Search Results

This paper presents a review on the fatigue mechanisms in automotive valve springs manufactured on high-strength steel, as well as in other similar parts, like as helical suspension spring. The review was conducted with a phenomenological focus to support new developments in material for use in Otto and Diesel engines. Mechanical fatigue is a common process of damage that occurs in components subjected to cyclic loads, but in the particular case of valve springs, this problem is controlled through the project restriction, usually with the limitation of higher levels prescription of shear stress. In an attempt to increase this limit, allowing greater efforts at the elastic region the Material Engineering designs materials with higher toughness and the Manufacturing Engineering plays in the prevention or defects minimization, often inherent to the material.

This paper describes the development of a low pressure die casting process for cylinder heads, with focus on the minimization and control of the micro-constituents in an aluminum alloy. The increasing demand for new designs of auto-parts which are interchangeable among platform and global powertrain, confirm the need for good quality equalization in a globalized market. However, in the specific case of engine aggregates, there is a strong complicating factor which is the fuel mixture variation used in several regions of the world, which create distinct combustion rates and thermo-mechanical efforts. In view of such scenario, a Low Pressure Die Casting process (LPDC) was developed as an alternative for the current process by Gravity Sand process (GS). Their objective is to fulfill the material requirements, focusing on the minimization of the Secondary Dendrite Arm Spacing (SDAS), which exert a significant influence on the most critical mechanical properties.