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Addressing Thermal Distortion in Additive Manufacturing of Topology Optimized Structures Through Reverse Shape Morphing
Get PDFDesign of light weight structures is an important aspect in the aircraft industry, since minimizing the weightof components improves the overall aircraft performance. However, conventional manufacturing methods work on standard geometries and shapes, and often lead to overdesigning of parts. Additive Manufacturing (AM) overcomes these issues by allowing more design freedom. The present study focuses on two aspects of AM: (1) part consolidation through topology optimization, and (2) addressing thermal distortion through reverse shape morphing. An assembly of two load bearing brackets is first amalgamated into a single Topology Optimized (TO) part, which satisfies the displacement and stress requirements of the original design. After a series of optimization iterations, the final TO part (278 g) weighs 69 % lesser than the original assembled design (909 g), still meeting the design constraints. The TO part thus eliminates the need of fasteners to join both the brackets, thereby, making the design simpler yet effective. Moreover, a homogeneous stress distribution in the optimized part allows for efficient material utilization. In order to overcome thermal distortion that results during the AM process, the shape of the TO part is transformed in a sense opposite to the distortions produced. This is achieved through reverse shape morphing technique, that reduces thermal distortions in the printed part to sub-micron levels, and the morphed TO part conforms to the requirements meeting the design constraints. Therefore, the implementation of topology optimization along with reverse shape morphing makes the design simple and efficient having reduced distortion. This is achieved without any need of modifications in the manufacturing system or equipment, and such a strategy can be replicated and implemented at industrial scale as well
A Study on Effect of Operating Conditions on Gerotor Pump Performance
Get PDFOne of the important accessories of the lubrication system of an aero-engine is the oil pump which consists of multiple pumps with tandem gerotor elements housed in a single casing. This paper presents the volumetric efficiency variation of a single-stage gerotor pump specially designed for aero-engine by conducting experiments at on and off-design conditions and comparing it with the CFD analysis. A Gerotor pump having fixed geometrical parameters designed based on a athematical 1D model using MatLab and AMESim is manufactured and tested. Performance evaluation of these pumps for pressure and temperature has been discussed in this paper. Commercial CFD code ANSYS-Fluent with a standard k- ε turbulence model has been used for performance evaluation of gerotor pump. Flow characteristics studies on the prototype pump indicate that simulation results closely matched the experimental data. The study concludes that the simulation method adopted is appropriate for predicting the performance of the gerotor pump and the contribution of outlet pressure to the pump volumetric efficiency is significant
Noise Reduction in the Cab of a Special Vehicle
Get PDFNoise is highly associated with adverse effects on health, the human psyche and performance. Current special vehicles do not possess sufficient technologies to suppress the transmission of noise or vibration, which typically results in loss of control, comfort, driving safety, the performance of tasks, etc. At the same time, noise reduces attention and work efficiency while increasing fatigue, leading to hazards, dangerous situations, and missions that may not be completed. This article briefly presents selected parts of a project which included additional soundproofing of a special armoured mobile vehicle on a TATRA wheeled chassis. Basic theoretical, experimental, and practical information about this project is presented. To reduce noise, a selected damping material was used, which is a combination of recycled PUR foam and black rubber with a rough structure. The damping material was selected based on repeated experimental testing of sound absorption measurements from several damping materials. The material was chosen for suitable damping effects and corresponding technological properties (resistance to high temperatures, non-flammability, etc.). In the engine compartment and the cab of the vehicle, the damping properties were experimentally verified after retrofitting, while the noise was significantly reduced
Evaluation of Steel and Tungsten Carbide Cobalt (WC 8Co) 5.56 x 45 mm Caliber Projectile Penetration into Silicon Carbide (SiC) Experiment and Numerical Simulation
Get PDFThis study aims to evaluate WC-8Co as a substitution material in a standard steel core projectile commercially produced by PT Pindad (Persero). The enhanced performance of 5.56 x 45-millimeter ammunition after the addition of WC-8Co hard metal was evaluated in terms of penetration into a silicon carbide (SiC) target. Numerical simulations and analysis of the ballistic impact of WC-8Co on ceramic targets were verified by experimental data. The results show that front core substitution in SS109 bullets from steel (Pindad standard) to WC-8Co resulted in 1.5 times greater DoP. Although projectiles with steel (Pindad standard) as the front core have a muzzle velocity higher than those using WC-8Co, they have a lower kinetic energy than the latter. In addition, WC-8Co cemented carbides also displayed higher crater and residual velocity on SiC targets; around 1.8 and 1.3 times higher, respectively. These findings demonstrate the potential use of WC-8Co for development as front core material to improve the penetration of projectiles into ceramic armour
Temperature based rapid SAW humidity sensor
Get PDFThis paper investigates the effect of temperature on the sensitivity of a thin-film Polyvinyl alcohol (PVA) based SAW humidity sensor. A PVA coated 433.92 MHz SAW resonator-based humidity sensor was fabricated and tested with different levels of humidity (0.5 to 95% RH) at different operating temperatures (10°C to 70°C). The sensor response was recorded through in-house developed data acquisition software and it was observed that PVA thin film coated SAW sensor shows the maximum sensitivity for trace level moisture detection at a lower temperature (≤10 °C). The sensor sensitivity has been recorded >400Hz/% RH for trace level detection (0.5–30% RH). It has been observed that sensor sensitivity deteriorates when temperature increased to 40 °C from 10 °C. The sensor has a fast response (~1s) and recovery time (<3s) for trace level humidity detection. The proposed sensor can be used in many applications, including fabrication of electronic devices, IC fabrication, pharmaceutical, textile industries, food processing, semiconductor device fabrication, and packaging
Optimal Design of Multilayered Radar Absorbing Structures (RAS) using Swarm Intelligence based Algorithm
Get PDFThe steady progress in the fields of material science and processing technologies has made multi-layered radar absorbing structures (RAS) an attractive option w.r.t. stealth technologies. They possess the ability to reduce radar cross-section with minimum thickness and is therefore most preferred in airborne applications. As far as their electromagnetic performance is concerned, the sequence of material layers and thickness profile plays a pivotal role. Optimization of these two factors becomes complex in case of availability of large number of potential materials. Commonly used EM simulation software can be employed for the optimization of thickness profile. However, selection of suitable material layer sequence is out of their scope. In this context, a particle swarm optimization (PSO) based algorithm is presented for sequencing of material layers and optimization of thickness profile of multi-layered RAS configurations. The fitness function has been appropriately formulated to achieve maximum power absorption over broad band of frequencies and wide range of incident angles. Further, the efficacy of the algorithm has been demonstrated using a suitable case study
Object Detection using Particle Swarm Optimisation and Kalman Filter to Track Partially occluded Targets
Get PDFMotion estimation, object detection, and tracking have been actively pursued by researchers in the field of real time video processing. In the present work, a new algorithm is proposed to automatically detect objects using revised local binary pattern (m-LBP) for object detection. The detected object was tracked and its location estimated using the Kalman filter, whose state covariance matrix was tuned using particle swarm optimisation (PSO). PSO, being a nature inspired algorithm, is a well proven optimization technique. This algorithm was applied to important real-world problems of partially-occluded objects in infrared videos. Algorithm validation was performed by realizing a thermal imager, and this novel algorithm was implemented in it to demonstrate that the proposed algorithm is more efficient and produces better results in motion estimation for partially-occluded objects. It is also shown that track convergence is 56% faster in the PSO-Kalman algorithm than tracking with Kalman-only filter
A Novel Traffic Based Framework for Smartphone Security Analysis
Get PDFAndroid Operating system (OS) has grown into the most predominant smartphone platform due to its flexibility and open source characteristics. Because of its openness, it has become prone to numerous attackers and malware designers who are constantly trying to elicit confidential information by articulating a plethora of attacks through these designed malwares. Detection of these malwares to protect the smartphone is the core function of the smartphone security analysis. This paper proposes a novel traffic-based framework that exploits the network traffic features to detect these malwares. Here, a unified feature (UF) is created by graph-based cross-diffusion of generated order and sparse matrices corresponding to the network traffic features. Generated unified feature is then given to three classifiers to get corresponding classifier scores. The robustness of the suggested framework when evaluated on the standard datasets outperforms contemporary techniques to achieve an average accuracy of 98.74 per cent
A PSO Optimized Model for Identifying Spatio Temporal Hotspots of Terrorist Incidents in India
Get PDFTerrorism is a global issue that prevails throughout the world on all scales. As the distribution of terrorist activities does not follow a random pattern in space and time, its spatiotemporal analysis has drawn considerable attention in recent years. Further, timely identification of Spatio-temporal terrorist activity hotspots is vital to prioritize the security efforts put by a country’s security enforcement agencies. The state-of-the-art methods for Spatiotemporal hotspot detection are based on scan statistics, which enumerates many Spatio-temporal cylinders, making it a computationally expensive approach. Therefore, this paper presents a time-efficient Particle Swarm Optimizer (PSO) based algorithm to detect the most significant Spatio-temporal hotspots. We formulated an optimization model for the problem and applied three variants of PSO viz. conventional PSO, HCL-PSO, and Ensemble PSO. Finally, these schemes have been used to detect spatio-temporal hotspots of different terrorist attacks in India. The results obtained by PSO-based methods have been compared with SaTScan over two parameters: the time required to detect the hotspot and its quality. All the PSO-based schemes significantly outperformed SaTScan in the timely identification of the hotspots. In addition, the quality of hotspots detected by HCL-PSO is at par with SaTScan, whereas the quality of hotspots detected by the other two approaches is slightly lesser than SaTScan. However, the quality of hotspots detected by the other two variants of PSO is slightly lesser than SaTScan. The results are statistically validated using Friedman’s statistical test
Wideband Radar Cross Section Reduction of Microstrip Patch Antenna using Polarization Converter Metasurface
Get PDFAntenna is the key device of communication on stealth platform. It is the greatest contributor to the overall RCS. So, it is desired to reduce the radar signature of the antenna. In this paper, a novel antenna is designed using polarization converter metasurface. The polarization converter metasurface converts the polarization of the incident wave into its orthogonal component. This PCM structure is loaded around patch antenna to reduce the RCS of the antenna over wide frequency range. With this novel design, the overall RCS reduction bandwidth of 140.57% is obtained for the frequency range of 3.49 GHz – 20 GHz. In addition to this, the 10 dB RCS reduction bandwidth is obtained for the frequency ranges of 8.84 GHz – 10.42 GHz (16.41%) and 16.99 GHz – 17.81 GHz (4.71%). The design shows excellent angular stability for both TE and TM polarization. Discernible Bistatic Radar Cross Section reduction is obtained over a wide frequency range. Simulation and experimental results show that there is no degradation in antenna radiation pattern and other parameters. So, with this novel design the problem of obtaining wideband RCS reduction of a microstrip patch antenna is addressed without degradation in radiation pattern along with excellent angular stability for both the polarization modes.