Wei Xiao Tang

Friction Stir Welding of DH36 Steel

Abstract Hot rolled DH36 carbon steel, 6.4 mm in thickness, was friction stir welded at speeds of 3.4 mm s-1 (8 in min-1), 5.1 mm s-1 (12 in min-1), and 7.6 mm s-1 (18 in min-1). Single pass welds free of volumetric defects were produced at each speed. The relationships between welding parameters and weld properties are discussed. Optical microscopy, microhardness testing, and transverse and longitudinal tensile tests have been performed. Bainite and martensite are found in the nugget region of the friction stir welds whereas the base material is comprised of ferrite and pearlite. The maximum hardness is observed in the weld nugget, and the hardness decreases gradually from the weld nugget, through the heat affected zone, to the base metal. Tensile testing also indicates overmatching of the weld metal relative to the base metal. Maximum hardness and longitudinal (all weld metal) tensile strengths increase with increasing welding speeds. Weld transverse tensile strengths are governed by the base metal properties, as all transverse tensile bars fail in the base metal.

Relationships between weld parameters, hardness distribution and temperature history in alloy 7050 friction stir welds

Abstract Aluminium alloy 7050 was friction stir welded using three different ratios of tool rotation rate to weld travel speed. Welds were made using travel speeds of between 0·85 and 5·1 mm s−1. Weld power and torque were recorded for each weld. An FEM simulation was used to calculate the time–temperature history for a subset of the welds. For each weld the hardness distribution with and without post-weld heat treatment was determined. The hardness distributions within the welds are rationalised based on the friction stir welding parameters and the resulting temperature histories. The analysis provides a basis for manipulation of weld parameters to achieve desired properties.

Process response parameter relationships in aluminium alloy friction stir welds

Abstract In the present paper, an attempt has been made to link friction stir welding (FSW) process control and response variables. Substantial similarities among the relationships between torque, nugget grain size, x axis force and tool rotation rate have been elucidated for three different aluminium alloys. Comparison of the experimental work to results from process simulation indicates that in each case a temperature limit is reached above some critical value of tool rotation rate. A simple method of estimating the strain and strain rate in friction stir welds is presented. The flow stress during FSW is calculated from measured torque values and analysed with respect to aluminium alloy flow stresses measured in standard, high temperature torsion and tensile tests. Results indicate that perhaps either sticking friction conditions are not always applicable during FSW (on all or part of the tool) or that, above a critical tool rotation rate, intermittently lubricated contact is present due to local melting in the weld process zone.

Friction stir welding of single crystal aluminium

Abstract Friction stir welds were prepared in different orientations in an aluminium single crystal. The welds were quenched to preserve the microstructure surrounding the tool and then electron backscattered diffraction was used to reveal the generation of grain boundaries and the evolution of crystallographic texture around the tool in each weld. The extent of both dynamic recrystallisation and conventional recrystallisation varied considerably as a function of weld orientation. As the base plate begins to interact with the deformation field surrounding the tool, regions of the single crystal rotate to new crystal orientations, producing new grain boundaries in the process. These refined grains develop a {112}<110> texture closer to the tool. Large conventionally recrystallised grains sometimes form in the outer regions of the refined grain structure, but become ever more deformed as they approach the tool until they are indistinguishable from the surrounding material.

Structure dynamic modification and optimization for high-speed face milling cutter

Due to the complexity of high-speed milling process by high relative speed and interrupted cutting, the face milling cutters possess the multi-order modes and the vibrating displacements of the cutting edges under each modes affect adversely both the surface roughness and the life of machine/tool system worse than other structures. In order to improve the stability of milling process, this work focuses on the influence of the variables such as structure geometries and constraint conditions on the eigenfrequencies and modeshapes of cutter. As an example, the dynamic characteristics of several face cutters are analyzed and optimized by structural dynamic modification (SDM) techniques.

A New Variable Feedrate CNC Interpolator for Abrasive Waterjet System

It is becoming general that the contour of part is defined with free-form curves for abrasive waterjet cutting. In this paper, the effect of the traverse speed on cut surface quality is discussed. After that, the free-form Pythagorean Hodographs (PH) curve is defined and its main characteristics are discussed. A new CNC interpolator capable of driving the nozzle along the PH curves at the feedrate adaptable of the curvature of the contour is presented. The taper shape or jet lag can be minimized with it through the variation of the traverse speed. Experimental data indicate that a decrease of about 58 per cent in kerf taper angle can be obtained under a given condition.

Development of an Internet-Based Interactive Globoidal Indexing Cam Mechanisms Design System

This paper addresses the development of an internet-based interactive globoidal indexing design system and methods. We adopt a client/server architecture. The developed system uses Java as the programming language, Java3D as the graphics API and XML as the information exchange file format so as to provide the flexibility of interoperability on a variety of operating platforms. The system embeds the cam shape data of the B-spline model into the XML file. This enhances the profile representation of a cam, yet keeps the representation compact. The interactive cam optimization design methodology is integrated. The prototype system indicates that the system can serve as the effective tool for designing globoidal indexing cam mechanism with the better properties of interaction and expansion. Introduction Present day customer demands point towards a need for greater customization and for shorter product lead times. To meet this demand, new manufacturing concepts such as computer integrated manufacturing , agile Manufacturing and recently Internet-based manufacturing have been implemented. The ultimate aim of internet-based manufacturing is to resolve problems with heterogeneous manufacturing software products and create a seamless collaborative manufacturing environment. The globoidal indexing cam mechanisms are widely used in the industry. Typical applications can be found in conveyors, machine tools and assembly systems. In such a system, when it is in motion, the different load torque will induce different deflections and create vibrations. Under high speed condition, the load characteristics and special need of customers can influence on the dynamic performance of the indexing cam mechanism [1]. Therefore, it is very important that customers participate in design. An efficient globoidal indexing cam mechanisms design system is essential to cut costs and reduce the product lead-time. The globoidal indexing cam mechanisms design system based on web server should be able to timely transfer information between customer and producer to bring about a seamless product design and manufacturing environment [2]. System Architecture The developed system uses Java as the programming language, Java3D as the graphics API and XML as the information exchange file format so as to provide the flexibility of interoperability on a variety of operating platforms. The architecture of the developed system, shown in Fig. 1, is generally known as thin client/fat server architecture. In this architecture, there is a clear distinction between the client and the server share of program execution. The client serves as a means for user input and visualization of the 3D models. The server executes the various modeling operations and the database houses the modeling and mechanism elements data. Server. The database houses the solid mode files in Parasolid’s XML format. The functionality to retrieve information from the XML file and carry out polygonization of the model is provided by the Materials Science Forum Online: 2004-12-15 ISSN: 1662-9752, Vols. 471-472, pp 513-517 doi:10.4028/www.scientific.net/MSF.471-472.513

Web Based Virtual Design of Dynamics of Roller Gear Cam System

The remote virtual design system based on B/S framework is investigated in the paper. On reviewing the current virtual design system situation, the control system dynamics simulation is integrated into the virtual design system of roller gear cam mechanism. Simulink and Matlabserver are employed to realize the dynamics simulation for the system, and COM and VRML technologies are used to browse the virtual model on the network platform. The prototype system indicates that the system can serve as an effective tool for designing roller gear cam mechanism with the better properties of interactive dynamics performance design and expansion usage.

Balancing of Tool/Toolholder Assembly for High-Speed Machining

High-speed machining has become mainstream in machining manufacturing industry. In industries such as moldmaking and aerospace, it has become the norm rather the exception. The centrifugal force increases as the square of the speed. At rotational spindle speeds of 6,000 r/min and higher however, centrifugal force from unbalance becomes a damaging factor and it reduces the life of the spindle and the tool, as well as diminishes the quality of the finished product. Under high rotational speed, good balance becomes issue. High-speed machining experimental results shown that a well-balanced tool/toolholder assembly could obviously improve machining quality, extend tool life and shorten downtime for spindle system maintenance etc.