Process modelling of linear friction welding (LFW) between AA2124/SICp composite and unreinforced alloy

In the present study, the Linear Friction Welding (LFW) process between a bar of Metal Matrix Composite (MMC) AMC225xe (AA2124 with 25% SiC particulate reinforcement) and a bar of unreinforced base alloy was simulated using the commercial finite element package ABAQUSTM. Fully coupled implicit thermo-mechanical analysis procedure was employed, with semi-automatic re-meshing using Python scripting and output database scripting methods for extracting deformed configurations. Due to the large deformation near the weld region, multiple analyses were carried out between each re-meshing stage in order to limit the element distortion. Comparison of the simulation results with the experimental data collected during welding, and with post-weld optical section micrograph has shown satisfactory agreement

Analysis of increasing torque with recurrent slip in interference-fits

Previous research associated with interference-fitted assemblies has shown that as recurring slip occurs (i.e. load to total slip, unloading and reload to total slip) there is an observed increase in the holding torque after each loading cycle. The aim of this work was to identify the reasons for this ‘torque strengthening’ phenomenon. The work also has industrial relevance in the optimum design of interference-fitted rolls used for the hot rolling of steel sections. Previous work has shown that the major contributors to the overall holding torque were the interface pressure, material properties and the coefficient of friction between component materials. In this work, neutron diffraction tests and crack compliance tests showed no correlation between the interface pressure and increased holding torque. Meanwhile, experimental holding torque tests on sample interference-fits showed that for each recurring holding torque failure (slip) in a test cycle, the holding torque increased. Subsequent wear investigations showed that the wear of the surfaces increased throughout the testing and once a specific type of wear had occurred through a ‘ploughing’ mechanism, significant damage could be done to the more expensive shaft component. These observations suggest that an effective increase in the coefficient of friction between shaft and hub is responsible for the increase in holding torque, while the same level of interface pressure is maintained throughout slipping. The research provides a basis for the optimisation of interference-fit design in order that the working lives of expensive shafts, which are prone to damage through ploughing, and brittle hubs, which are prone to sudden fracture, are maximised when experiencing recurrent slipping

The application of geometry corrections for Diffraction Strain Tomography (DST) analysis of a Ni-base superalloy blade

X-ray diffraction is commonly used for non-destructive and precise quantitative determination of internal strain distributions. In recent years tomographic imaging has also been established as a powerful tool for precise non-destructive evaluation of internal structure in materials offering submicron resolution 3D imaging of density distributions. Diffraction Strain tomography (DST) concept (Korsunsky, Vorster et al. 2006) has been introduced as a means of tomographic reconstruction of two-dimensional internal strain distributions. The application of this approach during in situ loading has been subsequently demonstrated (Korsunsky et al., 2011). In the present study, similar acquisition strategy was used for diffraction data collection from a Ni-base superalloy turbine blade fabricated by DMLS (Direct Metal Laser Sintering, also sometimes referred to as DLD, Direct Laser Deposition). The experiment was conducted on beamline I12 (JEEP) at Diamond Light Source, UK. Each location within the object was multiply sampled (i.e. diffraction patterns were collected containing its contribution) by incident X-ray beams travelling through the sample at different angles. The setup of the beamline also allowed to acquire simultaneously a conventional (absorption tomography) reconstruction of the sample shape. The aim of the experiment was to obtain detailed information about the sample shape, structure, and state. The interpretation of diffraction tomography data requires precise calibration of the sample detector distance at different rotations and positions across the sample, and subsequent application of corrections to remove geometry-induced strain aberrations. © 2013 JCPDS-ICDD

Texture analysis in cubic phase polycrystals by single exposure synchrotron X-ray diffraction

We discuss the possibility of determining orientation distribution function (ODF) of cubic phase polycrystals from single exposure Debye-Scherrer diffraction data by a systematic numerical simulation. The fundamental zone of cubic phase crystals is discretised as 5°× 5° × 5° cubic cells, and the aim is to find out those preferred orientations represented by the cells centres which cannot be determined by single exposure Debye-Scherrer diffraction data. Two simulated ODFs corresponding to two different types of linear combination of single preferred orientations are used to validate if the method is suitable for more complicated textures. A data processing routine as well as experimental procedure that enable texture evaluation in metallic cubic phase polycrystals by single exposure high energy monochromatic synchrotron X-ray diffraction with area detector is presented. MTEX is used to estimate ODFs from both single exposure and multi-exposure 2D diffraction patterns. An extruded tungsten wire and a copper cylinder machined from a rolled plate are used to illustrate the whole method. Careful error comparison is made between the ODFs obtained from single exposure and multi-exposure data. Besides, all the diffraction patterns are processed by MAUD to provide a comparison to the MTEX approach, and good agreement is seen between ODFs produced by MAUD and MTEX. © 2013 AIP Publishing LLC

Numerical simulation and experimental validation of texture in extruded wires of a BCC metal

We present a comparison between a viscoplastic crystal plasticity finite element simulation of the extrusion process applied to a bcc polycrystal and the experimental evaluation of the preferred orientation (texture) in a tungsten wire by monochromatic synchrotron X-ray diffraction with an area detector. We perform a numerical simulation of sample texture evolution during large extrusion deformation with the elongation factor up to the value of fifty. By matching the predicted Orientation Distribution Functions (ODF) and the pole figures generated on the basis of the simulations to the experimental observations, the extrusion strain experienced by the sample during processing can be estimated

The application of geometry corrections for Diffraction Strain Tomography (DST) analysis of a Ni-base superalloy blade

X-ray diffraction is commonly used for non-destructive and precise quantitative determination of internal strain distributions. In recent years tomographic imaging has also been established as a powerful tool for precise non-destructive evaluation of internal structure in materials offering submicron resolution 3D imaging of density distributions. Diffraction Strain tomography (DST) concept (Korsunsky, Vorster et al. 2006) has been introduced as a means of tomographic reconstruction of two-dimensional internal strain distributions. The application of this approach during in situ loading has been subsequently demonstrated (Korsunsky et al., 2011). In the present study, similar acquisition strategy was used for diffraction data collection from a Ni-base superalloy turbine blade fabricated by DMLS (Direct Metal Laser Sintering, also sometimes referred to as DLD, Direct Laser Deposition). The experiment was conducted on beamline I12 (JEEP) at Diamond Light Source, UK. Each location within the object was multiply sampled (i.e. diffraction patterns were collected containing its contribution) by incident X-ray beams travelling through the sample at different angles. The setup of the beamline also allowed to acquire simultaneously a conventional (absorption tomography) reconstruction of the sample shape. The aim of the experiment was to obtain detailed information about the sample shape, structure, and state. The interpretation of diffraction tomography data requires precise calibration of the sample detector distance at different rotations and positions across the sample, and subsequent application of corrections to remove geometry-induced strain aberrations. © 2013 JCPDS-ICDD

A review of recent in situ deformation studies using synchrotron X-ray (Micro) beams

The advent of (sub)microscopic focused X-ray beams at third generation synchrotron sources has opened up possibilities for the characterisation of material structure and mechanical behaviour with unprecedented spatial resolution. Crucially, the non-destructive nature and fast rate of X-ray data collection allow in situ deformation to be studied. In this review, we concentrate on the inelastic deformation response of ductile metallic (poly)crystals. We describe a range of diffraction-based techniques we have developed including monochromatic beam reciprocal space mapping, scanning "pink" beam micro-diffraction compound topography, and white beam Laue micro-diffraction. We compare the results obtained using each of the above techniques, and assess and review the insights that they afford into micro-scale material deformation. © 2012 Bentham Science Publishers

PROCESS MODELLING OF LINEAR FRICTION WELDING (LFW) BETWEEN AA2124/SICP COMPOSITE AND UNREINFORCED ALLOY

In the present study, the Linear Friction Welding (LFW) process between a bar of Metal Matrix Composite (MMC) AMC225xe (AA2124 with 25% SiC particulate reinforcement) and a bar of unreinforced base alloy was simulated using the commercial finite element package ABAQUS TM. Fully coupled implicit thermo-mechanical analysis procedure was employed, with semi-automatic re-meshing using Python scripting and output database scripting methods for extracting deformed configurations. Due to the large deformation near the weld region, multiple analyses were carried out between each re-meshing stage in order to limit the element distortion. Comparison of the simulation results with the experimental data collected during welding, and with post-weld optical section micrograph has shown satisfactory agreement

X-ray texture analysis and imaging of engineering materials at oxford HEX-lab

At the High Energy X-ray laboratory (HEX-lab, Department of Engineering Science, University of Oxford, UK) we carry out studies of deformation and structure of engineering materials and components. Laboratory and synchrotron X-ray beams provide the principal means of analysis and measurement. A variety of other techniques are also in use. We present a range of applications and case studies in high performance engineering materials

Numerical simulation and experimental validation of texture in extruded wires of a BCC metal

We present a comparison between a viscoplastic crystal plasticity finite element simulation of the extrusion process applied to a bcc polycrystal and the experimental evaluation of the preferred orientation (texture) in a tungsten wire by monochromatic synchrotron X-ray diffraction with an area detector. We perform a numerical simulation of sample texture evolution during large extrusion deformation with the elongation factor up to the value of fifty. By matching the predicted Orientation Distribution Functions (ODF) and the pole figures generated on the basis of the simulations to the experimental observations, the extrusion strain experienced by the sample during processing can be estimated