PSI - Issue 57

Ewelina Czerlunczakiewicz et al. / Procedia Structural Integrity 57 (2024) 743–753 / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The new and ever-increasing stringent regulations that have affected the automotive industry in the last 30 years has pushed all major automotive manufacturers to develop electrically driven vehicles. This has come with a huge effort in terms of R&D investments, in order to adapt the existing technology to the automotive market, as well as creating a new combinations of cars powertrains: fully electric cars (EV), mild hybrid electric vehicles (MHEV) and plug-in hybrid electric vehicles (PHEV)[Matulka (2014)]. The recent decision of the EU commission to ban the sale of combustion engine cars by 2035 is expected to increase the percentage of EV sales, however the automotive sectorstill is facingsignificant challenges in simply replacing fossil-fueled cars with electric ones. The electrification of the powertrain has brought an important change of architecture of the thermalsystems of the vehicle. The main design effort is currently focused on optimizing the size, shape and noise level of the components, without any negative effect on its performance and durability. Due to many possible combinations of products integrated into the system, many possible designs need to be considered for validation. The objective is therefore to make this process faster. Numerical simulation offers the possibility to validate the mechanical endurance of cooling systems without relying exclusively on physical tests on prototypes. The standard way to validate the design of automotive components was obtained through an iterative process that strongly relies on Finite Element Analysis (FEA) results. The mechanicalendurance was typically evaluated according to rather conservative criteria based on the material's ultimate tensile strength (UTS), and basically targeting an infinite fatigue life endurance. For many years, this degree of conservatism permitted a quicker design validation without incurring in unexpected design related field failure (warranty failures). However, since a decade, this approach has shown to be outdated in relation to a highly competitive market, where automotive components have to be designed with the goal of downsizing and design to cost. Their durability needs to be verified by tailored accelerated life tests based on a fatigue design criterion.

Nomenclature ALT

Accelerated Life Tests Design for Reliability

DfR DV

Design Validation ECM Engine Cooling Module EV Electric Vehicle FEA Finite Element Analysis HTR High Temperature Radiator MHEV Mild Hybrid Electric Vehicle MTD Modal Transient Dynamic OEM Original Equipment Manufacturer PHEV Plug-in Hybrid Electric Vehicle PSD Power Spectrum Density RFQ Response for Quotation RMS Root Mean Square SSD Steady State Dynamic UTS Ultimate Tensile Strength

1.1. Numerical Validation of the Engine Cooling Module The application of numerical modeling and validation of automotive components has experienced significant growth over the past two decades. The use of Finite Element Analysis (FEA) as a method to accelerate product development and reduce costs is not a new concept. However, it is the decision-making power of FEA results that is nowadays leveraged. If 20 years ago FEA results were the means to justify a design freeze and launch the physical tests, starting from 10 years ago FEA methods have been routinely adopted to optimize the design and increase the