Question

modern inspection technologies are either optical or non-optical, search for 5 different modern inspection technologies and summarize their: (a) working principle(s); (b) applications in the industry; (c) effectiveness in finding the defects; (d) speed of inspection in high-volume manufacturing settings, and (e) ability to perform non-destructive testing on the samples .for example Radiation techniques or Ultrasonic techniques.

Answer 1

INSPECTION TECHNOLOGIES (MEANING)-

Inspection is the means by which poor quality is detected and good quality is assured in products that are produced in a production process.

Inspection is usually carried-out via the use of various technologies that examine specific variables (quality characteristics of the product), or product attributes (to ensure product conformance to previously-set standards). The major steps in inspection include : 

1- Presentation of the item for inspection. 

2 - Examination of the item for nonconformance on certain product attributes 

3 - Decision-making, based on the results of the examination, whether the item passes the quality standards required, and assigning the product to a quality grade .

4 - Action, based upon the decision reached, such as accepting or rejecting the item.

5 DIFFERENT MODERN INSPECTION TECHNOLOGIES AND SUMMARIZED

A) Working principles

B) Applications in the industry

C) Effectiveness in finding the defect

D) Speed of inspection in high volume manufacturing settings

E) Ability to perform non-destructive testing on the samples

1 . Acoustic Emission Testing (AE)

This is a passive NDT technique, which relies on detecting the short bursts of ultrasound emitted by active cracks under a load. Sensors dispersed over the surface the structure detect the AE.    It is even possible to detect AE from plasticisation in highly stressed areas before a crack forms. Frequently a method for use during proof tests of a pressure vessel, AE testing is also a continuous Structural Health Monitoring (SHM) method, for example on bridges. Leaks and active corrosion are detectable AE sources too. Acoustic emission testing works by mounting small sensors onto a component under test. The sensors convert the stress waves into electrical signals, which are relayed to an acquisition PC for processing. The waves are captured when the component is submitted to an external stimulus, such as high pressures, loads or temperatures. As the damage grows in the component, there is a greater release of energy. The rates in which the acoustic emission is detected, the activity, and the intensity of the acoustic emission, the loudness, are monitored and used for assessing structural integrity and for health monitoring of components. The continuous method captures all AE within a set time period, for example 1/10th of a second. Then, features such as average signal level and root-mean squared (RMS) values are then extracted.

2. Electromagnetic Testing (ET)

This testing method uses an electric current or magnetic field which is passed through a conductive part. There are three types of electromagnetic testing, including eddy current testing, alternating current field measurement (ACFM) and remote field testing (RFT).

Eddy current testing uses an alternating current coil to induce an electromagnetic field into the test piece, alternating current field measurement and remote field testing both use a probe to introduce a magnetic field, with RFT generally used to test pipes.

3 . Radiographic Testing (RT)

Radiographic testing uses radiation passed through a test piece to detect defects. X-rays are commonly used for thin or less dense materials while gamma rays are used for thicker or denser items. The results can be processed using film radiography, computed radiography, computed tomography or digital radiography. Whichever method is used, the radiation will show discontinuities in the material due to the strength of the radiation.

4. Phased Array Ultrasonic Testing (PAUT)

PAUT probes are different from conventional UT probes in that they consist of an array of individual elements that can be pulsed independently. By controlling the times at which each element is fired, sound beams can be focussed or steered. By sweeping the beam through a range of angles or depths, cross-sectional views can be generated using one probe where several probe and wedge combinations may have been required with conventional UT. A virtual probe can be created from a number of elements and this can be electronically indexed along the length of the array to create a wide paintbrush scan.

5. Thermal/Infrared Testing (IRT)

Infrared testing or thermography uses sensors to determine the wavelength of infrared light emitted from the surface of an object, which can be used to assess its condition.

Passive thermography uses sensors to measure the wavelength of the emitted radiation and if the emissivity is known or can be estimated, the temperature can be calculated and displayed as a digital reading or as a false colour image. This is useful for detecting overheating bearings, motors or electrical components and is widely used to monitor heat loss from buildings.

Active thermography induces a temperature gradient through a structure. Features within it that affect the heat flow result in surface temperature variations that can be analysed to determine the condition of a component. Often used to detect near surface delaminations or bonding defects in composites.