bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Analysis of the System Ringing in Intermediate Strain Rate Tests
Authors: Qin Zihao , Li Wei , Zhu Juner , Xia Yong
Published: February 2017

Characterization of material property at intermediate strain rate is important in vehicle crashworthiness design. However, severe oscillations known as system ringing often exist at this range of strain rate, leading to undesirable data quality. Based on the two intermediate strain rate test machines in authors’ lab, including a hydraulic machine and a drop tower system, an experimental/numerical study is carried out to analyze the ringing phenomenon. Two principles for design of the load measurement chain derived from the simplified mass-spring-damper model and the structure of customized load sensor are concluded, and the practical designs and setups for reducing ringing are introduced. Finite Element models of the two test machines are constructed and different parameters in the design of the test setup and the tested specimens are studied based on the numerical simulations. Results show that the level of the system ringing largely depends on three aspects, the condition of the impact surfaces, the material properties and the test strain rate. Differences and similarities of the two test machines are discussed and the methods to reduce the oscillation are summarized.
A Variable-Gain Discrete Sliding Mode Control Strategy With PID-Type Sliding Surface for an Ultra-Precision Wafer Stage
Authors: Li Min , Zhu Yu , Yang Kaiming , Hu Chuxiong , Mu Haihua
Published: February 2017

The ultra-precision wafer stage is an important mechatronic unit in a wafer scanner for manufacturing integrated circuits while its motion control is still the main concern. To overcome the performance-limiting trade-offs of fixed-gain discrete sliding mode control (DSMC), a novel variable-gain DSMC strategy with PID-type sliding surface is proposed for an ultra-precision wafer stage. Specially, PID-type sliding surface is employed to avoid the steady-state error induced by external disturbances. Via the exponential reaching law approach, DSMC with PID-type sliding surface is synthesized. Variable-gain control methodology is newly introduced into DSMC, and the control gain varies with the trajectory phase that the wafer stage is in and the tracking error magnitude. Performance assessment on a developed wafer stage validates that with nano-scale tracking accuracy the proposed strategy not only improves the low-frequency tracking ability without the amplification of high-frequency noise, but also possesses the excellent robustness to external disturbances.
Experimental Study to Verify Elliptical Confidence Limit Method for Bolted Joint Tightening
Authors: Hareyama Soichi , Manabe Ken-ichi , Shimodaira Takayuki , Naganawa Takashi
Published: February 2017

The calibrated wrench method is often used for tightening. When tightening bolted joints, it is important to apply high axial tension. However, since the axial tension is indirectly applied in this method, it varies and has a distribution in the case of tightening carried out in the production line of a factory, for example. However, the calibrated wrench method is still widely used because of the simple tool and easy standardization. In our previous papers, we analyzed and discussed the main points of this research by a theoretical approach as discussed below. Conventionally, this type of distribution has been considered to lie within a rhombus (more precisely, within a rectangular area). However, when considering the tightening torque and axial tension as independent random variables, the distribution becomes elliptical. The same idea applies to the relation between the tightening torque and the equivalent stress for a bolt axis based on shear strain energy theory. On the other hand, regarding the variation in the tightening torque (tightening work coefficient a) actually applied to a bolt, it was reported by Bickford, Kawasaki, and others that it can vary by 15% or more from the target (indicated) tightening torque. However, the torques for wrenches used at actual assembly sites or under lubricated conditions were not reported. Therefore, it is necessary to experimentally verify that the relation between the tightening torque and the axial tension (axial stress) and equivalent stress of a bolt axis is distributed in an ellipse. Furthermore, the screw-thread characteristics (torque coefficient, equivalent stress coefficient, coefficient of friction, etc.) during the tightening process should be clarified by an experimental approach and observation. Thus, in this study, in experiments under dry (as-obtained) and lubricated (Loctite 263) conditions, the tool (preset-type and dial-type torque wrenches) and bolt strength classification (8.8 and 10.9) were changed, and the screw-thread characteristics were observed during actual bolt tightening and the characteristics under different conditions were analyzed. It was clearly shown that the tightening torque and the axial tension (axial stress) of a bolt axis and the equivalent stress vary with an elliptical distribution rather than a rhombic distribution. Finally, the validity of the tightening theory based on the elliptical confidence limit method was also verified experimentally.
Characterization of Fatigue Crack Propagation Under Complex Biaxial Loading
Authors: Neerukatti Rajesh Kumar , Datta Siddhant , Chattopadhyay Aditi , Iyyer Nagaraja , Phan Nam
Published: February 2017

Metallic aerospace components are subject to a variety of uniaxial and multiaxial loading conditions and therefore, characterizing and predicting the fatigue crack growth is of paramount importance to the aerospace industry. The fatigue behavior of metallic materials has been researched over the years and well understood under uniaxial loading conditions. However, aerospace structures are often subject to multiaxial loading and there are a very few studies reported on this topic. In this paper, extensive in-plane biaxial tension-tension fatigue tests were performed on an Al7075-T651 cruciform specimen under varying load conditions such as in-phase, out-of-phase and miniTWIST loading. The fatigue life and crack growth rate were evaluated and fractography was performed to understand the microscale crack initiation and growth under these complex loading conditions.
Post-Impact Thermo-Mechanical Response of Woven Mat Composites Subjected to Tensile Loading
Authors: Prakash Raghu V. , Sudevan Deepika
Published: February 2017

The thermo-mechanical response of carbon fiber reinforced polymer (CFRP) laminates subjected to continuous tensile loading and programmed interrupted tensile loading is examined to understand the changes due to damage progression. Quasi-isotropic laminates were prepared using 500 GSM twill weave carbon fabric with LY 556 resin and HY 991 hardener by hand lay-up technique, followed by curing under hot compression. A few specimens were subjected to an impact loading to 23 J and 51 J energy levels using a hemispherical tip to induce low velocity impact damage. Passive thermal imaging of woven CFRP laminates during tensile testing was captured using a TIM 160 Micro-epsilon infrared thermal camera. Temperature response during tensile testing provided a good correlation with deformation mode esp. for specimens impacted with 51 J of energy.

Tensile tests were interrupted at periodic loads and unloaded and reloaded to study the thermal response after prior plastic deformation damage in the specimen. Unlike the case of GFRP specimens, distinct changes in thermo-elastic slope due to prior plastic deformation damage could not be clearly identified. As impact damage resulted in de-lamination of some layers, active thermography technique was used to study the rate of cooling of specimen with time when the damage is closer to the camera face as well as when it is away from the camera face. The cooling curves obtained were found to be dependent on the location of the damage, as well as on heating face of the specimen.
Nonlinear Structural Behavior of Double-Layers Based MEMS Actuator
Authors: Al-oufi Abdulrahman , Ouakad Hassen M. , Firaque Mohammad Tausiff
Published: February 2017

In this paper, the static behavior of a micro-electromechanical system (MEMS) based on two electrically coupled parallel clamped-clamped microbeams is investigated. The assumed discretization technique in this investigation is the reduced-order modeling (ROM). The ROM was derived based on the Galerkin expansion method while assuming linear undamped mode shapes of a straight fixed-fixed beam as the basis functions. The results showed that the double-microbeam MEMS switch configuration requires a lower actuation voltage and a lower switching time as compared to the single microbeam actuator. Then, the effects of both microbeams air gap depths were investigated. Finally, the eigenvalue problem was investigated to get the variation of the fundamental natural frequencies of the coupled parallel microbeams with the applied actuating DC load.
Analysis of Vehicle Lateral Response During Regenerative Braking in a Turn
Authors: Nanda Kumar C. S. , Subramanian Shankar C.
Published: February 2017

Regenerative braking is applied only at the driven wheels in electric and hybrid vehicles. The presence of brake force only at the driven wheels reduces the lateral traction limit of the corresponding tires. This impacts the vehicle lateral response, particularly while applying the regenerative brake in a turn. In this paper, a detailed study was made on the impact of regenerative brake on the vehicle lateral response in front wheel drive and rear wheel drive configurations on dry and wet asphalt road surfaces. Simulations were done considering a typical set of vehicle parameters with the IPG CarMaker® software for different drive conditions and braking configurations along the same reference track. The steering wheel angle, yaw rate, lateral acceleration, vehicle slip angle, and tire forces were obtained. Further, they were compared against the conventional all wheel friction brake configuration. The regenerative braking configuration that had the most impact on vehicle lateral response was analyzed and response variations were quantified.
Simulation and Testing on Performance of the Woven Brush Seal in Vacuum Environment
Authors: Du Farong , Xu Zheng , Ji Fenzhu , Zhou Yu
Published: February 2017

The liquid lubrication is one of the most common lubrication modes in long-term space equipment, the sealing for liquid lubricants is thus important. Woven brush seal is motived by contact, which is able to achieve zero gap and thus have better performance than others. In this paper, we propose a woven brush seal system based on the model of porous medium with deformation of woven brush wire in anisotropic. For estimating the leakage and verifying availability of our system, we build calculation models by employing finite volume k-epsilon model and SIMPSON calculation method. Additionally, we run both simulation and experiments to evaluate our system, the calculation and experimental results show that: the leakage is much lower than traditional labyrinth seal, the amount of leakage increases gradually with the increase of rotational speed. The calculation method and boundary conditions are consistent with the actual situation. Namely, woven brush is able to satisfy the requirements in vacuum environment and thus considered as the corresponding seal component.
Research on the Simulation Method of Dynamic Response of High Voltage Circuit Breaker During Operation
Authors: Yang J. G. , Zhao K. , Pan Y. , Liu X. D.
Published: February 2017

High voltage circuit breaker (CB) is one of the most important components in high voltage circuit. In the process of operation, some kinds of mechanical faults such as jam fault, component deformation and component failure may occur and affect the performance of the circuit breaker. But, generally it is difficult to diagnose these faults. To obtain the characteristics of these faults in the high voltage circuit breaker, in this paper, a simulation method for high voltage circuit breakers is investigated. Firstly, the dynamic models of the operating mechanism of the high voltage circuit breaker are established and the simulations are performed; then the vibration signals at the monitoring points can be obtained based on finite element simulation. Based on these signals, the characteristics of some typical mechanical faults may be researched. The work in this paper is helpful to recognize the failure mechanism of the high voltage circuit breaker and improve the veracity of the fault diagnosis.
The Effects of Cubic Stiffness Nonlinearity on the Attenuation Bandwidth of 1D Elasto-Dynamic Metamaterials
Authors: Banerjee Arnab , Calius Emilio P. , Das Raj
Published: February 2017

Metamaterials demonstrate unique frequency dependent responses due to the presence of internal resonators; hence, it can be used to filter, absorb, cloak, or otherwise manipulate waves in unique ways. However, its applicability is normally limited to a very narrow frequency range (bandwidth) due to a dependency on linear resonance. The applications of these linear metamaterials are limited when used under the broadband excitation spectra that are common in real life applications. This paper numerically investigates the effect of introducing the two main classes of Duffing type cubic nonlinearities, namely monostable and bistable, on the attenuation bandwidth of an elasto-dynamic metamaterial.

From the analysis, it is found that the attenuation bandwidth of a bistable nonlinear system is two to three times wider than that of an equivalent linear system; whereas, in case of a monostable system the bandwidth is remained same. In both cases, the attenuation bandwidth shifts towards the higher end of the frequency spectra and for higher nonlinearity and excitation amplitude, second transmission zone completely vanishes.
A Multibody Dynamics Approach for Vibration Analysis of Horizontal Axis Wind Turbine Blades
Authors: Jiang Songyi , Duan Shanzhong (Shawn)
Published: February 2017

This paper presents a 4-rigidbody segment model to describe a generic flexible blade of a horizontal axis wind turbine (HAWT). The element is made up of four rigid bodies in a chain structure fashion. The bodies of each element are connected by two universal joints at two ends, and one cylindrical joint in the middle. So each element possesses six degrees of freedom, including four degrees of freedom for bending, one degree of freedom for axial stretching, and one degree of freedom for torsion. A spring is applied for each degree of freedom to describe the stiffness of the component. Through potential energy equivalence between a Timoshenko beam and these springs, the stiffness of each spring is calculated. A blade can then be simplified to several such elements connecting together.

With the 4-rigidbody segment model, blades of a HAWT are built up. Their equations of motion are then derived through Kane’s equations. The commercial computational multibody dynamic analysis software Autolev is applied for motion and vibration simulation of blades under given initial conditions. Simulation results indicate that the 4-rigidbody segment model is appropriate to analyze dynamic loads, modal, and vibration of HAWT blades for fixed and moving references at high computational efficiency and low simulation costs. The method can also be served as a good solution to simulate dynamical behaviors of wind turbines and avoid their fatigue failures in time domain.
Bifurcations and Uncertainty Quantifications in Nonlinear Acousto-Elastic Systems
Authors: Remigius W. Dheelibun , Sarkar Sunetra
Published: February 2017

The study of nonlinear aeroelastic instability mechanism of nonconservative acousto-elastic system is the focus here. The acousto-elastic system consists of a spinning disc in a compressible fluid filled enclosure. The nonlinear rotating plate is coupled with the linear acoustic oscillations of the surrounding fluid. Based on the acousto-elastic theory, the coupled field equations are discretized and solved for various rotation speeds in order to obtain the coupled system dynamics. The study shows that the coupled system undergoes a flutter instability at a particular rotation speed and the instability takes the form of supercritical Hopf bifurcation. Subsequently, the effect of randomness associated with the structural and the acoustic damping parameters are quantified on the nonlinear instability behaviour by means of a spectral projection based polynomial chaos expansion technique.
A CFD (Computational Fluid Dynamics) Based Thermal Performance of Solar Air Heater With Rib-Roughened Channels
Authors: Qureshi Mumtaz Hussain , Shakaib M.
Published: February 2017

Computational Fluid Dynamics (CFD) study is conducted to determine turbulent fluid flow and temperature profiles in rectangular ribbed channels of solar air heater. The results show significant effect of Reynolds number and ribs height and pitch on turbulence and heat transfer rates. When heat flux is defined at the bottom wall, the temperature values increase rapidly near the ribs due to stagnant zones. The heat transfer coefficients are lower at these locations. When heat flux is specified at the top wall, the variation in heat transfer coefficient is relatively smooth. From the research work, the channel containing ribs of 3mm and pitch 40mm are determined suitable due to higher heat transfer rates.
Pressure Effects on the Thermal Properties of Graphite
Authors: Cai Shuang , Liu Chenhan , Tao Yi , Duan Zaoqi , Chen Yunfei , Dong Yun
Published: February 2017

In this paper, the thermal properties of graphite under external pressure were systematically investigated based on first-principles calculations and Boltzmann transport equation (BTE). This method is relatively simple and general to any other crystals. It was found that a compressive pressure can significantly increase the interaction between the layers in graphite and increase the phonon group velocity, the phonon mean free paths, thus the cross-plane thermal conductivity decreases. The effects of pressure on the in-plane thermal conductivity are much weaker than those on the cross-plane value. Our results indicate that the thermal properties of graphite can be strongly modulated by pressure engineering. Moreover we extracted the phonon dispersion and phonon lifetime of graphite under or without external pressure. And changes in the density of states and the cumulative thermal conductivity under 12GPa pressure are analyzed by comparing with no pressure. Our investigation here provides a physical insight into the modulation and heat transfer mechanism of graphite theoretically, which can help the design of graphite-like materials in experiment and practical application.
Effect of Thermal Radiation on Accuracy of Restricted Domain Approach in a Square Open Cavity
Authors: Singh Om , Singh Suneet , Kedare Shireesh B.
Published: February 2017

To reduce computational time for simulation of natural convection in open cavities, it is quite common to use a domain restricted to the cavity with approximate boundary conditions at the cavity opening. It had been shown that such approach leads to quite accurate solutions for high Rayleigh number (Ra) flows. Such approach has been extended to flows involving radiative heat transfer as well. However, it is important to note that the effect of radiation on the accuracy of restricted domain approach has not been evaluated. In the present work, a comparison of Nusselt numbers is obtained by restricted domain approach with those obtained by using extended domain approach. The convective as well as radiative Nusselt numbers are considered for comparison for various values of Ra and radiation conduction parameter (Nr). It is observed that the accuracy of the restricted domain approach varies with the radiation conduction parameter as well and the approach is found to be quite accurate for high values of Nr.
Transient Modelling of Pneumatic Valves in Centrifugal Microfluidic Devices
Authors: Moon Michael R. , Lin Lin
Published: February 2017

Point of care medical instruments benefit from compact fluid handling systems in the microliter range. To handle fluid volumes this small, many novel technologies have been studied. Pneumatic valves offer advantages over other microfluidic valves, including robustness and low cost. These valves are used in centrifugal microfluidic devices, a very active area of research, and take advantage of pneumatic and centrifugal pressure to aliquot and control the flow of fluid. The physics of fluids at the micrometer scale are complex and modelling their behavior using CFD software is challenging. Representing adhesion, surface tension, and other multiphase interactions is critical to accurately model microfluidic behavior. Centrifugal devices must also consider Coriolis, centrifugal, and Euler effects.

In this study, a pneumatic valve was designed and simulated using commercial CFD software. The device was also fabricated for verification of the simulation. The simulation demonstrated the multiphase interactions of fluid and air within the rotating device. In a transient analysis of the model, a 6 μl volume of water is held in stable equilibrium by a compressed volume of air at low RPM, while at a higher RPM, the fluid is observed to displace the compressed air as a result of Rayleigh-Taylor instability. Actual devices with comparable geometry were built and tested. The behavior of the valve predicted in the model was in agreement with experimental results produced from the actual devices. The results of the simulation captured the stabilizing effect of both pneumatic pressure and surface tension at low RPM, as well as the instability that results from increased centrifugal and Euler pressure at higher RPM.
Simulation of the Flow Over the CAARC Standard Tall Building Using Different LES Turbulence Models
Authors: Lygidakis Georgios N. , Sarakinos Sotirios S. , Nikolos Ioannis K.
Published: February 2017

The simulation of unsteady turbulent flows remains a significant problem in CFD despite the tremendous advances in the performance of supercomputers during the past decades. Considering this state, the enhancement of the in-house academic CFD solver Galatea-I with the LES approach is reported in this study. LES is actually a compromise between the RANS and DNS methods, entailing though increased accuracy, comparing to the first one, and less computational load than the second. Particularly, four Sub-Grid Scale models have been incorporated, namely, the Smagorinsky, the WALE, the dynamic Germano-Lilly and the dynamic kinetic energy one. They were validated against a real 3D problem, concerning turbulent flow over the CAARC standard tall building model, a specially designed geometry for wind tunnel experiments on tall buildings. Independently of the implemented modelling approach, the extracted results appear to be close with the available experimental and numerically computed data, confirming the potential of Galatea-I to encounter such simulations. The last two models are revealed to be the most accurate ones, a conclusion actually expected due to their more sophisticated formulation. An additional simulation was performed with the RANS approach and the SST model, which confirmed the superiority of the LES methodology in terms of accuracy.
The Phonon Dissipation Mode in Nanofriction
Authors: Duan Zaoqi , Cai Shuang , Zhang Yan , Chen Yunfei , Dong Yun
Published: February 2017

The phonon dissipation is investigated through molecular dynamics (MD) simulation modeling graphene flake sliding on supported graphene in this paper. With the help of the advantage of MD, we explore the phonon mode variation of the substrate induced by the behavior of friction in terms of phonon densities of states. Moreover, phonon dissipation modes connected with the relative sliding velocity and the temperature of system are established respectively. The simulation results demonstrate phonon dissipation is represented as special phonon frequencies while those are closely related to the sliding velocities but would not shift as the change of temperatures. For an explanation of the special frequencies, we further simplify the model by directly adding the velocity to the atoms of the flake in the MD model, although it is impractical. It is found that a special frequency of phonon dissipation is generally in agreement with the sliding frequency at low temperature eliminating the interference of temperature in a range of velocities from 50m/s to 250m/s, namely, the velocity is directly related to the modes of phonon dissipation and friction, which is consistent with the previously reported result[1] that the velocity is an influence factor for friction both in experimental and theoretical researches. Therefore, the relationship makes possible the active control of friction. It is the first step toward using this method to reveal the fundamental questions in the study of atomic-scale friction.
Influence of Solution pH on DNA Translocation Velocity Through Alumina Nanopores
Authors: Yang Haojie , Duan Zaoqi , Si Wei , Li Kun , Chen Yunfei
Published: February 2017

Nanopores, which are promising as single-molecule sensing devices with low cost and high throughput, have offered significant insights into the research fields of static and dynamic molecular activities, properties, or interactions. In particular, due to its inherent sensitivity, high throughput, amplification-free sample preparation, nanopore will be potentially used in DNA sequencing. Nanopore-based sequencing is based on Coulter Counters, by measuring the distinct current reductions from individual DNA bases with different sizes as they are translocating through a nanopore. The sub-molecular details of an individual molecule can be gathered via recording modulations in the ionic current when a molecule passes through the nanopore under a bias voltage applied across the pore by two Ag/AgCl electrodes. The current blockage and dwell time obtained when the dsDNA translocates through nanopore are accumulated into scatter plots. Ionic current trace recorded at 1000 mv as 48kbp dsDNA translocate through 20 nm thickness with 35 nm alumina nanopore. Here, we apply Schrödinger’s first-passage-time distribution formula to study the distribution of DNA translocation time through alumina nanopores. The first-passage-time distribution is solved with the production of Fokker-Plank equation. Two useful parameters yielded the experimental results are analyzed: the diffusion constant of DNA inside the nanopore and the drift velocity of DNA translocation. By changing the pH value from 5.2 to 10.8 of the electrolyte solution, we notice that the drift velocity of DNA translocation and the diffusion constant of DNA inside the nanopore are extremely close to almost as 34 nm/μs. By changing the pH value of the electrolyte solution, we find that the surface charge density of the wall and the charge of the DNA molecule can be turned, which will result in different DNA molecule capture behaviors. The capture rate is about 17 s−1; the DNA molecule translocates through nanopore when the solution pH is 10.8; and 20 s−1 as the solution pH is 5.2. Theoretical modelling has also been conducted to analyze the experimental results. Hopefully, these findings will shed light on the transport properties of DNA in nanopores, which are relevant to future nanopore applications.
An Improved Model-Free Sampling Technique Based on Bootstrap Methods
Authors: Yu Xinshui , Yang Zhaohui , Song Kunling , Yu Tianxiang , Guo Bozhi
Published: February 2017

The distribution and parameters of the random variables is an important part of conventional reliability analysis methods, such as Monte Carlo method, which should be known fist before using these methods, but it is often hard or impossible to obtain. Model-free sampling technique puts forward a method to get the distribution of the random variables, but the accuracy of the extended sample generated by it is not enough. This paper presented an improved model-free sampling technique, which is based on Bootstrap methods, to increase the accuracy of the extended sample and decrease the iteration times. In this improved model-free sampling technique, the method of the selection of initial sample points and the generation of iterative sample is improved. Meanwhile, a center distance criterion, which considers the local characteristics of the extended sample, is added to the generating criterion of dissimilarity measure. The effectiveness of this improved method is illustrated through some numerical examples.
On the Use of Improved Radial Basis Functions Methods in Fluid-Structure Interaction Simulations
Authors: Strofylas Giorgos A. , Mazanakis Georgios I. , Sarakinos Sotirios S. , Lygidakis Georgios N. , Nikolos Ioannis K.
Published: February 2017

The development of an efficient partitioned FSI coupling scheme is reported in this paper, aimed to facilitate interaction between an open-source CSD software package and an in-house academic CFD code. The coupling procedure is based on Radial Basis Functions (RBFs) interpolation for both information transfer and mesh deformation, entailing no dependence on connectivities, and hence making it applicable to different type or even intersecting grids. However, the method calls for increased computational resources in its initial formulation; to alleviate this deficiency, appropriate acceleration techniques have been incorporated, namely the Partition of Unity (PoU) approach and a surface-point reduction scheme. The PoU approach was adopted in case of data transfer, localizing the interpolation process and therefore reducing the size of the coupling matrix. An alternative approach was applied to improve the efficiency of the mesh deformation procedure, based on the agglomeration of the flow/structure interface nodes used for the RBFs interpolation method. For the demonstration of the proposed scheme a static aeroelastic simulation of a real bridge model, during its construction phase, was performed. The extracted results exhibit its potential to encounter effectively such complicated test cases, in a computationally efficient way.
Stress Evaluation of Articular Cartilage Chondrocyte Cell by Using Multi-Scale Finite Element Method and Smoothed Particle Hydrodynamics Method
Authors: Nakahara Kaito , Morita Yusuke , Tomita Yoshihiro , Nakamachi Eiji
Published: February 2017

The morphology and function of articular cartilage tissue is regenerated through the metabolic activity of cells stimulated by the mechanical loading. In this study, a biphasic multi-scale analyses scheme is adopted for stress evaluation occurred in the chondrocyte cell. The dynamic-explicit finite element (FE) method was employed for the solid phase and the smoothed particle hydrodynamics (SPH) method was used for the fluid phase. A macro-scale 3D human knee joint FE model was constructed based on magnetic resonance (MR) cross sectional images. Further, we derived the Representative volume element (RVE) based on the Multiphoton microscopy (MPM) observation to build a micro-scale FE model of cartilage tissue. We characterized three layers in the articular cartilage tissue. Parameters of the visco-anisotropic hyperelastic constitutive law and SPH models were determined using experimental results. Biphasic multi-scale FE and SPH analyses were carried out under the maximum loading condition in the normal walking motion.

As a result, large flow velocity was observed around chondrocyte in the surface layer. The highest hydrostatic and shear stress occurred on chondrocyte in the surface layer. Numerical results shows a good agreement with experimental results.
Effect of the Gradient Magnetic Field Stimulation on Extracellular Matrix Synthesis of Chondrocyte
Authors: Saito T. , Morita Y. , Nakamachi E.
Published: February 2017

Many researchers tried to improve mechanical properties of the cultured cartilage by physical stimulation. However, its mechanical properties were insufficient. Extracellular matrix structure similar to natural articular cartilage is necessary to form mechanical properties of cultured cartilage. Gradient magnetic field was expected to change pericellular microenvironment associated with local chondrocyte activity. We investigated the effects of gradient magnetic field on chondrocyte activity and extracellular matrix structure.

Chondrocytes were cultured under the gradient magnetic field for 7 days, and stimulation time was 12 hours in a day. Intensity of magnetic field was 1.5 mT in the center of a dish. Intensity of gradient magnetic field was 0.03 mT/mm. Chondrocytes were cultured under the uniform magnetic field for control group. The synthesized extracellular matrix in a dish was observed with second harmonic generation, and GAG amount was measured after cultivation.

GAG amount in the gradient group was almost same with that in the uniform group. According to SHG image, the area and the thickness of extracellular matrix increased with increasing intensity of magnetic field in the gradient group. This study showed that the gradient magnetic field stimulation formed difference in extracellular matrix structure which depends on local chondrocyte activity.
Nonspherical Dynamics and Shape Mode Stability of Ultrasound Contrast Agent Microbubbles
Authors: Neu Sean S. , Brlansky John T. , Calvisi Michael L.
Published: February 2017

Ultrasound contrast agents (UCAs) are shell encapsulated, gas-filled microbubbles developed originally for ultrasound imaging enhancement. UCAs are approximately 1–10 micrometers in diameter with a shell typically comprised of lipid, protein, or polymer. When injected into the bloodstream, the high compressibility of these microbubbles, relative to the surrounding blood and tissue, and their highly nonlinear response to ultrasound, leads to strong enhancement of the blood-tissue contrast in the resulting ultrasound image. While UCAs have been commercially available since the early 1990’s [1] for ultrasound imaging, they are more recently being exploited for therapeutic applications, for example, as vehicles for drug delivery and gene therapy, and thermal and mechanical tissue ablation. The effectiveness of UCAs in therapeutic applications depends strongly on the nonspherical character of the bubble oscillation, which can effect the breakup and release of therapeutic agents from the UCA, as well as the formation of high-speed jets near the tissue interface. In this work, two different models for nonspherical oscillation of UCAs are presented: one for small shape oscillations of a lipid-coated bubble, and one for large nonspherical oscillations of a polymer-coated bubble. Nonspherical shape mode stability and dynamics are investigated with each model for ranges of ultrasonic frequency and amplitude relevant to medical applications.
An Enhanced Development of 3D Intra-Oral Scanner Using Fringe-Projection Technique for Dentistry
Authors: Park Hong-Seok , Shah Chintal , Shah Rima
Published: February 2017

3D shape recognization technique is rapidly advancing from last decade in the fields of manufacturing, computer science, entertainment and medical technology. Due to the restriction of size and area of cavity, it’s challenging to develop such non-contact optical technologies for scanning. 3D digitization technology plays a vital role in the field of dentistry benefiting dentists and patients by eliminating long time procedures for making the prosthesis/abutments and results into ultimate comfort. In this paper, we have recounted a design of a prototype for a three-dimensional intra-oral scanner using the principle of fringe projection and active triangulation method. LED as a light source passed through the liquid crystal on silicon (LCoS) which radiates the light into three colors and strikes onto the collimating lens assembly and then passed through the optical deflectors. Once the light strikes the object through scanning window it is guided back through the flat reflectors and the fringe pattern on the object is stored into the gray encoding plate. With the help of camera all these images are stored. After the acquisition of images, firstly it will calculate the phase distribution using four-step phase shifting algorithm and unwrap the wrap phase which helps us in getting accurate images. Later, we get display of scanned oral cavity onto the computer screen. Phase-height mapping algorithm has been realized for the reconstruction of the 3D real time reconstruction of the scanned oral cavity which helps us in fast scanning with accurate data. A novel approach of LED as a light source and LCoS display for scattering light fragments into three different colors helps us to scan more effectively for registration of dental surfaces from the patient’s mouth more accurately. Apart from that, its sleek design helps to scan with less pain to the patient’s having low mouth opening. Experiment was performed on the prototype of denture and using this proposed method we have achieved the accuracy of 25μm and it took around 180 sec for the full arc scan of the lower oral cavity. The result of scanned data was checked using the CAD/CAM software for dentistry and compared with the prototype data of denture. Further this image can be used for making prosthesis/abutment directly into production using 3D printing machine or the milling machine. Thus, an abutment or prosthesis obtained with this method is of high quality and eliminates conventional long procedures which helps in reducing pain of patient’s and helps dentists to attain more patients in less time.
Fatigue Crack Growth Behavior of Hybrid Glass Fiber Laminates With Embedded Functionalized Carbon Nanotube Membranes
Authors: Datta Siddhant , Yekani Fard Masoud , Chattopadhyay Aditi
Published: February 2017

This study focusses on investigating the fatigue crack growth behavior in glass fiber laminates embedded with carbon nanotube membranes consisting of different functional groups. In addition to fatigue behavior, quasistatic tensile properties were analyzed to gain better insight into the mechanical properties of these hybrid glass fiber laminates. It was found that tensile strength of the laminates increased by embedding the carbon nanotube membranes but elastic moduli showed different trends with respect to the type of functionalization that was done on the embedded carbon nanotube membranes. Fatigue life was seen to considerably increase in the case of amine functionalized and pristine carbon nanotube membrane embedded GFRPs.
Two-Scale Thermo-Crystal Plasticity Finite Element Analysis of Dynamic-Recrystallization Texture Evolution
Authors: Ueda Yuhei , Goto Yu , Yamaguchi Toshihiko , Tomita Yoshihiro , Morita Yusuke , Nakamachi Eiji
Published: February 2017

In order to predict dynamic recrystallization (DRX) texture evolution during the forming processes of aluminum alloy, we propose a hypothesis to predict DRX evolution and develop a comprehensive computational tool for the thermal process metallurgy simulation. It consists of the two-scale finite element method based on the thermo-coupled elasto-crystalline plasticity analysis and the dynamic-explicit finite element procedure. It can predict the heat generation and diffusion, and plastic anisotropy at the macro-scale, and the crystal texture evolution including DRX due to the plastic deformation and heat generation at the micro-scale.

The computationally evaluated texture evolution, which includes DRX texture, under the severe compression at high temperature is compared against the experimental results of pole figures and orientation distribution function (ODF) analyses. The results predict the evolution of the cube component which is observed in the experiments. Therefore, our proposed method is approved to have a potential predicting DRX texture evolution. Furthermore, we clarify the effect of DRX texture on the onset of such instabilities as necking, surface instability and shear bands which are closely related to the formability or failure of the materials.
Measurement and Evaluation of Temperature Change of Water Driven Spindle
Authors: Hayashi Akio , Nakao Yohichi
Published: February 2017

Recently, various precision products such as lenses or mirrors are produced by the ultra-precision machine tools. Then, the single-point diamond cutting is mainly carried out using the ultra-precision machine tool. In order to generate the high accuracy and high quality machined surfaces, the high stiffness and precise rotational accuracy of the spindle is required for the ultra-precision machining tools.

The water driven spindle had been developed for the precision machine tool spindle. This spindle is driven by the generated torque due to the water flow power. Then, the rotational speed can be controlled by the supplied flow rate of water. In addition, the spindle has the water hydrostatic bearings that achieve the high bearing stiffness and precise motion accuracy. Furthermore, it is expected that the water driven spindle has the high thermal stability since the water with low viscosity is used as a coolant media.

If the thermal deformation of the spindle is caused during the machining process, the deformation degrades the machining accuracy, accordingly. Thus, it is desirable that the thermal deformation and the temperature change of each part of the spindle and machine tool structure can be controlled and minimized during machining process.

In this paper, in order to investigate the thermal stability of the water driven spindle, the measurement tests of the temperature of the water driven spindle were carried out. In addition, the power loss due to the water viscosity between the rotor and the casing of the spindle is calculated.

As a result, this paper considers the temperature change and considers the thermal stability of the water driven spindle from the results of experiments.
CFD Modeling the Cooling Stage of Reflow Soldering Process
Authors: Ferreira Ana C. , Teixeira Senhorinha F. C. F. , Oliveira Ricardo F. , Rodrigues Nelson J. , Teixeira José C. F. , Soares Delfim
Published: February 2017

Reflow soldering is one of the most widespread soldering technologies used in the electronics industry. It is a method of attaching surface components to a circuit board with solder paste. The goal of the reflow process is to melt the solder and heat the adjoining surfaces, without overheating and damaging the electrical components. In the present study, computational fluid dynamics (CFD) was used to investigate the convection flow field during the cooling reflow process stage. The convection heat-transfer coefficient and temperature distribution within the board level were also studied. The analysis comprises three main objectives: (1) the simulation of the cooling process of a PCB in the final section of the reflow oven; (2) the calculation of the heat transfer from the PCB to the air as the PCB moves throughout the woven; and (3) use a “dummy” PCB with two generic components with different dimensions and analyze the heat dissipation. The geometry definition, the mesh generation, as well as the numerical simulations were carried out using the Workbench™ platform from ANSYS® 15. It was programmed an UDF to represent the relative motion between the PCB and the cooling air flow. Results shown that, during the cooling process, there is a gradient over the PCB board. It is also observed that there is a small differentiation in the temperatures’ profile along the board length probably because of the formation of recirculation areas inside the oven. Thus, nozzle spacing has a great impact in the formation of those recirculation areas, and consequently in heat dissipation.
Hydrogen Generation From Acetic Acid Catalyzed Magnesium Hydride Using an On-Demand Hydrogen Reactor
Authors: Jen Tien-Chien , Adeniran Joshua , Akinlabi Esther , Chao Chung-Hsing , Ho Yen-Hsi , De Koker Johan
Published: February 2017

This study reports an acetic acid catalyzed hydrolysis reaction for hydrogen generation from magnesium hydride (MgH2) using an on-demand hydrogen reactor. Acetic acid, a weak and benign organic acid, has been reported as a single catalyst in hydrolysis reaction for hydrogen generation using other substrates, but this is the first study where acetic acid has been employed as a catalyst in a magnesium hydride hydrolysis reaction for hydrogen generation. In this study, the effects of MgH2 weight, acetic acid concentration and external temperature on hydrogen generation from MgH2 were examined. The results of the hydrolysis reaction indicated that the weight of MgH2 was the major factor influencing hydrogen generation, followed by the concentration of acetic acid while the effect of external temperature was insignificant. Similarly, hydrogen yield was proportional to the weight of MgH2 with a reported maximum hydrogen yield at each weight been: 0.4g (∼ 0.07 L); 0.8 g (∼ 0.125 L) and 1.2 g (∼1.285 L). The successful use of acetic acid in the study reinforced the versatility of the on-demand hydrogen reactor and as a scalable technology for hydrogen generation.
Actuation of Parabolic Cylindrical Shell Panels With Light-Activated Shape Memory Actuators
Authors: Li Huiyu , Zhang Xufang , Tzou Hornsen
Published: February 2017

Parabolic cylindrical shell panels are used in optical and aerospace structures. Light-activated shape memory polymer (LaSMP) is a novel smart material and it is capable of offering a non-contact actuation and control in room temperature. In this study, the parabolic cylindrical shell panels laminated with LaSMP actuators are analyzed. Firstly the dynamic equations of the parabolic cylindrical shell panels coupled with the LaSMP actuators are established; the modal control force of LaSMP actuators is derived with the modal expansion method. Then the strain variation of the LaSMP actuators are modeled based on the chemical kinetics. Further, the shape-memory recovery effect of an LaSMP actuator with initial strains is measured in laboratory. The experiment data of strain variation are used to validate the established strain model. Finally, in the case study the modal control forces of LaSMP actuators for the first four shell modes, i.e., the (1,3), (1,4), (2,4) and (2,5) modes are analyzed. The study shows that LaSMP actuators can induce strains not only in the x, Ψ directions but also in the xΨ direction (induced by the warping effect). The reason is that LaSMP actuators are easy to be cut in any shapes and be deformed in any directions. Thus, LaSMP actuators have potential applications for the non-contact vibration control of double-curvature shells.
A Simplified Exact Compliance Normal-Directional Contact Model
Authors: Banerjee Arnab , Chanda Avishek , Das Raj
Published: February 2017

Contact is the most abundant phenomena in the field of multi-body dynamics, experienced when two or more bodies come in close vicinity to each other. During contact, one body virtually penetrates within other and therefore is subjected to a large impulsive force due to the deformation; this is the essence of the compliance based models. Subsequently, different compliance models were proposed, each having a different formulation for the impulsive force variation, which is always a function of time and deformation. A novel multi-linear compliance model, calculated on the basis of the Poisson’s law, is introduced in this work. The responses of all the available compliance models have been critically reviewed in previous studies and using the same study and the observed significant models, a comparative study is presented in this work for establishing the proposed model. A few significant models were selected according to the minimum amount of error induced by each while estimating the coefficient of restitution, impulse, and dissipating energy.

The contact force-penetration relationship in the compression phase and restitution phase are assumed to be linear with a sharp jump at their transition. The slope of the compression phase of the force-displacement diagram of the non-dimensional system is exactly as desired (1+coefficient of restitution) and moreover, the slope of the restitution phase is equal to the coefficient of restitution helping in retrieving the exact coefficient of restitution pertaining in the pre-impact condition. Also, the post-impact coefficient of restitution, impulse, and dissipating energy are exactly accurate, having 0% error, in accordance with that of the stereo-mechanical model, for the full range of the co-efficient of restitution.