Papers by Keyword: Stress Field

Abstract: The standard textbook analysis of dislocations is generally limited to the case of infinitely straight screw or edge dislocations, which do not exist. This is due to the complexity of the formulas for arbitrary dislocation loops, i.e., Burger’s equation for the displacement field, the Peach-Köhler equation for the stress field and Blin’s equation for the interaction energy, which involve line integrals along the dislocation loop. The integrands are complex, and integration often involves non-elementary functions. Elaboration of the integrands with symbolic mathematical software produces tensor formulas which can be reused at will. By formulating convenient parametric expressions for the configuration studied and using superposition, mathematical software can be used to perform the integrations for arbitrary Burgers vectors. Often, the resulting expressions for the tensorial fields are very long, but they can be easily incorporated as user-defined formulas for plotting, parametric analysis, and incorporation into routines for energy minimisation or the non-linear equations for force equilibrium. The effectiveness of this approach will be illustrated by the example of short straight dislocations, circular dislocations, the interaction between a pileup and dissociated dislocations in the grain boundary, and the nucleation of dislocations at grain boundaries.

Abstract: A finite element model of thermal coupling stress field during laser cladding plasma spraying of preset MCrAlY coating was constructed based on the finite element model of temperature field by using the indirect thermal coupling method in ANSYS finite element software. Moreover, stress field during laser cladding was analyzed. Through the constructed model, variation laws of stress field with time during laser cladding and cooling process could be mastered. Based on the stress field, the formation mechanism of cracks in laser cladding coating and influencing factors were further analyzed and some solutions to cracks of laser cladding coating were proposed.

Abstract: We investigated the effects of the stress field on acoustic emission (AE) during delayed fracture of glass. Delay fracture occurrence was controlled by the Vickers indentation load and kind of glass. Delayed fractures of glass were monitored by an AE method. After the Vickers hardness test, the glass surface was observed and its condition was compared with the AE signals. Characteristic AE signals were identified, and it was shown that the AE method is effective in measurements on the delayed fracture of glass.

Abstract: FIA regulations for the 2015 Formula One World Championship introduced an upper limit to the number of transmission assemblies employed during the season; a new approach to reliability has been forced on the designers, along with a reconsideration of the calculation procedures. Whereas mechanical transmission reliability calculations are well coded within the commercial transportations field, the peculiar aspects of the motorsport branch - namely a) the quest for an extreme lightweight design, b) the harsh dynamic transitions in speed and torque at gear shifts with a seamless shift transmission and wheel-road chattering, c) the circumscribed consequences of a breakage due to the controlled nature of the racing track environment, and d) the frenzied design procedures pace - urged for the development of specific validation procedures, that have to be rapidly redefined with the 2015 regulation adjustment. The present contribution rethinks those reliability assessment procedures - mostly based on nonlinear, dynamic Finite Element (FE) calculations - for a Formula One gearbox. In particular, the required model complexity is discussed with respect to the inclusion of shafts, bearings and carter compliance, chassis load induced deformation, significant load case selection, misuse robustness. The finalized validation procedure is shown to be predictive with respect to the augmented reliability requirements, while remaining feasible within the motorsport timescale environment.

Abstract: Based on the finite element model of high frequency welded pipe welded of composite aluminum alloy, the stress-time variation curves of welded pipe in different welding parameters were obtained. The analysis shows that the residual tensile stress in the weld zone is largest. At the same time, the weld tensile test and hydrostatic burst test were conducted. When the residual tensile stress in the weld zone is high, the blasting pressure which the weld can withstand is small, and the cracking position is often in the welded seam zone. To a certain extent, the change of the thermal stress in the welding process and the residual stress in the cooling process can be accurately reflected by the finite element analysis method.

Abstract: Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

Abstract: In-service welding of the pipeline steel is performed under the environment where the delivery of the high pressure pipeline doesn’t stop. When welding under the water, there are high-pressure gas flowing in the pipeline and water flowing outside, causing a difficult and possibly risky of the welding operation. The process of in-service welding with SYSWELD was adopted to establish a geometric model of pipeline repair that the pipeline steel using finite element numerical modeling of the underwater in-service welding was carried out. Furthermore, this study focused on the effect of water velocity on the temperature field and stress field when repairing the in-service pipeline by welding. The results indicated that the water velocity of the pipe has a great influence on the temperature field and the residual stress field.

Abstract: A comprehensive two-dimensional (2D) mathematical model based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT was developed to describe the interaction of the multiple physics fields during DC casting process. ANSYS was for calculation of the stress field and FLUENT was for calculation of the fluid flow, heat transfer of the solidification. The results show that: the model is reliable and accurate to simulate the multiple physics of DC casting. Consequently, the position, which was prone to hot tearing, was confirmed and the max velocity, at which the hot cracking might not occur, was determined. The numerical simulations will be very useful for preventing crack, optimizing casting parameters and obtaining high-quality ingots.

Abstract: This paper introduces fuel storage tank arrangement and the saddle structure of 296600 tons oil tanker (VLCC). According to the relevant standard, using ANSYS software, finite element modeling of the saddle and nearby hull structure is created. The radial force distribution function of the saddle is deduced under various conditions. The accurate stress state for saddle and nearby is found out by the application of finite element direct calculation method. Through the analysis of the results, the improvement measures are given and the reference for the saddle structure design is provided.

Abstract: This paper constructs aphysical model of aluminium alloy 7075-T6 welding based on ANSYS software, andsets simulation welding process to successfully obtain the change data anddistribution rule of welding temperature field and stress field for convenienceof providing guidance for welding technology of aluminium alloy 7075-T6.