ASTM E399 Standard Research Articles

PHYSICAL, MECHANICAL, AND MORPHOLOGICAL CHARCTERISTICS OF KAPOK (CEIBA PENTANDRA) TREE BARK AND EPOXY COMPOSITE WITH COATING (AESO) TREATMENT

Environmentally friendly composites continue to be developed from kapok tree fiber (Ceiba pentandra) with an epoxy matrix. This study aims to characterize the tensile behavior of single fiber and its composite, the pull-out properties of kapok tree fiber, and morphology of the fiber. Kapok tree fibers were varied in the NaOH solution and the AESO polymer. Single fiber tensile test and pull out refer to the ASTM D3379-75 and ASTM E399 standards, respectively. The composite manufacturing method used in this research was the infusion vacuum resin method with reference to the ASTM D638 standard. The results of the tensile test (composite) showed that the kapok bark fiber with the characteristics of NaOH + Coating had a greater tensile strength (197,88 Mpa), than that without treatment and NaOH treatment. Of all the characteristics of the kapok bark fiber, the highest value of the tensile strength was the fiber treated with NaOH + Coating (KNC). The results of fiber morphology showed proved that the NaOH treatment increased the surface hardness by eliminating the bonds of surface crystallinity, topography, water absorption, unit cell structure and fiber orientation. These results indicate that kapok tree fiber treated with 7% NaOH + coating with AESO polymer has high potential as a structural material to replace wood or textile materials.

Production of Reactive Alumina from Domestic Sources and Its Use in Alumina-Based Self-Flowing Castable Refractories

High-quality alumina raw materials allow corundum-based brick and monolithics to perform to the full potential of alumina as a refractory material. Dense packing of the matrix to a submicron range and reduction of water demand of castables can be facilitated by a new family of multimodal reactive alumina. Dispersing aluminas ensure uniform mixing of dispersion and setting adjustment additives. In this study, fine reactive alumina powder production was investigated using Bayer gibbsite as a starting material. Experimental studies consist of two steps; in the first step, the soda content was reduced by means of boric acid and distilled water and then the powders obtained optimum conditions were ground in an attritor ball mill using distilled water for 8 hours. In the second step, physical characteristics such as rheological behaviours, bulk density, open porosity and thermal shock resistance, bending and compressive strength and fracture toughness in accordance with ASTM E399 standard were determined. Finally, KIC values of the refractory samples which was prepared with the reactive alumina produced from Seydişehir gibbsite were higher than that of the refractory mixture containing commercial reactive alumina obtained from a refractory company.

Study of geometric parameters and TiC reinforcements in aluminium metal matrix composite on fracture toughness using Taguchi method

In aluminum alloy, Titanium carbide (TiC) reinforcements act as nucleation sites and refine grain structure during solidification. Al-TiC particulate composites find major applications in structural and automobile parts due to their attractive features such as high elastic modulus and hardness. Therefore, attempts are made in the present work to know the fracture behavior of metal matrix composites prepared with varied fraction of reinforcement particles (3 wt%, 5 wt%, 7 wt% of TiC) under various notch sizes of the compact tension (CT) specimen. Al6061-TiC MMCs compact tension specimens are prepared as per ASTM E399 standards, to examine the fracture toughness (KIC). The CT specimens are machined to obtain the desired geometry i.e. crack to width (a/W) ratio of 0.3, 0.4 and 0.5 and thickness to width (B/W) ratio of 0.3, 0.4, and 0.5. Taguchi L9 orthogonal array experiments are conducted to study the effect of the factors (TiC reinforcements, a/W and B/W) on the performance of fracture toughness of the composites. The contribution of each factor is evaluated on the fracture toughness of Al6061-TiC composites. The maximum values of fracture toughness was observed for the optimized set of Al6061-TiC (3 wt%), a/W ratio and B/W ratio maintained equal to 0.4. Taguchi method results could help any novice user in obtaining the optimum fracture toughness without much efforts, materials and time.

Fracture Mechanism and Fracture Toughness at the Interface Between Cortical and Cancellous Bone.

The microstructure at the interface of cortical and cancellous bone is quite complicated. The fracture mechanisms at this location are necessary for understanding the comprehensive fracture of the whole bone. The goal of this study is to identify fracture toughness in terms of J integral and fracture mechanism at the interface between cortical and cancellous bone. For this purpose, single edge notch bend (SENB) specimens were prepared from bovine proximal femur according to ASTM-E399 standard. Bone samples were prepared such that half of the sample width consists of cortical bone and other half of the width was cancellous bone; this interfacial bone is referred as a corticellous bone. Elastic-plastic fracture mechanics was used to measure fracture toughness. The J integral (both elastic and plastic) was used to quantify the fracture toughness. The plastic part of J integral value (Jpl) of corticellous specimen was 9310 J m-2, and shown to be 27 times of the J integral of the elastic part (Jel), 341 J m-2. The total J integral of the corticellous bone was found to be 9651 J m-2, which is close to two times of the cortical bone, 4731 J m-2. This study observed that J integral of corticellous bone is higher than the cortical bone since more energy is required for plastic deformation of corticellous bone due to crack branches and slowdown at the interface between cortical and cancellous bone.

Fracture Toughness of AZ61 Magnesium Alloy with Various Thickness

The critical fracture toughness parameter KΙC of AZ61 magnesium alloy was determined on the three point bent specimens with notch designed according to ASTM E399 standard. Five specimens having different thickness, i.e., 2, 4, 6, 8 and 10 mm were considered in order to evaluate the effect on fracture toughness. The stress intensity factor range ΔK was constant ~1x 10-8 for every specimen until the critical crack length reached half of the width of the specimens. The fracture test was done with the speed rate 0.12-0.15 MPa√m/sec until the specimens broke. The experimental results showed that the critical plain strain fracture toughness KΙC is 12.6 MPa√m and the highest plain stress fracture toughness KC is 16.5 MPa√m.

점탄성을 고려한 고체추진제의 파괴인성 평가

A crack in a solid propellant increases the area of burning surface, which leads to excessive burning that causes motor failure. Therefore, it is necessary to evaluate fracture toughness of solid propellants. However, it is very difficult to measure fracture toughness of solid propellants because of the nonlinear mechanical behavior. In this study, evaluation of fracture toughness on a solid propellant was carried out under the assumption that the solid propellant is a linear viscoelastic material. Actual displacements from fracture toughness tests using CCT specimens were converted into pseudo-elastic displacements by using stress relaxation characteristics and fracture toughness was evaluated using ASTM E399 standard. Also, effects of test temperature and speed on the fracture toughness were considered.

Fracture Toughness Determination for Aluminium Alloy 2011-T6 using Tensile Notched Round Bar (NRB) Test Pieces

While the use of notched round bar (NRB) test pieces to determine planestrain fracture toughness K Ic is not novel, relatively few authors have so far attempted this. This letter serves to report a series of such tests conducted on Al 2011-T6, a high mechanical strength, free-machining aluminium alloy. A total of 9 specimens was used, comprising 3 specimens each of 3 different notch root radii, ρ. No fatigue precracking was carried out. A graph of apparent fracture toughness K ρ versus ρ / D was extrapolated to zero, corresponding to a fatigue pre-cracked configuration. The resulting K Ic for this alloy tested using the NRB specimens was thus found to be 27.9 MPa√m. This is a valid K Ic value, as there is only a 6.8% difference between it and the median value (26.0 MPa√m) determined previously from 67 tests using the existing ASTM E399 standard. A new geometric correlation based on ρ, D and d is proposed to linearly extrapolate K ρ values, measured on NRB specimens with arbitrary geometries (but assuming plane-strain conditions hold), back to a single value of K Ic.

A new method for determining the fracture toughness of main pipeline steels

ABSTRACTOne of the fundamental aims of fracture mechanics is to define fracture toughness KIC of a material. Hence, the ASTM E399 standard was developed. However according to the standard, large‐sized specimens are required to determine the fracture toughness of low alloy carbon steels. ASTM E1921 standard was developed on the fracture toughness of ferritic steels. In this study, a new method was proposed to determine the fracture toughness of ferritic steels. The purpose of the present paper is to compare the results of the method with the experimental results. Two steels that are used in gas and oil main pipelines were investigated in this study.

Microstructure and mechanical properties of MgO-stabilized ZrO2–Al2O3 dental composites

The aim of the present study was to investigate the production of tetragonal zirconia (t-ZrO2) particles (experimental t-ZrO2) from monoclinic zirconia (m-ZrO2) and to evaluate the effect of the t-ZrO2 content on the fracture toughness of alumina–zirconia composites by conducting ASTM E399 standard test. In the laboratory study, t-ZrO2 powder was produced by heat treating m-ZrO2 containing 10wt.% MgO. Alumina and alumina–zirconia composite powders containing various types and amounts of m-ZrO2 and t-ZrO2 were prepared (0–20wt.%), shaped by slip casting to achieve a uniform distribution and homogeneous microstructure in accordance with the dimensions of ASTM E399 standards, dried, sintered at three different temperatures: 1400, 1500 and 1600°C for two hours, and characterized. The results of the XRD analysis showed that t-ZrO2 was produced at 1400°C. In t-ZrO2-doped alumina composites, t-ZrO2 partially transformed to m-ZrO2 after sintering, whereas commercial t-ZrO2 (Tosoh TZ-3Y) remained intact. SEM studies on samples sintered at 1600°C revealed that the addition of zirconia inhibited abnormal grain growth of alumina, leading to a homogeneous and equiaxed grain structure, especially at high concentrations of zirconia. ZrO2-doping enhanced the fracture toughness of the composites, which increased with an increase in the t-ZrO2 content. The maximum fracture toughness was 11.5MPam1/2 and was observed when the t-ZrO2 content was equal to 20wt.%. Alternatively, the maximum fracture toughness for pure alumina was 5.9MPam1/2.

Microstructure and mechanical behavior of functionally graded Al A359/SiC p composite

The microstructure and mechanical behavior including tensile and fracture properties of a functionally gradient Al A359/SiC p composite processed by centrifugal casting have been investigated. The particle volume fraction and, therefore, elasticity modulus was gradually changed in the continuous form along a certain direction by using the centrifugal casting. The effect of SiC particulate reinforcement on strengthening of A359 Al alloy was experimentally studied by tensile testing specimens with different SiC contents. There was a continuous increase in tensile and yield strength with increasing SiC volume fractions in the range of 0.20–0.30. On the contrary, there was a reduction in tensile and yield strength for SiC concentrations in the range of 0.30–0.40. The fracture experiments were performed according to the ASTM E399 standards. Single edge cracked plate tension (SECT) and single edge cracked four point bending (4PB) specimens, which are taken from rectangular Al/SiC p blocks, were used for fracture tests. The fracture toughness, K IC, and fractographic characteristics of the material were determined by using MTS 810 servohydraulic machine and Hitachi S-800 scanning electron microscopy (SEM), respectively. At elevated SiC concentrations (low values of crack length), limited dissipation of energy by restrained plastic deformation of the matrix at the crack tip produced low fracture toughness values. On the contrary, at longer crack lengths SiC content decreased and there was more absorption of energy, resulting in higher fracture toughness values. A ductile failure process of void coalescence type fracture in the matrix of the composite was observed but the void size was less when the SiC concentration was higher. In addition, SEM fractographs also displayed that fracture and de-cohesion of SiC occurred with particle fracture dominating over de-cohesion and with fracture incidence increasing as particle concentration increases.

ANN back-propagation prediction model for fracture toughness in microalloy steel

Fracture toughness of microalloy steel was evaluated as per ASTM E399 standard. Artificial neural network back-propagation model was developed to predict the behavior of fracture toughness and tensile strength as a function of microstructure. Both fracture toughness and tensile strength were found to increase with the increase in martensite content in a dual phase microstructure of microalloy steel. The primary objective of the ANN Back-propagation (BP) prediction model was to validate and extend the application of microalloy steels for various engineering applications. ANN training model was found to be in good agreement with the experimental results. The ANN training model has been used to predict the best/optimum toughness properties in terms of intercritical annealing temperature and martensite content. This can be used as a practical tool for predicting the fracture toughness in other series of steels comprising dual-phase microstructures and also to optimize strength and ductility properties.

Accurate measurement of strength and fracture toughness for miniature-size thick diamond-film samples by three-point bending at constant loading rate

Fracture strength and fracture toughness (K IC) of miniature-size thick freestanding diamond film samples were accurately measured by three-point bending at a constant loading rate. A specially designed testing rig, capable of achieving a constant loading rate as small as <0.5 N s −1 was used, which is beneficial for accurate measurement of the fracture strength and toughness for brittle materials like diamond films. A novel method was employed to nucleate and accurately control the length of the pre-crack. A specially designed loading fixture was used to ensure that the diamond film sample was tested in a near-perfect vertical position, as required by the ASTM E399 standards. Effects of sample dimensions on the measurement of fracture toughness and fracture strength are discussed; it was shown that miniature-size freestanding diamond film samples can be used for the accurate determination of fracture strength and fracture toughness. However, for accurate measurement of fracture toughness, the use of pre-cracked diamond film samples is absolutely necessary. The effect of loading configuration on the measurement of fracture strength is discussed in detail. In addition to the frequently reported two loading configurations (with the nucleation and growth surface in tension, respectively), a third loading configuration with the edge surface in tension is also discussed. The Weibel modulus was also found to be strongly dependent on the loading configuration. The significance of these findings is discussed.

Crack-tip plastic constraint activators and the application to plane-strain fracture toughness test:: Proposal on small-size fracture toughness specimen

This study develops a new method for elevating plastic constraint in front of the crack tip of small-size (very thin-thickness) fracture toughness specimen. The method can be used for quality assurance of pressure vessels in service. Two approaches are adopted to create high-plastic constraint at the crack-tip region. First, the application of geometrical discontinuity by using side groove which keeps stress levels nearly constant through the thickness direction. Second, the application of mechanical heterogeneity using strength mismatching which significantly elevates the stresses ahead of the crack tip and creates high triaxiality which imposes nearly plane-strain conditions. Experimental verification is presented where 2.5 mm thick specimen with strength mismatching provided nearly the same K c value as full thickness specimen extracted from a pressure vessel after long-term service. The parameters controlling the stress level for such specimens (thin, strength mismatched) are discussed and quantitatively evaluated using a local approach with Weibull stress calculation. The conditions for plastic constraint are determined based on the requirements of the ASTM E399 standard. A `valid zone diagram' is developed based on the Weibull conditions and ASTM E399 standard requirements. A new small-size fracture toughness specimen is then proposed for an example material, A204A steel. A comparison is presented with specimens having side grooves with different groove depths and loading modes.

Acceptance criterion on the invalid fracture toughness data of m250 grade maraging steel sheet material

M250 grade maraging steel is used for the construction of 7.8-mm-thick space vehicle pressure vessels. Fracture toughnesses of this material obtained from compact tension (CT) specimens are found to be invalid due to thickness as per ASTM E399 standard. For acceptance of the material, the maximum failure load of a CT specimen obtained from the R-curve of the material is used for comparing the failure load of the test coupon. The relation for the maximum failure load determination of a CT specimen suggested in this note can be used as a criterion for accepting the material.