A strain energy criterion for failure of floating ice sheets

1978 ◽  
Vol 5 (3) ◽  
pp. 352-361 ◽  
Author(s):  
S. Beltaos
Keyword(s):  
Failure Criterion ◽  
Strain Energy ◽  
Unit Volume ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Energy Criterion ◽  
Failure Criteria ◽  
Test Results ◽  
Practical Limit ◽  
Loading Tests

A failure criterion for floating ice sheets under stationary loads is presented, based on the concept of strain energy per unit volume and the results of some 40 prototype loading tests. The practical requirement for a time-independent failure criterion for ice, which is a viscoelastic material and thus subject to creep, is noted. Existing failure criteria are reviewed and shown to be unable to handle many practical situations. Subsequently, the concept of strain energy per unit volume is formulated and shown to provide a satisfactory failure criterion under varied loading histories. Analysis of the test results indicated the existence of a distinct instant marking the onset of failure of a loaded ice sheet. Because the behaviour of a loaded ice sheet between this instant and the final breakthrough of the load is partially random, it is suggested that the former be used as the practical limit of safety.

scholarly journals Comparative Analysis of Common Strength Criteria of Soil Materials

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4302
Author(s):  
Ping Xu ◽  
Zhijun Sun ◽  
Shengjun Shao ◽  
Lingyun Fang
Keyword(s):  
Failure Criterion ◽  
Triaxial Test ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Failure Criteria ◽  
Theory And Practice ◽  
Engineering Practice ◽  
Test Results ◽  
True Triaxial Test ◽  
True Triaxial

In this paper, the common failure criteria of existing soil materials, such as the Mohr–Coulomb criterion, Drucker–Prager criterion, Lade–Duncan criterion, Matsuoka–Nakai criterion andAC-SMP criterion are systematically discussed, and the applicability of these criteria is quantitatively analyzed through the true triaxial test results of loess, so as to provide reference for the accurate selection of specific criteria in engineering practice. The failure criteria are classified from several aspects, such as whether the influence of the intermediate principal stress and the change of spatial moving plane are considered, analyzed and discussed, respectively. According to the true triaxial test results of undisturbed loess, the difference of strength criterion between the three-dimensional failure plane and p-q plane is analyzed, and based on the true triaxial test data of undisturbed loess, the error analysis of each failure criterion is carried out. The results show that the AC-SMP criterion is in good agreement with the test results, and can accurately evaluate the true triaxial test of loess. For different soil materials or different stress states, it is necessary to select appropriate failure criteria. This study shows how to choose the corresponding failure criterion under specific circumstances, so as to better satisfy the theory and practice and provide reference for engineering.

Investigation of Local Failure Criteria of Wall-Thinned Area by Simulated Specimen Tests

2006 ◽  
Vol 326-328 ◽  
pp. 1165-1168
Author(s):  
Do Hyung Kim ◽  
Jin Won Kim ◽  
Yeon Soo Na ◽  
Chi Yong Park
Keyword(s):  
Failure Criterion ◽  
Equivalent Stress ◽  
Stress Triaxiality ◽  
Maximum Load ◽  
Tensile Tests ◽  
Failure Criteria ◽  
Local Failure ◽  
Test Results ◽  
Final Failure ◽  
Smooth Bars

The objective of this study is to develop a local failure criterion at wall-thinning defect of piping components. For this purpose, a series of tensile tests was performed using several types of specimens with different stress state under tension, including smooth bars, notched round bars and grooved plates. In addition, finite element (FE) simulations were performed for all tests, and its results were compared to the test results. From the comparisons, the equivalent stress and strain corresponding to maximum load and final failure of the notched round bar specimens were proposed as the local failure criterion which is a function of stress triaxiality at notched area. The criteria were verified by employing them to the estimation of maximum load and final failure of grooved plate specimen tests.

On Utilization of Material Failure Criterion in Modeling Pull-Out Failure of Spot-Welded Joints

2013 ◽  
Author(s):  
Long Zeng ◽  
Yong Xia ◽  
He Zhao ◽  
Qing Zhou
Keyword(s):  
Test Data ◽  
Failure Criterion ◽  
Welded Joints ◽  
Failure Modes ◽  
Failure Criteria ◽  
Spot Weld ◽  
Test Results ◽  
Pull Out ◽  
Metal Sheets ◽  
Spot Welded

Two distinct failure modes of spot welds, interfacial and pull-out failure, are observed in impact of spot-welded structures. Automotive industries prefer pull-out as the predominant failure mode since it makes more use of load-bearing capacity of a joint. For the time being, finite element models for predicting pull-out failure of spot weld have not been well developed. The dependence of failure on the stress state, i.e., a locus in the space of failure strain and stress triaxiality, needs to be known for base metal sheets when modeling spot weld pull-out. Existing failure criteria, with or without physical base, were formulated to provide an effective way to utilize a limited number of tests to reconstruct the failure locus. This paper is aimed to evaluate influence of failure criterion form for identifying failure parameters on modeling spot weld pull-out. As for material tests, various specimen configurations of metal sheets were designed to obtain stress states around a number of typical stress triaxialities. These test results constructed a set of test data for calibrating failure criterion. The spot-welded joints were also tested two different coupon configurations. The force-displacement curves were obtained, and the deformation fields around the spot weld nugget were achieved with DIC. These test results of joints were utilized to validate the model of spot weld pull-out. Two prevailing failure criteria, shear-modified Gurson model and Modified Mohr-Coulomb model, were selected to predict the complicated spot weld pull-out failure. Parameters in each of the two failure criteria were identified with material test data. Various simulation results were thereafter obtained based on different failure criteria. The two criteria were evaluated in terms of their predictive capabilities for spot weld pull-out failure.

A topological approach to the strain-rate pattern of ice sheets

1993 ◽  
Vol 39 (131) ◽  
pp. 10-14 ◽  
Author(s):  
J. F. Nye
Keyword(s):  
Strain Rate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Point Of View ◽  
Principal Strain ◽  
Topological Approach ◽  
Contour Maps ◽  
Isotropic Point ◽  
Horizontal Strain

AbstractThe pattern of horizontal strain rate in an ice sheet is discussed from a topological point of view. In a circularly symmetric ice sheet, the isotropic point for strain rate at its centre is degenerate and structurally unstable. On perturbation the degenerate point splits into two elementary isotropic points, each of which has the lemon pattern for the trajectories of principal strain rate. Contour maps of principal strain-rate values are presented which show the details of the splitting.

Analysis and Simulation of Altimeter Performance for the Production of Ice Sheet Topographic Maps

1986 ◽  
Vol 8 ◽  
pp. 141-145 ◽  
Author(s):  
K.C. Partington ◽  
C.G. Rapley
Keyword(s):  
High Precision ◽  
Systems Analysis ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Data Interpretation ◽  
Topographic Maps ◽  
Error Signal ◽  
Tracking Systems ◽  
Tracking Mode ◽  
Non Linear

Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets. Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regions of the ice sheet to ± 72° latitude. ERS-1 will extend coverage to ± 82° latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.Altimeter performance over the ice sheets has been investigated through a study of Seasat tracking behaviour and the use of an altimeter performance simulator, with a view to assessing the likely performance of ERS-1 and the design of improved tracking systems. Analysis of Seasat data shows that lock was frequently lost, as a result of possessing a non-linear height error signal over the width of the range window. Having lost lock, the tracker frequently failed to transfer rapidly and effectively to track mode. Use of the altimeter performance simulator confirms many of the findings from Seasat data and it is being used to facilitate data interpretation and mapping, through the modelling of waveform sequence.

scholarly journals Attention Multi-Scale Network for Automatic Layer Extraction of Ice Radar Topological Sequences

2021 ◽  
Vol 13 (12) ◽  
pp. 2425
Author(s):  
Yiheng Cai ◽  
Dan Liu ◽  
Jin Xie ◽  
Jingxian Yang ◽  
Xiangbin Cui ◽  
...  
Keyword(s):  
Deep Learning ◽  
Global Climate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Learning Methods ◽  
Convolutional Network ◽  
Multi Scale ◽  
Ice Surface ◽  
Layer Extraction

Analyzing the surface and bedrock locations in radar imagery enables the computation of ice sheet thickness, which is important for the study of ice sheets, their volume and how they may contribute to global climate change. However, the traditional handcrafted methods cannot quickly provide quantitative, objective and reliable extraction of information from radargrams. Most traditional handcrafted methods, designed to detect ice-surface and ice-bed layers from ice sheet radargrams, require complex human involvement and are difficult to apply to large datasets, while deep learning methods can obtain better results in a generalized way. In this study, an end-to-end multi-scale attention network (MsANet) is proposed to realize the estimation and reconstruction of layers in sequences of ice sheet radar tomographic images. First, we use an improved 3D convolutional network, C3D-M, whose first full connection layer is replaced by a convolution unit to better maintain the spatial relativity of ice layer features, as the backbone. Then, an adjustable multi-scale module uses different scale filters to learn scale information to enhance the feature extraction capabilities of the network. Finally, an attention module extended to 3D space removes a redundant bottleneck unit to better fuse and refine ice layer features. Radar sequential images collected by the Center of Remote Sensing of Ice Sheets in 2014 are used as training and testing data. Compared with state-of-the-art deep learning methods, the MsANet shows a 10% reduction (2.14 pixels) on the measurement of average mean absolute column-wise error for detecting the ice-surface and ice-bottom layers, runs faster and uses approximately 12 million fewer parameters.

Experimental study of moment carrying behavior of typical Tibetan timber beam-column joints

2021 ◽  
pp. 136943322110015
Author(s):  
Ting Guo ◽  
Na Yang ◽  
Huichun Yan ◽  
Fan Bai
Keyword(s):  
Bending Moment ◽  
Structural Performance ◽  
Test Results ◽  
Timber Beam ◽  
Rotational Stiffness ◽  
Trilinear Model ◽  
Column Joint ◽  
Loading Tests ◽  
The Moment ◽  
Relationship Of

This study aimed to investigate the moment carrying behavior of typical Tibetan timber beam-column joints under monotonic vertical static load and also evaluate the influence of length ratio of Gongmu to beam (LRGB) and dowels layout on the structural performance of the joint. Six full-scale specimens were fabricated with same construction but different Gongmu length and dowels position. The moment carrying performance of beam-column joints in terms of failure mode, moment resistance, and rotational stiffness of joints were obtained via monotonic loading tests. Test results indicated that all joints are characterized by compressive failure perpendicular to grain of Ludou. Additionally, it was found that greater LRGB leads to greater initial rotational stiffness and maximum moment of the joint by an increase of restraint length for beam end; however, offsetting dowels toward column resulted smaller stiffness and ultimate bending moment of joints, particularly, offsetting Beam-Gongmu dowels toward column changed the moment-rotation curve pattern of the beam-column joint, accompanied by a hardening stiffness at last phase. Furthermore, a simplified trilinear model was proposed to represent the moment-rotation relationship of the typical Tibetan timber beam-column joint.

scholarly journals Measurement of ice-sheet topography using satellite-radar interferometry

1996 ◽  
Vol 42 (140) ◽  
pp. 10-22 ◽  
Author(s):  
Ian Joughin ◽  
Dale Winebrenner ◽  
Mark Fahnestock ◽  
Ron Kwok ◽  
William Krabill
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Surface Displacement ◽  
Horizontal Resolution ◽  
Radar Interferometry ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Digital Elevation ◽  
Satellite Radar ◽  
Ice Sheet Topography

AbstractDetailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

scholarly journals Dynamical processes involved in the retreat of marine ice sheets

2001 ◽  
Vol 47 (157) ◽  
pp. 271-282 ◽  
Author(s):  
Richard C.A. Hindmarsh ◽  
E. Le Meur
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
Neutral Equilibrium ◽  
Generally True

AbstractMarine ice sheets with mechanics described by the shallow-ice approximation by definition do not couple mechanically with the shelf. Such ice sheets are known to have neutral equilibria. We consider the implications of this for their dynamics and in particular for mechanisms which promote marine ice-sheet retreat. The removal of ice-shelf buttressing leading to enhanced flow in grounded ice is discounted as a significant influence on mechanical grounds. Sea-level rise leading to reduced effective pressures under ice streams is shown to be a feasible mechanism for producing postglacial West Antarctic ice-sheet retreat but is inconsistent with borehole evidence. Warming thins the ice sheet by reducing the average viscosity but does not lead to grounding-line retreat. Internal oscillations either specified or generated via a MacAyeal–Payne thermal mechanism promote migration. This is a noise-induced drift phenomenon stemming from the neutral equilibrium property of marine ice sheets. This migration occurs at quite slow rates, but these are sufficiently large to have possibly played a role in the dynamics of the West Antarctic ice sheet after the glacial maximum. Numerical experiments suggest that it is generally true that while significant changes in thickness can be caused by spatially uniform changes, spatial variability coupled with dynamical variability is needed to cause margin movement.

Change of the critical thickness in the preferred orientation of TiN films

1995 ◽  
Vol 10 (3) ◽  
pp. 634-639 ◽  
Author(s):  
U.C. Oh ◽  
Jung Ho Je ◽  
Jeong Y. Lee
Keyword(s):  
Strain Energy ◽  
Unit Volume ◽  
Critical Thickness ◽  
Preferred Orientation ◽  
Rf Power ◽  
X Ray Diffraction ◽  
Working Pressure ◽  
Cross Sectional ◽  
Tin Films ◽  
Tin Thin Films

Recently it was observed through cross-sectional TEM that the preferred orientation of the TiN thin film was changed from (200) to (111) with thickness. In this study, the process of the change in the preferred orientation was studied near the critical thickness by x-ray diffraction, and the value of the critical thickness could be estimated. The change of the critical thickness was also investigated with the strain energy per unit volume. The strain energy could be changed by controlling the energy of the bombarding particle, i.e., by adjusting the rf power, the working pressure, and the substrate bias in sputtering. The critical thickness was decreased monotonically in all cases as the energy of the bombarding particle or the strain energy per unit volume was increased. These results surely show the dependence of the change of the preferred orientation on the strain energy in the TiN thin films.

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