scholarly journals Failure of Laminated Composites at Thickness Discontinuities Under Complex Loading and Elevated Temperatures

2000 ◽  
Author(s):  
S. Lee ◽  
W. G. Knauss
Keyword(s):  
Elevated Temperatures ◽  
Laminated Composites ◽  
Failure Process ◽  
Bending Moment ◽  
Complex Loading ◽  
Matrix Cracking ◽  
Interface Failure ◽  
Element Analysis ◽  
Initiation Point ◽  
Failure Initiation

Abstract Failure initiation of laminated composites with discontinuous thickness has been studied in terms of typical structural load description (tension, shear force and bending moment) rather than in terms of micromechanics considerations. Four types of specimens of different stacking sequence were examined to determine failure initiation, analyzed subsequently via a finite element analysis (ABAQUS), divided into two groups that evoke cross-ply failure, on the one hand, and delamination type failure on the other. For unidirectional fiber orientation in the tension direction and across the interface, failure occurs through cracking and delamination. While the initiation strength for this failure mode is significantly higher than for cross-ply configurations, the residual strength after initiation increases only marginally (10%) beyond the initiation point. For cases involving cross-plies on either side of the interface, failure initiation occurs by matrix cracking. In these cases the residual load bearing capability was 20 to 30% higher than the corresponding failure initiation loads. The data are analyzed in terms of the Tsai-Hill criterion and in terms of an energy release criterion that has been discretized in a manner consistent with a non-singular treatment of the step “discontinuity”. Assuming that time dependent aspects of the failure process are not dominant, elevated temperatures did not change the general results of how bending and tension loads interact; however the magnitude at which the failures occur depends on the temperature, with increasing temperature leading to decreasing load tolerance.

Non-Linear Kinematic Hardening Identification for Anisotropic Sheet-Metals With Bending-Unbending Tests

2000 ◽  
Author(s):  
M. Brunet ◽  
F. Morestin ◽  
S. Godereaux
Keyword(s):  
Kinematic Hardening ◽  
Bending Moment ◽  
Complex Loading ◽  
Sheet Metals ◽  
Element Analysis ◽  
Initial Anisotropy ◽  
Non Linear ◽  
Identification Technique ◽  
Stress Behaviour ◽  
Constitutive Parameters

Abstract An inverse identification technique is proposed based on bending-unbending experiments on anisotropic sheet-metal strips. The initial anisotropy theory of plasticity is extended to include the concept of combined isotropic and non-linear kinematic hardening. This theory is adopted to characterise the anisotropic hardening due to loading-unloading which occurs in sheet-metals forming processes. To this end, a specific bending-unbending apparatus has been built to provide experimental moment-curvature curves. The constant bending moment applied over the length of the specimen allows to determined numerically the strain-stress behaviour but without Finite Element Analysis Four constitutive parameters have to be identified by an inverse approach. Our identification results show that bending-unbending tests are suitable to model quite accurately the constitutive behaviour of sheet metals under complex loading paths.

Finite Element Analysis of Flange Joint With Single and Twin Gaskets Under External Bending Load

2015 ◽  
Author(s):  
N. Rino Nelson ◽  
N. Siva Prasad ◽  
A. S. Sekhar
Keyword(s):  
Finite Element ◽  
Work Performance ◽  
Elevated Temperatures ◽  
Bending Moment ◽  
Element Model ◽  
Pressure Vessels ◽  
Flange Joint ◽  
Element Analysis ◽  
Bending Load ◽  
Gasket Material

Gasketed flange joint is a vital component in pressure vessels and piping systems. Flange joint is usually subjected to bending load due to expansion, wind load, self-weight, etc. Most of the flange design methods use equivalent pressure to include the effect of external bending loads. It becomes complex when the joint is subjected to bending load at elevated temperatures, due to the nonlinear behavior of gasket material. In the present work, performance of the flange joint has been studied under external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature dependent material properties. The performance of the joint under different bolt preloads, internal fluid pressures and temperatures is studied. Flange joint with two gaskets (twin gasketed joint) placed beside each other radially, is also analyzed under external bending moment. The maximum allowable bending moments at different internal temperatures, for single and twin gasketed joints with spiral wound gasket are arrived.

Study on Numerical Simulation for Failure Process of Girder Bridge under Seismic Influence

2012 ◽  
Vol 530 ◽  
pp. 122-129
Author(s):  
Hong Kai Chen ◽  
Hong Mei Tang ◽  
Ting Hu ◽  
Yi Hu ◽  
Xiao Ying He
Keyword(s):  
Seismic Response ◽  
Axial Force ◽  
Response Spectrum ◽  
Failure Process ◽  
Bending Moment ◽  
Shearing Force ◽  
Element Analysis ◽  
Seismic Force ◽  
Plane Bending ◽  
Girder Bridge

Based on the finite element analysis software Midas, it takes response spectrum analysis, and posts the failure mechanism and characteristics of Girder Bridge under intense earthquake. Through the seismic response spectrum displacement maps of Girder Bridge, it finds out that the abutment and foundation deformation is in evidence, especially the top of abutment foundation. Through the study of seismic internal force variation on girder and pier, it indicates that the longitudinal earthquake controls axial force, vertical shearing force and in-plane bending moment, transversal earthquake dominates transversal shearing force and out-planes bending moment. And it shows that the pier and mid-span section are seismic response sensitivity parts. The three parts, axial force, longitudinal shearing force and in-plane bending moment, becomes the controlling index of pier intensity. According to the seismic response spectrum displacement for pier and abutment, the transversal anti-seismic stiffness of pier is smaller than longitudinal one, longitudinal seismic force shows no effect on transversal displacement, and the transversal seismic force can augments longitudinal displacement. At the same condition, longitudinal seismic force changes the longitudinal distributing form of abutment and concaves it deeply, and the transversal seismic force can not change its shape, but augment its value.

Nonlinear Kinematic Hardening Identification for Anisotropic Sheet Metals With Bending-Unbending Tests

2000 ◽  
Vol 123 (4) ◽  
pp. 378-383 ◽  
Author(s):  
M. Brunet ◽  
F. Morestin ◽  
S. Godereaux
Keyword(s):  
Kinematic Hardening ◽  
Bending Moment ◽  
Complex Loading ◽  
Tensile Tests ◽  
Sheet Metals ◽  
Element Analysis ◽  
Inverse Approach ◽  
Initial Anisotropy ◽  
Identification Technique ◽  
Constitutive Parameters

An inverse identification technique is proposed based on bending-unbending experiments on anisotropic sheet-metal strips. The initial anisotropy theory of plasticity is extended to include the concept of combined isotropic and nonlinear kinematic hardening. This theory is adopted to characterize the anisotropic hardening due to loading-unloading which occurs in sheet-metals forming processes. To this end, a specific bending-unbending apparatus has been built to provide experimental moment-curvature curves. The constant bending moment applied over the length of the specimen allows one to determine numerically the strain-stress behavior but without Finite Element Analysis. Four constitutive parameters have been identified by an inverse approach performed simultaneously on the bending and tensile tests. Our identification results show that bending-unbending tests are suitable to model quite accurately the constitutive behavior of sheet metals under complex loading paths.

Study on Interface Failure of Propellant and Liner Material with Mechanics Analysis

2012 ◽  
Vol 568 ◽  
pp. 291-294
Author(s):  
Ai Min Jiang ◽  
Gao Chun Li ◽  
Ai Ping Tian
Keyword(s):  
Failure Process ◽  
Adhesive System ◽  
Cohesive Element ◽  
Stress Distributions ◽  
Interface Failure ◽  
Element Analysis ◽  
Liner Material ◽  
Localization Zone ◽  
The Finite Element Analysis ◽  
Mechanics Analysis

In order to analyze failure phenomena and mechanical properties of propellant-liner interface material, both experimental study and modeling were carried out. The adhesive system was observed under tensile. Based on experiment, the finite element analysis was implemented. Results show that the failure is initiated on a certain point near the propellant and the deformation concentration of localization zone and the macro-cracks occur. The failure process can be modeled and stress distributions can be obtained by introducing cohesive element. The method offers references to interface designing

Failure Analysis of a Hammer Drill Shaft under Complex Loading Paths and Severe Environmental Conditions

2010 ◽  
Vol 638-642 ◽  
pp. 3889-3894 ◽  
Author(s):  
Priya A. Manohar
Keyword(s):  
Elevated Temperatures ◽  
Sliding Friction ◽  
Failure Process ◽  
Complex Loading ◽  
Careful Examination ◽  
Rough Machining ◽  
Preventative Measures ◽  
Failure Investigation ◽  
Design Changes ◽  
Rotating Bending Fatigue

This paper describes the failure investigation of a tubular shaft that is part of a hammer drill assembly. The failure investigation was particularly challenging as the fracture surfaces were completely damaged during and subsequent to the failure process. However, careful examination of the component and its assembly revealed many clues that pointed to the root causes of failure. It was determined that the shaft was subjected to impact, fatigue, bending and torsional loads simultaneously at elevated temperatures. The basic failure mode was identified as a combination of torsional fatigue and rotating bending fatigue failure that originated on the inside diameter of the shaft. The root causes were determined to be operational overload in combination with rough machining marks on the bore surface and higher than necessary operating torque required to overcome the dry adhesive friction in the system. The preventative measures recommended were many-fold including improving surface finish on the bore diameter, reducing dry sliding friction, decreasing the overall level of dynamic loads by appropriate design changes and adding a surface strengthening heat treatment

Lithium-ion Battery Degradation Mechanisms and Failure Analysis Methodology

2012 ◽  
Author(s):  
Bhanu Sood ◽  
Lucas Severn ◽  
Michael Osterman ◽  
Michael Pecht ◽  
Anton Bougaev ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Lithium Ion Batteries ◽  
Elevated Temperatures ◽  
Failure Process ◽  
Lithium Ion ◽  
Degradation Mechanisms ◽  
Analysis Methodology ◽  
Depth Of Discharge ◽  
Battery Degradation ◽  
Non Destructive

Abstract A review of the prevalent degradation mechanisms in Lithium ion batteries is presented. Degradation and eventual failure in lithium-ion batteries can occur for a variety of dfferent reasons. Degradation in storage occurs primarily due to the self-discharge mechanisms, and is accelerated during storage at elevated temperatures. The degradation and failure during use conditions is generally accelerated due to the transient power requirements, the high frequency of charge/discharge cycles and differences between the state-of-charge and the depth of discharge influence the degradation and failure process. A step-by-step methodology for conducting a failure analysis of Lithion batteries is presented. The failure analysis methodology is illustrated using a decision-tree approach, which enables the user to evaluate and select the most appropriate techniques based on the observed battery characteristics. The techniques start with non-destructive and non-intrusive steps and shift to those that are more destructive and analytical in nature as information about the battery state is gained through a set of measurements and experimental techniques.

Finite Element Analysis of Composite Ceramic-Concrete Slab Constructions Exposed to Fire

2016 ◽  
Vol 861 ◽  
pp. 88-95
Author(s):  
Balázs Nagy ◽  
Elek Tóth
Keyword(s):  
Composite Structures ◽  
Elevated Temperatures ◽  
Cfd Simulation ◽  
Concrete Slab ◽  
Composite Ceramic ◽  
Reinforced Concrete Beam ◽  
Element Analysis ◽  
Standard Fire ◽  
Using Data ◽  
Dynamics Simulations

In this research, conjugated thermal and fluid dynamics simulations are presented on a modern hollow clay slab blocks filled pre-stressed reinforced concrete beam slab construction. The simulation parameters were set from Eurocode standards and calibrated using data from standardized fire tests of the same slab construction. We evaluated the temperature distributions of the slabs under transient conditions against standard fire load. Knowing the temperature distribution against time at certain points of the structure, the loss of load bearing capacity of the structure is definable at elevated temperatures. The results demonstrated that we could pre-establish the thermal behavior of complex composite structures exposed to fire using thermal and CFD simulation tools. Our results and method of fire resistance tests can contribute to fire safety planning of buildings.

Thermal Modeling of a Railroad Tapered-Roller Bearing Using Finite Element Analysis

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Constantine M. Tarawneh ◽  
Arturo A. Fuentes ◽  
Javier A. Kypuros ◽  
Lariza A. Navarro ◽  
Andrei G. Vaipan ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Surface Temperature ◽  
Elevated Temperatures ◽  
Roller Bearing ◽  
Fe Model ◽  
Element Analysis ◽  
Tapered Roller Bearing ◽  
Outer Race ◽  
Railroad Industry

In the railroad industry, distressed bearings in service are primarily identified using wayside hot-box detectors (HBDs). Current technology has expanded the role of these detectors to monitor bearings that appear to “warm trend” relative to the average temperatures of the remainder of bearings on the train. Several bearings set-out for trending and classified as nonverified, meaning no discernible damage, revealed that a common feature was discoloration of rollers within a cone (inner race) assembly. Subsequent laboratory experiments were performed to determine a minimum temperature and environment necessary to reproduce these discolorations and concluded that the discoloration is most likely due to roller temperatures greater than 232 °C (450 °F) for periods of at least 4 h. The latter finding sparked several discussions and speculations in the railroad industry as to whether it is possible to have rollers reaching such elevated temperatures without heating the bearing cup (outer race) to a temperature significant enough to trigger the HBDs. With this motivation, and based on previous experimental and analytical work, a thermal finite element analysis (FEA) of a railroad bearing pressed onto an axle was conducted using ALGOR 20.3™. The finite element (FE) model was used to simulate different heating scenarios with the purpose of obtaining the temperatures of internal components of the bearing assembly, as well as the heat generation rates and the bearing cup surface temperature. The results showed that, even though some rollers can reach unsafe operating temperatures, the bearing cup surface temperature does not exhibit levels that would trigger HBD alarms.

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