Papers by Author: Ping Ma

Abstract: A special clamp for fatigue of shaft under bending-torsion that used on the fatigue machine is designed and manufactured. For the medium carbon steel, the low-cycle fatigue experiments of shaft with annular notch under bending-torsion have been made on Shimadzu EHF-EM100kN high-frequency electro-hydraulic fatigue testing machine. Through experiments and analysis, the effects of tip radius, depth and open angle of notch on low cycle fatigue life of shaft with annular notch under bending-torsion are obtained. The method and results will play an important role on the fatigue life prediction and anti-fatigue design.

Abstract: A model of notched shaft in which the crack, V-notch, U-notch and arc were described as notch uniformly, was put forward. The stress field near the notch tip of notched shaft was given using quadric coordinate system by selecting an appropriate displacement function at first, and then the stress field in Cartesian co-ordinates system was obtained. The 3-D model was set up and the local stress and strain near the tip of notch was calculated by using finite element software ANSYS, and the effect of notched parameters of shaft on stress was analysed. The results show that there is a small region, in which the effect of the tip radius and depth on the stresses is obviously. The effect of an open angle of notch on stress is very small. The smaller the ratios between the tip radius and depth of notch, the larger the stress concentrations near the tip of notch.

Abstract: 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 Miner's 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.

Abstract: A group of geometrically similar elements is automatically generated layer by layer around the tip of crack. By taking advantage of the same stiffness and similar mass of similarly shaped elements, the combined stiffness matrix and combined inertia matrix in area
can be expressed by the displacement row matrix of outer polygon. The global stiffness matrix will be obtained if the combined stiffness matrix and combined inertia matrix of area
are assembled to those of another elements according to corresponding nodes. The small set of generalized coordinates can be obtained through solving the equation, and then the dynamic stress intensity factor of crack will be obtained. The three points bending with single crack and shearing model with double cracks in explosive loading were calculated with finite geometrically similar element method.

Abstract: 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.

Abstract: A finite geometrically similar element method is proposed to determine the dynamic stress intensity factor. 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 tip of singularity is 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 similarly shaped elements, the combined stiffness matrix of super-element is obtained directly. The small set of generalized coordinates can be obtained through solving the equation, and then the dynamic stress intensity factor of V-notch (crack) will be obtained. There are some advantages for this method such as good adaptability, high precision and good convenience.

Abstract: The eigen-equation of bi-materials cracks was founded on the basis of the stress field and displacement field. The influence of shearing modulus and Poisson’s ratio of matrix material and additive material to eigen-values were analyzed through the results of calculating. The stress intensity factors at the tip of matrix crack were calculated. The suitable parameters of bi-steel materials crack in fracture design were obtained. The results show that the effect of Poisson’s ratio on eigen-values is not obviously and the effect of shearing modulus is obviously. The shearing modulus of additive material should bigger than that of matrix material.

Abstract: 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.

Abstract: The application of regular blanking for brass under extra-low cycle rotating bending fatigue was studied. The experiments of rotating bending fatigue have been made in special equipment designed by us. Several problems, the relations of the cycle times of fracture, the strain amplitude near the tip of notch and fracture toughness of fatigue to the presetting deflection, the effects of depth and tip radius of notch to the cycle times of fracture, were discussed through the experiments. The formulae of stress amplitude at the tip of notch and fracture toughness of brass to presetting deflection were obtained. The suitable parameters of fracture in rotating bending fatigue for blanking of brass under extra-low cycle times have been proposed.

Abstract: Rotating bending and inverse rotating bending are the two different forms of fatigue. The application of regular blanking for brass under extra-low cycle inverse rotating bending fatigue was investigated. The principle of inverse rotating bending fatigue was explained at first. And then the experiment of inverse rotating bending fatigue was made in special equipment designed by the authors. Several problems, i.e. the relations of the quantities such as cycle times of fracture, the strain amplitude near the notch tip and fracture toughness of fatigue to the presetting deflection, the effects of depth and tip radius of notch on the cycle times of fracture, were discussed with the helps of experiment. Finally, The relation of depth of crack propagation to cycle times were discussed also. The suitable parameters of inverse rotating bending fatigue for blanking of brass were obtained.