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1
Vápeník, Martin. "Stanovení hodnoty společnosti Moravia Steel a.s." Master's thesis, Vysoká škola ekonomická v Praze, 2010. http://www.nusl.cz/ntk/nusl-16592.
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The contents of this work was to determine the value of Moravia Steel a.s. on the basis of income, namely the discounted free cash flow to firm (FCFF). In particular parts of the work I have reviewed the financial health of the company, defined the market, carried out strategic analysis, defined operationally necessary and unnecessary assets, created a financial plan for the company, provided the cost of capital, computed free cash flow and ultimately determine the value of the company. To determine the value of the company I used two periods, the first discount the cash flows each year and summed up, the second period is called continuing value. The sum of the values I get the value of the company.
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Kim, Hyunok. "Prediction and elimination of galling in forming galvanized advanced high strength steels (AHSS)." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1204515296.
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Falk, Johannes. "Fracture prediction of stretched shear cut edges in sheets made of Dual-Phase steel." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13956.
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Dual-Phase (DP) steels, part of the group of Advanced High Strength Steels (AHSS), are used by car manufactures due to its large strength to weight ratio. The high strength of the DP steel does have a negative impact on the formability during sheet metal forming and stretch forming, e.g. fractures often appear in shear cut edges during forming of blanks made of DP steel. The main objective with this thesis is to develop a new punch for Volvo Cars that concentrates the strain to the sheared edges of a test specimen made from different types of DP steel. This is done to be able to measure and obtain maximum fracture strain during stretch forming tests in a press. The newly developed test method is called CTEST (Concentrated Trim Edge Strain Test). The tests are performed with DP steel specimens with three different qualities of the shear cut edges; fine cut, medium cut and worn cut. DP steels tested are DP600GI, DP600UC and DP800GI from three different suppliers. 10 different types of DP steels are tested in this study with different thickness. Thickness of specimens tested are 1 mm, 1.1 mm, 1.5 mm and 2 mm and all specimens tested have a lengthwise (RD) rolling direction. The quality of the sheared cut edge has a great impact to the formability and maximum fracture strain of the specimen. A specimen with a fine cut endures higher fracture strain than medium cut and a worn cut for all types of DP steel with different thickness. A 1 mm thick specimen endures a lower fracture strain than 1.5 mm and 2 mm specimen for all cut qualities. Further, the impact of the orientation of the burr zone of a shear cut edge is studied. With the burr zone facing upwards from the CTEST punch the formability of the specimens is decreased compared to a burr zone facing downwards, especially for a worn cut specimen with micro cracks and imperfections in the edge surface. ARAMIS Digital Image Correlation (DIC) system is used to analyze the specimen edges during press experiments. The ARAMIS results unveil that several small fractures appear in the sheared edges of a specimen just before the specimens split into two pieces. This phenomenon was seen for specimen with worn and medium shear cut qualities. Finite Element (FE) simulations of the CTEST is performed in AutoForm to determine maximum values of the true strain for the three different cut qualities. The simulation in AutoForm does show a slightly higher value of the force and press depth than the value from the press test before maximum fracture strain in reached. The small fractures seen in ARAMIS just before the specimen split into two pieces cannot be seen in the simulation in AutoForm.
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Groseclose, Adam Richard. "Forming of AHSS using Servo-Presses." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408548321.
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Císař, Likáš. "Stavebně technologický projekt výrobní haly RZ INDUSTRY a.s.,Zaječí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225444.
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This thesis addresses the technological process of building production halls and SS INDUSTRI Hare. In this work the author deals with the description of the most important stages of construction technology. More attention is given to drátkobetonové floors and steps of construction steel buildings. Finally he was taken into account in the way of material resources and ensuring the continuity of time stages.
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JIANG, ZHUOYING. "A Study of the Fate and Effect of Steel Sheet Surface Oxides on Galvanizing Bath Management." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1395924244.
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Gibbs, Parker Kenneth. "Strain Path Effect on Austenite Transformation and Ductility in TBF 1180 Steel." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7127.
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TBF 1180 steel was studied under various conditions focusing on the correlation of ductility and amount of retained austenite. Samples were prepared from sheet stock and then strained using limiting dome height tooling (LDH), a standard uniaxial test frame, and a tensile stage for use in an electron microscope. The steel was observed in plane, biaxial, and uniaxial strain to determine its effect on retained austenite transformation and ultimately, ductility. Retained austenite was observed using a scanning electron microscope (SEM) equipped with an electron backscatter detector (EBSD) to distinguish the different phases present. Initial austenite levels were around 5% by volume and was quickly reduced as the sample was strained. The biaxial samples were the slowest to transform, having about 2.5% austenite at .05 effective strain, which allowed the specimen to reach an effective strain of .3 with 1.1% austenite remaining. In contrast, the plane strain samples had the fastest rate of transformation having only 1.2% austenite at .05 effective strain and .7% austenite at a final effective strain of .18. Both forms of uniaxial, (in-situ and ex-situ), were near identical, as expected, and exhibited an austenite transformation curve between that of the plane and biaxial curves. The uniaxial austenite level at .05 strain was 2.1% and was able to reach about .15 strain with a final austenite percentage around 1%. It was concluded that the biaxial strain path had the greatest ductility due in part to its slower austenite transformation rate while plane and uniaxial strain paths were not as ductile with their faster austenite transformation rates.
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Aykas, Berk. "Evaluation of Edge Fracture in Flanging Advanced High Strength Steel (AHSS) Using the Double Bending Test." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557210237260137.
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Allen, Quentin Scott. "Microstructural Evaluation of Hydrogen Embrittlement and Successive Recovery in Advanced High Strength Steel." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6617.
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Advanced high strength steels (AHSS) have high susceptibility to hydrogen embrittlement, and are often exposed to hydrogen environments in processing. In order to study the embrittlement and recovery of steel, tensile tests were conducted on two different types of AHSS over time after hydrogen charging. Concentration measurements and hydrogen microprinting were carried out at the same time steps to visualize the hydrogen behavior during recovery. The diffusible hydrogen concentration was found to decay exponentially, and equations were found for the two types of steel. Hydrogen concentration decay rates were calculated to be -0.355 /hr in TBF steel, and -0.225 /hr in DP. Hydrogen concentration thresholds for embrittlement were found to be 1.04 mL/100 g for TBF steel, and 0.87 mL/100g for DP steel. TBF steel is predicted to recover from embrittlement within 4.1 hours, compared to 7.2 hours in DP steel. A two-factor method of evaluating recovery from embrittlement, requiring hydrogen concentration threshold and decay rate, is explained for use in predicting recovery after exposure to hydrogen. Anisotropic hydrogen diffusion rates were also observed on the surface of both steels for a short time after charging, as hydrogen left the surface through <001> and <101> grains faster than grains with <111> orientations. This could be explained by differences in surface energies between the different orientations.
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Alaoui, Mouayd Amine. "Oxidation, pickling and over-pickling mechanisms of high silicon alloyed steel grades." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066020.
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Les mécanismes d'oxydation, de décapage et sur-décapage d'un acier bas carbone est d'un acier fortement allié au silicium (1,6 et 3.2 % en masse de silicium) ont été étudiés. Le suivi de l'oxydation par thermogravimétrie et la caractérisation de la calamine des aciers fortement alliés au silicium a montré un effet très marquant de passivation de la couche de silice. Les calamines des échantillons modèles sont composées de couches d'hématite, magnétite et wüstite partiellement décomposée en fer et magnétite pour l'acier bas carbone. Pour l'acier au silicium, la fayalite est présente à l'interface acier/wüstite sous forme de grains ou d'une couche interne. Le suivi du potentiel de circuit ouvert pendant le décapage et sur-décapage de ces échantillons a montré un potentiel de corrosion stable et anodique pour les oxydes de fer et une chute drastique de ce potentiel au contact de l'acide avec le métal. Le suivi du taux de dissolution totale par ICP-AES combiné avec des mesures de courant de corrosion par la méthode de Tafel a montré une contribution importante de la dissolution électrochimique par oxydation de la wüstite et la magnétite et réduction de Fe3+ issu de la dissolution chimique de l'hématite et la magnétite. La fayalite est libérée dans la solution par dissolution de la wüstite ou du métal adjacents. Après le contact acide/metal, toutes les dissolutions sont exclusivement électrochimiques par corrosion du métal et réduction de la magnétite (cas des calamines industrielles). La spectroscopie d'impédance électrochimique a été utilisée pour la première fois pour ce type d'étude. L'estimation des valeurs de capacité a montré un comportement pseudo passif pour la couche d’hématite et d’électrode poreuse pour la wüstiteOxidation, pickling and over-pickling mechanisms of a low carbon steel and a high alloyed steel (1.6 and 3.2 wt.% Si) were investigated. The monitoring of oxidation with thermogravimetry and characterization of scale showed a very important passivating effect of the silica layer. Model scales are composed of layers of hematite, magnetite and partially decomposed wüstite into iron and magnetite for the low carbon steel. For the silicon steel, fayalite is present in the steel/wüstite interface as grains or an internal layer. Open circuit potential measurements during pickling and over-pickling of these samples showed a stable and anodic corrosion potential for iron oxides and a significant potential jump once the acid reaches the metal. The monitoring of the total dissolution rate with ICP-AES coupled with corrosion current measurements with the Tafel method showed an important contribution of electrochemical dissolution by oxidation of wüstite and magnetite and reduction of Fe+3 from chemical dissolution of hematite. Fayalite is liberated in the solution by dissolution of the surrounding wüstite or metal. After the contact acid/metal, all dissolutions are exclusively electrochemical by corrosion of the metal and reduction of magnetite (case for industrial scales). Electrochemical impedance spectroscopy was used for the first time for this kind of studies. The estimation of the capacitance values showed a passive like behaviour for hematite and a porous electrode one for wüstite
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Lolla, Sri Venkata Tapasvi. "Understanding Microstructure Evolution in Rapid Thermal Processing of AISI 8620 Steel." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262203896.
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Wang, Yueyue. "Theoretical experiment of GISSMO failure model for Advanced High Strength Steel." Thesis, Högskolan Väst, Avdelningen för produktionssystem (PS), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-11658.
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When developing an electric vehicle, it is essential to evaluate the deformation in and around the battery box for different crash scenarios, and it is necessary to develop a more advanced model that would take into account all the stress modes. Thanks to the excellent properties of Advanced High Strength Steel (AHSS) combine with high strength for more safety and weight reduction for less exhaust emission, AHSS is more and more commonly used in automobile industry. The material employed in this project is DOCOL 900M and it is a martensitic steel with yield strength higher than 700MPa. The focus of the current work is to describe the experimental setup for the GISSMO model used in LS-DYNA. A number of experimental methods and theories have been reviewed. Different geometries of the test specimens under different stress triaxialities have been discussed. The study also compares the accuracy and robustness of each of the testing methods and setups. The effect of anisotropy of materials on the mechanical properties was studied. Some summaries about how to reduce errors in the experiment under the conditions of low costing and high efficiency have been discussed. According to the stress-strain response of ductile materials, the parameters of plasticity model can be calibrated. The material can be implemented in finite element software to calibrate the parameters of damage and the prediction of material failure can be achieved. The experiment and simulation are always good to be used together in the research.
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Hedman, Daniel. "Casting and Characterization of Advanced High Strength Steels." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81098.
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The Latin American steel making company Ternium S.A. aims to develop and produce a new type of advanced high strength steel (AHSS) in which the main alloying elements are carbon, aluminium, manganese, and silicon. The present work is the first phase of the development project and it involves casting and characterization of four steel compositions with varying amounts of the aforementioned elements. The results revealed that the Mn-content had a large impact on the development of hard phases during solidification. A steel with a Mn-content of 2 %wt. had almost completely transformed to pearlite during cooling, while a steel with a 4 %wt. Mn-content consisted of primarily martensite and retained austenite. Only the impact of the Mn-content is evaluated. The columnar grain size for two of the four steel compositions were in the range of 20-30 mm, which is similar to those observed from continuous casting. This indicate that the heat transfer rate was slow enough to allow these grains to grow. Measurements during casting showed an initial cooling rate of 10-20°C/min at a distance of 10 mm inside the ingot, which is much slower than the surface cooling rate during continuous casting (100-150°C/min). It was assumed that the cooling rate was similar for all castings since the methodology was identical. However, the steel used for cooling rate measurements was not characterized, why a correlation between cooling rate and composition could not be obtained. A heat transfer model was developed to gain further knowledge of the solidification process. As a reference to the heat transfer model, a eutectic Bi-42Sn alloy was cast with temperaturemonitoring using a casting setup identical to that of the steel castings. A similar cooling rate tothe Bi-42Sn reference casting was obtained where the cooling was faster from above of the ingot than below. Thus, the last part of the metal to solidify during the simulation was situated in the lower half of the ingot. This provides a model for testing future steel compositions.
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Godha, Anshul. "Microstructural effects on fatigue damage evolution in advanced high strength sheet (AHSS) steels." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53510.
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An understanding of the damage evolution prior to crack initiation in advanced structural materials is of vital importance to the fatigue community in both academia and industry. Features known as the Persistent Slip Bands (PSBs) play an integral role in this damage evolution. Therefore, PSBs have been the focus of a lot of science-based investigations over the years. However, most existing studies in this area are restricted to analysis of PSBs in single crystal face centered cubic (FCC) materials. Moreover, these studies lack a quantitative analysis of the evolution of the fatigue damage (or PSBs) as a function of the material microstructure. This is especially true for relatively modern materials such as the Advanced High Strength Structural (AHSS) steels that are gaining a lot of importance in the automotive sector. Accordingly, the objective of this research is to quantitatively characterize evolution of PSBs in three AHSS steels having different microstructures as a function of number of fatigue cycles and strain amplitude. For this purpose strain controlled interrupted fatigue tests have been performed on two dual phase steels (DP-590 and DP-980) having different relative amounts of tempered martensite and a ferritic high strength low alloy steel (HR-590). Digital image analysis and Stereology have been used for unbiased quantitative characterization of the evolution of global geometry of the PSB colonies as function of number of fatigue cycles and strain amplitude. Evolution of PSB colonies has been couched in terms of variation of PSB colony volume fraction and total surface area unit volume, and total surface area of individual PSBs per unit volume and three-dimensional angular orientation distribution of the PSBs. For this purpose, new stereological techniques have been developed for estimation of the three-dimensional angular orientation distribution. The stereological data reveal that during strain controlled in these AHSS steels, volume fraction of the PSB colonies varies linearly with the their total surface area per unit volume. Detailed analysis of the stereological data leads to a simple geometric model for evolution of the PSB colonies in the three AHSS steels, which accounts for all observed data trends.
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Doležal, Petr. "Výroba a vady masivních odlitků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228894.
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Object of this master’s thesis is accomplished analyze the range of foundry of steel ŽĎAS a.s., Zdar nad Sazavou and make the type massive steel castings and analysis of existing technology foundry and metallurgical defect. The beginning of this master’s thesis is dedicated to the manufacturing of steel foundries range ŽĎAS a.s., Zdar nad Sazavou. The following section is devoted to manufacturing technologies for the production of massive steel castings. In the final part of this thesis are described metallurgical and foundry defects of the typical castings of steel foundry and proposals to eliminate these undesirable defects. End thesis includes a summary of the results and trends in the development of research in the production of massive steel casting.
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Jiadong, Zhu. "Wall Panel Optimization for Refugee Shelters in Germany: An AHP Study." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1962.
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The German government is experiencing difficulties housing and assimilating Syrian refugees in its borders. Erecting temporary shelters on location is one way to deal with the current crises. This thesis attempts to use Analytic Hierarchy Process (AHP) to determine the optimum combination of materials and construction methods to be used in the shelter’s walls in order to improve the living conditions of the refugees and to ensure that the cost is acceptable to the German government. This thesis compares six existing wall panel products from China, which have the lowest cost on the worldwide market. The R-value, strength, price, weight, durability, ease of assembly, assembly time, maintenance costs, comfort, resale value, and appearance were evaluated. Assumptions were made on what the German government would require and on standard building practices in Europe and America. The analysis indicates that the steel frame house from YONGYANG Steel best satisfies the needs in this situation. This thesis produced an AHP template, which is flexible. This model that was developed for the German scenario can be effectively applied to differing emergent situations in other parts of the world.
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Shrestha, Alina. "Fatigue Testing and Data Analysis of Welded Steel Cruciform Joints." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1670.
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In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate the S-N data well. The equivalent structural stress parameter is introduced to investigate the fatigue behavior of welded joints using the traction based structural stress approach on finite element models of specimens, and representing the data as a single Master S-N curve.
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Cramer, Jeffrey Grant. "Strain Path Effect on Austenite Transformation and Ductility in Q&P 1180 Steel." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6650.
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The ductility of Q&P 1180 steel was studied with regard to retained austenite transformation under different strain paths. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Stretching experiments were also performed using limiting dome height (LDH) tooling, where specimens were strained in both biaxial and plane strain tension. The experiments were done incrementally, for each strain path, and the retained austenite at each level of strain was measured using electron backscatter diffraction (EBSD). Retained austenite levels in the uniaxial tension case dropped from an initial measured level of about 8% to about 2% during an initial strain increment of 0.02, but then stabilized as the specimen was strained to 0.1. In the plane strain and biaxial tension cases retained austenite also dropped significantly during an initial strain increment of about 0.04, but then continued to decrease as the specimens were strained to failure. Biaxial tension, in particular, was the most effective strain path for transforming retained austenite to martensite, resulting in a final volume fraction of 0.3% at an effective strain of 0.3. Retained austenite in the plane-strain tension case dropped at a faster rate than in the biaxial tension case, but finished at about 1% at a strain of 0.1. The greatest limit strains were seen in the biaxial tension case, which may be partly explained by the more effective conversion of retained austenite than was seen in the uniaxial tension case.
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Smith, Anthony Justin. "Procedure and Results for Constitutive Equations for Advanced High Strength Steels Incorporating Strain, Strain Rate, and Temperature." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343150464.
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Chen, Meng-Hsien. "A STUDY OF SELECTIVE SURFACE AND INTERNAL OXIDATION OF ADVANCED HIGH STRENGTH STEEL GRADES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1401380512.
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Gupta, Tanmay. "Predicting and Reducing Springback in Bending of an Aluminum Alloy and Selected Advanced High Strength Steels (AHSS)." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555599407775667.
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Diaz, Infante Hernandez David Alberto. "Prediction and Prevention of Edge Fracture in Forming of AHSS." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563371149338966.
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Demiralp, Yurdaer. "Determination of Material Properties and Prediction of Springback in Air Bending of Advance High Strength Steel (AHSS) and Commercially Pure Titanium (CP) Sheet Materials." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339768136.
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Cora, Omer Necati. "DEVELOPMENT OF RAPID DIE WEAR TEST METHOD FOR ASSESSMENT OF DIE LIFE AND PERFORMANCE IN STAMPING OF ADVANCED/ULTRA HIGH STRENGTH STEEL (A/UHSS) SHEET MATERIALS." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/2003.
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Automotive companies are actively pursuing to increase the use of high-strength-lightweight alloys such as aluminum, magnesium, and advanced/ultra high-strength steels (A/UHSS) in body panel and structural part applications to achieve fuel efficiency while satisfying several environmental and safety concerns. A/UHSS sheet materials with higher strength and crashworthiness capabilities, in comparison to mild steel alloys, are considered as a near-term (i.e., ~5 years) choice of material for body and structural components due to their relatively low cost when compared with other lightweight materials such as aluminum and magnesium. However, A/UHSS materials present an increased level of die wear and springback in stamping operations when compared to the currently used mild steel alloys due to their higher surface hardness and high yield strength levels. In order to prevent the excessive wear effect in stamping dies, various countermeasures have been proposed such as alternative coatings, modified surface enhancements in addition to the use of newer die materials including cast, cold work tool, and powder metallurgical tool steels. In this study, a new die wear test method was developed and tested to provide a cost-effective solution for evaluating various combinations of newly developed die materials, coatings and surfaces accurately and rapidly. A new slider type of test system was developed to replicate the actual stamping conditions including the contact pressure state, sliding velocity level and continuous and fresh contact pairs (blank-die surfaces). Several alternative die materials in coated or uncoated conditions were tested against different AHSS sheet blanks under varying load, sliding velocity circumstances. Prior to and after wear tests, several measurements and tribological examinations were performed to obtain a quantified performance evaluation using commonly adapted wear models. Analyses showed that (1) the rapid wear method is feasible and results in reasonable wear assessments, (2) uncoated die materials are prone to expose severe form wear (galling, scoring, etc.) problems; (3) coated samples are unlikely to experience such excessive wear problems, as expected; (4) almost all of the the recently developed die materials (DC 53, Vancron 40, Vanadis 4) performed better when compared to conventional tool steel material AISI D2, and (5) in terms of coating type, die materials coated with thermal diffusion (TD) and chemical vapor deposition (CVD) coatings performed relatively better compared to other tested coating types; (6) It was seen that wear resistance correlated with substrate hardness.
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Sung, Ji-Hyun. "The Causes of “Shear Fracture” of Dual-Phase Steels." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268039436.
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Báborský, Tomáš. "Charakterizace automobilových vysokopevnostních ocelí pomocí elektronového mikroskopu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400477.
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The diploma thesis deals with the determination of the structure of AHSS steels and offers solutions in the form of new observation methods with the aid of a scanning electron microscope using filtration of slow secondary electrons. The thesis describes electron filtration in order to display secondary electrons in a certain energy range which carry a surface information that is not normally visible. The advantages and benefits of such observation are clearly demonstrated.
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Stiel, Daniel Verfasser], and Franz [Akademischer Betreuer] [Hacker. "Die Verkehrsdurchsetzung von Marken nach § 8 Abs. 3 MarkenG unter dem Blickwinkel der Demoskopie / Daniel Stiel. Betreuer: Franz Hacker." Augsburg : Universität Augsburg, 2015. http://d-nb.info/1077816529/34.
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Rosado, Diego Belato. "Comparação do efeito da fragilização por hidrogênio em aços com resistência à tração acima de 1000 MPa." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/37374.
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Este trabalho tem por objetivo avaliar os efeitos do hidrogênio em três diferentes tipos de aços de alta resistência mecânica. São descritos os fenômenos de introdução, difusão e aprisionamento de hidrogênio (H) dentro dos metais, em conjunto com os diferentes tipos de danos provocados devido à presença do hidrogênio. Os materiais de estudo são aços da família Advanced High Strength Steels (AHSS): aços Dual Phase (DP 1000 e DP 1200) e aço Martensítico (M 190). A introdução de hidrogênio nos materiais foi realizada através de carregamento catódico, o qual é representativo para as condições industriais a que se destinam. De modo a avaliar a influência do H nas propriedades mecânicas dos aços, os seguintes ensaios foram propostos: ensaio de carregamento com H, para determinar o conteúdo total de H (saturação) e conteúdo de H difusível (suscetibilidade a fragilização); ensaio de tração ao ar, para determinar a tensão no final da região elástica e resistência à tração na região do entalhe e ensaio de tração com carga constante em ambiente hidrogenado, para avaliar os efeitos provocados pela presença do H e determinar o patamar abaixo do qual o H não apresenta efeito crítico sobre o material. Os efeitos provocados pela aplicação de diferentes densidades de correntes (0,2 – 1,0 mA/cm²) foram avaliados nos ensaios de quantificação de H difusível. Conforme os resultados obtidos todos os aços apresentaram perdas na resistência mecânica à tração quando em ambiente hidrogenado, ou seja, sofreram fragilização por H. Os aços DP 1200 e M 190 (de microestrutura predominantemente martensítica) foram fortemente afetados, conforme evidenciado pela notável queda nos valores de tensão necessários para provocar a falha. Por outro lado, o aço DP 1000, de menor resistência mecânica, demonstrou menor suscetibilidade à fragilização, o que é atribuído a menor permeabilidade do H na microestrutura austenítica.This work aims to evaluate the effects of hydrogen in three high- strength steel grades. The phenomena of hydrogen (H) entry, transport and trapping inside the metals, together with the different types of damages due to the presence of hydrogen are presented. The study materials are a range of AHSS steel grades: Dual Phase Steel (DP 1000 and DP 1200) and Martensitic Steel (M 190). The hydrogen entry was performed by cathodic charging, which is suitable for industrial applications. In order to evaluate the influence of H on the steel mechanical properties, the following tests were done: H charging, to measure total H content (saturation point) and diffusible H content (embrittlement susceptibility); uniaxial tensile test of uncharged samples to determine notched tensile strength values and the strength levels at the end of elastic region and constant load tensile testing carried out in hydrogen environment, to determine the threshold values where hydrogen has an effect on the material. DP 1200 and M 190 were strongly affected by H pre-charging, as shown by the significant drop in stress required to break them. On the other hand, DP 1000 showed a lower embrittlement susceptibility, which is attributed to its lower mechanical strength. The current densities effects (0.2 up to 1.0 mA/cm²) were evaluated during H charging to measure diffusible H content. All steels showed a drop in the tensile strength i.e. experienced hydrogen embrittlement. Steels with higher tensile strength, as DP 1200 and M 190, showed a much bigger drop that is related to the favorable characteristics of martensitic microstructure regarding to the hydrogen permeability and diffusivity.
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Yin, Zeming. "A Numerical and Practical Investigation for the Edge Fracture of Advanced High Strength Steels (AHSS) Using the Half Dome Test." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460739619.
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Srinivasan, Ganapathy. "Flanging and Bending of Advanced High Strength Steels." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408716079.
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Mousavinejad, Seyed Eman. "Advanced Terminal Sliding Mode Control Approach to Integrated Steer-by-Wire and Differential Braking of Ground Vehicles." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367350.
Full textAbstract:
Advances in electronic technology have had a profound impact on the design and development of modern vehicle systems. These advances have provided the basis for a research into active vehicle control paradigm with the aim of improving vehicle safety and its dynamic performance.
The vehicle stability control (VSC) concept has recently been born in response to such a research challenge. Its refinement is looking for an algorithm able of integrating vehicle dynamics control (IVDC) by way of coordinating the active front steering (AFS) system and direct yaw-moment control (DYC) system. Thus, when the vehicle is in the normal driving situation, the AFS system is involved for handling enhancement; however, as the vehicle reaches the handling limits, both the AFS and DYC systems are integrated to ensure the vehicle stability.
Recent research into VSC has indicated that the IVDC concept may be able to enhance the handling and stability of ground vehicle by controlling the main two control objectives, yaw rate and body sideslip angle, effectively in severe cornering manoeuvres and the steady-state condition, and several control strategies have been investigated to design an IVDC system. However, most of these control methods have not been focused on improving the transient response for vehicle yaw rate and sideslip angle tracking controllers in the presence of vehicle dynamics uncertainties and external disturbance. Therefore, further improvement of the transient response for the tracking controllers is still the most needed research topics.Thesis (Masters)
Master of Philosophy (MPhil)
Griffith School of Engineering
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BALIJEPALLI, SANTOSH KIRAN. "Application of surface analysis for characterization of metallurgical systems." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2014. http://hdl.handle.net/2108/203082.
Full textAbstract:
Lo scopo della presente tesi di dottorato è lo studio di vari sistemi metallurgici mediante l’utilizzo di tecniche di analisi della superficie: X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Scanning Photoemission Microscopy (SPEM). Mediante tali tecniche, è stato possibile ottenere informazioni sulla composizione chimica, stechiometria, stato di ossidazione e distribuzione laterale (mappe chimiche) degli elementi che compongono i campioni analizzati. Il lavoro è suddiviso in tre argomenti: (i) effetto dei due trattamenti di carbo-cementazione dell’acciao inossidabile a bassa temperatura; (ii) investigazione micro-chimica di rivestimenti spessi a base di tungsteno su un acciaio inossidabile martensitico AISI 420; (iii) studio della disomogeneità micro-chimica in una lega eutettica di Pb-Bi allo stato liquido. Grazie alla loro grande versatilità e flessibilità, le tecniche XPS e AES sono utilizzate per l’investigazione di materiali che trovano applicazione in vari campi tecnologici quali metallurgici, materiali compositi, ceramici, ecc. In futuro, il potenziale delle tecniche di analisi della superficie sarà esplorato per lo studio di differenti sistemi metallurgici.The aim of this work is to investigate the metallurgical systems by using the surface characterization techniques: X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Scanning Photoemission Microscopy (SPEM) at the ELETTRA synchrotron (Trieste, Italy). By using this type of surface-sensitive techniques on metallurgical systems, it is possible to obtain the information on the materials chemical composition, stoichiometry, chemical states and electronic configuration of constituent elements and surface chemical maps. This work can be subdivided into three topics that are linked by the use of the same experimental techniques. These topics are the following: (i) comparison of two different low temperature carburizing treatments of the steel, (ii) micro-chemical investigation of tungsten thick coatings on AISI 420 martensitic stainless steel, (iii) study of micro-chemical inhomogeneity in eutectic Pb-Bi alloy quenched from melt. Thanks to the wide range of variety and flexibility of applications of XPS and AES, these techniques can be used for the investigation of various systems, such as metallurgical, composite materials, ceramics, etc. In future, the potential of surface analysis techniques will be explored for application in different metallurgical systems.
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Mallick, Dwaipayan. "Hydrogen behavior in first and second generation of advanced high strength steels." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI052.
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Les aciers AHSS sont largement utilisés pour les caisses des véhicules, en raison de leurs bonnes propriétés mécaniques et de leurs capacités à réduire l'empreinte carbone. Toutefois, leur utilisation est limitée par leur sensibilité à la fragilisation par l'hydrogène (HE). La présente étude vise à comprendre l'influence de l'hydrogène sur quatre aciers AHSS : deux biphasés (DP), un phase complexe (CP) et un à plasticité induite (TWIP). Les résultats montrent une forte susceptibilité à l’HE pour les aciers DP et TWIP par rapport aux aciers CP. Le comportement de CP est attribuée à une microstructure plus homogène, une densité de piège plus petite (mais à énergie élevé) et une concentration en H plus faible. Dans les aciers DP, la forte densité de pièges à faible énergie et la forte absorption de H augmentent la susceptibilité à l’HE. Les dislocations et les joints de grains sont les principaux sites de piégeage pour tous ces aciers, ainsi que la cémentite dans les aciers CP et les particules AlN et l’austénite pour les aciers TWIP. Sous chargement mécanique, la désorption de l'hydrogène s’accélère avec l'expansion du réseau cristallin et les mouvements des dislocations (jusqu'à la limite d'élasticité), alors qu'elle diminue en raison de la génération de défauts dans la domaine plastique. Pour l'acier CP, l'hydrogène piégé fortement désorbe à l'UTS alors que dans l'acier TWIP, la génération de défauts libère l'hydrogène. Pour l’acier DP galvanisés, la couche de Zn se comporte une couche barrière à l’hydrogène sous polarisation fortement cathodiques, tandis qu'à potentiels cathodique plus faible, elle favorise la perméation de l'hydrogène en raison de sa dissolutionAdvanced High Strength Steels (AHSS) are increasingly used as fabrication material for vehicle Body In White (BIW), owing to their superior properties and ability to reduce carbon footprint. However, its susceptibility to hydrogen embrittlement (HE) restricts the use of AHSS. The present study aims to understand the H influence on four commercial-grade AHSS steels, two Dual Phase (DP), one Complex Phase (CP), and one Twinning Induced Plasticity (TWIP) steel. Results show high HE susceptibility for DP and TWIP steel compared to CP steel. The superior HE resistance in CP steel was attributed to a more homogeneous microstructure, smaller yet stronger trap density, and lower H concentration. In DP steels, a high density of weak traps and high H uptake increased HE susceptibility. During charging, H preferentially adsorbed along the grain boundaries and interfaces for all steels along with grain interior in TWIP steels. Dislocations and grain boundaries were the main trap sites for all steels, along with cementite particles in CP steels and AlN particles and austenitic grain interior in TWIP steels. For all steels under stress, hydrogen desorption increased up to yield point due to lattice expansion and dislocation movement, whereas decreased in the plastic region due to defect generation. For CP steel, strongly trapped hydrogen desorbed at UTS whereas in TWIP steel, generation of deformation twinning released hydrogen. The study of the galvanized layer showed that at higher cathodic overpotential, the Zn layer behaved as a barrier layer protecting the steel, while at a lower potential, it increased the HE susceptibility due to Zn layer dissolution. Overall, CP steel was the most resistant steel to HE, followed by TWIP and DP steels
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Montesano, João Augusto. "Caracterização mecânica e microestrutural de um aço bifásico DP980 empregado na indústria automobilística. /." Guaratinguetá, 2019. http://hdl.handle.net/11449/181690.
Full textAbstract:
Orientador: Marcelo dos Santos PereiraResumo: O desenvolvimento dos aços avançados de alta resistência tem sido a principal estratégia por parte das siderúrgicas para atenderem às demandas das indústrias automobilísticas por um material que permita a redução de peso, diminuição do consumo de combustível e, simultaneamente, que possibilite uma melhora na resistência ao impacto e na segurança dos passageiros. Neste contexto, o aço bifásico apresenta grande potencial tecnológico de aplicação, principalmente em componentes estruturais, em virtude de suas propriedades mecânicas especiais, como alta resistência à tração, alta taxa de encruamento e muito boa ductilidade. No entanto, é necessário minimizar os problemas dimensionais provocados pelo efeito do retorno elástico (springback) durante a estampagem, assim como, as falhas durante o processamento. Este trabalho tem por objetivo caracterizar um aço bifásico da classe 1000 MPa (DP980), quanto à microestrutura e propriedades mecânicas. A caracterização microestrutural, por meio de técnicas de microscopia óptica e eletrônica de varredura, determinaram as fases presentes de maneira qualitativa e quantitativa, assim como suas morfologias, com o objetivo de correlacionar a microestrutura com as propriedades mecânicas. Evidenciou-se a presença de grãos alongados, acompanhando o sentido de laminação da chapa e uma fração volumétrica de martensita de 51,4%. As características em relação aos processos de estampagem foram estudadas por meio do ensaio de dobramento para determinar o r... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The development of advanced high strength steels (AHSS) has been the main strategy for steelmakers to meet the demands of the automotive industry for a material that reduces weight and fuel consumption, provides shock resistance and vehicle safety. Within this context, dual-phase steel (DP) shows great technological potential, mainly in structural parts, due to its special mechanical properties, such as high tensile strength, work hardening, and ductility. However, it is necessary to minimize the dimensional problems caused by springback during stamping, along with the processing failures. This work aims to characterize a 1000 MPa (DP980) dual-phase steel regarding its microstructure and mechanical properties. The microstructural characterization, through optical microscopy and scanning electron microscopy, determined the present phases in a qualitative and quantitative manner, as well as their morphologies, in order to correlate microstructure with mechanical properties. The presence of elongated grains, following the direction of lamination of the sheet, as well as a volumetric fraction of martensite of 51.4% were observed. Features of the stamping processes were examined through a bending test to determine the springback in samples submitted to bending punches with radii of 5 mm and 0.3 mm. The samples tested with the 5 mm radius punch show a strong springback in function of the high strength of the steel. With the 0.3 mm radius punch, the springback decreases significantl... (Complete abstract click electronic access below)
Doutor
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Katre, Aanandita Ramakant. "Developing Methods for Prediction and Reduction of Springback using a Practical Method to Estimate E-Modulus." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500028074848847.
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Kroll, Martin, Peter Birnbaum, Josephine Zeisig, Verena Kraeusel, and Martin Franz-Xaver Wagner. "Manufacturing of 42SiCr-Pipes for Quenching and Partitioning by Longitudinal HFI-Welding." MDPI AG, 2019. https://monarch.qucosa.de/id/qucosa%3A34778.
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In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P process is to establish a martensitic structure with increased retained austenite content. This allows for the beneficial use of both phases: the strength of martensite as well as the ductility of retained austenite. A 42SiCr steel, developed for Q&P processes, was joined at the longitudinal seam by a high-frequency induction (HFI) welding process and was subsequently heat-treated. The applied heat treatments included normalizing, austenitizing, quenching, and two Q&P strategies (Q&P-A/Q&P-B) with distinct quenching (Tq = 200/150 °C) and partitioning temperatures (Tp = 300/250 °C). Investigations of the microstructures revealed that Q&P tubes exhibit increased amounts of retained austenite in the martensitic matrix. Differences between the weld junction and the base material occurred, especially regarding the morphology of the martensite; the martensite found in the weld junction is finer and corresponds more to the lath-type morphology, compared to the base material in the circumference. In all zones of the welded tube circumference, retained austenite has been found in similar distributions. The mechanical testing of the individual tubes demonstrated that the Q&P treatments offer increased strength compared to all other states and significantly improved ductility compared to the quenched condition. Therefore, the approach of Q&P treatment of HFI-welded tubes represents a route for the mass production of high-strength tubular products with improved ductility.
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SINGH, ASHWANI KR. "SIMULATION OF CRASH TEST OF A SALOON CAR WITH SKIN PANELS MADE OF IF AND AHS STEEL." Thesis, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18162.
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Car crash test analysis is widely performed to determine the level of safety provided
by the car to its passengers. This thesis focusses on the similar study. There are
several factors which contribute to the safety of passengers, specially front seat
travellers based on which the star ratings are provided to every car by the standard
testing organisations.
The study involves all the standards as set by NCAP and also uses the model of
Toyota Yaris with the conditions and specifications assigned to it by NCAP
officially. The FE model was observed on the software LS-Dyna. The study of the
car involves material change for the skin and frame of the car on software. The new
material whose specifications were used on the software were IF (Interstitial Free)
steel for the skin material and AHSS(Advanced High Strength Steel) for the frame
which require comparatively higher strength. The tensile testing results were
obtained which were helpful in defining the Load Curves for the respective materials.
The load curves were used in the software simulation for definition of material
deformation in its plastic state.
The simulation in full frontal orientation which is one of the standard tests involved
in Crash analysis was performed with changed material. The results and observations
have been limited to the materials’ properties during impacts. Although there are
numerous factors which involve the safety of a vehicle, the focus was primarily on
the skin and frame material change which can increase the crashworthiness and make
vehicle safer. The crash pulse and energy absorption was primarily focussed directly
v
determining the materials’ effectiveness in crash. Also, the deceleration curve and
velocity curve for the driver’s seat was drawn with respect to time in order to
determine effect of the change of material on the shock propagation through the car
body.
The net increase in the energy absorption was slightly less than 2 percent which is
small but significant taking into the account of others parameters which have been
excluded like the change in parameters for the Cowper-Symonds material model.
Also, the average decrease in acceleration and velocity of the driver’s seat was less
than 2 percent too. Along the thesis, the reason can be discerned behind this increase
and decrease which is primarily based on the limitations and assumptions.
Based on those results, the thesis concludes the study with the scope of work that can
be done in future with relaxation in the limitations.
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Khan, Mohammad Ibraheem. "Spot Welding of Advanced High Strength Steels (AHSS)." Thesis, 2007. http://hdl.handle.net/10012/2777.
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Efforts to reduce vehicle weight and improve crash performance have resulted in increased application of advanced high strength steels (AHSS) and a recent focus on the weldability of these alloys. Resistance spot welding (RSW) is the primary sheet metal welding process in the manufacture of automotive assemblies. Integration of AHSS into the automotive architecture has brought renewed challenges for achieving acceptable welds. The varying alloying content and processing techniques has further complicated this initiative. The current study examines resistance spot welding of high strength and advance high strength steels including high strength low alloy (HSLA), dual phase (DP) and a ferritic-bainitic steel (590R). The mechanical properties and microstructure of these RSW welded steel alloys are detailed. Furthermore a relationship between chemistries and hardness is produced.
The effect of strain rate on the joint strength and failure mode is also an important consideration in the design of welded structures. Current literature, however, does not explain the effects of weld microstructure and there are no comprehensive comparisons of steels. This work details the relationship between the joint microstructure and impact performance of spot welded AHSS. Quasi-static and impact tests were conducted using a universal tensile tester and an instrumented drop tower, respectively. Results for elongation, failure load and energy absorption for each material are presented. Failure modes are detailed by observing weld fracture surfaces. In addition, cross-sections of partially fractured weldments were examined to detail fracture paths during static loading. Correlations between the fracture path and mechanical properties are developed using observed microstructures in the fusion zone and heat-affected-zone.
Friction stir spot welding (FSSW) has proven to be a potential candidate for spot welding AHSS. A comparative study of RSW and FSSW on spot welding AHSS has also been completed. The objective of this work is to compare the microstructure and mechanical properties of Zn-coated DP600 AHSS (1.2mm thick) spot welds conducted using both processes. This was accomplished by examining the metallurgical cross-sections and local hardnesses of various spot weld regions. High speed data acquisition was also used to monitor process parameters and attain energy outputs for each process.
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Sreenivasan, Narasimhan. "Effects of Laser Welding on Formability Aspects of Advanced High Strength Steel." Thesis, 2008. http://hdl.handle.net/10012/3538.
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Limiting dome height (LDH) tests were used to evaluate the formability of both base
metal and laser butt welded blanks of AHSS (including High strength low alloy (HSLA),
Dual phase (DP) steels of different grades). Mechanical properties of the base metal and
welded blanks were assessed by uniaxial tensile and biaxial LDH tests, and related to
measured microhardness distributions across the welds. The formability ratio of laser
welded dual phase sheet steels generally decreases with increased base metal strength. A significant decrease of LDH was observed in the higher strength DP steel welded specimens due to the formation of a softened zone in the Heat Affected Zone(HAZ).
Softened zone characteristics were correlated to the LDH. Larger softened zones led to a larger reduction in the LDH. HAZ softening has been shown to be a function of the base metal martensite content and the weld heat input. Formability also decreased with increased weld heat input. Both in experiment and numerical simulations strain is localized in the softened HAZ in the uniaxial tensile testing, indicating that strain localization decreases tensile strength and elongation of laser welds in DP980.
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Liu, Chia-Chou, and 劉佳宙. "Injection Molding of Stainless Steel Fiber/Carbon Fiber/ABS and Its Properties." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/v7dx77.
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碩士逢甲大學
紡織工程所
90
Stainless steel fiber (SSF) and carbon fiber (CF) reinforced ABS composites were made by injection molding, and effectiveness electromagnetic interference (EMI) shielding was also evaluated in this study. In this experiment, capillary viscometer was used to examine the effect of testing temperature and shear rate on plastic viscosity. Plastic chips were made by single-screw extruder with different fibers and fiber contents. EMI specimens were made in accordance with ASTM D4935-89 specification, and the specimens for testing mechanical properties were made in accordance with ASTM specification, respectively. The values of shielding were measure by Coaxial Transmission Line. Otherwise, tensile strength, flexural strength, impact strength, surface and volume electrical resistances, and heat distortion temperature (HDT) were also examined. The result showed that the effectiveness of EMI shielding of SSF reinforced ABS composites were poor, and CF reinforced ABS composites showed the batter effectiveness of EMI shielding the SFF one in the same weight content. It can be seen that the fibers were well-distributed in the specimens by scanning electron microscope (SEM) and optical microscope (OM), but the interface of SSF and ABS was worse. There was an obvious void on the interface. EVA which was used to envelop SSF might be degraded at exceeding high injection temperature, but, however, the degraded EVA enhanced the effectiveness of EMI shielding. Fiber volume content affected the fluidity of ABS, but the effect of fiber volume was not as significant as that of temperature and shear rate. The difference on the mechanical properties of SFF and CF specimens were due to the voids and fiber volume content.
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Figueira, José Tomé Serra Afonso. "Study and Validation of Constitutive Models for AHSS Steels." Master's thesis, 2018. http://hdl.handle.net/10362/66169.
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Advanced High Strength Steels have been extensively used in automotive industry due to their high yield and ultimate tensile strengths, allowing the production of lighter structural components for the car body structure without compromising safety requirements, however these steels exhibit a large springback phenomenon, after forming processes. To deal with this challenge, constitutive material models have been studied to capture the material behaviour under plastic deformation, and accurately predict the springback.
Making use of the material characterization tests previously performed, the aim of this dissertation is to study and validate constitutive material models for Dual-Phase steels, DP1000, and DP1200. For that, FEM simulations with LS-DYNA software were performed to study which material models better describe the material behaviour under different loading paths and in springback prediction. The Nakajima and notch tensile tests simulations were performed using explicit time integration to study the different loading paths, while for the U-shaped bend tests the simulation procedure was separated into two distinct simulations. A forming simulation with explicit time integration and a springback simulation with implicit time integration to validate constitutive models in its application for springback prediction. The results of the simulations were compared with the data obtained from experimental testing.
Regarding the loading path behaviour, the results indicate that most of the material models followed accurately the elementary loading paths, such as biaxial tension and uniaxial tension. As for the U-shaped bend test for the setup with the higher punch and die radiuses, the Yoshida-Uemori material model considering transverse anisotropy performed well in springback prediction.
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YAO-TING, WU, and 吳曜廷. "A Study of Improving Steel Structural Company Process Quality Using AHP and QFD Methods." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5mfx9q.
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碩士國立高雄科技大學
土木工程系
107
The main idea of this research is to investigate the improvements toward process quality in the steel structure factories . Through the survey on construction and steel structure factories, the process quality assessment system of steel structure factories can handle the process quality requirements of practitioners, by analytic. Next, through importing the model of analytic hierarchy process(AHP), we comprehend the priority of process quality technology. Further, we could build a management model toward process quality for our country’s steel structure factories appropriately. According to the research outcomes and analyses, among the three facets on the first level, the constructioriers and steel structure practitioners consider that the priority of process quality need of steel structure are:「management function」, 「production installation」,and 「bidding planning」. Among 15 assessment principles on the second level, the foremost one is 「designer experience」; from the second to the 7th ,they are 「site area and production equipment」, 「on-site construction personnel management ability」, 「pre-assembly test」, 「technology and design capabilities」, 「professional competence certification」,and「product storage system」. Besides, from the process quality requirements and the matrix, the methods to improve are 「strengthen workplace discipline」, 「the improvement and development of QT」, 「production process standardization」, 「eliminate old process equipment」, 「de-bottleneck production process」, and 「set up the honor sense of production quality」. It shows that steel structure factories are supposed to reinforce the workplace disciplines of production operators, proceed the process education training constantly, and to cooperate with the reward and punishment systems. It not only makes the operators abide by the work requirements of standardized production process to produce all kinds of zero-defected members , but also enables to deal with the ill- performance operators by transferring the production lines or dismissing.
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Shen, Bao-Hong, and 沈保宏. "Applying AHP to Investigate the Selection Criteria of Steel Bar Suppliers for Taiwan’s Construction Industry." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/63427948213954701910.
Full textAbstract:
碩士國立交通大學
管理學院管理科學學程
103
In recent years, our government has cut its budget of public project and due to the fiscal policy; which prevent Real Estate Speculation. The construction industry performance had rapidly deteriorated. It does not only make a huge impact of steel bar price but also result in poor construction quality; in other words, we must choose carefully of our material supplier. Domestic steel bar industry market has been in a long-term oversupply situation; and recently facing oversea competition from China steel mills; they have very large economic scale advantage, which provides extremely low production cost. In next decade, the potential threat from China might be increase enormously; Local manufacturers should make good use of local advantages and understand the demand of their consumers in order to seek sustainable business survival. This study may consider conditions upon the selection of domestic construction industry steel bar suppliers through professional questionnaires and Analytic Hierarchy Process. By analyzing and sorting of its importance, the following order would be "product quality", "product price", "lead time", and "steel bar cut length" as a decision-making reference for the relevant personnel.
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Knobloch, Martin Weiß Mathias. "Realisierung einer Steer-by-Wire-Einrichtung für eine selbstfahrende Arbeitsmaschine /." 2007. http://www.gbv.de/dms/ilmenau/abs/528998757knobl.txt.
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As'ad, Rami Afif. "Integrated Production-Inventory Models in Steel Mills Operating in a Fuzzy Environment." Thesis, 2010. http://spectrum.library.concordia.ca/7406/1/As%22ad_PhD_S2011.pdf.
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Despite the paramount importance of the steel rolling industry and its vital contributions to a nation’s economic growth and pace of development, production planning in this industry has not received as much attention as opposed to other industries. The work presented in this thesis tackles the master production scheduling (MPS) problem encountered frequently in steel rolling mills producing reinforced steel bars of different grades and dimensions. At first, the production planning problem is dealt with under static demand conditions and is formulated as a mixed integer bilinear program (MIBLP) where the objective of this deterministic model is to provide insights into the combined effect of several interrelated factors such as batch production, scrap rate, complex setup time structure, overtime, backlogging and product substitution, on the planning decisions.
Typically, MIBLPs are not readily solvable using off-the-shelf optimization packages necessitating the development of specifically tailored solution algorithms that can efficiently handle this class of models. The classical linearization approaches are first discussed and employed to the model at hand, and then a hybrid linearization-Benders decomposition technique is developed in order to separate the complicating variables from the non-complicating ones. As a third alternative, a modified Branch-and-Bound (B&B) algorithm is proposed where the branching, bounding and fathoming criteria differ from those of classical B&B algorithms previously established in the literature. Numerical experiments have shown that the proposed B&B algorithm outperforms the other two approaches for larger problem instances with savings in computational time amounting to 48%.
The second part of this thesis extends the previous analysis to allow for the incorporation of internal as well as external sources of uncertainty associated with end customers’ demand and production capacity in the planning decisions. In such situations, the implementation of the model on a rolling horizon basis is a common business practice but it requires the repetitive solution of the model at the beginning of each time period. As such, viable approximations that result in a tractable number of binary and/or integer variables and generate only exact schedules are developed. Computational experiments suggest that a fair compromise between the quality of the solutions and substantial computational time savings is achieved via the employment of these approximate models.
The dynamic nature of the operating environment can also be captured using the concept of fuzzy set theory (FST). The use of FST allows for the incorporation of the decision maker’s subjective judgment in the context of mathematical models through flexible mathematical programming (FMP) approach and possibilistic programming (PP) approach. In this work, both of these approaches are combined where the volatility in demand is reflected by a flexible constraint expressed by a fuzzy set having a triangular membership function, and the production capacity is expressed as a triangular fuzzy number. Numerical analysis illustrates the economical benefits obtained from using the fuzzy approach as compared to its deterministic counterpart.
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FANG-LING, KUO, and 郭芳伶. "The Studies of the Electromagnetic Interference Shielding Effectiveness and properties of Acrylonitrile-Butadiene-Styrene (ABS)/Stainless Steel Fiber Composites." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/49995117920418339133.
Full textAbstract:
碩士大同大學
材料工程研究所
90
In this study, the stainless steel fibers (SSF) and carbon fibers (CF) were added into Acrylonitrile-Butadiene-Stryene (ABS) to form conductive composites. The effect of fiber content, fiber length, kind of fiber and coupling agent on the electromagnetic interference (EMI) shielding effectiveness (SE) of composites were investigated. The stainless steel fibers have electrically conductivity and good toughness which could be prevented the fibers to break during processing. The fiber content and the characteristics of composite material affect the properties of the EMI SE and the impact strength. The results show that the more the fibers were added, the higher EMI SE was attained. The result also shows that the higher the aspect ratio of the fiber was, the higher the EMI SE was attained. In this investigation, the stainless steel fibers (aspect ratio = 166) at 4phr content gave EMI SE of 7 dBm, whereas the stainless steel fiber at 16phr content gave EMI SE of 28dBm. The resistivity of ABS/SSF (with coupling agent) was higher than that of ABS/SSF (without coupling agent) for the reason of contact electrical resistance. When the SSF (3mm) content of ABS/SSF (3mm) composite was 4phr, the reflection loss was higher than that of the other contents in the composites. The reflection loss of ABS/SSF (3mm, without coupling agent) was higher than that of ABS/SSF (5mm, without coupling agent) at the same loading of SSF.
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Fuertes, Nuria. "Use of local electrochemical techniques for corrosion studies of stainless steels." Licentiate thesis, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-186206.
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The excellent corrosion resistance of stainless steels arises from the presence of a passive film on its surface. Above 10.5wt% Cr a chromium oxide of 1-3 nm is formed on the surface of the metal that in case of damage will reform and hinder further dissolution of the metal. However, the passivity of the stainless steel can be altered by material factors and external factors; such as the composition of the underlying phases, external loads or thermal treatments. In this work the local electrochemical techniques Scanning Vibrating Electrode Technique (SVET) and Scanning Kelvin Probe Force Microscopy (SKPFM) and the local characterization techniques X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) have been used to investigate corrosion phenomena of stainless alloys based on measurements of corrosion current density, work function, thickness and composition of the oxide. The effect on work function of the thickness of the passive film and composition of the underlying phases was investigated for 301LN austenitic stainless steel (Paper I) and a heat treated superduplex 25Cr7Ni type stainless steel (Paper II). It was shown that the work function can be an indicator of corrosion resistance of the phases in the microstructure, and that the composition of the underlying phases had a greater effect on the work function than the thickness of the passive film. External factors such mechanical deformation (Paper I) and welding (Paper III) altered the passivity of the steel and work function. It was found that plastic deformation decreased irreversibly the work function, whereas elastic deformation did not have any permanent effect. Thermal oxides affected the passivity of stainless steels welded joints and were detrimental for its corrosion resistance. Anodic activity, observed with SVET, and pitting corrosion were detected at the heat tint and attributed to the interaction between the composition and the thickness of the oxide. Brushing combined with pickling was recommended for recovering the passivity of stainless steels.QC 20160516
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Biermann, M. C. (Marthinus Christoffel). "A critical assessment of the current understanding of chromium passivation treatments in tinplate." Diss., 2006. http://hdl.handle.net/2263/23985.
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Chromium passivation treatment on tinplate is important in stabilising the active tin surface in terms of oxidation resistance, sulphide stain resistance and ensuring good lacquer adhesion properties. Through this research, the reason was explored why dip passivation treatment, in sodium dichromate, provides superior lacquer adhesion properties on tinplate compared to electrolytic sodium dichromate (CDC) treatments. A critical assessment of the current knowledge of chromium passivation treatments on tinplate formed the basis of the experimental work. Through electrochemical and surface analytical techniques (X-Ray Photoelectron Spectroscopy and Auger Electron Spectroscopy) both dip and CDC treated tinplate surfaces were characterised in terms of surface species. It was shown through XPS, using angle resolved techniques, that no metallic chromium forms on the tinplate surface during CDC treatments. Furthermore, a difference in chromium surface species was established for the dip and CDC processes showing additional SnO and Cr(OH)3.nH2O species for the latter. Complementary to these findings, it was verified that the formation of additional chromium hydroxide species is a function of pH, governed by the applied cathodic current during the CDC process itself. The inferior adhesion properties of CDC treated tinplate were shown to be related to the difference in the respective surface species formed during dip and CDC applications. Copyright 2004, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Biermann, MC 2004, A critical assessment of the current understanding of chromium passivation treatments in tinplate, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-04172007-123305 / >Dissertation (MSc(Applied Sciences))--University of Pretoria, 2007.
Materials Science and Metallurgical Engineering
unrestricted
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Cheng-Wei, Yang, and 楊澄偉. "Using Analytical Hierarchy Process (AHP) to Examine the Basic Index Factors of Occupational associated – Dragon Steel Company as an Example." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/77eh3a.
Full textAbstract:
碩士國立勤益科技大學
工業工程與管理系
102
This study employs Analytic Hierarchy process (AHP) to examine the indicating factors of occupational injury. In Dragon Steel, many employees and contractors suffer from occupational injuries each year. To solve the problems, it is necessary to find out the key factors related to the occupational injuries to consolidate the industrial safety and prevent the happening of occupational injury. This research intends to provide references to enhance and improve the company’s management to minimize the happening of occupational injury. This research employs AHP to examine the indicating factors of the occupational injuries of the employees and contractors. With the information derived from the statistics of the occupational injuries in the company over the past ten years, the factors were summarized into six basic indicators: hazard recognition, management mechanism, management personnel, educational training, code of practice, and automatic inspection. This research interviewed 5 management experts and 5 site technicians, who were requested to fill out the questionnaire. The results were processed with AHP to find out the correlations between the factors and the priority of the indicating factors in occupational safety and health as the guidelines for enhancing and improving management to minimize injuries and death caused by occupational hazard.
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Jurek, Adam. "Zwiększenie zasięgu operacyjnego podestu ruchomego pojazdów samochodowych przy zachowaniu masy własnej pojazdu." Rozprawa doktorska, 2021. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=73263.
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