A Simulation Prediction Method of Transient Forming Limit in Hot Forming of Ultra-high Strength Steel

Abstract

The invention discloses a method for simulating and predicting a transient thermoforming limit of ultra-high strength steel. The method comprises the steps as follows: a material constitutive model under a stable equilibrium condition is determined; a thermoforming limit model is determined on the basis of a localized instability theory of a material uneven groove hypothesis under a stable condition, wherein the material constitutive model determined under the stable equilibrium condition is adopted in the thermoforming limit model under the stable condition; and the thermoforming limit model is utilized to predict and simulate the thermoforming limit under a transient technological condition.

Description

technical field [0001] The invention relates to a method for simulating and predicting the transient hot forming limit of hot forming, especially a concentrated instability theory (M-K theory) based on the assumption of uneven material grooves under the transient process conditions of ultra-high strength steel hot forming Determination of the forming limit. Background technique [0002] Lightweight is one of the main methods to achieve energy saving and emission reduction of automobiles. At the same time, in order to improve the impact resistance and anti-collision performance of automobiles, the material selection of automobile structural parts must change to light weight and high strength. High-strength steel and ultra-high-strength steel as well as aluminum and magnesium Alloy materials are gradually replacing steel used in traditional automobile bodies, and have become an important way to reduce weight and increase crash safety performance of automobiles. However, the p...

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Problems solved by technology

However, the actual hot forming process is a non-equilibrium transient process in which the temperature of the sheet material changes continuously (cooling from a temperature above A3 to room temperature at a cooling rate of 50-100°C / s), and the material formability is not only affected by strain and temperature, At the same time, it is also affected by transient process factors such as strain rate, temperature gradient, and microstructure changes during the deformation process. The complexity of experimental control and accurate measurement of transient process conditions makes it difficult to determine the transient hot forming limit by experimental methods.

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