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CONTENTS
Volume 4, Number 1, January 2019
 

Abstract
Recent generations of smartphones offer accelerometer sensors as a standard feature. While this has led to the development of a number of related applications (apps), there has been no study on their comparative or individual performance against a benchmark. This paper investigates the comparative performance of a number of smartphone accelerometer apps amongst themselves and to a calibrated benchmark accelerometer. A total of 12 apps were selected for testing out of 90 following an initial review. The selected apps were subjected to sinusoidal vibration testing of varying frequency and the response of each compared against the calibrated baseline accelerometer. The performance of apps was quantified using analysis of variance (ANOVA) and test of significance was carried out. The apps were then compared for a realistic dynamic scenario of measuring the acceleration response of a bridge due to the passage of a French Train à Grande Vitesse (TGV) in a laboratory environment.

Key Words
accelerometer; mobile app; train-bridge dynamics; experimental data; analysis of variance (ANOVA); fast fourier transform (FFT)

Address
Paul Cahill and Vikram Pakrashi: Dynamical Systems & Risk Laboratory, School of Mechanical and Materials Engineering and Centre for Marine and Renewable Energy Ireland (MaREI), University College Dublin, Dublin, Ireland
Lucy Quirk: Centre for Marine and Renewable Energy Ireland (MaREI), Environmental Research Institute, University College Cork, Cork, Ireland
Priyanshu Dewan: Indian Institute of Technology-Benaras Hindu University, Benaras, India

Abstract
One of the efficient and useful tools to achieve the optimal design of structures is employing the sensitivity analysis in the finite element model. In the numerical optimization process, often the semi-analytical method is used for estimation of derivatives of the objective function with respect to design variables. Numerical methods for calculation of sensitivities are susceptible to the step size in design parameters perturbation and this is one of the great disadvantages of these methods. This article uses complex variables method to calculate the sensitivity analysis and combine it with discrete sensitivity analysis. Finally, it provides a new method to obtain the sensitivity analysis for linear structures. The use of complex variables method for sensitivity analysis has several advantages compared to other numerical methods. Implementing the finite element to calculate first derivatives of sensitivity using this method has no complexity and only requires the change in finite element meshing in the imaginary axis. This means that the real value of coordinates does not change. Second, this method has the lower dependency on the step size. In this research, the process of sensitivity analysis calculation using a finite element model based on complex variables is explained for linear problems, and some examples that have known analytical solution are solved. Results obtained by using the presented method in comparison with exact solution and also finite difference method indicate the excellent efficiency of the proposed method, and it can predict the sustainable and accurate results with the several different step sizes, despite low dependence on step size.

Key Words
complex variables method (CVM); discrete sensitivity method (DSM); linear structures; semi-analytical method

Address
Mojtaba Sheikhi Azqandi: Department of Mechanical Engineering, Bozorgmehr University of Qaenat, Qaen, Iran
Mahdi Hassanzadeh: Department of Mechanical Engineering, Islamic Azad University, Gorgan Branch,
Kordkuy Center, Golestan, Iran
Mohammad Arjmand: Department of Civil Engineering, Bozorgmehr University of Qaenat, Qaen, Iran

Abstract
In this study, 2-mm Al/Cu bimetallic laminates were produced using asymmetric roll bonding (RB) process. The asymmetric RB process was carried out with thickness reduction ratios of 10%, 20% and 30% and mismatch rolling speeds 1:1, 1:1.1 and 1:1.2, separately. For various experimental conditions, finite element simulation was used to model the deformation of bimetallic Al/Cu laminates. Specific attention was focused on the bonding strength and bonding quality of the interface between Al and Cu layers in the simulation and experiment. The optimization of mismatch rolling speed ratios was obtained for the improvement of the bond strength of bimetallic laminates during the asymmetric RB process. During the finite element simulation, the plastic strain of samples was found to reach the maximum value with a high quality bond for the samples produced with mismatch rolling speed 1:1.2. Moreover, the peeling surfaces of samples around the interface of laminates after the peeling test were studied to investigate the bonding quality by scanning electron microscopy.

Key Words
asymmetric roll bonding; bond strength; peeling test; bimetal laminates; finite element method

Address
Mohamad Heydari Vini: Department of Mechanical Engineering, Mobarakeh Branch, Islamic Azad University, Mobarakeh, Isfahan, Iran
Saeed Daneshmand: Department of Mechanical Engineering, Majlesi Branch, Islamic Azad University, Isfahan, Iran

Abstract
Variation Analysis (VA) is used to simulate final product variation, taking into consideration part manufacturing and assembly variations. In VA, all the manufacturing and assembly processes are defined at the product design stage. Process Capability Data Bases (PCDB) provide information about measured variation from previous products and processes and allow the designer to apply this to the new product. A new challenge to this traditional approach is posed by the Industry 4.0 (I4.0) revolution, where Smart Manufacturing (SM) is applied. The manufacturing intelligence and adaptability characteristics of SM make present PCDBs obsolete. Current tolerance analysis methods, which are made for discrete assembly products, are also challenged. This paper discusses the differences expected in future factories relevant to VA, and the approaches required to meet this challenge. Current processes are mapped using I4.0 philosophy and gaps are analysed for potential approaches for tolerance analysis tools. Matching points of simulation capability and I4.0 intents are identified as opportunities. Applying conditional variations, incorporating levels of adjustability, and the un-suitability of present Monte Carlo simulation due to changed mass production characteristics, are considered as major challenges. Opportunities including predicting residual stresses in the final product and linking them to product deterioration, calculating non-dimensional performances and extending simulations for process manufactured products, such as drugs, food products etc. are additional winning aspects for next generation VA tools.

Key Words
industry 4.0, variation analysis, Monte Carlo, conditional variation, selective manufacturing

Address
Technical University of Denmark, Department of Mechanical Engineering, 2800 Kgs. Lyngby, Denmark

Abstract
Safety measures for tower cranes are extremely important among the seismic countermeasures at high-rise building construction sites. In particular, the collapse of a tower crane from a high position is a very serious catastrophe. An example of such an accident due to an earthquake is the case of the Taipei 101 Building (the author was the project director), which occurred on March 31, 2002. Failure of the bolted joints of the tower-crane mast was the direct cause of the collapse. Therefore, it is necessary to design for this eventuality and to take the necessary measures on construction sites. This can only be done by understanding the precise dynamic behavior of mast joints during an earthquake. Consequently, we created a new hybrid-element model (using beam, shell, and solid elements) that not only expressed the detailed behavior of the site joints of a tower-crane mast during an earthquake but also suppressed any increase in the total calculation time and revealed its behavior through computer simulations. Using the proposed structural model and simulation method, effective information for designing safe joints during earthquakes can be provided by considering workability (control of the bolt pretension axial force and other factors) and less construction cost. Notably, this analysis showed that the joint behavior of the initial pretension axial force of a bolt is considerably reduced after the axial force of the bolt exceeds the yield strength. A maximum decrease of 50% in the initial pretension axial force under the El Centro N-S Wave (vmax = 100 cm/s) was observed. Furthermore, this method can be applied to analyze the seismic responses of general temporary structures in construction sites.

Key Words
elastoplastic analysis; FEM; tower crane; bolted tensile joints; seismic responses; numerical modeling

Address
Yoshitaka Ushio and Yasuyuki Nagano: Graduate School of Simulation Studies, University of Hyogo 7-1-28 Minatojima-Minamicho, Chuo-ku, Kobe 650-0047, Japan
2Engineering Technology Div. JSOL Corporation, 2-2-4 Tosabori,
Tomoharu Saruwatari: Engineering Technology Div. JSOL Corporation, 2-2-4 Tosabori, Nishi-ku, Osaka, 550-0001, Japan


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