Papers by Keyword: Stress-Strain Curve

Abstract: To research the effect of a elastic modifier on the mechanical properties of epoxy/rubber concrete, series of epoxy/rubber concretes were prepared with different elastic modifier content, the relationship between elastic modifier content and stress-strain curve of epoxy/rubber concretes were investigated. Results show: as the increase of elastic modifier content, both the compressive and bending stress-strain curves of epoxy/rubber concretes experience a stage transition of elastic-elastoplasticity-plastic apparently; the slope in the rising and falling section of stress-strain curves are gradually decreased; the peak stress decrease while the corresponding strain and stain energy increase. Content of elastic modifier between 40pbw and 60 pbw is proposed in order to attain better properties of epoxy/rubber concrete. Compared with ordinary concrete and rubberized concrete, Improved epoxy/rubber concrete has better comprehensive mechanical properties and larger rubber content.

Abstract: This article introduces evolutionary algorithms and their utilization in mechanical engineering. First part of this work describes evolutionary algorithms and their characteristica. The main body of evolutionary algorithms, the selection methods for parents and the types of reproduction are explained in the next part of this article. Termination conditions are also discussed. Finally, the application of evolutionary algorithms to a problem in mechanical engineering is described. Thereby, the material parameters for a Bodner-Partom model describing visco-elastoplastic material behavior are determined by fitting data from experiments on Aluminum test samples under tension load.

Abstract: A short split Hopkinson bar system with a total bar length of 3 m (a 2 m input bar plus a 1 m output bar), a striker length of 254 mm, and a diameter of 25.4 mm, is designed. Through numerical experiments, the stress vs. strain curve and the rate vs. strain curve of the specimen are obtained from the bar signals. These measured curves are reasonably consistent with the input stress-strain curve of the specimen for the numerical experiment and the prediction by the recently reported rate equation, respectively, verifying the reliability of the designed SHPB system.

Abstract: Mechanical properties of two stainless steels (AISI 316L and AISI 410) processed by spark plasma sintering (SPS) were evaluated by four different types of indentation-based tests: hardness mapping, evaluation of indentation stress-strain curves, instrumented indentation and bonded-interface technique. Obtained results showed that the used combination of relatively simple experiments may provide a deeper understanding of mechanical behavior of materials prepared by SPS.

Abstract: The advanced high strength (AHS) steels, for example, dual phase (DP) steels, transformation induced plasticity (TRIP) steels and complex (CP) steels principally exhibit multiphase microstructure features. Thus, mechanical behavior of the constituent phases significantly affects the resulting overall properties of such AHS steels. Novel material characterization techniques on micro- and nano-scale have become greatly more important. In this work, stress-strain response of the DP steel grade 1000 was determined by using the Nanoindentation testing. The DP steel showed the microstructure containing finely distributed martensite islands of about 50% phase fraction in the ferritic matrix. The nano-hardness measurements were firstly performed on each individual phase of the examined steel. In parallel, finite element (FE) simulations of the corresponding nano-indentation tests were carried out. Flow curves of the single ferritic and martensitic phases were defined according to a dislocation based theory. Afterwards, the load and penetration depth curves resulted from the experiments and simulations were compared. By this manner, the proper stress-strain responses of both phases were identified and verified. Finally, the effective stress-strain curve of the investigated DP steel could be determined by using 2D representative volume element (RVE) model.

Abstract: Previous researchers reported that problematic soft clay can be improved by deep lime stabilization. However, due to low confining pressure of surrounding soil, problems often occurred at top part of column which reduced the performance of lime column, such as: crushing at column head and higher settlement for surrounding soil at the upper part of column. Geotextile encapsulated lime column (GELC) was proposed in this study. The stresses on column are essential in the analysis on columnar improved soil. Multi-stage loading test was conducted on lime column and GELC stabilized Pontian marine clay aged 14 days, 28 days and 56 days in order to investigate axial stress on lime column and GELC stabilized Pontian marine clay. Geotextile encapsulation increased the compressive strength of lime column about 70 percent at axial strain of 8 percent.

Abstract: Optical measuring systems enable a very accurate determination of the flow stress for the hydraulic bulge test. The flow stress is strain rate and temperature dependent and for the description of work hardening an approximation of the temperature during the test is required. Measuring the temperature during the test usually interferes with the optical strain measurement. A model for the temperature distribution on the bulged surface is developed based on heat generated by plastic work, convection to air on the outer surface, conduction to the tools at the die diameter and conduction to oil on the inside. The plastic work is derived from an approximation of the shape of the bulged surface and an approximation for the thickness distribution, starting from the initial thickness at the die ring to the established thickness at the pole, making use of volume conservation for the bulged sheet. The parameters of the model are tuned to bulge test temperature measurements of four different steel grades using a thermo couple at the pole. The results of the analytical temperature model are in good agreement with the measurements.

Abstract: The study aimed to investigate the compression behaviors of syntactic foam reinforced by warp knitted spacer fabric (SF-WKSF). Two kinds of SF-WKSF samples were prepared with warp knitted spacer fabric (WKSF) of different surface layer structures. The compression tests were carried out by MTS 810 material test system and the compression properties of SF-WKSF were analyzed based on its compressive stress–strain curves and modulus values obtained from test results. It is indicated that the surface layer structure of WKSF has significant effects on the compression performance of SF-WKSF, the SF-WKSF made with denser surface layer structure shows higher compressive modulus and yield strength compared to neat syntactic foam (NSF).

Abstract: In order to make the new composite wall structure the group developed to adapt different regional natural conditions, and along with the demand of gradually in-depth study the damage characteristics of the new composite wall, need to research the mechanical properties of the wall filling materials. In this paper, the ZG-CSS Electronic Universal Testing Machine was used on the uniaxial compressive test of the three blocks(the mud billet block, the cotton stalk block, the recycled EPS lightweight concrete block), to analyze the failure characteristics of the blocks and the other mechanical properties, such as Poisson’s ratio, elastic modulus, then the full compressive stress-strain curves are given, and at last fitting the mathematical expression of the uniaxial compressive stress - strain curves. And this paper also gives the yield criterion based on the unified strength theory of the three ecological filling blocks.

Abstract: This paper proposes an integrated hydraulic bulge and forming limit testing method and apparatus for sheet metals. By placing a PU (Polyurethane) plate between molds and uniformly applying hydraulic pressure to sheet metals, a biaxial stress-strain relationship and forming limit diagram (FLD) displaying both left and right sides were acquired using the same apparatus. An uniaxial tension test and traditional drawing test were conducted to compare the results obtained from the proposed hydraulic bulge and forming limit testing methods, respectively. A close correlation between the results of the stress-strain relationship and FLD in both comparisons verified the feasibility and capability of this integrated hydraulic testing method and apparatus for use with sheet metals.