Stainless steel profiled walls have increasingly been used in the process and other industries to protect people and personnel against hydrocarbon or chemical explosions. The existence of various uncertainties, in particular the ones associated with explosion loading and parameters, make the current design and assessment which are based on single degree of freedom (SDOF) and deterministic approach, very complicated and in many cases leading to unreliable design assessment. Therefore, developing an appropriate reliability approach for assessing and designing blast wall structures would greatly assist in improving the safety of personnel and plant facilities. The objective of this research study is to develop a practical framework for performance based design of stainless steel profiled barrier blast walls, with specific focus on reliability assessment by implementing stochastic finite element analysis (SFEA). Initially, the current traditional SDOF method is reviewed to identify the related issues and weaknesses and accordingly an appropriate method for structural assessments of the blast walls is proposed. Furthermore, a comprehensive investigation on various available methods is carried out to identify a suitable probabilistic approach for the reliability assessments. The corresponding reliability of these structures is evaluated with a MCS method, implementing the Latin Hypercube Sampling (LHS) approach. A programming package is developed using Ansys Parametric Design Language (APDL), to generate parametric finite element models and to perform automated reliability assessments. The significant uncertainties are combined with an advanced analysis model to investigate the influence of loading, material and geometric uncertainties on the response of these structures under realistic boundary conditions and connection configuration. Effective implementation of the framework is achieved by the development of a combined programming package to deal with both finite element and reliability analyses. A further development for this research study is associated with the development of performance based design approach, using the results of the probabilistic and finite element assessments. This can be utilised for optimum and appropriate design of the blast wall structures, based on the defined performance levels. Application and practicality of the developed approach and associated programming package is demonstrated through a number of case studies of realistic stainless steel profiled barriers subject to explosion loading. The results of the preliminary probabilistic case studies confirm that the explosion loading is the main influential input parameter and also nonlinearities are more critical than dynamic effects for unstiffened profiled barrier blast walls. An appropriate dynamic load factor (DLF) is proposed for the preliminary stage of the design and assessments. It is observed that using the probabilistic approach can help identify the important variables and parameters to optimize the design of profiled blast walls, and to perform risk assessments for these structures. The study is expanded to develop a performance based design methodology, linking the probabilistic results with various performance levels and associated parameters (e.g., damage levels). The results and discussions of the case studies associated with performance based design assessments confirm the suitability of the proposed framework, and also highlight the complications in defining intermediate levels, without preliminary investigations. This shows that QRA approach and involvement of professionals can play an important role to develop performance levels and the associated objectives. The developed programming package and associated framework are expected to provide valuable guidance to professional design engineers and researchers, by obviating the need for complex computational requirements.

A friction stir welding equipment with high rotation speed and constant load is successfully developed in this study to weld the multi-laminated silicon steel sheets widely used on regular transformers. This equipment consists of a spinning unit, a loading unit, and a feeding unit. A WC round rod with 3 mm diameter is used as welding tool. Under different operating conditions, such as the normal load(140~480 N), the spindle speed (12000~24000rpm), the feeding rate (0~1.58 mm/s), the welding characteristics and the welding mechanism of multi-laminated silicon steel sheets, and the welding feasibility of the transformer are investigated. Firstly, the contour map of welding depth in terms of spindle speed,normal load, and depth of point welding is established for dwell welding time 15 seconds. Secondly, based on this contour map, two experimental conditions of the long-pass welding tests are selected to investigate the effect of normal load (Fd), the spindle speed (Ns), and the feeding rate (f) on the failure load of weld under the shear. According to the experimental results, the empirical formula is obtained as Ff =40.6(Fd¡DNs)1.123(f)-0.791. In this formula,(Fd¡DNs)1.123(f)-0.791 is proportional to the frictional work per unit moving distance. With the larger frictional work, this represents the heat generation of the workpiece material is higher with more uniform friction stir, so that the bonding strength of the material increases and the failure load of weld is larger. According to the micrograph observations, the thermo-mechanically affected zone is significantly influenced by high heat action generated from the friction between the tool and the weld surface region, so that the plastic flow of the workpiece material occurs to cause the multi-laminated silicon steel sheets bonding together. Finally, the transformer is successfully welded under the experimental conditions of the long-pass welding tests with the smaller welding depth and the better failure load.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Richard W. Neu; Committee Member: Dr. David L. McDowell; Committee Member: Dr. Itzhak Green.

No description available.

The objective of this research was to establish a relationship between arc spot weld shear strength and the arc time used to form the weld. Lap shear tests were performed on both 3/4 in. and 5/8 in. nominal diameter welds. Each weld was formed in one-, two-, or four-layers of sheet steel ranging from 22 gauge (0.028 in.) to 16 gauge (.057 in.). Three distinct time series were tested for each unique weld size, thickness of sheet steel and layer configuration. The first of these series were the full-time welds. The two remaining series, 2/3-time and 1/3-time welds, had arc times equal to 2/3 and 1/3 of the average full-time weld arc time, respectively. Both weld shear strength tests and weld sectioning were performed for each series of weld. Strength tests were performed on a minimum of three specimens from every weld series. If the strength of any specimen deviated by over ten percent from the mean strength, an additional specimen was tested, helping to better understand the true behavior of the weld. Comparisons were made between the strengths of full-time, 2/3-time and 1/3-time welds. Comparisons were also made between the observed strength of each weld and the strengths calculated using the 2001 AISI Specification. Each sectioning test involved measuring and documenting the visual diameter, average diameter and effective diameter of the weld. Weld penetrations were also documented as sufficient or insufficient and any porosity was noted. A single sectioning test was performed for each full-time series, while three were performed for every 2/3-time and 1/3-time series. The data taken from the strength tests and the sectioning samples proved that welds formed using reduced arc times were considerably smaller and weaker than full-time welds. The tests also proved that proper penetration is not dependent on the arc time, but is instead a function of the welding current and sheet steel thickness. / Master of Science

Among global steel markets in recent years, China steel industry expands the fastest with the largest capacity and most fiercest competitions, also bringing the greatest impacts to global and Taiwan steel markets. A few aggressive Taiwan mills have set up their production facilities in China and commissioned. This study conducts in-depth analysis on the leading Taiwan middlestream galvanizers & coil coaters (the products are hot-dip galvanized & pre-painted steel sheets, hereinafter called ¡§galvanized & pre-painted steel¡¨). Besides, the steel works are categorized into Taiwan works, China works-Taiwan capital, China works-foreign capital, and China local works based on different capital sources. Analysis and evaluation are done in light of every activity in value chain. Six types of galvanizers & coil coaters are categorized based on different facilities and processes. Type I: Integrated galvanizers & coil coaters Type II: CSP galvanizers & coil coaters Type III: Independent galvanizers Type IV: Independent coil coaters Type V: Independent galvanizers & coil coaters Type VI: Independent full-process galvanizers & coil coaters Owing to their different market environments, development backgrounds, technologies, human resources and management, this study will analyze their strengths, strategies adopted, possible future development trends and potential challenges. This study especially focuses on one issue: in the atmosphere of competition and cooperation between steel mills in Taiwan and China, how China independent galvanizers & coil coaters-Taiwan capital and Taiwan parent company upgrade their competitiveness is crucial. Synthesizing related literature & theories, market & mill information and interviews, verifying by comparison, four conclusions are obtained as follows. 1. The more value chain activities a mill has, the more profits and stronger competitiveness it acquires. 2. Taiwan markets of galvanizing & pre-painted steel are already saturated. The competitiveness & development strategy a globalization enterprise should adopt is to increase its export percentages and establish offshore production bases. 3. For those mills setting up independent galvanizers & coil coaters in both China and Taiwan, the marketing strategies they should employ are described as follows. 3.1 Both China and Taiwan works receive orders and manufacture for their domestic markets. In terms of exports, only Taiwan parent company receives orders for both. But they export through Taiwan¡¦s existing channels globally. 3.2 To ally with different downstream industries and benefit each other. 3.3 China products are exported to ASEAN 10 nations, or 10+3, or 10+4, or any country that hasn¡¦t accuse China mills of dumping, whereas Taiwan products are sold to China, or any country that hasn¡¦t accuse Taiwan mills of dumping. 3.4 Products should be differentiated. Order receiving, production planning, lead-time and customer service should be flexible and elastic. 3.5 The chosen customers and suppliers must be big and strong in their region. Thus, the overall enterprise competitiveness is excellent. 4. In the past, steel companies self-expand to grow whereas today they grow via merger and acquisition. Any enterprise must have its value-creation strategy, i.e. it must have a growth strategy to react to the fierce market competitions. This study provides six recommendations for the competitiveness & growth strategies which could be adopted by domestic Taiwan independent galvanizers & coil coaters. 1. For the investors who invest in independent galvanizers & coil coaters for the first time, the first choice should be Type VI: independent full-process galvanizers & coil coaters. The second choice should be Type V: Independent galvanizers & coil coaters. Next, to set up an independent galvanizer is superior to an independent coil coater. 2. Independent Galvanizers & Coil Coaters should adopt the growth strategy that horizontal developing to a certain scale at the outset is the priority. Next, they should develop toward upstream instead of downstream. In order to eliminate capacity, they should ally with different downstream industries. 3. In the market of demand exceeding supply, mills usually self-expand to achieve larger scale. Nevertheless, when the market is oversupplied, it is recommended to adopt acquisitions. 4. Independent galvanizers & coil coaters choose the most beneficial investment items & scale and start their oversea development based on their growth strategies. 5. In the initial phase of plant construction, independent galvanizers & coil coaters should negotiate with upstream raw material suppliers regarding raw material supply matters. A good relationship should be built in order to secure stability of raw material sources. 6. To manage China mills-Taiwan capital and compete with other mills, the following measures are recommended. 6.1 To take advantage of the enterprise strength, develop specialized products and promote marketing features. 6.2 To promptly establish market reaction mechanism via the internationalization strategy of ¡§Integration-Responsiveness¡¨. 6.3 To employ human resources management to aid internationalization strategy. 6.4 Integration model created by overseas plant construction or acquisition can be adopted to integrate an enterprise¡¦s organization, culture and resources via dynamics management system.

The aim of this research work is to study the inter-relationship, under controlled industrial conditions, among skin pass reductions, surface topography characterized by 2D and 3D roughness parameters, stampability and painted surface finish quality for automotive steel sheet stampings. Different surface textures obtained from cold rolling finishing have been evaluated in terms of paint appearance (rating and spectral curve) and tentatively related to roughness parameters (2D and 3D) obtained from the cold finished sheets. Some relevant tendencies have been established amongst these parameters. The results presented here are in accordance with other recently published research showing that there is a clear relationship between these parameters, and that further detailed studies are needed. / O foco do presente trabalho é o estudo, em condições industriais, da inter-relação entre grau de redução do passe de acabamento, topografia superficial caracterizada pelos parâmetros de rugosidade 2D e 3D, estampabilidade e aparência de pintura de chapas de aço para painéis automotivos. Diferentes texturas superficiais de chapas de aço foram analisadas em termos de aparência de pintura (rating e curvas espectrais) e tentativamente relacionadas com os parâmetros de rugosidades (2D e 3D) obtidos na chapa antes de estampar. Algumas tendências relevantes foram estabelecidas entre estes parâmetros. Os resultados presentes aqui estão de acordo com publicações recentes mostrando uma clara relação entre estes parâmetros e que trabalhos futuros ainda são necessários.

Fretting, which can occur when two bodies in contact undergo a low amplitude relative slip, can drastically reduce the fatigue performance of a material. The extent of fretting damage is dependent on the material combination and is affected by many parameters, making it difficult to design against fretting. Some of these parameters include contact force, displacement amplitude, and contacting materials. This work develops a method for quantifying the extent of damage from fretting as a function of these parameters for a thin sheet of AISI 301 stainless steel in the full hard condition in contact with both ANSI A356 aluminum and AISI 52100 steel contacting bodies. Fretting experiments were conducted on a Phoenix Tribology DN55 Fretting Machine using a fixture which was developed for holding thin specimens. The displacement amplitude and normal force were systematically varied in order to cover a range that could typically be experienced during service. The tribological behavior was studied by analyzing friction force during cycling and inspecting the resulting surface characteristics. Fretting damaged specimens were cycled in tension in a servohydraulic test system to failure. The decrease in fatigue life caused by fretting damage was determined by comparing the stress-life (S-N) response of the fretted specimens to the S-N response of the virgin material, thus characterizing the severity of the fretting damage. The conditions that lead to the greatest reduction in life were identified in this way. Using the fracture mechanics based NASGRO model, an Equivalent Initial Flaw Size (EIFS) was used to quantify the level of fretting damage, thus separating the life of the component into crack nucleation and subsequent propagation. This method and data will allow engineers to design more robust components that resist fretting damage, thus increasing the safety and reliability of the system.

Made available in DSpace on 2014-07-29T15:03:30Z (GMT). No. of bitstreams: 1 Dissertacao ariovaldo ecivil 2009.pdf: 972968 bytes, checksum: 9d1288c7a6be7d0bce6e1136f5b34c12 (MD5) Previous issue date: 2009-09-23 / The cold-formed steel sheets have been sufficiently used when it is thought of manufacturing a metallic structure with reduced weight. Its use until some time ago in construction was limited to the secondary structures, but, with considerable growth in research involving this type of material together with development of technical standards, made its use a good solution for certain types of light structures. The present work presents considerations on cold-formed steel sheets, the patened steel, processes of welding and the result of experimental tests with beams with composed section of two profiles U constituted with cold-formed steel sheets, manufactured with two types of patened steel produced in Brazil. In some of these beams, welded sections with coated electrode had been used and were made the comparison with the reference beam, where it was possible to study the influence of the process of welding in the ultimate resistance and the ductility of the beam. / Os perfis metálicos formados a frio tem sido bastante usados quando se pensa em fabricar uma estrutura metálica com peso próprio reduzido. O seu uso até a algum tempo atrás na construção civil estava limitado apenas a estruturas secundárias, mas, com o crescimento considerável de pesquisas envolvendo este tipo de material associadas ao desenvolvimento de normas técnicas, fez com que o seu uso apresentasse uma boa solução para determinados tipos de estruturas leves. O presente trabalho apresenta considerações sobre perfis formados a frio, aços patináveis, processos de soldagem e o resultado de ensaios experimentais de vigas bi-apoiadas constituídas de perfis formados a frio compostas pela junção de dois perfis U enrijecidos, fabricadas com dois tipos de aço patináveis produzidos no Brasil, comparando-se os resultados. Em algumas destas vigas foram feitas emendas soldadas com eletrodo revestido e foi feita a comparação com vigas de referência, sem emenda soldada, possibilitando o estudo da influência do processo de soldagem na resistência à flexão e na ductilidade das vigas.

The aim of this research work is to study the inter-relationship, under controlled industrial conditions, among skin pass reductions, surface topography characterized by 2D and 3D roughness parameters, stampability and painted surface finish quality for automotive steel sheet stampings. Different surface textures obtained from cold rolling finishing have been evaluated in terms of paint appearance (rating and spectral curve) and tentatively related to roughness parameters (2D and 3D) obtained from the cold finished sheets. Some relevant tendencies have been established amongst these parameters. The results presented here are in accordance with other recently published research showing that there is a clear relationship between these parameters, and that further detailed studies are needed. / O foco do presente trabalho é o estudo, em condições industriais, da inter-relação entre grau de redução do passe de acabamento, topografia superficial caracterizada pelos parâmetros de rugosidade 2D e 3D, estampabilidade e aparência de pintura de chapas de aço para painéis automotivos. Diferentes texturas superficiais de chapas de aço foram analisadas em termos de aparência de pintura (rating e curvas espectrais) e tentativamente relacionadas com os parâmetros de rugosidades (2D e 3D) obtidos na chapa antes de estampar. Algumas tendências relevantes foram estabelecidas entre estes parâmetros. Os resultados presentes aqui estão de acordo com publicações recentes mostrando uma clara relação entre estes parâmetros e que trabalhos futuros ainda são necessários.