Session 2 - Joining
Chair: Frank BusenbeckerExecutive Director - Erbslöh Aluminium GmbH, Velbert, Germany
Session 2 consists of four presentations dealing with various aspects
of joining and fastening. The session presentations run from 15:00
until 18:00 o'clock.
15:00-15:30 A new type of sheet metal screws in practise – new possibilities with a new joining method
Prof. Dr.-Ing. Carsten ByeUniversity of applied science, Diepholz, Germany
Abstract
In modern lightweight construction often designer used aluminium components. One of the biggest problems is to join for example aluminium ore other material metal sheets and aluminium closed extruded profiles. The standard solution for joining often is welding. An alternative solution is to use the mechanical joining technology. To use mechanical joining technologies in car production is state of the art. For example clinching and self piercing riveting are two technologies we can detect by production of a lot of cars from the OEM like BMW, Daimler or Audi. This report gives information about the possibilities to join Aluminium sheets and extruded profiles with this special FDS fastener. The presentation of the investigations gives an overview about quality relevance process parameters, about static and dynamic loads, results about corrosion tests and first steps to a way for calculation this connections. The presentation of the strength test results of the sheet metal screw connection are compared to results of self piercing rivet and blind rivet connections. All investigated joining methods are typical for car production industry. The last point of the presentation of the static loads is to compare the results of singular mechanical joints to the hybrid joints, means adhesives and rivets respectively screws.
In modern lightweight construction often designer used aluminium components. One of the biggest problems is to join for example aluminium ore other material metal sheets and aluminium closed extruded profiles. The standard solution for joining often is welding. An alternative solution is to use the mechanical joining technology. To use mechanical joining technologies in car production is state of the art. For example clinching and self piercing riveting are two technologies we can detect by production of a lot of cars from the OEM like BMW, Daimler or Audi. This report gives information about the possibilities to join Aluminium sheets and extruded profiles with this special FDS fastener. The presentation of the investigations gives an overview about quality relevance process parameters, about static and dynamic loads, results about corrosion tests and first steps to a way for calculation this connections. The presentation of the strength test results of the sheet metal screw connection are compared to results of self piercing rivet and blind rivet connections. All investigated joining methods are typical for car production industry. The last point of the presentation of the static loads is to compare the results of singular mechanical joints to the hybrid joints, means adhesives and rivets respectively screws.
15:30-16:00 Mechanical Joining of Aluminum Lightweight Constructions
Dr.-Ing. Torsten DrahtResearch and Development, Wilhelm Böllhoff GmbH & Co. KG, Bielefeld, Germany
Abstract
Today more than in the past materials and construction concepts are essential drivers for innovations in vehicle manufacturing. The rising individualisation of new constructions asks for new solutions in the value added chain of joining. One main target is productiveness by cost attractive and flexible joining techniques. With regards to new materials and constructions, the cost pressure leads to a methodical and comprehensive approach to the three fields construction (design), materials (characteristics) and procedures (manufacturing, assembling). As examples for indirect joining in this article applications of HELICOIL® thread inserts that create high-strength fastenings in thick-walled casted aluminum parts are presented. For the installation of joining points at thin-walled aluminum parts and hollow profiles with one-sided accessibility applications of RIVKLE® blind rivet nuts and studs will be shown. This is the most versatile solution for fastening high-strength nut or bolt threads to components when tapped threads are not possible due to small wall thicknesses.
Today more than in the past materials and construction concepts are essential drivers for innovations in vehicle manufacturing. The rising individualisation of new constructions asks for new solutions in the value added chain of joining. One main target is productiveness by cost attractive and flexible joining techniques. With regards to new materials and constructions, the cost pressure leads to a methodical and comprehensive approach to the three fields construction (design), materials (characteristics) and procedures (manufacturing, assembling). As examples for indirect joining in this article applications of HELICOIL® thread inserts that create high-strength fastenings in thick-walled casted aluminum parts are presented. For the installation of joining points at thin-walled aluminum parts and hollow profiles with one-sided accessibility applications of RIVKLE® blind rivet nuts and studs will be shown. This is the most versatile solution for fastening high-strength nut or bolt threads to components when tapped threads are not possible due to small wall thicknesses.
16:00-16:30 Threaded fastening systems with aluminum components - special characteristics for light weight design
Prof. Dr.-Ing. Christoph FriedrichInstitute of Engineering Design, Machine Elements - Fastening Systems - Product Innovation, University of Siegen, Germany
Abstract
Since long years threaded fastening systems are established all over the world. General design rules are well known like VDI 2230. But today new materials and numeric simulation tools lead to more detailed results as well as to significant improvements – the design of an optimized screw joint for tomorrow looks largely different compared to a traditional bolted joint calculation. Nowadays it is the continuous ambition to design lighter and more compact parts. According to that, the engineering of new parts and assemblies with more efficient screw joints in light weight materials is required. But in most cases common screw joints can not conform to that. This problem is mainly effected by the material characteristics of aluminium, which cannot effort the needed length of thread engagement with requested short assembly-times and also smaller thickness of light weight parts. Thread inserts can improve the screw joints active. Besides the length of thread engagement by using light weight materials the tribology of mechanical contacts plays an important role during tightening. This refers to both, increased friction coefficients and limited loading capacity for contact pressure. The result is that the desired preload is seldom reached with a standardized tightening specification from steel applications. Another aspect is the mismatch of thermal properties between steel and aluminium. Resulting from this it is likely that the preload stability is poor for components which are used at elevated temperatures (e.g. engine parts). These mentioned facts incorporate a hidden risk when using aluminium components and steel screw joints which are not adapted for aluminium assemblies. Using light weight materials in bolted joints the center of attention must be e.g. friction coefficient, required min. length of thread engagement and the resulting preload behavior. A verification of the reference values according mechanical stresses will result from these elements. The paper shows all necessary aspects to obtain reliable screw joints with aluminum and shows examples from measurement and calculation.
Since long years threaded fastening systems are established all over the world. General design rules are well known like VDI 2230. But today new materials and numeric simulation tools lead to more detailed results as well as to significant improvements – the design of an optimized screw joint for tomorrow looks largely different compared to a traditional bolted joint calculation. Nowadays it is the continuous ambition to design lighter and more compact parts. According to that, the engineering of new parts and assemblies with more efficient screw joints in light weight materials is required. But in most cases common screw joints can not conform to that. This problem is mainly effected by the material characteristics of aluminium, which cannot effort the needed length of thread engagement with requested short assembly-times and also smaller thickness of light weight parts. Thread inserts can improve the screw joints active. Besides the length of thread engagement by using light weight materials the tribology of mechanical contacts plays an important role during tightening. This refers to both, increased friction coefficients and limited loading capacity for contact pressure. The result is that the desired preload is seldom reached with a standardized tightening specification from steel applications. Another aspect is the mismatch of thermal properties between steel and aluminium. Resulting from this it is likely that the preload stability is poor for components which are used at elevated temperatures (e.g. engine parts). These mentioned facts incorporate a hidden risk when using aluminium components and steel screw joints which are not adapted for aluminium assemblies. Using light weight materials in bolted joints the center of attention must be e.g. friction coefficient, required min. length of thread engagement and the resulting preload behavior. A verification of the reference values according mechanical stresses will result from these elements. The paper shows all necessary aspects to obtain reliable screw joints with aluminum and shows examples from measurement and calculation.
16:30-17:00 Arc Joining of Steel-Aluminium-Tailored-Hybrid-Blanks
Dipl.-Ing. Marius SteinersWelding and Joining Institute (ISF), RWTH Aachen University, Germany
Abstract
Increasing demands made on ecology and economics bring up the necessity to reduce the weight of vehicles considerably. Different possibilities for achieving this aim are available. There is, for one, the application of higher-strength steel materials with, at the same time, the reduction of wall thickness. There are limitations, namely the tendency to bulging is strongly increased through the reduced wall thickness. Another possibility is the application of expensive composite materials. In order to combine all advantages and disadvantages, the trend in modern vehicle manufacturing points clearly towards a material mix. This so-called material mix design fulfils all demands with regard to strength, weight and formability. The implementation is less expensive and their integration into the existent production chain is simple. Tailored hybrid blanks are a good choice since, after joining, these banks receive their final shape by forming. Great importance is attached to the combination of steel and aluminium.
Increasing demands made on ecology and economics bring up the necessity to reduce the weight of vehicles considerably. Different possibilities for achieving this aim are available. There is, for one, the application of higher-strength steel materials with, at the same time, the reduction of wall thickness. There are limitations, namely the tendency to bulging is strongly increased through the reduced wall thickness. Another possibility is the application of expensive composite materials. In order to combine all advantages and disadvantages, the trend in modern vehicle manufacturing points clearly towards a material mix. This so-called material mix design fulfils all demands with regard to strength, weight and formability. The implementation is less expensive and their integration into the existent production chain is simple. Tailored hybrid blanks are a good choice since, after joining, these banks receive their final shape by forming. Great importance is attached to the combination of steel and aluminium.
17:00-17:30 Bonded drive shafts made of Al-tube with steel load transfer elements
Manfred PeschkaFraunhofer Institute for Manufacturing Technology and Applied Materials Research (IFAM), Bremen, Germany
Abstract
The presentation describes different methods which can be used for the design of bonded shaft/hub joints. Using the example of a drive shaft, it is demonstrated that the use of an aluminum tube instead of a steel shaft can result in a weight saving of ca. 35%.
The design is based on analytical methods laid down in DIN 7190 and guidelines for the design of adhesive bonds. Due to the use of the material AA7075T6 and its properties, the temperature increase for fitting a transverse press fit connection, and correspondingly also the realizable oversize, is limited. The necessary tolerances of the components are also discussed as is the possibility for a “pseudo press fit“.
Results using different types of adhesives are presented. It is shown that the statement given in teaching books that an increase in the insert depth beyond a maximum value does not improve the load transfer does indeed apply for anaerobic-curing adhesives. With 1-component epoxy resin adhesives, these limits can however be shifted.
The presentation describes different methods which can be used for the design of bonded shaft/hub joints. Using the example of a drive shaft, it is demonstrated that the use of an aluminum tube instead of a steel shaft can result in a weight saving of ca. 35%.
The design is based on analytical methods laid down in DIN 7190 and guidelines for the design of adhesive bonds. Due to the use of the material AA7075T6 and its properties, the temperature increase for fitting a transverse press fit connection, and correspondingly also the realizable oversize, is limited. The necessary tolerances of the components are also discussed as is the possibility for a “pseudo press fit“.
Results using different types of adhesives are presented. It is shown that the statement given in teaching books that an increase in the insert depth beyond a maximum value does not improve the load transfer does indeed apply for anaerobic-curing adhesives. With 1-component epoxy resin adhesives, these limits can however be shifted.
17:30-18:00 Innovative Joining Methods for Lightweight Designs
Michael Marreiwb, Technische Universität München, München, Germany
Abstract
The application of lightweight design principles as well as new materials are contributing to a reduction of weight and therefore to an overall decrease of exhaust emissions in automotive transport. Aluminium space frames are characteristically lightweight frame structures in the automotive industry. Novel joining strategies and technologies have to be developed to provide appropriate joining quality for standard aluminium alloys as well as new types of composite material to manufacture lightweight frame structures using multi material design. For the above described issues joining strategies are primarily focussing on the material, the fundamental process of joining and the joints quality. This article presents the joining technologies investigated in the Collaborative Research Centre TR10 under consideration of these major-factors. They are able to join modern aluminium alloys as well as novel aluminium based reinforced composite materials. Therefore, the joining characteristics of the pure aluminium alloy, being the matrix material for the reinforcing elements, as well as the composite material are under consideration. To assemble composite aluminium profiles, joining processes and strategies have to be developed taking into account the special characteristics of basic aluminium alloy and the composite material. The joining technologies in focus are Friction Stir Welding (FSW), Bifocal Hybrid Laser Welding (BHLW), joining by hydroforming and joining by electromagnetic compression. FSW is a solid state joining process, combining frictional and deformation heating to obtain defect free high quality joints. The BHLW system incorporates an Nd:YAG laser and a high power diode laser. Both lasers are combined in one process zone by a dedicated optical head. This arrangement allows for a hot crack free joining of hardly fusion weldable aluminium alloys. The feasibility of joining by forming has been shown experimentally both for conventionally extruded and for reinforced profiles. Joining profiles to lightweight frame structures by both expansion and compression has been examined. The necessary forming pressure for the joining by forming processes was applied by a medium (hydroforming) and by a magnetic field (electromagnetic compression). To generate high-quality joints by forming the milling of the connecting elements (nodes) and the preparation of contact areas are necessary. The machined contact areas affect the joint characteristics through surface quality, burr formation, dimensional accuracy and influence of the peripheral zone. Metallurgical investigations and the characterisation of the mechanical properties of all produced joints were accomplished in order to evaluate the individual welding joints and joints by forming. In conclusion, the experimental investigations and the influences of the different materials on the joining processes are outlined and discussed.
The application of lightweight design principles as well as new materials are contributing to a reduction of weight and therefore to an overall decrease of exhaust emissions in automotive transport. Aluminium space frames are characteristically lightweight frame structures in the automotive industry. Novel joining strategies and technologies have to be developed to provide appropriate joining quality for standard aluminium alloys as well as new types of composite material to manufacture lightweight frame structures using multi material design. For the above described issues joining strategies are primarily focussing on the material, the fundamental process of joining and the joints quality. This article presents the joining technologies investigated in the Collaborative Research Centre TR10 under consideration of these major-factors. They are able to join modern aluminium alloys as well as novel aluminium based reinforced composite materials. Therefore, the joining characteristics of the pure aluminium alloy, being the matrix material for the reinforcing elements, as well as the composite material are under consideration. To assemble composite aluminium profiles, joining processes and strategies have to be developed taking into account the special characteristics of basic aluminium alloy and the composite material. The joining technologies in focus are Friction Stir Welding (FSW), Bifocal Hybrid Laser Welding (BHLW), joining by hydroforming and joining by electromagnetic compression. FSW is a solid state joining process, combining frictional and deformation heating to obtain defect free high quality joints. The BHLW system incorporates an Nd:YAG laser and a high power diode laser. Both lasers are combined in one process zone by a dedicated optical head. This arrangement allows for a hot crack free joining of hardly fusion weldable aluminium alloys. The feasibility of joining by forming has been shown experimentally both for conventionally extruded and for reinforced profiles. Joining profiles to lightweight frame structures by both expansion and compression has been examined. The necessary forming pressure for the joining by forming processes was applied by a medium (hydroforming) and by a magnetic field (electromagnetic compression). To generate high-quality joints by forming the milling of the connecting elements (nodes) and the preparation of contact areas are necessary. The machined contact areas affect the joint characteristics through surface quality, burr formation, dimensional accuracy and influence of the peripheral zone. Metallurgical investigations and the characterisation of the mechanical properties of all produced joints were accomplished in order to evaluate the individual welding joints and joints by forming. In conclusion, the experimental investigations and the influences of the different materials on the joining processes are outlined and discussed.