bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis on Mechanical Properties and Corrosion Behavior of Friction Stir Processing of Commercially Pure-Titanium
Authors: Velukkudi Santhanam Senthil Kumar , Jeyarajan Joshua Richard , Manivannan Sathish Kumar , Jayamanickam Joseph Beski , Kuppusamy Raman , Nambi Nitin
Published: February 2023

Friction Stir Processing has become the ideal way to refine the grains which increases the mechanical properties like formability, microhardness, yield strength and Tensile Strength, also increases the corrosion resistance, which emerged as the effective way for selective surface modification and also retaining the bulk properties. In this present work, Titanium grade 2 (Commercially Pure Titanium) is selected as the material of choice due to its superior corrosion resistance compared to other grades of titanium, high tensile strength and high hardness. Due to soft, excellent corrosion resistance and ductile properties Cp - Ti is used in automotive parts and airframe structure application. Friction stir processing is being used to improve mechanical properties such as tensile and microhardness, as well as corrosion properties. Friction stir processing (FSP) is used to fabricate the Titanium plate, by varying the process parameters such as Tool Rotation Speed (rpm), Traverse Speed (mm/min), and Number of Passes. The process parameters used in this experiment are Tool Rotational speed of 1000 rpm, 1200 rpm and 1400 rpm, Traverse speed of 30 mm/min, 45 mm/min, and 60 mm/min and single pass, double pass and triple pass. Taguchi’s L9 Orthogonal array is used to conduct the experiment, which considers three parameters at three separate levels. A tapered cylindrical pin of HSS (High Speed Steel) with Rockwell hardness of 65 HRC is designed and fabricated to provide material flow while simultaneously minimizing the tool wear.

The tensile test was carried out using Universal Testing Machine (UTM) as per ASTM E8 standard to determine the ultimate tensile strength and yield strength of FSPed CP – Ti (grade 2), microhardness test was carried out using Vickers Hardness with a diamond indenter and corrosion values are evaluated using Immersion corrosion testing method by weighing the before and after weights of the sample as per ASTM G31 – 72. Since Titanium Grade 2 offers very high corrosion resistance, the rate of corrosion is negligible when done in 24 hours. Thus, immersion corrosion test is done over 120 hours, so that corrosion rate can be measured efficiently. And also evaluate the torque induced in this process. Grey Relational Analysis (GRA) is performed on the multiple test results such that tensile strength, microhardness and corrosion resistances to find the optimum process parameters, by applying the test results as inputs. Analysis of variance (ANOVA) is the most efficient parametric method for analyzing friction stir processing data from experiments results.
Soft Artificial Muscle Actuators for Undersea Launch and Recovery Systems
Authors: Cavallaro Paul V. , Smith Michael P. , O’Donnell Jacob D. , Redington Allison , Warner Eric
Published: February 2023

The pursuit of increased autonomy for undersea and surface vehicles presents challenges for their launch, recovery, positioning and control (LRP&C). Traditional rigid handling and actuator systems are often volume constrained and can limit payloads capacities and operational effectiveness. The need to innovate high capacity and compact actuation technologies is intensified by increasing demands for rapid deployability and stowability, scalability, adaptability, temporary buoyancy and connectivity across the undersea and surface domains. On-demand inflatable and compactable soft actuators may provide unique solutions with robustness needed to operate in extreme underwater environments. This preliminary research investigated the mechanical behaviors, load and stroke capacities, end termination designs and limitations of artificial soft fabric muscles (ASFMs), also known as McKibben muscles, constructed of High Performance Fibers (HPF) for potential launch, recovery, positioning and control of undersea and surface vehicles and interface platforms. Computational mechanics and experimental tests were performed on air-inflated ASFMs constructed of braided fabrics to evaluate their quasi-static behaviors. Both glass and aramid braid materials were studied for a range of diameters and lengths. The computational models supported the fluid/structure interactions by using an Equation of State (EOS) that governed the thermomechanical behaviors of the internal air during volumetric expansion and axial contraction of the ASFMs.
Design of a Miniature HVAC System to Function As a Multipurpose Cooling Shirt
Authors: Gale Jess , Cesmeci Sevki
Published: February 2023

The purpose of this project was to design and optimize a portable miniature cooling system. The device functions as a cooling shirt, which is particularly useful in high-temperature environments where maintaining a healthy body temperature is a concern. The design cooling capacity of the system is 0.586 kW, where it provides a circulating cooling fluid temperature of 21.1 °C, with an ambient temperature of 35 °C using refrigerant R-134A for the prototype. The circulating cooling fluid consists of a loop that is pumped through a brazed plate heat exchanger on the evaporator side of the system. The prototype used water for initial testing. Examples of high-temperature environments include a tradesperson working in an attic during the summer (i.e., HVAC technician and electrician). The device is not limited to only high-temperature environments. It could be used in many other applications, such as health care or physical therapy settings. Certain spinal injuries can cause the human body to lose the ability to regulate its core temperature. This could result in a scenario of the body overheating during physical therapy sessions. This device could help regulate core body temperatures when overheating is a major risk. An additional application includes the possible treatment of sports-related concussions and other sports-related injuries. Targeting specific areas for cooling could potentially increase recovery time when compared to standard ice treatments. Another example application may include certain military aircraft. Pilots can experience periods of thermal discomfort during flight. A greenhouse effect happens in aircraft that contain large window areas such as the V-22 helicopter. The device could potentially be used to offset the higher heat loads experienced during flights. In conclusion, in this paper, a benchmark study, which included the design, fabrication, and testing of a working prototype by using the off-the-shelf components, was presented. The COP of the prototype was tested at different settings. The percent error between the theoretical and actual COP was calculated to be about 19%. The sources of error were discussed. The future studies will include simulations in commercially available software such as AxCYCLE to reduce the percent error between the design and actual working conditions as well as further downsizing of the device by using customized cycle components.
Design and Fabrication of an Atmospheric Water Generator Based on Vapor Compression Refrigeration Cycle
Authors: Alshahrani Saad
Published: February 2023

Water generation from the atmosphere is an environmentally friendly alternative and a sustainable process to extract pure and fresh water. An atmospheric water generator (AWG) is a device that uses dehumidification to generate potable water out of moisture present in the air. The moisture or humidity present in the air is cooled below the dew point temperature and as a result, water vapor is condensed into water droplets. The collected water droplets are filtered and re-mineralized to produce fresh and potable drinking water. Using these principles, we have designed and fabricated a prototype system for extracting clean drinking water from atmospheric air using a vapor compression refrigeration cycle. An AWG is fabricated by using a secondhand window air conditioning unit with a capacity 18000 Btu/h. The device consists of an air filter, compressor, condenser, throttling device, and cooling coils. In addition, the device utilizes the dehumidified cool air to cool the condenser and improves its effectiveness considerably. During two operating days, the system was able to collect 5800 mL. Initially it was employed for two days starting from 12 noon, on October 3, 2020 to 12 noon, October 5th 2020. After that, the AWG was employed for two more days, staring from 12:30 pm, October 5th 2020 to 12 noon, October 7th 2020. During this run, 4100 mL of water was collected. It was found that the quality of collected water from the AWG was on par with that of normal drinking water. The quality of the collected water was assessed by an Oakton PC 450 waterproof portable meter with a combination probe and calibration system. The instantaneous temperature and relative humidity values are represented on the psychrometric chart to understand the possibility of water generation and are shown in results and discussions. During the aforementioned trial between 12:30 pm, October 5th 2020 and 12 noon, October 7th 2020, temperature and relative humidity readings were recorded.
Finite Element Simulation and Micro-Grain Size Analysis of Sheet Metal Casing by Hot Power Spinning
Authors: Xia Yingxiang , Shu Xuedao , Ye Bohai , Zheng Jiabin , Liu Yanli
Published: February 2023

Spinning is a typical continuous local plastic forming and an advanced manufacturing technology to achieve less cutting machining of thin-walled rotary parts. As the external bearing component of aero-engine, the mainstream manufacturing method of sheet metal casing is hot power spinning. Its forming quality includes dimensional, shape accuracy and macroscopic defects. The refinement and uniformity of micro grain size are also important indicators. The FE finite element) model of tapered sheet metal casing with variable wall thickness in hot power spinning was established by DEFORM-3D. The average deflection angle deviation Δθ and standard deviation of wall thickness error Δt was used as the evaluation indexes of 13 simulation schemes. The effect of the mandrel speed, the roller feed ratio, the roller fillet radius and the initial temperature on the forming quality was analyzed. Through the spinning experiment of SXY1000 double-roller CNC spinning machine, the metallographic structure of different forming regions and the micro grain size under different temperatures and roller feed ratios are explored. The micro grain size of the formed part is more refined with the increase of the initial temperature. It decreases as the feed ratio increases, while the microscopic grain size uniformity decreases.
MATLAB Toolbox for Design and Motion Analysis of Compliant Mechanisms and Soft Robots
Authors: Contreras Esquen Andrea , Delgado Juan , Soo Lance , Saldivar Kevin , Schwenck Lucas , Amiri Moghadam Amir Ali , Tekes Ayse
Published: February 2023

Despite the advantages and superiorities of compliant mechanisms and soft robots over rigid mechanisms, optimizing the stiffness of flexible links and dynamic properties of complex and high mobility designs is increasingly challenging. Additionally, the largest challenge in the design and modeling of such systems is understanding the deformation of the two bodies when connected along with their interaction in complex cases such as large deflecting buckling beams, especially for people who are new in the area. There exist several methods and techniques for obtaining kinematic relations as pseudo rigid body modeling (PRBM), first and second kind of Elliptica theory, discrete beam element method for simple geometries of compliant mechanisms, and nonlinear dynamical modeling of soft robots assuming using constant curvature spatial curves, and also machine learning. To address this issue, we present the user-friendly and open-access MATLAB Toolbox for the design and motion analysis of compliant mechanisms and soft robots. The developed toolbox serves as a platform to visualize the deformation of compliant joints and compliant beams (Module 1), visualize the displacement of various compliant mechanisms (Module 2), design simple and complex compliant mechanisms using the hinges and beams, and design and motion analysis of soft robots (Module 3).
Nonlinear Vibration Analysis of High-Speed Rotating Pre-Twisted FGM Blades Considering Initial Large Deformations
Authors: Chen Yukun , Jin Guoyong , Ye Tiangui , Li Shanjun
Published: February 2023

Rotating pre-twisted blades made of functionally graded materials (FGMs) have broad application prospects in engineering owing to their superior properties. With a high-velocity rotational motion, the blades would exhibit large-amplitude deformations due to the severe centrifugal forces and their vibration behaviors might be affected. This paper presents a nonlinear vibration analysis of rotating pre-twisted FGM blades considering the large-amplitude deformations caused by centrifugal forces. Based on the Carrera unified formulation and 3-D nonlinear elasticity shell theory, a prior large deformation analysis of the FGM blades under centrifugal forces is performed considering the geometrical nonlinear characteristics. The nonlinear vibration analysis of the system about the equilibrium position is then performed taking into consideration the deformed configuration and rotational motion. A systematic comparison of the present results with the 3D FEM solutions is performed to verify the correctness of the present method in determining the large deformation and vibration characteristics of the high-speed rotating pre-twisted FGM blades. The comparative performances of the linear and nonlinear models are assessed in the vibration analysis of the pre-twisted FGM blades with different rotating speeds and material parameters.
Model Order Reduction of Scramjet Isolator Shock Dynamics During Unstart
Authors: Sullivan Jack , Gaitonde Datta
Published: February 2023

The unsteady shock dynamics occurring in a numerically simulated unstarting scramjet isolator are examined using a novel model order reduction technique. The key challenges associated with the non-stationary nature of the phenomenon are overcome by leveraging a combination of Empirical Mode Decomposition (EMD) followed by time dependent snapshot shifting. The EMD method serves two purposes: to identify the oscillation modes of the unstarting shock train and to subsequently use the calculated non-stationary residual function to invoke a translating frame of reference that is co-moving with the unstarting shock system. Each snapshot is then shifted into the determined reference frame and subsequently windowed in space, creating a smaller, subset of snapshots from the original database. The windowing is informed by the physics of pseudo-shocks, and has the benefits of ensuring that each new snapshot contains the entire unstarting shock train, while simultaneously preventing the effects of circular shifting that have plagued other model order reduction techniques based on shift operators. When applied to the unstart problem, the shifting and windowing technique presents a more statistically stationary view of the unstarting shock dynamics in the frame of reference of the moving shock train. Dynamically relevant modes associated with upstream and downstream propagating pressure waves at the peak shock oscillation frequency in the boundary layers and separation regions are further extracted from the shifted and windowed snapshots using the sparsity promoting Dynamic Mode Decomposition algorithm.
3D Printing Material Testing and Applications in Biomaterial Modeling for Pediatric Medical Trainers
Authors: Perry Sheridan , Huayamave Victor , Gonzalez Bryan , Nadeau Zachary , Rodriguez Rafael
Published: February 2023

Additive manufacturing technologies have become increasingly prevalent in recent years and, with their abundance, have opened many doors in the field of manufacturing and design. The field of medicine has always been in high demand for new manufacturing techniques to create medical prostheses, devices, and trainers. With this increased need, 3D printing has become the obvious solution, and with it, a major problem has arisen. The lack of material property data on 3D printing filament post extrusion leaves designers and engineers having to perform extraneous tests to create accurate models. This paper summarizes an analyses of a common 3D printing filament known as Thermoplastic Polyurethane (TPU). The analysis included tensile testing in accordance with ASTM D638-14 and preliminary FEA based on the material properties found. It was found that TPU is a material that behaves in a similar manner to an elastomer with a low ultimate stress (50% infill yields 23.92 MPa +1.38 −1.12) and relatively low moduli of elasticity (50% infill sample 23.13 MPa +0.91 −0.87). TPU’s material characteristics change in respect to its infill percentage. A preliminary FEA analysis was also performed with results that agree with the material testing. Overall, the results from the physical testing and the FEA analysis were in agreement and allows for the creation of a foundation to extend the FEA validation with complex geometric models modeled after organic biomedical components.
Multibody Representation on the Coupling Between Wave Generator and Flexspline in Strain Wave Gears
Authors: Raviola Andrea , Bertolino Antonio Carlo , De Martin Andrea , Guida Roberto , Mauro Stefano , Sorli Massimo
Published: February 2023

Strain wave gears are widely employed in aerospace and industrial applications due to their capability to obtain a high reduction ratio with low backlash through light and compact design. Since this component is mostly used in applications requiring repeatable and high precision movements, its health assessment is crucial in assuring the required performance and avoiding unexpected failures. A detailed model of the gear, able to replicate its behavior in both nominal and degraded operating conditions, would allow simulating the presence of faults and to study their effects on the behavior of the machine on which the faulty component is mounted. The present paper describes how the initial conditions of a high-fidelity gear model can be obtained by simulating the insertion of the wave generator inside the flexspline. To do this, each tooth has been modeled as a single body with its own dynamics, connected to the surrounding teeth by equivalent visco-elastic models. The final deformed configuration of the flexspline is not imposed a priori, as commonly done, but it is directly obtained by the contact with the wave generator outer race. The simulation outcomes have been then validated with experimental data from the literature.
Unsupervised Online Anomaly Detection of Metal Additive Manufacturing Processes via a Statistical Time-Frequency Domain Approach
Authors: Chen Alvin , Kopsaftopoulos Fotis , Mishra Sandipan
Published: February 2023

Fault detection techniques in metal additive manufacturing (AM) have explored a variety of monitoring methods to flag anomalies as they occur during the sintering process. Although many in-situ techniques are able to adeptly detect these abnormalities, several utilize machine learning black box methods that do not easily transfer to varying print geometries. An approach that is adaptable to a multitude of geometries holds an advantage in determining anomalies for more complex cross-sections and raster patterns. To address this lack of a geometry agnosticism, we propose a method that detects faults using the frequency content of the melt pool image response through an unsupervised approach. Scan line length and scan speed extracted from known geometry can be translated to associated frequencies via a spectrogram. We examine three specific geometries to determine detection performance on each by comparing the frequency content to the nominal response. A deviation from the expected performance will signify that an anomaly has occurred. We verify this approach is feasible for fault detection and is accurate in detecting anomalies that are hard to observe in the image time series. A feasible geometry agnostic method and the current interpretability will be discussed in this paper. The results reached in this paper strongly indicate that the approach is promising, has potential for improvement, and that a geometrically independent method is sensible. With further work, a generic algorithm applicable on any geometry will be achievable.
Dynamics of a Cantilevered Pipe Aspirating Fluid and Subjected to Reverse External Flow: the Effect of External Flow Confinement
Authors: Shaaban Ahmed , Chehreghani Mahdi , Misra Arun K. , Païdoussis Michael P.
Published: February 2023

The dynamics of a hanging cantilevered pipe aspirating fluid and simultaneously subjected to a partially confined external axial flow in the reverse direction has been investigated experimentally. A bench-top-size apparatus is used in this experiment consisting of a pressure vessel filled with water, a hanging cantilevered pipe and a shorter concentric outer rigid tube which is also vertically cantilevered. The flow configuration investigated in this paper is a simplified representation of the hydrocarbon storage mode of salt-mined caverns, which are large underground cavities used for storing hydrocarbons.

An experimental investigation has been conducted to determine the effect of the size of the annular gap on the onset of instability for various external to internal flow velocity ratios, Uo/Ui, ranging from 0.015 to 0.80. It was found that, for the range of flow velocity ratios investigated, the pipe loses stability via first-mode flutter. For the lower ratios of flow velocity, namely Uo/Ui = 0.015–0.06, the bifurcation diagrams show an increase in the root-mean-square (rms) amplitudes at three different ascending rates as the internal flow velocity Ui increased. In contrast, for high flow velocity ratio bifurcation diagrams, i.e., for Uo/Ui = 0.40–0.80, there is an increase in rms amplitude at a certain rate, followed by a diminished rate of growth as the internal flow velocity is increased further. The results demonstrate that the onset of instability occurs at relatively lower flow velocities as the Uo/Ui ratio is increased. Moreover, enlarging the annular gap has a stabilizing effect on the aspirating pipe. In comparison with the narrower rigid tube, with a wider rigid tube the signal power of the second-mode frequency was significantly amplified.
Development of a Holistic Data-Driven Detection and Diagnosis Approach for Operational Faults in Public Buildings
Authors: Alghanmi Ashraf , Yunusa-Kaltungo Akilu , Edwards Rodger
Published: February 2023

The data-driven approach prioritises operational data and does not require in-depth knowledge of system background; nevertheless, it requires considerable amounts of data. Obtaining faulty building data is a significant challenge for researchers. As a result, employing simulated data can be beneficial in data-driven faults detection and diagnosis (FDD) analysis because it is inexpensive and can run multiple sorts of faults with varying severities and time periods. The predominant implementation of FDD techniques within the building sector is done at the system level. However, as useful as system-level analysis is, typical buildings are comprised of multiple systems with their peculiar characteristics. Also, individualised system level-based analysis makes it challenging and sometimes impossible to visualise system-to-system interactions. However, there is a glaring underrepresentation of literatures that explore the development of whole building models that diagnose faults over the entire building energy performance sphere. Therefore, this paper presents a work to detect and diagnose building systems (HVAC, lighting, exhaust fan) faults in whole building energy performance within hot climate areas, using energy consumption and weather data. The detection process on the main building meter was conducted using LSTM-Autoencoders, and different multi-class classification methods were compared for the diagnosis phase. Moreover, feature extraction approaches were included in the comparison to quantify their performance in improving the diagnosis.
Design and Development of a Fish-Like, Soft Biomimetic Robot
Authors: Pai Nikhil , Contreras Esquen Andrea , Tekes Coskun , Amiri Moghadam Amir Ali , Tekes Ayse
Published: February 2023

Among the robotic systems, biomimetic robots performing fish-like locomotion have been the focus of much attention recently as there are many applications for swimming robots, including monitoring of underwater environments, detection of pollution, and disaster relief. This study presents the design and development of a biomimetic fish-like robot based on real carp locomotion. The robot has five main body parts including the head, soft neck, hinged body, compliant tail, and caudal fin. The head houses three ultrasonic sensors to guide the robot while connected to the body through two degrees of freedom (DOF) soft link resembling the neck vertebrate. The 2 DOF soft link enables the head to bend up, down, left, and right which is essential for controlling the soft robot’s direction. The body is connected to the soft tail using a quick return crank mechanism to actuate the tail. The tail integrates a soft tail and a rigid caudal fin. While all parts of the soft fish-like robot are 3D printed using polylactic acid (PLA), thermoplastic polyurethane (TPU), the mold is made from silicone rubber to waterproof. The ultrasonic sensors are utilized to detect obstacles so that the robot may maneuver around. The swimming pattern only for two-dimensional motion is tested in the air and underwater. According to the experimental results, the proposed robot better imitates the fish through its soft 2 DOF link and tail.
Design Strategies for Flywheel Energy Storage Systems in EV Fast Charging
Authors: Basaure Francisco , Mertiny Pierre
Published: February 2023

With rising numbers of electric vehicles to curb greenhouse gas emissions, mitigating strain on the electrical grid from EV charging, specifically fast-charging applications, has become a significant challenge, especially since adapting grid infrastructure is not only complex but costly. Long service life, high power charge capacity, and the ability to mitigate peak loads to the electrical grid are some of the requirements for energy storage systems (ESS) to support electric vehicle fast charging. In this context, interest in flywheel energy storage systems (FESS) has been growing in recent years due to the favorable power characteristics and lack of cycle aging that FESS offer over electrochemical ESS such as second-life batteries. Typically, flywheel design has focused on small-scale transportation and large-scale grid frequency regulation applications. The present paper presents design strategies for FESS in fast-charging applications, which signifies a promising and innovative approach for reducing the strain that fast EV charging imposes on the electrical grid. This study considers design strategies to achieve low material and fabrication costs, a high safety standard, and operational advantages.
Finite Element Analysis of the Critical Buckling Load in Hollow Microneedles With Lateral Support
Authors: Poudel Biswas , Ozsoy Istemi B.
Published: February 2023

Hollow microneedles provide minimum invasion to the skin and painless drug and vaccine delivery. However, there is a risk of fracture due to insufficient mechanical strength. The strength of microneedles might be increased by mimicking the bite of a mosquito. A mosquito has a proboscis that consists of a long needle (fascicle) surrounded by a protective sheath (labium). This sheath (labium) folds back as the fascicle pierces the skin, which provides lateral support to the fascicle. The lateral support increases the force that can be applied at the tip of the needle without buckling. In this study, the effect of lateral support on the buckling strength of a hollow microneedle made of chitin is analyzed numerically by using ABAQUS Finite Element Analysis software. The needle is modeled as a slender rod subjected to non-conservative (Beck) and conservative Euler loads simultaneously at the end. For a prescribed Beck load, the critical Euler load for buckling is obtained for various lateral elastic foundation stiffnesses. It is shown that the results of this computational study agree well with the analytical solution found in the literature. In addition, a three-dimensional finite element model is considered to study the effect of the needle tip geometry on the buckling and bending behavior of the needle.
Full-Field Operating Deflection Shape Measurement of a Structure With a Curved Surface Using a Three-Dimensional Continuously Scanning Laser Doppler Vibrometer System
Authors: Yuan Ke , Zhu Weidong
Published: February 2023

This study proposes a novel general-purpose 3D continuously scanning laser Doppler vibrometer (CSLDV) system to measure 3D full-field vibration of a structure with a curved surface in a non-contact and fast way. The proposed 3D CSLDV system consists of three CSLDVs, a profile scanner, and an external controller, and is experimentally validated by measuring 3D full-field vibration of a turbine blade with a curved surface under sinusoidal excitation and identifying its operating deflection shapes (ODSs). A 3D zig-zag scan path is proposed for scanning the curved surface of the blade based on results from the profile scanner, and 6scan angles of mirrors in CSLDVs are adjusted based on relations among their laser beams to focus three laser spots at one location, and direct them to continuously and synchronously scan the proposed 3D scan path. A signal processing method that is referred to as the demodulation method is used to identify 3D ODSs of the blade. The first six ODSs from 3D CSLDV measurement have good agreement with those from a commercial 3D SLDV system with modal assurance criterion values larger than 95%. In the experiment, it took the 3D SLDV system about 900 seconds to scan 85 measurement points, and the 3D CSLDV system 115.5 seconds to scan 132,000 points, indicating that the 3D CSLDV system proposed in this study is much more efficient than the 3D SLDV system for measuring 3D full-field vibration of a structure with a curved surface.
Experimental Characterization of Surge Cycles in a Centrifugal Compressor
Authors: Serena Alberto , Bakken Lars Eirik
Published: February 2023

Compressor operation under off-design conditions generates undesirable instabilities and detrimental effects both on system stability and machine reliability perspectives.

The main objective is to provide a suitable approach and proper description of the flow and machine behaviour in the surge inception to reverse flow operating area, yielding valuable data for a deeper understanding of the underlying flow mechanisms, useful for tuning prediction models.

A literature review, with a particular focus on the experimental method, test rig layout, and instrumentation when handling with reverse and pulsating flow, is presented.

The need for a clear setting of test procedure and key parameters measurements to detect unsteady phenomena under transient conditions, with instrumentation available for field operation and separating compressor behaviour from system response, is specifically addressed. To perform this, the experimental technique is employed and described in detail in this paper, while performance modeling validation, object of parallel studies, will be presented in future publications.

The test facility allows the required responsive dynamic measurements; tests cover a broad range of flow rates and two different rotational speeds. The aim is to specifically approach the instabilities sections and characterize the positive slope area, featuring rapid cycles between surge line and zero-flow.

The results, presented as pressure and flow fluctuations, play a key role for the simulation of more complex dynamic scenarios. This wide collection of test data is of great value for a further understanding of the phenomenon, the development of reliable surge onset prediction models and control strategies.
Unsteady Dynamics of a Low Aspect Ratio Mixing Layer
Authors: Eckstein Adam , Banko Andrew , Benson Michael
Published: February 2023

This work examines the temporal dynamics in the near-field of a low aspect ratio mixing layer. Using Planar Laser Induced-Fluorescence (PLIF), we investigate mixing dynamics between a rhodamine dye contaminated stream and a clean water uncontaminated stream at different velocity ratios. An in-situ calibration experiment is performed to verify the linearity of the image intensity with rhodamine concentration and to account for spatial variations in laser sheet intensity. The mixing dynamics are analyzed for velocity ratios ranging from one to three, defined as the ratio between the bulk velocity in the small channel to the bulk velocity in the large channel. This range yields mixing layer Reynolds numbers based on the velocity difference, channel width, and kinematic viscosity of water ranging from zero to approximately 1,600. The average and transient properties of the mixing layer are analyzed. The average concentration distribution is presented to quantify the spreading rate of the mixing layer. Of particular interest is the intermittency of the concentration time series at the channel centerline and the nominally clean and contaminated streams, both of which are related to the formation of large scale vortical structures.
Nonlinear Electro-Mechanical Impedance Spectroscopy for Comprehensive Monitoring of Carbon Fiber Reinforced Composite Laminates
Authors: Lu Runye , Shen Yanfeng
Published: February 2023

This paper presents a Nonlinear Electromechanical Impedance Spectroscopy (NEMIS) methodology for the comprehensive monitoring of carbon fiber reinforced composite (CFRC) laminates. This method can obtain structural impedance spectra and capture nonlinear ultrasonic features for damage detection, combining the merits of the conventional EMIS and the nonlinear ultrasonic techniques. A comparative illustration between the conventional EMIS and NEMIS is presented. Various damage types and damage mechanisms of CFRC laminates are reviewed. Numerical investigation on a reduced-order 1-D Contact Acoustic Nonlinearity (CAN) model are conducted to demonstrate the chirp-induced nonlinear features. Furthermore. a finite element (FE) model is established to verify the feasibility of the NEMIS for damage detection. The macro-scale damage types are modeled by the changes of material properties, while the incipient damage like delamination is simulated by setting the contact interfacing condition between the laminate debonding areas. Correspondingly, the chirp-based impedance spectra are employed to detect the macro-scale damage via the deviation of resonance peaks, while the nonlinear features, such as higher harmonics and wave modulation are utilized to monitor the delamination. Two damage indices are developed to quantify the severity of both the macro and incipient damage. This paper finishes with conclusion and suggestions for future work.
Prediction of the Generation of Intergranular Cracking in Stainless Steels Under Creep Loading at Elevated Temperatures
Authors: Suzuki Ken , Nakayama Koki , Nakayama Ayumi , Tezuka Shogo , Miura Hideo
Published: February 2023

Initiation mechanism of intergranular cracking in SUS316L under creep loading at elevated temperatures was investigated quantitatively by applying electron back-scatter diffraction (EBSD) analysis. It was found that intergranular cracking started to appear by 40% of the normalized lifetime of the steel and the cracked grain boundaries were close to perpendicular to the direction of the applied load and the Schmid factor of one of the grains which consisted of the cracked grain boundaries was larger than 0.43. In addition, the difference of the Schmid factor between the nearby grains was large. Not only dislocations but also vacancies were found to accumulate faster around the cracked grain boundaries. The reason for the accelerated accumulation was attributed to the local mechanical stress concentration around the grain boundaries, which was caused by the large lattice mismatch between the nearby grains. The degradation process of the crystallinity of the grain boundaries was continuously monitored by using the image quality (IQ) value obtained from the EBSD analysis. The degradation process was analyzed by using the modified Arrhenius equation, in which the effective activation energy of the damage accumulation decreased locally with the large strain around the cracked grain boundaries. The local activation energy was confirmed to be more than 30% lower than that obtained under the thermodynamically stable condition.
Strain-Induced Change of Adsorption Behaviour of Gas Molecules on Graphene Analyzed by Density Functional Method
Authors: Yin Meng , Qiao Xiangyu , Zhang Qinqiang , Suzuki Ken , Wang Lei
Published: February 2023

In Aging society, health monitoring sensors are indispensable for reliable daily care. Graphene has been suggested to be capable of detecting gas compositions in a person’s breath to diagnose sickness down to the ppb-level, because of its large surface-to-volume ratio and high carrier mobility. The resistance of graphene was found to change clearly due to the adsorption of gas molecules such as NH3, NO2, and so on. When plural different molecules adsorb on graphene at the same time, however, it is impossible to identify the adsorbed molecules individually. The development of the selectivity of the adsorbed molecules, therefore, is indispensable for applying this gas-adsorption-induced resistance change of graphene to a health monitoring sensor.

In order to improve the selectivity, the interaction between graphene and various gas molecules (CO, H2O, and NH3) with and without applied mechanical strain were calculated using the density functional theory (DFT) method. It was found that the adsorption behaviour of gas molecules on graphene changed under the application of strain and shows different dependence of the adsorbed gas species. Some gas molecules such as CO and NH3 gradually desorbed, while other gas molecule such as H2O, on the contrary, adsorbed more stably under tensile strain. This work revealed that the selectivity could be improved by applying the appropriate mechanical strain to graphene, paving the path for a graphene-based gas sensor in biosensing applications.
Stress Concentration Mechanism in Superconducting Coil Quench Phenomenon by Large-Scale Finite Element Analysis
Authors: Hisakuni Yousuke , Kano Akira , Uehara Hideaki , Monda Tomoko , Hirokawa Junko , Nishimura Osamu , Hirohata Kenji , Ito Toshinobu , Takami Shohei , Sato Kiyokazu
Published: February 2023

A quench is the transition from a superconducting state to a normal conducting state. Elucidating the mechanism of quenching caused by mechanical disturbances (training quench) requires a detailed understanding of the stress state in the coil during excitation. In this study, we developed a large-scale analysis method that can precisely analyze where strain energy is concentrated and loss energy is generated due to thermal stress and electromagnetic force in superconducting coils by considering the detailed structure of superconducting wires and the wire alignment disorder caused by constraints during winding. The results showed that strain energy in the resin is concentrated in the region of overlap between the strain energy distribution caused by the macroscopic deformation of the coil and the geometrically inhomogeneous region, including the wire transfer zone. Furthermore, comparative verification using acoustic emission measurements to determine damage locations suggests that quench is also concentrated at the transfer zone in the actual coil, thus demonstrating the validity of the analysis. A sub-model of the area around the transfer zone, which was found in the large-scale analysis, was created, and crack propagation analysis was conducted using the phase-field method. Crack propagation in the resin and increased deformation of the wire due to weakening of the supporting rigidity of the wire caused by the crack propagation were observed.
Numerical Investigation of Ultrasonic Phased Array Reverse Time Migration Technique Considering Spatial Wave Characteristics
Authors: Zhou Shulong , Shen Yanfeng
Published: February 2023

This paper presents a systematic numerical research on ultrasonic phased array reverse time migration technique for damage evaluation in bulk materials. In this study, a thick aluminum bulk is used as the target structure to be tested, and an ultrasonic phased array composed of piezoelectric elements and damping blocks is prosed as the transducers for generating and receiving elastic waves. Firstly, a Finite Element Model (FEM) of a pair of transducers is established to study the wave generation and reception performance. In particular, the suppression effect of different backing material parameters (damping ratio, thickness, implementation details) on the piezo-elements to absorb excessive resonant vibrations is investigated, in order to send out and receive spatially squeezed mechanical pulses into the target medium. Then, a full-scale FEM is established with the complete probe set and typical structural damage types to understand the wave propagation and its interaction with damage. Both longitudinal (L) and shear (S) waves are studied, while they interact with a hole and cracks with different orientations with respect to the incident wave direction. Finally, the reverse time migration algorithm is further developed by considering the spatial wave characteristics. The amplitude variation along the propagation distance is taken into account to form a time/space-gain compensation function to improve the damage imaging quality and sensitivity, especially for far field damage sites. At the same time, the imaging algorithm is tested for the single L-wave, the single S-wave, and the fused LS-wave scenarios. It was found that the combination of L-mode and S-mode can significantly improve the damage imaging results. This numerical investigation may lay a solid foundation for the development of ultrasonic phased array technique for non-destructive evaluation (NDE) of bulky materials. This paper ends with a summary, concluding remarks, and suggestions for future work.
Influence of Surface Roughness on Heat Transfer and Flow-Induced Vibrations of a Circular Cylinder
Authors: Ali Ussama , Islam Md. , Janajreh Isam
Published: February 2023

In this study, two-dimensional numerical analysis was done to investigate the influence of surface roughness on the heat transfer and flow characteristics for a circular cylinder subjected to crossflow. Numerical solution of the URANS and energy equation was sought using Ansys Fluent for the transient analysis at Reynolds number of 100. The roughness was induced in the cylinder surface by considering the sand surface roughness model. Four levels of roughness were studied with the roughness coefficient (Ks/D) varying between 0.01 and 0.06. The cylinder was allowed to move in transverse as well as streamwise direction to study the two-degree of freedom motion. The reduced velocity was varied in the range of 1–10, covering the region with maximum amplitude of vibration. The cylinder was heated at 300°C above the freestream fluid temperature. The numerical model was validated with the results from the literature. The analysis was done in terms of vorticity and temperature contours, Nusselt number, Strouhal number, and lift and drag coefficients. The results indicated that the surface roughness affected the flow characteristics and heat transfer in such a way that Strouhal number increased, while the lift and drag coefficients and Nusselt number decreased with the increase in the surface roughness. However, the effect of Nusselt number was much higher in comparison to the effect on the Strouhal number and lift and drag coefficients.
Design and Development of Novel α-SiAlON/Co and α-SiAlON/TiCN Composites for Cutting Tool Inserts
Authors: Alotaibi Amer D. , Abubakar Abba A. , Akhtar S. Sohail , Hakeem Abbas S. , Al-Athel Khaled S. , Arif Abul Fazal M.
Published: February 2023

The present study deals with the development of α-SiAlON-4%Co and α-SiAlON-20%TiCN ceramic composites with desirable properties tailored for enhanced high-cutting tool performance. The effective medium theories and mean-field homogenization schemes are used to design and optimize the volume fractions, the interfacial thermal resistance, and reinforcement particle sizes while incorporating the influence of porosity on the effective properties of the ceramic composites. The designed composites are fabricated via the spark plasma sintering process. The ceramic samples are characterized/analyzed via scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. The effective thermal and structural properties of the composites are measured and compared to that of the computational predictions. The results indicate that excellent densification in α-SiAlON-based composites can be achieved by the use of spark plasma sintering process. Experimentally measured properties of SiAlON-20%TiCN composite compare well with that of the computational predictions and have shown significant enhancement in its effective thermal conductivity and fracture toughness. The measured properties of SiAlON-4%Co composite did not meet the predictions due to Co agglomeration and the large thermal mismatch between the matrix and the inclusion, which emphasizes the need to optimize the synthesis process and establish volume fraction limits of Co in α-SiAlON ceramic composites.
A Sensitivity Analysis Method of Shot Peening Parameters Based on Probabilistic Surface Damage Tolerance Assessment
Authors: Li Guo , Teng Yida , Zhang Xingyu , Ding Shuiting
Published: February 2023

Enhanced life management methods have been developed by the Federal Aviation Administration to address the rare but significant threats posed by the manufacturing anomalies of aeroengine life-limited parts. The probabilistic damage tolerance assessment provides guidance for life management methods by requiring clarification on the effect of manufacturing on life-limited parts in the design stage. Shot peening, a typical manufacturing process, is frequently used to improve fatigue performance. In this study, a new method to correlate manufacturing with engineering that combines shot peening parameters with probabilistic surface damage tolerance assessment is proposed. Through the secondary development of the simulation’s pre-processing and post-processing, the results of residual stress are adopted as input variables of the modified probabilistic surface damage tolerance assessment to calculate the probability of failure, which is closely related to the selection of shot peening parameters. Accordingly, a new integrated model is developed for the sensitivity analysis by automating parametric modeling to improve efficiency and avoid complex workflows. Specifically, the parameters required for simulation are used as input, including the diameter, velocity, and number of shots; and the probability of failure and key parameter are used as output. Results of a sensitivity analysis case show that the probability of disk failure is reduced with the increase of shot peening parameters (number, diameter, speed), where the effect of the diameter is greater within a given range. Therefore, the method proposed in this study can efficiently and intuitively identify the key parameter in the design stage.