bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards Use of Structural Equation Modelling in Enumerating Correlation of Qualitative and Quantitative Factors With Manufacturing Part Deviation
Authors: Srinivasan Karthik , Kumar G. V. V. Ravi
Published: February 2024

A typical gas turbine part that is fitted into an aero engine goes through many manufacturing processes spread across multiple supply chain organizations. Despite high precision standards in comparison to other industry segments, geometrically complex parts in gas turbine do end up deviating from design geometries. These parts go through visual inspection at every stage in addition to dimensional measurement of critical characteristic features. Operator involvement is un-avoidable at present and despite being process driven, operator level variances are not ignorable in manufacturing operations. With Industry 4.0 being adopted by many industries, and 5.0 emerging, user involvement is minimized, and a large amount of data is generated and captured throughout the process of manufacturing, testing, verification, assessment and sentencing of parts for use in aerospace industry. As data is becoming increasingly centralized by adoption of cloud technologies, it becomes more efficient to troubleshoot problems through mathematical modelling — the brain behind Artificial Intelligence (AI). Structural Equation Modelling (SEM) has been in use for long in management sciences and decision making involving ill-defined factors and that have strong interdependencies.

This article presents a methodology of leveraging SEM technique in identifying correlation of qualitative and quantitative factors with part deviation assessment. A framework for converting qualitative inspection information to quantitative information is presented to leverage SEM. The implementation is explained using a representative data for a turbomachinery airfoil to demonstrate the approach and considerations. Few use cases of SEM in the industry are also presented.
Inlet Distortion Studies on a Centrifugal Compressor
Authors: Jaiswal Sujeet Kumar , Bubanale Sadashiv , Keerthi M. C.
Published: February 2024

Centrifugal compressors can be subjected to non-uniformity in inlet flows due to complicated inlet pipe geometries arising from space constraints and the wakes of protruding instrumentation, impacting the compressor’s performance. Inlet distortion can cause premature stall initiation and surge, effectively reducing the operating range of the device. This motivates a detailed characterization of the performance for different types of inlet distortion. While the impact of distortion in axial compressors is studied extensively, there are relatively fewer studies for centrifugal compressors. The present study investigates the effects of inlet total pressure distortion on the performance of a centrifugal compressor. The rig employing a centrifugal compressor of a turbocharger is developed and built for the study to analyze full-speed compressor aerodynamics. The experimental setup comprises of a turbocharger, whose turbine is driven through flow-metered compressed air, enabling independent control of the shaft speed by adjusting the flow rate and pressure. The compressor section line is instrumented with pressure sensors, thermocouples, shaft RPM sensor, to enable the measurements required to generate the compressor characteristics. A typical operating point of the compressor with clean inflow at 130,000 RPM is a pressure ratio of 1.4 with a mass flow rate of 0.02 kg/s. Provision is added to include distortion screens to generate total pressure distortion at the inlet duct of the compressor. A PC-based data acquisition program is developed to acquire and monitor the compressor map data as well as monitor other parameters for the purposes of safety and maintenance. The distortion screens are fabricated and characterized as per the SAE ARP 1420 distortion descriptors to generate circumferential and radial total pressure distortion for different cases. The compressor performance with clean inflow is compared with different distortion screens in terms of the static pressure ratio, isentropic efficiency, for a given normalized mass flow rate and normalized RPM. In the presence of inflow distortion, the compressor performance is expectedly found to deteriorate, particularly with a lower pressure rise at the same RPM and flow rate. For a given RPM, the effect is substantial near choke compared to the near-surge region. The decrease in isentropic efficiency is more significant at higher RPMs and near choke. A detailed account of the impact of different types of distortion, in terms of their circumferential and radial distortion intensities, on the compressor global performance, along with insights gained from the local measurements, are presented.
Structural Validation of Portable Compressor Trailer Under Dynamic Conditions
Authors: Bhirud Mehul , Valand Bharatkumar , Rathod Ankit
Published: February 2024

Portable air screw compressors are the most reliable, effective, and well-suited for the unique needs of building roads, performing restoration work, conducting civil engineering, mining, sandblasting, oil and gas exploration etc. This compressors must be designed to withstand tough site circumstances and difficult-to-reach site locations that may have challenging topography. Compressed air at remote locations is also used to power tools on the site, such as power hammers, drills, saws, wrenches, nail guns etc. These portable compressors are exposed to higher load such as dynamic load, lifting/towing load and random vibration load during their operation such as towing/lifting and transportation from one location to another. Fatigue life, stability and performance of majority of the structures and systems depend significantly on dynamic loadings applied on them. In order to guarantee effective product performance without trolley base frame failure over product life, it is crucial to examine the structural strength of the compressor base frame under such dynamic loading scenarios.

Ingersoll Rand India is equipped a portable compressor unit using cutting-edge technology to meet the requirements of the business. The Modal and random vibration analysis of the portable compressor trolley base frame has been analyzed in the current study to evaluate the compressor trolley base frame. To verify dynamically, the unit’s Natural Frequency has been computed using modal analysis. According to SAE J 2380 standard, random vibration analysis has been performed to examine the base frame’s strength and its fatigue life against random loading for 92.6 hours of testing duration. Successful validation of a given equipment implies 100000 miles of life with 90% success probability without any random vibration fatigue failure. A thorough investigation of modal and random vibrations analysis was performed using ANSYS 2020 R2. Random vibration analysis was performed by applying PSD G acceleration at support base as per SAE J 2380 standard. The strength of the trolley base frame has been evaluated through a number of parameters, such stress accumulation, natural frequencies, fatigue life, and damage factor.

According to the results of the investigation, estimated system natural frequency was found away from the operating frequency of the system which ensure the system will operate without critical resonance and high stresses while in operation. Under the random vibration analysis, random fatigue life, random fatigue damage factor and equivalent stress were found to be acceptable. According to the numerical investigation, the compressor’s base frame was unlikely to fail during its service life against the dynamic loads random in nature. Physical test of the compressor unit was also carried out for various road profiles and found the system structurally strong enough & having good degree of agreement with virtual validation.
Application of Machine Learning Based Meta Models for Predicting Film Cooling Effectiveness in Gas Turbine Blades
Authors: Grover Amit , Shrivastava Rishabh
Published: February 2024

In Large Gas Turbines, turbine components in particular blades and vanes operate at significantly high temperatures. As a result, cooling of these components becomes one of the prime objectives during the design phase. There are different cutting-edge internal cooling techniques such as convection cooling - internal ribbed surface heat transfer only, serpentine passage, impingement cooling, film cooling and combination of all these methods are used to meet the heat transfer design requirements. Among all methods, film cooling plays a vital role in the improvement of heat transfer and is extensively applied to ensure thermal protection of hot gas path components especially blades and vanes. A precise estimation of film cooling effectiveness is critical for evaluating external heat transfer and metal temperature. Conventional approach based on heat transfer correlations and finite element method with varied film cooling scheme is highly resource intensive which involves setting up different cooling schemes. The model setup process includes geometrical modeling, meshing of model, boundary conditions application and performing thermal simulation to achieve optimal design. This constrained the number of film cooling hole configuration which could be evaluated, resulting in sub-optimal design in terms of cooling effectiveness.

In this work Machine learning approach is explored for establishing optimal film cooling hole configuration with minimal time and efforts and can be applied during early design phase. Film cooling effectiveness is influenced by several factors like coolant & mainstream conditions, cooling hole arrangement and other geometrical parameters such as cooling hole diameter, inclination, pitch, breakout, coverage, and location on the airfoil geometry etc. In current scope cooling hole diameter, pitch, cooling hole count, and surface angle is used as input feature to the Machine Learning model and cooling effectiveness as target variable. The input to the Machine learning model is derived from physics-based heat transfer calculations. A comparative study is introduced between linear regression, K-nearest neighbour, random forest, and gradient boost Machine learning methods using root mean square values as an evaluation metrics. Optimal hyperparameter were calculated for each model using grid search method. It was observed that gradient boost method shows minimum error, additionally cooling hole count is the most significant factor in predicting cooling effectiveness.
Application of Advanced Sampling Techniques to Handle Class Imbalance in GT Blade Failure Prediction
Authors: Shrivastava Rishabh , Lalchandani Rohan , Pohekar Advait , Sharma Krishnandu , Vodnala Pavan
Published: February 2024

The Blades of a Gas Turbine Engine are subjected to an exceedingly high temperature, pressure, and centrifugal load during its operation. Consequently, they exhibit a heightened susceptibility to failure modes such as creep, crack initiation and growth, HCF, Flutter, and Oxidation. Attaining accuracy in the prediction of these failure modes is of paramount importance. Traditionally this has been achieved by Finite element packages, discretizing the problem into finite elements, applying the necessary boundary conditions, and solving a mathematical equation for each of these finite elements. The process involves a numerical solution of differential equations that govern these physical phenomena. However, this pursuit is not without tradeoff, as it demands a significant investment of temporal, human, and computational resources. To minimize mentioned efforts, advanced data-driven techniques can be implemented to predict the creep failure instances. Machine learning is gaining significant traction for solving these kinds of problems because of advances in storage and computational power. Machine learning focuses on using data and algorithms to learn the pattern and make prediction on unseen data with substantial accuracy. Generally, machine learning can be classified into supervised and unsupervised learning. In this work we are developing a machine learning based classification model (supervised learning) to capture the failure instances. Failure prediction using Machine learning is generally encountered with higher prediction error because of imbalanced dataset (minority class is the focus of attention — less than 5% of data). This paper deals with the approach of improving turbine failure prediction using various sampling techniques. Random Oversampling, Synthetic Minority Oversampling Technique – SMOTE, Tomek Links and combine SMOTE-Tomek links sampling methods are utilized to generate a balanced dataset for improving Machine Learning model performance. Coolant mass flow rate, Hot gas mass flow rate, Coolant Temperature, Turbine Inlet Temperature and Blade Material are provided as an input to the Machine Learning model, and on the other hand, a binary variable indicating creep failure instances is set to be the target variable for the model. The Machine Learning models used for prediction are Naïve Bayes classifier, Random Forest, Adaboost and gradient boost methods. The results demonstrate that among all the sampling technique mentioned above, combined SMOTE-Tomek link sampling method resulted in maximum improvement of recall and F1 score.
Characteristics of Laminar Separation Bubble With Varying Leading-Edge Shapes and Deflections of the Trailing-Edge Flap
Authors: Sarvankar Sumit S. , Sarkar Drik , Sureshbhai Mistry Chetankumar , Rao Vadlamani Nagabhushana
Published: February 2024

A series of Implicit Large Eddy Simulations (ILES) is carried out to examine the characteristics of a leading edge (LE) separation bubble. The test case comprises a flat plate with an elliptic leading edge which is equipped with a trailing edge flap. Simulations are carried out (a) at three different flap angles (20°, 30°, 90°) and (b) using two different geometries of Elliptic Leading Edge (ELE) where the ratio of the semi-major to semi-minor axis is set to either 2:1 or 4:1. The flap is modeled using the immersed boundary method which is computationally economical as it avoids regenerating the grid for varying flap angles. The results show that (a) the flow separates at lower flap deflection angles with a decrease in the aspect ratio of the ELE from 4:1 to 2:1 (b) an increase in the flap angle promotes separation at the LE due to an increase in the blockage in the bottom passage and a subsequent increase in the flow incidence at the leading edge. Simulations are also carried out using the γ – Reθ transition model and comparisons are drawn against ILES and experiments. Although the qualitative trends predicted using both ILES and Reynolds Averaged Navier-Stokes (RANS) are in agreement with the experiments, both approaches predict relatively shorter separation bubbles. This is attributed to the excess flow blockage in experiments due to the support plates which are not modeled in the simulations. Nevertheless, the results demonstrate the superior accuracy of ILES over the Reynolds Averaged Navier Stokes (RANS) model.
Aerodynamic Design Aspects for Small-Size Transonic Contra-Rotating Fan Stage
Authors: Pasupula Manideep , Mistry Chetan S.
Published: February 2024

Contra-Rotating fan stage presents a potential solution to address the demand for sustainable and efficient aircraft requirements. The objective of this work is to design and investigate numerically a contra-rotating axial fan stage for a compact transonic engine. The design process begins with the use of mean-line analysis and fundamental work balance method to determine the initial design parameters. This design is then optimized through computational fluid dynamics (CFD) analysis. The fan stage is designed using a constant-tip design approach with a tip diameter of 300 mm. To design the rotors, the double circular arc (DCA) airfoil is utilized with an elliptical leading edge and a cut-off trailing edge. The front rotor is designed with an aspect ratio of 0.8, while the aft rotor has an aspect ratio of 0.6. The overall pressure ratio of the contra-rotating fan stage is 3.5. The study investigates various pressure loading ratios between the front and aft rotors, with a tip-loaded configuration for both rotors. The SST k-ω and BSL turbulence models are used for numerical investigation, with the γ-θ model used to capture the transitional turbulence. The CFD analysis reveals that the flow reaches supersonic speeds in the front rotor’s upper half and the aft rotor’s entire span. This suggests that the design and optimization of the blade for the fan stage must take into account the effects of supersonic flow on the performance and efficiency of the fan stage. Many parameters are considered while designing the blade such as blade thickness, chord length, leading edge radius, trailing edge radius. Varying the blade thickness moves the contact point of the adjacent blade’s leading edge bow shock towards the trailing edge thus ensuring acceleration of the flow on the most of suction surface and reducing the risk of flow detaching & stall. The maximum relative Mach number for the front rotor is 1.3 and for the aft rotor is 2.7. The flow physics of the aft rotor is much more complex and unconventional than the front rotor’s, as the rotor’s whirl velocity is relatively much higher due to the opposing rotation. Results indicate that in the aft rotor, the blade throat is shifted significantly due to the high stagger, causing shock interactions and increasing the complexity of the downstream flow.
Design of a Facility for Testing Centrifugal Compressors
Authors: C. Kishore Kumar , Anand Jaiprakash , S. Ganesan , Govardhan Raghuraman N.
Published: February 2024

Centrifugal compressors are key elements in turbochargers and small gas turbines, making their performance evaluation essential for system efficiency and energy savings. This paper outlines creating and validating a specialized experimental setup designed for in-depth research on centrifugal compressors. The setup allows for the study of various impeller and diffuser configurations, flow-field analysis using Particle Image Velocimetry, and the investigation of inlet distortions, among other future research topics. The paper details the approach used to build the setup and validates its functionality through a case study featuring a research compressor with a vaneless diffuser. A characteristic map generated using Computational Fluid Dynamics (CFD) is used as a benchmark for comparison with experimental data. Initial results show a strong correlation between the CFD and experimental data in terms of flow rate and pressure ratio, validating the setup’s effectiveness. The overall performance aligns with existing research, confirming the setup’s value as a reliable platform for future studies on centrifugal compressors.
Effects of Recess Length of Bluff Body on Lean-Premixed Swirl-Stabilized CNG-Air Flame Structure
Authors: Huda Noorul , Soni Surendra Kumar , De Santanu
Published: February 2024

The stability of lean premixed turbulent swirl flames has been investigated using a laboratory-scale swirl-stabilized gas turbine combustor by varying the position of the bluff body inside the premixing tube. The relative location of the bluff body with respect to the dump plane is characterized in terms of a recess length, which is varied during the experiment. The resultant flame structure and dynamics have been studied for different bluff body recess lengths and bluff body shapes based on highspeed OH*-chemiluminescent images. Herein, we employ two different tapered bluff body shapes of an area ratio of 40% (B40) and 60% (B60). For the bluff body B40, a stable flame is mainly attached to the burner at a higher equivalence ratio. For a lower equivalence ratio, a lifted and elongated flame is formed. The increase in the recess length brings the flame closer to the burner surface, and a stable and intense flame is observed. For the bluff body B60, a less stable elongated and columnar type of flame is formed, and the flame stability slightly improves with the increase in recess length. The change in recess length significantly improves combustor performance when B40 is used instead of B60.

The increase in recess length is supposed to bring the recirculation created in the wake of the bluff body close to the exit of the premixing tube, resulting in better mixing of the inlet reactants and hot combustion products. This effect is less prominent for the B60 case, and high bulk velocity squeezing from the edges of B60 may not result in the effective mixing of inlet reactants and hot combustion products. The high bulk velocity for the B60 case may result in the delayed expansion of the inflow reactants, and all these combined effects may render ineffective for the B60 case.
Exploring the Effects of Synthetic Gaseous Fuels on the Performance, Combustion, and Emission Characteristics of a Dual Fuel Diesel Engine
Authors: Das Samar , Kalita Pankaj
Published: February 2024

This current experimental investigation attempts to explore the engine performance, combustion behaviour, and exhaust emission of a 3.5 kW capacity diesel engine utilizing synthetic-biogas (SBG), synthetic producer gas (SPG), and SBG-SPG mixture under dual fuel (DF) mode. SBG is prepared by mixing methane (CH4) and carbon dioxide (CO2) at 60:30 ratio. Similarly, hydrogen (H2) and carbon monoxide (CO) are also mixed at a 50:50 ratio for the preparation of SPG. Again, H2 and CO at a 50:50 ratio is mixed with a 60:30 ratio of CH4 and CO2 to simulate the SBG-SPG mixture. Engine experiments were executed at standard engine conditions of injection timing (IT) of 23° BTDC and compression ratio (CR) of 17.5 with five different engine loading conditions viz. 20%, 40%, 60%, 80%, and 100%. Maximum brake thermal efficiency (BTE) and pilot fuel replacement (PFR) were obtained at full engine loading condition. At this operating condition, SBG, syngas, and SBG-SPG mixture showed a BTE of 18.2%, 15.92%, and 18.89% respectively. Similarly, PFR of 84%, 78.74%, and 82.92% was found in case of SBG, SPG, and SBG-SPG mixture respectively. The combustion data indicated a decrement in ignition delay (ID) and increment in cylinder pressure with higher engine load. At 100% engine load, minimum ID of 20, 21 and 22° crank angle (CA) was obtained for SBG, SPG, and SBG-SPG mixture respectively. Again, highest peak cylinder pressure (PCP) was obtained for SBG-SPG mixture. It has also been observed that on an average, SPG resulted in higher emission including oxides of nitrogen (NOx), hydrocarbon (HC) and carbon monoxide (CO) compared to SBG. However, mixture of SBG-SPG resulted in 57.48, 0.09 and 5.6% reduction in NOx, HC and CO emissions respectively as compared to SPG.
Turbo-Rotor Balancing and Optimization Using Groove-Geometry Simulation Approach
Authors: Pagar Nitin D.
Published: February 2024

Turbochargers use the energy from the exhaust gases to power the compressor, improving the engine’s efficiency and reducing emissions. Working fluid runs past the turbine spin blades while the wheel rotates at high speeds with centrifugal forces acting on it. The primary focus of the work is on the turbine wheels of turbochargers. The wheels are prone to faults because they are manufactured using a casting process. Many failures and vibrations in the turbocharger are caused by mass imbalance. In order to mass balance the turbine wheel, back face material must be removed. The wheel’s strength and load-carrying capacity must be preserved when material is removed. The turbine wheels are made of inconel. Two-plane balance is used to make several adjustments to the back face. The balancing cut could put the wheel under more stress depending on a number of factors. Trial and error is still used frequently, but it is a time-consuming procedure that involves many iterations. The goal of this research is to determine the key elements that cause stress to rise during balancing cut, as well as how their behaviour can change, and to identify locations on the back face of the turbine wheel where stress levels are acceptable and material can be removed. In this work, the ANSYS simulation is used to validate analytical calculations for the cut and back face of the turbine wheel. Optimisation is used to determine the best location for the groove on the turbine wheel back face. Optimisation methods are applied within the ANSYS software to comprehend the nature of the response and DOEs and to obtain the best feasible solutions for the problem. High depth of cut and tip radius contribute to higher material removal, enhancing the balancing capacity by approximately 22.44%. The provided parametric correlation table allows for simple to understand the connection between all of the parameters considered in the balancing groove optimisation.
A New Perspective on Measuring Compressor Characteristics
Authors: Jing Zhenhao , Neumeier Yedidia , Prasad J. V. R. , James Darrell K.
Published: February 2024

This paper describes a method that enables the identification of compressor characteristics in parts that cannot be measured in traditional core test procedures. This capability is expected to help in identifying needed design changes following core tests. The method uses measurements of the mass flow rate in the compressor inlet along with the plenum pressure to infer the equilibrium characteristic of the compressor even as the compressor experiences non-equilibrium conditions, particularly so during transients to stall. A throttle control with feedback from the measured mass flow rate is used to drive the compressor into growing oscillations around the stability boundary, and a dynamic correction method is used to collapse the growing oscillations into a single line on the compressor map, which estimates the equilibrium characteristic. An unsteady mean line compressor flow model that is capable of capturing acoustic waves propagating through the rotor and stator blade cascades is used as a test compressor to evaluate the method. Results obtained using simulated compressor flow transient data demonstrate that the proposed identification method estimates both the smooth and the non-smooth characteristics with satisfactory accuracy.
Safety Evaluation of Isolated Island Operation on 1000MW Steam Turbine in NPP
Authors: Hu Xiao-dan , Chen Xu , Wu Fan , Shi Rui , Jiang Wei , Chen Tao , Yue Ya-nan , Xie Dan-mei
Published: February 2024

Steam turbine in NPP (nuclear power plant) will suffer drastic changes in load, mass flow and temperature during isolated island operation, which increases the chance of unit failure. In fact, cases of unsuccessful isolated island operation tests have occurred. Therefore, it is necessary to analyze the safety of steam turbine in NPP under isolated island operation condition. For safety assessment, the key factors influencing the safety of steam turbine in NPP under isolated island operation condition were simulated. The results shows that: under 100%PN load rejection, the highest dynamic speed overshoot of steam turbine is 4.99%, the maximum centrifugal stress of rotor is 262.61 MPa, the exhaust steam temperature of HP cylinder is increased by 47°C, and the critical mass flow condition for flutter of a typical type LSB (last-stage blade) is predicted. These results are within the range specified in the operating regulations for NPPs’ isolated island operation, indicating that the safety of 1000MW steam turbine is satisfactory.
Effects of Thermal Mechanical Fatigue on a 2.25Cr-1Mo Steam Header
Authors: Zimnoch Michael , Haddadi Elnaz , Perrin Ian , Tabarraei Alireza
Published: February 2024

Thermal-mechanical fatigue (TMF) is a common problem that restricts the life expectancy of high-temperature components. TMF is often caused by inelastic strains arising from cyclic loading at high temperatures and pressures. Finite Element Analysis (FEA) is frequently employed to predict the development of inelastic strains within components. This study evaluates the predicted inelastic strain accumulation of a 2.25Cr-1Mo power plant header represented using the Chaboche non-linear kinematic hardening (NLKH) model. The Chaboche NLKH model coefficients were established for temperatures up to 600°C using data from virgin machined samples. The representative header unit is evaluated using Abaqus finite element software under operating conditions that simulate a typical pressure and temperature profile. The findings indicate that low-cycle fatigue is not likely to occur in response to a common transient. However, the results conflict with industrial experience, indicating that other factors may contribute to component failure.
Approximate Solutions to Governing Heat Conduction Equations With Uniform Heat Generation in Semi-Infinite Plates
Authors: Haidar Salim M. , Mohammadzadeh AliReza
Published: February 2024

In a previous paper, we introduced a new methodology for using integral methods to solve governing linear partial differential equations in the undergraduate heat transfer course [1]. In it, we considered heat conduction problems solely over finite domains. In this paper, we extend our approach to the case of linear transient heat conduction problems with a uniform internal energy generation over semi-infinite domains. In particular, we use the superposition principle and the heat-balance integral to determine the transient response of a semi-infinite solid with a volumetric heat generation that may be constant or time-dependent over the domain subject to prescribed uniform initial and boundary-surface temperatures. In effect, we construct approximate analytic solutions to the problem in question with accuracy acceptable by most engineering standards.
Classifying Human Thermal Images Using Deep Learning Technique in Artificial Intelligence
Authors: Gurupatham Sathish Kumar , Purimetla Ujjwal , Kumar Kaliga
Published: February 2024

Deep learning is a sub-field of machine learning that uses multi-layered artificial neural networks which has become very popular in recent times to perform tasks such as image and speech recognition, natural language processing, decision making and so on. It has several applications in mechanical engineering and especially in the manufacturing field, too. Applying image recognition concepts to inspect the defects in products (Quality control), scheduling maintenance of equipment based on the sensor data (Predictive maintenance), applying deep learning concepts to train the movements of robotic arms timely for welding & assembly in production workshops (Robotics), and using deep learning to optimize schedules & logistics (Supply chain optimization) could be some of the applications worth to mention. This paper focuses on classifying the thermal images of objects, especially thermal ones. This work discusses the application of three pre-trained convolutional neural network (CNN) models namely VGG16, MobileNetV2, and InceptionResNetV2 for classification of thermal images of two classes (two human faces) belonging to the same family with more resemblance in their appearance so as to increase the complexity in classifying. The procedure had two phases: The first phase has the training and testing with thermal images whereas the second phase has increased number of images with image augmentation technique to repeat the same process to improve the performance the models. The data-set used in the models consists of thermal images of two slightly different faces of the same family that were taken using a thermal imaging camera (Flir-E6). In the first phase, the data-set was divided into training, validation, and testing sets with each set consisting of 50 images, 30 images, and 20 images respectively. In the second phase, after the image augmentation, the data-set was divided into 350 training images, 120 validation images, and 50 testing images. The performance of the models was observed for 10,20, and 30 epochs. The learning rate was assigned to 0.0001 with Adam optimizer and a batch size of 10. The results showed that the model VGG16, in the initial phase, yields training and validation accuracy of 100% and 90% respectively. In the second phase, it yields training and validation accuracy of 100% and 90.83% respectively. The model could classify 19 out of 20 images correctly before image augmentation and 49 out of 50 images correctly after the image augmentation was applied. It shows an increase of 3% from 95% to 98% before and after image augmentation was applied. For the given input images, the other models, though they are well-established ones, did not perform better than VGG16.The confusion matrix was plotted for all the models for important results.
System Identification and Controller Design of Propeller Driven Pendulum (Bi-Copter)
Authors: Enikov Eniko T. , Zhang Qiuchen , Creery Lucas
Published: February 2024

Undergraduate control courses are usually significantly improved when in-class instruction is backed up with experiments aimed at providing the students an opportunity of experiential learning. The rapid development of computer multimedia technology has resulted in a tendency toward a hands-on laboratory that incorporates simulation tools and computer-controlled equipment. However, most of the open-source hardware prototyping platforms require programming environments, installation of additional software, and additional plug-in modules that hinders the large-scale deployment of such systems. Therefore, the goal of this project was to create a simple mechatronic system (the “Bi-Copter”) that uses broadly available components along with MATLAB computing environment, in order to demonstrate an experiment that can be adopted at any educational institution with access to MATLAB.

The main part of the setup consists of two small dc electric motors attached to each side of the beam with the propellers. By controlling the motors, the angular position of the beam can be changed to a desired one. A circuit board utilizing a breadboard and off-the-shelf plug-in microcontroller connected to a serial-to-USB cable is used to control the motors. Unlike traditional controls experiments which start with a modelling task based on first principles, in this experiment a black-box model auto-regressive model with exogenous input (ARX) is used. Model parameters are obtained from open-loop experiment. The extracted model is then used to design a feedback controller and evaluate its performance.

The bicopter system was tested with over 50 students coming from the courses “Design of Mechatronic Systems” and “System Identification” of the academic years 2020–2022. The activity lasts eight weeks including 6 home assignments. During this period students work in groups of two and learn how to program the micro-controllers, carry out the system identificaiton experiments, design and implement feedback controllers. The laboratory allows students to build models of various complexity. To provide laboratory experience to students with various levels of expertise, this lab makes use of the Control Systems and System Identification toolboxes of MATLAB. Both graduate and undergraduate students utilized the apparatus and completed the design tasks. The bi-copter project was tested in a Design of Mechatronic Systems course at the University of Arizona. Since mechanical engineering students typically lack formal training in system identification methods, the course includes a brief introduction of this topic. One of the main outcomes from their experiments is appreciation of the importance of selecting proper input test sequence and the sensitivity of the resulting model to the bandwidth and amplitude of the input test sequence.
A Thorough Characterization Study of the Critical Al-Fin Bond Between the Ni-Resist Insert and Aluminum Base Material in a Heavy-Duty Engine Piston
Authors: Kumpaty Subha , Coen Nolan , Coen Liam
Published: February 2024

The Ni-Resist insert used in the INNIO Waukesha’s VHP piston is bonded to the piston during casting by the Al-Fin bond process. This bond is critical to the manufacture and performance of pistons used in heavy duty engines with aluminum pistons.

Iron has a strong solubility in the molten aluminum but does not at room temperature. The typical preparation of the Ni-Resist inserts to be installed in a piston mold prior to filling the mold is to immerse the insert in a bath of molten aluminum for a predetermined amount of time. The dissolution of alloys from the Ni-Resist insert into the bath make control of the bath composition a critical parameter. Negligent bath maintenance can result in the potential of forming undesirable intermetallics in the bond region. This means the Al-Fin bond can be brittle and sensitive to variation in tooling pressure during machining.

Any flaws introduced the bond during piston casting or machining can propagate during engine operation and result in a power cylinder failure, leading to collateral damage of other engine components and a lengthy repair time. The disciplined use of ultrasonic inspection in the rough machined as well as the finished piston will catch defects and prevent faulty pistons from being released to a customer. However, if problems are identified at these late stages, they can result in product delivery delays and even the shutting down of the engine factory assembly line.

This paper will highlight the modern material characterization methods used to identify a satisfactory bond. The understanding of the challenging nature of the bond between the Ni-Resist insert and the piston material has been gained through these methods. This knowledge has helped resolve problems by both quickly getting to their root cause and taking corrective action.
Failure Analysis of Transmission Components of Rail Transit Vehicles
Authors: Zhang Long , Yin Yanbo , Shan Zhenghui , Wang Zida , Zhang Yanping , Wu Lvxian , Lu Hang , Zhang Hong
Published: February 2024

This paper presents a recent gearbox failure in a rail transit vehicle. The damaged components, pinion bearing and large gear, were analyzed from macroscopic, microscopic, and performance perspectives. Through a comprehensive analysis of the test results, the two main factors causing the failure were identified: fatigue damage of the pinion bearing due to abnormal external load and the presence of brittle non-metallic inclusions, which initiated fatigue cracks leading to gear drop blocks. To improve gearbox reliability, suggestions were made to optimize operating conditions and improve the metallurgical purity of metal materials.
Computational Fluid Dynamics and Heat Transfer for Maze Solving and Piping Applications
Authors: Zhang Kevin , Li Puxuan
Published: February 2024

Solving mazes is an important scientific and engineering topic with various applications in the areas of image processing, intelligent traffic control, pipe network flow assurance, etc. There are many existing algorithms for solving mazes, which are mostly in the field of computer science. In this paper, two engineering approaches using computational fluid dynamics (CFD) and computational heat transfer (CHT) are presented. The hypothesis is, if a maze is injected with water or heat from the entrance, the water and heat should find their way to the exit naturally. If we can visually track the movement of the water and heat, the maze pathways can be shown and the maze can be solved. Computer simulations using both CFD and CHT methods were conducted to test the hypothesis and to analyze the performance of the two methods. The results show that both flow and heat from the inlet of the maze successfully find the outlet and the movement of water and heat can be clearly shown by the visual tools from the simulation soft, therefore the maze is successfully solved by both methods. The performance and simulation time between CFD and CHT approaches were compared, and it can be concluded that using CHT is more efficient than CFD since the heat transfer equations are less expensive to solve. In addition, a maze-solving-related application was presented in the paper to analyze the flow distributions of pipes in a network arrangement.
Numerical and Experimental Investigation for Recoil Dynamics of Machine Gun Used in Small Size – Unmanned Aerial Vehicle
Authors: Gümüşel Hasan Tolga , Acar Bülent , Yetgin Ali
Published: February 2024

In Unmanned Aerial Vehicle (UAV) with machine gun system, recoil dynamic is very critical phenomenon that occurs when a fast-moving object collides with a stationary or moving object causing a transfer of momentum. In this study, the main objective is to quantify differences in the recoil dynamic behavior of the machine gun affected by UAV structure including its weight, recoil reduction spring and damping pad properties. To do this, dynamic modeling of the whole system is established. Through the study, the effect of UAV structural properties is investigated to meet design requirements basically defined as higher shooting performance and higher stability of platform. The significance of all parameters is evaluated using with Pareto chart. Also, to verify these simulations, a recoil force measurement system on the ground is developed. In this equipment, a compression-type load cell is used together with the data acquisition system to measure the recoil forces. Since the recoil event is expected to be quite short, a high data sample rate is needed. The sampling frequency of the data acquisition system is selected as 20 kHz to be able to observe the recoil dynamics. Several firing tests have been conducted on the ground and impact force versus time data has been presented for each test. In addition, a finite element model of the UAV structure with a machine gun is generated to obtain the dynamic response of the structure in the air. It is found that the numerical simulation with ground test condition results show a good agreement with the data gathered from the experiments. In future, with the help of the verified model, it is aimed that firing performance during a mission in the air can be estimated according to main design goal which is to have higher platform stability while firing.
Resonator-Based Piezoelectric Metastructures: Efficient Bandgap Estimation and Parametric Analysis
Authors: Astudillo Diego , Ruiz Rafael O.
Published: February 2024

The integration of piezoelectric elements as resonators inside a periodic structure for vibration suppression and energy harvesting (at low frequencies) was experimentally demonstrated recently. In particular, employing a square array of free-standing piezoelectric cantilevers attached to a primary structural frame. The configuration could be understood as a periodic cell that contains a series of cantilevered Piezoelectric Energy Harvesters (PEHs). This work aims to implement a finite element model of a piezoelectric periodic structure capable of presenting vibration suppression and energy harvesting and use it to study the influence of the model parameters on the generated bandgaps. Different frame geometries with cantilever piezoelectric beams are studied. Through these geometrical arrangements, it is found that the domain of the wave vectors that must be evaluated in the Floquet-Bloch periodic condition to identify bandgaps can be restricted to only 5 wave vectors contained in the first Brillouin zone. This issue can be exploited to generate a large decrease in computational resources when optimizing this configuration. The work also presents a parametric analysis to identify the model parameters’ influence on the bandgap’s location and size. The parametric analysis also reveals the need to incorporate uncertainty quantification in the design and optimization process, simultaneously offering comprehensive information about the continuity of the bandgap in relation to the model parameters.
A Numerical Model of Microstructure Formation Considering Nanoparticle Distribution During Selective Laser Melting Process
Authors: Alam Taosif , Amin M. Ruhul
Published: February 2024

Selective laser melting (SLM) is a popular metal additive manufacturing technique that allows the development of new metal matrix nanocomposites by fusing metallic powders with nanoparticles. In the current study, a novel numerical model was proposed to simulate microstructure formation considering local nanoparticle distribution during the SLM process. The proposed model formulates a three-dimensional computational fluid dynamics (CFD) model with Lagrangian particle tracking to simulate a single-track, single-layer SLM process of aluminum alloy reinforced with TiB2 nanoparticles in ANSYS FLUENT. A very low weight fraction (0.0009%) of nanoparticles was considered due to the computational limitations of the software package. The temperature distribution and particle distribution results calculated by the 3D CFD model were one-way coupled with a 2D Cellular Automata (CA) model to predict the solidified microstructure using MATLAB. The coupled CFD-CA model and Lagrangian particle tracking were separately validated in this study. The result showed that the nanoparticles move along the recirculation zones generated by the Marangoni and natural convection in the molten pool fluid. The microstructure predicted by this model showed that the introduction of the nanoparticles increased bulk nucleation during solidification. It disrupted columnar grain growth by promoting small, randomly oriented equiaxed grains. The average grain diameter decreased by 40% when nanoparticles were present compared to microstructures without nanoparticles.
Numerical Simulation of Rotary Friction Welding of a Titanium Alloy
Authors: Chen Wenxue , Xu Yaxin , Vairis Achilles , Bikmeyev Alexander , Li Wenya
Published: February 2024

A two-dimensional model of continuous drive friction welding (CDFW) of Ti-6Al-4V tubes was developed using the ABAQUS modeling software. The effect of interface temperature on frictional behavior was investigated during welding, where non-linear temperature dependent material properties were considered. The effects of rotational speed and friction pressure on the temperature field, flash morphology, interface temperature and axial shortening of the joints were studied. Results show that the interface temperature rises rapidly early in the process, to reach a plateau at 1270 °C. For a constant welding time, the temperature gradients and axial shortening of the joints increase with increasing the rotating speed and friction pressure; The steady-state temperature of the interface increases with the increase of rotational speed and decreases with the increase of axial pressure; Following welding, the expelled material in the form of a flash curls on the outer wall of the pipe, while being symmetrical about the welding interface. Modeling results were validated with CDFW experiments.