| On the basis of research methods for multiaxial fatigue strength, the study of multiaxial fatigue testsand life evaluation for Electronic Beam Welded(EBW) joint of TC17titanium alloy is conducted inthis thesis.The uniaxial and multiaxial fatigue tests for the TC17EBW joints under multiaxial load have beenperformed. The results indicated the fatigue life of TC17welded joint under multiaxial load is muchlower than the one under pure torsion load. The tension-torsion ratios in the tests have little influenceon the fatigue life of TC17welded joints.The metallographic organizations of the base metal zone, the heat affected zone, and the weldedmetal zone are obtained, and the fracture surfaces of multiaxial fatigue joints are observed by scanelectronic microscope. The results show the fatigue cracking always appears in the welded beam.The stresses and strains are computed for thin-wall pipe specimen on the basis of elasticity theoryand finite element method separately. The maximum shear stress plane or the maximum shear strainplane is defined as the critical plane.Then, through research on multiaxial fatigue models, a modified definition for the factor k in theFindley Criterion is presented, which can be effectively used in the fatigue life evaluation of TC17welded joint. Finally, the Modified Wohler Curve Method is also adopted in the fatigue life evaluationof TC17welded joint, and the test results are in good coincidence with predicted ones. |
PDF Full Text Request