Dent Type Research Articles

Integrity Assessment of an In-Service Gas Pipeline Featuring Dent Defect at a Highway Crossing

Underground pipelines are susceptible to different types of damage/flaws such as metal loss, buckling, dents, gouges, cracks, etc. during installation and operation. The structural integrity of the pipelines featuring such defects needs to be ensured for safe operation and to avoid serious hazards (fire/explosion/fatality/injury etc.). This paper discusses the integrity assessment of an actual case of an in-service gas pipeline featuring dent damage located at a highway crossing. A routine in-line inspection (ILI) of the considered pipeline showed the presence of a dent type of damage with a maximum depth of 5% spread over an area of 325 mm x 275 mm. Since the pipeline is located approximately 7.5 m below a 10-lane expressway with heavy traffic, dig verification of the dent was found to be not feasible. Level-3 integrity assessment based on API 579-1/ASME-FFS-1 2021 Fitness-For-Service standard has been performed using commercial finite element (FE) software ABAQUS/CAE. The considered pipeline is subjected to overburden pressure of soil embankment and cyclic loads such as vehicular loads (as per IRC: 6-2017) and internal pressure. The dented pipeline segment was assessed for potential failure modes i.e., protection against plastic collapse, local failure, collapse from buckling, and fatigue damage. FE analysis of the pipeline-soil system has been carried out considering the material and geometric nonlinearity, and contact interactions. The study suggests the pipeline is safe for further operation with existing dented defects. The methodology presented in this paper can act as a guide for the integrity assessment of pipelines with dent damage located at highway crossings.

Kernel properties related to carotenoid release during in vitro gastrointestinal digestion in commercial dent maize hybrids

The objective of study was to investigate the relationships between maize kernel properties and carotenoid release during simulated gastrointestinal digestion of 103 hybrids of dent type. Commercial maize hybrids significantly differed in kernel hardness, chemical composition and carotenoid profile. Across all hybrids, the amount of digestible individual carotenoids increased as follows: β-carotene < α-cryptoxanthin < β-cryptoxanthin < lutein < zeaxanthin. The amount of digested carotenoids correlated negatively with amylose content and amylose-to-amylopectin ratio, while it correlated positively with the content of neutral detergent fibres and amylopectin as well as the Stenvert index. However, the content of endosperm lipids could not be related to carotenoid digestibility. Findings clearly indicate that the carotenoid release from the kernel during digestion is related to specific physical and chemical properties, leading to a better understanding of the effects of kernel matrix structure on carotenoid digestibility in dent-type maize hybrids.

Fertilizer Effects on Endosperm Physicochemical Properties and Resistance to Larger Grain Borer, Prostephanus truncatus (Coleoptera: Bostrichidae), in Malawian Local Maize (Zea mays L.) Varieties: Potential for Utilization of Ca and Mg Nutrition

Maize grain hardness influences storage pest resistance, a key characteristic valued by smallholder farmers. The structural changes in the endosperm determine grain hardness and are influenced by agronomic practices. The purpose of this study was to establish whether supply of calcium and magnesium based fertilizers can alter physicochemical properties of local and hybrid maize varieties and reduce the infestation by larger grain borer (Prostephanus truncatus (Coleoptera: Bostrichidae)) during storage. Two local and one hybrid maize varieties commonly grown by smallholder farmers in Malawi were cultivated under three fertilizer treatments (NPK (nitrogen, phosphorous, potassium), NPK plus gypsum, and NPK plus dolomite). After harvest, the grains were classified into flint and dent types, followed by P. truncatus infestation and determination of their physicochemical properties. The addition of gypsum and dolomite fertilizers led to higher levels of amylose, total zein and β-14 zein, traits associated with kernel hardness, compared to the application of NPK fertilizer. Moreover, local maize varieties showed higher resistance to P. truncatus infestation, hardness and biochemical properties associated with hardness (total zein, α-19 and β-14 zein, starch lysophosphatidylcholine, and non-starch free fatty acid) compared to hybrid variety. Our study suggests the potential for utilizing Ca and Mg nutrition in maize to improve kernel hardness, thus adoption of gypsum and dolomite by smallholder farmers may be beneficial against P. truncatus during storage.

Seed longevity of maize conserved under germplasm bank conditions for up to 60 years.

The long-term conservation of seeds of plant genetic resources is of key importance for food security and preservation of agrobiodiversity. Nevertheless, there is scarce information available about seed longevity of many crops under germplasm bank conditions. Through germination experiments as well as the analysis of historical monitoring data, we studied the decline in viability manifested by 1000 maize (Zea mays subsp. mays) seed accessions conserved for an average of 48 years at the CIMMYT germplasm bank, the largest maize seedbank in the world, under two cold storage conditions: an active (-3 °C; intended for seed distribution) and a base conservation chamber (-15 °C; for long-term conservation). Seed lots stored in the active chamber had a significantly lower and more variable seed germination, averaging 81.4 %, as compared with the seed lots conserved in the base chamber, averaging 92.1 %. The average seed viability detected in this study was higher in comparison with that found in other seed longevity studies on maize conserved under similar conditions. A significant difference was detected in seed germination and longevity estimates (e.g. p85 and p50) among accessions. Correlating seed longevity with seed traits and passport data, grain type showed the strongest correlation, with flint varieties being longer lived than floury and dent types. The more rapid loss of seed viability detected in the active chamber suggests that the seed conservation approach, based on the storage of the same seed accessions in two chambers with different temperatures, might be counterproductive for overall long-term conservation and that base conditions should be applied in both. The significant differences detected in seed longevity among accessions underscores that different viability monitoring and regeneration intervals should be applied to groups of accessions showing different longevity profiles.

Damage Accumulation Model of a Dented Pipeline Subject to Water Hammer Waves

During service, pipelines are likely to have mechanical damage, such as dents that can contribute to local stress concentration and alter the proper functioning of the structure. A dent may cause significant structural damage, especially if the pipeline is subject to water hammer waves. In this article, the investigation of pipes subjected to water hammer waves due to the event of a sudden change in valve status or pump failure is carried out. A numerical damage accumulation model that takes into account the load interaction effect is developed and validated in order to assess the harmfulness of the dent defect. This model uses the pressure peaks induced by the water hammer phenomenon as input. Based on a fatigue life estimation model, taking into account the mean stress effect, the damage is calculated for each loading level. A non-linear interpolation analysis is performed on the results obtained from a finite element model in order to determine the stress concentration factor for any dent depth value, which is used to estimate the fatigue life of the damaged structure. A model is used to take the effect of dent re-rounding into consideration. Then the developed damage accumulation model is used for a parametric analysis. The parameters considered are the dent type (spherical, rectangular longitudinal and rectangular transverse), the dent configuration (constrained and unconstrained), the dent depth, and the fluid inside the pipe. This study will allow the most damaging indentation defect to be concluded, as well as the factors that could make the defect more harmful.

Residual Stress in Oil and Gas Pipelines with Two Types of Dents during Different Lifecycle Stages

The residual stress at a dented area is critical to oil and gas pipelines' integrity and safe operation. A three-dimensional (3D) finite element-based model was developed to investigate the residual stresses in two typical dented areas during the lifecycle stages (pipeline construction and pipeline operation stages). Use of this model enables study of the distribution of the maximum residual stress (σRS) in the dented area. The effects of indenter size, pipeline size, internal pressure and dent depth on the residual stress of two types of dented pipelines were analyzed. A nonlinear regression analysis was used to obtain multi-factor formulas for predicting the σRS for different dents during different lifecycle stages. The results show that the σRS distribution in the dented area changes with dent depth. With σRS for a transversal dent being almost always greater than that for a longitudinal dent. During the pipeline construction stage, the influence of indenter size or pipeline size on σRS is almost the same for the two types of dent, whereas, during the pipeline operation stage, the influences are distinct. The tendency for pipeline size to affect σRS differs slightly as the dent depth increases. Multivariate fitting formulas can provide a reference for estimating σRS.

Surface defect identification of aluminium strips with non-subsampled shearlet transform

Surface defects have a significant effect on the mechanical properties of aluminium strips. However, the current defect identification algorithm needs to be further improved to meet the quality inspection requirements for aluminium products. The scheme of non-subsampled shearlet transform and the kernel locality preserving projection (NSST-KLPP) are applied to identify surface defects of aluminium strips. The defect images collected from a cold rolling line of aluminium strips were tested, including five true defect types of point imprints, scratches, dents, roll marks and wrinkles, and three pseudo defect types of lighting variation, water marks and oil stains. The test results show that a 97.71% recognition rate is achieved, which is higher than those obtained from the commonly used methods published in literature. The NSST-KLPP provides a new scheme for the identification of surface defects of aluminium strips.

FEATURES OF CORN CONSUMPTION IN THE FOOD PRODUCTION INDUSTRY

This paper presents the features of corn as raw material for groat industry. Corn is used in many segments of the food andprocessing industry. corn is processed for traditional food products — groats, flakes, flour, extruded foods, and other corn byproductsare widely used for the production of dry breakfast cereals, snacks, cereal bars. In terms of using of the advanced processingtechnologies, the industry produces starch, gluten, and germs. Corn germ is used to produce the high-value vegetable oil, aswell as starch — for both food and non-food purposes. More than half (65%) of corn is used for feed purposes, 25% –technical purposes,and nearly 20% – for various types of food production. corn is processed for traditional food products — groats, flakes, flour,extruded foods, and other corn by-products are widely used for the production of dry breakfast cereals, snacks, cereal bars. For thecolour, corn is divided into white and yellow types. According to the literature data analysis, yellow corn is more used in China,Argentina, Brazil, while white corn — in some countries of Asia, Latin America, and the Balkan countries. Depending on itsmorphological features, the corn kernelis divided into various groups, species and subspecies.In Ukraine corn kernel is classified into 8 types, with separately defined limitations on the content of the major crop in thebatch, grains of other type, etc. Corn of І-VІІІ types with the quality indicators specified in the standard, for the production of foodproducts. Flint and dent corn types are the most applied grain varieties in the industry, they are widely used in the production segmentof food and feed products. Sweet corn is widely used as a vegetable crop in the food canning, food concentrates, starch andbrewing industries due to its flavor properties. Popped corn is not only the most convenient raw material for the production of popcorn,but it also can be used as the raw material for the production of corn curls and dry breakfast cereals By analyzing the weightfraction of fat in kernels of different corn varieties we can note that the lowest number of fat is typical for popped corn (4.0%) andthe largest – for sweet corn (9.1%); dent and flint corn have the same total fat number (4.5-4.9%).Test weight of corn types – poppedcorn ranges within 712-826 g/l, dent corn - 875-893 g/l, and flint corn - 768-786 g/l. The weight of 1000 kernels of corn dependingon the varieties changes within 150-600 g.

Phase resolved method using the Hill-Climbing Metaheuristic Algorithm applied for the spectral separation from photoacoustic spectra of chilli pepper skin and yellow corn pericarp

The phase-resolved method has been widely used in photoacoustic spectroscopy for separating the contribution of different optical absorption centers to a spectrum. However, the procedure is lengthy, tedious and without precision control, because one has to calculate several spectra to search for the phase angle at which only one contribution is present every time. In this work, this limitation is avoided by the implementation of a method as a search and optimization problem using the Hill Climbing Metaheuristic Algorithm. As test examples, the photoacoustic spectra of chilli fruit skin of Anaheim type (Capsicum Annuum L.) and yellow corn grain pericarp of dent type (Zea Mays L.) were analyzed in the wavelength ranges where there is optical absorption of the photoprotective pigments of these samples.

Generalized expressions for stress concentration factors of pipeline plain dents under cyclic internal pressure

The present work follows a previous study devoted to developing a new methodology for fatigue life assessment of steel pipelines with plain dents, under cyclic internal pressure, based on the estimation of SCFs to modify appropriate S–N curves. SCFs were estimated from a non-linear finite element model and the methodology was validated according to experimental results. A comprehensive parametric study was then carried out for spherical, longitudinal and transverse plain dents, with varying pipe and dent dimensions, and analytical expressions to provide SCFs were developed for each dent type. The aim of this work is to simplify these expressions, which have the disadvantage of being related to particular dent types (geometries). Here, a new analytical formulation is developed and simpler expressions are obtained to estimate SCFs. The proposed methodology becomes then more practical and easy to be used in the fatigue life assessment of steel pipelines with plain dents of different types, based only on measurements of dent dimensions without the need of classifying them according to their types.

Pogodnost različitih hibrida kukuruza za razviće Plodia interpunctella (Hübner)

Plodia interpunctella (Hubner), the Indian meal moth (IMM), is a major lepidopteran storage pest worldwide. IMM larvae can be found in high abundance in stored maize and cause huge losses in seed germination and seed viability. This work aimed to assess the susceptibility of six maize hybrids (NS 6140, NS 640, NS 1090, NS 444 - dent type, NS 620k - pop-corn type, Red-aleurone maize - maize with an altered aleuron color) to IMM attack and suitability for pest's development. Standard laboratory diet (SLD) was used as a positive control. Under laboratory conditions, the following IMM life history parameters were monitored: larval mortality, mean developmental duration (egg to adult), adult emergence, adult lifespan and female fecundity. Kernel susceptibility was determined based on the Susceptibility Index (SI). The highest mortality of IMM larvae was on NS 620k (35.25%) compared to the other maize hybrids (11.2-19.5%). The highest number of emerged adults was on Red-aleurone maize (17.5), and the lowest on NS 620k (4.0). The longest lifespan was recorded for moths reared on NS 6140 and NS 640 (8.5 and 8.7 days, respectively). The highest female fecundity was on SLD (115.8 eggs), on Red-aleurone maize (44.3 eggs), while females reared on NS 620k laid the lowest number of eggs (22.8 eggs). Moths reared on NS 620k had the shortest body sizes (0.9 cm), which indicated reduced moths fitness. SI showed that Redaleurone maize (SI=7.79) was the most susceptible to IMM attack, while NS 620k (SI=3.08) was the least susceptible.

Fatigue Life Analysis of Dented Pipes Subjected to Internal Pressure

Steel pipelines that transport pressurized fluids can contain a dent defect which is a permanent deformation of the outer wall due to an impact with a foreign body. This defect induces a high local stress concentration. This paper presents an optimized numerical model based on finite elements to assess the stress concentration factor around constrained and unconstrained dents in an API X52 steel pipe subjected to internal pressure. The simulation of the finite element model is conducted in two phases; the first phase concerns the realization of the dent, while the second one takes as initial geometry the dented pipe and subjects it to an internal pressure. The validation results of this finite element model show that it can precisely provide Von Mises stress around the defect needed to calculate the stress concentration factor. The fatigue life is then estimated based on S-N curves with the Gerber criterion to account for the mean stress effect for various pipe geometries, dent depths and dent types. These dents are generated using spherical and rectangular indenters in longitudinal and transverse orientations under constrained and unconstrained configurations. A parametric study conducted on 150 cases of dented pipes subjected to internal pressure between 0% and 50% MOP (maximum operating pressure) enabled us to analyze the effect of the various types of dents on the integrity of the structure.

Experimental study on the effect of dents induced by impact on the fatigue life of 2024-T3 aluminum alloy plate

Local dent is one of the typical damages of the aircraft’s skin panels. However, to the best of our knowledge, very few studies focus on the fatigue lives of dented aluminum plates which commonly used as aircraft skin panels. In this study, drop-weight impact tests were conducted on 2024-T3 aluminum plates to obtain spherical, conical, and U-shape dents on specimens. Subsequently, fatigue tests were performed on the dented specimens to investigate the effect of the dents on specimen’s fatigue lives. It is found that all these three types of dents can obviously reduce the fatigue lives of 2024-T3 aluminum plates. Moreover, the empirical models representing relationships between residual fatigue lives and dent depths were proposed. At last, fatigue tests were carried out on specimens with both pre-cracks and dents to explore the effect of the dent on crack growth. The experimental results showed that, for the dent with medium depth relative to ultimate depth, the conical dent can aggravate the crack “macro-growth” while the spherical and U-shape dent can retard it. The observed features can provide certain references for repairing aircraft skin panels with dents.

Mathematical Modelling and Solar Tunnel Drying Characteristics of Yellow Maize

Solar drying experiments of maizes were conducted at Gape- Kpodzi, in southern Togo. In this purpose, new type tunnel solar dryer was used. Solar dryer consist of an air collector, drying chamber and an air circulation system. Heated air in solar air collector was forced through the maizes by a blower. Yellow dent type maize was used for drying experiments. During the drying period, drying air temperature, relative humidity, air flow rates, solar radiation, and lose of mass were measured continuously in different levels of the dryer. Maize with initial moisture content of 0.37 dry basis (kg water / kg dry matter) were dried until they reached a final moisture content of 0.13 (kg water / kg dry matter) at different temperatures with respect to solar radiation variation. Drying time was examined with moisture content ratio as exponential and polynomial correlations. The effective diffusivity varied from 1.938x10-10 to 1.164x10-10 m2/s over the different level of temperature range. Fourteen different mathematical models available in literature were compared using their coefficient of determination to estimate solar drying curves. According to statistical analysis results, Midilli et al. drying model has shown a better fit to the experimental drying data of maize with a coefficient of determination R2 = 0.9975 as compared to other models. The results of this study revealed that the developed solar tunnel dryer can used for dehydration of maize crops under the climatic conditions of southern Togo.

Effect of corn grain variety on the bioethanol production efficiency

The impact of corn grain variety on the ethanol production effectiveness was determined. The screening of 258 various corn samples were done. The endosperm of recognized 258 types of corn was semi flint as a consequence of crossing between female parent with dent type seeds and male parent with flint type seeds. The tested cultivars fall into two groups, ie. 133 belong to single cross (SC) and 125 belong to three-way cross (TC) hybrids. These hybrids of corn were created with four male parents: 96 with S61328, 61 with S80660A, 20 with S07787A and 8 with S09347. The corn samples were mashed and fermented with distillery yeast Saccharomyces cerevisiae which produced ethanol from corn mashes yielding maximum 81.33% of the theoretical value. It was noted that the corn samples with higher starch content had lower efficiency of starch saccharification (−0.35, p<0.05). This fact generates negative correlation between variables ethanol (L/100kg starch) and starch content (−0.43, p<0.05). The highest level of reducing sugars in grains led to higher productivity of ethanol. The comparisons in groups generated with multivariate exploratory techniques (cluster analysis, k-means clustering, PCA) showed that it is possible to distinguish a statistically different cluster with the highest ethanol yield (35.6L of ethanol per 100kg grains). Moreover, the PCA analysis showed that hybrids of corn with S80660A male parent have the biggest impact on efficiency of ethanol. The presented results clearly prove that not only starch content in corn grains determine the ethanol productivity.

Influence of residual stresses on the fatigue crack growth from surface anomalies in a nickel-based superalloy

The present study evaluates the influence of initial residual stresses surrounding scratch or dent type surface anomalies on the fatigue crack growth of Direct Aged (DA) Inconel 718 alloy. A heat treatment has been used to at least partly relax these residual stresses in order to evaluate their effect on the fatigue crack initiation and propagation starting from scratches and dents. In the presence of compressive residual stresses under the surface anomaly, the first stages of crack propagation are slowed down. The evolution of the crack front shape is also strongly influenced by the residual stress field and leads to the formation of an “ear-shaped” crack front for dents and initiation in the corners for scratches. The initiation fatigue life is short for both type of surface anomalies and a competition between the stress concentration and the initial microstructural state was noted for the control of this stage of the fatigue life. These results highlight the need to characterize the residual stress field resulting from the introduction of the surface anomaly in order to predict accurately the fatigue life of DA Inconel 718 alloy components containing scratches and dents. A preliminary finite element simulation is developed in this study to address this issue.

The reflection of guided waves from simple dents in pipes

Guided elastic waves have been anticipated as a rapid screening technique for pipe inspection. Dents occurring in pipes are a severe problem which may lead to the possibility of pipe failure. A study of the reflection characteristics of guided waves from dents of varying geometrical profile in pipes is investigated through experiments. Dented region is represented by a series of circumferential cross-sections and its geometric parameters are described by axial length and the maximum and minimum outer diameters. Both single and double sided dents are mechanically simulated in hollow aluminum pipes and then experimentally tested by exciting the longitudinal L(0,2) mode. A quantitative parameter, so-called deformation rate relating to the maximum and minimum outer diameters of the dents is defined to evaluate the effect of the extent of the deformation on the reflection. For both types of dents, it is shown that the reflection coefficients of the L(0,2) mode are all approximately a linear function of their respective deformation rates. Mode conversion occurs at the dents and reflections of the F(1,3) mode are identified. The results show that the amplitude of the reflected F(1,3) mode is generally higher when the dent has stronger non-axisymmetric features.

Influence of dent on residual ultimate strength of 2024-T3 aluminum alloy plate under axial compression

Drop-weight impact tests were conducted on 2024-T3 aluminum plates with five types of impactors, and then the effects of the dent on the residual ultimate strength of the 2024-T3 specimens were investigated through axial compression tests. Results indicate that with increase in dent depth, the five types of dents affect the ultimate strength of the plate in different trends. Nevertheless, other than the plate global deflection caused by impacting, the dent itself has unremarkable effect on the ultimate strength. The mathematical expressions are derived regarding the relationship between impact energy factor and the dent depth factor as well as the compressive ultimate strength reduction rate and the dent depth factor.

The effect of local dents on the residual ultimate strength of 2024-T3 aluminum alloy plate used in aircraft under axial tension tests

Local dent is a typical damage of aircraft, however, very few studies have investigated the effect of dents on the residual ultimate strength of the aluminum plate under different loading conditions, especially under tensions. In this study, drop-weight impact tests were conducted on the 2024-T3 aluminum alloy plate to generate 5 types of dents, and then tension tests were performed on the dented specimens to investigate the effects of the dents on the residual ultimate strength. Results show that the residual ultimate strength and the fracture displacement of the plate are significantly affected by the local dents. With increase in the depths of spherical, V-shape, and elliptical dents, the ultimate strengths decrease in quadratic trend. Whereas, for the conical and U-shape dent, linear relationships were observed between dent depth and the ultimate strength. The mathematical formulas between the ultimate strength reduction rate and the dent depth reduction factors were derived through regression analysis on the experimental results.

GENETIC VARIATION AND PHYLOGENETIC RELATIONSHIPS AMONG MAIZE TYPES AND TEOSINTE AS REVEALED BY ISOZYMES AND RAPD MARKERS

Genetic variation and phylogenetic relationships among four types of yellow maize (Zea mays L.); dent, flint, sweet and pop corn, and their wild relative; teosinte (Zea mexicana), were assessed using isozymes and random amplified polymorphic DNA (RAPD) markers. The results indicated that the percentage of polymorphic loci; for peroxidase and esterase isozymes, were 66.67% and 92.59%, respectively. By applying RAPD analysis, 116 bands were obtained from seven primers with 87.07% polymorphism. The UPGMA dendrogram based on genetic distance segregated the five genotypes into two main clusters. Both isozymes and RAPD markers separated teosinte into the first cluster, whereas the four maize types were grouped together in the seconds cluster. Dent and flint types were much close to each other with high similarity indices; 0.842 and 0.792 based on peroxidase and esterase isozymes, respectively. Furthermore, the flint type closely related to sweet type in RAPD cluster (similarity index of 0.588). This high variability detected among maize types and teosinte can be used in breeding programs to maximize the use of genetic resources.