Energy absorption in actual tractor rollovers with different tire configurations

In order to better understand the complexities of modern tractor rollover, this paper investigates the energy absorbed by a Roll-Over Protective Structure (ROPS) cab during controlled lateral rollover testing carried out on a modern narrow-track tractor with a silent-block suspended ROPS cab. To investigate how different tractor set-ups may influence ROPS and energy partitioning, tests were conducted with two different wheel configurations, wide (equivalent to normal ‘open field’ operation) and narrow (equivalent to ‘orchard/vineyard’ operation), and refer to both the width of the tires and the corresponding track. Dynamic load cells and displacement transducers located at the ROPS-ground impact points provided a direct measurement of the energy absorbed by the ROPS cab frame. A trilateration method was developed and mounted onboard to measure load cell trajectory with respect to the cab floor in real-time. The associated video record of each rollover event provided further information and opportunity to explain the acquired data. The narrow tire configuration consistently subjected the ROPS cab frame to more energy than the wide tire arrangement. To better evaluate the influence of the ROPS cab silent-blocks in lateral rollover, static and dynamic tests were performed. The results confirm that tires influence the energy partition significantly and that further understanding of silent-blocks’ dynamic performance is warranted

Advances in metal additive manufacturing: A review of common processes, industrial applications, and current challenges

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. In recent years, Additive Manufacturing (AM), also called 3D printing, has been expanding into several industrial sectors due to the technology providing opportunities in terms of improved functionality, productivity, and competitiveness. While metal AM technologies have almost unlimited potential, and the range of applications has increased in recent years, industries have faced challenges in the adoption of these technologies and coping with a turbulent market. Despite the extensive work that has been completed on the properties of metal AM materials, there is still a need of a robust understanding of processes, challenges, application‐specific needs, and considerations associated with these technologies. Therefore, the goal of this study is to present a comprehen-sive review of the most common metal AM technologies, an exploration of metal AM advancements, and industrial applications for the different AM technologies across various industry sectors. This study also outlines current limitations and challenges, which prevent industries to fully benefit from the metal AM opportunities, including production volume, standards compliance, post processing, product quality, maintenance, and materials range. Overall, this paper provides a survey as the benchmark for future industrial applications and research and development projects, in order to assist industries in selecting a suitable AM technology for their application

Erosion wear characterisation of an open ductile iron butterfly valve subjected to aluminium oxide particle slurry flow

This study attempts to identify the most erosion-sensitive valve locations due to aluminium oxide particle impingement under various pressure drops and valve closing angles, utilising the Ansys discrete phase model (DPM). Additionally, this research explores the feasibility of integrating laser scanning technology into the fields of tribology and particle erosion analysis. The results indicate higher erosion damage on the top valve surface due to the direct effects of particle velocity and impingement angles compared to the underside of the valve, where particle trajectories are highly affected by turbulence. Moreover, smaller closing angles proved to be detrimental to valve service life, due to accelerated wear at both the leading and trailing edges, which are identified as the most vulnerable locations

Investigation of Damper Valve Dynamics Using Parametric Numerical Methods

The objectives of this study are to identify the dynamics of a Tenneco Automotive hydraulic damper valve and to predict valve performance. Accurate simulations of damper valve performance can be used to improve valve designs without the expense of physical testing. The Tenneco damper valve consists of thin shims and a spring preloaded disc that restricts fluid from exiting the main flow orifices. The deflection of the shims and spring are dependent on the flow-rate through the valve. The pressure distribution acting on the deformable valve components is investigated numerically using a dynamic modelling technique. This technique involves sequential geometry and simulation updating, while varying both the geometry and flow-rate. The valve deflection is calculated by post-processing the pressure distribution. Valve performance can be predicted by coupling the valve deflection with CFD pressure results

Numerical investigation of the thermo-hydraulic performance of a shark denticle-inspired plate fin heat exchanger

Growing demand for increased power dissipation is fuelling the need for the design of more efficient heat exchangers. Modifying fin geometry is an effective way of improving heat transfer efficiency and of reducing flow resistance for plate fin heat exchangers. To date, fin designs have mostly revolved around classical shapes such as pins, ellipses, and rectangles, due to limitations of conventional manufacturing technologies. However, with recent advancements in metal additive manufacturing, there is an opportunity of redesigning approaches and ways of thinking to create novel fin geometries. In this study, biomimicry was used as a tool to reverse engineer a novel geometry for a plate fin heat exchanger based on a denticle, which is a mesoscopic structure on the skin of sharks. The shape of the denticle is streamlined; therefore, showing the possibility of enhancing fluid-to-solid contact if used as geometry for a plate fin heat exchanger. The thermo-hydraulic performance of the denticle was evaluated with respect to a rectangular, cylindrical and an elliptical fin (NACA 0030), using conjugate-heat-transfer simulations on ANSYS-Fluent. The numerical model was calibrated and validated based on experimental results from an additively manufactured rectangular plate fin heat exchanger. Results demonstrated that over the range of tested Reynolds Numbers, 9.8x104 \u3c Re ≤ 22.9x104, the denticle fin had average Nusselt number improvements of 13.1 %, 5.4 % and 75.7 % with respect to the rectangular fin, the NACA 0030 and cylindrical fin, respectively. At Re = 22.9x104, a 26 % decrease in pressure drop was noted for the denticle with respect to the rectangular fin, with maximum thermal performance factors ( ) of 1.29, 0.81 and 1.53 as noted for the denticle fin with respect to the rectangular fin, NACA 0030 fin and cylindrical fin, respectively

Thermo-hydraulic performance evaluation of a NACA 63-015 heat exchanger with shark denticles as surface textures

In this study, the effect of using bio-inspired surface texturing as a technique to further enhance the efficiency of a single Plate Fin Heat Exchanger (PFHX) was investigated experimentally. By using biomimicry across disciplines, the denticle, which is a body adaptation from shark skin for enhanced hydrodynamics, was identified as a surface texture to be used on the fin of a PFHX. A smooth NACA 63-015 PFHX (HX0) was used as baseline for thermo-hydraulic performance comparisons. Initially, three PFHXs (HX1, HX2 and HX3), consisting of arrays of denticles upscaled to different scale factors, were designed and printed in ABS plastic to evaluate Additive Manufacturing (AM) limits. By analysing optical images and pressure drop results, HX2 was found to be the best performing array in terms of printing quality and pressure drop performance. Both HX0 and HX2 were then printed in stainless steel 17-4PH by using a Markforged Metal X printer, and then experimentally compared to evaluate their flow and heat transfer behaviours. Results demonstrate that the addition of shark denticles as surface textures on HX2 shifted the onset of turbulence from a fully turbulent to a transitional regime compared to HX0. For Re \u3c 5.7×104, the friction factor for HX2 was less than that of HX0, while at higher Re values the trend was reversed due to increases in skin friction drag. At Re = 3.9×104, the friction factor for HX2 was 56% lower than that of HX0. Overall, a mean improvement of 14% in Nusselt number was noted for HX2 compared to HX0. Further, a mean thermo-hydraulic performance of 1.11 was noted for HX2 for the range of tested Re values, which demonstrated that the addition surface textures in the form of shark denticles to a NACA 63-015 profile yielded a more efficient PFHX compared to a smooth one

Optimised PVDF Placement Inside an Operating Hydrodynamic Thrust Bearing

In our previous work we demonstrated the feasibility of using Polyvinylidene Fluoride (PVDF) sensors inside an operational thrust bearing and were able to measure the blade passing frequencies (BPF) due to an asymmetric flow around different propellers. In that work however the sensors were positioned inside the flat surface of the stationary portion of the bearing with the tilted pads rotated on the opposite side. Due to this configuration the output signal of the PVDF consisted of a superposition of the pad passing frequency (PPF) and the blade passing frequency (BPF) making it difficult to extract useful information from the results. Here, an improved bearing pad-film configuration is proposed in order to minimise the effects of the PPF. By embedding the films inside the pads, positioned on the stationary side of bearing, and rotating the flat surface, it was possible to eliminate the PPF and significantly increase the signal to noise ratio. The measured results give a better understanding of the fundamental vibratory components that arise from the propeller-shaft system

Rocketing restoration : enabling the upscaling of ecological restoration in the Anthropocene

In the 25 years during which the Society for Ecological Restoration (SER) has overseen the publication of Restoration Ecology, the field has witnessed conceptual and practical advances. These have become necessary due to the scale of environmental change wrought by the increasing global human population, and associated demands for food, fiber, energy, and water. As we look to the future, and attempt to fulfill global restoration commitments and meet sustainable development goals, there is a need to reverse land degradation and biodiversity loss through upscaling ecological restoration. Here, we argue that this upscaling requires an expanded vision for restoration that explicitly accounts for people and nature. This expansion can assess success in a future-focused way and as improvements relative to a degraded socio-ecological system. We suggest that upscaling requires addressing governance, legal and ethical challenges, investing in technological and educational capacity building, bolstering the practical science necessary for restoration, encouraging adoptable packages to ensure livelihoods of local stakeholders, and promoting investment opportunities for local actors and industry. Providing SER embraces this socio-ecological vision, it is ideally placed to aid the achievement of goals and remain globally relevant. SER needs to harness and coordinate three sources of potential energy (global political commitments, the green economy, and local community engagement) to rocket restoration into the Anthropocene. With principles that can embrace flexibility and context-dependency in minimum restoration standards, SER has the potential to guide socio-ecological restoration and help realize the ultimate goal of a sustainable Earth

Selecting ROPS safety margins for wheeled agricultural tractors based on tractor mass

Forestry and agricultural tractors are required to have roll-over protective structures (ROPS) for use on European roads. To that end, the ROPS must conform to a series of strength tests in accordance with the Organisation for Economic and Co-operation Development (OECD) Standard Codes or the relevant European Community (EC) Directives. Within these Codes, ROPS force and energy absorption test requirements are typically defined in terms of a \u2018reference mass\u2019. This mass, along with mass values for \u2018unladen\u2019, \u2018ballast\u2019, and \u2018maximum laden\u2019, required for the homologation documentation, is given by the tractor manufacturer. Recent international interest in operator safety has questioned the appropriateness of the mass definitions and specifically the use of the currently defined reference mass as the basis for ROPS testing. In this work, mass information pertaining to 24 wheeled type tractors was considered: 13 were T1 (Standard) type and 11 were T2 (Narrow track) type. Although tractors may have similar reference mass values (and hence ROPS testing requirements) it was found that their ballast and maximum laden masses can differ greatly. The average ratios to reference mass values were for ballast and maximum laden values 1.13 and 1.60 for T1 tractors and 1.12 and 1.64 for T2 tractors. Both tractor categories had some ratios with values greater than 1.80. This implies safety margins determined by reference mass vary depending on the tractor under consideration. The results highlight some criticisms of ROPS testing procedures and these are discussed