Failure Prediction Approach Research Articles

Explicit phantom paired shell element approach for crack branching and impact damage prediction of aluminum structures

The main objective of this paper is to exploit an efficient and a simplified extended finite element shell formulation for prediction of ductile fracture and crack branching of thin-walled aluminum structures subjected to impact loading. In order to characterize an arbitrary crack initiation, propagation and brunching, a phantom paired shell element approach is further developed and implemented into Abaqus' explicit solver via its user defined element (VUEL). The energy dissipation due to failure is captured by a cohesive force along the crack interface when its accumulative plastic strain reaches a critical value. A numerical technique for modeling out-of-plane crack branching phenomena is also developed by activating the phantom nodes and re-grouping the element connectivity. Four numerical examples are used to demonstrate the applicability and accuracy of the extended shell element approach for ductile failure prediction of an indentation test, a multi-bay stiffened panel with crack branching, an explosively loaded plate, and a cylinder subjected to impulsive loading.

Predicting Failing Queries in Video Search

The ability to predict when a video search query is not likely to deliver satisfying search results is expected to enable more effective search results optimizations and improved search experience for users. In this paper, we propose a novel context-aware query failure prediction approach that predicts whether a particular query submitted in a user's search session is likely to fail. The approach builds on the well-known concept of query performance prediction introduced in conventional text-based Web search to estimate the query's retrieval performance, but extends this concept with two novel characteristics, user indicators and engine indicators. User indicators are derived from transaction logs, capture the patterns of user interactions with the video search engine, and exploit the context in which a particular query was submitted. Engine indicators are derived from the search results list and measure the consistency of visual search results at the level of visual concepts and textual metadata associated with videos. Extensive evaluation of the approach on a test set containing over one million video search queries shows its effectiveness and demonstrates a significant improvement over traditional and state-of-the-art baseline approaches.

Failure of high strength steel sheets: Experiments and modelling

Failure in sheet metal structures of ductile material is usually caused by one of, or a combination of, ductile fracture, shear fracture or localised instability. In this paper the failure of the high strength steel Docol 600DP and the ultra high strength steel Docol 1200M is explored. The constitutive model used in this study includes plastic anisotropy and mixed isotropic-kinematic hardening. For modelling of the ductile and shear fracture the models presented by Cockroft–Latham and Bressan–Williams have been used. The instability phenomenon is described by the constitutive law and the finite element (FE) models. For calibration of the failure models and validation of the results, an extensive experimental series has been conducted including shear tests, plane strain tests and Nakajima tests. The geometries of the Nakajima tests have been chosen so that the first quadrant of the forming limit diagram (FLD) were covered. The results are presented both in an FLD and using prediction of force–displacement response of the Nakajima test employing element erosion during the FE simulations. The classical approach for failure prediction is to compare the principal plastic strains obtained from FE simulations with experimental determined forming limit curves (FLCs). It is well known that the experimental FLC requires proportional strains to be useful. In this work failure criteria, both of the instability and fracture, are proposed which can be used also for non-proportional strain paths.

Reliability analysis and micromechanics: A coupled approach for composite failure prediction

This work aims at associating two classical approaches for the design of composite materials: first, reliability methods that allow to account for the various uncertainties involved in the composite materials behaviour and lead to a rational estimation of their reliability level; on the other hand, micromechanics that derive macroscopic constitutive laws from micromechanical features. Such approach relies on the introduction of variabilities defined at the microscale and on the investigation of their consequences on the material macroscopic response through an homogenization scheme. Precisely, we propose here a systematic treatment of variability which involves a strong link between micro- and macroscales and provides a more exhaustive analysis of the influence of uncertainties. The paper intends to explain the main steps of such coupling and demonstrate its interests for material engineering, especially for constitutive modelling and composite materials optimization. An application case is developed throughout on the failure of unidirectional carbon fibre-reinforced composites with a comparative analysis between experimental data and simulation results.

Sheet metal formability evaluation using continuous damage mechanics

This paper presents a numerical approach for failure prediction in sheet metal forming operations. The approach is based on the coupling of anisotropic elasto-plasticity and ductile damage, described by Lemaitre´s damage evolution law, within the framework of Continuum Damage Mechanics. The constitutive relations were assessed and the developed model was implemented in ABAQUS/Explicit code. Two different coupling strategies are presented and corresponding numerical results are compared with an experimental failure case, in order to test and validate each of these strategies.

A boosting approach for corporate failure prediction

Predicting corporate failure is an important management science problem. This is a typical classification question where the objective is to determine which indicators are involved in the failure/s...

Bank Failure Prediction: A Two-Step Survival Time Approach

In this paper we develop a novel bank failure prediction approach that uses the output of a multiperiod logit model to assess banks' risk situations and then estimates a survival time model for the subset of at-risk (ill) banks. Our empirical analysis reveals that this two-step approach significantly outperforms benchmark logit models with respect to out-of-sample prediction performance. Furthermore, we identify important differences between the subset of at-risk banks and the entire population of banks regarding the set of significant predictive variables. Management efficiency and size relative to geographically close competitors, for example, are important default predictors for at-risk banks but not for the entire banking population. Consequently, these results have notable policy implications for the design of off-site banking supervision.

A generalized stress singularity approach for material failure prediction and its application to adhesive joint strength analysis

The concept of stress is very useful to describe the effect of external loads on structures. However, as a basis for the prediction of failure the concept of stress becomes meaningless when the structure encompasses singularities as a result of discrete stiffness steps or geometric anomalies such as cracks. In this article it is argued that the concept of failure stress is incorrect and should be replaced by a generalized concept based on stress intensity factors and singularity orders. It appears that material failure stress is the critical stress intensity factor for a zero-order singularity stress field. By plotting the critical stress intensity factor as a function of singularity order, the strength of a material can be characterized in a general fashion that integrates tensile strength, fracture toughness and critical singularities in adhesive joints. It is also shown that plasticity does not eliminate the stress singularity in an adhesive joint but changes the order of the singularity due to the induced change in interface corner angle between the dissimilar materials in the joint.

New experimental approach for failure prediction in electronics: Topography and deformation measurement complemented with acoustic microscopy

Topography and Deformation Measurements (T.D.M.) under thermo-mechanical solicitation is a new approach for localising and quantifying deformation of electronic assemblies. Cooling and heating capabilities, with different temperature rate and maximum, following JEDEC thermal profiles for example, have been applied on different components before and after assembly using real time Topography and Deformation Measurements. The interest in being able to perform z and ( x, y) deformation measurements for traction /compression and shear stress evaluation will be shown. Using acoustic microscopy before and after thermal stress gives the possibility to detect both the conditions in which elastic limits may have exceeded at interfaces, which interface is concerned and the speed at which delamination occurs. Complementarities of this new technique with acoustic microscopy and simulation will be shown for failure prediction applications.