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.
Fatigue analysis and the local stress–strain approach in complex vehicular structures
Abstract In the last 20 years the `strain-life' fatigue analysis philosophy has achieved the status of industry standard in the automotive, truck and earth moving industries in North America. Although the fundamental concepts of the method are quite simple, the recent massive computerization of the techniques, and their incorporation into large dynamically loaded body and chassis durability calculation models, has resulted in new capabilities and insights for engineers, but also has meant new challenges for the creators of fatigue simulation software. This paper gives a brief history of the evolution of this type of calculation software in the vehicular industry from the observation of stress–strain hysteresis behavior, through the early development of computer versions of the stress–strain shape and memory models, to their evolution into routines that are closely linked to vehicle dynamics models that calculate loads in structures, finite element models that transform the loads into local stresses, and subsequent plasticity correction and damage evaluation routines which yield expected life color contour plots for vehicle body and chassis.
On the Plasticity of Crystals
In the following, a theory is given with the purpose of establishing a mathematical relation between the stress and the strain in a crystal when plastically deformed. The existence of a "secondary structure" in crystals is adopted as a basic hypothesis. This structure was pointed out by Professor F. Zwicky to be a consequence of what he calls "cooperative phenomena." The assumption that gliding in crystals takes place between the blocks of the secondary structure is the starting point of the following theory. The additional hypothesis of assuming a statistical distribution of the different forces which produce gliding between the blocks, gives us the means for going further in the calculations. The final result which is the stress strain curve of a crystal, is an exponential law containing three constants, i.e., the torsional modulus G, the elastic limit, (γs,τs) and the maximum applicable stress τm. The form of the hysteresis cycles is deduced from the same considerations and moreover a formula is obtained for the areas of the cycles. Experimental verifications were made on a single crystal of copper, and also on ordinary microcrystalline copper.