Question

Liquid penetrant testing is a suitable method for almost any material. What can not be inspected by liquid penetrant testing method?

Explain why pre-cleaning is the most important step

Imagine a part that contains fatigue cracks which are detectable under no load using liquid penetrant technique. Would they still be detectable under tensile and compressive loads and why?

List the main human factors that affect the probability of detection in liquid penetrant testing.

What control measures should be considered in developer thickness layer?

List the advantages and disadvantages of the various developer types.

Additionally there are 10 marks given for organisation and presentation. You will be expected to show evidence of research and well balanced arguments supported by academic literature relevant to the problem (in addition to the learning package material). Note that that the marking scheme gives an indication of the expected length of each section. Explanations and descriptions should reflect this balance between sections and sub-sections.

Answer 1

Liquid penetrant test is used to detect the surface cracks. so this test can not be employed for internal cracks present inside the material. It is also not suitable for materials which are very porus, fibrous like wood or very rough surfaces. Make sure that material to be tested must not react chemically with the penetrant. All such material which are chemically reactive with the penetrant; proper penetrant must be selected.

Pre-cleaning is the most important step because the presence of dirt, oil , any types of fluid or any other contaminants prevents penetrant to enter inter into the flaws or cracks. so surface preparation is necessary in oder to get best result with high relaibility. these contaminants actually block the mouth of cracks so after applying penetrant, pentrant does not enter into the cracks so after test these types of cracks are undetectable.

Fatigue cracks which are detectable under no load using liquid penetrant technique, They are very easily detectable under tesile load because under tensile load the mouth of the crack is opened more. but it may or may not be detectable under comressive load dpending upon the size of cracks and amount of compressive load. As comressive load shut down the mouth (opening) of the cracks.

proper inspection, sufficient dwell time, pre-cleaning and post cleaning, temperature control,chemical handling precautions, evalution for documentation (severity of cracks) etc.

State of material to be tested i.e. dry, wet or nonaqueous wet.