Papers by Keyword: Strain Energy Density

Abstract: This research discussed on the determination of the appropriate fatigue damage parameter to predict the fatigue life when material subjected to the biaxial loading condition with the consideration of the energy dissipated. Servo-hydraulic machine is used for the constant amplitude cyclic testing on smooth solid mild steel. The results showed that in the low cycle fatigue, the total strain energy density can represent the accumulative of fatigue damage and characterize on the damage parameters. The relationship has been proposed which the data satisfactorily correlated for the R² is 0.8656. In addition, the hysteresis loop represent the area under the graph was the energy stored in the material during the loading and unloading condition. Hence the circumstances showed the deformation process governing the nucleation and propagation of fatigue cracks associated with the energy dissipated.

Abstract: The paper presents strength machine control system for characterization of fatigue properties of materials based on recently defined energy fatigue damage parameter under polyharmonic bending and torsion.

Abstract: Effects of loading rates on deformation and mechanical properties of adhesive joints are examined in this study. For this purpose, acrylic foam pressure sensitive adhesive (PSA) was employed with aluminum adherents. Tensile loading of the adhesive joint was applied at displacement rates ranging from 5 to 500 mm/min. Results show that the tensile load-displacement response is characterized by three regimes, namely an initial non-linear behavior with initiation of cavities, a hardening behavior through fibrillation process and the final fracture of the stretched fibrils. The strengths of the adhesive joints increases asymptotically from 0.56 to 1.92 MPa over the displacement rates from 5 to 500 mm/min. Both modulus and strain energy density at fracture reach optimum level around a displacement rate of 100 mm/min. Adhesive failure of the joint dominates at low loading rate (below 10 mm/min.) while cohesive failure is prominent at faster loading rates above 250 mm/min.

Abstract: This paper presents 25 new experimental results from gray cast iron notched specimens tested under torsion loading. V-notch (with an opening angle of 120°) is considered with a root radius ranging from 0.1 to 2.0 mm. Plots of torque loads versus twist angles are recorded varying the notch root radius. Such results can help in evaluating numerical and theoretical models of the fracture of notched components under mode III loading. The second part of the paper deals with a discussion on the experimental results. A non-conventional application of the strain energy density is carried out showing a good agreement between experimental results and theoretical fracture assessments and it is used to justify the link between nominal and local fracture approaches.

Abstract: Cast aluminium alloy 354 has become an important industrial material owing to its excellent mechanical properties and good castability. It finds widespread use in the manufacture of compressor wheel castings. Castings have been studied since long and different approaches have been attempted to improve their quality. One such approach is Hot Iso-static Pressing (Hipping). This paper studies the effect of Hipping on the strength, ductility, strain energy density W and quality rating Q_o of the alloy 354. The study shows that Hipped samples have better % elongation to fracture, higher W and Q_o values as compared to non-Hipped samples. This behavior is consistent across different aging conditions of the alloy. Hipping also results in a reduction in scatter of ultimate tensile strength of 354, thus making it valuable to industries that demand high material consistency.

Abstract: In this paper the results of fatigue tests under cyclic bending of 2024 aluminium alloy with amplitude of strain energy density parameter control are presented. Based on these tests, energy fatigue characteristic of the tested material was elaborated.

Abstract: Brittle fracture of polycrystalline graphite under tension, in-plane shear and torsion loading is studied experimentally and theoretically using prismatic and axisymmetric specimens weakened by sharp and rounded-tip V-notches. The main purpose is twofold. First, to provide a new set of experimental data from notched samples made of isostatic polycrystalline graphite with different values of notch opening angles and root radii, which should be useful to engineers engaged with static strength analysis of graphite components. At the best of authors' knowledge, data from notch specimens are very scarce in the literature for this material. Second, to apply a fracture criterion based on the strain energy density (SED) averaged over a well-defined control volume surrounding the notch tip, extending what was made by the present authors for in-plane tension-shear loading conditions in notched specimens made of other materials. Good agreement is found between the experimental data related to the critical loads to failure and the theoretical assessments based on the constancy of the mean SED over the material-dependent control volume.

Abstract: Cast aluminium alloy 354 has found widespread application in the automotive industry for its excellent mechanical properties and good castability. The stringent emission norms and demands for improved fuel economy have pushed automobile technology to new frontiers. This has led to efforts to reduce weight while maintaining higher vehicle performance. Cast aluminium alloy 354 is a material that performs with reasonable effectiveness in the high stress automobile environment. The present study looks at the use of strain energy density W and the quality index Q_o to determine the effect of process parameters like aging temperature and modification on the quality of the alloy 354 and also to monitor the effect of interrupted heat treatments T6I4 and T6I6 on the quality of the material. The strain energy density W calculated for the interrupted heat treatments on alloy 354 show a broad inverse relation with yield strength R_p. An improvement in the yield strength and the strain energy density of the alloy is observed when the alloy is subjected to modification. At artificial aging temperatures lower than the artificial aging temperature adopted in standard aging treatment an improvement in the Qo and W quality of the alloy 354 have been observed.

Abstract: The paper presents strength machine control system for characterization of fatigue properties of materials based on a new, recently defined, energy fatigue damage parameter. It is used in new procedure for precise determination of the fatigue characteristics of materials with the controlled strain energy density parameter. The new parameter distinguishes positive and negative values strain energy density histories during variable loading. In case of modern, cyclically unstable materials the new closed-loop control system of strength machine allows to univocally establish the relevant stress-strain based fatigue characteristic under bending and torsion. This control system has been implemented with the use of National Instruments LabVIEW software. The mechatronic stand based on fatigue machine for material testing under bending moment and torsion moment has been described and preliminarily material tests have been done.

Abstract: Currently, titanium dominates the dental implant materials due to its strength and bio-inerrability. The use of titanium implant had demonstrated considerable surgical success. However, researchers are spontaneously pursuing better materials to achieve better osseointegration in the early stage of implantation. Recently, dental implants based on functionally graded material (FGM) were introduced in pursuit for the goal of enhanced bio-compatibility. The concept for FGM dental implant is that the property would vary in certain pattern to match the biomechanical characteristics required at different regions in the oral bone. However, mating properties do not necessarily guarantee better osseointegration and bone remodelling. There is no existing report available on the long-term effect of FGM dental implant on its hosting bone tissues. This paper aims at exploring this critical problem by using computational bone remodelling technique. The magnitude of bone remodelling due to use of FGM implant is identified over a healing period of four years. Comparisons were made between titanium and various FGM designs, the interesting differences were observed and the optimum FGM design was suggested based on the remodelling results.