A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components

• In the last decade, hot metal forming of advanced high strength steel (AHSS) have improved passenger safety and open possibilities for lightweight design. Hot metal forming can be applied to locally tailor the microstructure of components and gradual vary mechanical properties to improve crash resistance behaviour and optimized weight for e.g. safety related parts. Sometimes post punching or trimming must be done on hardened parts. Such conditions induce damage and fractures in the trimmed edge. Another issue is that high pressures are required in cutting operations due to the high yield stress of press hardened parts, which accelerate wear and produce premature fracture in tools. Optimizing cutting operations to minimize damage and wear are essentials and numerical simulations of cutting operations can be of good assistance. One of the main challenges in the numerical modelling consists of numerically be able to treat the extremely large deformation occurring in the cutting zone. A second challenge is to find suitable failure models. In this work, the punching process of soft and hard microstructures obtained by press hardening is experimentally studied, but also modelled with a combination of smoothed particle Galerkin (SPG) method and finite element method (FEM). Laboratory punching tests with different clearance values were carried out using sheets of different fracture strengths. All experimental cases are numerically modelled. Validation is conducted by comparing numerical results with experimental measurements of punch force and displacement. In addition, morphology of the final cutting edges from both real and virtual are compared. Numerical results show good agreement against experimental measurements. Furthermore, the combined method gives robust-ness and stability as it can handle large deformations efficiently.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

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Hållfasthetslära

Solid Mechanics

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