Failure Behavior of Belled Pile under Combined Loads

Author(s):  
Song-Lin Wen
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa

Abstract This paper presents a numerical study using the finite element method to assess the structural integrity of welded plates. Different levels of weld misalignment were introduced on the FEM models to investigate the influence of this welding imperfection parameter on the limit state of the structure. The models were loaded under displacement-controlled condition to introduce traction and torsion loads seeking to understand the effects of combined loads on the strain capacity of the misaligned welded structure. Surface elliptical cracks having different crack-size ratios were modeled to study the crack growth behavior by taking into account the misalignment of the weld and combined loads. The damage model is based on a failure surface and post-initiation behavior to model the ductile crack initiation and propagation steps, respectively. The models provide useful information to track the evolution of damage on the hot spot point of the welded structure. The model used is dependent on stress triaxiality and a Lode-based parameter and the damage level is driven by the plastic strain. The evolution of stress triaxiality and Lode parameter with loading are presented, and the influence of misalignment on them are shown. An exponential softening law was adopted to predict post-initiation failure behavior. The calibration steps of the parameters required for damage model application are shown for a A285 pressure vessel steel. Overall, the numerical models reveal the deleterious effects of weld misalignment and combined torsional and tensile loads on the strain capacity of the weld.


Author(s):  
Jun Shi ◽  
Yuzhuo Miao ◽  
Xiang Li ◽  
Guangzhong Li ◽  
Yu Wan ◽  
...  

Abstract Polyethylene pipes reinforced by winding steel wires (PSP) have been widely used in many fields such as chemical engineering, pulp conveying, water supply, etc. The combined loads of inner pressure and bending sometimes leads to the failure of PSP, and for engineering projects it is still not proposed that the failure criterion of PSP subject to combined loads. In this paper, full-size finite element models (FEM) of PSP under inner pressure and bending were established to investigate the engineering failure criterion. In the FEM the steel wires and HDPE matrix were modeled separately. The freedom degrees of steel wires and HDPE were coupled together as the interface between these two constituents were considered intact. The investigation contains two parts: firstly, a FEM was established in reference to the details of an existing experiment, including the pipe specimen and relative boundary condition. The validation of the FEM was carried out and the simulation result agreed well with test result indeed. Subsequently, the model was optimized to undertake four-point bending under inner pressure, to analyze the failure behavior of PSP under this kind of condition, with three factors such as varied ratio of diameters to thickness, inner pressure and volume ratio of steel wires. In the end, the curvature of failed PSP was considered as the failure criterion, and the relationship of curvature and the three factors were discussed. This paper is useful for the safety of PSP subject to inner pressure and bending load.


Author(s):  
Sukho Lee ◽  
John van den Biggelaar ◽  
Marc van Veenhuizen

Abstract Laser-based dynamic analysis has become a very important tool for analyzing advanced process technology and complex circuit design. Thus, many good reference papers discuss high resolution, high sensitivity, and useful applications. However, proper interpretation of the measurement is important as well to understand the failure behavior and find the root cause. This paper demonstrates this importance by describing two insightful case studies with unique observations from laser voltage imaging/laser voltage probing (LVP), optical beam induced resistance change, and soft defect localization (SDL) analysis, which required an in-depth interpretation of the failure analysis (FA) results. The first case is a sawtooth LVP signal induced by a metal short. The second case, a mismatched result between an LVP and SDL analysis, is a good case of unusual LVP data induced by a very sensitive response to laser light. The two cases provide a good reference on how to properly explain FA results.


2021 ◽  
Vol 160 ◽  
pp. 107278
Author(s):  
Erdong Wang ◽  
Guangyong Sun ◽  
Gang Zheng ◽  
Qing Li

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3657
Author(s):  
Alexander E. Wilson-Heid ◽  
Erik T. Furton ◽  
Allison M. Beese

This study investigates the disparate impact of internal pores on the fracture behavior of two metal alloys fabricated via laser powder bed fusion (L-PBF) additive manufacturing (AM)—316L stainless steel and Ti-6Al-4V. Data from mechanical tests over a range of stress states for dense samples and those with intentionally introduced penny-shaped pores of various diameters were used to contrast the combined impact of pore size and stress state on the fracture behavior of these two materials. The fracture data were used to calibrate and compare multiple fracture models (Mohr-Coulomb, Hosford-Coulomb, and maximum stress criteria), with results compared in equivalent stress (versus stress triaxiality and Lode angle) space, as well as in their conversions to equivalent strain space. For L-PBF 316L, the strain-based fracture models captured the stress state dependent failure behavior up to the largest pore size studied (2400 µm diameter, 16% cross-sectional area of gauge region), while for L-PBF Ti-6Al-4V, the stress-based fracture models better captured the change in failure behavior with pore size up to the largest pore size studied. This difference can be attributed to the relatively high ductility of 316L stainless steel, for which all samples underwent significant plastic deformation prior to failure, contrasted with the relatively low ductility of Ti-6Al-4V, for which, with increasing pore size, the displacement to failure was dominated by elastic deformation.


2021 ◽  
Vol 120 ◽  
pp. 105000
Author(s):  
Bowen Wang ◽  
Liyang Xie ◽  
Jiaxin Song ◽  
Xuehong He ◽  
Weifeng Luo ◽  
...  

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangzhong Guo ◽  
Wei Liu ◽  
Xiqing Li ◽  
Haowen Shi ◽  
Zhikun Song

AbstractPenetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars, while their fatigue performances and the difference between them are not completely understood. In this study, the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated. The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance, and their hardness was lower than that of the plates. The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes, whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes. The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture, respectively, and the primary cracks were initiated at welding fusion lines on the lap surface. There were long plastic ribs on the penetration plate fracture, but not on the non-penetration plate fracture. The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa, respectively, which can be used as reference stress for the fatigue design of the laser welded structures. The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.


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