CHAPTER 2 LITERATURE REVIEW The literature review chapter presents critical points regarding current knowledge of PZT sensors and SHM. The existing approach to SHM is discussed and analysis of the PZT technology with statistical indices is included as well. 2.1 Structural Health Monitoring Structural health monitoring (SHM) is defined as the process of implementing a a damage identification strategy for aerospace, civil and mechanical engineering infrastructure. In this case, damage can be defined as changes introduced into a system that adversely affects its current or future performance (Farrar & Worden, 2006). Damage are considered flaws and these flaws originate from the material level. Under certain conditions specific to the specimen alone, the flaws can grow to a point which is undesirable for the material and thus lead to failure. Failure could lead to loss of lives or great economic consequences depending on the degree of the failure. Thus, there is a greater awareness in SHM over the past decade by governments and industries to prevent such unwanted events. There are an increased number of approaches toward SHM in the past decade due to the increased interest. One such effective approach to note would be the statistical pattern recognition paradigm (Farrar, Duffey, Doebling, & Nix, 1999). This approach consists of 4 stages: (a) Operational Evaluation (b) Data Acquisition & Cleansing (c) Feature Selection & Data Compression (d) Statistical Model Development The stage of great interest would be the data acquisition and cleansing stage. This component would comprise of the excitation methods, sensor types and locations as well as other methods of data collection. Aside from this, the time aspect of data collection is a gr... ... middle of paper ... ...D serves as a good characterization for damages in SHM. Changes in the signals obtained can show changes in the structure and is statistically quantified by values. RMSD has been effectively used previously such as between the signatures of two states as the suitable damage index (Guirguitiu and Rogers, 1998). RMSD is widely accepted and used for the estimation of the amount of variation between two signatures (Annamdas, 2012). The formula is given by: The RMSD index reflects the changes in the structure at different stages as the damage propogates along the material. There are limitations to the use of RMSD which include the difficulty in locating the damage and the severity due to the inconsistencies. However, it is capable of predicting cracks and provides statistical patterns in calculating the readings obtained and hence is still a useful tool in EMI for SHM.
Following the collapse of the I-35 Bridge, other bridges in the country, with similar construction designs, were scrutinized. According to federal statistics, more than 70,000 of the 607,363 or roughly 12 percent of the bridges in the United States are classified as “structurally deficient.”
Multiscale PCA (MSPCA) combines the capability of PCA to extract the cross-correlation between the variables and wavelets to divide deterministic features from stochastic processes and approximately de-correlate the autocorrelation among the measurements. Figure 2.3 illustrates the MSPCA procedures.
Parts, when in service and while forming, are subjected to forces. It is necessary to know the characteristics of the material to design and form the component so that any resulting deformation will not result in failure of the component in service and while forming.
In this section, the results of the research are presented. For each task carried out, the most important information obtained is presented.
From recent technological research it is observed that most of the component fails due to the fatigue. Hence our efforts have focused on Fatigue analysis of automobile components. In today’s competitive environment it is very crucial task to produce lighter; cheaper and more efficient automotive components. In engineering design of any component, analysis of structural aspects is to be done at early stage to reduce the development time and cost. Dr. S.S. Khandare et. Al [1] explained that finite Element analysis is important tool for analyzing structural design, it helps to determine critical region of the...
The objective of this lab is to illustrated the procedures required to perform tensile tests. Using data obtained from the test will enable the student to determine various material characteristics that affect the design process. Some findings/interpretations are the stress vs strain curve will help us show how the metal reacted to the forces applied, and the point of failure is very important as it is the ultimate strength.
In fabrication micro-sensors and devices micro-electro-mechanical systems (MEMS) provides significant opportunities, which are borrowed it fabrication abilities from semiconductor technology.
The ZnO crystallizes in a few forms which are wurtzite, zinc blende and rocksalt as shown in Figure 2.4. The wurtzite structure is the most thermodynamically stable phase under ambient temperature and also very common. The zinc blende ZnO geometry can be stabilized only by growth on cubic lattice substrates and the rocksalt structure (NaCl structure) can be obtained at relatively high pressures using ultrasonic wave velocity measurements of up to 10 GPa. (Morkoc).
... different layers such as ETL stage, SIF, BDW and how data is processed to generate reports according to the requirement. The processing of information from raw data to different processing stages culminating in coherent information is fascinating.
Corrosion is by far the greatest concern when it comes to aging aircraft. Corrosion is a deformity that occurs at the surface and subsurface of the structure and components of aircraft. This creates a greater need for advance techniques and inspections used to detect these deformities. Some techniques talked about in this paper that are used to detect corrosion are non-destructive testing, and different scheduled inspections.
Jurafsky, D. & Martin, J. H. (2009), Speech and Language Processing: International Version: an Introduction to Natural Language Processing, Computational Linguistics, and Speech Recognition, 2nd ed, Pearson Education Inc, Upper Saddle River, New Jersey.
As the development of aviation industry grows, more and more aircraft crashes occur. There are many reasons that lead to aircraft crashes, but one of them, is because of improper aircraft maintenance. Why is proper aircraft maintenance so important? Proper aircraft maintenance is critical in order to keep the aircraft can function properly, every aircraft part is in good condition and ensure the safety of pilots and passengers. Proper maintenance has many parts. The most common part is inspections, which pilots do them every day; the main part is overhaul and repair of an aircraft; and maintenance documentation is another important part of aircraft maintenance which improper maintenance documentation has caused many incidents.
Engineers set up all building codes based on accurate calculations that are based on theories and actual observations known as seismic assessment. . There are two different types of seismic performance assessments, experimental assessment and numerical assessment. Experimental assessments are very expensive since engineers need to build a scaled m...
Structural Engineering deals with the design and construction of all types of structures including buildings and bridges. Emphasis is placed on mechanics and the behaviour of materials.
No operator wants to set machine every time to get the best and same result. This is why; measurement of accuracy is a hot topic of research now a days and many processes and methods have been invented to investigate these processes. In this project we are going to talk about the indirect measurement of machines.