16 剛度 硬度 強度strength hardness stifness

1、強度結(jié)構(gòu)桿件所用材料在規(guī)定的荷載作用下，材料發(fā)生破壞時的應(yīng)力稱為強度。 根據(jù)外力作用方式不同，材料的抗拉強度、抗壓強度、抗剪強度等。StrengthDefinition: In materials science, the strength of a material is its ability to withstand an applied load without failure or plastic deformation.Material strength refers to the point on the engineering stress-strain curve (yiel

2、d stress) beyond which the material experiences deformations that will not be completely reversed upon removal of the loading and as a result the member will have a permanent deflection. The ultimate strength refers to the point on the engineering stress-strain curve corresponding to the stress that

3、 produces fracture. 剛度剛度是指材料或結(jié)構(gòu)在受力時抵抗彈性變形的能力。是材料或結(jié)構(gòu)彈性變形難易程度 的表征。在宏觀彈性范圍內(nèi)，剛度是零件荷載與位移成正比的比例系數(shù)，即引起單位 位移所需的力。一個結(jié)構(gòu)的剛度(k)是指彈性體抵抗變形拉伸的能力。計算公式：k=P/8P是作用于結(jié)構(gòu)的恒力，6是由于力而產(chǎn)生的形變。剛度的國際單位是牛頓每米(N/m)StiffnessDefinition:Stiffness is the rigidity of an object the extent to which it resists deformation in response to an

4、applied forceThe stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (DOF) (for example, stretching or compression of a rod), the stiffness is defined aswhere,F is the force applied on the body，6 is the

5、 displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring)In the International System of Units, stiffness is typically measured in newtons per meter.In Imperial units, stiffness is typically measured in pounds(lbs) per inch.彈性模量一般地

6、講，對彈性體施加一個外界作用，彈性體會發(fā)生形狀的改變(稱為應(yīng)變),彈 性模量的一般定義是：應(yīng)力除以應(yīng)變。楊氏模量(Youngs modulus)，又稱拉伸模量(tensile modulus)是彈性模量(elastic modulus or modulus of elasticity)中最常見的一種。公式記為E = z/ 其中，E表示楊氏模數(shù)，z表示正向應(yīng)力，表示正向應(yīng)變。楊氏模量The modulus of elasticityDefinition: The modulus of elasticity (also known as the elastic modulus, the tensi

7、le modulus, or Youngs modulus) is a number that measures an object or substances resistance to being deformed elastically (i.e., non-permanently) when a force is applied to it. The elastic modulus of an object is defined as the slope of itsstress -strain curve in the elastic deformation region:1 A s

8、tiffer material will have a higher elastic modulus. An elastic modulus has the formX def stress strainWhere, stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some length parameter caused by the deformation to the o

9、riginal value of the length parameter. If stress is measured in pascals, then since strain is a dimensionless quantity, the units of 人 will be pascals as well. 剛度與彈性模量區(qū)別一般來說，剛度和彈性模量是不一樣的。彈性模量是物質(zhì)組分的性質(zhì)；而剛度是結(jié)構(gòu) 的性質(zhì)。也就是說，彈性模量是物質(zhì)微觀的性質(zhì)，而剛度是物質(zhì)宏觀的性質(zhì)。材料力 學(xué)中，彈性模量與相應(yīng)截面幾何性質(zhì)的乘積表示為各類剛度，如GI為扭轉(zhuǎn)剛度，EI 為彎曲剛度，EA為拉壓剛度。Re

10、lationship to elasticityIn general, elastic modulus is not the same as stiffness. Elastic modulus is a property of the constituent material; stiffness is a property of a structure. That is, the modulus isan intensive property of the material; stiffness, on the other hand, is an extensive property of

11、 the solid body dependent on the material and the shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness isAEWhere, A is the cross-sectional area,E is the (tensile) elastic modulus (or Youngs modulus),L is the length of the element.硬度 硬度，物理學(xué)專業(yè)術(shù)語，材料局

12、部抵抗硬物壓入其表面的能力稱為硬度。固體對外界 物體入侵的局部抵抗能力，是比較各種材料軟硬的指標。由于規(guī)定了不同的測試方法， 所以有不同的硬度標準。各種硬度標準的力學(xué)含義不同，相互不能直接換算，但可通 過試驗加以對比。洛氏硬度 這種硬度測定法是美國的S. P.洛克韋爾于1919年提出的，它基本上克服了布氏測定 法的上述不足。洛氏硬度所采用的壓頭是錐角為120的金剛石圓錐或直徑為1/16英寸 （1英寸等于25.4毫米）的鋼球，并用壓痕深度作為標定硬度值的依據(jù)。測量時，總 載荷分初載荷和主載荷（總載荷減去初載荷）兩次施加，初載荷一般選用10千克力， 加至總載荷后卸去主載荷，并以這時的壓痕深度來衡量

13、材料的硬度。洛氏硬度記為HR, 所測數(shù)值寫在HB后，洛氏硬度值計算公式為：式中h表示塑性變形壓痕深度（毫米）；k是規(guī)定的常量；分母中的0.002 （毫米） 每洛氏硬度單位對應(yīng)的壓痕深度。對應(yīng)于金剛石圓錐壓頭的k=0.20 （毫米），對應(yīng) 鋼球壓頭的k=0.26 （毫米）。HardnessHardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied Some materials, such as metab are harder than others. Macroscopic hardness is generally characterized bystrong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, there are diff