bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Free Vibration Analysis of a Sandwich Beam With Tip Mass
Authors: Joubaneh E. F. , Barry O. R.
Published: January 2019

This paper presents the free vibration analysis of a sandwich beam with a tip mass using higher order sandwich panel theory (HSAPT). The governing equations of motion and boundary conditions are obtained using Hamilton’s principle. General Differential Quadrature (GDQ) is employed to solve the system governing equations of motion. The natural frequencies and mode shapes of the system are presented and Ansys simulation is performed to validate the results. Various boundary conditions are also employed to examine the natural frequencies of the sandwich beam without tip mass and the results are compared with those found in the literature. Parametric studies are conducted to examine the effect of key design parameters on the natural frequencies of the sandwich beam with and without tip mass.
Identification of Vehicle Inertia Parameters: From Test Bench Design to Movement Trajectory Optimization
Authors: Yao Di , Büttner Kay , Prokop Günther
Published: January 2019

This work presents a new systematic solution to identify the vehicle inertia parameters which are essential inputs for vehicle simulation and vehicle safety research. In conceptual design phase of this work, a virtual three Degree-of-Freedom (DoF) test bench/ parallel manipulator (PM) whose moving platform is used to clamp vehicle under test is developed. In order to realize the kinematic characteristics of the proposed PM, the kinematic analysis consists of inverse kinematic and singularity architecture is carried out. Aiming at obtaining all ten vehicle inertia parameters (i.e., mass, center of gravity and inertia tensor), the observation matrix for parameter identification is derived from the dynamic model of PM. To get the dynamic model, the Euler’s equation and Lagrange approach are applied to implement the dynamic analysis for PM’s moving platform and actuators, respectively. It is beneficial to reduce the complexity of dynamic model and load of numerical computation. In the following section, to minimize the sensitivity of parameter identification to measurement noise, an optimization process of searching for the optimal movement trajectory of PM is proposed. For this purpose, the parameterized finite-Fourier-series are used to definite the general movement trajectory of PM firstly. Subsequently, the parameters of general trajectory are optimized by employing a nonlinear iterative algorithm. Objective of this algorithm is to obtain the minimal condition number of observation matrix and meanwhile to ensure the PM still works in the achievable working space during the test. The results show that the vehicle inertial parameters can be effectively identified by executing the single optimal movement trajectory on the PM. It is expected that the proposed systematic solution could be an important approach to improve the identification efficiency and identification accuracy of vehicle inertial parameters.
Improve Enterprise Resources Management Through the Usage of IoT in the Shopfloor
Authors: Cunha Adriana , Silva João
Published: January 2019

Industrial demand has changed and present increasingly demanding requirements. Companies need to evolve and innovate to be able to go along and fulfill its customers requirements. Currently, major players have the capacity, resources and money, to install the most innovate and expensive machines, tools and devices on its shop-floor. SMEs on its side, face several challenges to manage its limited resources. SME aims to maximize the usage of the available resources to continue its activity and if possible to grow. The usage of low-cost IoT devices allow companies to monitor the usage of its resources and the quality of its products without the need to made a huge investment that wouldn’t be affordable for them.

The results presented were a result of the C2NET Project that was designed to comprehensively cover the entire supply chain considering all stages of manufacturing, distribution and sales to supply a product to market.

The results achieved were able to fulfill specific needs of the industrial partners of the project, and were validated by 6 companies from Automative, DermoCosmetics, Metalworking and OEM (Original Equipment Manufacturer) Industries from Spain, France, Portugal and Finland.[1] A Metalworking SME was used as an use case due to its complexity and diversity, although most of the achievements can be replicated in other industries, even the more traditional ones.
Investigation of Non-Pneumatic Tires Based on Helical Hexagonal Cellular Structure
Authors: Pewekar Mihir Mangesh , Sandye Pranit Pravin , Chaudhari Kiran
Published: January 2019

Non-pneumatic tires (NPTs) have drawn attention mainly due to low contact pressure and low rolling resistance due to use of hyper-elastic materials in their construction. In this paper, an attempt to innovate the conventional design of NPT with hexagonal honeycomb cellular structure is made by creating the boundary planar geometries of the tire, skew to each other at a certain angle. Adding to the functionality as a tire, this modified structure increases the performance of automobile components by rejection of heat through convection (forced) at the expense of engine power. The primary investigation includes study of the effects of variation in degree of skewness with the strength and flow of air through the tire. The flow parameters are computed for rotational case and the heat transfer is computed for flow over a brake disk. The secondary investigation consists of finding an optimum range of the degree of skewness. The validation for strength is computed through Finite Element Analysis. The fluid flow is computed through Computational Fluid Dynamics approach in ANSYS Fluent. This modified structure improves the aerodynamic condition near the brake rotor that increases the rate of heat rejection by forced convection from the brake rotor surface.
An Embedded Mechatronic Device for Real-Time Monitoring and Prediction of Occupants’ Thermal Comfort
Authors: Pavlin B. , Carabin G. , Pernigotto G. , Gasparella A. , Vidoni Renato
Published: January 2019

It is well recognized in the literature that thermal sensation and comfort are dependent on both core and skin temperatures. In particular, some regions of the human skin, such as the forehead, have a higher density of thermal receptors, giving a higher sensitivity to the skin temperature. Some studies suggest that the forehead skin temperature and its rate ofchange alone could potentially be a good indicator of one’s overall thermal comfort. To validate this claim, an idea for a smart sensor which would be able to read the occupants’ forehead temperature and other environmental parameters in a proximal way is here considered. Moreover, with the aim of exploiting the system not only in lab or test facility environments but, considering the 4.0 revolution, also in the building automation context, a non-invasive solution has been searched so as the occupants are not disturbed while the measurement is performed. Therefore, in this study, a new cheap and smart mechatronic sensor device for a non-invasive measurement of the occupants’ thermal comfort is proposed. The main components consist of a central unit, i.e. microprocessor, a small infrared sensor for thermal imaging, i.e a Lepton infrared camera by FLIR, as well as other sensors for measuring distance, humidity and temperature. The setup was imagined as the sensor being placed on the top of each desk, so it is not easily obstructed by a laptop or a similar object that can be found on top of the working surface. After the conceptual hardware definition and software development, an accurate experimental calibration has been performed exploiting an ad-hoc developed set-up based on a hot plate with an emissivity factor similar to the one of the human skin and with adjustable temperature. Finally, a first design for embedding the whole smart mechatronic system in a unique box has been developed and built.
Dislocation Theory of Orthogonal Metal Cutting of Cu-Zn Alloys
Authors: Payton Lewis N.
Published: January 2019

The effects of stacking fault energy and hardness on the shear process during low-speed orthogonal metal cutting were examined in a designed experiment of 1680 tests in Copper Zinc (CU-ZN) alloys. Existing shear zone models were compared to the experimental results generated by a Videographic Quick Stop method.

Analysis of the data indicates that the onset of shear plane is more properly viewed as the activation of glide plane. This in turn is a result of the available slip planes, which are a function of the materials crystalline structure, the stacking fault energy and the dislocation density (i.e., the amount of work-hardening), as constrained by the tool’s rake face angle. Merchant’s Force Diagram is revised using an extension of the existing diagram to incorporate the material’s crystalline structure, incorporating well established dislocation theory.
On Novel Dynamic Displacement Amplification Using Compliant Mechanisms
Authors: Tanksale Abhijit A. , Gandhi Prasanna S.
Published: January 2019

Flexure based micro or nano positioning systems are among the most widely used positioning systems in micro or nano engineering domain. More often, piezoelectric actuators (PZTs) or voice coil actuators are used for the actuation of such highly precise flexure based positioning systems. However, the range of motion or stroke of these actuators is limited. Previous literature shows the use of various displacement amplifying compliant mechanisms (DACMs) to address this problem. This paper proposes a novel approach of dynamic displacement amplification using the compliant mechanism (DDACM). The well-known vibration absorber effect is observed and employed to amplify the displacement (rather than for suppressing vibrations) of output mass as compared to intermediate mass using double parallelogram compliant mechanism. Different amplification ratios can be obtained by tuning the frequency of excitation. We, further propose a nonlinear model that effectively captures the resulting behaviour of DDACM. Simulation results with the proposed model are validated with corresponding experimental results on DDACM within the accuracy of 10%.
Non-Isothermal Phase Change Behaviors of Binary Mixtures of D-Dulcitol and Pentaerythritol As Novel Heat Storage Materials
Authors: Shao Xue-Feng , Wang Jun , Fan Li-Wu
Published: January 2019

As a promising Phase Change Material (PCM) candidate for low-to-medium temperature (100–250 °C) latent heat storage, sugar alcohols undergo serious supercooling during cool-down for crystallization. Technical efforts need to be dedicated to suppression or control of the supercooling of sugar alcohols. In this work, the supercooling of D-dulcitol, with a melting point of around 186 °C, was attempted to be reduced by mixing with a solid-solid PCM Pentaerythritol (PE) as the nucleation agent, which has a solid-solid phase transition temperature (∼186 °C) similar to the melting point of d-dulcitol. Such novel binary mixtures were prepared by dispersing PE powders at various mass fractions into d-dulcitol melt. The non-isothermal phase-change-related properties, with emphasis on the crystallization properties, were tested on a heat-flux differential scanning calorimeter at a constant heating/cooling rate of 5 °C/min. The preliminary results showed that both the crystallization point and latent heat of crystallization strongly depend on the mass fraction of PE, and both decrease in magnitude with the increasing in mass fraction of PE. The degree of supercooling of the binary mixtures also depend on the mass fraction of PE, and a reduction of up to 10 °C was obtained at 50 wt.% PE, as a result of the decrease in the melting points of the binary mixtures.
A Numerical Study of the Influence of Different Factors on Mechanical Characterization of Tumors via a 2D Tactile Sensor
Authors: Abshier Nathan , Genoese-Zerbi Cristina , Jobe James , Kohl Kylee , Tison Charles , Watjen Timothy , Hao Zhili
Published: January 2019

This paper presents a numerical study of the influence of different factors on tumor detection via a 2D tactile sensor. The 2D tactile sensor entails a polydimethylsiloxane (PDMS) microstructure embedded with a 3 × 3 sensing-plate/transducer array. By pressing the sensor against a tissue region with a predefined indentation depth pattern, the tissue stiffness distribution is extracted from the measured slopes of the deflections of the sensing-plate array versus the indentation depth. In this work, we numerically investigate the influence of curved tissue surface, curved substrate and tissue viscoelasticity on the measured sensor deflection distribution, which is representative of the tissue stiffness distribution. A set of numerical models are created in COMSOL Multiphysics to investigate the influence of the above-mentioned factors separately. A purely elastic numerical model with a flat substrate and a flat tissue surface is created as the reference model. Two other numerical models are created with one having a curved surface and the other having a curved substrate. The same tumor is embedded in these three models. Given the same 2D sensor, how the measured sensor deflection distribution is affected by different curved surfaces and curved substrates is compared with the results from the reference model. The three tumor parameters (elasticity, size and depth) are also varied for their influence on the measured results. A separate viscoelastic numerical model is created to study how the time-dependent behavior of a tumor varies with its viscoelasticity. This model provides the guidance on tailoring the testing parameters in a pre-defined indentation protocol for quantitatively maximizing the difference in viscoelasticity among different tumors.
Computational Analysis for Validation of Blast Induced Traumatic Brain Injury and Protection of Combat Helmet
Authors: Tan X. Gary , Bagchi Amit
Published: January 2019

Current understanding of blast wave transmission and mechanism of primary traumatic brain injury (TBI) and the role of helmet is incomplete thus limiting the development of protection and therapeutic measures. Combat helmets are usually designed based on costly and time consuming laboratory tests, firing range, and forensic data. Until now advanced medical imaging and computational modeling tools have not been adequately utilized in the design and optimization of combat helmets. The goal of this work is to develop high fidelity computational tools, representative virtual human head and combat helmet models that could help in the design of next generation helmets with improved blast and ballistic protection.

We explore different helmet configurations to investigate blast induced brain biomechanics and understand the protection role of helmet by utilizing an integrated experimental and computational method. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we solved the dynamic problem of helmet and head under the blast exposure. Experimental shock tube tests of the head surrogate provide benchmark quality data and were used for the validation of computational models. The full-scale computational NRL head-neck model with a combat helmet provides physical quantities such as acceleration, pressure, strain, and energy to blast loads thus provides a more complete understanding of the conditions that may contribute to TBI. This paper discusses possible pathways of blast energy transmission to the brain and the effectiveness of helmet systems at blast loads. The existing high-fidelity image-based finite element (FE) head model was applied to investigate the influence of helmet configuration, suspension pads, and shell material stiffness. The two-phase flow model was developed to simulate the helium-air shock wave interaction with the helmeted head in the shock tube.

The main contribution was the elucidation of blast wave brain injury pathways, including wave focusing in ocular cavities and the back of head under the helmet, the effect of neck, and the frequency spectrum entering the brain through the helmet and head. The suspension material was seen to significantly affect the ICP results and energy transmission. These findings can be used to design next generation helmets including helmet shape, suspension system, and eye protection.
PittPack: Open-Source FFT-Based Poisson’s Equation Solver for Computing With Accelerators
Authors: J. Hasbestan Jaber , Senocak Inanc
Published: January 2019

Many environmental flows are simulated in a Cartesian domain using buoyancy-driven incompressible Navier-Stokes equations. A significant cost of the simulation is devoted to the solution of the elliptic pressure equation to enforce the conservation of mass principle. The legacy software, FISHPACK, has been used for this purpose for many years. We present a new software package for the direct solution of the pressure Poisson’s equation on a directionally uniform Cartesian mesh with a second-order accurate finite-difference formulation. We use the separation of variables principle and adopt fast Fourier transforms (FFT) to convert the system to a group of independent tridiagonal systems that can be solved directly. The computational complexity of the present methodology is proportional to N2 (O(NlogN)). However, each stage of the solution algorithm can be performed simultaneously leading to a pleasingly parallel problem that is well suited for massively-threaded accelerators, such as modern graphics processing units (GPU). Theoretically speaking, if an accelerator can sustain N2 resident threads, the computational complexity will drop to O(NlogN). We use OpenACC directives with cuFFT library on a GPU to realize substantial acceleration of the overall solution algorithm and compare its performance relative to an implementation that used the FFTW library on central processing units (CPU). For a problem with 5123 points, the GPU version is about 17 × faster than the CPU version.
Biomaterial Models Adjustment and Comparison for Ultra-High Molecular Weight Polyethylene in Finite Element Models
Authors: Corro-Hernández Humberto , Vidal-Lesso Agustín , Ledesma Elías , Balvantín-García Antonio de Jesús
Published: January 2019

GUR1050 is a medical grade variety of ultra-high molecular weight polyethylene (UHMWPE) intended for use on total joint prosthesis and implants. Probes of this material were characterized on a compression test following ASTM norms and lineaments.

Available data from these mechanical tests is fitted on multiple material models. Achieved results on numerical solutions of finite element modeling (FEM) of the tests are discussed, looking for the best one available in order to simulate with accuracy GUR1050 behavior, with specific interest on the load curve results, showing the pertinence of using certain models on different conditions.

It was found that the use of a bilinear isotropic hardening model assures the best fit for GUR1050 behavior in uniaxial compression under a constant strain rate.
Study of Symmetric Solutions of an Underactuated Bipedal Robot
Authors: Shah Prachi , Sangwan Vivek
Published: January 2019

Underactuated bipedal walking has been intensively studied for the past few decades and several methods have been proposed to design trajectories; however, quickly generating trajectories with varying speeds remains a challenge. One solution is to have a library of trajectories precomputed from which a new one can be picked or constructed quickly based on specific requirements. For this to become feasible one needs to develop a good understanding of the solution space. This is non-trivial for a non-linear hybrid system such as a walking robot. The goal of this study is to explore a two parameter solution space of simple underactuated biped, under a specific virtual constraint, used in literature, to enforce a symmetric gait. The family of feasible walking solutions identified is further evaluated for performance and energy efficiency. This analysis can potentially facilitate quick selection of walking trajectories for meeting specific walking speed and efficiency requirements.
Design and Analysis of the Self-Powered 2-Lobe and 3-Lobe Continuous Mud-Pulse Turbo Siren
Authors: Peng Xiaobo , Zhang Diwei
Published: January 2019

The Measurement While Drilling (MWD) tool is used by oil and gas industry to provide the directional survey information while drilling. With rig rates exceeding $1 million per day and wells that are drilled at depths of over 30,000 ft (9144 m), operators needs to have an MWD tool that can self-power itself to provide high data rates and strong signal strength. Among different types of MWD tool, the Continuous Mud-Pulse Telemetry (C-MPT) can generate high data rates and signal strength. The C-MPT has a rotating valve that propagates signal upstream through the drilling fluid in the drill string. However, the ability to power a C-MPT for the MWD tool using the existing hydraulic forces of the drilling fluid has not been extensively researched. The focus of this study was to propose the 2-lobe and 3-lobe turbo siren designs that can provide power to an alternator while maintain high data rates and signal strength. All turbo siren designs are based on a vein, rotor, and stator. The turbo siren systems were manufactured with 3D printing. An experimental wind tunnel was designed and built to simulate the downhole drilling environment. The testing results of the turbo siren systems are presented and discussed, including no-load rotation speed (RPM), stall torque, power and data rate. The results provide the guidance for the optimization of the self-powered MWD turbo siren design.
Process Planning Strategies to Reduce Energy Consumption in Machining
Authors: Unnikrishnan Arun , Rao P. V. M.
Published: January 2019

Continuous need to increase productivity and reliability in machining has led to high-performance machines that are often characterized by high energy demands. As a result, energy minimization is identified as one of the key goals in machining. With the availability of improved predictive models for energy estimation in machining, energy-conscious process planning for machining is now possible. The present work focuses on the assessment of process plans of machined parts from energy consumption point of view. An experimentally validated model for energy estimation is first presented. Using this model two important process planning variables on energy consumption in machining has been studied. Firstly selection of tool paths including curvilinear tool paths has been considered from energy consumption point of view. Secondly, strategies for the selection of cutting parameters for roughing, semi-finishing and finishing from energy consumption perspective are discussed.
Elastic Metamaterial Design to Filter Harmonic Mechanical Wave Propagation
Authors: Rodrigues Gustavo Simão , Weber Hans Ingo , Driemeier Larissa
Published: January 2019

The metamaterial concept was first oriented to electromagnetic field applications and the main objectives were to develop materials with peculiar properties such as negative dielectric constant, negative magnetic permeability and negative refraction index. Gradually, other areas started using parameters that do not exist in the materials found in nature and, classifying them as metamaterials. So, areas such as acoustics, optics and mechanics opened up space for applications of this innovative “material”. Many efforts for an adequate modeling were made searching also for all kinds of possible applications. One example of application in optics is the use of conformal transformation to design devices with new functionalities from non-homogeneous isotropic dielectric media. The mirages created in the desert are the result of these non-homogeneities. These studies are supposed being helpful to develop invisible cloaks using metamaterials. The present work deals with elastic metamaterial application in mechanical engineering. It is well knowing that metamaterials are able to filter harmonic wave propagation and many works present this capability caused by a bandgap that appears in some range of frequency due to the system’s features. However, it is not very clear how the parameters used for the metamaterials design should be defined. The purpose of this work is to propose a methodology to design an optimized metamaterial component to filter the mechanical wave propagation in a finite chain of masses. It is also in the scope of this work to analyze the borders of the bandgap of the studied chain of masses and how the propagated wave is attenuated along this region.
The Study of Holey Cavity in the Application of Thermoacoustics Imaging
Authors: Liu Chang , Ghanbarzadeh-Dagheyan Ashkan , Heredia-Juesas Juan , Molaei Ali , Martinez-Lorenzo Jose Angel
Published: January 2019

Microwave-induced Thermoacoustics (TA) sensing has the potential to be a breakthrough in subsurface imaging applications. This is because it combines the advantages of high contrast of microwave imaging and high resolution of ultrasound imaging. However, state-of-the-art TA hardware requires that the receiving transducer is scanned in a linear or rotational fashion in order to be able to collect enough orthogonal data needed to produce a TA image possessing high-spatial resolution both in range and cross-range. This process is slow, increases the detection time, and adds an extra complexity to the system. In order to address these problems, a Compressive Sensing (CS) methodology is presented in this paper as a mechanism to reduce the minimum number of data samples required to reconstruct a sparse signal. Furthermore, in order to reduce the mutual information shared by different measurements, a holey cavity structure is proposed to be used to perform 4D coding. In this work, the TA imaging theory is introduced; and the impact that the holey cavity parameters have in the imaging performance is studied. The imaging results in this work are carried out using a distributed Alternating Direction Method of Multipliers (ADMM) algorithm, capable of using norm-1 and norm-2 regularizers; and they reveal the effectiveness of the proposed holey-cavity and CS TA imaging approach.
Voltage Response of Circular Plate MEMS Resonators Under Superharmonic Resonance
Authors: Botello Martin , Beatriz Julio , Caruntu Dumitru I.
Published: January 2019

The superharmonic resonance of second order of microelectro-mechanical system (MEMS) circular plate resonator under electrostatic actuation is investigated. The MEMS resonator consists of a clamped circular plate suspended over a parallel ground plate under an applied Alternating Current (AC) voltage. The AC voltage is characterized as hard excitation, i.e. the magnitude is large enough, and the operating frequency is near one-fourth of the natural frequency of the resonator. Reduced Order Model (ROM), based on the Galerkin procedure, transforms the partial differential equation of motion into a system of ordinary differential equations in time using mode shapes of vibration of the circular plate resonator. Three numerical methods are used to predict the voltage-amplitude response of the MEMS plate resonator. First, the Method of Multiple Scales (MMS) is directly applied to the partial differential equation of motion which is this way transformed into zero-order and first-order problems. Second, ROM using two modes of vibration is numerical integrated using MATLAB to predict time responses, and third, the AUTO 07P software for continuation and bifurcation to predict the voltage-amplitude response. The nonlinear behavior (i.e. bifurcation and pull-in instability) of the system is attributed to the inclusion of viscous air damping and electrostatic force in the model. The influences of various parameters (i.e. detuning frequency and damping) are also investigated in this work.
Advanced Modeling and Experimental Validation of an Optimized Power Transformer Tank
Authors: Mendes Hélder F. G. , Coutinho Cristiano J. P. , Tavares Sérgio M. O. , Félix Luís M. R. , de Matos Agostinho N. Martins , Meireles José F. B. , Pinho António C. Marques , Teixeira Joel R. S.
Published: January 2019

Even though the power transformers are electrical machines, their design includes several important steps with strong emphasis on mechanical engineering topics, such as the design of welded metallic structures. Indeed, the tank and its cover are typically manufactured from steel sheets or plates to which a group of stiffeners are added, with the objective of reducing the bending stress, transverse displacements and/or buckling.

The current communication presents and discusses several incremental innovations in the structural design and simulation of tanks for Core type power transformers, including: (i) optimization of the stiffeners design and welding bead volume reduction; (ii) optimization of panels curvature; (iii) simulation of the transformer tank loaded by both hydrostatic pressure and vacuum conditions; and (iv) inclusion of non-linear behavior to more accurately simulate representative structures.

Achieved numerical results are compared with obtained experimental data, to evaluate the design procedures and the potential of virtual testing of new solutions.
The Cooling Process of Agricultural Products After Boxing and Palletizing
Authors: Giorges Aklilu T. G. , Pierson John A.
Published: January 2019

Assuring that food products have acceptable quality and are safe to consume requires maintaining adequate nutrition levels and fulfilling consumer expectations. Quality losses can lead to food waste, resulting in increased economic costs and low consumer confidence. Therefore, quality expectations should be maintained at an acceptable level for consumer purchase and consumption. It is well known that a cold environment reduces the respiratory activities and kinematics of nutritional degradation. The cooling temperature is critical since lower than recommended cold temperatures may cause chill damage. Therefore, the food industry intensively employs cold storage methods to slow respiration rates, inhibit harmful bacterial growth, reduce water loss, and prolong shelf life in order to maintain product nutritional value and quality. Improving product cooling efficiency will reduce energy costs that are a significant expense for fruit and vegetable processors. Understanding the cooling process is key to the development of new technology and processes. However, most natural food products are not conformed to simple geometric shapes or uniform properties and distributions. Thus, the cooling process of an agricultural product (cucumbers) was investigated in this study. The study was conducted in a packing house, where the cooling temperature of the cucumbers was recorded by placing multiple thermocouples in the produce after boxing and palletizing as well as cold storage. The test results showed that individual produce cooling was relatively easy to predict. However, boxed and palletized cucumber cooling showed significant variations. For example, the temperature of the cucumbers changed depending on their location in the box in addition to the box location on the stack. In the case of boxed produce cooled by natural convection cooling, the temperature changed from 25 to 18 °C after three hours. However, in the case of palletized tunnel cooled, the temperature change ranged from 25 to 11 °C and 25 to 18 °C after nearly three hours of cooling. Indeed, the temperature differences indicated that the cooling rate has significant variations depending on the location of the produce. Some parts of the pallet received more direct contact with the forced cold air than other parts. Thus, it is very important for produce processors to understand cooling system performance. The study emphasized that efficient use of energy is one of the areas that can have not only significant cost savings but can also improve produce shelf life, reduce food waste, and maintain consumer confidence.
Influence of the Microstructure on the Creep Behaviour of Tin-Silver-Copper Solder
Authors: Ribeiro Pedro E. , Soares Delfim F. , Cerqueira Maria F. , Teixeira Senhorinha F. , Barros Daniel A. , Teixeira José C. , Capela Pauline , Macedo Francisco
Published: January 2019

A common failure mode of electronic printed circuit boards (PCB’s) is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles and, thus, should be studied. Through the cooling phase, on the production of PCB assembly’s by the reflow technology, the hoven atmosphere temperature is adjusted in order to control the cooling rate. Narrow criteria is used so as to control the inter-metallic compounds (IMC) thickness, PCB assembly distortion and defects due to thermal shock. The cooling rate also affects solder microstructure, which has direct impact on creep behaviour and, thus, on the soldered joint reliability.

In this paper, a dynamic mechanical analyser (DMA) is used to study the influence of the solder cooling rate on its creep behaviour. SAC405 samples with two distinct cooling rates were produced: inside a hoven cooling and by water quenching. Creep tests were made on three-point-bending clamp configuration, isothermally at 25 °C, 50 °C and 75 °C and under three separate levels of stress, 3, 5 and 9 MPa. The results show that creep behaviour has a noticeable cooling rate dependence. It was also noticed that creep propensity is exacerbated by the temperature at which stresses are applied, especially for the slower cooling rates. Creep mechanisms were related to the solder microstructural constituents, namely by the amount of phases ant their morphology.
Vibration Energy Harvesting to Power Ultrasonic Sensors in Heavy Haul Railway Cars
Authors: Santos Auteliano A. , Lopes Matheus V. , Gonçalves Vanessa , Eckert Jony J. , Martins Thiago S.
Published: January 2019

Long heavy-haul trains are now a reality, especially for ore transportation. In some railways, compositions of up to 330 wagons are in service, requiring several locomotives. Trains like that travel long distances, sometimes through cities or in uninhabited regions. They are driven by just one driver which must keep the whole train working safely on the track. The wagons don’t have any source of electrical energy to power sensors and to transmit their signals to the locomotive; nor wireless communication. In fact, in some of these railways, there is no internet along with the track out of the cities. One important indicator of the safety of the train is the force between the wagons during the trip, through the shunting. Using strain gauges to measure these forces is a possible solution and ultrasonic stress sensors (UST) is a suitable alternative. UST with Lcr waves requires a low amount of energy and can be employed in rusty and dirty places. However, they also need an energy source. Wind and solar solutions are not always adequate because, unfortunately, there are places where these components have economic value and they can be stolen. A possible source of energy to power the USTs could be the Vibration Energy Harvester (VEH). These simple and not expensive systems can be built in small packs, giving the energy to measure the forces and transmit the data to the locomotive or designated sites along the track. This work aims to evaluate the possibility of using VEH to power USTs to measure the forces between the wagons during the journey. Knowing that the oscillation in the shunting has a very low frequency, the work intent to optimize a multi-beam VEH to be able to capture the highest amount of energy possible, in a very small arrangement, using genetic algorithm. The result shows that VEH is an adequate alternative to power autonomous UST sensors.
Dynamic Behavior of Biologically Inspired 3D Printed Visco-Elastic Heterogeneous Structures
Authors: Lai Heather L. , Beahan Jennifer
Published: January 2019

Many jumping insects such as locusts have a composite leg structure which is a combination of a hard material called cuticle and a rubber-like protein called resilin. Research has shown that the muscular excitation during kicking is greatly amplified by the composite structure of the leg which combines the stiffness of the cuticle and the elasticity of the resilin in a catapult behavior. The composite structure has a modulus of elasticity close to that of cuticle, but has the added elasticity of the resilin, allowing energy to be stored in the structure without bending the brittle cuticle past its breaking point. With the advancement of heterogeneous 3D printing, it has become possible for multi-material models to be seamlessly printed in ways that mimic the mechanical behavior of biological structures such as the semi-lunar process of the jumping locust. The uses of this type of composite structure opens up a wide range of application for multi-material additive manufacturing. In the presented research, FEA is used to model the behavior of the locust semi-lunar process based on the material properties of both the natural tissues, and 3D printed materials. The mechanical behavior of 3D printed composite structures will then be compared with the modeled behavior.
Full Scale Testing of Pulse Jet Mixer Operating Control
Authors: Moualeu Leolein , Wand Aaron , Herman Klemme , Trenidad Michaela , Hall Michael , Springer Bethany , McAdams Nathan , Holton Langdon
Published: January 2019

A standard high-solids vessel (SHSV) concept design approach using pulse jet mixers (PJM) has been proposed by the US Department of Energy (DOE) for the Hanford Tank Waste Treatment and Immobilization Plant (WTP) as a potential replacement for several vessels that will be used to process highly radioactive waste. To assist with the evaluation of the SHSV concept, at DOE’s direction, the WTP Project recently completed qualification testing of the SHSV PJM mixing system to verify the design. Testing of the SHSV design, conducted at full scale, was split into two phases. The first phase of testing developed PJM controls that supported all operational modes under a set of most adverse fluid conditions. The second phase of testing used the PJM operating strategy, established during the first phase, to perform qualification testing to verify that the mixing system design supports the transfer, de-inventory, throughput, and sampling functional requirements of the SHSV. The different control methods that were used to operate PJMs in simulants exhibiting Newtonian and non-Newtonian rheological properties with high solids loading are presented.

The PJM system of the SHSV uses six pulse tubes distributed in a circular array. Each pulse tube (3000 liters nominal volume) is connected to a jet pump pair (JPP) by means of an air link line. The JPP powers the PJM operation by applying a vacuum to refill the PJM (suction phase), pressurizing the PJM to discharge the pulse tube content at a target velocity (drive phase), and releasing the compressed air to allow the PJM to depressurize into a ventilation system (vent phase) designed for contaminated air. A PJM control system was developed to maximize the PJM operation and minimize potential impact to the structural integrity of the vessel. The experimental results showed effective control of the system parameters. The system response demonstrated reliable control of the drive set pressure, the drive time, and synchronization. The PJM control system design also proved robust in mobilizing settled solids.
Assessment of Different Turbulence Models on Simulations of Confined Jets in a Crossflow at Supercritical Pressure
Authors: Janani Saeid , Gada Komal , Rahai Hamid , Davoudzadeh Farhad
Published: January 2019

Numerical investigations of using two different turbulence models of K-ε and K-ω on mixing characteristics of two confined jets in a crossflow at supercritical pressure have been performed. The confined jets were at 180 degrees from each other injecting into a round tube. The jet to crossflow mass flows ratio, r, was 2.96. Reynolds Averaged Navier Stokes (RANS) equations were solved using Siemens PLM CCM+ software. Results indicate higher mixing rate with K-ω turbulence model. Higher vorticity and lower turbulent kinetic energy are observed with k-ω turbulence model. Increased mixing indicate reduced velocity and pressure gradients and cooler fluid toward the tube wall.
Porosity Analysis in Metal Additive Manufacturing by Micro-CT
Authors: Shrestha Subin , Starr Thomas , Chou Kevin
Published: January 2019

This study aims at analyzing process-induced pores in selective laser melting (SLM), a laser powder-bed fusion additive manufacturing (AM) process. Porosity is one of the most problematic defects in SLM parts; it impairs the part performance, and yet, is sharply sensitive to the parameters of the SLM process itself. Detailed analysis of SLM pore formations using a computed tomography (CT) technique is desired in order to understand the porosity level under different process conditions. In this study, an SLM system was used to fabricate samples, using Ti-6Al-4V powder, with single tracks formed, at 60 μm layer thickness, with different laser powers and scanning speeds to vary the energy density. A micro-CT (μ-CT) scanner was used to measure the internal features of the SLM specimens without any post-build treatments and to analyze the porosity inside single tracks formed with different energy densities. There are different mechanisms of pore formation in SLM, in particular, this study first focuses on the pore formation due to the keyhole phenomenon, caused by a high energy density. μ-CT scanning at a 6 μm resolution is able to clearly reveal the pores in the SLM samples. From the CT scan and analysis results, it is observed that increasing the energy density increases the volume of pores. For example, with 195 W and 200 mm/s, the number of pores is 93 and the total pore volume is 0.014 mm3 for a scanning length of 12 mm. On the other hand, if the energy density is less than 0.24 J/mm, few or no pores were observed, because possibly the melting process changes from the keyhole mode to the conduction mode.
Design of Damped Structures to Increase Machine Tool Dynamical Performance
Authors: Aggogeri Francesco , Borboni Alberto , Merlo Angelo , Pellegrini Nicola , Adamini Riccardo , Taesi Claudio
Published: January 2019

The demand of ultra-high precision (UHP) machining is growing word-wide, driving the study and development of new solutions to increase the machine tool (MT) functionalities and performance. This trend has generated a request of smart, flexible and faster MTs that are able to reduce machining time and improve the final accuracy. The material selection in MT structure design and building may play a fundamental role to satisfy the customer’s requirements. In addition, the application of innovative materials in today’s technology may solve many issues that affect the machining quality due to static, dynamic and thermal behaviors.

This paper presents a set of hybrid materials that may be used to fabricate the moving parts of a machine tool. The proposed solutions aim to guarantee lightness, capacity to damp vibrations and high stiffness limiting static and dynamic issues. The study focuses on four types of hybrid materials: sandwich structures based on Aluminium Foam, in open and closed cells configuration, sandwich panels with a corrugated core and Carbon Fiber Reinforced Plastic (CFRP) materials. A number of prototypes (milling MT ram – z axis) has been designed, manufactured and tested for high speed applications, evaluating both static and dynamic properties and highlighting potential advantages, drawbacks and new opportunities respect to conventional materials (e.g. iron, steel).
A Comprehensive Parametric Study of Minichannel Based Liquid Cooling of Li-Ion Battery Pack
Authors: An Zhoujian , Shah Krishna , Ma Yanbao , Li Jia
Published: January 2019

Li-ion based energy storage devices have highly temperature dependent characteristics such as performance, life-cycle, efficiency and safety. Large temperature gradient within a cell results in thermal stresses and nonuniform current density leading to accelerated degradation. This adversely affects the life cycle of the cell due to capacity and power fade. There are similar issues due to large temperature variation within a battery pack. Operation of Li-ion cell outside the desirable temperature range also leads to lower efficiency, degradation and safety related issues. Different thermal management approaches have been proposed and demonstrated in past. The present work focuses specifically on minichannel based liquid cooling for conducting a parametric study. Minichannels have been found effective in various thermal management applications due to their simple construction and high convective heat transfer. In past, minichannels have been proposed and used in battery thermal management. However, designing of such systems has been somewhat arbitrary without considering various factors and trade-offs involved. There is a lack of rigorous studies for determining various parameters related to thermal management system that would result in adequate thermal management in a cost-effective manner. In the present work, a comprehensive parametric study has been carried out on the minichannel based liquid cooling for thermal management of Li-ion battery pack. A simplified computationally efficient numerical simulation-based approach has been used to conduct parametric study for optimizing the design and operating parameters of the thermal management system.
Low-Temperature Thermal Energy Harvesting Using Solid/Liquid Phase Change Materials
Authors: Wang Guangyao , Ha Dong Sam , Wang Kevin G.
Published: January 2019

This paper presents the design, fabrication, and analysis of a prototype system that demonstrates the use of a solid/liquid phase change material (PCM), namely pentadecane (C15H32), to harvest thermal energy associated with relatively low temperature and small temperature variation (e.g., 1°C to 20°C). The fundamental idea is to utilize the volume expansion of the PCM in the melting process to pressurize a hydraulic fluid, which is then released to drive a direct current (DC) water turbine generator. The prototype features the use of a tube system to store degassed and encapsulated PCM packages, therefore can be easily scaled to meet different energy output requirements. The performance of the prototype is assessed through measurements of the peak pressure of the hydraulic fluid and the produced power profile. The dependence of the electrical energy output on external load resistance is investigated within the range of 25 Ohm to 250 Ohm. Further, a thermomechanical model is developed to characterize the energy conversion process. Specifically, the thermodynamic behavior of PCM and hydraulic fluid is modeled with the Tait equation of state. The structural mechanics is modeled using the linear elasticity theory. The peak pressure predicted by the model agrees reasonably well with the experimental measurement, with a discrepancy of 3.40%. Finally, a series of numerical parameter studies are conducted to investigate the effects of the structural stiffness and the volume fraction of the PCM, indicating possible methods to improve the thermal efficiency and the specific energy output of the prototype system.