Anton Egorov and Vitaly Egorov
The purpose of this paper is to expand possibilities of stability computing method when performing a dynamic analysis of bar- or rod-shaped elements for actual structures.
Abstract
Purpose
The purpose of this paper is to expand possibilities of stability computing method when performing a dynamic analysis of bar- or rod-shaped elements for actual structures.
Design/methodology/approach
The methodology is based on the changes of stress–strain state of the bar-shaped elements at the moment of buckling. The proposed method is based on three assumptions. Firstly, the spatial stress–strain state is determined in the bar. Secondly, technological deviations inherent in real structures are introduced into the bar. Thirdly, mechanical behaviour of the bar is investigated in the mode of real time, which makes it possible to take into account wave deformation processes in the bar. To implement the suggested method of analysis, LS-DYNA package was selected in a dynamic formulation using solid finite elements.
Findings
Validity of the proposed method is shown by an example of dynamic stability analysis of a steel flat thin bar with two types of loads: short-time and long-term axial compressions. Comparison of the results showed different nature of the mechanical behaviour of the bar: wave processes are observed under short-time loading, and continuous monotone ones are stated under long-term loads.
Practical implications
Research results are applicable in the rocket and space industry.
Originality/value
A new computer-based methodology for dynamic analysis of heterogeneous elastic-plastic bar-, rod-shaped structures under shock axial compressive loads is proposed.
Details
Keywords
Data on the behaviour of materials at high temperatures are needed to improve current designs for missile skins, rocket motors, gas turbines and nuclear applications, but it is…
Abstract
Data on the behaviour of materials at high temperatures are needed to improve current designs for missile skins, rocket motors, gas turbines and nuclear applications, but it is only within the last few years that new research tools have been developed to enable materials to bs studied under such conditions in the laboratory. This paper reviews the available techniques, with emphasis placed on the range 2,000–5,000 deg. K.: furnaces (electric resistance, induction, arc, solar), high‐intensity electric arcs, flames, combustion of molten metals, shock tubes, ultra‐high‐frequency are discharges, plasma jets, thermonuclear reactions.
José Luis Dávila, Bruna Maria Manzini, Marcos Akira d'Ávila and Jorge Vicente Lopes da Silva
This study aims to report the development of an open-source syringe extrusion head for shear-thinning materials. The target is to adapt open-source 3D printers to be helpful in…
Abstract
Purpose
This study aims to report the development of an open-source syringe extrusion head for shear-thinning materials. The target is to adapt open-source 3D printers to be helpful in research lines that use gels, hydrogels, pastes, inks, and bio-inks.
Design/methodology/approach
This hardware was designed to be compatible with a Graber i3-based 3D printer; nevertheless, it can be easily adapted to other open-source 3D printers.
Findings
The extrusion head successfully deposits the material during the 3D printing process. It was validated fabricating geometries that include scaffold structures, which are a possible application of bioprinting for tissue engineering. As reported, the extruded filaments allowed the porous samples' structuration.
Practical implications
This system expands the applications of open-source 3D printers used at the laboratory scale. It enables low-cost access to research areas such as tissue engineering and biofabrication, energy storage devices and food 3D printing.
Originality/value
The open-source hardware here reported is of simple fabrication, assembly and installation. It uses a Cardan coupling and a three guides system to transfer the stepper motor motion. This approach allows continuous movement transfer to the syringe piston, producing an adequate deposition or retraction. Thus, the effect of misalignments is avoided, considering that these latter can cause skipping steps in the motor, directly affecting the deposition.
Details
Keywords
Mengxia Du, Qiao Wang, Yan Zhang, Yu Bai, Chunqiu Wei and Chunyan Liu
As to different angles of attack and nonlinear problems caused by high temperatures in coexisting hypersonic aircraft, people mainly rely on fluid software for research but lack…
Abstract
Purpose
As to different angles of attack and nonlinear problems caused by high temperatures in coexisting hypersonic aircraft, people mainly rely on fluid software for research but lack analysis of flow mechanisms. Owing to computational difficulties, few people use numerical algorithms to combine them for discussion. Hence, this study aims to make a deep inquiry into the laminar flow and heat transfer of compressible Newtonian fluid in hypersonic aircraft with small attack angles.
Design/methodology/approach
In this paper, on the basis of mass, momentum and energy conservation laws, the governing equations of the hypersonic boundary layer are established. Viscosity, specific heat capacity and thermal conductivity are considered nonlinear functions concerning temperature. In virtue of the MacCormack finite difference method, the stationary numerical solutions are solved directly, and the validity of the algorithm is verified.
Findings
The results demonstrate that at Mach number 5, compared to the 0° attack angle, the maximum temperature near-wall at the 3° attack angle increases by about 25%. An enjoyable phenomenon is discovered, where the position corresponding to the maximum wall shear force shifts back as the attack angle and Mach number increase. The relationship between the near-wall maximum temperature versus attack angle and Mach number is fitted through numerical calculation results.
Originality/value
Empirical formulas can be used to estimate heat transfer characteristics at small attack angles, which will guide the design of aircraft thermal protection systems.
Details
Keywords
This paper aims to develop a definition of brand addiction and a valid brand addiction scale (BASCALE).
Abstract
Purpose
This paper aims to develop a definition of brand addiction and a valid brand addiction scale (BASCALE).
Design/methodology/approach
The authors used focus-group results to define brand addiction and generate items for the BASCALE and validated the BASCALE with survey data collected in the UK.
Findings
Based on the 11 brand-addiction features found from the focus groups, the authors define brand addition as an individual consumer’s psychological state that pertains to a self-brand relationship manifested in daily life and involving positive affectivity and gratification with a particular brand and constant urges for possessing the brand’s products/services. Based on the survey study, the authors have established a valid ten-item BASCALE.
Research limitations/implications
Due to the survey’s setting in the fashion context in the UK, the authors do not intend to generalize the results to other product types and countries. Future research should replicate the BASCALE in different product categories and different countries.
Practical implications
The BASCALE can serve marketers in the behavioral segmentation and assist brand managers to identify brand addict consumers and maintain long-term relationships with them.
Originality/value
The authors have developed a definition of brand addiction and a valid BASCALE, which one can use for a wide range of theoretical and empirical research in the marketing and psychology fields. The definition and BASCALE also serve to differentiate brand addiction from other consumer–brand relationships and addiction constructs (e.g. compulsive buying, brand love and brand trust).
Details
Keywords
Steffany N. Cerda-Avila, Hugo Iván Medellín-Castillo and Theodore Lim
This paper aims to investigate the structural behaviour of polylactic acid (PLA) parts fabricated by fused deposition modelling (FDM) to support the development of analytical and…
Abstract
Purpose
This paper aims to investigate the structural behaviour of polylactic acid (PLA) parts fabricated by fused deposition modelling (FDM) to support the development of analytical and numerical models to predict the structural performance of FDM components and categories of similar additive manufactured parts.
Design/methodology/approach
A new methodology based on uniaxial tensile tests of filaments and FDM specimens, infill measurement and normalization of the results is proposed and implemented. A total of 396 specimens made of PLA were evaluated by using variable process parameters.
Findings
The infill and the build orientation have a large influence on the elastic modulus and ultimate tensile stress, whereas the layer thickness and the infill pattern have a low influence on these properties. The elongation at break is not influenced by the process parameters except by the build orientation. Furthermore, the infill values measured on the test specimens differ from the nominal values provided by the system.
Research limitations/implications
The analysis of the structural properties of FDM samples is limited to uniaxial loading conditions.
Practical implications
The obtained results are valuable for the structural analysis and numerical simulation of FDM components and for potential studies using machine learning techniques to predict the structural response of FDM parts.
Originality/value
A new experimental methodology that considers the measurement of the real infill percentage and the normalization of the results for inter-comparison with other studies is proposed. Moreover, a new set of experimental results of FDM-PLA parts is presented and extends the existing results in the literature.