Identification method for plastic compression molding critical damage

Abstract

The invention discloses an identification method for plastic compression molding critical damage. The method comprises the following steps that: 1) under a condition of an equal temperature and a constant strain rate, carrying out compression molding on a round rod material through an upper die, and evenly dividing whole compression molding into N control periods; 2) extracting the internal stressof the material after compression molding is carried out, and carrying out calculation to obtain the cumulative damage value of each control period; 3) establishing the function of cumulative damageand macroscopic equivalent strain, on the basis, establishing the function of a damage sensitivity coefficient and the macroscopic equivalent strain, the corresponding macroscopic equivalent strain iscritical fracture strain when the damage sensitivity coefficient approaches to 0, and carrying out calculation to obtain a critical damage value; and 4) repeatedly adopting the above method to establish an association model of the critical damage value, the temperature and the strain rate. By use of the method, the critical damage of a plastic compression process can be effectively identified, defects including product cracking and the like due to blind forming technical design are avoided, and a scientific guidance is provided for the product technical design.

Description

technical field [0001] The invention relates to a method for identifying critical damage in plastic compression forming. Background technique [0002] At present, there are many studies on the critical damage in the plastic stretch forming process, but there are few studies on the critical damage in the plastic compression forming process. Domestic Quan Guozheng et al. carried out the "Critical Damage Factor of AZ80 Magnesium Alloy under Different Temperature and Strain Rate Conditions" Research" (Functional Materials, No. 5(41), 2010), mainly using the Cockcroft-Latham damage factor model built in the numerical simulation software, the software automatically calculates the damage value in the plastic compression forming process, because the numerical simulation software The calculated damage value display accuracy and other cumulative error problems, the damage sensitivity coefficient obtained by using the ratio of the difference between the adjacent step damage value and t...

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Problems solved by technology

[0002] At present, there are many studies on the critical damage in the plastic stretch forming process, but there are few studies on the critical damage in the plastic compression forming process. Domestic Quan Guozheng and others have carried out "Critical damage factors of AZ80 magnesium alloy under different temperature and strain rate conditions". Research" (Functional Materials, Issue 5 (Volume 41) in 2010), mainly adopts the Cockcroft-Latham damage factor model included in the numerical simulation software, and the software automatically calculates the damage value in the process of plastic compression forming. The calculated damage value display accuracy and other cumulative error problems, the damage sensitivity coefficient obtained by using the ratio of the difference between the damage value of adjacent steps to the cumulative damage often has a large number of 0 values ​​in the gap, and it is impossible to effectively study the change law of the damage sensitivity coefficient

More importantly, the above-mentioned literature has not carried out in-depth calculation and analysis of the damage value in compression plastic forming, and has not revealed the internal relationship between the cumulative damage and the equivalent strain and strain rate under the condition of isothermal constant strain rate, and the damage in the literature reports is sensitive. Most of the points on the relationship curve between coefficient and displacement or time are very scattered, and the critical damage strain calculated by linear fitting has a large error, which cannot guide the design process design and development

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