Analysis of Interfacial Crack by Means of Hypersingular Integro-Differential Equations

Numerical solutions of hypersingular integro-differential equations are discussed in the analysis of interfacial crack in two and three dimensional bimaterials subjected to general internal pressure. The problem is formulated on the basis of the body force method. In the numerical analysis, unknown body force densities are approximated by the products of the fundamental density functions and power series, where the fundamental density functions are chosen to express singular behavior along the crack front of the interface crack exactly. The present method gives rapidly converging numerical results and highly satisfied boundary conditions throughout the crack boundary. The stress intensity factors are given with varying the material combination and aspect ratio of the crack. It is found that the stress intensity factors KI and II K are determined by the bimaterials constant ε alone, independent of elastic modulus ratio and Poisson\u27s ratio.22rd International Congress of Theoretical and Applied Mechanics (ICTAM 2008), August, 24-30, 2008, Adelaide, Australi

Effects of Geometry on Intensity of Singular Stress Fields at the Corner of Single-Lap Joints

This paper discusses effects of adhesive thickness, overlap length and material combinations on the single-lap joints strength from the point of singular stress fields. A useful method calculating the ratio of intensity of singular stress is proposed using FEM for different adhesive thickness and overlap length. It is found that the intensity of singular stress increases with increasing adhesive thickness, and decreases with increasing overlap length. The increment and decrement are different depending on material combinations between adhesive and adherent.WASET 2011:INTERNATIONAL CONFERENCE PROGRAM Holiday Inn Paris Montparnesse-Avenue du Maine, June 24-26, 2011, Paris, Franc

Single and double edge interface crack solutions under arbitrary material combinations

In this paper interfacial edge crack problems are considered by the application of the finite element method. The stress intensity factors are accurately determined from the ratio of crack-tip-stress value between the target given unknown and reference problems. The reference problem is chosen to produce the singular stress fields proportional to those of the given unknown problem. Here the original proportional method is improved through utilizing very refined meshes and post-processing technique of linear extrapolation. The results for a double-edge interface crack in a bonded strip are newly obtained and compared with those of a single-edge interface crack for different forms of combination of material. It is found that the stress intensity factors should be compared in the three different zones of relative crack lengths. Different from the case of a cracked homogeneous strip, the results for the double edge interface cracks are found to possibly be bigger than those for a single edge interface crack under the same relative crack length

Strength Analysis of Adhesive Joints for Riser Pipes in Deep Sea Enviroment Loading

Nowadays, adhesive joints are widely used in riser pipes, which are subjected to many kinds of loadings in deep sea, such as external pressure, internal pressure, tension, torsion, bending, and also a combination of these loadings. Adhesive joints of riser pipes are the most dangerous parts in term of strength, as singular stress fields exist at the end of the interface between the adhesive and the adherends, so it is very important to evaluate the strength of adhesive bonded joints for riser pipes in deep sea environment loadings. In this research, the strength of adhesive joints of riser pipes is studied under external pressure, internal pressure, tension, torsion, bending loadings, and it is found that singular stress fields exist around the end of the interface. The riser pipe under external pressure, internal pressure and tension loading is more prone to break than under bending and torque loading

Critical Intensity of Singular Stress for Adhesive Joints

In this study debonding conditions of an adhesively bonded joint are discussed in terms of the intensities of the singular stress fields. Here, two types of models are considered; one is the perfectly-bonded strip model, and the other is partially-debonded model assuming different debonded lengths. The previous experimental data are examined, which were obtained for S35C JIS medium carbon steel plates bonded with epoxy resin Epikote 871. It is found that the critical values of the intensity of singular stress are almost constant independent of the adhesive thickness. In other words, the adhesive strength can be estimated from the intensities of singular stress from both of the perfectly-bonded and partially-debonded models.23rd International Congress of Theoretical and Applied Mechanics, August 19-24, 2012, Beijing, Chin

Strength Analysis for the Adhesive Layer on the Basis of Intensity of Singular Stress

In this paper the strength of adhesive joint under tension and bending is discussed on the basis of intensity of singular stress by the application of FEM. A useful method is presented with focusing on the stress at the edge of interface between the adhesive and adherent obtained by FEM. After analyzing the adhesive joint strength with all material combinations, it is found that to improve the interface strength, thin adhesive layers are desirable because the intensity of singular stress decreases with decreasing of the thickness.11th International Conference on the mechanical behavior of Materials (ICM11), 5-9 June 2011, Como, Ital

Intensity of Singular Stress Field at the Corner of Adhesive Layer in Bonded Plate

In this paper the strength of adhesive joint under tension and bending is discussed on the basis of intensity of singular stress by the application of FEM. A useful method is presented with focusing on the stress at the edge of interface between the adhesive and adherent obtained by FEM. After analyzing the adhesive joint strength with all material combinations, it is found that to improve the interface strength, thin adhesive layers are desirable because the intensity of singular stress decreases with decreasing the thickness.WASET 2011:INTERNATIONAL CONFERENCE PROGRAM Holiday Inn Paris Montparnesse-Avenue du Maine, June 24-26, 2011, Paris, Franc

Theory of magnetic field-induced metaelectric critical end point in BiMn2_2O5_5

A recent experiment on the multiferroic BiMn$_2$O$_5$ compound under a strong applied magnetic field revealed a rich phase diagram driven by the coupling of magnetic and charge (dipolar) degrees of freedom. Based on the exchange-striction mechanism, we propose here a theoretical model with the intent to capture the interplay of the spin and dipolar moments in the presence of a magnetic field in BiMn$_2$O$_5$. Experimentally observed behavior of the dielectric constants, magnetic susceptibility, and the polarization is, for the most part, reproduced by our model. The critical behavior observed near the polarization reversal $(P=0)$ point in the phase diagram is interpreted as arising from the proximity to the critical end point.Comment: Theory; relevant experiment uploaded as arXiv:0810.190

Effect of Pitch Difference on Anti-loosening Performance and Fatigue Strength for High Strength Bolts and Nuts

A slight pitch difference is considered between the bolt and nut in this study. Here, the pitch ofnut is α μm larger than the pitch of bolt. In the first place, the distance δ, of nut screwed onto bolt withoutany prevailing torque, is experimentally and analytically obtained for each level of α. Then, the relationshipbetween axial force and prevailing torque during tightening process is tested. According to the obtainedtorque-axial force relationship, for four different levels of α, the loosening experiment based on NAS3350(National Aerospace Standard) is performed, and the loosening and dropping status of the nuts areinvestigated. Considering both the anti-loosening ability and the clamping ability of the nut, the desirablerange of α is discussed. After that, according to the loosening experiment results, three levels of α areselected to make a further study about the effect of the pitch difference on the fatigue life of bolt. The fatigueexperiment is performed and the S-N curves are obtained. Finally, the finite element method is used to makea simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of boltare analyzed.13th International Conference on Fracture, June 16–21, 2013, Beijing, Chin