Modal Approach for Processing One‐ and Three‐point Bend Test Data for Dsif‐time Diagram Determination Part I—theory

Rokach, IV

doi:10.1046/j.1460-2695.1998.00087.x

Cited by 20 publications

(13 citation statements)

References 15 publications

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“…Since the deformed structure is assumed to be the same as that defined under static conditions, the maximum tensile stress and the bending moment can be expressed in terms of the displacement. Some authors have developed the dynamic response of the test specimens even further by superposing several modes [20], [21]. In the case of a notched beam with a short time to fracture subjected to one-point bending tests, the latter authors established that the beam model is not relevant.…”

Section: Introductionmentioning

confidence: 99%

A non-equilibrium approach to processing Hopkinson Bar bending test data: Application to quasi-brittle materials

Delvare

Hanus

Bailly

2010

International Journal of Impact Engineering

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International audienceThe aim of this paper was to describe a method of analysing the test data recorded during a Hopkinson Bar bending test. This three-point dynamic bending test was designed for testing the strength of materials under dynamic loads. It is carried out on a specimen consisting of a beam placed on two supports, which is subjected to an impact. The use of Hopkinson Bar as supports makes it possible to determine the forces and displacements at these points. An analytical solution for the transient response of a long beam subjected to a transverse impact was used to determine the impact force and the displacement. This procedure applies for the first few instants when the motions generated by the impact have not yet reached the supports, and the mechanical state of the specimen is identical to that of an unsupported beam. It is suitable for use with quasi-brittle materials for which failure occurs at the very beginning of the test. The material strength is determined at the time of failure, which is characterised by a sudden decrease in the bending moment. The results of a test in which a quasi-brittle material was loaded up to failure are presented and analysed as outlined above. The results obtained confirm the relevance of the present method

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Section: Introductionmentioning

confidence: 99%

A non-equilibrium approach to processing Hopkinson Bar bending test data: Application to quasi-brittle materials

Delvare

Hanus

Bailly

2010

International Journal of Impact Engineering

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“…This phenomenon was observed during 3PB tests for the specimens with relatively short overhangs (Böhme and Kalthoff, 1982;Dear, 1990) and should be expected for all similar impact bend tests. Numerical simulation shows that ignoring this fact by assuming permanent contact between the specimen and supports causes large errors in DSIF determination (Rokach, 1998). Second, nonlinear phenomena in the contact zones (local plasticity, material crushing) affect contact forces.…”

Section: Theory and Calculationsmentioning

confidence: 99%

“…A mixed experimental-numerical DSIF determination was used previously by Rokach (1998) for one-point bending (1PB) and 3PB tests. This paper extends this approach to the 4PB impact test results.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Dynamic Stress Intensity Factor for the Four-Point Bend Impact Test

Rokach

Łabędzki

2009

Int J Fract

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A simple method for determination of the dynamic stress intensity factor (DSIF) variation with time during a four-point impact bend test has been proposed. A formula for DSIF calculation from the recorded loading has been obtained using modal superposition method. Results of calculations for different specimens have been compared with the experimental data and the results of the direct finite element analysis.Keywords: four-point impact bend test, modal superposition method, dynamic stress intensity factor 1. Introduction. Four-point bend (4PB) impact test can be used as an alternative to the conventional three-point bend (3PB) impact test for determination of the dynamic fracture toughness of brittle materials. Sometimes, this test has advantages over the 3PB one. First, in a 4PB test, the contact zone between the striker and the specimen is moved away from the crack tip. Thus, the stress field near the crack tip is less affected by this contact zone. Second, in a 4PB test the central part of the specimen is in pure bending. Therefore, this test can be more suitable if a crack-like defect in the modelled structure is loaded by pure bending too. Additionally, pure bending means that the crack in a 4PB test is loaded in a simpler way than in a 3PB one.To evaluate the dynamic fracture toughness, the dynamic stress intensity factor (DSIF) variation with time need to be either determined directly during the test or calculated from the test results.A mixed experimental-numerical DSIF determination was used previously by Rokach (1998) for one-point bending (1PB) and 3PB tests. This paper extends this approach to the 4PB impact test results.

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“…The dynamic stress intensity factor (DSIF) histories for the specimen were evaluated by means of a dynamic finite element technique based on the measured dynamic loads. Thereafter, a lot of work has been carried out on the evaluation of DFT for different materials based on the SHPB method [13][14][15][16][17][18][19][20][21][22]. In these studies, the loading rates were elevated to over 1 TPa · m 1/2 /s; the tested specimens were mainly 3PB, Charpy V-notch, or edge notched shear specimens.…”

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confidence: 99%

Application of split Hopkinson tension bar technique to the study of dynamic fracture properties of materials

Huang

2012

Acta Mech Sin

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A novel approach is proposed in determining dynamic fracture toughness (DFT) of high strength steel, using the split Hopkinson tension bar (SHTB) apparatus, combined with a hybrid experimental-numerical method. The center-cracked tension specimen is connected between the bars with a specially designed fixture device. The fracture initiation time is measured by the strain gage method, and dynamic stress intensity factors (DSIF) are obtained with the aid of 3D finite element analysis (FEA). In this approach, the dimensions of the specimen are not restricted by the connection strength or the stress-state equilibrium conditions, and hence plane strain state can be attained conveniently at the crack tip. Through comparison between the obtained results and those in open publication, it is concluded that the experimental data are valid, and the method proposed here is reliable. The validity of the obtained DFT is checked with the ASTM criteria, and fracture surfaces are examined at the end of paper.

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Modal Approach for Processing One‐ and Three‐point Bend Test Data for Dsif‐time Diagram Determination Part I—theory

Cited by 20 publications

References 15 publications

A non-equilibrium approach to processing Hopkinson Bar bending test data: Application to quasi-brittle materials

A non-equilibrium approach to processing Hopkinson Bar bending test data: Application to quasi-brittle materials

Determination of the Dynamic Stress Intensity Factor for the Four-Point Bend Impact Test

Application of split Hopkinson tension bar technique to the study of dynamic fracture properties of materials

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