Load-elongation Diagram Research Articles

Deformation steel rods periodic profile with operational damages

Introduction. In the transverse and longitudinal sections of the rods with a periodic profile, there are layers with different structural and phase states, physical and mechanical characteristics, stress state and resistance to external influences. The appearance of plastic deformations in the bases of the depressions and other defects of a periodic profile during stre­tching of the rods leads to a decrease in the resistance to corrosion damage due to the occurrence of galvanic pairs between inhomogeneous sections of the rod. This makes the computational and experimental studies of the deformed state of such rods under tension urgent.
 
 Materials and methods. The finite element modeling of the deformation process during the elastic-plastic work of steel was carried out using the ANSYS software complex and solid models of the rods under study. Experimental tests of the samples were carried out using an R-50 tensile testing machine with the recording of a load-elongation diagram in accordance with the requirements of GOST 1497. The process of deformation of the samples was displayed by photographic recording. After the destruction of the samples, the geometric dimensions (lengths, changes in cross-sections) were measured, the typical types of samples and their fragments, and fractures were photographed.
 
 Results. On experimental and finite-element models, it was found that during elastic-plastic deformation of steel rods in dangerous sections, a change in the angle of inclination of the banks of periodic protrusions (undercuts) affects the volume of plastically deformable material at the base of the undercuts. Such an analysis of the models in the limiting state has shown that the volume of the plastically deformed material is significantly reduced at the angles of the protrusions at their bases with the axis of the rod close to 900. The calculation established that the plastically deformed area at the base of sharp undercuts is more than a hundred times smaller than the corresponding volume at the base of the gently sloping undercuts. In samples with a group of protrusions, constraint of plastic deformations at the base occurs only for protrusions, the width of which is comparable to the diameter of the rod in weakened sections. The greatest development of equivalent plastic deformations is observed at the base between narrow projections. Damage to the outer layers of quasi-composite rods with a periodic profile causes significant changes in the stress-strain state of the rods under tension.
 
 Conclusions. The finite element modeling of the tensile work of steel rods with a periodic profile with a quasi-composite structure is a complex multifactorial problem. Plastic deformations develop in the depressions of the periodic profile. At the same time, undeformed areas remain in the metal of the protrusions. These zones have different potentials and between them the occurrence of internal galvanic currents is possible, leading to the acceleration of corrosion processes.

The Structure of the Strength of Riveted Joints Determined in the Lap Joint Tensile Shear Test

Abstract The article presents the analysis of the structure of the load capacity of riveted joints. For the four joining systems the lap joint specimens were made and tested in the shearing test. The joints were prepared for the three combinations of the DC01 steel and EN AW- 5754 aluminium alloy sheets with the thickness of 2mm. On the basis of the obtained load-elongation diagram tensile shear test curves, the basic parameters defined in the ISO/DIS 12996 standard were determined. In the case of the conventional riveted joints the maximum load capacity of the joint is determined by the strength of the fastener. For the joints with aluminium-steel blind rivet , the load capacity of the joint was on the strength limit of the rivet tubular part and on the strength limit of the sheet material. The strength of the SSPR joint is determined by the mechanical properties of the material of the joined sheets. From all sheets and rivet specimens arrangements the highest load capacity of the joint was obtained for the DC01 sheet material joints, and the lowest load capacity of the joint was obtained for the EN AW-5754 sheet material joints.

Fracture toughness evaluation using miniature specimen test and neural network

Fracture toughness value of in-service materials is predicted in a virtually non-destructive fashion. Standard test methods for predicting the fracture toughness require the removal of large material samples from the in-service component, which is impractical. To overcome this difficulty, artificial neural network model has been employed over the miniature test on currently developed dumb-bell shaped miniature specimen. The model is based on feed-forward neural networks, trained with comprehensive dataset collected from various sources of literature and also from the load–elongation computed from the finite element (FE) simulation. The miniature test load–elongation diagram is given as the input to the neural network model. This model is used for predicting the fracture toughness value of the materials. The results obtained from the present study revealed that neural network model predicted the fracture toughness value close to the standard test value.

An inverse finite element algorithm to identify constitutive properties using dumb-bell miniature specimen

An inverse finite element algorithm is established to extract the tensile constitutive properties such as Young's modulus, yield strength and true stress–true strain diagram of a material in a virtually non-destructive manner. Standard test methods for predicting mechanical properties require the removal of large size material samples from the in-service component, which is impractical. To circumvent this situation, a new dumb-bell shaped miniature specimen has been designed and fabricated which can be used for evaluation of properties for a material or component. Also test fixtures were developed to perform a tension test on this proposed miniature specimen in a testing machine. The studies have been conducted in low carbon steel, die steel and medium carbon steel. The output from the miniature test, namely, load–elongation diagram, is obtained and used for the proposed inverse finite element algorithm to find the material properties. Inverse finite element modelling is carried out using a 2D plane stress analysis. The predicted results are found to be in good agreement with the experimental results.

Tensile testing of ultra fine grained metals

A simple model of neck evolution during tensile testing is suggested. Approximate true stress–true strain diagrams are calculated and analyzed for fine grained and ultra fine grained aluminum alloy Al0.5%Cu. In comparison with ordinary load-elongation diagrams, true diagrams reveal many additional details of the material behavior. Deformation/fracture mechanisms at different tensile stages are discussed.

Fracture Behavior of Woven Composites Containing Various Cracks Geometry

Recently, polymeric composite materials are widely used in automotive applications for reducing structural weight, saving fuel, and improving performance. Accidentalimpact damage is an important issue in the use of these composite materials as body components. The damages or cracks in the present work were represented by notched specimens. The test specimens were fabricated from polyester resin reinforced by woven E-glass fiber. A series of tests were conducted to measure the notched strength of composite laminates with various types of through-the-thickness cracks such as central normal notch (CNN), center inclined notch (CIN), single edge notch (SEN) and double edge notch (DEN). A Modified Point Stress Criterion (MPSC) was proposed for predicting the tensile strength of composite laminates with various aspect ratio (a/w), that is, notch length to specimen width ratio. The results show that the load–elongation diagrams of notched and unnotched glass fiber reinforced polyester (GFRP) specimens have a nonlinear behavior, with clear “Knee”, associated with audible noises. For the same notch length, the notched strength of GFRP specimens with symmetric cracks (CNN, CIN and DEN) is quite consistent. The lowest notched strength is for SEN specimens. An excellent agreement is found between the experimentalresults of centralnotched specimens (CNN and CIN) and the predicted values using the MPSC than the reviewed published theories. The critical stress intensity factor ( KIC) was determined from the centralnotched specimens and used to predict the notched strength of edge notched specimens (SEN and DEN). The type of the central notch (inclined or normal) insignificantly affects the values of the stress intensity factor, KIC.

Mechanical comparative analysis of three different types of sutures in different dimensions tendons: experimental study

The aim of this experimental investigation was study of mechanical profile of three kinds of suture, between tendons with different dimensions. Were utilized 21 mongrel dogs ( 11males, 10 females) of wich were obtained the tendon comum flexor and tendon tibial cranial of both pelvic limbs. After the dissection of the tendons, suture was done, seven animal per group. The tendons utilized allways were from the right limb and from the left limb side utilized as control. After the suture, we performed axial traction tests, rate level of 30mm /min, using special jaws. After the test the machine's program informed the values of ultimate load, elongation and strain, and load elongation diagram. The results were submite to statistical study, that showed no difference between the technics utilized. The values of suture groups were smaller than the control, for ultimate load, and higher for elongation and strain.

Stick-Slip Interface Motion as a Singular Limit of the Viscosity-Capillarity Model

This work is a follow-up on a study by Vainchtein and Rosakis of interface dynamics and hysteresis in materials undergoing solid-solid phase transitions. The author investigates the dynamics of a bar with a nonconvex double-well elastic energy density. The model includes both viscosity and strain-gradient capillarity terms. Viscous stress provides eiergy dissipation. The capillarity term models interfacial energy. The bar is subject to time-dependent displacement boundary conditions. Numerical simulations predict hysteretic behavior in the overall load-elongation diagram. The hysteresis is primarily due to metastability and persists even at very slow loading when viscous dissipation is small. At a given loading, a large capillarity coefficient a results in a smooth interface motion and small hysteresis loop. As a becomes smaller, the loop grows and acquires serrations, while the interface motion alternates between slow and fast regimes. The results suggest that the stick-slip interface motion and serrated hysteresis loop predicted by Vainchtein and Rosakis in the absence of interfacial energy are a singular limit of the viscosity-capillarity model as the capillarity coefficient tends to zero. The irregular interface motion and serrated load-elongation curves qualitatively agree with some experimental observations in shape-memory alloys.

Effect of the temperature on the structure and mechanical properties of poly(ethylene terephthalate) fibres and yarns

The load—elongation diagrams were obtained for PETP yarns and monofilaments at different deformation temperatures, demonstrating the dependence of the σ(e) curves on the testing temperature and the thermomechanical history of the samples. The dependences of the basic strain characteristics determined from the σ(e) curves on the temperature can be used to predict the change in the mechanical properties of PETP yarns and fibres at high temperatures. In addition to the fundamental relaxation transition, the σ(e) curves can be used to find a new transition in the 180°C region which controls the behavior of PETP yarns and fibres above the transition temperature. The thermomechanical tests and structural studies of the fibres at different temperatures allow correlating the transition found with crystallites and assigning it to an αc transition based on the characteristic set of properties.

Elevated Temperature Tensile Strength of thin sheet Phosphor bronzes

Elevated temperature and room temperature tension properties of phosphor bronzes containing 4%, 5%, 6%, 7% and 8% Sn, with thickness of 0.3mm are investigated. Results are as follows;1) Serration appears at 473-573K on Load-Elongation diagrams for elevated temperature tension test. And the relation has nothing to do with Sn content. Serration does not appear in case of room temperature tension test.2) Tensile strength does not depend on Sn content above 623K for elevated temperature tension test. Tensile strength depends on Sn content above 723K for room temperature tension test.3) Reduction of area of Sn 4%, 5% reaches to the minimum at 373K and reaches to the maximum at 750K, and that Sn 7%, 8% reaches to the minimum at 623K and reaches to the maximum at 740K for elevated temperature tension test.Shortness temperature area does appear in case of elevated temperature tension test. Shortness temperature area does not appear in case of room temperature tension test.4) There is an inflection point at around 280MPa, HV180 on the curve of relation between elevated temperature tensile strength and Vickers hardness. This relation seems to be represented by two straight lines, and the relation has nothing to do with Sn content.

ＦＲＰ用ガラス繊維の縦弾性係数の温度依存性

Elastic moduli of glass fiber that is used for reinforcement of FRP are measured in the temperature range from 20 to 300°C.In this experiment, three kinds of glass fiber samples were prepared; E-glass, C-glass and T-glass. Load was placed on a specimen in a transparent furnace controlled at predetermined temperatures. The elongation of specimen was read by a reading microscope and the diameter of specimen was measured by a micrometer. The elastic modulus of glass fiber was calculated by the gradient of load-elongation diagram, the diameter of glass fiber and the distance between the marks on the glass fiber specimen.The results obtained are as follows;(1) The elastic modulus of glass fiber obtained was 60-80GPa at room temperature, and depended on composition and diameter of glass fibers.(2) The elastic modulus of E-glass decreased with increasing temperature, while that of C-glass did not change very much with temperature and that of T-glass increased with temperature.(3) In any case, the elastic moduli of small size fibers were larger than those of large size fibers.

Load Elongation Properties of Filaments in a Multifilament Yarn

This paper describes the technique of finding the distribution of load-at-break and elongation-to-break of filaments in a multifilament yarn from the breaking steps in a load-elongation diagram. There is a correlation between the distribution data and the performance of undrawn nylon 6 yarn on the draw-twisting machine. The dis tribution in the drawn yarn is correlated with that of the undrawn yarn. The effect of spinning speed of the filament yarn on the distribution is brought out using low- speed spun nylon 6 yarn and MOY and POY polyester. The effect of the hot water relaxation process and aqueous dyeing process on the distribution is also studied.

Orientation processes in spinning man-made fibres

The appreciable specific surface of stretched gel-fibres based on semirigid polymers increases their sorptive power, which ensures the possibility of combining fibre strengthening with inclusive fibre modification. The high activity of surfaces of the oriented polymer substrate which have been newly generated during the process of fibre formation predetermines the possibility of effecting rapidly occurring polymer-analogous transformations in making special-purpose fibres. The form of the load-elongation diagrams, which are recorded under isothermal conditions at a constant rate of deformation, depends on the spinning conditions and is determined by all the conditions of supermolecular organization of the polymer substrate. The initial fibre modulus, compliance, and porosity depend on the method and efficiency of orientation stretch of the fibre. The diversity of the regions of application of man-made fibres requires using various effects which are realizable during orientation: strength, relaxation, and sorption activity.

Load-Elongation Properties of Filaments in a Multifilament Yarn

The load-elongation values of individual filaments in a multifilament yarn were studied. The behavior of individual filaments in a bundle is not the same as that of filaments tested individually; therefore, the load-elongation diagram of a multifilament yarn has to be used to arrive at tenacity values of individual filaments in a yam. A technique for obtaining load-elongation values of individual filaments was developed using the breaking steps in a load-elongation diagram of a multifilament yam. Preliminary results are described.

Lattice parameters, stacking fault probability and plastic deformation of lead-thallium single crystals

Lead-Thallium alloys have been investigated in order to try to explain the previously reported “heterogeneous deformation” occurring during tensile deformation at 90°K of lead-50 at. % thallium single crystals. It was believed that either ordering or twinning could be responsible for this phenomenon. So lattice parameters and stacking fault probabilities at 90°K were determined. The lattice parameter vs. composition curve is smooth and does not support the idea of ordering. Tensile tests were performed on crystals of 50 at.% thallium and of other alloy compositions at 90, 200 and 295°K. It has been found that twinning, taking place in the “elastic region” of the load-elongation diagram, probably due partially to a maximum stacking fault probability, accounts for the peculiar deformation mode. However, there still are other factors which may intervene, since alloys on both sides of the above mentioned composition twin only “visibly” after considerable deformation and at much higher stresses, though their stacking fault probabilities are not much lower than for the 50-50 alloys.

Biaxial Tensile Tester for Flat Plates

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.

An Apparatus to Depict the Load-Elongation Diagram of Yarn at Five Cycles per Second

An apparatus is described which presents on a cathode-ray oscilloscope the load-elongation hysteresis diagram, loading and unloading, of a length of yarn. The frequency may be adjusted from 1.7 to 5 cycles per second, the constant minimum load per cycle at any value from several grams to several thousand grams, and the percent extension per cycle from several percent down to several tenths of one percent. The growth of the sample as a function of time is automatically plotted, and, in addition, the stretch modulus of the sample at any time may be determined from the setting of an amplifier dial. As way of illustration of the type of data which may be obtained with this apparatus, there are shown both the absolute and percent energy losses exhibited by tire cords of widely different constructions. For the somewhat arbitrary condition of load increment 2 kilograms over a minimum load of 0.6 kilogram, at a frequency of 5 cycles/second, both the percent and absolute energy losses increase very rapidly with increasing twist in the plies, less rapidly with increasing twist in the cord. Of interest, also, is the extremely high energy losses shown by cords which are made by plying together two plies of originally zero twist, thus giving a cord whose ply and cord twist are approximately the same, and in the same direction. Some other interesting features regarding energy losses in cords are pointed out.

Mechanics of Abrasion of Textile Materials

A method is described for predicting the inherent abrasion resistance of textile materials substantively by the use of load-elongation diagrams of mechanically conditioned specimens. Immediate and delayed deflections are discussed as they affect energy coefficient E. This coefficient is shown to be a function of: ( 1) low modulus of elasticity; (2) large immediate elastic deflection; (3) high ratio of primary to secondary creep; ( 4) high magnitude of pri mary creep; and (5) high rate of primary creep. Nylon shrunk, nylon unshrunk, acetate, and viscose yarns are evaluated on the Taber Abraser, and from rate-of-destruction curves durability coefficients D are obtained. Corre lation is shown to exist between durability coefficients and energy coefficients for the four yarns.

金屬材料の不連續變形

The load-elongation diagram of a soft steel tested at the temperature of blue shortness indicates continuous serrations after yield point up to the breaking stage. Although this phenomenon has been widely investigated, no satisfactory cxplanation has yet been given. Moreover, such a serrated deformation is not peculiar for a low carbon steel, as it is observable in some ferrous and non-ferrous alloys tested under a suitable condition. In order to contribute some light for this problem, the present author has studied it with carbon steels of various compositions and structures, some special steels, single cr_??_ stals of iron, duralumin, brass, copper, nickel, aluminium and zinc at temperatures ranging from the liquid nitrogen to the red heat. From these experiments two cases are classified for the serrated elongation. The one case is that when the materials having, to a certain extent, impurities or structural flaws are tested at a proper temperature and under a slow rate, if possible. The other is observable when the metals of high purity are tested at a rate as quickly as possible. These results are explained as follows:- In the fomer case the crystal grains are temporarily brought to an unstable state, by concentrated stress due to notch effect and in the latter case they are brought successively to an unstable state by overstress due to rapid loading and followed by yielding.