Bolts and nuts are one of most common joining methods since they are simple and low-cost to connect parts. Appropriate clamp force from bolted joint remains resultant joints secured, but higher/lower preload on bolted joint increases risk of the failure of mechanism. Therefore, achieving accurate clamp force in bolted joint is always the aim of tightening process. Torque control tightening tool are the most common tightening tool present in the market. The clamp force obtained from torque control tightening is highly dependent upon friction. Only small part of applied torque is transferred into the effective torque that turns in to clamp forces because most of applied torque is consumed by friction forces under bolt /nut head and in a thread interface. However, friction coefficient does not remain constant during tightening process and it relates to many factors such as tightening speed, speed profile, tightening time, joint’s material, etc. Hence, it changes the distribution ratio and leads to an error in estimation of clamp force between the components. This project aims to develop a tribometer which is capable of operating in different speeds and load conditions corresponding to different tightening process. A new concept of pin-on-disc tribometer is proposed and the speed and load profile are achieved by using closed loop control in the linear actuator and the motor. The test rig was built up and the several validation tests were done. / Skruv och mutter tillhör bland de vanligaste medlen att binda ihop två ytor med varandra då det är ett billigt och enkelt sätt att uppnå det önskade resultatet. Det är viktigt att rätt klämkraft uppnås i skruvförbandet, vid för låg/hög klämkraft är risken för haveri i konstruktionen stor. Därför är att uppnå korrekt klämkraft i ett skruvförband alltid målet i en åtdragningsprocess. Skruvdragare som drar åt med ett förinställt moment (torque control) är för tillfället det vanligaste verktyget på marknaden för att uppnå rätt klämkraft. Klämkraften som uppstår vid åtdragning av ett skruvförband med ett sådant verktyg är i största del beroende på friktionskraften i skruvförbandet för korrekt moment. Endast en liten del av momentet som påverkar skruven övergår till effektivt fasthållande moment i skruvförbandet, det mesta momentet går åt för att övervinna friktionen mellan skruv och mutter. Friktionskoefficitenten håller sig inte konstant vid ett åtdragande moment utan beror på flera faktorer såsom åtdragningshastighet, profilhastighet, åtdragningstid och vilket material skruvförbandet är gjort av bland annat. Eftersom friktionskoeffiecienten ständigt ändrar sig leder detta till ett fel då man ska uppskatta klämkraften mellan två ytor. Detta examensarbete ämnar till att bygga en tribometer som är kapabel till att fungera vid olika hastigheter och kraftförhållanden som korresponderar till olika åtdragningsprocesser. Ett koncept på en ny pin-on-disc tribometer föreslås och hastighets samt kraftprofiler skapas genom ett closed-loop reglertekniksystem i ett linjärt ställdon och motorn. Testriggen konstruerades och flertalet utvärderingstester utfördes.

Ancillary structures are highway support structures such as traffic signals, sign structures, luminaires, and high-mast light towers which are typically fastened to a concrete foundation using embedded anchor rods and anchor nuts. The inventory of ancillary structures across the United States is huge, and these structures vary dramatically in type, age, size, and material. There have been reported cases of anchor nut loosening on ancillary structures in the past few decades, but the cause of loosening is still unknown. Ancillary structures are susceptible to vibrations due to different wind loadings like natural gusts, vortex shedding, galloping, and truck-induced gusts. Wind-induced vibrations are believed to be one of the potential causes of anchor nut loosening. Previous research also suggests that vibrations can lead to loosening of nuts in structural and mechanical connections. There is concern regarding the current tightening procedures specified in the various federal and state specifications. Improper tightening can potentially lead to anchor nut loosening under the effect of wind-induced vibrations. In ancillary structures, the anchor rods and nuts are first snug-tightened using a wrench before fully pretensioning them as per the current specifications. The snug-tight condition is vaguely defined at present and needs revisions to avoid any under-tightening or over-tightening. Galvanization and overtapping of the anchor nuts also pose a potential concern. Anchor nuts are tapped oversize after galvanization to ensure the nuts fit well on the galvanized rod. American Society for Testing and Materials (ASTM) standards provide specific allowable tolerances on the thread parameters of the anchor rod and nut after galvanization and overtapping. Any deviation from the allowable tolerances can lead to gaps between the mating threads, which can contribute to the loosening of nuts under vibrations. This study focuses on investigating the following potential causes of loosening: improper tightening, wind-induced vibrations, snug-tight condition, and thread fabrication tolerance. Current tightening procedures for double-nut and single-nut connections on ancillary structures were verified using a tightening study as part of the investigation. New revisions to the specified nut rotation values for double-nut connections and a draft for proposed new specifications on single-nut connections has been provided as a result of discrepancies and inconsistencies in the current specifications. Vibration testing of a full-scale traffic signal was conducted on the basis of results from a four-month field monitoring program in order to investigate the effects of wind-induced vibrations on anchor nut loosening. It was concluded from testing that improper tightening (pretension < 5ksi) can lead to loosening of anchor nuts under wind-induced vibrations. A small-scale testing was also conducted to verify the results from the large-scale vibration testing. Snug-tight pretension in grade 55, 1-inch and 2-inch anchor rods was found to be highly variable due to different wrench lengths and personnel strength. Thread parameters of galvanized anchor rods and nuts procured from 3 different regional suppliers were found to be within specified tolerances. Various recommendations were then made as a result of the above tightening, vibration, and thread tolerance studies in an effort to reduce the cases related to anchor nut loosening in the future. / Doctor of Philosophy / Ancillary structures like traffic signals, sign structures, and light poles are typically connected to the ground using anchor rods and anchor nuts. There is a very large number of ancillary structures throughout the United States and vary in type, age, size, and material. There have been reported cases of anchor nut loosening on ancillary structures in the past few decades, but the cause of loosening is still unknown. Different types of wind loadings like natural gusts, vortex shedding, galloping, and truck-induced gusts vibrate the ancillary structures. These vibrations due to the wind are believed to be one of the potential causes of anchor nut loosening. Vibrations in the past have been shown to cause loosening of nuts in other structural and mechanical connections. There is also concern that the anchor rods and anchor nuts are not tightened properly as per the specifications, which can lead to loosening of nuts when the ancillary structures vibrate due to wind loadings. In ancillary structures, the anchor nuts are first made tight using a wrench with the full effort of a worker, also known as the snug-tight condition. The snug-tight condition is not properly defined at present and needs to be changed to prevent any under-tightening or over-tightening of the anchor nuts. Also, the anchor rods and nuts are generally coated with a hot zinc layer to prevent their corrosion when exposed to environmental effects like ice, snow, humidity, and rain. This process is called galvanization. The American Society for Testing and Materials (ASTM) provides some guidelines on the amount of coating allowed on the threads of the anchor rods and nuts. Any deviation from the allowable tolerances can lead to gaps between the threads of the anchor rod and nut, which can contribute to the loosening of nuts during vibrations of ancillary structures due to wind. This study focuses on investigating the following potential causes of loosening: improper tightening, vibrations of ancillary structures due to wind, snug-tight condition, and allowable tolerances for the amount of galvanization. Current tightening procedures for anchor rods and nut on ancillary structures were verified using a tightening study as part of the investigation. New revisions to the current tightening procedures have been provided as a result of discrepancies and inconsistencies observed in the current specifications. A traffic signal and a light pole were instrumented with sensors for four months to measure wind-related forces acting on these structures. Further, a full-scale traffic signal was vibrated in the laboratory using an electric motor to simulate the vibrations due to the measured wind forces. It was determined from the testing that if the anchor nuts were not properly tightened, they could become loose during vibrations due to wind. A small-scale testing was also conducted to check the results from the full-scale vibration testing. The snug-tight force in the anchor rods was also found to be dependent on the length of the wrench and the worker tightening it. The amount of galvanization on the rods and nuts procured from 3 different suppliers were found to be within allowable tolerances. Various recommendations were then made as a result of the conclusions in an effort to reduce the cases related to anchor nut loosening in the future.

A proposta deste estudo foi avaliar o comportamento mecânico de dois designs de conexão implante/abutment; hexágono externo e triângulo interno, utilizando parafusos convencionais e parafusos experimentais cone morse. O estudo foi dividido em duas fases: na primeira, foi avaliado o efeito do carregamento mecânico na perda de torque dos parafusos. 40 implantes foram utilizados. Os implantes e abutments foram divididos em 4 grupos: Grupo 1: hexágono externo/parafuso convencional (HE); Grupo 2: triângulo interno/parafuso convencional (TI); Grupo 3: hexágono externo/parafuso cone morse (HECM); Grupo 4: triângulo interno/parafuso cone morse (TICM). Os abutments foram instalados em seus respectivos implantes com torque de aperto de 32Ncm; após intervalo de 10 minutos, foram medidos os valores dos torques de desaperto. Os abutments foram instalados novamente com torque de 32Ncm, e após 10 minutos foram carregados mecanicamente, simulando 1 ano de função oral normal; após o carregamento, os torques de desaperto dos parafusos foram medidos novamente. Os dados foram analisados com o teste one-way ANOVA, com nível de significância de p&le;0,05%. Análises por microscopia óptica foram realizadas antes e após os ensaios. Na segunda fase, foi avaliada a resistência à flexão dos conjuntos implante/abutment. Os mesmos 40 conjuntos foram utilizados. Os testes foram realizados em máquina universal de ensaios, com célula de carga de 500 kgf, deslocamento de 1mm/min, e inclinação de 45&deg;. A força máxima de flexão (FMF) e a força de ruptura (FR) foram determinadas. As informações coletadas foram analisadas com o teste one-way ANOVA, para p&le;0,05. Análises por microscopia óptica foram realizadas para estudo dos componentes após os ensaios de resistência flexural. Os resultados sugeriram que houve diferença significante (p=0,000) na pré-carga residual antes e após carregamento mecânico entre os dois tipos de parafuso: os parafusos cone morse apresentaram torques de desaperto significativamente superiores aos apresentados pelos parafusos planos convencionais. Houve diferença significante nos resultados da FMF obtidos pelos parafusos planos convencionais e pelos parafusos cone morse (p=0,011), sendo que os conjuntos implante/abutment com parafusos cone morse apresentaram maior resistência à flexão. Para os resultados da FR houve influência significante do tipo de conexão (p=0,019), com melhores resultados para a conexão triângulo interno. Considerando as limitações deste estudo, concluiu-se que os parafusos cone morse apresentaram maiores torques de desaperto em comparação aos parafusos planos convencionais; que o design da conexão protética não teve influência significante sobre o torque de desaperto dos parafusos; que os parafusos cone morse obtiveram maiores valores de resistência à flexão, e que a conexão em triângulo interno obteve maiores valores para a força de ruptura. / The purpose of this study was to evaluate the mechanical behavior of two implant/abutment connection designs; external hex and internal tri-channel, using conventional screws and experimental conical screws. The study was divided in two parts; the first evaluated the effect of mechanical loading in the torque loss of the screws. 40 implants were used. The implants and abutments were divided in 4 groups: Group 1: external hex/conventional screw (HE); Group 2: tri-channel/conventional screw (TI); Group 3: external hex/conical screw (HECM); Group 4: tri-channel/conical screw (TICM). The abutments were installed in their respective implants with a tightening torque of 32Ncm, after a 10 minute interval, loosening torque were measured. The abutments were installed again with a 32Ncm torque, and after 10 minutes, they were mechanically loaded, simulating 1 year of normal oral function; after loading, loosening torques of the screws were measured again. Data were analyzed with one-way ANOVA test, with significance level of p&le;0,05. Optical microscopy analysis were performed before and after the tests. The second part evaluated the flexural resistance of the implant/abutment assemblies. The same 40 assemblies were used. The tests were performed in an universal testing machine, with a 500kgf load cell, 1mm/min displacement, and 45&deg; angulation. Maximum bending moment (FMF) and rupture force (FR) were determined. Collected information were analyzed with one-way ANOVA test, for p&le;0,05. Optical microscopy analysis were performed for study of the components after the flexural resistance tests. The results suggested that there were significant differences (p=0,000) in the residual preload before and after mechanical loading between the two types of screws: conical screws showed significantly higher loosening torques than conventional flat screws. There were significant differences in the FMF obtained by the conventional flat screws and by the conical screws (p=0,000); the implant/abutment assemblies with conical screws presented higher flexural resistance. For the FR results, there was significant influence of the type of connection (p=0,019); the tri-channel connection presented better results. Considering the limitations of this study, it was concluded that the conical screws presented higher loosening torques compared to conventional flat screws; the design of the implant/abutment connection presented no significant influence on the loosening torques of the screws; conical screws showed higher bending moment values; and the tri-channel connection obtained higher rupture force values.

A proposta deste estudo foi avaliar o comportamento mecânico de dois designs de conexão implante/abutment; hexágono externo e triângulo interno, utilizando parafusos convencionais e parafusos experimentais cone morse. O estudo foi dividido em duas fases: na primeira, foi avaliado o efeito do carregamento mecânico na perda de torque dos parafusos. 40 implantes foram utilizados. Os implantes e abutments foram divididos em 4 grupos: Grupo 1: hexágono externo/parafuso convencional (HE); Grupo 2: triângulo interno/parafuso convencional (TI); Grupo 3: hexágono externo/parafuso cone morse (HECM); Grupo 4: triângulo interno/parafuso cone morse (TICM). Os abutments foram instalados em seus respectivos implantes com torque de aperto de 32Ncm; após intervalo de 10 minutos, foram medidos os valores dos torques de desaperto. Os abutments foram instalados novamente com torque de 32Ncm, e após 10 minutos foram carregados mecanicamente, simulando 1 ano de função oral normal; após o carregamento, os torques de desaperto dos parafusos foram medidos novamente. Os dados foram analisados com o teste one-way ANOVA, com nível de significância de p&le;0,05%. Análises por microscopia óptica foram realizadas antes e após os ensaios. Na segunda fase, foi avaliada a resistência à flexão dos conjuntos implante/abutment. Os mesmos 40 conjuntos foram utilizados. Os testes foram realizados em máquina universal de ensaios, com célula de carga de 500 kgf, deslocamento de 1mm/min, e inclinação de 45&deg;. A força máxima de flexão (FMF) e a força de ruptura (FR) foram determinadas. As informações coletadas foram analisadas com o teste one-way ANOVA, para p&le;0,05. Análises por microscopia óptica foram realizadas para estudo dos componentes após os ensaios de resistência flexural. Os resultados sugeriram que houve diferença significante (p=0,000) na pré-carga residual antes e após carregamento mecânico entre os dois tipos de parafuso: os parafusos cone morse apresentaram torques de desaperto significativamente superiores aos apresentados pelos parafusos planos convencionais. Houve diferença significante nos resultados da FMF obtidos pelos parafusos planos convencionais e pelos parafusos cone morse (p=0,011), sendo que os conjuntos implante/abutment com parafusos cone morse apresentaram maior resistência à flexão. Para os resultados da FR houve influência significante do tipo de conexão (p=0,019), com melhores resultados para a conexão triângulo interno. Considerando as limitações deste estudo, concluiu-se que os parafusos cone morse apresentaram maiores torques de desaperto em comparação aos parafusos planos convencionais; que o design da conexão protética não teve influência significante sobre o torque de desaperto dos parafusos; que os parafusos cone morse obtiveram maiores valores de resistência à flexão, e que a conexão em triângulo interno obteve maiores valores para a força de ruptura. / The purpose of this study was to evaluate the mechanical behavior of two implant/abutment connection designs; external hex and internal tri-channel, using conventional screws and experimental conical screws. The study was divided in two parts; the first evaluated the effect of mechanical loading in the torque loss of the screws. 40 implants were used. The implants and abutments were divided in 4 groups: Group 1: external hex/conventional screw (HE); Group 2: tri-channel/conventional screw (TI); Group 3: external hex/conical screw (HECM); Group 4: tri-channel/conical screw (TICM). The abutments were installed in their respective implants with a tightening torque of 32Ncm, after a 10 minute interval, loosening torque were measured. The abutments were installed again with a 32Ncm torque, and after 10 minutes, they were mechanically loaded, simulating 1 year of normal oral function; after loading, loosening torques of the screws were measured again. Data were analyzed with one-way ANOVA test, with significance level of p&le;0,05. Optical microscopy analysis were performed before and after the tests. The second part evaluated the flexural resistance of the implant/abutment assemblies. The same 40 assemblies were used. The tests were performed in an universal testing machine, with a 500kgf load cell, 1mm/min displacement, and 45&deg; angulation. Maximum bending moment (FMF) and rupture force (FR) were determined. Collected information were analyzed with one-way ANOVA test, for p&le;0,05. Optical microscopy analysis were performed for study of the components after the flexural resistance tests. The results suggested that there were significant differences (p=0,000) in the residual preload before and after mechanical loading between the two types of screws: conical screws showed significantly higher loosening torques than conventional flat screws. There were significant differences in the FMF obtained by the conventional flat screws and by the conical screws (p=0,000); the implant/abutment assemblies with conical screws presented higher flexural resistance. For the FR results, there was significant influence of the type of connection (p=0,019); the tri-channel connection presented better results. Considering the limitations of this study, it was concluded that the conical screws presented higher loosening torques compared to conventional flat screws; the design of the implant/abutment connection presented no significant influence on the loosening torques of the screws; conical screws showed higher bending moment values; and the tri-channel connection obtained higher rupture force values.

La maîtrise de la pré-tension revêt d’une grande importance pour garantir la tenue mécanique des assemblages boulonnés, et ce quel que soit le mode de sollicitations auquel ils sont soumis. En particulier, pour les chargements transverses et sous sollicitations de fatigue, un niveau de pré-tension insuffisant ne permet pas d’exploiter la capacité de transfert d’effort des interfaces entre pièces assemblées. Un niveau de pré-tension très important n’est pas souhaitable non plus, car cela génère des phénomènes de fatigue de contact ou de matage excessif sous tête qui ont un effet néfaste sur la durée de vie des assemblages et des structures aéronautiques. Le serrage contrôlé des fixations permet ainsi de produire et de maintenir un équilibre entre les modes de transfert d’effort, permettant ainsi d’exploiter pleinement leur potentiel et obtenir une tenue optimale de l’assemblage. L’objectif de ce travail est d’apporter une contribution à la compréhension et à l’exploitation des assemblages boulonnés à serrage contrôlé. Une approche hybride a été adoptée afin de démontrer l’effet bénéfique d’une pré-tension contrôlée. La modélisation numérique a permis de comprendre les mécanismes de transfert d’effort et de prédire la tenue mécanique des assemblages aéronautiques de façon satisfaisante. La démarche expérimentale a été exclusivement basée sur des techniques dites de serrages alternatifs. L’objectif est d’avoir une faible incertitude sur la valeur de la précontrainte installée, permettant d’évaluer la performance mécanique des assemblages boulonnés. La tenue en fatigue des assemblages boulonnés, travaillant en matage-cisaillement, est largement améliorée grâce à l’application d’une précontrainte précise. La maîtrise des paramètres intrinsèques au maintien de la force axiale de serrage tel que la nature de l’interface entre pièces assemblées, la rigidité des fixations et la nature de l’ajustement, permet également d’esquisser un potentiel d’optimisation non négligeable des assemblages boulonnés. / Axial preload is a fundamental parameter that needs to be correctly mastered in order to ensure the mechanical strength of bolted joints. In the case of bolted shear joints under fatigue solicitations, a low preload does not allow to exploit the load carrying capacity of the friction interfaces. A high preload is undesirable as it can generate fretting fatigue phenomena or excessive under head contact pressure that may lead to decrease fatigue lives of aeronautical joints and structures. Controlled preload application generates and maintains equilibrium of load transfer mechanisms, inducing a full use of their potential and leading to an optimal fatigue life of the joint. This study focuses on aeronautical preloaded joints with the objective of understanding the effects of controlled preload over the mechanics of shear joints and exploiting the contribution of preload to enhance their fatigue lives. For this purpose, a hybrid approach has been adopted to demonstrate the beneficial effect of controlled preload. Numerical modelling has been carried out to better understand the preload influence but also to predict the mechanical strength of bolted joints. The experimental database has been generated using exclusively alternative tightening techniques, in order to reduce the scatter on final preload and therefore evaluate the effect of controlled preload in a more accurate way. The fatigue strength of bolted shear joints has been significantly improved for most of tested configurations due to the application of accurate axial preload. The effects of many other parameters, as the nature of interface, the stiffness of fasteners or the radial adjustment has also been assessed and permits to identify an additional potential optimization of bolted joints.

This thesis solves the problem of design and production of a special mounting device for the impeller nut of the main circulation pump GCN-317. The proposed device is intended to solve the problems associated with the mounting and dismounting of this nut. The work provides basic information about the Dukovany Nuclear Power Plant and VVER-440 systems in general, including their brief history. It also introduces the operational and legislative environment of the primary circuit of the nuclear power plant. It deals with the task and technical description of the main circulation pump and its overhaul. The following sections present the basic principles of construction of the device and an overview of its components with a description of their purpose and method of production. The last part of the thesis describes the function of the device and its verification and reports on its deployment.

The theme of this master thesis is the revision and repair design of the condensing steam turbine SST 600 in Bielsko-Biala. The thesis deals with the revision of the steam turbine and the repair design of the damaged parts, the overall analysis of the separation of the steam of the split plane and the calculation of the parameters for tightening the new screws. The master thesis is given for a specific case. The introductory part of the master thesis deals with a basic description of the repaired steam turbine. Subsequently, a review of individual disassembled parts is given and the scope of the repairs is stated. In the next part of this thesis are summarized the causes of the steam leakage of the dividing plane at the points of the cross section and in the area of the control stage. The last part deals with the sealing problem of the split plane and the related main part of the master thesis is the calculation of the tightening parameters of bolts in the turbine housing. Another aim of the master thesis is to create drawings of the lightening of the split plane on turbine house.

Threaded fasteners tend to break and loosen when exposed to cyclic loads or potent temperature variations. Additionally, if the joint is held tightly to the structure, distortion will occur under thermal expansion issues. These complications can be prevented by identifying and regulating the clamping force to an appropriate degree – adapted to the properties of the joint. Torque-controlled tightening is a way of monitoring the clamping force, but it assumes constant friction and therefore has low accuracy, with an error of around 17% - 43%.This thesis investigates if the friction and clamping force can be estimated using the Extended and Unscented Kalman filters to increase the precision of the torque-controlled methodology. Before the investigation, data were collected for two widely used tightening strategies. The first tightening strategy is called Continuous Drive, where the angular velocity is kept at a constant speed while torque is increased. The second strategy is TurboTight, where the angular velocity starts at a very high speed and decreases with increased torque. The collected data were noisy and had to be filtered. A hybrid between a Butterworth lowpass filter and a Sliding Window was developed and exploited for noise cancellation.The investigations revealed that it was possible to use both the Extended and Unscented Kalman filers to estimate friction and clamping force in threaded fasteners. In Continuous Drive tightening, both the EKF and UKF performed well - with an averagequality factor of 81.87% and 88.38%, and with an average error (at max torque) of 3.54% and 4.09%, respectively. However, the TurboTight strategy was much more complex and had a higher order of statistical moments to account for. Thus, the UKF outperformed the EKF with an average quality factor of 93.02% relative to 24.49%, and with an average error (at max torque) of 3.50% compared to 4.19%

No description available.

Production lines for assembling two parts by screwing require flexible positioning and accurate tightening torque. Working with screwed products in process lines can cause bodily harm. The project aims to develop an application to compensate for the monotonous and tiring work. This report reviews the integration of Bosch Rexroth’s Compact module, and Linear module with an ErgoSpin. The project’s objective entails a turnkey solution for a developed application to be implemented in production lines. The ErgoSpin is a fast, self-tightened screwdriver placed over the screw by measuring the angle, gradient, and tension with the optimal tightening torque. The integration of the products is both electrical and mechanical. Mechanical elements were designed to merge the products into an application. The electrical interfaces between the products were connected and programmed through Bosch Rexroth IndraDrive, and a motion control system. By integrating these products, and implementing them in a production line, the work can be performed more efficiently, and the employees can focus on other tasks. The application is intended to work beside a conveyor unit in assembly stations. Tests were performed to assemble plates with different distances between the hotels and different sizes of screws. The test measured the time it took the application to assemble parts with different distances between the holes and the actual tightening torque it entailed. The results from the tests indicated that optimal tightening torque was achieved for all tests and that the execution of the application has no influence on the mechanical performance. The time difference for the various distances between the holes was almost negligible, and indicated rapid changes between the holes. The time difference between the different screw dimensions proves a slight increase in time for the larger dimensions. The risk assessment was conducted on the application by FMEA to account for all potential hazards based on events in the application’s area of use. The FMEA also provides the proposed actions to prevent the risks.