Study of the dynamic response of a CAARC building by the synthetic wind method and comparison with different approaches

Purpose This paper analyzes the effect that is generated in the dynamic response of a Commonwealth Advisory Aeronautical Council building for different types of power spectra. This article also compares synthetic wind method (SWM) results with wind tunnel tests and other numerical approaches.Design/methodology/approach One of the main methodologies developed in Brazil, the SWM, is employed to determine the dynamic wind loads. The Davenport, Lumley and Panowski, Harris, von Karman and Kaimal model are used in SWM to generate the resonant harmonics. Lateral pressures are calculated by the wind speed deflection profile for 30, 35, 40 and 45 m/s. The structure is processed in Autodesk Robot Structural Analysis with numerical analysis in FEM by the Hilber–Hughes–Taylor method. To corroborate the synthetic wind with experimental results, displacement curves are developed for wind tunnel experimental results, Davenport method, Eurocode and NBR 6123, together with the SWM.Findings Results show that for 30 m/s, the lowest convergence of the power spectra models was presented and that the greatest difference found was below 10%. In addition, it was shown that Eurocode 1-4 can lead to oversizing, while NBR 6123 can lead to undersizing, compared with the experimental results. Finally, results by the Davenport method, wind tunnel test and synthetic wind showed good accuracy.Originality/value By carrying out this comparative analysis, this work presents an important contribution in the field of calculating the dynamic response of tall buildings. Studies with these comparisons to corroborate the SWM had not yet been carried out.

Effect of high-frequency PCB laminate on thermal cycling behavior of electronic packaging structures

PurposeAs the solution to improve fatigue life and mechanical reliability of packaging structure, the material selection in PCB stack-up and partitioning design on PCB to eliminate the electromagnetic interference by keeping all circuit functions separate are suggested to be optimized from the mechanical stress point of view.Design/methodology/approachThe present paper investigated the effect of RO4350B and RT5880 printed circuit board (PCB) laminates on fatigue life of the QFN (quad flat no-lead) packaging structure for high-frequency applications. During accelerated thermal cycling between −50 °C and 100 °C, the mismatched coefficients of thermal expansion (CTE) between packaging and PCB materials, initial PCB warping deformation and locally concentrated stress states significantly affected the fatigue life of the packaging structure. The intermetallics layer and mechanical strength of solder joints were examined to ensure the satisfactorily soldering quality prior to the thermal cycling process. The failure mechanism was investigated by the metallographic observations using a scanning electron microscope.FindingsTypical fatigue behavior was revealed by grain coarsening due to cyclic stress, while at critical locations of packaging structures, the crack propagations were confirmed to be accompanied with coarsened grains by dye penetration tests. It is confirmed that the cyclic stress induced fatigue deformation is dominant in the deformation history of both PCB laminates. Due to the greater CTE differences in the RT5880 PCB laminate with those of the packaging materials, the thermally induced strains among different layered materials were more mismatched and led to the initiation and propagation of fatigue cracks in solder joints subjected to more severe stress states.Originality/valueIn addition to the electrical insulation and thermal dissipation, electronic packaging structures play a key role in mechanical connections between IC chips and PCB.

Comparison of flexural capacity of different hollow slab beams with/without pavement layer reinforced by steel plates

PurposeReinforcement of reinforced concrete (RC) beams in-service have always been an important research field, anchoring steel plate in the bottom of the beams is a kind of common reinforcement methods. In actual engineering, the contribution of pavement layer to the bearing capacity of RC beams is often ignored, which underestimates the bearing capacity and stiffness of RC beams to a certain extent. The purpose of this paper is to study the effect of pavement layer on the RC beams before and after reinforcement.Design/methodology/approachFirst, static load experiments are carried out on three in-service RC hollow slab beams, meanwhile, nonlinear finite element models are built to study the bearing capacity of them. The nonlinear material and shear slip effect of studs are considered in the models. Second, the finite element models are verified, and the numerical simulation results are in good agreement with the experimental results. Last, the finite element models are adopted to carry out the research on the influence of different steel plate thicknesses on the flexural bearing capacity and ductility.FindingsThe experimental results showed that pavement layers increase the flexural capacity of hollow slab beams by 16.7%, and contribute to increasing stiffness. Ductility ratio of SPRCB3 and PRCB2 was 30% and 24% lower than that of RCB1, respectively. The results showed that when the steel plate thickness was 1 mm–6 mm, the bearing capacity of the hollow slab beam increased gradually from 2158.0 kN.m to 2656.6 kN.m. As the steel plate thickness continuously increased to 8 mm, the ultimate bearing capacity increased to 2681.0 kN.m. The increased thickness did not cause difference to the bearing capacity, because of concrete crushing at the upper edge.Originality/valueIn this paper, based on the experimental study, the bearing capacity of hollow beam strengthened by steel plate with different thickness is extrapolated by finite element simulation, and its influence on ductility is discussed. This method not only guarantees the accuracy of the bearing capacity evaluation, but also does not require a large number of samples, and has certain economy. The research results provide a basis for the reinforcement design of similar bridges.

Finite element analysis on the thermal fatigue life of full vs peripheral array packages

PurposeThis paper aims to examine the thermal cycling fatigue life performance of two-common solder array configurations, full and peripheral, using three-dimensional nonlinear finite element analysis.Design/methodology/approachThe finite element simulations were used to identify the location of the critical solder interconnect, and using Darveaux's model, solder thermal fatigue life was computed.FindingsThe results showed that the solder array type does not significantly influence thermal fatigue life of the interconnect. However, smaller size packages result in improved life by almost 45% compared to larger package designs. Additionally, this paper provided an engineered study on the effect of the number of rows available in a perimeter array component on solder thermal fatigue performance.Originality/valueGeneral design recommendations for reliable electronic assemblies under thermal cycling loaded were offered in this research.

Prediction of load requirement and instabilities during end forming of friction stir processed AA 6063-T6 thin-walled tubes

PurposeThe current work aims to propose a finite element (FE) simulation methodology to predict the formability of friction stir processed (FSPed) tubes by end forming. Moreover, a strain mapping method is also presented to predict the end forming instabilities.Design/methodology/approachIn this work, FE simulation of end forming of raw tubes and FSPed AA6063-T6 tubes are done using Abaqus (explicit) incorporating anisotropic properties of the raw tube and FSPed zone. Actual thickness of the FSPed zone is also implemented. Expansion, reduction and beading are the end forming operations considered. Load requirement and instabilities are predicted. A new method “strain mapping method” is followed to predict the failure instabilities in expansion and beading, while during reduction, wrinkling is predicted by FE simulations. Lab scale experiments on FSP and end forming are done for validation at various rotational speeds.FindingsResults reveal that in the case of expansion and reduction of FSPed tubes, forming load predictions are accurate, while in beading, after initiation of bead, predictions are not accurate. Experimental observation on the type of instability is consistently predicted during numerical simulations. Prediction of displacement at failure by strain mapping method is encouraging in most of the cases including those that are FSPed. Hence, it is suggested that the method can be utilized to evaluate the onset of failure during tube expansion and beading.Originality/valueFE simulation methodology including anisotropic properties of raw tube and FSPed tubes is proposed, which is not attempted until now even for normal tubes. Strain mapping method is easy to implement for instability predictions, which is done usually by failure theories and forming limit diagram.

Three-dimensional finite element analysis for temperature filed of composite materials during the cure

PurposeThe cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.Design/methodology/approachFinite element method is employed in this work.FindingsThe simulated results match the experimental results well, which demonstrates the finite element analysis models are reliable. Compared with the one- and two-dimensional finite element analysis, temperature and degree of cure can be calculated at any point within composite structures in the present simulation analysis. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.Originality/valueA coupled thermokinetic simulation of the liquid composite molding process based on a three-dimensional finite element method is presented. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.

Study on anti-aged durability of HMA based on inherent and improved performance

PurposeThe purpose of this study is to compare and analyze the anti-aging durability of asphalt and asphalt mixture under the conditions of inherent and improved performance. The research contents include: the mechanical properties (dynamic stability, bending strain, freeze-thaw splitting tensile strength ratio (TSR)) of different modified asphalt mixtures were tested by using the best modified asphalt.Design/methodology/approachThe anti-aging durability of different modified asphalt was analyzed by using the results of macro tests such as penetration and softening point as evaluation indexes. Meanwhile, the change of the asphalt colloid instability index (Ic) in the aging process was used as the evaluation index to verify the results of the macroscopic test, and the best modified asphalt was obtained. On this basis, the composition of different modified asphalt mixtures was designed by using the best modified asphalt. Meanwhile, water stability was used as evaluation indexes to study the anti-aging durability of different modified asphalt mixtures.FindingsThe results show that styrene-butadiene-styrene (SBS) modified asphalt has better aging resistance. Due to the special storage time, the performance of rubber asphalt is also the best. Meanwhile, in terms of modified asphalt mixture, its high temperature performance and durability of anti-aging is as follows: 4% SBS /16% rubber modified asphalt mixture (IV) > 4% SBS modified asphalt mixture (II) > asphalt mixture (90#) (I) > 16% rubber modified asphalt mixture (III). The low temperature performance and durability of anti-aging is as follows: Ⅱ > IV > Ⅰ > Ⅲ. The water stability performance and durability of anti-aging is as follows: IV > Ⅲ > Ⅱ > Ⅰ.Originality/valueThe research results have important theoretical and guiding significance for exploring the change of intrinsic properties and improved properties of asphalt and asphalt mixture in the aging process and revealing the anti-aging mechanism of different modified asphalt mixtures.

Improvement on modal curvatures methods for multiple damage identification in beams

PurposeThe purpose of this paper is to present a study on the application of four damage factors to several single and multiple damage scenarios of aluminium beams. Each one of these damage factors is defined by the information given by modal curvatures of the beams.Design/methodology/approachThe methodology consisted of a first experimental stage in which the modal rotations were measured with shearography and a subsequent numerical analysis in order to obtain the modal curvatures. To this end, three finite difference formulae were applied. The modal curvatures were then used to calculate the damage factors.FindingsIt was found that the profile of the damage factors varies according to the finite difference formula used. In view of the findings, the differences among the damage factors analysed are highlighted and some final recommendations to improve damage identifications via modal curvature-based are presented.Originality/valueTo the best of the authors’ knowledge, the application and comparison of several finite difference formulae and corresponding optimal sampling has not been carried out before. With the proposed approach, it is possible to identify multiple damages, which is still a great challenge. The post-processing of shearography measurements with a numerical method, which is inherently a multidisciplinary approach, is also a substantial improvement upon other type of approaches found in the literature.

Robust optimization of EMU brake module based on interval analysis

PurposeThis study aims to research the influence of non-probabilistic design variables on interval robust optimization of electric multiple units (EMU) brake module, therefore obtain the reasonable of design variables of the EMU brake module.Design/methodology/approachA robust optimization model of the EMU brake module based on interval analysis is established. This model also considers the dimension tolerance of design variables, and it uses symmetric tolerance to describe the uncertainty of design variables. The interval order relation and possibility degree of interval number are employed to deal with the uncertainty of objective function and constraint condition, respectively. On this basis, a multiobjective robust optimization model in view of interval analysis is established and applied to the robust optimization of the EMU brake module.FindingsCompared with the traditional method and the method proposed in the reference, the maximum stress fluctuation of the EMU brake module structure is smaller after using the method proposed in this paper, which indicates that the robustness of the maximum stress of the structure has been improved. In addition, the weight and strength of the structure meet the design requirements. It shows that this method and model introduced in this research have certain feasibility.Originality/valueThis study is the first attempt to apply the robust optimization model based on interval analysis to the optimization of EMU structure and obtain the optimal solution set that meets the design requirements. Therefore, this study provides an idea for nonprobabilistic robust optimization of the EMU structure.

Optimization of structural parameters for the sound absorption performance of a cellular ceramic foam

PurposeThe purpose of this paper is to provide an optimization schedule of structural parameters for the sound absorption performance of a cellular ceramic foam in the sound frequency range of 200–4,000 Hz.Design/methodology/approachThe cellular ceramic foam with porosity of about 60–75% and the pore size of about 1–7 mm was successfully prepared by using natural zeolite powder as the main raw material. For this ceramic foam, the sound absorption performance was measured, and the absorption structure was optimized by some important structural parameters. With orthogonal experiment, optimization of structural parameters was found for absorption performance. By means of the range analysis method, the main factor is known to influence the performance of ceramic foam.FindingsThe present ceramic foam may have good absorption performance although at relatively low frequencies of 400–4,000 Hz while structural parameters of sample are appropriately combined. With orthogonal experiment, optimization of structural parameters for the absorption performance was found to be as follows: sample thickness, 25 mm; porosity, 73.5%; pore size, 4–5 mm and air gap depth, 20 mm. To influence the performance, sample thickness is the main factor, air gap depth is the second and both of pore size and porosity would have a relatively slight effect.Originality/valueThis paper presents a method to optimize the structural parameters of a cellular ceramic foam for sound absorption performance by means of orthogonal experiment.