Search

The design process is difficult to accelerate due to its iterative nature, which increases project cost and delays completion time of a design project. Many previous studies tried to find the optimal structure and sequence of a design process minimizing iteration. In a multiproject environment, however, waiting time caused by resource shortage is a more critical reason for a lengthy project than iteration time. In this paper, we propose a novel sequencing method that reduces waiting time in a multiproject environment by dynamically changing the sequence of design tasks, according to availability of resources. It is called a dynamic sequencing method, as opposed to the traditional static sequencing method by which every design project follows a predefined optimal sequence. In order to evaluate the effect of this method, we developed a design-process model for simulating iteration and waiting in a multiproject environment. The simulation results show that dynamic sequencing is significantly better than traditional static sequencing with respect to average duration of projects. It is noted that more significant improvements can be obtained for the bottlenecked and unbalanced processes, both of which conditions would otherwise have negative effects on process performance. [DOI: 10.1115/1.3066599] Keywords: design process, multiproject environment, dynamic sequencing, DSM, stochastic processing network

In this paper, we present a methodology that helps select the distribution parameters in degrading multiresponse systems to improve dependability at the lowest lifetime cost. The dependability measures include both quality (soft failures) and reliability (hard failures). Associated costs of scrap, rework, and warrantee work are included. The key to the approach is the fast and efficient creation of the system cumulative distribution function through a series of time-variant limit-state functions. Probabilities are evaluated by Monte Carlo simulation although the first-order reliability method is a viable alternative. The cost objective function that is common in reliability-based design optimization is expanded to include a lifetime loss of performance cost, herein based on present worth theory (also called present value theory). An optimum design in terms of distribution parameters of the design variables is found via a methodology that involves minimizing cost under performance policy constraints over the lifetime as the system degrades. A case study of an over-run clutch provides the insights and potential of the proposed methodology. [DOI: 10.1115/1.3013295] Keywords: dependability, quality, reliability, design, limit-state function, loss of performance cost, present worth

Product development (PD) processes are complex and unstructured compared to business or manufacturing processes, as they have iterative, evolutionary, uncertain, and cooperative features. In order to effectively manage and control a complex PD process, appropriate and logical descriptions are needed. This requires a modeling framework that can capture its characteristics. However, previous modeling methodologies are limited in terms of representing the characteristics. To cope with this limitation, we propose a modeling framework that can address the typical features of the PD process. To this end, we classify PD characteristics systematically and define modeling constructs for the PD process with modeling patterns and parameters. The proposed modeling framework will provide engineers and managers with a basis for planning, organizing, analyzing, and monitoring complex PD processes effectively. Index Terms--Design iteration, modeling framework, overlap, patterns, product development (PD) process.

New classes of compliant long dwell mechanism designs are introduced, formulated, and simulated. These classes of compliant dwell mechanisms incorporate the buckling motion of flexible members. Long dwell motion is obtained throughout the buckling motion of a flexible follower. Flexible buckling members are modeled using polynomial functions fitted to nonlinear inextensible exact elastica theory. The displacement analysis of the mechanisms is done quasi-statically using loop closure theory, static equilibrium of flexible parts represented by polynomial load deflections. One example of each new mechanism and its simulation results are presented. [DOI: 10.1115/1.2735337]

This paper presents the design of a mechanism with the following specifications: continuous alternate motion, wide motion phases with constant angular velocity, parallel input and output shafts, and great strokes. Those specifications derive from a possible application in the textile field. The mechanism is composed of two star wheels properly coupled together: there are two counter-rotating input wheels, alternately coupling with slots first, then teeth at each side of the output wheel. As usual for star wheels, pins and slots handle the acceleration and deceleration phases, while the constant velocity phase is performed by coupling sectors of toothed gears. A proper design of pins and slots is performed, so that at the same time when a pin from one input wheel is releasing a slot, a pin from the other input wheel engages a slot on the other side of the output wheel, forcing the latter to an opposite motion. In this way the output wheel has a continuous and smooth alternate motion. By annihilating the arrest phases typical of star wheels, the proposed system eliminates the discontinuities in the acceleration diagram. The paper develops a complete parametrical analysis of the device, underlining the effect of the constraints on the shape of the motion laws with particular emphasis on the acceleration and deceleration phases. In this way the output wheel has a continuous and smooth alternate motion. With respect to an analogous mechanism realizing the same laws of motion, e.g., cams, this device is very compact and economical, also presenting parallel input and output shafts, and significantly reduces sliding and wear. [DOI: 10.1115/1.2735638] Keywords: kinematics, mechanism design, star wheel, alternate motion

High mast lighting structures are being used to provide illumination for large intersections, particularly for highways located in rural areas. These structures, ranging from approximately 15-40 m (50-130 ft) in height, are exposed to high wind forces that in turn produce a tremendous number of loading cycles each year. A recent high mast lighting structural support failure in the high plains of Colorado near Denver International Airport provided the impetus for this study. These high-mast structures are less than one meter (3.28 ft) in diameter and are quite flexible relative to many civil engineering structures. This flexibility results in large deformations when compared to their diameter, i.e., when combined with the height of these structures. Furthermore, large forces and moments at the base are produced that result in large stresses and stress reversals during multimode excitation. This paper presents the process and results for the development of a reliability-based design procedure for high-mast lighting structural supports based on fatigue life. The resulting procedure is prescriptive in that a series of design charts result from full nonlinear finite element analysis. The loading on the slender body is characterized by Morison's equation, essentially providing the nonlinear loading relationship for the wind on the moving structure. Then, a well-known random vibrations approach was coupled with Miner's rule to estimate the fatigue life of the structural support. Several illustrative design examples are presented and shown to compare very well with full simulations. DOI: 10.1061/(ASCE)0887-3828(2007)21:3(193) CE Database subject headings: Fatigue; Lighting; Structural reliability; Steel; Wind loads.

This paper describes the development and application of design charts for piled embankment designs. It outlines the computational approach adopted, the geotechnical profiles used, and the application of the design procedure using the charts. The soil profile used for the charts is representative of a Malaysian soft clay profile, involving a more or less normally consolidated soil, with a strength and stiffness that varies linearly with depth. Such a profile is typical of the ground conditions in a variety of countries in the Southeast Asian region. The design charts address the issues of pile capacity, settlement due to embankment load, settlement due to a temporary piling construction platform, and lateral response of piles near the edge of the embankment. The charts consider variations in ground conditions, embankment height, pile length, and pile spacing. An illustrative example is given to demonstrate the use of the charts. DOI: 10.1061/(ASCE)1090-0241(2007)133:5(493) CE Database subject headings: Embankments; Foundation design; Lateral displacement; Pile foundations; Settlement; Soil settlement; Clays; Soft soils.

Because deterministic optimum designs obtained without taking uncertainty into account could lead to unreliable designs, a reliability-based approach to design optimization is preferable using a Reliability-Based Design Optimization (RBDO) method. A typical RBDO process iteratively carries out a design optimization in an original random space (X-space) and a reliability analysis in an independent and standard normal random space (U-space). This process requires numerous nonlinear mappings between X- and U-spaces for various probability distributions. Therefore, the nonlinearity of the RBDO problem will depend on the type of distribution of random parameters, since a transformation between X- and U-spaces introduces additional nonlinearity into the reliability-based performance measures evaluated during the RBDO process. The evaluation of probabilistic constraints in RBDO can be carried out in two ways: using either the Reliability Index Approach (RIA), or the Performance Measure Approach (PMA). Different reliability analysis approaches employed in RIA and PMA result in different behaviors of nonlinearity for RIA and PMA in the RBDO process. In this paper, it is shown that RIA becomes much more difficult to solve for non-normally distributed random parameters because of the highly nonlinear transformations that are involved. However, PMA is rather independent of probability distributions because it only has a small involvement with a nonlinear transformation.

We present a method for estimating the parameter sensitivity of a design alternative for use in single objective robust design optimization. The method is non-gradient based: it is applicable even when the objective function of an optimization problem is non-differentiable and/or discontinuous with respect to the parameters. Also, the method does not require a presumed probability distribution for parameters, and is still valid when parameter variations are large. The sensitivity estimate is developed based on the concept that associated with each design alternative there is a region in the parameter variation space whose properties can be used to predict that design's sensitivity. Our method estimates such a region using a worst-case scenario analysis and uses that estimate in a bi-level robust optimization approach. We present a numerical and an engineering example to demonstrate the applications of our method.

This paper focuses on the potential of programming as a link between design and facility management. Not well understood and usually avoided, the promise of programming as a key activity is presented as a dynamic and flexible tool for identifying client-user facility expectations and requirements in the entire project-delivery process. In this context, facility management is proposed as a strategic resource and partner together with all the parties involved. Hinging on the design perspective, an analysis of the current practice and a modified framework are introduced, which suggests relying on facility management data, feedback, and involvement throughout the project delivery process. DOI: 10.1061/(ASCE)0887-3828(2003) 17:1 (4) CE Database keywords: Facilities; Design; Management

Surgical instruments consist of basic mechanical components such as gears, links, pivots, sliders, etc., which are common in mechanical design. This paper describes the application of a method in the analysis and design of complex surgical instruments such as those employed in laparoscopic surgery. This is believed to be the first application of type synthesis theory to a complex medical instrument. Type synthesis is a methodology that can be applied during the conceptual phase of mechanical design. A handle assembly from a patented laparoscopic surgical stapler is used to illustrate the application of the design method developed. Type synthesis is applied on specific subsystems of the mechanism within the handle assembly where alternative design concepts are generated. Chosen concepts are then combined to form a new conceptual design for the handle assembly. The new handle assembly is improved because it has fewer number of parts, is a simpler design and is easier to assemble. Surgical instrument designers may use the methodology presented here to analyze the mechanical subsystems within complex instruments and to create new options that may offer improvements to the original design. [DOI: 10.1115/1.1468635]

The designers of the Superconducting Super Collider (SSC) near Dallas are making use of novel construction techniques that incorporate underground experimental halls. Proton beams traveling at almost the speed of light would be collided by 10,000 superconducting magnets used by the SSC. Basic principles of matter can be understood by examining the resulting shower of subnuclear particles. Construction work includes the digging of 70 miles of tunnels, 54 mile main ring, 43 vertical shafts and 16 miles of injector and accelerator tunnels. It would be world's largest pure science project if the US government allows it to be completed.

The paper looks at a four-step process to facilitate design for a particular market, in this case old people. A key element is to enable the visualization of possible design solutions and for this an important ingredient has been found to be story-telling about what people want and scenario building for products and services in use. This is particularly true when crossing national boundaries, and some demographic and geographic differences between the USA and Europe are highlighted.

The paper presents the theory of performance sensitivity distribution and a novel robust parameter design technique. In the theory, a Jacobian matrix describes the effect of the component tolerance to the system performance, and the performance distribution is characterized in the variation space by a set of eigenvalues and eigenvectors. Thus, the feasible performance space is depicted as an ellipsoid. The size, shape, and orientation of the ellipsoid describe the quantity as well as quality of the feasible space and, therefore, the performance sensitivity distribution against the tolerance variation. The robustness of a design is evaluated by comparing the fitness between the ellipsoid feasible space and the tolerance space, which is a block, through a set of quantitative and qualitative indexes. The robust design can then be determined. The design approach is demonstrated in a mechanism design problem. Because of the generality of the analysis theory, the method can be used in any design situation as long as the relationship between the performance and design variables can be expressed analytically. [DOI: 10.1115/1.1333095]

This paper investigates the response model approach for the dynamic robust design problem. We derive relationships between the effect estimates of the loss model approach and those of the response [...]

RP models are being used as a major tool for the entire design and manufacturing process, including testing, modelling for presentations, design evaluations, product costing and certification, instead of their earlier, restricted use as concept models. RP systems are available only from bureau services because of the high purchase cost which many manufactures cannot afford. RP techniques include stereolithography, selective laser sintering, laminated object manufacturing and fused deposition modelling.

Many new products were introduced in A/E/C systems '93, the annual computer and management show for design and construction industry held in June, with the theme of 'Advanced Technology Goes Mainstream.' It was stated that Windows NT-based products would be released in the end of 1993 by developers such as Autodesk Inc., California and Intergraph Corp. Huntsville, Ala. Cyberscope, a three dimensional viewing device was one of the exhibits of Simsalabim Systems Inc., California. An inexpensive mapping and management technology code-named Anaheim was demonstrated by Autodesk.