bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flexible, User- and Product-Centered Framework for Developing Frugal Products Based on a Case Study of a Vehicle for Sub-Saharan Africa
Authors: Šoltés Martin , Kappler Daniel , Koberstaedt Sascha , Lienkamp Markus 
Published: January 2018

Through design thinking, a team of researchers and students from Nigeria, Ghana and Germany has identified rural transportation as a key enabler for addressing the most pressing challenges in the developing world. Since 2013, the team has been working together on designing a new vehicle concept for Sub-Saharan Africa.
The aim of the project is to provide the rural population in Sub-Saharan Africa with an attractive mobility concept that helps to prevent the rural exodus and strengthens the independence of the rural regions. A promising concept must consider the specific market requirements and the resources available locally in order to address the heart of the problem as a “First Mile Vehicle”.
This paper aims to introduce a holistic framework for frugal innovation and to analyze the process of deriving the vehicle concept meeting regional requirements until it is ready for serial production. The focus, therefore, is demand-driven development of a multifunctional electric vehicle that primarily provides mobility for the individual and transport of people and goods as a possible commercial basis.
The result of the research and design process is a vehicle concept that meets the needs of the people living in rural areas of Sub-Saharan Africa. The first fully functional prototype of this vehicle was presented to the public at the Technical University of Munich in May 2016.
Effect of Inclination on Heat Transfer in Large Flattened-Tube Steam Condensers
Authors: Davies William A. , Kang Yu , Hrnjak Pega , Jacobi Anthony M. 
Published: January 2018

An experimental study of convective steam condensation inside a large, inclined, flattened-tube air-cooled condenser for power plants is presented. This is the second of a two-part study. The first part presents pressure drop and visualization results, while this study presents the experimental method along with heat transfer results.
The condenser in this study is steel with brazed aluminum fins. The condenser measures 10.72m in length, with a cross section of 214 mm × 18 mm. The condenser tube was cut in half lengthwise and covered with a polycarbonate viewing window in order to provide visualization access simultaneously with the heat transfer measurements. Inlet steam mass flux ranged from 6.2–9.5 kg m−2 s−1, and condenser capacity varied from 25–31 kW. The angle of inclination was varied from horizontal to 75° downward. The experiments were performed with a uniform fin-face velocity of crossflowing air at 2.2 m/s.
Condenser capacity was found to increase linearly with increasing downward inclination angle of the condenser, at a rate of 0.048% per degree of inclination below horizontal. This improvement was found to be the result of improved drainage and increased void fraction near the condenser outlet.
Design for Disassembly Method As Sustainable Product Evaluation Tool: Example of Underground Escalator
Authors: Shetty Devdas , Xu Jiajun 
Published: January 2018

Sustainable design and manufacturing considers a product’s full life cycle and the impact that its design, manufacture, use, and retirement can have not only on business but also the environment and society. Designers are becoming steadily aware of this problem, and are employing techniques that allow them to design with greater responsibility – Sustainable Product Design; in particular, the Design for Disassembly (DFD) is recommended as a technique of sustainable product design. In the case of a durable good with a long-life cycle or a product with parts subject to wear, maintainability/serviceability may be more important than initial product acquisition cost, and the product must be designed for easy maintenance. The DFD principles identify the ease with which products can be fabricated, maintained, serviced, and recycled.
This paper examines and identifies a “Rating Chart” technique which can be used to evaluate DFD. It is demonstrated through a case study of underground escalator housing, in which different types of failure modes and defects occur in the major components of escalator drive systems, such as the motor and its drive chain system, handrail and its drive system, bearings/lubrication systems that are in adjunct with the bearing shaft assembly. Through the Rating Chart method proposed for DFD, the deficiency of the original design of escalator drive system was accessed and compared with the proposed sustainable design approach, in which the product maintainability can be significantly improved and the maintenance time can be greatly reduced. The paper concludes by showing the importance of sustainable product design for products working under extreme working conditions.
Comparison of Different Sensitivity Analysis Methods in the Context of Dimensional Management
Authors: Heling Björn , Oberleiter Thomas , Schleich Benjamin , Willner Kai , Wartzack Sandro 
Published: January 2018

Although mass production parts look the same, every manufactured part is unique, at least on a closer inspection. The reason for this is that every manufactured part is inevitable subjected to different scattering influencing factors and variation in the manufacturing process, such as varying temperatures or tool wear. All these factors inevitably lead to parts, which deviate from their ideal shape. Products, which are built from these deviation-afflicted parts consequently show deviations from their ideal properties. To ensure that every single product nevertheless meets its technical requirements, it is necessary to specify the permitted deviations. Furthermore it is necessary to estimate the consequences of the permitted deviations, which is done via tolerance analysis. During this process the imperfect parts are assembled virtually and the effects of the geometric deviations can be calculated during a variation simulation.
Since the tolerance analysis is to enable engineers to identify weak points in an early design stage it is important to know which contribution every single tolerance has on a certain quality-relevant characteristic, to restrict or increase the correct tolerances. In this paper two different approaches are shown and compared to represent the statistical behavior and the strongly connected sensitivity analyses. In particular a newly developed approach, which is based on fuzzy arithmetic, is compared to the established EFAST-method. The exemplary application of both methods and the comparison of the results are illustrated on a case study.
A Design of Experiment to Study the Effects of Cutting Speed and Feed on the Generated Drilling Thrust and Torque in Aluminum Alloys
Authors: Seif Charbel Y. , Hage Ilige S. , Ismail Fathi , Hamade Ramsey F. 
Published: January 2018

This work reports on an empirical study to account for the effects of the drilling parameters of cutting speed: V, m/s (max at the outer periphery), tool feed (f, mm/rev)), and drill diameter (D, mm) on the generated thrust (T, N) and torque (M, N.m). A total of 50 drilling tests were conducted on a vertical machining center based on design of experiment (DOE) test matrix using JMP-SAS/STAT® software. The test matrix employed 2 different aluminum alloys: one wrought (6061-T6) and another cast (A356-T6) with both tempered to the T6 condition. Two classical chisel drills of different diameters (10mm and 12.7mm) were used. Drilling parameter variables employed varied from very mild to very aggressive combinations including 5 values of spindle speeds (796, 1592, 3183, 6366, and 9868 rpm) and 5 values of drilling feeds (0.04, 0.08, 0.16, 0.32, 0.64 mm/rev). Drilling forces and torques were recorded using a 4-component dynamometer (Kistler model 9123) at sampling rate of 200 Hz. At full drill engagement, cutting torque and thrust status were identified for each drilling test case.
By fitting to the measured drilling forces, power law equations with parametric variables D, f, and V are developed. Initial values of the model’s power coefficients were initially identified using Matlab® using a least square optimization function with target to minimize the difference between the predicting model and the experimental data. These values were fed as initially-guessed values to the nonlinear modeling Gauss method in JMP-SAS/STAT® with 50 observations for each set of experiments. For both torque and thrust and for both aluminum alloys employed, the model’s coefficient values were identified setting the convergence criteria to 10−15 with total of 60 iterations. For both thrust and torque, it was found that the power coefficients for feed and cutting speed are statistically significant (better than p-values < 0.05) with values of about 0.7 and −0.1, respectively.
Test Analysis of Youth and Adult Football Helmet Head Injury Risk Resulting From Repeat Impacts in High Humidity and Temperature
Authors: Saczalski Kenneth J. , West Mark N. , Saczalski Todd K. , Frausto Luis , Pozzi Mark C. 
Published: January 2018

Design of an optimally safe football helmet system requires an awareness and evaluation of the factors and variables that can adversely affect the impact attenuating performance of energy absorbing (EA) pad materials needed to minimize transmission of linear and rotational forces applied to the head so that risk of head injury is reduced. For instance, player head sweating can induce high temperatures and moisture within a helmet system (i.e. a Hot-Wet condition) which can result in degradation of helmet EA capacity and cause increased measures of head injury risk levels, which are often used for comparative evaluation of helmet designs.
In this study, a “multivariable” experimental method was utilized to demonstrate an efficient means for assessment and comparison of currently representative adult and youth football helmet system designs when subjected to a range of variables that included, among other factors: temperature-moisture effects; impact energy; and, repeat impacts. Both quasi-static (QS) compression testing of commonly used EA materials and dynamic impact testing of full helmet systems were conducted and the results are presented in Tables and graphic form.
The EA pad types that were QS tested included: Thermoplastic-Polyurethane (TPU) “waffle shaped” EA pad configurations; load rate sensitive “Gel” foam padding; and, dual and single density elastomeric foam padding. Dynamic helmet repeat impact tests were conducted by using a pendulum impact test device where various helmet designs were mounted to a Hybrid-III head and neck system and impacted against a non-yielding surface at energy levels of 108J and 130J after being subjected to ambient and Hot-Wet conditions.
The QS tests showed that a short Hot-Wet soak time of only a few hours’ noticeably diminished EA levels. Also, the dynamic full helmet system testing demonstrated that the “Hot-Wet” condition tended to degrade helmet impact attenuation performance such that, depending on the size and type of EA material provided in the crush zone, head injury risk measures tended to increase. Finally, examples of the use and benefits of a “multivariable” experimental method for helmet injury risk assessment, not reported on previously, are provided.
Experimental Investigation on the Dynamic Behaviour of a Dacron Graft Used for the Treatment of Descending Thoracic Aortic Aneurism
Authors: Amabili Marco , Balasubramanian Prabakaran , Ferrari Giovanni , Tubaldi Eleonora 
Published: January 2018

The dynamic behavior of a woven Dacron graft, currently used in thoracic aortic reconstructions in the case of aneurysm or dissection, has been experimentally investigated for the first time.
Dacron grafts are widely used in cardiovascular surgery to replace segments of diseased large blood vessels; however, scarce data are available about their durability. The dynamic modeling of such prostheses may fill this gap and may provide guidelines for the study of human aortic segments as well. Dynamic phenomena such as vibrations are being included among the most likely causes of important aortic pathologies, such as dissections and consequent ruptures. The compatibility of the dynamic behavior of Dacron grafts and human arteries seems a characteristic worthy of experimental investigation as well. For this reason, a cylindrical Dacron graft has been subjected to fixed boundary conditions and to a physiological value of static axial pre-stretch. A constant internal pressure, equal to the average value of the physiologic blood pressure, was exerted by a liquid mixture of suitable viscosity and density. A three-dimensional quasi-linear viscoelastic model was fitted onto the Dacron fabric by means of dedicated traction and relaxation tests. Forced linear and large-amplitude vibrations were imposed and measured. An identification tool recently developed by this research group is being used to study the change of the equivalent modal damping ratio with vibration amplitude during nonlinear vibrations. Furthermore, an ongoing study is revealing a dependence of dissipation on frequency that is coherent to the most common model for biological materials adopted by the medical community.
Trimming of Flat and Tubular Components by High Speed Impact Cutting (HSIC)
Authors: Landgrebe Dirk , Barthel Tom , Schieck Frank 
Published: January 2018

The trend for lightweight construction, especially in the automotive industry, leads to increased use of corresponding lightweight materials. In addition to novel construction materials such as fiber-reinforced plastics, established materials such as steel or aluminum are continuously being further developed, which is usually accompanied by a distinct increase in their strength. Beside material-related lightweight construction, new designs are applied such as the profile design.
The disadvantage of this development is that established forming processes such as deep drawing, profile bending, hydroforming but also shearing of high-strength components increasingly reach their process limits. Particularly, in the case of trimming of high-strength components such as press-hardened components, it is hard to present conventional shearing processes in serial processes due to low tool life and deficient cutting surface quality. For this reason the laser cutting technology is often used. It is characterized by high flexibility and can largely meet the requirements regarding component quality. In contrast to shearing, however, it requires very long process cycle times due to its process rate, which makes it significantly less productive.
High speed impact cutting offers an alternative. By exploiting high speed effects in the material, which leads to adiabatic heating of the shearing zone and a related significant reduction in strength, even ultra-high strength steel materials with tensile strengths of above 1500 MPa can be cut at high quality and with a short cycle time. In order to transfer this technology to serial applications and to develop process limits, extensive investigations were carried out using high-strength sheet metal materials and tube materials. The results are presented in this paper.
Rheology Characterization of Solder Paste
Authors: Barbosa Flávia V. , Ribeiro Pedro E. A. , Cerqueira Maria F. , Soares Delfim F. , Teixeira José C. F. , Teixeira Senhorinha F. C. F. , Lima Rui A. M. M. , Pinho Diana M. D. 
Published: January 2018

Reflow soldering process is widely implemented in the electronics industry. This method allows the attachment of electronic components to a printed circuit board (PCB) through the melting of solder paste, which makes the interconnection between them. The reflow soldering process must ensures the correctly melting of the solder paste and heating of the adjoining surfaces, without the electronic components suffer overheating or any other type of damage.
Solder paste is the most widespread material in the SMT (Surface Mount Technology) process using reflow soldering. An ideal solder paste will increase production efficiency, decreasing the amount of defects associated with the reflow soldering process. However, several factors affects the performance of the solder paste, from rheology, printability, and reliability to the adhesion strength of components and the ability to avoid defects related to reflow. Therefore, all these factors need to be considered during the selection of a solder paste for a specific application.
The rheological properties were determined using both a double cylinder (PHYSICA-RHEOLAB MC1) and a double plate (Malvern) rheometers. The later enable the determination of viscoelastic properties.
The present paper analyses the rheological behavior of a SAC405 solder paste, a mixture containing a metal alloy powder (25–45 μm) and a flux which at its base is a resin. The tests were carried out at conditions (temperature and shear rate) of relevance to the printing process. The results obtained show that the paste viscosity closely follows the Herschel-Bulkley model and shows a thixotropic behavior without fully recovery between applications. In addition, the viscosity decreases with the increase of shear rate confirming that the solder paste is a non-Newtonian fluid, shear thinning in behavior. The oscillatory tests have shown that the transition from elastic to viscous behavior occurs at a shear stress above 35 Pa. On the other hand, the creep/recovery test confirms that the level of solicitation influences the capacity of recovery of the solder paste.
Three Dimensional Measurements of a Turbine Blade Using Magnetic Resonance Thermometry and Magnetic Resonance Velocimetry
Authors: Williams Elliott T. , Caniano Daniel C. , Davis Gregory , Ferrell Angus M. , Benson Michael J. , Van Poppel Bret P. , Elkins Christopher J. 
Published: January 2018

A hollowed NACA-0012 airfoil with removable inserts was developed to study the complex flow through two interior chambers. The geometry represented an internally cooled gas turbine blade with internal impingement in several locations. A fully turbulent water flow passed the airfoil. Within the airfoil, a second fluid at a different temperature was mixed through the insert nearest the leading edge and recirculated to the aft chamber for additional internal cooling before exiting the airfoil as film cooling on the suction side and at the trailing edge. Time-averaged, three-dimensional temperature and three-component velocity measurements were collected using Magnetic Resonance Imagery (MRI) based techniques.
Magnetic Resonance Velocimetry (MRV) and Thermometry (MRT) are techniques for measuring the velocity and temperature of fully turbulent flows at sub-millimeter-scale resolution. The benefits of these techniques over similar measuring techniques include the ability to collect full-field, three-dimensional, nonintrusive, non-optical measurements for conjugate heat transfer simulation validation in complex, turbulent flows. Multiple MRI-based techniques can be combined within the same experiment to explore the interaction between the mean fields of multiple quantities. The experimental setup employed in this work produced time-averaged velocity and temperature data illustrating flow details through the airfoil’s interior chambers and heat flux through the entire airfoil and at specific locations.
An Empirical Stretch Bending Failure Criterion for AHSS
Authors: Shih Hua-Chu , Gambon Taylor 
Published: January 2018

The failure mechanism in stretch bending over a small die radius for Advanced High Strength Steels (AHSS), commonly referred as “shear fracture”, has rendered the Forming Limit Diagrams (FLD) fail to predict it based on the initiation of a localized neck. As shown in previous studies using a Stretch-Forming Simulator (SFS) and Bending Under Tension (BUT) test, shear fracture depends not only on the radius-to-thickness (R/T) ratio but also on the tension/stretch level applied to the sheet during bending. Although the stress-base empirical fracture limit criterion was developed for various AHSS grades, the fracture limit was not well implemented in the computer simulations to predict stretch bending fracture.
In this paper, the new developed experimental analysis is conducted on the modified bending under tension test to further investigate the stretch bending fracture mechanism under the production die condition. Various AHSS grades including DP590, DP780, DP980 and DP1180 are included in the study. Based on numerous experimental results, the maximum shear stress at failure, the thinning strain and strain gradient across the die radius are obtained for all test materials. Results demonstrate that the presence of the large strain gradient is the cause for fracture in stretch bending AHSS over a small die radius. The maximum shear stress at failure and the limit thinning strain on the die radius in the stretch bending condition are determined and used as the new fracture criteria, which can be easily implemented in the computer simulations.
Modeling Reichardt’s Formula for Eddy-Viscosity in the Fluid Film of Tilting Pad Thrust Bearings
Authors: Deng Xin , Weaver Brian , Watson Cori , Branagan Michael , Wood Houston , Fittro Roger 
Published: January 2018

Oil-lubricated bearings are widely used in high speed rotating machines such as those used in the aerospace and automotive industries that often require this type of lubrication. However, environmental issues and risk-adverse operations have made water lubricated bearings increasingly popular. Due to different viscosity properties between oil and water, the low viscosity of water increases Reynolds numbers drastically and therefore makes water-lubricated bearings prone to turbulence effects. The turbulence model is affected by eddy-viscosity, while eddy-viscosity depends on wall shear stress. Therefore, effective wall shear stress modeling is necessary in producing an accurate turbulence model. Improving the accuracy and efficiency of methodologies of modeling eddy-viscosity in the turbulence model is important, especially considering the increasingly popular application of water-lubricated bearings and also the traditional oil-lubricated bearings in high speed machinery. This purpose of this paper is to study the sensitivity of using different methodologies of solving eddy-viscosity for turbulence modeling.
Eddy-viscosity together with flow viscosity form the effective viscosity, which is the coefficient of the shear stress in the film. The turbulence model and Reynolds equation are bound together to solve when hydrodynamic analysis is performed, therefore improving the accuracy of the turbulence model is also vital to improving a bearing model’s ability to predict film pressure values, which will determine the velocity and velocity gradients in the film. The velocity gradients in the film are the other term determining the shear stress. In this paper, three approaches applying Reichardt’s formula were used to model eddy-viscosity in the fluid film. These methods are for determining where one wall’s effects begin and the other wall’s effects end. Trying to find a suitable model to capture the wall’s effects of these bearings, with aim to improve the accuracy of the turbulence model, would be of high value to the bearing industry. The results of this study could aid in improving future designs and models of both oil and water lubricated bearings.