Papers by Keyword: Intensity Factor

Abstract: This work consists of the study is to analysis by the finite element method the effect of the ageing of the adhesive exposed simultaneously to the temperature and water on the degradation of its mechanical properties and consequently on the transfer of loads from the plate to patch. The stress intensity factor was evaluated according to immersion time and temperature. Several parameters have been taken into consideration, namely the properties of the composite patch, temperature, water absorption, rate and length of crack, the distribution of maximum shear stresses in the adhesive and peel in the patch were also analyzed.

Abstract: The asphalt surface crack fracture mainly includes load cracks and non-load cracks. The former is due to the weight of the vehicle itself causing excessive fatigue weight, therefore, this crack is also known as road load fatigue crack. Non-load crack is affected by nature factors such as temperature and humidity, which makes the road structure cracking. In this paper, finite element method is used to analyze the transient temperature field, and on this basis, the temperature stress simulation of pavement structure is carried out. The stress intensity factor of asphalt surface crack tip is analyzed by finite element method. The results show that the modulus of the surface and the base layer and the increase of the temperature coefficient of the base layer will lead to the increase of the stress intensity factor of the crack tip. The temperature coefficient of the surface layer has no obvious effect on the stress intensity factor. In addition, increasing the thickness of the surface layer can effectively reduce the stress intensity factor at the crack tip. The paper also concludes that the gravel base can effectively slow down the expansion of the road refection crack.

Abstract: A 2D time-domain boundary element method (BEM) is developed to study the fracture problems in thin piezoelectric structure. The nearly singular integrals arisen in thin structures are calculated in two ways. One is based on a nonlinear coordinate transformation for curve-quadratic element, and the other one is an analytical integration method for straight quadratic element. Numerical examples are presented to verify the effectiveness and stability of the present BEM in thin piezoelectric structure.

Abstract: The results of experimental and theoretical study of the load-bearing capacity and stiffness of wooden beams with through-thickness cracks depending on their length and location throughout the height of cross-section are given. The analysis of the regularity of change of stress-strain state, stress intensity factors (SIF) and at crack tips, deflections and timber beams load-bearing capacity depending on beam span length versus cross-section height, crack length versus span length, crack location throughout beam height was made. It has been established that load-bearing capacity and stiffness of timber beams with through-thickness cracks depends not only on the crack length, but its location throughout cross-section height as well. Procedure of assessing load-bearing capacity and stiffness of timber beams with through-thickness cracks based on fracture mechanics methods is given.

Abstract: This paper is based on fracture mechanics to calculate the arch bridge crack spacing circle and the stress intensity factor. Then the relation between the cracks spacing limit problem is calculated. And stress intensity factor relations under the same crack length and the same pull force is discussed. Finally the analysis shows that the height of the fracture cracks into the crack width as the impact factor is feasible.

Abstract: According to the fatigue and fracture reliability theory, the criterion of piston fatigue crack growth rate da / dN is induced using set-value theory of fatigue and fracture mechanics on the basis of actual safety and life of the marine diesel engine piston. Life analysis and security evaluation of large marine diesel engine piston was implemented with this criterion, which affords an important reference for the application of large marine diesel engine.

Abstract: A crack problem in a micropolar piezoelectric solid is considered. By using simplified constitutive relations, the problem can be reduced to the solution of a set of Cauchy singular integral equations with the help of Fourier integral transform technique. Numerical results for stress intensity factors, couple stress intensity factors and electric displacement intensity factors show that micropolar theory can be expected to explain certain size effects in piezoelectric solids.

Abstract: This paper is concerned with the interaction of a piezoelectric screw dislocation with a semi-infinite dielectric crack in a piezoelectric medium with hexagonal symmetry. The solution of the considered problem is obtained from the dislocation solution of a piezoelectric half-plane adjoining a gas medium of dielectric constant ε0 by using the conformal mapping method. The intensity factors of stress, electric displacement and electric field and the image force on the dislocation are given explicitly. The effect of electric boundary conditions on the dislocation-crack interaction is analyzed and discussed in detail. The results show that ε0 only influences the electric displacement and electric field intensity factors and the image force produced by the electric potential jump.

Abstract: The problem of an interface edge crack between two dissimilar piezoelectric materials is analyzed under the conditions of anti-plane shear and in-plane electrical loading. The crack is considered to be traction-free, but electric permeable one across which the normal component of the electric displacement are continuous. A series form of electromechanical solution and field intensity factors are obtained. The results show that all fields including strain, stress, electric field strength and electric displacement are singular in the front of crack tip. At last, the stress intensity factor is solved by the boundary collocation method (BCM), numerical results are given and discussed.

Abstract: The problem involving a center crack in a rectangular piezoelectric body under anti-plane mechanical shear loading and plane electrical loading is analyzed for the permeable crack face conditions. The so-called general solutions of stress and electric fields are obtained, which is satisfied both the governing equations of anti-plane problems and the boundary conditions of the crack face. It is shown that electric field is nonsingular near right crack tip, while strain, stress and electric displacement have crack-tip singular behavior, the energy release rate has the same form as that without the electromechanical interaction, which is always positive. At last, the boundary collocation method is used to calculate the energy release rate. Numerical values are obtained to show the influence of the material properties and the electric field. The results show that the method of half analytical and half numeral is simple, accurate and widely applicable.