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Spring clip are widely used in modern rail fastening systems. Cyclically varying stress appear in the spring clip when the railway vehicle passes. This leads to fatigue cracks in the spring clip and their subsequent destruction. Thus, increasing the fatigue strength of spring clips is an urgent task in the development of railway transport. The paper considers a spring clip in the fastening of a rail with reinforced concrete sleepers (fastening ZhBR-65). The finite element modeling of the loading process of the ZhBR-65 spring clip has been carried out. The maximum stress intensity σi was 411 MPa. A new design of a spring clip has been developed, in which the arc sleeper sections (adjacent to the sleepers) are made with a barrel-shaped cross-section. The safety factor of the resulting structure is 1.22 times higher than that of the standard ZhBR-65 spring clip. [ABSTRACT FROM AUTHOR]

In automated manufacturing, cutting process monitoring is vital, because without an operator, significant machine downtime associated with cutting tool failures is possible. The vibroacoustic signal parameters during cutting have long been used as a source of information about the cutting process state. This paper presents the results of the investigation of the spectral composition changes of vibrations over time during the cutting process due to changes in the quality of fastening of cutting inserts and modules of a modular boring tool setup with a large number of elements. [ABSTRACT FROM AUTHOR]

During the past years, there is an increased derailment scenario due to track faults. To resolve this issue, an intelligent visualization-built rail inspection system, which is automatic and real time has been developed. The system strongly notices important rail components like draws, tie plates and nuts and bars which helps in rail fastener with more accurateness and effectiveness. In current years, the railway transportation system developed as one of the chief resources of transport. Hence, the safety in the railway line is of more important. However, due to the expected multiple breaks of elastic rail clips in a fixed rail, accidents may rise when a train is permitted through the track. To attain this goal, a group of image analytics have been developed first and then planned an original universal optimized outline to associate evidence from numerous television camera, sensors and remoteness gauging device to further progress the detection routine. Complete track analyses have been ensured and provide clearance to the train motion only when the track health is perfect. This paper aims at completely reducing the human interference. Quantitative analysis has been completed on a big image set of data taken with diverse track and light circumstances and on a real–time field test. The fist system used to handle and resolve both module and omission finding and exception handling problems. [ABSTRACT FROM AUTHOR]

Cold formed steel sections are extensively used in developed countries for a wide range of applications like roofs in the form of deck sheeting and also as structural elements like beam and column. In a developing country like India, where use of conventional hot rolled steel sections itself is in developing stages, the use of cold formed steel is very less. But if cold formed built-up sections are developed efficiently, cold formed sections can be used for wide range of applications where spans are minimum and fewer loads are acting. Structural behaviour of cold formed sections based on the different type of fasteners was studied in this paper. Behaviour of cold formed sections mainly based on welding and bolts are compared and studied. Strength aspects of cold formed sections due to different types of fasteners along with their mode of connection was studied. Studies shows significant changes in behaviour of similar members were obtained by varying the type of fasteners. [ABSTRACT FROM AUTHOR]

Structural materials, such as composite panels, can only be assembled, and in most cases through the use of fasteners, which are fitted into the drilled holes. However, drilling is costly and time consuming, thus affecting productivity. This research aims to develop an alternative method to drilling. In this paper, the precision of the holes was measured and the effects of the die clearance to the areas around the holes were evaluated. Measurement and evaluation were performed based on the profile of the holes constructed using Alicona IFM, a 3D surface measurement technique. Results showed that punching is a potential alternative to drilling but still requires improvements. [ABSTRACT FROM AUTHOR]

The paper demonstrates the process of development of a bending device for a springback study. The numerical analysis of a V-bending device work as well as its optimization and experimental verification are presented. The study was conducted for the samples made of S235 structural steel. The main difference between the proposed device and a well-known device for V-bending lies in sample fastening to the punch head and a larger die radius in relation to the sample thickness. The presented bending device is characterized by a larger springback angle, less dispersion of the results and lack of the sample reverse loading. [ABSTRACT FROM AUTHOR]

An investigation has been made to predict the accurate fastener stiffness for the Aircraft metallic joints that can be used in Finite element models to simulate realistic behaviour. There exist several semi empirical equations like Tate & Rosenfeld (1946), Huth-Schwarmann (1986), Swift (1971) & Grumman (1983) etc. that can be used to calculate the shear and stiffness of fasteners. However the stiffness calculated varies for each of these methods and eventually leading to varying load distribution. In this paper a parametric study has been conducted to identify the most accurate method to identify the fastener stiffness. The relevant shear stiffness calculated adds certain flexibility to fasteners and peak loads tend to distribute across all the fasteners matching with the real scenario. [ABSTRACT FROM AUTHOR]

The utilization of embossing process is in order to improve the mechanical characteristic of sheet metal. With using this technique subject to sheet metal, cross-section shape changed to be wave, hence, the section modulus of the embossed sheet metal is increased. In this present paper, we did the deep drawing test using duplex embossed sheet metal and measured the variation of flange position in case of the first half stroke. The flange deformation behavior was investigated. Furthermore, from the variation of strain ratio, material flow and fundamental planar deformation was clarified. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present a comprehensive approach to image processing for Giant Magnetoresistive (GMR) array sensors with sheet current sources for the inspection of fatigue cracks in complex metallic structures. The approach incorporates optimal phase angle adjustment, array sensitivity compensation, fastener site identification, an adaptive edge evaluation and removal algorithm and a classification metric. Processing examples are presented that highlight the benefits of these algorithms for improving crack detection for challenging edge and fastener spacing conditions. [ABSTRACT FROM AUTHOR]

The detection of embedded cracks under fastener heads (CUF) in multilayer structures is a major challenge facing the aviation industry. Eddy current (EC) based techniques, such as Magneto-Optic Imager, Sliding probe and Self-nulling EC probes, and low frequency EC methods have been investigated. The prior work of authors presented an EC system using a uniform field excitation combined with giant magnetoresistive (GMR) sensors for imaging the normal component of magnetic flux density, has improved the effectiveness in detecting 2nd and 3rd layer CUFs with aluminum fasteners. However, detection of CUFs with ferromagnetic fasteners remains a major challenge. This paper presents the experimental study of automatic crack detection under steel fastener sites using low frequency EC with 3D GMR sensors that measure all 3 components of the induced magnetic flux density. A finite element model based study is used to optimize the system design and the experimental validation is presented. [ABSTRACT FROM AUTHOR]

This paper explores feature extraction algorithms for crack characterization in eddy current inspection of fastener sites. A novel feature extraction method fitting approximate models to data associated with geometric part features addressing adjacent fastener sites and panel edges is developed. Data classification methods in the circumferential direction around fastener sites are developed to better characterize fatigue cracks with improved noise invariance. Model-assisted probability of detection results are presented highlighting the benefit of automation in NDE. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Criteria for predicting the workability limits for internal failure in dual-phase steel cold-headed parts are presented in this paper. This workability criterion is divided into two sub-criteria to predict the two internal defect types triggered by the adiabatic shear band (ASB) phenomena. These defects are internal voids and cracks (deformed ASB) and/or development of brittle martensite inside the band as a result of phase transformation due to the temperature rise inside the ASB (transformed ASB). The presence of one or both failure types may result in splitting of the fastener’s heads. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In order to analyze the influence of the change of axial position on the performance of labyrinth gear, the Fluent is used to simulate the airflow in the labyrinth in this paper. The leakage coefficient and heat transfer coefficient of the sealing teeth under different axial positions are obtained. The comparisons of results shows that the change of the axial position of the stepped labyrinth seals and the bushing has little effect on the airflow inside the cavity, and the change of axial position has little influence on the leakage coefficient of labyrinth seal; The change in the axial position of the stepped labyrinth seals and the bushing does not lead to a significant effect on the heat transfer characteristics of the airflow and the cavity channel. [ABSTRACT FROM AUTHOR]

An in situ ultrasonic angle beam method has been developed to detect and size fatigue cracks emanating from fastener holes. The method employs transducers mounted in a pitch-catch configuration on each side of the hole, and the modulation of received signals with load is used to detect and size small fatigue cracks. The focus of this paper is the monitoring of a series of critical fastener holes during a full scale fatigue test of an aircraft wing. Essential to the success of this method is the ability to use the same ultrasonic signal as is used for crack monitoring to estimate the instantaneous load. The applied load causes a time shift in ultrasonic echo arrivals resulting from both dimensional changes and the acoustoelastic effect. Waveforms are recorded randomly during fatiguing, and the dynamically applied load associated with each waveform is estimated from the measured time shift. Additionally, small cracks near the hole open and close during fatigue loading, causing a modulation of the amplitude of the received signals with load. The amount of energy reduction as a function of load is analyzed to estimate the cumulative area of cracks near the fastener hole. The load monitoring capability of the ultrasonic method is also valuable for quantitatively assessing the degree of local loading experienced by a specific fastener hole, which may not be possible with strain gauges. The wing panel test reported here took place over about seven weeks with near real time reporting of results, which has demonstrated the robustness of the ultrasonic method and its ability to both detect cracks and monitor their growth. [ABSTRACT FROM AUTHOR]

The work characterizes possible types of failure in the Self-Pierce Riveting Process. It illustrates mechanical material investigations and the simulation of fracture according to a micro-mechanical model of Rousselier. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper explores the propagation and scattering of spiral creeping waves around a fastener hole. Preliminary experimental data demonstrates the presence of spiral creeping waves in angled beam inspection and the benefit for detecting cracks of varying angular location. Analytical models are used to provide insight into the propagation and focusing of spiral creeping waves around cylindrical holes. A hybrid numerical method is proposed as a measurement model for 3D scattering from holes with cracks. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper explores feature extraction and signal classification for crack characterization in eddy current inspection of fastener sites. Using simulated studies, a promising feature extraction method with broad noise invariance is presented associated with changes in the eddy current response in the circumferential direction. An experimental study is also presented demonstrating the ability of this measure to improve the capability to detect and potentially size cracks around fasteners while maintaining a low false call rate. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Ultrasonic techniques have the potential to provide early detection of fatigue induced cracks originating from fastener holes with the long term goal of structural health monitoring. This paper considers energy-based algorithms for analyzing ultrasonic waveforms obtained using fixed angle beam transducers in a through-transmission configuration. The transducers were located on either side of the fastener hole with the sound beam oriented along the loading direction, and waveforms were obtained as a function of applied load. Previous work has shown that the ratio of the received ultrasonic energy at under tensile loading to the energy with the sample under no load is a robust method for determining the presence of cracks. The reason for the effectiveness of this metric is that the energy reduction from the crack opening is accentuated by the applied load. For structural health monitoring applications, the earliest possible detection of cracking is desired, and the total energy ratio method does not utilize information contained in different time and frequency windows of the received signals. Considered here are energy ratio parameters derived from multiple time and frequency windows in order to optimize sensitivity of detection to the widest range of crack sizes and geometries. An algorithm was developed to automate crack detection and was applied to the various energy ratio parameters. Results indicate that cracking can be detected significantly earlier in the fatiguing process compared to the total energy ratio method. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

To reduce the cost of conducting experimental probability of detection (POD) trials, methods which utilize models to account for factors that influence the inspection reliability are being developed. This paper reports the application of POD modeling to ultrasonic detection of cracks emanating from fastener holes. The differences between ultrasonic responses from EDM notches compared to fatigue cracks are examined, including the effects of natural variation in fatigue cracks and crack closure due to residual stresses. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A quantitative detection study was conducted on samples representative of lap joints in wing structure of the P- 3 Orion airframe. These samples contained EDM notches in the bottom of the top layer and the top of the second layer, which radiated from ferrous fasteners holding the lap joint together. These aircraft are based on a damage tolerant design, so, consequently, defects would normally only make up a small fraction of the data (<= 5%). To detect the notches, a novel pulsed eddy current probe and robust cluster analysis were used to provide blind automatic detection of the notches without removal of the ferrous fasteners. Detection could then be confirmed using traditional bolt-hole eddy current. Because the samples are defect rich, statistical simulations were used to create samples more representative of what would be found on actual aircraft. Such modelling also allowed the effects of sample size and defect number to be investigated. With a false call rate of 10%, the a90/95 observed empirically was 2.1 mm (0.082 inch). This represents a marginal probability as the results indicate that other variables affect the POD. The technique did not require calibration as used in most eddy current inspections. In addition, sample statistics can be used to show that the assumptions of the technique (i.e. very small fraction of the fasteners have associated defects) are not violated and that the inspector performed the inspection in a suitable manner. [ABSTRACT FROM AUTHOR]

In this work, the wear of apex seal's running face under mixed lubrication is studied. Numerical simulation is carried out by employing the couple model of Reynolds equation, Greenwood and Tripp model and Archard's wear law. The simulation is performed both for one circle and multi circle. In the multi circle simulation, the change of contact position due to wear is considered. A method that is able to find the new contact position based on the updated apex seal's contour profile is proposed, validated and used. The result of multi circle simulation indicates that contact position changes obviously around the maximum swing angles both on leading and trailing sides with the increase number of circles. The wear depth distribution becomes more uniform with the increase of operation circle number. [ABSTRACT FROM AUTHOR]

Structural materials, such as composite panels, must be assembled, and such panels are typically constructed via the insertion of a fastener through a drilled hole. The main problem encountered in drilling is delamination, which affects assembly strength. The cost of drilling is also high because of the severe wear on drill bits. The main goal of this research is to develop a new punching method as an alternative to drilling during hole preparation. In this study, the main objective is to investigate the effect of different puncher profiles on the quality of holes punched into carbon fiber reinforcement polymer (CFRP) composite panels. Six types of puncher profiles were fabricated with minimum die clearance (1%), and two quality aspects, namely, incomplete shearing and delamination factor, were measured. The conical puncher incurred the least defects in terms of delamination and yielded an acceptable amount of incomplete shearing in comparison with the other punchers. [ABSTRACT FROM AUTHOR]

The use of the Smallest Half Volume (SHV) robust statistics method and the Mahalanobis distance to blindly distinguish fasteners with cracks from fasteners without is examined. Pulsed eddy current data obtained from CP140 Aurora wing structures is used to test the approach. It is shown that the method can achieve levels of detection very close to those obtained when the same measurement technique is applied with full knowledge of which fasteners have no cracks. The method is applicable to a broad range of similar situations when an objective hit/miss criterion is used. [ABSTRACT FROM AUTHOR]

Results are presented from a highly collaborative project that builds on previous research designed to improve ultrasonic (UT) localization of damage in mutli-layer metallic structures. One of the primary objectives of the project is to test existing acoustic models for cracks around fastener holes, and further develop a model as necessary to achieve the accuracy required for Air Force applications. For the first phase of the project, CIVA modeling results have been compared to ultrasonic measurements on aluminum plates with fatigue cracks and EDM notches at different locations around throughthickness holes. Variables include the diameter of the holes, length/width of notches/cracks, position of notches/cracks on the hole (angle with respect to the probe) and position in depth (surface, mid bore, backwall and through thickness). Baseline measurements have also been made on side-drilled and spherical-tip holes. Modeling challenges include accurately accounting for reflections arising from the cracks and the specimen geometry, mode conversion, contact conditions between fasteners and fastener holes, and reflection/transmission coefficients at interfaces between layers. [ABSTRACT FROM AUTHOR]

The main scientific ingredients are recalled for developing a general finite element code and model accurately large plastic deformation of metallic materials during joining processes. Multi material contact is treated using the classical master and slave approach. Rupture may occur in joining processes or even be imposed in self piercing riveting and it must be predicted to evaluate the ultimate strength of joins. Damage is introduced with a generalized uncoupled damage criterion, or by utilizing a coupled formulation with a Lemaître law. Several joining processes are briefly analyzed in term of specific scientific issues: riveting, self piercing riveting, clinching, crimping, hemming and screwing. It is shown that not only the joining process can be successfully simulated and optimized, but also the strength of the assembly can be predicted in tension and in shearing. [ABSTRACT FROM AUTHOR]

Calculation of Probability of Detection (POD) curves based on simulation results are presented in the case of the Eddy Current Testing (ECT) configurations involving a flaw buried inside a riveted structure. In order to overcome some accuracy limitations and to optimize calculation speed, the semi-analytical model used in simulation has been improved in order to handle separate discretizations of objects. New possibilities consecutive to this development are presented, as well as two parametric models used for the computation of interactive POD curves with the CIVA software. [ABSTRACT FROM AUTHOR]

Ultrasonic in situ monitoring of metal alloys has been successfully demonstrated for determining the presence and size of fatigue damage within a structure. Ultrasonic techniques, however, only provide an estimate of the state of the structure at that time and do not predict the remaining fatigue life. On the other hand, a statistical crack propagation approach, which models the expected remaining life based on an assumed fatigue process, specimen geometry and material properties, allows for the fatigue life to be estimated. To maintain the safety of the structure, this approach typically requires assuming a worst case initial flaw size. Presented here is a Bayesian estimation approach for incorporating both the measurement and modeling methodologies. An Extended Kalman Filter approximation is used to combine ultrasonic estimates of fatigue cracking with a crack propagation model. The measurement model is based upon recent work by the authors on a shear wave, angle-beam method for monitoring fastener holes, and the crack propagation model is based upon Paris's Law. Simulated and experimental results are shown to assess the performance of the estimation approach, where the resulting crack size determination is more accurate than either the ultrasonic method or the crack propagation model alone. [ABSTRACT FROM AUTHOR]

The forming processes for two industrial cold-formed fasteners are examined. The first is a tubular component formed into a “top-hat” shape during a single-stage operation. The second is an axi-symmetric stepped rivet formed in a multi-stage process. In each case the deformation of the work-piece is modelled using an elastic-plastic finite-element method, to indicate how the material is flowing during the forming process. In both examples the final predicted shape is compared to production-line components to demonstrate the effectiveness of the numerical model. In the first example, the influence of preform geometry on the formation of geometric defects during the process is examined. Mesh refinement is also examined but shows little effect in this type of constrained process. In the second example the effect of preform geometry is examined. The studies show how changes in the preform design may lead to geometric defects developing in the process. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]