Dynamic Tear Test Research Articles

Study on the tearing behaviour of woven shirting fabrics – the effect of yarn and fabric properties

PurposeOccurrence of fabric rupture is a problem that can influence fabric performance during wear. In this regard, fabric tearing resistance is considered by manufacturers and consumers and enhancing tear resistance through optimization of related parameters is beneficial.Design/methodology/approachIn this study, the tearing resistance of a series of shirting fabrics with various weave patterns and weft densities were investigated by both static and dynamic tear test methods. Moreover, the constituent yarn's frictional and tensile behaviour was evaluated and their relation with tear resistance was analysis.FindingsAccording to the outcomes, the fabric firmness and density and friction of yarns affect the tear resistance, reversely. However an improvement in yarn's tenacity can raise the tear resistance.Originality/valueIn this study it was aimed to not only consider influence of both static and dynamic tear test approach on the tearing performance of fabrics regarding their structural parameters, the impact of the constituent's yarn properties include tensile behaviour and friction coefficient on the tearing performance of fabric considered, as well.

Explosion Bulge Test of High Srength Low Alloy Steel PFS-700 in Air and Underwater

Explosion Bulge Test in air has been carried out in order to evaluate base metal and weldment of pre-heating free steel, PFS-700 which was developed for using in submarine, destroyer and aircraft carrier and specified as Korean military specification, KDS-9515-3001. PFS-700 steel has good weldability so that it can be welded without pre-heating before welding. 1.4wt.% of Copper is added to compensate for the decrease of strength due to the decrease of Carbon in PFS-700. Usually, PFS-700 is aged at the temperature of about 650°C for the combination of strength and toughness. PFS-700 of the thickness of 25mm aged at 650°C was used for explosion bulge test. Underwater weapon system demands to conduct this test for the security of weld structures, and test method and procedure are specified in the military specification, MIL-STD-4139(SH). PFS-700 was explosion bulge tested as specified in this spec. Mechanical tests such as tensile test, CVN impact test, dynamic tear test and bend test are conducted from the specimens taken from prolonged EBT specimen and compared with the properties specified in KDS-9515-3001. EBT results show that PFS-700 welded with the welding material of spoorlarc-120 has over the thickness reduction of 14% without propagation of crack to the hole-down area.

Analysis of toughness of welding alloys for high strength low alloy shipbuilding steels

In previous work by the present authors a model was developed for the estimation of the tensile properties (strength and ductility) of ferrous alloys intended for the welding of high strength low alloy steels used in the construction of ships. The method used to model the properties as a function of a large number of variables was based on a neural network within a Bayesian framework. This method is particularly useful when attempting to understand complex non-linear phenomena where the distribution of data within the input space is not obvious. In the present work, a similar approach is used to model the toughness (characterised by Charpy and dynamic tear tests) of the same alloys. The level of noise in the experimental data is perceived to be high, but it has nevertheless been possible to recognise reasonable trends and uncertainties when making predictions. For example, the toughness shows a non-linear deterioration as the oxygen concentration is increased; this behaviour is expected but can now be expressed quantitatively.

Analysis of toughness of welding alloys for high strength low alloy shipbuilding steels

In previous work by the present authors a model was developed for the estimation of the tensile properties (strength and ductility) of ferrous alloys intended for the welding of high strength low alloy steels used in the construction of ships. The method used to model the properties as a function of a large number of variables was based on a neural network within a Bayesian framework. This method is particularly useful when attempting to understand complex non-linear phenomena where the distribution of data within the input space is not obvious. In the present work, a similar approach is used to model the toughness (characterised by Charpy and dynamic tear tests) of the same alloys. The level of noise in the experimental data is perceived to be high, but it has nevertheless been possible to recognise reasonable trends and uncertainties when making predictions. For example, the toughness shows a non-linear deterioration as the oxygen concentration is increased; this behaviour is expected but can now be expressed quantitatively.

Expression for the Dynamic Yield Stress from Instrumented Dynamic Tear Specimens and Plastic η-Factor for Three-Point Bend Specimens: Results for AISI 308 Weld and AISI 316 Stainless Steels

Abstract An empirical expression for computing the dynamic yield stress, σyd, from the general yield load, PGY, of dynamic tear (DT) specimens has been derived by comparing the results from instrumented drop-weight/impact tests of DT and Charpy V-notch (CVN) specimens of AISI 308 weld and AISI 316 stainless steels. This is based on the following assumptions: the functional expression relating σyd to PGY is the same for both DT and CVN specimens except for a dimensionless proportionality constant: and σyd from both the specimens has the same value. Plastic η-factors obtained by analyzing instrumented DT test results are also presented. The work reported earlier by the authors based on instrumented CVN and precracked Charpy specimen test results showed the dependence of the plastic η-factor on the crack aspect ratio; the present results indicate that the plastic η-factor shows an additional specimen size dependence. However, the new estimates based on the larger size specimens are only slightly larger than the lower-bound estimates reported earlier, but much below the upper-bound curve reported at the same place. Similar size dependence has been reported in the literature.

Effect of thickness on the relationship between shear lip and energy in dynamic tear specimens

In two previous papers, a relationship was shown to exist between the fracture energy and shear lip in 16–25 mm thick dynamic tear (DT) tests of quench and tempered carbon and low alloy steels and their weldments over a wide range of temperatures, compositions and locations in the weldments. The relationship between shear lip and energy was found to be independent of specimen thickness for the 16–25 mm thicknesses. In this paper it will be shown that the relationship holds for 7–15 mm thicknesses as well. Data used in these studies have been acquired from samples of 350 WT, A517 Grade F, HY80, HY100 and HLES steels and submerged arc, shielded metal arc, flux cored arc and gas metal arc welds of these steels.

On the relationship between shear lip, shear index and energy in dynamic tear specimens

In a previous paper [J. R. Matthews, On the relationship between shear index and energy in dynamic tear specimens. Engng Fracture Mech. 39, 131–140 (1991)], a relationship was shown to exist between the fracture energy and shear index in a series of dynamic tear (DT) test of quench and tempered carbon and low alloy steels, and their weldments over a wide range of temperatures, compositions and locations in the weldments. In this paper it will be shown that a relationship also exists between the shear lip size and the energy that fractured the specimen. More importantly the relationship between shear lip and energy is independent of specimen thickness as will be shown for a series of 16 and 25 mm specimens. Data used in this study have been acquired from samples of HY80, HY100 and HLES steels and gas metal arc welds of HY80 and HY100 steels.

Repetitive- and Single-Blow Impact Testing of Wear-Resistant Alloys

Abstract Repetitive-impact and impact toughness tests provide two distinct measures of a material's ability to resist impact-related wear phenomena. These tests are described in detail and results are presented for a variety of cast and forged wear-resistant alloys. In particular, past research at the U.S. Bureau of Mines using the ball-on-block and ball-on-ball repetitive-impact test is reviewed and the wear-related phenomena associated with repetitive impact are described. Impact toughness was measured using a modified dynamic tear test. To account for the heterogeneous and brittle nature of many wear-resistant alloys, a new tear test specimen was developed. Impact energies are presented for a variety of cast alloys and compared against literature values for static and dynamic fracture toughness of similar alloys. It is shown that repetitive-impact and single-blow impact tests allow a unique characterization of the material's behavior to crack initiation and propagation that dominate many wear environments.

A method of caustics for the direct experimental measurement of the [formula omitted] in nonlinear and dynamic fracture mechanics problems

This paper presents a methodology for the direct experimental measurement of the T ∗- integral . The method of caustics (the shadow pattern method) has proven to be a powerful optical method with which to measure stress intensity factors in static and dynamic fracture mechanics problems. An attempt has been made to extend the method of caustics to problems in nonlinear and dynamic fracture mechanics. The formation process of the caustic pattern for an elastoplastic crack tip in a compact-tension specimen was simulated by a finite-element analysis. The stimulated and actual caustic patterns agreed with each other very well. The relations between the T ∗- integral and the size of the caustic pattern were obtained for various optical set-ups. The experimental measurement of the caustic pattern in the dynamic tear test specimen of a nuclear pressure vessel steel was also carried out. High-speed photographs of the caustic patterns were taken using a laser caustic method, which can be quickly synchronized to the initiation of impact loading by a hammer that was dropped on the specimen. The time variation of the T ∗- integral during impact loading was evaluated by using the relation between the T ∗- integral and the size of the caustic pattern that was obtained by the numerical simulation. The hybrid numerical-experimental method developed here, in conjunction with laser caustic high-speed photography, has made it possible to measure the T ∗- integral for an elastoplastic material under impact loading conditions.

On the relationship between shear index and energy in dynamic tear specimens

Comparison of fracture energy and shear index in a series of dynamic tear (DT) tests of quench and tempered carbon and low alloy steels and their weldments has shown that the shear index is related to the fracture energy of the specimens over a wide range of temperatures, compositions and weldment locations. Data have been acquired from samples of HY80, HY100 and QT28 steels, submerged arc welds of HY80 and HSLA80, gas metal arc welds of HY80 and shielded metal arc welds of HY100.

Effect of First Reflections in Dynamic Tear Test

The dynamic tear (DT) test is often used to obtain key dynamic fracture parameters. Previous work indicates that the first impact waves arriving at the test specimen notch may not create a stress state critical for fracture. In this article, a finite element program for the transient dynamic simulation of an actual DT test is first compared with an analytical solution for the time interval prior to the arrival of wave reflections from the specimen surfaces. The program, which uses a uniform spatial mesh size and does not require singular elements, is then used to determine the transient notch stress field at any time. It is found that the arrival of the first reflected waves generate the stress field necessary for fracture. A critical dynamic stress intensity factor value for the DT test is then estimated. This estimate shows good agreement with other experimentally based results.

７０７５合金のＲ曲線法によるじん性評価

Direct current electrical potential method, instrumented Charpy impact test, key curve method, compliance changing rate method, fractography or NRL type dynamic tear test are carried out for the evaluation of static and dynamic crack initiation resistance toughness (JId, JIC) and crack propagation resistance toughness (JR curve, Tmat).The static JR curve and Tmat shows plate thickness dependency; the crack propagation resistance toughness is larger as plate thickness is smaller. The dynamic Tmat shows strain rate dependency. Each method is proved to be sufficiently effective for the toughness evaluation of the aircraft material; 7075 (Al-Zn-Mg-Cu type) alloy.

Dynamic Impact Over a Subsurface Crack: Applications to the Dynamic Tear Test

Dynamic fracture is often studied by means of the dynamic tear (DT) test, which involves transverse impact by a mass on a beam. This process generates a complicated elastic wave pattern in the beam which, however, consists of two wave types: impact waves and reflected waves. The former are the compression wave radiating from the impact line and its diffractions at the notch end, while the latter are all waves originated by reflections from the beam surfaces. To gain insight into the role of specific waveforms in generating the fracture at the notch end in this process, the effects of the impact waves on the dynamic notch end stress field is studied. For both an idealized and an experimentally determined impact force, these waves are shown to initially place the notch end in compression. Moreover, even when a tensile stress state is eventually achieved, the stress intensity factor levels lie well below experimentally determined fracture toughness values. These results suggest that reflected waves generate the fracture, which agrees with experimental evidence.

Task Group Report: Results of the Interlaboratory Test Program to Determine Percent Shear of Dynamic Tear Test Specimens

Abstract ASTM Task Group E24.03.02 on Dynamic Tear Testing evaluated the various procedures used for determining the percent shear fracture surface appearance of dynamic tear (DT) test specimens. The entire gage range of standard DT specimens was investigated. The techniques used ranged from direct visual inspection of the fracture surface to various cleavage area measurement methods using fracture surface photographs. Results based on 35 DT specimens indicated that very consistent and reproducible data can be obtained regardless of the method used. In most cases, either the original or the final specimen cross section can be used as reference, the percent shear results differing by only 5 to 10% between the two areas. Careful visual rating by a trained individual can give results very similar to the more time-consuming methods and is acceptable in most cases. Based on these results a set of recommended procedures was appended to ASTM Test Method for Dynamic Tear Energy of Metallic Materials (E 604) under the title, Determination of Percent Shear Fracture Appearance.

The Crack-Arrest Properties of 9% Ni steel and its Weldment (4th Report)

The objective of this paper is to clarify the mechanism of crack arrest behavior using surface-notched double tension test proposed in previous papers.The static and dynamic deformation behavior of the system measured were compared with the results of numerical analysis on centre crack model and single-edge crack model. The full thickness dynamic tear test was carried out to observe fracture phenomena associated with the crack initiation, propagation and arrest. The surface-notched Dynamic Tear test using the specimen with the sharp surface notches located in the crack initiation part and the crack propagation part was also performed to clarify the effect of the deformation at the surface portion of the specimen on the behavior of the crack initiation and propagation.It is noted that the test results obtained could deny the evaluation of the crack arrest toughness based on the K concept. According to the full thickness Dynamic Tear test, the main factor affecting the crack arrest should be considered the macroscopic plastic deformation and the resulting ductile fracture. The significance of the crack arrest was also confirmed by the surface-notched Dynamic Tear test.Many similarities in the fracture appearances were observed between in the surface-notched double tension test and in the Dynamic Tear test. It can be clearly seen that there was a close relationship between both test results.As a result, the full thickness Dynamic Tear test would be a convenient engineering test method in order to evaluate the crack arrest properties of materials.

高強度Ａｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ合金のじん性に及ぼす時効組織の影響

Tinsile, impact, fracture mechanics and dynamic tear tests were carried out on 7075, 7175 and 7475 alloy extrusions. Fracture toughness of Al-Zn-Mg-Cu alloys is considerably influenced by aging condition. Under-aging results in high fracture toughness and resistances to crack propagation and unstable fracture. The fracture toughness decreases with increasing yield strength. The fact is related to localized plastic deformation due to finely distributed precipitate particles and to the resulting strengthened matrix. Over-aged meterials have lower fracture toughness than the other aged materials. Precipitate particles coagulate at the grain boundary and transgranular fracture at under- and peak-aging conditions transits to intergranular fracture at over-aged condition as the aging proceeds.

Dynamic tear tests of carbon weldable steels

For determining the crack arrest temperature of structural weldable steels of mass production, it is convenient to use the dynamic tear test because of its simple and low cost application using drop weight testers or pendulum testing machines. The dependence of the dynamic tear energy on temperature can in fact represent the curve of the crack arrest temperatures. The energy/temperature results have to be transformed into the nominal stress vs. temperature coordinates to permit a better review and simpler application. This work describes two methods of making such transformations and shows some results acquired with carbon weldable structural steels.

An Analysis of Dynamic Fracture in an Impact Test Specimen

Numerical simulations of fast fracture in four cases of dynamic tear test experiments on 4340 steel are performed using a moving singular finite element method. The experimentally measured crack propagation histories are used as input data to the so-called generation phase simulations to determine the dynamic stress intensity factor histories. In most numerical analyses of dynamic fracture specimens, the load and support points have been treated as fixed boundary conditions. In the present paper, more realistic boundary conditions (contact/no-contact), in which the specimen can separate from the tup and the supports are introduced. The results are also discussed in the light of current controversies surrounding the dynamic fracture toughness properties governing crack propagation under impact loading.

A method for determining dynamic stress intensity factors from cod measurement at the notch mouth in dynamic tear testing

A formula is derived for determining dynamic stress intensity factors directly from crack mouth opening displacements in dynamic tear test specimen. The results obtained by the present estimation method for stationary as well as propagating cracks agree excellently with those directly obtained through a highly accurate moving-singularity finite element method. The present method can also be applied for other types of specimen which have a relatively short edge crack without any loading on the crack surface. The present simple estimation method should be of great value in the experimental measurement of dynamic stress-intensity factors for propagating cracks in (opaque) structural steel dynamic tear test specimens.

Task Group Report: Results of Interlaboratory Test Programs to Evaluate the Dynamic Tear Test Method

Abstract An ASTM Task Group evaluated the revised Standard Test Method for Dynamic Tear Energy of Metallic Materials (E 604). The revised method expanded the range of specimen thickness from the 16 mm (⅝ in.) specified in E 604-77 to include specimens ranging from 4.8 to 16 mm (3/16 to ⅝ in.) in thickness. The minimum impact velocity was also changed from 4.9 to 4 m/s (16 to 13 ft/s). Three series of tests were conducted by 16 laboratories on steels of low, intermediate, and high yield strength. A total of 1300 specimens were involved over a two-year period, and the results were analyzed statistically to support the modifications in the dynamic tear test method. No variations of engineering significance in dynamic tear energy were found with respect to between-laboratory variation in procedures, testing machine type, impact velocity, and specimen preparation within the tolerances set for the dimensions of the test specimens and the critical parameters of the testing procedure.