• Analysis and design of cold-formed dimpled steel columns using Finite Element techniques

      Nguyen, Van Bac; Mynors, Diane; Wang, Chang; Castellucci, Michael; English, Martin; Hadley Industries plc; University of Sussex (Elsevier, 2015-10-21)
      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.
    • Design of new cold rolled purlins by experimental testing and Direct Strength Method

      Nguyen, Van Bac; Pham, Cao Hung; Cartwright, Brian; English, Martin; University of Derby; University of Sydney; Hadley Industries plc (Elsevier, 2017-05-17)
      New cold roll formed channel and zed sections for purlins, namely UltraBEAM™2 and UltraZED™2, have been developed by Hadley Industries plc using a combined approach of experimental testing, finite element modelling and optimisation techniques. The new sections have improved strength to weight ratio by increasing the section's strength through the use of stiffeners in the section webs. The European standard, Eurocode 3 [1], uses the traditional Effective Width Method to determine the strength of a cold formed steel member. However, the design of the new sections UltraBEAM™2 and UltraZED™2 using this method is very complicated in calculating the effective section properties as these sections contain complex folded-in stiffeners. In addition, the incorporation of competing buckling modes such as distortional buckling of these sections can be difficult to analyse. To overcome difficulties of using Eurocode 3 or such a standard with the Effective Width Method for determining the strength of these sections, the Direct Strength Method is adopted in this paper. Four-point beam bending tests were carried out to determine the buckling and ultimate bending capacities of the UltraBEAM™2 and UltraZED™2 sections. Results from both experimental testing and Finite Element analysis were initially used as validation for the design using the Direct Strength Method. The Direct Strength Method's results were then compared with the experimental test results for a broader data in which the UltraBEAM™2 and UltraZED™2 sections had a range of different width-to-thickness ratios. It showed an excellent agreement between test and Direct Strength design values suggesting that the Direct Strength Method is a powerful tool for the design and optimisation of the new cold roll formed channel and zed purlins.
    • Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

      Nguyen, Van Bac; Arjunan, Arun; Wang, Chang; Mynors, Diane; Morgan, Tertia; English, Martin; University of Wolverhampton; Hadley Industries plc; University of Sussex (Elsevier, 2014-07-26)
      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 Rw along 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.
    • Dimpling process in cold roll metal forming by finite element modelling and experimental validation

      Nguyen, Van Bac; Wang, Chang; Mynors, Diane; English, Martin; Castellucci, Michael; Hadley Industries plc; University of Wolverhampton; University of Sussex (Elsevier, 2014-08)
      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.
    • Finite element analyses of mini combined harvester chassis and hitch.

      Abdulkarim, K. O.; Abdulrahman, Olajide; Ahmed, Ismaila I.; Abdulkareem, Suleiman; Adebisi, Jeleel Adekunie; Harmanto, Dani; University of Johannesburg; University of Ilorin; University of Derby (University of Novi Sad, 2017-06)
      The perennial problems associated with harvesting of agricultural products in sub-Sahara Africa are not unconnected with financial limitations of the farmers. The design of low cost mini combine harvester was aimed at ameliorating the challenges of agricultural products harvest in Nigeria. The work presented here was a detailed analysis of low cost mini combine harvester chassis and hitch. The need for cost effectiveness, affordability, durability and efficiency of the designs necessitated detail analysis of the design to achieve the above objectives. Solidworks Finite Element Analysis (FEA) software was employed in carrying out both static and fatigue analysis of a low-cost mini combine harvester chassis and hitch design. The results were compared and contrasted, with appreciable improvements on available existing data. The stresses, displacements and strains on the chassis were significantly low with factors of safety of 2.48 and 2.80 for chassis and hitch respectively.
    • Vibro-acoustic performance of different steel studs in double-leaf walls by Finite Element analysis

      Nguyen, Van Bac; Morgan, Tertia; English, Martin; Castellucci, Michael; Hadley Industries plc; University of Sussex (Sage, 2015-06)
      Cold-formed steel studs are often used in lightweight partition walls to provide structural stability but in the same time they change the acoustic performance of the whole system. The overall design of such lightweight structures for acoustic sound insulation becomes very complicated as the sound passing through stud needs to be quantified. One of the greatest challenges is to characterize the stud's geometric effects on the sound transmission of the partition walls. This paper presents a 2-D Finite Element modelling approach and results into the vibro-acoustic performance of different studs in double-leaf walls which are placed in between a reverberant source room and a receiving room. The acoustic medium inside rooms was modelled using fluid elements and the structure was modelled with plane strain elements. The interaction between the acoustic medium and the structure was modelled in a coupled structural-acoustic analysis. An FE modelling setup which includes appropriate model parameters to be used in the structural-acoustic analysis was presented. The FE sound reduction of double-leaf walls using two different stud profiles was then calculated. Experimental tests complying with standards ISO 717-1:1997 and 140-3:1995 were also carried out to evaluate the FE results. It has shown that the stud's shape have significant effects on the sound reduction of the double-leaf walls, and the FE results have similar trends are in fair agreement with the experimental results. A parametric study was conducted and the effects of the stud's shapes on the sound reduction were presented and discussed.