Tensile Strength Distribution Research Articles

Relationship between the mass profile and the strength property profile of decayed wood

To resolve degradation problems of timber structures, analysis of the development of a fungal attack on structural timber is important. The progression of wood decay especially that of structural timber is not always uniform and reduces strength locally. Therefore, the strength profile is important in estimating the strength of decayed wood. In this study, Sitka spruce (20 mm × 20 mm × 100 mm (longitudinal direction)) was exposed to brown- and white-rot fungi for 3 to 15 weeks from the end surface. After decay, mass profiles of an oven-dried specimen were obtained by X-ray densitometry, and specimens for compressive and tensile tests were cut from the decayed wood to determine both compressive and tensile strength distribution profiles in the longitudinal direction. Except for some results of the tensile strength, after 3 weeks treatment with brown-rot fungus, both strength and mass were reduced. For the same decrease in mass, the tensile strength was reduced more by the brown-rot fungus than by the white-rot fungus, whereas the results for compression strength were almost the same for the two fungi. The results suggested that it is possible to estimate the strength loss of the decayed wood from the mass profile.

Tensile fracture behavior and strength distribution of SiCf/SiC composites with different SiBN interface thicknesses

The borosilicate nitride (SiBN) interface was firstly fabricated in SiC fibers reinforced SiC matrix (SiCf/SiC) composites by low-pressure chemical vapor infiltration (LPCVI). Tensile fracture behavior and strength distribution of SiCf/SiC composites with different SiBN thicknesses were investigated. The results showed that the tensile strength first increased and then declined with increasing interface thickness. The maximum value of tensile strength was 550.8MPa with a 1000nm SiBN interface. Non-brittle tensile fracture behavior of SiCf/SiC composites with a SiBN interface was demonstrated. The pull-out length and amount of fibers had a similar variation trend with increasing interface thickness. Strength distributions of SiCf/SiC composites with different interface thicknesses followed Weibull distribution with two parameters. Weibull modules of tensile strength increased first, and then decreased with increasing interface thickness. The maximum value of the Weibull module was 11.0224 when the interface thickness was 1000nm, which indicated the highest reliability of SiCf/SiC composites. The mean value of tensile strength for SiCf/SiC composite with 1000nm interface was 576.82MPa obtained by the theory calculation, which was consistent with the result of experiment (550.8MPa) very well.

Strength prediction of annealed glass plates – A new model

A new model for assessing the strength of structural members made of annealed glass plates is presented. The model refers to a glass plate that is supported at its ends and loaded by a given loading system. To fully determine the mechanical behavior of the glass plate, a flaws distribution function is presented, from which the critical stress distribution is calculated. These critical stresses determine the local ultimate resistance of the plate. The model determines the flaws distribution over the area of a large basic plate, from which plates of different sizes are cut out. Each cut out plate is characterized by a different map of flaws that is distributed over its surface and it behaves differently as a result. The flaws shape, size and location determine the critical tensile stresses that are required for crack opening. These critical stresses are compared with the growing stresses during loading, to determine at which point and at what loading level fracture is initiated. The model is capable of predicting the tensile strength distribution of a large group of glass plates of a given geometry and boundary conditions. The model provides much information concerning the probabilistic distribution of the tensile strengths and the location of the fracture origin.For an examined case the model yields an almost symmetrical tensile strengths distribution, and although it is somewhat different than existing statistical functions, it is similar to the normal distribution.It is shown that the entire analysis of determination of the critical tensile strength is independent on the plate’s thickness, although the latter is important to determine the magnitude of the bending moment at failure and the magnitude of the applied load that causes that failure. The model is found to be in close agreement with test data; it may explain the inspected and measured results and provide insight to glass plate behavior.

Tensile strength distribution of carbon fibers at short gauge lengths

In this study, we determined the strength distribution of high-strength polyacrylonitrile-based carbon fibers of different short gauge lengths (~1 mm) using both the single-fiber-composite four-point bending test and the single-fiber tensile test. We employed the bimodal Weibull model to explain the experimental data. We found that the value of the Weibull shape parameter for short gauge lengths was higher than that for long gauge lengths. This implies that the tensile strength distribution of carbon fibers is governed by two different flaw populations. The tensile strength of resin-impregnated fiber bundles predicted on the basis of the bimodal Weibull distribution was in better agreement with the experimental result than the tensile strength of those predicted on the basis of the unimodal Weibull distribution.

Statistical methodology for assessing manufacturing quality related to transverse cracking in cross ply laminates

Abstract We present a statistical analysis based methodology for making assessment of the manufacturing quality of cross ply composite laminates as it relates to its effect on transverse cracking evolution. Assuming a two-parameter Weibull distribution of tensile strength of the transverse plies to represent randomly distributed manufacturing defects, multiple crack formation in the plies is simulated in the non-interactive and interactive regimes of cracking using the local stress fields calculated by a variational analysis. The statistical methodology is demonstrated on crack density evolution in cross ply laminates manufactured by four different processing routes and loaded in monotonic tension in the axial direction. The differences in the crack density evolution, supposedly due to different defect population induced by the four manufacturing conditions, could be described by the proposed statistical simulation method.

OS0528 キンク損傷を与えたPBO繊維の引張強度の確率分布

OS0528 キンク損傷を与えたPBO繊維の引張強度の確率分布

Importance of particle size and shape on the tensile strength distribution and de-agglomeration of cohesive powders

PurposeThe purpose of the study was to understand the role of particle size and shape changes in modifying agglomerate strength distribution and de-agglomeration of cohesive lactose powders. MethodsThe relative de-agglomeration of three lactoses of different particle size distributions (Lactohale 201 or LH201, Lactohale 210 or LH210 and Lactohale 220 or LH220) was determined from laser diffraction particle sizing of the aerosol plume at different air flow rates. The agglomerate strength distributions were estimated by Monte Carlo simulation using the primary particle size, work of cohesion and tapped density distributions determined by laser diffraction, inverse gas chromatography and tapping apparatus, respectively. The morphology and particle shape parameters were determined by scanning electron microscopy and the Morphologi G3. ResultsThe estimated agglomerate strength correlated well with the de-agglomeration of all lactose samples at different air flow rates. While the work of cohesion of the lactose samples was not significantly different, the packing fraction was dependent on the proportion and shape of intermediate-sized, cohesive particles between 5.4 and 14μm. For example, while the proportion of particles <5.4μm was similar for all lactose samples, the proportion of intermediate-sized, cohesive particles increased in the order of LH201<LH210<LH220. The intermediate-sized, cohesive particles were more elongated than the <5.4μm fraction and the extent of elongation of the lactose samples increased in the order of LH220>LH210>LH201. ConclusionThe study reinforced the role of agglomerate strength distributions in understanding de-agglomeration of cohesive materials. Modification of particle size distributions and shape characteristics contributed to the agglomerate strength changes in the lactose samples. The study enhanced the fundamental understanding of powder de-agglomeration and provided strategic approaches that could be used to improve inhalation product performance.

Strength prediction and failure modes of concrete specimens subjected to the split test

This paper deals with modelling and test of concrete specimens subjected to the Brazilian split test. Based on the fictitious crack concept, a simple model for the crack propagation process in the splitting plane is developed. From the model, it is possible to determine the distribution of residual tensile strength as crack propagation take place. The residual tensile strength is thereafter used in a rigid plastic analysis of the splitting failure. Based on this combined approach, the ultimate load may either be governed by crack propagation or by a plastic failure, which then terminates the crack growth process. It is shown that the model is able to replicate a number of experimental observations. This includes size effect and influence of loading width.

A new technique for the strengthening of aluminum tungsten inert gas weld metals: Using carbon nanotube/aluminum composite as a filler metal

The effect of multi-walled carbon nanotube (MWCNT) on the mechanical properties of aluminum multipass weld metal prepared by the tungsten inert gas (TIG) welding process was investigated. High energy ball milling was used to disperse MWCNT in the aluminum powder. Carbon nanotube/aluminum composite filler metal was fabricated for the first time by hot extrusion of ball-milled powders. After welding, the tensile strength, microhardness and MWCNT distribution in the weld metal were investigated. The test results showed that the tensile strength and microhardness of weld metal was greatly increased when using the filler metal containing 1.5wt.% MWCNT. Therefore, according to the results presented in this paper, it can be concluded that the filler metal containing MWCNT can serve as a super filler metal to improve the mechanical properties of TIG welds of Al and its alloys.

Structure changes during tensile deformation and mechanical properties of a twisted carbon nanotube yarn

The small-angle X-ray scattering measurements during tensile deformation have been performed for studying the structure and mechanical property relationships of twisted carbon nanotube (CNT) yarns. The tensile strength distribution and the diameter changes during tensile deformation have also been measured. The orientation distribution of the CNTs in the yarn has been determined and its changes during tensile deformation have been related to the variation of the tensile modulus with the twist angle. The tensile modulus and Poisson’s ratio of the yarns decreased with increasing twist angle, whereas the tensile strength of the yarn showed a maximum at the twist angle of 25°. At this twist angle, the distribution width of the tensile strength was minimum indicating the higher uniformity of the yarn structure.

Mechanical properties of full austenitic welding joint at cryogenic temperature for the ITER toroidal field coil structure

ITER toroidal field coil (TFC) structures are large welding structures composed of coil case and support structures made of heavy thick high strength and high toughness stainless steels. Japan Atomic Energy Agency plans to apply narrow gap Tungsten Inert Gas (TIG) welding with FMYJJ1 (0.03C–10Mn–12Cr–14Ni–5Mo–0.13N) which is full austenitic stainless filler material. In order to evaluate effect of base material thickness and combinations of base material on tensile properties, tensile tests were performed at room temperature, 77K and 4K by using tensile specimens taken from 200mm thickness welded joints of two combinations of base materials and 40mm thickness welded joints of four combinations of base materials. As the results, it was confirmed that there were no large distribution of yield and tensile strength along the thickness of welded joints of 200mm thickness and yield and tensile strengths of welded joints were decreased with decreasing of C+N contents of base material.

Controlling mechanical and physical properties of Al-Si alloys by controlling grain size through grain refinement and electromagnetic stirring

The present study concerns the influence of a travelling magnetic field (TMF) on the hardness, tensile strength and electrical conductivity of directionally solidified grain-refined and non-refined Al-7 wt.% Si alloys. Upwards and downwards travelling fields have been applied to force convection within the solidifying melt. Modifications of the examined physical and mechanical properties depend on the formation of a fine equiaxed structure caused by both the addition of grain refining AlTi5B1-particles and by electromagnetic stirring as well. Electromagnetic stirring without grain refining particles leads to an increase in tensile strength. The addition of grain refiners into the melt leads to the highest reduction of the mean grain size and results in a decrease in electrical conductivity. A melt stirring by a sufficiently high magnetic field provides a homogeneous grain size distribution in the sample volume which impacts the distribution of hardness, tensile strength and electrical conductivity.

Scaling Effects on the Tensile Strength of Fibrous Composites

The primary objective of this paper is to illustrate the effects of weak-link scaling on the tensile behaviour of fiber-reinforced composites. The proposed model takes into account the random nature of fiber strength, which is given by a two-parameter Weibull distribution function. Several hundred Monte-Carlo replications are executed to simulate the statistical strength distributions of the composites. It is shown that probabilistic tensile strength distributions and size scaling is dependent on both the stress redistribution and the fiber strength statistics.

A modified Weibull model for tensile strength distribution of carbon nanotube fibers with strain rate and size effects

Fundamental studies on the effects of strain rate and size on the distribution of tensile strength of carbon nanotube (CNT) fibers are reported in this paper. Experimental data show that the mechanical strength of CNT fibers increases from 0.2 to 0.8 GPa as the strain rate increases from 0.00001 to 0.1 (1/s). In addition, the influence of fiber diameter at low and high strain rate conditions was investigated further with statistical analysis. A modified Weibull distribution model for characterizing the tensile strength distribution of CNT fibers taking into account the effect of strain rate and fiber diameter is proposed.

High-strength bolt-forming of fine-grained aluminum alloy 6061 with a continuous hybrid process

It is well known that the development of a continuous manufacturing process to apply severe plastic deformation (SPD) is a major challenge for industrial usages to improve the mechanical properties of the material through grain refinement. In this study, fine-grained AA6061-O wire was manufactured by a two-pass hybrid process consisting of drawing, equal channel angular pressing and rolling in a continuous manner to investigate the effects of processing routes for two different routes, A and C, on the variation of ultimate tensile strength (UTS) and micro-hardness distribution. The UTS value (185MPa) of the specimen processed by the two-pass hybrid process with route A was higher than that of 171MPa obtained from the two-pass wire-drawing process and was equivalent to the level of 184MPa processed by the three-pass wire-drawing process. The average micro-hardness value (Hv 58.0) obtained from the two-pass hybrid process through route C was the highest among all the cases. According to transmission electron microscopy, the original grain was subdivided and elongated owing to deformation during the processes. The specimen processed by the two-pass hybrid process through route C showed smaller deformation bands and had potentially higher angle grain boundaries compared to the specimen processed by the two-pass wire-drawing process. Finally, the high-strength bolt was manufactured using the fine-grained AA6061-O wire prepared by the continuous hybrid process to check its formability. A ductile fracture at the first thread right above the jaw was observed in the bolt tension test of the manufactured bolt. The average micro-hardness value (Hv 56.1) obtained from the bolt manufactured with the specimen produced by the two-pass hybrid process through route C was higher than the one of Hv 50.5 obtained from the two-pass wire-drawing. It is demonstrated that the hybrid process might be useful in producing the grain-refined wire in a continuous process to manufacture high-strength bolts for practical applications.

Study of Tensile Strength Distribution Based on Composite Materials for Aeronautical Engineering

The Tensile strength of an composite materials for aeronautical engineering was tested and its distribution was analyzed based on the two parameter weibull distribution?The maximum normed residual (MNR) test was applied to eliminate abnormal data. A graphical method was used to estimate parameters. Furthermore?the validity of the assumed distribution was examined by the kolmogorov test (KS). The results show that MNR test can be used to exclude abnormal data. It also suggests that the gained two parameter weibull distribution can be used to express the tensile strength and predict its values accurately.

GS22 結晶化度の異なるPBO繊維の引張強度と圧縮強度の確率分布の比較検討

In this paper, distributions of tensile and compressive strength of PBO fibers were investigated in tensile test and compression test. Two types of PBO fibers were used in the experiment. One is conventional type of fiber. Another is high modulus type of fiber, and its crystal orientation is higher than conventional type of the fiber. Weibull analysis was performed to compare distribution of tensile strength and compressive strength. It was found that tensile strength and compressive strength of each type PBO fibers were well fitted the Weibull distribution function with 2 parameters regardless of degree of crystallization. Then, in tensile strength, shape parameter of HM type PBO fiber was lower than that of AS type PBO fiber. Also, in compressive strength, shape parameter of HM type PBO fiber was a little higher than that of AS type PBO fiber.

Effect of statistical yarn tensile strength on the probabilistic impact response of woven fabrics

The probabilistic impact response of flexible woven fabrics can be described through the V 0– V 100 or probabilistic velocity response (PVR) curve which describes the probability of fabric penetration as a function of projectile impact velocity. One source of variability that affects the probabilistic nature of fabric impact performance is the statistical distribution of yarn tensile strengths. In this paper the effects of the statistical yarn strength distribution characteristics on the probabilistic fabric impact response are computationally studied using five different strength distributions with differing mean strengths and distribution widths. Corresponding fabric PVR curves are generated for each strength distribution using a probabilistic computational framework that involves randomly mapping yarn strengths onto the individual woven yarns of a fabric finite element model and then running a series of impact simulations for the case of a four-sided clamped fabric impacted at the center by a spherical projectile.

Evaluation of interfacial shear strength by tensile tests of impregnated flax fiber yarns

Adhesion of flax fibers and polymer matrix as well as mutual bonding of elementary fibers in a technical fiber are among the principal factors governing the mechanical response of flax fiber-reinforced polymer–matrix composites. A method for evaluation of adhesion is proposed based on tension tests of impregnated fiber yarns, with subsequent characterization by optical microscopy of length distribution of fibers pulled out of the yarn fracture surfaces. An elementary probabilistic model is derived relating aspect ratio distribution of the pulled-out fibers to the fiber tensile strength distribution and the effective interfacial shear strength (IFSS). The method was applied to flax fiber/vinylester resin yarns and an estimate of IFSS at 17 MPa was obtained.

Variability of the Mechanical Properties of Wrought Iron from Historic American Truss Bridges

The mechanical properties of wrought iron from multiple elements of six late 19th-century truss bridges is evaluated by a program of destructive and nondestructive testing, including hardness testing and tension tests to evaluate the yield stress (Fy), tensile strength (Fu), and ductility of the material. The yield stress and tensile strengths are found to be in accordance with those published in period reports and in other modern evaluations of the mechanical properties of wrought iron. The main findings of this work come from a statistical analysis of the test results and are (1) that hardness is a poor predictor of yield stress and tensile strength but has some predictive ability for ductility; (2) that there is a statistically significant difference in the distribution of yield stress and tensile strength between material samples from different bridges and, in some cases, between material samples from different members within a single bridge; and (3) that a size effect is present in the material that results in lower yield stress and tensile strength for larger members. These results provide guidance to engineers in the evaluation of historic iron trusses for rehabilitation and suggest that although nondestructive hardness testing is of limited value, a limited program of destructive testing can provide an adequate characterization of the mechanical properties throughout the bridge. DOI: 10.1061/(ASCE)MT .1943-5533.0000220. © 2011 American Society of Civil Engineers.