bluuebunny/crossref_metadata_2025 huggingface dataset:
Preemptive Strikes: Women Strike for Peace, Antinuclear Pacifism, and the Movement for a Biological Democracy, 1961–1963
Authors: Ross Andrew J.
Published: April 2021

This article examines the social, political, and environmental features of the Women Strike for Peace (WSP) movement from its inception in 1961 to the passage of the Partial Test Ban Treaty (PTBT) in 1963. I offer the analytical framework of “biological democracy” as a conceptual bridge between environmental and sociopolitical approaches to WSP. The movement’s gendered critiques of US foreign policymaking, its organizational structure, and its participation in the production and distribution of scientific knowledge demonstrate how progressive women used maternalist discourse to oppose US Cold War policies in the early‐1960s. WSP participants leveraged their social proximity to the biological condition of the family as “givers and guardians” of life to dissent against the nuclear arms race, heighten female voices within Cold War geopolitics, and increase public awareness of the hazards of radioactive fallout caused by ongoing atmospheric nuclear weapons testing. By coopting conventions of maternalism and domesticity as justification for their cause, WSP women effectively mollified patriarchal and anti‐communist attacks as they organized against Cold War militarism and nuclear irradiation. In so doing, they offered a vision of US democracy that responded to individualized, feminine activism and prioritized public health over nuclear armament.
The Systemic Affect of Culture, Power, and Terror in the Southern Public Space
Authors: Evans Jocelyn J. , Gåddie Keith
Published: April 2021

Objective

We explore how political space is disrupted by racialized politics, and how differentiated affect among racial groups emerge in the political space.

Method

We use Goodsell's architectural classifications of public space in conjunction with systems theory to ascertain how differing architectural affects of pride and heritage versus terror and oppression are experienced in the post‐bellum South. Historic data of lynchings and Klan activity are accompanied by examination of individual narratives and multiple qualitative case analysis of architectural elements of courthouse squares, courthouses, and courtrooms to illustrate racial affect and social meaning in the built environment of the Jim Crow era.

Results

Hyperlocalism in southern government and racial violence and also symbolism and the elements of courthouse design reinforce white supremacy.

Conclusions

Individual and collective memory are influenced by the reinforcement of a racial order through systematic design, architectural design, and symbols. To understand community memory requires a more granular and contextual examination to understand the role of the built environment in defining, parameterizing, and understanding systemic racism.
Strigolactone mimic 2‐nitrodebranone is highly active in Arabidopsis growth and development
Authors: Li Suhua , Li Yuwen , Chen Linhai , Zhang Chi , Wang Fei , Li Haiou , Wang Ming , Wang Yupei , Nan Fajun , Xie Daoxin , Yan Jianbin
Published: April 2021

Strigolactones play crucial roles in regulating plant architecture and development, as endogenous hormones, and orchestrating symbiotic interactions with fungi and parasitic plants, as components of root exudates. rac‐GR24 is currently the most widely used strigolactone analog and serves as a reference compound in investigating the action of strigolactones. In this study, we evaluated a suite of debranones and found that 2‐nitrodebranone (2NOD) exhibited higher biological activity than rac‐GR24 in various aspects of plant growth and development in Arabidopsis, including hypocotyl elongation inhibition, root hair promotion and senescence acceleration. The enhanced activity of 2NOD in promoting AtD14–SMXL7 and AtD14–MAX2 interactions indicates that the molecular structure of 2NOD is a better match for the ligand perception site pocket of D14. Moreover, 2NOD showed lower activity than rac‐GR24 in promoting Orobanche cumana seed germination, suggesting its higher ability to control plant architecture than parasitic interactions. In combination with the improved stability of 2NOD, these results demonstrate that 2NOD is a strigolactone analog that can specifically mimic the activity of strigolactones and that 2NOD exhibits strong potential as a tool for studying the strigolactone signaling pathway in plants.
International trade and employment: Theory and evidence from Korean firms
Authors: Jha Priyaranjan , Lee Jae Yoon , Liang Yang , Mitra Devashish
Published: April 2021

We extend the small country trade model with firm heterogeneity (Demidova and Rodriguez‐Clare, Journal of International Economics, 90, 2013 and 266) to incorporate offshoring (along with final goods trade). We derive the firm‐level employment implications of output and input trade and trade costs and test them using Korean firm‐level data for the period 2006–2016. A key theoretical result is that the impact of a change in offshoring cost on employment depends crucially on the net substitutability between inputs where net substitutability is the difference between the elasticities of input substitution and output substitution. Empirically, we find that a decrease in the input trade cost reduces employment and the impact is stronger, the greater the net substitutability between inputs. Our 2SLS results with firm‐level imports (in place of trade costs) are consistent with our results with trade costs.
A Hybrid Computational System for Mechanical Engineering Design
Authors: Sahu K. , Grosse I. R.
Published: April 2021

In this paper we discuss a hybrid computational design tool, called CSN-Designer (Cognitive Symbolic Numeric), which is currently under development at the University of Massachusetts. The objectives of the system are two fold: to foster concurrency in the early stages of design, and to facilitate and automate as much as possible the design of mechanical components. To meet these goals, the system integrates human cognition, symbolic computation, and numerical simulations within a single computational environment. All three of these knowledge sources are exploited in pursuit of the design objective. The computational system is currently being tested in the domain of preliminary design of 3-D load-carrying injection molded parts. Several design examples in this domain are presented in this paper.
Automated Process Planning and Machining for Sculptured Surface Cavities
Authors: Lee Yuan-Shin , Chang Tien-Chien
Published: April 2021

Sculptured surfaces often appear in mechanical parts of various industrial products as external form or the functional surface and are commonly found in molds and dies. In this study a sculptured surface is defined by a Non-Uniform Rational B-spline (NURB) surface that provides the flexibility and freedom for surface description. The work proposed here includes the evaluation of machining information, decision for machining process sequence selection, automatic cutter selection, and cutter path generation. Machining information is first evaluated by using series of hunting planes, calculating the geometric shape and constraints of the machining cavity. A decision on the process sequence is made based on the evaluated machining information. The cutter size is automatically determined by considering geometric constraints, the maximum material removal rate in roughing process and the minimum cutter movement with the required accuracy in finishing process. The roughing process is done by some pocketing procedures that consider arbitrary shaped pockets with islands on the cutting planes. Cutter movement and cutter selection are optimized by considering machining conditions on adjacent cutting planes. An integrated system called CASCAM has been developed to prove the feasibility of the proposed approach.
Solid Modeling of Subsea Telerobotic Manipulators Using Superquadrics for High Fidelity Simulation
Authors: Agba Emmanuel I. , Wong Tin-Lup , Huang Ming Z. , Clark Andrew M.
Published: April 2021

In this paper, we describe how manipulator arms with end-effectors and payloads, if any, can be modeled using superellipsoids. Superellipsoids are very flexible convex solids. They are easy to manipulate by mathematical transformations and also possess a well defined inside-outside function, which to a great extent facilitates simulation of object interactions. A systematic way of determining transformation matrices between manipulator links, which are described as superquadric links, is presented. We also present how object detection and collision avoidance can be achieved. This technique has been implemented in a hybrid telerobotic simulator for undersea operations. It has also proved to be efficient for simulation of pick-and-place operations.
A Combined Knowledge-Based and Finite Element Approach to Forging Die Design
Authors: Haque Imtiaz , Dabke P. D. , Rowe Chesley , Jackson John
Published: April 2021

This paper presents the use of a knowledge-based system to provide the link between computer-aided rule-of-thumb procedures and a finite element simulation package for the design of forging dies. The knowledge-based system automates the mesh generation and regeneration procedure that is traditionally the most cumbersome aspect of such a process. The system is programmed in Prolog, C, and Fortran. It is based on parametric mapping approach and generates 2-D quadrilateral meshes. Results are presented to show its effectiveness in reducing the effort and skill required for conducting forging simulations.
Breathing Life Into Computer Aided Drafting
Authors: Serrano David
Published: April 2021

Mechanical design concepts evolve from rough sketches at the preliminary design stages to full working drawings at the detail design stage. Traditional computer aided drafting systems allow designers to document and detail a design once it has been completed. These systems allow very little flexibility in the geometric modification of these drawings when design revisions are required. A large quantity of design information is stored in paper drawings and/or formats compatible with traditional CAD systems. Constraint based modelers, on the other hand, allow the designer to generate the shape (topology) of a component without defining the dimensions. In order to perform any modifications to the geometry the geometric entities (points, lines, etc.) must be constrained via dimensions. Parametric Modelers and Variational Geometry Systems, are examples of such technology. In these systems the components must be correctly dimensioned by the designer before the geometry can be manipulated. Dimensioning schemes are not unique and selecting a consistent dimensional scheme is a non-trivial, error prone task for any geometric component of reasonable complexity. Computational tools that bridge the gap between traditional CAD tools and constraint based systems will be extremely valuable to the designer, not only as a means to completely dimension an undimensioned component or partially dimensioned design but to access existing CAD data for manipulation and parametrization. The paper describes a constraint management approach to the automatic generation of consistent dimensioning schemes.
A Feature Extraction Interface for CAD Part Models
Authors: Nitschke David R. , Chen Yuh-Min , Miller R. Allen
Published: April 2021

The concept of “Features” has been recognized as a neutral form of communication between design and manufacturing. Since virtually all CAD systems define part models using B-Rep or CSG formats, a facility is needed to convert geometry based part models to ones which are feature based. This paper outlines the framework of a facility which would enable part models from any type of CAD system to be converted to a format which could be analyzed using a knowledge based design system. This facility relies on the user to recognize and isolate the individual features of the model and then extracts the dimensions, locations and relative positioning of the features within the model. These features are then organized into a feature graph for the construction of a feature based part representation. The procedures for the construction of this part representation include feature instantiation, feature placement and functional specification.
On Design Interfaces in Mechanical Engineering Design
Authors: Bjärnemo Robert , Burman Ake
Published: April 2021

In this paper a concept is presented for identifying and handling interface problems. An interface problem is at hand when the input/output relation between compatible subsystems miss-matches. By utilizing a product modeling concept based on the existence of an object-oriented product structure, two types of interface problems are identified and elaborated.
Structural Analysis, Design, and Optimization With High-Order Finite Elements
Authors: King R. , Katsis C. , Balch C. , Filip D.
Published: April 2021

This paper discusses an approach to structural analysis, design, and optimization that is intended for use by mechanical design engineers who need not be specialists in analysis. The approach uses p-type (high-order polynomial) finite elements combined with a procedural geometry representation that is capable of accurately modeling a wide variety of geometric shapes. Only a few elements are needed to accurately model both the geometry of complex parts and the deformations they undergo. Adaptive analyis can readily be performed, and because of the shape-insensitivity of the elements, general shape design sensitivity and optimization studies are possible.

Examples are presented which illustrate these, which have been implemented in the commercial software package Applied Structure.
A CAD System for Designers’ Decision Making: An Approach With 2D and 3D Integrated and Hierarchical Assembly Models
Authors: Minami S. , Ishida T. , Yamamoto S. , Tomita K. , Odamura M.
Published: April 2021

A concept for the initial stage of the mechanical design and its implementation in the computer-aided design (CAD) are presented. The process of decision making in design is: (1) determining an outline of the whole assembly using a 2-dimensional model that is easy to operate; (2) checking the outline using a 3-dimensional model in which it is easy to identify the spatial relationships; (3) determining details of its sub-assemblies or their components using the 2-dimensional model; and (4) checking the details using the 3-dimensional model. The CAD system must provide consistent relationships through all the steps. For that, following functions are implemented in our prototype system: (1) a 2D and 3D integrated model for consistency between 2- and 3-dimensional shapes, (2) a hierarchical assembly model with dimensional constraints for consistency within an assembly and their components, and (3) a check on constraints for consistency between shapes and designers’ intentions. As a result, the system can provide an environment well fitted to the designers’ decision making process.
Prediction and Flow Visualization of Air Flow in Clean Environments
Authors: Busnaina Ahmed A. , Ljungqvist Bengt
Published: April 2021

A Study of airflow and particle transport in two types of clean room is presented. The study investigates the flowfield and contaminant particle transport in mixed flow and Vertical Laminar Flow (VLF) cleanrooms. The study consisted of modeling and evaluating the effect of using perforated or raised floors in combination with clean hoods. The considered air velocities in the room were 20, 30 and 50 feet/min. Contaminant particle sizes considered were 0.5 and 5 microns. The particles were injected at six different locations in the room. A simulation of a mixed flow clean room with side return (without raised floors) is also enclosed for comparison. Artistic impressions of flow visualization of the flow is also presented for comparison.
Full Beam Formulation for Coupled Elastic and Rigid Body Motion
Authors: Venkatakrishnan C. , Fallahi B. , Lai H. Y.
Published: April 2021

The need for higher operating speeds has led to the study of flexibility in mechanisms. In most of the previous works, rotary inertia, normal, tangential and coriolis terms are neglected. These assumptions are valid at lower speeds and for slender links. In this paper, a procedure to include all inertia terms in a local moving coordinate system is introduced. It is shown that the inertia terms lead to the introduction of three element matrices in the finite element formulation. The proposed approach is used to model the rotating beam problem. The results of a numerical solution is reported and validated.
A Collision Check Program for the IBM Sedab Two-Arm Robot
Authors: Eppinger Mike , Derby Stephen
Published: April 2021

This paper proposes an algorithm to check for collision between the two arms of the IBM SEDAB robot The collision check is based on static interference checks at discrete points along the selected trajectory. The points are equidistant and chosen such that the motion of all joints involved does not exceed given limits. The robot arms are modeled by a series of boxes, with each box representing a link. A collision check is performed by testing critical pairs of boxes for interference. The box - box interference tests involve excessive computation and are therefore time consuming. To reduce the number of necessary box interference tests, a quick test based on a rough model of the arms is used to determine the critical box pairs. This model consists of a series of spheres with one or two spheres circumscribing a box completely. Tools or parts fixed to the grippers can be included into the collision check.
Functionality in Surface Design
Authors: Lowe T. W. , Bloor M. I. G. , Wilson M. J.
Published: April 2021

The partial differential equation (PDE) method is used to generate surfaces which can be completely described using few parameters all of which have a global influence on the surface shape. We show how this method is suitable for the design of surfaces which optimize some property of the surface subject to certain given design restrictions. This is illustrated by considering two examples: the design of a yacht and the reduction of stress in a loaded blend.
Dynamic Collision Detection Using Space Partitioning
Authors: Ganter M. A. , Isarankura B. P.
Published: April 2021

A technique termed space partitioning is employed which dramatically reduces the computation time required to detect dynamic collision during computer simulation. The simulated environment is composed of two nonconvex polyhedra traversing two general six degree of freedom trajectories. This space partitioning technique reduces collision detection time by subdividing the space containing a given object into a set of linear partitions. Using these partitions, all testing can be confined to the local region of overlap between the two objects. Further, all entities contained in the partitions inside the region of overlap are ordered based on their respective minimums and maximums to further reduce testing. Experimental results indicate a worst-case collision detection time for two one thousand faced objects is approximately three seconds per trajectory step.
Sensitivity Analysis With the Shape Optimization Program
Authors: Atrek Erdal
Published: April 2021

SHAPE is an industry oriented commercial finite element based computer program for the shape optimization of continuum structures. It employs sensitivity analysis extensively during optimization. A new option allows the user to create, access, and plot sensitivity information for any prescribed design that can be processed by SHAPE. This feature of the program is described herein, and is illustrated by means of numerical examples.
Dimensional Tolerance Allocation of Stochastic Dynamic Mechanical Systems Through Performance and Sensitivity Analysis
Authors: Lee S. J. , Gilmore B. J. , Ogot M. M.
Published: April 2021

Uncertainties due to random dimensional tolerances within stochastic dynamic mechanical systems lead to mechanical errors and thus, performance degradation. Since design standards do not exist for these systems, analysis and design tools are needed to properly allocate tolerances. This paper presents probabilistic models and methods to allocate tolerances on the link lengths and radial clearances such that the system meets a probabilistic and time dependent performance criterion. The method includes a general procedure for sensitivity analysis, using the effective link length model and nominal equations of motion. Since the sensitivity analysis requires only the nominal equations of motion and statistical information as input, it is straight forward to implement. An optimal design problem is formulated to allocate random tolerances. Examples are presented to illustrate the approach and its generality. This paper provides a solution to the tolerance allocation problem for stochastic dynamically driven mechanical systems.
Engineering Design: A Perspective on U.K. and Swiss Developments
Authors: Eder W. Ernst
Published: April 2021

Historic developments, and the current state of the art are surveyed in thought, theory, methods and methodology, and education for and about engineering design. This survey covers two particular and disparate regions, the United Kingdom, and Switzerland, the latter including the activities of an international group centered in Zürich known as WDK — Workshop Design-Konstruktion.
Design-Science Interactions
Authors: Willem Raymond A.
Published: April 2021

Design and science interact in important ways for achieving both the goals of design (to create) and science (to know). Various forms of interactions are identified and discussed. It is concluded that due to the nature of science and design, these interactions are intinsic and vital to achieving the goals of both.
Design Science: Meta-Science to Engineering Design
Authors: Eder W. Ernst
Published: April 2021

Following on from a paper presented at a previous Design Automation Conference (Eder 1986), this paper outlines some of the more recent insights concerning engineering design that have been developed by a small international group. Some of the models of designing and technical systems have been improved. A morphology of knowledge about designing and technical systems has been proposed, and extended to a morphology of knowledge itself. Some consequences are drawn from these developments, and summarized in this paper.
Accelerated Testing for Reliability
Authors: Smith C. O.
Published: April 2021

The designer of a product must determine if the design objective of reliability and/or product life has been met. This is normally accomplished by testing prototypes or early production units. Because of the time required to test, it is not very realistic to test under normal operating conditions. Accelerated testing is highly desirable. This paper discusses (1) some testing methods for determining the most significant variables affecting performance and (2) some techniques for reducing the time required to estimate reliability or product life.
Comparison of Weibull Strength Parameters From Flexure and Spin Tests of Brittle Materials
Authors: Holland Frederic A. , Zaretsky Erwin V.
Published: April 2021

Fracture data from five series of four-point bend tests of beams and spin tests of flat annular disks were reanalyzed. Silicon nitride and graphite were the test materials. The experimental fracture strengths of the disks were compared with the predicted strengths based on both volume flaw and surface flaw analyses of four-point bend data. Volume flaw analysis resulted in a better correlation between disks and beams in three of the five test series than did surface flaw analysis. The Weibull slopes (moduli) and characteristic gage strengths for the disks and beams were also compared. Differences in the experimental Weibull slopes were not statistically significant. It was shown that results from the beam tests can predict the fracture strength of rotating disks.
A Criticism of an Undergraduate Design Curriculum
Authors: West Harry
Published: April 2021

The mechanical engineering design curriculum of one university (MIT) is outlined. The sophomore level Introduction to Design course and the senior level Design Projects course are described in more detail, and compared and criticized.

The challenge of design education is ascribed to two sources: (a) the reach of design development that is expected of the students, and (b) the difficulty of providing adequate feedback to the students. It is proposed that (i) the limitations on the science based undergraduate curriculum for providing a professional education in design be formally recognized, and that there be a clearer understanding of what a graduating engineer is expected to be capable of, and what is to be provided by graduate school and/or company based on-the-job training programs; (ii) that established principles of design be taught at appropriate stages in the undergraduate curriculum to the extent that they match the students’ design development and experience; and (iii) that undergraduate design courses incorporate projects in which students’ designs are manifested in hardware to provide an effective complement to the feedback provided by the faculty teaching the course.
Multivariate Yield Maximization Using CAD/CAE Models: Efficient Approximations Based on Mean and Variance
Authors: Barton Russell R. , Tsui Kwok-Leung
Published: April 2021

A product contributes to yield if all of its performance functions fall within their upper and/or lower limits. For example, a piston connecting rod may be required to provide rigidity along several axes. The actual connecting rod deflection will vary, depending on variations in the materials and forging conditions, but the deflection must remain less than an upper limit. Designing for maximum yield for multivariate performance limits is a difficult task. Direct optimization may require excessive computing resources. We discuss two efficient methods for yield improvement: ‘performance centering’ and a method based on Taguchi’s ‘parameter design’ philosophy. Both are shown to be motivated by the Chebychev inequality. It is important to remember that these are approximate methods. An example shows that they may produce sub-optimal yield, even when the random components of the performance functions are independent and identically distributed.
A Methodology for Conversions of Feature-Based Representations
Authors: Rosen David W. , Dixon John R. , Dong Xin
Published: April 2021

Computer integrated manufacturing practices require the sharing of product information between functions, which is the larger context for the work presented in this paper. We are addressing the problem of converting from one feature-based representation to another, where the second representation is for a different application than the first. In particular, we are focusing on converting a design-with representation of a component into representations suitable for manufacturability evaluations. We offer a methodology for describing conversions as a three-step process: filtering information, such as features and geometry, out of the primary representation, selecting those entities that satisfy conditions appropriate to the secondary viewpoint, and aggregating entities into secondary viewpoint features. This methodology is applied to the conversion of a component from the design viewpoint to the injection molding viewpoint for the purposes of tooling cost evaluation. Results from the injection molding conversion, and several others under development, show that our methodology supports conversions at early design stages and suggests broad applicability.
Conceptual Design of Mechanical Systems
Authors: Welch Richard V. , Dixon John R.
Published: April 2021

This paper presents a method for generating solutions to a class of conceptual design problems. We define conceptual design as the transformation of functional requirements to abstract physical systems in two stages: 1) phenomenological design — transforming a functional requirement to a behavior description by using physical principles; and 2) embodiment design — transforming the behavior specification to a physical embodiment that exhibit the required behavior. In order to reason about the behavior of in-progress designs, a new representation called behavior graphs has been defined. Behavior graphs are similar to bond graphs but have been developed as a design tool. (Bond graphs were developed as an analysis tool.) In order to guide the design process, the iterative redesign model of design is used at both the phenomenological and embodiment levels. The behavior graph representation and iterative redesign model constitute the conceptual design method presented here. A experimental computer program implementing this method is discussed and illustrative examples presented.
A Knowledge Base Data Representation for Collaborative Mechanical Design
Authors: Nagy Richard L. , Ullman David G. , Dietterich Thomas G.
Published: April 2021

Collaborative design projects place additional burdens on current design documentation practices. The literature on group design has repeatedly documented the existence of problems in design decision making due to the unavailability of design information. This paper describes a data representation developed for collaborative mechanical design information. The data representation is used to record the history of the design as a sequence of design decisions. The resulting knowledge base records the final specifications, the alternatives which were considered during the design process, and the designers’ rationale for choosing the final design parameters. It is currently used in a computerized knowledge base system under development by the Design Process Research Group (DPRG), at the authors’ institution (OSU).
Solving Parametric Design Problems Requiring Configuration Choices
Authors: Ramaswamy Rajan , Ulrich Karl T. , Kishi Norimasa , Tomikashi Minoru
Published: April 2021

Many design tasks involve selection from a set of configurations followed by parametric optimization of the chosen configuration. The models used for these tasks tend to be large, non-linear and involve both discrete and continuous variables. It is rarely possible to use any single formal algorithm to solve these problems and as a result there are few tools to help designers solve such problems. We believe computer environments that allow flexible access to a varied set of tools will help designers rapidly generate high quality solutions. We demonstrate our arguments on a design problem taken from a commercial auto manufacturer, propose a framework for dealing with the general class of problems and describe an implementation of a novel design system that integrates math programming, knowledge-based and graph theoretic tools.
Methods for Analyzing Design Procedures
Authors: Gebala David A. , Eppinger Steven D.
Published: April 2021

This paper surveys several common models which can be used to represent and study design procedures. A matrix representation of design is discussed in detail and both new and existing analysis tools are presented. Enhanced models are proposed to incorporate more information into the matrix representation and to allow more sophisticated analysis to be performed. The paper describes a testbed for the development and testing of algorithmic analysis tools and concludes with suggestions for further research into improving the design process.
A Robust Optimization Approach Using Taguchi’s Loss Function for Solving Nonlinear Optimization Problems
Authors: Ramakrishnan Balaji , Rao S. S.
Published: April 2021

The application of the concept of robust design, based on Taguchi’s loss function, in formulating and solving nonlinear optimization problems is investigated. The effectiveness of the approach is illustrated with two examples. The first example is a machining parameter optimization problem wherein the production cost, tool life and production rate are optimized with limitations on machining characteristics such as cutting power, cutting tool temperature and surface finish. The second example is a welded beam design problem where the dimensions of the weldment and the beam are found without exceeding the limitations stated on the shear stress in the weld, normal stress in the beam, buckling load on the beam and tip deflection of the beam. The results are highlighted by comparing the solutions of the robust formulation with those obtained from the conventional formulation. The methodology presented in this work is expected to be useful in the design of products and processes which are least sensitive to the noises and which reflect in higher quality.
Geometric Reasoning Based on Graph Grammar Parsing
Authors: Fu Zhuo , de Pennington Alan
Published: April 2021

It has been recognized that future intelligent design support environments need to be able to reason about the geometry of products and to evaluate product functionality and performance against given constraints. A first step towards this goal is to provide a more robust information model which directly relates to design functionality or manufacturing characteristics, on which reasoning can be carried out. This has motivated research on feature-based modelling and reasoning. In this paper, an approach is presented to geometric reasoning based on graph grammar parsing. Our work combines methodologies from both design by features and feature recognition. A graph grammar is used to represent and manipulate features and geometric constraints. Geometric constraints are used within symbolic definitions of features and also to define relative position and orientation of features. The graph grammar parsing is incorporated with knowledge-based techniques to derive feature information and propagate constraints. This approach can be used to the transformation of feature information and to deal with feature interaction.
Analysis of 3-D Elastic Contact Stresses for the Cylinder Head of an Internal Combustion Engine: An Improved Mixed Finite Element Method
Authors: Li Ming-Zhang , Jun Yu , Huang Yu-Ying , Zha Jian-Zhong
Published: April 2021

In this paper, an improved mixed finite element method (FEM) for analysing elastic contact stresses is presented. Since the corresponding softness matrix symmetrized, the main advantage is that not only is the computation efficiency is improved, but also the data storage is reduced in comparison with the usual mixed FEM. A set of computation formulas of FEM for 3-D elastic contact problems with friction is established and realized on digit computers. A numerical example compared with the results obtained by ADINA shows that the present approach is very efficient and reliable.
Dynamic Analysis of a Turbocharger Centrifugal Compressor Impeller
Authors: Ramamurti V. , Subramani D. A. , Sridhara K.
Published: April 2021

Stress analysis and determination of eigen pairs of a typical turbocharger compressor impeller have been carried out using the concept of cyclic symmetry. A simplified model treating the blade and the hub as isolated elements has also been attempted. The limitations of the simplified model have been brought out. The results of the finite element model using the cyclic symmetric approach have been discussed.
An Approach to Dynamic Distance Calculations for Obstacle Avoidance Problems
Authors: Liu C. Y. , Chen W. R. , Mayne R. W.
Published: April 2021

This paper presents a distance calculation method which can be used in machine motion planning optimizations where interference is a concern. Dynamic distance calculations are discussed which use the quadratic programming method combined with an approximate swept volume approach. Distance-to-contact calculations can be obtained for both interference and non-interference situations. The swept volume of a moving polygon is constructed through a series of overlapped swept volume segments. Each of the swept volume segments is efficiently developed by checking the inner products of polygon outward boundary normals with velocity vectors for polygon vertices. Two dimensional examples of distance-to-contact computations and robot path planning problems are presented for a sample three link robot with three rotational joints.
Design Considerations for Vibration Assisted Compliant Assembly
Authors: Liu Y. , Leu Ming C.
Published: April 2021

This paper presents design considerations for vibration assisted compliant assembly involving peg-in-hole insertion. We propose a feasible parts mating assembly model, based on the positional uncertainty and tolerance of an assembly task. For an infeasible task, whose tolerance set does not contain the uncertainty set, it is proposed to introduce a relative motion between the two mating parts, so as to enlarge the task tolerance relative to its uncertainty. A specific type of such motion, viz vibration in two orthogonal directions, is studied in detail. The amplitudes and frequencies of vibrations are determined for given tolerance, uncertainty, and other assembly parameters. A numerical procedure is devised to select the ratio of the two orthogonal vibration frequencies, for minimum search time of parts engagement. Criteria on suitable compliances for assembly are proposed, with consideration of insertion failure.
Noise Reduction of Engine Component Covers Using the Finite Element Method
Authors: Sivakumar Jayaraman , Sung Shung H. , Nefske Donald J.
Published: April 2021

Radiated noise from an engine component cover is predicted by using a structural finite element model of the cover to predict its forced vibration response, and then by using the Rayleigh integral method to predict its radiated noise. Applications to evaluate the radiated noise from an engine rocker cover and an engine front cover are presented. Measurements of the radiated noise from actual covers installed on a running engine show the predicted noise reduction due to structural modifications is achieved.
A Singular Perturbation Analysis of Eigenvalue Veering and Mode Localization in Perturbed Linear Chain and Cyclic Systems
Authors: Happawana G. S. , Bajaj A. K. , Nwokah O. D. I.
Published: April 2021

An investigation into the eigenvalue loci veering and mode localization phenomenon is presented for mistuned structural systems. Examples from both, the weakly coupled uniaxial component systems and the cyclic symmetric systems, are considered. The analysis is based on singular perturbation techniques. It is shown that uniform asymptotic expansions for the eigenvalues and eigenvectors can be constructed in terms of the mistuning parameters, and these solutions are in excellent agreement with the exact solutions. The asymptotic expansions are then used to clearly show how the singular behavior in the eigenfunctions or modeshapes leads to mode localization.
Analysis of Dynamic Systems With Periodically Varying Parameters via Chebyshev Polynomials
Authors: Sinha S. C. , Wu Der-Ho , Juneja Vikas , Joseph Paul
Published: April 2021

In this paper a general method for the analysis of multidimensional second-order dynamic systems with periodically varying parameters is presented. The state vector and the periodic matrices appearing in the equations are expanded in Chebyshev polynomials over the principal period and the original differential problem is reduced to a set of linear algebraic equations. The technique is suitable for constructing either numerical or approximate analytical solutions. As an illustrative example, approximate analytical expressions for the Floquet characteristic exponents of Mathieu’s equation are obtained. Stability charts are drawn to compare the results the proposed method with those obtained by Runge-Kutta and perturbation methods. Numerical solutions for the flap-lag motion of a three blade helicopter rotor are constructed in the next example. The numerical accuracy and efficiency of the proposed technique is compared with standard numerical codes based on Runge-Kutta, Adams-Moulton and Gear algorithms. The results obtained in the both examples indicate that the suggested approach extremely accurate and is by far the most efficient one.
Analytical and Experimental Simulation of Loose Pedestal Dynamic Effects on a Rotating Machine Vibrational Response
Authors: Goldman Pavel , Muszynska Agnes
Published: April 2021

This report presents experimental, analytical, and numerical results describing vibrational phenomena in a rotating machine with one loose pedestal. The loose-pedestal machine rotor vibrations represent unbalance-related excited vibrations of synchronous and fractional subsynchronous regimes. In this study the loose-pedestal machine is first simulated by a simple vibrating beam excited by a shaker mounted on it. The shaker simulates an unbalanced machine rotor. The beam occasionally enters in contact with the foundation. The excited vibrations are modified by impacting occurrences, and by periodic changes in system stiffness. A new model of the impact has been developed. The results of analytical and experimental studies stand in a good agreement. They illustrate the existence of the synchronous regime and several subsynchronous fractional regimes in various excitation frequency ranges. The analysis adequately predicts the occurrence of these regimes and determines the physical parameters affecting them. The analytical and experimental results are then compared with the responses of experimental rotor rig with one bearing pedestal looseness. They show the same qualitative pattern.
Active Vibration Control of Flexible Rotor Using H∞ Control Theory
Authors: Nonami K. , Wang J. W. , Sampei M. , Mita T.
Published: April 2021

This paper investigates about H∞ control for a flexible rotor model and suppression of spillover phenomena caused by modelling of reduced order. A H∞ control system is designed such that unmodelled vibration modes in a high frequency range are not excited, i.e., a spillover phenomena are not caused to happen. Simulation results are presented to demonstrate the control effects. Since the H∞ control problem in this paper reduces to a special case in the standard H∞ control problem, a new method is employed to solve it.
Accurate Free Vibration Analysis for Rotating Shaft
Authors: Yang Bo Suk , Pilkey Walter D.
Published: April 2021

This paper presents an approach for the derivation of dynamic mass, gyroscopic and stiffness matrices for rotor dynamics analyses. The axial, torsional and bending dynamic stiffness matrices are deduced from transfer matrices, and, in turn, the frequency-dependent element matrices are derived. The relationships between the dynamic stiffness matrix and the frequency-dependent element matrices are defined. Numerical examples show that this method gives more accurate results than those obtained using the conventional static shape function based element matrices.
The Rocketdyne Multifunction Tester: Operation of a Radial Magnetic Bearing As an Excitation Source
Authors: Hawkins L. A. , Murphy B. T. , Lang K. W.
Published: April 2021

The operation of the magnetic bearing used as an excitation source in the Rocketdyne Multifunction Tester is described. The tester began operation during the summer of 1990. The magnetic bearing can be used in two control modes: 1) open loop mode, in which the magnetic bearing operates as a force actuator, and 2) closed loop mode, in which the magnetic bearing provides shaft support. Either control mode can be used to excite the shaft; however, response of the shaft in the two control modes is different due to the alteration of the eigenvalues by closed loop mode operation. A rotordynamic model is developed to predict the frequency response of the tester due to excitation in either control mode. Closed loop mode excitation is shown to be similar to the excitation produced by a rotating eccentricity in a conventional bearing. Predicted frequency response of the tester in the two control modes is compared, and the maximum response is shown to be the same for the two control modes when synchronous unbalance loading is not considered. The analysis shows that the response of this tester is adequate for the extraction of rotordynamic stiffness, damping, and inertia coefficients over a wide range of test article stiffnesses.
Estimation of Response and Loss Factor of Damped Sandwich Beam
Authors: Markuš Š. , Nánási T.
Published: April 2021

Classical governing equations of a three-layered sandwich beam are generalized with the aim to avoid the necessity of identical arrangement of both face layers at the end of the beam. In this way more shear deformations in the core are allowed for. This may significantly contribute to the increased dissipation of vibratory energy. Estimation of the response of the damped sandwich beam and the loss factor are based on truncated integral modal transformation in which the base functions are the modal data from the associated undamped system. Simple formula expressing the modal loss factor in terms of the portion of strain energy due to shear deformations in the core is developed. Presented approach is in fact a reinterpretation of the concept of damped normal modes in such a way that numerical computations are to be carried out only in the real domain while the previous formulation required numerical treatment in the complex domain.
Characteristic Study of Torsional Vibration on a Full Size Turbine-Generator Unit
Authors: Xiuzhu Huang , Xueyan Zhang , Daixia Sun , Qing Gong
Published: April 2021

Taking a 200MW turbine-generator unit and its connected transsmision network as a study object, torsional vibration characteristics of the shaft system caused by faulty synchronization, different disturbances in the network and switch operation were analysed and calculated. The effect of intensive excitation and “fast valve closing” on the torsional response is also discussed. It is concluded that large mechanical torque of shaft system would be encountered if there is a 3-phase fault in the network, and the shaft torque would be reduced to a certain extent by giving the “fast valve closing” if the network experience a fault.
Vibrations of Spinning Rings With Radial and Circumferential Displacement Constraints
Authors: Huang Shyh-Chin , Su Chen-Kai
Published: April 2021

The frequencies and mode shapes of rolling rings with radial and circumferential displacement constraints are investigated. The displacement constraints practically come from the point contact, e.g., rolling tire on the road, or other applications. The proposed approach to analysis is calculating the natural frequencies and modes of a non-contacted spinning ring, then employing the receptance method for displacement constraints. The frequency equation for the constrained system is hence obtained, and it can be solved numerically or graphically. The receptance matrix developed for the spinning ring is surprisingly found not symmetric as usual. Moreover, the cross receptances are discovered to form complex conjugate pairs. That is a feature that has never been described in literature. The results show that the natural frequencies for the spinning ring in contact, as expected, higher than those for the non-contacted ring. The variance of frequencies to rotational speeds are then illustrated. The analytic forms of mode shapes are also derived and sketched. The traveling modes are then shown for cases.
Dynamics of Flexible Beams and Plates Under Large Overall Motions
Authors: Boutaghou Z.-E. , Erdman A. G. , Stolarski H. K.
Published: April 2021

The dynamic response of flexible beams, plates, and solids undergoing arbitrary spatial motions are systematically derived via a unified approach. This formulation is capable of incorporating arbitrary representation of the kinematics of deformation, phenomenon of dynamic stiffening, and complete nonlinear interaction between elastic- and rigid-body dynamics encountered in constrained multi-body systems. It is shown that the present theory captures the phenomenon of dynamic stiffening due to the transfer of the axial and membrane forces to the bending equations of beams and plates, respectively. Examples are presented to illustrate the proposed formulations.