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Article

Jaroslav Mackerle

Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the…

Abstract

Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.

Details

Engineering Computations, vol. 14 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Abstract

Details

Quantitative and Empirical Analysis of Nonlinear Dynamic Macromodels
Type: Book
ISBN: 978-0-44452-122-4

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Article

Anil Kumar Gulivindala, M.V.A. Raju Bahubalendruni, S.S. Vara Prasad Varupala and Sankaranarayanasamy K.

Parallel assembly sequence planning (PASP) reduces the overall assembly effort and time at the product development stage. Methodological difficulties at framework…

Abstract

Purpose

Parallel assembly sequence planning (PASP) reduces the overall assembly effort and time at the product development stage. Methodological difficulties at framework development and computational issues at their implementation made the PASP complex to achieve. This paper aims to propose a novel stability concept for subassembly detection to minimize the complexities in PASP.

Design/methodology/approach

In this research, a heuristic method is developed to identify, represent and implement the stability predicate to perform subassembly detection and assembly sequence planning (ASP) at the further stages. Stability is organized into static, dynamic, enriched and no stability between the mating assembly parts. The combination of parts that possesses higher fitness is promoted to formulate the final solution about PASP.

Findings

The results obtained by applying the proposed concept on complex configurations revealed that stability predicate plays a dominant role in valid subassembly detection and final sequence generation further.

Originality/value

The value of the presented study lies in the three types of stability conditions and effective integration to existed ASP method. Unlike the existed heuristics in subassembly detection, the proposed concept identifies the parallel subassemblies during ASP.

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Article

Khalil Alipour and S. Ali A. Moosavian

A suspended wheeled mobile robot (SWMR) that consists of one or more manipulators can be exploited in various environmental conditions such as uneven surfaces. The purpose…

Abstract

Purpose

A suspended wheeled mobile robot (SWMR) that consists of one or more manipulators can be exploited in various environmental conditions such as uneven surfaces. The purpose of this paper is to discuss the requirements for stable motion planning of such robotic systems to perform heavy object manipulation tasks.

Design/methodology/approach

First, a systematic procedure for dynamics modelling of such complicated systems for planar motion is presented and verified using ADAMS simulation software. Next, based on the new dynamic moment‐height stability (MHS) measure, the stability of such systems will be investigated using the obtained dynamics. To this end, introducing the concept of a virtual frame, the obtained model of SWMR has been employed for investigating the effect of the base suspension characteristics as well as terrain roughness on the stability of the system. Next, the stability evaluation of the system is investigated after toppling down which has been rarely addressed in the literature. In addition, using the aforementioned model, the effect of stiffness is examined after instability.

Findings

First, a systematic procedure for dynamics modelling of such complicated systems for planar motion is presented and verified using ADAMS simulation software. Next, based on the new dynamic MHS measure, the stability of such systems will be investigated using the obtained dynamics. To this end, introducing the concept of a virtual frame, the obtained model of SWMR has been employed for investigating the effect of the base suspension characteristics as well as terrain roughness on the stability of the system. Next, the stability evaluation of the system is investigated after toppling down which has been rarely addressed in the literature. In addition, using the aforementioned model, the effect of stiffness is examined after instability.

Originality/value

A general procedure for dynamics modelling of SWMRs is presented. To verify the obtained dynamics model, another model for the considered system has been developed by ADAMS software. Next, using the obtained dynamics, the postural stability of such systems is investigated, based on the new postural MHS measure extended for SWMRs. The obtained simulation results show that by decreasing the stiffness coefficients of suspension subsystem the stability of the system weakens.

Details

Industrial Robot: An International Journal, vol. 38 no. 2
Type: Research Article
ISSN: 0143-991X

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Article

Changqing Bai and Qinyu Xu

The purpose of this paper is to investigate the dynamic stability of liquid hydrogen turbopump rotor system in rocket engine under the effects of seal and internal rotor damping.

Abstract

Purpose

The purpose of this paper is to investigate the dynamic stability of liquid hydrogen turbopump rotor system in rocket engine under the effects of seal and internal rotor damping.

Design/methodology/approach

The dynamic modeling of a liquid hydrogen turbopump rotor system in rocket engine is presented in this paper with the aid of the finite element technique. The mathematical model takes into account the seal hydrodynamic forces described by Muszynska model and the internal rotor damping, viscous damping, and hysteretic damping. The shooting method and Floquet theory are employed to investigate the effects of seal and internal rotor damping on the nonlinear dynamic stability of two turbopump designs, the original and the modified design with a flexible bearing support.

Findings

The numerical results, which are in good agreement with test data, show that the destabilizing effect of internal rotor damping play a key role in the original design. In the modified design, the stability margins are enhanced and the vibration response levels are minimized. The onset speed of instability increases in original design and decreases in modified design as the effects of seal nonlinearities are considered. The predicted results indicate that the seals have a great destabilizing effect in the modified design and the turbine end bearing is the most dangerous hardware in both designs. The system stability analysis shows that the effect of seal length on the system stability is significant comparing with that of seal radius.

Practical implications

The results can be used in the design and operation of a liquid hydrogen turbopump rotor system to improve its stability performance and eliminate its subsynchronous problem.

Originality/value

Since seal and internal damping are two key destabilizing factors in liquid hydrogen turbopumps and the seal nonlinearities are inevitable, the use of nonlinear theory to study their effects on nonlinear stability and dynamic performance can lead to accurate prediction and explain the nature of the subsynchronous motion.

Details

Aircraft Engineering and Aerospace Technology, vol. 83 no. 1
Type: Research Article
ISSN: 0002-2667

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Article

Agnieszka Kwiek

The purpose of this paper is to present the results of a conceptual design of Martian aircraft. This study focuses on the aerodynamic and longitudinal dynamic stability

Abstract

Purpose

The purpose of this paper is to present the results of a conceptual design of Martian aircraft. This study focuses on the aerodynamic and longitudinal dynamic stability analysis. The main research questions are as follows: Does a tailless aircraft configuration can be used for Martian aircraft? How to the short period characteristic can be improved by side plates modification?

Design/methodology/approach

Because of a conceptual design stage of this Martian aircraft, aerodynamic characterises were computed by the Panukl package by using the potential flow model. The longitudinal dynamic stability was computed by MATLAB code, and the derivatives computed by the SDSA software were used as the input data. Different aircraft configurations have been studied, including different wing’s aerofoils and configurations of the side plate.

Findings

This paper presents results of aerodynamic characteristics computations and longitudinal dynamic stability analysis. This paper shows that tailless aircraft configuration has potential to be used as Martian aircraft. Moreover, the study of the impact of side plates’ configurations on the longitudinal dynamic stability is presented. This investigation reveals that the most effective method to improve the short period damping ratio is to change the height of the bottom plate.

Practical implications

The presented result might be useful in case of further design of the aircrafts for the Mars mission and designing the aircrafts in a tailless configuration.

Social implications

It is considered by the human expedition that Mars is the most probable planet to explore. This paper presents the conceptual study of aircraft which can be used to take the high-resolution pictures of the surface of Mars, which can be crucial to find the right place to establish a potential Martian base.

Originality/value

Most of aircrafts proposed for the Mars mission are designed in a configuration with a classic tail; this paper shows a preliminary calculation of the tailless Martian aircraft. Moreover, this paper shows the results of a dynamic stability analysis, where similar papers about aircrafts for the Mars mission do not show such outcomes, especially in the case of the tailless configuration. Moreover, this paper presents the results of the dynamic stability analysis of tailless aircraft with different configurations of the side plates.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 6
Type: Research Article
ISSN: 1748-8842

Keywords

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Article

Hussein Adam Abdalla Gibreil and Cheng Pei Feng

In high-temperature regions (tropical regions) temperatures rises in summer, which affects the performance of asphalt pavement. Therefore, we must consider the conditions…

Abstract

Purpose

In high-temperature regions (tropical regions) temperatures rises in summer, which affects the performance of asphalt pavement. Therefore, we must consider the conditions of asphalt pavement, especially in these regions. This study aims to investigate the influence of high temperature on the stability performance of high-density polyethylene (HDPE) and crumb rubber powder (CRP) modified hot mix asphalt (HMA) using Marshall design parameters and rutting test.

Design/methodology/approach

In this study, three HMA mixtures with 4 per cent HDPE and 15 per cent CRP, 5 per cent HDPE and 10 per cent CRP, and 6 per cent HDPE and 5 per cent CRP concentrations were used for the Marshall stability test and dynamic stability (rutting test) at 60-75°C, and water stability test at 60°C.

Findings

The results showed that when test temperature was increased from 60°C to 75°C, the Marshall stability and dynamic stability of three HDPE- and CRP-modified HMA mixtures decreased, and these three HDPE- and CRP-modified HMA mixtures have a good moisture damage resistance. Of the three HMA mixtures with different HDPE and CRP concentrations, HMA mixtures with 5 per cent HDPE and 10 per cent CRP concentration exhibit optimal Marshall stability, dynamic stability and water stability.

Originality/value

This study showed the effects of high-temperatures changes on the stability performance of HDPE- and CRP-modified HMA mixtures.

Details

Journal of Structural Fire Engineering, vol. 9 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

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Article

Jiusheng Bao, Yan Yin, Lijian Lu and Tonggang Liu

The purpose of this study is to establish an effective method for characterizing the tribological properties of friction brakes during continuous braking because they have…

Abstract

Purpose

The purpose of this study is to establish an effective method for characterizing the tribological properties of friction brakes during continuous braking because they have direct influences on the reliable operation of transport vehicles and industrial equipments.

Design/methodology/approach

First, tribological tests were carried out with the X-DM type friction tester, and changing curves of friction coefficient and temperature were obtained. Second, a novel tribological characteristic parameter set characterizing the tribological properties of brake pair in continuous braking was extracted from some important experimental data such as friction coefficient, wear rate and temperature. Finally, the influence of law and mechanism of braking number on dynamic tribological parameters was studied through continuous braking experiments.

Findings

The extracted tribological characteristic parameter set includes two subsets: dynamic characteristic parameter subset and overall characteristic parameter subset, which is composed of ten parameters: dynamic parameters of friction coefficient (including average, trend coefficient and stability coefficient), dynamic wear rate, dynamic average temperature, dynamic temperature rise, overall average friction coefficient, overall wear rate, overall average temperature and overall temperature rise.

Originality/value

Conclusively, the novel tribological characteristic parameter set is more comprehensive and objective, and it can provide a theoretical basis for the study of tribological properties in continuous braking.

Details

Industrial Lubrication and Tribology, vol. 70 no. 1
Type: Research Article
ISSN: 0036-8792

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Article

P. WRIGGERS and C. CARSTENSEN

Many engineering structures exhibit loss of stability under static and dynamic loading. Due to the significance of these phenomena in engineering design this topic has…

Abstract

Many engineering structures exhibit loss of stability under static and dynamic loading. Due to the significance of these phenomena in engineering design this topic has attracted considerable attention during the last decades. In recent years much effort has been made to devise algorithms within finite element analysis to investigate the static stability behaviour of structures. With these methods stable and unstable paths can be traced, and limit or bifurcation points can be computed efficiently. The associated arc‐length or branch‐switching procedures are today standard tools in existing finite element codes.

Details

Engineering Computations, vol. 9 no. 6
Type: Research Article
ISSN: 0264-4401

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Article

Yan Li, Desheng Zhang and Fuhai Duan

The purpose of this paper is to investigate dynamic characteristics of opposed-conical gas-dynamic bearings considering five degree-of-freedom motion, including…

Abstract

Purpose

The purpose of this paper is to investigate dynamic characteristics of opposed-conical gas-dynamic bearings considering five degree-of-freedom motion, including translation and tilt.

Design/methodology/approach

The steady-state Reynolds equation and perturbed Reynolds equations are solved on the surface of conical bearings, and both stiffness and damping coefficients are calculated. A formula for quickly calculating critical mass is deduced to discriminate the stability of the rotor considering the five degree-of-freedom motion.

Findings

Results show that the stability of the rotor is mainly determined by translation rather than tilt. The formula of critical mass is validated by comparing the results with traditional Routh–Hurwitz criterion.

Originality/value

The formula proposed in this paper greatly simplifies the solution of critical mass, which facilitates the rotor stability design. It is applicable for opposed-conical bearings, opposed-hemispherical bearings and spherical bearings. The results provide theoretical guidance for the design of gas-dynamic bearings.

Details

Industrial Lubrication and Tribology, vol. 72 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

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