Search results for: weld defect

Authors: Jasvinder Singh, Manjinder Singh

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Welding of dissimilar materials is a complicated process due to the difference in melting point of two materials. Thermal conductivity and coefficient of thermal expansion of dissimilar materials also different; therefore, residual stresses produced in the weldment and base metal are the most critical problem associated with the joining of dissimilar materials. Tensile strength and impact toughness also reduced due to the residual stresses. In the present research work, an attempt has been made to weld SS304 and MS1018 dissimilar materials by submerged arc welding (SAW). By conducting trail, runs most effective parameters welding current, Arc voltage, welding speed and nozzle to plate distance were selected to weld these materials. The fractional factorial technique was used to optimize the welding parameters. Effect on tensile strength (TS), fracture toughness (FT) and microhardness of weldment were studied. It was concluded that by optimizing welding current, voltage and welding speed the properties of weldment can be enhanced.

Keywords: SAW, Tensile Strength (TS), fracture toughness, micro hardness

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Authors: N. Dahbi, R. B. Taleb

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This study concerns the ion implantation of oxygen in two semiconductors Si and GaAs realized by a simulation using the SRIM tool. The goal of this study is to compare the effect of implantation energy on the distribution of implant ions in the two targets and to examine the different processes resulting from the interaction between the ions of oxygen and the target atoms (Si, GaAs). SRIM simulation results indicate that the implanted ions have a profile as a function of Gaussian-type; oxygen produced more vacancies and implanted deeper in Si compared to GaAs. Also, most of the energy loss is due to ionization and phonon production, where vacancy production amounts to few percent of the total energy.

Keywords: defect profile, GaAs, ion implantation, SRIM, phonon production, vacancies

Procedia PDF Downloads 186

Authors: Samira Cherid, Samir Bentata, F. Zahira Meghoufel, Sabria Terkhi, Yamina Sefir, Fatima Bendahma, Bouabdellah Bouadjemi, Ali Z. Itouni

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In this work, we examined the propagation of light in one-dimensional systems is examined by means of the random dimer model. The introduction of defect elements, randomly in the studied system, breaks down the Anderson localization and provides a set of propagating delocalized modes at the corresponding conventional dimer resonances. However, tuning suitably the defect dimer resonance on the host ones (or vice versa), the transmission magnitudes can be enhanced providing the optimized ballistic transmission regime as an average response. Hence, ballistic optical filters can be conceived at desired wavelengths.

Keywords: photonic crystals, random dimer model, ballistic resonance, localization and transmission

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Authors: Bouzaki Mohammed Moustafa, Benyoucef Boumediene, Benouaz Tayeb, Benhamou Amina

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The ambient temperature and the defects density in the Hetero-junction with Intrinsic Thin layers solar cells (HIT) strongly influence their performances. In first part, we presented the bands diagram on the front/back simulated solar cell based on a-Si: H / c-Si (p)/a-Si:h. In another part, we modeled the following layers structure: ZnO/a-Si:H(n)/a-Si:H(i)/c-Si(p)/a-Si:H(p)/Ag where we studied the effect of the ambient temperature and the defects density in the gap of the crystalline silicon layer on the performance of the heterojunction solar cell with intrinsic layer (HIT).

Keywords: heterojunction solar cell, solar cell performance, bands diagram, ambient temperature, defect density

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Authors: Ryu Wonjin, Choi Hyeok, Park Joonhong

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Overlay welding for improving surface properties is a method of the surface treatments which improve surface properties of material by welding materials of alloy having corrosion resistance on the basic material surface. Overlay welding affects contents of chemical components and weld hardness from different parts by dilution of the lamination layer thickness, and it determines surface properties. Therefore, overlay welding has to take into account thickness of the lamination layers with the process. As a result in this study examined contents of Fe, weldability of the base metal and monel materials, hardness and surface flatness from different parts according to each the lamination layer parameters by overlay welding monel materials with corrosion resources to the base material of carbon steel. Through this, evaluated effect by the lamination layer parameters of welding and presented decision methods of the lamination layer parameters of the overlay welding by the purpose of use.

Keywords: clad pipe, lamination layer parameters, monel, overlay welding

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Authors: Yi-Hua Chen, Hsiang-Wen Tang, I-Ling Chang, Lien-Wen Chen

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The defect mode of two-dimensional phononic crystals with Archimedean tilings was explored in the present study. Finite element method and supercell method were used to obtain dispersion relation of phononic crystals. The simulations of the acoustic wave propagation within phononic crystals are demonstrated. Around the cavity which is created by removing several cylinders in the perfect Archimedean tilings, whispering-gallery mode (WGM) can be observed. The effects of the cavity geometry on the WGM modes are investigated. The WGM modes with high Q-factor and high cavity pressure can be obtained by phononic crystals with Archimedean tilings.

Keywords: defect mode, Archimedean tilings, phononic crystals, whispering-gallery modes

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Authors: Jalel Khelil

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In order to improve reliability of Gas Turbine machine especially its generator equipment, a fault diagnosis system based on fuzzy approach is proposed. Three various methods namely K-NN (K-nearest neighbors), F-KNN (Fuzzy K-nearest neighbors) and FNM (Fuzzy nearest mean) are adopted to provide the measurement of relative strength of vibration defaults. Both applications consist of two major steps: Feature extraction and default classification. 09 statistical features are extracted from vibration signals. 03 different classes are used in this study which describes vibrations condition: Normal, unbalance defect, and misalignment defect. The use of the fuzzy approaches and the classification results are discussed. Results show that these approaches yield high successful rates of vibration default classification.

Keywords: fault diagnosis, fuzzy classification k-nearest neighbor, vibration

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Authors: Eyob Messele Sefene, Atinkut Atinafu Yilma

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The highest strength-to-weight ratio criterion has fascinated increasing curiosity in virtually all areas where weight reduction is indispensable. One of the recent advances in manufacturing to achieve this intention endears friction stir welding (FSW). The process is widely used for joining similar and dissimilar non-ferrous materials. In FSW, the mechanical properties of the weld joints are impelled by property-selected process parameters. This paper presents verdicts of optimum process parameters in attempting to attain enhanced mechanical properties of the weld joint. The experiment was conducted on a 5 mm 6061 aluminum alloy sheet. A butt joint configuration was employed. Process parameters, rotational speed, traverse speed or feed rate, axial force, dwell time, tool material and tool profiles were utilized. Process parameters were also optimized, making use of a mixed L18 orthogonal array and the Grey relation analysis method with larger is better quality characteristics. The mechanical properties of the weld joint are examined through the tensile test, hardness test and liquid penetrant test at ambient temperature. ANOVA was conducted in order to investigate the significant process parameters. This research shows that dwell time, rotational speed, tool shape, and traverse speed have become significant, with a joint efficiency of about 82.58%. Nine confirmatory tests are conducted, and the results indicate that the average values of the grey relational grade fall within the 99% confidence interval. Hence the experiment is proven reliable.

Keywords: friction stir welding, optimization, 6061 AA, Taguchi

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Authors: Hye-Young Shin, Hae-Young Lopilly Park, Chan Kee Park

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We compared the 24-2 and 10-2 visual fields (VFs) and investigate the degree of discrepancy between the two tests in glaucomatous eyes with central VF defects. In all, 99 eyes of 99 glaucoma patients who underwent both the 24-2 VF and 10-2 VF tests within 6 months were enrolled retrospectively. Glaucomatous eyes involving a central VF defect were divided into three groups based on the average total deviation (TD) of 12 central points in the 24-2 VF test (N = 33, in each group): group 1 (tercile with the highest TD), group 2 (intermediate TD), and group 3 (lowest TD). The TD difference was calculated by subtracting the average TD of the 10-2 VF test from the average TD of 12 central points in the 24-2 VF test. The absolute central TD difference in each quadrant was defined as the absolute value of the TD value obtained by subtracting the average TD of four central points in the 10-2 VF test from the innermost TD in the 24-2 VF test in each quadrant. The TD differences differed significantly between group 3 and groups 1 and 2 (P < 0.001). In the superonasal quadrant, the absolute central TD difference was significantly greater in group 2 than in group 1 (P < 0.05). In the superotemporal quadrant, the absolute central TD difference was significantly greater in group 3 than in groups 1 and 2 (P < 0.001). Our results indicate that the results of VF tests for different VFs can be inconsistent, depending on the degree of central defects and the VF quadrant.

Keywords: central visual field defect, glaucoma, 10-2 visual field, 24-2 visual field

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Authors: Naqoosh Haidry

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Objective & Goal: Enucleation of the maxillomandibular cysts will lead to the creation of post-surgical bone defects which may take more than a year for complete bone healing. The use of bone grafts is common to aid bone regeneration in large defects. The study aimed to evaluate the healing and bone formation capabilities of polymer of injectable platelet fibrin (i-PRF) and hydroxyapatite (HA) as bone graft substitute in maxilla-mandibular postsurgical defects compared to hydroxyapatite alone. The primary objective was to find out the clinical and radiological assessment of healing postoperatively and compare the outcome of both groups. Material and Methods: After surgical enucleation of 19 maxillomandibular cysts/tumors, either HA or HA+ i-PRF graft was adapted to the defect. Clinical outcome variables such as pain (VAS score), edema, and mucosal color were evaluated on postoperative days 01, 03, and 07 while radiological outcome variables such as volume of defect (cc), density of new bone (HU) on computed tomography were evaluated at 2nd and 4th month. The results obtained were tabulated and compared with the inferential analysis. Results: Clinical parameters seem to be better in the HA + i-PRF group, but the result was non-significant. Radiologically, the mean healing ratios were significantly greater in the HA + i-PRF group (63.5 ± 2.34 at 2nd month, 90.3 ± 7.32 at 4th month) compared to the HA group (57.2 ± 5.21at 2nd month, 80.8 ± 5.33 at 4th month). When comparing the mean density of new bone, there was a statistically significant difference with a mean difference of 95.2 HU more in the HA + i-PRF (623 HU ± 42.9) compared to the HA group (528 HU ± 96.5) in 2nd month. Conclusion: The polymer of i-PRF and HA prepared as the sticky bone yields faster and better bone healing in post-enucleation maxillomandibular bony defects as compared to hydroxyapatite alone based on radiological findings till four months.

Keywords: bone defect, density of new bone, hydroxyapatite, injectable platelet rich fibrin, maxillomandibular cysts, surgical defect

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Authors: Evy Van Puymbroeck, Wim Nagy, Ken Schotte, Heng Fang, Hans De Backer

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The knowledge of residual stresses for welded bridge components is essential to determine the effect of the residual stresses on the fatigue life behavior. The residual stresses of an orthotropic bridge deck are determined by simulating the welding process with finite element modelling. The stiffener is placed on top of the deck plate before welding. A chained thermal-mechanical analysis is set up to determine the distribution of residual stresses for the bridge deck. First, a thermal analysis is used to determine the temperatures of the orthotropic deck for different time steps during the welding process. Twin wire submerged arc welding is used to construct the orthotropic plate. A double ellipsoidal volume heat source model is used to describe the heat flow through a material for a moving heat source. The heat input is used to determine the heat flux which is applied as a thermal load during the thermal analysis. The heat flux for each element is calculated for different time steps to simulate the passage of the welding torch with the considered welding speed. This results in a time dependent heat flux that is applied as a thermal loading. Thermal material behavior is specified by assigning the properties of the material in function of the high temperatures during welding. Isotropic hardening behavior is included in the model. The thermal analysis simulates the heat introduced in the two plates of the orthotropic deck and calculates the temperatures during the welding process. After the calculation of the temperatures introduced during the welding process in the thermal analysis, a subsequent mechanical analysis is performed. For the boundary conditions of the mechanical analysis, the actual welding conditions are considered. Before welding, the stiffener is connected to the deck plate by using tack welds. These tack welds are implemented in the model. The deck plate is allowed to expand freely in an upwards direction while it rests on a firm and flat surface. This behavior is modelled by using grounded springs. Furthermore, symmetry points and lines are used to prevent the model to move freely in other directions. In the thermal analysis, a mechanical material model is used. The calculated temperatures during the thermal analysis are introduced during the mechanical analysis as a time dependent load. The connection of the elements of the two plates in the fusion zone is realized with a glued connection which is activated when the welding temperature is reached. The mechanical analysis results in a distribution of the residual stresses. The distribution of the residual stresses of the orthotropic bridge deck is compared with results from literature. Literature proposes uniform tensile yield stresses in the weld while the finite element modelling showed tensile yield stresses at a short distance from the weld root or the weld toe. The chained thermal-mechanical analysis results in a distribution of residual weld stresses for an orthotropic bridge deck. In future research, the effect of these residual stresses on the fatigue life behavior of welded bridge components can be studied.

Keywords: finite element modelling, residual stresses, thermal-mechanical analysis, welding simulation

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Authors: Ana Claudia Muniz Rennó, Karina Nogueira

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This study aimed to investigate the in vivo tissue response of the introduction of the bioactive mesh (BM) scaffolds using a model of tibial bone defect implants in rats. Although a previous in vivo study demonstrated a highly positive response of particulate bioactive materials in the morphological and biomechanical properties of the bone callus, the effects of material with superior bioactivity, present in form of meshes have not been studied yet. Eighty male Wistar rats with 3 mm tibial defects were used. Animals were divided into four groups: intact group (IG) – tibia without any injury; bone defect day zero (0dD) – bone defects, sacrificed immediately after injury; bone defect control group (CG) – bone defects without any filler and bone defect filled with BM scaffold. The animals of BM and CG groups were sacrificed 15, 30 and 45 days post-injury to compare the temporal-special effects of the scaffolds on bone healing. The histological analysis revealed an organized newly formed bone at 30 and 45 days post-surgery in the BM. Also, this group presented an increased COX-2 expression on days 15 and 30 post-surgery. Furthermore, the immunohistochemistry analysis revealed that, BM presented a positive immunoexpression of RUNX-2 during all periods evaluated. The biomechanical analysis revealed that at 15 day after surgery, no significant statistically difference was observed between BM and CG and both groups had significantly higher values of maximal load compared to 0dG and significantly lower values than IG. On days 30 and 45 post-surgery, BM presented statistically lower values of maximal load compared to the CG. Nevertheless, at the same periods, BM did not show statistically significant difference compared to the IG maximal load values (p > 0, 05). Our results revealed that the implantation of the BM scaffolds was effective in stimulating newly bone formation.

Keywords: bone, biomaterials, scaffolds, cartilage

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Authors: Amrane Meriem, Oukid Salyha

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The presence of defects or bugs in software can lead to costly setbacks, operational inefficiencies, and compromised user experiences. The integration of Machine Learning(ML) techniques has emerged to predict and preemptively address software defects. ML represents a proactive strategy aimed at identifying potential anomalies, errors, or vulnerabilities within code before they manifest as operational issues. By analyzing historical data, such as code changes, feature im- plementations, and defect occurrences. This en- ables development teams to anticipate and mitigate these issues, thus enhancing software quality, reducing maintenance costs, and ensuring smoother user interactions. In this work, we used a recommendation system to improve the performance of ML models in terms of predicting the code severity and effort estimation.

Keywords: software engineering, machine learning, bugs detection, effort estimation

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Authors: M. Ridwanul Hassan, Samuel George

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Aims: Steroid injections are commonly used as a diagnostic tool or an alternative to surgical management of carpal tunnel syndrome (CTS) and are generally safe. Ischaemia is a rare complication with very few cases reported in the literature. Methods: We report a case of a 50-year-old female that presented with a necrotic wound to her left palm one month after a steroid injection into the carpal tunnel. She had a 2-year history of CTS in her left hand that was treated with six previous steroid injections in primary care during this period. The wound evolved from a blister to a necrotic ulcer which led to a painful, hollow defect in the centre of her palm. She did not report any history of trauma, nor did she have any co-morbidities. Clinical photographs were taken. Results: On examination, she had a 0.5 cmx1 cm defect in the palm of her left hand down to aponeurosis. There was purulent discharge in the wound with surrounding erythema but no spreading cellulitis. She had full function of her fingers but was very tender on movements and at rest. She was admitted for intravenous antibiotics and underwent a debridement, washout, and carpal tunnel release the next day. The defect was packed to heal by secondary intention and has now fully healed one month following her operation. Conclusions: This is an extremely rare complication of steroid injections to the carpal tunnel and may have been avoided by earlier referral for surgery rather than treatment using multiple steroid injections.

Keywords: hand surgery, complication, rare, carpal tunnel syndrome

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Authors: Atabak Rahimzadeh Ilkhch

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Friction stir processing (FSP) has promised for application of thermo-mechanical processing techniques where aims to change the micro structural and mechanical properties of materials in order to obtain high performance and reducing the production time and cost. There are lots of studies focused on the microstructure of friction stir welded aluminum alloys. The main focus of this research is on the grain size obtained in the weld zone. Moreover in second part focused on temperature distribution effect over the entire weld zone and its effects on the microstructure. Also, there is a need to have more efforts on investigating to obtain the optimal value of effective parameters such as rotational speed on microstructure and to use the optimum tool designing method. the final results of this study will be present the variation of structural and mechanical properties of materials in the base of applying Friction stir processing and effect of (FSP) processing and tensile testing on surface quality. in the hand, this research addresses the FSP f AA-7020 aluminum and variation f ration of rotation and translational speeds.

Keywords: friction stir processing, AA-7020, thermo-mechanical, microstructure, temperature

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Authors: A. Benyahia, M. Zergoug, M. Amir, M. Fodil

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The main objective of this work is to enhance the Pulsed Eddy Current (PEC) response from the aluminum structure using signal processing. Cracks and metal loss in different structures cause changes in PEC response measurements. In this paper, time-frequency analysis is used to represent PEC response, which generates a large quantity of data and reduce the noise due to measurement. Power Spectral Density (PSD) after Wavelet Decomposition (PSD-WD) is proposed for defect detection. The experimental results demonstrate that the cracks in the surface can be extracted satisfactorily by the proposed methods. The validity of the proposed method is discussed.

Keywords: DT, pulsed eddy current, continuous wavelet transform, Mexican hat wavelet mother, defect detection, power spectral density.

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Authors: Nyiko M. Chauke, James Ramontja, Richard M. Moutloali

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The zeolite ZSM-22 material demonstrated effective hydrophilic character as a nanoadditive filler in the preparation of nanocomposite membranes. In this study, nanorods ZSM-22 zeolite materials were hydrothermally synthesised from a homogenous gel mixture prepared using different silica precursors: colloidal silica, fumed silica, tetraethylorthosilicate (TEOS), and aluminium precursor: aluminium sulphate octadecahydrate (Al₂(SO₄)₃.18H₂O to Si/Al of 60. This was focused on developing a defect-free zeolite framework for effective use in applications such as membrane separation process, adsorption, and catalysis. The obtained ZSM-22 zeolite materials with 60 Si/Al ratio exhibits high crystallinity, hydrophilicity, and needle-like morphologies, suggesting successful synthesis as shown by X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier-Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) physicochemical analysis. It was revealed that the use of different nature of silica precursors significantly influenced the properties of the final product and contributed to the development of defect-free zeolite material. As such, the crystalline nanorods of Theta-1 (TON) ZSM-22 obtained from TEOS silica showed high phase purity, defect-free, and narrow particle size distribution. Morphological analysis exhibited that the use of TEOS as silica precursor was effective than its counterparts and produced high crystalline need-like agglomerated particles.

Keywords: silica precursor, hydrothermal synthesis, zeolite material, ZSM-22

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Authors: Allal Bedlaoui, Hamid Boutoutaou

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Due to its superior economics, shrink-fit assembly is one of the best mechanical assembly methods. There are simply two components, the axis and hub. It is used in many different industries, including the production of trains, cars, and airplanes. The outer radius of the inner cylinder must be greater than the inner radius of the outer cylinder for this operation; this difference is referred to as the "interference" between the two cylinders. There are three ways to accomplish this: heating the outer cylinder to cause it to expand; cooling the cylinder's inside to cause it to contract; and third, finishing the fitting under a press. At the intersection of the two matched parts, a contact pressure and friction force are generated. We consider interference and form defects in this article because they prevent the connection between the axis and the hub from having a perfect form surface and because we will be looking at how they affect the assembly. Numerical simulation is used to ascertain if interference and form defects have a beneficial or negative influence in the distribution of stresses, assembly resistance, and plasticity.

Keywords: shrink-fit, interference, form defect, plasticity, extraction force

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Authors: Ssembatya Joseph Mary

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Introduction: Omphalocele, an abdominal wall defect, occurs in 1 out of 4,000 to 6,000 live births. It is characterized by visceral herniation of small and large intestines, liver, and sometimes spleen and gonads are involved. The viscera is always covered by a three-layered sac. The defect in the mesoderm is mainly due to the failure of lateral abdominal wall folds to unite. About 350,000 ventral hernia repairs are done annually in the united states of America. Surgical repair with a mesh is the gold standard surgical method. With conservative management of Omphalocele, children are eventually closed between the age of 1 and 5 years. Herein, we present a late manifestation of ventral hernia following Omphalocele in a female Ugandan. Case presentation: A 56-year-old female with no known chronic illnesses and normal perinatal history presented with an umbilical swelling since birth with no associated symptoms. She is a married woman to one husband and has five children, and all of them are in good general condition with no such symptoms. She had normal vitals with an umbilical defect measuring about 20cm from the xiphoid process and 10 cm from the symphysis pubis. Surgery was done (component separation) on the second inpatient day, and it was uneventful. The patient was discharged on the 4th postoperative day in good general condition with a dry and clean surgical site. Conclusion: Despite adequate literature about Omphalocele and clear management guidelines, there have been reported cases of adult presentation of ventral hernias secondary to Omphalocele.

Keywords: omphalocele, ventral hernia, uganda, late presentation

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Authors: Dongju Kim, Youngjoo Suh, Hyojin Kim, Gyeongyeong Kim

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Acoustic Emission Testing (AET) is widely used to test the structural integrity of an operational hydrogen storage container, and clustering algorithms are frequently used in pattern recognition methods to interpret AET results. However, the interpretation of AET results can vary from user to user as the tuning of the relevant parameters relies on the user's experience and knowledge of AET. Therefore, it is necessary to use a deep learning model to identify patterns in acoustic emission (AE) signal data that can be used to classify defects instead. In this paper, a deep learning-based model for classifying the types of defects in hydrogen storage tanks, using AE sensor waveforms, is proposed. As hydrogen storage tanks are commonly constructed using carbon fiber reinforced polymer composite (CFRP), a defect classification dataset is collected through a tensile test on a specimen of CFRP with an AE sensor attached. The performance of the classification model, using one-dimensional convolutional neural network (1-D CNN) and synthetic minority oversampling technique (SMOTE) data augmentation, achieved 91.09% accuracy for each defect. It is expected that the deep learning classification model in this paper, used with AET, will help in evaluating the operational safety of hydrogen storage containers.

Keywords: acoustic emission testing, carbon fiber reinforced polymer composite, one-dimensional convolutional neural network, smote data augmentation

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Authors: Muhammad Habib, Xuefan Zhou, Lin Tang, Guoliang Xue, Fazli Akram, Dou Zhang

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Defect engineering approach is a well-established approach for the customization of functional properties of perovskite ceramics. In modern technology, the high multiferroic properties for elevated temperature applications are greatly demanding. In this work, the Bi-nonstoichiometric lead-free 0.67Biy-xSmxFeO3-0.33BaTiO3 ceramics (Sm-doped BF-BT for Bi-excess; y = 1.03 and Bi-deficient; y = 0.975 with x = 0.00, 0.04 and 0.08) were design for the high-temperature multiferroic property. Enhanced piezoelectric (d33  250 pC/N and d33* 350 pm/V) and magnetic properties (Mr  0.25 emu/g) with a high Curie temperature (TC  465 ℃) were obtained in the Bi-deficient pure BF-BT ceramics. With Sm-doping (x = 0.04), the TC decrease to 350 ℃ a significant improvement occurred in the d33* to 504 pm/V and 450 pm/V for Bi-excess and Bi-deficient compositions, respectively. The structural origin of the enhanced piezoelectric strain performance is related to the soft ferroelectric effect by Sm-doping and reversible phase transition from the short-range relaxor ferroelectric state to the long-range order under the applied electric field. However, a slight change occurs in the Mr 0.28 emu/g value with Sm-doping for Bi-deficient ceramics, whereas the Bi-excess ceramics shows completely paramagnetic behavior. Hence, the origin of high magnetic properties in the Bi-deficient BF-BT ceramics is mainly attributed to the proposed double exchange mechanism. We believe that this strategy will provide a new perspective for the development of lead-free multiferroic ceramics for high-temperature applications.

Keywords: BiFeO3-BaTiO3, lead-free piezoceramics, magnetic properties, defect engineering

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Authors: Pawan S. Nagda, Purnank S. Bhatt, Mit K. Shah

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Earing defect in drawing process is highly undesirable not only because it adds on an additional trimming operation but also because the uneven material flow demands extra care. The objective of this work is to study the earing problem in the Deep Drawing of circular cup and to optimize the blank shape to reduce the earing. A finite element model is developed for 3-D numerical simulation of cup forming process in ABAQUS. Extra-deep-drawing (EDD) steel sheet has been used for simulation. Properties and tool design parameters were used as input for simulation. Earing was observed in the simulated cup and it was measured at various angles with respect to rolling direction. To reduce the earing defect initial blank shape was modified with the help of anisotropy coefficient. Modified blanks showed notable reduction in earing.

Keywords: anisotropy, deep drawing, earing, finite element simulation

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Authors: Jay J. Vora, Vishvesh J. Badheka

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This work attempts to investigate the effect of oxide fluxes on 6mm thick Reduced Activation ferritic/martensitic steels (RAFM) during Activated TIG (A-TIG) welding. Six different fluxes Al₂O₃, Co₃O₄, CuO, HgO, MoO₃, and NiO were mixed with methanol for conversion into paste and bead-on-plate experiments were then carried out. This study, systematically investigates the influence of oxide-based flux powder and carrier solvent composition on the weld bead shape, geometric shape of weld bead and dominant depth enhancing mechanism in tungsten inert gas (TIG) welding of reduced activation ferritic/martensitic (RAFM) steel. It was inferred from the study that flux Co₃O₄ and MoO₃ imparted full and secure (more than 6mm) penetration with methanol owing to dual mechanism of reversed Marangoni and arc construction. The use of methanol imparted good spreadabilty and coverability and ultimately higher peak temperatures were observed with its use owing to stronger depth enhancing mechanisms than use of acetone with same oxide fluxes and welding conditions.

Keywords: A-TIG, flux, oxides, penetration, RAFM, temperature, welding

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Authors: Dong Liu

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By sending a high-frequency probe wave and a low-frequency pump wave to a specimen, the vibroacoustic method evaluates the defect’s severity according to the modulation index of the received signal. Many studies experimentally proved the significant sensitivity of the modulation index to the tiny contact type defect. However, it has also been found that the modulation index was highly affected by the frequency of probe or pump waves. Therefore, the chirp signal has been introduced to the VAM method since it can assess multiple frequencies in a relatively short time duration, so the robustness of the VAM method could be enhanced. Consequently, the signal processing method needs to be modified accordingly. Various studies utilized different algorithms or combinations of algorithms for processing the VAM signal method by chirp excitation. These signal process methods were compared and used for processing a VAM signal acquired from the steel samples.

Keywords: vibroacoustic modulation, nonlinear acoustic modulation, nonlinear acoustic NDT&E, signal processing, structural health monitoring

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Authors: Mohamed El Morsy, Gabriela Achtenová

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Research on damage of gears and gear pairs using vibration signals remains very attractive, because vibration signals from a gear pair are complex in nature and not easy to interpret. Predicting gear pair defects by analyzing changes in vibration signal of gears pairs in operation is a very reliable method. Therefore, a suitable vibration signal processing technique is necessary to extract defect information generally obscured by the noise from dynamic factors of other gear pairs. This article presents the value of cepstrum analysis in vehicle gearbox fault diagnosis. Cepstrum represents the overall power content of a whole family of harmonics and sidebands when more than one family of sidebands is present at the same time. The concept for the measurement and analysis involved in using the technique are briefly outlined. Cepstrum analysis is used for detection of an artificial pitting defect in a vehicle gearbox loaded with different speeds and torques. The test stand is equipped with three dynamometers; the input dynamometer serves as the internal combustion engine, the output dynamometers introduce the load on the flanges of the output joint shafts. The pitting defect is manufactured on the tooth side of a gear of the fifth speed on the secondary shaft. Also, a method for fault diagnosis of gear faults is presented based on order cepstrum. The procedure is illustrated with the experimental vibration data of the vehicle gearbox. The results show the effectiveness of cepstrum analysis in detection and diagnosis of the gear condition.

Keywords: cepstrum analysis, fault diagnosis, gearbox, vibration signals

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Authors: Egoitz Aldanondo, Ekaitz Arruti, Amaia Iturrioz, Ivan Huarte, Fidel Zubiri

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Manufacturing aeronautic structures joining extruded profiles or stringers to sheets or skins of aluminium is a typical manufacturing procedure in aeronautic structures. Although riveting is the conventional manufacturing technology to produce such joints, the Friction Stir Welding (FSW) and Laser Beam Welding (LBW) technologies have also demonstrated their potential for this kind of applications. Therefore, FSW and LBW technologies have the potential to continue their development as manufacturing processes for aeronautic structures showing benefits such as time-saving, light-weighting and overall cost reduction. In addition to that, new aluminium-lithium based alloy developments represent great opportunities for advanced aeronautic structure manufacturing with potential benefits such as lightweight construction or improved corrosion resistance. This work presents the main approaches by FSW and LBW to develop those technologies to produce stiffened panel structures such as fuselage by stringer-skin joints and using innovative aluminium-lithium alloys. Initial welding tests were performed in AA2198-T3S aluminium alloys for LBW technology and with AA2198-T851 for FSW. Later tests for both FSW and LBW have been carried out using AA2099-T83 alloy extrusions as stringers and AA2060-T8E30 as skin materials. The weld quality and properties have been examined by metallographic analysis and mechanical testing, including shear tensile tests and pull-out tests. The analysis of the results have shown the relationships between processing conditions, micro-macrostructural properties and the mechanical strength of the welded joints. The effects produced in the different alloys investigated have been observed and particular weld formation mechanics have been studied for each material and welding technology. Therefore, relationships between welding conditions and the obtained weld properties for each material combination and welding technology will be discussed in this presentation.

Keywords: AA2060-T8E30, AA2099-T83, AA2198-T3S, AA2198-T851, friction stir welding, laser beam welding

Procedia PDF Downloads 201

Authors: Mariam Bibi, Rubab Mehboob, Mehreen Sirshar

Abstract:

Satisfying the customer requirements is the ultimate goal of producing or developing any product. The quality of the product is decided on the bases of the level of customer satisfaction. There are different techniques which have been reported during the survey which enhance the quality of the product through software defect prediction and by locating the missing software requirements. Some mining techniques were proposed to assess the individual performance indicators in collaborative environment to reduce errors at individual level. The basic intention is to produce a product with zero or few defects thereby producing a best product quality wise. In the analysis of survey the techniques like Genetic algorithm, artificial neural network, classification and clustering techniques and decision tree are studied. After analysis it has been discovered that these techniques contributed much to the improvement and enhancement of the quality of the product.

Keywords: data mining, defect prediction, missing requirements, software quality

Procedia PDF Downloads 469

Authors: Saleh Abu Dabous, Khaled Hamad, Rami Al-Ruzouq

Abstract:

Bridge condition assessment and rating provide essential information needed for bridge management. This paper reviews bridge inspection and condition rating practices and introduces a defect-based urgency index. The index is estimated at the element-level based on the extent and severity of the different defects typical to the bridge element. The urgency index approach has the following advantages: (1) It facilitates judgment submission, i.e. instead of rating the bridge element with a specific linguistic overall expression (which can be subjective and used differently by different people), the approach is based on assessing the defects; (2) It captures multiple defects that can be present within a deteriorated element; and (3) It reflects how critical the element is through quantifying critical defects and their severity. The approach can be further developed and validated. It is expected to be useful for practical purposes as an early-warning system for critical bridge elements.

Keywords: condition rating, deterioration, inspection, maintenance

Procedia PDF Downloads 453

Authors: Mustafa Kemal Bilici, Memduh Kurtulmuş, İlyas Kartal, Ahmet İrfan Yükler

Abstract:

Friction stir welding is a solid-state joining process that has gained acceptable progress in recent years. This method which was first used for welding of aluminum and its alloys is now employed for welding of other materials such as polymers and composites. The aim of the present work is to investigate the mechanical properties of butt joints produced by friction stir welding (FSW) in high density polyethylene sheets of 4 mm thickness. The effects of critical welding parameters and tool design have affected on mechanical properties, weld surface and macrostructure of friction stir welded polyethylene. Experiments were performed at tool rotational speeds of 600, 900, 1200 and 1500 r/min and traverse speeds of 30, 45 and 60 mm/min, tool diameters (d) of 4, 5, 6 mm and tool shoulder diameters (D) 20, 25, 30 mm. A strength value of 80 % of the base material was achieved at the isolated optimum welding condition. According to the tool design, the welding parameters and the mechanical properties changed to a great extent. The highest tensile strength was achieved at low feed rates, high tool rotation speeds and shoulder diameters/pin diameters ratio.

Keywords: friction stir welding, mechanical properties, polyethylene, high density polyethylene, tool design

Procedia PDF Downloads 395

Authors: Jooyoung Park, Junkyeong Kim, Aoqi Zhang, Seunghee Park

Abstract:

Non-destructive testing on cable is in great demand due to safety accidents at sites where many equipments using cables are installed. In this paper, the quantitative change of the obtained signal was analyzed using a magnetic flux leakage (MFL) method. A two-dimensional simulation was conducted with a FEM model replicating real elevator cables. The simulation data were compared for three parameters (depth of defect, width of defect and inspection velocity). Then, an experiment on same conditions was carried out to verify the results of the simulation. Signals obtained from both the simulation and the experiment were transformed to characterize the properties of the damage. Throughout the results, a cable damage detection based on an MFL method was confirmed to be feasible. In further study, it is expected that the MFL signals of an entire specimen will be gained and visualized as well.

Keywords: magnetic flux leakage (mfl), cable damage detection, non-destructive testing, numerical simulation

Procedia PDF Downloads 383