Dissertations / Theses on the topic 'Bolt-on'

This degree project is a verification of a hand made calculation made by Semcon CAE inGothenburg, Sweden. The main purpose has been to investigate how loads in a pre-tensionedbolt appear and how material displacement and contact pressures in the nuts affect bolt joints.A FEM-model has been created to imitate the reality as much as possible this to verifySemcon’s calculations. The result of the FEM-model has been compared with the result fromSemcon report 87-082-008, see appendix 2. Thus the Semcon original report has beenverified.The results between the Semcon report 87-082-008and the FEM calculations can be seen inchapter 2 and appendix 1.The basic data of the degree exam is the Semcon report and is the starting point of the wholeproject. All data regarding dimensions, geometry, materials and so on is based on the datafrom the Semcon report.A fatigue analysis based on the FEM-results was not conducted. This was due to thesimilarities in result between the previous Semcon report and this study

This dissertation presents the results of testing to determine the load-slip characteristics of single-shear single lag screw connections subjected to monotonic lateral loading parallel to grain. Of particular importance was the comparison of experimental capacity and 5% offset yield load resistances to load resistances as predicted by the American Forest & Paper Association's (AF&PA) publication General Dowel Equations for Calculating Lateral Connection Values, Technical Report 12 (TR-12). Additionally some other tests were conducted, including fracture, tension strength perpendicular-to-grain, lag screw connection inking, dowel embedment, specific gravity and moisture content. The results for the testing program are presented. Four hundred and forty eight lateral tests were conducted on lag screw connections. Each connection was comprised of a 2 x 6 x 14 in. long wood main member, 1/4 in. thick steel side plate, and a single lag screw. The parameters of interest were specific gravity, lag screw diameter, and pilot hole diameter. Two species of wood, Douglas-fir and spruce-pine-fir, three lag screws diameters, and three pilot hole diameters for each species of wood were implemented. Models were developed to predict lag screw connection capacity and 5% offset yield and are contained herein. Models were based on results from connection and inking tests and mechanical analysis. Recommendation for ASD and LRFD design values were derived from connection test results for connections that used AF&PA's National Design Specification for Wood Construction (NDSb) specified pilot holes. Using fracture mechanics results, work was performed to determine the effective load required to crack and separate fracture surfaces of wood main members due to the installation of lag screws with varying pilot hole diameters.
Ph. D.

Les assemblages à brides boulonnées munis de joints d’étanchéité sont les systèmes de raccordement les plus répandus entre les différents éléments des réservoirs sous pression. Ils sont largement utilisés dans l'industrie chimique, pétrochimique et nucléaire. Ce sont des structures simples et des assemblages démontables. Ce qui les rend plus attractifs pour connecter des équipements sous pression et la tuyauterie. En plus des risques de fuite, ils ont besoin de maintenance en cours de fonctionnement au cas où les boulons doivent être resserrés ou dévissés pour être remplacés. Bien que les arrêts de fonctionnement coûteux soient à éviter, l’entretien en fonctionnement expose l'opérateur à un risque potentiel, car le desserrement d’un boulon peut produire un déséquilibre de la contrainte de compression sur le joint d’étanchéité entraînant un contact local du joint d’étanchéité en dessous d’une certaine valeur critique, provoquant une fuite majeure et de ce fait pouvant mettre en péril la vie de l'opérateur. Cette proposition aborde la question de la variation de la déflexion du rebord de la bride afin d'enquêter sur le déséquilibre de la contrainte de compression dans le joint lorsque les boulons sont soumis à une modification de charge en fonctionnement. Cette étude peut être utilisée pour aider à limiter l'augmentation de la charge de serrage ou le nombre maximum de boulons qui doivent être remplacés en même temps et identifier les boulons qui ne peuvent pas être remplacés en service. L'objectif de cette étude est de développer une approche théorique pour identifier et analyser les effets de la charge précontrainte et de la pression sur les assemblages à brides boulonnées afin d’obtenir l'espacement optimal entre les boulons en fonction de la variation de la contrainte de compression sur le joint d’étanchéité. Notre recherche comprend trois parties. La première partie qui est une méthode analytique basée sur la théorie de la poutre circulaire reposant sur une fondation élastique linéaire, sera développée pour prédire la distribution circonférentielle de la contrainte de compression sur le joint d’étanchéité. Des modèles éléments finis de brides boulonnées symétriques seront créés pour valider cette analyse. Une comparaison des résultats d'études antérieures est nécessaire pour valider la solution analytique linéaire. Ensuite, la deuxième étape de cette recherche consiste en une approche qui a été construite à partir de la théorie de l'anneau sur le comportement d’une fondation non linéaire élastique, permettant d’obtenir des résultats plus précis. La solution non-linéaire doit être validée avec une analyse par la méthode des éléments finis. Dans la troisième partie, un modèle de régression linéaire pour des brides boulonnées sera proposé pour une procédure de calcul d’espacement de boulons. Ce travail aidera les services techniques sur la conception, la maintenance et l'exploitation des réservoirs sous pression et systèmes de tuyauterie.

The aim of this thesis was to investigate the effect of clearance and tolerance in bolted joints when there is a mismatch between the bolt holes. A parametric study with seven different cases was analyzed in this project; four double bolt configuration and three triple bolt configuration, with variation of the size of the bolt hole misalignment, the diameter of the bolt and the thickness of the plates. All analyses were performed with the aid of the FEM commercial software Abaqus, all the models were modelled with 3D brick elements. Despite bolted connections being subject of several investigations, no study about this matter for structural engineering purposes had been performed before. The results indicate that for connections with a low number of bolts a misalignment of the bolt clearance can cause a serious reduction in the ultimate bearing capacity of a joint and it indicates that the Eurocode 1993 1-8 might be overestimating the ultimate bearing capacity for some cases.

In health economics benefits are often measured in terms of quality adjusted life years (QALYs), an index that combines the length of life and the health related quality of life (HRQoL) of patients. HRQoL is usually estimated using generic preference based measures (GPBMs). To ensure comparable decisions it would be recommended to use only one GPBM in all assessments, but this is not always appropriate due to validity and responsiveness problems of these measures. When this happens, bolt-ons represent a potential solution. Bolt-on research is at an early stage, and the process of how to identify and select bolt-ons is still unclear. To address this gap, this thesis examines methods for identifying and selecting bolt-on dimensions, using the EQ-5D as a case study. This thesis summarizes the results of four studies. The first study examined the performance of the 5 most commonly used GPBMs across all disease areas and conditions, using an overview of systematic reviews. The second study investigated the possibility of using factor analysis techniques to identify bolt-on dimensions. The third study explored whether it is possible to select between bolt-ons using their ability to predict differences in HRQoL. The fourth study examined whether it is possible to select between bolt-ons using preferences elicited from pairwise choices over health states. A number of important findings were made. First, GPBMs appear generally valid and responsive across many disease areas, but the quality, nature and breath of evidence makes difficult to draw definitive conclusions. Second, factor analysis techniques can be used to identify bolt-on dimensions. Exploratory and confirmatory factor analysis need to be used in conjunction. Third, bolt-ons differ in their ability to predict differences in HRQoL and for this reason they might be selected based on this information. Fourth, bolt-ons differ in terms of their impact on preferences and for this reason they might be selected based on this information. Overall, a key contribution of this thesis is to systematically examine methods for identifying and selecting bolt-ons for generic preference based measures.

Much previous experimentation related to wood structures has employed monotonic loading to replicate static situations. However, instances of natural hazards have raised interest in the response of structural connections to dynamic loads. This increased interest led the Consortium of Universities for Research in Earthquake Engineering (CUREE) to develop a testing protocol for reverse-cyclic loading, which involves cycling loads through zero in order to test specimens in both tension and compression. With the CUREE testing protocol in place, recent research has been devoted to understanding the effects of reverse-cyclic loading on multiple-fastener connections. Experimentation by Heine (2001), Anderson (2002), Billings (2004) and others contributed to a better understanding of bolted connection behavior under reverse-cyclic loading. However, some questions remained. Billings was unable to consistently produce yield modes III and IV, meaning that her suggested bolt spacing of seven times the bolt diameter (7D) could not be applied to connections subject to these yield modes without further testing. In addition, the work of Anderson and Billings raised questions regarding the proper measurement of bending yield strength in bolts and the relationship between the bending yield strength and the tensile yield strength. These topics are each addressed by this project and thesis report. Results of the connection testing presented in this report can be used in conjunction with the work of Anderson and Billings to critically evaluate the 4D between-bolt spacing recommended by the National Design Specification (NDS) for Wood Construction (AF&PA, 2001). Results of the bolt testing provide a supplement to the search for a reliable method for the measurement of bending yield strength in bolts.
Master of Science

Tumbling mills describe a class of mechanical systems defined by a cylindrical chamber filled with balls and/or rocks that rotate around their own longitudinal axis. Due to the action of charges, the lifters/liners wear significantly and their shape will be changed which will influence the efficiency of the mill. Liner bolts are the mill components which connect the mill interior with the exterior environment. With this property, bolts have been paid more and more attention. The first part of the thesis covers the structural analysis of the lifter/liner bolts, and the possibility for on-line charge motion measurement with the aid of bolts is discussed by comparing the strain distributions at the bolt areas where the bolts occupy different mill circumferential positions. In order to measure the lifter/liner wear, a real-time, on-line wear sensor was developed by the Comminution Dynamics Laboratory. However, the positioning of the sensor/sensors affects the strength of the mill is unknown. The second part of the project provides detailed research on this issue by FEA analysis so as to provide a basis for the practical application of this kind of sensors. Finally, during the grinding process of tumbling mills, some mills can vibrate greatly at some ranges of mill rotating speeds and as a result the mills cannot work properly because of this vibration or resonance. With six different mill models, the final part of the thesis investigates the mill natural frequencies and their modes by FEA and furthermore, explores the effect of mill diameter, length on these frequencies and modes.

The industry is moving towards a higher degree of automation and connectivity, where previously manual operations are being adapted for interconnected industrial robots. This thesis focuses specifically on the automation of tightening applications with pre-tightened bolts and collaborative robots. The use of 3D computer vision is investigated for direct localization of bolts, to allow for flexible assembly solutions. A localization algorithm based on 3D data is developed with the intention to create a lightweight software to be run on edge devices. A restrictive use of deep learning classification is therefore included, to enable product flexibility while minimizing the computational load. The cloud-to-edge and cluster-to-edge trade-offs for the chosen application are investigated to identify smart offloading possibilities to cloud or cluster resources. To reduce operational delay, image partitioning to sub-image processing is also evaluated, to more quickly start the operation with a first coordinate and to enable processing in parallel with robot movement. Four different hardware architectures are tested, consisting of two different Single Board Computers (SBC), a cluster of SBCs and a high-end computer as an emulated local cloud solution. All systems but the cluster is seen to perform without operational delay for the application. The optimal hardware architecture is therefore found to be a consumer grade SBC, being optimized on energy efficiency, cost and size. If only the variance in communication time can be minimized, the cluster shows potential to reduce the total calculation time without causing an operational delay. Smart offloading to deep learning optimized cloud resources or a cluster of interconnected robot stations is found to enable increasing complexity and robustness of the algorithm. The SBC is also found to be able to switch between an edge and a cluster setup, to either optimize on the time to start the operation or the total calculation time. This offers a high flexibility in industrial settings, where product changes can be handled without the need for a change in visual processing hardware, further enabling its integration in factory devices.
Industrin rör sig mot en högre grad av automatisering och uppkoppling, där tidigare manuella operationer anpassas för sammankopplade industriella robotar. Denna masteruppsats fokuserar specifikt på automatiseringen av åtdragningsapplikationer med förmonterade bultar och kollaborativa robotar. Användningen av 3D-datorseende undersöks för direkt lokalisering av bultar, för att möjliggöra flexibla monteringslösningar. En lokaliseringsalgoritm baserad på 3Ddata utvecklas med intentionen att skapa en lätt mjukvara för att köras på Edge-enheter. En restriktiv användning av djupinlärningsklassificering är därmed inkluderad, för att möjliggöra produktflexibilitet tillsammans med en minimering av den behövda beräkningskraften. Avvägningarna mellan edge- och moln- eller klusterberäkning för den valda applikationen undersöks för att identifiera smarta avlastningsmöjligheter till moln- eller klusterresurser. För att minska operationell fördröjning utvärderas även bildpartitionering, för att snabbare kunna starta operationen med en första koordinat och möjliggöra beräkningar parallellt med robotrörelser. Fyra olika hårdvaruarkitekturer testas, bestående av två olika enkortsdatorer, ett kluster av enkortsdatorer och en marknadsledande dator som en efterliknad lokal molnlösning. Alla system utom klustret visar sig prestera utan operationell fördröjning för applikationen. Den optimala hårdvaruarkitekturen visar sig därmed vara en konsumentklassad enkortsdator, optimerad på energieffektivitet, kostnad och storlek. Om endast variansen i kommunikationstid kan minskas visar klustret potential för att kunna reducera den totala beräkningstiden utan att skapa operationell fördröjning. Smart avlastning till djupinlärningsoptimerade molnresurser eller kluster av sammankopplade robotstationer visar sig möjliggöra ökad komplexitet och tillförlitlighet av algoritmen. Enkortsdatorn visar sig även kunna växla mellan en edge- och en klusterkonfiguration, för att antingen optimera för tiden att starta operationen eller för den totala beräkningstiden. Detta medför en hög flexibilitet i industriella sammanhang, där produktändringar kan hanteras utan behovet av hårdvaruförändringar för visuella beräkningar, vilket ytterligare möjliggör dess integrering i fabriksenheter.

Business has seen tremendous growth through internationalization over the last several decades.  As  one  of  the  strategies  for  companies  to  internationalize,  acquisition  has since then been a well-studied subject. Various steps have to be gone through in order to  acquire  a  company.  Afterwards,  companies  need  to  take  different  measures  to ensure  the  success  of  the  acquisition.  Culture  is  usually  considered  as  the  most important  aspect  which  determines  post-acquisition  success.  The  purpose  of  this master dissertation is to thus investigate company’s internationalization via acquisition regarding    the    pre-acquisition    decision-making    and    post-acquisition    cultural management. The  theoretical  framework  consists  of  literature  of  pre-acquisition  decision-making process and post-acquisition culture management. These theories are put together in an analytical  model  where  possible  connections  are  intended  to  achieve.  It  will  also  be used as a foundation in gathering and analyzing the empirical data.   In  a  qualitative  approach,  the  empirical  data  was  gathered  through  semi-structured interview with the president of Getinge International Group. These findings were also complemented with secondary data such as corporate websites, documents and various scientific articles. The findings of the study show that planning, evaluating, negotiating, making the deal and    integration    are    the    five    essential    steps    concerning    the    process    of internationalization  through  acquisition.  The  authors  find  out  that  identifying  of acquisition  candidates  is  not  necessarily  a  part  of  pre-acquisition  as  the  theory  may suggest.  The  distinction  between  bolt-on  and  platform  acquisition  is  of  critical importance to determine the different criteria and procedure certain company is going to take. This proves to be much more practical, where theoretical support has not been fully established. Both national and corporate cultures are of crucial importance for the success of company’s post-acquisition culture management. According to the finding of this research, two factors seem to link pre and post acquisition process; one is the planning of how future organization is managed; the other is the appropriate choice of managing director.

Finding ways to objectively measure welfare within different sectors of the beef industry is necessary to continually improve cattle welfare from birth to slaughter. The first objective of Study 1 was to benchmark cow-calf producer perspectives on management strategies and challenges that ultimately affect cattle welfare on ranches in the United States. The second objective of Study 1 was to quantify how producers are marketing their calf crop, their priorities when selecting replacements, and if producers saw value in handling and care guidelines. A total of 1,414 responses from cow-calf producers in 44 states were collected through a survey done in partnership with BEEF Magazine. Thirty questions were asked of producers to gather demographic information, producers’ current handling and health management practices, and how they prioritized industry challenges. As well as establish at what age and through what avenue producers are marketing their calf crop, and gauge producer perspectives on a quality assessment outlining handling and care guidelines.

After analyses of producer responses, it was concluded that the frequency of management methods and decisions are impacted by age, operation size, location, and BQA certification. A higher percentage of respondents who were BQA certified used electronic eartags, followed by freeze branding. A higher percentage of respondents not BQA certified used basic eartags and hot branding. 74.5% of respondents were preconditioning their calf crop. A higher percentage of respondents were preconditioning their calf crop that were BQA certified, than those who were not BQA certified. The most important beef industry challenge identified was cow-calf health and the biggest challenge to producer’s own operation was identified as land availability/price. The most important animal health issues on producers’ operations were identified as Bovine Respiratory Disease, flies, Pinkeye, and reproductive health. By producer age, calf/neonate health was identified as the biggest challenge for respondents under the age of 30. Respondents age 55-70 responded that Veterinary Feed Directive (VFD)/regulations was more of a challenge than any other age group. Respondents with 50 head or less or more than 1,000 head more frequently retained their calf crop through finishing and respondents with 51 to 200 head and 201 head to 500 head more frequently backgrounded and then sold their calf crop. 13.5% of respondents answered yes, a veterinarian had offered to administer a drug for pain management when castrating or dehorning. Of those 13.5% who responded yes pain management had been offered, 54.55% of respondents chose to use a pain relief method. A higher percentage of producers that precondition also indicated that they use a pain relief method when castrating or dehorning more frequently, though it was still a low percentage. Overall, 46.3% of respondents saw value in handling and care guidelines and 54.9% of respondents saw value in a program including source and age verification, a vaccination plan, and handling and care guidelines. Respondents who were BQA certified, had a beef cow inventory of 501 to 1,000 head, who preconditioned their calves and backgrounded them before selling, and who lived in the West more frequently saw value in a quality assessment outlining handling and care guidelines.

The objective of Study 2 was to examine the effects of captive bolt length and breed type on post-stun leg activity in cattle. A total of 2,850 Holstein (HOL) and non-Holstein British/Continental bred (NHOL) steers and heifers were observed post-stunning at a large commercial slaughter facility. A penetrating pneumatic captive bolt stunner was used with three different bolt lengths: CON, 15.24 cm; MED, 16.51 cm; and LON, 17.78 cm. Hind limb kicking, forelimb activity, take away belt stops, carcass swing and number of knife sticks during exsanguination were recorded for each animal from video recording. Hind limb and forelimb kicks observed ranged from 0 to 25 and 0 to 8, respectively. A significant main effect of treatment, breed type and an interaction between treatment and breed type on hind limb activity was found. Analysis of post-stun hind limb and forelimb activity indicated that increasing pneumatic captive bolt length does not decrease post-stun leg activity but alternatively can increase kicking when using the longest bolt tested in particular types of cattle, i.e. Holsteins. Other parameters associated with the shackling and hoisting process were impacted by breed type as well. There was a higher percentage of cattle experiencing take away belt stops and carcass swing in HOL as compared with NHOL. (Abstract shortened by ProQuest.)

Full scale field trials, carried out during the construction of the Penmaenbach Tunnel in North Wales, have shown that two-speed resin bonded rock bolts are resilient to close proximity blasting. Fully grouted 6m long rock bolts, installed within 0.7m of the tunnel face, have shown no significant signs of distress or failure. Instantaneous loads of up to 40% of the characteristic strength of the bolt were observed together with average residual load losses of 5% of the working load, which compares favourably with the acceptable tolerance of 10% working load stipulated by current practice. Analysis has also shown that rock bolts with low prestress sustain greater vibrations and proportionately higher dynamic load changes during blasting. However, bolts with relatively high prestress loads sustain greater induced loads. Empirical relations have been established to describe rock bolt behaviour in terms of induced vibration and scaled distance. In particular, a predictive equation relating dynamic load changes in the experimental rock bolts to scaled distance, is presented. Calculations based on approximate bolting costs have indicated that cost savings of up to 38% of the total bolting cost could have been effected if the results of this work had been implemented at the design stage. Physical modelling work has confirmed that the distribution of loads in the fixed anchor of a resin bonded bolt are non-linear when both static and impulsive loads are applied to the bolt head. Corroboration of the field results has also been established with respect to the significant influence of initial prestress load on dynamic load change. Complementary finite element modelling work has successfully predicted fixed anchor load distributions under static and dynamic loading conditions. Attempts to establish a detailed relation between distance from blast, magnitude of charge and change in residual load, for low to medium capacity rock anchorages on the West Portal of the tunnel, were thwarted by the poor performance of instrumentation with respect to temperature sensitivity. However, a simplistic approach to analysis has enabled the establishment of a tentative predictive relationship.

Understanding the true behaviour of impacted structures is the only way to assess their robustness under exceptional events such as vehicle collision. The primary objective of this master’s thesis was to perform a finite element parametric investigation on the influence that some parameters have in steel buildings subjected to vehicle impacts. The parameters chosen for the study, involved uncertainties in the material definition and in the load configuration of the bolts used in the impacted column end-connections. By using the Abaqus software, a finite element model of the structure has been created. The five storey steel building considered has been modelled in a simplified manner with the exception of the impacted area which, instead, has been defined in a more detailed fashion. During the simulations, different preload conditions have been used, comparing cases with and without the preload force. Regardless its variation, it has not been observed any increase in the structural resistance. On the other hand, the simulation provided interesting results for what concerns the material variations in the bolts. Although the changes have been small in magnitude, the effect on the structural response during the impact was remarkable. For all the cases considered, an increase of the material ductility, achieved by increasing the ultimate strain at failure, entailed higher resistance of the connections. Various failure modes have been observed when the material properties have been changed. Having clarified the influence of the assumptions made, the results provided helpful information in sight of future studies. Although the model still needs to be validated, the research clarified which of the parameters investigated are to be collected with more attention. Keywords: Vehicle collision, steel building, FE model, Abaqus/Explicit, parametric investigation, bolt preload, bolt material.

Bolted joints are integral parts of mechanical systems, and bolt preload loss is one of the major failure modes for bolted joint structures. Understanding the damping and frequency response to a varying preload in a single-bolted lap-joint structure can be very helpful in predicting and analyzing more complicated structures connected by these joints. In this thesis, the relationship between the bolt preload and the natural frequency, and the relationship between the bolt preload and the structural damping, have both been investigated through impact hammer testing on a single-bolted lap-joint structure. The test data revealed that the bolt preload has nonlinear effects on the structural damping and on the natural frequency of the structure. The damping ratios of the test structure were determined to increase with decreasing preload. An increase in structural damping is beneficial in most engineering circumstances, for it will reduce the vibrational response and noise subjected to external excitations. It was also observed that the modal frequency increased with increasing preload, but remained approximately constant for preload larger than 30% in the bolt yield strength. One application for studying the preload effect is the detection for loose bolts in structures. The possibility of using impact testing for estimating preload loss has been confirmed, and the modal damping was determined to be a more sensitive indicator than the natural frequency in a single-bolted lap-joint structure.

Block shear is a limit state that should be accounted for during the design of the steel tension members. This failure mechanism combines a tension failure on one plane and a shear plane on a perpendicular plane. Although current design specifications present equations to predict block shear load capacities of the connections, they fail in predicting the failure modes. Block shear failure of a structural connection along a staggered path may be the governing failure mode. Code treatments for stagger in a block shear path are not exactly defined. A parametric study has been conducted and over a thousand finite element analyses were performed to identify the parameters affecting the block shear failure in connections with multiple bolt lines and staggered holes. The quality of the specification equations were assessed by comparing the code predictions with finite element results. In addition, based on the analytical findings new equations were developed and are presented herein.

Recycling of plastics always plays an important role in keeping our environment better and safe. With the rise in usage of plastics and industrialization, the need for recycling the plastics has become a big business and is getting bigger. This thesis work was done for a company called Rapid Granulator AB, which works with the recycling of plastics as a big trade in Sweden. Like all the industries across the globe are trying to be economical in every way, Rapid Granulator AB wanted to develop an economical design of their high quality granulating knife. For achieving the economical design, they wanted to study the behaviour of the rotating knife during the process of producing plastic granules. The granulator cutting process was simulated and numerical analysis was done on the rotating knife of a plastic granulator machine by using the finite element code ABAQUS with 3D stress elements to find out the critical stresses and forces acting on the rotating knife. The bolt preload was applied by Abaqus/Standard, and the results of implicit analysis were imported to Abaqus/Explicit for the impact analysis where the flow of stresses on the rotating knife during the impact with materials were simulated and studied. The study was done on knife models of different thickness to see if the thickness of the current knife model can be reduced. Analysis were done also on a knife model assembly with a double sided cutting edge knife to see if the knife model can be used to its full extent. The simulation models and analysis results were given to the company to develop a more economical knife model.

碩士
高苑科技大學
機械與自動化工程研究所
100
Hexagonal flange bolt is the second popular bolt in usage compared to hexagonal bolt. It has been generally used in the parts assembly for automotive and motorcycle industries. The advantages are as below: the bearing surface area gets bigger after locking, the clamping force gets distributed, and the stability of the clamping part is higher. The study is mainly to improve the traditional cold multi-stage forming of hexagonal flange bolt, with a view to reaching the goal of near-net-shape forming the forming method of each pass to produce hexagonal flange bolt without flash is replanned. Tool life can be extended, the production costs can be saved, and the product competition can be enlarged. The “SolidWorks” and “Deform 3D” software under condition of the constant shear friction are used to design and simulate the optimal forming process, the forging force loading of each pass, the effective stress, effective strain, the velocity field, and appearance dimensions for each pass can be analyzed, besides an actual experiment is performed to compare with the appearance dimensions of FEM to verify the feasibility of simulation for FEM analysis. The simulation and experimental results show that the near-net-shape forming for hex flange bolts is feasible. Comparing to the traditional way, the new forming method reduces material loss 7%, no flash is generated, 15% percentage of the forging load is reduced, the die life is improved, the production equipment maintenance cost is decreased, furthermore the product quality is improved and the competitiveness is promoted.

碩士
國立臺北科技大學
製造科技研究所
101
In this study, the joint is presented for the screw under axial load. As the load and different boundary conditions, the screw will have non-uniform stress or stress concentration problem of a particular few teeth. Therefore, the screw will have local damage and service life be reduced. According to material deformation and stress theory, the study appropriate modify the gap of screw. Let the place contact with the force in first where stress distribute smaller than another part. On the contrary, let the place that has a little gap to contact with the force in second where stress concentration, by this way, the life of the screw will be added. The stress distribution of the contact part of the thread root was analyzed by ANSYS/Workbench. Finally, the balance indicators of stress have been established as the reference of screw stress distribution.

碩士
國防大學理工學院
兵器系統工程碩士班
100
ABSTRACT The purpose of this study is to create a simple approach to obtain optimum design for T91 rifle using Solid Works CAD and ADAMS software. First, the problems are identified by reviewing literature. Next, T91 rifle model is built in Solid Works CAD software according to actual size. Third, the created model is transferred into a new model for ADAMS software. The parameters of components of T91 rifle and Heydenreich experience function are also embedded in ADAMS software. Finally, by means of simulating, some critical parameters for designing T91 rifle are obtained. These parameters are verified to be approximate to T91 rifle by compare with the design data of T91 rifle. Therefore, the approach created here is verified to be available. In addition, the approach created here is also demonstrated to be able to save duration and cost of R＆D and reduce the risks of tests with live ammunition. Keywords: ADAMS mechanism dynamic simulate and analyze, postprocessing, automatic weapon, interior ballistic, SolidWorks computer aided design

碩士
國立高雄大學
化學工程及材料工程學系碩士班
101
Torque control bolt is the most common and important fastener in structural steel industry. Torque is often considered as a standard to determine whether the fastener is locked or not. Therefore, a stable torque can ensure that if the fastener is in its service properly or not. Furthermore, it can increase the safety by preventing fastener from breaking or loosing while the fastener is locked too tight or too loose. This study selected the 10B33 torque control bolt as the experimental material. After quenching and tempering, the torque value was measured and broken surface was analyzed by the torque testing machine. The Rockwell hardness tester was adopted to test the hardness of each specimen with different tempering conditions. According to the combination of results, including torque, hardness and the microstructure, the effect of tempering on the properties of 10B33 torque control bolt could be totally clarified. The experimental results showed that the higher tempering temperature is the lower torque value. The soaking time of tempering exhibited a similar result as tempering temperature. The longer time caused a lower torque value. There was also found that when the tempering temperature was fixed the longer soaking time could stabilize the torque value. In other words, the deviation of torque value was getting smaller and smaller. Besides, torque, hardness and tensile strength were proportional to each other. Nevertheless, the torque was inversely proportional to ductility and toughness. On the basis of the microstructure, when the ferrite content increased significantly then the microstructure became more homogeneous either with the higher tempering temperature(467℃, 487℃, 507℃) or the higher soaking time(85minutes, 95 minutes, 105 minutes). This phenomenon had a positive influence on the mechanical properties.

碩士
國立高雄第一科技大學
機械與自動化工程研究所
101
Abstract The study aims at hexagonal flange vehicle bolt to carry out the design development of mold and dies. The four-stage forming has been considered, and two forming methods have: (1) open die forging (case 1), at the last flange trimming, the flash is occurred; (2) closed die forming (case 2 and case 3), the net shape forming is taken into account, no flash is occurred with direct flange forming. The forming characteristics for both methods have been evaluated, considering three cases the net shape forming (case 3) is finally chosen to do the design of mold and dies. In this study, the multi-stage forging analysis of hexagonal flange vehicle bolt can be simulated by three-dimensional rigid-plastic finite element method. Using the SolidWorks drawing software to conduct the dies and the work-piece, the DEFORM 3D finite element software can be used to simulate and analyze assuming constant shear friction; the effective stress, the effective strain, the velocity field, the forging force and the shape dimensions of fastener can be obtained. Moreover, the stress of dies and forging stream line can be analyzed using DEFORM 3D. From the analysis results to realize the bearing stress of dies fasteners for each stage, the failure of mold and dies. Finally, the dimensions of products have been compared to verify the applicability of the FEM simulation analysis. The research results show the flash loss in case 3 of closed die forging is reduced, the forging force 6,057kN is lower than 6,107kN in case 1 of open die forging. The improvement of die stress in case 3 is better than case 2, The maximum error of dimensions is 2.43 % for case I, 1.91% for case 2, 1.23% for case 3. Therefore, the mold and dies of net shape forming in case 3 can reach the forming requirement of hexagonal flange vehicle bolt. Keywords: Hexagonal flange vehicle bolt, Net shape forming , Die stress, Forging force.

碩士
高苑科技大學
機械與自動化工程研究所
103
Originating in 1969, the Taiwan fastener industry has existed for 45 years. A wide variety of fasteners are produced, including those for the automobile industry, household electrical appliances industry, architectural engineering, and even the aviation industry. The effects of the high-tensile bolt dephosphoring process on the entire fastener manufacturing process and its organizational characteristics and mechanical properties are analyzed and discussed in this study. Our experimental results reveal that the bolt dephosphoring process must be completed before heat treatment, which can be confirmed with a dephosphoring reagent or metallographic observation. Once bolt heat treatment is completed, bolts without dephosphoring appear to be coated with δ ferrite (delta ferrite) composed of a phosphate coating and a phosphatizing coating, which are not easily removed. Heat treatment with phosphorus results in grain boundary segregation, causing embrittlement and a reduction in lattice bonding forces and resulting in a high risk of fracturing when bolts are used in high-temperature environments or undergo multiaxial stresses. The results could be used as a reference for manufacturers of high-tensile bolts so as to reduce the risk of delayed fractures in fasteners.

碩士
逢甲大學
土木工程學系
107
Because the traditional seismic design code cannot bear the damage brought by devastating earthquakes, in addition to keeping the houses from being destroyed by earthquakes, what an earthquake protection technology shall focus on and pursue is the safety of the articles in buildings. Hence, the development and progress of the earthquake protection technology is even more important. The earthquake protection of the structures mainly takes the passive control technology, which can be divided into two major categories of seismic isolation and energy dissipation. Building upon the works of the predecessors, we continued researching and reforming, and have made an innovative development of the earthquake protection technology that is different from those in the past, enabling this technology to be applied to structures more commonly. Because the material used by most dampers is the structural steel of integrally forming, the research utilized the method of screw bolt to connect the aluminum alloy substrate with the energy dissipation bar. Via the test results, we learned that the damper’s energy absorption effect would be affected by the tolerance between the bolted joints if we used the all direction damper connected by the screw bolts. Our suggestion is not to use the bolted joint as the connection method of the damper substrate and the energy dissipation bar. If you really need to use the method of screw bolt to connect them, you can use the material of same properties as the energy dissipation bar to do the welding.

碩士
國立高雄應用科技大學
模具系碩士在職專班
104
In this research, it focuses on the washer roundness of Hexagon washer bolt. The company of product is our main product. Because of material cost, the material diameter were divided into 8.5 9.5and 10.5mm in three parts. For identifying the difference on washer roundness, we use 10.5mm to analyze product by DEFORM and improve the problem . The study for the effects of difference diameters. Adopting the extrusion method to find the relation between Percentage of area reduction and load are in direct proportion on first stage. The heading stress at second stage, which is concentrated on the head. The load will reduce by 1.4%~11.9% through the change of head thickness. The pre-forming at third stage, which is important process to directly impact the appearance of product. In this study, the key to shortage of washer roundness in the pre-forming. The height of pre-forming Hexagon must be higher than final product at 55%. finally, we find out the washer of product is close to circle.

碩士
國立勤益科技大學
機械工程系
106
Precision locked nut is an indispensable part of the ball screw and the precision high rotating spindle. If the ball screw or the precision high rotating spindle bearing is not subject to axial force preloading, the ball in the bearing will slide so that the bearing inner ring track and the outer ring track will cause greater friction. However, the high temperature will generate under long-time rotation or high-speed rotation; the temperature rise will affect the overall precision and life of the machine tools or special machine. When the precision locked nut was locked on the bearing by a proper axial force preload, the balls in the bearing will roll between the inner ring track and the outer ring track of the bearing so that is reduce the sliding friction and causing a lesser temperature rise. Machine tools or special machines will cause vibration during heavy cutting and the bearing temperature to rising, after a long period of vibration, the tightening force of the precision lock nut may be reduced, which indirectly affects the bearing's pre-axial force. The temperature rise will reduce the axial force of the ball screw or the precision high rotating spindle. An experiment is simulate by simulating a real dynamic testing machine, and the characteristic equation of temperature rise prediction was established. In addition, Taguchi method design experiments are conduct to investigate the installation of precision lock nut under different conditions, to reduce the effect of temperature rising on the reduction of axial force. In this study, the quality characteristics are axial ratio of temperature rise, temperature after bearing testing, axial displacement, ratio of axial force and ratio of anti-loosening torque. The control factors are the fit clearance of the thread, the viscosity of the lubricant, and the bearing contact angle. The best quality characteristics were obtain through the Taguchi method.

碩士
國立臺灣科技大學
營建工程系
105
In this study, the behavior of single Hollo-bolt and steel column joint is discussed. This thesis also includes bolt material test, sleeve material test, Hollo-bolt pre-tension test, Hollo-bolt direct tensile test, Hollo-bolt direct shear test, Hollo-bolt holes bearing test and steel tube connection joint test. The experimental results show that: (1) The applied tightening torque of Grade 8.8 Hollo-bolt is the same as that of Grade 8.8 high-strength bolt. The pre-tensioning force of Grade 8.8 Hollo-bolt can only reach 29% to 75% of the specified value in the provision. The applied tightening torque of Grade 10.9 Hollo-bolt is lower than that of Grade 10.9 high-strength bolt. The pre-tensioning force of Grade 10.9 Hollo-bolt can only reach 18% to 38% of the specified value in the provision. In addition, the direct tensile test and direct shear test show that the Hollo-bolt slips earlier than high-strength bolts. This result indicates that the pre-tensioning force of Hollo-bolt is lower than that of high-strength bolts. (2) The pre-tensioning force of Hollo-bolt cannot reach the value which is specified in the provision. For joint design, the use of slip-critical connection is not recommended. (3) The failure mode of Hollo-bolt direct tensile test is sleeve leg fracture. To evaluate the tensile strength of Hollo-bolt, the tensile strength formula of high-strength bolts should not be used. In this study, an equation is proposed to evaluate the tensile strength of Hollo-Bolt. The proposed strength reduction factor is 0.63. (4) To evaluate the shear strength of Hollo-bolt, it is recommended to assume the shear plane cuts through the sleeve and the strength reduction factor of 0.7 is used in the calculation. (5) To evaluate the hole bearing strength of Hollo-bolt, the clear end distance of 1.53 times the sleeve diameter is recommended to be used for the calculation of the bearing strength upper limit. (6) When Hollo-bolt is used together with rubber washer, the thickness of the connection plate should be greater than 8 mm to avoid the bolt head failure mode. (7) When torque is applied to Hollo-bolt, metal washer is not necessary to be tightly fixed with a wrench. To have metal washer tightly fitted with the steel plate, force is applied to the bolt head. In addition, it is noted that rubber washer should not be outside the bolt hole.

碩士
國立雲林科技大學
機械工程系
102
The deformations and stresses on the flange joint during the bolt clamping are related to the sequences of bolt tightening locations. The preload on the bolt is generated by the torque control method. Nonlinear finite element method is used to simulate the effects of bolt tightening sequences on the contact stresses between the gasket and joint as well the deformations of flange joint. 　　The commercial finite element software ANSYS is used to build the 3-D model of flange joint. The threads on both bolts and nuts are generated to consider the contact forces between threads. Various sequences of bolt tightening on the joint are simulated to compare the effects of the tightening sequences on the mechanical behaviors of the joint. Based on the simulated results, the optimal sequence can be chosen.

碩士
國立高雄應用科技大學
模具工程系
99
In this study, the size of the t-head bolt which used at automobile needs high-value precision. The t-head bolt are produced by multi-stage cold heading processes. Because the compression rate of head is pretty high during forging, in addition to work-hardening effect, the head is prone to surface crack and affect product strength. At current fastener industry, the design of forming die at fasteners is mainly used by trial-and-error experiences. This study utilizes t-head bolt as an example. Based on the theory of metal forming, and used the software Pro/Engineer to construct the geometry of billet, bolt and die. By using the software DEFORM-3D to analyze multi-stage cold heading processes of the t-head bolt, and then adopt Cockcroft and Latham's ductile fracture criterion to evaluate the workability of the t-head bolt after forming. We could predict timing and location of fracture at the t-head bolt, and compare with the actual results is good agreement. Finally, successfully designed the geometry of die which can reduce the damage value of the original process.

碩士
國立中山大學
機械與機電工程學系研究所
106
In this study, a 3D finite element PEMFC (Proton Exchange Membrane Fuel Cell) model has been built and performed the structural analysis, the commercial software ANSYS Workbench 15.0 was adopted in order to observe the effect of bolt pre-loading variation on the contact resistance and porosity of GDL (Gas Diffusion Layer) in PEMFC. The obtained values of contact resistance and porosity of GDL were substituted into the electro-chemistry simulation software Fluent 15.0 to investigate bolts locking sequence on the efficiency of PEMFC was discussed. In structural analysis, the 3D PEMFC model with the reactive area of 9cm2 had been established through 3D drawing software SolidWroks. The model includes membrane, catalyst layer, gas diffusion layer, flow channel plate, current collector and body plate which all elements were assembled by 8 pairs of bolt and nut. In order to apply bolt pre-loading on each pair of bolt and nut, the nuts were assumed to be constrained on xy plane and the ANSYS built-in function, bolt pretension, was adopted. Temperature effect do not consider in this study. In addition, in the order of bolt locking, the bolts are locked in eight times, so the boundary conditions of the model are changed; three different bolt locking sequences (diagonal symmetric lock, intermediate symmetric lock, and clockwise lock) were selected as the purposes of case studies. Different displacements and stress distributions on the inside layers of PEMFC model due to boundary condition changed in each sequence of the bolt locking. From the simulation results, the gas diffusion layer is subjected to the intermediate symmetric locking sequence would maximize the contact resistance and the porosity would be minimal; that lead to increase the ohmic loss as well as reduce the efficiency of PEMFC. Conversely, the diagonal symmetrical locking sequence performed the lowest contact resistance and the largest porosity, so the efficiency of PEMFC is better than the other two locking methods; it could increase the efficiency about 5% by compared with the clockwise locking sequence and about 10.8% by compared with the intermediate symmetrical lock sequence.

碩士
國立臺灣科技大學
機械工程系
99
This work studies tolerance analysis methods for the derived dimension of assemblies with double bolt-hole fits. The research starts from investigating the corresponding tolerance chains as the components are dimensioned by conventional or geometrical method. Then factor simulation method is used to analyze the tolerance of a derived dimension of the assembly. It is found that the number of iterations and computation time required in simulation can be significantly reduced by applying the combined factor method to the tolerance chains. Since analytical methods for the tolerance analysis of assemblies with double bolt-hole fits is not available, the data obtained from Monte Carlo simulation is used as the reference for comparison.

碩士
國立臺灣大學
森林環境暨資源學研究所
98
Generally, the tensile strength of wood is larger than that of compression strength in longitudinal direction. Because wood tissue could be damaged by metal connector or fastener, stress concentration always occurred at wood near the interface between wood and metal. This is the reason why the tensile strength value is almost close to or even lower than compression value in structural design. In previous reviews, pioneers usually solved many problems by finite element analysis (FEA) simulation and assumed that the wood was isotropic. However, the wood is a kind of anisotropic material rather than isotropic. In fact, it is orthotropic. In this study, a software called Solid Works2008 was used to find the results by FEA. The computer simulation is a tool that an assumed force can apply on a new type of bolt connection in order to reduce stress concentration. Douglas fir (Pseudotsuga menziesii) was selected as the wood member. The material of the bolt was common steel. In this computer simulation, steel was set as an isotropic material. In Cartesian coordinate, the x-direction was assumed in longitudinal direction of the wood. The y- and z-direction represented radial and tangential directions of the wood respectively. The total length of the member is 250 mm, and the width and the thickness are 60 and 12 mm. The hole is drilled in the central. The right side of the hole is a semicircle with 9.5 mm radius a, and the left side is a semiellipse with b mm semimajor axis (or with semiminor axis, if b<a). All the initial sizes are constant, but the length of the semi axis of the semiellipse is variable, so that the definition of the axis ratio R is b/a, where a is the radius of the semicircle. R is set starting from 0.75, and each model with an increment of 0.25 for R was built and analyzed. The applied load was a concentrated force of 980.67 N（100 kgf） on the metal bolt towards the left. The right side of the member would be fixed and could not be moved and there was no deformation or displacement at the end surface. The interface between the wood and the metal bolt was set to free. There was neither glue nor adhesive between them, so there was a clearance while the deformation and displacement happened. Friction was neglected, however. Compared with simulation results, it is evident that the distribution of stress is quite different between isotropic and orthotropic member. But stress concentration still exists in both models at same locations. To enhance the utilization of wood material, the good property of tensile strength of wood should be considered. But stress concentration around the hole will reduce this property. Adjusting the ratio of the axes of R can find a way to reduce the stress concentration. One of the concentrated stresses must be increased while another must be decreased whether the ratio increases or decreases. The simulation show that a good result can be obtained when the ratio R is about 1.2 to 1.25. In the experiment, strain gauges and the universal testing machine were used. Signals were measured and converted through the written computer program. Basically, some of the results are similar with computer simulations. While the applied load is constant, the value of strain at the tensile area by the bolt hole decreases with R increasing, and the value of strain at the compression area by the bolt hole increases with R increasing. However, there were some disadvantages for mechanism such as nodes of wood, grain. And the dimension of the models was too small (limited by the testing machine) that the disadvantages appeared obviously. Because of the small dimension, the scale of strain gauges was enlarged, so that a part of the results were not so accuracy.

碩士
大葉大學
機械工程學系碩士班
92
An experimental investigation of thermal contact resistance of aluminum foams (Al6061) was conducted. The aluminum foam with a diameter of 63.5 mm was sandwiched between two aluminum cylinders and the whole assembly was fasten by bolts. The heat was transferred through the sample by the one-dimensional thermal conduction. Two types of bolt patterns were used in this study: the first type has 3 bolts with the diameter of 5 mm, and the second type has 6 bolts of 5 mm in diameter. Effects of physical properties of Al foams, such as PPI (pores per inch), R.D. (relative density), and sample height on the thermal contact resistance of Al foams were studied. In addition, the influence of bolt pattern was also discussed. The torque applied on each bolt was in the range from 0.1 to 0.5 N-m. The heat flux through the test specimen was about 50~150KW/m2. In this study, the interfacial pressure between Al foams and Al cylinder was measured by the pressure measuring film. Results show that the interface pressure increases with the increase of applied torque. The contact surface area increases with the interfacial pressure. The variation in bolt pattern produced almost no effect on the interfacial contact pressure. Experimental results indicated that the temperature drop across the Al foam decreases and the total thermal conductance increases when the relative density of Al foam increases. The thermal contact resistance decreases with increasing applied torque, due to the increase of interfacial pressure and contact area. However, the increase of number of bolts from 3 to 6 produced nearly no influence on the contact resistance. An increase in the sample height led to the increase of total thermal resistance, but the contact resistance was independent of the sample height. Among all of the properties, the PPI has most pronounced effect on the thermal resistance. Both total and contact resistances increase with an increase in the PPI value of the Al foam.

碩士
國立臺灣科技大學
機械工程系
98
This work studies the tolerance analysis of the unconstrained assemblies with double bolt-hole fits. The research starts from investigating the variations of dimension chains for the assemblies with double bolt-hole, clearance fit at different contact positions. Then, the components dimensioned by conventional and geometrical methods are discussed separately. This research focuses on the variations of key dimensions of the assembly while the dimensions of the components have different distributions within the allowable limits. It is found that the factor simulation method can effectively estimate the nominal value and tolerance of the resultant dimensions. Since analytical methods are not applicable to the tolerance analysis of assemblies with bolt-hole fits, the data obtained from Monte Carlo simulation is used as the reference for comparison.

碩士
國立高雄應用科技大學
精密模具與機械產研碩士外國專班
99
ABSTRACT Cold forging process can be described as the process where a metal is plastically deformed at room temperature with application of huge pressure. The process not only changes the shape but also improves the properties of the forged parts. In cold forging process, forming load is one of the most important factors. It affects mechanical durability as well as fatigue life of die. Forming load is expected as low as possible. This study will investigate the design of cold forging die for hex bolt M8x25. DEFORM 3D software and Taguchi method was used to optimize forming load by changing some design parameters. The simulation was carried out with an orthogonal array (L9) based on the Taguchi method. The results showed that the optimal values of parameters are rake angle in process 2 at level 1 (1o), across flats distance in process 2 at level 1 (12.7 mm), draft angle in process 2 at level 1 (25o) and rake angle in process 3 at level 3 (3o). After optimizing, the optimized parameters reduced the forming load of top die in process 3 by 26.6% (5.13x104N comparison with initial value 6.99x104N).

碩士
逢甲大學
機械工程學所
99
In structural design, a bolt joint is a very critical issue that can never be ignored. This thesis uses a nonlinear finite element method to study the stress distribution of the single-row multi-lap joint under different bolt-hole clearances and pre-loads. Under the condition of no pre-load, comparisons of five bolts structure with non-clearance and five bolts structure with the same clearance showed that the stiffness of the bolt joint decrease and the stress reduces and becomes nearly equal. After increasing the clearance of the first bolt-hole, with applied shear and torsion loading, the second bolt withstands the stress from the first bolt and reduces the load. However this trend does not exist when bending load is applied. In the bolt structure, regardless of the clearance, with pre-load the bolt stiffness increases and both plates bond closely withstanding the load evenly, which results in stress reduction for each bolt. Although the bolt withstand a larger load, when the load is too heavy the bolt joint fails to bond together.

碩士
國立交通大學
土木工程系所
107
In this study, thermal sprayed coating was applied to the faying surface of steel plates in order to increase the slip coefficient and enhance the slip resistance of the slip-critical joint. Moreover, this study aims to explore the effect of bolt arrangement on slip resistance. Slip tests of slip-critical connection using eight high-strength bolts were carried out to explore the effects of different bolt arrangement on the slip coefficient, bolt pretension, stress on the splice plate, and slip resistance. Splice plates of the specimens were thermal sprayed coated with 150

碩士
大葉大學
機械工程研究所
90
This thesis is divided into two parts: the first part of this thesis is “Research on Thermal Contact Resistance of Bolt-Jointed Interface”, and the second part of this thesis is “Research on Heat Conduction Characteristics of Aluminum Honeycombs”. The first part of this thesis was an experimental study of thermal contact conductance which was conducted with pairs of aluminum alloy specimens (6061-T6) jointed by bolts. Three different bolt patterns and three different bolt-shaft diameters were adopted in this study, and the torque applied on each bolt was between 1 and 10 N-m. A pressure-measuring film was inserted between samples to determine the interfacial contact pressure of bolt-jointed specimens. Results show that the interfacial contact pressure increases with an increase of either the applied torque or the number of bolts. The interfacial temperature difference across the junction was substantially reduced for bolt-jointed specimens, when compared with two superimposed samples without bolts. With the same bolt number, the variation of bolt-shaft diameter from 5 to 8 mm yields nearly no influence on the thermal contact conductance. However, with the same bolt size, the thermal contact conductance of samples jointed by 8 bolts was much larger than that of 4-bolt samples. The increase of contact surface roughness of test specimens leads to a decrease of thermal contact conductance. When an RTV silicon layer was used as the interstitial material, the total joint conductance was increased with a decrease of the thickness of RTV silicon layer. The second part of this thesis was to study experimentally the heat conduction characteristics of aluminum honeycombs. The honeycombs used in this study were made of Al3104-H19 and Al3003-H16. The cell diameters of honeycombs were 6.3 and 12.7 mm. Temperature measurement shows that the temperature drop across the honeycomb sample is lower for the honeycomb with a smaller cell diameter. Results indicate that the axial total thermal conductance is higher for samples with a smaller cell diameter. For honeycombs with different materials, the axial total conductances were very close in the torque range used in this study. The increase of either the number of bolts or the bolt-shaft diameter leads to an increase of the axial total conductance. The axial contact resistance between aluminum honeycomb and aluminum alloy sample about 10﹪of the axial total resistance. In addition the axial contact resistance of honeycombs with a cell diameter of 6.3 mm decreased with the increasing torque. However for the honeycombs with a cell diameter of 12.7 mm, the torque and the bolt pattern produce nearly no influence on the thermal contact resistance. In the same direction of the aluminum honeycomb, the contact resistance is almost independent of the honeycomb height, but the total resistance decreases with the increasing height of samples.

碩士
國立臺灣科技大學
營建工程系
88
Fire —resistant steel (FRS) possesses good mechanical properties at high temperature. Using FRS can reduce the demand of fire proofing material, shorten the construction period, and increase the usable inner space of a building. Since the behavior of connections play an important role on the safety of steel structures, this research studies the properties of weld and bolt connections of FRS members due to fire load. A series of experiments including residual stress, welding property and the pre-stress loss of high-tension bolt were conducted. The test results shows that the maximum residual stresses of a built-up sections could exceed the yield strength of the steel, while it drops down noticeably after fire exposure. The distribution of residual stress depends on the cooling rate of the welded members. The strength and toughness of the welding material do match that of the FRS material, however the impact toughness is a little insufficient after fire exposure. The mechanism of load transmission of bolt connection has two types, i.e., the friction type and the bearing type. This research evaluates the pre-stress loss of high-tension bolt due to fire temperature by investigating the slip behavior of the bolt at high temperature. The result shows that under the action of temperature below 400℃, the pre-stress of FRS bolt increases a little bit as compared with that at room temperature. It decreases rapidly at temperatures over 400℃, and drop down to about 10% of that at room temperature as the temperature goes beyond 600℃.

碩士
高苑科技大學
機械與自動化工程研究所
102
The main purpose in this study is to investigate the relations among hardness-(H-M) -parameter curve and microstructure for the rod wire materials which are normally applied in carbon steel and alloy steel of screws, bolts, and so on by using quenching and different tempering temperature and time and also to investigate the change between tempering temperature and structure through analyses by Electron Microscopes and Energy Diffusion Spectrum. The results are shown from the H-M curve that the SCM wire material is the best one for the resistant ability under high temperature tempering but the 10B33 wire material is the worst. Also the tempering hardness can be figured out from the curved diagram under any temperature and any time and all the mechanical properties like the yielding strength, tensile strength, elongation and surface reduction rate with different bolt wire materials can be derived. If the tempering time is prolonged to 24 hours, then the crystal granules on the base structure will grow onto coarse crystal types. This causes tensile strength, yielding point, and hardness to decrease gradually according to the increase of the tempering temperature. On the other hand, SCM435 is added with stable carbon elements like Cromium and Molybdenum, so when the heat treatment is under quenching or tempering, decarbonizing becomes slower. Therefore, the S45C and 10B33M wire materials are easier to be oxidized to stain skin. This appears a so-called heat treatment coarse grain soft point defect.

The transmission line (TL) tower is an important component in electrical network system. These towers consist of members (angle sections) and connections (bolted connections) plus foundation, which act together to resist externally applied loads. The latticed towers are used to support conductors in transmission network for transmission and distribution of electricity. These towers are constructed in large numbers all over the world. The connections in electric TL classical latticed towers are peculiar compared to other types of bolted connections in buildings and bridges because (i) the angle members are connected directly or through gusset plates with bolts, (ii) the eccentric application of load due to the non-coincidence of centroid axes of angle members near the connection and (iii) members are designed as beam column element to sustain tensile or compressive forces. Bearing type bolts are used in TL towers in preference to friction type bolts, because they (i) connect thin walled angle members, (ii) are easy to use for erection at all heights, (iii) can be galvanized, (iv)erosion of galvanizing can be remedied and (v) do not require skilled personnel for installation. However, these connections are subjected to reversal of stresses due to wind load. Damage in the bolted connections generally occur due to loosening of bolts due to stress reversals (Feenstra et al. (2005) [23). The damage induced after extreme wind and earthquake may lead to collapse of the whole tower. The failure of a TL tower results in power shut down, which has huge impact on national economy. Hence, the structural safety and reliable performance of these towers are extremely important. The design of TL tower is based on minimum weight philosophy. The TL towers are highly repetitive and therefore, their designs need to be commercially competitive. The TL tower design has the following deficiencies such as misappropriate design assumptions, deficit detailing, defects in material, errors in fabrication, force fitting of members during erection, variation in grade of bolts, improper gusset plate detailing, notch cutting of member, vocalization of bolt holes, etc. Hence, to check the design and detailing aspects of members along with bolted connections and to study the behavior of tower under complex loading conditions, the prototype testing of tower is made mandatory requirement in many countries throughout the world. The structural behavior of TL tower is determined from its deflection response. Thus, the full scale testing of the towers is the only way that one can counteract the un conservatism due to structural analysis. The premature failure of TL towers occurs during prototype testing due to deficiencies in joint detailing, uncertainties in framing eccentricity, force fitting of members, unequal force distribution in bolts and gusset plate connections, etc. To have better structural response of TL tower to be tested, there is need to develop reliable model for bolted connections in TL towers. The bolted connection model plays an important role in determining the deflection response and predicting the premature member buckling failure of TL towers. The issues related to prototype testing of full scale TL towers such as fabrication errors, force fitting and notch cutting of members, application of loads, joint and crossarm detailing are discussed. The need to develop bolt slip model to simulate the actual behaviour of bolted connection in TL towers is also discussed. The bolted connections in TL towers play an important role in determining its structural behavior. The angle members used in TL towers are subjected to bi-axial bending in addition to axial load. The slip will occur in the bolted connections, due to the provision 1.5 mm bolt hole clearance. In the conventional Finite Element Analysis (FEA), the bolted connections are modeled as pin joint assuming the axial load transfer. The deflection predicted from pin joint analysis in TL towers generally does not match with experimental results. The analytical and experimental deflection value varies in the range of 30 to 50%. Hence, there is need to develop model to account bolt slip for accurate deflection and dynamic characteristic prediction of TL towers. Experimental and analytical investigations have been carried out to develop and validate bolt slip model for bolted connections in TL towers. All six degrees of freedom (both translational and rotational) have been considered to simulate the exact behaviour of bolted connections in TL towers. The model is developed based on experimental results of Ungkurapinan’s bolt slip model for axial stiffness. The rotational stiffness is formulated based on the component level experiment conducted on lap joint made of steel angle with single and double bolt subjected to tensile loading. The axial and rotational stiffness for different stages of bolt tightening is also formulated based on component level experimental investigation on lap joint. The proposed model is validated by comparing with experimental results at sub-structural level on full scale king post truss subjected to tensile loading. Further the bolt slip model is validated for different bolt tightening and failure prediction of TL tower sub panel subjected to tensile loading. Finally the proposed model is also validated for full scale TL tower for deflection prediction. NE NASTRAN, a nonlinear finite element analysis (FEA) software is used for analytical simulation and the load-deflection predictions, which are compared with the corresponding experimental results. The experimental and analytical results are in good agreement with each other. The steel pole structures are replacing the conventional lattice towers, because they have smaller plan dimension and occupy less space, when compared to lattice towers. The steel pole structures are dynamically sensitive structures and the determination of their natural frequency is extremely important. For the calculation of wind load through gust factor method, the preliminary estimation of natural frequency is required. Hence, the primary step involved in dynamic analysis is the evaluation of its natural frequency. Hence, a simplified model is proposed based on model order reduction technique for the evaluation of natural frequency of TL towers and steel pole structures. For the development of base line model to detect damage in TL towers, the natural frequency has to be updated. A semi empirical approach is proposed based on the deflection by using the proposed bolt slip model. The proposed approach of updating natural frequency is validated for different cases of member damage in TL tower sub panel, such as removal of tension, compression and hip bracing members. The transmission pole structures accumulate damage during their service life. Damage in these structures will cause a change in stiffness of the system and the physical properties of these structures, such as modal frequencies and mode shapes. Hence in the present study, the damage localization study based on modified modal strain energy approach is carried out for steel pole structures and the location of damage is identified correctly. To prevent premature failure of towers during its service life testing and failure analysis of TL towers is a mandatory requirement. In the present study, forensic failure investigation of a full scale TL tower due to deficient design of a redundant member is emphasized and the remedial measures are explained in detail. The stub failure of TL tower due to reduction in cross sectional area due to unfilled bolt hole is also discussed. To investigate the effect of unfilled bolt holes on the compression capacity of leg member, detailed FEA is carried out and compared with experimental results. The reason for failure of 9 m roof top communication tower due to redundant member deficiency is also discussed. The importance of guyed tower accessories in the guy rope design of 7 m roof top guyed pole structure is also investigated. Finally, failure investigation of compression bracing member, which has failed during testing of TL tower sub panel has been investigated. The failure load is predicted by using the proposed bolt slip model in the analysis. Thus the overall research contributions emerging from this thesis are, i) development of bolt slip model accounting for rotational stiffness, ii) development of direct method of damage detection for steel pole structures based on modified modal strain energy approach, iii) development of simplified model for prediction of natural frequency of TL tower and steel pole structures, iv) development of model updating technique through natural frequency based on semi-empirical approach and v) prediction of failure load for TL tower panel using the proposed bolt slip model.