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Fluids for Aerospace Hydraulic Systems

2022-05-13
This four-hour short course provides an introduction to fluids for aerospace hydraulic systems. Topics covered include an introduction to basics fluid properties, rheology, tribology, and fluid product development. In addition, the history and performance of different classes of fluids are discussed in detail, and specific failure modes such as erosion and sludge formation will be described. Along with an introduction to fluid degradation, information on used oil analysis test methods and interpretation will be provided.
Technical Paper

Use of Thermally Conductive Electrically Insulative (TCEI) Materials in E-motor Slot Liner Applications

2022-03-29
2022-01-0198
Slot liners are commonly used in electric motors to electrically insulate the motor windings from the laminated core. However, thermal conductivity of materials commonly used as slot liners is very low compared to other components in the motor thus creating a barrier for heat transfer. This thermal barrier affects overall motor performance and efficiency. Also, slot liners typically lack intimate contact with the laminated core resulting in air gaps which further increase thermal resistance in the system. Slot liners are traditionally made from high temperature films/papers that are cut and slid into slots of motors. The proposed work looks at developing an injection moldable slot liner to minimize air gaps. Additionally, use of TECI materials further lowers thermal resistance. A thermal finite element model has been developed to evaluate effects of slot liner thermal properties and air gaps on temperature distribution within the motor.
Technical Paper

Influences of Martensite Morphology and Precipitation on Bendability in Press-Hardened Steels

2022-03-29
2022-01-0238
Performance evaluation of martensitic press-hardened steels by VDA 238-100 three-point bend testing has become commonplace. Significant influences on bending performance exist from both surface considerations related to both decarburization and substrate-coating interaction and base martensitic steel considerations such as structural heterogeneity, i.e., banding, prior austenite grain size, titanium nitride (TiN) dispersion, mobile hydrogen, and the extent of martensite tempering as result auto-tempering upon quenching or paint baking during vehicle manufacturing. Deconvolution of such effects is challenging in practice, but it is increasingly accepted that surface considerations play an outsized role in bending performance. For specified surface conditions, however, the base steel microstructure can greatly influence bending performance and associated crash ductility to meet safety and mass-efficiency targets.
Technical Paper

True Fracture Strain Measurement and Derivation for GISSMO Calibration

2022-03-29
2022-01-0237
The importance of true fracture strain was initially highlighted in the context of local versus global formability considerations used in material selection among advanced high strength steels (AHSSs) of similar tensile strength. Inspired by the relative studies, a precedent work had compared the discrepant fracture strain results from the digital image correlation (DIC) and the optical measurement techniques. This work further investigated various factors, such as the measurement techniques, the effective strain formula, and the fracture surface morphology, which could affect the true fracture strain measurement and derivation results, and subsequently the calibration of the Generalized Incremental Stress State dependent damage Model (GISSMO) used in crash simulations. In the meantime, explanations and discussions on the possible mechanisms behind these effects were also presented.
Technical Paper

Forming Characteristics of Very Low Carbon High strength Dual Phase Steels Produced through a Flex Mill Continuous Galvanizing Line

2022-03-29
2022-01-0239
A low carbon, lean alloyed chemistry was selected for the development of high strength dual phase (DP) steels with enhanced global and local formability. Optimized best process conditions including clean steel practices, choice of suitable casting powder, hot rolling and continuous anneal set points resulted in excellent mechanical properties and formability characteristics of DP steels. The enhanced balance of strength and formability is attributed to the optimization of the microstructure through refinement, uniformity and balancing microconstituents mechanical response and guaranteeing outstanding internal cleanliness. In this contribution, production strategy and formability characterization of DP steels with tensile strengths of 780 MPa and above relevant to automotive body structure applications will be discussed.
Technical Paper

Development of a transmission-illumination-based crack detection method using translucent tools for testing of thin-walled metal sheets and foils

2022-03-29
2022-01-0242
The formability of thin-walled metallic sheets and foils is increasingly gaining in importance in the automotive industry and in medical and food packaging. As a result, the demand for methods to test the deep drawing and stretch forming capabilities of these materials is increasing significantly as well. In deep drawing and stretch forming, the in-situ crack detection is either performed manually by purely visual evaluation by the machine operator or automatically by a crack detection system. The automatic crack detection method commonly integrated in sheet metal testing machines functions by analyzing the drawing force during forming. However, friction, vibration, and machine noise are disturbance variables that prevent crack detection in thin sheets and foils. The same disturbance variables also prevent robust crack detection in thin sheets and foils by systems that analyze structure-borne sound.
Technical Paper

Local Thermomechanical Processing for Improving Formability of High Strength Aluminum Sheets

2022-03-29
2022-01-0244
Limited room temperature formability hinders the wide-spread use of high strength aluminum alloys in structural body-in-white parts. Stamping or extrusion at warm temperatures or from softer tempers are the current solutions. In this work, our approach is to start with age- and work-hardened sheets from 7xxx, 6xxx, and 5xxx family of alloys and improve their formability using local thermomechanical processing only in the regions demanding highest ductility in the forming processes. The processes used were friction stir processing (FSP) and roller bending-unbending. In both the methods sheets were locally deformed and heated simultaneously without any change in the final sheet geometry or chemistry. Initial results indicated significant deformation in the processed zones with minimal sheet distortion. FSP also resulted in dynamically recrystallized, fine grained (d <5 µm) microstructures in the processed regions with textures significantly different from the base material.
Technical Paper

Adjoint method in optimizing conformal cooling channels of 3-D printed high-pressure tools for aluminium casting

2022-03-29
2022-01-0246
The emergence of additive manufacturing (AM) technology has enabled the internal cooling channel layout for high pressure aluminium die casting (HPADC) tools to be designed and modified without topological constraint. Optimisation studies of a full industrial HPADC mould for extending the tool service life has received limited attention due to the high geometrical complexity and the various physics with multi time and length scales in addition to the manufacturability limitations. In this work a new computational efficient algorithm that employs the adjoint optimization method has been developed to optimize the coolant channels layout in a complete mould with various 3D printed inserts. The algorithms reduced significantly the computational time and resources by decoupling the fluid flow in the coolant channels from the tool and simulating them separately.
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