bluuebunny/crossref_metadata_2025 huggingface dataset:
Orthogonal Functions Used in the Solution of Linear Difference Problems
Authors: Benscoter S. U.
Published: March 2021

A method of solution of linear difference equations is presented in which the solution is assumed in terms of a finite set of orthogonal functions which satisfy the boundary conditions. A formula for the latent roots of the matrix of the system of equations is obtained. A simple formula is then derived for the reciprocal matrix in terms of the latent roots and latent vectors. A simple numerical example is presented.
Vibration of a Beam With Concentrated Mass, Spring, and Dashpot
Authors: Young Dana
Published: March 2021

An analytical method is developed for determining the natural frequencies of a composite system which consists of a uniform beam with a concentrated mass, spring, and dashpot attached at any point along the length of the beam. The method makes use of a series expansion in terms of the set of orthogonal functions which represent the normal modes of vibration of the beam alone. Numerical examples are given for a beam with a combined concentrated mass and spring, for a beam with two concentrated masses, and for a beam with an attached dashpot.
Experimental Studies of Biaxially Stressed Mild Steel in the Plastic Range
Authors: Fraenkel S. J.
Published: March 2021

This paper describes static tests of tubular specimens of medium steel under biaxial stresses and at room temperature. The purposes of the tests were: (1) to obtain an experimental check on the so-called “third rule of plastic flow;” (2) to study the absorption of energy as a function of the biaxial stress ratio; and (3) to determine the effect of the path of loading as symbolized by the strain path. Within the range of conditions investigated, the path of loading was found to be immaterial. A relation between strain energies absorbed under biaxial and uniaxial stress states up to a common maximum strain is tentatively formulated.
Behavior of Steel Under Biaxial Stress as Determined by Tests on Tubes
Authors: Davis H. E. , Parker E. R.
Published: March 2021

The experimental work is described and results presented for tests on twelve 5¼-in-diam thin-walled tubes of low-carbon steel subjected to various conditions of biaxial stress. These experiments composed the “pilot” series of tests in a larger investigation on the behavior of ship-plate steel under multiaxial stress conditions. The ductility of the metal under various biaxial stress conditions and at two temperatures, 70 F and −138F, is reported. The evidence indicates that the metal is reasonably ductile, even at the low temperature, provided it is subjected only to a state of plane stress. If a state of triaxial stress is induced by restraint or by discontinuities in the material, the ductility may be greatly reduced at the low temperature. Evidence is presented to indicate that fracture may occur either by shear or by cleavage, depending upon the stress and temperature conditions. In a majority of cases, reasonable prediction of the stress-strain behavior of the metal in the plastic range can be made for various biaxial stress conditions from the data of the simple tension test, by use of the modified octahedral-shear concept.
A Generalized Deformation Law
Authors: Davis E. A.
Published: March 2021

According to Hooke’s law the magnitude of infinitesimal elastic strains depends upon two independent constants. In this paper equations are developed which express the magnitude and the distribution of the strains in terms of two independent functions of the stresses. One function is related to the stress-strain diagram while the other is concerned with the distribution of the strains in a state of combined stress. The equations are easily adaptable to the relations between the strain rates and the stresses in combined stress-creep tests. It is the opinion of the author that two independent functions are necessary and that the behavior under a state of combined stress cannot be predicted from data obtained in pure-tension tests.
A Method of Making High-Speed Compression Tests on Small Copper Cylinders
Authors: Habib E. T.
Published: March 2021

In mechanical gages used to measure the pressure from an underwater explosion, small copper cylinders are compressed at high speeds. This paper describes the test apparatus designed for the dynamic calibration of these cylinders, presents the results obtained with this apparatus, and compares these results with those obtained by other experimenters.
Unsteady Steam Turbine Optimization Using High-Fidelity Computational Fluid Dynamics
Authors: Iranidokht Vahid , Papagiannis Ilias , Kalfas Anestis I. , Abhari Reza S. , Senoo Shigeki , Momma Kazuhiro
Published: March 2021

This paper presents the computational methodology and experimental investigations accomplished to enhance the efficiency of a turbine stage by applying non-axisymmetric profiling on the rotor hub wall. The experimental setup was a two-stage axial turbine, which was tested at “LISA” test facility at ETH Zurich. The first stage was considered to create the flow history for the second stage, which was the target of the optimization. The hub cavity of the second stage was designed with large dimensions as a requirement of a steam turbine. The goal was to optimize the interaction of the cavity leakage flow with the rotor passage flow to reduce the losses and increase efficiency. The computational optimization was completed using a genetic algorithm coupled with an artificial neural network on the second stage of the test turbine. Unsteady time-accurate simulations were performed using in-house developed “MULTI3” solver. Besides implementing all geometrical details (such as hub and tip cavities and fully 3D blade geometries) from the experimental setup into the computational model, it was learned that the unsteady upstream effect could not be neglected. A novel approach was introduced using unsteady inlet boundary conditions to consider the multistage effect while reducing the computational cost to half. The importance of this implementation was tested by performing a steady simulation on the optimized geometry. The predicted efficiency gain from steady simulations was 4.5 times smaller (and negligible) compared to the unsteady approach. Excluding the cavity geometry was also assessed in a different simulation setup showing 3.9% over-prediction in the absolute efficiency value. Comprehensive steady and unsteady measurements were performed utilizing pneumatic, fast response aerodynamic probe (FRAP), and fast response entropy probe (FENT) on the baseline and profiled test cases. The end wall profiling was found to be successful in weakening the strength of the hub passage vortex by a 19% reduction in the under-over turning. As a result, the blockage was reduced near the hub region leading to more uniform mass flow distribution along the span. The flow angle deviations at the higher span position were also corrected due to better control of the flow angles. Furthermore, the improvements were confirmed by reductions in entropy, secondary kinetic energy, and pressure unsteadiness. The accurate computational implementations led to an excellent agreement between the predicted and measured efficiency gain.
Surface Texture Characterization of Metal Selective Laser Melted Part With Varying Surface Inclinations
Authors: Narasimharaju Shubhavardhan Ramadurga , Liu Weidong , Zeng Wenhan , See Tian Long , Scott Paul , Jiang Xiangqian (Jane) , Lou Shan
Published: March 2021

Additive manufacturing offers the advantage of infinite freedom to design and fabricate complex parts at reduced lead-time. However, the surface quality of additively manufactured parts remains well behind the conventionally processed counterparts. This paper aims to systematically investigate the impact of varying surface inclination angles with respect to the build direction on the resultant surface textures. A bespoke metal truncheon artifact with inclination angles varying from 0 deg to 180 deg was built by selective laser melting. Focus variation microscopy was used to measure the topography of inclined surfaces with a tilt angle of up to 132 deg. The measurement data were then analyzed to characterize the staircase effect and the particles adherent to the artifact surface. Areal surface texture parameters, including height parameters, spatial parameters, functional parameters, and feature parameters, were explored to quantify the general surface topography, the staircase effect, and the particle features. The areal surface texture characterization and particle analysis reveal the resulted surface topographies are strongly correlated with the surface inclination angles.
Influence of Paint Baking on the Energy Absorption and Failure Mode of Resistance Spot Welds in TRIP1180 Steel
Authors: Marshall D. V. , Bhattacharya D. , Speer J. G.
Published: March 2021

Resistance spot welds (RSWs) in advanced high strength steels frequently exhibit interfacial failure during cross-tension testing: a mode of fracture associated with low-energy absorption. Automotive assembly lines include a paint application and baking cycle after the vehicle assembly and joining processes to cure paint and any adhesives used for assembly. In this article, the effects of a typical baking cycle: 180 °C for 20 min, on the failure mode and energy absorption during cross-tension testing of RSWs made in a TRIP1180 steel are reported. Further, short-time baking cycles of 30 s, 90 s, and 4 min were employed to investigate how quickly these baking effects are activated. RSWs, which exhibited interfacial failure and a low-energy absorption of 30.9 J in the as-welded condition, saw a change in a failure mode to partial interfacial failure and a 260% increase in energy absorption after baking for 30 s. After baking for a longer time (4 min), welds failed by button pull-out and exhibited a 296% increase in energy absorption during cross-tension testing. Baking for the full 20 min resulted in no additional improvement than was observed in the 4 min condition. The mechanisms responsible for the majority of the improvement in weld performance during baking are found to be activated after only 30 s of baking.
Milling Force Prediction Model for Five-Axis Machining of Freeform Surface Considering Mesoscopic Size Effect
Authors: Guo Minglong , Wei Zhaocheng , Wang Minjie , Wang Jia , Liu Shengxian
Published: March 2021

The core parts with the characteristic of freeform surface are widely used in the major equipment of various fields. Cutting force is the most important physical quantity in the five-axis CNC machining process of core parts. Not only in micro-milling, but also in macro-milling, there is also an obvious size effect, especially in medium- and high-speed milling, which is frequently ignored. In this paper, the milling force prediction model for five-axis machining of a freeform surface with a ball-end mill considering the mesoscopic size effect is established. Based on the characteristics of cutting thickness in macro-milling, a new dislocation density correction form is proposed, and a new experiment is designed to identify the dislocation density correction coefficient. Therefore, the shear stress calculated in this paper not only reflects the cutting dynamic mechanical characteristics but also considers the mesoscopic size effect. A linear function is proposed to describe the relationship between friction coefficient and cutting speed, cutter rake angle, and cutting thickness. Considering cutter run-out, the micro-element cutting force in the shear zone and plough zone are analyzed. The cutting geometry contact between the freeform surface and the ball-end mill is analyzed analytically by the space limitation method. Finally, the total milling force is obtained by summing all the force vectors of cutting edge micro-elements within the in-cut cutting edge. In the five-axis machining experiment of freeform surface, the theoretically predicted results of milling forces are in good agreement with the measured results in trend and amplitude.
Design Optimization and Performance Analysis of a Multi-Kilowatt Thermoacoustic Electric Generator Using DeltaEC Model
Authors: Somu Srinath , Lacoste Deanna , Saxena Saumitra , Roberts William L. , Keolian Robert M.
Published: March 2021

Waste heat recovery from power plants and industries requires a new type of electricity generator and related technological developments. The current research work is aimed at the design of a multi-kilowatt thermoacoustic electric generator, which can be employed as the bottoming cycle of a gas turbine power plant or for industrial waste heat recovery. The proposed device converts thermal energy into acoustic power and subsequently uses a piezoelectric alternator to convert acoustic power into electricity. The challenge in designing such a device is that it has to be acoustically balanced. The performance of the device is greatly affected by numerous parameters such as frequency of the traveling acoustic wave, heat exchanger parameters, regenerator dimensions, and acoustic feedback loop. The proposed device is a lab-scale demonstration targeted to produce few kilowatts of electric power from a 20 kWth heat source. DeltaEC software is used to achieve the acoustically balanced configuration of the device. The DeltaEC model outcomes are used to arrive at the optimized design of the device and its components. The analytical method, the optimized geometrical dimensions of thermoacoustic components, and the minimum required conditions of heat source input are presented in this paper.
Nonlinear Interactions of Lamb Waves With a Delamination in Composite Laminates
Authors: Gangwar Akhilendra S. , Agrawal Yamnesh , Joglekar D. M.
Published: March 2021

In view of their higher sensitivity in localizing an incipient damage, methods of non-destructive evaluation based on the nonlinear wave-damage interactions have been of continued interest in the recent past. In this paper, the propagation of guided waves through a delamination with contacting interfaces is studied numerically using a finite element-based framework. In particular, influence of the interlaminar location of the delamination on the nonlinear acoustic features in the response spectrum is investigated in detail. The numerical framework is validated by an in-house experimentation performed on a unidirectional glass fiber reinforced polymer (GFRP) laminate containing a through-width delamination. A parameter, referred to as the nonlinearity index (NI), is defined for quantifying the strength of the nonlinear wave-damage interactions and its dependence on the interlaminar location of the delamination is studied across a range of interrogation frequencies. The notion of contact energy intensity is introduced and further used for justifying the trends of variation of the NI obtained numerically and observed experimentally. Results indicate that two fundamental parameters govern the underlying contact phenomenon; they are the phase difference between the wave packets passing through the two sub-laminates and the flexural rigidities of the two sub-laminates present at the site of the delamination defect. While the former controls the relative displacement between the two sub-laminates, the latter governs the propensity of collisions between the two sub-laminates. Finally, a diametric effect of these two parameters on the generation of nonlinear harmonic signals with varying interlaminar locations of the delamination is brought out.
Experiments With the Integration of Reasoning, Optimization and Generalization in Process Planning
Authors: Váncza József , Márkus András
Published: March 2021

The paper describes a feature-based process planning model and planning methods as verified in a prototype system with the following distinctive properties: (1) reasoning over a detailed model of the part, the manufacturing processes and resources, (2) detection of conflicts and combinatorial conflict resolution among pieces of technological advice, (3) optimization of the manufacturing cost with a genetic algorithm, (4) generalization of plans by omitting incidental detail. Generalization, being the newest development in the system, is discussed more thoroughly. While the focus of attention is on the fundamental assumptions, the technical feasibility of the approach is illustrated by an example.
Adaptivity and Mesh Generation in 2-D Finite Element Analysis
Authors: Almeida C. A.
Published: March 2021

A methodology for the automatic mesh generation of triangular and quadrilateral finite element discretizations for two-dimensional elasticity problems is proposed. The methodology is based on: i) an h-adaptive process with powerful mesh generator facilities capable of achieving meshes of specified density, ii) a general stress recovery technique developed for determining the element solutions at the nodes, and iii) an a posteriori error estimation. The h-adaptive process used is based on a complete mesh regeneration procedure which is guided by specified mesh requirements such as geometry definitions, boundary conditions, and space node functions to achieve an optimal refinement. This optimality condition is, as established by Zienkiewicz and Zhu, the mesh refinement with the least number of elements that yields a uniform strain energy norm error distribution in all elements. In the stress recovery process, the nodal values are assumed to belong to a polynomial expansion of the same complete order in the interpolation function basis used, which is valid over all elements adjoining a particular node. A least-squares fit of superconvergent sampling points existing in the path is used to obtain the recovered nodal point parameters for each element. These parameters are averaged to all elements adjoining the node of interest. The technique is simple and cost-effective, and the recovered nodal values of derivatives are superconvergent at the Gauss integration points, which are used as sampling points for quadrilateral elements. This condition is also achieved when centroid and mid-side points are used for triangular elements. The error estimation is done evaluating differences between the post-processed stress gradients and those from the finite element solutions. The energy error norm associated with stress field differences and the finite element predicted strain energy gives an effective error estimate which can be used for comparison with the process tolerance. The technique has been implemented and allows for a fully automatic numerical analysis under a specified global energy error norm. Numerical tests conducted with various planar element formulations illustrate that the proposed technique converges in fewer steps than with previous methods of adaptive mesh refinement.
Computer Simulations for Frontal Impact
Authors: Doong Jiamaw , Cheng James C.
Published: March 2021

Vehicle crash performance is different for various testing configurations. The current NCAP fixed rigid barrier frontal impact test and FMVSS regulations have significantly improved occupant safety during a frontal crash. However in order to better represent and reduce fatal injuries in real world frontal impacts, several new frontal impact test configurations are being proposed and studied.

This paper compares four different frontal impact configurations with 35 mph impact speed, in terms of finite element crash simulation. The four configurations are 1) 90 degree fixed rigid barrier, 2) 50% offset rigid barrier, 3) 30 degree angular fixed rigid barrier, without anti-slide device, and 4) 30 degree angular fixed rigid barrier, with anti-slide device. This advanced computer simulation technology is now widely used in the auto industry and, in terms of the efficiency, timing and cost, it is the only tool powerful enough to face the technical challenges in future vehicle design.

The comparison is made from a structural point of view. Impact force, deceleration, deformation, and dash/toeboard intrusion are compared. Based on the performance of a given vehicle structure, a qualitative assessment of occupant behavior/injury can be drawn. The general relationship between occupant behavior and vehicle structural response, during a crash event, is well known, e.g. lower vehicle deceleration and less deformation of the passenger compartment will produce better occupant injury performance. The results of this study might be used as a reference for vehicle front end design or potential rulemaking for frontal impact tests.
Three-Dimensional Flowfield Prediction
Authors: Lin T.-K. , Lilley D. G.
Published: March 2021

The development, use and application of a three-dimensional fluid flow computer code is described. The code runs on microcomputers with effective 3-D perspective color graphic displays of the results. The present version of the code retains several simplifications, uses a uniform rectangular grid system, and runs on microcomputers, thus providing a powerful and economical software capability. Equations are solved for the fully 3-D problem, including pressure, three velocity components and species mass fractions. The simulation is a finite difference time-marching procedure using an explicit formulation of the conservation equations, followed at each step by an iteration updating pressures and velocities so as to impose the continuity requirement. The present paper documents the problem, describes briefly its simulation, theory and assumptions, and gives results showing an application of the code to co-flowing round jet mixing.
Examination of a “Map-Based” Approach to Modeling Steady State Heat Pump Performance With Variable Air Flow Rates
Authors: Mawasha P. , Rooke S. P. , Gross R.
Published: March 2021

Performance map-based modeling has been commonly employed for the rapid prediction of air conditioning and heat pump steady state performance. This approach requires that performance characteristics of the compressor and heat exchangers can be expressed in the form of simple algebraic functions. The growth of microprocessor based control, particularly in residential systems, has led to more frequent off-design operation. This study explores the ability of the map-based modeling approach to predict off-design operating performance of a single air-source heat pump operating in the cooling mode. Off-design conditions were simulated by varying the evaporator air flow rate over a wide range. Performance predictions are compared with the predictions of a more rigorous heat pump simulation program which utilizes heat transfer correlations for the heat exchangers rather than performance maps. A PC math package was used to generate results for the map-based model, while a Fortran compiler was used to generate results for the more rigorous model. The benefits of the map-based approach in predicting system performance are presented and discussed.
A New Method and Device for Temperature Measurement Using One-Dimensional Heat Equation
Authors: Damean Nicolae A.
Published: March 2021

A new method and device for temperature measurement are presented. The method reduces the measurement of the unknown temperature to the solving of an optimal control problem, using a numerical computer. The device consists of a hardware part including some conventional transducers and a software one.

The problem of temperature measurement, according to this method, is mathematically modelled by means of the one-dimensional heat equation, describing the heat transfer through the device.

The principal component of the device is a rod. The variation of the temperature which is produced near one end of the rod is determined using some temperature measurements in the other end of the rod, the mathematical model and a type of gradient algorithm.

This device works as an attenuator of high temperatures and as an amplifier of low temperatures.
Development of a Prototype Design Process Recorder Based on Hypergraphs
Authors: Hirose Atsushi , Cannon David M. , Leifer Larry J.
Published: March 2021

We describe a design process recording method and a prototype implementation. They are being developed from data on several design projects, including an in-depth study of a 6-month long design effort, itself part of a multi-year aerospace research and design project. The work is also influenced by the larger context of other design research projects at Stanford. The recording method focuses on information generated in early stages of design that is at the same time easiest to capture and most useful to designers and engineers downstream. It does this by being based primarily on a design process model intended to reflect a designer’s point of view, and by taking advantage of practices that designers currently find useful. The method builds on the concept of an electronic notebook that has been described previously (Lakin et al., 1989). The record consists of connected pieces of information about the various concepts, notes, and documents that are central to an evolving design. We call the framework for the record a hypergraph: ‘graph’ because of its node-arc structure, and ‘hyper’ because it spans several types of information that are created during design work. To effectively convey the record’s contents to a downstream user, we propose a design story-teller style: the system’s response to a query takes the form of a storyboard of notes about related design episodes.
Physical Synthesis in Case-Based Design
Authors: Michelena Nestor , Sycara Katia
Published: March 2021

Common design practices rely heavily on searching and studying of prior designs, patents, past design rationale, standards and new product announcements. An important step toward automating these activities is the creation of repositories of design information indexed by abstract attributes in addition to low-level structural descriptions. By reusing prior designs or their components an engineer can save design time, by leveraging off previous worked-out solutions, and avoid repeating past mistakes, by accessing information on manufacturing or field failures linked to the retrieved design. Under the case-based design paradigm, an engineer combines parts of different design cases to synthesize a device that satisfies a useful need. Physical synthesis entails taking into account possible interactions between components and sub-assemblies as well as reasoning about the dynamics of the system. In this paper we present a methodology for physical synthesis of design cases and components retrieved by a case-based design tool. Connecting elements for the design cases and components are retrieved from a casebase of connections. Indexing of these connections is based on the mobility restrictions that they impose on the connected parts. The information necessary to accomplish this task is still of a high-level nature, namely, the topology of the artifact and its abstract behavior specification.
Automatic Generation of 3-D Solid Models From Orthographic Projections
Authors: Saha K. , Gurumoorthy B.
Published: March 2021

This paper describes an algorithm to generate 3-D solid models of objects from their orthographic projections. This approach is entirely different from the earlier bottom-up approaches. Instead of generating the 3-D vertices, edges and faces sequentially, this approach considers an object to be the boolean combination of a number of elementary objects, which are 2.5D solids. The elementary objects are formed by decomposing a given view into loops and sweeping each loop perpendicular to the direction of projection. This algorithm can handle objects whose projections have curved edge(s) in one view of the orthographic projection. It is believed that proper extension of this algorithm can handle sectional views and multiple views, which has not been addressed in the bottom-up approach.
Goal-Directed Geometry: Beyond Parametric and Variational Geometry CAD Technologies
Authors: Rosen David W. , Chen Wei , Coulter Stewart , Vadde Srinivas
Published: March 2021

Improved computer-aided design tools can significantly impact designer productivity. The ability to formulate and solve “What if” questions is critical in early design stages. In this paper, a new computational framework for preliminary design, called Goal-Directed Geometry, is presented that provides such an exploratory environment for early stages. Tools for parametric geometry, variational modeling, and feature-based design are combined with a multiobjective optimization code to provide robust support for parametric design problems, where parameter values are desired that best meet a set of goals and constraints. Geometric and engineering models of a design are combined into a multiobjective optimization formulation called a Compromise Decision Support Problem, which can be solved by the existing package DSIDES (Decision Support In the Design of Engineering Systems). A prototype CAD system is under development that integrates DSIDES, a geometric modeler, and variational, parametric, and feature capabilities. The system aids a designer in evaluating competing alternatives, common during preliminary design, and in answering “What if” types of questions. Two examples illustrate the use of Goal-Directed Geometry in formulating and solving parametric design problems involving engineering and geometric constraints and goals.
Fatigue Life Simulation for Reliable Thick-Walled Cylinder Design
Authors: Eggert R. J.
Published: March 2021

Primary considerations for hydraulic cylinder and piston design include loading, geometry and material properties. However, variations in as-manufactured dimensions, as-processed material properties, and actual pressure histories propagate through the piston-seal-cylinder system often resulting in intolerable behaviors.

Variations are evaluated using design variation simulation, namely the Monte Carlo simulation technique and available statistical information, to evaluate a high-pressure piston-seal-cylinder system for servo-hydraulic fatigue testing experiments.

The numerical results indicate that the fatigue life as measured by number of cycles to failure, has a significant 140.8% coefficient of variation and 57.2% reliability for nominal design values. When the coefficients of variation of the input variables are maintained below 1%, the fatigue life coefficient of variation is approximately 13.3% and the reliability is 99.06%.
A Domain Decomposition Method for Large Scale Structural Optimization
Authors: Spengemann Frank , Booz Walter
Published: March 2021

A domain decompostion method for large scale structural optimization is proposed. A block diagonal preconditioning scheme is used to partition the structural model into a number of smaller subsystems and to approximate the state variables. In this two level approach the optimization is done on the lower level, on the upper level the coordination of the subsystems is performed by approximating the multipliers of the optimality criteria.
A Simulated Annealing-Based Approach to Three Dimensional Component Packing
Authors: Szykman Simon , Cagan Jonathan
Published: March 2021

This paper introduces a computational approach to three dimensional component layout that employs simulated annealing to generate optimal solutions. Simulated annealing has been used extensively for two dimensional layout of VLSI circuits; this research extends techniques developed for two dimensional layout optimization to three dimensional problems which are more representative of mechanical engineering applications. In many of these applications, miniaturization trends increase the need to achieve higher packing density and fit components into smaller containers. This research addresses the three dimensional packing problem, which is a subset of the general component layout problem, as a framework in which to solve general layout problems.
Recycling Oriented Fasteners: A Critical Evaluation of VDI 2243’s Selection Table
Authors: VerGow Zachary , Bras Bert
Published: March 2021

A growing concern about the environment, and especially about waste and landfill, has spurred research into the design of more environmentally benign products. A dramatic reduction in environmental impact can be made by recycling. A critical issue in recycling is the separation of joints in the disassembly process. In product recycling (also referred to as reuse) non-destructive disassembly is desired, whereas in material recycling destructive disassembly is allowed (e.g., shredding). This has an impact on the selection of fasteners. In this paper, we provide an overview of the issues involved and specifically we evaluate the selection of fasteners in the context of product recycling, material recycling, and technical aspects as documented in the new German standard VDI 2243, “Designing Technical Products for Ease of Recycling – Fundamentals and Rules for Design”. The results of this evaluation provide insight in future areas of research and fastener selection models for life cycle design.
Optimization of Multibody Systems Using Sequential Linear Programming
Authors: Etman L. F. P. , Thijssen E. J. R. W. , Schoofs A. J. G. , van Campen D. H.
Published: March 2021

Design optimization is far less developed for multibody analysis than for structural analysis. However, multibody design problems can be solved by optimization strategies applied in structural analysis. To illustrate this, a design optimization tool has been developed for a multibody analysis software package. It is based on a linear approximation concept. An optimization process results that consists of a sequence of linear programming problems. The design optimization tool has been successfully tested for three multibody design examples.
Application of Topological Optimization Techniques to Structural Crashworthiness
Authors: Mayer Robert R. , Kikuchl Noboru , Scott Richard A.
Published: March 2021

The topological optimization of components to maximize crash energy absorption for a given volume is considered. The crash analysis is performed using a DYNA3D finite element analysis. The original solid elements are replaced by ones with holes, the hole size being characterized by a so-called density (measure of the reduced volume). A homogenization method is used to find elastic moduli as a function of this density. Simpler approximations were developed to find plastic moduli and yield stress as functions of density.

Optimality criteria were derived from an optimization statement using densities as the design variables. A resizing algorithm was constructed so that the optimality criteria are approximately satisfied. A novel feature is the introduction of an objective function based on strain energies weighted at specified times. Each different choice of weighting factors leads to a different structure, allowing a range of design possibilities to be explored.

The method was applied to an automotive body rear rail. The original design and a new design of equal volume with holes were compared for energy absorption.
Circuit Analysis of Stephenson Chain Six-Bar Mechanisms
Authors: Davis Henry P. , Chase Thomas R. , Mirth John A.
Published: March 2021

A circuit quantifies a complete range of motion that a linkage can achieve without disassembly. A Stephenson linkage may have from one to six circuits. Current computer simulation packages are unable to define a circuit. Therefore, the simulations are limited to a small fraction of the total motion capability of a Stephenson linkage.

This paper presents a method to completely and unambiguously define all circuits of any pin-jointed Stephenson linkage. The method has been optimized for conversion to a computer algorithm. Once the circuits are known, any set of design positions can be matched to the circuits to determine if the mechanism can reach all positions without disassembly.
Closed Solution for the Elastic-Dynamic Behavior of an Industrial Press Feed Mechanism
Authors: Xu Tao , Lowen Gerard G.
Published: March 2021

A new linearized two degree of freedom model of an industrial press feed mechanism, containing an RSSR linkage, a bent coupler, an overrunning sprag clutch, a feed strip and a brake, is presented. By introducing a double cantilever model of the coupler with an assumed quarter sine shape function, simplifying certain terms of secondary importance and replacing the non-linear clutch spring by a linear torsional spring with a deflection dependent stiffness, it was possible to develop a set of two linear differential equations for the all important feed stroke, which could be fully solved in an analytic manner for the dynamic responses of the coupler strain and the clutch windup angle.
An Object-Oriented Differential-Geometric Approach to Spatial Mechanism Dynamics
Authors: Kecskeméthy Andrés G.
Published: March 2021

Described in this paper is a novel approach for the computer-generation of the dynamical equations of complex spatial mechanisms. A coordinate-free, intrinsic representation of the underlying equations is developed from well-known concepts of differential-geometry. The resulting objects are shown to be amenable to an object-oriented implementation based on the client-server paradigm, allowing for an open, intuitive and formalism-independent generation of corresponding computer models. We develop here primarly the theoretical foundations of the approach, referencing to applications in the literature.
Design of a Knee Mechanism for a Knee Disarticulation Prosthesis
Authors: Srinivasan Sujatha , Kramer Steven
Published: March 2021

A new knee mechanism has been designed which is a significant improvement over existing designs used in knee disarticulation (K/D) prostheses. These are prostheses used when the amputation is performed through the knee joint as opposed to amputation performed above the knee. The new four-bar mechanism has a more desirable locus of instant centers thereby improving the gait for K/D amputees. In this paper, the design process involving the kinematics is discussed. A prototype has been made and is currently undergoing testing with a prosthetist.
Design of a Walking Simulator
Authors: Bejune David , David John , Ouellette William , Zeilinski Brian , Chen Neal , Peura Brent , Norton Robert L.
Published: March 2021

A prototype of a simple, footwear-testing machine which mimics the physiologic motions and forces of walking in one plane has been designed, developed and tested. Eleven ROTC students were measured and filmed to obtain information on the kinematics of the lower limb and the dynamic forces exerted by their footwear on the ground while walking across a load plate. A machine was then designed which uses the coupler curve of a fourbar linkage to simulate the planar kinematics of the heel-strike and toe-off portions of walking. A standard-issue U. S. Army combat boot is attached to the fourbar linkage’s coupler link on a prosthetic foot such that the heel and sole are close to the moving centrode of the coupler. The ground plane is the fixed centrode. Thus their relative motion approximates pure rolling. The boot is “walked” against a force-plate which is loaded by an air cylinder. This force plate is pulled away during the walking “backstroke”. The dynamic forces of impact are measured by two force transducers. These measured forces simulate the vertical physiologic forces of walking and the kinematics provides realistic physiologic motions to the boot in a vertical plane.
Integrated and Intelligent Database Systems for Plant Engineering Framework
Authors: Narikawa N. , Sato T. , Sasaki N.
Published: March 2021

This paper gives an overview of an integrated and intelligent database system for a plant engineering framework. We have integrated existing two-dimensional (2D) CAD systems, a three-dimensional (3D) CAD system, and a relational database system which stores engineering information such as design conditions, maintenance histories, and inherent properties. By integrating these systems, the infrastructure for concurrent engineering has been realized. As for design knowledge, we treat object-oriented programming as a useful knowledge representation method. We analyze the plant structure and functional requirements of the system, and then represented them by using the hierarchical Class structure. Design knowledge accompanies the Class, so we represent it using Method. As a design automation system, we develop an automated design check system. This is implemented by using the Common Lisp Object System. These systems are the main parts of the plant engineering framework, and are utilized in the practical design. We intend to develop a mechanical/electronic design framework using the same approach.
STEP-Based CAD/CAPP/CAM Integrated Systems: CADMIS
Authors: Huang Jinguo , Wang Tongyang , Wan Li , Zhang Xinfang , Zhou Ji
Published: March 2021

This paper introduces the architecture of the STEP-based mechanical manufacturing integrated system CADMIS, and discusses STEP implementation methodologies. The system framework is based on an architecture that promotes better integrity and extendibility. It supports the integration of current existing systems and supports the entire procedure of the design and manufacturing of parts. This paper presents the development and trends of the CADMIS system integration.
Thermal atomic layer etching: A review
Authors: Fischer Andreas , Routzahn Aaron , George Steven M. , Lill Thorsten
Published: March 2021

This article reviews the state-of-the art status of thermal atomic layer etching of various materials such as metals, metal oxides, metal nitrides, semiconductors, and their oxides. We outline basic thermodynamic principles and reaction kinetics as they apply to these reactions and draw parallels to thermal etching. Furthermore, a list of all known publications is given organized by the material etched and correlated with the required reactant for each etch process. A model is introduced that describes why in the nonsaturation mode etch anisotropies may occur that can lead to unwanted performance variations in high aspect ratio semiconductor devices due to topological constraints imposed on the delivery of reactants and removal of reactant by-products.
Forward masking of amplitude modulation across ears and its tuning in the modulation domain
Authors: Füllgrabe Christian , Sęk Aleksander , Moore Brian C. J.
Published: March 2021

Frequency selectivity in the amplitude modulation (AM) domain has been demonstrated using both simultaneous AM masking and forward AM masking. This has been explained using the concept of a modulation filter bank (MFB). Here, we assessed whether the MFB occurs before or after the point of binaural interaction in the auditory pathway by using forward masking in the AM domain in an ipsilateral condition (masker AM and signal AM applied to the left ear with an unmodulated carrier in the right ear) and a contralateral condition (masker AM applied to the right ear and signal AM applied to the left ear). The carrier frequency was 8 kHz, the signal AM frequency, fs, was 40 or 80 Hz, and the masker AM frequency ranged from 0.25 to 4 times fs. Contralateral forward AM masking did occur, but it was smaller than ipsilateral AM masking. Tuning in the AM domain was slightly sharper for ipsilateral than for contralateral masking, perhaps reflecting confusion of the signal and masker AM in the ipsilateral condition when their AM frequencies were the same. The results suggest that there might be an MFB both before and after the point in the auditory pathway where binaural interaction occurs.
Intelligibility of first-language (L1) and second-language (L2) speech by switched-dominance Spanish-English bilinguals
Authors: Blasingame Michael , Bradlow Ann R.
Published: March 2021

Recordings of Spanish and English sentences by switched-dominance bilingual (SDB) Spanish (i.e., L2-dominant Spanish-English bilinguals) and by L1-dominant Spanish and English controls were presented to L1-dominant Spanish and English listeners, respectively. At –4 dB signal-to-noise ratio (SNR), Spanish and English productions by SDBs were equally intelligible with both reaching L1-dominant control levels. At –8 dB SNR, SDB English intelligibility matched that of L1-dominant English controls, yet SDB Spanish intelligibility was significantly lower than that of L1-dominant Spanish controls. These results emphasize that extended (but not early) exposure is both necessary and sufficient for robust speech learning.
A fast computational model for near- and far-field noise prediction due to offshore pile driving
Authors: Peng Yaxi , Tsouvalas Apostolos , Stampoultzoglou Tasos , Metrikine Andrei
Published: March 2021

This paper presents a computationally efficient modeling approach for predicting underwater noise radiation from offshore pile driving. The complete noise prediction model comprises two modules. First, a sound generation module is adopted to capture the interaction between the pile, the fluid, and the seabed, aiming at modeling the sound generation and propagation in the vicinity of the pile. Second, a sound propagation module is developed to propagate the sound field at larger distances from the pile. To couple the input wavefield obtained from the sound generation module, the boundary integral equations (BIEs) are formulated based on the acousto-elastodynamic reciprocity theorem. To advance the mathematical formulation of the BIEs, the Green's tensor for an axisymmetric ring load is derived using the complex wavenumber integration technique. The model advances the computational efficiency and flexibility of the noise prediction in both near- and far-fields from the pile. Finally, model predictions are benchmarked against a theoretical scenario and validated using measurement data from a recent offshore pile-installation campaign.
The Physiological, Neuromuscular, and Perceptual Response to Even- and Variable-Paced 10-km Cycling Time Trials
Authors: Veneman Tim , Schallig Wouter , Eken Maaike , Foster Carl , de Koning Jos J.
Published: March 2021

Background: During self-paced (SP) time trials (TTs), cyclists show unconscious nonrandom variations in power output of up to 10% above and below average. It is unknown what the effects of variations in power output of this magnitude are on physiological, neuromuscular, and perceptual variables. Purpose: To describe physiological, neuromuscular, and perceptual responses of 10-km TTs with an imposed even-paced (EP) and variable-paced (VP) workload. Methods: Healthy male, trained, task-habituated cyclists (N = 9) completed three 10-km TTs. First, an SP TT was completed, the mean workload from which was used as the mean workload of the EP and VP TTs. The EP was performed with an imposed even workload, while VP was performed with imposed variations in workload of ±10% of the mean. In EP and VP, cardiorespiratory, neuromuscular, and perceptual variables were measured. Results: Mean rating of perceived exertion was significantly lower in VP (6.13 [1.16]) compared with EP (6.75 [1.24]), P = .014. No mean differences were found for cardiorespiratory and almost all neuromuscular variables. However, differences were found at individual kilometers corresponding to power-output differences between pacing strategies. Conclusion: Variations in power output during TTs of ±10%, simulating natural variations in power output that are present during SP TTs, evoke minor changes in cardiorespiratory and neuromuscular responses and mostly affect the perceptual response. Rating of perceived exertion is lower when simulating natural variations in power output, compared with EP cycling. The imposed variations in workload seem to provide a psychological rather than a physiological or neuromuscular advantage.
KDM2B Overexpression Facilitates Lytic
De Novo
Kaposi's Sarcoma-Associated Herpesvirus Infection by Inducing AP-1 Activity through Interaction with the SCF E3 Ubiquitin Ligase Complex
Authors: Naik Nenavath Gopal , Lee See-Chi , Alonso Juan D. , Toth Zsolt
Published: March 2021

The expression of epigenetic factors is often dysregulated in cancers or upon specific stress signals, which often results in a display of noncanonical functions of the epigenetic factors that are independent from their chromatin-modifying roles. We have previously demonstrated that KDM2B normally inhibits KSHV lytic cycle using its histone demethylase activity.