直杆轴向拉压的强度和变形Strengthanddeform.pptxVIP

直杆轴向拉压的强度和变形Strengthanddeformationofstraightrodunderaxialtensionandcompression主讲人：王雅君

12目录CONTENTS强度变形StrengthDeformation

1拉、压的强度StrengthoftensionandcompressionONE

一、拉、压的强度Strengthoftensionandcompression?

一、拉、压的强度Strengthoftensionandcompression对于塑性材料，当应力达到屈服极限σs时，整个杆件都会发生比较大的变形且不能恢复，因此塑性材料以σs为极限应力;对于脆性材料，当应力达到强度极限σb时发生断裂，故对脆性材料以σb为极限应力。Forplasticmaterials,whenthestressreachestheyieldlimitσAts,theentirerodwillundergosignificantdeformationandcannotberestored,sotheplasticmaterialwillσSistheultimatestress;Forbrittlematerials,whenthestressreachesthestrengthlimitσFractureoccursattimeb,therefore,forbrittlematerialsσBistheultimatestress.

一、材料力学的基本概念Basicconceptsofmaterialmechanics?σs一屈服极限σs--yieldlimitns一安全系数，一般塑性材料ns=1.3~2.0Ns-safetyfactor,forgeneralplasticmaterials,ns=1.3-2.0

一、材料力学的基本概念Basicconceptsofmaterialmechanics?σb一强度极限σb-Strengthlimitnb一安全系数，脆性材料nb=2.0~3.5Nb-safetyfactor,brittlematerialsnb=2.0~3.5

一、拉、压的强度Strengthoftensionandcompression因为断裂破坏比屈服破坏更危险，所以nbns。此外，安全系数的选取还要考虑对安全要求的高低和经济等因素的影响。Becausefracturefailureismoredangerousthanyieldfailure,nbns.Inaddition,theselectionofsafetyfactorsalsoneedstoconsidertheimpactoffactorssuchasthelevelofsafetyrequirementsandeconomy.

一、拉、压的强度Strengthoftensionandcompression根据强度条件，可以解决三类强度计算问题Accordingtothestrengthconditions,threetypesofstrengthcalculationproblemscanbesolved1.强度校核Strengthverification确保危险点的最大工作应力不超过材料的容许正应力，就能保证杆件正常工作Toensurethatthemaximumworkingstressatthedangerouspointdoesnotexceedtheallowablenormalstressofthematerial,thenormaloperationoftherodcanbeensuredFNmax--杆的最大轴力，即危险截面上的轴力FNmax-Themaximumaxialforceoftherod,thatis,theaxialforceonthedangeroussection

一、拉、压的强度Strengthoftensionandcompression?

2拉、压的变形DeformationcausedbytensionandcompressionTWO

二、拉、压的变形Deformationcausedbytensionandcompression