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The purpose of this paper is to investigate the possibility of in situ flaw detection for powder bed, beam‐based additive manufacturing processes using a thermal imaging system.

The authors compare infrared images (IR) which were taken during the generation of Ti‐6Al‐4V parts in a selective electron beam melting system (SEBM) with metallographic images taken from destructive material investigation.

A good match is found between the IR images and the material flaws detected by metallographic techniques.

First results are presented here, mechanisms of flaw formation and transfer between build layers are not addressed in detail.

This work has important implications for quality assurance in SEBM and rapid manufacturing in general.

FLAW detection processes utilizing dye penetrants are now extensively used throughout the aircraft industry. They are a logical development of the lard oil and chalk method popular in the early days, a system which is still occasionally used for economic reasons and where only the more obvious flaws are of significance. Briefly, this method consists of immersing the parts to be tested in hot lard oil, wiping off the excess, and then applying a film of chalk; oil which has seeped into surface flaws eventually exudes out and is absorbed into the chalk, revealing itself as typical oily stains. It was reasoned that if lard oil were substituted by a penetrating medium which was highly coloured, the exudations would then become much more obvious and from then on intensive research programmes were started which have culminated in the very efficient processes now available.

Experimental research was conducted on the effects of surface roughness on ultrasonic non-destructive testing of electron beam melted (EBM) additively manufactured Ti-6Al-4V. Additive manufacturing (AM) is a developing technology with many potential benefits, but certain challenges posed by its use require further research before AM parts are viable for widespread use in the aviation industry. Possible applications of this new technology include aircraft battle damage repair (ABDR), small batch manufacturing to fill supply gaps and replacement for obsolete parts. This paper aims to assess the effectiveness of ultrasonic inspection in detecting manufactured flaws in EBM-manufactured Ti-6Al-4V. Additively manufactured EBM products have a high surface roughness in “as-manufactured” condition which is an artifact of the manufacturing process. The surface roughness is known to affect the results of ultrasonic inspections. Experimental data from this research demonstrate the ability of ultrasonic inspections to identify imbedded flaws as small as 0.51 mm at frequencies of 2.25, 5 and 10 MHz through a machined surface. Detection of flaws in higher surface roughness samples was increased at a frequency of 10 MHz opposed to both lower frequencies tested.

The approach is to incorporate ultrasonic waves to identify flaws in an additive manufactured specimen

A wave frequency of 10 MHz gave good results in finding flaws even with surface roughness present.

To the best of the authors’ knowledge, this was the first attempt that was able to identify small flaws using ultrasonic sound waves in which surface roughness was present.

Presents an overview of automated fabric flaw detection immediately after the knitting process. Considers the classification of fabric flaws and how image processing techniques can be applied to their classification, via an introductory example. Outlines problems associated with automating this inspection process and discusses possible flaw sensing systems and techniques.

Magnetic particle flaw detection is one of the longest established and most commonly used methods of non‐destructive testing. It can often be applied in a relatively quick and simple manner. Because of this, it is frequently treated as the “poor relation” in present day non‐destructive test methods and regarded as a method which can be performed by unskilled labour. While this may sometimes be true in semi‐automatic production line testing there are many applications which require considerable knowledge and experience. The use of magnetic particle flaw detection has increased considerably in the past few years. It is now being recognised as essential to supplement visual examination in many areas of in‐service inspection on all types of plant. This article, to be published in four parts, is directed towards maintenance engineers and inspectors who may wish to use the method themselves or would like to have the basic knowledge to ensure that any such tests requested and performed on their behalf, are carried out correctly.

The continued improvement of additive manufacturing (AM) processing has led to increased part complexity and scale. Processes such as electron beam directed energy deposition (DED) are able to produce metal AM parts several meters in scale. These structures pose a challenge for current inspection techniques because of their large size and thickness. Typically, X-ray computed tomography is used to inspect AM components, but low source energies and small inspection volumes restrict the size of components that can be inspected. This paper aims to develop digital radiography (DR) as a method for inspecting multi-meter-sized AM components and a tool that optimizes the DR inspection process.

This tool, SMART DR, provides optimal orientations and the probability of detection for flaw sizes of interest. This information enables design changes to be made prior to manufacturing that improve the inspectabitity of the component and areas of interest.

Validation of SMART DR was performed using a 40-mm-thick stainless-steel blade produced by laser-based DED. An optimal orientation was automatically determined to allow radiographic inspection of a thickness of 40 mm with a 70% probability of detecting 0.5 mm diameter flaws. Radiography of the blade using the optimal orientation defined by SMART DR resulted in 0.5-mm diameter pores being detected and indicated good agreement between SMART DR’s predictions and the physical results.

This paper addresses the need for non-destructive inspection techniques specifically developed for AM components.

This paper presents a numerical study of inverse parameter identification problems in fracture mechanics. Inverse methodology is applied to the detection of subsurface cracks and to the study of propagating cracks. The procedure for detecting subsurface cracks combines the finite element method with a sequential quadratic programming algorithm to solve for the unknown geometric parameters associated with the internal flaw. The procedure utilizes finite element substructuring capabilities in order to minimize the processing and solution time for practical problems. The finite element method and non‐linear optimization are also used in determining the direction a crack will propagate in a heterogeneous planar domain. This procedure involves determining the direction that produces the maximum strain energy release for a given increment of crack growth. The procedure is applied to several numerical examples. The results of these numerical studies coincide with theoretical predictions and experimentally observed crack behavior.

MODERN aircraft inspection methods are a combination of practices evolved over the years combined with advanced technology introduced as new materials and processes are developed. Particular attention is directed to the detection of corrosion with considerable emphasis in the case of so‐called geriatric aircraft. The potential flaws being searched for may be of a different type from the fatigue or other signs occurring generally. In addition, large areas of structure for these older aircraft must be inspected rapidly to ensure the maintenance of safety standards. Visual methods play an important part in these procedures but where these are insufficient, some form of non‐destructive testing (NDT) technique becomes necessary.

There are several techniques for producing a magnetic field, one of which is the magnetic flow technique.

Fatigue is a problem which all designers have to face. If they are starting on the design of an aeroplane, they will work out all the high loading cases first, make sure that the design will be good enough to meet them, then they will turn their thoughts to the survival of the proposed structure within the lower stress levels of every‐day operations.