The Largest Open Access Portal of Nondestructive Testing (NDT)

3D structural investigations are described by X-ray laminography studies of sandwich shell segments, made of a PVC foam core, covered by non-crimp fabric glass fibre composite lay-ups processed by vacuum assisted resin infusion of epoxy. The specific scope of this study is to image transversal flaws within the foam core (joints) and of single ply overlaps. Test flaws were purposely implemented in order to simulate typical failure under cyclic load. In a dedicated test rig for shell structures, the flaw evolution/propagation is monitored by thermography and optical 3D inspection of deformation. Due to the unfavourable preconditions for classical computed tomography as of large aspect ratio, the samples were investigated by coplanar translational laminography. Its limited range of observation angles of ± 45°, results in anisotropic artefacts about the normal to the sample surface, but the typical flaws are well visualized in the as-prepared state, in a state of early damage, and in the repaired state.

Classical film radiography is a well-established NDT technique and it is most commonly used for testing weld seams and corroded pipes e.g. in oil and gas industry or in nuclear power plants. In the course of digitization, digital detector arrays (DDA) are finding their way into industrial applications and are replacing film radiography step by step. This study deals with the latest generation of DDAs, the photon counting and energy resolving detectors (PCD), and their characteristics compared to charge integrating detectors (CID). No matter which technology to use, radiography still lacks a general issue: A three-dimensional object is projected onto a two dimensional image. Of course, advanced computed tomography (CT) algorithms exist since many years, but if the object to investigate is too large to fit into the manipulation system or its shape is not appropriate, CT is not feasible or sensible to be applied. To overcome this limitation, numerous laminographic algorithms have been developed in the past. In this study, photon counting detectors are used in combination with co-planar translational laminography to gain reconstructed three-dimensional volumes. Both laminographic testing and PCDs require a serious knowledge of many parameters that can influence the image quality in the resulting datasets. These are e.g. the detector efficiency and calibration procedure, setting of energy thresholds, exposure data, number of projections, beam length correction and spatial resolution. The use of PCDs yields more variables to be considered compared to CIDs. The most important parameters in laminographic testing and in the use of PCDs are described in this study and limits are discussed.

Ultrasonic processing is known to be an efficient means of aluminium melt degassing with additional benefits of being economical and environment friendly. This paper describes the performance of ultrasonic degassing in preparing melt for low pressure die casting (LPDC). Efficiency of ultrasonic degassing is compared with conventional Ar rotary degassing by direct measurements of hydrogen concentration in the melt with a Foseco Alspek-H probe and by reduced pressure test in different stages of the casting process. Significant reduction in dross formation along with similar efficiency of hydrogen degassing was shown for ultrasonic degassing as compared with conventional Ar rotary degassing. Mechanical properties, microstructure and porosity level of the components produced by LPDC after both degassing techniques are determined. Results show that the components produced after ultrasonic degassing treatment have similar hardness, tensile properties, porosity level and microstructure as the components degassed with conventional Ar rotary degassing.

This paper describes the development of an innovative carbon nanotube-based non-woven composite sensor that can be tailored for strain sensing properties and potentially offers a reliable and cost-effective sensing option for structural health monitoring (SHM). This novel strain sensor is fabricated using a readily scalable process of coating Carbon nanotubes (CNT) onto a nonwoven carrier fabric to form an electrically-isotropic conductive network. Epoxy is then infused into the CNT-modified fabric to form a free-standing nanocomposite strain sensor. By measuring the changes in the electrical properties of the sensing composite the deformation can be measured in real-time. The sensors are repeatable and linear up to 0.4% strain. Highest elastic strain gage factors of 1.9 and 4.0 have been achieved in the longitudinal and transverse direction, respectively. Although the longitudinal gage factor of the newly formed nanocomposite sensor is close to some metallic foil strain gages, the proposed sensing methodology offers spatial coverage, manufacturing customizability, distributed sensing capability as well as transverse sensitivity.

When determining the most effective way to ultrasonically inspect bi-metallic welds, it is important to understand how the microstructure of the weld affects the sound propagation in the part. This presentation will demonstrate how simulation software can be used to determine the most effect type of transducer to successfully inspect different types of welds. Inspection options such as longitudinal or transverse wave, pulse echo or TOFD and single element, dual element, phased array or dual element phased array transducers will be compared.

Aim was to investigate the refinement of primary silicon in hypereutectic aluminium-silicon alloys Al Si15, Al Si19 and Al Si24. In addition the degree of the primary silicon was determined by ultrasound. By measuring the speed of sound (by ultrasound) and ultrasonic microscopy the refinement of the primary silicon was confirmed. In order to refine Al-Si alloy melts were treated with AlCuP and purging gas and subsequently poured into a stepped plate mould. Additionally, the refinement was evaluated by metallographic examinations. The differences between the alloys with and without AlCuP treatment were determined by hardness and tensile tests. It was possible to obtain a qualitative dependence between speed of sound and silicon content respectively the particle size of the primary silicon. Furthermore, a treatment with purging gas was found to improve mechanical properties. However, a homogeneous distribution of the primary silicon could not be determined by purging gas treatment. The silicon content of the alloy as well as the refinement of the primary silicon can be determined by non-destructive testing.

Typical casting defects are known to influence the mechanical properties of castings massively. In contrast to common non-destructive test procedures computed tomography (CT) permits the detection of these defects three-dimensionally (3D). However, there is no standard for the assessment of CT data regarding 3D defect distributions and their correlation with mechanical properties so far. The present work is aimed at a standardized description of porosity in aluminium cast parts by means of CT. For this purpose material testing specimens of two different aluminium alloys were produced by high pressure die casting and scanned with a micro-focus CT facility with a resolution of 100 µm. For the volume porosity analysis a reference body with known void volume was designed permitting the determination of the adequate grey scale threshold. After the mechanical testing the CT scans were reanalysed regarding the local volume porosity at the crack. A distinct correlation between this local volume porosity and the mechanical properties of flat tensile specimens of industrial Al alloys was determined. Furthermore detailed investigations have taken into account the distance of the respective porosity to the sample surface as well as the shape of the porosity in order to account for its notch effect. First results have shown an influence of the porosity shape on the static-mechanical properties. Keywords: 3D, computed tomography, aluminium cast parts, volume porosity, mechanical.....

One of the key properties of special steels is the cleanliness. The cleanliness is determined by the size, distribution and amount of non metallic inclusions. These inclusions are formed during the steel production process. Non metallic inclusions consist of e.g. oxygen, sulphur and different metals e.g. Al, Si, Mg, Mn, … . The size, the typ, chemical analysis, distribution are quality criteria for the steel and influences for example mechanical properties, corrosion resistance and polishability. State of the art of testing steel cleanliness is using light optical microscopes (LOM) according to international test standards. The aim of this work is the comparison of LOM-results to results derived from more time consuming, if possible 3-dimensional tests like extraction, fatigue tests and X-ray computed tomography (CT).

In May of 2009, the NRU (National Research Universal) reactor was forced to shut down after a small heavy water leak. In 2009-2010 repairs were performed in order to restart medical isotope production mid-August 2010. Since the NRU vessel?s return to service, a series of periodic inspections is required to ensure the safe operation of the reactor. Eclipse Scientific was mandated to develop the NDE procedures and robotic manipulator for the In-Service Inspection program of the NRU vessel. This included the development and implementation of phased array ultrasonic inspection techniques and eddy current array technology techniques to be used with unique material characteristics, property and physical state changes. The inspection mandates were required in a short time frame and environmental conditions represented very difficult delivery and inspection circumstances. This paper presents how modeling was used in the development process to achieve the inspection mandates. The modeling software used ranged from advanced ray tracing (ESBeamTool) to full UT/ET simulation (CIVA) and was key in obtaining approval of the procedures, developing good training material and obtaining excellent data from the inspections.

For more than 10 years, it is possible to numerically simulate the solidification process in castings. Since then this technique has rapidly progressed with increasing available computing power permitting more accurate and complex algorithms to be implemented. Hence the foundry industry is able to continuously advance their production processes. An important aspect of casting simulation is the prediction of areas that are prone to porosity. Such areas are identified only according to their probability of porosity occurrence. No information of morphology and distribution of pores can be obtained. X-ray computed tomography (CT) opens the possibility to visualise the three-dimensional structure of castings and their imperfections. This permits the detection of porosities and their distribution in the entire casting. By comparing the data obtained by numerical simulation and CT, the simulation data can be validated for the whole casting. This is normally done by sectioning the cast part at regions of interest, which can give only limited information about the three-dimensional distribution of porosities. The more exact data of the CT regarding distribution and type of pores together with the solidification parameters from the numerical simulations permit more accurate relations to be derived between the process parameters and the casting. In that way the casting process can be further advanced. Numerical simulations of different castings were performed using FLOW-3D, a general computational fluid dynamics (CFD) software, as well as MAGMASOFT, a specialised software for casting processes. For CT a v|tome|x c - system by phoenix|x-ray with a 240 kV microfocus tube and 16 bit detector with 1024x512 pixel resolution has been used. Further x-ray investigations have been accomplished using a phoenix|x-ray x|argos - system with a 320 kV x-ray tube and a 32 bit line-detector. The reconstruction was accomplished using Volume Graphics Studio Max including a module for pore calculation. Different parts of industrial production produced by high pressure die-casting were investigated.