FEM
Lesjöfors uses FEM for mechanical springs with geometries where the conventional calculation methods do not give required reliability and for geometries where the conventional methods can not be used. The method is also used for load cases where the spring has loads and deflections in different directions. For normal spring geometries and normal load and deflection systems the conventional methods give reliable and precise results for correct dimensioning.
High precision calculations
The Finite Element Method (FEM) is basically a numerical technique foremost used to solve partially differential equations. The method got a rigorous mathematical foundation in 1973 by work of Strang and Fix; An Analysis of The Finite Element Method, and has after that been developed for solving different physical problems in for example mechanical strength, electromagnetism and fluid dynamics.
The method works well for strength calculations of complicated geometries and it often predict results with good precision. The method generates large data volumes for three dimensional complex structures. The development of new software and new, fast computers has strongly contributed to the spread and availability of the method to many branches including the engineering industry.
Examples of use
Some examples where use of FEM can be favourable:
• Wire forms http://www.lesjoforsab.com/
• Complex flat/leaf springs
• Torsion springs http://www.lesjoforsab.com/
• Non-symmetric coil springs
The process actions
Lesjöfors´ FEM process for springs has principally the following steps:
• Collection of data – for example geometry, deflection, loads, material data
• Modelling – create the model, apply loads and conditions, define material properties
• Calculation – choice of calculation and type of result data, calculation
• Evaluation – analyse of deflection, loads and stresses, judgement of reliability
• Result – production of result pictures, result analysis, conclusions
The complexity of FEM calculations leads to a much longer process time compared to calculations with traditional methods. Therefore the cost is also considerably higher which often limits the use of FEM to larger projects.
Photo:
http://www.prlog.org/
