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Content 01 Introduction Abstract Five reasons for the calculation of bolted joints Pages 3-4 02 Basics Calculation of bolted joints according to VDI 2230 Common joints and special cases Calculation of multibolted joints in compliance with standards Pages 5-7 03 Targets Time saving: No more formulas Standardization Easy usability Targeted optimization of bolted joints Variant construction for new opportunities Approximation method for the ideal threaded fastener Digitalization of engineering Pages 8-11 2
01 Introduction Abstract Spreadsheet analysis or calculator: These are tools that have been tried and tested for decades for the calculation of bolted joints. But CAx technologies are also finding their way into this field - with a versatile calculation tool for the design of safe and reliable bolted joints in accordance with VDI guideline 2230. This tool also provides additional functions, such as the recalculation of threaded fasteners and the iterative optimisation of available bolted joints. Five reasons for the calculation of bolted joints The design of connections is one of the core competencies of most designers who work in mechanical construction. Previous generations often relied on their own practical knowledge. Today, they calculate each individual or at least each critical bolted joint, and there are several good reasons for this. First of all: The requirements for the safety and productivity of machines are increasing steadily. The malfunction of a bolted joint is not tolerated - either by the mechanical engineer or by the machine user. The same goes for vehicles and systems. Second of all: At the same time, designers strive to build all the components exactly according to the individual requirements (i.e. load spectra). The components and also the bolted joint should not be significantly oversized, but correctly sized. Otherwise, other construction targets such as lightweight construction, efficiency and sustainability will not be sufficiently met. In other words: The joint should not be as safe as possible, but as safe as required, and with the highest reliability. 3
Third of all: Sets of rules are available for dimensioning and calculation, which the designer can orient himself/herself with. The VDI guideline 2230 must primarily be mentioned here. Along with DIN EN and ISO calculation methods, Eurocode 3 as well as industry-specific sets of rules are also worth mentioning. Relevant technical standards and guidelines in the area of bolt calculation Fourth of all: Mechanical engineers and components suppliers are more and more frequently confronted with extensive documentation obligations. The verification of bolted joints suitability is also required for the respective application. This is primarily the case for new machines, but can also be requested for existing machine series. In this case, a recalculation also requires a verification. Fifth of all: Lastly, designers have modern calculation tools at their disposal today which are based on the relevant guidelines and allow a reliable and standard-compliant as well as time-saving calculation of bolted joints. 4
02 Basics Calculation of bolted joints according to VDI 2230 MDESIGN bolt demonstrates which functions these tools provide. This calculation and information software is one of the many libraries of the MDESIGN family for the calculation of machine and drive elements. With around 35.000 users, this software is widespread around the world. The target and the purpose of MDESIGN bolt is to guide the designer through a safe calculation of a single bolt connection according to the VDI guideline 2230. In this guideline, processes on the pre-dimensioning of bolt nominal diameters and on systematic recalculation of bolt connections have been published for many years, and this is periodically revised. Even if this guideline has no binding effect, in the construction world this has become a recognised basis for the calculation of bolt connections, and not only in Germany. With MDESIGN bolt, designers have a user interface at their disposal in which they enter the relevant environmental conditions and loads of the bolted joint which is to be built or verified. This procedure is facilitated by an almost intuitive operation with aids, suggestions and information. For instance, many text and graphics aids are available for tightening factors, friction coefficients and factors for load applications. Context-sensitive support with the definition of relevant boundary conditions 5
The integrated technology and material database simplifies bolt calculation: Many common parameters for the calculation (strength grades, material properties of the clamped components or factors for load application) are already stored, and all customary bolt types on the market can be calculated. Database with standardized properties for numerous bolt materials Common joints and special cases However, at the same time, MDESIGN bolt is also ideal for special cases of bolted joints. The designer can insert or read individual materials and bolt geometries or inch-based bolts. In addition other standards are taken into consideration - for example technical rules from the Eurocode 3 to design and calculate steel bolts. Furthermore, MDESIGN bolt also calculates eccentric load cases and various parameters such as the surrounding temperatures of the bolt connection can be considered. In this way, the calculation tool takes into account the fact that the coefficient of thermal expansion of the components or materials used affects the safety of the bolted joint. 6
Calculation of multibolted joints in compliance with standards With MDESIGN multibolt, a tool is available for the calculation of multibolted joints as an extension of MDESIGN bolt. The basis of this is VDI 2230 Part 2. By using the Finite Element Method (FEM) the designer can indicate the framework conditions of the joint and determine the occurring loads and strengths, especially for the bolt subject to the highest load. The FEM is linked to analytical calculation methods of the VDI 2230 for many standard cases. For selected bolt sections, MDESIGN multibolt takes on the large part of the complex and time-consuming calculation task, which otherwise requires a sophisticated FEM software. Calculation of highly stressed multibolted joints 7
03 Targets Time saving: No more formulas Using the MDESIGN bolt calculation tool creates the conditions for a significantly more modern, time-saving working method. The designer neither has to look up formularies nor calculate the desired values with a calculator or Excel. Instead, he/ she inserts the values based on which the bolt connection is designed and receives a result in compliance with the standards. MDESIGN bolt takes on the calculation. Numerical and analytical calculation processes are applied here. The result is an easy as well as safe calculation of bolted joints which can be integrated into the documentation of the machine or system. Standardization Companies desire for standardization is frequently their main reason for using MDESIGN bolt and other MDESIGN libraries. These tools simplify and standardize not only the calculation of machine elements. They also improve the safety level of the entire construction and form the basis for consistent documentation, which can be issued in various languages and guarantees the transparency of the machine for the user, as information is given on the standards according to which the bolted joint and other machine elements are selected and built. Easy usability Despite the complex calculation method and the many options, calculating bolted joints with MDESIGN is very easy from the designer s point of view. The fact that all libraries and modules of MDESIGN (with which shafts, shaft-hub connections, gears, springs, welded joints and much more can be calculated) are equipped with a 8
uniform user interface also contributes to this. This simplifies work significantly. But hardly any designer builds bolted joints predominantly or exclusively. Thats why MDESIGN is used - if required - quickly and efficiently for other machine elements. Performance scope of tools for the calculation of machine elements and component groups Targeted optimization of bolted joints Along with these benefits, there are others which are just as or even more important, as they open up brand new opportunities. For instance, the engineer has the chance to recalculate existing connections specifically with MDESIGN bolt with the aim of improving them. This can determine whether, to name but a few examples, one can use a bolt with a smaller diameter or reduce the length of engagement in a specific case. 9
Variant construction for new opportunities Another possibility resulting from the use of MDESIGN bolt (and of other MDESIGN modules) is variant construction, for which there is an internal template. With this, alternative bolted joints can be calculated carefully and compared. Various parameters such as size, material and bolt type may vary until the best solution is found for the respective threaded fastener. Individual contributing factors such as friction can also be modified and optimised in this manner. This is an advantage which should not be underestimated compared to the good old bolt calculation with Excel, which does not provide these possibilities. Parametrical optimization with modern CAx tools Approximation method for the ideal threaded fastener But the functions that MDESIGN bolt provides for construction optimization go further. There are also templates for serial and parameter analysis, so that the engineer can approach the optimal construction and choose the optimal bolted joint in each case. 10
Digitalization of engineering With these properties, MDESIGN bolt simplifies the calculation of bolted joints and assists the engineer with the development of machines, vehicles and systems. This helps reduce the construction time and shorten the time to market. At the same time, this increases the safety level because the respective safety checks are performed. In many mechanical engineering construction departments, MDESIGN bolt has already proved successful as a modern instrument for bolt calculation and for verification in accordance with VDI 2230. As part of digitalization in construction, this calculation tool creates an essential condition for a simplified calculation of machine elements in compliance with the standards. At the same time, all MDESIGN modules allow the use of construction data across components and disciplines and thus also simplify the documentation. Thus MDESIGN becomes an integral part of CAD and PLM systems. Your personal appointment: You have questions which the whitepaper has not answered yet? We will be glad to talk to you personally about the topic calculation of bolted joints. Just fill in our contact form and request a callback or send us a message. >> Request a consultation by contact form! 11
Speed up your engineering with the proven MDESIGN libraries for the calculation of machine elements Design Calculation Optimization Documentation Your contact for successful digital engineering: Dipl.-Ing. Reinhard Blömer Technical managing director reinhard.bloemer@mdesign.de + 49 234 30703-60 MDESIGN Vertriebs GmbH Königsallee 45 44789 Bochum Germany Phone: +49 234 30703-60 Email: info@mdesign.de Editing: Dipl.-Ing. Reinhard Blömer Layout & Design: M.A. Nicola Grade Pictures: Shutterstock / Fotolia www.mdesign.de www.mdesign.de