bluuebunny/crossref_metadata_2025 huggingface dataset:
Operational Characteristics of Internally Geared Positive Displacement Screw Machines
Authors: Read Matthew , Stosic Nikola , Smith Ian
Published: January 2018

Cylindrical helical gearing profiles can allow an externally lobed inner gear to rotate inside an internally lobed outer gear while maintaining continuous lines of contact between the gears. A series of separate working chambers are formed between the rotors, and this paper investigates the use of ported end plates to control the period during which fluid is allowed to enter or leave these working chambers. A simple method of defining the rotor profiles is considered, allowing the geometry of such internally geared screw machines to be characterised. The performance of the machine is then investigated for particular applications. The key considerations in this preliminary study are the effect of geometry on the forces and torques that act on both the inner and outer rotors. The results suggest that low rotor contact forces are possible, which is necessary to ensure high efficiency and low wear in practical machines.
Heat Conduction in Si/Ge Superlattices: A Molecular Dynamics Study
Authors: Ji Pengfei , Rong Yiming , Zhang Yuwen , Tang Yong
Published: January 2018

Owing to the exceptional low thermal conductivity, Si/Ge superlattices becomes an attractive thermoelectric material to convert thermal energy into electric power. The heat conduction process in Si/Ge superlattices is studied by employing the molecular dynamics (MD) simulation in this paper. For the purpose of investigating the role of Si and Ge interface to the contribution of overall thermal conductivity reduction in Si/Ge superlattices, convergent and divergent cone nanostructures are designed as interfaces between Si layer and Ge layer. By keeping fixed temperature difference between the left and right sides of Si/Ge superlattices with constant length, the spatial distribution of temperature and temporal evolution of heat flux flowing through Si/Ge superlattices are calculated. Comparing with the Si/Ge superlattices with even interface, the nanostructured interface contributes to impede the heat conduction between Si and Ge atoms. Si/Ge superlattices with divergent cone interface presents the most excellent performance among all the simulated cases. The design of nanostructured interface paves a promising path to enhance the efficiency of Si/Ge thermoelectric material.
The Experimental Investigation of the Internal Support Effects on Exhaust Casing Pressure Recovery
Authors: Kalista Robert , Mrózek Lukáš , Hoznedl Michal
Published: January 2018

As is well known, the performance of the last stage of the low pressure part of a steam turbine is strongly influenced by the effectivity of the downstream exhaust casing. The efficiency of the exhaust hood depends on many structural factors such as the design of the diffuser parts, dimensions of the outer casing or arrangement of internal supports. The aim of this paper is the experimental study of the influence of the internal supports of the axial-radial exhaust hood on its pressure recovery factor. For one geometry of its diffuser parts a few different variations of internal supports such as T-rib, tube grid or BV were tested. The effect of reducing the width of exhaust hood in the horizontal joint and the changing of axial length of the diffuser were observed. The width of exhaust hood in horizontal joint and the axial length of the diffuser define the area in the horizontal joint of the exhaust hood. How the diffuser behaves when reducing this area is very important in retrofitting of old machines, where there are so many geometric constrains. The effect of wall jet blowing into the diffuser wall was also evaluated. In this paper we concentrate to examine the sensitivity of these certain geometrical parameters of exhaust hood on the pressure recovery of the whole exhaust system of the low pressure part of the steam turbine.

The main purpose of our analysis and experimental measuring was optimising the axial-radial exhaust hood of the steam turbine. For this reason, wind tunnel facilities with relevant measuring and traversing systems were designed and built. The measurements have been performed on 1/5th scale test rig which enabled rapid and efficient evaluation of multiple geometrical variants. The observed exhaust hood was designed for an extra long 54inch last stage blade. For measurements of flow parameters was used multi-hole pneumatic pressure probes and wall pressure taps in conjunction with CFD tools to explore physics based alterations to the exhaust configuration.
Measurement of Dynamic Performances of High-Speed Rotating Spindle by Non-Contact Electromagnetic Loading Device
Authors: Wan Shaoke , Hong Jun , Su Wenjun , Li Xiaohu , Sun Yanhui , Chen Wei
Published: January 2018

When spindle rotates, the stiffness and natural frequency that reflect the dynamic performances of spindle system, vary with different rotating conditions. Therefore, the measurement of stiffness and natural frequency is highly needed. However, it is difficult to apply excitation to the rotating spindle during the measurement. In this paper, a non-contact electromagnetic loading device is developed to provide desirable excitation for the measurement. Next, an experimental spindle test rig with constant pressure preload is established. With the help of the proposed loading device, stiffness and natural frequency of the experimental spindle at different rotating states are measured. Finally, the effects of rotation speed and temperature on the natural frequency and stiffness of spindle are discussed based on the measurement results. The results show that the rotation speed and temperature have the similar influence trend on the experimental spindle’s softening.
ADI-CRSTS: A New Method for the Moving Heat Sources — Application to a Train Pantograph Strip
Authors: Delcey Nicolas , Baucour Philippe , Chamagne Didier , Wimmer Geneviève , Bouger Odile , Auditeau Gérard , Blanvillain Gérard , Bausseron Thomas
Published: January 2018

The pantograph strip interface involves many physical phenomena. Temperature evolution is one of them. This problem includes various thermal flux and sources. More specifically, due to the train motion, a moving zigzag heat source occurs.

This paper deals with a thermal 2D Alternating Direction Implicit (ADI) numerical method for temperature estimations in the train pantograph carbon strip, the aims being a better wear problems anticipation and the creation of a preventive maintenance. For that, an electrical model is coupled to the thermal one to take into account all Joule effects.

The ADI strategy enables a significant computation time reduction against most classical resolution methods. Besides, the model involves two mathematical processes: the first one is an appropriate variable transform which induces a fixed surface heat production, while the second is based on locally refined meshes.

Various numerical tests are presented and discussed in order to show the accuracy of the scheme. From a physical point of view, the results are much interesting. Further investigations, depending on the different parameters, should lead us to predict the strip critical thermal phases.
Numerical Efforts of Aerodynamic Re-Design in a Transonic Centrifugal Compressor: Part 1 — Basic Approach
Authors: Oh Justin (Jongsik)
Published: January 2018

Growing demands for higher specific output power in turbomachinery applications have drawn attention to aerodynamic design philosophy for a single-stage transonic centrifugal compressor with higher pressure ratios. As Part 1 of numerical efforts, some fundamental approaches in aerodynamic design were carried out in a classical 6:1 pressure-ratio compressor design of 1970’s which was selected as a baseline. The effects of the impeller blade angle distribution, the addition of the splitter blade, the changes of the tangential divergence angle of the channel-wedge diffuser and some tweaks in diffuser vane shapes near the trailing-edge were investigated in steady-state RANS CFD solutions with the conventional mixing plane interface. New blade angle distributions together with the introduction of splitter blades in the impeller brought significant improvements in the compressor pressure ratio, efficiency and operability, thanks to reduced shock strengths and enhanced blade loadings in the spanwise direction. Helicity contours on the cross sectional planes in the impeller support the benefits observing a power balance among the shroud passage vortex, the blade vortices and the tip leakage vortex. With a reduced tangential divergence in the channel-wedge diffuser passage from the original design, an impressively extended surge margin was obtained. It was confirmed from the helicity contours that a streamwise vortex structure at the entrance region of the diffuser vane plays a key role in the range of operation. A diffuser vane shape with the curved pressure surface near the trailing-edge provided a slightly higher pressure ratio and efficiency around design flow than that with the original cut-off trailing-edge. An elliptical trailing-edge diffuser vane showed rather performance drops because of the counter-clockwise hub vortex breakdown near the suction surface, resulting in less flow diffusion. Through investigations of a set of design cases, two final compressor designs, differing in the diffuser vane shape near the trailing-edge, were obtained within the work scope of the present study. However, selecting one of the two will depend on design duties for the following component because of the level of exit swirls and their rate of changes over the flow rates.
Synthesizing Bidirectional Constant Torque Compliant Mechanisms
Authors: Reddy Bhavanam Praveen , Zhou Hong
Published: January 2018

The output or resisting torque from a constant torque compliant mechanism keeps invariant in a large range of input rotation. Unlike regular constant torque compliant mechanisms that have only one input rotation direction, the input rotation of a bidirectional constant torque compliant mechanism can be either clockwise or counter-clockwise. Its resisting or output torque reverses its direction with the change of the input rotation direction. The unique feature of bidirectional constant torque compliant mechanisms makes their synthesis challenging. In this paper, a synthesis method is introduced to surmount the synthesis challenges. The constant resisting torque is generated through a set of curved beams that are mounted within an annular design domain. Because of the bidirectional requirement, the two ends of each curved beam are aligned along radial direction before deformation to avoid rotational bias. Spline curves are employed to describe curved beams and defined by their control parameters. The synthesis of a bidirectional constant torque compliant mechanism is systematized as optimizing the control parameters of its curved beams. The presented method is demonstrated by the synthesis of bidirectional constant torque compliant mechanisms that have different arrangements of curved beams in the paper.
Multiscale Sheet Metal Hydroforming and Burst Pressure Estimates
Authors: Emblom William J. , Olayinka Ayotunde , Wagner Scott W. , Pesacreta Thomas C. , Wahab Muhammad A.
Published: January 2018

Micro- and multiscale material properties must be considered when manufacturing miniature devices, especially when considering utilizing multiscale sheet metal hydroforming processes. One of the critical considerations during the design process is the burst pressure for the sheet metal which is a limiting factor for potential hydroforming operations. In order to simplify determining tearing or rupture conditions, it is sometimes desired to use analytical methods for estimating material properties, including burst pressures, which occur shortly after material instability. Many researchers have developed approximate methods for predicting deformation during open die hydroforming based upon analytical approaches for biaxial conditions for circular and elliptical dies. Additionally, extracting material properties of sheet metal under biaxial conditions such as bulge hydroforming more closely matches forming conditions that the sheet metal will undergo for actual parts. The objective of the current research was to evaluate the analytically developed models’ ability to predict burst conditions and compare those burst results to those obtained from finite element models and experimentation. Stainless steel (annealed 0.2-mm thick AISI 304) was hydroformed in a circular open die with diameter of 11mm. Elliptical dies were also evaluated that had minor diameters of 11mm and aspect ratios down to 0.5. It was found that using the analytical method developed specifically for circular dies was a good predictor for the burst pressure while the more general analytical method for elliptical dies did not agree with either results from finite element analysis or experimental results.
Design and Manufacturing of Implantable Expanding Cage
Authors: Wang Z. Y. , O’Toole B. , Nunez V. Carbajal , Ta D.
Published: January 2018

This paper discusses the design and manufacturing of the Universal Expanding Cage (UEC), which is a biomechanical device that is implantable in the human spinal cord region. It compensates for disc height loss and relieves pressure that causes nerve damage. Forces surrounding the UEC are analyzed, stresses on the UEC body and resulting displacement are calculated, and materials suitable for the human biological vertebra environment are studied. Manufacturing methods for implantable UEC are also discussed using 3D direct metal print technique.
Implementation of Additive Manufacturing Into Engineering and Engineering Technology Curriculum
Authors: Springer Scott L. , Johnson Jerome , Bushendorf Glenn
Published: January 2018

Public universities have a responsibility to continuously improve instruction and maintain currency with new technological advances. Simultaneously many public universities are under budget constraints seeking to maintain or reduce costs. One recent technological advance is the adoption of additive manufacturing by an increasing number of manufacturing industries. While machine costs of additive manufacturing have dropped in recent years, machine and consumable material costs remain significant. Hence, there is a need in the manufacturing, engineering and technology education community for methods to introduce additive manufacturing concepts into the curriculum while doing so with a minimum required investment.

In this paper we discuss the methods used to implement additive manufacturing theory and applications into the Engineering and Engineering Technology curriculum at the University of Wisconsin-Stout. Applications of the additive manufacturing technologies have been successfully included in traditional courses covering sophomore level research and development, upper level computer-aided design, upper-level research and development, capstone courses, and the introduction of a new course focused on additive manufacturing. The implementation of commercial, low cost open-source hobbyist kits and new hybrid student designs of AM machinery is discussed, along with the process used to develop additive manufacturing equipment in the Advanced Manufacturing Lab.
Fire Protection Systems for Tanks Made of GFRP
Authors: Pötzsch Sina , Timme Sebastian , Sklorz Christian , Skoczowsky Danilo , Otremba Frank , Krüger Simone
Published: January 2018

The application of lightweight materials for tanks for transportation appears promising. Besides saving weight and therefore transportation costs, new complex geometries that depart from common cylindrical shapes of steel tanks can be manufactured. For transportation of dangerous goods, fire and explosion safety must be maintained to prevent accidents with serious consequences. In this work the fire behavior of lightweight tanks made from glass fiber reinforced plastics (GFRP) with complex geometries is investigated. Pretests on intermediate scale GFRP plates are conducted to identify suitable fire protection systems and surface treatments for composite tanks. The fire resistance is shown to be improved by addition of fire protective coatings and integrated layers. Finally, a complex rectangular GFRP tank with a holding capacity of 1100 liters is fire protected with an intumescent fire coating. The tank is filled up to 80 % with water and burned under an engulfing fully developed fire. It was shown that the intumescent layer could expand before the decomposition of the resin occurred. Furthermore, the adhesion between tank surface and coating was maintained. The structure could withstand a fire for more than 20 min.
Contactless Measurement of Spindle Stiffness by Using Lateral Stator Magnetic Loader
Authors: Su Wenjun , Wan Shaoke , Sun Yanhui , Hong Jun , Li Xiaohu
Published: January 2018

In this paper, a novel radial loading topology is proposed for various spindle test application where the space in the tool head is limited or the performance to the length is sensitive. The stator of the loading device grows in the lateral direction, allowing for a compact axial length design. Finite element analysis (FEA) is carried out and the device design is optimized for the specifications of a radial loading device for high speed spindle. Finally, the designed device were manufactured and tested. By using this magnet loader, measurement results are given and the effectiveness of the designed prototype has been verified.
Computational Three-Dimensional Microstructure Defect Distributions in Thermal Barrier Coatings
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G. , Gorzkowski Edward P. , Drazin John
Published: January 2018

Thermal protection of components such as turbine blades is often done with thermal barrier coatings which are typically ceramic materials. Methods to manufacture ceramic coatings are being developed to create microstructures that optimize thermal protection without degrading mechanical properties of the coating. The coating requires sufficient mechanical properties to remain in place during loads associated with the operation of the component. The work presented in this paper is part of a broader effort that focuses on novel processing techniques. A fabrication method of interest is the inclusion of spherical micron-sized pores to scatter photons at high temperatures along with nano-sized grains to scatter phonons. Pores are sized and distributed so that mechanical strength is maintained. In the current work, yttria-stabilized zirconia (YSZ) is modeled. Three-dimensional microstructures representing YSZ are computationally generated. The defect sizes and orientations are generated to match an experimentally observed distribution. The defects are either randomly or regularly placed in the microstructural models. Stress-displacement analysis is used to determine effective bulk material properties. Comparisons are made to prior two-dimensional work and to experimental measurements available in the literature as appropriate. The influences that defect distributions and three dimensional effects have on the effective bulk material properties are quantified. This work is a preliminary step toward understanding the impacts that micron sized pores, voids and cracks have on thermal and mechanical characteristics. The goal is to facilitate optimizing the microstructure for thermal protection and strength retention.
Impact Performance of Cellular Core Hybrid Tubes Under Axial Compressive Loading
Authors: Ohioma Eboreime , Ali Muhammad , Alam Khairul
Published: January 2018

Thin wall structures are primarily deployed in automotive chassis to increase the energy absorption capacity of the automobiles in the event of an accident. Researchers have delved into developing lighter structures for improving automobiles’ fuel efficiency with a challenge of maintaining or preferably exceeding the energy absorption properties of the structure. In this study, the work presented is a continuation of research conducted on exploring the effects of the introduction of cellular core in tubular structures under axial compressive loading. The crushing response of cellular core hybrid tube was numerically studied using ABAQUS/Explicit module. The characteristics such as deformation or collapsing modes, crushing/ reactive force, locking strain, energy curves, and specific energy absorbed were studied. The cellular core hybrid tube shows significant potential for reducing the weight of automobile structure while giving positive indication towards enhancing the specific energy absorption capacity.
A Study on the Use of Graphene-PEEK Composites As High Temperature Adhesives: Mechanical Properties and Microwave Activation
Authors: Littlefield Andrew G. , Bartolucci Stephen F. , Mauer Joshua A.
Published: January 2018

Polyetheretherketone is a widely used engineering polymer that is especially suitable for high-temperature applications. Graphene is a two-dimensional form of carbon nanomaterial that has been studied extensively for its mechanical, electrical and thermal properties and its use as a filler in polymer matrices. Compounding graphene into polymers has the potential to improve various properties, even at very low concentrations. In this work, we have examined the incorporation of graphene nanoplatelets (GNP) into PEEK. We have fabricated composites using melt-mixing techniques, as well as by graphene functionalization and in-situ polymerization of the PEEK. In this way, we can compare the performance of the composites by two different processing methods. The GNP-PEEK composites were characterized by DSC, TGA, and SEM. Lap-shear joints using the GNP-PEEK as the adhesive were made and mechanically tested. Results show that the weight fraction of GNP has a major effect on the strength of the joint. In this work, we aim to produce a material that functions as a reusable high-temperature, thermoplastic adhesive, which can be activated by conventional heating methods, or by microwave heating. The GNPs act as microwave absorbers and heat the surrounding PEEK matrix to the point of melting, in contrast to the neat PEEK, which does not melt upon exposure to the microwaves under the same parameters. Additionally, we explore 3D printing methods to fabricate a lap shear joint, where the adherends are pure polymer and the adhesive region is a polylactic acid/carbon nanofiber (PLA/CNF) composite that can be activated by microwaves. We show that solid adherends can be bonded together when a solid PLA/CNF piece is placed between the adherends and melted by microwave exposure. The microwave absorption properties and adhesive properties will be discussed.
Nonlinear Vibrations of a Beam-Spring-Large Mass System
Authors: Bukhari Mohammad A. , Barry Oumar R.
Published: January 2018

This paper presents the nonlinear vibration of a simply supported Euler-Bernoulli beam with a mass-spring system subjected to a primary resonance excitation. The nonlinearity is due to the mid-plane stretching and cubic spring stiffness. The equations of motion and the boundary conditions are derived using Hamiltons principle. The nonlinear system of equations are solved using the method of multiple scales. Explicit expressions are obtained for the mode shapes, natural frequencies, nonlinear frequencies, and frequency response curves. The validity of the results is demonstrated via comparison with results in the literature. Exact natural frequencies are obtained for different locations, rotational inertias, and masses.
Development of Automatic System for Process Planning and NC Program Generation on Turning-Milling Machine Tool With Three Turrets
Authors: Fukuda Ryo , Kiyooka Ririko , Aoyama Hideki
Published: January 2018

The objective of this study is to develop an automatic process planning and a numerical-control (NC) program generation system for free-form machining, using a turning-milling machine tool with multi-turrets. In this research, machining feature recognition was carried out based on the delta-volume decomposition to achieve process planning. This system can recognize machining features that include one free-form surface and can create a tool path for the free-form surface. A process plan candidate is generated via the assignment of machining features to each turret and the determination of the processing order of the machining features in each turret. The system generates many process plan candidates, and evaluates them based on the evaluation point of the user. In this research, the plan with the shortest machining time is selected. Next, the system automatically generates an NC program for each turret. Ultimately, a machining experiment using a turning-milling machine tool with three turrets was conducted to verify the usefulness of the system.
Pretension Analysis for Piezoelectric Stack Actuator in Nano-Positioning Stage
Authors: Zhang Meng , Liu Zhigang , Bu Mingfan , Zhu Yu
Published: January 2018

Taking advantages of high stiffness, fast response, high-bandwidth as well as large pushing force capability, piezoelectric stack actuators have been widely used in the fields of high speed nano-positioning stages and precision systems. An inevitable disadvantage of piezoelectric actuators is that they are highly intolerant to shear and tensile forces. During high speed scanning operations, the inertial forces due to the effective mass of the stage may cause the actuators to withstand excessive shear or tension forces. To protect the actuators, preload is often applied to compensate for these forces. Flexures have been used to supply preload to the piezoelectric stack actuators in many high-speed nano-positioning stages. Nevertheless, for nano-positioning stages with stiff flexures, it is a difficult job to displace the flexures and slide the actuators in place to preload them. This paper proposed a novel preloading nano-positioning stage which allows the piezoelectric stack actuator to be preloaded and mounted easily without obviously reducing the stiffness and speed of the nano-positioning stage. A preloading nano-positioning stage is designed and the flexible hinge and piezoelectric stack actuator of the stage are analyzed. The stiffness and resonance frequency of flexible hinge and optimal preload for the proposed stage is obtained by kinetics analysis. In order to verify the effectiveness of preloading nano-positioning stage, an online test system is established. The system mainly composed by a force sensor module, a capacitive sensor module and the preloading nano-positioning stage. A force sensor is applied between piezoelectric actuator and flexible hinge which can directly measure the preload in real time. The displacement of the flexible hinge is measured by a capacitive sensor to evaluate the positioning accuracy. Experiments are conducted, and the results demonstrate the effectiveness of the proposed approach.
Bolt Loosening Behavior of Bolted Joints Under Repeated Transverse Loads
Authors: Sawa Shunichiro , Ishimura Mitsutoshi , Sawa Toshiyuki , Nagao Takanori
Published: January 2018

The objective of the paper is to examine bolt loosening behavior in a bolted joint under transverse loading both experimentally and numerically. Bolt loosening tests were carried out using Junker’s type loosening machine. In the Junker’s loosening tests, repeated transverse displacements (displacement range S = ±0.35mm were applied to a bolted joint with a M10 hexagon bolt and nut, and then a reduction in the axial bolt force was measured. In the FEM calculations, bolt loosening behavior was examined for a model of Junker’s type loosening machine. In addition, the effects of the flatness and the surface roughness at the bearing surfaces in a clamped part on the reduction in the axial bolt force were examined in the FEM calculations. As a results, it was found that the nut rotation occurred when a glider plate moved toward to the center of the joint from the right and the left dead points. In addition, bolt loosening mechanism was elucidated using the change in the contact stress distribution at the engaged screw threads. The reduction in axial bolt force was found to be the largest for the first 1 cycle loading and then it decreased gradually as the loading cycles increased. An amount of the reduction in the axial bolt force was predicted in the FEM calculation taking account of the flatness (inclined of clamped part) and the surface roughness (contact surface ratio) in 10 loading cycles. The contact surface ratio (surface roughness) was found to significantly affect the reduction in axial bolt force. The predicted results were in a fairly good agreement with the experimental results. Furthermore, the effects of the grip length and the nominal bolt diameter were examined on the bolt loosening behavior experimentally.
Stability Influence of Different Eccentric Phases in a Rotor-Bearing System
Authors: Mo Wenchao , Jiao Yinghou , Chen Zhaobo , Zhang Enjie
Published: January 2018

A dynamic model of a rotor–bearing system with two discs is proposed in this study. The effect of eccentric phases of two discs on the oil-film stability is investigated. Considering the gyroscopic effect, the nonlinear dynamic behavior of the rotor-bearing system with two discs is analyzed based on the Finite Element Method. Two sliding bearings are simulated by the unsteady nonlinear oil-film force based on the assumption of short bearing model. The Newmark integration method is adopted to solve the equation. The research focuses on the stable region considering the eccentric phases of two discs and nonlinear responses of the rotor–bearing system by using the Poincaré maps, bifurcation diagrams and spectrum cascades. The results indicate the influence of different eccentric phases of two discs on dynamic response. The relationship between the stable region of the rotor-bearing system and eccentric phases of two discs is obtained, which is very important for the design of the rotor-bearing system.
Hydrodynamic Characteristics of Micro Heat Sinks With In-Line and Staggered Arrangements of Cylindrical Micro Pin Fins
Authors: Mohammadi Ali , Koşar Ali
Published: January 2018

This study compares the hydraulic performance of rectangular micro heat sinks (MHS) with different in-line and staggered arrangements of micro pin fins (MPF). With fixed MHS dimensions of 50 × 1.5 × 0.1 mm3 (1 × w × h), the height (H) and diameter (D) of MPFs are both set to be 0.1 mm which corresponds to a fixed H/D ratio of 1 in all cases. Four in-line and four staggered arrangements of MPFs with alternative horizontal and vertical pitch ratios (SL/D and ST/D) of 1.5 and 3 are considered. Streamline profiles are used to illustrate the flow patterns and wake regions. Using ANSYS FLUENT v.14.5 for this single phase study, the simulations are done at five Reynolds numbers of 20, 40, 80, 120 and 150, ensuring the flow remains in the laminar flow regime. Considering water as the coolant, a constant heat flux of 30 W/cm2 is applied through the bottom surface of the MHS and the MPFs liquid interacting surfaces. The results show a great dependency of the evaluating parameters on the arrangement type, geometrical specification and Reynolds numbers. For pressure drop, clear comparison could be made regarding each of the geometrical specifications. However, the trends with friction factor depend on geometrical specification and Reynolds number at the same time.
Finite Element Study of Double-Gasket Bolted Joint Connection for Different Gaskets and Bolt Torques
Authors: Ghafouri-Azar Reza , Banan Rosha , Stojakovic Miodrag (Mike)
Published: January 2018

In order to understand the behavior of bolted joints and select a right size, type and gasket load combination, a detailed analysis tool is very helpful. However, the modeling and analysis of a bolted joint connection is a complicated, complex process; particularly if multiple parts are considered in the Finite Element (FE) modeling. Analysis results are often sensitive to bolt pre-torque, gasket type, gasket thickness and other challenges of Finite Element (FE) modeling. In addition, often credible and reliable gasket deflection-load data are not readily available. The bolted joint under study was a double-gasket joint with inner gasket leakoff. The joint has leaked on several occasions, sometimes after several years of service due to warmup/cooldown cycling and sometimes immediately after installation and pressurization. A 3-D FE model was developed for assembly of tubesheet, bolt, two inner and outer gaskets, and vessel cover. Different cases were studied by changing gasket load-deflections for different gasket materials, gasket thicknesses and bolt loads. The outcome of the analyses was used to predict the behavior of bolted joints and understand the root cause of leakage. The results provided guidance for choosing the right combination of bolt pre-torque and gasket type.
A Flexible Microfluidic-Based Sensor for Monitoring the Bending and Tilting of a Metal Bar for Pectus Excavatum (PE) Patients
Authors: Wang Dan , Yang Yichao , Vahala Linda , McKenzie Frederic D. , Hao Zhili
Published: January 2018

In this paper, a flexible microfluidic-based sensor is investigated for monitoring the bending and tilting of a metal bar for miniature access pectus excavatum repair (MAPER). Built on a polyethylene terephthalate (PET) substrate, the sensor contains a polydimethylsiloxane (PDMS) microstructure embedded with an electrolyte-enabled 5×1 resistive transducer array. One end of the metal bar is fixed and the sensor is attached to different locations of the bar. The other end of the metal bar is connected to a 5-lb weight for controlling the bending of the bar. Manually holding and releasing the weight bends the metal bar, which translates to strain in the PET substrate and consequently causes resistance changes in the transducer array. Upon the same amount of bending, resistance change of the sensor varies with the location of the sensor on the metal bar, due to the bending (or strain) variation along its length. Tilting of the metal bar relative to a rigid object (i.e., sternum) introduces force acting on the microstructure of the sensor, and thus gives rise to resistance changes in the transducer array. As a result, this sensor shows the potential of being used in MAPER to minimize tissue injury in vivo application.
Environmental Effects on the Mechanical Behavior of Covetic Aluminum MEMS Components
Authors: Allameh Seyed M. , Wardlow Jennifer
Published: January 2018

Covetic aluminum has been researched for its mechanical properties. It has been credited with higher strength in tensile and fatigue loading [1,2]. Modest changes in temperature during tensile testing of covetic aluminum causes significant changes in the ductility and tensile strength. Increasing the temperature from 15 °C to 44 °C causes a decrease in the tensile strength down to 63.8% but an increase in the ductility up to 117% [3]. To further study the environmental effects, microtensile testing was carried out in an environmentally-controlled chamber using a hybrid microtester at high and low relative humidity. MEMS-scale dog-bone shaped specimens with a cross section of 200 × 250 microns were machined from bulk covetic aluminum using a CNC for milling their contours and a ram-type EDM for detaching them from the work piece. The chamber was purged with gases low or high in moisture maintaining a positive pressure. An Omega sensor-controller unit was used to regulate the temperature and relative humidity of the chamber. The results of the tests show a reduction of ductility at high relative humidity. The implications of the results are discussed in relation to the reliability of MEMS structures.
Numerical Analysis of Elasticity Measurement of Soft Tissues via a 2D Distributed-Deflection Sensor: Significance of Tissue Parameters
Authors: Yang Yichao , Weidemann Arthur , Tison Charles , Hao Zhili
Published: January 2018

This paper reports on a numerical study on how the elasticity of soft tissue measured by a Compression-Relaxation (C-R) testing method via a two-dimensional (2D) distributed-deflection sensor varies with the tissue parameters (i.e., elasticity, thickness and in-plane dimension). The 2D sensor entails a polydimethylsiloxane (PDMS) micro structure embedded with a 3×3 sensing-plate/transducer array deposited on a Pyrex substrate. By moving the 2D sensor against a soft tissue region with a pre-defined compression pattern, the average deflection-depth slope of the deflections of the sensing-plate array versus the compression depth of the testing tissue is measured, and is translated to the measured tissue elasticity via a 1D theoretical model. Since the measured tissue elasticity arises from the tissue-sensor interaction, a numerical model, which includes the 2D sensor and a soft tissue underneath, is created in COMSOL to investigate the sensitivity of the measured tissue elasticity to tissue parameters including tissue thickness, in-plane dimension and elasticity. The numerical results reveal that the theoretical model causes a 20% overestimate on the inherent tissue elasticity in the range of 25kPa∼200kPa. The measured tissue elasticity does not vary with tissue thickness when tissue thickness is above 6mm. However, a relatively thin tissue leads to higher measured tissue elasticity. As long as the tissue in-plane dimension is larger than the sensor in-plane dimension, the measured tissue elasticity is insensitive to the tissue in-plane dimension.
Using a Six-Axis Articulated Robot Arm for Teaching Mechanical Engineering Students Software Development
Authors: Weber Moritz , Pitz Katrin , Anderl Reiner
Published: January 2018

Software development is a key skill for all engineers and is therefore part of the first semester curriculum for mechanical engineering at Technische Universität Darmstadt (TU Darmstadt).

A new method in engineering studies at TU Darmstadt based on project-based learning is being introduced to give students the opportunity to gain experience in software development using MATLAB and controlling real world objects. In this project, a 6-axis articulated robot arm similar to the ones used in industrial applications is being used.

In addition to the motors used to drive the robot arm it is equipped with a color sensor. The students are thus encouraged to familiarize themselves with processing sensor data and incorporating it into their problem-solving approaches.

The students are given a newly developed virtual model of the robot also implemented in MATLAB, which enables them to develop and test their solutions even when there is no access to the physical robot.

To communicate with the robot the same methods for both the real and the virtual robot is provided to control the angles of the joints of the robot. As the students are only given Cartesian coordinates they have to convert these for the robot to use.

The task given to the students comprises the development of an algorithm to solve a specific problem using the robot, programming a graphical user interface and a documentation of the project’s results.

Students solve the given programming task in self-organized groups of four and undergo a team-based software project with focus on engineering from the beginning to the end. This allows them to reflect on personal competencies and to find their respective roles in a team at a very early stage of their studies. The project applies various aspects taught in the corresponding lecture and thereby emphasizes the practical use of the subject matter.

In the concluding presentation, the students are encouraged to reflect their work, summarize the results and show the special features of their implementation.
Continuously Varying Exhaust Pipe Length and Diameter to Improve the Performance of a Naturally Aspirated SI Engine
Authors: Aradhye O. , Bari S.
Published: January 2018

Wave tuning is a concept which increases the volumetric efficiency of a naturally aspirated engine by providing a scavenging effect to clear out residual gases and increase inflow of fresh charge. This paper analyses the effects of tuning pulsating sonic wave produced over a broad range of speeds in the exhaust manifold of a single cylinder 510 cc SI engine, on the power and torque of the engine. 1-D model of the engine is modeled using Ricardo Wave. The simulation results obtained through the parametric analysis are compared with the standard data provided by the engine testing. On average, 7% increase in torque and 6% increase in power are observed by continuously varying exhaust pipe length. While continuously varying exhaust pipe diameter, 6% increase in torque and power is observed. When combined together, the continuously varying exhaust pipe length and diameter produce 8.5% increased torque and 9% increased power, respectively.
Frequency Response of Parametric Resonance of Double Wall Carbon Nanotube Under Electrostatic Actuation for Noncoaxial Vibration
Authors: Caruntu Dumitru I. , Juarez Ezequiel
Published: January 2018

In this paper, the Method of Multiple Scales is used to investigate the influences of dimensionless damping and voltage parameters on the amplitude-frequency response of an electrostatically actuated double-walled carbon nanotube. The forces responsible for the nonlinearities in the vibrational behavior are intertube van der Waals and electrostatic forces. Soft AC excitation and small viscous damping forces are assumed. Herein, the noncoaxial case is investigated at near-zero amplitude conditions in the free vibration, which eliminates the influence of the cubic van der Waals in the first-order solution. The DWCNT structure is modelled as a cantilever beam with Euler-Bernoulli beam assumptions since the DWCNT is characterized with high length-diameter ratio. The results shown assume steady-state solutions in the first-order MMS solution. The importance of the results in this paper are the effect of damping and detuning frequency on the stability of the DWCNT vibration.
Casimir Effect on Voltage Response of Superharmonic Resonance of NEMS Resonators
Authors: Botello Martin , Reyes Christian , Beatriz Julio , Caruntu Dumitru I.
Published: January 2018

This paper investigates the voltage response of superharmonic resonance of the second order of electrostatically actuated nano-electro-mechanical system (NEMS) resonator sensor. The structure of the NEMS device is a resonator cantilever over a ground plate under Alternating Current (AC) voltage. Superharmonic resonance of second order occurs when the AC voltage is operating in a frequency near-quarter the natural frequency of the resonator. The forces acting on the system are electrostatic, damping and Casimir. To induce a bifurcation phenomenon in superharmonic resonance, the AC voltage is in the category of hard excitation. The gap distance between the cantilever resonator and base plate is in the range of 20 nm to 1 μm for Casimir forces to be present. The differential equation of motion is converted to dimensionless by choosing the gap as reference length for deflections, the length of the resonator for the axial coordinate, and reference time based on the characteristics of the structure. The Method of Multiple Scales (MMS) and Reduced Order Model (ROM) are used to model the characteristic of the system. MMS transforms the nonlinear partial differential equation of motion into two simpler problems, namely zero-order and first-order. ROM, based on the Galerkin procedure, uses the undamped linear mode shapes of the undamped cantilever beam as the basis functions. The influences of parameters (i.e. Casimir, damping, fringe, and detuning parameter) were also investigated.
Methane Steam Reforming and Steam Injection for Repowering Combined Cycle Power Plants
Authors: Carapellucci Roberto , Giordano Lorena
Published: January 2018

Repowering existing power plants represents a potential route to meet the increasing energy demand, in a context of more and more stringent environmental regulations, hindering the construction of new facilities. Conventionally, repowering is operated into existing steam power plants, thus allowing to increase the design capacity to such an extent that depends on the type of strategy to exploit the waste heat from the additional gas turbine.

In this study a new repowering concept is proposed. It involves the integration of an additional unit based on a gas turbine into an existing combined cycle gas turbine (CCGT). Based on this concept, two repowering options are examined. In the first one (Option A), the waste heat from gas turbine flue gases is used to produce steam in a one pressure level steam generator. In the second option (Option B), the exhaust waste heat recovery promotes the generation of a synthesis gas in a methane steam reformer. The integration of the additional unit is operated by the injection of superheated steam (Option A) and the reformed fuel (Option B) into the combustor of the main power plant, thus allowing for a further increase in power output of both topping and bottoming cycles. The simulation study allows to compare the repowering options with respect to the potential increase of power capacity, as well as in terms of energy marginal performance parameters.
Measurement of Glioma Viscoelasticity Using a Handheld Palpation Imitation Device
Authors: Hayashi Shigeto , Sakuma Atsushi , Sasayama Takashi , Kohmura Eiji
Published: January 2018

We examined glioma tissues immediately after en-bloc removal during surgery and measured elastic modulus, viscosity, and viscoelasticity of the gray and white matter to confirm the feasibility of measurement using an indentation device. Measurements were obtained from excised parenchymal brain tumor tissue of four adult patients. The white matter exhibited higher elastic modulus than the gray matter in all patients. Viscoelasticity analysis was performed in two patients, with viscoelastic behavior observed in the white but not in the gray matter in both patients. The loss of viscoelasticity in the white matter observed in one patient may be related to the calcification visible in the preoperative computed tomography image.
Study on Thermal Deformation Behavior of Wire Electrical Discharge Machining Thin-Wall Components
Authors: Zhang Zhen , Zhang Yanming
Published: January 2018

The geometric error is an important indicator for the product performance in the Wire Electric Discharge Machining (WEDM) process, however, few studies have focused on the geometric error caused by thermal deformation, which can reach as high as 6.5% when machining thin-wall components. In this paper, some complex thermal deformation phenomena were found and analyzed in wire electric discharge machining different materials under different conditions (such as different thickness, various process parameters). Based on a large number of experiment, the reasons for these thermal deformation were figured out by studying the effect of various process parameters on thermal deformation and mechanical properties of thin-wall components, and the results revealed that the water pressure and pulse duration are two most significant factor influencing the thermal deformation. It’s concluded that a long pulse duration for rough cut and a short pulse duration for trim cut under low water pressure is recommended to decrease the geometric error caused by thermal deformation.