Showing papers on "Tensile testing published in 1970"

Yield-point phenomena in substitutional alloys

Abstract: A material exhibits a yield point when a larger stress is required to initiate deformation by slip than to continue it. In a normal tensile test this is usually observed as a drop in load at the start of gross yielding. Load drops may also be observed that are due to deformation twinning, but this will not be discussed here. Annealed mild steel was once thought to be unique in showing an initial yield point but it is now known that the effect is quite general, and many examples occur in substitutional alloys.

Bending Behavior and Tensile Strength of Carbon Fibers

Abstract: The strength of anisotropic polycrystalline carbon fibers was investigated. Theoretical estimates of the strength of graphite are far higher than observed values for carbonized rayon fibers, and we have searched for an explanation. Internal ``grain boundaries'' in the fibers can account for the reduced strength inasmuch as the fracture appears to be intergranular. The ``grains'' are believed to be axially oriented fibrils, ap‐approximately 500‐A across. Experimental evidence for some inelastic behavior in carbon fibers at room temperature was obtained from bending experiments on single filaments. The results were interpreted in terms of local ``yielding'' or rupture of cross‐link bonds between adjacent fibrils. The stress at which such ``yielding'' takes place in bending is approximately equal to the failure stress in a tensile test. Although a Griffith model of completely brittle fracture in tensile tests was considered, the possibility that local ``yielding'' might precede tensile fracture seemed more likely. Consideration of the brittle failure model and the localized plastic flow model both lead to the same conclusion: The tensile strength of carbonized rayon fibers is limited by the fibrillar microstructure and cannot be expected to approach the theoretical estimates for graphite single crystals.

Evaluation of a Tensile Test for Direct Filling Resins

Abstract: Dental filling resins bond to enamel and dentin with varying ability. Quantitative determination of the strength of these resintooth bonds has been reported after shear loading,'-3 tensile loading,4'5 and complex loading.6,7 The shear tests require relatively simple equipment for specimen preparation, conditioning, and testing, and offer a relatively high degree of reliability. The test methods, using complex loading, do not permit the determination of either the tensile strength or the shear strength of the adhesive bond because of specimen geometry, although the clinical situation is closely approximated in that adhesive fillings are actually pulled from human teeth. The tests described by Swartz and Phillips4 and Bowen5 measure the tensile strength of the adhesive bond, which is probably the governing parameter in clinical adhesion. Neither test, however, controls the thickness of the adhesive resin, which is shown here to affect bond strength. In addition, Bowen's test requires complicated machined subassemblies whose cost limits the sample size; Swartz and Phillips4 test requires large sample sizes because of poorer test sensitivity. The subcommittee on testing methods for direct filling resins of the IADR had proposed a test method8 intended to eliminate the disadvantages inherent in these tensile tests. The purpose of this research was to eval-

A method of estimating tensile properties of materials tested in indirect tension

Abstract: Equations were developed for estimating values of modulus of elasticity, Poisson's ratio, and tensile failure strains for circular specimens based upon total horizontal and vertical deformations created in the specimen during indirect tensile testing. A study was undertaken to verify the theoretical relationships for estimating the elastic constants of modulus of elasticity, Poisson's ratio, and tensile strains. To substantiate the equations a circular aluminum specimen, which is considered to exhibit a high degree of elasticity, was tested in indirect tension. The aluminum specimen was instrumented with rosette strain gages at the center. The results indicated that the elastic properties can be obtained from total horizontal and vertical deformations of an elastic material tested in indirect tension. Additional tests were conducted to evaluate the effect of the dimensions of the curved loading strip used in the indirect tensile test and to evaluate the effect of loading rate (vertical strain rate). The results indicated that for best results a 1/2-inch-wide curved loading strip should be used to estimate the modulus of elasticity and Poisson's ratio from total deformation information. It was also found that the dimensions of the curved loading strip used had no significant effect on the tensile strain at the center of the circular aluminum specimen. The loading rate had a significant effect on Poisson's ratio but had no practical engineering effect on the modulus of elasticity.

Tensile strength of rocks

Abstract: THE MOST OFTEN USED METHODS OF MEASURING THE TENSILE STRENGTH OF ROCKS ARE THE DIRECT TENSILE TEST AND THE BRAZILIAN TEST. THIS REPORT STUDIES BOTH METHODS IN DETAIL AND INTERPRETS THEM AS A FUNCTION OF THE EXISTENCE OF DISCONTINUITIES IN THE ROCK. THE BRAZILIAN TEST CAN ONLY BE REGARDED AS A VALID TENSILE TEST IF A PIECE OF CARDBOARD IS PLACED BETWEEN THE SAMPLE AND THE BASE OF THE COMPRESSION MACHINE. THE WIDTH OF VISIBLE CONTACT IN THE CARDBOARD AT RUPTURE POINT MUST BE APPROXIMATELY EQUAL TO 1/5 OF THE DIAMETER OF THE CYLINDER. FOR NON-CRACKED MEDIA, STRENGTH VALUES ARE THE SAME IN THE DIRECT TENSILE TEST AND THE BRAZILIAN TEST. IF CARDBOARD IS NOT USED IN THE BRAZILIAN TEST, THE STRENGTH IS MUCH LOWER. FOR DISCONTINUOUS MEDIA, BOTH TESTS HAVE A VERY DIFFERENT SIGNIFICANCE: THE BRAZILIAN TEST DOES NOT TAKE ACCOUUNT OF DISCONTINUITIES AT THE SCALE OF CRYSTAL, WHILE DIRECT TENSILE STRENGTH IS CONDITIONED BY LARGER CRACKS. ONE CHARACTERIZES THE STRENGTH OF THE ROCK MATRIX, THE OTHER ITS STATE OF FISSURATION. THUS WHEN CRACK DENSITY INCREASES IN THE SAME ROCK (THE VELOCITY OF LONGITUDINAL WAVE PROPAGATION DECREASING IN A PARALLEL WAY) A MARKED DECREASE IN DIRECT TENSILE STRENGTH IS OBSERVED WHILE BRAZILIAN STRENGTH DECREASES ONLY VERY SLIGHTLY. THE COMPARISON OF THE TWO RESULTS CAN BE A GOOD CRITERION FOR MEASURING CRACK INTENSITY, BOTH RESULTS BEING THE SAME FOR NON-FISSURED CONTINUOUS MEDIA. IN ALL TESTS WHERE STRESSES TEND TO COMPRESS THE ROCK, AS IN THE BRAZILIAN TEST, CRACKS CLOSE AND THE CONTINUITY OF THE MATRIX IS RESTORED. IN THIS CASE, DEFORMATION MODULI DO NOT VARY MUCH WITH THE STATE OF CRACKING. BUT IN DIRECT TENSION, ALL CRACKS PARTICIPATE TO THE DEFORMATION AND THE MODULUS DECREASES MARKEDLY AS CRACKING INCREASES. IT WAS OBSERVED THAT FOR NON-FISSURED MEDIA, MODULI ARE IDENTICAL UNDER DIRECT TENSILE STRESS AND COMPRESSION. THE OTHER PARAMETERS IN THESE TESTS ARE ALSO STUDIED IN THIS REPORT WITH A VIEW TO DEFINING A TEST PROCEDURE, IN PARTICULAR FOR THE BRAZILIAN TEST IN WHICH ONLY VARIATIONS IN THE THICKNESS OF THE CARDBOARD USED LEAD TO MARKED VARIATIONS IN TEST RESULTS. /TRRL/

A Possible Fracture Criterion For The Dynamic Tensile Strength Of Rock

Abstract: An attempt is made to shed some light on the mechanisms of scabbing, spalling or slabbing by stress waves created by explosives or impacts. The dynamic tensile strength behavior under various stress waves is examined. The primary objective is to present the critical normal fracture strain energy theory and suggest its potential for some rocks. Also, it is pointed out that the dynamic tensile strength of rock and concrete (a pseudo rock) is not constant and varies with straining rate. Generally, the significance of the slabbing problem has been examined, and it's relation to dynamic tensile strength has been pointed out. The significance of the basic critical fracture strain energy is discussed, and its application to concrete is shown. Some work with quartz monzonite rock is presented. Recommendations are made for the potential application to and extension of the slabbing problem. A theory is propounded to explain dynamic tensile strength behavior, tests having verified the theory in the laboratory. The theory is extrapolated from concretes to a specific rock. (12 refs.)

Factors affecting the tensile strength of cement-treated materials

Abstract: RECENT THEORETICAL AND ANALYTICAL ADVANCES CONCERNED WITH PAVEMENT FAILURES DUE TO EXCESSIVE TENSILE STRESSES OR STRAINS OR BOTH WITHIN THE SOIL-PAVEMENT SYSTEM HAVE PLACED ADDED EMPHASIS ON THE INVESTIGATION OF TENSILE PROPERTIES OF HIGHWAY CONSTRUCTION MATERIALS. THIS STUDY EVALUATES THE FACTORS AND INTERACTIONS AFFECTING THE TENSILE CHARACTERISTICS OF CEMENT-TREATED MATERIALS. NINE FACTORS WERE INVESTIGATED: CEMENT CONTENT, MOLDING WATER CONTENT, AGGREGATE GRADATION, CURING TIME, CURING TEMPERATURE, TYPE OF AGGREGATE, TYPE OF CURING, TYPE OF COMPACTION, AND COMPACTIVE EFFORT. THE FIRST FIVE WERE INVESTIGATED AT 3 LEVELS AND THE LAST FOUR AT 2 LEVELS IN A STATISTICALLY DESIGNED FRACTIONAL FACTORIAL EXPERIMENT. THE PARAMETER CONSIDERED AS A PRIMARY INDICATOR OF THE TENSILE PROPERTIES OF CEMENT-TREATED MATERIALS WAS THE INDIRECT TENSILE STRENGTH. AN ANALYSIS OF VARIANCE WAS USED TO DETERMINE THE SIGNIFICANCE OF ALL MAIN FACTORS, 2-FACTOR INTERACTIONS, AND 3-FACTOR INTERACTIONS IN THE EXPERIMENT. THE HIGHLY SIGNIFICANT EFFECTS THAT ARE ALSO OF PRACTICAL SIGNIFICANCE TO THE ENGINEER ARE DISCUSSED, AND TABLES OF ALL ADDITIONAL FACTORS AND INTERACTIONS SIGNIFICANT AT ALPHA LEVELS OF 1 AND 5 PERCENT ARE SHOWN. A REGRESSION EQUATION THE PREDICTS VALUES OF INDIRECT TENSILE STRENGTH WITHIN THE FACTOR SPACE DEFINED BY THE EXPERIMENT IS PRESENTED. /AUTHOR/

Tensile strength of compacted soils

Abstract: In this study, an attempt has been made to determine the tensile strength of compacted soils and its variation with respect to molding water content by diametral compression tests. The ratio of unconfined compressive strength and tensile strength at the optimum moisture content, and the relationship of this ratio with simple soil properties has also been determined.

Tensile strength of butt-joined epoxy-aluminum plates

Abstract: Tensile tests conducted on butt joined epoxy-aluminum plates containing single cracks along the bond surfaces showed that there exists a characteristic crack length below which the fracture strength of the composite is mainly influenced by the stress concentrations at the bond edges. For specimens with cracks longer than the characteristic length the fracture of the composite is entirely controlled by the stress concentrations at crack tips. In the latter case the stress intensity factors defined by Sih and Rice, and Erdogan appeared to agree reasonably well with test results.

Strength and deformation of concrete in uniaxial tension and compression

Abstract: Synopsis The paper examines the influence of mix parameters upon the strength and deformation of plain concrete subjected to uniaxial tensile or compressive stress. Parameters considered are the effective water/cement ratio, aggregate/cement ratio, aggregate maximum size and grading defined in terms of mean particle size, and the strength, elastic modulus and crushing value (B.S. 812) of the coarse aggregate. Tensile and compressive strength, tensile strain at failure and compressive strain at 50 % compressive strength are related to each parameter in turn, often by expressing the values in relative terms. The results obtained from 94 mixes are used to develop charts which permit reasonably accurate prediction of any of the four properties listed above for a wide range of mixes.

Evaluation of factors affecting the tensile properties of lime-treated materials

Abstract: THE INDIRECT TENSILE TEST WAS USED TO STUDY THE TENSILE PROPERTIES OF LIME-TREATED MATERIALS. ONLY FACTORS INDICATED TO BE IMPORTANT BY A LITERATURE REVIEW (COMPACTIVE EFFORT, COMPACTION TYPE, CURING PROCEDURE, LIME CONTENT, CURING TEMPERATURE, CURING TIME, MOISTURE CONTENT, AND CLAY CONTENT) WERE INCLUDED IN A FRACTIONAL FACTORIAL EXPERIMENT CONSISTING OF THREE EXPERIMENTAL BLOCKS. AN ANALYSIS OF VARIANCE WAS RUN FOR INDIRECT TENSILE STRENGTH TO DETERMINE THOSE FACTORS AND THEIR INTERACTIONS WHICH SIGNIFICANTLY AFFECTED STRENGTH AT PROBABILITY LEVELS OF 0.05 OR LOWER. THOSE EFFECTS AND INTERACTIONS WHICH WERE FELT TO BE SIGNIFICANT IN PRACTICAL APPLICATION OF THE RESULTS ARE PRESENTED IN GRAPHS AND DISCUSSED. IN ADDITION, ALL OF THE DATA FROM THE THREE EXPERIMENTAL BLOCKS WERE POOLED FOR A LARGE REGRESSION WHICH PRODUCED A PREDICTIVE EQUATION FOR INDIRECT TENSILE STRENGTH IN TERMS OF THE SIGNIFICANT FACTORS AND INTERAC- TION. THIS EQUATION CAN BE USED TO ESTIMATE THE TENSILE STRENGTH OF LIME TREATED MATERIALS AND TO AID IN THE DESIGN OF LIME TREATED MIXTURES

The tensile creep behaviour of cold-drawn low-density polyethylene

Abstract: Sheets of highly anisotropic low-density polyethylene possessing transverse symmetry were prepared by the simple tensile drawing at room temperature of initially isotropic sheets. Classical elasticity theory shows that five constants are necessary to characterize the deformation behaviour of a linear elastic material possessing such symmetry. The time-dependent equivalents of these constants were determined from the simultaneous measurement of longitudinal and lateral strain during tensile creep of specimens cut at 0°, 45° and 90° to the draw direction. Creep measurements were also made on specimens cut at intermediate angles from the drawn sheets and on specimens cut at various angles from the isotropic sheets. A wide range of tensile creep strains, from 0·1% upwards, was used for all specimens to enable the extent of linear behaviour to be examined. For the oriented material, the tensile strain at the onset of non-linear behaviour varied systematically with angle, being lower than 0·2% for the 90° specimen. The isotropic material exhibited non-linear behaviour down to at least 0·1% tensile strain. At low strains it is found that the formalism of classical elasticity theory holds if isochronous creep data are used, and the extension and contraction results are combined to calculate volume changes occurring during tensile creep. It is shown that at angles away from 0° and 90° the deformation behaviour of the oriented material is dominated by an easy-shear mechanism, parallel to the oriented chains, for a wide range of tensile strains.

Comments on the long-term tensile strength of plain concrete

Abstract: Synopsis The variation of the tensile strength of concrete with age, and the relationship between the compressive and the tensile strength during the period of hardening, are investigated. Some fac...

Optimization of Abs 3D-Printing Method and Parameters

Abstract: The paper presents research on the method of 3D-printing ABS (Acrylonitrile butadiene styrene). Series of specimens were 3D-printed in FDM (Fused Deposition Modelling) technology with variable parameters. The influence of the following parameters has been checked: temperature of printing and infill density. Moreover, the material properties of raw, unprocessed ABS have been inspected. The tensile strength of specimens and Young’s modulus have been determined in a static tensile test. Tests were carried out in compliance with the ASTM D638-14 standard. Obtained results were then compared with the material datasheet. Optimum printing method has been defined. The carried out research resulted in optimizing the printing method for ABS vehicle parts applied in Silesian Greenpower electric car. The car has been developed by students of The Silesian University of Technology in Gliwice, Poland as an interfaculty students’ project. Results of the tensile test research have been analysed and discussed and conclusions have been presented in the following article.

Effect of tensile strain on the use of the WLF equation

Abstract: The effect of finite elongation on superposed infinitesimal torsional oscillations has been determined on two propellants, a carbon black-filled rubber and Solithane 113 (Galcit I), as a function of temperature at various fixed frequencies. Torsional storage modulus—temperature data for carbon black-filled rubber and propellant show that the effect of the imposed tensile elongation cannot be explained by any simple temperature–elongation shift relationship. The shift factors for the torsional moduli of these two polymeric systems have been calculated as a function of temperature at various tensile elongations. The WLF constants C1 and C2 have been computed for these systems as a function of the elongation. The constants decrease with increasing elongation. The values of the constants at 0% elongation are larger than those commonly found in unfilled materials. The temperature dependence of the shift factor of the torsional storage modulus was found to differ from that of the loss modulus in the cases of carbon black-filled rubber and propellant. This difference is slight for the rubber and large for the propellant. The effect of increased elongation is to increase the difference in the shift behavior of the moduli for each of these filled polymers. The shape of the loss tangent curve of the propellants examined indicates that these propellants are not thermorheologically simple.

A Tensile Test Method for Fibers

Abstract: Considerable confusion exists in the reported tensile properties of fibers as there has been a lack of differentiation between single-filament data and fiber strand data as well as inadequate test methods and specimen preparation procedures. Until recently fiber tensile strength has been based on testing single filaments, but most fibers are produced and used in strand form. It is a known fact

A new approach to the prediction of low-cycle fatigue data

Abstract: Low-cycle fatigue data for annealed AISI Type 304, 316, and 348 stainless steel to 816°C have been analyzed and a new relationship has been identified associating fatigue data with shortterm tensile behavior. A logarithmic plot of plastic strain range vs time to fracture was shown to be linear with a slope of minus unity. This line was also found to originate at the point corresponding to the tensile ductility. A similar analysis for elastic strain range data revealed a relationship with the strain-hardening exponent measured in a short-term tensile test at the same temperature and strain rate. These correlations have been combined to provide an equation for predicting the relationship between total strain range and cycles to fracture. This approach has been termed the Method of Characteristic Slopes.

Evaluation and prediction of tensile properties of cement-treated materials

Abstract: THIS REPORT DESCRIBES THE CONTINUATION OF AN INVESTIGATION OF THE INDIRECT TENSILE PROPERTIES OF CEMENT TREATED MATERIALS AND WAS ACCOMPLISHED WITH A STATISTICALLY DESIGNED EXPERIMENT. THE SIX FACTORS INVESTIGATED WERE MOLDING WATER CONTENT, AGGREGATE GRADATION, CURING TEMPERATURE, COMPACTIVE EFFORT, CEMENT, AND AGGREGATE TYPE. THE INDIRECT TENSILE STRENGTHS, VERTICAL FAILURE DEFORMATIONS, AND HORIZONTAL FAILURE DEFORMATIONS WERE THE PARAMETERS MEASURED. MAIN EFFECTS, INTERACTION EFFECTS, AND CURVILINEAR EFFECTS ON INDIRECT TENSILE STRENGTH HAVE BEEN SUMMARIZED. IN ADDITION, THROUGH REGRESSION ANALYSIS, A PREDICTIVE EQUATION FOR INDIRECT TENSILE STRENGTHS WAS DEVELOPED FOR THE SIX FACTORS EVALUATED. TWO ADDITIONAL EXPERIMENTS WERE PERFORMED IN AN ATTEMPT TO DEVELOP CORRELATION EQUATIONS RELATING INDIRECT TENSILE STRENGTHS WITH THE UNCONFINED COMPRESSION STRENGTHS AND THE COHESIOMETER VALUES FOR CEMENT-TREATED MATERIALS. ONE COMPARED THE INDIRECT TENSILE STRENGTHS WITH THE UNCONFINED COMPRESSIVE STRENGTHS AND COHESIOMETER VALUES OF CEMENT-TREATED MATERIALS COMPACTED AND CURED IN A MANNER OTHER THAN THAT UTILIZED BY THE TEXAS HIGHWAY DEPARTMENT. THE OTHER MADE USE OF TEXAS HIGHWAY DEPARTMENT PROCEDURES. THROUGH REGRESSION ANALYSES, PREDICTION EQUATIONS WERE DEVELOPED FROM BOTH EXPERIMENTS. A THIRD EXPERIMENT INDICATED THAT SPECIMEN SIZE HAD NO EFFECT ON INDIRECT TENSILE STRENGTH. /AUTHOR/

Density measurements after tensile and creep tests on pure and slightly oxidised aluminium

Abstract: In order to investigate the influence of dispersed oxide particles on crack-formation in Al-Al2O3 alloys, series of tensile tests (20 to 550† C) and creep tests (450† C) were carried out on pure Al and on Al-0.7wt% Al2O3 specimens. Density measurements performed on broken samples showed no changes in pure Al but considerable decreases in the slightly oxidised Al. The observed influence of oxide is strong for the small percentage if compared with the behaviour of Al-Al2O3 alloys with much higher oxide contents.

Evaluation and prediction of the tensile properties of lime-treated materials

Abstract: THIS STUDY WAS DIVIDED INTO FOUR PHASES. EACH PHASE CONSISTED OF A STATISTICALLY DESIGNED EXPERIMENT. AN EXPERIMENT WAS CONDUCTED TO EVALUATE THE EFFECTS OF FIVE FACTORS ON THE TENSILE PROPERTIES OF LIME-TREATED MATERIALS. THE FACTORS INVESTIGATED WERE COMPACTIVE EFFORT, LIME CONTENT, CLAY CONTENT, MOLDING WATER CONTENT, AND CURING TEMPERATURE. THE INDIRECT TENSILE STRENGTH, VERTICAL FAILURE DEFORMATION, AND HORIZONTAL FAILURE DEFORMATION WERE THE PARAMETERS EVALUATED IN THIS EXPERIMENT. TABLES OF ALL MAIN FACTORS, INTERACTIONS, AND CURVILINEAR EFFECTS SIGNIFICANT AT ALPHA LEVELS AT 1 AND 5 PERCENT ARE SHOWN FOR EACH PARAMETER. THOSE WHICH HAD A SIGNIFICANT EFFECT ON INDIRECT TENSILE STRENGTH ARE DISCUSSED IN THIS REPORT. THROUGH REGRESSION ANALYSIS, AN EQUATION FOR INDIRECT TENSILE STRENGTH WAS DEVELOPED IN TERMS OF THE FIVE FACTORS STUDIED. TWO EXPERIMENTS WERE CONDUCTED TO CORRELATE THE INDIRECT TENSILE TEST WITH THE UNCONFINED COMPRESSION TEST AND THE COHESIOMETER TEST FOR LIME-TREATED MATERIALS. IN ONE OF THE CORRELATION EXPERIMENTS THE SPECIMENS WERE CURED ACCORDING TO PROCEDURES ESTABLISHED AT THE CENTER FOR HIGHWAY RESEARCH. IN THE OTHER CORRELATION EXPERIMENT THE SPECIMENS WERE CURED ACCORDING TO STANDARD TEXAS HIGHWAY DEPARTMENT PROCEDURES. THROUGH REGRESSION ANALYSIS, EQUATIONS FOR INDIRECT TENSILE STRENGTH IN TERMS OF UNCONFINED COMPRESSIVE STRENGTH AND/OR COHESIOMETER VALUE WERE DEVELOPED. THE FOURTH PHASE OF THIS STUDY CONSISTED OF AN EXPERIMENT IN WHICH IT WAS FOUND THAT SPECIMEN SIZE DID NOT HAVE A SIGNIFICANT EFFECT ON THE INDIRECT TENSILE STRENGTH OF LIME-TREATED MATERIALS. /AUTHOR/

Prediction of failure time for some adhesive-bonded joints

Abstract: Data are given for shear and tensile testing of adhesive bonds under conditions of a constant rate of loading. A rate equation is then used to predict lifetime from the mechanical data. The correlations appear to be satisfactory providing that the failure is cohesive within the adhesive.