Papers by Keyword: Uniaxial Tension

Abstract: The flangeability of sheared edges in sheet metal forming is commonly evaluated using the ISO 16630 Hole Expansion Test (HET), in which fracture initiates at the edge under predominantly uniaxial tensile loading. For high-quality edges, this test can be interpreted as providing the strain to fracture under proportional uniaxial tension; however, the measured fracture strain is restricted to a single material-dependent sheet orientation. In this work, a novel experimental approach is proposed to directly measure the uniaxial tensile fracture strain in a predefined sheet orientation using digital image correlation (DIC). The method, termed the Asymmetric Hole Expansion Test (aHET), is derived from the standard HET through the introduction of a novel asymmetric punch geometry. This modification promotes accelerated edge stretching along a controlled direction, enabling orientation-specific characterization of fracture strain. The capability of the aHET to characterize direction-dependent strains to fracture under uniaxial tension is demonstrated on a DP450 dual-phase steel. The consistent fracture initiation at the edge along the predefined fracture direction, combined with the low scatter of the measured fracture strains across repeated tests for all three investigated sheet orientations, demonstrates that the aHET is well suited for identifying the strain to fracture under proportional uniaxial tensile loading for the calibration of fracture initiation models.

Abstract: Ni-Ti-based shape memory alloy (SMA) finds extensive applications, yet its high cost presents a challenge. As a cost-effective alternative, Fe and Cu-based SMAs have gained popularity. In this context, the present experimental study conducts tensile and cyclic tests on Ni-Ti, Cu-Al-Ni, and Fe-Mn-Si SMA bars to compare their mechanical behavior and assess their performance regarding stress-strain response, energy dissipation capacity, and residual deformation. The tensile test results show that Ni-Ti and Fe-based SMAs exhibit higher yield and ultimate stress, as well as failure strain, compared to Cu-based SMA. Moreover, cyclic tension-compression test results reveal that Ni-Ti SMA demonstrates a stable hysteresis loop with higher recovery residual strain compared to Cu-based and Fe-based SMAs. These findings underscore the potential of combining Ni-Ti and Fe-based SMAs as a viable alternative material for smart vibration control system design and retrofitting devices, offering higher energy dissipation capacity and larger ductility with good recentering ability.

Abstract: Stress-strain behavior of austenitic stainless steel grade AISI 304 was investigated by means of uniaxial tensile tests and magneto-phase analysis. The test materials were strained in tension within the temperature range of-100 ≤ T ≤ +100 °C. According to the results, intensive strain hardening occurs in austenitic stainless steel when strain-induced α’- martensite is present in the material, and stress-strain behavior is associated with the increase yield strength and tensile strength with decreasing temperature. The analysis of the hardening kinetics reveals that kinetics are affected by the temperature and by the amount of α’- martensite content.

Abstract: This paper provides a comparative assessment of the results of modeling the processes of deformation and destruction of objects under uniaxial tension in the MSC.Marc and DEFORM software packages and in a full-scale experiment, as well as a study of the influence of the form factor of these objects and the form of unit cells on the fracture parameters in modeling and experiment.

Abstract: The accuracy of the rubber constitutive model characterizing experiment data has a crucial influence on the mechanical analysis of rubber structures. In this paper, a new improved hyperelastic constitutive model is proposed, and the model is derived into the stress-strain forms of uniaxial tension, equibiaxial tension and pure shear. Based on the experimental data of filled rubber, the material parameters of each deformation state are obtained by using the newly proposed rubber hyperelastic constitutive model, and the uniaxial tensile (UT), Equibiaxial tension (ET) and Pure shear (PS) specimens are simulated and calculated in the finite element software. the stress state of each finite element specimen is analyzed and the obtained simulation data are compared with the experimental data. It is found that the new model can accurately characterize the hyperelastic mechanical properties of the experimental specimens in different deformation states. At the same time, the reasons for the deviation from the experimental data in the process of plane tensile simulation are analyzed and explained comprehensively. The reliability and accuracy of the classical rubber constitutive relations of polynomial models and eight-chain model are studied. the results show that different hyperelastic models have different ability to describe the hyperelastic behavior in different deformation states. the hyperelastic constitutive model proposed in this paper can be easily embedded into finite element software and has the advantages of accurate results, few material parameters and simple testing.

Abstract: Four model alloys of the Fe-Cr-Co system have been tested under elongation at a standart rate and under pure bending with a constant load in air and in a corrosive medium after different treatment. Fractographic studies were performed depending on the cobalt content and duration of thermal aging at 450 °C. The experiment results are that the Fe-Cr-Co-based alloys with 5–10 % of cobalt are an acceptable composition for maraging steels since they have high strength and ductility, as well as corrosion resistance and low sensitivity to stress corrosion cracking.

Abstract: The risk of error in using only uniaxial data for fitting constitutive model curves is emphasized by many hyperelastic material researchers over the years. Unfortunately, despite these indications, often the method is utilized in finding material constants for mathematical models. The reason behind this erroneous practice is the difficulty in obtaining biaxial data. Therefore, as a remedial measure, in this research work we suggest a method of forecasting biaxial data from uniaxial data with a reasonable accuracy. Initially, a set of data is collected through standard uniaxial test. A predefined generalized function is then used to generate a set of values which subsequently used as multiplication factors in order to get biaxial tension data. Eventually, with availability of two data sets, Mooney-Rivlin two parameter model was used for combined data fitting. Material constants were then obtained through least squares approach and thereby theoretical load curves namely uniaxial, equi-biaxial tension and pure shear were drawn. The results of this work suggest a definite improvement related to three curves when compared with only uniaxial test data fitted outcomes. For validation of secondary biaxial data, separate eqi-biaxial test was done and resulting curves were compared. Biaxial primary data curve and forecasted data driven curve show identical data distribution pattern though there is a shift and therefore provide a basis for further research in this direction.

Abstract: Evolution of localized plastic deformation in tri-layered metal material casting consistng of the working part (layer) from austenitic stainless steel and bearing part from low-carbon steel was investigated. The pictures of localization of the plastic flow during the process of uniaxial tension were obtained by means of the digital image correlation method (DIC). Using optical microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for deformed samples of tri-layered metal. These were found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Lüdwik-Holomon equation. The analysis of the plastic flow stages and localized plastic deformation parameters was performed.

Abstract: A wire brushing and annealing process is developed and utilized to modify the surface layer microstructure of AZ31 magnesium sheet material and assess its effect on uniaxial tensile ductility and bendability. Wire brushing process utilizing fine brass wires is optimized to minimize deterioration in original surface quality by varying spindle rotational speed and depth of cut per wire brushing pass. Wire brushed material is then subjected to annealing to recrystallize the severely deformed surface layer. Rotational speed of 2800 RPM, feed rate of 1 mm/s, and a very small depth of cut coupled with annealing at 200 °C for 60 minutes results in a refined grain layer of grain size 5.5 μm and depth 30 μm on the surface. A texture study of wire brushed and annealed surface by X-ray diffraction reveals a randomized texture on the surface. Refined grain size and randomized texture result in about 38% enhancement in uniaxial tensile elongation in AZ31 compared to non-wire brushed annealed material. The role of surface microstructure and texture in improving sheet tensile ductility and bendability is discussed.

Abstract: MEMS nickel material is commonly used for structural material in micro devices. In order to study the effect of environmental temperature on its mechanical properties,this paper has built up a experimental system which can measure the temperature-related static mechanical parameters of the UV-LIGA nickel material. By using the system for uniaxial tensile experiments of the micro specimen under different temperature, the stress-strain curves of the micro specimen under different temperature were obtained; the mechanical parameters of the micro specimen such as elastic modulus, yield stress and failure stress under different temperature were also calculated out;Finally, the relationship between temperature and mechanical parameters including elastic modulus, yield stress and failure stress was analyzed.