To expertise the materials and products by adapting the protocol to the sample and its history.
Critical learnings:
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Performing sample collection and adapting their packaging based on their origin and nature.
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Gathering and analyzing information.
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Establishing the connection between properties, structure, and process.
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Selecting and adhering to a standard/norm.
By collecting relevant information related to the expertise. By implementing a characterization methodology.
By selecting suitable characterization techniques.
By mastering the sampling process.
By reporting findings and results.
By proposing corrective actions.
I. Industrial SAE
Do you want to:
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Learn more about the nature of unknown compounds?
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Compare the physical and/or mechanical properties of multiple materials?
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Understand the causes of part failures?
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​Material expertise can answer your questions by utilizing a comprehensive range of characterization methods, including SEM, IR spectroscopy, X-ray analysis, mechanical testing, and more.
Context : Industrial SAE (Academic and Professional Bachelor's Degree Project) in a group of 3, with Villanova company as the client, a manufacturer of ocular prostheses.
Problem : An issue of ink adhesion on the polymer arises during the coloring process of iris on ocular prostheses.
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Global Approach of My Eye Expertise
Collecting information
Sample collection
Following a standard
Choosing characterization techniques
Establishing the link between properties and structure
Reporting
IR Caracterisation
Expertising materials and products involves assessing and analyzing their characteristics and properties in a comprehensive manner.
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This expertise encompasses various characterization techniques such as detecting defects or wear, evaluating their performance, and verifying compliance with required standards and specifications.
01 - Global approach to expertise
1. collect informations :
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I retrieved the polymer on which Villanova had conducted some iris printing tests. I could observe with the naked eye that the ink peels off the polymer when scraped with a fingernail.
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Bibliographic study on ocular prostheses indicates that the polymer should be PMMA (biocompatible) according to the NOR standard: SJSS0768371A.
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2. Performing sampling sampling examples
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Cutting a rectangle of L = 15 mm, l = 10 mm with scissors.
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3. Choice of characterisation techniques
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Buoyancy characterization
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immersion in water: The polymer floats (density < 1)
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Flame test characterisation
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It ignites easily and continues to burn after removing the flame - slight candle-like odor - blue flame with a yellow tip (as expected for PMMA: sweet fruity odor).
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IR spectroscopy characterisation
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Obtained spectrogram : polypropylene (PP)
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4. Reporting
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IR Spectroscopy Report
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5. Linking Properties and Material: Wettability
"In order for a material to be wetted, its surface energy must be higher than that of the liquid. If the material's surface energy is lower than that of the liquid, adhesion issues may arise."
We can understand why it is difficult to print on PP. The issue arises because the surface energy of PP is 29-31 DIN, while the surface energy of UV inks is around 40-42 DIN. Since 29<40, we know that there will be an adhesion problem. (1 dyne/cm is equal to 1 mJ/m)
II. NDT
Ready to conduct an expertise on a part and check for any defects, cracks, or foreign bodies that could potentially cause deformation under stress and compromise reliability or safety?
I suggest performing the following inspections :
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Dye penetrant testing (liquid penetrant inspection)
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Magnetic particle testing (magnetic particle inspection)
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Eddy current testing
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Ultrasonic testing
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Radiography (X-ray inspection)
Can we inspect everything?
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As explained, it is necessary to consider the nature of the material, the defects, and the appropriate techniques.
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For example:
Regarding dye penetrant testing, as detailed above, ceramics cannot be effectively inspected as they act as "sponges" for the penetrant, resulting in an unusable inspection result due to significant background noise. Moreover, the porous nature of ceramics makes it challenging to clean the part, which can lead to aesthetic damage. Therefore, the surface condition of a component strongly influences its suitability for dye penetrant inspection.
Reflective Analysis
This skill is closely related to the skill of characterization, as characterization techniques enable us to provide answers in our expertise.
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I find it interesting because it draws upon scientific resources such as physics, with techniques like magnetic particle testing or ultrasonic testing.
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During the activities related to this skill, I worked in groups of 3 or 10. At first, I had some apprehension, but as time went on, I became more trusting and less focused on controlling my colleagues' work.
I regret not having a better understanding of the theoretical aspects during the preparation of the practical work. Theoretical courses on wave physics or magnetism would have been helpful in improving our analysis skills.
The main advantage of non-destructive testing is the ability to inspect an object without altering or disassembling it. NDT allows for the assessment of material quality (such as detecting discontinuities in a component) without causing damage, both during production and maintenance. The key aspect is to be able to evaluate the quality and potentially certain characteristics of an object without compromising its integrity.
01 - Choosing appropriate characterisation techniques
In the case of defect detection, the choice should be made taking into account the general characteristics of the 'part-defect' couple, as well as those of the environment. The selection of an NDT method depends on several criteria, including:
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the nature of the defects
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the material to be inspected
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the required accuracy, cost, and client expectations
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the implementation conditions
02 - by following a protocol
