Indentation Plastometry for Study of Anisotropy and Inhomogeneity in Maraging Steel Produced by Laser Powder Bed Fusion

This work concerns the use of profilometry-based indentation plastometry (PIP) to obtain mechanical property information for maraging steel samples produced via an additive manufacturing route (laser powder bed fusion). Bars are produced in both “horizontal” (all material close to the build plate) and “vertical” (progressively increasing distance from the build plate) configurations. Samples are mechanically tested in both as-built and age-hardened conditions. Stress–strain curves from uniaxial testing (tensile and compressive) are compared with those from PIP testing. Tensile test data suggest significant anisotropy, with the horizontal direction harder than the vertical direction. However, systematic compressive tests, allowing curves to be obtained for both build and transverse directions in various locations, indicate that there is no anisotropy anywhere in these materials. This is consistent with electron backscattered diffraction results, indicating that there is no significant texture in these materials. It is also consistent with the outcomes of PIP testing, which can detect anisotropy with high sensitivity. Furthermore, both PIP testing and compression testing results indicate that the changing growth conditions at different distances from the build plate can lead to strength variations. It seems likely that what has previously been interpreted as anisotropy in the tensile response is in fact due to inhomogeneity of this type

Indentation Plastometry of Welds

This investigation concerns the application of the profilometry-based indentation plastometry (PIP) methodology to obtain stress–strain relationships for material in the vicinity of fusion welds. These are produced by The Welding Institute (TWI), using submerged arc welding to join pairs of thick steel plates. The width of the welds varies from about 5 mm at the bottom to about 40–50 mm at the top. For one weld, the properties of parent and weld metal are similar, while for the other, the weld metal is significantly harder than the parent. Both weldments are shown to be approximately isotropic in terms of mechanical response, while there is a small degree of anisotropy in the parent metal (with the through-thickness direction being slightly softer than the in-plane directions). The PIP procedure has a high sensitivity for detecting such anisotropy. It is also shown that there is excellent agreement between stress–strain curves obtained using PIP and via conventional uniaxial testing (tensile and compressive). Finally, the PIP methodology is used to explore properties in the transition regime between weld and parent, with a lateral resolution of the order of 1–2 mm. This reveals variations on a scale that would be very difficult to examine using conventional testing

Indentation Plastometry of Particulate Metal Matrix Composites, Highlighting Effects of Microstructural Scale

Herein, it is concerned with the use of profilometry-based indentation plastometry (PIP) to obtain mechanical property information for particulate metal matrix composites (MMCs). This type of test, together with conventional uniaxial testing, has been applied to four different MMCs (produced with various particulate contents and processing conditions). It is shown that reliable stress–strain curves can be obtained using PIP, although the possibility of premature (prenecking) fracture should be noted. Close attention is paid to scale effects. As a consequence of variations in local spatial distributions of particulate, the “representative volume” of these materials can be relatively large. This can lead to a certain amount of scatter in PIP profiles and it is advisable to carry out a number of repeat PIP tests in order to obtain macroscopic properties. Nevertheless, it is shown that PIP testing can reliably detect the relatively minor (macroscopic) anisotropy exhibited by forged materials of this type

A review of recent work on discharge characteristics during plasma electrolytic oxidation of various metals

The review describes recent progress on understanding and quantification of the various phenomena that take place during plasma electrolytic oxidation, which is in increasing industrial use for production of protective coatings and other surface treatment purposes. A general overview of the process, and some information about usage of these coatings, are provided in the first part of the review. The focus is then on the dielectric breakdown that repeatedly occurs over the surface of the work-piece. These discharges are central to the process, since it is largely via the associated plasmas that oxidation of the substrate takes place and the coating is created. The details are complex, since the discharge characteristics are affected by a number of processing variables. The inter-relationships between electrical conditions, electrolyte composition, coating microstructure and rates of growth, which are linked via the characteristics of the discharges, have become clearer over recent years and these improvements in understanding are summarized here. There is considerable scope for more effective process control, with specific objectives in terms of coating performance and energy efficiency, and an attempt is made to identify key points that are likely to assist this

Solidification cracking of aluminium alloys.

This thesis is not available on this repository until the author agrees to make it public. If you are the author of this thesis and would like to make your work openly available, please contact us: [email protected] Library can supply a digital copy for private research purposes; interested parties should submit the request form here: http://www.lib.cam.ac.uk/collections/departments/digital-content-unit/ordering-imagesPlease note that print copies of theses may be available for consultation in the Cambridge University Library's Manuscript reading room. Admission details are at http://www.lib.cam.ac.uk/collections/departments/manuscripts-university-archive

Profilometry‐Based Indentation Plastometry and Uniaxial Testing of Pipelines: Detection of In‐Plane Anisotropy and Potential for Simplification of Test Procedures

This article concerns anisotropy in stress–strain relationships exhibited by steel pipelines. Since the stress from internal pressurization is highest in the hoop direction, standard industrial practice to measure these properties has focussed on tensile testing in this direction, requiring a prior flattening operation. The associated plastic deformation may affect properties, typically causing a (poorly‐defined) degree of hardening and the creation of inhomogeneity. Field testing of such pipelines, requiring in situ measurement of tensile properties (yield stress (YS) and ultimate tensile stress (UTS)), is based on indentation testing of the outer surface. One such test (profilometry‐based indentation plastometry (PIP)), not only gives the stress–strain curve, but also allows detection of any (in‐plane) anisotropy, with a high sensitivity. Both PIP testing and compression testing (with and without prior flattening) have confirmed that none of the eight pipes examined in the current work exhibited any such anisotropy, although the effects of flattening did tend to generate apparent anisotropy in the tensile test outcomes. It may therefore be appropriate to switch the focus of tensile testing to the axial direction, such that no flattening would be required.</jats:p

Profilometry‐Based Indentation Plastometry and Uniaxial Testing of Pipelines: Detection of In‐Plane Anisotropy and Potential for Simplification of Test Procedures

Publication status: PublishedThis article concerns anisotropy in stress–strain relationships exhibited by steel pipelines. Since the stress from internal pressurization is highest in the hoop direction, standard industrial practice to measure these properties has focussed on tensile testing in this direction, requiring a prior flattening operation. The associated plastic deformation may affect properties, typically causing a (poorly‐defined) degree of hardening and the creation of inhomogeneity. Field testing of such pipelines, requiring in situ measurement of tensile properties (yield stress (YS) and ultimate tensile stress (UTS)), is based on indentation testing of the outer surface. One such test (profilometry‐based indentation plastometry (PIP)), not only gives the stress–strain curve, but also allows detection of any (in‐plane) anisotropy, with a high sensitivity. Both PIP testing and compression testing (with and without prior flattening) have confirmed that none of the eight pipes examined in the current work exhibited any such anisotropy, although the effects of flattening did tend to generate apparent anisotropy in the tensile test outcomes. It may therefore be appropriate to switch the focus of tensile testing to the axial direction, such that no flattening would be required.</jats:p

Research data supporting "A methodology for obtaining plasticity characteristics of metallic coatings via instrumented indentation"

This is supporting data to "A Methodology for Obtaining Plasticity Characteristics of Metallic Coatings via Instrumented Indentation", which will be published in the International Journal of Solids and Structures.Indentation finite element models"This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/I038691/1]" EPSR

Indentation Plastometry for study of anisotropy and Inhomogeneity in maraging steel produced by laser powder bed fusion

This work concerns the use of profilometry-based indentation plastometry (PIP) to obtain mechanical property information for maraging steel samples produced via an additive manufacturing route (laser powder bed fusion). Bars are produced in both “horizontal” (all material close to the build plate) and “vertical” (pro?gressively increasing distance from the build plate) configurations. Samples are mechanically tested in both as-built and age-hardened conditions. Stress–strain curves from uniaxial testing (tensile and compressive) are compared with those from PIP testing. Tensile test data suggest significant anisotropy, with the horizontal direction harder than the vertical direction. However, systematic compressive tests, allowing curves to be obtained for both build and transverse directions in various locations, indicate that there is no anisotropy anywhere in these materials. This is consistent with electron backscattered diffraction results, indicating that there is no significant texture in these materials. It is also consistent with the outcomes of PIP testing, which can detect anisotropy with high sensitivity. Furthermore, both PIP testing and compression testing results indicate that the changing growth conditions at different distances from the build plate can lead to strength variations. It seems likely that what has previously been interpreted as anisotropy in the tensile response is in fact due to inhomogeneity of this type </p

Indentation plastometry of welds

This investigation concerns the application of the profilometry-based indentation plastometry (PIP) methodology to obtain stress–strain relationships for material in the vicinity of fusion welds. These are produced by The Welding Institute (TWI), using submerged arc welding to join pairs of thick steel plates. The width of the welds varies from about 5 mm at the bottom to about 40–50 mm at the top. For one weld, the properties of parent and weld metal are similar, while for the other, the weld metal is significantly harder than the parent. Both weldments are shown to be approximately isotropic in terms of mechanical response, while there is a small degree of anisotropy in the parent metal (with the through-thickness direction being slightly softer than the in-plane directions). The PIP procedure has a high sensitivity for detecting such anisotropy. It is also shown that there is excellent agreement between stress–strain curves obtained using PIP and via conventional uniaxial testing (tensile and compressive). Finally, the PIP methodology is used to explore properties in the transition regime between weld and parent, with a lateral resolution of the order of 1–2 mm. This reveals variations on a scale that would be very difficult to examine using conventional testing