铝合金挤压工模具技术的现状与发展趋势

从模具新材料的开发与应用、模具设计结构的研制与开发,模具CAD/CAM/CAE技术的发展、模具复合加工技术的开发和应用、模具自动加工系统的研制与开发、激光加工在模具制造中的应用、研磨抛光技术的发展、模具标准化的发展趋向及模具制造行业的发展动向等方面对现代挤压工模具生产技术的发展动向进行了较系统的分析讨论。

航天工模具的价值分析

在价值分析中,产品的价值是指其功能与成本的比较.价值=功能/成本.进行价值分析,就是以最低限度的成本,实现产品的必要功能,亦即通过各种途径尽量提高产品的价值.目前在航天工模具设计、创造过程中除必要功能外,还出现了不必要的功能.具体反映在:①不适当地加大安全系数;②一般用途的零件采用优质钢材;③所规定的公差、表面粗糙度超过工模具适用性的要求.航天工模具总成本与功能的关系由下图表示.

国内外铝挤压工模具技术

本文简略地论述了工模具在铝合金挤压生产中的重要作用与特殊地位:介绍了铝挤压工模具技术的主要内容;着重分析了国内外挤压工模具设计制造水平及创新亮点,以及铝挤压工模具的使用、修理、氮化技术及现代化管理工具。

有关设计规范编制中技术问题的处理

结合4项工模具设计规范的编制,对有关工模具设计中的模具部件配合、收缩率的选择、闭模间隙、导向定位机构的作用作了具体介绍,同时谈了几点工作体会。

Fabrication of fine-grained,high strength and toughness Mg alloy by extrusion−shearing process

A novel extrusion-shearing(ES) composite process was designed to fabricate fine-grained, high strength and tough magnesium alloy. The structural parameters of an ES die were optimized by conducting an orthogonal simulation experiment using finite element software Deform-3D, and Mg-3 Zn-0.6 Ca-0.6 Zr(ZXK310) alloy was processed using the ES die. The results show that the optimized structural parameters of ES die are extrusion angle(α) of 90°, extrusion section height(h) of 15 mm and inner fillet radius(r) of 10 mm. After ES at an extrusion temperature and a die temperature of 350 °C, ZXK310 alloy exhibited good ES forming ability, and obvious dynamic recrystallization occurred in the forming area. The grain size decreased from 1.42 μm of extrusion area to 0.85 μm of the forming area. Owing to the pinning of second phase and formation of ultrafine grains, the tensile strength, yield strength and elongation of alloy reached 362 MPa, 289 MPa and 21.7%, respectively.

Nonlinear State Feedback Control of PEM Fuel Cell Systems

In this paper, the nonlinear state feedback controller has been developed to control the pressures of the oxygen and the hydrogen in the PEM（Proton Exchange Membrane） fuel cell system. Nonlinear model of the PEM fuel cell system was introduced to study the design problems of the state observer and model based controller. A cascade observer using the filtering technique was used to estimate the pressure derivatives of the cathode and the anode in the system. In order to estimate the pressures of the cathode and the anode, the sliding mode observer was designed by using these pressure derivatives. To estimate the oxygen pressure and the hydrogen pressure in the system, the nonlinear state observer was designed by using the cathode pressure estimates and the anode it. These results will be very useful to design the state feedback controller. The validity of the proposed observers and the controller has been investigated by using a Lyapunov＇s stability analysis strategy.

Analysis and Design of Flexible Pavements by Empirical Tools

This paper falls into two parts. In the first part, the widely used analytical-empirical method of pavement design and evaluation is discussed and in the second part two simulation models are presented to predict the design of flexible pavement. Analytical results are compared with simulation models.

Design of a Simulation Tool for Steam Assisted Gravity Drainage： Based on the Concept of Unified Feature Modeling Scheme

CPS （cyber-physics system） engineering brings new revolutionary opportunities for multi-disciplinary and complex processes, like oil extraction from oil sands. Based on an established unified feature modeling scheme, a software modeling framework to simulate the process of SAGD （steam-assisted gravity drainage） is proposed. The main purpose of this work was to apply CPS in the complex production engineering informatics modeling as it applied to SAGD. Existing physics models and simulation algorithms for main SAGD phenomena were reviewed, and an integrated ontology model via a feature-based approach has been developed. Conservation laws were used as the governing principles, while the transport phenomena were modelled via the primary phenomenon features. The representation of typical data flows targeting to the functional simulation scenarios by applying the concept of phenomenon features was also done. The definition of this feature type represents a new expansion of the emerging unified feature scheme for engineering software modeling. Slotted liners were taken as the well-completion option and their design and specifications were included in the case study model. The unique representation of the planned software design is developed and expressed with graphical diagrams of the UML （unified modelling language） convention.

Measuring Contribution of BIM （Building Information Modeling） to the Construction Sustainability Goals

＂BIM （building information modeling）＂ and ＂sustainability＂ are two frequently used words in construction and academia today. BIM is a design-oriented tool, which generates a virtual three-dimensional model of a project. Sustainability refers to prudent use of earth＇s natural resources, and construction sustainability is the application of this principle to building activities. Societies in general and the construction industry in particular--one of the largest in terms of natural resources consumed and waste produced--place high hopes on BIM and the principles of sustainability to reduce consumption and waste and to increase industry productivity. BIM＇s capabilities and limitations, currently more focused on model creation and energy simulations, are not well understood as they relate to construction sustainability and its goals. No method yet exists to evaluate BIM＇s contribution comprehensively to construction sustainability goals. This study presents a construction sustainability goals contribution matrix for BIM. The matrix indicates that this contribution may be more limited than it is commonly thought.

Implementation of Cooling Systems to Enhance Dairy Cows＇ Microenvironment

A tool was developed to assist the cooling systems designer in designing and installing the microsprinklers and fan cooling system. The tool was developed by integrating a mathematical model into an electronic spark map in order to use the mathematical model practically. The mathematical model was developed using the designs, parameters, variables, and constant values of the microsprinklers and fans cooling system. Subsequently, an electronic spark map （decision tree） was developed, and then the mathematical model was integrated into the electronic spark map. Afterwards, C# （C Sharp） programming language was used to develop a computer system via the electronic spark map, and to make the user interface. The developed computer system assists the designer in making decisions to specify and to calculate the required discharge of cooling system pump, length and diameter of cooling system pipelines, number of cooling fans, and number of microsprinklers. Moreover, this tool calculates the capital investment and the fixed, variable, and total costs of the cooling system. However, the mathematical model of the spark map requires some input data such as： pressure and discharge of microsprinklers, and some other engineering parameters. Data of 4 cooling systems were used to carry out the model validation. The differences between actual and calculated values were determined, and the standard deviations were calculated. The coefficients of variation were between 2.25% and 4.13%.

The Principle of Square Hole Machining and It＇s Tooling Structure Design

In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.

A Review of Modeling Approaches and Tools for the Off-design Simulation of Organic Rankine Cycle

Organic Rankine Cycles(ORCs) are an effective way to produce electricity from low-grade heat sources, which cannot be effectively obtained using conventional high-temperature Rankine cycles. Due to the lack of available information regarding the real Organic Rankine Cycle units on industrial level, off-design simulation under diversified operating conditions plays a significant role for both the system performance prediction and control strategy design. This paper summarizes the theoretical basis, modeling approaches and tools for ORC off-design simulations. Firstly, a review was conducted on the individual state-of-the-art convective heat transfer correlations and void fraction models. Secondly, different kinds of modeling approaches and simulation tools were proposed, highlighting their relevant characteristics, and were categorized for their specific applications. Moreover, an in-depth analysis of technical challenges related to various applications and focusing on the model accuracy and complexity, computational efficiency, as well as the model compatibility were extensively described and discussed. Finally, the current research trends in this field and the development for further investigations were presented.

An elastic-plastic contact model for line contact structures

Although numerical simulation tools are now very powerful,the development of analytical models is very important for the prediction of the mechanical behaviour of line contact structures for deeply understanding contact problems and engineering applications.For the line contact structures widely used in the engineering field,few analytical models are available for predicting the mechanical behaviour when the structures deform plastically,as the classic Hertz’s theory would be invalid.Thus,the present study proposed an elastic-plastic model for line contact structures based on the understanding of the yield mechanism.A mathematical expression describing the global relationship between load history and contact width evolution of line contact structures was obtained.The proposed model was verified through an actual line contact test and a corresponding numerical simulation.The results confirmed that this model can be used to accurately predict the elastic-plastic mechanical behaviour of a line contact structure.