工程力学知识点(英文)

"Engineering Mechanics B"I. Statics part1, three engineering mechanics used in analysis:1) Mechanical Analysis: Solid in the external force, either in whole or in which any part of the body as well as a unit, must meet the dynamic equations (Newton's second law).When an object is in constant motion or stationary, it must satisfy the equilibrium equations. 2) Geometric Analysis: To displacement and deformation (strain) is a solid force. There should be some relationship between displacement and strain. Adjacent solid objects (including bearings, etc.) in contact, on the boundary will be bound by certain geometric or kinematic properties.3) the relationship between physical properties: physical sexual relations: relations deformation and external forces, usually expressed as a stress-strain relationship.Such relationships associated with the material itself is sometimes called constitutive relations materials.Generalized Hooke's law is the relationship between the physical properties of a linear elastic, consider these three aspects can constitute three equations, namely mechanical equations, geometric equations, physical equations, and the necessary boundary conditions.2, plane force system simplification: principal vector. Main clause :( algebra and)3, co-moment theorem:Force equal to that of each component of the moment of moments to change the point of algebra and.4, three of the Concurrent: the role of the three forces on the same object if the balance, the three forces (or Fangxiang Yan long) post and point.Objects stress analysis: concentration, distribution force (uniform and non-uniform)Linear distribution q, surface distribution of p, body distribution5, two force components: Only two forces (trusses are two force members), and other large, reverse, acting on the two connections.Couple: Fd (couple only force even balance).6, plane forces in equilibrium conditions:AndA moment formula:; two moments formula: X axis and A,B torque balanceThree moments of the formula: The A, B, C :( three moments moments from three points wherein A, B, C three o'clock not collinear)Second, the material mechanics section(One)A relationship between internal forces and bending differential between;; distributed load qTwo shear Q, bending moment M relationship between figure and force:a) within a period of no beam load, shear Pictured a horizontal line, a moment Pictured oblique line.b) within a certain period of load beam uniformity role in an oblique shear Pictured straight Pictured moment a parabola.c) a cross section of the beam. , Zero shear, moment there is a maximum or minimum.d) on the left and right, shear force Q by centralized there is a sudden change in cross-section, theslope of the bending moment diagram is also a turning point for the formation of an abrupt change Three combined deformation: torsion and bending combination (a) external to the rod cross-section centroid simplify (2) to determine the risk of internal force diagram drawing section(3) to determine the danger point and build strength conditions4 Press the third strength theory, strength conditions: Or, for a round shaft,, its strength conditions:.(B) the tension and compressionA plane hypothesis: the deformation of the front cross-sectional plane after deformation remains flat:Stress on the oblique section 2:3, axial tension or compression strength calculation: maximum normal stress4, three types of calculation:1) strength check rod known Nmax, A, [σ], strength checking component meets the conditions2) Design section: Known Nmax, [σ], depending on the intensity condition, seeking A3) determine the permissible load: Known A, [σ], depending on the intensity condition, seeking Nmax5, the axial tensile deformation and Hooke's law when: longitudinal strain transverse strainPortrait Landscape, μis called lateral deformation coefficient or Poisson (Poisson) ratio6, (experimental)Mild steel tensile test: the proportional limit σp yield limit σs ultimate strength σbWhere σs and σb is an important indicator to measure the strength of the material.(C) reverse1, the curvature of the neutral layer formula2, the normal stress formula:3, tensile and compressive deformation energy:4, thin cylinder torque demand5, cut Hooke's lawShear modulus GMaterial constants: tension and compression modulus EPoisson's ratio μ6, torsional shear force:7, the polar moment of inertia:Hollow circle polar moment of inertia:Solid circles torsional section modulusHollow circle anti-torque modulus:8, a circular shaft torsion angle:9, stiffness conditions:(Intensity conditions:)Oblique section of stress:10, and other straight rod torsion strain energy:(Four) bending1, the sign of the provisions of the shear Q: upper left lower right is positiveSymbol prescribed bending moment M: Pull the pressure (on the concave or convex) is positive 2, (1) the degree of load sets, shear and bending moment differential relations:(2) Set the integral relationship between the degree of load, shear and bending moment(1)(2)3, the neutral axis through the centroid of the cross-section:Pure bending beam cross section normal stress:Curvature of the neutral layer of the formula:Bending beam intensity conditions of normal stress4, shear stress :( non-rectangular cross-section beam focus)5, I-section beam shear stress: On the web:6, circular cross-section beam shear stressFlexural strength shear stress conditions7, deflection and rotation states: upward deflection angle is positive counterclockwise positive The curve y = f (x) of curvature of8, with the integration requirements deformed beamsWhere integration constant C, D are determined by the boundary conditions and continuity conditions9, stiffness BeamStiffness conditions: [v], [θ] is permissible deflection and rotation components, they decided to component normal10, require at work.11, deformation of the beam is calculated using superpositionCan be calculated separately for each deformation under load alone, then superimposed.Factors affecting the beam bending load cases and only with the support beams, but also on the material of the beam, cross-sectional size, shape and span beams relevant. Therefore, in order to improve the bending stiffness, it should start with these various factors.(1) increasing the beam flexural rigidity EI(2) the support is reduced or increased span(3) changes in loading and seat location(Five) stress analysis strength theory1, three-dimensional stress state conditions:In parallel to the plane of σ1 σ2 and σ3 direction angle of 45 °on the role τmax2, the rod3, generalized Hooke's law:4, the tensile deformation energy5, the intensity of the theory:1) the maximum tensile stress theory (first strength theory)2) The maximum elongation of wire strain theory (second strength theory)3) the maximum shear stress theory (third strength theory)4) The fourth strength conditions:Four intensity condition unified strength theory can be written in the form:Called fairly stress6, the normal stress and shear stress on any slope:In parallel to the plane of σ1 σ2 and σ3 direction angle of 45 °on the role τmax(Six) lever stability1, Euler's formula hinged at both ends of slender columns critical pressureOther constraints rod ends slender columns under critical pressure:The critical stress bar:Flexibility is defined to calculate the critical stress bar Euler's formula2, Euler formula Scope:。