G15
Fatigue 2

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08:35
conference time (CEST, Berlin)
Fatigue Analysis of Solder-joints for Vibration and Shock Loads
28/10/2021 08:35 conference time (CEST, Berlin)
Room: G
H. Ziegelwanger, W. Hinterberger (Magna Powertrain Engineering Center Steyr GmbH & Co KG, AUT)
H. Ziegelwanger, W. Hinterberger (Magna Powertrain Engineering Center Steyr GmbH & Co KG, AUT)
The trend towards electrification of the powertrain requires the development of electronic components that can withstand various types of mechanical loads, e.g., harmonic and stochastic vibrations or mechanical shocks. In the automotive sector, electronic components must be tested according to the mechanical requirements of relevant standards, e.g., to the VW80000. A major challenge in this context is the fatigue strength of solder joints, for which these loads are usually considered to be an undesirable condition. In this talk, a comprehensive simulation process for assessing the fatigue strength of solder joints is presented. In a nutshell, first, a modal-based frequency response analysis is performed for the finite element model (FE-model) of an electronic component containing a printed circuit board (PCB) equipped with substitute FE-models of surface mount devices (SMDs), in whose pins the nodal displacements are measured as a function of frequency. These nodal displacements of each single pin are then scaled by static analyses of a corresponding solder-joint sub-model to retrieve the solder-joint stresses and the solder-joint damage or safety factor is finally calculated in FEMFAT max, FEMFAT spectral, or FEMFAT break for harmonic, random, or shock loads, respectively. Since the number of SMDs on a single PCB can be very large and the simulation process requires substitute FE-models for each SMD and an individual solder-joint sub-model for each solder-joint footprint, it was essential to develop and implement algorithms, which build the substitute FE-models for the SMDs and sub-models for the solder joints automatically. Therefore, the proposed process consists of three core technologies: semi-automatic generation of substitute FE-models for SMDs, automatic placement of these substitute FE-models on FE-models of PCBs and automatic generation of solder-joint sub-models, for which the geometry is calculated based on pin dimensions of the SMD, the pad dimensions on the PCB, solder volume, surface tension and gravitation.
PCB, Solder Joints, Fatigue, Dynamic Analysis, Vibration, Mechanical Shock
08:55
conference time (CEST, Berlin)
Influence of the Additive Manufacturing Process on CAE-based Life Estimation of a Medical Application
28/10/2021 08:55 conference time (CEST, Berlin)
Room: G
S. Vervoort (Hottinger Brüel & Kjaer GmbH, DEU)
S. Vervoort (Hottinger Brüel & Kjaer GmbH, DEU)
The results of CAE-based fatigue analysis depend on the quality of the inputs, especially the material properties. Generally, the properties are an outcome of physical material tests with a natural scatter. The material variability is influenced by material composition, the heat treatment, and the manufacturing process, such as additive manufacturing. Modern additive manufacturing processes also known as rapid prototyping or 3-D printing are used in multiple industrial sectors because of cost-effectiveness and the complexity of the component geometry. Individual components can be produced at comparable costs of a series production. The component is constructed in computer-controlled layers of one or more liquid or solid materials based on CAD-based geometries. Different additive manufacturing powder bed fusion methods have been established classified by their energy source: electron beam melting and selective laser melting. They could be combined with (powder metallurgical) hot isostatic pressing to improve the material structure and properties. The lecture shows the overview of fatigue material properties out of material tests with additive manufactured blanks and conventional manufactured specimens of the material Ti-6Al-4V. All subsequently tested in standardized strain-controlled fatigue tests. Based on the test results strain-life curves and cyclic stress strain curves are detected. Afterwards the fatigue material properties of the different manufactured material variations are used in a CAE-based fatigue analysis of a medical application, a hip joint implant, and the life predicted. The life predictions also include the influence of the effects in the additive manufacturing process, such as anisotropy and porosity. A vertical component of a transmitted force is assumed for the load. It is based on a published investigation. A comparison of the fatigue life results shows a clear dependence of the manufacturing process. The prediction of the fatigue life and the time of failure of a Ti-6Al-4V hip joint implant can be important for humans in relation to importance of perhaps necessary additional operations or exchange of implants.
Fatigue, Additive Manufacturing, Material Properties, Ti-4Al-6V, Medical Application
09:15
conference time (CEST, Berlin)
Multi-axial Fatigue simulation of Dishwasher Door Tab
28/10/2021 09:15 conference time (CEST, Berlin)
Room: G
N. Bhargava, K. Kusupudi, A. Nalawade (Whirlpool of India Ltd, IND)
N. Bhargava, K. Kusupudi, A. Nalawade (Whirlpool of India Ltd, IND)
Whirlpool Corporation designs and develops appliances which are intended for household and commercial purpose and Dishwasher is one such appliance. The Dishwashers are handled by consumers, children, or others who may be unskilled. Every time a consumer uses the dishwasher, they open the door to keep the utensils inside. This door is connected to the dishwasher tub with a door tab. The integrity of this door tab is important from the performance aspect of the door. The failure of the door tab may also lead to the safety hazard issue and hence it becomes important to provide a robust and reliable door tab. During door cycle testing which is cyclic in nature, failure of the tab is observed. The tab sustains for around 25% of the required door cycles (opening and closing of door). In order to understand the root causes of the failure and to identify significant factors, the simulation studies are carried out. The simulation methodology is developed to replicate the door cycle test. The door cycles are simulated in order to evaluate the bending stresses developed on the door tab during its real time application for one cycle. The fatigue life of the door tab is predicted using a uniaxial fatigue approach. This approach is utilized to correlate the simulation results with actual test data. There is a significant difference in the test and simulation results. To improve the correlation, a multi-axial fatigue approach is adopted in order to incorporate the non-proportional loading which is observed to be critical during door cycling operation. Using a multi-axial approach, good correlation is observed on the door tab failure cycles. To evaluate and improve the current design of the door tab, the root causes and factors are identified in simulation studies. Alternatively, the fatigue life was also evaluated using a commercial fatigue software and compared with the analytical outcomes. This paper also extends its scope on suggesting countermeasures to fix the issue and drive improvement to enhance the life and the reliability of the Dishwasher door tab.
Dishwasher, Door cycle testing, Door cycles, Fatigue life, Uniaxial Fatigue, Multi-axial Fatigue
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