Failure Behavior and Mechanisms in Dense Highly Aligned Brittle Nanowire Structures

2020 ◽  
Author(s):  
Rebecca Anne Gallivan
Keyword(s):  
Failure Behavior

Interpreting Laser-Based Fault Localization Results: Case Studies

2019 ◽  
Author(s):  
Sukho Lee ◽  
John van den Biggelaar ◽  
Marc van Veenhuizen
Keyword(s):  
Case Studies ◽  
Circuit Design ◽  
High Sensitivity ◽  
Failure Behavior ◽  
Process Technology ◽  
Resistance Change ◽  
Voltage Imaging ◽  
Root Cause ◽  
First Case ◽  
Proper Interpretation

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.

On multiaxial failure behavior of closed-cell aluminum foams under medium strain rates

2021 ◽  
Vol 160 ◽  
pp. 107278
Author(s):  
Erdong Wang ◽  
Guangyong Sun ◽  
Gang Zheng ◽  
Qing Li
Keyword(s):  
Failure Behavior ◽  
Strain Rates ◽  
Aluminum Foams ◽  
Closed Cell

scholarly journals Contrasting the Role of Pores on the Stress State Dependent Fracture Behavior of Additively Manufactured Low and High Ductility Metals

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3657
Author(s):  
Alexander E. Wilson-Heid ◽  
Erik T. Furton ◽  
Allison M. Beese
Keyword(s):  
Stainless Steel ◽  
Stress State ◽  
Pore Size ◽  
Fracture Behavior ◽  
316L Stainless Steel ◽  
Equivalent Stress ◽  
Failure Behavior ◽  
High Ductility ◽  
State Dependent ◽  
Fracture Models

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.

Failure behavior of aerial bomb lifting lug under variable amplitude loading: Failure analysis and life prediction

2021 ◽  
Vol 120 ◽  
pp. 105000
Author(s):  
Bowen Wang ◽  
Liyang Xie ◽  
Jiaxin Song ◽  
Xuehong He ◽  
Weifeng Luo ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Life Prediction ◽  
Failure Behavior ◽  
Variable Amplitude Loading ◽  
Variable Amplitude

scholarly journals Fatigue Resistance and Failure Behavior of Penetration and Non-Penetration Laser Welded Lap Joints

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangzhong Guo ◽  
Wei Liu ◽  
Xiqing Li ◽  
Haowen Shi ◽  
Zhikun Song
Keyword(s):  
Fatigue Resistance ◽  
Failure Modes ◽  
Plate Thickness ◽  
High Stress ◽  
Lap Joints ◽  
Failure Behavior ◽  
Passenger Cars ◽  
Plate Fracture ◽  
The Difference ◽  
Railway Passenger

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.

scholarly journals Analytical Investigation of Tension Loaded Deformed Rebar Anchors in Concrete

CivilEng ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 442-458
Author(s):  
Sandip Chhetri ◽  
Rachel A. Chicchi
Keyword(s):  
Test Data ◽  
Parametric Study ◽  
Failure Modes ◽  
Experimental Testing ◽  
Analytical Investigation ◽  
Failure Behavior ◽  
Capacity Design ◽  
Simulation Results

Experimental testing of deformed rebar anchors (DRAs) has not been performed extensively, so there is limited test data to understand their failure behavior. This study aims to expand upon these limited tests and understand the behavior of these anchors, when loaded in tension. Analytical benchmark models were created using available test data and a parametric study of deformed rebar anchors was performed. Anchor diameter, spacing, embedment, and number of anchors were varied for a total of 49 concrete breakout simulations. The different failure modes of anchors were predicted analytically, which showed that concrete breakout failure is prominent in the DRA groups. The predicted concrete breakout values were consistent with mean and 5% fractile concrete capacities determined from the ACI concrete capacity design (CCD) method. The 5% fractile factor determined empirically from the simulation results was kc = 26. This value corresponds closely with kc = 24 specified in ACI 318-19 and ACI 349-13 for cast-in place anchors. The analysis results show that the ACI CCD formula can be conservatively used to design DRAs loaded in tension by applying a kc factor no greater than 26.

Finite Element Modeling of a Mechanically Stabilized Earth Trial Wall

2021 ◽  
pp. 036119812110164
Author(s):  
Andrew Lees ◽  
Michael Dobie
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Retaining Wall ◽  
Back Analysis ◽  
Soil Parameters ◽  
Failure Behavior ◽  
Valuable Insight ◽  
Deformation And Failure ◽  
First Case ◽  
Soil Shear Strength

Polymer geogrid reinforced soil retaining walls have become commonplace, with routine design generally carried out by limiting equilibrium methods. Finite element analysis (FEA) is becoming more widely used to assess the likely deformation behavior of these structures, although in many cases such analyses over-predict deformation compared with monitored structures. Back-analysis of unit tests and instrumented walls improves the techniques and models used in FEA to represent the soil fill, reinforcement and composite behavior caused by the stabilization effect of the geogrid apertures on the soil particles. This composite behavior is most representatively modeled as enhanced soil shear strength. The back-analysis of two test cases provides valuable insight into the benefits of this approach. In the first case, a unit cell was set up such that one side could yield thereby reaching the active earth pressure state. Using FEA a test without geogrid was modeled to help establish appropriate soil parameters. These parameters were then used to back-analyze a test with geogrid present. Simply using the tensile properties of the geogrid over-predicted the yield pressure but using an enhanced soil shear strength gave a satisfactory comparison with the measured result. In the second case a trial retaining wall was back-analyzed to investigate both deformation and failure, the failure induced by cutting the geogrid after construction using heated wires. The closest fit to the actual deformation and failure behavior was provided by using enhanced fill shear strength.

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