Television holography (TVH) can be defined as `the family of optical measurement techniques based on the electronic recording and processing of holograms'. Image-plane TVH was introduced in the early 1970s with the name `electronic speckle-pattern interferometry' (ESPI). Since then, TVH has undergone an impressive development and become one of the most promising optical techniques for non-destructive testing and industrial inspection. The aim of this review is to propose an original scheme for the systematic treatment of TVH and to review the existing techniques according to it. In this approach we split the measurement process into four highly independent stages (illumination and observation geometry, temporal treatment, secondary-correlogram generation and fringe-pattern analysis) and establish a common notation to formulate the corresponding techniques. Such a strategy allows the free combination of the techniques proposed for each stage as building blocks to obtain every particular variant of the whole TVH measurement process, whether it has already been reported or not, and also the incorporation of new techniques while retaining compatibility with the existing variants of the previous and following stages.

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A systematic approach to TV holography

Publisher Summary This chapter focuses fringe formations in deformation and vibration measurements using laser light. The chapter discusses a survey on the formation of the fringe patterns observed in these methods. The chapter helps in deriving dependences of their shape and visibility on object deformation parameters and optical systems by starting from the correlation properties of the light scattered from diffuse objects, and discuss the mutual relationships and features of each method by putting physical interpretations on derived mathematical relations. In holographic interferometry and speckle interferometry, the fringe shape represents the distribution of the phase change of the scattered light caused by object deformation, while the fringe visibility depends on the overlap of the corresponding speckle pair, therefore, on speckle displacement and speckle size. In speckle photography, on the other hand, the fringe shape represents the speckle displacement, while the fringe visibility is affected by the speckle decorrelation accompanying the displacement. In addition the relations derived in the present chapter would deliver a quantitative basis for selecting an adequate method of measurement and the optimum manner of signal processing in these modem interferometric techniques.

V Fringe Formations in Deformation and Vibration Measurements Using Laser Light

A method to measure the derivative of displacement using time variation changes in the object together with Fourier transform analysis in speckle shear interferometry is presented. The concept of the method is that the object is deformed continuously and a large number of sheared images of the object motion are acquired using a high speed CCD camera. The derivative of the object deformation is then retrieved from this large set of data using Fourier transformation. The method is capable of obtaining information for object displacements over 500 µm, which is a very difficult task when using conventional electronic speckle pattern shearing interferometry. Theory as well as some of the experimental results with the new method are delineated.

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Novel temporal fourier transform speckle pattern shearing interferometer

There is a tremendous increase in the demand for converting biomaterials into high-quality industrially manufactured human body parts, also known as medical implants. Drug delivery systems, bone plates, screws, cranial, and dental devices are the popular examples of these implants - the potential alternatives for human life survival. However, the processing techniques of an engineered implant largely determine its preciseness, surface characteristics, and interactive ability with the adjacent tissue(s) in a particular biological environment. Moreover, the high cost-effective manufacturing of an implant under tight tolerances remains a challenge. In this regard, several subtractive or additive manufacturing techniques are employed to manufacture patient-specific implants, depending primarily on the required biocompatibility, bioactivity, surface integrity, and fatigue strength. The present paper reviews numerous non-degradable and degradable metallic implant biomaterials such as stainless steel (SS), titanium (Ti)-based, cobalt (Co)-based, nickel-titanium (NiTi), and magnesium (Mg)-based alloys, followed by their processing via traditional turning, drilling, and milling including the high-speed multi-axis CNC machining, and non-traditional abrasive water jet machining (AWJM), laser beam machining (LBM), ultrasonic machining (USM), and electric discharge machining (EDM) types of subtractive manufacturing techniques. However, the review further funnels down its primary focus on Mg, NiTi, and Ti-based alloys on the basis of the increasing trend of their implant applications in the last decade due to some of their outstanding properties. In the recent years, the incorporation of cryogenic coolant-assisted traditional subtraction of biomaterials has gained researchers' attention due to its sustainability, environment-friendly nature, performance, and superior biocompatible and functional outcomes fitting for medical applications. However, some of the latest studies reported that the medical implant manufacturing requirements could be more remarkably met using the non-traditional subtractive manufacturing approaches. Altogether, cryogenic machining among the traditional routes and EDM among the non-traditional means along with their variants, were identified as some of the most effective subtractive manufacturing techniques for achieving the dimensionally accurate and biocompatible metallic medical implants with significantly modified surfaces. 

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A comprehensive review on metallic implant biomaterials and their subtractive manufacturing

A simple electronic speckle-shearing-pattern interferometer, in which the image of an object is focused and sheared with a split lens onto a diffuser, is described. The sheared images on the diffuser are focused by a television camera and then digitized and processed in a host computer. The results obtained for two basic types of shearing, lateral and radial, are presented.

Simple electronic speckle-shearing-pattern interferometer

The main methods of speckle shear interferometry include Michelson's interferometric arrangement, two or multiple apertures in conjunction with a lens and defocusing, and use of parallel plates and wedges in front of the lens with or without apertures. It has been our experience that the partial slope fringes are not localized at the plane of the specklegram in the case when defocusing is used for shear.

Speckle shearing interferometry: a new method

Diaphragms and plates were examined with a speckle-shearing interferometer which utilized a split lens both for imaging and shearing functions. It was found that the location, shape and size of the defect could be ascertained accurately under certain conditions. The experiments showed that the fringe pattern of a defective diaphragm under pressure loading could be simulated on a good diaphragm by subjecting it to a combined loading (pressure and a concentrated load) with the proper shear orientation. However, in extreme situations — not likely to occur in practice — a defect could behave as a mini diaphragm with an elastic boundary. Lens aberrations degraded the contrast of slope fringes considerably.

Detection of defects in plates and diaphragms using a split-lens speckle-shearing interferometer

Micro ED milling is one of the widely applied processes to generate microfeatures on electrically conductive materials. However, the drawbacks associated with this process namely low MRR and high surface roughness limits its wide applicability. To enhance the rate of metal removal and surface finish an investigation is carried out by mixing SiC nano powders with dielectric media. Experimental trails were conducted at different settings of discharge energy and powder concentration to identify the optimum condition for responses namely MRR, Ra and Micro hardness. Full factorial design is used to design the experiments for both plain dielectric and powder mixed µEDM process. The morphology of milled surface with plain /nano powder mixed dielectric has also been analyzed. The findings revealed that the break down voltage of SiC nano powder mixed dielectric was 40% lower than plain dielectric media due to this enhancement in MRR and surface finish. Lower values of powder concentration (2 g/l) favors the MRR and surface finish but the higher value of powder concentration (6 g/l) favors the microhardness. Crater size, voids and cracks were reduced with SiC mixed dielectric than plain dielectric under considered settings of discharge energy due to increase in sparking area. Material removal efficiency is found to be high with medium range of discharge energy for both plain and SiC mixed dielectric used.

Micro ED Milling of Ti-6Al-4V with SiC Nano Powder Mixed Dielectrics at Different Ranges of Discharge Energy

This paper investigates the tribological behaviour of grey cast iron (GCI) and its counter face material (EN31 steel) under various environmental conditions. In many applications, GCI is subjected to different metal-to-metal contact under dry, lubricated and high temperature conditions. The main phenomenon in metal-to-metal sliding is wear; it may occur on either surface or any one of the surfaces due to the property of material or nature of contact or the sliding parameter of the test. Adhesive wear can occur on the surface due to the presence of localized bonding or oxide formation. As a result of this metal-to-metal contact, localized bonding may occur, leading to material transfer from GCI to EN31 steel or vice versa. This situation brings up the new era of positive or negative wear, at various environmental conditions in practical applications. If the material transfer is observed, then the surface could be subjected to adhesive wear. If oxidation takes place, then the material is subjected to rolling wear. Sometimes both surfaces may be subjected to material transfer due to severe sliding action. This work aims to determine the states of wear and sliding parameters under which slight and severe wear occurs. The states of wear include dry, lubricated and heated conditions. The sliding parameters are applied load, sliding speed and sliding distance. The combinations of sliding parameters were selected based on the principle of full factorial method, and L27 orthogonal array was employed.

R. Krishna Murthy

Papers

Speckle shearing interferometry: a new method

Detection of defects in plates and diaphragms using a split-lens speckle-shearing interferometer

Micro ED Milling of Ti-6Al-4V with SiC Nano Powder Mixed Dielectrics at Different Ranges of Discharge Energy

Tribological Behaviour of Grey Cast Iron–EN31 Steel Contact Under Sliding Conditions