Key Engineering Materials Vols. 577-578

Abstract: An efficient structure design using welding of dissimilar steels is a common strategy in the process and construction industries. This study investigates the temperature distribution in the HAZ due to multi pass welding of an austenitic stainless steel SUS316 pipe to carbon steel S610 plate. A nonlinear transient thermal FE analysis is performed using ANSYS software. An APDL (ANSYS Parametric Design Language) program is developed to define moving double ellipsoidal heat source model, nonlinear thermal properties and thermal boundary conditions. Addition of filler metal is simulated using element death and birth technique. Transient effect of heat and cooling slopes during welding are studied. The present work offers a basis for future prediction of welding residual stresses and distortions in joint between pipe and plate.

Abstract: According to salt rock creep test data and strain variation regulation of a salt mine, salt rock creep parameters are obtained based on Burgers creep model fitting. Statistical study of the probability distribution of the salt rock Burgers model creep parameters is carried out by K-S, A-D and C-M test method, from which probability model for each creep parameters is obtained. To achieve the purpose of determining the optimal probability model for each creep parameters, considering the acceptable level of various test method to different hypothesis probability model, the author put forward the comprehensive optimal acceptance criteria on the basis of limited comparison method, the correctness of which is proved by test result.

Abstract: The buried pipeline will be spanning and subject to dynamic load under flooding, which may induce a damage failure of pipeline. In this paper, a mechanical analysis model of spanning pipelines is established under different levels of flood load. The mechanical response and the information entropy based on strain energy of the pipeline are calculated through global analytical searching method. In addition, the recognition of damage failure of pipeline is achieved according to the value of strain energy entropy of pipeline under different flood levels. The study shows that the strain energy entropy varies with the change of deformation reflects the damage failure feature of pipeline well, which can be used as a new method to identify the failure of pipeline.

Abstract: Some fundamental issues, such as stress wave dispersion effect, loss of contact, pulse shaping effect are still needed to thoroughly understand in Hopkinson pressure bar loaded fracture experimental techniques. In order to avoid the influence of stress wave dispersion on the analysis of dynamic experimental results, a computational procedure has been developed based on the combined analytical solution of Pochhammer-Chree with Fourier spectroscopy analysis. The validity of this proposed computational procedure was confirmed via the comparison with the experimental stress pulses obtained from pulse-shaped tests. The experimental results can be easily interpreted and the testing accuracy can be improved using this computational procedure.

Abstract: Based on the Upper Bound Theory, a Simplified Engineering Approach is Presented to Determine the Ultimate Strength of a pin-Loaded Composite Laminate in this Papaer. According to the Upper Bound Theory, the Displacement Rate in a Given Ply is Divided into Two Zones: the Moving Zone and the Static Zone. the Applied Load Q that Associated with Displacement must be Less than the Maximum Resistance of the Laminate. in this Paper we have Discussed the Failure Region, Failure Type of each Ply and Simplified the Tsai-Wu Failure Criterion. Experiments of Single-Bolt Double-Lap Joints have been Conduncted According to ASTM D5961 Test Standard. Finally, we can Observe that the Engineering Approach is in Good Agreement with the Test Results.

Abstract: Removed at authors request

Abstract: This paper presents a damage constitutive model to characterize the softening behavior of asphalt mastic in the fracture process. The three-point bending asphalt mixture beams with different crack locations and aggregate distributions are modeled with the parameterization modeling method. It is found that there is good agreement between the predicted and experimental results. The effects of crack location and coarse aggregate distribution on the crack path are numerically evaluated, and damage distributions near the crack tip are analyzed. Some conclusions are given.

Abstract: Ceramic particles reinforced metal matrix functional gradient armor is a terrific protective material for helicopter gunship armor to gain light weight and improve anti-penetration performance. However, the anti-penetration mechanism is still not understood. In view of this fact, this paper aims to investigate the penetration mechanism of functional gradient armor. LS-DYNA software is used to simulate the processes of armor-piercing projectile oblique penetrating an optimal ceramic particles reinforced metal matrix functional gradient armor. The armor’s geometry of the calculation model considered is a four-sides-fixed supported round plate whose side length is far longer than its thickness. The penetrator considered is a long rod projectile. The results show that: when the oblique angle is relatively small, the projectile will turn to the vertical direction, that is to say, the oblique angle will diminish during the oblique penetration, and this phenomenon will do harm to the anti-penetration performance of the armor; when the oblique angle increases to a certain degree, the oblique angle will be enlarged during the oblique penetration, and this phenomenon will be beneficial to the anti-penetration performance of the armor. The bigger the oblique angle is, the easier the ricochet phenomenon will become. When design armors, the oblique angles of 0~15 degree should be avoided, and the oblique angles greater than 35 degree are preferred.

Abstract: The effects of loading rate on splitting test, uniaxial compression strength, strength parameters in triaixal compression test, and creep failure of Hangcheng coal rock were investigated through indoor mechanical experiments. Experimental results shown that tensile strength, uniaxial strength and Youngs modulus of coal rock increased with the increase of loading rate and the increment is very small. Triaixal compression strength and loading rate has a linear relation. Brittleness was very marked under high loading rate. Ductility of coal rock in the steady creep stage diminished with the increase of loading rate, and failure mode of coal rock had a change from low ductility failure mode to ductile-to-brittle failure mode. The results of experimental researches can be used to determine the bottom hole flowing pressure of coalbed methane well.

Abstract: The steam turbine rotors represent large components both in radial and axial directions. Their local properties generally differ from one forging to another, or if we compare head and bottom parts of the original ingot, or central and circumferential localities of one rotor body respectively, or if we compare the properties of separate discs e.g. in the case of welded rotors. These differences stem from both even slight changes in the chemical composition (of separate heats or even within one ingot) and thermo-mechanical treatment and in the differences in technology with respect to the real shape and size of the forgings in question. In the paper, the consequences of the differences in fracture toughness characteristics in various rotor localities are discussed with respect to the rotors operational safety taking into account the existence of cracks and material degradation.