Additive manufacturing (AM) offers many advantages to make objects compared to traditional subtractive manufacturing methods. For example, complex geometries can be easily fabricated, and lightweight parts can be formed while maintaining the parts strength for the low carbon footprint, low material consumption and waste. But there are some areas for AM to improve in sustainability, reliability, productivity, robustness, material diversity, and part quality. Life-cycle assessment studies have identified that the AM printing stage has a big impact on the life-cycle sustainability of 3D printed products. AM building parameters can be properly selected to improve the sustainability of AM. This paper explores the fused deposition modeling (FDM) process parameters for sustainability to reduce the process energy and material consumption. Investigated parameters include the printing layer height, number of shells, material infilling percentage, infilling type, and building orientation. Taguchi design of experiments approach and statistical analysis tools are used to find optimal parameter settings to improve the sustainability of the FDM process. Models formulated in this research can be easily extended to other AM processes.

Increasing performance demands and constraints are necessitating the design of highly complex, integrated systems across multiple sectors, including transportation and energy. However, conventional design approaches for such systems are largely siloed and focused on steady-state operation. To accommodate tightening operating envelopes, new design paradigms are needed that explicitly consider system-component interactions and their implications on transient performance at the system design stage. In this work, we present a model fidelity-based decomposition (MFBD) hierarchical control co-design (HCCD) algorithm designed to optimize system performance characteristics, with an emphasis on robustness to transient disturbances during real-time operation. Our framework integrates system level control co-design (CCD) with high-fidelity component design optimization in a computationally efficient manner for classes of highly coupled systems in which the coupling between subproblems cannot be fully captured using existing analytical relationships. Our algorithm permits scalable decomposition of computationally intensive component models and addresses coupling issues between subproblems in part by introducing an intermediate optimization procedure to solve for reduced-order model parameters that maximize the accuracy of the lumped-parameter control model required in the CCD algorithm. We demonstrate the merits of the MFBD HCCD algorithm, in comparison to an all-at-once (AAO) CCD approach, through a case study on aircraft dynamic thermal management. Our results show that our decomposition-based solution matches the AAO optimal cost to within 2.5% with a 54% reduction in computation time.

Due to the nested optimization loop structure and time-demanding computation of structural response, the computational accuracy and cost of reliability-based design optimization (RBDO) have become a challenging issue in engineering application. Kriging-model-based approach is an effective tool to improve the computational efficiency in the practical RBDO problems; however, a larger number of sample points are required for meeting high computational accuracy requirements in traditional methods. In this paper, an adaptive directional boundary sampling (ADBS) method is developed in order to greatly reduce the computational sample points with a reasonable accuracy, in which the sample points are added along the ideal descending direction of objective function. Furthermore, only sample points located near the constraint boundary are mainly selected in the vicinity of the optimum point according to the strategy of multi-objective optimization; thus, substantial number of sample points located in the failure region is neglected, resulting in the improved performance of computational efficiency. Four numerical examples and one engineering application are provided for demonstrating the efficiency and accuracy of the proposed sampling method.

Inherent in biologically inspired design (BID) is the selection of one or more analogs from which one or more strategies are extracted and transferred into the engineering domain. The selection of an analog is a fundamental step in biomimetic process, but locating relevant biological analogies can be challenging. Often, designers may fixate on an analogy or choose an established analogy without rigorous examination of alternatives. This practice is problematic—as basing a new design on an invalid assumption can lead to suboptimal results. This paper makes contribution to evaluation of analogy utility. The contribution is made by combining stochastic multicriteria acceptability analysis (SMAA) with a set of criteria, derived from BID, to assist multidisciplinary decision makers (DMs) in evaluating candidate design analogs. The resulting framework, which we call the biotransferability framework, is being developed to assist multidisciplinary teams to choose, rank, or sort candidate design analogs by assessing biology-to-engineering transfer risk.

This paper proposes a new tooling system and performs an optimum design on it to minimize the amount of thinning during a forming process of aluminum beverage can end shells. Numerical simulations of the shell forming process and structural performance of the shell under internal pressure have been performed. Influences of the upmost surface profiles and initial positions of the tool in the new tooling system on the shell forming quality have been investigated, and a structural optimization method based on the numerical simulations has been then applied to find optimum design points subject to constraints of the shell geometrical dimensions. A comparison shows that thinning of the shell formed by the proposed new tooling system can be reduced approximately 3.6% compared to a conventional tooling system. Optimization results of the new tooling system show that the amount of thinning can be reduced almost 4%. It is also confirmed that the buckle pressure resistance of the shell is improved 5.5%. The new tooling system may reduce the amount of thinning; hence, may improve the structural performance of the can and may save metal.

This paper addresses two important fundamental areas in product family formulation that have recently begun to receive great attention. First is the incorporation of market demand that we address through a data mining approach where realistic customer preference data are translated into performance design targets. Second is product architecture reconfiguration that we model as a dynamic design entity. The dynamic approach to product architecture optimization differs from conventional static approaches in that a product architecture is not fixed at the initial stage of product design, but rather evolves with fluctuations in customer performance preferences. The benefits of direct customer input in product family design will be realized through the cell phone product family example presented in this work. An optimal family of cell phones is created with modularity decisions made analytically at the engineering level that maximize company profit.

The transport of hazardous materials in truck cargo tanks can cause severe environmental damage as a result of the tank’s failure during a collision. Impact due to collision involves the transient dynamic response of the tank, fluid and their interaction. This paper develops a design oriented computational approach to predict the dynamic transient response of the tank shell structure subjected to impact loads during crash accidents. In order to compute the fluid and structural interaction, the finite element formulations for the added mass to the structure are developed and integrated with DYNA3D, a nonlinear dynamic structural finite element code, and they are validated by pendulum impact experiment. This paper presents the lumping process required by the added mass approach for cargo tanks under impact conditions. Thus, due to its efficiency the computer based approach provides a design tool for fluid filled thin walled structures in general and cargo tanks subjected to an impact situation. The structural performance of cargo tank shell construction is investigated. This research will contribute to improvement in design, modeling, and analysis techniques for crashworthiness and integrity of liquid mechanical structure systems which are subjected to impulsive loads like those found in vehicle collisions.

A software shell called “Learning Shell for Iterative Design,” L’SID, has been developed in conjunction with a simple data matrix, the “learn table.” Histories of design are utilized in aiding the acceleration of routine design problems. The class of problems addressed are non-convex, noninvertible and with multiple performance criteria. The design parameters can be of any definable type; continuous, integer or nonordered feature based. L’SID is domain independent and highly modular. The ability of L’SID to aid deterministic methods is shown statistically with two example problems (extrusion die and airfoil). Results also show the ability of the technique to surmount nonconvexity in design space and computational noise related to roundoff.

A method of cooperatively using Knowledge Based and Case Based Reasoning is proposed to assist designers in the design of flat composite panel structures. A Prototype Design Advisory system is constructed of heuristic and experiential rules which are acquired from composites design experts, and published text which is implemented in the CLIPS Knowledge Based System shell. The system includes design cases of previous composites design scenarios implemented in a Case Based Reasoning System using DesignMUSE. The cases all depict design of composites applied to commercial and military aircraft. The application of heuristic rules and prior similar design cases is focused upon the early stages of the design process. It is believed that such a design advisory system can aid in preventing unforeseen mistakes during the design and manufacture of composite structures, can assist in predicting the results of candidate designs, and can ultimately reduce the design cycle time.

A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that even the optimization of the top plate alone is effective in reducing total gearbox vibration.

A knowledge-based dwell mechanism design program has been developed on the premise that mechanism design can be considered as an example of general mechanical design. The program, called DWELL-ASSIST, was built using a knowledge based system shell, MIDAS, developed to embody a new model of conceptual and preliminary design. Based on required dwell and entire-motion characteristics, plus any designer preferences, DWELL-ASSIST proposes mechanism types and synthesis methods, in the context of prespecified “problem statements,” which the program judges to be compatible with the problem requirements. DWELL-ASSIST can choose from among cam, geared, and linkage mechanisms, and among path curvature, precision-point, optimization, and other specialized synthesis methods in its search for solutions. As a final step, DWELL-ASSIST has the capability of developing these chosen solutions and evaluating them based on problem requirements.

Smart materials have created new paradigms for structural design by introducing new concepts for vibration, damage, and structural control. Shape memory alloy reinforced composites are some of the newest and most versatile of this category of novel materials. They have shown tremendous versatility to adaptively and actively tailor mechanical and physical properties of structures and to perform shape and damage control. Moreover, the have generated new concepts for acoustic and vibration control. However, the unique behavior of the shape memory alloy fibers used as active elements within the composite also poses some difficult and interesting problems for describing the mechanical behavior of SMA reinforced structures. This paper will describe the formulation of a generalized laminate shell theory that incorporates embedded distributed actuators, i.e., shape memory alloy fibers or piezoelectric films. The theories consider the nonlinear strain-temperature-stress coupling for shape memory alloy actuators and the simplifications for analyzing piezoelectric actuators. Some of the computational difficulties of predicting the behavior of SMA reinforced shells will be discussed.

The layout of fiber composite structures compared to that of structures made from conventional homogeneous isotropic materials is far more difficult, because a fiber composite (laminate) is built up of several unidirectional layers (UD-layers) with fibers set at different angles. A contribution to the structural analysis and preliminary design of a fiber-reinforced conical shell is made in this paper. The equations of the membrane theory are used for analyzing the shell behavior. The design, with the objective of obtaining minimal deformation at minimal weight, subject to a set of failure constraints, is achieved by formulating and solving a compromise Decision Support Problem. Some designs of a fiber reinforced conical shell subjected to pressure load and temperature are presented.

The fracture strengths of two large batches of A357-T6 cast aluminum coupon specimens were compared by using two-parameter Weibull analysis. The minimum number of these specimens necessary to find the fracture strength of the material was determined. The applicability of three-parameter Weibull analysis was also investigated. A design methodology based on the combination of elementary stress analysis and Weibull statistical analysis is advanced and applied to the design of a spherical pressure vessel shell. The results from this design methodology are compared with results from the applicable ASME pressure vessel code.

The foundations for an expert system shell for implementing mechanical design applications are presented in this paper. The shell supports facilities for knowledge acquisition, quasi-reactive planning, design evaluation, and subjective explanation. The underlying philosophy of each of these facilities and some preliminary implementation issues are discussed. A brief summary of a recent research effort and its implications on the development of a generalized expert system shell for implementing mechanical design applications are also presented.

This paper presents application examples of vector optimization (Pareto-optimization) especially for the design of beam and shell components. A deterministic as well as a stochastic optimization model is formulated. Stochastic models will be important in the future because many factors in fabrication and operation are of random nature (fabrication tolerances, loads, etc.). For the special case of a sandwich beam these influences are demonstrated by means of a sensitivity analysis. For all examples presented (shell-flange structure, sandwich beam, panel-truss structure) the solution of the optimization problem results from transformation into scalar substitute problems by means of preference functions. In the examples, various optimization algorithms (e.g., sequential linear programming) were tested.

Asymmetric free vibrations of layered truncated conical shells are studied. Individual layers made of special orthotropic materials and both symmetric and asymmetric stacking with respect to the middle surface are considered. An energy-method based on the Rayleigh-Ritz procedure is employed. The influence of layer arrangements and that of the coupling between bending and stretching on the natural frequencies and mode-shapes are analyzed. Experimental results from tests on two shell models are provided for comparison with theoretical predictions. Numerical results based on extensive parametric studies are presented.

The design of a continuous fiber composite surface femoral shell having the same elastic properties as bone is presented. Contact between the femoral ball and acetabular cup was modeled as an elastic spherical ball loaded on an elastic semi-infinite body. The elastic constants of the composite were obtained by using empirically modified and experimentally verified rule-of-mixture equations relating the elastic properties of bone to those of both the fibers and matrix. The stresses were calculated for the contact problem and applied to a cross-ply laminate made up of orthotropic lamina. An interactive tensor failure criterion was used to select a safe design for polyimide, ultra-high molecular weight (U.H.M.W.), high density polyethylene, acrylic bone cement and epoxy composites using either glass or kevlar fibers. The safest composite design appears to be that made with a polyimide or epoxy matrix and glass or kevlar fibers.

Ellipsoids are frequently used for end closure of cylindrical pressure shells. Toroids of elliptic or circular cross-section, are widely used, e.g., for connecting two parallel legs in a U-shape. This paper presents equations for the means and standard deviations of stresses developed in ellipsoids and toroids with internal pressure. Inherent in these equations are the facts that: (a) design variables are generally characterized by spectra of values, rather than by unique values, and (b) a small, but finite, probability of failure must be recognized in any design. By coupling the stresses due to the applied loading as calculated by the equations given in the paper with the strength available in a material, reliability (or the alternative probability of failure) can be calculated. Conversely, for a given reliability the appropriate size can be determined. Appropriate illustrations of application of these equations are provided through tables and figures. The difficulty of relying on a factor of safety is demonstrated.

The problem of designing a set of rolls exerting a uniform pressure on material passing between them has elicited many different solutions, none quite satisfactory. A new solution, presented here, uses composite rolls having a cigar-shaped inner core and a cylindrical outer shell, the gap between them being filled with a soft elastomer containing approximately 15 percent air bubbles. The core profile is calculated according to equations derived here. The solution produces even roll pressure for any load, without the need for making adjustments to match changing loads. At the same time, the solution is mechanically very simple and reliable.