Showing papers in "Journal of Mechanical Science and Technology in 2011"
TL;DR: In this article, the buckling analysis of laminated composite plates reinforced by single-walled carbon nanotubes (SWCNTs) is carried out using an analytical approach as well as the finite element method.
Abstract: In this paper, the buckling analysis of laminated composite plates reinforced by single-walled carbon nanotubes (SWCNTs) is carried out using an analytical approach as well as the finite element method. The developed model is based on the classical laminated plate theory (CLPT) and the third-order shear deformation theory for moderately thick laminated plates. The critical buckling loads for the symmetrical layup are determined for different support edges. The Mori-Tanaka method is employed to calculate the effective elastic modulus of composites having aligned oriented straight nanotubes. The effect of the agglomeration of the randomly oriented straight nanotubes on the critical buckling load is also analyzed. The results of analytical solution are compared and verified with the FEM calculations The critical buckling loads obtained by the finite element and the analytical methods for different layup and boundary conditions are in good agreement with each other. In this article, the effects of the carbon nanotubes (CNTs) orientation angle, the edge conditions, and the aspect ratio on the critical buckling load are also demonstrated using both the analytical and finite element methods.
139 citations
TL;DR: In this article, the authors investigate process capability of polyjet printing (PP) for plastic components, starting from the identification of component, prototypes with three different type of plastic material were prepared at different orientations and measurements on the coordinate measuring machine helped in calculating the dimensional tolerances of the plastic components produced.
Abstract: The purpose of the present study is to investigate process capability of polyjet printing (PP) for plastic components. Starting from the identification of component, prototypes with three different type of plastic material were prepared at different orientations. Measurements on the coordinate measuring machine helped in calculating the dimensional tolerances of the plastic components produced. Some important mechanical properties were also compared to verify the suitability of the components. Final components produced are acceptable as per ISO standard UNI EN 20286-I (1995) and DIN16901. The results of study suggest that PP process lies in ±4.5sigma (σ) limit as regard to dimensional accuracy of plastic component is concerned. This process ensures rapid production of pre-series technological prototypes and proof of concept at less production cost and time.
115 citations
TL;DR: In this paper, various carbon-based particles such as graphite, carbon black, graphite nanofibers and carbon nanotubes were dispersed in mineral oil to systematically examine the effect of the size and shape of particles on the properties of friction performance.
Abstract: Various carbon-based particles such as graphite, carbon black, graphite nanofibers and carbon nanotubes were dispersed in mineral oil to systematically examine the effect of the size and shape of particles on the properties of friction performance. As the results of friction tests using a disc-on-disc tribotester, the friction coefficient of a disc specimen was significantly reduced when nano-sized spherical particles were suspended in mineral oil. This was attributed to the presence of spherical nanoparticles, which prevented direct contact between frictional surfaces. However, the fibrous nanoparticles with high aspect ratios deteriorated the lubrication performance between friction surfaces due to a higher degree of agglomeration.
103 citations
TL;DR: This paper discusses mobile robot position estimation without using external signals in indoor environments and proposes a Kalman filter that estimates the orientation and velocity of mobile robots, which combines INS and odometry and delivers more accurate position information than standalone odometry.
Abstract: Inertial navigation systems (INS) are composed of inertial sensors, such as accelerometers and gyroscopes. An INS updates its orientation and position automatically; it has an acceptable stability over the short term, however this stability deteriorates over time. Odometry, used to estimate the position of a mobile robot, employs encoders attached to the robot’s wheels. However, errors occur caused by the integrative nature of the rotating speed and the slippage between the wheel and the ground. In this paper, we discuss mobile robot position estimation without using external signals in indoor environments. In order to achieve optimal solutions, a Kalman filter that estimates the orientation and velocity of mobile robots has been designed. The proposed system combines INS and odometry and delivers more accurate position information than standalone odometry.
96 citations
TL;DR: In this article, the effects of cutting parameters on flank wear and surface roughness using CBN tool were investigated under turning conditions of hardened AISI H11 (X38CrMoV5-1), and the relationship between the variables and the technological parameters was determined using a quadratic regression model.
Abstract: The present study, aims to investigate, under turning conditions of hardened AISI H11 (X38CrMoV5-1), the effects of cutting parameters on flank wear (VB) and surface roughness (Ra) using CBN tool. The machining experiments are conducted based on the response surface methodology (RSM). Combined effects of three cutting parameters, namely cutting speed, feed rate and cutting time on the two performance outputs (i.e. VB and Ra), are explored employing the analysis of variance (ANOVA). Optimal cutting conditions for each performance level are established and the relationship between the variables and the technological parameters is determined using a quadratic regression model. The results show that the flank wear is influenced principally by the cutting time and in the second level by the cutting speed. Also, it is that indicated that the feed rate is the dominant factor affecting workpiece surface roughness.
65 citations
TL;DR: In this article, a low-frequency vibration on a stainless steel (SS 304) was used to increase the material removal rate and decrease the surface roughness and tool wear rate.
Abstract: High-frequency vibration aided EDM has become one of the ways to increase material removal rate in EDM process, due to the flushing effect caused by vibration. However, utilizing high-frequency vibration, especially in ultrasonic range consumes a lot of setup cost. This work presents an attempt to use a low-frequency vibration on workpiece of stainless steel (SS 304) during EDM process. The workpiece was vibrated with variations of low-frequency and low-amplitude. The results show that the application of low-frequency vibration in EDM process can be used to increase the material removal rate, and decrease the surface roughness and tool wear rate.
62 citations
TL;DR: In this paper, Eringen's equa- tions of nonlocal elasticity are incorporated into the classical beam theories for buckling of nanobeams with rectangular cross-section.
Abstract: Buckling analysis of nanobeams is investigated using nonlocal continuum beam models of the different classical beam theories namely as Euler-Bernoulli beam theory (EBT), Timoshenko beam theory (TBT), and Levinson beam theory (LBT). To this end, Eringen's equa- tions of nonlocal elasticity are incorporated into the classical beam theories for buckling of nanobeams with rectangular cross-section. In contrast to the classical theories, the nonlocal elastic beam models developed here have the capability to predict critical buckling loads that allowing for the inclusion of size effects. The values of critical buckling loads corresponding to four commonly used boundary con- ditions are obtained using state-space method. The results are presented for different geometric parameters, boundary conditions, and values of nonlocal parameter to show the effects of each of them in detail. Then the results are fitted with those of molecular dynamics simulations through a nonlinear least square fitting procedure to find the appropriate values of nonlocal parameter for the buckling analy- sis of nanobeams relevant to each type of nonlocal beam model and boundary conditions.analysis. Based on the above introduction, it seems that size-effects consideration in the analysis of nanobeams is necessary. In this work, different nonlocal beam models corresponding to the different classical beam theories (22-24) are presented on the basis of Eringen's equations of nonlocal elasticity (25) to predict the buckling behavior of nanobeams with four com- monly used boundary conditions. State-space method is used to solve the governing differential equations for each type of nonlocal beam model with different boundary conditions. Various numerical results are given to show the influences of boundary conditions, aspect ratio, and values of nonlocal con- stant, separately. Then the results are matched with those of molecular dynamics simulations which are available in the literature to extract the correct values of nonlocal parameter corresponding to each type of nonlocal beam model and boundary conditions.
59 citations
TL;DR: In this paper, both experimental study and mathematical modeling on microwave drying of white mulberry was performed, and the microwave drying process which reduced the moisture content of mulberry from 3.76 to 0.25 (g water/g dry matter) was carried out at 90, 180, 360, 600, and 800 W in a modified microwave drying setup.
Abstract: The literature surveyed revealed that drying kinetics of white mulberry under microwave treatment has not been investigated. In present study, both experimental study and mathematical modeling on microwave drying of white mulberry was performed. The microwave drying process which reduced the moisture content of mulberry from 3.76 to 0.25 (g water/g dry matter) was carried out at 90, 180, 360, 600, and 800 W in a modified microwave drying set-up. The effects of microwave drying technique on the moisture ratio and drying rate of white mulberry were investigated experimentally. Both the effects of microwave power level (under the range of 90–800W) and initial sample weight (50–150g) were studied. No constant rate period was observed. Mathematical modeling of thin layer drying kinetics of white mulberry under microwave treatment was also investigated by fitting the experimental drying data to eight thin layer drying models. Among the models proposed, Midilli et al. model precisely represented the microwave drying behavior of white mulberry with the coefficient of determination higher than 0.999 and mean square of deviation (χ2) and root mean square error (RMSE) lower than 1.1×10−4 and 8.9×10−3, respectively for all the microwave drying conditions studied. The effective moisture diffusivity (Deff) of white mulberry varied from 0.45×10−8 to 3.25×10−8 m2s−1. Both the drying constant (k) and Deff increased with the increase of microwave power level.
59 citations
TL;DR: In this article, the laser assisted machining (LAM) method was proposed to cut and remove softened parts by locally heating the ceramic with laser, where the laser power is the machining factor that controls the temperature.
Abstract: This paper describes the Laser Assisted Machining (LAM) that cuts and removes softened parts by locally heating the ceramic with laser. Silicon nitride ceramics can be machined with general machining tools as well, because YSiAlON, which was made up ceramics, is soften at about 1,000°C. In particular, the laser, which concentrates on highly dense energy, can locally heat materials and very effectively control the temperature of the heated part of specimen. Therefore, this paper intends to propose an efficient machining method of ceramic by deducing the machining governing factors of laser assisted machining and understanding its mechanism. While laser power is the machining factor that controls the temperature, the CBN cutting tool could cut the material more easily as the material gets deteriorated from the temperature increase by increasing the laser power, but excessive oxidation can negatively affect the quality of the material surface after machining. As the feed rate and cutting depth increase, the cutting force increases and tool lifespan decreases, but surface oxidation also decreases. In this experiment, the material can be cut to 3mm of cutting depth. And based on the results of the experiment, the laser assisted machining mechanism is clarified.
57 citations
TL;DR: In this article, the splashing and spreading resulting from drop impact on liquid film has been numerically investigated by using a Level Set method for the interface tracking of the two-phase flow simulation.
Abstract: Splashing and spreading of a liquid by drop impact on liquid film depends on the impact velocity, drop size, drop properties and liquid film thickness. These parameters can be summarized by three main dimensionless parameters: Weber number, Ohnesorge number and non-dimensional film thickness. Upon impact of a drop on liquid film, these parameters influence the shape of the splash and the forma- tion and propagation of the crown. In the present study, the splashing and spreading resulting from drop impact on liquid film has been numerically investigated by using a Level Set method for the interface tracking of the two-phase flow simulation. For various dimen- sionless parameters, characteristics of the crown formation and spreading were predicted, and the results were found to show good agreement with available experimental data in the earlier stage of crown formation and show some discrepancies in the later stage of crown spreading due to the present 2D axi-symmetric computation, which cannot predict the secondary drops.
57 citations
TL;DR: An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece as discussed by the authors.
Abstract: An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand, an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.
TL;DR: In this article, second-order shear deformation theory is employed to analyze vibration of temperature-dependent solar functionally graded plates (SFGP) and the energy method is applied to derive equilibrium equations, and solution is based on Fourier series that satisfy the boundary conditions.
Abstract: Second-order shear deformation theory (SSDT) is employed to analyze vibration of temperature-dependent solar functionally graded plates (SFGP’s). Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Two different types of SFGP’s such as ZrO2/Ti-6Al-4V and Si3N4/SUS304 are considered. Uniform, linear, nonlinear, heat-flux and sinusoidal thermal conditions are imposed at the upper and lower surface for simply supported SFGPs. The energy method is applied to derive equilibrium equations, and solution is based on Fourier series that satisfy the boundary conditions (Navier’s method). Non-dimensional results are compared for temperature-dependent and temperature-independent SFGP’s and validated with known results in the literature. Numerical results indicate the effect of material composition, plate geometry, and temperature fields on the vibration characteristics and mode shapes. The results obtained using the SSDT are very close to results from other shear deformation theories.
TL;DR: In this paper, the authors developed test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique.
Abstract: Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration’s direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition.
TL;DR: In this article, the effect of the weld current on the nugget diameter and load-carrying capacity was evaluated by observing the diameter and performing a tensile-shear test.
Abstract: Recently, in the automotive industry, Al-coated boron steel sheets (22MnB5) have been used for hot stamping, and the use of these sheets makes it possible to achieve a tensile strength of over 1,500 MPa, since a metallurgical transformation from austenite to martensite occurs during the process. In this study, resistance spot welding (RSW) experiments were performed in order to evaluate the weldability of single-lap joints between GA780DP and 22MnB5. The effect of the weld current on the nugget diameter and load-carrying capacity was evaluated by observing the nugget diameter and performing a tensile-shear test. Furthermore, the fracture behavior was evaluated by carrying out optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) observations. Ductile regions were observed on the interfacially fractured surface of the weld, and this implies that a high load-carrying capacity can be obtained even when interfacial fracture (IF) occurs. IF is caused by the stress concentration resulting from the presence of the sharp notch at the boundary of the nugget as well as by the high hardness and the brittle microstructure of the weld; the microstructure is brittle because of the high carbon equivalent (Ceq) and the penetration of Al in the weld.
TL;DR: In this paper, a computational model is developed to analyze the effects of magnetic field in a pulsatile flow of blood through narrow arteries with mild stenosis, treating blood as Casson fluid model.
Abstract: A computational model is developed to analyze the effects of magnetic field in a pulsatile flow of blood through narrow arteries with mild stenosis, treating blood as Casson fluid model. Finite difference method is employed to solve the simplified nonlinear partial differential equation and an explicit finite difference scheme is obtained for velocity and subsequently the finite difference formula for the flow rate, skin friction and longitudinal impedance are also derived. The effects of various parameters associated with this flow problem such as stenosis height, yield stress, magnetic field and amplitude of the pressure gradient on the physiologically important flow quantities namely velocity distribution, flow rate, skin friction and longitudinal impedance to flow are analyzed by plotting the graphs for the variation of these flow quantities for different values of the aforesaid parameters. It is found that the velocity and flow rate decrease with the increase of the Hartmann number and the reverse behavior is noticed for the wall shear stress and longitudinal impedance of the flow. It is noted that flow rate increases and skin friction decreases with the increase of the pressure gradient. It is also observed that the skin friction and longitudinal impedance increase with the increase of the amplitude parameter of the artery radius. It is also found that the skin friction and longitudinal impedance increases with the increase of the stenosis depth. It is recorded that the estimates of the increase in the skin friction and longitudinal impedance to flow increase considerably with the increase of the Hartmann number.
TL;DR: In this paper, a soda-lime glass with a V-notch under tensile-shear loading was experimentally investigated and a fracture model was used to estimate the experimental results.
Abstract: Fracture phenomenon was experimentally investigated in a soda-lime glass weakened by a V-notch under tensile-shear loading. Fracture tests were conducted using a new test sample called the V-notched Brazilian disc (V-BD) specimen. The fracture resistance and fracture initiation angle were obtained initially from the test results. Afterward, a fracture model was utilized to estimate the experimental results. Very good correlation was found between the experimental and theoretical results both for the fracture resistance and the fracture initiation angle in notches having different notch angles and various notch tip radii. Experimental results revealed that for a constant notch tip radius, the failure load under pure tensile loading conditions decreases as the notch angle increases. For a constant notch angle, as the notch tip radius increases, the fracture load in the soda-lime glass V-BD specimens enhances in the whole domain from pure tensile to pure shear loading. Moreover, for a constant notch tip radius, the notch angle has almost no effect on the fracture initiation angle when the specimen is predominantly under tensile loading conditions.
TL;DR: In this article, the application of electrochemical polishing to the machining of nitinol SMA has been investigated and the most suitable EP machining conditions for the SMA were derived.
Abstract: Nitinol, a shape memory alloy (SMA), is manufactured from titanium and nickel, and is employed in various fields for use in devices such as micro sensors, ultra-precision devices and satellite wings. It is also highly recommended as a material in medical stents for insertion into the human body because it has excellent organic compatibility. However, because they are intended to be inserted into the human body, products such as medical stents require a high-quality surface. Because nitinol has more of the characteristics of titanium than of nickel, one of its drawbacks is that heat generated in nitinol during machining is not discharged smoothly and inner stress occurs when traditional machining methods are used. To overcome this difficulty, various non-traditional machining methods, including non-contact machining, have been investigated for use with nitinol. To further explore non-traditional machining methods that may be appropriate for use with nitinol, this study investigates the application of electrochemical polishing to the machining of nitinol. Characteristics of the electrochemical polishing (EP), a representative non-traditional machining, for nitinol SMA are studied. Nitinol SMA of the EP machining parameters such as electrolyte composition, applied current, machining time and inter electrode gap (IEG) are researched and the machined surface state is analyzed according to each parameters parameter. So, the most suitable EP machining conditions for nitinol SMA are derived.
TL;DR: In this paper, He's Homotopy Perturbation Method (HPM) is used to analyze the nonlinear free vibrational behavior of clamped-clamped and clamped free microbeams considering the effects of rotary inertia and shear deformation.
Abstract: This paper uses He’s Homotopy Perturbation Method (HPM) to analyze the nonlinear free vibrational behavior of clamped-clamped and clamped-free microbeams considering the effects of rotary inertia and shear deformation. Galerkin’s projection method is used to reduce the governing nonlinear partial differential equation. to a nonlinear ordinary differential equation. HPM is used to find analytic expressions for nonlinear natural frequencies of the pre-stretched microbeam. A parametric study investigated the effects of design parameters such as applied axial loads and slenderness ratio. The effect of rotary inertia and shear deformation on the nonlinear natural frequency was investigated. For verification, a numerical approach was implemented to solve the nonlinear equation. of vibration. A comparison between analytical and numerical results shows that HPM can predict system nonlinear vibrational behavior significantly more accurately than previously used methods in the literature.
TL;DR: In this paper, a finite element method (FEM) free and forced lateral vibration analysis of beams made of functionally graded materials (FGMs) is presented, where the material properties are 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.
Abstract: 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 with the analytical solution and the results for ANSYS and NASTRAN software. Finally, dynamic responses were obtained for damped and un-damped systems. Numerical results were obtained to show the influences of the temperature dependency of the materials properties, the boundary conditions, the volume fraction distribution (the index of power law, N) and the geometrical parameters.
TL;DR: In this article, a new dynamic slip region method that combines the dynamic mesh method with the non-conformal grid boundaries is proposed to resolve the transient flows caused by the started impeller.
Abstract: Transient characteristics and flows in a centrifugal pump during its starting period were experimentally and numerically investigated. The two-dimensional particle image velocimetry technique was used to capture transient flow evolutions in the pump’s diffuser. A new dynamic slip region method that combines the dynamic mesh method with the non-conformal grid boundaries is proposed to resolve the transient flows caused by the started impeller. Numerical self-coupling was realized by establishing a circulation pipe system along with the pump model equivalent to the experimental pump system. Numerical and experimental results agree well in both explicit characteristics and internal transient flow structures, confirming the validity of the proposed method. Analysis of the instantaneous flow in the impellers indicates that for the early stage of the startup, the transient vortex evolution between blades is the main reason for the transient head coefficient being lower than the steady state value. The reversed flow at the blade inlet is a less important reason for this effect. In later stages, the weakening of the intensity of the spatial vortex visible on S2m and the main flow stream are the main reasons for the explicit performance slowly rebounding to the steady value.
TL;DR: In this article, a signal processing method for acoustic emission (AE) signal by envelope analysis with discrete wavelet transforms is proposed for early detection of bearing misalignment and bearing faults.
Abstract: Vibration analysis is widely used in machinery diagnosis, and wavelet transform and envelope analysis have also been implemented in many applications to monitor machinery condition. Envelope analysis is well known as a useful tool for the detection of rolling element bearing faults, and wavelet transform is used in research to detect faults in gearboxes. These are applied for the development of the condition monitoring system for early detection of the faults generated in several key components of machinery. Early detection of the faults is a very important factor for condition monitoring and a basic component to extend CBM (Condition-Based Maintenance) to PM (Prediction Maintenance). The AE (acoustic emission) sensor has a specific characteristic on the high sensitivity of the signal, high frequency and low energy. Recently, AE technique has been applied in some studies for the early detection of machine fault. In this paper, a signal processing method for AE signal by envelope analysis with discrete wavelet transforms is proposed. Through the 15 days test using AE sensor, misalignment and bearing faults were observed and early fault stage was detected. Also, in order to find the advantage of the proposed signal processing method, the result was compared to that of the traditional envelope analysis and the accelerometer signal.
TL;DR: In this article, an accurate calibration scheme of kinematic parameters is proposed by extending the conventional UMBmark, which remarkably reduces the systematic error of odometry using wheel encoders.
Abstract: Odometry using wheel encoders provides fundamental pose estimates for wheeled mobile robots. Systematic errors of odometry can be reduced by the calibration of kinematic parameters. The UMBmark method is one of the widely used calibration schemes for two wheel differential mobile robot. In this paper, an accurate calibration scheme of kinematic parameters is proposed by extending the conventional UMBmark. The contributions of this paper can be summarized as two issues. The first contribution is to present new calibration equations that remarkably reduce the systematic error of odometry. The new equations were derived to overcome the limitation of the conventional schemes. The second contribution is to propose the design guideline of the test track for calibration experiments. The calibration performance can be significantly improved by appropriate design of the test track. The numerical simulations and experimental results show that the odometry accuracy can be improved by the proposed calibration schemes.
TL;DR: In this article, a two-dimensional model with two-layer masses was used to simulate the transition zone of a railway track transition zone, where the slab track connects to a conventional ballasted track, where rigid culverts are placed close to the bottom of sleepers.
Abstract: Railway track transition zone is a zone where track stiffness changes abruptly. This change occurs where the slab track connects to a conventional ballasted track, at the abutments of open-deck bridges, at the beginnings and ends of tunnels, at road and railway level crossings, and at locations where rigid culverts are placed close to the bottom of sleepers. In this paper, ballasted and slab tracks are simulated by two-dimensional model with two-layer masses. The transition zone is divided into three segments, each having a length of 6 meters with different specification and stiffness. The model of track consists of a Timoshenko beam as a rail and slab, lumped mass as sleepers, and spring and damper as ballast, sub-grade, and rail pad. The results of the dynamic analysis are presented and compared in two circumstances — one considering the transition zone and the other its absence.
TL;DR: In this paper, the effect of five parameters, namely, sheet thickness, tool radius, step size, wall angle, and pre-straining level of sheet, on the profile accuracy of the produced part of AA1060 with SPIF is experimentally investigated.
Abstract: In single-point incremental forming (SPIF) process, a number of parameters are involved and need to be adjusted before the commencement of the forming operation. The inappropriate selection of these parameters could be detrimental to process accuracy. In this paper, the effect of five parameters, namely, sheet thickness, tool radius, step size, wall angle, and pre-straining level of sheet, on the profile accuracy of the produced part of AA1060 with SPIF is experimentally investigated. A response surface method is employed for the experimental design and regression analysis. The experimental results are presented in the form of graphical three-dimensional response surfaces. The results of ANOVA show that the sheet thickness, wall angle, step size, and the interaction between the sheet thickness and wall angle are extremely significant in terms of their effect on profile accuracy. Furthermore, an empirical model is proposed to achieve improved profile accuracy in terms of the optimized parameters.
TL;DR: In this paper, a method of modeling for vehicle crash systems based on viscous and elastic properties of the materials is proposed, which is suitable for localized collisions simulation. But it is not suitable for simulation of vehicle-to-pole collisions.
Abstract: In this paper, we propose a method of modeling for vehicle crash systems based on viscous and elastic properties of the materials. This paper covers an influence of different arrangement of spring and damper on the models’ response. Differences in simulating vehicle-torigid barrier collision and vehicle-to-pole collision are explained. Comparison of the models obtained from wideband (unfiltered) acceleration and filtered acceleration is done. At the end we propose a model which is suitable for localized collisions simulation.
TL;DR: In this paper, the temperature distribution on a fin is obtained using the residual theorem in a complex plan for the inverse Laplace transform method, and the thermal shock is generated at the base of the fin, which moves toward the tip of a fin and is reflected from the tip.
Abstract: Fourier and hyperbolic models of heat transfer on a fin that is subjected to a periodic boundary condition are solved analytically. The differential equation in Fourier and non-Fourier models is solved by the Laplace transform method. The temperature distribution on the fin is obtained using the residual theorem in a complex plan for the inverse Laplace transform method. The thermal shock is generated at the base of the fin, which moves toward the tip of the fin and is reflected from the tip. The current study of various parameters on the thermal shock location shows that relaxation time has a great influence on the temperature distribution on the fin. An unsteady boundary condition in the base fin caused the shock, which is generated continuously from the base and has interacted with the other reflected thermal shocks. Results of the current study show that the hyperbolic heat conduction equation can violate the second thermodynamic law under some unsteady boundary conditions.
TL;DR: In this article, a multi-scale simulation method is proposed to simulate filling during the micro-injection molding process, which is comprised of two steps. In the first step, the macro-scale flow is analyzed using the conventional method.
Abstract: This work proposes a multi-scale simulation method that can simulate filling during the micro-injection molding process. The multi- scale simulation is comprised of two steps. In the first step, the macro-scale flow is analyzed using the conventional method. In the sec- ond step, the micro-scale simulation is conducted taking the slip and surface tension into consideration to investigate the filling of micro- cavity. Moreover, a conservative level set method is employed to accurately track the flow front. First, numerical tests have been done for circular micro-channels. The results show that slip and surface tension play important roles in the micro-regime. Second, to verify the multi-scale method, filling of a thin plate with micro-channel patterns has been simulated. The results show that the proposed multi-scale method is promising for micro-injection molding simulations.
TL;DR: In this article, the effect of surface cracking on the relationship between the normal load and the square of scratch depth was studied, and a prediction model for the size of damage zone induced by lateral cracking was established and was compared with experimental results.
Abstract: In order to obtain the fundamental information on the deformation and fracture behavior of brittle materials during precision and ultra-precision grinding, micron and sub-micron scale scratch tests were conducted on optical glass BK7 using Vickers indenters. Three types of surface cracking were observed around the scratch grooves. They are lateral cracking, radial cracking and cracking in front of the moving indenter. It is found that lateral cracking is the main damage type due to its large damage size and low crack initiation load. The effect of surface cracking on the relationship between the normal load and the square of scratch depth was studied. The plastic zone size as well as the sliding blister field strength was expressed as a function of the contact zone size of the indenter. A prediction model for the size of damage zone induced by lateral cracking was established and was compared with experimental results.
TL;DR: In this paper, the authors present a mathematical model of a system describing the interaction between an unactuated ship and tugboats, which is solved by using the redistributed pseudo-inverse (RPI) algorithm to determine the thrust and direction of each individual tugboat.
Abstract: In harbor areas, precise ship steering is the most important operation. This requires a set of adequate thrust devices taking into account surge, sway and yaw motions precisely. However, the effectiveness of actuators during low-speed maneuvering is reduced, making it necessary to use tugboats to ensure safe berthing. In this paper, we present a mathematical model of a system describing the interaction between an unactuated ship and tugboats. Thrust allocation is solved by using the redistributed pseudo-inverse (RPI) algorithm to determine the thrust and direction of each individual tugboat. The main goal of this method is to minimize the power supplied to tugboats and increase their controllability. The constraints are twofold. First, the tugboat can only exert a limited pushing force, and second, it can only change directions slowly. Additionally, an adaptive control law is proposed to capture the draft coefficients of the ship, which are known as uncertainty parameters. The controller guarantees that the ship follows a given path (geometric task) with desired velocities (dynamic task). The specifications of Cybership I, a model ship, are used to evaluate the efficiency of the proposed method through Matlab simulations.
TL;DR: In this article, material ablation in nano-second region is simulated by using a finite element method (FEM) commercial package and its result has been compared with experiment results focused on the difference in the ablation depth and its shape occurred after each laser pulse hitting.
Abstract: For the pulsed laser ablation in nanosecond fields, the key physical phenomenon of the removing process is thermal evaporation. For the process optimization of the nano-second laser ablation, it is essential to set up effective simulation that can reflect material absorption coefficient, energy intensity of laser, laser pulse shape, and so forth. In this research, material ablation in nano-second region is simulated by using a finite element method (FEM) commercial package and its result has been compared with experiment results focused on the difference in the ablation depth and its shape occurred after each laser pulse hitting. Finally, the effect of the parameter variation on the ablation process has been verified.