Manufacturing has provided growth and employment opportunities to many developed countries. Digital technologies have further enhanced these opportunities and diversified manufacturing activities. However, it has not been as successful in developing countries, such as Botswana, due to the low absorptive capacity, lagging digital infrastructure, and the slow development of people who need upskilling or an entirely new skill set. The increase in access to the Internet and the extensive adoption of information and communication technologies by manufacturing companies are driving competition and disrupting the present circumstances. This study aims to assess the digital skills students acquire when studying an industrial design programme and compare them with the skills needed by digital manufacturing small and medium enterprises. A case study was adopted for this study because it can capture the relationship among the phenomena, context, and people in the lived realities of the participants. The findings indicate an alignment of the skills students acquire during their studies with those needed by digital manufacturing small and medium enterprises. However, the level at which students are exposed to these digital manufacturing skills is skewed towards basic awareness, with very few students reporting competency in digital manufacturing skills, such as using a laser cutter, plasma cutter, 3D printing, and a router machine. The emphasis could be shifted to developing digital manufacturing skills, as this is the future of manufacturing in the fourth and fifth industrial revolutions.
{"title":"Integration of digital manufacturing skills in industrial design education and its impact on small and medium enterprises","authors":"Yaone Rapitsenyane, Richie Moalosi, Oanthata Jester Sealetsa, Victor Ruele, Thatayaone Mosepedi, Botumile Matake","doi":"10.3389/fmech.2023.1254866","DOIUrl":"https://doi.org/10.3389/fmech.2023.1254866","url":null,"abstract":"Manufacturing has provided growth and employment opportunities to many developed countries. Digital technologies have further enhanced these opportunities and diversified manufacturing activities. However, it has not been as successful in developing countries, such as Botswana, due to the low absorptive capacity, lagging digital infrastructure, and the slow development of people who need upskilling or an entirely new skill set. The increase in access to the Internet and the extensive adoption of information and communication technologies by manufacturing companies are driving competition and disrupting the present circumstances. This study aims to assess the digital skills students acquire when studying an industrial design programme and compare them with the skills needed by digital manufacturing small and medium enterprises. A case study was adopted for this study because it can capture the relationship among the phenomena, context, and people in the lived realities of the participants. The findings indicate an alignment of the skills students acquire during their studies with those needed by digital manufacturing small and medium enterprises. However, the level at which students are exposed to these digital manufacturing skills is skewed towards basic awareness, with very few students reporting competency in digital manufacturing skills, such as using a laser cutter, plasma cutter, 3D printing, and a router machine. The emphasis could be shifted to developing digital manufacturing skills, as this is the future of manufacturing in the fourth and fifth industrial revolutions.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"183 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135884407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.3389/fmech.2023.1228696
Wael Masmoudi, Jean-Luc Wojtowicki, Giuseppe Petrone, Francesco Franco, Sergio De Rosa
With the growing demand for lightweight gear transmission systems, composite materials have emerged as a promising solution due to their high specific properties. However, the complexity of designing gear pairs with composite materials necessitates the development of reliable numerical procedures. This study presents a robust numerical approach using a flexible multibody method through the MSC MARC solver to accurately estimate static transmission error (STE) in lightweight gears, considering the nonlinear behavior caused by gear contact. The Finite Element (FE) model uses the Multi-Point Constraint equations (MPCs) to ensure the non-penetration condition considering a node-to-surface contact detection. The proposed method is compared against commercial software for standard gear pair cases, demonstrating its effectiveness in addressing complex structures based on composite materials. The numerical procedure is further applied to analyze hybrid metal-composite gear pairs and compared to a holed one. The results provide insights into the time evolution and harmonic components of STE, highlighting the advantages of hybrid gears in terms of reduced vibrations and noise for the same mass reduction compared to holed gears. Additionally, ply arrangements resulting in quasi-isotropic properties of the composite disc are compared to unidirectional laminates to highlight the fiber orientation effect on the STE results.
{"title":"Evaluating lightweight gear transmission error: a novel nonlinear finite element approach using direct constraint contact algorithm","authors":"Wael Masmoudi, Jean-Luc Wojtowicki, Giuseppe Petrone, Francesco Franco, Sergio De Rosa","doi":"10.3389/fmech.2023.1228696","DOIUrl":"https://doi.org/10.3389/fmech.2023.1228696","url":null,"abstract":"With the growing demand for lightweight gear transmission systems, composite materials have emerged as a promising solution due to their high specific properties. However, the complexity of designing gear pairs with composite materials necessitates the development of reliable numerical procedures. This study presents a robust numerical approach using a flexible multibody method through the MSC MARC solver to accurately estimate static transmission error (STE) in lightweight gears, considering the nonlinear behavior caused by gear contact. The Finite Element (FE) model uses the Multi-Point Constraint equations (MPCs) to ensure the non-penetration condition considering a node-to-surface contact detection. The proposed method is compared against commercial software for standard gear pair cases, demonstrating its effectiveness in addressing complex structures based on composite materials. The numerical procedure is further applied to analyze hybrid metal-composite gear pairs and compared to a holed one. The results provide insights into the time evolution and harmonic components of STE, highlighting the advantages of hybrid gears in terms of reduced vibrations and noise for the same mass reduction compared to holed gears. Additionally, ply arrangements resulting in quasi-isotropic properties of the composite disc are compared to unidirectional laminates to highlight the fiber orientation effect on the STE results.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135853409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-13DOI: 10.3389/fmech.2023.1240761
S. Castellani, P. C. Nassini, A. Andreini
In the gas turbine framework, the adoption of carbon capture and storage (CCS) systems coupled with strategies to improve the exhaust CO 2 content is a promising technology to abate the carbon footprint of such machines. However, any departure of the oxidant from the air can compromise the accuracy of the conventional models to represent the combustion process. In this work, the effect of the CO 2 enrichment of the mixture on an atmospheric premixed swirled flame is investigated by means of large eddy simulation (LES), comparing the numerical predictions with the experimental results. The high-fidelity numerical model features a dedicated global reaction mechanism derived through an in-house optimization procedure presented in this study. The chemical scheme is obtained by optimizing a widely used CH 4 –air two-step mechanism to improve key flame parameters such as the laminar flame speed and thickness and the resistance of the flame to the stretch with moderate CO 2 dilution. The numerical results are analyzed in terms of flame shape, heat losses, and pressure fluctuations, showing a promising agreement with the experimental measurements and demonstrating the capabilities of the numerical model for CO 2 -diluted combustion.
{"title":"Optimization of a two-step CH4/air reaction mechanism in a CO2-enriched environment for high-fidelity combustion simulations","authors":"S. Castellani, P. C. Nassini, A. Andreini","doi":"10.3389/fmech.2023.1240761","DOIUrl":"https://doi.org/10.3389/fmech.2023.1240761","url":null,"abstract":"In the gas turbine framework, the adoption of carbon capture and storage (CCS) systems coupled with strategies to improve the exhaust CO 2 content is a promising technology to abate the carbon footprint of such machines. However, any departure of the oxidant from the air can compromise the accuracy of the conventional models to represent the combustion process. In this work, the effect of the CO 2 enrichment of the mixture on an atmospheric premixed swirled flame is investigated by means of large eddy simulation (LES), comparing the numerical predictions with the experimental results. The high-fidelity numerical model features a dedicated global reaction mechanism derived through an in-house optimization procedure presented in this study. The chemical scheme is obtained by optimizing a widely used CH 4 –air two-step mechanism to improve key flame parameters such as the laminar flame speed and thickness and the resistance of the flame to the stretch with moderate CO 2 dilution. The numerical results are analyzed in terms of flame shape, heat losses, and pressure fluctuations, showing a promising agreement with the experimental measurements and demonstrating the capabilities of the numerical model for CO 2 -diluted combustion.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135853858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-09DOI: 10.3389/fmech.2023.1242612
Achraf Haibi, Kenza Oufaska, Khalid El Yassini, Mohammed Boulmalf, Mohsine Bouya
Radio Frequency Identification (RFID) is a contactless technology that has developed over the 90s and 20th centuries. It employs electromagnetic or electrostatic coupling in the radio frequency part of the electromagnetic spectrum to uniquely identify traceable objects, and is widely used in various sectors (e.g., medical, Supply Chain Management, transportation, and IoT applications.). Through the supply of real-world monitoring and context information about things, the integration of this technology in such areas delivers various benefits in the future of ubiquitous computing. However, one of the primary challenges will be the capacity to manage data since RFID events have specific characteristics and requires special treatment, such as the large volume of data flow, inaccuracy, temporal and spatial data, are typical examples of RFID event data. The goal of this research is to first highlight the concerns and limitations of existing middleware architectures before introducing and implementing a new Middleware architecture to address the identified issues, specifically real-time processing of massive volumes of data coming from physical RFID infrastructure. This middleware combines role-based access control with an encryption algorithm to increase security, a NoSQL database for storing large amounts of data, complex event processing (CEP) to provide high-volume data stream processing, and improved interoperability via the Data Transformation Module. Finally, our architecture is evaluated and compared to several middleware architectures based on standard ISO/IEC 9126 metrics.
{"title":"A new RFID Middleware architecture based on a hybrid security technique using data encryption and RBAC for modern real-time tracking applications","authors":"Achraf Haibi, Kenza Oufaska, Khalid El Yassini, Mohammed Boulmalf, Mohsine Bouya","doi":"10.3389/fmech.2023.1242612","DOIUrl":"https://doi.org/10.3389/fmech.2023.1242612","url":null,"abstract":"Radio Frequency Identification (RFID) is a contactless technology that has developed over the 90s and 20th centuries. It employs electromagnetic or electrostatic coupling in the radio frequency part of the electromagnetic spectrum to uniquely identify traceable objects, and is widely used in various sectors (e.g., medical, Supply Chain Management, transportation, and IoT applications.). Through the supply of real-world monitoring and context information about things, the integration of this technology in such areas delivers various benefits in the future of ubiquitous computing. However, one of the primary challenges will be the capacity to manage data since RFID events have specific characteristics and requires special treatment, such as the large volume of data flow, inaccuracy, temporal and spatial data, are typical examples of RFID event data. The goal of this research is to first highlight the concerns and limitations of existing middleware architectures before introducing and implementing a new Middleware architecture to address the identified issues, specifically real-time processing of massive volumes of data coming from physical RFID infrastructure. This middleware combines role-based access control with an encryption algorithm to increase security, a NoSQL database for storing large amounts of data, complex event processing (CEP) to provide high-volume data stream processing, and improved interoperability via the Data Transformation Module. Finally, our architecture is evaluated and compared to several middleware architectures based on standard ISO/IEC 9126 metrics.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135044558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.3389/fmech.2023.1273447
M. Hafid, Jos Istiyanto, Nasruddin Nasruddin
In this study, the crashworthiness performance of a thin-walled square steel-tube structure with an elliptical crush initiator under impact loading was investigated. The effect of the height, width, and distance of the crush initiator from the top of the tube on the crashworthiness performance was analyzed using several numerical simulations using ABAQUS Explicit. The response surface methodology was used to predict the crashworthiness performance indices, and optimization was performed to determine the optimal dimensions and position of the crush initiator. The optimization was aimed at minimizing the peak force (PF) while maximizing the mean crushing force (MCF), crush force efficiency (CFE), and specific energy absorption (SEA). The result was an elliptical crush initiator with a height of 15 mm, width of 24.784 mm, and distance of 15.08 mm. Validation was performed to verify these results. The optimal crush initiator effect resulted in a 10.12% decrease in the peak force, 13.67% increase in the crush force efficiency, and 2.23% increase in the mean crushing force. However, a slight decrease of 0.82% in specific energy absorption was observed.
{"title":"Multiobjective optimization of dimension and position of elliptical crush initiator on crashworthiness performance of square tube using response surface methodology","authors":"M. Hafid, Jos Istiyanto, Nasruddin Nasruddin","doi":"10.3389/fmech.2023.1273447","DOIUrl":"https://doi.org/10.3389/fmech.2023.1273447","url":null,"abstract":"In this study, the crashworthiness performance of a thin-walled square steel-tube structure with an elliptical crush initiator under impact loading was investigated. The effect of the height, width, and distance of the crush initiator from the top of the tube on the crashworthiness performance was analyzed using several numerical simulations using ABAQUS Explicit. The response surface methodology was used to predict the crashworthiness performance indices, and optimization was performed to determine the optimal dimensions and position of the crush initiator. The optimization was aimed at minimizing the peak force (PF) while maximizing the mean crushing force (MCF), crush force efficiency (CFE), and specific energy absorption (SEA). The result was an elliptical crush initiator with a height of 15 mm, width of 24.784 mm, and distance of 15.08 mm. Validation was performed to verify these results. The optimal crush initiator effect resulted in a 10.12% decrease in the peak force, 13.67% increase in the crush force efficiency, and 2.23% increase in the mean crushing force. However, a slight decrease of 0.82% in specific energy absorption was observed.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135350661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-03DOI: 10.3389/fmech.2023.1255051
Md. Mahbubur Rahman, Ved Prakash, Sunil Chandel, D. G. Thakur, Robert Čep, Nitin Khedkar, Sachin Salunkhe, Emad S. Abouel Nasr
In the present work, an investigation of the aerodynamic characteristics of an ejection seat occupant is carried out using the commercially available computational fluid dynamics software ANSYS Fluent. 3D Reynolds-averaged Navier–Stokes equations are solved to obtain the aerodynamic coefficients of the ejection seat system. For this analysis, an unstructured grid is generated for the ejection seat occupant using ANSYS meshing. Validation is carried out and the performance of three different turbulence models is analyzed at Mach 0.6. Based on the most suitable turbulence model, further analysis of the aerodynamic coefficients of the ejection seat occupant is calculated at Mach numbers of 0.35, 0.45, 0.55, 0.65, and 0.75. For all values of Mach, the angle of attack is varied from −15° to 15° in 5° increments and the yaw angle is varied from 0° to 60° in 10° increments. Based on the results, it is observed that the magnitude of the axial force decreases with increasing angle of attack and yaw angle. Similarly, the normal force coefficient and pitching moment coefficient decrease with increasing angle of attack. Finally, the side force coefficient, yawing moment, and rolling moment coefficients increase with increasing yaw angle.
{"title":"Analysis of the aerodynamic characteristics of an ejection seat system using computational fluid dynamics","authors":"Md. Mahbubur Rahman, Ved Prakash, Sunil Chandel, D. G. Thakur, Robert Čep, Nitin Khedkar, Sachin Salunkhe, Emad S. Abouel Nasr","doi":"10.3389/fmech.2023.1255051","DOIUrl":"https://doi.org/10.3389/fmech.2023.1255051","url":null,"abstract":"In the present work, an investigation of the aerodynamic characteristics of an ejection seat occupant is carried out using the commercially available computational fluid dynamics software ANSYS Fluent. 3D Reynolds-averaged Navier–Stokes equations are solved to obtain the aerodynamic coefficients of the ejection seat system. For this analysis, an unstructured grid is generated for the ejection seat occupant using ANSYS meshing. Validation is carried out and the performance of three different turbulence models is analyzed at Mach 0.6. Based on the most suitable turbulence model, further analysis of the aerodynamic coefficients of the ejection seat occupant is calculated at Mach numbers of 0.35, 0.45, 0.55, 0.65, and 0.75. For all values of Mach, the angle of attack is varied from −15° to 15° in 5° increments and the yaw angle is varied from 0° to 60° in 10° increments. Based on the results, it is observed that the magnitude of the axial force decreases with increasing angle of attack and yaw angle. Similarly, the normal force coefficient and pitching moment coefficient decrease with increasing angle of attack. Finally, the side force coefficient, yawing moment, and rolling moment coefficients increase with increasing yaw angle.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135696395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.3389/fmech.2023.1253207
Wonhyeok Lee, Melih Eriten
Past decades featured significant advancements in additive and micromanufacturing that facilitated the creation of functional patterned surfaces with impressive spatial resolutions. However, these techniques are expensive and require a considerable amount of time and energy, and hence lack scalability to practical surfaces. Recent techniques employing spinodal decomposition and instabilities amplified via centrifugal acceleration offer viable and cheaper alternatives. The patterns created by those techniques, however, vary randomly in geometry. When interfacing those patterned surfaces with other components and under self-contact scenarios, geometric variations lead to stress concentration and abrupt failure around the contact. In this study, we investigate numerically real contact areas, contact tractions, and stress concentration. We generate patterned surfaces in congruence with actual surfaces created by those techniques. Then, we conduct normal-contact analyses of those surfaces boundary element method (BEM) under nominal mean pressures ranging from 0.001 E * to E *, where E * is the contact modulus. We record real contact areas and stress concentration as a function of nominal mean pressures. We compare these values with the analytical solutions from sinusoidally-patterned and randomly rough surfaces. Randomness in pattern geometry is primarily influenced by the processing parameters such as the degree of anisotropy in spinodal decomposition and acceleration in amplified instabilities. To understand the influence of the processing parameters, we perform a parametric study. We find isotropic spinodal decomposition creates patterns that deliver contact area and traction distributions similar to randomly rough surfaces, and lead to high-stress concentrations. Such high-stress concentrations are expected to occur under self-contact loading scenarios, and thus can explain the compromised resilience and strength in recently-proposed spinodal metamaterials. For patterned surfaces created by amplified instabilities, high-stress concentrations are obtained for the surfaces created at high accelerations. At high accelerations, increased elastic instabilities and stochastic growth result in a more skewed and broader distribution in heights. Therefore, high-stress concentrations are inevitable. To account for combined loading scenarios, we conduct additional simulations on the same surface patterns with frictional pre-sliding contacts. We find the frictional tractions play a secondary role in stress concentrations where the primary factor is the processing parameters determining the degree of randomness in pattern geometry.
在过去的几十年里，增材制造和微制造取得了重大进展，促进了具有令人印象深刻的空间分辨率的功能性图案表面的创造。然而，这些技术是昂贵的，需要大量的时间和精力，因此缺乏实际表面的可扩展性。最近的技术采用了独立分解和通过离心加速放大的不稳定性，提供了可行且更便宜的替代方案。然而，这些技术创造的图案在几何上是随机变化的。当这些有图案的表面与其他部件接触时，在自接触情况下，几何变化会导致接触周围的应力集中和突然破坏。在这项研究中，我们调查了数值实际接触面积，接触牵引力和应力集中。我们生成与这些技术创建的实际表面一致的图案表面。然后，我们在名义平均压力范围为0.001 E *至E *(其中E *为接触模量)的条件下对这些表面进行法向接触分析。我们记录实际接触面积和应力集中作为名义平均压力的函数。我们将这些值与正弦图案和随机粗糙表面的解析解进行比较。图案几何的随机性主要受处理参数的影响，如旋量分解的各向异性程度和放大不稳定性的加速度。为了了解加工参数的影响，我们进行了参数研究。我们发现各向同性旋量分解产生的模式提供了类似于随机粗糙表面的接触面积和牵引力分布，并导致高应力集中。这种高应力集中预计会发生在自接触加载情景下，因此可以解释最近提出的spinodal超材料的弹性和强度受损。对于由放大的不稳定性产生的图案表面，在高加速度下产生的表面获得高应力集中。在高加速度下，增加的弹性不稳定性和随机增长导致高度分布更偏和更宽。因此，高应力集中是不可避免的。为了考虑组合加载场景，我们对具有摩擦预滑动接触的相同表面模式进行了额外的模拟。我们发现摩擦牵引力在应力集中中起次要作用，主要因素是决定图案几何随机性程度的加工参数。
{"title":"Real area of contact and tractions on the patterned surfaces generated by spinodal decomposition and amplified instability","authors":"Wonhyeok Lee, Melih Eriten","doi":"10.3389/fmech.2023.1253207","DOIUrl":"https://doi.org/10.3389/fmech.2023.1253207","url":null,"abstract":"Past decades featured significant advancements in additive and micromanufacturing that facilitated the creation of functional patterned surfaces with impressive spatial resolutions. However, these techniques are expensive and require a considerable amount of time and energy, and hence lack scalability to practical surfaces. Recent techniques employing spinodal decomposition and instabilities amplified via centrifugal acceleration offer viable and cheaper alternatives. The patterns created by those techniques, however, vary randomly in geometry. When interfacing those patterned surfaces with other components and under self-contact scenarios, geometric variations lead to stress concentration and abrupt failure around the contact. In this study, we investigate numerically real contact areas, contact tractions, and stress concentration. We generate patterned surfaces in congruence with actual surfaces created by those techniques. Then, we conduct normal-contact analyses of those surfaces boundary element method (BEM) under nominal mean pressures ranging from 0.001 E * to E *, where E * is the contact modulus. We record real contact areas and stress concentration as a function of nominal mean pressures. We compare these values with the analytical solutions from sinusoidally-patterned and randomly rough surfaces. Randomness in pattern geometry is primarily influenced by the processing parameters such as the degree of anisotropy in spinodal decomposition and acceleration in amplified instabilities. To understand the influence of the processing parameters, we perform a parametric study. We find isotropic spinodal decomposition creates patterns that deliver contact area and traction distributions similar to randomly rough surfaces, and lead to high-stress concentrations. Such high-stress concentrations are expected to occur under self-contact loading scenarios, and thus can explain the compromised resilience and strength in recently-proposed spinodal metamaterials. For patterned surfaces created by amplified instabilities, high-stress concentrations are obtained for the surfaces created at high accelerations. At high accelerations, increased elastic instabilities and stochastic growth result in a more skewed and broader distribution in heights. Therefore, high-stress concentrations are inevitable. To account for combined loading scenarios, we conduct additional simulations on the same surface patterns with frictional pre-sliding contacts. We find the frictional tractions play a secondary role in stress concentrations where the primary factor is the processing parameters determining the degree of randomness in pattern geometry.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135864863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Due to the high specific stiffness, high specific strength, good fatigue resistance and high structural reliability, the integrally stiffened shells are widely applied in the sealed cabins. In order to enhance the detection distance of the deep space and improve the payload detection capability, it is of great significance to carry out lightweight design for the integrally stiffened shells. However, it is challenging to perform optimization for the structures due to the strict loading conditions, complicated structures and short development cycles. In this work, a novel layout design framework for the integrally stiffened shells under complex loading conditions is proposed. The topology optimization method is employed to obtain an innovative layout design of the integrally stiffened shells firstly, and then the mesh-mapping technique is utilized to assist the reconstruction and modeling process of the optimization result. Compared with the traditional design of orthogonal stiffeners, the weight of the optimized configuration of the integrally stiffened shell reduces by 17.1%, demonstrating excellent lightweight design effects. Moreover, a sealed cabin is constructed based on the optimization and numerical analysis result by taking the manufacturing requirement into consideration. With the purpose of assessing the bearing ability of the welded seam and evaluating the airtight performance of the sealed cabin, experimental validations of the hydrostatic test and airtight test are carried out, and the experimental results validate the applicability and effectiveness of the proposed framework.
{"title":"Structural lightweight design and experimental validation for aerospace sealed cabin","authors":"Zhizhong Cheng, Hongqing Li, Zengcong Li, Chen Yan, Chang Jie, Xiaoqi Li","doi":"10.3389/fmech.2023.1265734","DOIUrl":"https://doi.org/10.3389/fmech.2023.1265734","url":null,"abstract":"Due to the high specific stiffness, high specific strength, good fatigue resistance and high structural reliability, the integrally stiffened shells are widely applied in the sealed cabins. In order to enhance the detection distance of the deep space and improve the payload detection capability, it is of great significance to carry out lightweight design for the integrally stiffened shells. However, it is challenging to perform optimization for the structures due to the strict loading conditions, complicated structures and short development cycles. In this work, a novel layout design framework for the integrally stiffened shells under complex loading conditions is proposed. The topology optimization method is employed to obtain an innovative layout design of the integrally stiffened shells firstly, and then the mesh-mapping technique is utilized to assist the reconstruction and modeling process of the optimization result. Compared with the traditional design of orthogonal stiffeners, the weight of the optimized configuration of the integrally stiffened shell reduces by 17.1%, demonstrating excellent lightweight design effects. Moreover, a sealed cabin is constructed based on the optimization and numerical analysis result by taking the manufacturing requirement into consideration. With the purpose of assessing the bearing ability of the welded seam and evaluating the airtight performance of the sealed cabin, experimental validations of the hydrostatic test and airtight test are carried out, and the experimental results validate the applicability and effectiveness of the proposed framework.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"80 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90286714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.3389/fmech.2023.1226857
Jurij Prezelj, N. Cerkovnik
This paper proposes innovative numerical methods for calculating the chamber volumes and tangential leakage gaps in a scroll compressor, a critical aspect of enhancing its performance and efficiency. It proposes two methods, namely, moving away from traditional analytical approaches and presenting a 0D model for mass flow delivery at varying rotational frequencies and discharge pressures. The first method utilizes the numerical identification of conjugate points with a minimum distance within the fixed and orbiting involute pair to calculate chamber volumes. This approach compensates for integration errors by considering the subareas defined by the normal distance of each involute to the other. The second method simplifies the process by assuming that the line defining the orbital angle intersects the involutes at the conjugate points, with volumes calculated using area discretization on triangles. Both methods underwent validation against three analytical calculations, showing an agreement within an overall uncertainty error of 3% for the maximum suction volume. The 0D model’s results were compared with Ma et al.'s hybrid method and actual measurements. Upon improving Ma’s model by accounting for intake air heating and negative pressure in the intake volume, a significant agreement between modeling and measurements was observed. This study concludes that the proposed numerical methods can enhance the accuracy of scroll compressor geometry calculation and mass flow delivery, considering the tangential gap.
{"title":"Numerical calculation of scroll compressor geometry and assessment of its delivery","authors":"Jurij Prezelj, N. Cerkovnik","doi":"10.3389/fmech.2023.1226857","DOIUrl":"https://doi.org/10.3389/fmech.2023.1226857","url":null,"abstract":"This paper proposes innovative numerical methods for calculating the chamber volumes and tangential leakage gaps in a scroll compressor, a critical aspect of enhancing its performance and efficiency. It proposes two methods, namely, moving away from traditional analytical approaches and presenting a 0D model for mass flow delivery at varying rotational frequencies and discharge pressures. The first method utilizes the numerical identification of conjugate points with a minimum distance within the fixed and orbiting involute pair to calculate chamber volumes. This approach compensates for integration errors by considering the subareas defined by the normal distance of each involute to the other. The second method simplifies the process by assuming that the line defining the orbital angle intersects the involutes at the conjugate points, with volumes calculated using area discretization on triangles. Both methods underwent validation against three analytical calculations, showing an agreement within an overall uncertainty error of 3% for the maximum suction volume. The 0D model’s results were compared with Ma et al.'s hybrid method and actual measurements. Upon improving Ma’s model by accounting for intake air heating and negative pressure in the intake volume, a significant agreement between modeling and measurements was observed. This study concludes that the proposed numerical methods can enhance the accuracy of scroll compressor geometry calculation and mass flow delivery, considering the tangential gap.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"13 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88763037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-30DOI: 10.3389/fmech.2023.1266729
S. Azadi, Ali Abjadi, Abazar Vahdat Azad, Hossein Ahmadi Danesh Ashtiani, H. Afshar
Improving the performance of heat sinks is very important in the development of cooling systems. In this study, the use of a novel combination method [magnetic field impingement jet (MF-IJ)] to improve the convective heat transfer coefficient in a designed heat sink is numerically investigated. To model heat transfer, a steady three-dimensional computational fluid dynamics (CFD) approach is employed. Numerical results including velocity and temperature contours, as well as the distribution of wall temperature of the heat sink and also the convective heat transfer coefficient are analyzed. The results show that the use of ferrofluid (Fe3O4/water) flow with an external magnetic field alone increases the heat transfer coefficient by 10%, while the use of an air impingement jet with pure water and without a magnetic field increases it by 22.4%. By using the MF-IJ method, a 32% enhancement of heat transfer coefficient is achieved compared to the case of pure water flow and without MF-IJ. Based on results, at a Reynolds number of 600, by applying the magnetic field intensities of 400, 800, and 1600 G, the average heat transfer coefficient increases by 5.35, 11.77, and 16.11%, respectively. It is also found that the cooling of the heat sink and temperature distribution is improved by increasing the Reynolds number and the inlet mass flow rate of the impingement jet. For instance, at z = 0.02 m, the application of an impingement jet with mass flow rates of 0.001, 0.004, and 0.005 kg/s results in a respective decrease of 0.36, 1.62, and 1.82% in wall temperature. The results of the current study suggest that the combination method of MF-IJ can be utilized for heat sinks with high heat flux generation as a flow control device.
{"title":"Enhancement of heat transfer in heat sink under the effect of a magnetic field and an impingement jet","authors":"S. Azadi, Ali Abjadi, Abazar Vahdat Azad, Hossein Ahmadi Danesh Ashtiani, H. Afshar","doi":"10.3389/fmech.2023.1266729","DOIUrl":"https://doi.org/10.3389/fmech.2023.1266729","url":null,"abstract":"Improving the performance of heat sinks is very important in the development of cooling systems. In this study, the use of a novel combination method [magnetic field impingement jet (MF-IJ)] to improve the convective heat transfer coefficient in a designed heat sink is numerically investigated. To model heat transfer, a steady three-dimensional computational fluid dynamics (CFD) approach is employed. Numerical results including velocity and temperature contours, as well as the distribution of wall temperature of the heat sink and also the convective heat transfer coefficient are analyzed. The results show that the use of ferrofluid (Fe3O4/water) flow with an external magnetic field alone increases the heat transfer coefficient by 10%, while the use of an air impingement jet with pure water and without a magnetic field increases it by 22.4%. By using the MF-IJ method, a 32% enhancement of heat transfer coefficient is achieved compared to the case of pure water flow and without MF-IJ. Based on results, at a Reynolds number of 600, by applying the magnetic field intensities of 400, 800, and 1600 G, the average heat transfer coefficient increases by 5.35, 11.77, and 16.11%, respectively. It is also found that the cooling of the heat sink and temperature distribution is improved by increasing the Reynolds number and the inlet mass flow rate of the impingement jet. For instance, at z = 0.02 m, the application of an impingement jet with mass flow rates of 0.001, 0.004, and 0.005 kg/s results in a respective decrease of 0.36, 1.62, and 1.82% in wall temperature. The results of the current study suggest that the combination method of MF-IJ can be utilized for heat sinks with high heat flux generation as a flow control device.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"56 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81525255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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