Ultrasonic Fatigue Analysis on Steel Specimen with Temperature Control : Evaluation of Variable Temperature Effect

Non peer reviewe

In-Service Performance of Emergency Shutdown Valves and Dependent Operational Relationships in the Offshore Oil and Gas Industry

Industrial process plants use emergency shutdown valves (ESDVs) as safety barriers to protect against hazardous events, bringing the plant to a safe state when potential danger is detected. These ESDVs are used extensively in offshore oil and gas processing plants and have been mandated in the design of such systems from national and international standards and legislation. This paper has used actual ESDV operating data from four mid/late life oil and gas production platforms in the North Sea to research operational relationships that are of interest to those responsible for technical management and operation of ESDVs. The first of the two relationships is between the closure time (CT) of the ESDV and the time it remains in the open position, prior to the close command. It has been hypothesised that the CT of the ESDV is affected by the length of time that it has been open prior to being closed (Time since last stroke). In addition to the general analysis of the data series, two sub-categories were created to further investigate this possible relationship for CT and these are “above mean” and “below mean”. The correlations (Pearson’s based) resulting from this analysis are in the “weak” and “very weak” categories. The second relationship investigated was the effect of very frequent closures to assess if this improves the CT. ESDV operational records for six subjects were analysed to find closures that occurred within a twenty-four hour period of each other. However, no discriminating trend was apparent where CT was impacted positively or negatively by the frequent closure group. It was concluded that the variance of ESDV closure time cannot be influenced by the technical management of the ESDV in terms of scheduling the operation of the ESDV

From Uniaxial to Multiaxial Ultrasonic Fatigue Component Frequency Modulation and Experiment

Ultrasonic fatigue experiments demand meticulous monitoring, control, and precise measurement equipment, alongside rigorous design considerations for all present components. Ultrasonic fatigue testing (UTF) has continuously evolved towards proven methodology that is simpler, more reliable, and therefore standardizable. This study addresses the challenges and limitations inherent in UTF with regards to the specimen design and modulation. Analytical and computational methods prevalent in published research on specimen and ultrasonic component design are discussed. All discussed challenges are greatly enhanced when regarding multiaxial ultrasonic fatigue. Ultrasonic machine components and specimen setup must resonate at explicit high frequencies, exhibiting the desired mode shapes that induce targeted stresses. The interconnection between components, the desired frequency and associated mode shape, and the displacement-to-strain relationship are critical to successfully execute and monitor any ultrasonic fatigue experiment. Furthermore, this study dwells in a new proposed intricate semi-analytical formulation model for ultrasonic specimen geometries catered towards both uniaxial and multiaxial specimens. The significance of this work lies in its potential to empower researchers with a tool that enhances the design and execution of ultrasonic fatigue experiments. The proposed semianalytical method offers a more versatile and time-efficient approach for future exploration on optimization algorithms for ultrasonic fatigue components and specimens. To showcase its capabilities, all available and applied methods are revised and compared against the model analytically and then with experimental measurement results

Preliminary Numerical Modelling of a Dynamic Spring-Mounted Wing System to Reduce the Drag of Vehicles at Higher Speeds

The dynamic behaviour of a spring-mounted symmetrical NACA0012 wing in a freestream flow of air is studied in the pre-stall region, over 0◦ to 12◦ angles of incidence. The primary aim of this work is for use within the automotive sector to reduce drag and fuel emissions. However, this work will also be of interest in the motorsport sector to improve performance, and also have some applications within the aerospace and renewable energy sectors. The general operation of the concept has previously been verified at these low angles in the pre-stall region with that of a theoretical estimation using finite and infinite wings. This paper provides a numerical solution of the same problem and is compared with the previous experimentation. At these low angles, the computations yield a dynamic response settling into a static equilibrium. The stable solutions match the start of a steady regime well, when compared with the experiment. The trends are also comparable with the experiment, but the velocities at which they occur are underestimated in the computation. The computations demonstrate a drag reduction of 59% when compared to a fixed wing, whereas the lift remains stable at a near constant value with increasing wind speed. Thence, downforce is maintained whilst drag is reduced, which will facilitate higher speeds on the straight whilst maintaining vehicle direction stability. Limitations to this proof-of-concept work are highlighted and future development work is suggested to achieve even further increases in performance

Chapter 5 - Introduction to Sensors and Signal Processing

Diogo Montalvao, 'Chapter 5 - Introduction to Sensors and Signal Processing' in Clarence de Silva, Farbod Khoshnoud, Maoqing Li, Saman Halgamuge Eds., Metatronics: Fundamentals and Applications (Boca Raton: CRC Press 2015) ISBN: 9781482239317This chapter presents the fundamentals on sensors and signal processing, with emphasizes on Mechatronics and applications. Sensors are used to measure signals that present changes in the time domain, e.g. waveforms or digital steps. Different technologies have been developed over the years in order to sense many different physical quantities, such as temperature, flow, force, acceleration, position, sound pressure and intensity of light, among others. Because of their varying nature, all these quantities may be measured under the form of waveforms. However, waveforms - which are analog signals – are often found difficult to interpret in the time domain and a transformation into the frequency domain is required. The Fourier transform still is the most popular technique used today for converting a time signal into a frequency spectrum. Nevertheless, in signal processing, an analog-to-digital conversion (ADC) of the time signal is required at some stage, even if the Fourier transform is not used. When proper treatment and filtering approaches are not followed, important features in the signal may be attenuated and others may be falsely indicated. This chapter discusses how signals can be measured in order to avoid common pitfalls in signal acquisition and processing. The theoretical background is set in a comprehensive yet practical way

Design and Assembly of an Ultrasonic Fatigue Testing Machine

The lifetime approach in fatigue design based on S_N curves establish an infinite life when the cyclic stress applied is below than the endurance limit. Results in this field revealed fatigue failures beyond 10e7 cycles, indicating that there´s no endurance fatigue limit, however obtaining this data with servo-hydraulic testing machine can be very timeconsuming and expensive. Ultrasonic fatigue testing machines are a new generation of devices designed to perform VHCF tests in a very short time. This paper describes the design and assembly of an ultrasonic fatigue testing device working at 20 kHz.Final Accepted Versio

Instumentation of Ultrasonic High-Frequency Machine to Estimate Applied Stress in Middle Section of Specimen

Paper Ref. 2807The objective of this paper is to describe the instrumentation of a new developed ultrasonic fatigue testing machine at 20 kHz working frequency and compare the possible solutions to estimate the stress applied in the middle section of the specimen. Stress is estimated by measuring the displacement on bottom of the specimen and their strain on middle section. The monitoring of the displacement, considered here in the bottom face of the specimen, is carried out using a high resolution laser, the strain using a strain gauge in middle of specimen and field temperature using a pyrometer and thermographic camera. A LabVIEW routine is used to control the initial parameters of the transducer, such as the frequency reset, the frequency seek, the load amplitude and to record data of all sensors. To manage and process the data, a data acquisition device working at 400 kHz from National Instruments is used.Final Accepted Versio

Harmonica: Stepped-Sine Spectrum Analyser for Transfer Function Measurement and Non-Linear Experimental Assessment

Non peer reviewe

Design and instrumentation of an ultrasonic fatigue testing machine

Non peer reviewedFinal Accepted Versio