Diplomarbeit: Remeshing of spot welds in FE meshes

Diplomarbeit Remshing of spot welds in FE meshes
This diploma/master thesis is a co-operation with LMS International, Kaiserslautern. Motivation: Finite Element Modeling (FEM) is a widely accepted technique in design departments of car manufactures for daily analysis of noise, vibration and durability problems with car bodies and fully assembled vehicles. It basically comes down to discretizing the CAD (Computer Aided Design) models into many small elements approximating the geometry and assign properties to those elements. Different element types are used such as triangular and quadrangle shell elements for thin plate structures, beam elements and 3D solid elements. Beam, shell and solid meshers are available on the market which generate the FE mesh (nodes and elements) from a CAD model. Changes of the CAD model require repeating the meshing step, which might be a tedious and time-intensive process for complex shapes. This is particularly important if the FE simulation itself is very time-consuming as e.g. in durability simulations. Therefore, in practice, not each design change/iteration is implemented on the CAD model. Engineers often prefer to directly modify the FE model for what-if analysis. Also, in some cases, only the FE model is available. So, it is of crucial importance that design engineers are able to locally modify the mesh, e.g. for connecting items such as battery, headlamps, brake booster, etc. with bolted connections. This requires drilling holes or placing spot welds (dt. Schweißpunkte) in the meshes. Objective: In the previous diploma thesis "Development and validation of a robust and fully automated algorithm for drilling holes in FE-meshes" a software prototype was developed to drill holes in industrial meshes of vehicle structures preserving mesh quality (see pictures below). With regards to spot welds this approach needs to be refined. Especially mesh patterns should not be descroyed and should be used for filling the so-called transistion area between a spot weld and the rest of the mesh. Important aspects for spot welds are quality measures of LMS must be meet, number of triangles less than 20%, input of pattern in arbitrary position and oriantation, pattern should be preserved during successive operations, robustness in curved mesh areas, robustness near edges, tuning of parameters.
Bad elements are high-lighted in dark-blue.	Patter inserted into a mesh manually.
Fragen? Georg Umlauf (Raum 36-236) Burkhard Lehner (Raum 36-234) Details on LMS: LMS is the fastest-growing provider of solutions that integrate functional performance engineering into the digital development pipeline. We provide the testing systems, multidisciplinary virtual prototyping software, engineering services and collaborative engineering tools that enable our customers to turn product refinement and superior process efficiency to their strategic competitive advantage. Through our technology, software, and people, LMS has become the partner of choice for Fortune 500 companies in the automotive, aerospace, and other advanced manufacturing industries around the world. LMS is the recognized leader of predictive technologies for the critical functional disciplines such as structural integrity, acoustics, durability, and dynamic motion simulations. Our integrated range of solutions can handle the most sophisticated of modeling situations: the operating dynamics of high performance engines with flexing parts and clashing springs, the fatigue life of spot-welded bodies subject to multiple loads, the sound field inside a car as mount stiffnesses are varied... They use patented technologies. They are unrivalled in their accuracy. They are also very fast: seamless integration with the CAD model, automated meshing, efficient algorithms and parallel processing mean that individual simulations can often be set up and completed in hours. This means that virtual models can be tested and refined at the component, sub-assembly, and full system levels early enough in the design process to make a real difference. More details on LMS can be found on www.lmsintl.com.