STRAIN HARDENING OF STEEL SHEETS IN MULTI-PHASE THICKNESS REDUCTION

The results of investigation of strain hardening phenomena in model investigated ironing process are presented. As a characteristic model we used the strip-ironing of larger thickness steel sheets between inclined die surfaces. The low carbon mild steel sheet C0148 P3, suitable for plastic forming was used. It was measured deformation force (tensile force) in conditions of changing the relevant tribo-influences in multi-phase ironing. Also, the stress intensity distribution for different conditions were obtained by using micro hardness method. Finally, the micro hardness was measured and then stress intensity fields are determined. In each phase of ironing the hardening increas was determined as well.Publishe

FRICTION AT SHEET METAL TESTING BY IRONING IN CONDITIONS OF HIGH PRESSURE

In cold metal forming processes characterized by high contact pressures, local tool loading, generation of new workpiece surfaces etc., realization of appropriate lubrication regime and micro-welding elimination are of great importance. Correct choice of tribo-conditions and identification of boundary relations at this contact surfaces enables controled flow in surface layer which has the yield stress enough lower then basic material. Results of presented investigations are related to cold metal forming, especially to ironing.Publishe

SPECIFIC FORMABILITY CHARACTERISTICS OF HIGH STRENGTH SHEET METAL INTENDED FOR AUTOMOBILE INDUSTRY

Presented in the paper are the results of investigations of high strength steel sheet metal (HSS), especially 'bake hardening" sheets which have the yield strength increased to a high value in the course pf baked paint treatment. For the assesment of deflection tendency we employed YOSHIDA buckling test, and the indicators obtained relate to the HSS capabilities toward shape fixability and fittability. The other formability tests (biaxial stretching) was made in the conditions of realization of a very intensive aging accompanied by hardening, thus simulating the final phase of car body painting (paint baking in accordance with a prescribed thermal regime). In addition to the standard formability characteristics (Rp, Rm, A80, n-value) the hardening intensity was also investigated by determining stress and strain fields in biaxial stretching in different experimental conditions: temperature, depth of draw, contact states etc. Special attention was paid to the determination of stress field in aging specimens from known strain field in nonaging specimens and strengthening curves of aging sheet metal. Determined also were strain fields in nonaging specimens from known stress fields of aging specimens and strengthening curves of nonaging material.Publishe

SUITABILITY OF HIGH-STRENGTH SHEET METAL FOR DEEP DRAWING FROM THE STANDPOINT OF FURTHER HARDENING BY AGING

Presented in the paper are the results of tests made with high-strength steel in the conditions of realization of a very intensive aging accompanied by hardening, thus simulating the final phase of car body painting (paint baking in accordance with a prescribed thermal regime). In addition to the standard formability chatacteristics (Rp, Rm, A80, "n" factor), the hardening intensity was also investigated by determined stress-strain fields in biaxial stretching in different experimental conditions: temperature, depth of draw, contact states, etc.Publishe

SOME ASPECTS OF HIGH STRENGTH STEEL USE FOR DEEP DRAWING

Presented in the paper are comparative results of testing high strength, and low carbon sheet metal steels for deep drawing. Main testing procedure emloyed was YOSHIDA-test, and the indicators obtained relate to the HSS capabilities toward fixability and fittability.Publishe