Assessment of Current Health of Hard Disk Drives

Prognostics and health management of computer hard disk drives is beneficial from two different angles: it can help computer users plan for timely replacement of HDDs before they catastrophically fail and cause serious data loss; it can also help product recover facilities reuse hard disks recovered from the end-of-life computers for building refurbished computers. This paper presents a HDD health assessment method using Self-Monitoring, Analysis, and Reporting Technology (SMART) attributes. It also presents the state-of-the art results in monitoring the condition of hard disks and offers future directions for distributed hard disk monitoring.

Optimisation of an SMA-Based Morphing Architecture

Aircraft morphing architectures are currently worldwide investigated to explore the possibility of attaining better performance while reducing weights, volumes and costs of the whole wing system. It is well-known that a 3-flap wing, for instance, shall pay a penalty up to 100% due to the insertion of mechanical devices in its body. Moreover, the insertion of nacelles, aimed at covering the mechanical devices, disturb the wing aerodynamics itself. Also, flapped wings are noisy. The introduction of deformable instead of the classical slotted and flapped wings may lead to significant enhancement also in this field. In the frame of the Joint European Initiative on Green Regional Aircraft, inside a cooperation with the University of Naples, Department of Aerospace Engineering, the authors with their colleagues came to the definition of novel architectures, aimed at those aims. These structures are characterized by load-bearing actuators, a concept that allows overcoming the classical paradox of smart structure systems: capability of bearing loads while attaining (very) large deformations.

Adaptive Control of a Sliding Seat Using Magnetorheological Energy Absorbers

Feasibility of a sliding seat utilizing adaptive control of a magnetorheological (MR) energy absorber (MREA) to minimize loads imparted to a payload mass in a ground vehicle for frontal impact speeds as high as 7 m/s (15.7 mph) is investigated. The crash pulse for a given impact speed was assumed to be a rectangular deceleration pulse having a prescribed magnitude and duration. The adaptive control objective is to bring the payload (occupant plus seat) mass to a stop using the available stroke, while simultaneously accommodating changes in impact velocity and occupant mass ranging from a 5th percentile female to a 95th percentile male. The payload is first treated as a single-degree-of-freedom (SDOF) rigid lumped mass, and two adaptive control algorithms are developed: (1) constant Bingham number control, and (2) constant force control. To explore the effects of occupant compliance on adaptive controller performance, a multi-degree-of-freedom (MDOF) lumped mass biodynamic occupant model was integrated with the seat mass. The same controllers were used for both the SDOF and MDOF cases based on SDOF controller analysis because the biodynamic degrees of freedom are neither controllable nor observable. The designed adaptive controllers successfully controlled load-stroke profiles to bring payload mass to rest in the available stroke and reduced payload decelerations. Analysis showed extensive coupling between the seat structures and occupant biodynamic response, although minor adjustments to the control gains enabled full use of the available stroke.

System Design and Modeling of a Thermally Activated Reconfigurable Wing

Reconfigurable structures such as morphing aircraft generally require an on board energy source to function. Frictional heating during the high speed deployment of a blunt nosed low speed reconnaissance air vehicle can provide a large amount of thermal energy during a short period of time. This thermal energy can be collected, transferred, and utilized to reconfigure the deployable aircraft. Direct utilization of thermal energy has the ability to significantly decrease or eliminate the losses associated with converting thermal energy to other forms, such as electric. The following work attempts to describe possible system designs and components that can be utilized to transfer the thermal energy harvested at the nose of the aircraft during deployment to internal components for direct thermal actuation of a reconfigurable wing structure. A model of a loop heat pipe is presented and used to predict the time dependant transfer of energy. Previously reported thermal profiles of the nose of the aircraft calculated based on trajectory and mechanical analysis of the actuation mechanism are reviewed and combined with the model of the thermal transport system providing a system level feasibility investigation and design tool. The efficiency, implementation, benefits, and limitations of the direct use thermal system are discussed and compared with currently utilized systems.

Two Tiered Analysis of a CFRP Laminate Imbedded With Magnetostrictive Particles

The overall purpose of this research is to characterize the affects of imbedding magnetostrictive particles (MSP) in a CFRP laminate for the purpose of nondestructive evaluation. This paper details an investigation using an analytical and experimental approach. At the time of this publication, both the analytical and experimental investigations are in a preliminary stage and the results have not yet converged. The analytical investigation utilizes fundamental equations for the magnetomechanical properties of the MSP and classical laminate theory for the strength and stiffness of the CFRP laminate to obtain a model of the combination. It is assumed that the magnetomechanical relationship of the MSP layer is a function of the prestress acting on the layer. This relationship is nonlinear in nature but is broken down into a number of linear sections to facilitate analysis. This prestress acting on the MSP layer is a result of the CFRP laminate’s stiffness resisting the induced strain of the MSP layer. Classical laminate theory is used to obtain the value of the prestress as a function of this induced strain. As would be expected, this analysis becomes an iterative process. The induced strain is calculated based on a prestress level of zero. This strain is then used to calculate the amount of stress in the CFRP laminate which becomes the prestress value, and the process is repeated until convergence is reached. Unidirectional CFRP laminates are used in this analysis. The experimental approach involved testing a collection of composite beams imbedded with MSP using a scanner that surrounded the beams. The scanner was composed of an excitation coil and a sensing coil. A detailed schematic of the scanner is included in the paper showing the slide along which the scanner apparatus moved, and the sensing coil surrounded by the excitation coil. The samples used in this analysis were constructed from unidirectional prepreg carbon fiber with varying internal delaminations, ply orientations, and number of plies. A program was constructed that allowed the user to control the signal being output to the excitation coil as well as record data from the sensing coil. The results presented in this paper are not final and will be used to create a foundation for continuation of this research.

Improvement on Thermal Shock Resistance of Ceramic Components by Using Self-Healing

Availability of self-healing on the thermal shock resistance of ceramic components was investigated. Using gas quenching method, the crack-healed alumina-18 vol% SiC composite, which has excellent self-healing ability, was applied to thermal shock of the arbitrary quenching rate. The procedure could give rise to the thermal stress fracture at high temperature. The critical quenching rate at thermal stress fracture of the healed specimen was found to be 6.47 K/s, corresponding to the thermal stress of 452.3 MPa. Alternatively, that of the cracked specimen was found to be 5.02 K/s, corresponding to the thermal stress of 350 MPa. From the obtained results, usage of self-healing was confirmed to improve extremely thermal shock resistance. The present result suggests that usage of self-healing gives a large advantage to design the high temperature ceramic components, because the mechanically reliable design and thermal shock resistance cannot coexist due to low thermal conductivity.

Damage Tracking Using Smart Sensor Network

Sensors are frequently used in damage diagnosis for structural health monitoring (SHM) of aerospace structures. This process typically requires a considerably large number of sensors. By increasing the number of sensors, the amount of data collected, though useful, becomes a burden due to the required computational overhead. In this paper, a random correlation cumulative approach is used to track damage intensity and propagation. The relative correlation between any two randomly chosen sensors is recorded and compared over time. The randomness of the process leads to detecting and tracking any arbitrary crack propagation. A case study for damage detection and tracking using 40 sensors in a steel plate is presented and discussed. It is shown that the proposed method can successfully allow damage tracking while limiting the data considered in the sensor network.

Multi-Location Actuators and Piezoceramic Based 2-D Spiral Array for Structural Health Monitoring: Thin Isotropic Panels

In this paper, a new and robust 2-D phased array technique with multiple distributed actuators is studied for damage detection application based on Guided Lamb Wave (GLW) interrogation in a thin isotropic panel. A 2-D phased array technique using a single actuator located near the center of the 2-D phased array is unable to detect a linear crack oriented normal to the wavefront of the GLW excited from the actuator. To overcome this limitation, the 2-D phased array is coupled with multiple actuators in this study where the actuators are positioned at various locations on a test panel while the 2-D phased array is mounted at the center of the panel. A piezoceramic based 2-D phased array with a spiral configuration is used as a sensor array and the corresponding 2-D phased array signal processing is used to produce array responses and detect various damages. An innovative GLW propagation and reflection analysis technique is implemented to evaluate the damage locations in the panel. Experimental results demonstrate that the 2-D phased array damage detection technique using multiple distributed actuators can provide more robust damage detection scheme in thin isotropic panels than a technique with a single actuator element.

Impact Detection Using an Array of Piezoelectric Wafer Active Sensors and a Microcontroller Unit

This report discusses the development of an embeddable impact detection system utilizing an array of piezoelectric wafer active sensors (PWAS) and a microcontroller. Embeddable systems are a critical component to successfully implement a complete and robust structural health monitoring system. System capabilities include impact detection, impact location determination and digitization of the impact waveform. A custom algorithm was developed to locate the site of the impact.. The embedded system has the potential for additional capabilities including advanced signal processing and the integration of wireless functionality. For structural health monitoring applications it is essential to determine the extent of damage done to the structure. In an attempt to determine these parameters a series of impact tests were conducted using a ball drop tower on a square aluminum plate. The response of the plate to the impact event was recorded using a piezoelectric wafer sensor network attached to the surface of the plate. From this testing it was determined that several of the impact parameters are directly correlated with the features recorded by the sensor network.

Metal-Core Piezoelectric Fibers for the Detection of Lamb Waves

Metal-core piezoelectric fiber (MPF) is a new type of piezoelectric ceramic device with small size, and has great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. This paper focuses on the use of MPF as ultrasonic Lamb wave receivers. First, the MPF sensor voltage response is derived by coupling the direct piezoelectric effect to the wave strain field excited by circular crested actuator. The obtained theoretical result is validated on an aluminum plate. Furthermore, the experiment that compares the MPF response to Lamb wave with the PZT response is performed. The results show that MPF sensors can be used to sense Lamb waves clearly. In the end, the directivity of MPF response to Lamb waves was investigated, and another experiment is performed to examine the directivity of MPF response to Lamb waves. The result shows that MPF has high directivity, which can be exploited to triangulate the location of an ultrasound source without prior knowledge of the wave velocity in the medium.