Optimization of friction stir welding process using NSGA-II and DEMO

In welding processes, the selection of optimal process parameter settings is very important to achieve best weld qualities. In this work, neuro-multi-objective evolutionary algorithms (EAs) are proposed to optimize the process parameters in friction stir welding process. Artificial neural network (ANN) models are developed for the simulation of the correlation between process parameters and mechanical properties of the weld using back-propagation algorithm. The weld qualities of the weld joint, such as ultimate tensile strength, yield stress, elongation, bending angle and hardness of the nugget zone, are considered. In order to optimize those quality characteristics, two multi-objective EAs that are non-dominated sorting genetic algorithm II and differential evolution for multi-objective are coupled with the developed ANN models. In the end, multi-criteria decision-making method which is technique for order preference by similarity to the ideal solution is applied on the Pareto front to extract the best solutions. Comparisons are conducted between results obtained from the proposed techniques, and confirmation experiments are performed to verify the simulated results.

     

Defect identification in friction stir welding using discrete wavelet analysis

This article discusses on the detection of fault occurred during friction stir welding using discrete wavelet transform on force and torque signals. The work pieces used were AA1100 aluminum alloys of thickness 2.5 mm. The plates were 200 mm in length and 80 mm in width. Presence of defect in welding causes sudden change in force signals (Z-load), thus it is easier to detect such abrupt changes in a signal using discrete wavelet transform. Statistical features like variance and square of errors of detail coefficients are implemented to localize the defective zone properly as it shows better variations (in defective area) than the detail coefficient itself.     

Function-oriented design of a friction stir welding robot

The paper starts with the analysis on the need for intelligent manufacturing systems, and proposes our view of the solution to the problem from a mechatronic point of view. It discusses issues related to the flexible modular systems that produce modular flexible products. The paper takes a novel welding technology called friction stir welding as a case study, and investigates issues related to the design of a machine that could automate the process. It presents a function-oriented approach that could provide the guidelines in development of such a system. Along with the various alternatives of the friction stir welding machines concepts, various types of welding configurations are discussed in detail thereby providing necessary details for function-oriented conceptual design of a general-purpose robotic system. The paper, then, presents the system model for an articulated robot manipulator, as suggested by functional design, followed by simulations to investigate its suitability for such an application. The proposed solution not only ensures the achievement of requirements for the intelligent manufacturing systems, but also provides the necessary guidelines in design and development of such systems, as the concluding remarks. The paper is finalized by future developments and suggestions.     

Development of an automatic arc welding system using an adaptive sliding mode control

This paper develops an automatic welding control scheme for alternating current shielded metal arc welding (SMAW) system. A mathematical model of the welding control system is derived and the system parameters identified. An adaptive sliding mode controller is designed to estimate the bound of the system uncertainties and to modulate the electrode feed rate in such a way that the desired arc length and arc current are maintained as the electrode melts during the welding process. The proposed control method is suitable for any consumed electrode welding technique. The simulation and experimental results show that the automatic welding control system successfully maintains the magnitude of the arc current at the desired value and preserves the arc stability, thereby obtaining an enhanced SMAW control system performance.     

Viscoelastic flow in an undulating tube using spectral methods

The flow of a viscoelastic fluid through an undulating tube is considered. The fluid is modelled using the UCM constitutive equation. The governing set of equations is solved using a time-splitting technique. This is based on separate treatments of the convection and generalised Stokes operators. The spatial discretisation is based on a spectral discretisation in which the radial basis functions satisfy the conditions along the axis of symmetry of the tube explicitly. Compatible approximation spaces are chosen for velocity, pressure and extra-stress. The convection problem is solved in a type-sensitive manner using a high-order Runge-Kutta method. The weak formulation of the generalised Stokes problem is discretised and solved using a nested conjugate gradient technique. The effect of elasticity on flow resistance is investigated and comparisons made with other results in the literature.     

A tool breakage detection system using an accelerometer sensor

An on-line and in-process based monitoring system to detect tool breakage via an accelerometer was developed and successfully evaluated in an end milling operation. Prior to testing and evaluation of the tool breakage condition, a simulation model was developed. Transfer of the on-line vibration signal to the frequency domain employed the fast fourier transfer function, and set thresholds were used to determine the tool condition after various experimental tests. In comparison to other in-process methods, such as those that employ dynamometers and acoustic emission sensors, the proposed system is easy to set up and does not require changing of the mechanism. Additional benefits of the system are its high reliability and low cost. Thus, the new monitoring system is potentially useful for untended milling operations in on-line and real-time tool breakage detection in linked-cell manufacturing systems (L-CMS).     

Optimization of folded plate roofs

Increased usage of prefabricated structural components and the advantages offered by folded plate roofs necessitates the optimization of their configurations. In order to reduce the material expenditure, transportation and erection costs the dead-weight of the roof systems need to be minimized.The reported study defines a technique for the optimization of the structural weight of the folded plate roof without intermediate stiffeners and subjected to one loading system. The developed method enabled the generation of the different, and consequently the optimum, geometries by starting with an arbitrary initial geometry. The azimuthal angles, the width and the thickness of the individual panels were permitted to vary. The optimization employed a variational approach and flexibility formulation. The total weight of the roof was taken as the target function, subject to minimization. The equilibrium equations for the panels were taken as the constraint equations for the optimization process. The pseudo-weight function was established through the use of the Lagrangian multipliers. The standard Lagrangian formulation was then applied to the pseudo-weight function, and a set of optimization equations were generated. These equations, along with the original equilibrium equations, formed a system of simultaneous nonlinear transcendental equations. This set was solved using an iterative approach.The overall formulation was kept general enough to permit the inclusion of any given loading condition to permit the application of the given methodology to any folded plate roof system.     

PE管热熔焊接系统的研制

针对PE管件焊接的国际标准,研制了高性能PE管焊接系统。系统以89C51RD2单片机为控制核心,分析了热熔焊接系统的工作原理,利用中断和定时技术,以A/D采样反馈电压为比较条件,通过改变可控硅导通角的大小,实现了输出可调高精度焊接电压。     

User-centric image segmentation using an interactive parameter adaptation tool

Creating successful machine vision systems often begins a process of developing customised reliable image segmentation algorithms for the detection, and possibly categorisation of regions of interest within images. This can require significant investment of time from both the image processing and the domain experts to set up. Frequently this process is mediated via interviews, or language-based systems which may not fully capture the visual decision-making process of the domain experts. The resulting algorithms can also often be “brittle” in the sense of being highly specialised to the task for which they are tuned, and are consequently sensitive to changes in operating conditions or image specifications.One approach is to use interactive evolution for developing rapidly reconfigurable systems in which the users’ tacit knowledge and requirements can be elicited and used for finding the appropriate parameters to achieve the required segmentation without any need for specialised knowledge of the underlying machine vision systems. This paper presents an interactive tool that can be used to quickly and easily evolve optimal image segmentation parameters from scratch. Building on previous work, the new algorithm reported here incorporates user-guided local search and makes the fitness function more flexible to facilitate the underlying multi-objective decision-making process.One of the key requirements for any interactive system is a high level of usability, both in terms of effectiveness—being able to build accurate models that meet end-user requirements—and efficiency—being able to achieve the required results within a minimal amount of time and undue effort. The system described in this paper has been designed with these considerations in mind to ensure a high level of user-experience of the interaction process. We present results from a series of experiments with a range of users to analyse the effect of the improvements that have been made over the previous system. The efficiency of the tool is also tested with “novice users”, and its usability by “novice users” is analysed.     

一种弧焊机器人工具标定方法

利用七点法确定工具坐标系末端点相对于机器人法兰中心的位置与姿态的偏置,通过机器人运动学推导,并根据工具末端点与法兰中心的几何关系,确定工具末端点相对于法兰的位置与姿态,不需要借助测量工具。本方法已应用到Efort机器人工具标定系统中,而且经过激光跟踪仪计算,机器人的直线度和圆弧度均控制在±0．5mm之内,证明了此方法是切实可行的。     

Optimization of tool change timing in a nut forming process using genetic algorithms

In this study, we consider an optimization problem arising from tool change scheduling of a nut forming process. The process has nine punches with different life spans. The objective of the study is to optimize the tool change timing of the nine punches in order to maximize the production yield. The punch life spans can be extended by means of Ti coating, but coated punches are more expensive. We also evaluate whether it is worth using coated punches. A cost model is developed for the nut forming process. In the developed cost model, we consider the reliability of the nine punches, the periods taken for changing punches, scrap cost and production yield. The cost function for the process is complex, and is difficult to be solved using conventional optimization methods. Therefore, genetic algorithms are used to solve the problems. We have developed our own genetic algorithms using Java programs and applied the developed genetic algorithms to provide solutions to the optimization problem.     

钢管焊缝射线透视检验系统的研制

介绍了一种应用于钢管焊接接头检验的射线透视系统的设计原理与实现方法。通过MeteorⅡ／Digital图像采集卡和编制的图像处理软件WZL-1实现了实时采集和处理X射线透视图像。经过生产运用表明，该系统的分辨力可达到5．01p／mm，检验一个焊接接头所需时间平均约为20s，其性能优于目前市场上的同类系统。     

Optimization of hybrid steel plate girders

An efficient procedure is presented for minimum weight design of unstiffened and stiffened hybrid steel plate girders subjected to arbitrary loading using the General Geometric Programming technique. The nonlinear optimization problem is formulated on the basis of the current American Institute of Steel Construction specification. Four examples are presented to show the application of the algorithm for practical optimization of hybrid steel plate girders.     

Application of genetic algorithm to external noise cancellation and compensation in automatic arc welding system

This paper develops an automatic welding control system which uses a genetic algorithm to carry out external noise cancellation and compensation. In the proposed approach, the genetic algorithm is used to identify the polynomial form or parameters of the external force or disturbance, including the amplitude, frequency and phase to compensate for nonlinear phenomenon such as disturbance in the mechanical system. In compensating for the nonlinear phenomenon, a piecewise linearization of the approximation polynomial is performed and the genetic algorithm optimization process is then used to identify the parameters of the polynomial function. The simulation and experimental results confirm that the proposed automatic welding control system provides an effective means of compensating for the effects of the external force or disturbance and therefore results in an enhanced welding performance.     

Optimization of a plate with holes

We consider a simply supported plate with constant thickness, defined on an unknown multiply connected domain. We optimize its shape according to some given performance functional. Our method is of fixed domain type, easy to be implemented, based on a fictitious domain approach and the control variational method. The algorithm that we introduce is of gradient type and performs simultaneous topological and boundary variations. Numerical experiments are also included and show its efficiency.     

Analysis of an electrohydraulic servo system subject to Stribeck-type friction

The main objective of this paper is to study the phenomena of the electrohydraulic servo system under the influence of the Stribeck-type friction. Owing to the nonlinear nature of this friction, a sustained oscillation, or limit cycle, might appear in the system behaviour. The system is first divided into two parts, the linear and the nonlinear. For the nonlinear Stribeck-type friction, a flexible model is proposed to represent the whole friction family, and the describing function of this nonlinear friction is generated. The system characteristic equation is established by correlating the frequency response of the linear part and the describing function of the nonlinear part. The existence and stability of the limit cycle are predicted based on the characteristic equation. Finally, by using the sinusoidal, step and ramp input, respectively, the numerical simulation is adopted to observe the system response. All predicted limit cycles can be verified by the simulation results, and the effects of stable and unstable limit cycles are clarified. The dynamic characteristics obtained in this study help to bring insight into this important engineering configuration and throw some light on the possibilities for improvement.     

肋板结构外保温设计方法

为合理设计肋板外保温结构2层保温材料的厚度,采用稳态热平衡理论计算初步确定厚度方案,采用Abaqus软件对外保温结构进行仿真分析,结果认为规则部位内保温层与外保温层之间的界面温度满足工程要求,验证理论计算的合理性.保温层圆角过渡部位内保温层与外保温层之间界面温度不满足设计要求,采用Abaqus优化模块对局部尺寸进行优化...