Optimum Structural Design of Internal Combustion Engine Systems by Branch-and-Bound Algorithm

This paper presents a dynamic reliability-based optimization technique for the seismic design of structures with tuned mass damper (TMD). Firstly, the governing equation of multi-degree-of-freedom structure with TMD is established. Then, the main structure is unfolded by the first mode. Considering that the damping is non-classical and the total main structure and TMD system is un-symmetric, the complex modal analysis is adopted to uncouple the governing equation and the analytical solutions of stochastic seismic response under the Kanai-Tajimi spectrum loading are obtained. Taking the ratio between the first-order modal displacement standard deviation of the structure with TMD and the one without TMD as the objective function, the dynamic reliability of the TMD system displacement as the constraint, the optimal design parameters of the TMD system are obtained through the penalty function method. A 10-story building with TMD system illustrates the proposed dynamic reliability-based optimization method. It is believed that such an optimization technique provides an effective tool for the seismic design of structures with TMD.

This paper presents a computer-based shape configuration design methodology to generate optimum design of specified structures satisfying the structural performance requirements and the geometric connectivity of the model. Mathematically, this problem can be categorized as a large-scale, nonconvex and nonlinear problem. The solution methods, grouped into two main categories, deterministic and stochastic approaches, require enormous computational efforts to find global optimum designs, a matter of major importance since many local suboptimal solutions can exist. In this study, two popular methods belonging to each class are examined and compared. The methods understudied are selected as the enumeration technique for deterministic approach and the simulated annealing for the stochastic method. The advantages and disadvantages of each technique are investigated. Using the best properties of each method and an algorithm for phase change between the two, a hybrid global shape optimization approach is formulated. The hybrid method is structured to combine the enumeration method for local minimization process and the simulated annealing for global minimum search phase. The hybrid method can find global optimum designs in a robust and efficient way, contrary to the signle phase solutions examined in this study. To demonstrate the hybrid method and its effectiveness, several design examples are presented.

According to the geometric meaning of the structural reliability index, an unconstrained optimization model with structural reliability index and design point is obtained by exterior penalty function method. The Powell method, golden section method and extrapolation method are used to solve the unconstrained optimization problem. The proposed method not has to deal with the any derivative of the limited state function, and can been used to obtain structural reliability index and design point of the strong nonlinear limit state function, which first-order reliability method (FORM) may fail to converge. Three examples are given to compare penalty function method with the difference methods. The results show that the given method is simply, effective and precise enough.

Multi-objective optimization design of pile-anchor structures for slopes based on reliability theory considering the spatial variability of soil properties

Optimal custom design of both symmetric and unsymmetrical hexapod robots for aeronautics applications

We hypothesize that by providing decision support for designers in industry we can speed up the design process and facilitate the creation of quality cost-effective designs. One of the challenges in providing design decision support is that the decision workflows embody various degrees of complexity due to the inherent complexity embodied in engineering systems. To tackle this, we propose a Knowledge-Based Platform for Decision Support in the Design of Engineering Systems (PDSIDES). PDSIDES is built on our earlier work that is anchored in modeling decision-related knowledge with templates using ontology to facilitate execution and reuse. In this paper, we extend the ontological decision templates to a computational platform that provides knowledge-based decision support for three types of users, namely, Template Creators, Template Editors, and Template Implementers, in original design, adaptive design, and variant design respectively. The efficacy of PDSIDES is demonstrated using a Hot Rod Rolling System (HRRS) design example.

Artificially structured materials, known as metamaterials, have been widely explored for manipulating waves thanks to their unconventional properties beyond those found in natural materials. Unlike natural materials whose properties are determined by their chemical constituents, the physical properties of metamaterials depend largely on the internal structures of their building blocks, and thus by designing the internal structures, various properties/functionalities can be achieved. In the past two decades, many designs have been proposed, resulting in a range of materials with a variety of exotic properties, for example, negative refraction, super-resolution imaging, etc. However for practical applications, in addition to the desired properties, various design requirements and constraints such as broadband performance, robustness, multiple functionalities and tunability are needed. The conventional physical-guided design approach often leads to suboptimal solutions for design problems with multiple requirements. This thesis work aims to develop inverse design approaches based on topology optimization for systematic design of elastic metamaterials with multiple design objectives. A set of novel elastic metamaterials/metasurfaces with robust performance and multi-functionalities has been designed and verified numerically and/or experimentally. Firstly, a two-step topology optimization scheme is proposed for dispersion engineering of hyperbolic elastic metamaterials over a broad frequency range. The scheme is formulated based on the physical nature of the hyperbolic dispersion and is solved by a typical gradient optimizer. By manipulating the dispersion band structure, non-resonant hyperbolic metamaterials have been successfully designed. Novel features/applications such as negative refraction, wave partial focusing and super-resolution imaging have been numerically demonstrated. The optimized designs outperform the traditional designs in terms of working frequency bandwidth. Furthermore, polarization-dependent transmission has been found in the designed metamaterial, which is a unique feature due to the optimization scheme developed. The proposed two-step scheme is also applicable for general dispersion engineering of metamaterials. Secondly, a general design framework based on topology optimization is proposed for the design of elastic metasurfaces with multiple requirements/functionalities. The proposed design framework has been applied to design elastic metasurfaces with high-energy transmission and robust performance. Multifunctional metasurfaces that can simultaneously control longitudinal and shear wave have been designed and realized for the first time. Furthermore, multi-frequency metasurfaces that can realize different wave manipulation at different wave frequencies have also been designed. Such metasurfaces can serve as tunable materials that can switch wave control mode simply by changing operation frequencies. Compared with the existing tunable metamaterials, our metasurfaces are passive and do not need any control/actuation schemes, and thus are much easy to implement. Another application of the designed multi-frequency metasurfaces is to use them as demultiplexers, which is useful in a range of practical applications such as structural health monitoring and vibration control.

An optimization technique is used to investigate changes in structural design which will increase the energy-absorbing capabilities of a marine vessel during a low-speed collision. The idealized collision scenario is arigid, vertical bow striking a tanker at a right angle, midway between rigid bulkheads. Collision energy is most efficiently absorbed as membrane tension. A penalty function method is utilized to redesign a compartment of a large tanker for rupture resistance. Up to 130 percent increase of energy absorbed prior to rupture is obtained for optimal designs without increase in weight but with sacrifice of strength. Stronger, more conservative designs are investigated by restraining the parametric freedom. Trends for improving rupture resistance are presented.

The paper presents a simple yet efficient optimal design method based evolutionary structural optimization (ESO) to determine the minimum member sizes complying with an AISC-LRFD (an acronym for American Institute of Steel Construction – Load and Resistance Factor Design) specification. The influences of nonlinear (second-order approximation) geometry are realistically incorporated using an AISC 2010 direct analysis method. The optimization minimizes the total weight of structures subjected to the challenges associated with the simultaneous presence of nonlinear design formulations and discrete design variables realistically considering the availability of standard steel sections. This leads to a non-convex and/or non-smooth optimization program. The ESO algorithm overcomes the problem by performing iterative elimination procedures of ineffective sections, where the feasible design domain progressively converges to the minimum distribution of steel members satisfying limit state (ultimate strength and serviceability) criteria. The ESO design process is encoded within a visual basis application (VBA) framework having a direct interface with the commercial analysis and design software, called SAP2000. An illustrative example motivated by practical engineering applications has been successfully proceeded and hence highlighted robustness of the proposed approach in obtaining the optimal design of steel structures under applied forces.

Strategic Environmental Assessment (SEA) Process towards the Sustainable Design and Construction of Computer, Communication, Network Engineering, Machine Learning and Artificial Intelligence Systems

The design of complex engineering systems often relies on simulation-based models, which inherently introduce uncertainty. Consequently, effective system design necessitates the incorporation of robust design principles and metrics to manage the uncertainties. From a decision-based design perspective, metrics such as the Design Capability Index (DCI) and Error Margin Index (EMI) are employed in problem formulations to address this challenge. These metrics typically utilize Taylor series-based approximations to estimate variance. However, due to the structural limitations of the Taylor series expansion, these formulations may mislead designers toward local minima rather than guide them toward actual robust solutions. In this paper, we propose an alternative formulation of the Design Capability Index (DCI) and Error Margin Index (EMI) that leverages the multiple-point variance estimation method. This approach employs a weighted average of multiple points to assess variance estimations around the nominal design, ensuring that the solution is not confined to a local optimum by estimating the correct variance at the local optimum. The proposed alternative metrics are incorporated into the robust Concept Exploration Framework (rCEF) to find robust solutions for complex engineering systems. A machine learning-based visualization tool, the interpretable Self-Organizing Maps (iSOM), is used to visualize and explore the high-dimensional robust solution space generated using the updated rCEF. Two examples are used to evaluate the proposed formulation: (i) a polynomial function to examine the effect of the alternative variance estimation method on EMI and DCI metrics, and (ii) a comprehensive hot rod rolling problem, considering model parameters and model structure uncertainty.

Bi-level multi-objective fuzzy design optimization of energy supply systems aided by problem-specific heuristics

Integrating Core Systems Engineering Design Concepts into Traditional Engineering DisciplinesIn this study we describe the integration of core systems engineering design concepts intotraditional mechanical and electrical engineering curriculum at the University of Arkansas atLittle Rock (UALR) undergraduate Systems Engineering program. The program was launched in1999 in response to the industry demands for engineering graduates capable of managingcomplex engineering projects. The program has since graduated over 150 students who areworking in industry (aerospace, defense, manufacturing, design, and consulting), federal andstate government, or attending graduate school. The program curriculum has four broadcomponents: a 35 hour university core that covers basic math and science (11 hours) and generaleducation (24 hours); a 30 hour college core that enhances the math and science preparation witha course in engineering ethics; a 32 systems engineering component that introduces core systemsengineering concepts; and, a 32 hour option component that teaches the mechanical or electricalengineering disciplines. The program is accredited by ABET under general criteria, and plans areunderway to satisfy mechanical and electrical engineering program criteria. Students entering theprogram are introduced to systems engineering core concepts through courses in EngineeringEconomy, DES Modeling and Simulation, Optimization Methods, Decision and Risk Analysis,and Systems Engineering Design and Analysis. Among them, Engineering Economy coversengineering project evaluation and economic decision making. Optimization Methods in SystemsEngineering covers linear and nonlinear methods of engineering design optimization. DESModeling and Simulation covers theory and practice of discrete event simulation modeling.Decision and Risk Analysis covers uncertainty modeling and analytical techniques for rationaldecision making. Systems Engineering Design and Analysis covers the systems engineering life-cycle process, including identification of system requirements, engineering design andarchitecture, system modeling, testing and integration, and system operation and support. The128-hr program culminates in a two-semester Systems Engineering Capstone Design thatemphasizes the multi-disciplinary nature of the program. The students perform functional designin the first semester followed by detailed physical design and testing in the second semester. TheUALR program graduates skilled systems engineers who combine holistic thinking with deepproduct knowledge, strong technical background, effective communication skills, and goodinterpersonal skills.

The optimal and smart design of nonlinear building structures with and without passive dampers subjected to earthquake loading is of great concern in the structural design of building structures. The research started around 1980 and many investigations have been conducted. A comprehensive review on this subject is made in this article. After the description of essential features of the optimal design problem of nonlinear building structures under earthquake ground motions, analysis types of optimization problems are explained and the significance of the dynamic pushover analysis is discussed from the viewpoint of analysis of limit states under earthquake ground motions of magnitude larger than the code-specified level. Then, the categorization by the response of frames and dampers was made. In this categorization, several subjects are discussed first: 1) Optimal design of bare nonlinear building frames under seismic loading, 2) Optimal design of nonlinear dampers for elastic building frames under seismic loading, 3) Optimal design of linear dampers for nonlinear building frames under seismic loading, 4) Optimal design of nonlinear building frames with specified nonlinear dampers under seismic loading, 5) Optimal design of nonlinear dampers for specified nonlinear building frames under seismic loading, 6) Simultaneous optimization of elastic-plastic building structures and passive dampers. Finally, the classification of researches in view of solution strategies is conducted for providing another viewpoint.

Multiple objectives in the design of machine structures exist. Here, two types of priorities among these objectives are considered. One of these objectives is the absolutely necessary goal, the "required goal", and the other is the "requested goal". Few studies have been conducted with respect to the structural design problem of multiple goals with these kinds of priorities. Thus, a multilevel structural optimization strategy which is based on the lexicographic optimization method and modified so as to be available for structural design, is proposed in this paper. This strategy is demonstrated on an actual example of a motorcycle frame structural design which has three goals ; achievement of static torsional rigidity, reduction of dynamic response level and decrease in the weight of the motorcycle frame.