Дисертації з теми "Hot process"
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1
Kennedy, Jonathan Ian. "Hot mill process parameters impacting on hot mill tertiary scale formation." Thesis, Swansea University, 2012. https://cronfa.swan.ac.uk/Record/cronfa42262.
Анотація:
For high end steel applications surface quality is paramount to deliver a suitable product. A major cause of surface quality issues is from the formation of tertiary scale. The scale formation depends on numerous factors such as thermo-mechanical processing routes, chemical composition, thickness and rolls used. This thesis utilises a collection of data mining techniques to better understand the influence of Hot Mill process parameters on scale formation at Port Talbot Hot Strip Mill in South Wales. The dataset to which these data mining techniques were applied was carefully chosen to reduce process variation. There are several main factors that were considered to minimise this variability including time period, grade and gauge investigated. The following data mining techniques were chosen to investigate this dataset: Partial Least Squares (PLS); Logit Analysis; Principle Component Analysis (PCA); Multinomial Logistical Regression (MLR); Adaptive Neuro Inference Fuzzy Systems (ANFIS). The analysis indicated that the most significant variable for scale formation is the temperature entering the finishing mill. If the temperature is controlled on entering the finishing mill scale will not be formed. Values greater than 1070 °C for the average Roughing Mill and above 1050 °C for the average Crop Shear temperature are considered high, with values greater than this increasing the chance of scale formation. As the temperature increases more scale suppression measures are required to limit scale formation, with high temperatures more likely to generate a greater amount of scale even with fully functional scale suppression systems in place. Chemistry is also a significant factor in scale formation, with Phosphorus being the most significant of the chemistry variables. It is recommended that the chemistry specification for Phosphorus be limited to a maximum value of 0.015 % rather than 0.020 % to limit scale formation. Slabs with higher values should be treated with particular care when being processed through the Hot Mill to limit scale formation.
2
Omar, Fuad. "Hot embossing process parameters : simulation and experimental studies." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/51655/.
Анотація:
Fabrication processes for the high volume production of parts with micro and nano scale features are very important in the global research and industry efforts to meet the increasing needs for device miniaturisation in numerous application areas. Processes for the replication of surface geometries are promising technologies that are capable to meet the demand of manufacturing products at a low cost and in high volume. Among these technologies, hot embossing is a process which relies on raising the temperature of a sheet of polymer up to its melting range and on pressing a heated master plate into the polymer for triggering a local flow of the material to fill the cavities to be replicated. This technique has attracted increased attention in recent years in particular due to the relatively simple set-up and low cost associated with its implementation in comparison to other replication techniques. The present work is concerned with investigating the process factors that influence hot embossing outcomes. In particularly, a detailed study of the process parameters’ effect on the cavity pressure, demoulding force and uniformity of the residual layer for different materials is conducted to analyse the further potential of this process. A review of the current state of the art on these topics reported in Chapter 2, is also used to assess the capability of this replication technology. Chapter 3 presents an experimental study on the effects of process parameters on pressure conditions in cavities when replicating parts in PMMA and ABS. To measure the pressure state of a polymer inside mould cavities, a condition monitoring system was implemented. Then, by employing a design of experiment approach, the iii pressure behaviour was studied as a function of different process conditions. In particular, the effects of three process parameters, embossing temperature and force and holding time, on the mould cavity pressure and the pressure distribution were investigated. In addition, using a simple analytical model, the minimum required embossing force to fill the cavities across the mould surface was calculated. The theoretical value obtained was then used to inform the design of the experiments. It was shown that cavity pressure and pressure distribution were dependent on both materials and processing conditions. The obtained results indicate that an increase in temperature and holding time reduced the pressure in the central and edge cavities of the mould and the pressure distribution while the opposite effect takes place when considering the embossing force. Also, it was observed that an increase of the embossing force has a positive effect on cavity filling but a negative influence for homogenous filling. In Chapter 4, a theoretical model was proposed to predict demoulding forces in hot embossing by providing a unified treatment of adhesion, friction and deformation phenomena that take place during demoulding of polymer microstructures. The close agreement between the predicted results and those measured experimentally suggests that the model successfully captures the relationship between mould design, feature sidewall, applied pressure, material properties, demoulding temperature and the resulting demoulding force. The theoretical results have been confirmed through comparisons with the demoulding experiments. The temperature at which the demoulding force is minimised depends on the geometry of the mould features along with the material properties of the mould and replica. The applied pressure has an important influence on the demoulding force iv as the increase in pressure augments the adhesion force due to changes in material dimensions and reduces the friction force due to resulting decrease in the thermal stress. Furthermore, the relationship between the residual layer uniformity and three process parameters was investigated in Chapter 5, using simulation and experimental studies when processing PMMA sheets. In particular, the characteristics of the residual layer thickness of embossed parts were analysed as a function of the moulding temperature, the embossing force and the holding time. Increasing the moulding temperature resulted in a reduction on the average residual layer thickness and on its non-uniformity. An increase in the embossing force led to a decrease in the homogeneity of the residual layer. Also, an improvement of the residual layer thickness uniformity was also observed when embossing with a longer holding time. The results of the conducted experimental and simulation studies were analysed to identify potential ways for improving the hot embossing process. Finally, in Chapter 6 the results and main findings from each of the investigations are summarised and further research directions are proposed.
3
Luginbuhl, Katharine. "Process characterization of a PMMA hot embossing system." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92196.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 157-158).
Microfluidics devices are important both for research use and medical application. To create these microfluidics devices, the hot embossing process is commonly used. In order to characterize this process to enable cycle to cycle control, a small-scale system was developed, using a hot embossing machine, taping machine, and functional tester previously created. Parts were moved between these machines with an Epson GlO SCARA robot, which provided the appropriate efficiency and accuracy. This system was able to produce embossed parts with a takt time of less than 135 seconds, and over 1000 of such parts were produced. The system was analyzed to determine potential sources of variance, considering both things that would alter the part and things that would alter the measurements. This enabled the system to be run in a state of statistical control, which in turn allowed for a designed experiment to be done on the system. This designed experiment determined that the forming temperature, forming force, forming time, as well as the square terms for the forming temperature and forming force and the cross-terms of forming force with forming temperature and forming time with forming temperature, were all statistically significant in the formation of parts. With this data, cycle-to-cycle control can be enabled in the future.
by Katharine Luginbuhl.
S.M.
4
Wang, Xifan. "Ideal Process Design Approach for Hot Metal Working." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375222977.
5
Barrera, Cardiel Gerardo. "Hot model simulation of the bottom blown steelmaking process." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63927.
6
Li, Shimin. "Hot Tearing in Cast Aluminum Alloys: Measures and Effects of Process Variables." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/203.
Анотація:
Hot tearing is a common and severe defect encountered in alloy castings and perhaps the pivotal issue defining an alloy's castability. Once it occurs, the casting has to be repaired or scraped, resulting in significant loss. Over the years many theories and models have been proposed and accordingly many tests have been developed. Unfortunately many of the tests that have been proposed are qualitative in nature; meanwhile, many of the prediction models are not satisfactory as they lack quantitative information, data and knowledge base. The need exists for a reliable and robust quantitative test to evaluate/characterize hot tearing in cast alloys. This work focused on developing an advanced test method and using it to study hot tearing in cast aluminum alloys. The objectives were to: 1) develop a reliable experimental methodology/setup to quantitatively measure and characterize hot tearing; and 2) quantify the mechanistic contributions of the process variables and investigate their effects on hot tearing tendency. The team at MPI in USA and CANMET-MTL in Canada has collaborated and developed such a testing setup. It consists mainly of a constrained rod mold and the load/displacement and temperature measuring system, which gives quantitative, simultaneous measurements of the real-time contraction force/displacement and temperature during solidification of casting. The data provide information about hot tearing formation and solidification characteristics, from which their quantitative relations are derived. Quantitative information such as tensile coherency, incipient crack refilling, crack initiation and propagation can be obtained. The method proves to be repeatable and reliable and has been used for studying the effects of various parameters (mold temperature, pouring temperature and grain refinement) on hot tearing of different cast aluminum alloys. In scientific sense this method can be used to study and reveal the nature of the hot tearing, for industry practice it provides a tool for production control. Moreover, the quantitative data and fundamental knowledge gained in this thesis can be used for validating and improving the existing hot tearing models.
7
Favre, Julien. "Recrystallization of L-605 cobalt superalloy during hot-working process." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00876664.
Анотація:
Co-20Cr-15W-10Ni alloy (L-605) is a cobalt-based superalloy combining high strength with keeping high ductility, biocompatible and corrosion resistant. It has been used successfully for heart valves for its chemical inertia, and this alloy is a good candidate for stent elaboration. Control of grain size distribution can lead to significant improvement of mechanical properties: in one hand grain refinement enhance the material strength, and on the other hand large grains provide the ductility necessary to avoid the rupture in use. Therefore, tailoring the grain size distribution is a promising way to adapt the mechanical properties to the targeted applications. The grain size can be properly controlled by dynamic recrystallization during the forging process. Therefore, the comprehension of the recrystallization mechanism and its dependence on forging parameters is a key point of microstructure design approach. The optimal conditions for the occurrence of dynamic recrystallization are determined, and correlation between microstructure evolution and mechanical behavior is investigated. Compression tests are carried out at high-temperature on Thermec-master Z and Gleeble forging devices, followed by gas or water quench. Mechanical behavior of the material at high temperature is analyzed in detail, and innovative methods are proposed to determine the metallurgical mechanisms at stake during the deformation process. Mechanical properties of the material after hot-working and annealing treatments are investigated. The grain growth kinetics of L-605 alloy is determined, and experimental results are compared with the static recrystallization process. Microstructures after hot deformation are evaluated using SEM-EBSD and TEM. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T≥1100 ◦ C, strain rate < 0.1s−1), and at high strain rate (strain rate > 10s−1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging from grain boundaries and twin boundaries. A new insight of the modeling of dynamic recrystallization taking as a starting point the experimental data is proposed. By combining the results from the mechanical behavior study and microstructure observation, the recrystallization at steady-state is thoroughly analyzed and provides the mobility of grain boundaries. The nucleation criterion for the bulging from grain boundaries is reformulated to a more general expression suitable for any initial grain size. Nucleation frequency can be deduced from experimental data at steady-state through modeling, and is extrapolated to any deformation condition. From this point, a complete analytical model of the dynamic recrystallization is established, and provides a fair prediction on the mechanical behavior and the microstructure evolution during the hot-working process.
8
Schuh, Amy Jeanne. "Monitoring and control system for hot air solder leveling process." Master's thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-01122010-020101/.
9
Fereshtehi-Saniee, Faramarz. "3-D simulation of the fullering process in hot forging." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633094.
Анотація:
Elongated parts make up a considerable percentage of forged components used in various industries. In many cases, their production by means of a multi-impression forging operation involves fullering and rolling processes. These are two types of open-die forging process, the main function of which is to properly distribute the metal in the longitudinal direction of the component. Several sets of empirical rules for fuller and roller die design have been proposed previously and have also been incorporated into CAD/CAM systems. Since in these processes the metal can flow freely in certain directions, there is no guarantee that the desired preform shape will be produced and some means of predicting this shape would be beneficial. During the initial stages of this project, various methods of metalworking analysis were reviewed. The model material technique and the finite-element (FE) method were selected for the analysis of the deformation during the fullering process. A gravity drop model hammer was designed and constructed for the physical simulations of the fullering process using plasticine as the model material. Ring tests were performed to find a suitable lubricant and compression tests were used to obtain the flow stress of the plasticine as a function of strain and strain rate. For the physical simulation of different types of the fullering process, a typical elongated forging component was used. These tests were performed using die shapes described as flat-flat and crowned-flat. The main features of deformation studied by the model tests were the distribution of deformation, variations of elongation and maximum sideways spread and the elongation achieved during each blow in each of the processes. The results were discussed, compared to each other and employed for the validation of the FE results. The fullering processes that were modelled physically were also simulated numerically using an elastic-plastic thermo-mechanical code (EPFEP3). Different FE models were developed to investigate the effects of mesh density on material flow. Separate sets of material properties, namely those of hot steel and plasticine, were employed in the simulations. For each set, separate FE analyses of ring compression tests were conducted to ensure that the appropriate friction condition was provided for the simulations of the fullering processes. The material flow during the fullering process, and the effects of various parameters influencing this, were investigated. To validate the results obtained from the FE simulations, they were correlated with the available experimental data as well as with the results obtained from physical modelling of the process. In most cases there was very good agreement. Also, to evaluate the empirical design rules for the forging component under consideration, the total elongation and the required minimum fuller width gained from different physical and FE simulations of various fullering processes were compared to the mass distribution requirement and to the suggestions made by some investigators. There was good agreement between various estimated fuller widths. However, it was found that to improve the amounts of total elongation, the geometries of the designed fuller dies should be modified. To avoid a trial and error method of die modification which has economical disadvantages, it was decided to employ the FE results gained from the first simulation of the process together with a numerical predictive approach. The effects of two important parameters which influence the total elongation, namely fuller gap and fuller length, were studied in the fullering process of a square bar with flat-flat dies. A method of fuller gap modification was introduced and extended to other types of fullering processes. Also, the effect of fuller length on longitudinal and transverse flow of metal was interpreted based on previous experimental observations. This investigation has also shown the feasibility of developing the current fuller CAD/ CAM system into an expert system.
10
Abu, Qdais Hani A. "Management of municipal solid waste composting process in hot climates." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242361.
11
Endres, Matthew J. "Spray cooling of steel dies in a hot forging process." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0904102-141539.
12
Zhou, X. Y. "Mechanisms of cracking for iron base alloys in hot aqueous solutions." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295501.
13
Kjellberg, Jana. "Marknadsanpassning : hot eller möjlighet?" Thesis, Linköping University, Department of Management and Economics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-818.
Анотація:
Making the work in the public sector more efficient is something that has been seen as necessary during the later years. One way to do this on municipal level has been to apply solutions former used mostly by private companies. The organisational parts have also been adjusted to existing conditions in this work of change. For example more and more municipalities have come to use the purchaser-supplier model since the beginning of the 1990's. Norrköping, Linköping and Motala have been chosen in this essay for a closer study of the effects of the changes of the 90's, from an efficiency point of view. Even the process whereby the changes have been performed has been studied. The result that is being presented is that the purchaser-supplier model in many ways has contributed to an increased consciousness about the existing problems in the work and organisation in the municipalities. At the same time there is critics about the way the model is being used, and about the fact that the application isn't always adjusted to the existing reality.
14
Silva, Daniele Sales da. "Stability of the guava tropical juice (Psidium guajava L.) not sweetened gotten by the process hot fill and process aseptic." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1519.
Анотація:
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoO Brasil à um dos trÃs maiores produtores mundiais de frutas, sendo que a evoluÃÃo do consumo das frutas processadas nÃo sà no Brasil, mas a nÃvel mundial aponta caminho da agregaÃÃo de valor, na qual o mercado de frutas industrializadas apresenta maior destaque que o de frutas in natura. A praticidade aliada à preocupaÃÃo com a saÃde tem sido um dos fatores para o aumento do consumo de sucos industrializados. A goiaba à um dos frutos de maior importÃncia nas regiÃes tropicais e subtropicais nÃo sà pelo seu elevado valor nutritivo, mas tambÃm pela excelente aceitaÃÃo do consumo in natura, pela capacidade de desenvolvimento em condiÃÃes adversas e pela grande aplicaÃÃo industrial. A regiÃo Nordeste à a maior responsÃvel pela produÃÃo de goiaba no Brasil contribuindo com cerca de 45,40% da produÃÃo nacional. Este trabalho teve como objetivo avaliar e comparar a estabilidade do suco tropical de goiaba obtido pelos processos de enchimento à quente e assÃptico com relaÃÃo aos aspectos das alteraÃÃes quÃmicas, fÃsico-quÃmicas, microbiolÃgicas e sensoriais, durante um perÃodo de 250 dias de armazenamento em condiÃÃes similares Ãs de comercializaÃÃo (28  2ÂC). Os sucos estudados nÃo apresentaram interaÃÃo significativa entre as embalagens estudadas e o tempo de armazenamento. Os parÃmetros vitamina C, SO2 e fenÃlicos totais foram os mais afetados ao longo do armazenamento. Para os resultados da anÃlise sensorial, estes praticamente nÃo se alteraram atà o tempo 150 dias de armazenamento. Com relaÃÃo a avaliaÃÃo microbiolÃgica, os sucos encontram-se comercialmente estÃreis.
15
Wright, Benjamin Peter. "Thermal behaviour of work rolls in the hot mill rolling process." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/36081/.
Анотація:
This project continues the work of Daniel White which culminated in the thesis, "A Hot Strip Mill Work Roll Temperature Model", submitted to Cardiff University in 2007. The current project presents a combined thermal solution, incorporating a transient, two-dimensional model which predicts changes in the circumferentially averaged temperature profile with time, and a static, three-dimensional model which provides high-resolution results near the surface of the roll and uses the results of the two-dimensional model as boundary conditions. The material properties of both models can now exhibit temperature dependency and boundary conditions at the surface have been improved. The resolution of the static model has been increased dramatically after testing found that the temperature profile was being compromised. The stress models use ABAQUS, a finite element software package, and have been completely redesigned. The stress solution consists of three models, each successive model concentrating more resolution on the roll bite, using the sub-modelling technique. Temperature data is imported from the thermal models, mechanical loads are applied using process data taken from the hot mill database at Port Talbot and residual loads are applied using the best currently available experimental data. Residual and thermal stresses were found to be significant, but the mechanical loads made little difference to the peak or minimum stresses per roll revolution. A brief investigation showed that, for a high-reduction rolling schedule (40% reduction rates), increasing the work roll oxide layer thickness from 3μm to 10μm decreases the cyclic stress range by roughly 100MPa. Taking account of temperature variability in the material properties also made roughly 100MPa difference to the stress range. The radial temperature distribution in the roll was shown to have a strong effect on the stresses at the roll surface, with a cold roll core incurring large peak stresses for the same circumferential temperature profile.
16
Bageant, Maia R. (Maia Reynolds). "Development of a precision hot embossing machine with in-process sensing." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81732.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 121-123).
Microuidic technologies show great promise in simplifying and speeding biological, medical, and fluidic tasks, but transitioning these technologies from a laboratory environment to a production environment has proven difficult. This work focuses on hot embossing as a process suitable to produce these devices. In this work, a precision micro-embossing machine capable of maintaining precise setpoints in force and temperature input as well as displaying highly linear, repeatable motion and force application is developed and characterized. Additionally, this equipment is then outfitted with additional sensors that allow for three measurements relevant to process physics and product quality to be captured: initial substrate geometry; substrate bulk deformation; and glass transition temperature of the material. These measurements can be captured in-process without modifying the production cycle. The end goal is to incorporate this precision micro-embossing machine into a micro-factory cell and to implement closed-loop cycle-to-cycle process control.
by Maia R. Bageant.
S.M.
17
Vaitkus, Victor L. "A Process for the Direct Hot Extrusion of Hollow Copper Profiles." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1212718629.
18
Pangsrivinij, Suksant. "High Throughput Functional Material Deposition Using A Laser Hot Wire Process." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1464740037.
19
Mohamed, Mohamed Saad Kamel. "An investigation of hot forming quench process for AA6082 aluminium alloys." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6147.
Анотація:
This thesis is concerned with the mechanical properties and microstructure evolution during the novel solution Heat treatment Forming cold die Quenching (HFQ) process. HFQ is a hot sheet forming technology which incorporates the forming and quenching stages to produce high strength and high precision Al-alloy sheet parts. The work in the thesis divided into three main sections: Firstly, viscoplastic behaviour of AA6082 at different deformation temperatures and strain rates was identified through analysis of a programme of hot tensile tests. Based on the results from the hot tensile tests, a set of unified viscoplastic-damage constitutive equations was developed and determined for AA6082, providing a good agreement with the experimental results. SEM tests were carried out to investigate the damage nucleation and failure features of the AA6082 during hot forming process and the results are discussed. Secondly, the viscoplastic-damage constitutive equations were implemented into the commercial software ABAQUS via the user defined subroutine VUMAT for the forming process simulation. An experimental programme was designed and testing facilities were established for the validation of the FE process modelling results. A fairly good agreement between the process simulation and the experimental results was achieved. This confirms that the established FE process simulation model can be used for hot stamping of AA6082 panel parts. Further process modelling work was carried out to identify the optimal forming parameters for a simplified representation of a panel part. Finally, a precipitation hardening model was developed to predict the post-ageing strength of AA6082 panel parts, having varying amounts of forming-induced plastic strain. The model was tested against results of experiments which were carried out to investigate the effect of pre-deformation on the ageing kinetics of AA6082. The model is shown to fit and can be used to explain changes in the strength of the material. This set of equations was implemented in the VUMAT, in combination with the viscoplastic damage constitutive equation set, to model the whole HFQ process. The FE model was tested with experimental ageing and hardness results providing good agreements, which are discussed in light of the future development of the HFQ process.
20
McLaughlin, John. "The removal of volatile alkali salt vapours from hot coal-derived gases." Thesis, University of Surrey, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255851.
21
Chapman, Christopher Weeks. "The MANE process of generating continuous energy hot-operating temperature cross sections." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53037.
Анотація:
MANE (MCNP ACE from NJOY & ENDF), a code for generating continuous energy cross sections at arbitrary temperatures, was created. Cross sections were evaluated using NJOY99 such that they would agree with the cross sections provided by MCNP5. The MANE cross sections were found to be in very good agreement with those provided by MCNP5 with some minor exceptions caused by round-off errors and some differences in the unresolved resonance region. Differences in the resonance region are caused by differences in the random number generator used to start the cross section calculations. The MANE cross sections were verified against the MCNP5 cross sections in five unique MCNP configurations: an 8.7% enriched MOX fuel pin cell, a UO₂ assembly (controlled and uncontrolled), a MOX assembly, and a whole core configuration containing the 3 assemblies. In each of these cases, eigenvalue and tally density results were found to be in very good agreement with one another.
22
Musicka, Tom. "Application of non-linear modelling techniques to the hot strip rolling process." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430345.
23
Slaughter, Derek Emerson. "Strip Crown Prediction: Developing a Refined Dynamic Roll-Stack Model for the Hot Rolling Process." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34389.
Анотація:
The steel industry has been producing flat plates through the process of hot rolling since the late 1600s. Hot rolling uses a series of rolls to progressively thin a strip of steel to a desired thickness. In deforming the strip, the rolling process causes variations in thickness across the width of the strip. These variations are commonly referred to as crown, which is specifically the difference in thickness between the center and edge of a strip. For most applications steel mill clients require flat products, or products with little variation in thickness. Therefore, variations represent wasted material which must be removed before the plate or sheet can be used in consumer products. Controlling the flatness of the metal strip is a high priority for the hot rolling business.
The purpose of this work was to develop a 3-D dynamic model of the rolling process to simulate the behaviour of a strip while being rolled and predict its profile. To accomplish this task, much of the rolling process needed to be modeled. The profile of the strip is a product of the deformation of the rolls and frame within a mill stand. Therefore, not only did the geometry of these components need to be modeled, but the material properties and dynamic motion were required as well. The dynamic nature of the process necessitated the modeling of the rotation of the rolls and translation of the strip, aspects of rolling which are not typically simulated.
Five models were developed during the project. The purpose of the first two models was to find the stiffnesses of the roll-stack and stand frame. The roll-stack refers to the rolls and their arrangement. The reference mill from which data was provided used a four-high roll-stack with two rolls above the strip and two below. The frame that holds the roll-stack, while massive, stretches when the strip is deformed between the rolls. This stretch changes the position of the rolls affecting the load and deformation of the strip. A lumped-mass model was created to simulate the dynamics of the roll-stack and frame. When the strip enters the gap between the rolls, there is a large impact force which causes the rolls to vibrate. The lumped-mass model was used to determine parameters to bring the system to steady state. The final two models simulated the entire rolling process with rotating rolls and moving strip. The 3-D dynamic rolling model was capable of predicting the strip profile due after exiting the rolls. Two calibrations were used to reduce model error before running a validation.
The rolling causes thickness variation across the width of the metal strips; therefore, strips are intentionally rolled thick to meet a minimum thickness. In modern steel mills, specialized control systems are used to adjust parameters as the steel strip passes through each stand of rolls. Varying the parameters allows the thickness and profile of the strip to be controlled. Each stand may have several rolls in different configurations. These rolls are either work rolls, which directly contact the strip, or backup rolls, which contact the work rolls and stiffen the roll-stack. The stand frame holds the rolls and provides a means to position them.
The validation results showed that the exit thickness, strip crown, and rolling load were less than 5% different from the values measured in the test data. The calibrated model was then used to derive strip crown sensitivities to gap, entry crown, work roll crown, and bending force. The 3-D dynamic model was able to predict the strip crown accurately when given calibrated information about the system. This model will be a useful tool for exploring the mechanics of hot rolling in ways that were not previously possible.
Master of Science
24
Rieger, Michael. "The alkali sorption process by solid sorbents at high temperature." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843101/.
Анотація:
The aluminosilicate materials kaolinite, calcium montmorillonite and emathlite have been tested as solid sorbents for alkali vapour in controlled gaseous environments, in order to study their sorption characteristics. The study used pan pelletised and extruded pellets in single pellet and fixed bed reactor systems under gaseous environmental conditions containing water vapour, hydrogen chloride and nitrogen at a temperature of 850°C. The means of producing the pellets and the composition of the gaseous environment were shown to determine the sorption performance of the sorbent pellets. The physical properties of the pellet (particle size, total pore volume, surface area, crush strength) significantly affect the sorption effectiveness, while the formation of reaction products is dependent upon the sorbents' chemical composition and on the sorption conditions. Reaction products identified under the various sorption conditions indicated possible pathways for alkali capture. Hydrogen chloride mixtures were shown to cause a reverse of the sorption process for some sorbents. A leaching method for extracting sodium from treated pellets enabled the type of bonding to be determined but not necessarily the prime sorption mechanism. With the introduction of water vapour, some evidence was presented that the alkali sorption rate can change significantly. The previously reported effect of hydrogen chloride upon alkali capture by the sorbent material, calcium montmorillonite; shown by McLaughlin (1990) was confirmed and the effect was also investigated for emathlite and kaolinite. Reversibility depended upon the presence or absence of hydrogen chloride. Both water vapour and hydrogen chloride determine sorption activity and capacity. Likewise the structural characteristics of the pellet influences the sorption activity and capacity. The sorption process is not due to aluminosilicate reaction alone but also due to replacement mechanisms. Conclusions are drawn regarding mechanism and theoretical model proposed.
25
Yousaf, Naeem. "Calucaltion of waste heat from hot rolled steel coils at SSAB and its recovery." Thesis, Högskolan Dalarna, Maskinteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:du-4516.
Анотація:
Hot rolling process is heat input process. The heat energy in hot rolled steel coils can be utilized. At SSAB Strip Product Borlänge when the hot rolled steel coils came out of the hot rolling mill they are at the temperature range of 500°C to 800°C. Heat energy contained by the one hot rolled steel coil is about 1981Kwh whereas the total heat energy for the year 2008 is 230 GWh/year.The potential of heat is too much but the heat dissipation rate is too slow. Different factors on which heat dissipation rate depends are discussed.Three suggestions are proposed to collect the waste heat from hot rolled steel coils.The 2nd proposal in which water basin is suggested would help not only to collect the waste heat but to decrease in the cooling time.
26
Serbetci, Barbaros. "Finite Element Analysis And Manufacturing Of Fin Connector Rod By Hot Forging Process." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610739/index.pdf.
Анотація:
Forging operation is one of the most commonly used manufacturing techniques in defense industry. The products of forging operation have higher material strength when comparing to traditional manufacturing operations. Especially, for the mass production, it is a beneficial method considering metal and cost saving.
The commonly used part named Fin Connector Rod in defense industry requires high material strength due to working conditions. In this thesis, manufacturing of this part by hot forging operation is accomplished after analyzing by using the finite element method.
Two alternative forging processes are compared and the applicable alternative method is selected by using a finite element program. Dies are designed for applied processes. The stress distribution and the current temperature variation within the parts analyzed to evaluate the results. The fin connector rod is manufactured according to the results of the finite element analysis. It has been observed that, manufacturing of the fin connector rod by hot forging is succeeded and the waste material and cost is reduced when compared to the machining operation which is being used currently.
27
Siyasiya, Charles Witness. "The transformation behaviour and hot strength of 3CR12 during the continuous casting process." Diss., Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-06202005-134528.
28
Tepe, Bulent. "Evaluation of pre-treatment and powder paint process for hot rolled steel (HRS)." Thesis, Ulster University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516518.
29
Chun-Chi, Liao, and 廖俊棋. "Study on the hot injection upsetting process." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/29740516712231502068.
Анотація:
碩士國立臺灣科技大學
機械工程研究所
83
The main objective of this research is to analyze plastic deformation and heat transfer of hot injection upsetting process by applying the upper bound method and the finite difference method. The analytical model developed in this research has the merits of high efficiency and great accuracy. First, the kinematically admissible velocity field is established according to the assumed conditions, then the strain rate of the deformation zone is calculated. The heat transfer phenomena of raw material and die are discussed under the consideration of internal heat transfer and boundary heat transfer. The heat transfer model is established by the finite difference method and the variation of nodal temperature of raw material and die in the upsetting process are obtained. Strain, strain rate and temperature of each node are the variables in the process, substituting these variables into the equation of flow stress and applying upper bound method the load of injection upsetting can be obtained. Besides analytical simulation, some experiments are performed to compare with the results of numerical analysis. Injection upsetting dies with different thickness of spacing rings are designed. In order to catch temperature distributions in the die, thermal-couples are inserted in the drilled holes of lower die. From the results of injection upsetting with different flange thickness, the load and temperature change of material and die are obtained and the reliability of the analytical model established in this research is verified.
30
Tai, Ou Han, and 歐漢泰. "Robust Design of Hot Embossing Microlens Array Process." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75659662388775494023.
Анотація:
碩士國立臺灣科技大學
機械工程系
92
Due to the common use of microlens array in photoelectric industry, the research of microlens manufacturing tech becomes an important issue in today''s world. There are many methods to manufacture microlens. In this article we focus on the hot embossing method. The molds and the microlens are not contact in the hot embossing process; therefore, the produced microlens surfaces are well precision. However, the robust degree of microlens is usually poor. During the process of Ni-mold, high stress usually deforms Microlens. There are two primary purposes in this research, manufacturing robust photo-resist structures and low stressed Ni-mold. According to the analysis, the S/N ratio of the produced microlens array is 41.24, which is higher than the initial design 29.63. The result shows that the produced microlens array is robust. In this article, we use the Taguchi method and neural network to achieve the above two primary purposes. Besides, the experimental works is made to prove the correctness of theories. The conclusion from those experiments shows that the thickness of photo-resist layer is the primary factor which highly affects the change of photo-resist diameter during the process of photo-resist structure. On the other side, the most significant factor for stress is pH value. The stress of Ni-mold will be the lowest under the following process parameter conditions: 0.23% of saccharin, 4.05 pH value, temperature under 53˚C and 50mA/cm2 of the current density. Finally, we use variation analysis to obtain the contribution of control factors under two methods, photo-resist process and electroforming process.
31
Liu, Chun-Yu, and 劉俊佑. "The Study of an Innovative Hot Embossing Process." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/77501684564264303173.
Анотація:
碩士國立高雄應用科技大學
模具工程系
98
The main idea of this thesis is hot embossing forming technique, and takes its advantage to investigate optical lens manufacturing, high aspect ratio micro-pole forming and polymer thermal punching, then analysis the results by Taguchi quality engineering and one way analysis of variance method. For optical lens forming, the result shows that the longer the pre-press period, the better the lens be formed. This experiment uses PMMA powder as hot embossing material, during hot embossing process, the material can be soften and deform completely because of its small unit volume. From this experiment we can speculate that the smaller unit volume material is more appropriate than the larger ones. The result of high aspect ratio micro-pole experiment shows that the length of micro-poles increases with hot embossing time and temperature, and this tendency goes up with the micro-poles diameter obviously. The micro-poles at the vertical area show a non-uniform distribution. The central pole has a largest replicated height for the same diameter. The height becomes smaller as the micro-holes are away from the center. At the horizontal side, the micro-poles length of the same diameter will be symmetrical. Appropriate polymer thermal punching speeds guaranteed the sufficient plastic deformation time, and then trim the material in time before it over deformed. The glass transition temperature of the polymer is a demarcation line of the punching temperature; the cross-section quality rises with temperature increase before Tg.
32
Syu, Jhao-Yi, and 許昭益. "Neural Network Representation of Microlens Hot-Embossing Process." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/87551618311069703063.
Анотація:
碩士國立高雄第一科技大學
機械與自動化工程研究所
100
The technology of Micro hot-embossing is suitable for the manufacture of small size and large forming area. And its advantages as low cost、good reproducibility, and can be mass-produced for optical and biomedical products. This study investigates the use of hot-embossing simulation for microlens to find out the impact of differences for parameters to the feature size. In order to understand the aforementioned conditions, this study uses simulation software ABAQUS to carry out. As to back propagation neural network, using orthogonal arrays to produce 125 parameter combinations because lacking of times for neural simulation in training model and cannot present the accuracy of the system. In this study, three five-level control factors as the input value of the network input layer, with the feature size by ABAQUS simulation is the output value of the output layer. By neural network to train the network, the feature size of microlens in the neural network models will be showed, and then verify the control error for the feature size of microlens.
33
Tsai, Yen-Pin, and 蔡彥彬. "Ultrasonic Vibration-Assisted Optical Glass Hot Embossing Process." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36514384926452897708.
Анотація:
博士國立交通大學
機械工程系所
101
Glass hot embossing technique is essential in mass producing glass optical elements. With the vigorous developments, the process was capable to produce aspheric or complex optical elements with low cost. Ultrasonic vibration-assisted forming is extensively adopted in plastic manufacturing processes. With the effects of changing the frictional condition and raising the material temperature, the material formability is increased, the forming accuracy is improved and the cost is reduced. Thus, this study is aimed to integrate the ultrasonic vibration-assisted forming and the glass hot embossing process. The effect of changing material properties caused by ultrasonic vibration was applied to improve the glass forming efficiency and the product quality, and stretch the applications of glass hot embossing technique. In order to realize the ultrasonic vibration-assisted glass hot embossing process, an experimental apparatus was firstly developed to integrate the techniques of the ultrasonic vibration and the glass hot embossing. The output end of the ultrasonic vibration device was designated as the upper mold of the glass hot embossing; and the resonant frequency was compensated by modifying the dimensions on the ultrasonic horn, so the ultrasonic vibration device could be operated at the high working temperature of glass hot embossing process. With the built apparatus, the optical glass K-PSK100 (Sumita Co., Tg = 398°C) was adopted in molding experiments to investigate the effects of ultrasonic vibration on the glass hot embossing process. In the flat hot embossing experiments, the loads were reduced as the ultrasonic vibration applied; in molding V-groove and Fresnel structures, the formability on these complex structures were significantly enhanced with the assistance of the ultrasonic vibration.
34
Kuo, Hsien-Chang, and 郭献彰. "The study of microstructure process using hot embossing." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/42052295073154634818.
Анотація:
碩士大葉大學
機械工程研究所碩士班
93
In recent years, plastics have begun to show great commercial potential especially in manufacturing microstructured parts. Injection molding and hot embossing are two major microfabrication methods. Replication accuracy was investigated for these two methods. Polymethyl methacrylate (PMMA) was used as the polymer substrate. The mold insert (or master) was fabricated by LIGA-type method. Hot embossing was found to have better replication accuracy for microstructure than injection molding does. This research describes the application of hot embossing to produce parts with microstructure. An embossing machine, designed for microfabrication, was used to emboss PMMA substrate. Injection molding was also applied for comparison. Both the injection molded part and the hot embossed part were observed under microscope to compare the replication accuracy. During the production process, it is imperative to found out one set of appropriate processing parameters for the hot embossing so as to obtain better product quality. In the conventional parameter adjustment, most of them are adjusted by try and error method that has usually wasted lots of time and cost. Therefore, it is necessary to develop a wisest method (ex: Taguchi's quality method).
35
Tsai, Zhao-Yuan, and 蔡昭源. "Process Simulation of Hot Embossing on Polymeric Microstructure." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/54537771573352484385.
Анотація:
碩士大葉大學
機械工程研究所碩士班
94
This thesis discuss the simulation and process results difference. Make use of the Pro-E and ANSYS-APDL( ANSYS Parametric Design Language) parametric design as the Pre-Processor and the convergence of the element number analysis. At the same time, take the Finite element model describing by ASCII word file to edit the DEFORM executive Keyfile to carry out the simulation. The simulation of the phenomenon is the micro-structure forming by the hot-embossing. By the way that is a multi-body contact problem, stress-stain and heat transfer effect is dynamic change with the time and the process conditions. Besides, PMMA belongs to the polymer the forming viscosity change with the process temperature and shear force. In the thesis we will take the consideration of the heat transfer or not in 3-D model to discuss and compare the forming difference in the micro-structure number further in simplified the model as the 2-D cross section . The process make use of the Lab development in design and assembly hot-embossing machine including the structure and the Man Machine Interface to undergo the controlling and data derived as the hard and soft device. The material PMMA is directly purchased and the mold insert is produced by the semi-conductor process in the etching and electroplating reaching the micro scale .
36
邱治文. "Research of microlens array using hot intrusion process." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/00136665299396871322.
Анотація:
碩士國立中興大學
精密工程研究所
92
This dissertation describes a key factor to design and fabricate microlens array using hot intrusion technique. During hot intruding, polymers was compressed with temperatures exceeding the glass transition temperature (Tg) and taken off after cooling. Because the non- uniform pressure distributions and the temperature change during hot intruding and cooling, respectively, the final products will display non-uniform shrinkage. Therefore, uniform shrinkage was required for hot intruding procedures. This study thus designed a better intruding process control consisting of the following three stages. 1.Apply larger load during the embossing stage to improve replication. 2.Apply smaller load during the initial cooling stage, while the temperature still exceeds Tg, to minimize pressure variation and thus volume change variation. 3.Increase the holding load in the final cooling stage, when the temperature drops below Tg, to reduce the pressure variation and increase overall shrinkage uniformity. A 3mm thick PC (Polycarbonate) film is used as the raw material and hot intrusion with Ni-Co mold inserts that made by a single-layer LIGA process. High-aspect-ratio circular holes of 80μm in diameter are designed to form the plastic microlens. The plastic material is intruded into the circular holes and stopped at desired distance by adjusting the embossed load, temperature and time. The optical properties of these microlenses have been characterized by measuring their focal lengths. The radius of curvature is 196.3μm∼428μm and the heights is 1.87μm∼3.93μm.
37
Chang, Yen-Hui, and 張彥暉. "Determination of die surface temperature in hot forging process." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/93789772950182617262.
Анотація:
碩士國立高雄應用科技大學
模具工程系
98
This research has two parts, including the analysis of simulation and experiments, interactive comparison that contact of the die and workpiece with the surface temperature and thermal conductivity interface, Finally, analyze the difference of the simulation and experimental of the temperature of the die in the ideal state and the actual state. In hot forging, in addition to plastic deformation, the temperature change is also an important reason. The temperature of the hot forging process, in the past has attracted the attention and of scholars, among which how to obtain forgings and die heat transfer coefficient between the focus of our attention. In the simulation analysis part, used the Deform-2D (Design Environment For Forming) to solve, to analyzing of the die and workpiece that set of temperature transient changes in the grid points. Experimental process of the first part is heated using the heater to the top and bottom die, then put the workpiece into the furnace heating, when reaching the needs temperature and then starting hot forging, application thermocouple buried in the dies, with the temperature acquisition device and computer to record the distribution of mold temperature. Finally, we discuss in the hot forging process, obtained the die temperature by the experiment and simulation to analyze, unknown contact surface heat transfer rate and temperature, and further can be obtained by forging, the contact surface at different times of the heat transfer coefficient.
38
Wei, Lin Yun, and 林耘緯. "Simulation and experimental study of fast hot embossing process." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/48392861896709022029.
Анотація:
碩士國立臺灣科技大學
機械工程系
100
Micro/nano imprint technology is a commonly expected technique nowadays. It is very promising in the future because the technology has several advantages, such as having nano-scale resolution, forming three dimension structures and high throughput. This technology may be used to create the micro/nano structure for the next generation.However, a few steps of the whole process take a long time, including heating, pressing, and cooling. Only if the time for the process is reduced can the need for efficient mass-production be met. This is a study followed by previous research on “continuous sub-station synchronization process”, which is supplemented by a specially designed “holding pressure device”. In addition, this research also uses a theoretical simulation and improves the process and the parameters of the simulation results, so that it can shorten the time for the process. This study, based on the finite element method, uses commercial computational fluid dynamics software to create a 2D axis-symmetry model in order to simulate the filling behavior. Moreover, the Newtonian fluid is used to simplify the flowing pattern of the polymer materials in micro/nano imprint process, and the method of segmented isothermal is used to describe the non-isothermal process, so that the results of the present simulation can match with those of previous research. According to the results of the simulation along with another experiment added to it, when 150 Celsius degree is used as the transferring temperature and 105 Celsius degree is used as de-molding temperature, that filling rate can reach up to 94% and reduce half of the time spent in process (around 120 seconds), which can be helpful with the micro/nano imprint application in the future.
39
Karlberg, Mats. "Thermo-Mechanical Modelling of Hot Strip Coil Cooling Process." Licentiate thesis, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17274.
Анотація:
In hot rolled steel strip production the processed material are after the cooling section coiled into coils. Coils do normally weigh around 20 tons with a diameter of 2 m and heights equal to the strip width e.g. 0.8-1.4m. When processing HSLA (High Strength Low Alloy) steel grades the initial/coiling temperature is about 650°C but to achieve the full strength enhancement potential from the subsequent precipitation hardening the cooling history is crucial to control. A too high cooling rate will disable diffusion of alloying elements before the destined material properties have been achieved. This may result in downgraded or in worst case even scraped material. Having comprehensive knowledge of the thermal history is essential in controlling coiled material properties and in understanding root-causes for different mechanisms. A 2D thermo-mechanical FE model has in this licentiate work been developed to predict the transient temperature distribution as a function of position and stress state in coils when cooling. The model accounts for the imperfect and pressure dependent contact conditions between adjacent laps that cause anisotropic thermal properties in radial and axial directions. The imperfect contact is in a macroscopic level caused by oxide, dust, water and strip shape properties inherited from up-stream processes and in a microscopic level by surface conditions like roughness and slope of asperities etc. The stresses formed under coiling and cooling has a strong influence on the contact conditions and the thermal heat conductive properties in radial direction. In this model the total stress state during cooling is approximated as a combination of initial stresses set by the coiler and the thermally induced stresses caused by thermal gradients.The thermo-mechanical model developed and explained in this licentiate thesis has proven to be able to predict the thermal cooling of coils with good agreement in comparison with the performed measurements campaigns. Furthermore does the model form an accurate platform to be used in a continuing work for further investigations where the thermal trajectory and stresses have an influence e.g. on coil-set effects as length and cross bow or mechanical properties.Godkänd; 2014; 20141127 (vith); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Mats Karlberg Ämne: Materialmekanik/Material Mechanics Uppsats: Thermo-Mechanical Modelling of Hot Strip Coil Cooling Process Examinator: Professor Lars-Erik Lindgren, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Tekn dr Daniel Berglund, Gestamp Hardtech AB, Luleå Tid: Torsdag den 18 december 2014 kl 11,00 Plats: C305, Luleå tekniska universitet
40
林武伸. "Thermal Analysis of Work Roll after Hot Rolling Process." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/71811780812743324704.
41
Huang, Chung-Hsien, and 黃忠賢. "Micro Hot Spot and Micro Temperature Sensor Manufacturing Process." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/36380394724773648807.
42
YOU, ZHENG-YI, and 游政義. "Temperature predication of steel strip cooling during hot rolling process." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/10402912178293260885.
43
Ting, Fu-Pin, and 丁富彬. "The effect of hot press process parameter for MEA performance." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/09506395032005943277.
Анотація:
碩士國立中央大學
機械工程研究所
94
The paper will use hot press process to produce Membrane Electrode Assembly (MEA), and used I-V polarization curve to analyze the performance of the cell. However, the voltage loss of the MEA can not to explain from polarization curve, therefore the experiment to go a step further used Electrochemical Impedance Spectroscopy (EIS), and analyze the characteristic of contact interface of every component inside cell structure. Result of EIS to exhibit: the temperature and pressure of hot press process, and the thickness of proton exchange membrane, and the load of Nafion solution that have more effect of MEA performance. The best hot press temperature is 125℃ in MEA, if the temperature<125℃,then proton exchange membrane and catalyst particle can not bonding enough. On the other hand if the temperature>125℃, then catalyst particle will to warp by proton exchange membrane and to lose activity. On the other hand, the best hot press pressure is 50kgf/cm2 in MEA, if the pressure<50kgf/cm2, then the contract resistance is so high. On the other hand if the pressure>50kgf/cm2, then to cause between proton exchange membrane and catalyst particle bonding result not fine. Use proton exchange membrane of different thickness to compose MEA, when 50.8um (Nafion112) that is most thin and impedance is lowest, and 177.8um (Nafion117) that is most thick and impedance is highest. The electrochemical impedance value that major to depend on proton exchange transmission path is long or short, and catalytic reaction is good or bad to decide. The best Nafion solution load quantity is 1.0mg/cm2. If the load quantity is too less, then proton exchange transmission network is not enough. If the load quantity is too much, then the contract area that between catalyst and gas fuel is too less and can not to proceed catalytic reaction. The best operation temperature is 60℃ in MEA. If the temperature is lowest, then the effect of mass transmission and diffusion is not enough, and electrode reaction rate is to reduce. If the temperature is highest, then to cause catalyst ageing quickly, furthermore reduce electrode reaction rate. The best gas fuel feed quantity (anode/cathode chemical stoichiometry is 1.5:2.0). When the stoichiometry is reduce in cathode that to cause gas fuel feed is not enough. When the stoichiometry is to increase that to cause the contract time of between gas fuel feed and catalyst are not enough. Both of above condition are not effective operation for MEA.
44
周弘仁. "Thermal Analysis of the Work Roll in Hot Rolling Process." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/wd4rut.
45
Tsai, C. Y., and 蔡秋雲. "Investigation on the process design of a chisel hot forging." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/43256172188304046250.
Анотація:
碩士南開科技大學
車輛與機電產業研究所
103
A pneumatic chisel is often subjected a large shock wave, so that its mechanical properties need a higher strength and a higher toughness. However, in order to obtain the higher strength and the higher toughness of the part and to save the volume of the part material, a hot forging process is adopted most. In this paper, the hot forging design, the forging stage design, the die design and the flash trimming die design of a chisel forging are investigated. In this study, a commercial software DEFORM 3D based on the finite element method has been adopted for simulating and analyzing the material flow and the die stress, then the designed forging procedure could be evaluated efficiently during a design stage. The material SNCM439 is chosen for obtaining the needed strength and toughness after forging and heat treatment. An calculating excel program connected with SolidWorks software is set-up for drawing the die body automatically and saving the working time cost. From this study, a suitable hot forging die set of the chisel forging is developed. The results of this study could be a useful reference for a hot forging process design engineer.
46
Yang, Cheng-Yu, and 楊正鈺. "Study on Hot Stamping Process for Boron Alloys of 22MnB5." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22540289559496289867.
Анотація:
碩士國立高雄第一科技大學
機械與自動化工程研究所
101
Since the oil crisis in 1970s, People''s gradually increase awareness of environmental protection. Lightweight is one of the primary developing direction in automotive industry. The strength of Boron steel can reach more than 1300MPa by hot stamping process. Therefore, Boron steel (22MnB5) is more and more widely applied to automobile , such as bumper beams, A-pillars, B-pillars, etc. This paper investigated the parameters of hot stamping process for 22MnB5. At first, the parameters of hot stamping process were defined. The process parameters including heating temperature , holding time, cooling rate, rolling direction, etc. Specimens under various process parameters were tested by metallurgical analysis and tensile-testing to check by microstructure and tensile-strength. Then, the optimal process parameters are obtained by Taguchi method. Finally, the bumper beam is made to confirm hot stamping process parameters. Experimental results show that the optimal parameters of hot stamping for 22MnB5 with 1.8 mm thickness specimen are 850℃ for heating temperature , no holding time, water cooling, and transverse rolling direction. For bumper beam with optimal parameters of hot stamping, the microstructure is uniform martensite, the tensile strength is 1300 MPa, and the hardness is 500 HV. The results can meet the actual production requirements.
47
Huang, Zhong-yue, and 黃仲岳. "Study of the Micro Hot-embossing Process for Microlens Fabrication." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/49893160134641369134.
Анотація:
碩士國立高雄第一科技大學
機械與自動化工程所
95
This paper investigates microlens fabrication using micro hot-embossing process.Under the scaling law effect, both the height and radius of curvature of the microlens produced by micro hot-embossing are in connection with surface tension.When surface tension increases, the microlens height increases but the radius of curvature decreases.In order to understand the effect of surface tension,simulations of hot-embossing microlens are conducted using Marc simulation softwares are performed, and to fabricate a microlens with designated specifications(ie,height,radius of curvature and focal length),Marc simulations adopting the Taguchi method are carried out to obtain the optimal micro hot-embossing parameters and the experimental verification is then provided.In such away,the development time for microlesns fabrication can by highly reduced.
48
周村憲. "Hot Extrusion Process of Magnesium Alloy Sheet Under Converging Die." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/61001003155159072097.
Анотація:
碩士國立臺灣科技大學
機械工程系
91
Most parts of Mg Alloys are produced by die casting in industry. In general, products of die casting tend to have inferior mechanical properties compare with the forged parts. Furthermore, SF6, which has a strong global warming potential in environmental issues, is required as a protective gas in the die casting process. It is desirable to form the Mg alloys under hot extrusion having good mechanical properties and without any possible danger to the environment. During the hot extrusion of magnesium alloy, its structure is HCP, which has fewer slide surfaces than aluminum alloy. Experimental results show that if the hot extrusion of magnesium alloy sheets is performed under a die that has a high extrusion ratio of 35.9, and a fixed speed is adopted, all the final products carry defects. Further experiments are performed on the extrusion of magnesium alloy sheets by the multi-speed method , sound sheets can be obtained. In this study, using Taguchi experimental method , the experimental sequence is planned. Through ANOVA technique and from the test results of extruded material we can find the relationship between the process parameters and the mechanical properties of the products. Then the optimal combination of process parameters can be found.
49
Huang, Jian-Ming, and 黃建銘. "Investigation of the Clinching Process Combines with Hot Stamping Process for High-Strength Steel Sheets." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/5cfcgu.
Анотація:
碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班
103
The clinching process is a technique using punches and dies for activating local deformation of the sheets at low temperature, and then connecting the sheets each other. This technique is different from a traditional clinching process, because this technique results better seal property, well corrosion resistance, machining process simplifying, and stronger connecting strength (tensile strength and shear strength). The present research utilized the finite element analysis software DEFORM-3D to simulate the clinching process with hot stamping process for the high strength steel (CSC-15B22). The simulations are to present the temperature distribution and variation, the strength distribution on sheets, velocity field, stress, and strain conditions while conducting sheet forming, and to analyze how the connecting strength (tensile strength and shear strength) be affected by the neck thickness and interlock values. Furthermore, to study the parameters of die stress, cooling system, and the lifter floating pin design. The experiments are to validate the accuracy of our simulations, including the appearances of sheets, the neck thickness, the interlock values, the die temperatures and cooling rate etc. To realize the hardness and strength variation of sheet forming zone after hot stamping process and between the sheets of the shear strength, analyses of microstructure, Vickers hardness and shear strength are applied. Results have indicated that the cooling channel design could maintain the die temperature at around 59 ℃ after ten hot stamping process cycle and effectively took heat away from the sheet. The floating pin is reliably prevent the heat loss while the hot temperature sheets contacting the mold surface, otherwise the temperature difference between the sheet can be above 300 ℃ without floating pin. The human factors caused the interlock values deviation between simulations and experiments are up to 35%, but the simulation and experimental trends are coinciding. Therefore, the simulation results of the finite element software, DEFORM-3D, represented convincing reference. After hot stamping process conversion, microstructure of CSC-15B22 high strength steel sheets had been turned from ferrite and pearlite into martensite. While comparing properties of the deformed area and raw sheets, not only the Vickers hardness had changed from 209.7Hv to 407.2Hv but also the tensile strength had gone from 669.851MPa up to 1320.91MPa. The shear strength of combining hard upper sheet and soft lower sheet is 7.33% of the combination with two same sheets. The shear strength of combining thick upper sheet and thin lower sheet is 16.91% of the one with two sheets with the same thickness. Therefore, shear strength of the different sheets combination are stronger than that with duplicate sheets.
50
Shih, Po-Wen, and 施博文. "Studies on Process Parameter Characteristics in Hot-Die Forging of Titanium." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/30119034363364272540.
Анотація:
碩士國立成功大學
機械工程研究所
82
In this study, the hot-die forging process of ring and cylinder of Ti-6Al-4V was experimented. The software with thermalcoupled visco-plastic finite element method was applied to simulate those process. The effects of die temperature, billet temperature and deformation rate on the forging load and metal flow were investigated. Billet of hot-die forging exhibits large gradient of temperature distribution. Since the temperature has significant effect on the flow stress of Ti-6 Al-4V, the technique to compensate for history effects in the simulation of hot-die forging process was used. In the study of ring compression test, traditional calibration curve of constant shear friction coefficient can not exactly define the value of coefficient for hot-die forging process, since the non- uniform deformation of billet resulted by die chilling at initial stage was observed. The temperature distribution of billet depends mainly on the deformation time in cylinder compression test, and result in the variation of flow stress and forgiability.In the case of ring or cylinder compression test, however, in the same billet temperature the load increases with the decreasing die temperature. Temperature is the most important one of the hot-die forging process parameters. In the FEM simulation for forging process of axisymmetric disc it also shows that the higher forging temperature is, the lower forging load will be.