effects of build orientation on fatigue behavior of ti 6al 4v as built specimens produced by direct metal laser sintering

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Crack propagation in a brittle DCB specimen assessed by means of the Williams’ power expansion

A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams’ power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williams’ series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip

Analysis of participation motivation in sports for all among the male and female in Yazd City

Introduction: Exercise is an organized phenomenon that can be evaluated in various aspects. An important aspect of it is its universal and sense of public port, considering the important role of public sport on the health, social and economic aspects of the society; it was aimd to perform the study to analyze the participation motivation of male and female in Yazd City in the universal sports. Methods The statistical population consisted of 486152 participants between male and female above 15 years age in the Yazd City; obtained by the census data of 2011, the selected sample size was 400 people. This research was based on applied and field survey method. The data were quantitatively collected using questionnaire. After confirming the content validity of the questionnaire by the opinions of ten experts in the field of sport management, the reliability of the questionnaire was obtained using Cronbach's alpha coefficient. In this study, the strategies to motivate the participation of male and female of Yazd City in the universal sport in a qualitative way the data were analyzed using SPSS 16 software. Results: The results showed that the main factors influencing the motivation of participation of male and female in sports in Yazd City was management, cultural and preventive and therapeutic factors, respectively. Conclusion: Therefore, it is necessary to adopt regular planning by sports managers and to use mass media for encouraging people to participate in universal sports, and to develop a culture among people of Yazd City to participate in the daily life sports activit

A new fixture for fracture tests under mixed mode I/II/III loading

In this paper, a new loading device for general mixed mode I/II/III fracture tests is designed and recommended. Finite element analyses are conducted on the proposed apparatus to evaluate the fracture parameters of the tested samples under various mixed mode loading conditions. The numerical results revealed that the designed loading fixture can generate wide varieties of mode mixities from pure tensile mode to pure in‐plane and out‐of‐plane shear modes. The accuracy of the proposed fixture is evaluated by conducting a wide range of fracture tests on compact tension shear (CTS) specimens made of polymethyl methacrylate (PMMA). The experimental results are then compared with the theoretical predictions obtained by the Richard criterion. A good consistency is observed between the experimental results and theoretical predictions

Fatigueless structures inspired by Nature: a case study

Biomimetic has begun to offer significant potential in providing unique solutions in materials science. However, the full potential of mimicking natural systems can be fully exploited only if we start to look the problem of design of complex structures from the structural side. The present short letter is focused to investigate a simple case study to show the possibility of achieving an ideally fatigueless design inspired by nature. Materials cannot be immune from fatigue, but structures can. This case study is aimed to discuss a preliminary example

Directed Energy Deposition versus Wrought Ti-6Al-4V: A Comparison of Microstructure, Fatigue Behavior, and Notch Sensitivity

Laser Engineered Net Shaping (LENS), a Direct Energy Deposition (DED) additive manufacturing process is a 3D manufacturing process generally used to produce fully dense parts or to repair/add additional material to an existing component. The main aim of this work is to evaluate the fatigue behavior of LENS specimens in the presence of geometrical discontinuities and to compare its performance to the one obtained from wrought specimens. For this aim, axial fatigue tests are carried out on three sets of specimens namely, smooth, semi‐circular and V‐notched specimens to determine the fatigue strength and notch sensitivity of the LENS and wrought Ti‐6Al‐4V materials. The LENS material shows higher fatigue strength and notch sensitivity compared to wrought material which is attributed to the unique microstructural features leading to different fatigue failure mechanisms. Further, the fatigue data is assessed by use of strain energy density as a failure criterion

Application of an average strain energy density criterion to obtain the mixed mode fracture load of granite rock tested with the cracked asymmetric four-point bend specimens

Mixed mode brittle fracture behaviour of granite rock is studied experimentally and theoretically using Asymmetric Four Point Bend (AFPB) specimens containing pre-cracks subjected to different mixed mode loading conditions, ranging from pure mode I to pure mode II. The main aim of this paper is twofold. First, to present a complete set of experimental results on fracture of pre-cracked granite samples under various in-plane loading mixities, and second, to predict the fracture loads of the tested rock samples under mixed mode I/II conditions using an energy-based criterion, namely the Average Strain Energy Density (ASED) criterion. Good agreement is found between the experimentally obtained fracture loads and the theoretical predictions based on the constancy of the mean strain energy density over the material volume. It is shown that the ASED criterion is able to provide well predictions for the fracture loads of the investigated rock material containing a pre-crack

Crack propagation in a brittle DCB specimen assessed by means of the Williams? power expansion

A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams’ power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williams’ series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip

Thickness effect on the fracture behavior of structural components fabricated via Fused Deposition Modeling

In general, the mechanical properties of components produced with additive manufacturing (AM) are dependent on both the geometry and thickness of fabricated parts. Any change will influence the underlying fabrication process and inherent characteristics. Therefore, it is vital to understand the dependency of mechanical behavior of produced components to improve the designability and applicability. In this study, the thickness effect on fracture behavior of PLA specimens fabricated via FDM technology has been investigated. Overall, 15 double edged notched tension (DENT) specimens were produced layer by layer with three different thicknesses of 1mm, 3mm and 5mm. Fracture properties such as fracture load and critical stress intensity factor (SIF) were determined and analyzed from the experimental fracture tests and numerical simulations. 2D digital image correlation (DIC) analyses were performed to evaluate the full-field displacement and strain distributions around crack tips of the specimens. The experimental results indicated that there is a strong correlation between the building thickness and critical SIF. Specimens with larger building thickness experience lower critical SIF due to the fact that thicker specimens have a smaller plastic deformation zone which can lead to both smaller energy dissipation and smaller critical SIF. Furthermore, thinner specimens have higher possibility of developing fracture trajectories along the raster angles

Fatigue assessment of steel load-carrying cruciform welded joints by means of local approaches

In this paper, local approaches are employed to analyse stress distributions, local fatigue indicators of weld toe, and weld root in load‐carrying cruciform welded joints (LCWJs). An extension of previous available equations is applied herein to calculate the approximate notch strain energy density (SED) based on the notch stress intensity factors (NSIFs) of LCWJ. The extending range of applicability is useful to explain various geometry effects comprehensively of LCWJ under cyclic tension and bending. By employing these extended equations, SED values can be rapidly evaluated without any finite element calculations. The NSIF and SED values obtained according to proposed analytical solutions are first validated by comparing finite element data from several stimulations in LCWJ models, resulting in a good agreement. Moreover, the failure transition relationship between weld toe and weld root is assured by SED values considering variations of notch angles. As a preliminary validation, the accuracy and reliability of proposed analytical model in this paper are checked by several experimental data generated from testing under fatigue loading. The good agreements between the experimental results and existing scatter bonds based on local NSIF, SED, and peak stress method fatigue design standards establish reliable basis for validation of the present analytical equations