A FINITE ELEMENT MODELING ACCOUNTING FOR CASE-HARDENED STEEL WITH CONTINUALLY VARYING HARDNESS

Proposed is a finite element model for plate-structures within which the mechanical properties varies dramatically from their outer surfaces towards inside cores. Developing such a model truly representing what can be characterized as laminates has a great significance in the community of not only computer-aid-engineering but also material science. The benefits of this proposed methodology will be discussed by case studies of a centrifugal pendulum that has gained its popularity in high-end passenger cars because of its superior vibration suppression. The system in this work is subject to excessive and destructive load due to centrifugal forces at extremely high angular velocities. In this study, it can be shown that the inner core, with much softer mechanical properties, easily gets into the plastic state and significantly restrains it from continuing to carry more loads as the angular velocity ramps up. As the result, the outer case layers have to take an increased share of loads and their stresses are significantly raised. The author will show the effect of the thickness of hardened layer and hardness readings on the loading capacity. It is interesting to demonstrate that it is the outer surface that would start to crack first, even if it has much higher ultimate tensile strength throughout the body, provided the load is destructive and non-cyclic. The proposed material model has been found to be compared well with the test results for the load-carrying capability. This work will help engineers to design a robust mechanical structure with invisible laminated metallurgical characteristics, for example, due to the case-hardening heat treatment.