In this study the effect of heat treatment over the microstructural, mechanical and electrochemical properties of low carbon steel material is studied. Mainly quenching and annealing types of heat treatment was performed over the samples. Microstructure of the material before and after the treatments were examined by using optical microscope. Mechanical properties such as tensile strength, young modulus, and fracture strength and harness of the materials were also determined by tensile and hardness testers. Electrochemical measurements and corrosion testing are conducted using NaCl solution and sea water as the electrolyte. Hardness values were higher by 19 % for quenched sample than the original as the grain sizes were smaller for quenched sample and a less by 21% for annealed one from the original sample as the grain size was higher for the annealed sample from original sample.
Back-silvered glass mirrors exposed in Abu Dhabi outdoor conditions for 7 years along with corresponding as-received mirrors from the same manufacturing batch which were preserved in a warehouse are analyzed in the present study. The availability of both the as-received mirrors and the exposed ones over a time longer than that in previous studies presents an opportunity to validate accelerated aging tests through comparison with naturally aged mirrors. The exposed mirrors showed substantial reflectance degradation. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) was used to characterize both as-received and exposed samples and compare the as-received sample to a reference mirror from the state-of-the-art commercial solar mirrors. The analyses identified 5 possible causes of the rapid degradation observed for the mirrors in question in comparison to the lifetime expectation for commercial solar mirrors. The findings serve to guide ongoing accelerated-aging studies on the same mirrors.
In this work, we perform a nonlinear analysis of microcantilever beams subject to the combination of electrostatic forcing and mechanical shock for MEMS applications. Several research studies have showed that MEMS devices deploying electrically-actuated vibrating beams, such as resonant sensors and RF filters, may fail to operate when undergoing mechanical shocks due to the pull-in instability. The objective of the present study is to investigate the possibility to overcome or exploit this issue by considering different microsystem designs based on the application of interest. Towards this end, we develop a mathematical model to simulate the dynamic response of single and dual microbeams under varying electric actuation and shock loads. The actuation of the singlebeam system is made via a fixed electrode (uncoupled actuation) while the dual-beam system, composed of two movable microbeams, is actuated by applying a voltage among them (coupled actuation). It is shown that dual-beam system is more robust in terms of resistance to mechanical shock than the single-beam system.
Tuned vibration absorbers have long been used as a mean to suppress vibration. Despite their simplicity and effectiveness, they have a significant drawback, which is their limited effective bandwidth. Recent research efforts have been focused on development of solutions for passive vibration suppression that are effective over a wide frequency range, which resulted in the invention of metastructures. Metastructures contain local resonators that are distributed along the structure and tuned to specific frequencies. In many applications the addition of significant mass to the structure in the form of resonators is prohibitive, hence resonators must be integrated into structural members. The proposed metastructure will contain in-plane resonators acting as distributed vibration absorbers. In this research, zigzag elastic elements connected to a small mass will be used to function as in-plane resonators, which enables realizing low enough stiffness within a confined space to achieve low resonant frequencies.We describe the development of a lumped parameter model that could be used as a tool for design and optimization of in-plane resonators, while being more efficient computationally than traditional finite element models. We verify the developed model by comparing its predictions with results obtained using finite element models.
Corrosion of pipelines is one of the major problems faced by the oil and gas industry. Replacement or rehabilitation of the pipeline is the only option for corroded pipelines. Rehabilitation can be done by pipe-in-pipe technology which involves inserting a new pipe into an existing pipeline. However, the installation process of these liners is not an easy affair, and the pulling-in load has to be monitored carefully or else it might result in the failure of the liner. This paper involves the pulling-in analysis of a HDPE (High Density Polyethylene) liner through a pipeline. The simulation of pulling-in of the liner is conducted by using analytical as well as by using finite element analysis (FEA) on an arbitrary pipeline. The results obtained from both FEA model and the analytical model are to be compared.
Different navigation systems have different requirements for attitude estimation, positioning, and control. For higher accuracy, one can use array of MEMS Inertial Measurement Unit (IMU) sensors, to replace a single, high performance, high-cost, power-hungry mechanical counterparts. The lowcost MEMS sensors require a sensor fusion processing unit that plays a key role in achieving the required performance and should support signal processing algorithms, such as the Kalman Filter (KF). This paper addresses the scalability problem of IMU array sensor fusion using a specialized vector processor designed specifically to achieve real-time, high-throughput and low-power. The vector processor has been implemented in Artix-7 FPGA and shown to outperform a scalar processor by 100% in latency for a 100-component vector with the throughput being linear in the number of IMU sensors up to the limits of the FPGA resources. The tradeoffs between vector size, memory requirements, and sampling rates are also fully quantified.
Unmanned Aerial Vehicles (UAVs) have been widely used in many industrial, civilian and military applications. Moreover, the control of small size UAVs faces many challenges such as sensitivity to disturbances and the need for responsive controller. The aim of this paper is to compare the performance of PID controllers tuned using two different methods. The first PID controller is tuned using Ziegler-Nicholas (ZN) while the second PID controller is tuned via full state feedback Linear Quadratic Regulator (LQR). The results show that the PID tuned via LQR gives better performance measures than the PID tuned using ZN approach.
Passive gravity compensation for a mechanism is usually preferred to the active one for some reasons including cost consideration. Many technologies based on counterweight and linear springs have been widely developed, whereas the use of torsional springs is rarely discussed due to unavailability of exact mathematical manipulation to determine the required spring constants to achieve the static balance. This paper proposes the use of torsional springs for passive gravity compensation applied to a parallel kinematics mechanism. The spring constants are determined by constrained optimization approach aiming at minimizing the total potential energy of the mechanism along a prescribed trajectory within the range of motion. It is shown that the solution provides almost-statically-balanced state of the mechanism within its range of motion. This accordingly reduces the required actuation forces/torques and hence the power consumption.
In this paper, an example of applying the passive Discrete Variable Stiffness Joint (pDVSJ-II) is illustrated. A qualitative experiment in a teleoperation scenario is presented as a case study to demonstrate the effectiveness of the proposed haptic interface and to show how a human can take advantage of stiffness rendering by the proposed device in applications e.g. remote palpation. The results show that the device is capable of successfully providing information about the stiffness of two different objects through the forces acting at the remote site, thus improving the overall telepresence in such applications.
In this paper, we study a class of fractional nonlinear Volterra integro-differntial type of singularly perturbed problems with fractional order: We divide the problem into two problems. The first problem is the reduced problem when = 0: The second problem is fractional Volterra integrodifferential problem. We use the finite difference method to solve the first problem and the reproducing kernel method to solve the second problem. The results show that the proposed analytical method can achieve excellent results in predicting the solutions of such problems. Theoretical results are presented. Numerical results are presented to show the efficiency of the proposed method.
