bluuebunny/crossref_metadata_2025 huggingface dataset:
Contact Properties Research for Linear Sliding Guide Rail With the Fractal Theory
Authors: Li Xinxin , Li Zhimin , Jin Sun , Zhang Jichang , Niu Zhihua , Liu Jinyu
Published: January 2020

High quality products are primarily dependent on the accurate translation motion of each linear sliding guide rail (LSGR) of CNC machine tools in the advanced manufacturing industry. The existing researches about LSGR precision pay much more attentions on the components dimensional variation and deformations, while micro-geometric form errors (such as surface roughness) have been ignored in most previous studies. Therefore, the true contact interface property is so crucial that it will affect macro-mechanical performance, such as friction, wear, assembly relation, tightness, fatigue strength, etc. In order to obtain the contact behaviors of LSGR accurately, a novel finite element model contact analysis is proposed in this paper. Instead of adopting the conventional statistic characterization method, such as Greenwood-Williamson (GW) model, the rough slider surface generated by the fractal function get closer to the real surface topography. In this study, the true contact area, contact pressure, contact stress and deformation are all investigated. Furthermore, the contact properties results of the present model are in a good agreement with other analytical solutions. In conclusion, the proposed finite element model combining with the fractal theory may provide an accurate contact analysis for LSGR. It is also great of guiding significance for the prediction of assembly quality and operation performance in high-precision measurement region as well as other precise engineering applications.
The Relationship Between the Arterial Geometry and Wall Shear Stress in the Vertebrobasilar System
Authors: Pan Fangjia , Anzai Hitomi , Mugikura Shunji , Kitamura Ko , Ohta Makoto
Published: January 2020

Vertebrobasilar atherosclerosis is an arterial disease; without successful treatment, it has a mortality rate approximately 80%–95%. Thus, predicting risk factors of vertebrobasilar atherosclerosis is of utmost importance. Previous studies have demonstrated that wall shear stress (WSS) contributes to atherosclerosis. In addition, geometry and WSS are correlated. The present study focuses on the description of equation using detailed relationship between arterial geometry and WSS in the vertebrobasilar system (VBS); magnetic resonance (MR) imaging with computational fluid dynamics (CFD) was used for the analysis. Using constructed patient-specific models, WSS of basilar arteries (BAs) was calculated and then analyzed with morphological parameters. According to the statistical results, both the area and curvature of BAs are associated with WSS. Based on the relations, a liner fitted equation can be proposed. As this study is underway, more precise evaluation of the correlation between morphology and fluid shear stress could help predict risk factors and select treatment methods for this arterial disease.
Numerical Investigation of Nonlinear Lamb Wave Time Reversing for Fatigue Crack Detection
Authors: Wang Junzhen , Shen Yanfeng
Published: January 2020

This paper presents a numerical study on nonlinear Lamb wave time reversing for fatigue crack detection. An analytical framework is initially presented, modeling Lamb wave generation, propagation, wave crack linear and nonlinear interaction, and reception. Subsequently, a 3D transient dynamic coupled-field finite element model is constructed to simulate the pitch-catch procedure in an aluminum plate using the commercial finite element software (ANSYS). The excitation frequency is carefully selected, where only single Lamb wave mode will be generated by the Piezoelectric Wafer Active Sensor (PWAS). The fatigue cracks are modelled nucleating from both sides of a rivet hole. In addition, contact dynamics are considered to capture the nonlinear interactions between guided waves and the fatigue cracks, which would induce Contact Acoustic Nonlinearity (CAN) into the guided waves. Then the conventional and virtual time reversal methods are realized by finite element simulation. Advanced signal processing techniques are used to extract the distinctive nonlinear features. Via the Fast Fourier Transform (FFT) and time-frequency spectral analysis, nonlinear superharmonic components are observed. The reconstructed signals attained from the conventional and virtual time reversal methods are compared and analyzed. Finally, various Damage Indices (DIs), based on the difference between the reconstructed signal and the excitation waveform as well as the amplitude ratio between the superharmonic and the fundamental frequency components are adopted to evaluate the fatigue crack severity. The DIs could provide quantitative diagnostic information for fatigue crack detection. This paper finishes with summary, concluding remarks, and suggestions for future work.
Digital Tools to Capture Manufacturing Tacit Knowledge to Support Next Generation Automation Systems
Authors: Guerra-Zubiaga David A. , Schwaig Kathy S. , Nasir Sabih , Bondar Alex
Published: January 2020

In today’s complex environment, it is not only important to handle/control digital manufacturing tools, but also essential to capture tacit knowledge from people. Creating a digital twin, it is an extensive effort including different fields and subjects. For example, creating a physical prototype and connecting it with a virtual prototype. From this, two questions arise. What will be the framework used to create the digital twin and what method will be used to capture the experiences to develop Next Generation Automation System (NGAS). This research explores a new method capturing tacit knowledge creating a digital twin for a NGAS, worked at station level connecting machines and humans implementing knowledge modelling and providing guidance in design for manufacturability at NGAS. The motivation of this research is that capturing tacit knowledge is an important aspect in Industry 4.0.

According to literature review, different researchers have been exploring digital twins using digital tools. This research proposal explores the effects of automation in the workplace using Digital Manufacturing Tools (DMT). The proposed approach demonstrates how to capture valuable experiences we can transfer or communicate between the digital twins, increasing productivity to fulfill the need to adopt new and emerging technologies in the workplace. The research will talk about capturing Tacit Knowledge in different forms like experiences, analysis, and intuitions etc and how this type of knowledge is processed by DMT and communicated to the other digital twin. Tacit knowledge modeling and sharing is used by implementing the Internet of Things (IoT) to understand the interaction among humans, instruments, controls, and robots. Understanding tacit manufacturing knowledge types is required to create better digital twins.
Thermo-Mechanical Modeling of 3D Woven Fabric Composites Using Two-Step Homogenization Approach
Authors: Siddgonde Nagappa , Ghosh Anup
Published: January 2020

A 3D finite element based Representative Volume Element (RVE) model has been developed to predict the thermo-mechanical properties of 3D orthogonal interlock woven fabric composites (OIWFC) and angle interlock woven fabric composite (AIWFC) using a two-step homogenization approach. The first step homogenization, micro-homogenization, deals with resin infiltration effect of yarn as a unidirectional continuous fiber with an assumption of 80 percent of fiber volume fraction based on initial fiber and matrix properties. The second step, meso-homogenization, predicts effective thermo-mechanical properties of 3D woven fabric composites based on effective yarn and matrix properties. The RVE analysis has been performed using 3D FEA method with periodic boundary conditions (PBCs). Further, a void study has been performed considering the influences of void on thermo-mechanical properties of the 3D woven fabric composite. It is noted that the influence of void contents plays a significant role in predicting the thermo-mechanical properties of the 3D WFC. The thermo-mechanical properties gradually decrease with an increase of void contents. Studies have been carried out considering the same fiber volume fractions in both 3D WFC models. An AIWFC model predicts higher values of thermo-mechanical constants than OIWFC model.
Machining of High Aspect Ratio Micro-Holes on Titanium Alloy Using Silver Nano Powder Mixed Micro EDM Drilling
Authors: Liu Chong , Rashid Asif , Jahan Muhammad P. , Ma Jianfeng
Published: January 2020

Titanium alloy Ti-6Al-4V is used extensively in aerospace engines because of its high strength-to-weight ratio and corrosion resistance. Machining of cooling holes in turbine blades for aerospace engines is one of the major challenges faced in aerospace industries. Ti-6Al-4V is known as a difficult to be machined material by conventional machining processes, and machining of micro-through-holes with diameter less than 100 microns is even more challenging. Therefore, the objective of this study is to investigate the feasibility of machining high aspect ratio micro-through holes in Ti-6Al-4V using micro electrical discharge machining (micro-EDM) with the silver (Ag) nanopowder mixed dielectric. The machining time, overcut, recast layer, crater size, aspect ratio and surface finish of the micro-holes were evaluated. In order to minimize the positional inaccuracy and spindle runout, the microelectrodes were fabricated in-situ using block micro-EDM process. In this study, as received electrode of 300 microns diameter tungsten wire was reduced to about 50 microns diameter rod by micro block EDM using a tungsten carbide block. The effect of powder concentration, gap voltage, capacitance and electrode rotational speed was studied. It is found that high quality micro-holes of about 50 microns diameter can be achieved successfully and repeatedly using powder mixed micro-EDM (PM-μEDM). The micro-holes generated by PM-μEDM provides comparatively smoother surface finish and minimal recast layer around the rim of the micro-holes. In addition, PM-μEDM process improves machining stability, thus allowing to minimize the hole size and quality, thus enhancing the aspect ratio of micro-holes.
Development of Trends and Methodologies for Shaping Ceramics by Electrical Discharge Machining: A Review
Authors: Rashid Asif , Jahan Muhammad P. , Perveen Asma , Ma Jianfeng
Published: January 2020

Ceramic materials possess excellent properties like high hardness, superior corrosion resistance and great resistance to wear. These materials are low in density and demonstrate high strength to wear ratio. There is an increasing need to machine these hard and brittle materials as they have various engineering applications. The distinguishing properties of ceramics do not allow them to be machined by conventional processes. Electrical discharge machining (EDM) is a non-conventional process and a viable option to machine and generate complex shapes in hard materials. EDM can be used on materials irrespective of its hardness and wear resistance as it is a non-contact machining process and no active force is applied between the workpiece and electrode during machining. As EDM requires the workpiece to be electrically conductive, machining ceramics by this process is a challenge. Alterations need to be carried out in order for insulating ceramics to be machined by this process. This paper discusses the basics of EDM process and its control parameters. A classification of ceramic materials based on their electrical conductivity is established and their relevance to the respective material removal mechanisms have been identified. Different approaches to successfully machine ceramics by EDM have been reviewed. The challenges and modifications of each method have been discussed. An outline and expectations for machining a particular ceramic material and its composites have been generated. Finally, the prospects of future research in this area have been identified.
Comparative Study of the Dynamic Behavior of AA2519 Aluminum Alloy in T6 and T8 Temper Conditions
Authors: Olasumboye Adewale , Owolabi Gbadebo , Koya Olufemi , Whitworth Horace , Yilmaz Nadir
Published: January 2020

This study investigates the dynamic response of AA2519 aluminum alloy in T6 temper condition during plastic deformation at high strain rates. The aim was to determine how the T6 temper condition affects the flow stress response, strength properties and microstructural morphologies of the alloy when impacted under compression at high strain rates. The specimens (with aspect ratio, L/D = 0.8) of the as-cast alloy used were received in the T8 temper condition and further heat-treated to the T6 temper condition based on the standard ASTM temper designation procedures. Split-Hopkinson pressure bar experiment was used to generate true stress-strain data for the alloy in the range of 1000–3500 /s strain rates while high-speed cameras were used to monitor the test compliance with strain-rate constancy measures. The microstructures of the as received and deformed specimens were assessed and compared for possible disparities in their initial microstructures and post-deformation changes, respectively, using optical microscopy. Results showed no clear evidence of strain-rate dependency in the dynamic yield strength behavior of T6-temper designated alloy while exhibiting a negative trend in its flow stress response. On the contrary, AA2519-T8 showed marginal but positive response in both yield strength and flow behavior for the range of strain rates tested. Post-deformation photomicrographs show clear disparities in the alloys’ initial microstructures in terms of the second-phase particle size differences, population density and, distribution; and in the morphological changes which occurred in the microstructures of the different materials during large plastic deformation. AA2519-T6 showed a higher susceptibility to adiabatic shear localization than AA2519-T8, with deformed and bifurcating transformed band occurring at 3000 /s followed by failure at 3500 /s.
Predictive Modeling of Polymer Saturation in Porous 3D Printed Matrix
Authors: Mihalko Adam , Michael Robert , Piovesan Davide
Published: January 2020

Due to the accuracy, speed, and ability to produce controllable complex geometries, additive manufacturing has gained traction in the medical industry. Additive manufacturing based on powder binder-jetting allows fabricating composite ceramic artifacts to mimic the physical properties of cortical bone. Given the porous nature of the artifacts their physical properties can be manipulated based on the percentage of solid matrix and adhesive binder. It has been demonstrated that a reduction of porosity via infiltration greatly increases the mechanical properties of the artifact. In this paper experiments are presented investigating the post processing of porous materials using different adhesives to infiltrate the artifact. The resulting saturation and porosity profiles of the produced composite are analyzed.
Experimental Study on Geometric Precision of Microholes Drilling by Picosecond Laser
Authors: Zhang Zhanfei , Wang Wenhu , Jiang Ruisong , Jin Chengcheng , Zhu Xiaoxiang , Liu Xiaofen
Published: January 2020

The geometric precision of the film cooling hole has a great influence on the cooling efficiency and fatigue life of the turbine blade. In the paper, the processing of film cooling holes on DD6 single crystal superalloy by picosecond laser is investigated. The pulse laser at pulse duration of 2.1ps, the wavelength of 1030 nm and the repetition frequency of 75 kHz are selected to study the pulse energy, scanning speed, defocus and scanning width on the geometric precision of the film cooling hole. After drilling, the three-dimensional coordinates of the entrance and exit plane of the film cooling holes are obtained by using the three-dimensional surface measuring instrument. The diameter, roundness and taper of the film cooling holes are calculated by extracting and processing the coordinate points of the contour around the microholes. The experimental results show that defocusing has the greatest influence on the taper and roundness of film cooling holes. Negative defocusing can produce severe plasma shielding, which makes the exit roundness and taper larger. With larger pulses, positive defocusing and larger scanning width, smaller roundness and taper can be produced.
The Feasibility of Noise Insulating Materials With Variability of Frequencies and Amplitudes
Authors: Kitowski Zach , Marsh Andrew , Graves Roy
Published: January 2020

The objective of this experimental investigation was to determine the effectiveness of different thermal insulating materials noise reduction properties when exposed to acoustic signals of varying frequencies and amplitudes. The experimental system incorporated two boxes separated by a thermal insulation wall. A speaker was used in one box with varied sound amplitude and frequency to test how effective the insulating material was at reducing sound transmission through a wall. The sound level was measured with a microphone in each box and the values were used to calculate the Sound Transmission Loss (STL) for each trial. Fiberglass insulation and cork insulation were the two insulation materials tested. The frequency levels of500 Hz, 1000 Hz, and 2000 Hz were tested. A three factor ANOVA analysis was completed and the null hypothesis was rejected with 95% confidence for each of the three factors. A Tukey test was conducted to determine which factor, if any, had a significant impact on the STL value. The Tukey test determined that frequency had the most significant impact on the STL value followed by the material choice with the average difference of means for comparison groups being 17.92 dB and 7.74 dB, respectively. The Tukey test also determined sound level did not have a significant impact on the STL value. The fiberglass insulation tested had the highest STL value of the two materials tested, with a maximum STL of 49.5 dB at 2000 Hz while the minimum STL was 26.2 dB at 500 Hz. The cork insulation had a maximum STL of 44.4 dB at 2000 Hz and a minimum STL of 10.5 dB of 500 Hz. At 1000 Hz however, the cork insulation had a higher STL than the fiberglass insulation with 32.6 dB and 31.6 dB respectively. This discrepancy might be due to a specific property of the cork dictating how it interacted within a specific frequency range. The test had an overall uncertainty of ±1.34 STL which was much smaller than the difference between sample groups. The ANOVA analysis also showed a strong interaction between the insulating material and the frequency as it had a much greater F-value of 869.56 as compared with the F-critical value of 2.42.
Sensitivity of Thermal Transport in Uranium Dioxide to Fission Gas
Authors: Mitchell Katherine , Horner Hunter , Resnick Alex , Park Jungkyu , Farfán Eduardo B. , Yee Tien , Hummel Andrew
Published: January 2020

Understanding the effect of fission gas generation on thermal resistance in various nuclear fuels is critical for managing fuel performance. Fission gas in the fuels degrades its thermal properties by altering the lattice vibrations. It results in thermal expansion that increases the thermal resistance and decreases the structural stability of the fuels. In this research, thermal transport in uranium dioxide is studied at a microscopic level when Xe and Kr gasses interact with uranium and oxygen atoms. Reverse non-equilibrium molecular dynamics (RNEMD) is used to calculate the thermal resistances and provide an understanding about the effect of the fission gas release on phonon transport. The results show that the thermal conductivity of uranium dioxide is decreased nearly by 78% by the presence of only one fission gas bubble. The thermal transport in uranium dioxide is shown to become highly diffusive by a single fission gas bubble and a large temperature drop in temperature profiles are observed in all simulation structures with fission gas bubbles. The average interfacial thermal resistance across a fission gas bubble is estimated to be 2.1 × 10−9 Km2/W.
Transverse Vibrations of Annular Spinning Disk Subjected to Out-of-Plane Loads and Uniform In-Plane Follower Edge Forces
Authors: Guan Peng , Peng Meng , DeSmidt Hans , Yao Wei
Published: January 2020

This paper investigated the transverse vibration natural frequency and stability of an annular spinning disk subjected to concentrated uniform in-plane edge follower forces and out-of-plane loads including mass, damper, and spring. Linear plate theory is used to derive the plate model used in this research, both symmetric in-plane stress fields, due to plate rotation, and asymmetric in-plane stress fields, due to uniform edge follower forces, are considered. The asymmetric stress, which is a function of the rotation of the plate, is obtained from the steady-state response of the coupled in-plane vibration equations. The concentrated in-plane follower edge forces are expanded as Fourier series and the produced stress fields are also achieved from the corresponding Fourier components. To explore the system stabilities, natural frequency variations, in-plane and out-of-plane loads coupling effects, and the instability types, the eigenvalues are plotted with respect to rotation speeds. Based on the eigenvalue analysis, the effects of concentrated edge uniform follower forces on a spinning disk system with out-of-plane loads were concluded.
Numerical Analysis on Evaporation Assisted Convective Cooling: Effect of Surface Morphology
Authors: Saha Sudipta , Tikadar Amitav , Khan Jamil , Farouk Tanvir
Published: January 2020

With an escalating need to find ways to reduce the water consumption in industrial cooling system, on-demand hybrid cooling has been a topic of great interest. The main concept of this cooling method is centered upon the utilization of huge exchange of enthalpy associated with phase change process in a conventional convective cooling system. In this study, a multidimensional multi-physics model has been employed to study a system that undergoes this dual mode cooling process where both convection and evaporation contribute to the heat transfer process. The computational domain considered is comprised of a thin liquid film that undergoes evaporation with constant heat flux provided from the bottom and a convective loading of laminar air flow above it. Evaporation takes place at the liquid-gas interface and the evaporated mass is being carried away by the incoming air, hence augmenting the convective cooling through the phase change process. This is an extension of our prior work where the surface structure modification (i.e. undulated surface) on the performance of this proposed hybrid cooling method is numerically investigated. Array of hemispherical structures have been introduced as the surface introducing the heat flux to the liquid film. The objective is to increase the surface to volume ratio and decrease the thermal resistance across the liquid film. The predictions indicate that with the increase in the height of the undulated surface the thermal resistance across the liquid film tends to decrease. Results from these simulations show that a ∼50% reduction in the thermal resistance can be achieved by the surface structure modification while the net evaporation flux can be doubled compared to a flat film configuration.
Efficiently Predicting Fatigue Life of Drill Collars With Ports Subjected to Variable-Amplitude Bending or Torsional Loads
Authors: Song Fei , Li Ke , Ossia Sepand
Published: January 2020

To enable real-time monitoring of the physical condition of the drilling equipment such as drill collars, a methodology for efficiently predicting the fatigue life of ports subjected to variable-amplitude cyclic bending or torsional loads is needed. In this paper, such a method is reported, which involves several steps. Firstly, elastic finite element analysis (FEA) of a collar port was performed to determine the elastic stress states with unit loads. Secondly, the unit load-based linear elastic solutions with the loading history were superimposed to produce a time history of the stress tensor. Thirdly, the previously established pseudo-elastic stress states were transformed into the true elastoplastic stress and strain states with a cyclic plasticity model and a notch correction rule. Finally, the cumulative fatigue damage was computed with the rainflow counting algorithm and a damage accumulation rule. The resulting fatigue life predictions for the ports were found to agree favorably with the experimental measurements from full-scale fatigue tests of port-containing collar samples with variable-amplitude loads. This newly developed method can be used to predict the remaining useful life of a port in real time with the loads resulting from downhole measurements or a drill string dynamics simulation code.
Simulations of Online Non-Destructive Acoustic Diagnosis of 3D-Printed Parts Using Air-Coupled Ultrasonic Transducers
Authors: Rooney Sean , Pochiraju Kishore
Published: January 2020

The open-loop process by which 3D printers operate often leads to significant time and material losses due to print failures. A challenge in Additive Manufacturing (AM) is assessing 3D-printed parts mid-print for the dimensional stability of the internal structures and their microstructure and material properties. These internal features are typically opaque to visual inspections after print and can only be accessed for property characterization if the part is cut open. An assessment of methods for evaluating parts in situ using air-coupled ultrasonic transducers in this paper. The purpose is to determine the microstructure and limited effective properties (density and modulus) of internal structures during the print process using acoustic methods. We examine the effectiveness of acoustic wave reflection, absorption and propagation through the infill channels, which make up a part on a fused deposition modeling printer to obtain dimensional measurements while the part is on the print bed. We simulated the acoustic wave response for common frequencies of commercially-available air-coupled transducers (25–300 kHz) placed near simulated 3D-printed parts. We compared the return signals using the k-Wave Acoustics Toolbox, a time-domain model for acoustic wave propagation, and validated these simulations with physical readings. The results showed the behavior of the peak amplitude of the received signals for various materials and infill channel lengths. Simulations and physical experiments were conducted for both through-transmission and pulse-echo approaches. The simulations optimize parameters for a maximized peak received signal strength. The results will limit the scope of computationally expensive methods of observing obfuscated structural deficiencies and deformations in a 3D-printed part in situ using air-coupled ultrasonic transducers and similar ultrasonic NDE technologies.
Anisotropic Yielding Behaviour of Inconel 718 Alloy at Elevated Temperatures
Authors: Mahalle Gauri , Salunke Omkar , Kotkunde Nitin , Gupta Amit Kumar , Singh Swadesh Kumar
Published: January 2020

The study of anisotropic deformation behavior of material plays a key role in optimizing the hot working process parameters. Further, trustworthiness of Finite Element (FE) analysis in hot working condition is highly dependent on accurate input of mechanical properties and anisotropic yield parameters. In present work, two different anisotropic yield criteria, namely; Hill 1948 and Barlat 1989 are developed from Room Temperature (RT) to 500 °C and different slow strain rate conditions (0.01, 0.001 and 0.0001 s−1) for Inconel 718 alloy. First, uniaxial tensile test carried out from RT to 500 °C with an interval of 100°C and at quasi-static strain rate conditions at different orientation of a sheet (0°, 45° and 90°). Based on the tensile test data, extended Von-Mises isotropic criterion i.e. Hill 1948 and Barlat 1989 yield criterion were developed at different conditions. The predictability of yield criteria has been verified using yield loci, variation of anisotropic coefficient and yield stresses. The various static parameters such as correlation coefficient, relative error and standard deviation are considered to compare the yield criteria. Based on the comparison, Barlat 1989 yield criterion shows good in agreement with experimental data.
Performance Analysis of a Novel Parallel Turbine Reheat Cycle for High Speed Vehicles
Authors: Sun Jingchuan , Xu Guoqiang , Wen Jie , Dong Bensi , Zhuang Laihe , Liu Qihang
Published: January 2020

The optimization of the Brayton cycle has gained an increasing worldwide attention due to improve the specific thrust for achieving super cruise. This paper proposes a novel Parallel Turbine Reheat (PTR) cycle, which the second combustor would be placed at bypass of the expansion process, and presents an analytical methodology by which PTR can be simulated at ideal state and actual state. The motivation and the working principle of the PTR cycle are explained in detail. A performance simulation model for the PTR cycle is established with the assumption of equilibrium fuel rich gas as the working fluid in the gas generator. Then parametric cycle studies are performed with the variation of temperature rise ratio of the parallel combustion chamber and bypass ratio at the flight Mach number of 0 and 1.5 respectively. The interrelationships between cycle parameters and their effects on cycle performance are discussed. The results show that the specific thrust will be increased to 20% comparing with the conventional cycle for the reason that makes more fuel energy convert to the propulsion power without increasing the inlet temperature of turbines. The cycle parameters for a practical PTR cycle engine are more applicable for the flight speeds of Mach 1.5. The predicted engine performance shows that the PTR cycle concept exhibits a competitive specific thrust with respect to engine in the state of non-afterburning, and might be a promising propulsion system for super-cruise air-breathing flying vehicles.
Ballistic Penetration Performance of a Unidirectional Woven Basalt Fiber Laminated Protective Armor
Authors: David N. V. , Zurina A. , Aziz M. R. , Rafiq M. N. , Syafiq M. , Sundram Raja
Published: January 2020

Contemporary military and other law enforcement operations are technology-driven with weapons and ammunition that demand a flexible, damage- and moisture-resistant, and lightweight protective materials with superior energy absorbing capacity. Ballistic fabrics made from high performance synthetic fibers such as para-aramid and natural fibers including basalt, and composites utilizing these fabrics, are among the leading materials for armor systems. Basalt fibers, which are extracted from igneous volcanic rocks, are natural fibers with mechanical and thermo-physical properties that are generally comparable or superior to glass and other synthetic fibers at a lower cost. This gives basalt-based composites an edge over existing materials for potential application as anti-ballistic protective panels. The aim of the present study is to experimentally determine the V50 performance and penetration resistance of a unidirectional woven basalt fiber laminated epoxy system at three different combinations of ply orientations [0, 45 and 90 degrees at both CW and CCW directions] consisting of 48 layers of the woven fabric. The V50 performance test was conducted in accordance to the MIL-STD-662F standard using the Universal Test Gun model UZ-2002. The V50 ballistic velocity are computed based on a minimum of six shots including three complete penetrations and three partial penetrations. The optimum number of layers of the basalt fabric to sustain the reference penetration velocity of 367 m/s corresponding to threat level II of the NIJ Standard-0101.04 are calculated for the current test specimen for future development.
Numerical Investigation on Strain Properties of Ti6Al4V Alloy Processed by Constrained Bending and Straightening Severe Plastic Deformation
Authors: Mwita W. M. , Akinlabi E. T.
Published: January 2020

This paper presents a numerical investigation on strain properties of Ti6Al4V alloy processed by constrained bending and straightening (CBS) severe plastic deformation (SPD) technique. CBS is a new SPD method that has been proposed to enhance continuous processing of metal sheets and improve magnitude and homogeneity of induced properties such as strain. The model considers a rectangular sheet of Ti6Al4V alloy processed with CBS at 2, 4 passes denoted as N2, N4 each combined with 10, 5, 3 mm feed length denoted as F10, F5, F3 respectively. ABAQUS Standard FEA Software was used to simulate and investigate the magnitude and homogeneity of equivalent plastic (EP) strain induced in material. Results show that for all feeds, magnitude values of EP strain at N4 passes were higher than those at N2 passes. The magnitude of EP strain increased with the number of passes. Values of both magnitude and homogeneity of EP strain were highest at F3 feed followed by those at F5 and F10 feeds respectively. The study has promised that CBS is the potential process for continuous production of metal sheets with improved EP strain magnitude and homogeneity.
A Real-Time Image Matching Algorithm for Binocular Stereo Measurement System
Authors: Duan Jianyu , Sun Lingyu , Li Lijun , Dai Zongmiao , Xiong Zhenkai , Wang Jinxi
Published: January 2020

Binocular stereo measurement system can obtain accurate three-dimensional information from two-dimensional images. It has been widely applied in many fields such as vehicle tracking, robot navigating, automatic crane lifting, as well as other fields. The crucial step of binocular stereo measurement is image matching. For the image matching, it is a great challenge to ensure both real-time and matching accuracy simultaneously. The image matching algorithm has a great influence on the image matching time and accuracy. In this paper, a real-time image matching algorithm for binocular stereo measurement system is proposed based on Speedup Robust Features (SURF) algorithm. In the proposed algorithm, firstly, the key feature points are identified by the original SURF algorithm method. Secondly, the main direction of the key feature point is determined by intensity centroid method. Then, the feature descriptor is calculated by the BRIEF binary method so that the time of feature description can be shortened. Finally, RANSAC (Random Sample Consensus) method is adopted to remove mismatching points. The experiments results show that the proposed algorithm can shorten image matching time obviously and improve the accuracy of matching points.
Amplitude-Frequency Response for Superharmonic Resonance of Fourth Order of Electrostatically Actuated MEMS Cantilever Resonators
Authors: Caruntu Dumitru I. , Reyes Christopher
Published: January 2020

This paper deals with the frequency response of superharmonic resonance of order four of electrostatically actuated MicroElectroMechanical Systems (MEMS) cantilever resonators. The MEMS structure in this work consists of a microcantilever parallel to an electrode ground plate. The MEMS resonator is elelctrostatically actuated through an AC voltage between the cantilever and the ground plate. The voltage is in the category of hard excitation. The AC frequency is near one eight of the natural frequency of the resonator. Since the electrostatic force acting on the resonator is proportional to the square of the voltage, it leads to superharmonic resonance of fourth order. Besides the electrostatic force, the system experiences damping. The damping force in this work is proportional to the velocity of the resonator, i.e. it is linear damping. Three methods are employed in this investigation. First, the Method of Multiple Scales (MMS), a perturbation method, is used predictions of the resonant regions for weak nonlinearities and small to moderate amplitudes. Second, the Homotopy Analysis Method (HAM), and third, the Reduced Order Model (ROM) method using two modes of vibration are also utilized to investigate the resonance. ROM is solved through numerical integration using Matlab in order to simulate time responses of the structure. All methods are in agreement for moderate nonlinearities and small to moderate amplitudes. This work shows that adequate MMS and HAM provide good predictions of the resonance.
Adaptation of an Existing Impeller Design to Large Bore Requirements: Aerodynamic Considerations
Authors: Jariwala Vishal , Larosiliere Louis
Published: January 2020

Multistage process centrifugal compressor applications with single shaft rotors supported by only two bearings are quite common. It is sometimes desirable to operate impellers at higher rotational speeds, resulting in relatively compact and cost-effective machines. Such high-speed rotors can, however, pose rotordynamic challenges, and therefore require larger shaft or impeller bore diameters to increase rotor stiffness and rotordynamic stability. This work explores aerodynamically favorable ways to adapt an existing standard bore impeller design to large bore requirements. First, the stage aerodynamic performance and flow range implications of increasing bore diameter are discussed using meanline modeling and vector diagram arguments. Some strategies for adapting a standard bore design to large bore variant are then presented. Attempts are made to identify and clarify technical limitations to the degree of adaptability of an existing impeller to large bore requirements. Finally, a CFD-backed case study on a large-bore adaptation of a particular stage is presented to clarify practical considerations.
Coupled Flexural and Torsional Vibration Analysis of Composite Beams
Authors: Sarfaraz Ehsan , Afolabi Jeremiah O. , Hamidzadeh Hamid R.
Published: January 2020

An analytical method is presented to determine the dynamic response of a coupled flexural and torsional vibration of composite beams. The general governing equations of motion are presented and a closed form solution for free vibration of the composite beam that demonstrates both geometric and material coupling is developed. The proposed solution is used to compute the natural frequencies, modal loss factors, and mode shapes of the composite beam for several modes of the coupled bending and torsional vibrations for any boundary conditions. In this analysis, hysteretic damping for the composite beam is considered and its effects on mode shapes and modal loss factors are determined. In addition, the variation of modal parameters such as bending displacement, bending slope, torsional rotation, shear force, bending moment, and torque along the beam for the first four mode shapes are presented for the clamped-free boundary conditions. Moreover, to verify the validity of the presented analytical method, results for the cases with no damping are compared with the previously established results and good agreement is achieved. The presented results can provide a guideline for selecting appropriate geometries and materials to design composite beams.
Vibration Absorption in a Nonlinear Metamaterial Beam Incorporating Shape Memory Alloys
Authors: Fernandes Ralston , Boyd James G. , El-Borgi Sami , Lagoudas Dimitris C.
Published: January 2020

Locally resonant metamaterials are capable of demonstrating low-frequency vibration absorption due to the formation of stop-bands. In this work, the multi-mode vibration absorption capability of an adaptive nonlinear metamaterial beam is investigated. The metamaterial beam is idealized as a hinged-hinged finite Euler-Bernoulli beam with a von-Kármán geometric type nonlinearity that is attached to a distributed cellular array of shape memory alloy (SMA) spring–mass resonators. Numerical studies are performed to evaluate the effects of dissipation and change in elastic modulus due to material phase change of SMA pseudoelasticity on the dynamic response of the beam. Using a modal analysis approach, stop-bands are generated at the first three nonlinear frequencies of the beam. The frequency response demonstrates a hardening behavior at a temperature significantly higher than the austenite finish temperature while conversely demonstrating a softening behavior at a temperature slightly above the austenite finish temperature.
Computational Evaluation of a Novel Aerodynamic Road Vehicle Design and Drag Reduction Using Vortex Generators
Authors: Arora B. B. , Suri Ujjwal , Garg Utkarsh , Das Shraman , Kumar Sushrut
Published: January 2020

Vehicle aerodynamics is a prime domain of research and development. Multiple active and passive aerodynamic systems have been applied for its enhancement. The reduction of drag plays a pivotal role in the improvement of vehicle aerodynamic performance. The present paper studies the innovative design of a road vehicle for a fuel efficiency challenge, implemented for optimal drag reduction. Vortex generators are utilized as a passive aerodynamic feature for further minimization of the wake region size and reduction of pressure drag. High fidelity computational fluid dynamics simulations were applied for the evaluation of this design. Data was collated from simulations for both the cases, with and without the usage of vortex generators and compared objectively. The results of the study establish that the vehicle design has an exceptionally low drag coefficient. It also exhibits a strong reduction in drag when the vortex generators are fitted. These results reveal that the design can be deployed for production as a worthy competition vehicle.
Meshing Characteristics and Engagement of Anti-Backlash Single- and Double-Roller Enveloping Hourglass Worm Gear
Authors: Deng Xingqiao , Wang Jie , Wang Shike , Wang Shisong , Liu Yucheng , He Ge
Published: January 2020

Anti-backlash roller enveloping hourglass worm gears, as a new precision transmission system, has been extensively applied in robot joint design, packaging production line, and CNC (computer numerical control) machine tools. However, their corresponding transmission principles are seldom reported in the literature. Based on the theories of differential geometry and gear meshing, this paper carefully analyzes and compares meshing characteristics of anti-backlash single- and double-roller enveloping hourglass worm gears in terms of their transmission principle, engagement equation, induced normal curvature, lubrication angle, autorotation angle, entrainment velocity, helix angle, and distribution of contact curves. Major differences between these two roller enveloping hourglass worms are theoretically demonstrated through this study. Our results show that the anti-backlash single-roller enveloping hourglass worm (ASEHW) gears provide better performance with respect to gear meshing and transmission than the anti-backlash double-roller enveloping hour glass worm (ADEHW) gears. Also, compared with the ADEHW gears, the ASEHW gears are easier to fabricate, install, and calibrate. However, the ADEHW gears are more auto-adjustable in eliminating gear backlash. The outcomes of this study will form a theoretical background for futuristic design, application, and promotion of the anti-backlash roller enveloping hourglass worm gears.
Effect of Silicone Damping on Work Vibration in CNC Milling Process
Authors: Rahman AHM E. , Abu-Mahfouz Issam , Carbaugh Scott
Published: January 2020

Vibration dampening in machining processes is an important part of a machine being precise, low maintenance, and long lasting. Being able to utilize dampening materials in the design of machinery in existing structural tubing could allow designers to isolate vibration sources from critical components more effectively than with current methods. The purpose of this research was to show and analyze the effect of dampening materials undergoing specific machining vibration. An experiment was designed that used hollow columns both with and without dampening material and a CNC Mill to generate different types of vibration. These vibrations are detected using accelerometers at the top and bottom of the structure. By creating a variable matrix testing different viscosity dampening materials, different spindle speed, and different depth of cut, vibration with different frequency and amplitude was tested. By analyzing the characteristics of the vibration transmitted by the structure without a dampening material compared to that same vibration with a dampening material, a conclusion was made as to whether these materials dampen machining vibration.
Validation of an Atomistic Field Theory for Contact Electrification Using a MEMS Load Cell
Authors: Hieber Tyler J. , Cheikh Mohamad Ibrahim , Chen James M. , Leseman Zayd C.
Published: January 2020

This work depicts an experimental method for the validation of an Atomistic Field Theory (AFT) model for contact electrification of dielectrics. The AFT model is used to simulate the effects of Triboelectric Nanogenerators (TENGs) for energy harvesting. Recently, the AFT model has shown that contact electrification can be described by the induced surface dipoles when two dissimilar materials are brought into close contact assuming that the crystal lattices are free of defects, no residual strain in the materials is present and that the experiment is performed in vacuum. These simulations have been used to predict the induced contact potential between MgO and BaTiO3. To validate the AFT model, a set of quasi-static experiments will be conducted to test two different operating modes of TENGs, which can be mirrored in the simulations. The first experiment is a micro-scale pull-in/pull-off test in which a pad of single crystal Si (SCSi) will be brought into and out of contact with a dielectric substrate (thermally grown SiO2). The second experiment will mimic the TENG during sliding operation. A SCSi microcantilever will be brought into contact with the dielectric surface and displaced in sliding mode. These experiments will be conducted using a custom, reusable MEMS load cell and an electrometer to monitor the interaction forces and induced charge on the surfaces. To obtain the required displacement resolution of the load cell, a high-speed Michelson interferometer will be used. This allows for higher load cell stiffness to accommodate for surface adhesion effects. The load cell will be calibrated using the well-known technique of hanging masses from the load cell. The relative distance between the interacting surfaces in both experiments will be controlled by a piezo stage with 1 nm resolution. Results from these experiments are to be compared to the AFT model results.
Categorization of Design for Additive Manufacturing Concepts
Authors: Chekurov Sergei
Published: January 2020

Design for AM (DfAM) has become a widely followed research field with practitioners outside of the research community looking for instructions and inspiration on how to leverage the unique capabilities of AM in their products. The research community has responded by producing an abundance of valuable DfAM literature. However, although each individual research article is useful and can answer specific questions, the connection between them can be difficult to fathom due to the lack of a structured overview of DfAM.

This paper proposes a categorization framework to organize the many concepts of DfAM in a structured manner. The framework for the categorization used in this paper is based on a widely used generic product design workflow of Pahl and Beitz that is augmented with concepts from AM literature. The framework is a tool for researchers to position their work in relation to other literature, and it can also be used as a support to achieve novel product designs with AM.

To demonstrate how the framework can be used for guided design, the paper presents every stage of the design process in the context of designing a proof-of-concept heat exchanger that leverages the technical benefits of AM.