scholarly journals Fracture Toughness of Thin Plates by the Double-Torsion Test Method

2008 ◽  
pp. 63-73 ◽  
Author(s):  
Jonathan A. Salem ◽  
Miladin Radovic ◽  
Edgar Lara-Curzio ◽  
George Nelson
Keyword(s):  
Fracture Toughness ◽  
Torsion Test ◽  
Test Method ◽  
Thin Plates ◽  
Double Torsion

A Three-Dimensional Finite Element Analysis of the Double-Torsion Test

1979 ◽  
Vol 101 (4) ◽  
pp. 328-335 ◽  
Author(s):  
A. A. Tseng ◽  
J. T. Berry
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Crack Length ◽  
Three Dimensional ◽  
Torsion Test ◽  
Test Method ◽  
Fracture Toughness Test ◽  
Element Analysis ◽  
Three Dimensional Finite Element ◽  
Double Torsion

A special three-dimensional crack-tip element has been developed to investigate a simple and widely applicable fracture toughness test method. Previous experimental work with the double-torsion method has shown that the use of a relatively thin sectioned specimen may be permitted. The section concerned is considerably thinner than that used in conventional techniques, while the technique also simplifies the determination of the fracture toughness parameter. K IC values, which are independent of the crack length, have been obtained for glasses, ceramics, polymers, and a variety of metals and alloys. The numerical solution presented is supportive of many experimental observations made during testing. Excellent correlation between the finite element and experimental results has been obtained. The maximum stress intensity factor is shown to be almost independent of crack length over a considerable range.

Using Torsion Bar Testing to Determine Fracture Toughness of Ceramic Materials

2002 ◽  
Author(s):  
J. A. Wang ◽  
K. C. Liu ◽  
G. A. Joshi
Keyword(s):  
Fracture Toughness ◽  
Crack Opening ◽  
Torsion Test ◽  
Ceramic Materials ◽  
Type Specimen ◽  
Small Region ◽  
Fracture Load ◽  
Test Method ◽  
Finite Element Program ◽  
Spiral Line

A new method, designated as Spiral Notch Torsion Test (SNoTT), is introduced for determining fracture toughness KIC of materials ranging from metallic alloys to brittle ceramics and their composites. A round-rod specimen having a V-grooved spiral line with a 45° pitch is subjected to pure torsion. This loading configuration creates a uniform tensile-stress crack-opening mode, Mode-I, with a transverse plane-strain state along the grooved line. This technique is analogous to the conventional test method using a compact-type specimen with a thickness equivalent to the full length of the spiral line. KIC values are determined from the fracture load and crack length with the aid of an in-house developed 3-D finite element program (TOR3D-KIC). A mixed mode (modes I and III) fracture toughness value can be determined by varying the pitch of the spiral line or varying the ratio of axial to torsion loads. Since the key information needed for determining KIC values is manifested within a small region near the crack tip, the specimen can be significantly miniaturized without the loss of generality. Limited results obtained for various materials are compared with published KIC values, showing differences of less than 2% in general and 6% maximum in one case. The experimental technique and theoretical basis of the proposed method are presented in detail.

Crack propagation in thin plates under double torsion

1981 ◽  
Vol 16 (1) ◽  
pp. 9-14 ◽  
Author(s):  
C L Chow ◽  
K M Ngan
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Energy Method ◽  
Thin Plates ◽  
Loading Mode ◽  
Angular Deflection ◽  
Significant Difference ◽  
Non Linear ◽  
The Stability ◽  
Double Torsion

A method of analysis for characterizing non-linear crack propagation in thin plates under double torsion is presented. Quasistatic energy method is used to derive the fracture toughness and to study the stability conditions of crack propagation within the subcritical crack growth range. Non-linear relationship between the torque and angular deflection of a thin rectangular bar is well known. A thin rectangular plate containing a central longitudinal crack and acted upon by a system of four-point loading (two opposite forces on each side of the crack) causes non-linear structural response to this loading mode. The stability of crack propagation in thin plates under double torsion is examined for both the linear (thin plates) and non-linear (thick plates) cases. It is shown that improved stability can be attained if the specimen geometry and loading mode display a non-linear load-displacement relationship at constant crack area, as compared with the corresponding linear case. A series of experiments is conducted to measure the fracture toughness of PMMA material of different thicknesses. It is observed that the fracture toughness values evaluated analytically using the quasi-static energy method compare favourably with those measured experimentally. For the range of PMMA plate thicknesses considered, the effect of thickness on the fracture toughness of PMMA material is negligible. Finally, the validity of employing the double torsion specimen for fracture studies is examined by comparing the fracture toughness of thin plates of different thicknesses loaded separately by double torsion and by tension. No significant difference between the two sets of results is observed.

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