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1 – 10 of 62Masoud Behzad, Benjamin Herrmann, Williams R. Calderón-Muñoz, José M. Cardemil and Rodrigo Barraza
Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study…
Abstract
Purpose
Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress.
Design/methodology/approach
The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events.
Findings
The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions.
Originality/value
Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.
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Shujuan Hou, Zhidan Zhang, Xujing Yang, Hanfeng Yin and Qing Li
The purpose of this paper is to optimize a new thin-walled cellular configurations with crashworthiness criteria, so as to improve the crashworthiness of components of a vehicle…
Abstract
Purpose
The purpose of this paper is to optimize a new thin-walled cellular configurations with crashworthiness criteria, so as to improve the crashworthiness of components of a vehicle body.
Design/methodology/approach
ANSYS Parametric Design Language is used to create the parameterized models so that the design variables can be changed conveniently. Moreover, the surrogate technique, namely response surface method, is adopted for fitting objective and constraint functions. The factorial design and D-optimal criterion are employed to screen active parameters for constructing the response functions of the specific energy absorption and the peak crushing force. Finally, sequential quadratic programming-NLPQL is utilized to solve the design optimization problem of the new cellular configurations filled with multi-cell circular tubes under the axial crushing loading.
Findings
Two kinds of distribution modes of the cellular configurations are first investigated, which are in an orthogonal way and in a diamond fashion. After comparing the optimized configurations of the rectangular distribution with the annular distribution of the multi-cell fillers, it is found that the orthogonal way seems better in the aspects of crashworthiness than the diamond fashion.
Originality/value
The two new thin-walled cellular configuration are studied and optimized with the crashworthiness criteria. Study on the new cellular configurations is very valuable for improving the crashworthiness of components of a vehicle body. Meanwhile, the factorial design and the factor screening are adopted in the process of the crashworthiness optimization of the new thin-walled cellular configurations.
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Amador Chapa, Enrique Cuan-Urquizo, PD Urbina-Coronado and Armando Roman-Flores
Fused filament fabrication (FFF) is a popular technique in rapid prototyping capable of building complex structures with high porosity such as cellular solids. The study of…
Abstract
Purpose
Fused filament fabrication (FFF) is a popular technique in rapid prototyping capable of building complex structures with high porosity such as cellular solids. The study of cellular solids is relevant by virtue of their enormous potential to exhibit non-traditional deformation mechanisms. The purpose of this study is to exploit the benefits of the FFF technology to fabricate re-entrant honeycomb structures using thermoplastic polyurethane (TPU) to characterize their mechanical response when subjected to cyclic compressive loadings.
Design/methodology/approach
Specimens with different volume fraction were designed, three-dimensionally printed and tested in uniaxial cyclic compressions up until densification strain. The deformation mechanism and apparent elastic moduli variation throughout five loading/unloading cycles in two different loading orientations were studied experimentally.
Findings
Experimental results demonstrated a nonlinear relationship between volume fraction and apparent elastic modulus. The amount of energy absorbed per loading cycle was computed, exhibiting reductions in energy absorbed of 12%–19% in original orientation and 15%–24% when the unit cells were rotated 90°. A softening phenomenon in the specimens was identified after the first compression when compared to second compression, with reduction in apparent elastic modulus of 23.87% and 28.70% for selected samples V3 and H3, respectively. Global buckling in half of the samples was observed, so further work must include redesign in the size of the samples.
Originality
The results of this study served to understand the mechanical response of TPU re-entrant honeycombs and their energy absorption ability when compressed in two orientations. This study helps to determine the feasibility of using FFF as manufacturing method and TPU to construct resilient structures that can be integrated into engineering applications as crash energy absorbers. Based on the results, authors suggest structure’s design optimization to reduce weight, higher number of loading cycles (n > 100) and crushing velocities (v > 1 m/s) in compression testing to study the dynamic mechanical response of the re-entrant honeycomb structures and their ability to withstand multiple compressions.
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Vijayanand Rajendra Boopathy, Anantharaman Sriraman and Arumaikkannu G.
The present work aims in presenting the energy absorbing capability of different combination stacking of multiple materials, namely, Vero White and Tango Plus, under static and…
Abstract
Purpose
The present work aims in presenting the energy absorbing capability of different combination stacking of multiple materials, namely, Vero White and Tango Plus, under static and dynamic loading conditions.
Design/methodology/approach
Honeycomb structures with various multi-material stackings are fabricated using PolyJet 3D printing technique. From the static and dynamic test results, the structure having the better energy absorbing capability is identified.
Findings
It is found that from the various stacking combinations of multiple materials, the five-layered (5L) sandwich multi-material honeycomb structure has better energy absorbing capability.
Practical implications
This multi-material combination with a honeycomb structure can be used in the application of crash resistance components such as helmet, knee guard, car bumper, etc.
Originality/value
Through experimental work, various multi-material honeycomb structures and impact resistance of single material clearly indicated the inability to absorb impact loads which experiences a maximum force of 5,055.24 N, whereas the 5L sandwich multi-material honeycomb structure experiences a minimum force of 1,948.17 N, which is 38.5 per cent of the force experienced by the single material. Moreover, in the case of compressive resistance, 2L sandwich multi-material honeycomb structure experiences a maximum force of 5,887.5 N, whereas 5L sandwich multi-material honeycomb structure experiences a minimum force of 2,410 N, which is 40.9 per cent of the force experienced by two-layered (2L) sandwich multi-material honeycomb structure. In this study, the multi-material absorbed most of the input energy and experienced minimum force in both compressive and impact loads, thus showing its energy absorbing capability and hence its utility for structures that experience impact and compressive loads. A maximum force is required to deform the single and 2L material in terms of impact and compressive load, respectively, under maximum stiffness conditions.
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Chaitanya Dosapati and Mohan Jagadeesh Kumar Mandapati
Solar energy applications are limited because of its intermittent and discontinuous availability with respect to time. Hence, solar energy thermal conversion systems need…
Abstract
Purpose
Solar energy applications are limited because of its intermittent and discontinuous availability with respect to time. Hence, solar energy thermal conversion systems need integration with thermal storage units (TSUs) to use solar energy in off sunshine hours. This paper aims to perform thermal analysis of a solar air heater (SAH) integrated with a phase change material (PCM)-based TSU to supply hot air during night period.
Design/methodology/approach
An experimental setup with TSU as main component was prepared with SAH at its upward side, food chamber at its downward side as subcomponents. In TSU, paraffin wax was used as thermal energy storage material. Mass flow rate of air considered as an input parameter in the experiment. Two different absorber plates, namely, plane and ribbed absorber plates were used for the experimentation. Each day for a fixed mass flow of air, observations were made during charging and discharging of PCM.
Findings
Nusselt number and convection heat transfer coefficients were analytically calculated by considering flow through TSU as external flow over bank of tubes in a rectangular duct. A temperature drop of around 7-8°C during charging of PCM and temperature rise of around 4-5°C during discharging of PCM was observed from the experimental results. The average practical efficiency of TSU with ribbed absorber plate SAH during charging and discharging of PCM was 22 and 6 per cent, respectively, higher than that of TSU with plane absorber plate SAH.
Research limitations/implications
There are no limitations for research on SAH integrated with TSU. Different PCM including paraffin wax, Glauber’s salt, salt hydrates and water are used for thermal storage. Only limitation is lower efficiency of SAH integrated with TSU because of lower heat transfer coefficients with air as working medium. If it can improve heat transfer coefficients of air then heat transfer rates with these units will be higher.
Practical implications
There are no practical limitations for research on SAH integrated with TSU. Sophisticated instrumentation is needed to measure flow rates, temperatures and pressure variations of air.
Social implications
In poultry farms during night, chicks cannot survive at cold climatic conditions. Hence, hot air should be supplied to poultry farms whenever the atmospheric temperature drops. It is proposed that, in combination with TSUs, heat produced by SAH is stored in day time in the form of either sensible or latent heat and is retrieved to provide hot air in the night times. This will reduce total operating costs in poultry farms.
Originality/value
Conventionally, people are producing hot air by combusting coal in poultry forms. This cost around Rs. 75,000 per month for a batch of 225 to 250 chicks in a poultry form. Hot air could be produced economically during off sunshine hours from SAH integrated with TSU compared to the conventional method of coal burning. Present experimental investigations conducted to fill the literature gap in this area of research and to design a SAH integrated with TSU to produce hot air for poultry forms.
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Chunfu Wu, Guorui Ye, Yonghong Zhao, Baowen Ye, Tao Wang, Liangmo Wang and Zeming Zhang
Auxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper…
Abstract
Purpose
Auxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper aims to propose a novel auxetic honeycomb structure manufactured using selective laser melting and study the enhanced mechanical performance when subjected to in-plane compression loading.
Design/methodology/approach
A novel composite structure was designed and fabricated on the basis of an arrowhead auxetic honeycomb and filled with polyurethane foam. The deformation mechanism and mechanical responses of the structure with different structural parameters were investigated experimentally and numerically. With the verified simulation models, the effects of parameters on compression strength and energy absorption characteristics were further discussed through parametric analysis.
Findings
A good agreement was achieved between the experimental and simulation results, showing an evidently enhanced compression strength and energy absorption capacity. The interaction between the auxetic honeycomb and foam reveals to exploit a reinforcement effect on the compression performance. The parametric analysis indicates that the composite with smaller included angel and higher foam density exhibits higher plateau stress and better specific energy absorption, while increasing strut thickness is undesirable for high energy absorption efficiency.
Originality/value
The results of this study served to demonstrate an enhanced mechanical performance for the foam filled auxetic honeycomb, which is expected to be exploited with applications in aerospace, automobile, civil engineering and protective devices. The findings of this study can provide numerical and experimental references for the design of structural parameters.
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Tianbiao Yu, Yu Zhao, Xiaoxi Bi, Boxue Song and Ying Chen
The purpose of this paper is to study the influence of the porous structure on the maximum stress and modulus of elasticity of the specimens which are fabricated by rapid…
Abstract
Purpose
The purpose of this paper is to study the influence of the porous structure on the maximum stress and modulus of elasticity of the specimens which are fabricated by rapid prototypes. According to the experimental results, modify the theoretical formula of elastic modulus.
Design/methodology/approach
The Objet Eden 250 was used to prepare the Vero White photosensitive resin samples with different porosity (ranges from 25 to 65 per cent) and different pore structures. The mechanical properties of different samples were numerically simulated and the formulas of the modulus of elasticity were established. Through the compression test, the performance of the specimen is compared and analyzed, and the theoretical elastic modulus formula is optimized.
Findings
With the increase of porosity, the maximum stress of honeycomb structure specimens decreases. The maximum stress of the honeycomb structure specimen with circular pore shape is higher than the hexagon cross-section while the hexahedron and octahedron structure are the arms (wall thickness between pores) with a square cross-section. The error comparison between the modulus of elasticity before and after the structure models regression analysis shows that after the regression analysis, the error of theoretical value and the actual value is between 0 and 14 per cent which is lower than the value before the regression analysis which was between 5 and 27 per cent.
Originality/value
The paper obtains rules of the influence of different porous structures which were fabricated by the Vero White photosensitive resin material on mechanical properties and higher prediction accuracy formula of elastic modulus. The conclusions provide a theoretical basis for Northeastern University, China, to reduce mass and mechanical properties prediction of load-bearing parts.
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THE structural design of the BAC One‐Eleven generally follows closely that of the Vickcrs Vanguard and the VC10†—involving the use of a considerable number of integrally‐machined…
Abstract
THE structural design of the BAC One‐Eleven generally follows closely that of the Vickcrs Vanguard and the VC10†—involving the use of a considerable number of integrally‐machined components. As a short‐haul aircraft the average time per flight of the BAC One‐Eleven is expected to be of the order of 45 min. during which period full cabin pressure differential will be attained, speeds of the order of its design cruising speeds will be achieved and the undercarriage and flaps will be operated for take‐off and landing. Based on current estimations this involves a design aim of a minimum crack‐free life of 40,000 flights, landings and take‐offs —a much more severe requirement than that for the long‐range subsonic jets. Critical areas of the aircraft (undercarriage, flaps, tailplane and cabin pressure skins) are thus designed on fatigue considerations related principally to the number of flights made. The accent has therefore been placed on building a rugged structure which is easy to maintain and has a long service life. Small amounts of additional weight, properly disposed, can effect large improvements in the service life, particularly necessary on a short‐haul aircraft, and although weight saving is always of prime importance it must be balanced by other factors—especially in the primary structure.
M.A. Alghoul, M.Y. Sulaiman, B.Z. Azmi and M.Abd. Wahab
To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges.
Abstract
Purpose
To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges.
Design/methodology/approach
A range of published papers and internet research including research work on various solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube) were used. Evaluation of solar collectors performance is critiqued to aid solar technologies make the transition into a specific dominant solar collector. The sources are sorted into sections: finding an academic job, general advice, teaching, research and publishing, tenure and organizations.
Findings
Provides information about types of solar thermal collectors, indicating what can be added by using evacuated tube collectors instead of flat plate collectors and what can be added by using heat pipe collectors instead of evacuated tubes.
Research limitations/implications
Focusing only on three types of solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube).
Practical implications
Useful source of information for consultancy and impartial advice for graduate students planning to do research in solar thermal technologies.
Originality/value
This paper fulfils identified information about materials and heat transfer properties of materials and manufacturing challenges of these three solar thermal collectors.
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Hui Wang, Tianyu He and Chunjie Wang
In the field of planetary exploration, the legged-type lander is a common landing buffer device. There are two important performance metrics for legged-type landers: the energy…
Abstract
Purpose
In the field of planetary exploration, the legged-type lander is a common landing buffer device. There are two important performance metrics for legged-type landers: the energy absorption capacity and landing stability. In this paper, a novel method is proposed to optimize the honeycomb buffer of a legged-type lander. Optimization design variables are the dimension parameters of honeycomb and the objective functions are the evaluation parameters of the above two performance metrics.
Design/methodology/approach
A multi-body dynamic model of a lander and a finite-element model of the metal honeycomb are established. Based on the simulation results of the finite-element model and the quartic polynomial, the surrogate models are established to evaluate the energy absorption capacity of honeycomb. Considering both the multi-body dynamic model and the surrogate models, the study designed the optimization flow of dimension parameters of honeycomb. Besides, the non-dominated sorting genetic algorithm II is used for iterative calculation.
Findings
Images of surrogate models show the monotonous functional relationship between the honeycomb’s energy absorption characteristics and its dimension parameters. Optimization results show an apparent contradiction among the objective functions. Besides, according to the simulation results, this method can significantly improve the comprehensive performance of the lander.
Originality/value
The novel method can effectively reduce the cost of honeycomb compression tests and improve the lander’s design. Therefore, it can be used for optimizing buffers of other types of legged-type landers.
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