bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Design of the Path of Chain Link Systems
Authors: Peng J.-P. , Carpino M.
Published: April 2021

A general method for the design of the optimal chain path for a chain link system is presented. The dynamics of a chain link system are affected by both the kinematic effects of finite sized links and dynamic effects. Both of these effects have been incorporated into a dynamic model for arbitrary chain paths. This model is then used to determine chain paths which have been optimized for minimum position error and speed variation. Results of the dynamic analysis are presented for both low speed and high speed operations. An example of an optimized chain path for an oval configuration operating at low speed is also presented.
A Recursive Dynamic Formulation for Flexible Mechanisms
Authors: Souh Byung Yil , Kim S. S.
Published: April 2021

This paper presents a recursive dynamic formulation for modeling and simulation of spatial mechanisms with elastic beams. In order to circumvent some difficulties in the convential assumed mode approach, each flexible link is modeled with finite elements. The motion of the flexible link comprises the rigid body motion and elastic deformation. The elastic deformations are represented by nodal coordinates relative to the moving coordinate system fixed to the link. Recursive kinematic relationships are derived between finite beam elements. Using variational equations of motion for the one beam element and recursive relationships, the equations of motion for the open-chain flexible bodies are derived in terms of relative joint and nodal coordinates. For closed-loop systems, Lagrange multipliers are used to generate the equations of motion with kinematic constraints. The proposed method models geometric nonlinear effects and axial tensioning effects automatically. Also, the difficulties of the mode selection in the assumed mode approach is avoided. Numerical examples illustrate the effectiveness of this approach.
Efficient Dynamic Computer Simulation of Simple-Closed Spatial Linkages
Authors: Wang L. T.
Published: April 2021

A new method of formulating the generalized equations of motion for simple-closed (single loop) spatial linkages is presented in this paper. This method is based on the generalized principle of D’Alembert and the use of the transformation Jacobian matrices. The number of the differential equations of motion is minimized by performing the method of generalized coordinate partitioning in the joint space. Based on this formulation, a computational algorithm for computer simulation the dynamic motions of the linkage is developed, this algorithm is not only numerically stable but also fully exploits the efficient recursive computational schemes developed earlier for open kinematic chains. Two numerical examples are presented to demonstrate the stability and efficiency of the algorithm.
A Stress Based Methodology for the Design of Wire Rope Systems
Authors: Velinsky Steven A.
Published: April 2021

Wire ropes have been used extensively in a wide variety of applications for many years. However, detailed analysis capabilities for wire ropes have only been developed in the several years. Furthermore, these capabilities have not been exploited in the design of actual systems which are still designed in an empirical manner. This paper presents a stress based design methodology for wire rope systems based on these recent analysis capabilities. In addition to wire stress, this methodology allows multiple system properties to be considered during the design process. This is in opposition to current methods which only consider rope strength, and then size other components to match that particular rope. The optimum design problem is formulated for minimum weight design. Finally, examples illustrate the usefulness of the approach and its applicability to the improved design of real systems.
A Simplified Approach for Design Under Variable Amplitude Fatigue Loads
Authors: El-Sayed Mohamed E. M.
Published: April 2021

This paper presents an approach to simplify the design process for fatigue life requirement, when dealing with variable amplitude load history. The basic concept is to use the load history data and the material fatigue properties to calculate the fatigue life for different stress levels, using the contemporary fatigue life approach. The stress level and fatigue life data are then related by a simple power function and the constants of this function are calculated. The stress level for a required life, or the fatigue life at certain stress level, can be obtained using the power function in a way similar to the S-N curve. To demonstrate the approach some test cases using the SAE keyhole specimen fatigue data, for different load histories, are presented.
Critical Speeds of Geared Rotors by Including Mesh Stiffness and Using a Continuous System Model
Authors: Sener O. Sedat , Ozguven H. Nevzat
Published: April 2021

Dynamic analysis of high speed gearing for the computation of critical speeds and dynamic factors is a must in a proper design, while some other dynamic characteristics of the system such as dynamic transmission error are to be determined for more critical designs. Numerous different models have been suggested for the dynamic analysis of geared systems. These models differ both in the effects included and in the basic assumptions made. A continuous system model is used in this analysis in order to determine the torsional natural frequencies of a gear shaft system composed of two gears, two shafts and two inertias representing the drive and the load. Gear mesh is modelled as a spring connected between two gears. The natural frequencies of the same system are also calculated by using a four degree of freedom classical discrete model in which shaft masses are ignored. The percentage differences in the natural frequencies calculated with the discrete and continuous system models are determined for several values of some nondimensional system parameters. The results are presented in graphical form in terms of the nondimensional parameters defined. Some conclusions which may be important for designers are drawn.
A Variational Approach for Modeling Flexibility Effects in Manipulator Arms
Authors: Meghdari A.
Published: April 2021

This paper presents a general technique to model flexible components (mainly links and joints flexibilities are considered) of manipulator arms based on the Castigliano’s theorem of least work. The robotic arms flexibility properties are derived and represented by the matrix of compliance coefficients. Such expressions can be used to determine the errors due to the robotic tip deformations under the application of a set of applied loads at the tip in Cartesian space. Once these deformations are computed, they may be used to correct for the positional errors arisen from the robotic structural deformations in the motion control algorithms.
Syntax and Semantics of an Image Communications Language for Design Management
Authors: Willett Shirley
Published: April 2021

The apparel industry is currently in crisis because of the lack of communication between different points in the design to manufacturing process. For communications tools to be useful to design management in the industry as a whole, they must be based on a language that supports standardization of representation, linkage of production information and product requirements to product representation, use of basic building blocks to avoid repetitive effort, and incorporation of syntactical information to aid in understanding of the represented product. It is this language, rather than the CAD/CAM systems which it makes possible, which is our unique contribution to the computerization of the industry.
Organizing the Tasks in Complex Design Projects
Authors: Eppinger Steven D. , Whitney Daniel E. , Smith Robert P. , Gebala David A.
Published: April 2021

This research is aimed at organizing complex design projects in order to perform faster product development. We use a variation of Steward’s design structure matrix [Steward 1981a] to represent both the sequence of and the technical relationships among the many design tasks to be performed. These relationships define the “technical structure” of a design project. We will develop analytical techniques to find alternative sequences and definitions of the design tasks, offering opportunities to speed development progress by improved coordination and information transfer. Our algorithms will consider the technical structure of a project in order to identify which tasks should be resequenced and which tasks should be redefined or split into smaller sub-tasks to avoid development bottlenecks. We will develop these techniques into a strategy for design management which can significantly reduce the overall project complexity by reorganizing the few critical tasks. We expect that this research will benefit not only new design tasks that have never been structured before but also long-standing, often repeated design tasks that may have drifted into poor organizational patterns over many years.
A Recursive Model for Managing the Design Process
Authors: Ward Allen C.
Published: April 2021

This paper introduces a model of the design process which challenges some commonly stated assumptions about design. For example, it holds that design should be normally be recursive rather than iterative; that we design and reason about sets of artifacts, not an artifact; and that we should normally not design to meet specifications. The model integrates and provides perspective on a variety of design methodologies, including Taguchi methods and QFD. It allows formal treatment of some key issues; for example, formal conditions can be identified for the concurrent development of products and processes.
Constraint Reasoning in Concurrent Design
Authors: Rinderle James R. , Krishnan V.
Published: April 2021

One paradigm of concurrent design is based on the simultaneous consideration of a broad range of life-cycle constraints including those arising from function, manufacturing and maintenance. This simultaneous treatment of life-cycle issues results in a multitude of constraints, which not only increase the complexity of finding a design solution, but also make it difficult to understand the trends and interactions underlying the design. It is our goal to enhance the designer’s ability to identify and discriminate those constraints that critically impact the design from those that are irrelevant. We propose an interval analysis based approach, which is augmented with monotonicity and dominance principles. The approach helps in identifying regions of the design space where constraints possess certain desirable properties. It also enables reasoning with constraints in these regions. The regional inferences can then be reassembled to obtain global results. These ideas have been applied in the concurrent design of a fan blade, to identify the dominant, active and redundant constraints, enabling the designer to more clearly perceive and base his decisions on the critical design consideration. Furthermore, the identification of dominant constraints permits the easy evaluation of the significance of newly asserted constraints and frequently facilitates the automatic formulation of noniterative constraint satisfaction methods which guarantee a globally optimal design.
Improving Mechanical Design Decisions With Alternate Formulations of Constraints
Authors: Watton John D. , Rinderle James R.
Published: April 2021

Mechanical design equations which relate performance and functionality to design variables are often highly coupled, nonlinear parametric equations. The structure of these interacting equations can be simplified by a reformulation based on alternative design variables. For many design configurations the reformulation results in highly beneficial improvement in equation monotonicity and complexity. The benefits include convenience and expediency in quantitative evaluations in addition to enhanced physical insight. They facilitate such important design activities as computing satisfactory solutions, active constraint recognition for optimizations, and the decomposition of design decisions. The reformulations can be thought of as alternative views of the design configuration that provide abstractions that can promote design synthesis. In this paper we discuss and illustrate the nature of these benefits with a number of simple design examples.
A Method to Identify Reformulations of Mechanical Parametric Constraints to Enhance Design
Authors: Watton John D. , Rinderle James R.
Published: April 2021

The complexity of mechanical design is reflected in the complexity of the design equations which relate functional requirements to design parameters. Reformulations of the design equations can significantly reduce this complexity. This is accomplished by a transformation to alternative design parameters, such as a critical ratio, a nondimensional parameter, or a simple difference; e.g. the ratio of surface area to volume for heat transfer loss, the Reynold’s number in fluid mechanics, or the velocity difference across a fluid coupling. We have developed a method by which the alternative parameters are chosen for physical significance and for the ability to create a more direct correspondence to functional behavior as determined by measures of serial and block decomposability of the constraints. Rules have been developed for the creation of physically significant new parameters from the algebraic combination of the original parameters. The rules are based on engineering principles and rely on knowledge about what a parameter physically represents rather than other qualities such as dimensions. A computer based system, called EUDOXUS, has been developed to automate this procedure. The system operates on a set of design constraints to produce sets of transformed constraints in terms of alternative design parameters. The method and its implementation have demonstrated successful results for many highly nonlinear and highly coupled parameterized designs from many mechanical engineering domains.
Methods for Process Selection in Design
Authors: Ishii K. , Lee C. H. , Miller R. A.
Published: April 2021

This paper describes our proposed methodology for process selection that applies to the early stages of product design. We focus on net-shape manufacturing processes and identify the major factors that affect the selection of an appropriate process. The sequence at which designers typically make decisions depends largely on the nature of the product and the development environment. Thus, a versatile methodology should consider all the factors simultaneously in assessing the suitability of the candidate processes. The paper describes three types of knowledge that represent the compatibility of various processes to a given set of specifications: a) Case-based knowledge, i.e., templates of good, bad, and poor combination of decisions, b) Ordinal relationships among candidate processes based on interval analysis of cost, and c) Life-cycle cost estimate. Each type of knowledge gives an evaluation of suitability (compatibility) of candidate processes. Our future challenge lies in combining these measures at various stages of product development. Our initial studies on relationships between process selection and influencing factors lead to a HyperCard stack which stores information in an object-oriented fashion. This stack contains information which is the basis for our future computer-aid for process selection.
Feature Based Approach for Casting Design
Authors: Padhy Sisir K. , Sharan R. , Dwivedi S. N.
Published: April 2021

The conceptual stage design is very crucial in a design phase because maximum flexibility lies in this stage. The product can be changed or redesigned to achieve the optimum blend of quality and cost. The factors that influence the design include: shape complexity factor of the product, material, and processing parameters. In the casting design, the shape-complexity factor plays a vital role in deciding the location of the gates and risers and hence in feeding system design. Feature based design is adopted for the evaluation of the shape complexity factor. The implementation of this design approach is also discussed.
The Use of Function and Form When Reading Mechanical Engineering Drawings by Experts and Non-Experts
Authors: Chovan John D. , Waldron Manjula B.
Published: April 2021

Function to form information used in reasoning about mechanical engineering drawings based on experience in design was investigated. The verbal utterances of expert mechanical designers, quasi-experts (graduate students) and novices while reading 13 mechanical engineering line drawings were recorded and analyzed for function to form relationships. A discriminant analysis of descriptions of these drawings showed similarities and differences between the design features used by each group when reasoning about the drawings. The results of this analysis and their implications for the development of intelligent CAD systems are discussed.
Models of Visual Thinking by Novice Designers
Authors: Radcliffe David F. , Lee Tat Y.
Published: April 2021

Visual thinking is the creative process by which spatial, numerical and descriptive information is integrated to realize a design idea. A series of experiments have been conducted in which the role of freehand sketching in the design work of novice engineering designers and industrial designers was examined. Three types of sketches, functional, geometric and pictorial, can be identified, each related to the stage of concept development. An adequate sketching technique is essential for the smooth flow of design ideas during the formative stages of a design. Based upon these experimental observations, a model of the process of visual thinking is proposed. In it, sketching forms an interface and potential barrier between the cognitive processes and the physical domain. This barrier can be biased towards either the cognitive or the physical domain, resulting in two different types of impediment to idea development.
A Cognitive Approach to the Analysis of Design Processes
Authors: Takeda Hideaki , Hamada Susumu , Tomiyama Tetsuo , Yoshikawa Hiroyuki
Published: April 2021

The scientific analysis of design is indispensable in order to establish a rich and useful design theory. Accomplishing this, we propose a practical method to investigate design named design experiment and methods to analyze its results. Since the design experiment is performed mainly with the protocol analysis method, We start from discussing the experimental method in comparison to psychological experiments. Furthermore we introduce a new method using a CAD-like system which can record drawing processes precisely. We analyze the protocol data in two ways. One is the analysis by extraction of knowledge. Using this we can clarify how knowledge is used and what knowledge is needed in design processes. The other is based on the cognitive approach. Protocol data is transformed into the semantic network of concepts which is used as the network in the connectionist paradigm. We can identify what the designer pays attention to and how it is changing in design processes by regarding the activations of nodes as the intensity of the designer’s attention.
The Information Requests of Mechanical Design Engineers
Authors: Kuffner Tom A. , Ullman David G.
Published: April 2021

Design documentation does not typically include all of the information sought by mechanical design engineers. This paper reports on a study of practicing engineers making modifications to existing designs. Particular attention is paid to the design information required to answer questions about the design and to verify or refute conjectures about the design. A taxonomy of the questions asked by the designers in this study and the conjectures they formed is presented. It is proposed that an intelligent CAD system be developed to capture, structure, and re-play this information.
Design History Knowledge Representation and its Basic Computer Implementation
Authors: Chen Aihua , McGinnis Brian , Ullman David G. , Dietterich Thomas G.
Published: April 2021

This paper gives an introduction to the implementation of a Mechanical Design History. This history is a record of the constraints developed and decisions made in the evolution of a product from initial specification to final, detailed design. This history allows design, management, and manufacturing personnel to query not only the final drawings representing the design, but also the rationale behind each object in the design.
Learning to Be Skeptical in Engineering Design: A Backpropagation Search Algorithm
Authors: Kott Alexander
Published: April 2021

A human designer becomes skeptical about a particular design direction when his/her attempts to pursue that direction fail. Can we model this strategy in an automated problem solver? This paper describes BP* — an algorithm that attempts to model this strategy. BP* is a best-first algorithm with an A*-like heuristic evaluation function. To model the dynamic skepticism of a human designer, BP* uses the backpropagation mechanism. It dynamically penalizes the parent design state when its children fail to realize the “goodness” promised by the parent BP* is admissible in some probabilistic sense. We also discuss an application of the BP* algorithm, a system that automatically “invents” novel conceptual schemes for thermal systems.
Design Theory and Methodology in Eastern Europe
Authors: Arciszewski Tomasz
Published: April 2021

The paper provides a brief review of general tendencies and interesting developments in the area of engineering design theory and methodology in Eastern Europe. This review is limited to East Germany, Poland, and the Soviet Union. Particular attention was given to the design research environments in individual countries, and to developed design theories and methods in the context of these environments.
Functions, Structures, and Constraints in Conceptual Design
Authors: Kota Sridhar , Ward Allen C.
Published: April 2021

The authors discuss, from quite different perspectives, some commonly held intuitions about design. In particular, Kota presents a functional design methodology and argues that distinctions between functions, constraints, and structures are essential to well organized design processes, which he sees as involving a hierarchical process from conceptual to routine design. Ward disagrees.
Computer-Aided Generation of Function Block Diagrams in a Methodical Design Procedure
Authors: Hundal M. S. , Byrne J. F.
Published: April 2021

A method for generating function block diagrams with an interactive computer program using a functions data base is described. This step follows the generation of the requirements list, given in an earlier paper (Hundal and Byrne, 1989). The program prompts the user for system inputs and outputs, physical functions and their connectivity. Appropriate functions which may be used for realizing the function structure are suggested by the program. After the first function block diagram has been produced, variants can be generated by looking for alternatives for the chosen functions.
Design Relations
Authors: Rinderle James R. , Colburn Eric R.
Published: April 2021

During preliminary design, designers make critical design decisions based on their experiential knowledge of the characteristics of the components that comprise a system. In particular designers understand the inherent relationship between the form a device will take and the behavior it will exhibit and use this knowledge to estimate characteristics of components and thus evaluate a system. Knowledge of these design relations are gained with experience, but even an experienced designer may not understand the design relations for an unfamiliar device. It is therefore useful to obtain this information automatically and provide it directly to the designer to supplement experience.

In this paper we discuss the nature of design relations and show that these relations are inherent in the physics, shaped by the constraints, and dependent upon the context of the design. We describe a method for automatically identifying these relations from a constraint-based model of a device which is based on solving a sequence of constrained optimization problems.
“Knowledge Sifting” for Preliminary Design
Authors: Miller Victor Todd , Nevill Gale E.
Published: April 2021

This article describes the use of a new symbolic reasoning methodology, based on the use of matrix associative memories, in the domain of preliminary design. A candidate preliminary design is first formulated in terms of a symbolic constraint system. The symbolic reasoner can then derive information about free variables based on the constraints in the system. One of the major difficulties with current reasoning methodologies in artificial intelligence is the scalability problem; as a problem increases in size, interactions between the elements hinder the reasoning process. Initial investigation indicates that this new symbolic reasoning system provides a means to avoid some of the complications that AI search and logic techniques have when scaling up to real world problems. Also, the methodology appears applicable to both analysis and direct synthesis tasks.
Automated Modeling to Support Design
Authors: Rinderle James R. , Balasubramaniam L.
Published: April 2021

The need to consider a number of different alternatives at an early stage in design has been well established. It is hypothesized that providing a tool for automatically modeling and analyzing behavior of an artifact would aid the conceptual designer by facilitating the consideration of more varied alternatives. We describe a tool for automatic formulation of dynamic system models from user specified interconnection of components. The underlying methods are based on Bond Graph formalism using causal reasoning to simplify the model. The simplified model is not only more tractable for analysis and simulation but also facilitates inferences about the dominant characteristics of the designed artifact.
Determining Optimal Model Complexity in an Iterative Design Process
Authors: Bell David G. , Taylor Dean L.
Published: April 2021

In design, trade-offs are made between quality, cost and schedule. As the versatility of design tools has increased, so has the difficulty of making these trade-offs. This is especially true when choosing appropriate complexities for analytical and computational models. A fact known to designers and analysts is that more complex models yield more accurate results, but take longer to create and analyze. This paper shows that in an iterative design process there exists an optimal model complexity for each iteration, and alternatively, one optimal for the process as a whole. Quantitative methods for determining these complexities are developed, and three strategies for controlling the design modelling process are contrasted. Dependent on the stopping criteria, the best strategy will either minimize resource expenditure subject to quality requirements, or conversely, will maximize quality subject to resource constraints. These concepts are formalized with a view towards the design theory and methodology research community providing a first step in quantifying model trade-offs. An illustrative shape-optimal design example is shown wherein cost savings up to 84% were achieved. These savings were seen using several standard optimization algorithms. A customized optimization algorithm that incorporates this work should produce even better results.
Generic Classes of Iterative Behavior in Engineering Design Optimization
Authors: Burns Scott A.
Published: April 2021

The iterative dynamics of engineering design optimization processes are considered and generic features are identified. Two optimization methods are applied to the design of an elastic grillage structure and basins of attraction are produced to locate both simple and cyclic attractors. A phase-space portrait is constructed to visualize a complex non-cyclic attractor.
Knowledge-Based Computer-Aided Design System for Ingot Casting Processes
Authors: Viswanath R. , Jaluria Yogesh
Published: April 2021

Thermal manufacturing processes are typically those in which a material is subjected to a temporal thermal cycle like casting, extrusion and heat treatment of metals and plastics. The complexity of the design process for all these systems stems from the need to simulate complicated heat transfer, fluid flow and phase change phenomena and couple the results with the design rules and knowledge available on the manufacturing processes to obtain satisfactory designs. In this regard, the ability of expert systems to use heuristic reasoning has proved to be a powerful tool in the computer-aided-design of thermal manufacturing systems.

In this paper, the salient features of a knowledge-based system developed for the design of ingot casting process has been outlined. A Prolog based decision making front-end is interfaced with a Fortran based computational engine for rapid design. The results from the heat transfer analysis obtained from the computational module, are coupled to the evaluation module, which checks for satisfaction of the design criteria and violation of the design constraints. The decision making module uses a set of design rules to manipulate the variables until the design specifications are satisfied. Modularity and flexibility are maintained using an object-oriented format. Several interesting design acceleration features like learning from simple mathematical models and design extraction from previous designs are illustrated. The main features of this knowledge-based tool and the savings in time resulting from using these special features are discussed in detail.
Initial Design Strategies for Iterative Design
Authors: Ramachandran Natarajan , Langrana Noshir A. , Steinberg Louis
Published: April 2021

This paper discusses methods to retrieve design(s) from a design library in order to achieve a better initial starting point for the iterative model of the design process. The motivation for doing this is to reduce the extensive analysis time required for many iterative design problems. Starting a design at a favorable initial point should help reduce the number of iterations. Four initial design methods have been investigated varying from a simple non-library method to methods that use designs from a library. To evaluate the effectiveness of these methods, the initial design methods were tested on four example problems. They are, a cantilever beam, a gear-pair, a v-belt and an extruder-die. It was found that the number of iterations reduced approximately as 1/n, where n is the number of stored values in the design library.
Quantification of Operator Perceived Vibrations for a Consumer Product Design
Authors: Sheth Pradip N. , Shupert P. T.
Published: April 2021

The design process for the development of a new line of rear engine riding lawn mowers is described in this paper. In order to optimize the vibration behavior of this product, it was necessary to define a quantitative measure of the operator perception, or the “feel” of the vibrations at the operator/vehicle interfaces, i.e., the steering wheel, the footrests, and the seat. A Goodness of Vibration factor based on frequency weighting was devised for the design process. This quantitative measure in conjunction with the analytical/experimental tools of spectrum analysis, modal analysis, and finite element analysis during the design process are shown to produce a comfort optimized mower system. The Goodness of Vibration factors are shown to constitute a generic process which, in addition to quantifying the operator perception of vibrations, also help guide the product design process because of their direct relationships to the modal behavior of the system and also to the excitation spectra. This generic approach may have applications to the design process for other consumer power equipment, beyond the mower design demonstrated in this paper.
The Comparison of the Reliability of Three Psychometric Scales for Measuring Design Quality
Authors: Hyde Reva Slaughterbeck , Stauffer Larry Allen
Published: April 2021

Three scales for subjectively measuring design quality have been developed. Each scale represents a unique strategy for aiding a person in judging the quality of a solution to a design problem. The scales are compared with respect to how reliable these judgements are over time. The experimental results demonstrate that one of the scales is not reliable but that the other two are reliable.
Subjective Design Evaluation With Multiple Attributes
Authors: Thurston Deborah L.
Published: April 2021

A formal methodology is presented which may be used to evaluate design alternatives in the iterative design/redesign process. Deterministic multiattribute utility analysis is used to compare the overall utility or value of alternative designs as a function of the levels of several performance characteristics of a manufactured system. The evaluation function reflects the designers subjective preferences. Sensitivity analysis provides quantitative information as to how a design should be modified in order to increase its utility to the design decision maker. Improvements in one or more areas or performance and tradeoffs between attributes which would increase desirability of a design most may be quantified. A case study of materials selection and design in the automotive industry is presented. The methodology was applied to 6 automotive companies in the United States and Europe, and results are used to illustrate the steps followed in application.
DIscrepancy of Gear Tooth Allowable Bending Stress Using the Extreme Value Distribution From Different Test Methods
Authors: Hou Chienann A. , Ma Shijun
Published: April 2021

The allowable bending stress Se of a gear tooth is one of the basic factors in gear design. It can be determined by either the pulsating test or the gear-running test. However, some differences exist between the allowable bending stress Se obtained from these different test methods. In this paper, the probability distribution functions corresponding to each test method are analyzed and the expressions for the minimum extreme value distribution are presented. By using numerical integration, Se values from the population of the same tested gear tooth are obtained. Based on this investigation it is shown that the differences in Se obtained from the different test methods are significant. A proposed correction factor associated with the different experimental approaches is also presented.
A Bayesian Estimation of Reliability Measures of Stepwise Exponential Distribution System
Authors: Hu M. H.
Published: April 2021

This paper presents an analysis method for reliability measures of a system with step changes in failure and repair rates. Both failure and repair time have exponential function of time. Such a system is called a stepwise exponential distribution system. This kind of failure process can take place in various equipments. This paper deals with the system having components in series arrangement. Bayesian statistics is used in defining prior and posterior probability density functions of failure and repair rates. These functions provide information for the estimation of reliability measures: 1) failure and repair rates, 2) mean time to failure, 3) mean time to repair, 4) reliability function and 5) availability. A sample problem is given to illustrate the methodology. The Bayesian estimation of the stepwise exponential distribution model is useful in the planning of equipment predictive maintenance.
A Probabilistic Methodology for Random Stress-Strain Curves
Authors: Millwater H. R. , Harren S. V. , Thacker B. H.
Published: April 2021

This paper presents a methodology for analyzing structures with random stress-strain behavior. Uncertainties in the stress-strain curve of a structure are simulated by letting a small number of engineering parameters which describe the stress-strain curve be random. Certain constraints are imposed on the engineering parameters in order to have a physically realizable material. A general procedure to handle correlation among the stress-strain parameters has also been developed.

This methodology has been integrated into the NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) probabilistic structural analysis system. With this system, probabilistic finite element analysis of structures with random stress-strain behavior can be analyzed in an accurate, automated fashion.

An example problem is presented to demonstrate the capabilities of the code. The problem analyzed is that of a pressure vessel fabricated with a material exhibiting random stress-strain behavior.
Estimation of Structural Reliability Under Random Fatigue Conditions
Authors: Baldwin J. D. , Thacker J. G. , Baber T. T.
Published: April 2021

A procedure for determining the reliability of a structural element or machine part is presented. The solution assumes that the stress history in the part can be described by a narrow band, stationary, Gaussian random process and that the fatigue behavior of the part is governed by the classical S-N curve. Endurance limit modifications are discussed and a procedure is presented for determining the mean and standard deviation of the static stresses acting throughout a structure. A numerical example is presented showing the method applied to estimate the fatigue reliability of a power wheelchair frame.
Combined Stress and Resistance Modeling With the Nessus Software System
Authors: Thacker B. H. , Harren S. V. , Millwater H. R.
Published: April 2021

Computing the reliability of structural components with uncertainties in both stress and resistance variables is investigated. The NESSUS™ probabilistic software is used to perform the reliability computations using both Fast Probability Integration (FPI) and Monte Carlo methods. Results are compared for an example reliability analysis using both closed-form expressions and finite elements. The Advanced Mean Value probabilistic algorithm is used and is shown to yield highly accurate results, even for highly nonlinear response functions. The results show clearly the effectiveness of the newly incorporated algorithms available in the NESSUS software for computing structural reliability.
Fatigue Reliability Functions in Semilogarithmic Coordinates
Authors: Avakov Vladimir A.
Published: April 2021

In the previous publication [2], the transformation between fatigue life and strength distribution was established using double-logarithmic coordinate system (lnN-lnS). Here, a similar transformation is established using a semi logarithmic (lnN-S) coordinate system. With the aid of the developed orthogonal relations, lognormal, Weibull and three-parameter logweibull life distributions have been transformed into normal, asymptotic type 1 of smallest value, and three-parameter Weibull strength distributions, respectively. This procedure may be applied to other types of fatigue life distribution.
Computer Simulation and Reliability Analysis of Fatigue Crack Propagation Under Random Loading
Authors: Wu Wen-Fang
Published: April 2021

In order to study the behavior of fatigue crack propagation and fatigue reliability of a structural or mechanical component under random loading, a numerical simulation scheme and other analytical prediction models are proposed in this paper. The paper consists of (1) digital generation of random loading from random process theory; (2) numerical simulation of fatigue crack growth based on fracture mechanics concept; (3) a modified rain-flow cycle counting method for the identification of stress cycles and stress amplitudes; (4) Weibull probability density fit and other statistical analyses for the stress amplitudes as well as the crack growth curves; and (5) probabilistic models for the prediction of fatigue crack growth, fatigue life and fatigue reliability. Some conclusions are drawn at the end of this paper which can be used as references in the design of a structural or mechanical component under random loading.
Fatigue Design of Machine Components Using New Forms of S-N and Mean Stress Diagrams
Authors: Bagci Cemil
Published: April 2021

Article presents continuous forms of S-N and Mean Stress Diagrams for fatigue design of machine and structural components against breakage; and offers data verifying the proposed forms of the diagrams. Two forms of constructing the mean stress diagram — one for the test specimen, one for the critical section of the machine component — are offered. Defects in using conventional forms of the diagrams are removed. Discussions upgrading fatigue strength reduction factors are included. Computer-aided fatigue design applications are discussed. Determining remaining life considering cumulative damage effect using the offered forms of design diagrams is also included. Application examples are given.
Auger Elevator: Failure Modes and Effects Case Study
Authors: Brickman Dennis B. , Barnett Ralph L.
Published: April 2021

A fatal accident occurred when a right angle gear box on an auger elevator disintegrated freeing the outboard end of a rotating PTO shaft. The tractor, acting as a stationary power source, flailed the PTO shaft which then struck and killed a farmer. No similar occurrences have been reported for the nearly 2000 similar units which have been used for over a decade. This paper studies a number of fundamental failure modes in order to determine which failure modes created the accident. Systematic analysis showed that the accident was caused by unusual misuse of the product. Known safety control concepts do not preclude this unforeseeable event.
Estimation of Fatigue Crack Initiation and Early Growth in Resistance Spot Welds
Authors: Sheppard Sheri D. , Strange Michael
Published: April 2021

The main objective of this research is to develop a model of fatigue crack initiation and early crack growth in resistance spot welds that is specimen independent. This objective is achieved by examining the stress state around a resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only on the loading immediately surrounding the weld. As such, the expression is specimen independent.

An additional objective is to explore the feasibility of applying this fatigue crack initiation model to life estimation using structural response data from finite element analysis (FEA). This numerical technique is often used for evaluating structural integrity of assemblies. Limited verification examples show that the structural stress range as calculated from FEA reaction load data is capable of describing fatigue crack initiation and early crack growth in cyclically loaded resistance spot welds.
Electric Resistive Heat Curing of the Fiber-Matrix Interphase in Graphite/Epoxy Composites
Authors: Sancaktar Erol , Ma Weijian , Yurgartis Steven W.
Published: April 2021

A novel method for tailoring the interphase of carbon fiber-polymer composites by resistive electric heating is presented. The single fiber-epoxy resin tensile test is used to investigate the adhesion and fracture properties of the interphase. Electric resistive heating is shown to increase adhesion and toughness at the interphase region. In analyzing the results, the strength and fracture energy of the interphase are related to the thermal postcure conditions created by resistive electric heating. For this purpose, difference analysis method is used to obtain numerical solution for heat conduction problem in the single fiber test specimen and the temperature distributions are plotted. Improvements obtained using resistive electric heating via carbon fiber are compared with those obtained by postcuring of the whole sample via convective thermal postcuring. The results obtained using these two different postcure methods seem to be similar with electric heating procedure producing superior benefits in both increased toughness and adhesion.
Creep Rupture of an Alumina/Phenolic Resin Particulate Composite
Authors: Service Thomas H. , O’Keefe Kevin
Published: April 2021

The creep and creep rupture behavior of a resin-bonded particulate composite in a water environment was determined. The material exhibits power law creep behavior in which the steady state creep rate is a power function of the applied initial elastic stress. The creep exponent was found to be 4.8. The creep rupture behavior can be explained using a modified Monkman-Grant relationship where the time to failure times the creep rate is a constant.
Evaluation of Creep-Fatigue Damage Interaction in HK40 Alloy
Authors: Konosu Shinji , Koshimizu Tamotsu , Iijima Takahiro , Maeda Keikichi
Published: April 2021

In order to establish design criteria for materials which may sustain creep-fatigue damage, the creep rupture and creep-fatigue behavior of a high-carbon centrifugal cast steel was investigated at three different temperatures of 800, 900, and 1000°C, using HK-40 alloy which is a typical furnace tube material for fuel cell plant reformers and so on.

The strain waveforms used for the creep-fatigue tests consisted of triangular waveforms (pp waves [fast-fast waves], cc waves [slow-slow waves], pc waves [fast-slow waves], and cp waves [slow-fast waves]) and a trapezoidal waveform holding the peak strain at the tension side.

The applicability of various creep-fatigue interaction damage assessment methods were evaluated with particular emphasis on the life fraction rule (LFR) employed in ASME Section III, Boiler & Pressure Vessel Code Case N-47 and the strain range partitioning method (SRP). As it turned out that through the LFR life evaluation of HK-40 alloy subjected to strain cycling with holding at the tension side was well interpreted, design criteria for reformer tubes were established by applying the LFR to creep-fatigue life evaluation.
Prediction of the Strength of Ceramic Tubular Components: Part I — Analysis
Authors: Jadaan O. M. , Shelleman D. L. , Conway J. C. , Mecholsky J. J. , Tressler R. E.
Published: April 2021

The objective of this paper is to develop the analytical background for test methodologies that will enable accurate prediction of the strength distribution of ceramic tubular components from the strength distributions of simple specimens. Four simple specimen configurations and two tubular configurations were selected for this purpose. The simple specimen configurations were (1) four point bend, (2) c-ring tested in compression, (3) c-ring tested in tension and (4) o-ring tested in diametral compression. In addition, a short tube tested by axially compressing rubber inside the tube and a long tube subjected to internal pressure were analyzed. These specimen configurations were for the most part selected in a tubular shape in order to simulate the shape of tubular structural components. The prediction of the strength distribution of one specimen from that of another was based on Weibull statistical theory. Effective volume and area expressions, necessary for failure prediction, were derived for these specimen configurations.
Prediction of the Strength of Ceramic Tubular Components: Part II — Experimental Verification
Authors: Shelleman D. L. , Jadaan O. M. , Conway J. C. , Mecholsky J. J.
Published: April 2021

The strength distribution of reaction bonded silicon carbide tubes that failed by internal pressurization was predicted from strength distributions obtained from simple laboratory test specimens at room temperature. The strength distributions of flexure bars, C-rings tested in tension, C-rings tested in compression, diametrally compressed O-rings, and internally pressurized short tubes were compared to the strength distribution of internally pressurized long tubes. The methodology involved application of Weibull statistical theory using elasticity theory to define the stress distributions in the simple specimens. The flexural specimens did not yield acceptable results, since they were ground prior to testing, thereby altering their flaw population in comparison with the processing induced flaw populations of the tubular specimens. However, the short tube internal pressure test, the c-ring tested in tension and the diametrally compressed o-ring test configurations yielded accurate predictions, since these specimens more accurately represent the strength limiting flaw population in the long tubes.