Sharif Digital Repository

One of the important challenges in the auto industry is to reduce the mass of the vehicle while meeting structural performance requirements for Crashworthiness, Noise, Vibration and Harshness (NVH) etc. In this paper, a multidisciplinary optimization (MDO) of a car back-bonnet is investigated by using trie Response Surface Method (RSM). Firstly, a car body is fully surface modeled in CATIA and meshed in HYPERMESH software. Then, modal analysis of the finite element model is performed by NASTRAN software to find natural frequencies. Frequency map of that component is extracted and compared with a reference map to detect defects. Design of Experiments (DOE) methodologies is used for a... 

This work introduces a new concept in designing semi-active engine mounts. Engine mounts are under continuous development to provide better and more cost-effective engine vibration control. Passive engine mounts do not provide satisfactory solution. Available semi-active and active mounts provide better solutions but they are more complex and expensive. The variable stiffness engine mount (VSEM) is a semi-active engine mount with a simple ON-OFF control strategy. However, unlike available semi-active engine mounts that work based on damping change, the VSEM works based on the static stiffness change by using a new fast response force controlled variable spring. The VSEM is an improved... 

In this research, the handling behavior of an intermediate class passenger car has been optimized by altering its front suspension parameters. For this purpose, a validated virtual model of the car, constructed by Adams/Car software, has been used. The utilized objective function is a combination of eight criteria indicating handling characteristics of the car. To reduce the amount of optimization parameters, a sensitivity analysis has been done by implementing the Design of Experiments method capabilities. Optimization has been done using the Response Surface Method. The obtained optimization results show a considerable improvement in the system response. Copyright © 2006 SAE International  

Load-associated fatigue cracking is one of the major distress types occurring in flexible pavement systems. This paper identifies two important calibration factors for the dry-no freeze climatic region of Iran for use in the Mechanistic Empirical Pavement Design Guide (MEPDG). According to recent research, approximately 51~% of Iran's total land area is located in this region. Tehran, the capital of Iran, is located in this region and therefore three of its highways are selected for this research. The gathering of the data required for calibration is labor intensive because the data resides in various incongruent data sets. Spreadsheet templates specifically designed to manage the... 

Electrocoagulation is an effective, fast, and economic method for treatment of industrial wastewaters. In this study, effects of different parameters including electrolysis time, voltage, and pH on the reduction of chemical oxygen demand (COD), lignin, and color in pulp and paper wastewaters were studied. Iron and aluminum were used as anode and cathode electrodes, respectively. Under the optimal conditions (pH 5, 60 min, 10 V), this treatment method led to 85% removal of COD and 78.5% removal of lignin. Furthermore, clear treated water with complete color removal was generated that suggests the application of electrocoagulation for industrial wastewater treatment, especially in pulp and... 

One of the important challenges in the auto industry is to reduce the mass of the vehicle while meeting structural performance requirements for crashworthiness, noise, vibration and harshness, etc. In this paper, a multidisciplinary optimisation of a car back-bonnet is investigated by using the response surface method. A car body is fully surface modelled in CATIA and meshed in software. Then, modal analysis of the finite element model is performed by NASTRAN software to find natural frequencies. A frequency map of that component is extracted and compared with a reference map to detect defects. Design of experiments methodology is used for a screening of the design space and for the... 

This paper presents a finite element method (FEM) free and forced lateral vibration analysis of beams made of functionally graded materials (FGMs). The temperature dependency of material properties along with damping had not previously been taken into account in vibration analysis. In the present study, the material properties were assumed to be temperature-dependent, and were graded in the thickness direction according to a simple power law distribution of the volume fractions of the constituents. The natural frequencies were obtained for functionally graded (FG) beams with various boundary conditions. First, an FG beam was assumed to be isotropic (metal rich) and the results were compared... 

In this paper, effects of strain rate and mean strain on the cyclic behavior and the lifetime of aluminum-silicon alloys are investigated under thermo-mechanical and isothermal fatigue loadings. To achieve these goals, low cycle fatigue tests are accomplished at evaluated temperatures under various strain rates (by changing the loading frequency) and different strain ratios (minimum to maximum strain). Thermo-mechanical fatigue experiments are performed in an out-of-phase condition where the temperature varies between 50 and 250 °C. Various heating/cooling rates are taken into account to assess the strain rate effect and different starting temperatures are considered to study the mean strain... 

This paper incorporates a discrete wavelet transform and a radial basis function neural network to implement a vibration-based crack-like damage identification approach to the simulated welds of chassis cross members. After finite element method modelling of a vehicle, eight acceleration sensors are placed on the chassis, and their responses are measured to the upward displacement on the excitation of two tyres while the other two tyres are fixed. Then, a discrete wavelet transform with a Daubechies 3 mother wavelet is applied to the responses of the sensors. All detail coefficients and approximation coefficients of the nine levels of the discrete wavelet transform are introduced into the... 

Coral reefs around the discharge areas of desalination plants have effects on the distribution and dilution of discharged saline jet. In the present study, effects of bed obstacles with different heights on the behaviour of inclined negatively buoyant jets (INBJs), including dilution and spatial characteristics, are experimentally investigated using the light attenuation (LA) optical method. Present experiments show that as the confinement induced by the bed and obstacle intensifies, the maximum normalized jet centreline dilution decreases up to 40%. As the jet approaches the obstacle, spreading along the inner and outer edges of the jet increases. The present results also show that upstream... 

This study investigated the effect of SiO2 nanoparticles and SDS surfactant on the wetting properties of an enzyme-based liquid binder and granule size distribution in a fluidized bed granulation process. The nanofluids were prepared by adding different SiO2 and SDS concentrations to the alkaline protease enzyme liquor with sodium carboxymethylcellulose as the granulating binder. The surface tension (ST) and contact angle (CA) of nanofluids with powder compact were measured by the pendant and sessile drop methods. A new correlation was also proposed for the ST of nanofluids. Furthermore, the influence of the nanoparticle and surfactant on the enzyme activity of nanofluids was evaluated. The... 

The influence of enzyme liquid binder properties on wet granulation process was evaluated at both micro- and macro-scales. The micro-scale phenomena, including binder droplet spreading on and penetration into the powder bed, as well as liquid bridge shape and force, were analyzed by introducing SiO2 nanoparticles and SDS surfactant into the liquid binder containing a protease enzyme and 1 wt% of NaCMC. Moreover, the simultaneous effect of formulation variables, including NPs and SDS concentrations, and process conditions, such as binder spray rate and air temperature, was investigated using design of experiments. The average size and the span were considered as the responses. Nanofluid... 

An algorithm for investigation of nonlinear systems by the transfinite element method is presented. Basically, the transformation techniques have been developed for linear systems. Nonlinear transient heat transfer of a thick FGM cylinder with temperature-dependent material properties is investigated in the present paper to clarify the proposed algorithm. Two main novelties of the present research are: (1) incorporating the temperature-dependency of the material properties in the thermal analysis which lead to highly non-linear governing equations and (2) proposing an updating numerical transfinite element procedure to solve the resulted highly nonlinear governing equations. To reduce the... 

In this paper, nonlinear radial and hoop thermoelastic stress analysis of rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using the finite element method. In this method, one-dimensional second order elements with three nodes have been used. The geometrical and boundary conditions are in the shape of nonexistence of the pressure (zero radial stress) in both external and internal layers and zero displacement at the internal layer of rotating disk. Furthermore, it's assumed that heat distribution is as second order curve while material properties such as elasticity modulus, Poisson's ratio and thermal expansion coefficient vary by using a... 

In the present paper, fatigue analysis of an antiroll bar is investigated and compared for several criterions by using the finite element method (FEM) and also the experimental results. The validity of some of commonly used criterions in estimating fatigue life including Mcdiarmid and Von Misses theories is examined in which the inputs are considered as periodic data. For random inputs, some other methods are proposed including new suggestions and also a new criterion are established for estimation of fatigue life based on Mcdiarmid and Von Misses criterions. Prediction capability of mentioned new criterion which is evaluated for the antiroll bar, shows better results than other methods... 

Nonlinear transient heat transfer and thermoelastic stress analyses of a thick-walled FGM cylinder with temperature-dependent materials are performed by using the Hermitian transfinite element method. Temperature-dependency of the material properties has not been taken into account in transient thermoelastic analysis, so far. Due to the mentioned dependency, the resulting governing FEM equations of transient heat transfer are highly nonlinear. Furthermore, in all finite element analysis performed so far in the field, Lagrangian elements have been used. To avoid an artificial local heat source at the mutual boundaries of the elements, Hermitian elements are used instead in the present... 

Spinal fusion surgery is usually followed by accelerated degenerative changes in the unfused segments above and below the treated segment(s), i.e., adjacent segment disease (ASD). While a number of risk factors for ASD have been suggested, its exact pathogenesis remains to be identified. Finite element (FE) models are indispensable tools to investigate mechanical effects of fusion surgeries on post-fusion changes in the adjacent segment kinematics and kinetics. Existing modeling studies validate only their intact FE model against in vitro data and subsequently simulate post-fusion in vivo conditions. The present study provides a novel approach for the comprehensive validation of a lumbar... 

In this research, important parameters of a rack and pinion steering system in dynamic steady state and transient responses have been investigated. For this purpose, virtual model of a medium passenger car in ADAMS/Car has been used. The model has up to 121 kinematic degree of freedom and includes all components of the rack and pinion steering system. Several different experimental test results have confirmed the validity of the model. Sensitivity analysis have been done based on design of experiments (DOE) method. Two level fractional factorial designs have been selected for this purpose. Steady state cornering and step steer input are the analysis that used for this research. Understeering... 

More than 80% of desalination plants use the multi-stage flash (MSF) technology in the Persian Gulf and hence may have a severe irreversible impact on the marine environment. In the present study, geometrical, mixing, and turbulence characteristics of thermal-saline jets, similar to MSF effluents, are numerically investigated using the dynamic Smagorinsky sub-grid scale (SGS) model and UNESCO equation of state. For this purpose, two affecting dimensionless parameters are considered: (1) density ratio, which is thermal flux to salinity flux ratio, and (2) salinity Froude number. Examining the effects of density ratio reveals that the jet flow pattern only depends on the density ratio with a...