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12 pages, 2056 KiB

Open AccessArticle

Strain State in Metal Sheet Axisymmetric Stretching with Variable Initial Thickness: Numerical and Experimental Results

by Gillo Giuliano and Wilma Polini

Appl. Sci. 2021, 11(17), 8265; https://doi.org/10.3390/app11178265 - 6 Sep 2021

Cited by 1 | Viewed by 1893

Abstract

This work presents a finite element model to analyze the distribution of the strains due to an axisymmetric stretching of a metal sheet. The sheet is characterized by a variable initial thickness. The resulting strain state is compared with that of a sheet [...] Read more.

This work presents a finite element model to analyze the distribution of the strains due to an axisymmetric stretching of a metal sheet. The sheet is characterized by a variable initial thickness. The resulting strain state is compared with that of a sheet with a constant initial thickness. The results of the present study allow asserting that the distribution of strains in the sheet can be controlled by setting opportunely the trend of the sheet initial thickness. In this way, it is possible to see that, starting from a sheet with variable initial thickness, a lighter final product is obtained, whose final thickness distribution is more uniform than that of the product obtained from a classic stretching process that requires a sheet with constant initial thickness. Encouraging results from an experimental activity carried out on an AA6060 aluminum alloy sheet, whose trend of initial thicknesses was prepared by removing material from a commercial sheet with a constant thickness, allow us to note the good agreement with what was theoretically highlighted. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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21 pages, 5414 KiB

Open AccessFeature PaperArticle

Failure Detection for Semantic Segmentation on Road Scenes Using Deep Learning

by Junho Song, Woojin Ahn, Sangkyoo Park and Myotaeg Lim

Appl. Sci. 2021, 11(4), 1870; https://doi.org/10.3390/app11041870 - 20 Feb 2021

Cited by 8 | Viewed by 3726

Abstract

Detecting failure cases is an essential element for ensuring the safety self-driving system. Any fault in the system directly leads to an accident. In this paper, we analyze the failure of semantic segmentation, which is crucial for autonomous driving system, and detect the [...] Read more.

Detecting failure cases is an essential element for ensuring the safety self-driving system. Any fault in the system directly leads to an accident. In this paper, we analyze the failure of semantic segmentation, which is crucial for autonomous driving system, and detect the failure cases of the predicted segmentation map by predicting mean intersection of union (mIoU). Furthermore, we design a deep neural network for predicting mIoU of segmentation map without the ground truth and introduce a new loss function for training imbalance data. The proposed method not only predicts the mIoU, but also detects failure cases using the predicted mIoU value. The experimental results on Cityscapes data show our network gives prediction accuracy of 93.21% and failure detection accuracy of 84.8%. It also performs well on a challenging dataset generated from the vertical vehicle camera of the Hyundai Motor Group with 90.51% mIoU prediction accuracy and 83.33% failure detection accuracy. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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18 pages, 6245 KiB

Open AccessArticle

Design and Accuracy Analysis of a Micromachine Tool with a Co-Planar Driving Mechanism

by Shih-Ming Wang, Zhe-Zhi Ye and Hariyanto Gunawan

Appl. Sci. 2021, 11(3), 947; https://doi.org/10.3390/app11030947 - 21 Jan 2021

Cited by 2 | Viewed by 2477

Abstract

Due to the requirements of manufacturing miniaturized high-tech products, micromachining with micromachine tools has come to be regarded as an important technology. The main goal of this study is to build up the key technologies, including optimal structure and configuration design, synchronous driving [...] Read more.

Due to the requirements of manufacturing miniaturized high-tech products, micromachining with micromachine tools has come to be regarded as an important technology. The main goal of this study is to build up the key technologies, including optimal structure and configuration design, synchronous driving control, analysis of optimal accuracy, in order to develop a low-cost and high-accuracy micromachine tool with a multi-degrees of freedom (DOF) platform with a co-plane synchronous driving mechanism. Due to the advantages of such a mechanism, the machine is able to possess a high feed resolution and high accuracy without the use of expensive drive components and high-end CNC controllers. Because of the no pile-up structure, the machine has less movement inertia effect, as well as the merits of light weight, high stiffness, and increased stability. Furthermore, the machine has more DOF, resulting in a better cutting performance than that of 3-DOF machine tools. To better understand the characteristics of major error sources of the machine in order to further enhance its accuracy, hybrid error analysis, kinematics analysis, and a volumetric error model were conducted. Finally, a prototype of the designed micromachine tool was built, and cutting experiments for accuracy calibration and verification were carried out using this machine. The results showed that the machine was able to effectively execute 4-DOF microcutting with positioning accuracy of 800 nm. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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17 pages, 1930 KiB

Open AccessArticle

Analysis of Modal Parameters Using a Statistical Approach for Condition Monitoring of the Wind Turbine Blade

by Lukasz Dolinski and Marek Krawczuk

Appl. Sci. 2020, 10(17), 5878; https://doi.org/10.3390/app10175878 - 25 Aug 2020

Cited by 13 | Viewed by 3153

Abstract

The primary objective of the presented paper is the numerical and experimental investigation related to developing a useful diagnostic method, which can be used for determining the site and size of damage in laminated shells of wind turbine blades. The described detection technique [...] Read more.

The primary objective of the presented paper is the numerical and experimental investigation related to developing a useful diagnostic method, which can be used for determining the site and size of damage in laminated shells of wind turbine blades. The described detection technique is based on the analysis of low frequencies bending vibrations mode shapes of rotor blades. The authors used the commonly applied statistics methods that have been adapted to detect edges of damage, including the normalized determination coefficient fit, which is a measure of the absolute fit between two curves. The research was conducted for a scaled-down blade of a three-bladed horizontal-axis wind turbine with 36 m diameter rotor. The study was divided into two parts. The first stage included numerical calculations using the finite element method, which were supplemented in the second stage by measurements under laboratory conditions of the specially manufactured composite blade. The forms of natural vibrations for intact and damaged blade were determined using Laser Doppler Scanning Vibrometry. The results of the presented research confirm the effectiveness of the modal analysis combined with statistic calculation in damage detection. The method points out the location of relatively small damage. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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21 pages, 3482 KiB

Open AccessArticle

Pole Assignment for Active Vibration Control of Linear Vibrating Systems through Linear Matrix Inequalities

by Roberto Belotti, Dario Richiedei, Iacopo Tamellin and Alberto Trevisani

Appl. Sci. 2020, 10(16), 5494; https://doi.org/10.3390/app10165494 - 8 Aug 2020

Cited by 14 | Viewed by 3266

Abstract

This paper proposes a novel method for pole placement in linear vibrating systems through state feedback and rank-one control. Rather than assigning all the poles to the desired locations of the complex plane, the proposed method exactly assigns just the dominant poles, while [...] Read more.

This paper proposes a novel method for pole placement in linear vibrating systems through state feedback and rank-one control. Rather than assigning all the poles to the desired locations of the complex plane, the proposed method exactly assigns just the dominant poles, while the remaining ones are free to assume arbitrary positions within a pre-specified region in the complex plane. Therefore, the method can be referred to as “regional pole placement”. A two-stage approach is proposed to accomplish both the tasks. In the first stage, the subset of dominant poles is assigned to exact locations by exploiting the receptance method, formulated for either symmetric or asymmetric systems. Then, in the second stage, a first-order model formulated with a reduced state, together with the theory of Linear Matrix Inequalities, are exploited to cluster the subset of the unassigned poles into some stable regions of the complex plane while keeping unchanged the poles assigned in the first stage. The additional degrees of freedom in the choice of the gains, i.e., the non-uniqueness of the solution, is exploited through a semidefinite programming problem to reduce the control gains. The method is validated by means of four meaningful and challenging test-cases, also borrowed from the literature. The results are also compared with those of classic partial pole placement, to show the benefits and the effectiveness of the proposed approach. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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14 pages, 17388 KiB

Open AccessArticle

Evaluation of a Balloon-Type Vaginal Endoscope Based on Three-Dimensional Printing Technology for Self-Assessment of Pelvic Organ Prolapse

by Myoungjae Jun, Hieyong Jeong, Masayuki Endo, Michiko Kodama and Yuko Ohno

Appl. Sci. 2020, 10(15), 5108; https://doi.org/10.3390/app10155108 - 24 Jul 2020

Cited by 1 | Viewed by 6380

Abstract

Pelvic organ prolapse (POP) can occur if the support tissues or the pelvic floor muscles are weakened and damaged. There is increased probability for POP occurrence after childbirth, menopause, or in overweight women. Because the natural history and progression of POP is still [...] Read more.

Pelvic organ prolapse (POP) can occur if the support tissues or the pelvic floor muscles are weakened and damaged. There is increased probability for POP occurrence after childbirth, menopause, or in overweight women. Because the natural history and progression of POP is still unknown, the approaches used to prevent it have not been clear. POP is an uncomfortable condition that affects one every three women. However, most people feel uncomfortable to discuss it. Herein, we conducted a feasibility evaluation study for self-assessment approaches with a vaginal endoscope based on three-dimensional (3D) printing. The proposed endoscope has two parts: (a) rubber material used to cover it for its intended insertion, to avoid direct contact with the walls of the vagina, and (b) two types of sensors at the tip for measurements. The condition inside the vagina was observed with a camera and depth sensors based on the regulation of the amount of air. Arbitrary temporary prolapses from the testbed’s generator enabled us to perceive the location of the problem and symptoms that were regarded as the early stage. As discussed, the low-cost design of the 3D-printed-based vaginal endoscope provides a self-check capability and allows continuous observations that help prevent POP. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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30 pages, 9209 KiB

Open AccessArticle

Design of Wear-Resistant UHMWPE-Based Composites Loaded with Wollastonite Microfibers Treated with Various Silane Coupling Agents

by Sergey V. Panin, Qitao Huang, Vladislav O. Alexenko, Dmitry G. Buslovich, Lyudmila А. Kornienko, Filippo Berto, Svetlana A. Bochkareva, Iliya L. Panov and Natalya V. Ryabova

Appl. Sci. 2020, 10(13), 4511; https://doi.org/10.3390/app10134511 - 29 Jun 2020

Cited by 7 | Viewed by 3375

Abstract

The tribomechanical properties of the wear-resistant ultrahigh molecular weight polyethylene (UHMWPE)-based composites loaded with wollastonite microfibres silanized with various coupling agents (“KH-550”, “Penta-1006”, and “OTS”) were investigated. It was demonstrated that the mechanical properties of UHMWPE-based composites filled with various amounts of wollastonite [...] Read more.

The tribomechanical properties of the wear-resistant ultrahigh molecular weight polyethylene (UHMWPE)-based composites loaded with wollastonite microfibres silanized with various coupling agents (“KH-550”, “Penta-1006”, and “OTS”) were investigated. It was demonstrated that the mechanical properties of UHMWPE-based composites filled with various amounts of wollastonite (7–23 wt. %) increased by 1.3 times (yield strength) and by 1.8 times (elastic modulus), while the wollastonite silanization further improved yield strength by 9% in some cases. It was demonstrated that the composite loaded with 23 wt. % wollastonite silanized with the “KH-550” coupling agent possessed the maximum wear resistance under “moderate” conditions of tribological loading. Under “severe” conditions, the composites containing 23 wt. % wollastonite silanized with the less efficient “OTS” and “Penta-1006” agents showed the greatest wear resistance during dry sliding friction. Wear resistance significantly depended on filler weight fraction and the load–speed mode of the tribological tests. Based on the obtained experimental data on the mechanical (including impact toughness) and tribological properties of the UHMWPE-based composites loaded with wollastonite, the optimal compositions (the filler content and the type of the coupling agent) for two load–speed modes were designed using the developed computer algorithm. The composites provided the predefined high tribomechanical properties for operation in the metal-polymer friction units compared to neat polymer. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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43 pages, 11159 KiB

Open AccessArticle

A Robust Adiabatic Model for a Quasi-Steady Prediction of Far-Off Non-Measured Performance in Vaneless Twin-Entry or Dual-Volute Radial Turbines

by José Ramón Serrano, Francisco J. Arnau, Luis Miguel García-Cuevas and Vishnu Samala

Appl. Sci. 2020, 10(6), 1955; https://doi.org/10.3390/app10061955 - 12 Mar 2020

Cited by 6 | Viewed by 4519

Abstract

The current investigation describes in detail a mass flow oriented model for extrapolation of reduced mass flow and adiabatic efficiency of double entry radial inflow turbines under any unequal and partial flow admission conditions. The model is based on a novel approach, which [...] Read more.

The current investigation describes in detail a mass flow oriented model for extrapolation of reduced mass flow and adiabatic efficiency of double entry radial inflow turbines under any unequal and partial flow admission conditions. The model is based on a novel approach, which proposes assimilating double entry turbines to two variable geometry turbines (VGTs) using the mass flow ratio (

MFR

) between the two entries as the discriminating parameter. With such an innovative approach, the model can extrapolate performance parameters to non-measured

MFR

s, blade-to-jet speed ratios, and reduced speeds. Therefore, the model can be used in a quasi-steady method for predicting double entry turbines performance instantaneously. The model was validated against a dataset from two different double entry turbine types: a twin-entry symmetrical turbine and a dual-volute asymmetrical turbine. Both were tested under steady flow conditions. The proposed model showed accurate results and a coherent set of fitting parameters with physical meaning, as discussed in this paper. The obtained parameters showed very similar figures for the aforementioned turbine types, which allows concluding that they are an adequate set of values for initializing the fitting procedure of any type of double entry radial turbine. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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Review

Jump to: Research, Other

34 pages, 1365 KiB

Open AccessFeature PaperReview

A Review of Validation Methods for the Intracranial Response of FEHM to Blunt Impacts

by K. McGill, F. Teixeira-Dias and A. Callanan

Appl. Sci. 2020, 10(20), 7227; https://doi.org/10.3390/app10207227 - 16 Oct 2020

Cited by 3 | Viewed by 3337

Abstract

The following is a review of the processes currently employed when validating the intracranial response of Finite Element Head Models (FEHM) against blunt impacts. The authors aim to collate existing validation tools, their applications and findings on their effectiveness to aid researchers in [...] Read more.

The following is a review of the processes currently employed when validating the intracranial response of Finite Element Head Models (FEHM) against blunt impacts. The authors aim to collate existing validation tools, their applications and findings on their effectiveness to aid researchers in the validation of future FEHM and potential efforts in improving procedures. In this vain, publications providing experimental data on the intracranial pressure, relative brain displacement and brain strain responses to impacts in human subjects are surveyed and key data are summarised. This includes cases that have previously been used in FEHM validation and alternatives with similar potential uses. The processes employed to replicate impact conditions and the resulting head motion are reviewed, as are the analytical techniques used to judge the validity of the models. Finally, publications exploring the validation process and factors affecting it are critically discussed. Reviewing FEHM validation in this way highlights the lack of a single best practice, or an obvious solution to create one using the tools currently available. There is clear scope to improve the validation process of FEHM, and the data available to achieve this. By collecting information from existing publications, it is hoped this review can help guide such developments and provide a point of reference for researchers looking to validate or investigate FEHM in the future, enabling them to make informed choices about the simulation of impacts, how they are generated numerically and the factors considered during output assessment, whilst being aware of potential limitations in the process. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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23 pages, 4258 KiB

Open AccessReview

Recent Progress in Pressure Sensors for Wearable Electronics: From Design to Applications

by Yeongjun Kim and Je Hoon Oh

Appl. Sci. 2020, 10(18), 6403; https://doi.org/10.3390/app10186403 - 14 Sep 2020

Cited by 23 | Viewed by 6371

Abstract

In recent years, innovative research has been widely conducted on flexible devices for wearable electronics applications. Many examples of wearable electronics, such as smartwatches and glasses, are already available to consumers. However, strictly speaking, the sensors used in these devices are not flexible. [...] Read more.

In recent years, innovative research has been widely conducted on flexible devices for wearable electronics applications. Many examples of wearable electronics, such as smartwatches and glasses, are already available to consumers. However, strictly speaking, the sensors used in these devices are not flexible. Many studies are underway to address a wider range of wearable electronics and the development of related fields is progressing very rapidly. In particular, there is intense interest in the research field of flexible pressure sensors because they can collect and use information regarding a wide variety of sources. Through the combination of novel materials and fabrication methods, human-machine interfaces, biomedical sensors, and motion detection techniques, it is now possible to produce sensors with a superior level of performance to meet the demands of wearable electronics. In addition, more compact and human-friendly sensors have been invented in recent years, as biodegradable and self-powered sensor systems have been studied. In this review, a comprehensive description of flexible pressure sensors will be covered, and design strategies that meet the needs for applications in wearable electronics will be presented. Moreover, we will cover several fabrication methods to implement these technologies and the corresponding real-world applications. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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21 pages, 5477 KiB

Open AccessReview

A Review of In-Vivo and In-Vitro Real-Time Corrosion Monitoring Systems of Biodegradable Metal Implants

by Priscilla Yin Yee Chin, Quentin Cheok, Adam Glowacz and Wahyu Caesarendra

Appl. Sci. 2020, 10(9), 3141; https://doi.org/10.3390/app10093141 - 30 Apr 2020

Cited by 29 | Viewed by 4796

Abstract

In current modern medicine, biodegradable metal implants are still considered a work-in-progress between the collaborations of both scientists and engineers. As of now, one of the obstacles to this development is monitoring the corrosion rate of the implant. When a biodegradable metal implant [...] Read more.

In current modern medicine, biodegradable metal implants are still considered a work-in-progress between the collaborations of both scientists and engineers. As of now, one of the obstacles to this development is monitoring the corrosion rate of the implant. When a biodegradable metal implant (made of Mg, Zn, etc.) is introduced into the harsh environment of the human body, corrosion naturally occurs, causing metal ions to be released which may result in undesired health effects. The released products of the corroding implant can be used to monitor the implant condition. This paper discusses the current real-time corrosion monitoring systems (i.e., electrochemical-, microsensor-, and microdialysis-based) in-vivo and in-vitro. It is acknowledged that the progress in this sector still requires extensive research in order to obtain a desirable monitoring system and it is hoped that this review paper contributes to the research. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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60 pages, 2128 KiB

Open AccessReview

A Review on Thermoplastic or Thermosetting Polymeric Matrices Used in Polymeric Composites Manufactured with Banana Fibers from the Pseudostem

by Deesy G. Pinto, João Rodrigues and Luís Bernardo

Appl. Sci. 2020, 10(9), 3023; https://doi.org/10.3390/app10093023 - 26 Apr 2020

Cited by 5 | Viewed by 4722

Abstract

Recent manufacturing advancements have led to the fabrication of polymeric composites (PC) reinforced with fibers. However, to reduce the impact on the environment, efforts have been made to replace synthetic fibers (SF) by natural fibers (NF) in many applications. NF, e.g., as banana [...] Read more.

Recent manufacturing advancements have led to the fabrication of polymeric composites (PC) reinforced with fibers. However, to reduce the impact on the environment, efforts have been made to replace synthetic fibers (SF) by natural fibers (NF) in many applications. NF, e.g., as banana fibers (BF) possess higher cellulose content, a higher degree of polymerization of cellulose, and a lower microfibrillar angle (MFA), which are crucial factors for the mechanical properties (MP), namely tensile modulus (TM) and tensile strength (TS), and many other properties that make them suitable for the reinforcement of PC. This review paper presents an attempt to highlight some recent findings on the MP of PC reinforced with unmodified or modified BF (UBF, MBF), which were incorporated into unmodified or modified (synthetic (SPM) or a bio (BPM)) polymeric matrices (UPM, MPM). The experimental results from previous studies are presented in terms of the variation in the percentage of the MP and show that BF can improve the MP of PC. The results of such studies suggest the possibility to extend the application of PC reinforced with BF (PCBF) in a wide range, namely from automotive to biomedical fields. The meanings of all the acronyms are listed in the abbreviations section. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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Other

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16 pages, 5372 KiB

Open AccessPerspective

Electrical Monitoring under Transient Conditions: A New Paradigm in Electric Motors Predictive Maintenance

by Jose Antonino-Daviu

Appl. Sci. 2020, 10(17), 6137; https://doi.org/10.3390/app10176137 - 3 Sep 2020

Cited by 34 | Viewed by 8838

Abstract

Electric motors condition monitoring is a field of paramount importance for industry. In recent decades, there has been a continuous effort to investigate new techniques and methods that are able to determine the health of these machines with high accuracy and reliability. Classical [...] Read more.

Electric motors condition monitoring is a field of paramount importance for industry. In recent decades, there has been a continuous effort to investigate new techniques and methods that are able to determine the health of these machines with high accuracy and reliability. Classical methods based on the analysis of diverse machine quantities under stationary conditions are being replaced by modern methodologies that are adapted to any operation regime of the machine (including transients). These new methods (especially those based on motor startup signal monitoring), which imply the use of advanced signal processing tools, have shown great potential and have provided spectacular advantages versus conventional approaches enabling, among other facts, a much more reliable determination of the machine health. This paper reviews the background of this recent condition monitoring trend and shows the advantages of this new approach with regard to its application to the analysis of electrical quantities. Examples referred to its application to real motors operating in industry are included, proving the huge potential of the transient-based approach and its benefits versus conventional methods. Full article

(This article belongs to the Special Issue 10th Anniversary of Applied Sciences: Invited Papers in Mechanical Engineering Section)

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