【文章內(nèi)容簡介】 =566 MPa, 大于 520MPa, 因此產(chǎn)生塑性變形。 （ b）增長 . A0=?d02/4 =* mm2/4= ?=F/A0 ?= ?l /l0 , l0 = ?=F/A0 (MPa) ?= ?l /l0 0501001502002503003504000 StrainStress (MPa)0501001502002503000 Fracture （ a） E= (c) (d) (e) %EL=% (f) U r =117400 J/m3 (a) (a) ? T = l i = U T = *109 J/m3 （ a） 彈性變形應變數(shù)值大約： ， 塑性變形： (b) l= FfS=10161N (a) 從計算而言，該樣品斷裂。 (b) 但是不能 100%預測斷裂。 For Brass: TS(MPa)=?HB TS(psi)=469?HB For cast iron: TS(MPa)=?HB TS(psi)=449?HB For edge dislocation: the dislocation lines moves in the direction of the applied shear stress. For screw dislocation: the dislocation line motion is perpendicular to the stress direction. For mixed dislocation: the direction of motion line is neither perpendicular nor parallel to the applied shear stress, but lies somewhere in between. (a) Dislocations do not move with the same degree of ease on all crystallographic planes of atoms and in all crystallographic directions. Ordinarily there is a preferred plane, and in that plane there are specific directions along which dislocation motion occurs. This plane is called the slip plane。 it follows that the direction of movement is called the slip direction. This bination of the slip plane and the slip direction is termed the slip system. (b) No. The slip system depends on the crystal structure of the metal and is such that the atomic distortion that acpanies the motion of a dislocation is a minimum. (a) ?0=25MPa ky = MPa*mm1/2 (b) ?y=420MPa d= (a) CW%=( A0 Ad )/A0 100=(1Ad /A0)*100 A0 l0 =Ad ld Ad /A0= l0 / ld = l0 /( l0 +? l)=1/[ ( l0 +? l)/ l0]=1/[1+?] 所以 CW%=( A0 Ad )/A0 100=(1Ad /A0)?100=[11/(1+?)]?100 =[?/(1+?)]?100,即上式。 (b) CW%=% d2 =9mm Circular harder. d=(mm) (a) about 25%. (b) TS(MPa)=, Brinell hardness is about 690/=300 半晶聚合物的彈性形變產(chǎn)生的原因是鍵長、鍵角的微小改變所引起的，熵變化的因素很小。英文 p221， The mechanism of elastic deformation in semicrystalline polymers in response to tensile stresses is the elongation of the chain molecules from their stable conformations, in the direction of the applied stress, by the bending and stretching of the strong chain covalent bonds. In addition, there may be some slight displacement of adjacent molecules, which is resisted by relatively weak secondary or van der Waals bonds. Furthermore, inasmuch as semicrystalline polymers are posed of both crystalline and amorphous regions, they may, in a sense, be considered posite materials. As such, the elastic modulus may be taken as some bination of the moduli of crystalline and amorphous phases. 塑性形變主要是結晶區(qū)之間的無定形區(qū)域受外力作用變化引起的 :The mechanism of plastic deformation is best described by the interactions between lamellar and intervening amorphous regions in response to an applied tensile load. 彈性體的彈性形變是熵變化引起的 : The driving force for elastic deformation is a thermodynamic parameter called entropy, which is a measure of the degree of disorder within a system。 entropy increases with increasing disorder. (a) The magnitude of the tensile modulus does not seem to be influenced by molecular weight alterations. 模量與鍵長、鍵角有關。 (b) Tensile modulus increased. It has been observed that, for semicrystalline polymers, tensile modulus increases s