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Nguyen V.B.,University of Wolverhampton | Nguyen V.B.,Hadley Industries Plc | Wang C.J.,University of Wolverhampton | Mynors D.J.,University of Sussex | And 2 more authors.
Journal of Manufacturing Processes | Year: 2014

The dimpling process is a novel cold-roll forming process that involves dimpling of a rolled flat strip prior to the roll forming operation. This is a process undertaken to enhance the material properties and subsequent products' structural performance while maintaining a minimum strip thickness. In order to understand the complex and interrelated nonlinear changes in contact, geometry and material properties that occur in the process, it is necessary to accurately simulate the process and validate through physical tests. In this paper, 3D non-linear finite element analysis was employed to simulate the dimpling process and mechanical testing of the subsequent dimpled sheets, in which the dimple geometry and material properties data were directly transferred from the dimpling process. Physical measurements, tensile and bending tests on dimpled sheet steel were conducted to evaluate the simulation results. Simulation of the dimpling process identified the amount of non-uniform plastic strain introduced and the manner in which this was distributed through the sheet. The plastic strain resulted in strain hardening which could correlate to the increase in the strength of the dimpled steel when compared to plain steel originating from the same coil material. A parametric study revealed that the amount of plastic strain depends upon on the process parameters such as friction and overlapping gap between the two forming rolls. The results derived from simulations of the tensile and bending tests were in good agreement with the experimental ones. The validation indicates that the finite element analysis was able to successfully simulate the dimpling process and mechanical properties of the subsequent dimpled steel products. © 2014 The Society of Manufacturing Engineers.


Arjunan A.,University of Wolverhampton | Wang C.J.,University of Wolverhampton | Yahiaoui K.,University of Wolverhampton | Mynors D.J.,University of Sussex | And 2 more authors.
Building and Environment | Year: 2013

Optimum acoustic performance of building components is a fundamental factor towards sustainable building design. Accordingly, it is essential that designers have the capability to effectively predict the acoustic performance to achieve sustainable designs. This paper introduces a 2-D Harmonic Acoustic Finite Element Analysis to predict the sound insulation of stud based double-leaf walls. This research was motivated by the necessity to develop acoustically efficient light weight building structures, which are both affordable and sustainable. Prediction of the Sound Reduction Index (R) of plasterboard partitions with structural links is a challenging problem due to the fluid-structure interaction (FSI) between the structural and fluid systems. Several finite element models to predict the sound reduction index of double-leaf walls were developed in compliance with BSENISO 717 and 140. The validity of the finite element predictions were assessed by comparison with experimental test results carried out in a certified laboratory. The effect of using different mesh sizes, fixing mechanisms and sound source locations on the predicted sound reduction index were looked into. The effects of air humidity and temperature on the experimental measurements of R values were also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index (Rw) along with A-weighted pink noise (C) and A-weighted urban noise (Ctr) to within an accuracy of ±1dB. Furthermore, the finite element modelling procedure reported can be extended to efficiently predict the acoustic behaviour of other building components undergoing FSI. © 2013 Elsevier Ltd.


Arjunan A.,University of Wolverhampton | Wang C.J.,University of Sussex | Yahiaoui K.,University of Wolverhampton | Mynors D.J.,University of Sussex | And 3 more authors.
Journal of Sound and Vibration | Year: 2014

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index Rwalong with A-weighted pink noise C and A-weighted urban noise Ctr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid-structure interaction (FSI) to evaluate their acoustic insulation. © 2014 Elsevier Ltd. All rights reserved.


Nguyen V.B.,Hadley Industries plc | Nguyen V.B.,Honorary Senior Research Fellow | Mynors D.J.,University of Sussex | Wang C.J.,University of Sussex | And 2 more authors.
Finite Elements in Analysis and Design | Year: 2016

Dimpled steel products are produced from the combination of an innovative dimpling process and a traditional forming process such as cold-roll forming or press-braking. The wider use of cold-formed dimpled steel members has promoted considerable interest in the local instability and strength of these members. Of particular interest is their buckling behaviour and ultimate strength capacity in columns under compressive loading. However, the dimpling process produces cold-formed sections with a complex 'dimpled' surface topography and the 'dimpled' material is non-uniformly work hardened through the entire thickness. Owing to these complex issues, there are no existing analytical and design methods to calculate the buckling strength of dimpled products and validate against physical measurements. This paper presents the analysis of the compressive behaviour of cold-formed channel and lipped channel dimpled steel columns using Finite Element techniques. True stress-strain data obtained from physical tests were incorporated into nonlinear simulations of dimpled steel columns. It was found that the predicted buckling and ultimate loads correlated well with the experimental results. Based on the validated Finite Element results for different geometries, standard design formulae for determining buckling and ultimate loads of channel and lipped channel dimpled columns were developed. It is demonstrated that the Finite Element Analysis can therefore be used to analyse and design cold-formed dimpled steel columns. © 2015 Elsevier B.V. All rights reserved.


Nguyen V.B.,University of Wolverhampton | Nguyen V.B.,Hadley Industries Plc | Wang C.J.,University of Wolverhampton | Diane D.J.,University of Wolverhampton | And 2 more authors.
Special Edition: 10th International Conference on Technology of Plasticity, ICTP 2011 | Year: 2011

The mechanical properties and structural behaviour of cold-roll formed dimpled sheet steel were investigated using experimental tests and numerical simulation. A series of tensile and bending tests on plain and dimpled sheet steel originating from the same coil of material were conducted. Tensile test results showed that the yield and tensile strength of dimpled sheet samples were 9% and 6% higher than the plain sheet samples, respectively. Bending test results showed that the yield and maximum force were 23% and 21% greater in the dimpled sheet samples when compared to the plain sheet samples respectively. Finite element simulation of the dimpling process revealed that during the process, various levels of plastic strain were developed throughout the thickness of the steel sheet, resulting In strain hardening. This correlated to the increase in the strength of the dimpled steel. The simulation of the tensile and plate bending tests of the plain and dimpled specimens predicted similar behaviour to the experimental tests. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.


Wang C.J.,University of Wolverhampton | Sihra T.,University of Wolverhampton | Mynors D.J.,University of Wolverhampton | Nguyen B.,University of Wolverhampton | And 2 more authors.
Key Engineering Materials | Year: 2011

The novel surface dimpling UltraSTEEL™ process developed by Hadley Industries increases the strength of the final rolled products and enhances other product properties such as the load carrying capacity. The dimpled UltraSTEEL™ sheet is used in steel framing, ceilings and other structural components. The mechanical properties and structural behaviour of the dimpled sheet are different from plain sheet due to non-uniformly distributed plastic strain and geometry of the dimples.


Wang C.J.,University of Wolverhampton | Mynors D.J.,University of Wolverhampton | Morgan T.,Hadley Industries PLC | Cartwright B.,Hadley Industries PLC
Applied Mechanics and Materials | Year: 2012

Sleeved purlin systems are usually used in roof constructions. A non-linear relationship between the bolt hole extension and the load transferred to the bolt was derived with experimental testing and numerical simulation. Consequently, the non-linear rotational stiffness of sleeved joints was derived based on the configuration of sleeves in this paper. The procedure for calculating the deflection of purlin systems with non-linear rotational stiffness at the joints is presented. The analysis and calculation of the deflection is demonstrated through a case study © (2012) Trans Tech Publications, Switzerland.


Nguyen V.B.,University of Wolverhampton | Nguyen V.B.,Hadley Industries Plc | Wang C.J.,University of Wolverhampton | Mynors D.J.,University of Wolverhampton | And 2 more authors.
Thin-Walled Structures | Year: 2013

The dimpling process is a novel cold-roll forming process that can enhance the steel material and structural performance by plastically deforming the material surface prior to the section forming operation [1]. Owing to the complex and interrelated nonlinear changes in contact, geometry and material properties that occur in the process and section forming, there have been no existing methods to simulate the process and resultant dimpled products and validate through physical measurements. This paper describes a numerical modelling approach and results into the mechanical properties and structural behaviour of cold-formed dimpled steel. A series of mechanical tests including tensile, plate bending and column compression tests on cold-formed plain and dimpled steel material were conducted for evaluation of numerical results. A finite element approach to practically simulate the dimpling process and experimental tests was presented. True stress-strain data obtained from tests were incorporated into nonlinear simulations of dimpled steel sheets and sections. The simulation of the dimpling process revealed that during the process, various levels of plastic strain are developed throughout the thickness of the steel sheet; this could correlate to the increase in the strength of the dimpled steel as observed in experimental tests and simulations. The simulation of the mechanical tests of dimpled specimens predicted similar results to the experiments, in terms of mechanical properties and structural behaviour. Since the finite element approach was able to successfully represent mechanical properties and structural behaviour of dimpled steel, it can be a powerful method in analysis and design of dimpled steel material and completed sections. © 2012 Elsevier Ltd.


Nguyen V.B.,Hadley Industries Plc | Nguyen V.B.,University of Wolverhampton | Wang C.J.,University of Wolverhampton | Mynors D.J.,University of Wolverhampton | And 2 more authors.
21st International Specialty Conference on Cold-Formed Steel Structures - Recent Research and Developments in Cold-Formed Steel Design and Construction | Year: 2012

This paper presents the experiments and design formulae of cold-formed plain and dimpled steel columns. A series of compression tests on plain and dimpled channel columns were conducted over a range of different geometries and the strength of the columns were investigated. The change in strength of the dimpled columns resulting from the cold working associated with the dimpling process was considered. The results showed that the buckling and ultimate strengths of dimpled steel columns were up to 33% and 26% greater than plain steel columns, respectively. The test results were evaluated by comparing buckling and ultimate loads of plain and dimpled channel columns with the values predicted by theoretical and semi-empirical methods. It was found that the predicted buckling and ultimate loads correlated well with the experimental results. Based on the experimental results, expressions for determining buckling and ultimate strengths of component plate elements of plain and dimpled channel columns were formulated.


Nguyen V.B.,University of Wolverhampton | Nguyen V.B.,Hadley Industries Plc | Wang C.J.,University of Wolverhampton | Mynors D.J.,University of Wolverhampton | And 2 more authors.
Journal of Constructional Steel Research | Year: 2012

This paper presents compression tests of cold-formed plain and dimpled steel columns. A series of compression and tensile tests were conducted on plain and dimpled steel of different geometries. For each group of geometries the source of material for both the plain and dimpled steel columns was taken from a single coil. Within each group the sections were fabricated either by press-braking or cold-rolled forming. The buckling and ultimate strength of the columns was investigated. The change in strength of the dimpled columns resulting from the cold working associated with the dimpling process was also considered. This paper contains the results obtained when comparing the test strengths of short plain and dimpled steel columns using a compression test. In outlining the work the test setup and testing procedure will be described. Enhancements in buckling and ultimate strengths were observed in the dimpled steel columns-caused by the cold-work of the material during the dimpling process. The results showed that the buckling and ultimate strengths of dimpled steel columns were up to 33% and 26% greater than plain steel columns, respectively. © 2011 Elsevier Ltd. All rights reserved.

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