Flowserve (Germany)

Designing an industrial robotic structure is known to be a complex endeavor, owing to the different product specifications that must be met, while taking several constraints of the system’s structure such as weight limitations into consideration. In this work, an in-depth design approach is presented whereby theories of the mechanics of serial-linked robotic structures were critically investigated to adopt and present a concise analytical and computer-aided approach to the design of a 6-DOF industrial robotic structure. The CAE tools have come to make the job of design engineers incredibly easier, however, beyond just using these tools to obtain information about the system, it is necessary to set up a sufficiently representative mathematical model of the numerically simulated systems for verification purposes. Furthermore, by setting up and evaluating an analytical model, the engineer can easily vary the geometrical and natural parameters as well as the constraints within the system’s model to achieve an optimized structure according to the design expectation. One of such design requirements is attaining a sufficient stiffness of the robotic structure, within weight constraints to guard it from vibrations which could negatively impact its operational accuracy. To practically demonstrate this concept, numerical finite element analysis and mathematical modeling of the vibrations that could occur on the designed industrial robot’s link arm are presented in this study. The analytical procedure that is presented in this thesis report can be applied to both simplified robot model design, analysis, and verification, and it can also be adopted or serve as a basis for the design of a more complex robotic system than the one presented in this study.

Counter-rotating blade rows in single stage machines have been widely investigated in several applications like naval propulsion [1], axial fan [2] and axial pump design [3]. Previous publications have presented this design philosophy as a promising way to improve efficiency and cavitation performance [4]. Differently the goal of the presented design is to achieve lower required rotational speeds and at the same time a higher power density ratio, indirectly improving also the cavitation’s performance, aspiring actually to a compact design. However, a literature survey did not produce any evidence of significant advantage in axial-flow machines from this design philosophy in terms of machine power density. This paper presents a preliminary analysis of the applicability of the counter-rotating impeller concept on mixed-flow and radial-flow pumps. The design example presented in this paper constitutes a mixed-flow first rotor with a radial second rotor that rotates in opposite direction. A 1-D design model demonstrates that power density coefficient has a maximum for optimum speeds of the rotors range. The design example parameters were selected based on the highest power density coefficient and efficiency. Unlike most published literature where the rotor speed ratios are not fixed, instead the speeds can be independently varied through two separate electric drives. Both the front and rear rotor were developed using multi-streamline curvature analysis which combines fluid dynamic loss model [5] with a slip model at the rotor exit [6]. Several hypotheses were considered to determine the most significant and independent parameters that run through a response surface optimizer tool, scripted in MATLAB®. It detects optimum specific speed for the rotors which maximizes the benefits of counter-rotating impeller design compared to rotor-stator machine with same design point. Assuming steady numerical approximation error, the fitness function of the optimizer tool is based on steady state CFD results. The fitness function depends on total head and hydraulic efficiency, which show a maximum as a result. Optimum geometries were identified and one was chosen for manufacturing and testing in a test rig. Transient CFD analysis was also done to determine volute losses and incidence losses between first and second rotor and pressure pulsations generated. At this stage, manufacturing of hydraulic components of test model is in progress, while the mechanical design of the machine is close to completion.

Abstract This article discusses the five basic matrix structures in cast irons: ferrite, pearlite, bainite, martensite, and austenite. The alloying elements, used to enhance the corrosion resistance of cast irons, including silicon, nickel, chromium, copper, molybdenum, vanadium, and titanium, are reviewed. The article provides information on classes of the cast irons based on corrosion resistance. It describes the various forms of corrosion in cast irons, including graphitic corrosion, fretting corrosion, pitting and crevice corrosion, intergranular attack, erosion-corrosion, microbiologically induced corrosion, and stress-corrosion cracking. The cast irons suitable for the common corrosive environments are also discussed. The article reviews the coatings used on cast irons to enhance corrosion resistance, such as metallic, organic, conversion, and enamel coatings. It explains the basic parameters to be considered before selecting the cast irons for corrosion services.