School of Engineering
Module
Code
Title
Module Leader
EL3147
Digital Signal & Image Processing A
Yu ZHOU
Assessment
Title
Weighting
Non-Destructive Identification of
Mechanically Stronger Composite Plates
25%
Submit to:
Deadline
Post-box
Blackboard
Other
11:59pm, 28/02/2020
Late submissions will incur a penalty according to University regulations
Additional submission details:
• A full report including the program to perform non-destructive identification should be submitted through Turnitin by the deadline above.
• The report should be structured according to the requirements described in the following based on the marking scheme provided.
• The report length is expected to be around 15 pages.
In this assessment, the student will demonstrate the ability to:
• Demonstrate an understanding of, and an ability to use, appropriate analysis techniques for digital signals and images.
• Apply and assess 1-D digital filters and their design, analysis, representation and implementation using appropriate methods including computer-based simulations.
• Appraise an appropriate fast prototyping software development platform to analyse digital signals and/or images and thereby specify processing requirements for particular practical applications.
Feedback Arrangments
Feedback will be given within the University’s 15 working day policy for feedback and will be avaiable on 20/03/2020.
Assessment Brief
Aim
This assignment is designed to give students an introduction to digital signal and image processing (DSIP) through their applications in ultrasonic non-destructive evaluation of engineering structures. You are required to use the Matlab software package to design and implement a DSIP system to identify a mechanically stronger plate manufactured using composite carbon fibre materials.
Background and Problem
In a carbon fibre composite part, porosity is a defect that appears as small interlaminar voids. As the level of porosity increases, the mechanical strength of the composite part decreases. To evaluate the porosity level non-destructively, ultrasonic measurement is commonly employed. The process involves transmission of high-intensity ultrasonic waves through the component part under test and assessment of the relative amplitude values of the echoes reflected respectively from the front wall and the back wall of the composite part. A higher ultrasonic attenuation indicates a less dense composite part with higher porosity.
Two ultrasonic data files obtained from two laminated composite material plates with 3 mm thickness are provided as “CompositeX.mat” and “CompositeY.mat”. The data was acquired with a sampling frequency at 100 MHz over an area of 40 mm x 20 mm with 1 mm resolution. You are asked to produce a Matlab program to process the ultrasonic data and to identify which composite plate has the stronger mechanical strength overall.
Relevant files for the assignment are provided as email attachment together with this assignment brief and marking scheme for report writing.
Requirements
Task 1: Signal analysis
Ultrasonic signals are noisy in nature due to the back scattering phenomenon produced by the inherent microstructure of the material. The first step is to extract a typical ultrasonic signal from each composite part under test, and to carry out detailed signal analysis in the time and frequency domains to identify key signal features such as locations, magnitudes and frequencies for ultrasonic echoes and noise.
Task 2: Noise reduction
With the ultrasonic measurement operating at a particular frequency band, the second step is to implement a suitable digital filtering system to reduce the impact of out-of-band noise on ultrasonic echoes, and to demonstrate the effectiveness of the filter by comparing the output with respect to input in the time and frequency domains. A good filter should yield an output signal that is as similar to the original signal as possible in the two ultrasonic echo intervals (with minimum amplitude distortion) and as near to zero as possible outside the two ultrasonic echo intervals.
Task 3: Attenuation estimation
The fourth step is to estimate the attenuation of the back wall echo with respect to the front wall echo. This involves application of the filter developed in the second step to the whole ultrasonic record of each composite plate, extraction of the two peak values from the front wall and back wall echoes in each ultrasonic signal, and calculation of the echo attenuation at each ultrasonic measurement point. The results should lead to two echo attenuation images for comparative visualisation of two composite plates.
Task 4: Part sentencing
The final step is to show the two distributions of the echo attenuation values obtained from the third step, to compute basic statistics for the two distributions, and to use the results to determine which composite plate has the stronger mechanical strength overall.
Late work
Work submitted electronically may be submitted after the deadline to the same Turnitin assignment slot and will be automatically flagged as late.
Penalties for late submission
Except where an extension of the hand-in deadline date has been approved lateness penalties will be applied in accordance with University policy as follows:
(Working) Days Late
Penalty
1 – 5
maximum mark that can be achieved: 40%
more than 5
0% given
Plagiarism
During the induction and via your student handbook, you were informed of the serious consequences of using or attempting to use unfair means to enhance performance. This includes plagiarism. The work submitted must be your own and any information and material used properly identified and acknowledged.
The University operates an electronic plagiarism detection service where your work may be uploaded, stored and cross-referenced against other material. The software searches the World Wide Web and extensive databases of reference material to identify duplication
For detailed information on the procedures relating to plagiarism, please see the current version of the University Academic Regulations.
Task No
Task Description
Marks
T1
Signal Analysis
24
T1.1
T1.1.1
T1.1.2
T1.1.3
T1.2
T1.2.1
T1.2.2
T1.2.3
• Time domain analysis including
• Program with comments to read, extract and plot ultrasonic signals
• Waveforms produced with correct scale
• Comments on the waveforms observed
• Frequency domain analysis including
• Program with comments to plot magnitude frequency spectrum
• Spectrum produced with correct scale
• Comments on the spectrum observed for echo signal and noise
T2
Noise Reduction
36
T2.1
T2.2
T2.3
T2.4
T2.5
T2.6
• Program with comments to yield filter coefficients and filtered signal
• Filter frequency response produced with correct scale
• Filtered signal produced with correct scale
• Magnitude frequency spectrum of filtered signal
• Comments on output with respect to input in time and frequency domains
• Effects of cut-off frequency and filter order on filtered signal
T3
Attenuation Estimation
20
T3.1
T3.2
T3.3
T3.4
• Program with comments to filter all signals and generate attenuation image
• Illustration of echo peaks extracted and attenuation estimated
• Attenuation images of two different composite plates
• Comments on attenuation images observed
T4
Part Sentencing
20
T4.1
T4.2
T4.3
T4.4
• Program with comments for statistical analysis of ultrasonic attenuation
• Ultrasonic attenuation histograms
• Statistics derived from ultrasonic attenuation histograms
• Mechanically stronger composite plate identified with justification
Total
100
Marking Scheme