bluuebunny/crossref_metadata_2025 huggingface dataset:
The Bending of Symmetrically Loaded Circular Plates of Variable Thickness
Authors: Conway H. D.
Published: March 2021

This investigation was carried out with the object of obtaining a solution to the problem of a symmetrically loaded circular plate with a central hole, the thickness of the plate at any section being proportional to the distance of the section from the center of the plate. Six particular cases were investigated, and the values of the maximum stress and deflection calculated for various ratios of the external diameter of the plate to the diameter of the central hole. These values were compared with the corresponding values obtained for plates of constant thickness by A. M. Wahl and G. Lobo (1).
The Flutter of a Uniform Wing With Tip Weights
Authors: Goland Martin , Luke Y. L.
Published: March 2021

Forming an extension of a previously published work (1), the present paper investigates the flutter of a uniform wing in free flight carrying a fuselage at its semispan and a weight at each wing tip. Wing-tip weights arise in practice when, for example, wing-tip fuel tanks are installed. The flutter system is studied by solving the differential equations for the wing motion. Solutions are carried out for two representative airplane configurations and the resultant speeds, frequencies, and mode shapes at flutter are compared with those obtained on the basis of conventional, Rayleigh-type flutter analyses. The methods of the original paper (1) are considerably refined, resulting in a significant reduction in the amount of labor required to effect a solution.
Vibration of a Nonlinear System During Acceleration Through Resonance
Authors: Meuser R. B. , Weibel E. E.
Published: March 2021

During acceleration of a machine through a critical speed, displacements and stresses may attain large values. For linear systems F. M. Lewis (1), and J. G. Baker (2) have studied different aspects of this problem, the former analytically, the latter by mathematical-machine methods. This paper presents a generalized solution obtained on the mechanical analyzer (3) for the effect of an accelerated sine-wave force on a spring-mass system having linear plus cubic elasticity and linear damping. The range of accelerations covered applies to electrically driven reciprocating machines and to other rapid starting units. Some interesting effects of nonlinearity on displacements and forces are pointed out.
Effect of Bending Rigidity of Stringers Upon Stress Distribution in Reinforced Monocoque Cylinder Under Concentrated Transverse Loads
Authors: Levy Robert S.
Published: March 2021

Least-work analysis of stress distribution in a reinforced circular monocoque cylinder is extended to determine the effect of bending resistant stringers located at the points of application of concentrated transverse loads. Calculations for a numerical example, with applied loads diametrically opposed, indicate that neglect of stringer bending rigidity results in calculated maximum shear stresses approximately 20 per cent conservative in the fields of load application and 50 per cent unsafe in an intermediate field. Further calculations indicate that the bending rigidity of the stringer has less effect when all loads are applied at the same circumferential location. Comparison of shear stresses, calculated by the present method with strain-rosette readings, indicate good agreement.
Tensorial Analysis of Control Systems
Authors: Kron Gabriel
Published: March 2021

The equations of small oscillations superimposed upon a state of steady motion may usually be represented by a set of linear algebraic equations ZαβΔxβ = Δfα. When a complex dynamical system is given, such as a servomechanism, it is possible to establish the resultant equations by first removing all interconnections between the various amplification stages and finding the impedance matrix Zαβ of each isolated stage. The effect of their interconnection is representable by a matrix of transformation Cαα′. The impedance matrix Zα′β′ of the resultant system may be found without any physical analysis by a simple routine matrix manipulation involving Zαβ, Cαα′, its partial derivatives ∂Cαα′/∂xα and the steady-state force vector fα. (In oscillatory problems the law of transformation of the impedance matrix Zαβ is not that of a tensor.) The method is illustrated by setting up the differential equations of various types of speed-, pressure-, and position-governing systems used in central-station work.
The Effect of Size and Stored Energy on the Fracture of Tubular Specimens
Authors: Davis E. A.
Published: March 2021

Internal pressure tests on tubular specimens are described in this paper. Tests were run on three sizes of specimens. In one half of the tests, a high-pressure chamber was used in connection with the specimens to store additional energy in the test system. Both pure internal pressure and pure circumferential tension tests were made. The size effect as shown by the tests was negligible. The effect of the stored energy showed up only after the fracture actually started. In the high-energy tests, the extent of the fracture was much greater than in the low-energy tests.
The General Proof of the Principle of Maximum Plastic Resistance
Authors: Philippidis A. H.
Published: March 2021

In this paper the general proof of the principle of maximum plastic resistance of M. Sadowsky is given.
The Interaction of Discontinuity Surfaces in Plastic Fields of Stress
Authors: Winzer Alice , Carrier G. F.
Published: March 2021

A fundamental solution for problems associated with discontinuity surfaces in the field of stress has been developed by W. Prager, but the accuracy with which it approximates the stress field obtained in actual materials under the same boundary conditions has not been established. In this paper a study is made of the limited case in which the discontinuity surfaces may intersect when they separate fields of constant stress. The results may be applied to more general intersecting fields.
Investigations of the Flow in Curved Ducts at Large Reynolds Numbers
Authors: Weske J. R.
Published: March 2021

It is found that the flow in curved ducts at high Reynolds numbers may be analyzed by methods adapted from the theory of boundary layers. Integration of the equation of motion of the “shedding layer” led to relations for the net pressure drop of curved ducts as a function of radius ratio and of Reynolds number.
Thermodynamic Properties of Gas Mixtures Encountered in Gas-Turbine and Jet-Propulsion Processes
Authors: Kaye Joseph
Published: March 2021

The presentation of data for gas mixtures on a molal basis reduces greatly the number of gas tables required for calculations of processes in a wide variety of mixtures. This simplification of the tabular data is illustrated in detail by consideration of several gas mixtures and of the processes encountered in the design of gas turbines. Three tables of products of combustion of a hydrocarbon fuel with air are sufficient to permit calculations of all processes of interest, with an average error of about 0.1 per cent over a large range of hydrogen-carbon ratios of the fuel and over the range of fuel-air ratios for lean mixtures. Furthermore, these three tables may be used with the same error for calculations involving mixtures of air and octane vapor as well as for mixtures of air and water vapor.
Gyroscopic Effects on the Critical Speeds of Flexible Rotors
Authors: Green R. B.
Published: March 2021

The forces and moments on rotating disks are found for the general case, and the various possible criticals of common rotor systems are determined and plotted for all degrees of gyroscopic effect. Specific examples are shown of a cantilever system, two simply supported single-disk systems, a double-disk system, and an infinite-disk system. Methods of solution are indicated for any case. The gyroscopic effect is shown for all possible ratios of shaft rotating frequency to whirl frequency.
Heat-Exchanger Tube-Sheet Design
Authors: Gardner K. A.
Published: March 2021

A semitheoretical method for the design of circular tube sheets is outlined based upon “deflection and ligament efficiencies.” These are roughly known from past experience with other design formulas, but experimental work is advocated for more accurate evaluation. A bayonet or U-tube sheet is considered as a modified solid plate and other types as modified solid plates on elastic foundations (the tubes themselves). Design equations are presented for both types with either simply supported or rigidly clamped boundaries.
Exergy and Energy Analysis of α-Fe2O3-Doped Al2O3 Nanocatalyst-Based Biodiesel Blends—Performance and Emission Characteristics
Authors: Anderson A. , Al-Mohaimeed Amal M. , Elshikh Mohamed Soliman , Praveenkumar T. R. , Sekar M.
Published: March 2021

The current study emphasis on the engine performance and emission characteristics of rapeseed and soya biodiesel dispersion on a novel nanocatalyst at different concentrations of 25 ppm and 50 ppm. The results of this study were compared with those of conventional diesel at varying load conditions on a combustion ignition engine. An α-Fe2O3-doped Al2O3 was mixed with rapeseed biodiesel and soya biodiesel using an ultrasonicator at a frequency of 25 kHz. This study revealed that the incorporation of nanoparticles in biodiesel enhanced the performance of the blends by reducing the content of lignin and other unsaturated fatty acids. The improvement in the performance of the engine is mainly attributed to the high area-to-volume ratio of the nanocatalyst. Emissions of NOx. hydrocarbon and carbon monoxide during the combustion reaction increased significantly when nanoparticles were added at higher concentrations. Contrastingly, the emission of NOx in pure biodiesel was higher than that in conventional diesel. The addition of nanoparticles reduced CO emissions due to the presence of extra oxygen molecules and converted carbon monoxide into carbon dioxide. Soya seed biodiesel blends with 50 ppm nanoparticles showed better engine performance and emission characteristics as compared with all other blends.
Annual Evaluation of a Model Predictive Controller in an Integrated Thermal-Electrical Renewable Energy System Using Clustering Technique
Authors: Narayanan Muthalagappan
Published: March 2021

Whitebox model in a model predictive controller (MPC) for energy systems, though does help in developing an accurate system model, requires a long time for optimization. In this article, an adaptation of the clustering technique used in hardware-in-the-loop testbench is proposed for evaluation of the MPC on an annual scale with selected six representative days in a year for that particular system and location. Initially, the various input parameters for clustering (algorithm, distance metric, and datapoint input dimensions) are studied for the selected thermal-electrical integrated renewable energy system (with solar thermal collectors, auxiliary gas boiler, stratified thermal storage, micro fuel cell combined heat and power (FC-CHP), photovoltaic system, a lithium-ion battery) for a Sonnenhaus standard single-family residential building. Finally, the proposed methodology is used to compare the annual derived energy values and key performance indicators (KPIs) for an MPC implementation with a status quo controller as a reference. Also, extreme exemplary weather days are investigated as the selected representative days were only average days in each season. Despite the conflict of using the FC-CHP on cold sunny days, instead of utilizing the battery and increased gas boiler energy input, a 9% increase in decentral system fraction is reported. Via the use of MPC instead of status quo controllers, the results indicate −18% space heating (SH) demand; +30% solar thermal energy production; −29% gas boiler energy supply; −52% power-to-heat thermal energy supply; −52% electrical fuel cell production; +240 kWh battery utilization; and −52% reduced grid import at the expense of 1.2% of the electrical load demand as grid import.
A Computational Fluid Dynamics Coupled Multi-Objective Optimization Framework for Thermal System Design for Li-Ion Batteries With Metal Separators
Authors: Cui Xujian , Chen Siqi , Xiao Mi , Li Wei
Published: March 2021

Battery thermal management system (BTMS) has significant impacts on the performance of electric vehicles (EVs). In this research, a computational fluid dynamics (CFD) coupled multi-objective optimization framework is proposed to improve the thermal performance of the battery pack having metal separators. CFD is utilized to study the thermal and fluid dynamics performance of the designed battery pack. Input parameters include inlet air temperature, thermal conductivity of coolant, thermal conductivity of metal separator, and diameter of heat dissipation hole. Five vital output parameters are maximum temperature, average temperature, temperature standard deviation (TSD), maximum pressure, and volume of the pack. The support vector machine (SVM) model is used to replace the real output parameters of the battery pack. Sensitivity analysis results indicate that the diameter of heat dissipation hole is the main factor affecting the volume of the structure and the pressure drop, while the inlet air temperature has significant influence on the battery pack thermal behavior. The cooling efficiency and the uniformity of temperature distribution are mainly determined by the inlet air temperature. The decrease of inlet air temperature could lead to a rise of temperature standard deviation. The nondominated sorting genetic algorithm-II (NSGA-II) is taken to acquire the optimum set of input parameters. The obtained optimal scheme of battery pack can improve the cooling efficiency as well as reducing the volume cost and the energy consumption of the cooling system while such design may result in a higher level of nonuniformity of the temperature and pressure distribution.
Improved Tribological Performance of Polydopamine/Polytetrafluoroethylene Thin Coatings With Silica Nanoparticles Incorporated into the Polydopamine Underlayer
Authors: Abe Adedoyin , Choudhury Dipankar , Zou Min
Published: March 2021

Polytetrafluoroethylene (PTFE) is a solid lubricant with low friction coefficient. However, it lacks durability as a thin coating. Prior studies have shown that a polydopamine (PDA) underlayer enhances the coating durability. In this study, 100, 200, and 300 µL of aqueous silica nanoparticle (NP) dispersions were added to a 15 mL PDA deposition solution. Stainless steel substrates were coated with PDA + silica in the mixed dispersions and then coated with PTFE layers to form thin PDA + silica/PTFE coatings. The coatings were tested in ball-on-flat linear reciprocating motion under dry contact conditions. The durability of the PDA/PTFE coating was improved by 70% when 100 µL of aqueous silica NP dispersion was added. The significant improvement in the durability was attributed to the increased adhesion of the PTFE coating to the PDA underlayer, the fragmented wear debris, and the enhanced counterface transfer film. These samples also showed enhanced resistance under linearly increasing load scratch testing with lower coefficient of friction (COF) and higher delamination resistance when compared to samples without silica.
SAPEP: An Interactive System for the Appropriation of Planning Strategies in the Fabrication of Axisymmetrical Parts
Authors: Hernández José T. , Rodríguez Marcela , Serrano Maria C.
Published: March 2021

This article explains the system SAPEP: an interactive system for the appropriation of planning strategies in the fabrication of axisymmetrical parts. It obtains the solution to the fabrication problems with sub problem refinement using a feature-based representation not only for the final parts but for the manufacturing operations. The appropriation scheme is a process tracing variation that, by comparison with a “base strategy”, questions about the criteria used. The base strategy is structured by refinement criteria (Which sub-problem to refine, and How to do it), and choice criteria. The session output is the automatic history of the prototype and expert’s actions, improved with explanations.
Opportunistic Process Planning: A Knowledge Based Technique for CAPP Applications
Authors: Kruth Jean-Pierre , Detand Jan , Van Zeir Geert , Kempenaers Jan , Pinte Jos
Published: March 2021

Feature based Computer Automated Process Planning applications often suffer from exponential growth of the search space and thus CPU-time, with increasing complexity of a part. Opportunistic process planning can remedy this drawback. The approach consists of dividing the features into two sets : one set, called the important features, are used to generate a process plan; the other features, called non-important features, are added to the process plan afterwards. This generation method resembles much the reasoning pattern of a human process planner. The developments are carried out in the framework of the ongoing Esprit project 6805 COMPLAN. Other reasoning methods, used in the project and described in this paper, are : combined variant/generative planning, non linear process plans, Petri nets, and feature based reasoning.
Automatic Planning for 5-Axis Sculptured Surface Machining
Authors: Lee Yuan-Shin , Chang Tien-Chien
Published: March 2021

In modern product design, sculptured surfaces are commonly used for functional and artistic shape design. Design of sculptured surfaces is evolutionary, consisting primarily of incremental changes to existing part surfaces. Manual operation planning for sculptured surface machining is known to be error-prone and inefficient, which requires considerable checking, verification, and rework. Five-axis machining has higher productivity and better machining quality than 3-axis machining. However, the programming for 5-axis machining is more difficult due to the complex simultaneous cutter movements along the machine’s five axes. This paper presents a systematic methodology to generate operation plans for 5-axis sculptured surface machining. A complete operation plan and the error-free cutter path can be automatically generated from the CAD part design. To achieve design for manufacturing of sculptured surface products, the machining unfeasibility information can be fed back to the designer for further design modification. Results of computer implementation and testing examples are also presented.
Structure to Function Mapping via Behaviour in Automated Mechanism Design
Authors: Vissikirsky Vladimir A.
Published: March 2021

The paper presents an approach to organization and use of mechanism design knowledge based on the concept of design prototype. A role of behaviour as a link between structure and function of mechanism is in the focus of consideration. Function can be interpreted as a set of qualitative features that the designer uses in the search for a solution. Dependency network as an explicit representation between these features and behaviour of structural variables, has been suggested to reduce solution space in redesign process. Some questions of coordination between design prototypes of different levels are also discussed.
Maximum Stress at Intersecting Bores of Pressurized Blocks
Authors: Garg Ajay
Published: March 2021

In high pressure applications, rectangular blocks of steel are used instead of cylinders as pressure vessels. Bores are drilled in these blocks for fluid flow. Intersecting bores with axes normal to each other and of almost equal diameters, produce stresses which can be many times higher than the internal pressure. Experimental results for the magnitude of maximum tensile stress along the intersection contour were available. A parametric finite element model simulated the experimental set up, followed by correlation between finite element analysis and experimental results. Finally, empirical methods are applied to generate models for the maximum tensile stress σ11 at cross bores of open and close ended blocks. Results from finite element analysis and empirical methods are further matched. Design optimization of cross bores is discussed.
Simulation of Two-Dimensional Turbulent Recirculating Flow Field Behind a V-Shaped Bluff Body
Authors: Gu Z. , Sharif M. A. R.
Published: March 2021

The two-dimensional turbulent recirculating flow fields behind a V-shaped bluff body have been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The governing transport equations in conservative form are solved by a pressure based predictor-corrector method. The standard k-ϵ turbulence closure model and a boundary fitted multi-block curvilinear grid system are used in the computation. The code is validated against turbulent flow over a backward facing step problem. The predicted flow field behind the bluff body is also compared with experiment. It is found that while the qualitative features of the flow are well predicted, there is quantitative disagreement between the measurement and prediction. This disagreement can be partially attributed to the k-ϵ turbulence model which is known to be inadequate for recirculating flows. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed and the results are reported.
Linking Expert Group Technology With Parametric Design
Authors: Lee Joon Seok , Chang Kang J. , Lichten Larry
Published: March 2021

Expert systems can be integrated with databases and CAD/CAM systems using group technology (GT). By using information in a database, geometric features of parts can be specified by GT codes, and CAD models can be generated automatically using parameterized generic templates. This paper describes a microcomputer-based prototype implementation that merges database, expert, and CAD systems in order to perform GT classification and create CAD models with minimal manual intervention.
Design of Tolerances for Quality
Authors: Feng Chang-Xue , Kusiak Andrew
Published: March 2021

Design of a product (process) includes system design, parameter design, and tolerance design. Robust design is closely applicable to parameter design and tolerance design. The current literature on robust design is focused on parameter design while little attention has been paid to tolerance design. The current literature on tolerance design has focused on the use of optimization to minimize cost while little attention has been paid to minimizing manufacturing variations. This paper attempts to apply a robust design method, the design of experiments (DOE) approach, in tolerance synthesis to minimize manufacturing variations in the probabilistic case. Both, the manufacturing cost and the number of manufacturing defects are minimized in robust tolerance design. A solution procedure is proposed to apply the DOE approach to probabilistic tolerance design. The procedure is illustrated with an example. Special applications of the DOE approach to tolerance design are discussed. A brief comparison of the DOE approach with optimization, Taguchi methods, and zero defect design is presented.
A Hierarchy of Oct-Sphere Model and its Application in Collision Detection
Authors: Yang Heming , Zhang Xinfang , Zhou Ji , Yu Jun
Published: March 2021

Collision and interference detection among 3-D moving objects is an important issue in the simulation of their behavior. This paper presents a new model for representing 3-D objects and a corresponding effective algorithm for detecting collisions and interferences among moving objects. Objects can be represented for efficient collision and interference detection by a hierarchy of oct - sphere model (HOSM). Algorithms are given for building the HOSM and for detecting collisions and interferences between moving objects. On the basis of HOSM, the algorithm checks only intersections between the nodes of the models which are on the surfaces of the objects. Furthermore, because a node of HOSM represents a spherical region, the collision between the two nodes can be easily found just by calculating the distance between the centers of the two spheres corresponding to them no matter how the objects move. Finally, we discuss the efficiency of the algorithm through an example.
A Multibody/Finite Element Analysis Approach for Modeling of Crash Dynamic Responses
Authors: Ma Deren , Lankarani Hamid
Published: March 2021

Computer models of the human body are robust tools for gaining insight into the gross motion of ground vehicle or aircraft occupants and evaluating the loads and deformations of their critical parts. The knowledge of occupant responses will help in the determination of the type and probable causes of injuries that may be sustained during a crash. One important aspect in crash analysis is how the large motion of the relatively rigid segments of an occupant, such as the limbs, and the small deformations of flexible segments, such as the spine column, are inter-related. To this end, a general methodology for kineto-static analysis of multibody systems with flexible structures undergoing large motion and complicated structural deformations is developed. Rigid multibody dynamics is used to predict the gross motions and displacements at the boundaries. Finite element analysis is then performed to determine the corresponding loads and deformations of the entire structure. Based on this methodology, a multibody model of the occupant with a finite element model of the lumbar spine is developed for a Hybrid II (Part 572) anthropomorphic test dummy. The analytical results obtained from the code are correlated with the experimental results from the impact sled tests. Comparison of the results has shown much closer match between the analyses and the experiments.
The Development, Dynamic Simulation and Verification of a Half-Vehicle Model for Durability Testing
Authors: Belfiore D. A. , Gilmore B. J. , Wambold J. C.
Published: March 2021

Accelerated life testing analysis for transit buses requires a dynamic simulation model using road profiles as excitation inputs. This paper presents the modeling and parameter estimation required to conduct such a dynamic simulation of a small bus. The simulation preclude the necessity of measuring actual vehicle response traversing portions of selected roads. The results from the simulation correlate well with actual results in both magnitude and frequency distribution and thus, may be used for accelerated life test purposes.
Motion Interpolation Using Dynamics
Authors: Loduha T. A. , Ravani B.
Published: March 2021

In this paper we present a method for dynamically interpolating the motion of a rigid body in space between known end-positions. We begin by creating an image space representation of the equations of motion for a rigid body. These equations are written as a system of first-order state equations whose trajectory is optimized based on the minimization of a certain performance index. This leads to a set of boundary-value equations between the end positions, which when solved give the interpolated motion. Finally, a program developed to perform such interpolations numerically is utilized by generating a trajectory between given terminal states.
Motion Interpolation With G2 Composite Bézier Motions
Authors: Ge Q. J. , Kang Donglai
Published: March 2021

This paper deals with smooth motion interpolation. Recently, a direct construction algorithm was developed for designing piecewise parametric motions with second order geometric continuity (G2). The present paper provides a refined version of the G2 spline algorithm and shows how the G2 spline motion can be used to fulfill the task of motion interpolation by solving the problem of inverse design for the G2 spline motion. The results are useful for computer aided motion animation, and Cartesian trajectory generation for CNC machines and robot manipulators.
Robust Design by Tolerance Allocation Considering Quality and Manufacturing Cost
Authors: Söderberg Rikard
Published: March 2021

Involving customer values in the design process is necessary to improve the total quality of a product. The purpose of this work is to establish a theoretical base for tolerance allocation which allows both quality and manufacturing cost to be considered. The paper addresses functional tolerance chains, i.e. tolerance chains that involve a dimension important for the function of the product or component. The total loss to customer is determined as the sum of two tolerance dependent properties; the functionality loss and the component price. The functionality loss represents the customer’s economical loss due to poor functionality. The optimal tolerance limits are found by minimizing the total loss to customer. These are the limits that represent the best trade-off between cost and quality, from the customer’s point of view.

This work specially emphasizes a method for treating asymmetrical functionality loss, i.e. when the design is more sensitive to a deviation of a critical parameter in one direction than in the other. By moving the manufacturing target in a direction away from the most sensitive part, the total loss to customer can be reduced. This paper describes how the optimal manufacturing target and corresponding symmetrical tolerance band are found. This method thus increases the robustness of the design.

The method may be used for single tolerances or any resulting tolerance of a tolerance chain.
The Tolerance Optimization Problem Using a System of Experimental Design
Authors: Gadallah M. H. , ElMaraghy H. A.
Published: March 2021

A new algorithm for manufacturing tolerance synthesis is proposed. In complex mechanical assemblies, most tolerance analysis and synthesis methods tend to be impractical. In this article, a methodology is proposed to minimize manufacturing cost by tightening important dimensional and/or geometrical tolerances. Analysis of variance and experimental design techniques are used to discriminate among various design dimensions to the overall functional requirement of the mechanical assembly. In this case, some, but not all, design dimensions will be controlled. This paper reviews the state-of-the art in the area of tolerance analysis and synthesis and highlights the contribution of this work.
Triangulation Algorithm Based on Narrow Polygon Zone for Trimmed Parametric Surface
Authors: Gao Sande , Wang Qifu , Zhou Ji , Yu Jun
Published: March 2021

This paper presents a new approach to improving the triangulation of surfaces near intersection curves, i. e. “trim” regions. The main idea is based on constructing narrow polygons around trimming curves. The algorithm consists of: (1) Description of trimmed surface, (2) Reconstruction of intersection curve of surfaces, (3) Adaptive subdivision of the surface, (4) Construction of the narrow polygon zone, (5) Triangulation of the narrow polygon zone, (6) Reconstruction of topological relations.
Shape Optimal Design of Structures Based on Recent Developments of the Boundary Element Method
Authors: Portela A. , Mota Soares C. A.
Published: March 2021

This paper is concerned with the numerical implementation of the boundary element method for shape optimal design of two-dimensional linear elastic structures. The design objective is to minimize the structural compliance, subject to an area constraint. Sensitivities of objective and constraint functions, derived by means of Lagrangean approach and the material derivative concept with an adjoint variable technique, are computed through analytical expressions that arise from optimality conditions. The boundary element method, used for the discretization of the state problem, applies the stress boundary integral equation for collocation on the design boundary and the displacement boundary integral equation for collocation on other boundaries. The use of the stress boundary integral equation, discretized with discontinuous quadratic elements, allows an efficient and accurate computation of stresses on the design boundary. This discretization strategy not only automatically satisfies the necessary conditions for the existence of the finite-part integrals, which occur naturally in the stress boundary integral equation, but also circumvents the problem of collocation at kinks and corners. The perturbation field is described with linear continuous elements, in which the position of each node is defined by a design variable. Continuity along the design boundary is assured by forcing the end points of each discontinuous boundary element to be coincident with a design node.

The optimization problem is solved by the modified method of feasible directions available in the program ADS. Examples of a plate with a hole are analyzed with the present method, for different loading conditions. The accuracy and efficiency of the implementation described herein make this formulation ideal for the study of shape optimal design of structures.
On Modeling Multiple Objectives and Multi-Level Decisions in Concurrent Design
Authors: Mistree Farrokh , Patel Bharat , Vadde Srinivas
Published: March 2021

Modeling of multiple objectives in a decision and multilevel decisions are important in decision-based concurrent design. In this paper we address these twin issues in the context of a rotating disk. The initial mathematical description, referred to as the baseline model, of the rotating disk is independent of the strategies of modeling and solution, applied to it. Once the baseline model is established, it is modeled using two design strategies with different philosophical underpinnings, namely, one based on the notion of a unique optimum and the other on the notion of satisficing solutions. Our desire in writing this paper is to foster discussion rather than offering a prescription for solution.
On the Prediction of Extremal Material Properties and Optimal Material Distribution for Multiple Loading Conditions
Authors: Bendsøe Martin P. , Díaz Alejandro R. , Lipton Robert , Taylor John E.
Published: March 2021

This paper describes some recent developments that treats the simultaneous optimization of material and structure for minimum compliance. The basic idea is to represent the material properties for a linear elastic continuum in the most general form possible namely as the unrestricted set of elements of positive semi-definite constitutive tensors. The cost of resource is measured through certain invariants of the tensors, here the 2-norm or the trace of the tensors. The advantage of this general formulation is that analytical forms for the optimized material properties can be derived and that effective methods for computational solution can be devised for the resulting reduced structural optimization problem.
Applying Axiomatic Design to Interface Analysis in Modular Product Development
Authors: Hillström Fredrik
Published: March 2021

Modular products fulfil various overall functions through the combination of distinct building blocks or modules. This paper outlines a method that helps the designer clarify how interfaces between modules influence module functions, and select the best interface location. The method utilizes Suh’s axiomatic design theory together with conventional DFMA tools (Design For Manufacture and Assembly). In this approach, the information contained in the functional and physical hierarchies is utilized to clarify the interface/function interaction. DFMA tools are used to obtain a measure of the information content or complexity of each interface.

Furthermore, a product-modelling tool designed to support these activities (and axiomatic design in general) is discussed. An example that illustrates the use of the method is provided.
Simultaneous Type and Dimensional Synthesis of Mechanisms by Genetic Algorithms
Authors: Fang W. Eugene
Published: March 2021

Based on global search/optimization techniques called genetic algorithms, a new approach to the conceptual design of mechanisms is proposed. Emulating “natural” genetics and selection, competing types of mechanisms are treated as species and different dimensions are evaluated for each type simultaneously. The problem formulation is straight-forward, similar to an optimization problem. The result may be a spectrum of similar or different mechanisms, depending on whether multiple optimal solutions exist. The computational power required to utilize this approach is acceptable for most conceptual design problems.
Modular Third-Order Analysis of Planar Linkages With Applications
Authors: Pennestrí Ettore , Belfiore Nicola Pio
Published: March 2021

This paper reports analysis equations for the computerized third-order analysis of dyads. Such equations are an extension of those reported by C.H. Suh and C.W. Radcliffe.

Examples of tracing cubic of stationary curvature and quartic of derivative curvature for multiloop linkages are herein described.
Kinematic Design of a Large-Angular-Motion Constant-Velocity Coupling
Authors: Canfield Stephen L. , Salerno Robert J. , Reinholtz Charles F.
Published: March 2021

This paper describes a new type of constant-velocity coupling capable of producing solid joint angles greater than 180 degrees. Analytical expressions describing the range of motion are developed based on the kinematic closure equations of an equivalent spatial mechanism. This mathematical description is then used as a tool in the kinematic design and analysis of a constant-velocity coupling capable of producing a 240 degree solid angle output motion.
Quasi-Precision Position Synthesis of Four-Bar Linkages
Authors: Mirth John A.
Published: March 2021

Quasi positions describe portions of a mechanism’s motion that do not require an exact position. Quasi positions are combined with three exact positions to define a two-dimensional design plane for the synthesis of planar linkages. Quasi-precision position synthesis is based on precision position techniques. The method preserves the computational advantages of precision position synthesis with the added advantage of being able to specify a much greater number of design positions.
Designing Planar Mechanisms Using a Bi-Invariant Metric in the Image Space of SO (3)
Authors: Larochelle Pierre , McCarthy J. Michael
Published: March 2021

In this paper we present a technique for using a bi-invariant metric in the image space of spherical displacements for designing planar mechanisms for n (> 5) position rigid body guidance. The goal is to perform the dimensional synthesis of the mechanism such that the distance between the position and orientation of the guided body to each of the n goal positions is minimized. Rather than measure these distances in the plane, we introduce an approximating sphere and identify rotations which are equivalent to the planar displacements to a specified tolerance. We then measure distances between the rigid body and the goal positions using a bi-invariant metric on the image space of SO(3). The optimal linkage is obtained by minimizing this distance over all of the n goal positions.

The paper proceeds as follows. First, we approximate planar rigid body displacements with spherical displacements and show that the error induced by such an approximation is of order 1/R2, where R is the radius of the approximating sphere. Second, we use a bi-invariant metric in the image space of spherical displacements to synthesize an optimal spherical 4R mechanism. Finally, we identify the planar 4R mechanism associated with the optimal spherical solution. The result is a planar 4R mechanism that has been optimized for n position rigid body guidance using an approximate bi-invariant metric with an error dependent only upon the radius of the approximating sphere. Numerical results for ten position synthesis of a planar 4R mechanism are presented.
Stephenson Chain Branch Analysis: Four Generic Stationary Configurations and One New Linkage Polynomial
Authors: Davis Henry P. , Chase Thomas R.
Published: March 2021

The stationary configurations of the Stephenson linkages have been defined in the literature. All stationary configurations of the Stephenson six-bars are mapped to the Stephenson III linkage inversion and represented as four ‘generic’ stationary configurations. A graphical interpretation of these stationary configurations is presented. It may be used to determine these stationary configurations. Analytical solutions of the first two generic stationary configurations are referenced. A twentieth order polynomial, whose roots correspond to the third generic stationary configuration, is derived and discussed.
Evaluation of Equivalent Spring Stiffness for Use in a Pseudo-Rigid-Body Model of Large-Deflection Compliant Mechanisms
Authors: Howell Larry L. , Midha Ashok
Published: March 2021

Compliant mechanisms gain some or all of their mobility from the flexibility of their members rather than from rigid-body joints only. More efficient and usable analysis and design techniques are needed before the advantages of compliant mechanisms can be fully utilized. In an earlier work, a pseudo-rigid-body model concept, corresponding to an end-loaded geometrically nonlinear, large-deflection beam, was developed to help fulfill this need. In this paper, the pseudo-rigid-body equivalent spring stiffness is investigated and new modeling equations are proposed. The result is a simplified method of modeling the force/deflection relationships of large-deflection members in compliant mechanisms. Flexible segments which maintain a constant end angle are discussed, and an example mechanism is analyzed. The resulting models are valuable in the visualization of the motion of large-deflection systems, as well as the quick and efficient evaluation and optimization of compliant mechanism designs.
On the Matrix Algebra Realization of the Theory of Biquaternions
Authors: Ge Q. J.
Published: March 2021

This paper describes a matrix algebra presentation of Clifford’s theory of biquaternions. We examine 4 × 4 skew-symmetric matrices and use their exponentials to relate quaternions to equal-angle double rotations in Euclidean four-space E4. We show how double rotations in E4 expressed in terms of plane coordinates lead to elliptic biquaternions in both Plücker and Study forms and present the fundamental Plücker and Study conditions that govern the biquaternions. Finally, we show that a spatial displacement in E3 in terms of parabolic biquaternions (or dual quaternions) is a limiting case of a double rotation in E4 in terms of elliptic biquaternions.
Motion Synthesis of Mechanisms Using Constraint Manifolds
Authors: Wu Y. K. , Fischer Ian S.
Published: March 2021

The motion synthesis of a mechanism is obtained by curve fitting the intersection of the constraint manifolds representing each leg of the linkage in an image space to points obtained by the kinematic mapping of the prescribed positions and orientations. The dimensions of the mechanism can be found by using optimization algorithms to minimize the normal distance between all the desired image points and image curve of the tracer frame. The theory is illustrated by numerical examples.
Multiple-Mode Input Shaping Sequences for Reducing Residual Vibrations
Authors: Rappole B. Whitney , Singer Neil C. , Seering Warren P.
Published: March 2021

A closed-form method of calculating Input Shaping sequences for two modes of vibration is presented. The new method eliminates the optimization routines previously required to find the same solutions. Input Shaping is a feed forward method of reducing residual vibrations in flexible structures by convolving an Input Shaping sequence with a command profile. The two-mode sequences are installed on a four-axis robot used in the manufacture of silicon wafers — the Cassette Management System. The new sequences are found to significantly improve the performance of the system. In standard throughput tests, speed increases of 15%–25% were obtained on each axis while vibrations were simultaneously reduced by 20%–90%.
On the Surface Geometry of Variable Pitch Cylindrical Cams With Hyperboloidical Meshing Elements
Authors: Kang Yaw-Hong , Wu Feng-Chi , Cheng Hong-Yih , Yan Hong-Sen
Published: March 2021

The hyperpoloid of revolution is a kind of skew surface that has engineering applications. Based on differential geometry, theory of gearing, and coordinate transformation, this paper derive mathematical equations of the geometric profiles of a double threaded variable pitch cylindrical cams with four hyperboloidical meshing elements. And based on the developed surface equations, we develope a computer program for solid modeling to simulate the surface geometry. Two examples are given to prove the derived equations.
Dynamics of Mechanical Systems Solved by Quadratic Programming
Authors: Wang Deshi , Chen Xin , Chen Xindu , Yu Jun , Zhou Ji
Published: March 2021

A new method for dynamics of mechanical systems has been established and the new use of the optimum software has been shown in this paper. Gauss’ principle in the theory of mechanics has been employed to transform the dynamical control and simulation into the quadratic programming problems, which makes it possible that the optimum software developed in CAD systems is applied to obtain the dynamics of mechanical systems. Such a method is significant for systems which contain complex motion and constraints, since there is no longer necessity of reducing the analytical dynamic models, which are tedious and even impossible to obtain. Morever, it gives a new way of applying the optimum software package. The dynamics of a robot with sliding and revolving joints has been demonstrated in detail.
Flow Rate Regularity in Rotary Trochoidal-Lobe Pumps
Authors: Mimmi G. , Pennacchi P.
Published: March 2021

This paper analyses a particular type of rotary positive-displacement pumps with lobes having epitrochoidal flanks, whose distinctive feature is that of providing a strictly constant geometric instantaneous flow rate. The pump design is analysed from geometric and kinematical points of view. Then the behavior of this type of lobe pump is compared with that of involute gear pumps.
Dynamic Analysis of Mechanical Systems With Elastic Telescopic Members
Authors: Al-Bedoor B. O. , Khulief Y. A.
Published: March 2021

A dynamic model for the vibrational motion of an elastic beam-like telescopic member is presented. In addition to translation, the elastic member is allowed to execute large reference rotation. The Lagrangian approach in conjunction with the assumed modes technique are employed in deriving the equations of motion. The developed model accounts for all the dynamic coupling terms, as well as the stiffening effect due to the beam reference rotation. The tip mass dynamics is included together with the associated dynamic coupling between the modal degrees of freedom. In addition, the devised dynamic model takes into account the gravitational effects, thus permitting motions in either vertical or horizontal planes. Numerical simulation of a mechanical system with an elastic telescopic member is presented.
Application of Threshold Logic to the Design and Analysis of Latching Systems in Deployers of Deployable-Retractable Structures
Authors: Chew M. , Ho M. T.
Published: March 2021

To erect deployable structures from a compact folded state, a supplemental mechanism called a deployer is used. Many latches are present in the deployer and these are coordinated in some logical and systematic manner to bring about the deployment. This article presents an investigation into analyzing the logic behavior of a deployer and design such latching systems in deployers in a more systematic manner; the logic functions used are based on modifications of the Mechanical Threshold Logic approach.
Dynamic Response to Mass Reduction in Flexible Mechanisms
Authors: Yu Yue-Qing , Smith M. R.
Published: March 2021

A new investigation into the kineto-elastodynamic (KED) behaviour of flexible mechanisms is presented. The characteristic response of inertia forces, such as the shaking force and moment, input torque and bearing reaction, in addition to dynamic stress and energy are studied as the mass of a planar four-bar linkage is reduced.