Papers by Keyword: Failure Surface

Abstract: This article discusses effect of filler concentration on impact strength of an epoxy resin composite. The optimal ratio of resin and hardener is defined. Research of the effect of the concentration of the filler - carbon black P505 on the impact strength of a composite material based on epoxy resin ED-20 is made. According to the results of the study, it is shown that with an increase of concentration of the filler from P505 carbon black, the toughness decreases. Fractographic studies of the fracture surfaces of composites were also carried out, which indicate that the introduction of a filler leads to a decrease in the surface energy of destruction. Thus, studies of epoxy composite modified with technical carbon grade P505 showed a decrease in impact strength up to 4 times, depending on the increase in the mass fraction of the filler.

Abstract: As an alternative to classical retaining solutions, as gravity or flexible retaining walls, the reinforced earth retaining structures are successfully used. The interaction between the reinforcement and the soil fill and their failure mode as well, are important issues to take into account for the design of these types of structures and the corresponding calculation methods used for their design. From this point of view, an important element is the shape of the failure surface, considered in the design calculation as: plane, circular, etc., which has an important influence on the tensile forces values within reinforcements. This paper presents a new theoretical method for the calculations of the reinforced earth retaining structures and the corresponding results for failure surface shape and for tensile forces in the reinforcements. Considering the similarities between the theoretical results presented in this paper and the experimental results presented in the specialty bibliography, this method creates the possibilities to design in a more economical way, only by taking into consideration the correct interaction mechanism between the soil and the reinforcements

Abstract: Bismuth telluride-based alloys are the most widely used thermoelectric materials, which can obtain the conversion between heat energy and electricity. As a kind of lead-free solder alloy, Sn96.5Ag3.0Cu0.5 (SAC305) shows great potential in soldering between the thermoelectric element and electrode in thermoelectric couples. Cu/ SAC305 /Ni-plated Bi_0.5Sb_1.5Te₃ (n-type) and Cu/ SAC305/Ni-plated Bi_1.8Sb_0.2Se_0.15Te_2.85 (p-type) couples were connected at 250°C by reflow soldering to investigate effects of temperature and thermall aging on the efficiency and reliability of thermoelectric device. Effects of temperature and environmental aging on shear force of thermoelectric couples were studied respectively in the temperature range of 20°C to 180°C. At room temperature of 20°C, n-type thermoelectric couples showed higher shear force than p-type thermoelectric couples. N-type thermoelectric couple showed higher shear reliability than p-type thermoelectric couples after synchronized environmental aging. The shear force of both types of thermoelectric couples decreased with the growth of thermal aging cycles. Finally, the fracture surfaces of two types of thermoelectric couples were investigated respectively using SEM to further analyse the failure mechanism.

Abstract: The recent trend in automotive industry is characterized by the replacement of existing metal materials with composite ones or the combination of both for lightweight parts. This study 1) created single lap joint specimens of SPCC used for automobile frame and four adhesives; epoxy, urethane, acrylic, mixed (urethane and acrylic) and rivets to bind dissimilar materials of CFRP necessary for weight lightening, and 2) performed a tensile shear test on adhesive bonding versus adhesive bonding with rivets. In summary, this study investigated on the bonding performance of different specimens: bonding strength, shapes of the failure surface, and the effect of rivets on bond strength.

Abstract: This paper presents the study of failure surface obtained in the truss-like Discrete Element Method (DEM). The element constitutive law considers the fracture energy of the material and its spatial variation is used to take into account the heterogeneity of the simulated materials. It is studied the influence of spatial distribution of fracture energy and the spatial lattice perturbation on the DEM failure surface. A DEM failure criterion is compared with concrete and rock failure.

Abstract: Suction caissons attract the attention as the foundation of offshore wind turbines. Installation and resistance behaviors of the suction caisson are important factors for the design of foundation. An installation behavior into sandy seafloor was discussed by using a model suction caisson and the failure surfaces in the aluminum rod mass, as the model ground, subjected to lateral force were compared. Consequently, the installation of model suction caisson into sandy sea depended on the permeability of sandy seafloor and lateral resistance of suction caisson depended on the dimension of suction caisson which affected on the shape of failure surface in the ground.

Abstract: Anchors are widely used in foundation systems for structures requiring uplift resistance. As demonstrated by numerous theoretical and experimental studies on the subject, uncertainty remains as to both the theoretical uplift capacity of anchors in idealised soils and the suitability of the various modelling assumptions in capturing the responses observed during tests. This study, which deals exclusively with the theoretical uplift capacity, presents newly obtained predictions of uplift capacities and the corresponding collapse mechanisms for inclined strip anchors in sand. The analysis is based on the upper bound (kinematic) method of limit analysis and the so-called block set mechanism, in which a collapse mechanism consisting of sliding rigid blocks is optimised with respect to interior angles and edges of the blocks. It is demonstrated that the method provides lower (better) estimates of uplift capacity in some cases compared to previous upper bound calculations. Also, variations in the predicted collapse mechanism with changes in embedment and inclination are assessed in detail.

Abstract: This paper presents an experimental investigation on the failure surface and plastic potential in deviatoric plane of Bangkok Clay. The results of torsional shear hollow cylinder and triaxial tests with various principal stress directions and magnitudes of intermediate principal stress on undisturbed Bangkok Clay specimens are presented. The obtained stress-strain behaviors assert clear evidences of anisotropic characteristics of Bangkok Clay. Both failure surface and plastic potential in deviatoric plane of Bangkok Clay are demonstrated as isotropic and of circular shape (Drucker-Prager type) which implies an associated flow rule. Concerning the behavior of Bangkok Clay found from this study, the discussions on the effects of employed constitutive modeling approach on the resulting numerical analysis are made.

Abstract: Frost resistance research is one of the important subject of concrete durability, however strength criteria is an important part of the study of mechanical behavior of concrete. So far, about concrete failure criteria are almost for normal concrete, which the domestic and overseas scholars have comparative detailed research in every respect to it, and to freeze-thaw damage of concrete but few research. Based on the summary of the existing ordinary concrete strength and failure criteria in normal state and after freeze-thaw damage，this paper have a brief comment of failure criteria on concrete after freeze-thaw damage. For later research about concrete strength and failure criteria under freezing and thawing cycle provide the reference.

Abstract: The weighted stochastic response surface method (WSRSM) has been demonstrated to be effective in improving the accuracy of the estimation of statistical moments and probability of failure (PoF) upon the stochastic response surface method (SRSM). However, it has been noticed that the weighting method in WSRSM may have little and sometimes negative impact on PoF estimation especially in the cases of low PoF. To address this issue, an enhanced weighting strategy is proposed that the weights of sample points are determined based on their importance not only to regression but also to PoF estimation. Specifically, relatively larger weights are assigned to points closer to the failure surface, which significantly accounts for the accuracy of PoF estimation. Comparative studies show that SRSM with the proposed weighting method outperforms WSRSM producing more accurate PoF estimation without incurring additional function evaluations.