The inelastic response of materials to applied uniaxial loading is typically measured using tensile or compressive specimens of an initially circular cross-section. Under deformation, this cross-section may become elliptical due to anisotropic material behaviour. An optical technique for measuring the elliptical deformation of anisotropic, homogeneous cylindrical specimens undergoing uniaxial deformation is presented. It enables the quantification of anisotropic deformation in situ and provides data for material characterization. Three or more silhouette views of a specimen are obtained using multiple cameras or mirrored views. The positions of the edges are computed using a sub-pixel edge detection method, and 3D tangent rays from the camera through these positions are calculated. These bounding tangents are used as the basis for an elliptical fit by least squares at cross-sections along the length of the specimen. Stochastic error estimates are performed by simulation of the experiment. Error estimates, for the experimental set-up used, are also calculated by reconstructing elliptical prisms of precisely measured dimensions. Example reconstructions from specimens of rolled titanium deformed plastically in tension at quasi-static (7 × 10−4 s−1) and high strain rates (3 × 103 s−1) are presented.

Ring-rolling is an industrial forming process to produce high-strength metal rings up to 6m diameter. Thickwalled cylindrical workpieces of material, typically metallic alloys, are compressed between two or more internal and external rollers and rotated until a target geometry, often outer diameter, is achieved. The process is inherently unstable and the process is often constrained and/or controlled to improve its stability. This paper presents an image processing algorithm for the measurement of ring geometry through photogrammetry in real-time. These measurements will form part of the feedback control system for a ring-rolling process. An off-the-shelf USB webcam is used to capture images of the ring during forming and the scene is controlled to maximise contrast and minimise occlusions of the ring. The image processing tasks include object identification, edge detection, outlier rejection and distortion rectification. The process has been implemented on a desktopscale forming machine and has been shown to work at rates suitable for control the ring-rolling process using feedback.

This paper presents a novel approach to the classic Taylor impact experiment using an ultra-high-speed camera and mirror arrangement to measure the elliptical cross-section of a specimen in situ as a function of time. This optical measurement technique is used to quantify the key aspects of material behaviour, such as the area strain perpendicular to the impact direction and the lengths of the semimajor and semiminor axes of the elliptical sample cross-section, which were caused by anisotropic plastic deformation, as functions of time and the axial position. The application of this technique gives access to previously unattainable data on the anisotropic plastic deformation of Taylor impact specimens and therefore has the potential to provide a more rigorous method of validation for anisotropic constitutive material models. To demonstrate the feasibility of the new method, experiments were carried out on cylindrical Taylor impact specimens machined from strongly textured high-purity zirconium plate. The surface geometry of a recovered specimen was measured using a coordinate measurement machine and compared with the optically measured surface geometry reconstructed from post-impact images. Excellent agreement between the two methods was found

Ring-rolling is an industrial forming process for producing high-strength seamless metal rings up to 6m diameter. Thick-walled cylindrical rings of material, typically metallic alloys, are compressed between two or more internal and external rollers and rotated until a target geometry, often outer diameter, is achieved. A common plant configuration is that of a pair of radially acting rollers and a pair of axial rollers, the radial-axial ring rolling (RARR) machine. The most commonly produced product geometries have an axisymmetric cross-section profile. However, during the forming process the cross section is changed significantly as it passes through each pair of rollers. This irregular shape hinders geometry state measurement and this complicates modelling and control of the process. Recent developments in sensing capabilities offer high resolution measurement of ring geometry during forming. In this work, we present advances in these sensing techniques, a numerical method for storing and predicting the ring's geometrical state and control laws to achieve a nonaxisymmetric cross-section profile in rolled rings using existing RARR plant hardware.

Ring rolling processes today produce axisymmetric rings, wasting material, energy and labour if non-axisymmetric components such as eccentric bearing races and bossed pipe fittings are required. A new process is proposed to roll rings with variable wall thickness. In this work, roll gaps and speeds are controlled online in physical experiments to achieve a defined variable wall thickness, enabled by photogrammetry to capture the ring's shape and position. The trials revealed two new process limits for which new analytical explanations have been developed: a maximum rate of change of thickness around the circumference and a loss of circularity. Rolling, Process-Control, Ring Rolling.