bluuebunny/crossref_metadata_2025 huggingface dataset:
Ordinate Systems for Quadratures Similar to Tchebycheff’s Ordinates
Authors: Karelitz George B.
Published: February 2021

The author presents a geometrical interpretation of Tchebycheff’s rule for calculating quadratures and shows that other systems of ordinates can be chosen which will be as valid as Tchebycheff’s. A system of ordinates is proposed, the virtue of which lies in the fact that the longitudinal location of the center of gravity of the ship’s lines can be obtained with good accuracy without increasing the errors of area calculations.
Distributed Gravity and Temperature Loading in Two-Dimensional Elasticity Replaced by Boundary Pressures and Dislocations
Authors: Biot M. A.
Published: February 2021

This paper deals with two-dimensional stresses due to an important class of body forces. Gravity stresses and temperature stresses are produced by body forces of the type investigated.

In the case of gravity stresses it is proved that these stresses may be calculated by forgetting about the action of gravity on the body and applying instead only external normal loads that are identical with a hydrostatic pressure.

This opens the possibility of applying photoelastic tests to the measurement of gravity stresses; a model loaded by these external pressures would show an isochromatic fringe pattern identical with the one that would appear in a model submitted to an intense gravity field. In Fig. 5 is shown the type of external loading to be applied to find the gravity stresses in a dam.

In the case of two-dimensional temperature stress in cylindrical bodies where the temperature distribution is stationary, it is shown that a distinction is to be made between solid and hollow cylinders. For a solid cylinder the only thermal stress component appearing is an axial stress acting perpendicularly to cross-sectional planes. In other words, the solid cylinder expands freely along the cross-sectional planes. For a hollow cylinder a general stress condition may arise which is identical with the stresses produced by cutting a longitudinal slit of a certain small width in the cylinder wall and sticking together the two sides of the slit (dislocation).
Film Lubrication in Sleeve Bearings
Authors: Stone M.
Published: February 2021

The author discusses the design of bearings as based on fluid friction in hydrodynamic films and investigates the limiting design factors in such bearings. He points out that the thickness of the oil film is dependent on the viscosity of the lubricant alone and that this thickness may be controlled, thus making it possible to base the design of a bearing on a minimum thickness of the oil film. Two appendixes conclude the report, one which presents simplified theoretical considerations for the design of film-lubricated bearings while the other explains the highly accurate electromagnetic micrometer used for determining shaft positions in the bearing.
Journal Bearing Performance
Authors: Baudry R. , Tichvinsky L. M.
Published: February 2021

This paper contains an application of the hydrodynamical theory of lubrication to the practical design of journal bearings. In a simplified method satisfactory for most engineering applications the authors consider the journal bearing as a plane bearing. Then correction factors make allowance for (1) the type of the journal bearing, (2) the shape of the oil film and width-length ratio of the bearing, and (3) the losses in the nonactive parts of the bearing.

In a more accurate method, the same correction factors are applied to the rather complete data published on journal bearings of infinite width. It is also shown that the clearance of the bearing can vary between rather large values and still maintain closely optimum conditions of performance of the bearing. Results of tests are shown to be in close agreement with these methods of calculation.
A Method of Harmonic Analysis
Authors: Lewis Frank M.
Published: February 2021

The method of harmonic analysis described in this paper is of the selected ordinate type. It is similar to the Fischer Hinnen analysis in that a different spacing of ordinates is used for each harmonic component to be determined, and no multiplications are necessary. The basis of derivation is the assumption that the curve to be analyzed can be replaced by a parabola passing through certain ordinates in each half period of the harmonic component. A spacing of these ordinates is then found such that the sum of the ordinates is proportional to the harmonic component of the parabolas replacing the original curve.

Spacings have been determined for 3, 5, and 7 ordinates per half period, corresponding to parabolas of second, fourth, and sixth orders. In the five and seven ordinate rules it is necessary to use a multiplying factor of 1/2 for the end ordinates.

In use a set of transparent charts with the ordinates for each component are constructed. Laid over the curve to be analyzed, the ordinates can be quickly summed on a strip of paper.

The accuracy of the method is relatively high and in use it is of the utmost simplicity, so that with a set of charts once prepared, correct results can be obtained by the most unskilled computer.
The Strength and Stiffness of Cylindrical Shells Under Concentrated Loading
Authors: Roark R. J.
Published: February 2021

In certain structures and under certain conditions of use, cylindrical or nearly cylindrical shells are subjected to concentrated loading. This paper presents empirically derived formulas for the stresses and deflections produced by such loading, and describes the tests on which these formulas are based.
Predicting Track Geometry Defect Probability Based on Tie Condition Using Pattern Recognition Technique
Authors: Alsahli Ali , Zarembski Allan M. , Attoh-Okine Nii
Published: February 2021

Rail transportation plays a vital role in U.S. transportation. According to the National Transportation Statistics report from the Bureau of Transportation Statistics, railroads generate 29% of ton-miles of freight, whereas air, truck, water, and pipeline transportation represent the rest of the freight traffic. In the passenger spectrum, the 2016 National Transit Summary and Trends report stated that trips using rail transit modes increased from 2012 to 2016. These facts show the importance of rail transportation in the United States and highlight the critical importance of railroad traffic safety. Based on the FRA 2016 statistics, track-related defects are the second-largest cause of rail accidents. Furthermore, track irregularities resulting from defects in these parameters lead to an increase in dynamic forces that accelerate the rate of track deterioration. Consequently, the need to monitor and detect the presence and types of defects on railway tracks arises. The availability of track geometry cars and autonomous visual inspection vehicles has made acquiring track information easier. However, the need to study and understand these data remains unfulfilled. Machine learning has recently started to gain popularity in the field of railroad research due to increasing computational capacity and the need for such tools to provide information that is more useful. Techniques such as deep convolutional neural networks (DCNN), artificial neural networks, and support vector machines have been used for prediction problems in railroad research.

This paper combines engineering judgments and statistical analysis to develop analytical models to estimate the probability of developing geometry defects as a function of tie conditions. The analysis is based on data provided by Georgetown Rail’s AURORA tie inspection system and from a major US class 1 railroad track geometry cars. The data used in this analysis relates to a geometry defect dataset and a tie condition dataset. The geometry dataset covers 125,554 geometry defects taken from several years of track-geometry inspection data. The data collection period was from 2014 to 2016. Convolutional neural network models were developed to estimate the probability of defects given tie patterns, as well as the outputs of the models used to build multiple regression models. Additionally, various data analysis issues were addressed in this paper. This paper’s contribution includes predictive models of track geometry defects as a function of tie condition and position. The models provide approaches to predicting the probability of geometry defects as functions of tie conditions and positions.
Calculation of Convective and Radiative Heat Transfer Coefficient Using Thermography During a Physical Exercise
Authors: Gurupatham Sathish K. , Velumani Priyanka , Vaidhya Revathy
Published: February 2021

A detailed model of human thermoregulation and a numerical algorithm to predict thermal comfort is a novel field of research and has wide applications in the auto/transportation industry and in the heating, ventilating, and air-conditioning (HVAC) industry. Anatomically specific convective and radiative heat transfer coefficients for the human body will be required to understand the human thermal physiological and comfort models. It necessitates to create hygienic and thermally comfortable spaces for the best productivity of the users. The physiological nature of thermal comfort during a transient condition such as a physical exercise or travel in an automobile are not yet well understood. In this paper, thermography has been applied to measure the convective and radiative heat transfer coefficients which has not been done before. Three different recovery processes were considered after the running of a human model on a treadmill with a range of speeds starting from 2 miles/hour to 10 miles/hour for stretch of twenty minutes. The recovery process included, (a) fan-assisted cooling with an air velocity of 0.5 m/s for 30 minutes, (b) fan-assisted cooling with an air velocity of 1.5 m/s for 30 minutes, and (c) natural cooling with no assistance of fan for 30 minutes. Thermal images were taken for forehead, trunk, arms, hands, legs of the models and the convective heat transfer coefficient and radiative heat transfer coefficient were calculated. The human models included both male and female, and belonged to two different age groups of less than 15 and above 40 with a total of 24 participants. The results show that though the temperatures, measured using thermography, for various parts of the human body changed locally, the overall calculated radiative heat transfer coefficients matched with the ASHRAE handbook values, and the calculated convective heat transfer coefficient increased with the increase of air velocity, while the models cooled down after the workout. Interestingly, the skin temperature decreased, initially, as the exercise progressed. After the completion of exercise, the skin temperature exhibited a quick rise during the recovery period with a subsequent decrease in the temperature, later. This trend was the same with all different age groups and sex of the models. The results also confirm that thermal images can be relied on for calculating the convective and radiative heat transfer coefficients of the human body to determine the heat transfer rate.
Deep Learning for Intelligent Bubble Size Detection in the Spallation Neutron Source Visual Target
Authors: Rasheed Fayaz , Dominguez-Ontiveros Elvis E. , Weinmeister Justin R. , Barbier Charlotte N.
Published: February 2021

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) will undergo proton power upgrade (PPU), increasing the proton beam power from 1.4 MW to 2.8 MW. From 2.8 MW, 2.0 MW will go to the current First Target Station and the rest will go to the future Second Target Station (STS). The First Target Station uses a liquid mercury target that is contained in a 316L stainless steel vessel. The proton beam is pulsed at 60 Hz, with a pulse of about 0.7μs. When the proton beam hits the target, the intense energy deposition leads to a rapid rise in temperature in the mercury. This temperature rise creates pressure waves that propagate through the mercury and cause cavitation erosion. The power upgrade will cause stronger pressure waves that will further increase damage because of cavitation. Injecting small helium bubbles in the mercury has been an efficient method of mitigating the pressure wave at 1.4 MW. However, at higher power, additional mitigation is necessary. Therefore, the 2 MW target vessel will be equipped with swirl bubblers and an additional gas injection port near the nose to inject more gas in the target. To develop a gas injection strategy and design, flow visualization in water with a transparent prototypical target (“visual target”) was performed. Bubble sizes and their spatial distribution in the flow loop are crucial to understanding the effectiveness of the bubbles in mitigating pressure waves. Bubbles were generated in the visual target under varied conditions of input pressures with helium and air. Images were captured using a high-speed camera at varied frame rates at different positions away from the swirl bubbler and different depths in the flow loop under varying lighting conditions. Initially, methods such as circular Hough transforms were applied after a series of images processing to obtain a general distribution of bubble sizes. Bubbles smaller than 500 μm are preferred to effectively mitigate the effect of pressure waves, which demands an accurate bubble detection and sizing system. Intelligent detection and identification of bubble sizes alleviate misdetection and improves accuracies. Employing neural networks, intelligent detection of bubble sizes and their distribution was developed and provides a robust alternative to traditional techniques. Human intervention was employed to label in-focus and out-of-focus bubbles in the set of training images. An object detection network using a pretrained convolutional neural network was created that extracted the features from the training images. Data augmentation was used to improve network accuracy through a random transformation of the original data.
Efficiency Centered Maintenance of Preheat Train of a Crude Oil Distillation Unit
Authors: Fajardo J. , Yabrudy D. , Barreto D. , Negrete C. , Sarria B. , Cardona C.
Published: February 2021

Nowadays, maintenance is based on the synergistic integration of operational reliability and timely maintenance, which guarantees the required availability and optimal cost. Operational reliability implies producing more, better performance, longer life, and availability. Timely maintenance involves the least time out of service, fewer maintenance costs, fewer operating costs, and less money. In this work, we study the preheating train of a crude distillation unit of a refinery, which processes 994 m3/h, which presents a formation of a fouling layer inside it. Among the impacts of fouling is the reduction in the effectiveness of heat transfer, the increase in fuel consumption, the increase in CO2 emissions, the increase in maintenance costs, and the decrease in the profit margin of process. An appropriate cleaning program of the surface of the heat exchanger network is necessary to preserve its key performance parameters, preferably close to design values. This paper presents the maintenance method centered on energy efficiency, to plan the intervention of the preheating train equipment maintenance, which considers the economic energy improvement and the cost of the type of maintenance. The method requires the calculation of the fouling evolution from which the global heat transfer coefficient is obtained, and the heat flux is determined as a function of time. It was observed that, as time passes, the resistance provided by fouling increases and that the overall heat transfer coefficient decreases. The energy efficiency centered maintenance has an indicator of economic justification (factor J) that relates the economic-energy improvement achieved when performing maintenance, taking into account the economic effort invested. Depending on the cost of the type of maintenance to be performed, a threshold should be chosen, from which the maintenance activity is justified. The effectiveness values of the heat exchanger (ε) and the J indicator are used to form a criticality matrix, which allows prioritizing maintenance activities in each equipment. The planning of the implementation dates of the maintenance of each heat exchanger, from the maintenance method centered on energy efficiency applied to the crude distillation unit’s, preheat train, constitutes a contribution in this specific field. The conceptual design of the maintenance method centered on energy efficiency presented in this work is feasible for other heat transfer equipment used in oil refineries and industry in general. The procedure developed uses real operation values, and with its implementation, a saving of 150000 US dollars was achieved.
Conjugate Mixed Convection in a Differentially Heated Lid-Driven Square Cavity With Rotating Cylinders
Authors: Paul Durjoy Kumar , Al Mehedi Abdullah , Chowdhury Emdadul Haque , Saha Sumon , Ali Mohammad , Amin M. Ruhul
Published: February 2021

Conjugate mixed convection in a lid-driven differentially heated square cavity with two heat-conducting rotating cylinders is numerically investigated. The right and the left walls of the enclosure, respectively, are maintained at a constant higher temperature (Th) and lower temperature (Tc), keeping the horizontal walls adiabatic. Both the cylinders are rotating in the counterclockwise direction. Only the left wall is moving downwards with a constant velocity. The governing nondimensional partial differential equations are resolved by means of Galerkin weighted residual finite element formulation. The average Nusselt number (Nu) is calculated along the right vertical heated wall. Flow and thermal fields are presented via streamlines and isotherms. Parametric simulations are performed for various pertinent parameters which are Grashof number (Gr), Reynolds number based on lid velocity (Re), Reynolds number based on cylinders’ peripheral velocity (Rec), and Richardson number (Ri). At first, the effects of variation of cylinders’ diameter are observed by considering six different cases for a particular peripheral velocity. It is found that the maximum Nu is obtained when the diameters of both cylinders are 0.1L. Further simulation is done for varying the Rec in the range of 5 to 50, to observe the effect of cylinders’ rotational speed. It has been found that for a particular Re, Nu increases with increasing rotational speed, but the effect is more pronounced at low Re. Finally, the combined effects of both Re and Gr on Nu have been investigated, keeping the Ri in the laminar mixed convection region. It has been demonstrated that when the Ri is increased from 0.1 to 10, the Nu enhances about 395.7%.
Assessment of Weld Bead Performance for Pulsed Gas Metal Arc Welding (P-GMAW) Using Acoustic Emission (AE) and Machine Vision (MV) Signals Through NDT Methods for SS 304 Material
Authors: Addamani Rudreshi , Ravindra Holalu Venkatdas , Gayathri Devi S. K. , Gonchikar Ugrasen
Published: February 2021

To gain high cost effective products along with quality and productivity, Pulsed Gas Metal Arc Welding (P-GMAW) process is used in many highly developed industries for fabrication of welded joints. The input parameters are the most important factors which affects the productivity, quality and cost effective for the welding process. The processes enable low net heat input, stable spray transfer and with low mean current. To enhance efficiencies with constant voltage GMAW process, P-GMAW is an outstanding substitute for those industries which are looking to improve quality of welds since the process helps over varying operator’s skills. It is essential to determine the input/output relationship parameters, in order to recognize and control the P-GMAW welding process. P-GMAW applies waveform control logic to fabricate a very precise control of the arc during speed range and a broad wire feed.

The power source switches between low background current and a high peak current between 30 to 400 times per second to obtain modified spray transfer process. The peak current pinches off wire droplets and drive it to the welded joints over this period. The process produces low heat input allowing weld pool to solidify, that metal transfer cannot occur but by the mean time, background current maintains the arc with stable spray transfer.

Trials have been conducted on SS 304 material using copper coated filler wire of size 1.4 mm based on the Taguchi’s L27 standard orthogonal array. Current, Gas Flow Rate (GFR) and Wire Feed Rate (WFR) with a constant speed are the input parameters considered to carry out trials. The output parameters are Yield strength (YS, N/mm2), percentage of elongation and Ultimate Tensile Strength (UTS, N/mm2). Indirect response parameters are Viz., AE signals such as welding AERMS, welding AEENERGY, tensile AERMS and tensile AEENERGY along with MV signals like area and height of the weld bead are considered to assess the performance of the weld bead joint. It is clearly observed from the obtained results that an excellent relationship exists between welding AERMS welding AEENERGY with tensile AERMS and tensile AEENERGY along with MV signals which were taken at the time of tensile test to evaluate the performance of the weld bead joint.

Verification of the results are carried out through performing different NDT testing methods on weld bead joint Viz., X–radiography, Scanning Electron Microscope (SEM) images to analyse external defects in the welded joints. On different zones of welded joint, Energy dispersive analysis (EDX) examination is carried out for elemental composition.
Experiment Study on the Current Density Distribution of PEMFC by Segmented Cell Technology
Authors: Miao Tianwei , Xie Xu , Tongsh Chasen , Liang Jinqiao , Liang Yiqi , Liu Zhi , Du Qing , Bai Fuqiang , Jiao Kui
Published: February 2021

The homogeneous of current density distribution is very important for performance and lifetime of proton exchange membrane fuel cell. In this study the current density distribution of a fuel cell with an active area of 108 cm2 has been investigated by using segmented cell technology. The σc is introduced to evaluate the homogeneity of current density and the smaller value of σc represents better homogeneity of current distribution. Under normal conditions, the experimental results show that the current density decreases progressively along the flow field at low cathode stoichiometry. It is also found that the homogeneity of current distribution has a strong correlation with the membrane hydration condition and always performs best at cathode relative humidity of 80% when anode condition keeps constant. The value of σc can be significantly reduced when cathode stoichiometry increases from 1.5 to 2.5, but it changes little when cathode stoichiometry continues to increase. During the cold start process, the evolutions of current density distribution are consistent with the temperature mappings. The form of stabilized heat core in the middle regions and homogeneous current density distribution are necessary for successful cold start. The value of σc also can be used to evaluate that the cold start succeeds or not.
Simulation and Visualization of Dynamic Systems in Virtual Reality Using SolidWorks, MATLAB/Simulink, and Unity
Authors: Akharas Ismail , Hennessey Michael P. , Tornoe Eric J.
Published: February 2021

This paper introduces a novel method for playing dynamic animations of rigid body assemblies with internal motions in virtual reality (VR). Through previous research over a decade ago, an inexpensive, relatively straight-forward process has been developed that entailed using SolidWorks, MATLAB/Simulink, and movie player software to permit one to view 2D MP4 files, such as on a laptop, smart phone, etc. Inspired by the usefulness of these previous results, the approach presented here targets a VR environment, clearly representing a technological leap over viewing 2D MP4 files. It’s made possible by recent advances in VR & gaming software (e.g. Unity) along with some unique software interfacing, including use of CADLink, to permit importation of CAD files, such as from SolidWorks, into Unity. Those interested in VR visualization of their dynamic system can use the step-by-step process presented as a manual to guide them through the hardware and software setup and ultimately learn how to use SolidWorks, MATLAB/Simulink, and Unity interactively to visualize their simulations in VR. Another key point is that the analyst has considerable control and access over each step in the process, including the dynamic modeling, unlike that commonly found in large, structured dynamic simulation software packages.

As an example to illustrate the process, a dynamic simulation of a classic pendulum/slider system was created using MATLAB/Simulink, which in effect numerically solves the ordinary differential equations of motion. The time-dependent displacement data for both the slider’s lateral movement and the pendulum’s angle, along with a time vector in incremental difference form, was saved as an Excel file. In turn, it was read by a C# script residing within Unity to permit an animation playback scenario of the SolidWorks CAD model of the entire pendulum/slider system (previously brought into Unity via CADLink with some reassembly), viewed more generally as an assembly with internal motions. Unity, a popular open-source piece of VR game development software used to produce both 2D and 3D video games and simulations, then serves as a platform to access the virtual world with the aid of an Oculus Rift (or Quest) VR headset and two hand controllers. In the end, the VR viewer can physically move around in the VR environment while at the same time view the playback motion of the pendulum/slider system from varying vantage points, just as one would expect in the real world. This work significantly advances the typical visualization experience with respect to dynamic system simulation & animation in addition to being widely applicable to generic mechanical assemblies.
Analysis and Design of an Auxiliary Catching Arm for an Apple Picking Robot
Authors: Porter Andrew , Alhamid Jassim , Mo Changki , Miller John , Iannelli Joseph , Honegger Marcel , Lichtensteiger Lukas
Published: February 2021

The newly designed 3-dimensional catching robot consists of three revolute joints where the forward linkage is a parallelogram mechanism for keeping the catching end-effector parallel to the picking manipulator’s base. A virtual apple field of 505 apples, designed to test the picking abilities of 7 DOF arm, was used to determine the capabilities of this new catching arm design. The target catching efficiency was 90% for the provided virtual apple field with a maximum drop height of 30 cm. The target coordinates for each virtual apple were found by computer simulation in MATLAB. Geometric parameters were selected such that the catching manipulator could reach every possible drop position in the picking manipulator’s workspace. The design was completed, fabricated, and validated, utilizing the elegant mechanical linkage design. The workspace analysis showed that it had an acceptable 93% catching efficiency, and as the drop height increased, the efficiency approaches 100%. Definitive inverse-kinematics provided exact joint angles required to catch all catchable apples inside of the workspace. Using these angles, the general equation of motion, using Lagrangian mechanics, yielded the required torque outputs of each of the three motors on the arm. Validation of these torques through laboratory experimentation was considered adequate.
Thermomechanical Formulation of Freezing Point Depression Behavior of Liquid on Solid Surface With Nanostructure
Authors: Hanawa Y. , Sasaki Y. , Uchida S. , Funayoshi T. , Otsuji M. , Takahashi H. , Sakuma A.
Published: February 2021

In this study, we investigated the freezing point depression of liquids in nanostructures using a new thermomechanical method. First, we experimentally determined the freezing points of water, cyclohexane, and a certain organic material (Chem.A) in nanoscale structures using DSC measurements. Thereafter, we formulated a new equation by improving the Gibbs–Thomson equation, which is the conventional formula for representing the freezing point depression of a liquid in nanostructures. We introduced a new term in this new equation to represent the increase in the kinetic energy of the liquid molecule as a result of collision between the liquid molecules and nanostructure walls. Subsequently, we evaluated the solid–liquid interface free energy of sublimation materials by fitting the theoretical freezing point derived from the new equation to experimental data. In this study, we succeeded in reproducing the experimental data of freezing point depression using the proposed equation. In particular, the freezing points of cyclohexane and Chem.A in the nanostructure were better fitted by this new equation at 10 nm or more compared with the conventional equation. Our results show that the interaction between the wall of the nanostructure and liquid molecules affects freezing point depression.
Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation
Authors: Sadeghi Tabar Roham , Lorin Samuel , Cromvik Christoffer , Lindkvist Lars , Wärmefjord Kristina , Söderberg Rikard
Published: February 2021

Geometric variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometric variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components can be achieved using the Method of Influence Coefficients (MIC), based on the Finite Element Method (FEM). The sequence, with which the spot welding operation is performed, influences the final geometric deformations of the assembly. Finding the optimal sequence that results in the minimum geometric deformation is a combinatorial problem that is experimentally and computationally expensive. For an assembly with N number of welds, there are N! possible sequences to perform the spot welding operation. Traditionally, spot welding optimization strategies have been to simulate the geometric variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture, using an appropriate measure of variation. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, the cause of variation in the deformations after the springback, between different sequences is identified. The relative displacements of the weld points in the assembly fixture, when welded in a sequence, is the source of such behavior. Capturing these displacements leads to large time savings during sequence optimization. Moreover, this approach is independent of the inspection fixture.

The relative weld displacements have been evaluated on two sheet metal assemblies. The sequence optimization problem has been solved for the two assemblies using this approach. The optimal sequence, the corresponding final assembly deformations, and the time-consumption have been compared to the traditional approach. The results show a significant correlation between the weld relative displacements in the assembly fixture, and the assembly deformation in the inspection fixture. Considering the relative weld displacement makes each assembly evaluation less time-consuming, and thereby, sequence optimization time can be reduced up to 30%, compared to the traditional approach.
Design of a Compliant Based Biomimetic Planar Locomotive Mechanism
Authors: Loupe Dillon , Kim Hanseul , Tekes Ayse , Tekes Coskun , Ali Amiri Moghadam Amir
Published: February 2021

This paper presents the design, development, modeling and control of a biomimetic multi degree of freedom compliant locomotive mechanism that can follow a prescribed trajectory. The research objective of this study is the design of a high mobility and flexible planar locomotive mechanism incorporating large deflecting compliant hinges. The actuation is realized using servo motors. Mechanism is consisted of five sliding carts, rail, 3D-printed supplementary pieces to house motors and pins. Carts are connected by monolithically designed two arm links joined by a large deflecting flexure. Four servo motors are mounted on the driven carts. Since sliding carts are identical, forward motion is achieved by changing the friction of carts through the connecting pins. Dynamical model is created in Matlab Simulink using Euler’s laws of motion principle, pseudo rigid body modeling (PRBM), vector closure-loop equations and kinematic constraints. To robustly control the position of the mechanism, first its nonlinear dynamics replaced with a family of linear time invariant systems which have parameter uncertainty. Then a robust controller is designed based on the Quantitative Feedback Theory (QFT) for the desired robust tracking and stability bounds. QFT is one of the most powerful robust control techniques which can take into account both phase and magnitude information of the system and enables the designer to minimize the cost of feedback by clearly observing the design constraints through robust performance bounds. Finally, the performance of the designed controller is validated though nonlinear simulations using the nonlinear dynamics of the mechanism. It has been shown that the mechanism can consistently track the desired inputs both in frequency and time domains.
RPM-Synchronous Grinding: An Innovative and Efficient Manufacturing Method for the Production of Non-Circular Workpieces
Authors: Spenger Thomas , Haas Franz , Pichler Jonas , Weinzerl Martin , Eder Stefan J. , Weiß Markus
Published: February 2021

RPM-Synchronous Grinding (RSG) opens up a wide range of applications, as this manufacturing process enables the efficient production of components with a functional macro geometry as well as a functional micro geometry of the surface. Unlike conventional non-circular grinding approaches, the RSG process strategy requires no oscillation of the infeed axis of the grinding spindle generated by coupling the rotation with the workpiece spindle. By using a fixed ratio of grinding wheel and workpiece spindle speed in conjunction with a non-circular grinding wheel geometry, almost all workpiece macro geometries can be produced in a simple plunge grinding process. The topology of the grinding wheel, the kinematic parameters of the dressing and grinding process and the material parameters of the workpiece must be sensibly matched to each other for an advantageous application of the process. Experiments can help to identify relationships, but simulation tools are needed to derive general predictions. Therefore, Molecular Dynamics Simulation (MD) is used to analyze the material removal process. By considering synchronous grinding at this level, the microstructural development of the workpiece and the chip formation process follow directly from atomic interactions, thus yielding elementary relationships to describe grinding. In the presented application, a defined cam geometry for an established steel material is produced using a conventional vitrified grinding wheel in the RSG process. The surface quality and geometric accuracy of the manufactured workpieces are evaluated. A selection of the MD grinding simulation results (workpiece, abrasive, and their interactions) is presented, and their intended application to the grinding process is discussed.
The Condensation Heat Transfer Characteristics of Zeotropic Hydrocarbon Mixtures in a Helical Pipe
Authors: Li Shulei , Zhu Rui , Xie Gongnan , Jiang Yiqiang , Cai Weihua
Published: February 2021

In order to explore tube-side heat transfer characteristics in the spiral wound heat exchange (SWHE) used in liquid natural gas (LNG) plants, the study on zeotropic hydrocarbon mixtures condensation heat transfer in a helical pipe is proposed. Firstly, based on two-fluid model and thermal phase change model, a numerical method coupling with empirical correlations is established to predict condensation heat transfer for zeotropic mixtures, in which the mixed effects are taken into account. Meanwhile, the rationality of the above methods is verified based on existing experimental results. Then, the effects of refrigerant components and operating parameters on flow patterns, heat transfer coefficients and heat and mass transfer resistance are discussed as the ranges of mass flux, saturation pressure and vapor quality are 200–800 kg/(m2·s), 2–4MPa and 0.15–0.90, respectively. It can be found that the predicted results coincide with the experimental ones, with deviations within ±15%. For different zeotropic hydrocarbon mixtures, as the vapor quality increases, the stratified flow, half-annular flow and annular flow appears in turn. The condensation heat transfer coefficients are always smaller than film heat transfer coefficients owing to the existence of heat and mass transfer resistance in vapor core. Besides, both film and condensation heat transfer coefficients increase with the increase of vapor quality and mass flux, while decrease with the rise in saturation pressure. Further, heat and mass transfer resistances increase as the vapor quality and saturation pressure increase and the mass flux decreases. In addition, compared to methane/ethane/propane/nitrogen (65/25/5/5, mole%) mixture, the averaged heat transfer performance for methane/ethane (90/10, mole%) mixture improves by 19.55%, whereas, the average heat and mass transfer resistance decreases by 53.51%. This study is helpful for understanding the zeotropic mixtures condensation in tubes and gives some suggestions for the choice of refrigerant components used in LNG SWHE, to design more effective SWHE.
Reflector-Augmented Photovoltaic Power Output Incorporating Temperature-Dependent Photovoltaic Efficiency
Authors: Alasadi Habeeb , Mulford Rydge , Gilbert Robert
Published: February 2021

The power output produced by Photovoltaic (PV) panels depends on the quantity of solar energy incident on the PV surface, the surface area of the module and the efficiency of the system which is a function of the module’s surface temperature. Concentration of solar irradiation onto a PV surface augments the solar energy flux on the module surface as has been shown by published literature. However, concentrated solar irradiation increases the PV surface temperature, decreasing the efficiency of the module. The papers presented in the literature review do not exam the impact of PV models temperature on performance of PV efficiency. In this work, the influence of temperature-dependent module efficiency on the power extracted from a Reflector-Augmented Photovoltaic (PV) module is explored. A reflector-collector system is considered theoretically having a variable angle between the reflector and collector as well as a variable angle between the reflector and the horizontal axis. The hourly solar radiation incident on the PV module and the reflector are obtained using TMY3 data of Dayton. The total solar radiation (direct and reflected components) striking the collector is calculated on an hourly basis which is in turn used to determine the temperature of the PV module. The electrical power produced on an hourly basis is then calculated in Dayton, OH. In order to determine the influence of temperature-dependent PV efficiency on system behavior, this study determines the electrical power produced by the system for two separate cases: a constant PV efficiency (which does not vary with temperature) as well as a temperature-dependent PV efficiency. For both cases, four separate conditions are evaluated, being different combinations of reflector-collector angle as well as reflector-horizontal angle. Results indicate that the output power of a PV module with temperature-dependent efficiency is less than the output power of the same PV module having a constant efficiency. Monthly average power increase fractions variation of both cases follows a similar trend while power increase fractions are higher during summer times than winter times. Temperature-independent power increase fractions are also higher on average than temperature-dependent power increase fractions for all four conditions.
Mechanical Properties of Spider Silk for Use As a Biomaterial: Molecular Dynamics Investigations
Authors: Rawal Atul , Rhinehardt Kristen L. , Mohan Ram V.
Published: February 2021

Even though silkworm are the most dominant type of silk fibers used for commercial applications, spider silk has a definitive role in biomedical applications due to its biocompatibility and excellent mechanical properties as biomaterials. In recent years, recombinant production of the silk proteins at a larger scale has found new interest. Spider silk composites with a combination of a variety of other biomaterials have also been used to improve properties such as bio-compatibility, mechanical strength and controlled degradation. [1] A major constituent of spider silk fibers, are spidroin proteins. These are made up of repetitive segments flanked by conserved non-repetitive domains. The fiber proteins consist of a light chain and a heavy chain that are connected via a single disulfide bond. [2] Present paper employed steered molecular dynamics (SMD) as the principal method of investigating the mechanical properties of these nanoscale spider silk protein 3LR2, with a residual count of 134 amino acids. [3]. SMD simulations were performed by pulling on β-chain of the protein in the x-direction, while holding the other fixed. The focus of this paper is to investigate the mechanical properties of the nanoscale spider silk proteins with lengths of about 4.5nm in a folded state, leading to understanding of their feasibility in bio-printing of a composite spider silk biomaterial with a blend of various other biomaterials such as collagen. An in-depth insight into the fraying and tensile deformation and structural properties of the spider silk proteins are of innovative significance for a multitude of biomedical engineering applications. A calculated Gibbs free energy value of 18.59 kCal/mol via umbrella sampling corresponds with a complete separation of a single chain from a spider silk protein in case of fraying. Force needed for complete separation of the chain from the spider silk protein is analyzed, and discussed in this paper. It is found that the protein molecule undergoes a tensile stretch at strain rates of ≅ 11.65. An elastic modulus of 20.136 GPa, calculated via simple SMD simulations by subjecting the silk β-chain to a tensile stretch is also presented.
Energy Analysis and Waste Valorization in a Kraft Paper Plant
Authors: Antunes Pedro , Ferreira Manuel Eduardo , Vilarinho Maria Cândida , Teixeira José Carlos
Published: February 2021

Paper production is an energy intensive industry but due to the wastes of its process (black liquor, waste biomass, sludge) has the capacity to generate most of its energy internally. Central to this balance are cogeneration units that guarantee the internal production of heat and electricity. These are sized for the company’s thermal load, with excess electricity injected into the grid.

The efficient use of endogenous resources is a major route for improving the energy and environmental efficiency of the plant. Some of the waste materials include biomass wastes, sludges and other industrial wastes such as plastics.

The present work aims to identify the opportunity of introducing a waste biomass gasification plant and the use of the produced synthesis gas, replacing the natural gas currently used in the turbine included in the company’s cogeneration unit.

In this scenario, one of the cogeneration units in its current configuration has two steam boilers (one biomass; one black liquor) and a gas turbine whose waste heat feeds a recovery boiler to produce steam.

The work involved several steps: the energy balance of the unit, the characterization of biomass residues (mixing bark, pine bark, eucalyptus bark, and refuse fibers), the test experimental analysis of residual biomass gasification and the characterization of the synthesis gas produced.

In the electric and thermal energy producing units, gas turbines have a working efficiency above 35% while the steam turbines is considerably lower (15%). The efficiency of the chemical recovery boiler (79.5%) is lower than that of the biomass boiler (89.5%).

From the experimental analysis of biomass it was found that most of them have a carbon and hydrogen content higher than 48 % and 5 %, respectively. In terms of higher calorific value (HHV), for the biomass where it was possible to determine it, the value is between 19.3 and 23.6 MJ/kg. These properties reveal that the selected biomasses from within the company, have potential as fuels. The limitation on its use may be due to the ash content, which tends to exceed 10 %.

A gasification test (90 % eucalyptus biomass and 10 % mixture biomass) was also carried out to produce syngas and further characterization. The calorific value of the gas produced was 18 MJ/kg, with an absolute density of 1.17 kg/m3.

It can thus be seen that for a gas turbine with a 35.8 % efficiency with a workload of 29.9 MWe 4.6 kg/s of syngas is required.
Build Time Analysis of Additive Manufacturing for Next Generation SLS Systems
Authors: Machado Michael , Fangueiro Raul , Barros Daniel , Nobre Luís , Bessa João , Cunha Fernando , Silva João , Sousa João
Published: February 2021

With the recent advances in the additive manufacturing (AM) production technologies, AM is becoming more common in today’s industry, nowadays is a normal practice to use this solution either to test a new prototype or to manufacture a functional product. The increase application is mainly due to significant developments in the production solutions of the AM. These recent developments are resulting in an increase search for new and more efficient production solutions. This search is always focused in producing more efficiently, with a greater variety of materials and produce part with better quality and proprieties. From an industrial point of view, one of the types of additive manufacturing that is increasing the percentage of use is the selective laser sintering (SLS) technologies. Although this process was first used in the mid-80’s, it has shown great developments in the recent years. This evolution of the process allowed it to become a solid solution even if it is highly time consuming, especially when compared with other types of addictive manufacturing.

From the several aspects that make the SLS a robust solution is the fact that it offers a consistent solution to produce high complex part with good mechanical properties, and also the ability to use many core materials, from polymers, metal alloy, ceramics or even composites materials. Due to the fact that the production of part using SLS technologies takes a long time, shows the relevance to study the entire process in order to quantify the time spent in each stage a very important step.

This study can be conducted with two major goals, in one hand to be able to predict the build time needed to complete a predetermined task, and in other hand, to improve the overall efficiency of the process based on the knowledge acquired in the previous analysis. These two aspects are important because they allow the machine operator to choose the production plan more carefully and also to know all the parameters of the process to make it more efficient.

In this paper will be presented a survey of the major stages of a SLS process in order to quantify the time consumed in each one of the stages, and if possible, determine solution to reduce the time spent. To better understand the topic the paper will be divided according to the proprieties and time consumed in each of the elements of the process. In other words, it will be divided accordingly to a machine, laser and material point of view. Furthermore, this paper will be focused in the SLS process and the productions based in a polymeric powder, therefore also containing aspects related to the power source used.