Fracture Mechanics at Intermediate Rates of Loading : The Influence of the Acceleration on Compact Tension Tests

Results of an experimental study on the formation of crack patterns during drying of a soil paste are presented. The objective is to ascertain whether fracture mechanics plays a significant role in explaining the process of formation and propagation of cracks during drying of soils due to changes in environmental conditions such as temperature and humidity. The experiments consist of five geometrically similar rectangular specimens in two series of different thicknesses, subjected to drying conditions in an environment-controlled laboratory. Cracking initiates shortly before the soil reaches a near-solid quasi-brittle consistency. Although crack initiation can be explained by classical soil mechanics effective stress theory, crack development and propagation appear to be energy-driven. The results prove that cracking stress does depend on the size of the specimen and suggest that fracture mechanics might be applicable to soil cracking, at least in the context of the present research. Fracture toughness of the soil used was determined using compact tension tests at different water contents. Its tensile strength was also determined by a direct method for two natural specific weights (bulk density) and two dry specific weights with different water contents.

Download Full-text

Experimental evaluation of fracture properties of bovine hip cortical bone using elastic–plastic fracture mechanics

Bio-Medical Materials and Engineering ◽

10.3233/bme-211220 ◽

2021 ◽

pp. 1-10

Author(s):

Waseem Ur Rahman ◽

Rafiullah khan ◽

Noor Rahman ◽

Ziyad Awadh Alrowaili ◽

Baseerat Bibi ◽

...

Keyword(s):

Fracture Toughness ◽

Plastic Deformation ◽

Fracture Mechanics ◽

Cortical Bone ◽

Elastic Deformation ◽

Compact Tension ◽

J Integral ◽

Elastic Plastic ◽

American Society ◽

Fracture Specimens

BACKGROUND: Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. OBJECTIVE: This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. METHODS: The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. RESULTS: The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8–3 times less than the energy used in the plastic deformation. CONCLUSION: The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.

Download Full-text

Fracture Mechanics and Fractography of Creep and Fatigue Crack Propagation at Elevated Temperature

Journal of Engineering Materials and Technology ◽

10.1115/1.3443381 ◽

1976 ◽

Vol 98 (4) ◽

pp. 296-304 ◽

Cited By ~ 18

Author(s):

R. Koterazawa ◽

Y. Iwata

Keyword(s):

Fatigue Crack ◽

Fracture Mechanics ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Compact Tension ◽

304 Stainless Steel ◽

Bending Stress ◽

Type Specimens ◽

Creep Crack ◽

Repeated Stress

A fracture mechanics and fractographic study was conducted on creep and fatigue crack propagation of a 304 stainless steel under constant and repeated tensile stress at a temperature of 650°C. Linear elastic fracture mechanics could be applied to the test data fairly successfully in spite of the fact that the tests were conducted under creep conditions. A comparison with data in a literature indicated that this is not true for bending-type specimens such as the compact tension specimen because of redistribution of bending stress due to creep, and therefore a specimen geometry which avoids bending stress is preferred for creep crack testing. Under repeated stress, the crack generally started as a transgranular fatigue crack and changed to an intergranular creep crack at some length of the crack. The transition point moved to a later stage of crack propagation as the period of repeated stress increased. This transition phenomenon could be explained by assuming that the two crack propagation processes, the transgranular fatigue crack and the intergranular creep crack, are possible under repeated stress condition and that the one with the higher rate actually occurs.

Download Full-text

Numerical investigation of progressive damage and the effect of layup in overheight compact tension tests

Composites Part A Applied Science and Manufacturing ◽

10.1016/j.compositesa.2012.03.002 ◽

2012 ◽

Vol 43 (11) ◽

pp. 2137-2150 ◽

Cited By ~ 21

Author(s):

Xiangqian Li ◽

Stephen R. Hallett ◽

Michael R. Wisnom

Keyword(s):

Numerical Investigation ◽

Compact Tension ◽

Progressive Damage ◽

Tension Tests

Download Full-text

Experimental study of damage propagation in Over-height Compact Tension tests

Composites Part A Applied Science and Manufacturing ◽

10.1016/j.compositesa.2009.08.017 ◽

2009 ◽

Vol 40 (12) ◽

pp. 1891-1899 ◽

Cited By ~ 46

Author(s):

Xiangqian Li ◽

Stephen R. Hallett ◽

Michael R. Wisnom ◽

Navid Zobeiry ◽

Reza Vaziri ◽

...

Keyword(s):

Experimental Study ◽

Compact Tension ◽

Damage Propagation ◽

Tension Tests

Download Full-text

Neutron Diffraction Measurement of the Stress Field During Fatigue Cycling of a Cracked Test Specimen

MRS Proceedings ◽

10.1557/proc-166-317 ◽

1989 ◽

Vol 166 ◽

Cited By ~ 9

Author(s):

M.T. Hutchings ◽

C.A. Hippsley ◽

V. Rainey

Keyword(s):

Fracture Mechanics ◽

Neutron Diffraction ◽

Stress Field ◽

Test Specimen ◽

Maximum Stress ◽

Compact Tension ◽

Compact Tension Specimen ◽

Diffraction Measurement ◽

Tension Specimen ◽

Neutron Diffraction Measurement

ABSTRACTThe triaxial stress field has been measured along the centre line of a compact tension specimen in the direction of cracking. The specimen had been subjected to ∼60,000 cycles at δK=31 and Kmax = 34 MPa mm½ and was bolted open at maximum stress. The field was remeasured after the stress had been fully relaxed. The results are discussed in terms of expectations from fracture mechanics calculations.

Download Full-text

Fracture Toughness of PIR Foams Produced from Renewable Resources

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.525-526.29 ◽

2012 ◽

Vol 525-526 ◽

pp. 29-32 ◽

Cited By ~ 1

Author(s):

Janis Andersons ◽

E. Spārniņš ◽

Ugis Cabulis ◽

U. Stirna

Keyword(s):

Fracture Toughness ◽

Renewable Resources ◽

Petrochemical Industry ◽

Compact Tension ◽

Environmental Benefits ◽

Insulation Material ◽

Renewable Materials ◽

Tension Tests ◽

Closed Cell ◽

Rise Direction

Rigid low-density closed-cell polyisocyanurate (PIR) foams are used primarily as a thermal insulation material. Traditionally, they are manufactured from constituents produced by petrochemical industry. Introducing renewable materials in PIR formulation brings definite economical and environmental benefits. Fracture toughness of PIR foams obtained from renewable resources (with the polyol system comprising up to 80% of rapeseed oil esters) and petrochemical PIR foams has been characterized experimentally, by compact tension tests, for mode I crack propagation along the rise direction of the foams.

Download Full-text

FRACTURE MECHANICS OF CORTICAL BONE - EVALUATION BY THE COMPACT TENSION METHOD

Biomedical Engineering I ◽

10.1016/b978-0-08-028826-0.50077-9 ◽

1982 ◽

pp. 343-347

Author(s):

W. Bonfield ◽

J.C. Behiri

Keyword(s):

Fracture Mechanics ◽

Cortical Bone ◽

Compact Tension

Download Full-text

Effects of the Hygrothermal Conditions on the Fracture Energy of the Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.711.397 ◽

2016 ◽

Vol 711 ◽

pp. 397-403

Author(s):

Hatem Kallel ◽

Hélène Carré ◽

Christian Laborderie ◽

Benoît Masson ◽

Nhu Cuong Tran

Keyword(s):

Fracture Energy ◽

Mechanical Behaviour ◽

Water Saturation ◽

Compact Tension ◽

Severe Accident ◽

Temperature Level ◽

Accurate Knowledge ◽

Tension Tests ◽

Experimental Apparatus ◽

Temperature Levels

The scenario of a severe accident in the containment building of a nuclear plant results in an increase in pressure, temperature and relative humidity that can reach respectively 5 bars, 140 °C and the saturation of water vapour. As well as the regulatory calculations, accurate knowledge of the thermal and mechanical behaviour of materials and more specifically of concrete is required to carry out more precise numerical simulations. Our study aims to investigate the mechanical behaviour of concrete under homogeneous conditions of moisture and temperature. An experimental apparatus was designed in order to assess the evolutions of the fracture energy of concrete. Different temperature levels up to a maximum of 110 °C and at different values of the controlled moisture content were investigated. The equipment was used to perform DCT (Disk-shape Compact Tension) tests at 30, 90 and 110 °C. Five levels of degree of liquid water saturation (Sw) were investigated for each temperature level.

Download Full-text

Fracture Toughness Evaluation of S355 Steel Using Circumferentially Notched Round Bars

Periodica Polytechnica Transportation Engineering ◽

10.3311/pptr.11560 ◽

2018 ◽

Vol 47 (2) ◽

pp. 91-95 ◽

Cited By ~ 1

Author(s):

Fatih Bozkurt ◽

Eva Schmidová

Keyword(s):

Fracture Toughness ◽

Fracture Mechanics ◽

Compact Tension ◽

Compact Tension Specimen ◽

Fracture Load ◽

Alternative Methods ◽

Test Procedures ◽

Toughness Evaluation ◽

Fracture Toughness Evaluation

In engineering applications, steels are commonly used in various areas. The mechanical members are exposed to different loading conditions and this subject can be investigated in fracture mechanics. Fracture toughness (KIC) is the important material property for fracture mechanics. Determination of this properties is possible using a compact tension specimen, a single edge notched bend or three-point loaded bend specimen, which are standardized by different institutions. Researchers underline that these standardized methods are complex, the manufacturing process is difficult, they require special fixtures for loading during the experiment and the test procedures are time consuming. Alternative methods are always being sought by researchers. In this work, two different approaches are investigated for S355 steels. In the first method, a circumferentially cracked round bar was loaded in tensile mode and pulled till failure. Using suitable equations, fracture toughness can be calculated. In the second method, a circumferentially notched bar specimen without fatigue pre-cracking was loaded in a tensile machine. By means of fracture load values, fracture toughness was determined by the proposed equations. It can be stated that these two different approaches for calculating fracture toughness are simple, fast and economical.

Download Full-text