Nondestructive Tests

<div class="htmlview paragraph">A continuously growing demand comes from the automotive industry for optimization of materials and sound insulating product packaging inside the car, so as to propose the best acoustic performance at reduced costs.</div> <div class="htmlview paragraph">A new acoustical holography system provides part of the solution to meet such a demand. The capability of measuring the acoustic field inside a vehicle with high spatial resolution makes it an advanced tool for performing extensive studies of the acoustic transparency of car openings and interior components in various environmental conditions (acoustic chamber, on road, in wind tunnel). The method allows for:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Detailed localization of noise sources or leaks,</div></li> <li class="list-item"><div class="htmlview paragraph">Knowledge of the acoustic energy distribution on elementary surfaces (such as doors, windscreen, roof, sealing components, …),</div></li> <li class="list-item"><div class="htmlview paragraph">Reconstruction of the energy radiated by elementary surfaces in order to predict the acoustic pressure at driver's and passengers' ears,</div></li> <li class="list-item"><div class="htmlview paragraph">Introduction of local modifications on subsystems and components in order to predict their effect on the acoustic field.</div></li> </ul> </div> <div class="htmlview paragraph">In conjunction with some numerical prediction methods, this technique will allow to apply integrated acoustic engineering design methods for a complete understanding and control of the large variety of components and systems involved in the car performance.</div>

This paper presents the findings from a research study that evaluated nondestructive test (NDT) methods that may be useful for quality assurance purposes during construction of soil nail retaining walls. More specifically, the new NDT procedure will be used to evaluate the integrity of the grout column surrounding the steel tendon and to measure the grouted length of the installed soil nail. A preliminary evaluation of the existing NDT methodologies was undertaken to identify candidate NDT methods. The selected NDT methods, sonic echo and impact echo, were subjected to a detailed evaluation through three series of full-scale field NDT testing. The findings from the sonic echo tests are presented in this paper. The field studies demonstrated that the sonic echo method can be used successfully to detect major defects in installed soil nails. The nail condition predictions from sonic echo tests were confirmed by actual nail conditions observed after all the soil nails were exhumed.

<div class="htmlview paragraph">Nondestructive test methods have focused on specific and narrow properties of critical dimension, hardness, visual indications, or localized crack detection, while missing significant structural characteristics not apparent without destructive test.</div> <div class="htmlview paragraph">Multi-frequency resonant inspection is a new technology, which accomplishes a quantitative, whole-body, structural analysis using natural mechanical resonances of a powder metal part. The technology is applicable to a wide range of product size and geometries, and has been used successfully on powder metal connecting rods, timing gears, ABS rings, exhaust flanges, gerotors, and more.</div> <div class="htmlview paragraph">This paper describes measurement and application fundamentals in context of a connecting rod study on production parts. Data is presented which demonstrate the ability to detect structural defects in sintered powder metal parts.</div>

<div class="htmlview paragraph">A continuously growing demand comes from the automotive industry for optimization of materials and sound insulating products implementation inside the car, so as to propose the best acoustic performance at reduced costs.</div> <div class="htmlview paragraph">The acoustical holography system dBVISION developed by 01dB Acoustics & Vibration provides part of the solution to such a demand. Its demonstrated capability of measuring the acoustic field inside a vehicle makes it an advanced tool for performing extensive studies of the acoustic transparency of car openings as well as wind tunnel measurements. The developed technique allows now for:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">1-</span><div class="htmlview paragraph">Detailed localization of noise sources or acoustic weakness points inside the vehicle,</div></li> <li class="list-item"><span class="li-label">2-</span><div class="htmlview paragraph">Knowledge of the acoustic energy distribution on elementary surfaces (such as doors, windscreen, roof, sealing system, etc.),</div></li> <li class="list-item"><span class="li-label">3-</span><div class="htmlview paragraph">Reconstruction of the energy radiated by elementary surfaces in order to predict the acoustic pressure at the driver's and passengers' ears,</div></li> <li class="list-item"><span class="li-label">4-</span><div class="htmlview paragraph">Estimation of the acoustic incidence of local modifications on components of the tested car.</div></li> </ol> </div> <div class="htmlview paragraph">Technical background, together with the main features of this acoustical imaging system, will be exposed and the presentation will illustrate with practical examples how this fits to the project engineer process considering new acoustically driven design methods for a complete understanding and control of all components and systems involved in the car performance.</div>

<div class="htmlview paragraph">The use of composite materials in the automotive industry has become increasingly widespread. With this increase in use, techniques for non-destructive testing (NDT) have become more and more important. Various optical NDT inspective methods such as holography, moiré techniques, and shearography have been used for material testing. Among these methods, shearography appears to be most practical. Shearography has a simple optical setup due to its “self-referencing” system, and it is relatively insensitive against rigid-body motions. Measurements of displacement derivatives, and thus strain directly, rather than the displacement itself is achieved through this method. Therefore shearography detects defects in objects by correlating anomalies of strain which are usually easier than correlating the anomalies of the displacement itself, as in holography.</div> <div class="htmlview paragraph">To date shearography has shown potential as a NDT tool for identifying defects in small structures. Applications of this technique in automotive inspection and production have been difficult because a high-powered laser typically needs to be used, which limits its application due to cost, and employee safety. In this presentation, a portable self-contained digital shearographic system using multi-laser diodes for the illumination source will be described. This system demonstrates a way to measure both small and large-scale structures with an economical portable shearographic system. Its application for NDT of composite materials in automotive and aerospace industries will be presented.</div>

<div class="htmlview paragraph">Automobiles from all parts of the world are now being built with plastic fuel tanks made from high density polyethylene (HPDE). The most difficult aspect of the current manufacturing process for meeting environmental regulations is the need to work with hazardous chemicals such as fluorine and sulfur trioxide to reduce hydrocarbon permeation.</div> <div class="htmlview paragraph">Laminar barrier technology is a barrier process under development which meets EPA requirements, reduces costs and eliminates environmental and employee safety concerns. Laminar technology is a patented, one-step barrier process where 4-5% of a barrier resin is dry blended with HDPE and processed using standard blow molding equipment. The finished fuel tank will contain an integral barrier composed of overlapping barrier resin platelets within the HDPE matrix. Regrind can be effectively utilized and there are no restrictions for secondary assembly techniques such as hot plate welding.</div> <div class="htmlview paragraph">Barrier properties of a lamellar fuel tank can be instantaneously quantified using a non-destructive quality control test. This is a new Q.C. test for fuel tanks that will allow the barrier effectiveness of every tank produced to be verified.</div> <div class="htmlview paragraph">It is anticipated that laminar barrier technology will provide a more flexible process to further accelerate the trend toward plastic fuel tanks including tanks with better barrier to alcohol fuel blends. All processing and performance requirements have been met worldwide.</div>

This paper reviews the most common non-destructive testing (NDT) methods of concrete structures as utilized by the structural engineering industry. The fundamentals of NDT methods are explored in regards to their potential, limitations, inspection techniques and interpretations. The factors that influence the success of NDT methods are discussed and ways to mediate their influence are recommended. Reference is made to standard guidelines for the application and interpretation of the discussed NDT methods. NDT of concrete was found to be gaining increasing acceptance as a means of evaluating the strength, uniformity, durability and other properties of existing concrete structures. Perceptions of NDT inadequacy were attributable to lack of understanding construction materials and NDT methods themselves. The intent of this paper is to address these concerns by identifying and describing the most common successful methods of NDT as applied to concrete structures.

<div class="htmlview paragraph">The paper considers a drum brake mounted on a ½ vehicle test rig including suspension, cross beam and transmission differential. It is a continuation of earlier work (1) and so reviews the characteristics of a drum brake when generating noise on a ¼ vehicle test rig and compares them to those found on the ½ vehicle rig. Frequencies of 960, 850, 1400 and 4600Hz are examined in some detail using the technique of holographic interferometry. It is seen that the modes of vibration of the component parts vary notably over the frequency range considered. This observation allows the significance of each part to be evaluated for each frequency range. With the accumulated information it was possible to predict other possible unstable frequencies and although these were not observed within this series of test the predicted instability frequencies have been observed on earlier work.</div> <div class="htmlview paragraph">The suspension system parts are seen to play an important role at 960Hz and 1400Hz but at the higher frequency they appear less significant. It is suggested that the mode of vibration of the backplate, and its associated interface mounting with the suspension, may provide an answer as to why this is so. Additionally it is suggested that there is an influencing relationship between the trailing arm, the spring pan and the main cross beam, the spring pan exhibiting a complex mode. The same may be said in general terms for the frequency at 850Hz where the suspension spring pan is seen as the dominant feature. A series of time related holograms at the lower frequency allows the phase relationship of the spring pan structure, sidewall to base, to be established at 76°.</div> <div class="htmlview paragraph">A time series of holograms at 4600Hz shows a moving mode of vibration but with each nodal position moving at a different, varying rate. It is suggested that this may be due to in-plane vibration.</div> <div class="htmlview paragraph">A noise “fix” is suggested for the low frequency noise and additional suggestions are made to reduce the influence of the suspension system through basic design changes.</div>

Review of NDT methods in the assessment of concrete and masonry structures

Bridge deck condition assessments in Indiana are primarily reliant on visual inspection. The condition of bridge decks, however, is highly dependent on deterioration under the surface, which includes the corrosion of steel reinforcement and concrete delamination. The implementation of reliable nondestructive testing (NDT) methods can provide information about such internal deterioration, but considering the multiple NDT methods currently available, guidance is needed to find the best approach for assessing bridge decks in the state’s bridge inventory. A research program was conducted to examine various NDT methods with the objective of recommending an effective NDT strategy for network-level and project-level bridge inspections in Indiana that will complement information from traditional bridge inspections and provide asset engineers with improved information for long-term programming decisions. For the study, several consultants used various NDT methods to inspect a set of bridge decks that represented a range of desired test variables. Based on the test results, it was determined that aerial infrared thermography (IRT) is a good network-level method that is capable of scanning a large number of bridges and providing an initial assessment of bridge deck conditions. If significant delamination activity is detected, then follow-up network-level scanning limited to the problematic bridge decks should be performed using vehicle-mounted IRT. For project-level scanning of individual bridge decks, impact echo was found to be reliable and repeatable. For bridges with high-traffic volume for which project-level scanning is needed, a pole-mounted IRT system was found to be effective for evaluating the deck condition.

Aim of study: Analyze the behavior and predictive capacity of different non-destructive testing (NDT) methods—ultrasound, longitudinal and transverse vibrations, and static bending— for estimating the MOEGTO in two species of great forestry interest in Europe: Pinus sylvestris and Populus × euramericana. Additionally, this study focuses on developing global prediction models for MOEGTO using the NDT modulus of elasticity from both species, and on improving the reliability of prediction through the cross-validation process. Area of study: Provenance Region 8 (Northern Iberian System, Spain) and Ribera del Carrión (Palencia, Spain). Material and methods: A total 75 sawn lumber samples (45 of Pinus sylvestris and 30 of Populus x euramericana) with dimensions of 60 × 40 × 1200 mm were analyzed using ultrasonic testing, longitudinal and transverse vibration methods, and both destructive and non-destructive static bending tests performed with a universal testing machine. Regression models were developed to predict the static modulus of elasticity (MOEGTO). Main results: The prediction model using the NDT method of longitudinal vibrations with Fast Fourier Transform (FFT) software for Pinus sylvestris showed the highest coefficient of determination with R2= 0.56, while for Populus × euramericana, the ultrasound method with the Sylvatest 4 device yielded R2= 0.67. For both species, the best-fit global prediction model was obtained with the ultrasound method using the Sylvatest Trio device, achieving R2= 0.60. Additionally, the application of cross-validation improved the predictive performance of the global models, particularly for the three ultrasound methods and the longitudinal vibration method, all of which attained R2 values above 0.6. Research highlights: This study confirms the reliability of ultrasound and longitudinal vibration techniques for estimating MOEGTO and contributes new insights by comparing multiple NDT methods across two species and developing robust cross-validated global prediction models.

<div class="htmlview paragraph">The principal metals and alloys used for aircraft and aerospace tubing applications are 21-6-9, Type 304 stainless to MIL-T-6845 and commercially pure and alloyed (3A1-2.5V) titanium. Specifications covering this tubing require high quality with very tight defect levels. Very careful workmanship in processing and rigid inspection practices must be followed in order to meet the requirements.</div> <div class="htmlview paragraph">Many kinds of defects can befall the tubing. during processing. Some of these are common to all grades of tubing, while others are peculiar to individual alloys. Welded tubing is subject to more defects than seamless. Tubing in general is subject to more defects than almost any other kind of wrought steel product.</div> <div class="htmlview paragraph">Inspection practices include every kind of destructive and nondestructive tests applicable to tubing. Each test has certain capabilities and limitations. A combination of tests is required to give best assurance for critical applications.</div>

Corrosion of reinforcement can decrease the quality and cause damage to reinforced concrete, so it is necessary to know the resistance of concrete, especially with oil palm shells (OPS) and mask fibers in a corrosive environment. This study aims to determine the effect of corrosion levels on OPS concrete and mask fiber using the NDT (non-destructive testing) method. Oil palm shells are a 10% replacement for coarse aggregate in the concrete mix. The mask fiber is 0.2% of the volume of the specimen, and the superplasticizer is 0.25% of the cement used as an additive in the concrete mixture. The specimen is 50 cm long, 10 cm wide, and 10 cm high. There are two types of specimens, namely pre-corrosion and post-corrosion. In pre-corrosion specimens, corrosion acceleration of the reinforcement is carried out before the concrete molding process. While the post-corrosion specimen is being prepared, corrosion acceleration is carried out after the concrete is 28 days old. Corrosion acceleration is carried out by immersing the concrete specimen in a 5% NaCl solution and using a DC power supply. After the concrete is corroded, NDT is carried out. The NDT methods used are resistivity and impact-echo as analysis and detection tools for the effect of corrosion on palm shell concrete and mask fiber. The pre-corrosion specimen got the highest resistivity value on the 0% specimen at 21.35 kΩ.cm and the lowest resistivity on the 5% specimen at 16.70 kΩ.cm. The resistivity value decreases with increasing corrosion levels. The post-corrosion concrete has the highest resistivity on the 0% specimen, with 18.56 kΩ.cm, and the lowest resistivity on the 5% specimen, with 13.88 kΩ.cm. The resistivity value decreases with increased corrosion levels. The impact-echo testing on the pre-corrosion specimen yielded a 0% specimen with a value of 14394.53 Hz and a 1% specimen of 18266.6 Hz. The frequency value decreases with increasing corrosion levels. The result of impact-echo testing on post-corrosion concrete was 14394.53 Hz for the 0% specimen and 1567.38 Hz for the 5% specimen. The frequency value decreases with increasing corrosion levels.

Condition assessment and characterization of materials and structures by means of nondestructive testing (NDT) methods is a priority need around the world to meet the challenges associated with the durability, maintenance, rehabilitation, retrofitting, renewal and health monitoring of new and existing infrastructures including historic monuments. Numerous NDT methods that make use of certain components of the electromagnetic and acoustic spectrum are currently in use to this effect with various levels of success and there is an intensive worldwide research effort aimed at improving the existing methods and developing new ones. The knowledge and information compiled in this book captures the current state of the art in NDT methods and their application to civil and other engineering materials and structures. Critical reviews and advanced interdisciplinary discussions by world-renowned researchers point to the capabilities and limitations of the currently used NDT methods and shed light on current and future research directions to overcome the challenges in their development and practical use. In this respect, the contents of this book will equally benefit practicing engineers and researchers who take part in characterization, assessment and health monitoring of materials and structures.

Buildings constructed during early 70's & late 80's of the last century in India are found to be in distressed conditions due to inadequate specifications and poor construction practices. The continuous monitoring of concrete structures using suitable NDT (Non Destructive Testing) methods and use of possible restoration methods help in a considerable reduction of the rate of deterioration of concrete structures thereby increasing the life span of structures. NDT methods have greater advantage in evaluating the uniformity, homogeneity, approximate compressive strength, durability, the extent of corrosion of rebars in concrete etc. of damaged structures. The objective of the present study is to enhance the life of 50 year old existing hospital building (Partly RC and Brick masonry) in Kurnool, Andhra Pradesh. Condition assessments are carried out through a visual, field and laboratory evaluation of samples collected from the structure and results are presented in this paper. The paper also highlights the assessment of strength and durability of concrete to evaluate the extent of distress and damage in the building. Besides visual inspection, the Non Destructive Evaluation covering UPV & Rebound Hammer values and Half Cell Potential with respect to the status of corrosion of reinforcing bars and chemical tests on selected un-distressed RC columns, beams, and slabs are also presented and discussed. The repair and strengthening techniques using the latest materials and possible restoration works such as column jacketing, shotcreting, anticorrosive coatings, etc. have been suggested to enhance the life of the structure.