You Tang Li

The Application of Fracture for Middle Carbon Steel in Extra-Low Cycle Rotating Bending Fatigue Loading

Safety designs and fracture designs are the two important fields of crack theory. The fracture problems of middle carbon steel under extra-low cycle rotating bending fatigue loading are studied in this paper. The experiments have been made in special rotating bending fatigue fracture machine designed by us. Several problems, the relations of the cycle times of fracture and the strain amplitude near notch tip to the deflection, the effects of depth and tip radius of notch to the cycle times of fracture, are discussed through the experiments. The mathematical expression of fracture toughness to the cycle times of fracture is obtained. The suitable parameters of rotating bending fatigue fracture model for middle-carbon steel in extra-low cycle times has been proposed.

Anti-Fatigued Criterion of Annularly Breached Spindle on Mechanical Design

The anti-fatigued design is an important field in product lifecycle management. A uniform criterion of annularly breached spindle was put forward in this paper. The crack, V-notch, U-notch and arc were described as breach uniformly according to the tip radius, depth and field angle of breach in the method. The connection between sharp V-notch and crack, between V-notch and U-notch has been set up. We fuse the fatigue fracture theory and life prediction techniques together on the design technology of lifecycle safety guarantee of mechanical structures. The relationship between life and detectability of the breached spindle system was discussed to provide useful guidance for practical applications. The criterion for the safety design and fracture design both of which on fα was obtained. The criterion of annular breached spindle under torsion was obtained at first and then the effects of bending to lifecycle of spindle were analyzed.

Uniform Model and Fracture Criteria of Annularly Breached Bars under Bending

A uniform model, in which the crack, V-notch, U-notch and arc are described as breach uniformly, is put forward in this paper. The tip radius, depth and field angle of breach are regarded as the parameter of annularly breached bar. The stress field and displacement field near the tip of the annularly breached bar under bending, in which takes fα(a/b) as its descriptive parameter, was given. All forms of breaches according to the change of tip radius, depth and field angle were discussed. The effects of parameters on fα(a/b) in bending were analyzed. The criteria for the safety design and fracture design both of which on fα(a/b) were obtained. The results not only can be applied widely to anti-fracture design but also be used for reference in anti-fatigued design in product lifecycle management.

The Influencing Factors and Assessment Rule of Fatigue Life of Shaft Based on Product Lifecycle Management

Product lifecycle management is one of the main developmental aspects of advanced manufacturing technology. Anti-fatigue design is the key content in product lifecycle management. For designing the fatigue life of shaft exactly and determining the assessment method, the influencing factors must be realized roundly. The mechanical model of shaft is set up at first, and then the main factors that affect the fatigue life of shaft is discussed, the interrelations of the main factors and the framework are founded. The assessment equation of fatigue life for shaft is put forward and the influencing coefficient of multi-axial stress to fatigue life is analyzed. The results of this paper will establish the base of anti-fatigue and assessment life of shaft.

The Applied Research of Fracture for Low Carbon Steel in Extra-Low Cycle Rotating Bending Fatigue

The application of fracture for low carbon steel under extra-low cycle rotating bending fatigue is studied in this paper. The experiments have been made in special rotating bending fatigue fracture equipment designed by us. Several problems, the relations of the cycle times of fracture, the strain amplitude near notch tip and fatigue fracture toughness to the presetting deflection, the effects of depth and tip radius of notch to the cycle times of fracture, are discussed through the experiments. The suitable parameters of fracture in rotating bending fatigue for low carbon steel under extra-low cycle times have been proposed.

Effect of Wear on the Fatigue Life of Annular Notched Shaft Based on Product Lifecycle Management

Anti-fatigue design is a key content in product lifecycle management and there are many factors to affect the fatigue life of parts. For designing the fatigue life of shaft with a circumferential notch exactly, the influencing factors have been analyzed completely. The mechanics model for assessing the fatigue life of shaft is set up. The assessment method of fatigue life for shaft is set up according to the traditional fatigue life estimation. The effect of wearing parameter to fatigue life is analyzed and the results show that the wear is an important factor to affect the fatigue life.

Fracture Design of Metallic Matrix Crack for Bi-Materials

The fracture designs of metallic matrix crack for bi-materials were studied. The stress field and displacement field of plane matrix crack was setup at first. Then the finite element method is used to analyses the stress singularity of matrix cracks between different materials. The solutions of stress singularity of a cracked bi-materials beam under uniform tension, and the three-point bending of bi-materials specimen were computed. The result lays a theoretic and applied foundation for the practical engineering application of metallic matrix crack for bi-materials.

Effect of parameters of notch on fatigue life of shaft based on product lifecycle management

For designing the fatigue life of shaft with a circumferential notch exactly, the influencing factors have been analyzed completely. The modified mechanics model to estimate the fatigue life of shaft with a circumferential notch is set up. The assessment method of fatigue life for shaft with a circumferential notch is put forward. The effects of notch on stress concentration factor and fatigue life of shaft with a circumferential notch are discussed and the influencing parameters are obtained. The results show that the tip radius of notch has a great effect on fatigue life of shaft; on the other hand, the open angle of notch has a little effect on it. The results will establish the base of anti-fatigue design of shaft.

Effect of Supporting Conditions on the Fatigue Life of Shaft Based on Product Lifecycle Management

An anti-fatigued criterion of annularly breached shaft on mechanical design has been put forward, and the main factors that affect fatigue life of shaft are discussed. The interrelation of the main factors and the framework is founded. A new assessment method to fatigue life of shaft has been put forward according to Corten-Dolan’s theory modified Miners rule. The effect of supporting conditions to fatigue life of shaft is discussed and the influencing parameters are obtained. The results show that the fatigue life of broad support in two sides is longer than that of narrow support in two sides. The results will establish the base of anti-fatigue design of shaft.

Transition Method of Geometrically Similar Element for Dynamic V-Notch Problem

A semi-analytical method is proposed to determine the dynamic stress intensity factor of two-dimensional V-notch problems. A group of geometrically similar elements is automatically generated layer by layer around the point of singularity. The large number of degrees of freedom around the V-notch tip are transformed to a small set of generalized coordinates by means of the series expansion formulas of the displacement field. By taking advantage of the same stiffness and similar mass of 2D similarly shaped elements, a single transformation of the stiffness and mass for the first two layers of mesh is enough for all. As an example, the three points bending specimen with V-notch is analyzed.