Component Fatigue Behaviors And Life Predictions Of A Steering Knuckle Using Finite Element Analysis
The paper describes a vehicle steering knuckle undergoing time-varying loadings during its service life. Fatigue behavior is, therefore, a key consideration in its design and performance evaluation. This paper is aimed to assess fatigue life and compare fatigue performance of steering knuckles made from three materials of different manufacturing processes. These include forged steel, cast aluminum, and cast iron knuckles. In light of the high volume of forged steel vehicle components, the forging process was considered as base for investigation. Static as well as baseline cyclic deformation and fatigue properties were obtained and compared. The paper envisages that in addition, referring a number of load-controlled fatigue component tests conducted for the forged steel and cast aluminum knuckles. Finite element models of the steering knuckles were also analyzed to obtain stress distributions in each component. Based on the results of component testing and finite element analysis, fatigue behaviors of the three materials and manufacturing processes are then compared. The paper concludes with that forged steel knuckle exhibits superior fatigue behavior, compared to the cast iron and cast aluminum knuckles.
Durability Design Process of a Vehicle Suspension Component
An improved methodology to quantitatively assess fatigue lives of automotive structures and to identify critical and non-damaging areas for design enhancement and weight reduction is presented. The methodology of automated fatigue assessment, called CAE-FATIGUE (Computer Aided Engineering in Fatigue), combines a load-time history file with the result file from an elastic finite element analysis to estimate fatigue lives (damage contours). The CAE-FATIGUE methodology is of particular value when it is used as a proactive tool in the early design stage to reduce design iterations and prototype costs. CAE-FATIGUE is applicable to elastic finite element analysis results because the Glinka energy density method (plasticity correction approach) is used to approximate true stresses and strains from the elastic stresses. CAE-FATIGUE cannot be applied to cases where loading frequency is of importance, since the elastic stress components from all loading channels are superimposed to the resultant stresses at the same specific time. CAE-FATIGUE calculates fatigue lives based on the maximum normal stress and strain range on a critical plane on which maximum principal stresses for the entire loading history are maximized. Also, CAE-FATIGUE can generate life/damage contour plots to identify critical and nondamaging areas for design enforcement and weight reduction. This report focuses on practical aspects of designing automotive suspension components to avoid fatigue failure. The design process for a proposed front suspension knuckle is presented for illustration purposes. Critical planes highlighted with damage contours can also be used to develop “smart” and efficient prototype tests. Emphasis is placed on how to optimize the component to meet the durability criteria through mechanical life test procedure and test field endurance schedules.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.