A computationally-efficient numerical model to characterize the noise behavior of metal-framed walls

Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model consisting of two fluid-filled reverberation chambers, partitioned using a metal-framed wall, is to be simulated at one-third-octaves. This produces a large simulation model consisting of several millions of nodes and elements. Therefore, efficient meshing procedures are necessary to obtain better solution times and to effectively utilise computational resources. Such models should also demonstrate effective Fluid-Structure Interaction (FSI) along with acoustic-fluid coupling to simulate a realistic scenario. In this contribution, the development of a finite element frequency-dependent mesh model that can characterize the sound insulation of metal-framed walls is presented. Preliminary results on the application of the proposed model to study the geometric contribution of stud frames on the overall acoustic performance of metal-framed walls are also presented. It is considered that the presented numerical model can be used to effectively visualize the noise behaviour of advanced materials and multi-material structures

Acoustic absorption of passive destructive interference cavities

Acoustic products are primarily designed for broadband acoustic absorption. However, frequency-dependent acoustic absorption featuring passive design-based solutions are necessary to combat the growing noise pollution. Accordingly, this research investigates the targeted creation of sound absorption as a function of geometry utilising the principle of Acoustic Interference (AI). A methodology to design freeform geometries that can create targeted acoustic absorption is presented. The effectiveness of this methodology is then experimentally validated while quantifying the influence of length, diameter and geometry orientation. The results establish that AI has the potential to create ‘near perfect’ sound absorption that can be customised depending on the source frequency. The design freedom revealed by this study allows the exploitation of freeform geometries as passive high-efficiency sound absorbing devices

Fundamentals of laser powder bed fusion of metals, 1st Edition, Elsevier (2021), p. 676, Igor Yadroitsev, Ina Yadroitsava, Anton Du Plessis, Eric MacDonald, ISBN: 9780128240908 [book review]

© 2001 The Author. Published by Elsevier This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website:https://doi.org/10.1016/j.aime.2022.100070Accepted versio

Sound pressure level of a Formula 3 car and the influence of detachable muffler-tip

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.rineng.2021.100261This study presents the initial findings associated with the noise emission tests that were carried out in preparation of the UWR Formula 3 car. Even though Formula 3 (F3) race cars are excluded from road vehicle noise emission regulations (EU No. 540/2014), their emission is closely regulated by Fédération Internationale de l’Automobile (FIA) technical regulations. According to FIA regulations, the noise generated by participating cars must not exceed 110 dB (A-weighted) under specific test conditions. The acoustic tests presented in this study were carried out at RAF (Royal Air Force) Cosford airfield in the UK closely simulating FIA recommended conditions. The tests were established to characterise the noise emission of the car during drive-by and stationary conditions. In addition to measuring the Sound Pressure Level (SPL) emitted, the study was extended to evaluating the performance of a detachable muffler tip that is permitted under the FIA regulations. The study found that the tested muffler-tip did not reduce the LAeq acoustic emission under any of the test cases considered. Nevertheless, introducing muffler-tip worsened the LAeq levels by 0.2 dB which is within the standard acoustic measurement uncertainty. Overall, the paper establishes the noise levels associated with F3 cars and the requirement for customised muffler-tips as opposed to aftermarket ones for meaningful noise reduction without adversely affecting performance.Accepted versio

High-temperature oxidation and erosion of HVOF sprayed NiCrSiB/Al2O3 and NiCrSiB/WC Co coatings

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.apsadv.2021.100191Material deterioration due to erosion and oxidation in high-temperature environments is a major cause of wear in power plants, aircraft engines and petrochemical industries. NiCrSiB based surface coatings using thermal spray techniques such as High-Velocity Oxy-Fuel (HVOF) offer a cost-effective route to improve the tribological properties for a range of substrate materials. The study investigates the high-temperature oxidation and erosion resistance of HVOF coated NiCrSiB reinforced with Al2O3 and WC single bond Co on SS304 stainless steel substrate. The oxidation kinetics and erosion responses of the coatings at 750 °C were evaluated for a period of 160 hrs and the coating microstructure, morphology and chemical compositions characterised. A total of three coating compositions were studied namely: NiCrSiB/Al2O3, NiCrSiB/n-Al2O3 and NiCrSiB/WC single bond Co where the results indicate a superior oxidation and erosion resistance in all cases in comparison to uncoated SS304. However, it was found that the NiCrSiB reinforced with micro-structured Al2O3 outperformed all the other coatings in terms of oxidation resistance. When it comes to erosion resistance, NiCrSiB/WC single bond Co was found to demonstrate the highest performance.Accepted versio

Acoustic behaviour of 3D printed titanium perforated panels

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.rineng.2021.100252Titanium alloys such as Ti6Al4V is amongst the most widely studied metallic materials in the broad context of metal 3D printing. Although the mechanical performances are well understood, the acoustic performance of 3D printed Ti6Al4V, and Ti6Al4V ELI (Extra Low Interstitial) has received limited attention in the literature. As such, this study investigates the normal incidence sound absorption coefficient () and Sound Transmission Loss (STL) of both Ti6Al4V and Ti6Al4V ELI samples manufactured using Selective Laser Melting (SLM). The influence of material thickness on acoustic responses and the potential of developing Ti6Al4V micro-perforated panels (MPP) at 400–1600 Hz is also explored. The sound absorption of three aesthetic perforations printed using Ti6Al4V and the influence of a porous back layer was also investigated. The experimental measurements were carried out using an impedance tube following ISO10534-2. The result of the study establishes that 3D printed non-circular perforations featuring porous back-layer can exhibit improved sound absorption coefficient.This research was funded by the European Commission CALMERIC Grant 32R19P03053.Accepted versio

Investigation of Ti64 sheathed cellular anatomical structure as a tibia implant

In order to reduce stress shielding following a segmental bone replacement surgery requires stiffness matching strategies between the host bone and the implant are required. Carefully engineered implant geometry that can mimic the mechanical performance of the host bone is required to achieve this. The development of Additive Layer Manufacturing (ALM) techniques such as Direct Metal Laser Sintering (DMLS) allows for the fabrication of complex geometries that can achieve targeted mechanical performance. Consequently, this work introduces a sheathed Ti6Al4V additively manufactured tibial implant that mimics the circumferential anatomy of the host bone. Performance evaluation of the implant was carried using experimental and numerical technique under axial compression. Furthermore, the influence of sheathing strategy and sheath thickness on the compressive performance of the implant is parametrically analysed. The results of this study shows a promising sheathed implant that can replace a defective tibia bone segment. The implant is superior to conventional porous implants as it allows for easy implantation in surgical operation and allows for the reduction of stress shielding

Perforated steel stud to improve the acoustic insulation of drywall partitions

©2021 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/acoustics3040043Steel studs are an inevitable part of drywall construction as they are lightweight and offer the required structural stability. However, the studs act as sound bridges between the plasterboards, reducing the overall sound insulation of the wall. Overcoming this often calls for wider cavity walls and complex stud decoupling fixtures that increase the installation cost while reducing the floor area. As an alternative approach, this research reveals the potential of perforated studs to improve the acoustic insulation of drywall partitions. The acoustic and structural performance is characterized using a validated finite element model that acted as a prediction tool in reducing the number of physical tests required. The results established that an acoustic numerical model featuring fluid-structure-interaction can predict the weighted sound reduction index of a stud wall assembly at an accuracy of ±1 dB. The model was used to analyze six perforated stud designs and found them to outperform the sound insulation of non-perforated drywall partitions by reducing the sound bridging. Overall, the best performing perforated stud design was found to offer improvements in acoustic insulation of up to 4 dB, while being structurally compliant.Published onlin

Modelling and Fabrication of Groundnut Separating Machine

This project is mainly focused on design and fabrication of groundnut separating machine electrically powered by a 0.5HP motor. Farmers having large harvesting area can afford and use this machine. This separating machine is light-weight, time consume and low in cost. During the process of testing it was observed that majority of groundnuts were been separated without damaging the groundnut. Farmers and business -man start their business with less investment

3D printed auxetic nasopharyngeal swabs for COVID-19 sample collection

This is an accepted manuscript of an article published by Elsevier in Journal of the Mechanical Behavior of Biomedical Materials on 12/11/2020, available online: https://doi.org/10.1016/j.jmbbm.2020.104175 The accepted version of the publication may differ from the final published version.The COVID-19 pandemic has resulted in worldwide shortages of nasopharyngeal swabs required for sample collection. While the shortages are becoming acute due to supply chain disruptions, the demand for testing has increased both as a prerequisite to lifting restrictions and in preparation for the second wave. One of the potential solutions to this crisis is the development of 3D printed nasopharyngeal swabs that behave like traditional swabs. However, the opportunity to digitally conceive and fabricate swabs allows for design improvements that can potentially reduce patient pain and discomfort. The study reports the progress that has been made on the development of auxetic nasopharyngeal swabs that can shrink under axial resistance. This allows the swab to navigate through the nasal cavity with significantly less stress on the surrounding tissues. This is achieved through systematically conceived negative Poisson's ratio (-ν) structures in a biocompatible material. Finite element (FE) and surrogate modelling techniques were employed to identify the most optimal swab shape that allows for the highest negative strain (-∊lat) under safe stress (σvon). The influence and interaction effects of the geometrical parameters on the swab's performance were also characterised. The research demonstrates a new viewpoint for the development of functional nasopharyngeal swabs that can be 3D printed to reduce patient discomfort. The methodology can be further exploited to address various challenges in biomedical devices and redistributed manufacturing.This research was conducted with support from the CALMERIC grant [European Commission, Grant number: 32R19P03053]; 6DME Ltd. UK; and Formlabs GmbH.Published versio