Tension–tension fatigue tests of notched 18CrNi4A steel specimens were carried out under three different fatigue stresses, and metal magnetic memory (MMM) signals were detected. The effects of fatigue damage and fatigue stress on MMM signals were investigated. The results show that the absolute values of the feature parameters Hp(y)max, Hp(y)min and Hp(y)sub increase with the aggravation of the fatigue damage. There is an inherent relationship between the fatigue stress and the values of the Hp(y)sub; the larger the fatigue stress is, the larger the absolute values of the Hp(y)sub is. Fatigue-damaged locations can be effectively predicated according to the mutational character of the Hp(y) curve and the K curve, and zero-crossing points of the Hp(y) curve, respectively. Fatigue damage degree can be effectively predicated according to the value of the Kmax and the Hp(y)max, Hp(y)min and Hp(y)sub.

Multiaxial fatigue life of 50CrVA spring steel standard specimens and eccentric specimens under proportional loading was studied with MTS 809 tension-torsion electro-hydraulic servo tester. Both kinds of specimens were calculated by the finite element software ABAQUS and the fatigue life of specimens were predicted based on the finite element results. The results show that the additional bending moment will obviously reduce the life of specimens; only the Manson-Halford model and modified Manson-Halford model can obtain satisfactory results in many prediction models selected.

Fracture morphology analysis is an important way to understand material fracture process, find the reason of fracture and improve its performance. Nickel based powder metallurgy (P/M) superalloy is an important material which is widely used in the modern aeronautic and astronautic industry. In order to determine the fracture characteristic morpholgies and mechanisms of the P/M superalloy fractured at different conditions, the fracture surfaces of the high temperature low cycle fatigue,high cycle fatigue, high-low cycle complex fatigue, tension and creep specimens from the P/M superalloy were studied by scanning electron microscopy and stereo-microscopy. The mechanisms and influencing factors of high temperature fatigue crack initiation and propagation were emphatically analyzed, and creep and tension fracture mechanisms of the P/M superalloy were also discussed. The application of the fracture surface analysis for the fracture failure analysis of the P/M superalloy turbine disk were introduced finally.

Experimental and numerical studies of the 2D woven composite laminates under low-velocity impact with different energy are discussed in this paper. The traditional Hashin failure criteria are improved to cover the failure modes of fiber rupture and delamination. It is found that the damage level depend on the impact energy. The matrix deformation is the main reason of delamination. The simulating results are in good agreement with the experimental phenomenon observed by nondestructive examination (ultrasonic C scanning) and cross-section examination

This paper studied the effect of the ratio between the axial tensile force and the transversal vibration loads on the fatigue behavior and failure mode of the near alpha titanium alloy TA11, to simulate the service stress state applied on the engine blades, where a large centrifugal force is superimposed with bending vibration loads. The plate-like specimens were used in the fatigue tests by a special testing device which was designed and fabricated in the present research,where the vibration loads were applied by the electro-magnetic exciters. By experiments under various multi-axial fatigue loading cases with different ratios between the axial tensile force and the transversal vibration loads, the fatigue behavior and failure modes were observed and compared. Then, the energy based fatigue criteria were applied for correlation of the test results. The fatigue properties of titanium alloy TA11 under the specialized loading conditions are characterized and discussed. In addition, the experimental observations on the vibration behavior superimposed with different magnitude of axial tensile force are also helpful for understanding the real working conditions of the engine blades.