Search results

1 – 10 of over 2000
To view the access options for this content please click here
Article
Publication date: 15 July 2019

R.R. Kumar, P.K. Karsh, Vaishali , K.M. Pandey and S. Dey

The purpose of this paper is to investigate the first three stochastic natural frequencies of skewed sandwich plates, considering uncertain system parameters. To conduct…

Abstract

Purpose

The purpose of this paper is to investigate the first three stochastic natural frequencies of skewed sandwich plates, considering uncertain system parameters. To conduct the sensitivity analysis for checking the criticality of input parameters.

Design/methodology/approach

The theoretical formulation is developed based on higher-order-zigzag theory in accordance with the radial basis function (RBF) and stochastic finite element (FE) model. A cubic function is considered for in-plane displacement over thickness while a quadratic function is considered for transverse displacement within the core and remains constant in the facesheet. RBF is used as a surrogate model to achieve computational efficiency and accuracy. In the present study, the individual and combined effect of ply-orientation angle, skew angle, number of lamina, core thickness and material properties are considered for natural frequency analysis of sandwich plates.

Findings

Results presented in this paper illustrates that the skewness in the sandwich plate significantly affects the global dynamic behaviour of the structure. RBF surrogate model coupled with stochastic FE approach significantly reduced the computational time (more than 1/18 times) compared to direct Monte Carlo simulation approach.

Originality/value

The stochastic results for dynamic stability of sandwich plates show that the inevitable source uncertainties present in the input parameters result in significant variation from the deterministic value demonstrates the need for inclusive design paradigm considering stochastic effects. The present paper comprehensively establishes a generalized new RBF-based FE approach for efficient stochastic analysis, which can be applicable to other complex structures too.

To view the access options for this content please click here
Article
Publication date: 20 June 2017

Ebrahim Vahabli and Sadegh Rahmati

To improve the quality of the additive manufacturing (AM) products, it is necessary to estimate surface roughness distribution in advance. Although surface roughness…

Abstract

Purpose

To improve the quality of the additive manufacturing (AM) products, it is necessary to estimate surface roughness distribution in advance. Although surface roughness estimation has been previously studied, factors leading to the creation of a rough surface and a comprehensive test for model validation have not been adequately investigated. Therefore, this paper aims to establish a robust model using empirical data based on optimized artificial neural networks (ANNs) to estimate the surface roughness distribution in fused deposition modelling parts. Accordingly, process parameters such as time, cost and quality should be optimized in the process planning stage.

Design/methodology/approach

Process parameters were selected via a literature review of surface roughness estimation modelling by analytical and empirical methods, and then a specific test part was fabricated to provide a complete evaluation of the proposed model. The ANN structure was optimized by trial and error method and evolutionary algorithms. A novel methodology based on the combination of the intelligent algorithms including the ANN, linked to the particle swarm optimization (PSO) and imperialist competitive algorithm (ICA), was developed. The PSOICA algorithm was implemented to increase the capability of the ANN to perform much faster and converge more precisely to favorable results. The performances of the ANN models were compared to the most well-known analytical models at build angle intervals of equal size. The most effective process variable was found by sensitivity analysis. The validity of proposed model was studied comprehensively where different truncheon parts and medical case studies including molar tooth, skull, femur and a custom-made hip stem were built.

Findings

This paper presents several improvements in surface roughness distribution modelling including a more suitable method for process parameter selection according to the design criteria and improvements in the overall surface roughness of parts as compared to analytical methods. The optimized ANN based on the proposed advanced algorithm (PSOICA) represents precise estimation and faster convergence. The validity assessment confirms that the proposed methodology performs better in varied conditions and complex shapes.

Originality/value

This research fills an important gap in surface roughness distribution estimation modelling by using a test part designed for that purpose and optimized ANN models which uses purely empirical data. The novel PSOICA combination enhances the ability of the ANN to perform more accurately and quickly. The advantage in using actual surface roughness values is that all factors resulting in the creation of a rough surface are included, which is impossible if other methods are used.

To view the access options for this content please click here
Article
Publication date: 20 June 2016

Jatender Pal Singh, Pulak M. Pandey and Anita Kamra Verma

Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are…

Abstract

Purpose

Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more prone to compressive loading. Open porous structure lacks in strength in comparison to solid. Selective laser sintering (SLS) process is prominently used for fabrication of polymer/composite scaffolds. So, this paper aims to study for fabrication of three-dimensional open porous scaffolds with enhanced strength, process parameters of SLS of a biocompatible material are required to be optimized.

Design/methodology/approach

Regular open porous structures with suitable pore size as per computer-aided design models were fabricated using SLS. Polyamide (PA-2200) was used to fabricate the specimen/scaffold. To optimize the strength of the designed structure, response surface methodology was used to design the experiments. Specimens as per ASTM D695 were fabricated using SLS and compressive testing was carried out. Analysis of variance was done for estimating contribution of individual process parameters. Optimized process parameters were obtained using a trust region algorithm and correlated with experimental results. Accuracy of the fabricated specimen/scaffold was also assessed in terms of IT grades. In vitro cell culture on the fabricated structures confirmed the biocompatibility of polyamide (PA-2200).

Findings

Optimized process parameters for open cell process structures were obtained and confirmed experimentally. Laser power, hatch spacing and layer thickness have contributed more in the porous part’s strength than scan speed. The accuracy of the order of IT16 has been found for all functional dimensions. Cell growth and proliferation confirmed biocompatibility of polyamide (PA-2200) for scaffold applications.

Originality/value

This paper demonstrates the biocompatibility of PA-2200 for scaffold applications. The optimized process parameters of SLS process for open cell structure having pore size 1.2 × 1.2 mm2 with strut diameter of 1 mm have been obtained. The accuracy of the order of IT16 was obtained at the optimized process factors.

Details

Rapid Prototyping Journal, vol. 22 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

To view the access options for this content please click here
Article
Publication date: 18 April 2017

Jasgurpreet Singh Chohan and Rupinder Singh

The purpose of this paper is to review the various pre-processing and post-processing approaches used to ameliorate the surface characteristics of fused deposition…

Abstract

Purpose

The purpose of this paper is to review the various pre-processing and post-processing approaches used to ameliorate the surface characteristics of fused deposition modelling (FDM)-based acrylonitrile butadiene styrene (ABS) prototypes. FDM being simple and versatile additive manufacturing technique has a calibre to comply with present need of tailor-made and cost-effective products with low cycle time. But the poor surface finish and dimensional accuracy are the primary hurdles ahead the implementation of FDM for rapid casting and tooling applications.

Design/methodology/approach

The consequences and scope of FDM pre-processing and post-processing parameters have been studied independently. The comprehensive study includes dominance, limitations, validity and reach of various techniques embraced to improve surface characteristics of ABS parts. The replicas of hip implant are fabricated by maintaining the optimum pre-processing parameters as reviewed, and a case study has been executed to evaluate the capability of vapour smoothing process to enhance surface finish.

Findings

The pre-processing techniques are quite deficient when different geometries are required to be manufactured within limited time and required range of surface finish and accuracy. The post-processing techniques of surface finishing, being effective disturbs the dimensional stability and mechanical strength of parts thus incapacitates them for specific applications. The major challenge for FDM is the development of precise, automatic and controlled mass finishing techniques with low cost and time.

Research limitations/implications

The research assessed the feasibility of vapour smoothing technique for surface finishing which can make consistent castings of customized implants at low cost and shorter lead times.

Originality/value

The extensive research regarding surface finish and dimensional accuracy of FDM parts has been collected, and inferences made by study have been used to fabricate replicas to further examine advanced finishing technique of vapour smoothing.

Details

Rapid Prototyping Journal, vol. 23 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

To view the access options for this content please click here
Article
Publication date: 16 August 2019

Jafar Ali and Debasish Bandyopadhyay

Condition monitoring (CM) has become significantly important, particularly in the context of ensuring safety, reliability and future usefulness of civil infrastructural…

Abstract

Purpose

Condition monitoring (CM) has become significantly important, particularly in the context of ensuring safety, reliability and future usefulness of civil infrastructural systems. Most of the age old structures require immediate attention. Nondestructive tests and/or load tests along with routine maintenance inspections are common practice. However, most of the NDT techniques are location-dependent and are conducted in a piecewise manner. The paper aims to discuss these issues.

Design/methodology/approach

Numerical methods incorporating inverse techniques are a global approach to identify structural parameters using dynamic responses. However, measurement at all degrees of freedom does not seem to be feasible, due to practical constraints. Parameter identification of structures based on limited dynamic responses like modal slope and curvature mode shapes at the element level in a finite element platform is proposed in the present paper. The structural property for each element is derived adopting a two-phase analysis process, consisting modal extraction and structural parameter identification. It is important to study the accuracy of the predicted parameters with the number of measured modes. The structural property is identified using measured responses at those selected MDOF.

Findings

The proposed method is demonstrated in detail with a numerical example. The method seems to be an attractive proposition as the results obtained are very accurate even with noise-contaminated data.

Research limitations/implications

However, for practical problems, the experimental validation is significantly important prior to its application in real-life problems.

Practical implications

The developed model seems to be feasible for practical applications after experimental validation, as it is able to identify the structural parameters from limited noisy dynamic responses in frequency domains measured for few modes.

Social implications

Structural CM is the need of the hour, particularly for infrastructural systems including buildings and bridges, etc. System identification with a global dynamic response at few measurement locations may address the issue of health assessment of structures, which will have great social implications with respect to safety.

Originality/value

The proposed numerical model is originally developed by the authors with judicial modifications and combination of earlier research contributions to achieve greater accuracy. Limited measurement and the effect of random noise with numerical example are considered for the successful validation.

Details

International Journal of Structural Integrity, vol. 11 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

To view the access options for this content please click here
Article
Publication date: 5 April 2021

Jeyakumar Suppandipillai, Jayaraman Kandasamy, R. Sivakumar, Mehmet Karaca and Karthik K.

This paper aims to study the influences of hydrogen jet pressure on flow features of a strut-based injector in a scramjet combustor under-reacting cases are numerically…

Abstract

Purpose

This paper aims to study the influences of hydrogen jet pressure on flow features of a strut-based injector in a scramjet combustor under-reacting cases are numerically investigated in this study.

Design/methodology/approach

The numerical analysis is carried out using Reynolds Averaged Navier Stokes (RANS) equations with the Shear Stress Transport k-ω turbulence model in contention to comprehend the flow physics during scramjet combustion. The three major parameters such as the shock wave pattern, wall pressures and static temperature across the combustor are validated with the reported experiments. The results comply with the range, indicating the adopted simulation method can be extended for other investigations as well. The supersonic flow characteristics are determined based on the flow properties, combustion efficiency and total pressure loss.

Findings

The results revealed that the augmentation of hydrogen jet pressure via variation in flame features increases the static pressure in the vicinity of the strut and destabilize the normal shock wave position. Indeed, the pressure of the mainstream flow drives the shock wave toward the upstream direction. The study perceived that once the hydrogen jet pressure is reached 4 bar, the incoming flow attains a subsonic state due to the movement of normal shock wave ahead of the strut. It is noticed that the increase in hydrogen jet pressure in the supersonic flow field improves the jet penetration rate in the lateral direction of the flow and also increases the total pressure loss as compared with the baseline injection pressure condition.

Practical implications

The outcome of this research provides the influence of fuel injection pressure variations in the supersonic combustion phenomenon of hypersonic vehicles.

Originality/value

This paper substantiates the effect of increasing hydrogen jet pressure in the reacting supersonic airstream on the performance of a scramjet combustor.

Details

Aircraft Engineering and Aerospace Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1748-8842

Keywords

To view the access options for this content please click here
Book part
Publication date: 3 June 2021

Soma Pal, Chandrima Chakraborty and Dipyaman Pal

The present chapter examined the behavior of relative wage rate, productivity of labor, and total factor productivity growth (TFPG) and also attempted to explore the…

Abstract

The present chapter examined the behavior of relative wage rate, productivity of labor, and total factor productivity growth (TFPG) and also attempted to explore the causal relationship between relative wage rate and productivity of labor as well as relative wage rate and TFPG in food and beverage industry in India over the period 1980–1981 to 2017–2018. The result of Sen (2003) approach of endogenous structural break suggests that the series of relative wage rate, productivity of labor, and TFPG follows trend stationary process. A significant break is found for all the three aforementioned variables, being 1984–1985 for relative wage rate and productivity of labor whereas 2007–2008 for TFPG. For the three variables, growth rate has increased after the break. Bidirectional causality between relative wage rate and productivity of labor as well as relative wage rate and TFPG is evident.

To view the access options for this content please click here
Article
Publication date: 4 March 2021

Abhishek Kumar Kashyap and Dayal R. Parhi

Humanoid robots have complicated dynamics, and they lack dynamic stability. Despite having similarities in kinematic structure, developing a humanoid robot with robust…

Abstract

Purpose

Humanoid robots have complicated dynamics, and they lack dynamic stability. Despite having similarities in kinematic structure, developing a humanoid robot with robust walking is quite difficult. In this paper, an attempt to produce a robust and expected walking gait is made by using an ALO (ant lion optimization) tuned linear inverted pendulum model plus flywheel (LIPM plus flywheel).

Design/methodology/approach

The LIPM plus flywheel provides the stabilized dynamic walking, which is further optimized by ALO during interaction with obstacles. It gives an ultimate turning angle, which makes the robot come closer to the obstacle and provide a turning angle that optimizes the travel length. This enhancement releases the constraint on the height of the COM (center of mass) and provides a larger stride. The framework of a sequential locomotion planer has been discussed to get the expected gait. The proposed method has been successfully tested on a simulated model and validated on the real NAO humanoid robot.

Findings

The convergence curve defends the selection of the proposed controller, and the deviation under 5% between simulation and experimental results in regards to travel length and travel time proves its robustness and efficacy. The trajectory of various joints obtained using the proposed controller is compared with the joint trajectory obtained using the default controller. The comparison shows the stable walking behavior generated by the proposed controller.

Originality/value

Humanoid robots are preferred over mobile robots because they can easily imitate the behaviors of humans and can result in higher output with higher efficiency for repetitive tasks. A controller has been developed using tuning the parameters of LIPM plus flywheel by the ALO approach and implementing it in a humanoid robot. Simulations and experiments have been performed, and joint angles for various joints are calculated and compared with the default controller. The tuned controller can be implemented in various other humanoid robots

Details

International Journal of Intelligent Unmanned Systems, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2049-6427

Keywords

To view the access options for this content please click here
Article
Publication date: 9 April 2018

Hoejin Kim, Yirong Lin and Tzu-Liang Bill Tseng

The usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used…

Abstract

Purpose

The usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used as final products, AM product should be produced through advanced quality control process, which has a capability to be able to prove and reach their desire repeatability, reproducibility, reliability and preciseness. Therefore, there is a need to review quality-related research in terms of AM technology and guide AM industry in the future direction of AM development.

Design/methodology/approach

This paper overviews research progress regarding the QC in AM technology. The focus of the study is on manufacturing quality issues and needs that are to be developed and optimized, and further suggests ideas and directions toward the quality improvement for future AM technology. This paper is organized as follows. Section 2 starts by conducting a comprehensive review of the literature studies on progress of quality control, issues and challenges regarding quality improvement in seven different AM techniques. Next, Section 3 provides classification of the research findings, and lastly, Section 4 discusses the challenges and future trends.

Findings

This paper presents a review on quality control in seven different techniques in AM technology and provides detailed discussions in each quality process stage. Most of the AM techniques have a trend using in-situ sensors and cameras to acquire process data for real-time monitoring and quality analysis. Procedures such as extrusion-based processes (EBP) have further advanced in data analytics and predictive algorithms-based research regarding mechanical properties and optimal printing parameters. Moreover, compared to others, the material jetting progresses technique has advanced in a system integrated with closed-feedback loop, machine vision and image processing to minimize quality issues during printing process.

Research limitations/implications

This paper is limited to reviewing of only seven techniques of AM technology, which includes photopolymer vat processes, material jetting processes, binder jetting processes, extrusion-based processes, powder bed fusion processes, directed energy deposition processes and sheet lamination processes. This paper would impact on the improvement of quality control in AM industries such as industrial, automotive, medical, aerospace and military production.

Originality/value

Additive manufacturing technology, in terms of quality control has yet to be reviewed.

To view the access options for this content please click here
Book part
Publication date: 16 June 2021

Mohamed M. Sraieb and Ahmet Akin

We investigate the relationship between gender diversity on corporate boards and environmental performances of firms. Our central focus is the extent to which a country's…

Abstract

We investigate the relationship between gender diversity on corporate boards and environmental performances of firms. Our central focus is the extent to which a country's economic status (developed, developing) can shape such a relationship. We find evidence that gender diversity is positively correlated to environmental performances of firms. Interestingly, this correlation is not only stronger in developing countries but also increasing in gender diversity. These findings have considerable importance in terms of policy.

Promotion of gender diversity in developing countries, where abatement costs are the lowest, would improve global environmental quality in a cost-effective way. This is best achieved through building institutions and strengthening them. The benefits of such policy go beyond developing countries frontiers, particularly when global environmental problems (pollution, global warming, ozone layer depletion, loss of biodiversity, etc.) are concerned. These benefits can be a leverage for an efficient implementation of the United Nations Sustainable Development Goals (UN-SDGs) both as gender diversity stands as a goal by itself and also because it facilitates achieving other environmental-related SDGs.

Details

The Emerald Handbook of Women and Entrepreneurship in Developing Economies
Type: Book
ISBN: 978-1-80071-327-7

Keywords

1 – 10 of over 2000