bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterizations of Crack Growth Behavior of Porous Polymer Membranes Using Digital Image Correlation and Finite Element Method
Authors: Kodaira Yasuhisa , Miura Tatsuma , Ito Shoma , Yonezu Akio , Nagatsuka Hideki 
Published: February 2021

Abstract
This study investigated the crack growth behavior of porous polymer membranes, experimentally and numerically, in order to clarify the criterion of crack growth. A notch was introduced into the membrane as an initial crack (pre-crack) and a uniaxial loading was applied for the stable crack propagation. During the test, crack propagation behavior was observed using a CCD camera and Digital Image Correlation (DIC) method. The strain around the pre-crack tip at the onset of crack propagation was measured experimentally using DIC method. It was clarified that large-scale yielding developed before the onset of crack growth. The stable crack propagation was observed for all tensile tests. In parallel, a homogenized model that mimicked porous polymer membrane was created using finite element method (FEM) in order to investigate stress/strain distribution around the crack tip. This study employed the yield criterion proposed by Deshpande and Fleck. The computed strain distribution was compared with that of experiment, showing a good agreement each other. By using strain distribution from DIC method and FEM computation, J-integral value was calculated to investigate the criterion of crack growth. Regardless of the initial crack length, it is found that the J-integral value at the initiation of crack growth becomes constant for all tests. It is concluded that we successfully determined the criterion of crack propagation of porous polymer membrane. Therefore, our study using DIC experiment and FEM computation is useful to clarify the crack growth behavior of porous polymer membrane and determines the criterion of crack propagation.
The Condition of Dynamic Stability for Self-Paced Treadmill Walking Based on Inverted Pendulum Model
Authors: Qian Yuyang , Yang Kaiming , Zhu Yu , Wang Wei , Wan Chenhui 
Published: February 2021

Abstract
A self-paced treadmill automatically adjusts speed in real-time to match the user’s walking speed, presumably leading to a more nature gait than fixed-speed treadmill. However, previous study has proven that the acceleration applied to the subjects would influence the gait stability. In order to have insights on to which extent will the accelerations affect gait stability, simulation analysis based on conceptual model has been done in the current study. This paper utilized a non-inertial frame based spring-loaded inverted pendulum model to analysis the condition of stability during continuous self-paced treadmill walking. Simulations were done for 100 continuous self-paced treadmill walking at the normal walking speed. And 10ms impulse accelerations of different magnitudes with the range of (−1g, 1g) were applied at different gait events such as toe-off, foot-flat and heel-strike. The simulation results showed that the magnitude of the accelerations had significantly influence on continuous self-paced treadmill walking and directional-dependency was also found. However, no significantly difference was found when applying the impulse acceleration at different gait events.
Driving Wetting Transitions on Textured Surfaces Using Ultrasonic Vibration
Authors: Trapuzzano Matthew , Crane Nathan , Guldiken Rasim , Tejada-Martínez Andrés 
Published: February 2021

Abstract
Adhesives, medical devices, and many cleaning products depend on the wetting of liquids on solid surfaces. The liquid/solid interaction depends on chemistry, surface topology, and external energy input. For instance, surfactants are commonly used in cleaning solutions to improve their effectiveness, and electrical fields are frequently used to control the contact angle of liquid droplets. Low frequency vibration has been used to spread, move, and manipulate droplets using the mode shape oscillations of the droplet to displace the contact line. Ultrasonic vibration (above 20 kHz) can also cause a liquid droplet to wet or spread out on a solid surface under the right circumstances. We have previously demonstrated that ultrasonic vibration can be used to control the wetting/spreading of liquid droplets on smooth hydrophobic surfaces and that the response is relatively insensitive to excitation frequency or fluid properties [1]. This paper reports on the use of ultrasonic vibration to initiate spreading on surfaces with etched pillars. Ultrasonic vibration successfully initiated a transition from Cassie to Wenzel states in all geometries with no apparent need to tune excitation frequencies to the geometry. However, the magnitude of the acceleration required to initiate the transition decreased with increased pillar spacing. For small pillar spacing, some smooth spreading in the Cassie wetting mode was observed before transition.
Static Strength Reliability Analysis of the FLNG Compact and High Efficient Heat Exchanger
Authors: Tang Xu , Liu Tao , Song Wei , Wang Hongpu 
Published: February 2021

Abstract
Because of the harsh marine environment and limited offshore natural gas liquefaction work space, the compact and high efficient heat exchanger is the best choice for FLNG (floating liquefied natural gas) heat exchanger. To optimize the heat exchanger’s structural parameters and improve the performance, the factors mostly affecting the strength of the heat exchanger need to be determined, and static strength analysis and reliability analysis should be required. The strength of the heat exchanger core is analyzed by using the Static Structural, and the stress intensity distribution is obtained. According to the operation conditions, the temperature boundary condition has been set and the mechanical stress and thermal stress are considered to evaluate the strength. By choosing the thickness between the cold channels, cold channel pressure, hot channel pressure and elastic modulus as input random variables, the reliability analysis of heat exchanger has been done by using the Six Sigma Analysis of ANSYS Workbench, and next the cumulative distribution function curves of the membrane stress intensity, membrane plus bending stress intensity, response surface and the sensitivity are obtained. The reliability analysis results have shown that the cold channel pressure loading is found to be the greatest factor to the structural strength. The reliability of the heat exchange is more than 99.9% without considering thermal stress.
Dynamics Characterization of Paquitop: A Novel Platform for Robotized Domestic Applications
Authors: Carbonari Luca , Botta Andrea , Cavallone Paride , Tagliavini Luigi , Quaglia Giuseppe 
Published: February 2021

Abstract
In the last decades, an unprecedented decrease in fertility and mortality rates in industrialized countries yielded a general ageing of the population. Such phenomenon affected the everyday life of individuals as well as organizations, either government or private, to the point that they are nowadays seeking the solution to the increasing demand of health care, housing, care-giving, and social security. In this scenario, this piece of research aims to fulfil a design task, specifically oriented towards the field of assistance machines. The functionalities which should be guaranteed are mainly two: to follow and monitor reduced mobility subjects, to maintain a constant view contact with its targets, and to accomplish such duties in a non-structured and possibly peopled environment. In particular, the paper analyses the dynamics of Paquitop, a novel over-actuated mobile platform, aiming for a proper design strategy for its suspensions system. The main peculiarity of the robot is that of owning an innovative architecture expressly conceived to enhance the performance offered by the present-day solutions for omni-directional planar motions. Given its purpose, the robot architecture was thought for guaranteeing an effective fulfilment of its primary tasks. This arises a set of uncharted challenges, under both mechanical and control points of view.
Friction Surfacing From Radial Surface of A6063 Aluminum Alloy Consumable Tool Onto A36 Carbon Steel
Authors: Seidi Ebrahim , Miller Scott F. 
Published: February 2021

Abstract
Friction surfacing is an advanced technique to create solid-state deposition of wide range of materials onto a similar or dissimilar material substrate. This paper describes the study of a novel method to deposit material onto a substrate by friction surfacing. In the friction surfacing technique, the heat is generated entirely by friction. This metallic deposition technique consists of a rotating consumable tool that rubs against the surface of the substrate, and due to the frictional heat and forging generated between the tool and substrate, material is deposited onto the substrate. The material transferred from the consumable tool to the substrate occurs from the side of the tool, while in the conventional friction surfacing method, the material transfer happens from the end of the tool. In this investigation, the single and double-pass deposition of A6063 aluminum alloy onto an A36 carbon steel substrate was successfully carried out. To study the influence of the process parameters on the friction depositions, the substrate was divided into three sections, while the applying forces were varied in each section. Process parameters such as tool rotational speeds, table traverse speeds and normal force were experimented. A customized JET JMD-18 milling machine was used to carry out the experiments. The influence of process parameters on the material deposition was characterized by means of roughness tester and optical microscope. The results of the study reveal that this novel method is capable to create an ultra-thin and smooth metallic deposition with excellent coverage. The material consumption during the single and double-pass deposition was evaluated, and the coating cross-section was assessed using the optical microscope.
Edge Forces in Metal Cutting: Fundamental Analysis and Experimental Verification
Authors: Al Aridi Rimah S. , Baydoun Ahmad M. R. , Hamade Ramsey F. 
Published: February 2021

Abstract
In metal cutting, some of the generated forces do not contribute to chip formation. These forces are referred to as plowing forces and are induced mainly as result of the finite sharpness of the tool (cutting edge radius) and the tool’s land (flank). Determining the magnitude of these forces is essential to developing a better understanding of the mechanics and physics of applications that involve cutting at minimal feed values (e.g., micro-machining and vibration-assisted-micro-machining. It is well recognized that plowing forces increase with tool wear. This research estimates these forces by employing analytical and numerical simulations. An extensive experimental analysis is utilized to verify the simulated values of the plowing forces. The experimental verification is designed to measure these forces as a function of several cutting parameters. The developed methodology relates the plowing forces to geometric factors and process parameters such as cutting-edge radius, tool feed, and cutting speed.
A Spectral Correlation Based Nonlinear Ultrasonic Resonance Technique for Fatigue Crack Detection
Authors: Wang Junzhen , Shen Yanfeng 
Published: February 2021

Abstract
This paper presents a spectral correlation based nonlinear ultrasonic resonance technique for fatigue crack detection. A reduced-order nonlinear oscillator model is initially constructed to illuminate the Contact Acoustic Nonlinearity (CAN) and nonlinear resonance phenomenon. The tailored analytical model considers the rough surface condition of the fatigue cracks, with a crack open-close transition range for the effective modeling of the variable-stiffness CAN. Multiple damage indices (DIs) associated with the degree of nonlinearity of the interrogated materials are then proposed by correlating the ultrasonic resonance spectra. The frequency sweeping signals serve as the excitation waveform to obtain the structural dynamic features. The nonlinear resonance procedure is numerically solved using the central difference method. Short time Fourier transform (STFT) is utilized to extract the resonance spectroscopy. In this study, pristine, linear wave damage interaction case (an open notch case), and nonlinear wave damage interaction case (a fatigue crack case) with various damage severities are considered. Subsequently, three case studies taking advantage of different nonlinear oscillation phenomena are conducted based on the spectral correlation algorithm to detect and monitor the fatigue crack growth: time-history dependence, amplitude dependence, and breakage of superposition. Each of these three nonlinear behaviors can either work individually or collaborate synthetically to detect the nucleation and growth of the fatigue cracks. The proposed nonlinear ultrasonic resonance technique possesses great application potential for fatigue crack detection and quantification. This paper finishes with summary, concluding remarks, and suggestions for future work.
Effect of End Rubber Gasket on the Performance of Parabolic Leaf Spring
Authors: Zhang Junhong , Long Feiqi , Jia Hongjie , Lin Jiewei 
Published: February 2021

Abstract
Leaf springs play an important role in the handling stability and ride comfort of vehicle. End rubber gaskets are widely used to reduce the friction between leaves, but they also have considerable effect on the stiffness of the suspension assembly. The ride comfort may deteriorate with the stiffness of leaf spring changes. In this paper the influence of the end rubber gasket on the static stiffness performance of a parabolic leaf spring is studied. A finite element model of the leaf spring is developed and verified against the static stiffness test. Effects of the end rubber gasket parameters on the static stiffness of the leaf spring are analyzed based on an orthogonal experiment. The sensitivities of the five parameters are identified including the width, the length, the end thickness, the tail thickness and the distance to the end of the middle leaf. It is found that the contributions can be ranked in descending order as the tail thickness, the end thickness, the distance from end rubber gasket to the end of Leaf 2, and the width and length. The first two factors are considered of significant effects on the leaf spring stiffness. According to single-factor analysis, it is found that under the same load, as the tail thickness and the end thickness increase, the maximum deformation of the rubber gasket decreases, the stiffness of the rubber gasket increases, and the stiffness of the leaf spring increases, which provides a reference for the forward design of the end rubber gasket and the stiffness matching of leaf springs.
Squeak and Rattle Prevention by Geometric Variation Management Using a Two-Stage Evolutionary Optimisation Approach
Authors: Bayani Mohsen , Wickman Casper , Lindkvist Lars , Söderberg Rikard 
Published: February 2021

Abstract
Squeak and rattle are annoying sounds that often are regarded as the indicators for defects and quality issues by the automotive customers. Among the major causes for the generation of squeak and rattle sounds, geometric variation or tolerance stack-up is a key contributor. In the assembly process, the dimensional variation in critical interfaces for generating squeak and rattle events can be magnified due to tolerance stack-up. One provision to manage the tolerance stack-up in these critical interfaces is to optimise the location of connectors between parts in an assembly. Hence, the focus of this work is to prevent squeak and rattle by introducing a geometric variation management approach to be used in the design phase in the automotive industry. The objective is to identify connection configurations that result in minimum variation and deviation in selected measure points from the critical interfaces for squeak and rattle. In this study, a two-stage evolutionary optimisation scheme, based on the genetic algorithm employing the elitism pool, is introduced to fine-tune the connectors’ configuration in an assembly. The objective function was defined as the variation and the deviation in the normal direction and the squeak plane. In the first stage, the location of one-dimensional connectors was found by minimising the objective function in the rattle direction. In the second stage, the best combination of some of the connectors from the first stage was found to define planar fasteners to optimise the objective function both in the rattle direction and the squeak plane. It was shown that by using the proposed two-stage optimisation scheme, the variation and deviation results in critical interfaces for squeak and rattle improved compared to the baseline results.
Research on Fire Resistance of Stainless Steel Car Body Floor Structure in Urban Rail Vehicles
Authors: Jia Na , Zhang Haifeng , Liu Xiaofang , Cai Mingjun 
Published: February 2021

Abstract
At present, the fire performance of vehicles is highly concerned in domestic and international rail transit market projects [1], where the fire performance of the vehicle’s underframe is a crucial factor that restricts the fire safety of the entire rail vehicle. How to improve the fire resistance of vehicle underframe structure has become the focus and difficulty of vehicle fire engineering [2]. This article introduces main international fireproof standards applicable for urban rail vehicles. Then, based on the typical underframe structures of urban rail vehicles stainless steel body, three refractory structure models on different underframe structures are established by using different fireproof insulation materials as underframe fillers. Moreover, fire resistance tests are conducted on samples of three underframe models to verify the effectiveness of those fire performance. As per the fire test results, the crucial indexes such as heat insulation, fire resistance, temperature rise curve, fire resistance time and material cost of different filler insulation materials are compared and summarized. Finally, the standardized and modular design specification is suggested on refractory underframe structures in urban rail vehicles.
A Compound Recoil-Compensated Chamber Design for Free-Fall Absolute Gravimeters
Authors: Wen Yi , Wu Kang , Guo Meiying , Wang Lijun 
Published: February 2021

Abstract
The ballistic free-fall absolute gravimeters are most commonly-used instruments for high-precision absolute gravity measurements in many fields, such as scientific research, resource survey, geophysics and so on. The instrumental recoil vibrations generated by the release of the test mass can cause troublesome systematic bias, because these vibrations are highly reproducible from drop to drop with coherent phase. A compound counterbalanced design of chamber using both belt-driven mechanism and cam-driven structure is proposed in this paper. This structure is designed to achieve excellent recoil compensation as well as long freefall length for high precision measurements. Simulation results show that the recoil vibration amplitude of the compound recoil-compensated structure during the drop is about 1/4 of that with only belt-driven counterbalanced structure. This confirms the feasibility and superiority of the new design. And it is believed that the absolute gravimeter based on this newly proposed chamber design is expected to obtain more precise gravity measurement results in the future.
Second Modified Student Presentation Based Effective Teaching (SPET) Method Tested in COVID-19 Affected Senior Level Mechanical Engineering Course
Authors: Tyagi Pawan 
Published: February 2021

Abstract
Student presentation based effective teaching (SPET) approach was designed to engage students with different mindsets and academic preparation levels meaningfully and meet several ABET student learning outcomes. SPET method requires that students prepare themselves by guided self-study before coming to the class and make presentations to teach the whole class by (a) presenting complex concepts and systems appealingly and engagingly, and most importantly (b) serving as the discussion platform for the instructor to emphasize on complex concepts from multiple angles during different presentations. In class, SPET presentations address the conceptual questions that are assigned 1–2 weeks before the presentation day. However, the SPET approach becomes impractical for large class sizes because (i) during one class period all the students can not present, (ii) many students do not make their sincere efforts. This paper focuses on the second modification of SPET to make it practical for large classes. The method reported in this paper was tested on MECH 462 Design of Energy System Course. Unlike the first modified approach, all the students were expected to submit the response to the preassigned questions before coming to the class. In class, SPET group presentations were prepared by the group of 3–6 students, who prepared themselves by doing SPET conceptual questions individually. Students communicated with each other to make a cohesive presentation for ∼30 min. In two classes per week, we covered 5–6 group presentations to do enough discussions and repetition of the core concepts for a more in-depth understanding of the content. During the presentation, each student was evaluated for (a) their depth of understanding, (b) understanding other parts of the presentation covered by other teammates, and (c) quality of presentation and content. The student who appeared unprepared in the class group presentation were provided direct feedback and resources to address concerning areas. SPET approach was applied in the online mode during the campus shut down due to COVID-19. SPET was immensely effective and helped to complete the course learning outcomes without interruptions. SPET could be customized for the online version without any additional preparation on the instructor part.
Nanoscale Interphase Characterization of Porous CNT Buckypaper Composites in Correlation to Interlaminar Mode I Fracture
Authors: Yekani Fard Masoud , Mester Jack , Pensky Alek 
Published: February 2021

Abstract
In this conference paper, nanoscale material property data and ASTM mode I interlaminar fracture results for three-phase buckypaper samples are presented and analyzed. Vacuum filtration and surfactant-free methods were used to manufacture buckypaper membranes. Epoxy infused buckypaper membranes were placed in front of the crack tip in a stitch bonded carbon fiber polymer matrix composite. Peak Force Quantitative Nanomechanical Mapping (PFQNM), using probes with nominal tip radius in the range of 5–8 nm were used. PFQNM characterized the interphase region between a three-phase sample of carbon monofilament, epoxy resin, and multi-walled carbon nanotube (MWCNT) buckypaper. This experiment captured reproducible nanoscale morphological, viscoelastic, elastic and energy properties of porous MWCNT buckypaper samples. An enlarged interphase region surrounding the CNT buckypaper was found. The buckypaper and epoxy interphase thickness was found to be 50nm, higher than the 10–40nm reported for epoxy and carbon monofilaments. The observed MWCNT structure provides explanation of the increased surface roughness compared to the smooth carbon monofilaments. The increased surface roughness likely improves mechanical interlocking with the epoxy of adjacent lamina. The nanoscale interphase and subsurface characterization data provide explanation for a change in crack propagation toughness. Buckypaper exhibited inhomogeneous properties at micrometer length scales.