《土木工程专业英语 教学课件 ppt 作者 陈瑛 2.3 & 2.4 Steel Materials &Steel Types》由会员分享，可在线阅读，更多相关《土木工程专业英语 教学课件 ppt 作者 陈瑛 2.3 & 2.4 Steel Materials &Steel Types（23页珍藏版）》请在金锄头文库上搜索。
1、Chapter 2-3 Steel Materials,Material Properties of Steel,Constituents Iron (about 99%) Benificial alloy elements Carbon increase strength Silicon strong oxygen absorber Manganese weak oxygen absorber Copper corrosion resistance Chromium corrosion resistance Harmful elements Oxygen & Sulphur hot brit
2、tleness Phosphorous & Nitrogen cold brittleness Hydrogen hydrogen-induced brittleness,Steel Attributes, Strength Ability of a material to resist stresses - yield strength, ulitmate (or tensile) strength Stiffness Ability of a material to resist deformation - slope of the materials stress-strain curv
3、e Toughness Ability of a material to absorb energy before failure the area under the materials stress-strain curve Ductility Ability of a material to undergo large inelastic, or plastic, deformation before failure percent elongation or percent reduction in area of the specimen tested in uniaxial ten
4、sion,Stress-Strain Curve,Low carbon steel,High carbon steel,Steel Types,Carbon steels main ingredients carbon small amount of silicon and copper, i.e. Q235. High strength low alloy steels enhanced strength more alloying agents such as chromium, copper, nickel, silicon etc, and others in addition to
5、basic elements of iron, carbon, and manganese, i.e. Q345, Q390 and Q420. Quenched and tempered alloy steels heat treated by quenching, and tempering to enhance strength. Reduced ductility and plasticity.,Design Considerations,Fatigue caused by fluctuating loads occurs through initiation and propagat
6、ion of a crack welded connections have greatest effect on fatigue strength butt welds continuous fillet weld intermittent fillet weld residual stress & stress concentration tensile stress - fatigue crack propagation fatigue life determined by hot spot stress range S-N curve,Fatigue failure of a weld
7、ed tubular joint,S-N curves,Brittle fracture Fracture occurs at low stress below 0oC Charpy test Impact toughness Abrupt of cross section Stress concentration Residual stress caused by welding,Fire protection Solid casing Hollow casing Profile casing Intumescent paint,Corrosion protection Metallic c
8、oating Painting Surface preparation is critical,Steel Sections,Rolled and Formed Sections I-section H-section Channels Equal & unequal angles Structural tees Circular, square & rectangular hollow sections,Compound Sections Cover plate strengthening Combining two separate rolled sections Connecting t
9、wo members together to form a strong combined member,Built-up Sections Formed by welding plates together I, H and box members are mostly used Used to sustain heavy loads,Cold-rolled Open Sections Formed by cold rolling Suitable for thin steel plate Application purlins, side & sheeting rails others,B
10、rief review for steel materials Constituents Iron, carbon, silicon, manganese, Oxygen, sulphur, phosphorous, nitrogen, hydrogen, Material properties What mechanical properties can you find from the Stress-Strain curves？ Strength - yield stress, ultimate (tensile strength) Stiffness plasticity Toughn
11、ess area under the stress-strain curve Ductility percent elongation or percent area reduction Steel types Carbon steels High strength low alloy steels Quenched and tempered alloy steels,Review,Design considerations Fatigue which principal factors caused the fatigue failure developing rapidly? High s
12、tress concentration caused by abrupt sections or flaws Residual stress caused by welding Brittle fracture Fire protection Corrosion protection Steel sections Rolled and formed sections - What is the main types for this section？ I-section H-section Angle Channel Structural tee Hollow section (circular, square & rectangular) Compound sections Built-up sections Cold-rolled open sections,
