Surface Defects

Physiological studies have shown that focal articular surface defects in the human knee may progress to degenerative arthritis. Although the risk of this evolutive process is multifactorial, defect size is one of the most important factors. In order to determine the influence of osteochondral defect size and location on the stress and strain concentrations around the defect rim, a finite element model of the human knee was developed. From our results, it became clear that the size and location of cartilage defects drastically affect to those variables. No stress concentration appeared around the rim of small defects, being the stress distribution mainly controlled by the meniscus contact. On the contrary, important rim stress concentration was found for large osteochondral defects. This alteration of the stress distribution has important clinical implications regarding the long-term integrity of the cartilage adjacent to osteochondral defects. ᭧ (E. Peña), [email protected] (B. Calvo), [email protected] (M. Martínez), [email protected] (M. Doblaré). 0010-4825/$ -see front matter ᭧

Irradiation of highly dehydrated MgO by UV light in the presence of surface adsorbed hydrogen leads to the formation of particular types of surface colour centres indicated with F+ S (H ) (one-electron, paramagnetic) and F S (H ) (two electrons, diamagnetic). F S centres are the surface counterparts of the well-known F colour centres formed in the bulk of ionic solids by high-energy irradiation or metal addition. In the particular case of F+ S (H ), the unpaired electron is in magnetic interaction with a nearby proton belonging to a hydroxyl group deriving from H 2 heterolytic dissociative chemisorption (H 2 H++H−) and consequent H+ stabilization on a surface oxide ion. The joint use of EPR, FT-IR and DR-UV-vis spectroscopies has allowed clarification of the mechanism of formation of these centres, which is based on the ionization of adsorbed hydryde groups by UV light and stabilization of the ionized electron into suitable positively charged surface electron traps. A fraction of these traps coincides with the site capable of stabilizing the hydride ion (in the form of bridged Mg 3 H ), which is built up by an array of three Mg2+ ions reproducing a (111) facelet of the oxide. The same site can be also seen as a O2− 3c vacancy (3-coordinated surface anionic vacancy). Ab-initio quantum chemical calculations confirm the proposed assignment, which goes beyond the original model of 5-coordinated surface anion vacancies at the flat (100) MgO plane, which is thus left in favour of a new model that describes the surface electron traps as being localized in less coordinated regions of the surface.

Magnesium borate hydroxide (MBH) nanowhiskers were synthesized using a one step hydrothermal process with different surfactants. The effect surfactants have on the structure and morphology of the MBH nanowhiskers has been investigated. The X-ray diffraction profile confirms that the as-synthesized material is of single phase, monoclinic MgBO2(OH). The variations in the size and shape of the different MBH nanowhiskers have been discussed based on the surface morphology analysis. The annealing of MBH nanowhiskers at 500 °C for 4 h has significant effect on the crystal structure and surface morphology. The UV–vis absorption spectra of the MBH nanowhiskers synthesized with and without surfactants show enhanced absorption in the low-wavelength region, and their optical band gaps were estimated from the optical band edge plots. The photoluminescence spectra of the MBH nanowhiskers produced with and without surfactants show broad emission band with the peak maximum at around 400 nm, which confirms the dominant contribution from the surface defect states.

We report room temperature ferromagnetism in vacuum annealed ZnFe 2 O 4 ͑ZFO͒ nanoparticles. Upon vacuum and air annealing, ZFO nanoparticles show ferro and paramagnetic behavior, respectively. The well defined sextets along with doublet seen in the Mossbauer spectra confirms ferromagnetic coupling in vacuum annealed ZFO. After reannealing in air, the magnetization of vacuum annealed sample reduces from 62 to 1.5 emu/g. Both Mossbauer and micro-Raman results suggest that oxygen vacancies generated during vacuum annealing causes cation redistribution between the interstitial sites resulting in magnetic ordering. Our results show a unique possibility of switching the magnetic properties of ZFO between paramagnetic to ferromagnetic.

SBA15-TiO 2 samples prepared by introducing titanium with a grafting method and having TiO 2 loadings below 15 wt.% have been characterized by XRF, XRD, IR, porosimetry, SEM, HRTEM, and UV-Visible diffuse reflectance. Differently from the samples reported in the literature characterized by a high TiO 2 loading, no evidences have been found for the presence of titania particles inside or outside the mesopores of SBA-15. Three different titanium species were instead evidenced to be present. The first two derive from the reaction of titanium with silanol groups in the corona area of inner SBA-15 walls leading to the formation of either TiO 4 tetrahedral sites (by reaction by h ydroxyl nests of surface defect sites) and/or pseudo-octahedral surface sites anchored by two (or more) Si or Ti ions through bridging oxygens. The third species derives from the reaction of titanium in the regions with high sylanol density, e.g. in the micropores located in the corona of SBA-15 channels, leading to the formation of TiO 2-like nanoareas (probably Si-doped) with dimensions of around 1-2 nm maximum. The potential interest of these materials as photocatalysts, for the presence of a TiO 2-like nanoareas highly accessible by reactants, is discussed.

Titanium and its alloys are extensively used in aerospace and mechanical application because of their high specific strength and high fracture toughness. On the other hand, titanium alloys often show low hardness, very low load bearing capacity and poor resistance to sliding wear, so that surface properties improvement is in many cases recommended, often by PVD processes.

The fatigue crack initiation from a surface defect is analysed by means of a new attempt based on multiscale reduction of the stress distribution along the potential crack initiation plane. The reduction is performed by averaging process for shear and normal stresses over two critical areas (multiscale concept). The Matake multiaxial fatigue failure criterion was used to combine the effect of the reduced shear and normal stresses and to calculate the equivalent fatigue strength. The results were verified on defective material subjected to proportional loading. Elastic-plastic numerical simulations were performed for each defect geometry and type of loading (tension, torsion, and tension-torsion) to determine stress distribution. The analysis reveals that the proper calculation of the fatigue limit for defective materials requires performing the averaging process for shear and normal stresses separately.

Using Monte Carlo simulations, we have studied the influence of surface defects on the critical behavior of magnetic spin-1 2 Ising film on a cubic lattice structure. We derive the phase diagram and the critical exponent b in the case of a perfect surface. In such films, the critical temperature can shift to either lower or higher values compared to the corresponding bulk one. In the case of a surface with random, 'weak' or 'strong' interactions between neighboring spins, it is found that the critical exponent b 1 follows very closely that of the perfect surface case. Far from the critical temperature, the effective exponent decreases with increasing the concentration of strong interactions p.

The electrodeposition of Ag on HOPG (0001) substrate is studied using conventional electrochemical methods (cyclic voltammetry, chronoamperometry) and in situ scanning tunnelling microscopy (STM). Due to a weak substrate-deposit interaction the deposition of Ag occurs according to a Volmer-Weber island growth mechanism. At relatively low overpotentials the electrodeposition reaction is mainly initiated on steps and other surface defects. The initial deposition kinetics can be described by a model involving progressive nucleation on active sites and diffusion-controlled 3-D growth. The analysis of experimental results shows that the Catomic Ag cluster represents the critical nucleus in the overpotential interval-35 mV < q <-10mV. It is demonstrated that local nanoscale deposition of Ag on flat HOPG (0001) terraces can be induced using STM technique and specific pulse polarisation routines.

PBX 9501 contains ~95 wt% HMX and 5 wt% binder system comprised of a 1:1 mixture of Estane5703 and a nitroplasticizer (NP). Prior studies have shown that storage of PBX 9501 in humid environments leads to hydrolysis of the ester linkages in the Estane that reduces its molecular weight. In addition, some nitroplasticizer has been shown to migrate out of the formulation with time. Four lots of PBX 9501 were formulated using new Estane and virtuallyaged Estane which had been exposed to 70°C and 74% relative humidity for 14, 23 and 36 days. To mimic extreme NP migration, two lots of X-0557 were formulated similar to PBX 9501 but with reduced NP/Estane ratios in the binder. Quasi-static and dynamic (split-Hopkinson pressure bar (SHPB)) compression tests were conducted, in addition to quasi-static tension tests, at temperatures between -55 to 50°C. The dynamic compression data show significant differences between the baseline and VA Estane specimens only at -15°C; however, significant differences are observed in the quasi-static compression data at all three temperatures. Reduced NP content strongly increases the strength and modulus of X-0557 versus PBX 9501.

Quality control in ceramic tile manufacturing is hard, labour intensive and it is performed in a harsh industrial environment with noise, extreme temperature and humidity. It can be divided into colour analysis, dimension verification, and surface defect detection, which is the main purpose of our work. Defects detection is still based on the judgment of human operators while most of the other manufacturing activities are automated so, our work is a quality control enhancement by integrating a visual control stage using image processing and morphological operation techniques before the packing operation to improve the homogeneity of batches received by final users. An automated defect detection and classification technique that can ensured the better quality of tiles in manufacturing process as well as production rate.

Purpose – Laser milling is a recent process in mould making, providing several advantages over traditional mould making technologies by reducing manufacturing time, shortening the number of machining operations and avoiding expensive electrodes. This paper investigates the ...

The automatic visual inspection (AVI) systems are nowadays used with good results in a wide broad of applications. In particular we considered the problem of the defect detection of particle boards by means of a visual inspection of the printed surface. We propose an innovative defect detection approach capable to automatically extract the repetitive patterns that are generally present in the printed-matters. The extracted patterns are then used in the proper defect detection phase that can thus achieve high defect detection performances. Real wood patterns prove that our defect detection system achieves very high classification capability.

The durability of a As 2 S 3 chalcogenide glass composition was studied in de-ionized water at different temperatures (60-90°C) for different periods of time, up to 120 days. The evolutions of the chemical composition and the pH of the solutions as well as the optical transmission of bulk samples, in the 2-10 μm region, were measured as a function of corrosion time. Atomic force microscopy and optical microscopy were used to investigate the roughness of corroded surfaces and the evolution of surface defects. The water corrosion of As 2 S 3 glass was found to follow a congruent dissolution mechanism, a possible glass-water reaction mechanism was proposed. The optical transmission of the glass was found to be affected by the corrosion. The optical loss increased from 4 to 21% with corrosion time, this variation was attributed to the texturation of the surface by the reaction of corrosion. Moreover, the experimental results show that high temperature value enhances the corrosion reaction: an activation energy of 103 ± 2 kJ/mol was computed from experimental measurements.

High voltage cable terminations are widely used in power system networks. A proper design of cable termination is essential in reducing the electric field distribution around the end of high voltage cable. However, if there are defects exist at cable termination structure, the electric field can be enhanced significantly and can be the source of electrical discharges. Therefore, it is important to understand the effect of defects on the electric field distribution at cable terminations. In this work, a 132 kV XLPE outdoor cable termination has been modelled using finite element analysis (FEA) method. The model has been used to simulate the electric field distribution in the cable termination in the presence of defects. Defects that have been considered are void defect in porcelain, stress cone and fluid, sharp pin on the porcelain surface and delamination defect between the insulator and the stress cone. The effect of different void location, material dielectric constant and porcelain radius on the electric field magnitude at cable termination have also been investigated. From the results obtained in this work, a better understanding of the electric field distribution at the cable termination with defects can be attained.

First-principles calculations based on density functional theory in the generalised gradient approximation, together with pseudopotentials and plane-wave basis sets, have been used to investigate the energetics of oxygen adsorption on stoichiometric and weakly and strongly reduced SnO2(110) surfaces. It is shown that, if the surface species formed by oxygen adsorption are restricted to be charge neutral, then oxygen cannot be

It is well known that surface defect is a common problem encountered in the multi-stage hot bar rolling process of carbon steel. In this study, the phenomenon was investigated by simulating the process by the finite element technique to identify the location where the surface defect might occur and checking the surface qualities obtained from the compression tests at various temperatures and strain rates to clarify the important parameter governing the possible surface defect formation. Also, the surface temperature was measured by employing pyrometer to support the experimental observation. The levels of temperature and specific deformation energy obtained from finite element simulations depending on the roll groove geometry were compared with the experimental observation to better understand the formation of the surface defect in the hot rolled bar. Based on this study, the surface defect might be formed by dissipating the excessive deformation energy accumulated by generating the new surface at the lower level of temperature where recrystallization cannot occur. According to this work, the comparison of the specific deformation energy level for determining the instability of the hot working process might be interesting for further investigation.

High voltage cable terminations are widely used in power system networks. A proper design of cable termination is essential in reducing the electric field distribution around the end of high voltage cable. However, if there are defects exist at cable termination structure, the electric field can be enhanced significantly and can be the source of electrical discharges. Therefore, it is important to understand the effect of defects on the electric field distribution at cable terminations. In this work, a 132 kV XLPE outdoor cable termination has been modelled using finite element analysis (FEA) method. The model has been used to simulate the electric field distribution in the cable termination in the presence of defects. Defects that have been considered are void defect in porcelain, stress cone and fluid, sharp pin on the porcelain surface and delamination defect between the insulator and the stress cone. The effect of different void location, material dielectric constant and porcelain radius on the electric field magnitude at cable termination have also been investigated. From the results obtained in this work, a better understanding of the electric field distribution at the cable termination with defects can be attained. © 2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6416254

Abstract⎯ Quality control in ceramic tile manufacturing is hard, labor intensive and it is performed in a harsh industrial environment with noise, extreme temperature and humidity. It can be divided into color analysis, dimension verification, and surface defect detection, which is the main purpose of our work. Defects detection is still based on the judgment of human operators while most of the other manufacturing activities are automated so, our work is a quality control enhancement by integrating a visual control stage using image processing and morphological operation techniques before the packing operation to improve the homogeneity of batches received by final users.

Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power free electron lasers (FEL). Photocathode quantum efficiency degradation is due to residual gases in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include helium ion microscopy, Rutherford backscattering spectrometry (RBS), atomic force microscopy, and secondary ion mass spectrometry (SIMS). In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the continuous electron beam accelerator facility (CEBAF) photoinjector and one unused, were also analyzed using transmission electron microscopy (TEM) and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but show evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements, the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

Productivity of an integrated steel plant is improved by high-speed casting of hypo-peritectic steels that makes the productivity of caster meet basic oxygen furnace. In high-speed casting, however, strands of the steels tending to form cracks on the shell in the mold, require off-line conditioning that limits the plant productivity and premium yield. Hypo-peritectic transformation occurring on solidification in mold results in irregular shell-surface roughness that causes non-uniform heat transfer to the mold, causing local lifting of the shell from the mold, recalescence, and surface cracks. Influential factors are summarized on the development of the surface roughness, the non-uniform heat transfer and the decline of mechanical properties of the shell upon recalesce. Effective means are presented to reduce the non-uniformity and the cracks at high casting speeds by controlling the properties of mold flux film infiltrating into the solidifying shell/mold boundary.

Resumen. El número y la severidad de los defectos superficiales del acero de pretensado son variables aleatorias que deben ser caracterizadas probabilísticamente para valorar su efecto sobre la resistencia del acero a la fatiga y a la corrosión bajo tensión, ya que ambos procesos de fisuración comienzan en defectos superficiales. Las medidas realizadas en esta investigación con un rugosímetro de contacto confirman el resultado obtenido por observación directa de que la profundidad de defecto dominante en áreas de tamaño fijo se ajusta a la distribución de Gumbel. Asimismo se ha comprobado que el número y la profundidad de los defectos siguen respectivamente distribuciones de tipo Poisson y de tipo exponencial, y se ha establecido la relación existente entre sus valores medios, los parámetros de escala y de localización de la distribución de Gumbel y el área de medida del defecto dominante.

Localized corrosion damage in Type 7075-T73 aluminum alloy was investigated for various anodizing pretreatment solutions. The postexposure surface corrosion was characterized by use of scanning electron microscopy (SEM) examination. In addition, SEM and energy dispersive spectroscopy (EDS) were used for second-phase (constituent) particle identification for those found to induce pitting corrosion during solution exposure. The pitting mechanisms were identified as circumferential where the particles are noble with respect to the matrix phase and by selective dissolution where they are anodic. The designated category-1 degreasing and category-2 inhibited alkaline solutions did not initiate localized corrosion after 1200 s exposures. However, the category-3 high-pH NaOH and category-4 low-pH HNO3 based solutions were found to initiate pitting attack, with the NaOH being significantly more aggressive. It was hypothesized that if the pits initiating during the pretreatment exposures were beyond a threshold size, on the order of 10-20 μm, a higher current density existed at these locations during subsequent electrochemical processes, thus resulting in larger and deeper pit structures. These surface defects are of primary concern with respect to accelerated fatigue crack nucleation. For smaller pits, on the order of 1-5 μm, the anodic process had a smoothing affect where the film growth tended to passivate the pits.

The occurrence of shallow surface defects in extra low carbon cold rolled steel sheets was studied. The metallographic analysis of the defects was not enough to determine the origin of these defects. It was established that the extra low carbon steels are as prone to surface defects as ultra low carbon steels. This is due to the formation of a " hook " associated to oscillation marks of the slabs, with a deeper penetration than in low carbon steels. This " hook " prevents argon bubbles and mold powder macroinclusions close to the solidification front from flotation and detaching in the mold slag. This lead to subsurface defects in the first 2 mm of the slab shell. It was also concluded that the Mn to S ratio in the steel was very low, allowing the possibility of heat crack formation during rolling. The preheating conditions previous to rolling could help in solving the problem, or increase it. The actions undertaken related to these aspects led to the elimination of this sort of defects.

Vitreous coatings can be used as a means for the corrosion protection of metals and alloys due to their excellent dielectric properties. Their use is of particular interest in the case of highly aggressive media (different pH levels, temperatures up to 600 °C). However, ceramic coatings exposed to aggressive agents and thermal cycles can experience devitrification and spalling problems, with the consequent loss of their protective properties.The present study uses the electrochemical impedance spectroscopy technique to characterize, in a non-destructive way, the appearance of surface defects induced by the effect of temperature and chemical attack on a vitreous enamel deposited on steel. By means of analysis of the impedance diagrams obtained, a relationship is established between the loss of the coating's protective properties and the mechanism by which the corrosion process takes place.

Pulsed eddy-current (PEC) testing is an electromagnetic nondestructive testing & evaluation (NDT&E) technique and defect classification is one of the most important steps in PEC defect characterization. With pulse excitation, the PEC response signals contain more features in time domain and rich information in frequency domain. This paper investigates feature extraction techniques for PEC defect classification including rising time, differential time to peak and differential time to zero, spectrum amplitude, and differential spectrum amplitude. Experimental study has been undertaken on Al-Mn 3003 alloy samples with artificial surface defects, sub-surface defects, and defects in two-layer structures under different lift-off. Experimental results show that methods are effective to classify the defects both in single-layer structures and two-layer structures. Comparing the results of different methods, it is found that differential process can eliminate the lift-off in defect classification in both time domain and frequency domain. The study can be extended to defect classification in complex structures, where lift-off effects are significant.

In this paper an analytical model is proposed to study the nonlinear dynamic behavior of rolling element bearing systems including surface defects. Various surface defects due to local imperfections on raceways and rolling elements are introduced to the proposed model. The contact force of each rolling element described according to nonlinear Hertzian contact deformation and the effect of internal radial clearance has been taken into account. Mathematical expressions were derived for inner race, outer race and rolling element local defects. To overcome the strong nonlinearity of the governing equations of motion, a modified Newmark time integration technique was used to solve the equations of motion numerically. The results were obtained in the form of time series, frequency responses and phase trajectories. The validity of the proposed model verified by comparison of frequency components of the system response with those obtained from experiments. The classical Floquet theory has been applied to the proposed model to investigate the linear stability of the defective bearing rotor systems as the parameters of the system changes. The peak-to-peak frequency response of the system for each case is obtained and the basic routes to periodic, quasi-periodic and chaotic motions for different internal radial clearances are determined. The current study provides a powerful tool for design and health monitoring of machine systems. r

In this report we review the fundamentals, applications and future tendencies of dynamic atomic force microscopy (AFM) methods. Our focus is on understanding why the changes observed in the dynamic properties of a vibrating tip that interacts with a surface make possible to obtain molecular resolution images of membrane proteins in aqueous solutions or to resolve atomic-scale surface defects in ultra high vacuum (UHV). Our description of the two major dynamic AFM modes, amplitude modulation atomic force microscopy (AM-AFM) and frequency modulation atomic force microscopy (FM-AFM) emphasises their common points without ignoring the differences in experimental set-ups and operating conditions. Those differences are introduced by the different feedback parameters, oscillation amplitude in AM-AFM and frequency shift and excitation amplitude in FM-AFM, used to track the topography and composition of a surface.

A statistical approach to defect detection and disc rimination has been applied to the case of hot roll ed steel. The probability distribution of pixel intensities has been estimated from a small set of images without de fects, and this distribution is used to select pixels with unlikely values as candidates for defects. Discriminat ion of true defects from random noise pixels is achieved by a d ynamical thresholding procedure, which tracks the b ehaviour of clusters of selected pixels for varying threshol d level. Boundary levels of the dynamic threshold range are determined from the estimated probability distribut ion of the pixel intensities.

This paper presents the characterization of defects on rivets using an eddy current based measurement system and signal processing algorithms to increase the signal to noise ratio. The instrument includes a planar eddy-current probe having a giant magnetoresistor (GMR) based sensor. The characterization of surface and sub-surface defects is depicted and the metrological performance analyzed.

Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions. q

An innovative method has been developed for the quantification of the surface quality of Lambertian component materials, while in the presence of a complex coincident albedo pattern. The technique uses a generic lighting configuration and is insensitive to component object pose. This is of considerable advantage for the relaxation of environmental structuring during on-line component inspection. A two-stage inspection strategy is proposed, consisting of an initial global surface assessment, together with the subsequent classification of segmented surface defect features. The technique has particular application for the detection of characteristic surface faults, such as indentations, protrusions or missing surface topology, typical of a range of manufacturing processes, including injection moulding, machining and stone polishing. The technique has been validated using a variety of flat and curved specimen components. Experimental results are presented in the paper. ᭧

Hidden defect characterisation in some complex structures is difficult. Pulsed Eddy Current (PEC) imaging based on rectangular excitation coil is investigated in this paper and hidden defect nondestructive testing and evaluation (detection, classification, and quantification) is carried out based on the various C-scan images. Experimental results have illustrated that hidden defects can be identified effectively by particular character in C-scan imaging results and sub-surface defects can be discriminated to correct class by selecting the rising time from response in time domain. The quantification information of hidden defects is preliminarily obtained based on the contour and 3D images. In addition, PEC imaging and frequency spectrum analysis are effective to detect, classify, and evaluate the sub-surface defects under the influence of edge effect of specimen. To sum up, PEC imaging is an effective approach to characterise hidden defects and sub-surface defects.

A multipass plane parallel Fabry-Perot interferometer (FPP-M) can give extremely high contrast (in excess of 106) over a wide range of finesse values without reducing the transmission significantly. Curves and tables are provided along with a brief outline of Chabbal's analysis for the residual defects of the Fabry-Perot mirrors to aid a quick assessment of the optimum parameters for a desired spectrometric work. The exploitation of the advantages of an FPP-M depends upon the maintenance of its stability. So, we have constructed a passive interferometer of low thermal expansion material, Cer-Vit, along with nonkinematic design and thermally compensated mirror mounts to achieve long term stability without the use of a servo control device.

Surface defects are small concave imperfections that can develop during forming on outer convex panels of automotive parts like doors. They occur during springback steps, after drawing in the vicinity of bending over a curved line and flanging/hemming in the vicinity of the upper corner of a door. They can alter significantly the final quality of the automobile and it is of primary importance to deal with them as early as possible in the design of the forming tools. The aim of this work is to reproduce at the laboratory scale such a defect, in the case of the flanging along a curved edge, made of two orthogonal straight part of length 50 mm and joint by a curved line. A dedicated device has been designed and steel samples were tested. Each sample was measured initially (after laser cutting) and after flanging, with a 3D measuring machine. 2D profiles were extracted and the curvature was calculated. Surface defects were defined between points where the curvature sign changed. Isovalues of surface defect depth could then be plotted, thus displaying also the spatial geometry on the part surface. An experimental database has been created on the influence of process parameters like the flanging height and the flanging radius. Numerical simulations have been performed with the finite element code Abaqus to predict the occurrence of such surface defects and to analyze stress and strain distribution within the defect area.