Can a Weld in Welded Structure Be Made With Zero Residual Stress?

2015 ◽  
Author(s):  
Stanislav Tchernov ◽  
John A. Goldak
Keyword(s):  
Residual Stress ◽  
Optimization Problem ◽  
Design Space ◽  
Design Parameters ◽  
Cpu Time ◽  
Welded Structure ◽  
Transverse Distance ◽  
Heated Area ◽  
Open Question ◽  
Heater Design

While solving a sequence of seventeen optimization projects to predict the values of the side heater parameters that would be expected to minimize camber distortion in an edge welded bar, the design parameters that reduced distortion to effectively zero were not unique. This raised the question if any of the designs that minimized the distortion effectively to zero also minimized the residual stress. To answer this question three different measures of residual stress were evaluated for all 1451 designs. The Computational Weld Mechanics (CWM) optimization problem is to find the best point in the 4D space of side heater design parameters: flux, heated area, longitudinal and transverse distance from the weld such that the final residual stress is as low as possible (minimized). To evaluate the objective function for each point in the 4D design space, the associated 3D transient non-linear thermal visco-elastic-plastic stress analyzes was solved. A FEM mesh with 6600 8-node brick elements and 9438 nodes was solved for 166 time steps in 10 minutes of single-core CPU time. In the seventeen optimization projects, 1451 weld analyses were solved in 75 quad-core CPU hours by one person in two calendar weeks. The residual stress was effectively reduced to zero in some designs. These designs also reduced distortion to effectively zero. Whether a design that effectively reduces the residual stress to zero is unique remains an open question.

A Direct-Search Computational Weld Mechanics Optimization Using Least-Square Approximation

2011 ◽  
Author(s):  
Mahyar Asadi ◽  
John A. Goldak
Keyword(s):  
Optimization Problem ◽  
Search Algorithm ◽  
Direct Search ◽  
Least Square ◽  
Design Parameters ◽  
Transverse Distance ◽  
Heated Area ◽  
Direct Search Algorithm ◽  
Weld Distortion ◽  
Heater Design

Using a frame-work for exploring a design space in Computational Weld Mechanics (CWM), a recent direct-search algorithm from Kolda, Lewis and Torczon is modified to use a least-square approximation to improve the method of following a path to the minimum in the algorithm. To compare the original and modified algorithms, a CWM optimization problem on a 152 × 1220 × 12.5 mm bar of Aluminum 5052-H32 is solved to minimize the weld distortion mitigated by a side heating technique. The CWM optimization problem is to find the best point in the space of side heater design parameters: power, heated area, longitudinal and transverse distance from the weld such that the final distortion is as low as possible (minimized). This CWM optimization problem is constrained to keep the stress level generated by the side heaters, in the elastic region to avoid adding an additional permanent plastic strain to the bar. The number of iterations, size of DOE matrix required and CPU time to find the minimum for the two algorithms are compared.

An Integrated Computational Welding Mechanics With Direct-Search Optimization for Mitigation of Distortion in an Aluminum Bar Using Side Heating

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Mahyar Asadi ◽  
John A. Goldak
Keyword(s):  
Optimization Problem ◽  
Search Algorithm ◽  
Direct Search ◽  
Least Square ◽  
Design Parameters ◽  
Search Optimization ◽  
Transverse Distance ◽  
Heated Area ◽  
Direct Search Algorithm ◽  
Weld Distortion

Using a computational weld mechanics (CWM) frame-work for exploring a design space, a recent direct-search algorithm from Kolda, Lewis and Torczon is modified to use a least-square approximation to improve the method of following a path to the minimum in the algorithm. To compare the original and modified algorithms, a CWM optimization problem on a 152 × 1220 × 12.5 mm bar of Aluminum 5052-H32 to minimize the weld distortion mitigated by a side heating technique is solved. The CWM optimization problem is to find the best point in the space of side heater design parameters: power, heated area, longitudinal and transverse distance from the weld such that the final distortion is as low as possible (minimized). This CWM optimization problem is constrained to keep the stress level generated by the side heaters, in the elastic region to avoid adding an additional permanent plastic strain to the bar. The number of iterations, size of design of experiments (DOE) matrix required and CPU time to find the minimum for the two algorithms are compared.

A Framework for Designer-Driven Exploration of Computational Weld Mechanics Design Space

2011 ◽  
Author(s):  
Mahyar Asadi ◽  
John A. Goldak
Keyword(s):  
Thermal Stress ◽  
Design Space ◽  
Continuous Optimization ◽  
Displacement Function ◽  
Welded Structures ◽  
Cpu Time ◽  
Welded Structure ◽  
Isolated Points ◽  
Set Up ◽  
Transient Thermal

This paper demonstrates a framework for analyzing multiple analyses of welds and welded structures as a single run. For each point in the design space a 3D transient thermal-stress analyses is solved for the weld and/or a welded structure. This enables the designer to explore the design state space for the design points specified in a Design of Experiments (DOE) matrix. This makes it simpler and quicker for a human to set up tens or hundreds of analyses. Also the CPU time to solve each analysis must be sufficiently short. Examples of DOE matrices created for Computational Weld Mechanics (CWM) optimization analyses are presented; i) a discontinuous combinatorial optimization of the weld sequence to minimize distortion in a girth weld, ii) a continuous optimization to mitigate distortion of an edge welded bar using side heaters, pre-bending with prescribed deflections at isolated points and pre-bending with a smooth prescribed displacement function.

Parameter study and optimization design of a hat oblique tunnel portal

2021 ◽  
pp. 095440972110140
Author(s):  
Zijian Guo ◽  
Tanghong Liu ◽  
Wenhui Li ◽  
Yutao Xia
Keyword(s):  
High Speed ◽  
Optimization Design ◽  
Pareto Front ◽  
Optimization Problem ◽  
Optimization Method ◽  
Design Parameters ◽  
Parameter Study ◽  
Buffer Structure ◽  
Tunnel Entrance ◽  
The Ideal

The present work focuses on the aerodynamic problems resulting from a high-speed train (HST) passing through a tunnel. Numerical simulations were employed to obtain the numerical results, and they were verified by a moving-model test. Two responses, [Formula: see text] (coefficient of the peak-to-peak pressure of a single fluctuation) and[Formula: see text] (pressure value of micro-pressure wave), were studied with regard to the three building parameters of the portal-hat buffer structure of the tunnel entrance and exit. The MOPSO (multi-objective particle swarm optimization) method was employed to solve the optimization problem in order to find the minimum [Formula: see text] and[Formula: see text]. Results showed that the effects of the three design parameters on [Formula: see text] were not monotonous, and the influences of[Formula: see text] (the oblique angle of the portal) and [Formula: see text] (the height of the hat structure) were more significant than that of[Formula: see text] (the angle between the vertical line of the portal and the hat). Monotonically decreasing responses were found in [Formula: see text] for [Formula: see text] and[Formula: see text]. The Pareto front of [Formula: see text] and[Formula: see text]was obtained. The ideal single-objective optimums for each response located at the ends of the Pareto front had values of 1.0560 for [Formula: see text] and 101.8 Pa for[Formula: see text].

scholarly journals Evaluation of Static Mapping for Dynamic Space-Shared Multi-task Processing on FPGAs

2021 ◽  
Author(s):  
Umar Ibrahim Minhas ◽  
Roger Woods ◽  
Georgios Karakonstantis
Keyword(s):  
High Performance ◽  
Design Space Exploration ◽  
Design Space ◽  
System Throughput ◽  
Design Parameters ◽  
Temporal Constraints ◽  
Shared Resources ◽  
Task Processing ◽  
High Level ◽  
Performance Computing

AbstractWhilst FPGAs have been used in cloud ecosystems, it is still extremely challenging to achieve high compute density when mapping heterogeneous multi-tasks on shared resources at runtime. This work addresses this by treating the FPGA resource as a service and employing multi-task processing at the high level, design space exploration and static off-line partitioning in order to allow more efficient mapping of heterogeneous tasks onto the FPGA. In addition, a new, comprehensive runtime functional simulator is used to evaluate the effect of various spatial and temporal constraints on both the existing and new approaches when varying system design parameters. A comprehensive suite of real high performance computing tasks was implemented on a Nallatech 385 FPGA card and show that our approach can provide on average 2.9 × and 2.3 × higher system throughput for compute and mixed intensity tasks, while 0.2 × lower for memory intensive tasks due to external memory access latency and bandwidth limitations. The work has been extended by introducing a novel scheduling scheme to enhance temporal utilization of resources when using the proposed approach. Additional results for large queues of mixed intensity tasks (compute and memory) show that the proposed partitioning and scheduling approach can provide higher than 3 × system speedup over previous schemes.

Workspace, dexterity and dimensional optimization of microhexapod

2015 ◽  
Vol 35 (4) ◽  
pp. 341-347 ◽  
Author(s):  
E. Rouhani ◽  
M. J. Nategh
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Screw Theory ◽  
Design Parameters ◽  
Dimensional Synthesis ◽  
Content Type ◽  
Workspace Analysis ◽  
The Difference ◽  
Flexure Joints ◽  
6 Degrees Of Freedom

Purpose – The purpose of this paper is to study the workspace and dexterity of a microhexapod which is a 6-degrees of freedom (DOF) parallel compliant manipulator, and also to investigate its dimensional synthesis to maximize the workspace and the global dexterity index at the same time. Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Design/methodology/approach – Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Findings – It has been shown that the proposed procedure for the workspace calculation can considerably speed the required calculations. The optimization results show that a converged-diverged configuration of pods and an increase in the difference between the moving and the stationary platforms’ radii cause the global dexterity index to increase and the workspace to decrease. Originality/value – The proposed algorithm for the workspace analysis is very important, especially when it is an objective function of an optimization problem based on the search method. In addition, using screw theory can simply construct the homogeneous Jacobian matrix. The proposed methodology can be used for any other micromanipulator.

Adaptive Geometry Representation of Turbine Vane Frames for Use in Optimization

2021 ◽  
Author(s):  
Sebastian F. Riebl ◽  
Christian Wakelam ◽  
Reinhard Niehuis
Keyword(s):  
Design Space ◽  
Cfd Simulation ◽  
A Priori ◽  
Three Dimensional ◽  
Optimization Method ◽  
Three Dimensions ◽  
Design Parameters ◽  
Adjustment Process ◽  
Turbine Vane ◽  
Integrated Concept

Abstract Turbine Vane Frames (TVF) are a way to realize more compact jet engine designs. Located between the high pressure turbine (HPT) and the low pressure turbine (LPT), they fulfill structural and aerodynamic tasks. When used as an integrated concept with splitters located between the structural load-bearing vanes, the TVF configuration contains more than one type of airfoil with sometimes pronouncedly different properties. This system of multidisciplinary demands and mixed blading poses an interesting opportunity for optimization. Within the scope of the present work, a full geometric parameterization of a TVF with splitters is presented. The parameterization is chosen as to minimize the number of parameters required to automatically and flexibly represent all blade types involved in a TVF row in all three dimensions. Typical blade design parameters are linked to the fourth order Bézier-curve controlled camber line-thickness parameterization. Based on conventional design rules, a procedure is presented, which sets the parameters within their permissible ranges according to the imposed constraints, using a proprietary developed code. The presented workflow relies on subsequent three dimensional geometry generation by transfer of the proposed parameter set to a commercially available CAD package. The interdependencies of parameters are discussed and their respective significance for the adjustment process is detailed. Furthermore, the capability of the chosen parameterization and adjustment process to rebuild an exemplary reference TVF geometry is demonstrated. The results are verified by comparing not only geometrical profile data, but also validated CFD simulation results between the rebuilt and original geometries. Measures taken to ensure the robustness of the method are highlighted and evaluated by exploring extremes in the permissible design space. Finally, the embedding of the proposed method within the framework of an automated, gradient free numerical optimization is discussed. Herein, implications of the proposed method on response surface modeling in combination with the optimization method are highlighted. The method promises to be an option for improvement of optimization efficiency in gradient free optimization of interdependent blade geometries, by a-priori excluding unsuitable blade combinations, yet keeping restrictions to the design space as limited as possible.

Effect of precipitate–precipitate interaction on residual stress in welded structure

2012 ◽  
Vol 65 ◽  
pp. 207-215
Author(s):  
Hamida Fekirini ◽  
Boualem Serier ◽  
Farida Bouafia ◽  
Bel Abbes Bachir Bouiadjra ◽  
Sardar Sikandar Hayat ◽  
...  
Keyword(s):  
Residual Stress ◽  
Welded Structure

Qualitative Knowledge and Manufacturing Considerations in Multidisciplinary Structural Optimization of Hybrid Material Structures

2006 ◽  
Vol 10 ◽  
pp. 143-152 ◽  
Author(s):  
Martin Huber ◽  
Horst Baier
Keyword(s):  
Hybrid Material ◽  
Optimization Problem ◽  
Fuzzy Rule ◽  
Optimal Designs ◽  
Design Parameters ◽  
Optimization Approach ◽  
Structural Level ◽  
Design Problems ◽  
Qualitative Knowledge ◽  
Typical Design

An optimization approach is derived from typical design problems of hybrid material structures, which provides the engineer with optimal designs. Complex geometries, different materials and manufacturing aspects are handled as design parameters using a genetic algorithm. To take qualitative information into account, fuzzy rule based systems are utilized in order to consider all relevant aspects in the optimization problem. This paper shows results for optimization tasks on component and structural level.

A genetic algorithm–based design approach for smart base isolation systems

2017 ◽  
Vol 29 (7) ◽  
pp. 1315-1332 ◽  
Author(s):  
Mohtasham Mohebbi ◽  
Hamed Dadkhah ◽  
Hamed Rasouli Dabbagh
Keyword(s):  
Genetic Algorithm ◽  
Optimization Problem ◽  
Base Isolation ◽  
Design Procedure ◽  
Design Parameters ◽  
Linear Quadratic ◽  
Isolation System ◽  
Isolation Systems ◽  
Magneto Rheological ◽  
Smart Base Isolation

This article presents a new approach for designing effective smart base isolation systems composed of a low-damping linear base isolation and a semi-active magneto-rheological damper. The method is based on transforming the design procedure of the hybrid base isolation system into a constrained optimization problem. The magneto-rheological damper command voltages have been determined using H2/linear quadratic Gaussian and clipped-optimal control algorithms. Through a sensitivity analysis to identify the effective design parameters, base isolation and control algorithm parameters have been taken as design variables and optimally determined using genetic algorithm. To restrict increases in floor accelerations, the objective function of the optimization problem has been defined as minimizing the maximum base drift while putting specific constraint on the acceleration response. For illustration, the proposed method has been applied to design a semi-active hybrid isolation system for a four-story shear building under earthquake excitation. The results of numerical simulations show the effectiveness, simplicity, and capability of the proposed method. Furthermore, it has been shown that using the proposed method, the acceleration of the isolated structure can also be incorporated into design process and practically controlled with a slight sacrifice of control effectiveness in reducing the base drift.

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