Showing papers on "Tensile testing published in 1968"

Tensile failure of fiber composites.

Abstract: Composite tensile-failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects

Rapid Stress-Induced Crystallization in Natural Rubber

Abstract: Stress-induced crystallization in a rapidly stretched natural rubber gum vulcanizate has been studied using thermal techniques to follow the development of crystallinity. A special-purpose analog computer has been assembled and used online to process the thermal and mechanical data obtained in high speed tensile testing. Roughly first-order room temperature crystallization kinetics curves were obtained having time constants of 50–60 msec in the range of 400–540% extension. While the rate of this rapid, presumably primary crystallization appears rather insensitive to elongation in this limited range, the extent of crystallization at 400 msec increases smoothly from zero at 340% elongation to around 18% at 540% elongation. It is shown that our high-speed tensile tester can stretch this vulcanizate fast enough that most of the crystallization takes place after extension has been completed. Stress—strain curves obtained at this high rate are compared with those obtained at lower rates where crystalli...

A study of the tensile strength of short fiber reinforced plastics

Abstract: An experimental study of the tensile strength of unidirectional short fiber reinforced plastics is reported. The data indicate agreement with existing theories as modified to suit plastics. The theory is extrapolated to provide a means for computing the strength of a random composite.

Determining bond strength in fibre-reinforced composites

Abstract: Summary A pull-out technique suitable for determining the interfacial bond strength for various combinations of fibres and matrix is described. In this method, a thick fibre, 0·5 to 1·0 mm in diameter, is embedded perpendicularly through a matrix material contained in a special mould and is stressed on a tensile testing machine. The value of the maximum bond load corresponds to a sharp break in the load-extension curve. Results show that the bond strength between E-glass-fibre and cement is of the same order as that between steel and cement but higher than the values reported for asbestos and cement. The work has also shown that the strength of the bond between E-glass-fibre and gypsum plaster is of similar magnitude, but that it is affected significantly by variations in water/plaster ratio.

Tensile behavior and failure characteristics of asphalt cements in thin films

Abstract: THE REPORTED STUDY WAS CONDUCTED TO EXTEND THE KNOWLEDGE OF THE BEHAVIOR OF ASPHALT CEMENT IN THIN FILM SUBJECTED TO TENSILE STRESSES. THE TENSILE BEHAVIOR AND FAILURE CHARACTERISTICS OF 11 ASPHALT CEMENTS IN THIN FILMS WERE STUDIED. VARIABLES IN THE STUDY INCLUDED: (1) FILM THICKNESS, (2) RATE OF DEFORMATION, (3) TEMPERATURE, (4) CONSISTENCY, AND (5) SOURCE OF THE BITUMINOUS MATERIAL. A DEFINITE RELATIONSHIP WAS FOUND TO EXIST BETWEEN THE TENSILE PROPERTIES OF A GIVEN ASPHALT CEMENT AND THE FILM THICKNESS OF THE SPECIMEN. THE TENSILE STRENGTH OF ASPHALT CEMENTS IN THIN FILMS IS SIGNIFICANTLY INFLUENCED BY THE TEST RATE OF DEFORMATION AND/OR THE TEST TEMPERATURE. THE CONSISTENCY OF THE ASPHALT CEMENT HAS A SIGNIFICANT INFLUENCE ON TENSILE STRENGTH. THE SOURCE OF THE ASPHALT CEMENT MAY INFLUENCE THE TENSILE STRENGTH OF THE MATERIALS. IT APPEARS THAT THE ASPHALTENE CONTENT OF ASPHALT CEMENTS OBTAINED FROM A GIVEN SOURCE MAY HAVE A SIGNIFICANT INFLUENCE ON THE CONSISTENCY OF THE MATERIALS AND THUS, ON THE TENSILE STRENGTH. THREE MODES OF FAILURES WERE OBSERVED IN THE ASPHALT SPECIMENS. THE RANGE OF FILM THICKNESS EXHIBITING EACH FAILURE MODE WAS DEPENDENT UPON SPECIFIC COMBINATIONS OF: (1) ASPHALT SOURCE AND CONSISTENCY, (2) RATE OF DEFORMATION, AND (3) TEMPERATURE. THE OBSERVED MODES OF FAILURE WERE REFERRED TO AS: BRITTLE FRACTURE, FLOW FAILURE AND INTERMEDIATE FAILURE OR TENSILE RUPTURE. SPECIMENS WHICH EXHIBITED THE BRITTLE MODE HAD FAILURE SURFACES WHICH WERE SMOOTH AND GLASSY IN APPEARANCE. SPECIMENS WHICH EXHIBITED FLOW FAILURE USUALLY EXHIBITED A FAILURE SURFACE FORMED BY EXCESSIVE NECKING AND INTERNAL FLOW OF THE SPECIMEN. THE INTERMEDIATE MODE FAILURE SURFACE EXHIBITED A COMBINATION OF MULTIPLE DEPRESSIONS AND MULTIPLE RIDGES. THE LIMIT OF BRITTLE FRACTURE AND THE LIMIT OF FLOW FAILURE ARE: FUNCTION OF TEMPERATURE, RATE OF DEFORMATION, AND ASPHALT CONSISTENCY. THE TYPE OF FAILURE THAT OCCURS IN THIN FILMS OF BITUMINOUS MATERIAL SUBJECTED TO TENSILE STRESSES CAN GENERALLY BE CLASSIFIED AS A COHESIVE FAILURE RATHER THAN AN ADHESIVE FAILURE. A CONSTANT RATE OF LOADING TEST APPEARS TO BE A MORE DESIRABLE TEST METHOD THAN A CONSTANT RATE OF DEFORMATION TEST FOR DETERMINING ASPHALT CEMENT BEHAVIOR CHARACTERISTICS. BITUMINOUS MATERIALS IN THIN FILMS WHEN SUBJECTED TO TENSILE STRESSES EXHIBIT A CAVITATION PHENOMENA AND THE VOLUME OF THE SPECIMEN APPEARS TO INCREASE. THE AMOUNT OF DEFORMATION TO FAILURE APPEARS TO BE PARTIALLY DEPENDENT UPON FILM THICKNESS.

Tensile Strength of Granular Materials

Abstract: IN several communications1–4 on the tensile strength of granular materials bound by liquids, authors have tried to confirm or improve the equation of Rumpf5. At the Institute of Mechanical Process Engineering of the University of Karlsruhe, where the first measurements of the tensile strength of moist agglomerates started in 1957, investigations have recently led to a complete theoretical and experimental description of the tensile strength relationship in the whole moisture range.

Application of the indirect tensile test to stabilized materials

Abstract: THE IMPORTANCE OF THE TENSILE CHARACTERISTICS OF THE SUBBASE OF RIGID PAVEMENTS CAN BE DEMONSTRATED BOTH FROM THEORETICAL CONSIDERATIONS AND FROM FIELD OBSERVATIONS INFORMATION ON THE TENSILE BEHAVIOR AND PROPERTIES OF TREATED AND UNTREATED SUBBASE MATERIAL IS LIMITED PRIMARILY BECAUSE OF THE LACK OF A SATISFACTORY TENSILE TEST ON THE BASIS OF A LITERATURE REVIEW CONCERNED WITH TENSILE TESTING, IT WAS CONCLUDED THAT OF THE CURRENTLY AVAILABLE TENSILE TESTS THE DIRECT TENSILE TEST HAS THE GREATEST POTENTIAL FOR THE EVALUATION OF THE TENSILE PROPERTIES OF HIGHWAY MATERIALS THIS PAPER DISCUSSES TENSILE TESTING, THEORY OF THE INDIRECT TENSILE TEST, AND FACTORS AFFECTING THE TEST IN ADDITION, THE RESULTS OF A LIMITED TESTING PROGRAM TO EVALUATE THE EFFECT OF SUCH FACTORS AS COMPOSITION AND WIDTH OF LOADING STRIP, TESTING TEMPERATURE, AND LOADING RATE ON THE INDIRECT TENSILE TEST PARAMETERS OF STRENGTH, VERTICAL FAILURE DEFORMATION, AND A LOAD VERTICAL FAILURE DEFORMATION MODULUS FOR ASPHALT-STABILIZED AND CEMENT-TREATED MATERIALS ARE INCLUDED ON THE BASIS OF THE LITERATURE REVIEW AND EXPERIMENTAL INVESTIGATION, IT IS RECOMMENDED THAT THE INDIRECT TENSILE TEST BE USED FOR EVALUATING THE TENSILE PROPERTIES OF STABILIZED MATERIALS AND THAT THE TEST BE CONDUCTED UTILIZING A 10-IN WIDE STAINLESS STEEL LOADING STRIP, A LOADING RATE OF 2 IN/MIN, AND A TESTING TEMPERATURE OF 77F /AUTHOR/

Tensile failure analysis of fibrous composites.

Abstract: Composite tensile failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects

Tensile Deformation of Oriented Polyethylene

Abstract: Tensile test specimens have been cut from high‐density polyethylene sheet which had been fully cold‐drawn. The angle between the tensile axis and the draw direction was varied from 30° to 75°. The tensile deformation of such specimens was analyzed with the aid of a grid printing technique and was shown to be predominantly simple shear in the molecular chain direction. However, detailed analysis has shown that associated with the simple shear process there was a reorientation of the material, which is compared with the predictions of an aggregate theory for oriented polyethylene. A yield criterion and the absence of any work hardening for large deformations have been established.

A direct tensile test for concrete under long- or short-term loading

Abstract: Summary This paper describes details of a method of testing concrete in uniaxial tension. This method was devised to suit the requirements of a research programme started in 1965 to study the tensile creep andfailure of concrete. Details of the p.v.c. moulds for the manufacture of the specimens are given and a description of the arrangements for loading the specimens includes details of end attachments and a frame in which up to 30 specimens can be loaded in tension simultaneously. Typical experimental results of strain behaviour and strength are presented to indicate the performance of the method in the laboratory.

Tensile strength and failure mechanics of fibre composites

Abstract: This paper is concerned with the prediction of the tensile strengths of fibre composites where the fibres are aligned in the direction of tensile loads, and are flawed to some extent. A theory is derived for predicting the strengths and failure mechanisms of such composites. The theory agrees reasonably well with experiments, and may be qualitatively applicable to composites containing randomly aligned fibres.

Size Effects on Static Tensile Properties of Welded Joints including Soft Interlayer

Abstract: In the welded joint, chemical composition and structure of weld metal or heat-affected zone which is adjacent to it are different from those of parent metal. Hence, the mechanical properties, for example stress-strain relation, of the welded joints must also be different from those of parent metal and change continuously. In this way, considering macroscopically, the welded joints are not homogeneous nor isotropic. Concerning such welded joints which are heterogeneous, it matters a great deal to investigate their strength and ductility. The welded joints are fundamentally idealized as models which are joints consisting solely of parent metal and a soft or hard interlayer. By "soft interlayer" is meant apart of welded joint in which yield point is lower than that of parent metal.In the present report, such model specimens were made by flash butt welding. The parent metal was grade S35C, the soft interlayer grade S10C. The specimens were given post-weld heat treatment (850°C×10 min. water quenching and 500°C×30 min. tempering) to cause an abrupt change of the mechanical properties between parent metals and soft interlayer. Static tensile test was made for four kinds of specimen diameter, 3, 6, 10 and 15 mm, at room temperature.In the joints including a soft interlayer under tension, plastic flow will begin at first in the parts of a soft interlayer. The transverse plastic flow of interlayer at the contact surfaces and the neighbouring zone will be held in check by the stronger parent metal, and the interlayer will be in a triaxial stress state analogous to that in the neck of tension specimen. The triaxiality will be severe with a decrease in the thickness of soft interlayer. The ultimate tensile strength of the joints exceeds that of the material of interlayer, if the values of thickness of interlayer are sufficiently low. The present paper describes theoretical and experimental investigations on the effect of thickness of a soft interlayer or specimen diameter on mechanical properties of welded specimens under static tension. The results obtained are as follows.(1) The yeild stress, ultimate tensile strength, plastic constraint factor and reduction in area of the welded joint including a soft interlayer are represented as functions of the relative thickness X, or the ratio of thickness of soft interlayer to specimen diameter, regardless of the specimen diameter.(2) The yield stress and ultimate tensile strength increase and the elongation and reduction in area decrease as the relative thickness decreases. Fracture mode becomes brittle for a sufficiently small value of X, although the material of interlayer possesses high ductility under unidirectional tension at room temperature.(3) The test results on ultimate tensile strength agree with the results of the authors' theoretical analysis for a comparatively large value of X.

A Magnetostrictive Load Cell for Use under High Hydrostatic Pressures

Abstract: A load cell utilizing magnetostrictive strain gauges which is suitable for measuring loads up to 300 kg in tensile testing of materials under high hydrostatic pressures up to 15000 kg/cm2 is described. Temperature and pressure variations during tensile testing can be completely compensated by the use of a dummy gauge. The calibration of the load cell under pressure is performed by a coil spring which is calibrated at atmospheric pressure. The calibration curves under pressures up to 13400 kg/cm2 and 200 kg agree with the atmospheric calibration curve within 2%.

A hydrostatic tension test of a brittle material

Abstract: Thes report describes the development of a new method for testing materials in hydrostatic tension using a spherical specimen of the test material bonded into the center of a cube of matrix material which has tensile loads applied to the faces of the cube. The materials are chosen such that failure first occurs in the test material, in which the stress can be estimated by elastic theory. Failure is detected from edge displacements of the cube face. While the results for brittle dental plaster have been inconclusive to date, further development of the technique appears promising.

Determination of stress strain properties of metallic substances

Abstract: A PROCESS AND APPARATUS FOR THE RAPID DETERMINATION OF TENSILE PROPERTIES OF METAL SPECIMENTS, MORE PARTICULARLY STEEL SPECIMENS IN WHICH A TEST SPECIMENT OF THE METAL IN QUESTION IS PLACED UNDER TENSILE TEST, IN WHICH APPROPRIATE DETECTORS ARE EMPLOYED TO ESTABLISH THE VALUES OF SPECIFIC FACTORS OF THE SAID TENSILE TEST INCLUDING THE ELONGATION OF THE MEASURING BASE, THE LOAD, THE VARIATION IN THE WIDTH OF THE SAID MEASURING BASE, THESE DATA BEING TRANSMITTED TO A SET OF ELECTRONIC MODULES BUILT UP FROM ELEMENTS FOR ANALOGICAL CALCULATION, THE SIGNALS DELIVERED BY THE SAID SET BEING TRANSMITTED TO DEVICES SUCH AS RECORDERS OR THE LIKE, BY MEANS OF WHICH THE VALUES OF THE CHARACTERISTICS SOUGHT MAY BE OBTAINED. THE APPARATUS SPECIFICALLY COMPRISES A TENSILE TEST MACHINE IN WHICH IS COMPRISED, ON THE ONE HAND, A TENSILE TEST MACHINE EQUIPPED WITH DETECTORS OF LOAD, ELONGATION AND VARIATION IN THE WIDTH OF THE MEASURING BASE OF THE TEST SPECIMEN UNDERGOING A TENSILE TEST, THE DETECTORS OF ELONGATION AND OF VARIATION IN WIDTH BEING INTENDED IN PARTICULAR TO ALLOW OF SIMULTANEOUS MEASUREMENT OF THE ELONGATION AND OF THE VARIATION IN WIDTH OR OF MEASUREMENT OF THE VARIATION IN WIDTH CORRESPONDING TO A SPECIFIC ELONGATION OF THE SAID MEASURING BASE FOR CALCULATION OF THE COEFFICIENT R OF NORMAL ANISOTROPY, AND AN ASSEMBLY OF ELECTRONIC MODULES PREFERABLY BUILT UP FROM ELEMENTS FOR ANALOGICAL CALCULATION, THIS ASSEMBLY BEING CONNECTED TO THE DETECTORS OF THE SAID TENSILE TEST MACHINE AND BEING INTENDED TO EVALUATE THE SIGNALS RECEIVED FROM THE SAID DETECTORS.

Biaxial Tensile Tester for Flat Plates

Abstract: A new type of biaxial tensile tester for flat plates has been produced, which can make uniform extention of a square plate in biaxial directions. The tensile mechanism of this tester consists of two servomechanism for the control of the position of the two travelling beams on which cramp chacks are mounted. These chacks are capable of easy travelling on the beam surface by means of ball bearings. By the use of this tester it is made possible to perform such testing as tensile testing, stress relaxation measurement, creep testing and fracture strength testing, under homogeneous biaxial stress states.In this paper the mechanism of this tester is described, and the results of elastic property measurements of BR, SBR, and IR rubber sheets using this tester are reported. The load-elongation diagrams are obtained by this tester and energy function are calculated from it as a function of invarients I1, I2 of deformation tensor.

Design and evaluation of asphalt concrete with respect to thermal cracking

Abstract: THERMALLY INDUCED CRACKING OF ASPHALT PAVEMENTS INVOLVES TENSILE STRESSES, THEREFORE, A SUITABLE TEST METHOD SHOULD NECESSARILY UTILIZE THESE STRESSES. A REVIEW OF THE LITERATURE REVEALS A VARIETY OF METHODS AVAILABLE FOR THE TENSION TESTING OF ASPHALT CONCRETE AND PLAIN ASPHALT BITUMENS. IN VIEW OF ITS ACCEPTANCE AS A TEST METHOD FOR CONCRETE CYLINDERS, THE TENSILE SPLITTING TEST WAS INVESTIGATED AS A POSSIBLE APPROACH TO EVALUATING THE TENSILE STRESS-STRAIN CHARACTERISTICS OF ASPHALT CONCRETE AT LOW TEMPERATURES. A METHOD OF CONDUCTING THE TENSILE SPLITTING TESTS ON ASPHALT CONCRETE SPECIMENS WAS DEVELOPED WHICH IS CONSIDERED SUFFICIENTLY PRACTICAL TO BE USED AS A ROUTINE TEST. PREVIOUS CONCLUSIONS REGARDING THE EFFECTIVE ASPHALT CEMENT SUPPLY ON THE TENSILE PROPERTIES OF A GIVEN MIX AND ON THE OCCURRENCE OF CRACKING, HAVE BEEN SUBSTANTIATED. THE OCCURRENCE OF CRACKING WAS FOUND TO INCREASE AS THE FAILURE STRAIN DECREASED. FAILURE STRAIN IS CONSIDERED TO BE MOST SIGNIFICANT PARAMETER RESULTING FROM THE TENSILE SPLITTING TEST. FAILURE STRAIN APPEARS TO BE A FUNCTION OF THE ASPHALT CEMENT SUPPLY WHEN THE SAME AGGREGATE AND GRADE OF ASPHALT CEMENT IS USED. THERE ARE SOME INDICATIONS OF MIXES WHICH HAVE HIGH MARSHALL STABILITY VALUES AT 140 F, HAVE LOW FAILURE STRAINS AT 0 F. THE TENSILE SPLITTING TEST METHOD DEVELOPED IS CONSIDERED TO BE VALID AND WARRANTS INCLUSION IN A DESIGN METHOD FOR ASPHALT CONCRETE USED IN COLDER CLIMATES.

Helium embrittlement of type 316 stainless steel.

Abstract: : Helium was injected into small tensile samples of Type 316 stainless steel by alpha-particle irradiation from a cyclotron. Subsequent tensile testing in the temperature range 540 to 815 deg C revealed a loss of ductility, as measured by elongation at failure. The lowest temperature at which a ductility loss was manifest depended upon the microstructure of the samples. A fine dispersion of sigma particles within the matrix was capable of raising this temperature by retarding the accumulation of helium at grain boundaries. Reduced ductility was always accompanied by partial or complete intergranular failure and the presence of intergranular cracks. These cracks originated as small voids adjacent to grain-boundary carbide particles, presumably through the action of grain-boundary sliding. Large helium bubbles found attached to carbide particles are responsible for the relative ease of void formation, as compared to samples without helium.

Cracking of Reinforced Concrete Under External Load

Abstract: RECENT STUDIES OF CRACKING BY BROMS HAVE INDICATED THE PRESENCE OF INTERNAL CRACKS THAT ARE NOT VISIBLE ON THE SURFACE. THE COMPATIBILITY OF THIS PHENOMENA WITH THREE POSSIBLE CRACK MECHANISMS IS DISCUSSED. THE "CLASSICAL" MECHANISM WAS DEVELOPED FROM OBSERVATIONS OF SURFACE CRACKS. THE MECHANISM IS BASED ON THE ASSUMPTIONS THAT BOND STRESSES AT THE CONCRETE-REINFORCEMENT INTERFACE DEVELOP TENSILE STRESSES IN THE CONCRETE; TENSILE STRESSES ARE UNIFORMLY DISTRIBUTED OVER THE CONCRETE SECTIONS, AND A CRITICAL CONCRETE SECTION FAILS WHEN THE AVERAGE TENSILE STRESS EXCEEDS THE TENSILE STRENGTH. THESE ASSUMPTIONS ARE NOT COMPATIBLE WITH INTERNAL CRACKING, WHICH INDICATES A VARYING CONCRETE TENSILE STRESS. BROMS PROPOSED A CRACK MECHANISM BASED ON AN ELASTICITY STRESS ANALYSIS THAT INDICATED THAT BOND FORCES INDUCED LARGE TENSILE STRESSES NEAR THE REINFORCEMENT BUT LOWER TENSILE STRESSES NEAR THE SURFACE. CRACKS INITIATE NEAR THE REINFORCEMENT WHEN THE LOCAL STRESS EXCEEDS THE TENSILE STRENGTH. THE CRACK GROWS TOWARD THE SURFACE AND MAY BE ARRESTED WHEN THE REGION OF LOWER INITIAL TENSILE STRESSERS IS REACHED. ACTUALLY THE CRACK ALTERS THE INITIAL STRESS FIELD, AND THE CRACK TIP NEVER REACHES A REGION OF LOW TENSILE STRESS IF THE CONCRETE CARRIES A GIVEN BOND FORCE. A THIRD MECHANISM IS PROPOSED THAT IS BASED ON COMPATIBILITY OF CONCRETE AND REINFORCEMENT DISPLACEMENTS. CRACKS INITIATE IN THE REGION OF HIGH TENSILE STRESS NEAR THE REINFORCEMENT AND GROW TOWARD THE SURFACE. THE CONCRETE SECTION BECOMES MORE FLEXIBLE AS THE CRACK PROPAGATES. BOND AND TENSILE STRESSES REDUCE UNTIL THE CRACK BECOMES STABLE AND IS ARRESTED. THIS MECHANISM IS DISCUSSED IN TERMS OF FRACTURE MECHANICS. /ACIJP/

Apparatus for Mechanical Testing of Soft Crystals at High Pressure

Abstract: Apparatus which has sufficient sensitivity for the tensile testing of soft single crystals at pressure levels to approximately 30 kilobars is described. This equipment makes use of a tensile yoke and a load cell based on a linear variable differential transformer within the high pressure fluid. Strain is measured externally by monitoring the movement of the loading piston with a linear variable differential transformer and the load‐displacement relationship is displayed on an X‐Y recorder. Discussion of the calibration procedure and performance of the apparatus is included.

Some properties of iron, copper, and selected aluminum alloys including true stress-true strain at reduced temperatures

Abstract: : The metallurgical and mechanical properties of several face centered cubic materials (1100 Al, 7075-0 Al, 7075-T6 Al, OFHC Cu) and a body centered cubic material (Armco iron) were examined. Prior to undergoing tensile testing the materials were insured to have a nonoriented equiaxed grain structure and underween chemical analysis and hardness tests. The materials were then tensile tested at 296K in the atmosphere, at 77K in a liquid nitrogen bath, and at 4K in liquid helium. A continuous record of the axial load and of two perpendicular specimen profile traces produced a measurement of specimen true stress-true strain. Engineering stress-strain, elongation, and reduction in area were also calculated.