Methods of measuring residual stresses in components

Residual stresses occur in many manufactured structures and components. Large number of investigations have been carried out to study this phenomenon and its effect on the mechanical characteristics of these components. Over the years, different methods have been developed to measure residual stress for different types of components in order to obtain reliable assessment. The various specific methods have evolved over several decades and their practical applications have greatly benefited from the development of complementary technologies, notably in material cutting, full-field deformation measurement techniques, numerical methods and computing power. These complementary technologies have stimulated advances not only in measurement accuracy and reliability, but also in range of application; much greater detail in residual stresses measurement is now available. This paper aims to classify the different residual stresses measurement methods and to provide an overview of some of the recent advances in this area to help researchers on selecting their techniques among destructive, semi destructive and non destructive techniques depends on their application and the availabilities of those techniques. For each method scope, physical limitation, advantages and disadvantages are summarized. In the end this paper indicates some promising directions for future developments

Roadmap on structured light

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version

SAMBA RECEPTION DESK: COMPROMISING AESTHETICS, FABRICATION AND STRUCTURAL PERFORMANCE WITH THE USE OF VIRTUAL AND PHYSICAL MODELS IN THE DESIGN PROCESS

The present paper describes an integrative design experiment in which different types of models were used in order to achieve a design that compromises aesthetics, lightness, fabrication, assembly and structural performance. It shows how an integrative aproach, through the use of both virtual and physical models, can provide valuable feedback in different phases of the design and fabrication process. It was possible to conclude that the design method used allowed solving many problems and had a significant impact in the resulting object

Demonstration Structure for a 3D Holographic Sensor

Coherixhttp://deepblue.lib.umich.edu/bitstream/2027.42/96205/1/me450f12project12_report.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/96205/2/me450f12project12_photo.jp

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 18)

Abstracts are cited for 120 patents and patent applications for patents introduced into the NASA scientific system during the period of July 1980 through December 1980. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or application for patent

Material and structural behaviour of metal 3D printed elements

Wire arc additive manufacturing (WAAM) is a metal 3D printing method that enables large-scale structural elements with complex geometry to be built in a relatively efficient and cost-effective manner, offering revolutionary potential to the construction industry. Fundamental experimental data on the material and structural behaviour of WAAM elements are however lacking. Therefore, a comprehensive experimental study into the material properties, the cross-section and the member buckling behaviour of WAAM elements has been conducted and is reported herein. Tensile tests on 137 WAAM steel coupons, covering different steel grades, finishes, thicknesses, extraction directions and locations, and deposition strategies, have been conducted. Microstructural characterisation has also been performed by means of optical microscopy (OM) and electron backscatter diffraction (EBSD). At the cross-section and member levels, four-point bending tests on 14 WAAM stainless steel tubular beams and flexural buckling tests on 18 WAAM stainless steel tubular columns have been undertaken, respectively. Owing to the geometric undulations inherent to the WAAM process, 3D laser scanning and digital image correlation (DIC) were employed in the material, beam and column testing programme to capture the geometric properties and deformation responses of the specimens, respectively. The present research focuses on WAAM elements subjected to predominantly static loading (rather than fatigue loading), with an emphasis on structural stability. The examined WAAM steels exhibited consistent, almost isotropic mechanical properties, a Young’s modulus comparable to conventionally-produced steel plates, marginally lower strength, reflecting the slower cooling conditions than is customary, and good ductility. To describe the full stress-strain response of WAAM steels, material models were proposed and validated against the tensile test results and further experimental data collected from the literature. Following the beam and column tests, the applicability of the current cross-section and column design provisions in EN 1993-1-4 and AISC 370, as well as the continuous strength method (CSM), to WAAM stainless steel elements was assessed by comparing the test results with the strength predictions. The comparisons highlighted the need to allow for the weakening effect of the inherent geometric undulations of WAAM elements, in order to achieve safe-sided strength predictions.Open Acces

Plasma deposition of constrained layer damping coatings

Plasma techniques are used to generate constrained layer damping (CLD) coatings on metallic substrates. The process involves the deposition of relatively thick, hard ceramic layers on to soft polymeric damping materials while maintaining the integrity of both layers. Reactive plasma sputter-deposition from an aluminium alloy target is used to deposit alumina layers, with Young's modulus in the range 77-220GPa and thickness up to 335 μ, on top of a silicone film. This methodology is also used to deposit a 40 μ alumina layer on a conventional viscoelastic damping film to produce an integral damping coating. Plasma CLD systems are shown to give at least 50 per cent more damping than equivalent metal-foil-based treatments. Numerical methods for rapid prediction of the performance of such coatings are discussed and validated by comparison with experimental results

Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences