Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Selective Laser Melting based Additive Manufacturing Process Diagnostics using In-line Monitoring Technique and Laser-Material Interaction Model

2024-06-01
2024-26-0420
Selective Laser Melting (SLM) has gained widespread usage in aviation, aerospace, and die manufacturing due to its exceptional capacity for producing intricate metal components of highly complex geometries. Nevertheless, the instability inherent in the SLM process frequently results in irregularities in the quality of the fabricated components. As a result, this hinders the continuous progress and wider acceptance of SLM technology. Addressing these challenges, in-process quality control strategies during SLM operations have emerged as effective remedies for mitigating the quality inconsistencies found in the final components. This study focuses on utilizing optical emission spectroscopy and IR thermography to continuously monitor and analyze the SLM process within the powder bed, with the aim of strengthening process control and minimizing defects.
Technical Paper

Multi-Scale Modeling of Selective Laser Melting Process

2024-06-01
2024-26-0415
The Selective Laser Melting (SLM) process is employed in high-precision layer-by-layer Additive Manufacturing (AM) on powder bed and aims to fabricate high-quality structural components. To gain a comprehensive understanding of the process and its optimization, both modeling and simulation in conjunction with extensive experimental studies along with laser calibration studies have been attempted. Multiscale and multi-physics-based simulations have the potential to bring out a new level of insight into the complex interaction of laser melting, solidification, and defect formation in the SLM parts. SLM process encompasses various physical phenomena during the formation of metal parts, starting with laser beam incidence and heat generation, heat transfer, melt/fluid flow, phase transition, and microstructure solidification. To effectively model this Multiphysics problem, it is imperative to consider different scales and compatible boundary conditions in the simulations.
Technical Paper

Detecting the Anomalies in LiDAR Pointcloud

2024-04-09
2024-01-2045
LiDAR sensors play an important role in the perception stack of modern autonomous driving systems. Adverse weather conditions such as rain, fog and dust, as well as some (occasional) LiDAR hardware fault may cause the LiDAR to produce pointcloud with abnormal patterns such as scattered noise points and uncommon intensity values. In this paper, we propose a novel approach to detect whether a LiDAR is generating anomalous pointcloud by analyzing the pointcloud characteristics. Specifically, we develop a pointcloud quality metric based on the LiDAR points' spatial and intensity distribution to characterize the noise level of the pointcloud, which relies on pure mathematical analysis and does not require any labeling or training as learning-based methods do. Therefore, the method is scalable and can be quickly deployed either online to improve the autonomy safety by monitoring anomalies in the LiDAR data or offline to perform in-depth study of the LiDAR behavior over large amount of data.
Technical Paper

2D Diesel Spray Droplet Size Mapping Based on Planar Laser Induced Fluorescence and Mie-Scattering Technique

2024-04-09
2024-01-2622
The spray droplet size distribution plays a crucial role in internal combustion engine, which directly impacts on the fuel-air mixing, evaporation and combustion. The non-intrusive optical diagnostics is one of the most effective methods to obtain a temporally and spatially droplet size distribution in two-dimensional field. In the present study, the three-dimensional (3D) diesel spray droplet size mapping is investigated based on simultaneous planar laser induced fluorescence (PLIF) and Mie-scattering. The dependence of fluorescent and scattered light intensities from spherical droplets on droplet diameter can be evaluated using the ratio of laser-induced fluorescence and scattered light intensities (LIF/Mie technique). The spray structure is analyzed for a modified single-hole diesel injector. A calibration curve to convert the LIF/Mie ratio to droplet diameter is deduced using LIF/Mie imaging and analysis of single droplets generated by a droplet generator.
Technical Paper

Effect of ambient pressure on ammonia sprays using a single hole injector

2024-04-09
2024-01-2618
Ammonia has received attention as an alternative hydrogen carrier and a potential fuel for thermal propulsion systems with a lower carbon footprint. One strategy for high power density in ammonia applications will be direct injection of liquid ammonia. Understanding the evaporation and mixing processes associated with this is important for model development. Additionally, as a prior step for developing new injectors, it is of interest to understand how a conventional gasoline direct injection (GDI) injector would behave when used for liquid ammonia without any modifications. Pure anhydrous ammonia, in its liquid form, was injected from a single hole GDI injector at a fuel pressure of 150 bar into an optically accessible constant volume chamber filled with nitrogen for ammonia spray measurements. The chamber conditions spanned a wide range of pressures from 3 to 15 bar at an increment of 1 or 2 bar between the test points.
Technical Paper

Uncertainty Introduced by Image Projection in Video-Based Reconstructions of Vehicle Positions and Speeds

2024-04-09
2024-01-2485
Video evidence in collision reconstruction has become a common foundation for vehicle position and speed analyses. The goal of this study was to explore how the uncertainty of these position/speed analyses is affected by various camera-, scene-, and vehicle-related properties. To achieve this goal, we quantified how the size and aspect ratio of pixels in the pixel grid change as a result of correcting for lens distortion and projecting the pixel grid onto a real-world surface captured by the image. Relying on a combination of general and case-specific examples, we ran a series of Monte Carlo analyses exploring how uncertainty can be calculated and how it varies for different measurements and for different camera-, scene-, and vehicle-related properties.
Technical Paper

Importance of Casting Soundness in Aluminium Parts for Laser Weld Quality

2024-01-16
2024-26-0191
Light weight and Robust manufacturing technologies are always needed for transformation drive in the Automotive industry for the next-generation vehicles with greater Power to weight ratio. Innovations and process developments in materials and manufacturing processes are key to this light weighting transformation. Aluminium material has been widely used for these light weighting opportunities. However, aluminum joining techniques, characterized by their poor quality and consistency are limiting this transformation. This technical paper represents one of such case, where the part is made up of Aluminium through conventional casting route which has affected the laser weld quality due to poor casting soundness. This experiment explains in detail about the importance of Casting soundness for laser weld quality, weld penetration, strength etc., and the Product consistency.
Technical Paper

Review on Laser Welding of High Strength Aluminium Alloy for Automotive Applications

2024-01-16
2024-26-0193
High strength aluminium alloys are an ideal material in the automotive sector leading to a significant weight reduction and enhancement in product safety. In recent past extensive development in the field of high strength steel and aluminium was undertaken. This development has been propelled due to demand for light weight automotive parts. The high strength to weight ratio possessed by Al alloy helps in reducing the total weight of the vehicle without effecting the overall performance, thereby increasing the fuel economy, and reducing the carbon emission level. Joining of high strength aluminium alloy is critical to develop durable automotive products. Joining of high strength aluminium alloy for mass production in automobile industry is a challenging task. Laser welding is recognized as an advanced process to join materials with a laser beam of high-power, high- energy density.
Technical Paper

Bi-Directional Adjustable Holder for LiDAR Sensor

2024-01-16
2024-26-0024
LiDAR stands for Light Detection and Ranging. It works on the principle of reflection of light. LiDAR is one among the other sensors like RADAR and Camera to help achieve a higher level (Level 3 & above) of Autonomous driving capabilities. LiDAR, as a sensor, is used to perceive the environment in 3D by calculating the ‘Time of flight’ of the Laser beam transmitted from LiDAR and the rays reflected from the Object, along with the intensity of reflection from the object. The frame of perception is plotted as a point cloud. LiDAR is integrated in front of the vehicle, precisely in the grill of the car having a high vantage point to perceive the environment to extract the best possible sensor performance. LiDAR sensor needs to be held within the front panel cutout with uniform gap and flush condition.
Technical Paper

A Novel LiDAR Anchor Constraint Method for Localization in Challenging Scenarios

2023-12-20
2023-01-7053
Positioning system is a key module of autonomous driving. As for LiDAR SLAM system, it faces great challenges in scenarios where there are repetitive and sparse features. Without loop closure or measurements from other sensors, odometry match errors or accumulated errors cannot be corrected. This paper proposes a construction method of LiDAR anchor constraints to improve the robustness of the SLAM system in the above challenging environment. We propose a robust anchor extraction method that adaptively extracts suitable cylindrical anchors in the environment, such as tree trunks, light poles, etc. Skewed tree trunks are detected by feature differences between laser lines. Boundary points on cylinders are removed to avoid misleading. After the appropriate anchors are detected, a factor graph-based anchor constraint construction method is designed. Where direct scans are made to anchor, direct constraints are constructed.
Technical Paper

Research on Wall Temperature of Flame-wall Interaction Based on Laser-Induced Phosphorescence and Heat Transfer Simulation

2023-09-29
2023-32-0056
Heavy heat load is one of the bottlenecks restricting the highly intensive marine engine development. Reducing wall heat loss contributes to this target. The wall heat transfer is mainly influenced by flame-wall interaction (FWI). In this paper, a wall temperature distribution measurement system is developed based on the Laser-Induced Phosphorescence (LIP). The effects of the coating thickness and the laser fluence on LIP are studied to clarify the accuracy of wall temperature measurement based on LIP and the one-dimensional wall temperature distribution. In addition, a conjugate heat transfer model of FWI was established based on CONVERGE to simulate the FWI and the accompanying heat transfer process. The simulation is compared with the experimental wall temperature results and demonstrates the effectiveness of the conjugate heat transfer model. The influence of the initial velocity, the impinging distance and the wall roughness on the wall heat transfer are studied.
Technical Paper

Mixture Formation Process Analysis in Spray and Wall Impingement Spray under Evaporating Conditions for Direct injection S.I. engines

2023-09-29
2023-32-0015
In this study, the authors analyze the concentration distribution of an evaporative spray mixture with LIEF (Laser induced exciplex fluorescence) method, which is a type of optical measurement. LIEF method is one of the optical measurements for obtaining the spray concentration distribution for separating vapor/liquid phases based on the fluorescence characteristics. In this paper, a quantitative concentration distribution analysis method for wall impingement spray in heterogeneous temperature field has been proposed. Then, a series of experiments were performed in varying injection pressure and ambient density. As a result, a two-dimensional concentration distribution was obtained for the free spray and wall impingement spray.
Technical Paper

Development Of On-board Multi-component Gas Analyzer Toward Euro 7

2023-09-29
2023-32-0026
The Euro 7 emission regulations currently under consideration by the EU will adopt on-road emissions test as the main Type Approval procedure, and it has been proposed that the number of gas components to be measured will be increased. Therefore, the Portable Emissions Measurement System (PEMS) used for on- road emissions testing must be able to simultaneously measure more components with higher precision while maintaining the same compact and lightweight structure as in the existing PEMS. The authors have applied a relatively new technique, quantum cascade laser infrared spectroscopy (QCL-IR), to an on-board multi-component gas analyzer. Comparison with laboratory tests on a gasoline passenger car on a dynamometer showed that the newly developed QCL- IR PEMS correlated well with conventional PEMS and stationary conventional analyzers.
Technical Paper

A Study of Soot Formation Process in a Jet-jet Interaction Region of Diesel Spray Flames with LII/LS Measurement

2023-09-29
2023-32-0088
In a rapid compression and expansion machine (RCEM), spray flames from a two-hole injector are injected toward a wall to achieve jet-jet interaction after spray flames impinge onto the wall. Simultaneous laser-induced incandescence (LII) and laser scattering (LS) measurements were performed to investigate the soot formation process in the jet-jet interaction zone. The results showed that high LII and LS signals were detected in the interaction region and persisted for a considerable period and that soot particle size in the interaction zone was independent of the time and injection pressure.
Magazine

Aerospace & Defense Technology: September 2023

2023-09-07
How Thunderbolt 4 Helps Bring Fault-Tolerant, Distributed Systems to Market Delivering Operational Energy to Enhance Warfighter Capability Optoelectronic Analog Signal Transmission Takes Center Stage Amidst Aerospace and Defense Innovation Shaking Outside the Box to Advance Flight Research An Introduction to Quantum Computing How Laser Communications Innovation is Finally Coming of Age and Driving Innovation in Defense Spatial Calibration for Accurate Long Distance Measurement Using Infrared Cameras A new spatial calibration procedure has been introduced for infrared optical systems developed for cases where camera systems are required to be focused at distances beyond 100 meters. Towards Greater Sensitivity: A Brief FTIR and Infrared-Based Cavity Ring Down Spectroscopy Comparative Study A presentation of work comparing efficacy of a traditional IR method used as a standard within the U.S.
Technical Paper

High-Speed 2-D Raman and Rayleigh Imaging of a Hydrogen Jet Issued from a Hollow-Cone Piezo Injector

2023-08-28
2023-24-0019
This paper reports high-speed (10 kHz and 100 kHz) 2-D Raman/Rayleigh measurements of a hydrogen (H2) jet issued from a Bosch HDEV4 hollow-cone piezo injector in a high-volume constant pressure vessel. During the experiments, a Pa = 10 bar ambient environment with pure nitrogen (N2) is created in the chamber at T = 298 K, and pure H2 is injected vertically with an injection pressure of Pi = 51 bar. To accommodate the transient nature of the injections, a kHz-rate burst-mode laser system with second harmonic output at λ = 532 nm and high-speed CMOS cameras are employed. By sequentially separating the scattered light using dichroic mirrors and bandpass filters, both elastic Rayleigh (λ = 532 nm) and inelastic N2 (λ = 607 nm) and H2 (λ = 683 nm) Raman signals are recorded on individual cameras. With the help of the wavelet denoising algorithm, the detection limit of 2-D Raman imaging is greatly expanded.
Standard

Criteria for Laser Control Measures for Aviation Safety

2023-07-12
CURRENT
AS6029B
This document provides requirements and guidance for laser proponents and aviation authorities to determine the criteria that laser hazard control measures shall meet for the operation of an outdoor laser system in navigable airspace. This document has been developed to be used for a wide range of outdoor laser hazard control measures from completely manual systems to those with various levels of automation. This document applies to laser propagation which may expose persons in navigable airspace to laser energy above the applicable maximum permissible exposure limit or which emits visible light in excess of the visual interference limits in the applicable Laser-Free, Critical, and Sensitive Hazard Zones. The document does not cover systems intended to deliberately aim and or track lasers at aircraft, such as Federal Aviation Administration (FAA) approved purposes, including visual warning systems, search and rescue, etc.
Technical Paper

Large-Eddy Simulation of a NACA23012 Airfoil under Clean and Iced Conditions

2023-06-15
2023-01-1483
Predicting the aerodynamic performance of an aircraft in icing conditions is critical as failures in an aircraft’s ice protection system can compromise flight safety. Aerodynamic effects of icing have typically relied on RANS modeling, which usually struggles to predict stall behavior, including those induced by surface roughness. Encouraged by recent studies using LES that demonstrate the ability to predict stall characteristics on full aircraft with smooth wings at an affordable cost [1], this study seeks to apply this methodology to icing conditions. Measurements of lift, drag, and pitching moments of a NACA23012 airfoil under clean and iced conditions are collected at Re = 1.8M. Using laser scanned, detailed representations of the icing geometries, LES calculations are conducted to compare integrated loads against experimental measurements in both clean and iced conditions at various angles of attack through the onset of stall [2].
Technical Paper

Time Resolved 3D Scanning of Ice Geometries in a Large Climatic Wind Tunnel

2023-06-15
2023-01-1414
In the scope of development or certification processes for the flight under known icing conditions, aircraft have to be tested in icing wind tunnels under relevant conditions. The documentation of these tests has to be performed at a high level of detail. The generated data is used to prove the functionality of the systems, to develop new systems and for scientific purposes, for example the development or validation of numerical tools for ice accretion simulation. One way of documenting the resulting ice geometry is the application of an optical 3D scanning or reconstruction method. This work investigates and reviews optical methods for three-dimensional reconstructions of objects and the application of these methods in ice accretion documentation with respect to their potential of time resolved measurement. Laboratory tests are performed for time-of flight reconstruction of ice geometries and the application of optical photogrammetry with and without multi-light approach.
Technical Paper

Evaluation of Microstructure and Mechanical Properties of Additively- Manufactured Aluminium Alloy Automotive Component

2023-05-25
2023-28-1301
The present work focusses on development of AlSi10Mg alloy component from the pre-alloyed powder by laser powder bed fusion (LPBF), one of the popular additive manufacturing technologies. The effect of heat treatment on microstructure and mechanical properties has also been studied. In accordance with T6 heat treatment process, the LPBF specimens were solution treated at 535°C for 2 h, then water quenched and subsequently, artificially aged at 160°C for 10 h. The role of printing direction on microstructure and mechanical properties has also been investigated. The printing parameters such as laser power, scan speed and hatch space were optimized for defect free automotive component. The as-printed and heat treated components were subsequently evaluated to assess their performance.
X