scholarly journals Critical Stresses in Materials with Cracks

2019 ◽  
Vol 70 (7) ◽  
pp. 2442-2446
Author(s):  
Simona Eugenia Manea ◽  
Vali Ifigenia Nicolof ◽  
Teodor Sima
Keyword(s):  
Fracture Mechanics ◽  
Critical Stress ◽  
Crack Width ◽  
Crack Depth ◽  
Equivalent Stress ◽  
Critical Energy ◽  
Material Behavior ◽  
Experimental Results ◽  
Critical Stresses ◽  
Mechanics Concepts

The fracture mechanics concepts, as well as the concepts introduced on the basis of principle of critical energy, correlated with strength of materials with cracks is analysed. The equivalent stress method of strength was applied to cracked materials, by using the concept of local critical stress. This one depends on the material behavior and the deterioration due to crack. Experimental results have been obtained with specimens of OL304 steel with different cracks. The influence of crack depth and crack width is put into evidence.

Regularization of free discontinuity problem and its application in the simulation of brittle fracture of concrete

2020 ◽  
pp. 10-17
Author(s):  
FU JIAJIA ◽  
WANG YAO
Keyword(s):  
Fracture Mechanics ◽  
Brittle Fracture ◽  
Equivalent Stress ◽  
Tracking Algorithm ◽  
Experimental Results ◽  
Energy Threshold ◽  
Fracture Behaviors ◽  
Discontinuity Problem ◽  
Γ Convergence ◽  
Standing Problem

As a free discontnuity problem, the predicton of the path that a crack chooses while it propagates through a britle material has been a long standing problem in fracture mechanics. To circumvent the mathematcal difcultes in the modeling of fracture behaviors, this paper takes advantage of the regularizaton approach to approximate the Munford-Shah functonal with Γ-convergence. The governing equatons of physical felds are constructed based on the concept of energy minimizaton. This method is capable of capturing the crack initaton and propagaton without a specifc tracking algorithm. Additonally, a pure elastc phase can be considered by introducing an energy threshold. By the use of the concept of equivalent stress, a stress-based fracture governing criterion was established. The numerical implementaton is based on a standard fnite element discretzaton and on the staggered algorithmic. Two classic concrete fracturing tests were investgated to demonstrate the performance of the model by comparing the numerical results with experimental results.

Elastic Fracture Mechanics Concepts for Interfacial Cracks

1988 ◽  
Vol 55 (1) ◽  
pp. 98-103 ◽  
Author(s):  
J. R. Rice
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Phase Angle ◽  
Interface Crack ◽  
Crack Tip ◽  
Shear Loading ◽  
Material Behavior ◽  
Small Scale ◽  
Elastic Fracture ◽  
Mechanics Concepts

Elastic fracture mechanics concepts are reexamined for a crack on the interface between dissimilar solids. A derivation by function theory is given of the form of stress and displacement fields in the vicinity of the crack tip, equivalent to complete Williams expansions of both inner and outer (external to a nonlinear or contact zone) type. The complex stress intensity factor K associated with an elastic interface crack, for which contact is ignored, is discussed and, specifically, its validity as a crack tip characterizing parameter is noted for cases of small scale nonlinear material behavior and/or small scale contact zones at the crack tip. That is, similar values of K for two cracked bodies then imply similar states as the crack tip, so that conditions for crack growth can be phrased in terms of K reaching a critical failure locus in a complex plane. The maintenance of a similar state at a crack tip under change of crack length is shown to require alteration of both the magnitude and phase angle of a combined tension and shear loading. Some possible definitions of stress intensity factors KI and KII of classical type associated with interface cracks are discussed. Also, the scaling of interface crack tip plastic zone size with load under small scale yielding conditions is found to deviate from classical scaling, in proportion to the square of the applied load level, and dependences of the field on distance from the tip and on load phase angle are found to be linked together.

Experimental Study on the Failure Criterion for Brittle Materials in Compression

2011 ◽  
Vol 320 ◽  
pp. 259-262
Author(s):  
Xu Ran ◽  
Zhe Ming Zhu ◽  
Hao Tang
Keyword(s):  
Thin Film ◽  
Experimental Study ◽  
Compressive Strength ◽  
Fracture Mechanics ◽  
Failure Criterion ◽  
Brittle Materials ◽  
Experimental Results ◽  
Experiment Study ◽  
Confining Stress ◽  
Theoretical Results

The mechanical behavior of multi-cracks under compression has become a very important project in the field of fracture mechanics and rock mechanics. In this paper, based on the previous theoretical results of the failure criterion for brittle materials under compression, experiment study is implemented. The specimens are square plates and are made of cement, sand and water, and the cracks are made by using a very thin film (0.1 mm). The relations of material compressive strength versus crack spacing and the lateral confining stress are obtained from experimental results. The experimental results agree well with the failure criterion for brittle materials under compression, which indicates that the criterion is effective and applicable.

Structural Response and Remaining Life of Damaged Composites

2015 ◽  
Vol 813-814 ◽  
pp. 106-110
Author(s):  
Dalbir Singh ◽  
C. Ganesan ◽  
A. Rajaraman
Keyword(s):  
Hybrid Approach ◽  
Experimental Studies ◽  
Structural Response ◽  
Material Behavior ◽  
Experimental Results ◽  
Life Assessment ◽  
Nonlinear Material ◽  
Remaining Life ◽  
Design Effectiveness ◽  
Remaining Life Assessment

Composites are being used in variety of applications ranging from defense and aircraft structures, where usage is profuse, to vehicle structures and even for repair and rehabilitation. Most of these composites are made of different laminates glued together with matrix for binding and now-a-days fibers of different types are embedded in a composite matrix. The characterizations of material properties of composites are mostly experimental with analytical modeling used to simulate the system behavior. But many times, the composites develop damage or distress in the form of cracking while they are in service and this adds a different dimension as one has to evaluate the response with the damage so that its performance during its remaining life is satisfactory. This is the objective of the present study where a hybrid approach using experimental results on damaged specimens and then analytical finite element are used to evaluate response. This will considerably help in remaining life assessment-RLA- for composites with damage so that design effectiveness with damage could be assessed. This investigation has been carried out on a typical composite with carbon fiber reinforcements, manufactured by IPCL Baroda (India) with trade name INDCARF-30. Experimental studies were conducted on undamaged and damaged specimens to simulate normal continuous loading and discontinuous loading-and-unloading states in actual systems. Based on the experimental results, material characterization inputs are taken and analytical studies were carried out using ANSYS to assess the response under linear and nonlinear material behavior to find the stiffness decay. Using stiffness decay RLA was computed and curves are given to bring the influence of type of damage and load at which damage had occurred.

The Effect of Cracks on Chloride Penetration into Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 769-772 ◽  
Author(s):  
In Seok Yoon ◽  
Erik Schlangen ◽  
Mario R. de Rooij ◽  
Klaas van Breugel
Keyword(s):  
Service Life ◽  
Crack Length ◽  
Significant Influence ◽  
Crack Width ◽  
Chloride Transport ◽  
Crack Depth ◽  
Chloride Penetration ◽  
Critical Crack ◽  
Chloride Migration ◽  
Migration Testing

This study is focused on examining the effect of critical crack width in combination with crack depth on chloride penetration into concrete. Because concrete structures have to meet a minimum service-life, critical crack width has become an important parameter. Specimens with different crack width / crack length have been subjected to rapid chloride migration testing (RCM). The results of this study show a critical crack width of about 0.012 mm. Cracks smaller than this critical crack width are considered not to have a significant influence on the rate of chloride transport inwards, while chloride penetration does proceed faster above this critical crack width.

Fracture Mechanics in Pavement Engineering: The Specimen-Size Effect

1997 ◽  
Vol 1568 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Anastasios M. Ioannides
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Specimen Size ◽  
Pavement Design ◽  
Crack Model ◽  
Design Procedures ◽  
Engineering Discipline ◽  
Pavement Engineering ◽  
Slow Progress ◽  
Mechanics Concepts

Application of fracture mechanics concepts developed in various branches of engineering to the pavement problem can address current limitations, thereby advancing considerably existing pavement design procedures. The state of the art in fracture mechanics applications to pavement engineering is summarized, and an in-depth discussion of one of the major concerns in such applications, the specimen-size effect, is provided. It is concluded that the fictitious crack model proposed by Hillerborg appears most promising for computerized application to pavements. The similitude concepts developed by Bache will be very useful in such efforts. Both the desirability and the scarcity of suitable candidates to replace Miner’s cumulative linear fatigue hypothesis in conventional pavement design are confirmed. Fracture mechanics is shown to be a very promising engineering discipline from which innovations could be transplanted to pavement activities. Nonetheless, it is pointed out that rather slow progress characterizes fracture mechanics developments in general. Pavement engineers clearly need to remain abreast of and involved in fracture mechanics activities.

Shakedown of Torispherical Heads Using Plastic Analysis

1998 ◽  
Vol 120 (4) ◽  
pp. 431-437 ◽  
Author(s):  
A. Kalnins ◽  
D. P. Updike
Keyword(s):  
Equivalent Stress ◽  
Applied Pressure ◽  
Material Behavior ◽  
Parameter Range ◽  
Burst Pressure ◽  
Fatigue Stress ◽  
Stress Parameter ◽  
Hardening Models ◽  
Plastic Analysis ◽  
Definition Of

The condition of shakedown is examined for torispherical heads. The reason for using plastic analysis is to account for the strengthening that heads experience when subjected to internal pressure. Cyclic pressures are considered up to an allowable burst pressure that is based on the membrane stresses of the spherical part of the head. To simulate a proof test before service cycling, cases when the applied pressure is higher for the first cycle are also included. A definition of shakedown is used that places the limit of twice the yield strength on a fatigue stress parameter range that is defined in the paper. The equivalent stress and plastic strain ranges are calculated for ten head thickness-to-spherical radius ratios. From these data, shakedown pressures are obtained as fractions of the allowable burst pressure. By giving bounds for isotropic and kinematic strain-hardening models, the results are made independent from specific cyclic material behavior. It is also shown that if an elastic, geometrically linear algorithm is used, which is unable to account for the strengthening, the fatigue stress parameter range is overestimated for the thinner heads.

Constitutive modeling for the mechanical behavior of rubber with filler particles

2021 ◽  
Author(s):  
Sankalp Gour ◽  
Deepu Kumar Singh ◽  
Deepak Kumar ◽  
Vinod Yadav
Keyword(s):  
Mechanical Properties ◽  
Carbon Black ◽  
Mechanical Behavior ◽  
Experimental Observation ◽  
Continuum Mechanics ◽  
Constitutive Modeling ◽  
Carbon Nanoparticles ◽  
Material Behavior ◽  
Experimental Results ◽  
Filler Particles

Abstract The present study deals with the constitutive modeling for the mechanical behavior of rubber with filler particles. An analytical model is developed to predict the mechanical properties of rubber with added filler particles based on experimental observation. To develop the same, a continuum mechanics-based hyperelasticity theory is utilized. The model is validated with the experimental results of the chloroprene and nitrile butadiene rubbers filled with different volume fractions of carbon black and carbon nanoparticles, respectively. The findings of the model agree well with the experimental results. In general, the developed model will be helpful to the materialist community working in characterizing the material behavior of tires and other rubber-like materials.

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