the relevant factors for diagnostics. Machine Learning techniques are used as a part of prognostics to predict the comfortable work-duration time of a worker, based on his/her physical & mental status. Implementation methodology is explained along with a simulated experiment. © 2022 Elsevier B.V.. All rights reserved.

Procedia CIRP

A Dynamic System to Predict an Assembly Line Worker's Comfortable Work-Duration Time by Using the Machine Learning Technique

The present paper develops an integrated approach for joint optimization of preventive maintenance (PM) planning and quality control policy in a single machine manufacturing system. Considering the economic dependency between quality and maintenance parameters, the proposed model aims to optimize the four decision variables, viz. PM interval, sample size, sample frequency and control limit coefficient to minimize the expected total integrated cost per unit time. The imperfect age-based PM model is applied which addresses the most practical issue that a unit may not always be maintained to an as-good-as-new state. Analysing the problem to be NP-hard in nature, a recently developed meta-heuristic named Jaya algorithm is applied to retrieve the near-optimum solutions. The peculiarity of Jaya as compared to conventional heuristics is that it is a parameter-less algorithm thus does not require tuning to algorithm-specific parameters thereby minimizing computational complexity to a great extent. A numerical example is presented to demonstrate the effectiveness of the integrated economic design of PM and process quality control parameters. Computational results reveal the effectiveness of the proposed approach. © 2022 The Authors. Published by Elsevier B.V.

An Efficient Jaya Algorithm for Joint Optimization of Preventive Maintenance and Quality Policy in Production Systems

In the current study, the high temperature oxidation behavior of AlCoCrFeNi high entropy alloy (HEA) following severe shear deformation was investigated. X-ray diffraction and transmission electron microscopy analysis confirmed spinodal distribution of B2 and BCC phase in the as cast specimen. In contrast, the processed specimen showed a dual phase microstructure (B2/BCC+FCC) after shear deformation. Electron backscattered diffraction analysis revealed significant grain refinement from 90 µm for the as-cast HEA to nearly 2 µm for the processed specimen. The processed specimen showed up to 66% reduction in the oxidation kinetics compared to the as cast alloy. The remarkable improvement in the high-temperature oxidation performance following processing is attributed to complete microstructure refinement. The current study provides a sustainable solution and a new pathway for addressing the looming problem of material deterioration at high temperatures. © 2022 Elsevier B.V.

Journal of Alloys and Compounds

High oxidation resistance of AlCoCrFeNi high entropy alloy through severe shear deformation processing

In this article, a V-groove weld joint of P92 steel, typically used in ultra-supercritical power plants, has been numerically analyzed to estimate transient temperature distributions and residual stresses. A weld simulation model using Prescribed Temperature approach was developed. This approach was used to reduce the computational expenditure and speed up the time-intensive analysis setup. The finite element method was employed to compute the residual stresses generated in the weld region and the heat-affected zone along the thickness of the plate. In the experimental investigation, the through-thickness residual stresses were measured using the deep-hole drilling (DHD) method. Good agreement was observed between numerically and experimentally obtained residual stresses. The maximum temperature was observed at the weld pool area which decreased in the parabolic trend toward the base metal. © 2022, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

Numerical Simulation of Temperature Fields and Residual Stresses in Multi-Pass Weld Using the Novel Prescribed Temperature Approach with Experimental Validation