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The mechanical properties of metal

Author:admin Published:2015-03-25 20:03:02
  Refers to the mechanical properties of metallic materials in the external force demonstrated characteristics.
  
  1. Strength: materials under external force (load) action, the ability to resist deformation and fracture. Load per unit area of ​​said material by stress.
  
  2, the yield point (бs): said yield strength, refers to a material stretch the process, the material of the stress reaches a critical value, the load is no longer increasing or generating the deformation continues to increase by 0.2% when the stress value L, the unit with N / mm 2 (N / mm2) expressed.
  
  3, tensile strength (бb), also known as the ultimate strength of the material before the pull-off means to withstand the maximum stress value. Units in N / mm 2 (N / mm2).
  
  4, elongation (δ): After the tensile, elongation percentage of the total of the original gauge length of material.
  
  5, after the tensile fracture, the maximum cross-sectional area of ​​the reduced cross-sectional area percentage of the original off shrinkage (Ψ) material.
  
  6, hardness: that the material is more resistant to other hard objects surface pressure their ability, their usual range of hardness distribution measured hardness (HBS, HBW) and Rockwell hardness (HKA, HKB, HRC).
  
  7, toughness (Ak): material resistance to impact load capacity, joules / cm 2 (J / cm2).
  
  Tensile stress and stage
  
  1, the elastic: εe = σe / E, indicators σe, E
  
  2, rigidity: △ L = P · l / E · F elastic deformation resistance strength
  
  3, intensity: σs --- yield strength, σb --- Tensile strength
  
  4, toughness: impact energy Ak
  
  5, the fatigue strength: alternating load σ-1 <σs
  
  6, the hardness of HR, HV, HB
  
  a.Ⅰ stages: linear elastic stage, the initial tensile stress - strain curve is a straight line, this stage is called the maximum limit of the material stress proportional limit σe.
  
  b. Ⅱ stage: yield phase, when the stress increases to a certain value, the stress - strain curve appears horizontal segment (there are small fluctuations), in this stage, stress is almost constant, but is rising sharply deformed, lose the ability to resist deformation of the material, This phenomenon is known as the yield, the corresponding stress is called the yield stress or yield limit, and is represented by σs.
  
  c. Ⅲ stage: To strengthen stage, after the yield, but also enhance the ability of the material to resist deformation. Strengthening the highest point of the corresponding stage of stress, says the ultimate strength of the material. By σb said the ultimate strength of the material can withstand maximum stress.
  
  d. Ⅳ stage: for necking stage, to the maximum value when the stress σb, a partial specimen of significant shrinkage, and finally broken at the constriction point.
  
  Low carbon steel σs and σb is a key measure of its strength. Rigid: △ L = P · l / E · F, resistance to elastic deformation. P --- tension, l --- the original length of the material, E --- elastic modulus, F --- sectional area.