Papers by Keyword: Stress-Strain Curve

Abstract: This study attempts to emphasize a pre-step for determining the permitted deformations (strains) extents. This is for changing the original molecular architecture shape for the materials understudy (rubber band/stearic acid (RB/based SA) and Rubber band without stearic acid (RB without SA)). It is necessary as a basic controlling step in the choosing process of the appropriate programming method to show the shape memory effect (SME) property. By this property, the polymers are either described as shape memory effect (SME) or conventional polymers. If the material was proved to have the shape memory effect (SME) property, then it will be allowed to predict many thermo-mechanical properties. So for these materials, the (stress-strain) curve zones have been classified according to the ability of the deformation history memory, which can be erased and programmed again after the immediate removement of the applied tensile force. This can be achieved by calculating the residual strain ratio. The comparative results showed that the elastic and plateau zones were classified respectively as valid for the study of the (SME) property. While for the Hardening strain and fracture zones, they were classified as bad and very bad respectively for the study of this property.

Abstract: In this research, calcined diatomaceous earth from Aceh Besar, Indonesia was used as cement replacement in producing high strength concrete. Four concrete mixtures in which the percentage of cement replacement of 0%, 5%, 10% and 15% by weight were studied. Four cylinder-specimens with 100 mm diameter and 200 mm high were prepared for each mixture. The compression load was applied on the specimens at the age of 28 days until the specimens failed. The mixture without calcined diatomaceous earth was more workable than that with diatomaceous earth. The compressive strength of concrete with diatomaceous earth in this study was almost the same for all mixture. However, those compressive strength was lower than the compressive strength of concrete without calcined diatomaceous earth for about 14.6%. Modulus of elasticity of high strength concrete decreased with increasing of cement replacement percentage.

Abstract: Stress-strain curve construction for low-plastic alloys under severe plastic deformation conditions is considered. A material under investigation is cast bronze Cu85-Pb5-Sn5-Zn5. Experiments on upsetting and deep rolling were conducted. Based on these data, the initial hardening modular and the hardening modular at large strain were evaluated. Classic tests on determining an initial segment of stress-strain curve can lead to grate mistakes because shear band sliding can diminishes appreciably both yield stress and hardening modular. A correct methodology for stress-strain curve construction is proposed.

Abstract: The strength and deformation properties of carbon fiber reinforced concrete under different fiber volume loadings under impact loading were studied by using the ɸ100 mm split Hopkinson pressure bar (SHPB) test system. The results show that after the carbon fiber is added, the stress-strain curve of the specimen shows the platform section at the peak stress. The strength and peak strain of the concrete under the impact load increase first and then decrease with the increase of the carbon fiber volume. Trend, when the carbon fiber volume is 0.2%, the impact mechanical properties of concrete are significantly improved.

Abstract: The article provides an overview of existing methods of testing specimen for torsion, in order to determine the rheological properties of materials. In addition, the approaches to the post-processing experimental data, obtained in the form of torque-twist angle curve, are reviewed. It is shown that there is no universal and reliable method to study the rheological properties of materials that are sensitive to the strain rate. This paper proposes the new testing method that takes into account the effects of strain rate hardening initially. This method is that the torsion tests are carried out with the variable grips acceleration. The post-processing of obtained experimental data can be carried out with the use of modified Nadai method. In addition, with the use of mathematical modeling it is shown that the new method is reliable, regardless of material properties. The application for invention of the new testing method No2018132149 was directed in Federal Institute of Industrial Property on September, 7, 2018.

Abstract: Metallic infrastructures suffer deterioration during their service life. When the metallic component reaches a limit level of damage, it is replaced by a new one. This generates high costs of maintenance and residues management. However, the deposition of coatings by the cold spray technique would allow the repairing of these damaged components and extent their service life. In this work the effect of the spraying temperature and pressure on the mechanical behavior of 316L stainless steel coatings deposited on carbon steel by the cold-spray technique has been analyzed. Spraying gas temperatures of 800oC, 900oC and 1000oC combined with gas pressures of 50 and 60 bars were selected. Indentation stress-strain curves were determined for each spraying conditions. The results showed a significant effect of both spraying parameters on the work hardening of the coatings.

Abstract: A small punch testing (SPT)-related stress-strain relation (SPT-SR) model is used to obtain the stress-strain curve of DP600 according to Chen-Cai equivalent energy method. And then the SPT and notched small punch testing (NSPT) specimens were simulated in order to determine the critical fracture criterion of DP600 on the basis of the stress-strain curve obtained by SPT-SR model. Lastly, the J resistance curve of small C-shaped inside edge-notched tension (CIET) specimen for DP600 dual-phase steel was successfully predicted based on the aforementioned fracture criterion.

Abstract: The soil-cement columns are generally installed and cured in the soft clay layers under confining pressure. The strength of the soil-cement columns may be influenced by confining pressure during curing period. In this study, the main objective was to study the influence of curing pressure on unconfined compressive strength of cemented clay. A series of unconfined compression tests was performed on a cement admixed clay sample cured under pressure values of 0 kPa (atmospheric pressure), 25kPa, 50kPa and 100 kPa using a typical unconfined compression equipment. The test samples with values of cement content of 0.5, 1.0 and 2.0 percent were cured for 28 days.The stress-strain curves obtained from all tests show a peak value of stress. The unconfined compressive strength or peak stress obviously increased with increasing cement content for all curing pressure conditions. It can be observed that the strength of samples gradually increased with curing pressure for cement content of 0.5 percent. For cement contents of 1.0 and 2.0 percent, the strengths of samples cured under pressures of 25 kPa dramatically increased from the strength of samples cured without pressure (0 kPa), however, the strengths of samples for curing pressures of 25, 50 and 100 kPa were not clearly different.

Abstract: Formability in sheet forming processes are usually analyzed by standardized tests, which often requires different test equipment associated with high initial investment cost. The present study purposes a flexible test tooling system for hydraulic bugle test apparatus that allows to evaluate the impact of size effect on the formability of thin metallic sheets. Finite Element Method was used for concept and design of the tooling system and experimental tests were carried out with thin sheets of SUS316L stainless steel to assess the overall performance of the tooling system.

Abstract: This paper presents the degradation of compressive strength and stiffness of concrete after immersed in 2,5 % sulfuric acid solution. The durations of immersion are 0, 3, 7, 14, and 28 days. After the immersion, ultrasonic pulse velocity and compression tests are performed on the specimens. The relative dynamic elastic modulus, compressive strength and its initial stiffness decrease with increasing the duration of immersion, as a result of the increasing microcracks in the concrete. The strain at peak stress increases with increasing the duration of immersion. The degradation of compressive strength, the degradation of initial stiffness and the value of strain at peak stress of damaged concrete are formulated as a function of relative dynamic elastic modulus. A simple mathematical expression for stress-strain relationship of concrete damaged by sulfuric acid is proposed and stress-strain curves at different level of damage are compared.