Basic Knowledge of Steel and Plastic Mechanics 基础钢和塑性变形知识 Contents 1 Steel Mechanical properties Worldwide steel grades Advanced high strength steel AHSS 2 Plastic mechanics Sheet deformation modes Forming limits Yield criteria 2 Introduction to elasticity and plasticity 1 固体材料受外力作用产生变形 从变形开始到破坏一般要经历 两个阶段 弹性变形 elastic deformation 和塑性变形 plastic deformation 2 外力卸载后 弹性变形能够完全消失 而塑性变形不能消失 3 弹性变形和塑性变形的机理 材料原子之间的作用力平衡 4 位错 dislocation 理论 5 强化机制 work hardening mechanism Dislocation movement 3 Uniaxial tensile test GB T228 金属材料室温拉伸试验方法 EN10002 1 Metallic materials Tensile test Part 1 test method in ambient temperature Typical tensile test piece 4 Engineering stress strain curve 5 Engineering stress strain curve 6 Strength and Ductility Strength parameters Engineering stress Engineering strain Elongation Reduction of area Ductility 7 True stress strain curve True stressTrue strain 8 Working hardening strain hardening Strain hardening exponent n value 9 Influence of strain hardening exponent n3n2n1 10 Anisotropy R value Width strain w ln w w0 Thickness strain t ln t t0 R w t Planar anisotropy ratio Normal plastic anisotropy ratio 11 Strain rate sensitivity Strain rate Strain rate sensitivity exponent Strain rate sensitivity has a crucial influence on the research of crash resistance and high speed stamping formability 12 Worldwide steel grades 13 Worldwide steel grades 14 Common steel types and evolving AHSS types Interstitial free IF steels Mild steels Bake hardenable BH steels Isotropic IS steels Carbon manganese CM steels High strength low alloy HSLA steels Dual phase DP steels Transformation induced plasticity TRIP steels Complex phase CP steels Martensitic Mart steels 15 Strengthening mechanism 16 HSLA steel 17 Grades of HSLA steel in EU 18 Application of HSLA steel 19 Dual phase DP steel 20 EU steel grades Comparison European steel grades Mild steel HSLA Dual Phase Legend Cold Rolled Hot Rolled Dual Phase cold rolled values from ARCELOR Not for new products Availibility Availibility to be clarifiedto be clarified From Claus Unruh 21 Dimension availability Availability check materials Europe versus US update Nov 2006 only acc my information must be checked and confirmed by Purchasing department Material availibility of standard materials is given Material availibility of S460 MC is decreasing even in Europe Material availibility of Dual Phase and other special grades must checked for each dimensions From Claus Unruh 22 Dimension availability Availability check materials Europe versus China update Nov 2006 only acc my information must be checked and confirmed by Purchasing department Material availibility of standard materials is given Material availibility of S460 MC is decreasing even Europe Material availibility of Dual Phase and other special grades must checked for each dimensions From Claus Unruh 23 Standard thickness China vs Japan China Japan 24 HSLA steel grades overview Overview steel grades HSLA high strength low alloyed Steel family cold rolled hot rolled Legend Existing grades after standardisation Use only standard HSLA steel worldwide available H240 LA and S460 MC was cancelled caused by sourcing problems worldwide From Claus Unruh 25 Mild steel grades overview Overview steel grades Mild steel Steel familycold rolledhot rolledLegend Existing grades before standardisation Existing grades after standardisation Only 2 grades are allowed DC01 CS soft steel for simple low strength press parts DC04 DDS soft steel with good deep drawing properties for complex low strength press parts Brand names and other material designations will not be accepted From Claus Unruh 26 DP steel grades overview Overview steel grades Dual Phase steel Steel family cold rolled hot rolled Legend Japanese grades not exactly comparable DP400 and DP 500 are not relevant for seat structures DP1400 in development Standardisation of Dual Phase grades is difficult caused by missing European standard Availability has to be clarified for each grade and dimension Purchasing department must support the process From Claus Unruh 27 Products from Bao Steel for automobile structures Mild steels 28 Products from Bao Steel for automobile structures DP steelsHot rolled mild HSLA steels 29 Products from Bao Steel for automobile structures Cold rolled HSLA steelsHot rolled HSLA steels 30 VHSS category at Arcelor 31 Metallurgy of VHSS at Arcelor 32 Application of VHSS 33 Application of VHSS 34 Engineering stress strain curve of DP steel Higher tensile strength of DP steel larger n value Better stamping formability and crash resistance performance of DP steel 35 n value of DP steel 36 Application of DP steel 37 FEA results of DP steel 38 FEA results of DP steel 39 Sheet metal forming processes blanking piercing bending a Bending in a folding machine b Bending in a vee die c Section of a set of rolls in a roll former d Wiping down a flange 40 Sheet metal forming processes flanging stretching a A shrink flange with buckling b A stretch flange with crack