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The Dynamic Response of Ti521, a Titanium Alloy for Impact Containment:Rate Dependency and the Influence of Cooling Processes
Get PDFTi521, a titanium alloy with a tailored composition that provides an excellent balance of strength and ductility, was developed and manufactured. The effects of cooling rate on both quasi-static and dynamic mechanical behaviour were investigated. An extensive experimental campaign was undertaken to characterise the rate dependent properties of Ti521 and to evaluate the influence of manufacturing parameters on its mechanical performance. The alloy exhibited the highest yield strength under rapid cooling conditions, with values exceeding those of Ti6Al4V. Furthermore, the analysis of the energy dissipated during plastic deformation indicates that Ti521 has strong potential to outperform Ti6Al4V in impact containment applications.A novel experimental methodology, incorporating multiple camera setups, was introduced and employed to characterise anisotropy induced by variations in cooling rates and rolling directions. This approach enabled the accurate evaluation of the true stress-strain response in the presence of anisotropy and, consequently, the influence of rolling direction on the mechanical performance of the alloy. Cross rolled specimens exhibited no measurable anisotropic behaviour, whereas unidirectionally rolled material showed slight differences in mechanical properties between the rolling and transverse directions
Performance Improvement of a High-Speed On/Off Valve-Piloted Proportional Valve via Nonlinear Modeling and Load-Adaptive Sliding Mode Control
Get PDFHigh-speed on/off valves (HSVs) are recognized for their rapid response and high reliability, and are widely employed as pilot elements in proportional valves. However, their inherent switching behavior intensifies the nonlinear characteristics of the control system, thereby limiting fluid delivery precision. In addition, the main spool of the proportional valve is subjected to significantly time-varying load forces. To address these challenges, a nonlinear flow model of the HSV is established, and the dynamics of pressure pulsation propagation are systematically analyzed. Meanwhile, a dynamic model of the proportional valve main spool is developed, explicitly incorporating the effects of time-varying load forces. Based on these models, a load-adaptive sliding mode control (LASMC) strategy is proposed to improve the motion control performance of a high-speed on/off valve-piloted proportional valve (HSVPPV). Motion control experiments conducted on the HSVPPV and its valve-controlled system validated the proposed approach. Compared to conventional PI control, LASMC reduced the main spool's maximum displacement error from 0.696 mm to 0.312 mm (a 55.2% reduction) and standard deviation from 0.213 mm to 0.127 mm (a 40.4% reduction). At the actuator level, the cylinder's maximum error decreased from 14.996 mm to 11.527 mm (a 23.1% reduction) and standard deviation from 11.347 mm to 10.323 mm (a 9.0% reduction). These results demonstrate that the proposed controller significantly enhances both valve positioning accuracy and overall system tracking stability. Note to Practitioners - This study addresses the practical challenges associated with achieving high-precision motion control in HSVPPV-based hydraulic systems, such as those used in construction machinery, industrial automation, and aerospace actuation. Although HSVPPV offers fast response and high reliability, the switching operation of the pilot valves introduces significant nonlinearities and pressure pulsations. In addition, the main spool is often subjected to highly variable load forces. These factors collectively lead to notable performance degradation in conventional control methods such as PID. To address these challenges, an LASMC strategy is proposed to automatically compensate for load variations and suppress pressure pulsation disturbances. The approach employs a practical nonlinear model that accurately captures the dynamic coupling among PWM duty cycle, pressure drop, and flow rate in the HSV. A continuous saturation function is incorporated to smooth the control signals and reduce oscillation. Experimental results demonstrate that this method can reduce main spool displacement error by up to 55.2% and significantly improve trajectory tracking accuracy of the hydraulic cylinder under various operating conditions. The proposed controller can be implemented on real-time digital control platforms and is suitable for modern electro-hydraulic systems. Future work will focus on observer-based methods for main spool motion estimation and will extend the control framework to multi-actuator systems to support more complex industrial applications.</p
Performance Improvement of a High-Speed On/Off Valve-Piloted Proportional Valve via Nonlinear Modeling and Load-Adaptive Sliding Mode Control
Get PDFHigh-speed on/off valves (HSVs) are recognized for their rapid response and high reliability, and are widely employed as pilot elements in proportional valves. However, their inherent switching behavior intensifies the nonlinear characteristics of the control system, thereby limiting fluid delivery precision. In addition, the main spool of the proportional valve is subjected to significantly time-varying load forces. To address these challenges, a nonlinear flow model of the HSV is established, and the dynamics of pressure pulsation propagation are systematically analyzed. Meanwhile, a dynamic model of the proportional valve main spool is developed, explicitly incorporating the effects of time-varying load forces. Based on these models, a load-adaptive sliding mode control (LASMC) strategy is proposed to improve the motion control performance of a high-speed on/off valve-piloted proportional valve (HSVPPV). Motion control experiments conducted on the HSVPPV and its valve-controlled system validated the proposed approach. Compared to conventional PI control, LASMC reduced the main spool's maximum displacement error from 0.696 mm to 0.312 mm (a 55.2% reduction) and standard deviation from 0.213 mm to 0.127 mm (a 40.4% reduction). At the actuator level, the cylinder's maximum error decreased from 14.996 mm to 11.527 mm (a 23.1% reduction) and standard deviation from 11.347 mm to 10.323 mm (a 9.0% reduction). These results demonstrate that the proposed controller significantly enhances both valve positioning accuracy and overall system tracking stability. Note to Practitioners - This study addresses the practical challenges associated with achieving high-precision motion control in HSVPPV-based hydraulic systems, such as those used in construction machinery, industrial automation, and aerospace actuation. Although HSVPPV offers fast response and high reliability, the switching operation of the pilot valves introduces significant nonlinearities and pressure pulsations. In addition, the main spool is often subjected to highly variable load forces. These factors collectively lead to notable performance degradation in conventional control methods such as PID. To address these challenges, an LASMC strategy is proposed to automatically compensate for load variations and suppress pressure pulsation disturbances. The approach employs a practical nonlinear model that accurately captures the dynamic coupling among PWM duty cycle, pressure drop, and flow rate in the HSV. A continuous saturation function is incorporated to smooth the control signals and reduce oscillation. Experimental results demonstrate that this method can reduce main spool displacement error by up to 55.2% and significantly improve trajectory tracking accuracy of the hydraulic cylinder under various operating conditions. The proposed controller can be implemented on real-time digital control platforms and is suitable for modern electro-hydraulic systems. Future work will focus on observer-based methods for main spool motion estimation and will extend the control framework to multi-actuator systems to support more complex industrial applications.</p
The Dynamic Response of Ti521, a Titanium Alloy for Impact Containment:Rate Dependency and the Influence of Cooling Processes
Get PDFTi521, a titanium alloy with a tailored composition that provides an excellent balance of strength and ductility, was developed and manufactured. The effects of cooling rate on both quasi-static and dynamic mechanical behaviour were investigated. An extensive experimental campaign was undertaken to characterise the rate dependent properties of Ti521 and to evaluate the influence of manufacturing parameters on its mechanical performance. The alloy exhibited the highest yield strength under rapid cooling conditions, with values exceeding those of Ti6Al4V. Furthermore, the analysis of the energy dissipated during plastic deformation indicates that Ti521 has strong potential to outperform Ti6Al4V in impact containment applications.A novel experimental methodology, incorporating multiple camera setups, was introduced and employed to characterise anisotropy induced by variations in cooling rates and rolling directions. This approach enabled the accurate evaluation of the true stress-strain response in the presence of anisotropy and, consequently, the influence of rolling direction on the mechanical performance of the alloy. Cross rolled specimens exhibited no measurable anisotropic behaviour, whereas unidirectionally rolled material showed slight differences in mechanical properties between the rolling and transverse directions
Dataset for "Influence of Block Microstructure on the Interaction of Styrene-Maleic Acid Copolymer Aggregates and Lipid Nanodiscs"
No full textCopolymers between styrene and maleic acid are able to extract membrane proteins directly from cells, reconstituting lipid membranes into nanodiscs. RAFT copolymerisation was used to generate copolymers of equivalent molecular mass but inverted block sequences and end group termini. This dataset contains characterisation data for the copolymers (GPC, NMR, FTIR, UV-vis), included deuterated variants for neutron scattering experiments, as well as the structures formed in solution. Aggregates were assed by a combination of DLS and surface tension measurements, and nanodisc formation kinetics through UV-vis using both model DMPC vesicle and E.coli membrane suspensions. It was found that mismatched hydrophilic and hydrophobic end groups on the respective styrene block and alternating block, impeded membrane solubilisation. This highlights not only how the amphiphilic balance of these blocks is important for efficient nanodisc formation, but also how end groups influence these and may be optimised towards the extraction of more challenging MPs
Dataset for "Feasibility and acceptability of 7-day smartphone-based, activity-triggered Ecological Momentary Assessment among low-income older adults"
No full textSmartphone-based Ecological Momentary Assessment (EMA) is increasingly used to collect real-time data on physical activity behaviour. The current study aimed to assess the feasibility and acceptability of activity-triggered EMA in low-income older adults. For 7 days, 39 older adults (76.4 ± 8.5 years; 76% earning below £25,000/year) received EMA surveys, delivered via the movisensXS application (version 1.5.23, movisens GmbH, Karlsruhe, Germany) for Android operating systems, when they surpassed a predefined activity/inactivity threshold, or when two hours elapsed between prompts. Participants wore a Move 4 activity sensor (movisens GmbH, Karlsruhe, Germany) to measure their steps. A post-study questionnaire assessed perceptions of acceptability. The dataset includes all quantitative data needed to replicate analyses in the article "Feasibility and acceptability of 7-day smartphone-based, activity-triggered Ecological Momentary Assessment among low-income older adults." The "Descriptives" sheet contains a unique participant identifier, demographic information, and responses to the post-study questionnaire. The "EMA" sheet contains a unique participant identifier (Participant_ID), age (Age_years), biological sex (Biological_sex), time of day (Time_of_day), day of week (Weekday), and EMA compliance (EMA_compliance; whether participants completed the EMA prompt or missed the EMA prompt) variables needed to perform the multilevel logistic regression models. It also contains the data necessary to limit the sample to participants with valid activity sensor wear and run Model 2, including the length of time in minutes that participants were not wearing the activity sensor in the 15-minute window before (Nonwear_before) and after (Nonwear_after) the EMA survey, and concurrent physical activity (Concurrent_PA; the number of steps in the ± 15-minute window around the EMA prompt). Day of study (day number from 1 to 7), trigger type (whether participants received an activity-triggered, inactivity-triggered, or timeout EMA prompt), trigger time (absolute time of the auditory signal and/or vibration alerting participants that it was time to complete an EMA survey), EMA outcome (whether the EMA prompt was completed, not answered, or answered but incomplete), form start time (absolute time when the EMA survey was answered), form completion time (absolute time when the EMA survey was completed), observation number (variable that assigns the observation number to each row by participant ID), and observation counter (variable that assigns the number of total observations to each row of data for a given participant) variables are also provided to enable researchers to replicate all of the summary statistics presented in the article. A complete description of the variables, including the text of questionnaires (where relevant), is provided in the "Overview" sheet
A comprehensive comparison of dynamic strain localisation and mechanical behaviour in traditional and additively manufactured Ti6Al4V
Get PDFTitanium alloys are widely used in aerospace, defence, automotive, and biomedical engineering owing to their high specific strength and excellent corrosion resistance. Additive manufacturing has emerged as a promising alternative to conventional production methods, offering the capability to fabricate complex geometries while reducing processing time and material waste. In this study, the high strain rate deformation behaviour of Ti6Al4V produced by selective laser melting is investigated using a Split Hopkinson Tension Bar system equipped with a multi-camera high-speed imaging setup. A comprehensive experimental programme is conducted on specimens manufactured in three different build orientations to assess the influence of processing direction on dynamic strain localisation and true stress–strain response. The post-necking behaviour is examined and compared with that of conventionally forged Ti6Al4V, revealing notable differences in ductility and strain localisation mechanisms. In addition, the high strain rate compressive behaviour of both material variants and their temperature dependence are investigated using a Split Hopkinson Compression Bar system equipped with thermal conditioning. The deformation and failure mechanisms of additively manufactured specimens produced in different orientations are further examined through post-mortem analysis of the fracture surfaces
Getting the most from your data:Using Statistical Process Controls for Data Quality Assurance in Sport Science Data
Get PDFAll levels of sport have seen a surge in data availability, which has allowed for the prospective and retrospective monitoring and tracking of player performance metrics, physical outputs (e.g., distance run, number of accelerations), and injuries. Players, coaches, support staff, governing bodies, and researchers are trying to leverage data to support long-term player welfare and real-time decisions, and this is made possible with advances in data capture, processing, and analysis. Statistical process control (SPC) is a method of quality control designed for understanding, monitoring, and improving process performance over time, historically associated with manufacturing. Visualization of SPC, referred to as a run chart, is accompanied by a mean centerline to show how the underlying process is changing relative to a benchmark. The run chart is visualized with control limits, which are used to determine whether the process is, or is not, operating within statistical control. Deviation of process data outside of the control limits is deemed to be a cause for special variation, highlighting areas that may require investigation. The aims of this methodological report are (a) to provide an example of how SPC can be used in sport and athlete monitoring and (b) provide practical applications for the sports science practitioner. This tutorial provides specific examples from the author's experience in using SPC in the sport field and adjoining simulated data and code to reproduce these results, and more importantly, use as a template for the practitioner's own sport data
Convergence theory for two-level hybrid Schwarz preconditioners for high-frequency Helmholtz problems
Get PDFWe give a novel convergence theory for two-level hybrid Schwarz domain-decomposition (DD) methods for finite element discretizations of the high-frequency Helmholtz equation. This theory gives sufficient conditions for the preconditioned matrix to be close to the identity and covers DD subdomains of arbitrary size, arbitrary absorbing layers/boundary conditions on both the global and local Helmholtz problems, and coarse spaces not necessarily related to the subdomains. The assumptions on the coarse space are satisfied by the approximation spaces using problem-adapted basis functions that have been recently analyzed as coarse spaces for the Helmholtz equation, as well as all spaces in which the Galerkin solutions are known to be quasi-optimal via a Schatz-type argument. As an example, we apply this theory when the coarse space consists of piecewise polynomials; these are then the first rigorous convergence results about a two-level Schwarz preconditioner applied to the high-frequency Helmholtz equation with a coarse space that does not consist of problem-adapted basis functions.</p
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