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Role of Human Factors in Preventing Aviation Accidents: An Insight: by Kamaleshaiah Mathavara and Guruprasad Ramachandran
Get PDFFlight is one of the safest modes of travel even today. However, nearly 75 percent of civil and military aviation accidents around the globe have been attributed to
human errors at various levels such as design, drawing, manufacturing, assembly, maintenance, and flight operations. This paper traces the civil aviation accidents that
have occurred during the last eight decades and brings out the vital factors leading to the disaster by considering a few representative cases. The concept of human factors
is introduced, and the various models that have been in use to understand the root causes leading to aviation accidents are presented. An example of the application of human factors analysis and classification system (HFACS) framework is narrated.
It is found that majority of recent civil aviation accidents have occurred during the landing and approach phases, and it is possible to minimize the accidents by suitably maintaining situational awareness. Considering the growth of air traffic that is expected to double in the next 10–15 years, the role of human factors in preventing aviation accidents is even more relevant. A new model for human factors is proposed. Way forward to even safer skies is presented
High d 33 Lead-Free Piezoceramics: A Review
No full textOver the past two decades, lead-free piezoceramics have been developed aiming to replace toxic lead-bearing lead zirconate titanate (PZT). A large number of lead-free piezo systems were explored during this period as evidenced from the huge number of publications. At this juncture, it was felt necessary to publish a review article focusing on material systems and processes delivering high d33 in order to give direction to future research for its further improvement equivalent to or higher than the d33 level delivered by PZT. The important lead-free piezo systems under consideration are: modified barium titanates such as barium calcium titanate zirconate (BCTZ), barium calcium tin titanate (BCSnT), barium calcium hafnium titanate (BCHfT), and potassium sodium niobate (KNN). In this article, an effort has been made to review the high piezoelectric properties achieved on the above lead-free piezo systems explaining the reasons and mechanisms behind high piezo properties and possible future directions of the research for further enhancement of properties
Epidermal Inspired Flexible Sensor with Buckypaper/PDMS Interfaces for Multimodal and Human Motion Monitoring Applications
No full textThe advancements in the areas of wearable devices and flexible electronic skin have led to the synthesis of scalable, ultrasensitive sensors to detect and differentiate multimodal stimuli and dynamic human movements. Herein, we reveal a novel architecture of an epidermal sensor fabricated by sandwiching the buckypaper between the layers of poly(dimethylsiloxane) (PDMS). This mechanically robust sensor can be conformally adhered on skin and has the perception capability to detect real-time transient human motions and the multimodal mechanical stimuli of stretching, bending, tapping, and twisting. The sensor has feasibility for real-time health monitoring as it can distinguish a wide range of human physiological activities like breathing, gulping, phonation, pulse monitoring, and finger and wrist bending. This multimodal wearable epidermal sensor possesses an ultrahigh gauge factor (GF) of 9178 with a large stretchability of 56%, significant durability for 5000 stretching–releasing cycles, and a fast response/recovery time of 59/88 ms. We anticipate that this novel, simple, and scalable design of a sensor with outstanding features will pave a new way to consummate the requirements of wearable electronics, flexible touch sensors, and electronic skin
On the structural changes, mechanism and kinetics of stabilization of lignin blended polyacrylonitrile copolymer fiber
No full textPolyacrylonitrile(PAN)/lignin blend fiber prepared by continuous wet spinning process in dimethylsulfoxie(DMSO) was thermally stabilized under oxygen atmosphere in a continuous multizone oven at different heating temperature. The thermal behaviour of PAN/lignin fiber (PL fiber) stabilized were characterized by differential scanning calorimetry(DSC) under nitrogen atmosphere. The cyclization kinetics parameters such as activation energy(Ea), rate constant(k), pre-exponential factor(A) and extent of oxidation reaction (EOR) at different temperature were calculated from Kissinger and Ozawa method. FTIR analysis was used to investigate the structural changes and calculate the cyclization index and dehydrogenation index of stabilized PL fiber. The cyclization index values for the temperature of stabilization from 235 °C to 265 °C varied from 40 to 85%. The variation in density, elemental composition and mechanical properties of PL fiber stabilized at different temperature was determined. The density of the stabilized fiber varied from 1.225 to 1.385 g/cc as the stabilization temperature increased from 235 to 265 °C. The mechanism of thermal stabilization of and a set of temperature profile for a complete stabilization of PL fiber has been deduced from the various characterization
Influence of particle size on magnetic and electromagnetic properties of hexaferrite synthesised by sol-gel auto combustion route
No full textMagnetoplumbite barium hexaferrite (BaFe11.8Co0.2O19) is synthesised through sol-gel auto-combustion method under two pH conditions of precursor solutions (acidic i.e. pH < 1 and neutral i.e. pH = 7). The XRD analysis followed by Reitveld refinement indicates the formation of phase pure samples in both cases but the barium hexaferrite obtained from acidic precursor solution has smaller crystallite sizes. The Transmission Electron Microscopy (TEM) analysis followed by High Resolution Transmission Electron Microscopy (HRTEM) confirms a lower particle size of ∼20 nm for barium hexaferrite synthesised from acidic pH precursor solution. The shift in Raman peak (520-540 cm−1) by 20 cm−1, represents the whole structural block and further confirms the differences in the distribution of particle sizes due to the method of synthesis. The magnetic studies display a lower coercive field for the samples with smaller particle sizes. This is due to the crystalline size-induced microstrain that controls the magneto-crystalline anisotropy, shape anisotropy and stress anisotropy. The electromagnetic characterisation confirms broader absorption in the range of 8–18 GHz (X-band) with RL ≤ −7 db for the entire range for the samples with smaller particle sizes
Crystallographic evaluation of low cycle fatigue crack growth in a polycrystalline Ni based superalloy
No full textWe present the microscale fracture mechanics aspects of LCF cracks non-propagating till failure in the cylindrical specimens of Ni based superalloy Haynes 282 and attempt to unravel the underlying crystallographic factors. Two key parameters, Crack Tip Opening Angle (CTOA) and maximum tangential stress (θMTS) have been opted for characterization. CTOA variations along with a propagating crack, exhibit a non-linear decay followed by a stabilized regime and the fraction of the stabilized regime increases in lower strain amplitude where the fatigue life is more. Mixity of local KI and KII fields is directly proportional to θMTS and that has been assessed by measuring local deflections. The modal mixity has been found to be microstructure sensitive and an entirely statistical parameter. Different growth modes of these non-propagating cracks have been identified from the microstructural observations. The role of elasto-plastic incompatibility of neighboring grains has been addressed by conducting crystallographic analyses. There is a critical bound for Elastic Modulus (EM) and Schmid factor (SF) for the grains favoring subsurface crack propagation below which grains (mostly with high elastic compliance and low SF) are not participating in crack propagation. The favourable twin-matrix incompatibility of the microstructure has also been identified about the fatigue crack growth and twins in (211) plane is abundant in the cracked region. From the results of a detailed slip transfer analysis based on the Luster-Morris parameter (LMP), it is observed that there exists microstructurally controlled lower bounds that inhibits slip transfer (LMP value <0.1). Dislocation debris analysis using TEM has also been carried out to understand micromechanisms clearly. Both non coplanar and planar mode of dislocation activity has been observed and twin boundaries has been see to act as barrier to the planar dislocation motion
Unmanned Aerial Vehicle-Based Multispectral Remote Sensing for Commercially Important Aromatic Crops in India for Its Efficient Monitoring and Management
No full textAromatic plants cultivation, processing and marketing is an upcoming agro-industry. The yields from these plants are generally governed by its good management practices of timely, suitable and precise actions against damaging factors. Remote sensing in agriculture is not a new phenomenon anymore, but using unmanned aerial vehicle (UAV, commonly known as drones) for the same is a pertinent topic these days, especially in India. Therefore, the study seeks to perform UAV-based airborne data acquisition, processing and analysis for modernised agricultural practices, finding of which may lead to generate rapid and on-demand real-time remotely sensed data for precision agriculture of commercial crops, which require more care and timely inputs as compared to conventional crops. The UAV high-resolution (1.5 cm/pixel) data were acquired from Mica Sense Altum, a 6 bands multispectral sensor, mounted over an indigenous Quad-copter (< 5 kg). With the help of processed orthoimage, the 22 plots of Rosa damascena (Damask Rose) were precisely (95% accuracy) classified into 03 categories, i.e., rose canopy, weed and open soil areas. We have also estimated digital plant count, plant height derived from canopy height model (CHM), canopy temperature and the topographic conditions of the crop plots. The digital plant counting for R. damascena planted in 4323 m2 area took 1.2 h as compared to manual 5.94 h counting. Average plant height values derived from CHM ranged from 23–68 cm as compared to 28–71 cm manually measured heights. Results were compared with ground sampling data, with which high correlation was found in digital plant count (R2 = 0.99) and plant height (96.69% accuracy). The derived average moderate slopes and northeast aspect suggested suitable topographic conditions required for R. damascena cultivation. The image-derived canopy temperature was compared to the relative ground-based measurements, obtaining accuracy percent of 98.54%. The outcomes are encouraging and have potential to be applied for future UAV grounded applications by farmhands
Kinematic Synthesis and Optimization of a Double-Slotted Fowler Flap Mechanism
No full textA double-slotted Fowler flap in transport aircraft has more complexities in kinematic synthesis and design. The present research work presents a combination of six-bar mechanism, four-bar mechanism and a double-slotted mechanism configured for deployment of a Fowler flap arrangement. The mechanism is synthesized for cruise, take-off and landing conditions. A novel procedure for dimensional synthesis and optimization of the mechanism is developed for synchronizing flap and aft-flap positions. The complete synthesis, optimization procedures and parametric analysis are coded into MATLAB program. The results of the synthesis procedure are verified with 2D planar kinematic models and 3D solid models using SolidWorks. Also the novel kinematic synthesis procedure is validated by developing a prototype model of the mechanism using 3D printing technology
Maximum Amplitude Spectra of Propagating Guided Waves in Thin Isotropic Structure Employing Circular and Rectangular PZT Array Sensors for Structural Health Monitoring Applications
No full textStructural Health Monitoring of the aircraft using lamb waves can be achieved by deploying the proper sensor network on structures. Therefore, the present study compares two network topologies used to monitor the structures. MAS is the frequency spectrum, generated from the peak values of the positive envelop of response signal to a range of excitation frequencies of the Lamb wave. Aluminium/Isotropic rectangular plates and a shell structure are instrumented with surface mounted PZT sensors. Group velocity of the propagating Lamb waves are estimated between emitter and receivers signals for all the three structures in a range of frequencies. MAS plot variation between circular and rectangular PZT array networks are examined in rectangular plate structure. The parameters namely: MAS and Group velocity of the Lamb waves extracted from the Matlab® platform are validated with industry standard data processing tool: DATS® for all the three structures considered. Isotropic plates and shell structure are scanned using Laser Vibro-meter in order to examine the Lamb wave propagation patterns. The proposed Lamb wave-based methodology using different PZT sensors network and NI data acquisition system can be used for damage detection in real time applications
A study on the fatigue crack growth behaviour of GTM718 nickel based super alloy under cold-TURBISTAN spectrum loads
No full textIn this study, the fatigue crack growth (FCG) behavior of GTM718 nickel base super alloy subjected to cold-TURBISTAN spectrum load sequence was determined by three different methods i.e., (i) Experimental, (ii) Analytical prediction using cycle-by-cycle method and, (iii) Prediction by finite element analysis (FEA). In the experimental method, a standard compact tension (CT) specimen was prepared and pre-cracked to produce a sharp fatigue crack at the notch root. Then, the specimen was subjected to spectrum load blocks repeatedly and crack growth was measured as a function of applied number of flights. Two such tests were carried out in a servo-hydraulic universal test machine with triangular waveform and at an average frequency of 2 Hz. In the second analytical method, the individual load cycles in cold-TURBISTAN spectrum block were separated through rain flow cycle counting method. For each of this counted cycle, the crack extension was determined using crack growth law which was based on two-parameter crack driving force, ΔK*. An in-house MATLAB code was written and used to determine the FCG behavior by cycle-by-cycle method. In the third FEA method, a global model of CT specimen of GTM718 was created in HYPERMESH and a local model with a pre-crack was created in FRANC3D. The FCG behavior under spectrum load was determined using FRANC3D in conjunction with MSC NASTRAN. Two different types of ‘FCG law - stress ratio effect’ combinations were employed i e., Paris’-Walker (P-W) and Bi-linear-Walker (B-W). The required constants for these laws were derived from the available experimental data of the material. It was observed that the predicted FCG behavior by analytical and FEA methods, although conservative, were fairly good when compared to experimental results