This effect is generally handled by basing the **crack** initiation life prediction on a modified (lowered) strain-life or **stress**-life curve that includes the effect. In 1960 Schijve [2] observed that experimentally derived **crack** growth equations were independent **of** the loading sequence **and** depended only on the **stress** **intensity** range **and** number **of** cycles for a given portion **of** loading sequence. The central problem in the successful utilization **of** fracture mechanics techniques applied in a fatigue spectrum is to obtain a clear understanding **of** the influence **of** loading sequences on fatigue **crack** growth. **Of** particular interest in the study **of** **crack** growth under variable-amplitude loading is the decrease in growth rate called **crack** growth retardation that usually follows a high overload. Most **of** the reported theoretical descriptions **of** retardation are based on data fitting techniques, which tend to hide the behavior **of** the phenomenon. If the retarding effect **of** a peak overload on the **crack** growth is neglected, the prediction **of** the material lifetime is usually very conservative [3]. The small scale yield model employs the Dugdale [4] theory **of** **crack** tip plasticity, modified to leave a wedge **of** plastically stretched material on fatigue **crack** surfaces. Fatigue **crack** growth was simulated by Skorupa **and** Skorupa [5] using the strip model over a distance corresponding to the fatigue **crack** growth increment as shown in Fig. 1.

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Experimental studies reveal that fatigue **crack** growth rates (FCGR) in welds may display strong sensitivity to welding process, weld geometry, localized changes in material **and** mechanical properties **of** the weldment, including the heat affected zone. These effects arise from the complex interplay between macroscale fea- tures (**crack** size **and** geometry, material properties including weld strength mismatch, weld residual stresses, load ratio, etc.) **and** the micromechanism **of** fatigue **crack** growth. At the macroscale re- gime, there is a clear correlation between **crack** propagation rate under cyclic loading **and** load ratio (R) in which the FCGR increases with R. Here, **crack** **closure** effects play a key role in controlling the rate **of** **crack** propagation with varying load ratios by strongly affecting the (effective) **stress** **intensity** factor (SIF) range. However, despite the technological importance **of** fatigue **crack** extension in welded structural components, a full understanding **of** the fatigue **crack** growth phenomenon in welds remains limited as does a more extensive body **of** experimental data. Early work **of** Benoit et al. [13] on fatigue **crack** propagation in the heat affected zone (HAZ) for a structural steel weld showed that FCGR in welded materials are lower than the corresponding rates in the base plate material. Link [14] conducted FCGR experiments using compact tension specimens for both the base plate **and** weldments **of** a 5456-H116 aluminum alloy **and** an ASTM A710 Grade A steel with **and** without post-weld heat treatment (PWHT); these results show a strong influence **of** welding residual stresses on the measured FCGRs due to the effects **of** **crack** **closure**. Later, Shankar **and** Wu [15] showed that fatigue **crack** growth behavior in welded 5083- H321 aluminum alloys is essentially similar to the parent material. These previous research efforts clearly demonstrate that accurate evaluation procedures for effective **stress** **intensity** **factors** which are applicable to welded fracture specimens remain essential in more refined defect assessment procedures capable **of** including ef- fects **of** **crack** **closure** on fatigue **crack** growth rates.

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Consider a square plate, with a single **crack** normal to one edge, as represented in Figure 5. The **crack** length is denoted by a **and** the ratio between the height **and** the width **of** the plate is given by h/w = 0.5. The plate is loaded with a uniform traction t = σ, acting now in a direction parallel to the **crack** **and** applied anti-symmetrically at the sides which corresponds to a sliding- mode loading. This is a very difficult case, for which there are no published benchmark results, as far as the authors knowledge is concerned. Therefore, results have been obtained with the present formulation, in order to be compared with those obtained by the dual boundary element method **and** the J-integral technique, using the software [49]. This combination **of** the dual boundary element method with the J-integral technique is an extremely-accurate tool because it uses the elastic field computed at internal points which is a highly accurate operation in the boundary element method due to the fundamental solutions. Five cases were considered, with a/w = 0.2, 0.3, 0.4, 0.5 **and** 0.6, respectively. A convergence study was carried out with three different meshes; convergence was achieved, for all the five cases **of** **crack**-length considered, with a mesh **of** 512 finite elements, in which the discretization was refined around the tip. The results obtained with this finite element mesh, presented in Table II are remarkably accurate; the present results match those obtained with the dual boundary element method **and** the J- integral technique within two decimal places. It is important to note that the **stress**-**intensity** **factors** **of** the **opening**-deformation mode are always below 10 −3 , since this is mainly a sliding-

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resistance to fracture in the design **of** structural members. ASTM standards E399 **and** D5045 give some guidance for plane strain mode-I fracture toughness for metals **and** plastics, respectively. No standard requirements exist for the validity **of** linear elastic fracture mechanics **and** plane-strain conditions for tests with polymeric materials under mode-II **and** mixed-mode loading conditions. Therefore, it may be necessary to develop tests tailored for use with polymeric materials in order to investigate the role **of** mixed-mode loading conditions. This investigation seeks to extend under- standing **of** the polymeric materials fracture behavior under mixed-mode loading conditions through **numerical** **and** experimental analysis. Using finite element results, correction **factors** were applied to the specimen **and** a polynomial fit was proposed to evaluate the **stress** **intensity** **factors** **of** the spec- imen with a **crack** subjected to mixed-mode loading conditions. The research conducted for this study assumed that the polymeric material under consideration was homogenous **and** linear elastic. The main objective **of** this study was to determine the fracture toughness K IC **and** K IIC for the pol-

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This finite element appears as an attractive tool for definition **of** the **stress** field along notched surface shell element decoupled from the one-dimensional element proposed. Once defined the **stress** field along the edges **of** the component part containing notches, an approached procedure can be carried out even without a subsequent finite element analysis, using published graphical results (Harris 1997). The displacement field **of** the finite shell element results from the superposition **of** the rigid beam displacement **and** a complete Fourier terms development. The deformation model considered is a semi-membrane strain field, (Fonseca et al 2006). The SIF **determination** in a **crack** **opening** mode is function **of** an equation presented by (Harris 1997) from Neuber’s **stress** concentration **factors** in straight components as follows:

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Latin American Journal **of** Solids **and** Structures 11 (2014) 1886-1905 In ANSYS PLANE 82 elements are used. A concentration keypoint is generated at the **crack** tip. KCALC command is used for **determination** **of** **stress** **intensity** **factors** after the local coordinate system is defined **and** used at the **crack** tip **and** the **crack** path defined in the post processer using path operations. The model **of** **crack** eccentric in x-direction as modeled using ANSYS is shown in Figure 4. It is clear from Figure 5 that quarter point elements exist near the **crack** tip.

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Figure 7 illustrates the correlation between CMOD **and** CTOD for different notch locations. A nonproportional behavior may be observed when the notches are taken off-center. This effect in- creases as the notch tends to move towards the support span. It is associated with mixed mode condition, in which the effect **of** sliding mode-II in fracture is accentuated. It is important to em- phasize that, in the present work, CTOD values were obtained directly. However, the indirect measurement **of** CTOD is usually determined by measuring the value **of** CMOD, considering linear relationship between them. Therefore, the use **of** DIC method has been proved to be useful to measure CTOD.

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eneral aspects **of** the concept based on calculation **of** the average **stress** over the length **of** the process zone are described in Refs. [1-6] for a solid with cracks or notches. These references demonstrate an advantage **of** the critical average **stress** criterion over the classical elastic **and** elastic-plastic fracture mechanics criteria because this criterion avoids the confusion **of** applying the unrealistic continuum mechanics **stress** singularity to the fracture process zone in the vicinity **of** the **crack** (or notch) tip. For example, the failure criterion **of** the average **stress** within an effective distance has been successfully employed to relate the apparent fracture toughness in specimens with notches to the fracture toughness obtained from deeply cracked specimens (e.g., [4]). In this case, the effective distance corresponds to the point with a minimum **of** the **stress** gradient which requires finite element analysis to obtain the effective distance [5]. It should be noted that the effect **of** the high **stress** gradient ahead **of** the **crack**/notch tip can be taken into account by means **of** the theory **of** critical distance using the **stress** at some critical distance [6]. The theory **of** critical distances was very successful in predicting the fracture strength **of** ceramic materials.

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In this research, fatigue **crack** growth da/dN x ∆ K has been studied in two dual-phase steels broadly used in the automotive industry, with 7% to 12% **of** martensite volume fraction. The main difference between the steels is the chemical composition: one **of** the steels has chromium additions while the other has silicon as an alloy element. Besides the chemical composition, the effect **of** 10% **of** prestrain followed by a bake hardening heat treatment on the fatigue resistance was verified. This thermo-mechanical treatment was used to simulate the stamping **and** the paint baking **of** the wheels. C(T) specimens with 3.80 mm thickness **and** 50 mm width in T-L orientation were used for the experiments. Testing frequency was 30 Hz. The experiments were performed in ambient air (approximately 25ºC, R.H. = 60% ), at R **stress** ratio **of** 0.1. In the near-threshold ∆ K th region **and** in the final rupture region, the fatigue behavior

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18. Cavanaugh CE, Floyd LJ, Penniman TV, Hulbert A, Gaydos C, Latimer WW. Examining racial/ethnic disparities in sexually transmitted diseases among recent heroin-using **and** cocaine-using women. J Womens Health (Larchmt). 2011;20(2):197-205. 19. Lopes CLR, Teles SA, Espírito-Santo MP, Lampe E, Rodrigues FP, Motta-Castro ARC, et al. Prevalence, risk **factors** **and** genotypes **of** hepatitis C virus infection among drug users, Central-Western Brazil. Rev Saúde Pública. 2009;43 Suppl 1:43-50.

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While curvature is being decreased, the total number **of** atoms does not remain the same, this leads to affect the total potential energy **of** the system. Increasing the number **of** removed atoms to decrease the sharpness is the reason **of** decreasing the yield point. To gain higher curvatures we remove atoms **of** the right **and** left sides **of** the void. These atoms _as shown before_ feel almost no **stress**, but their removal leads to a decrease in the yield point. Removing these atoms or any atoms in the specimen changes potential energy **and** this will cause the system failure. So it seems that the yield point is more sensitive to the total number **of** removed atoms than the **stress** concentration **of** the sample.

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Based on the impressive increase in the number **of** dependent elderly persons, **and** in view **of** the institutional incapability **of** meet these needs, the informal caregiver has emerged as a key figure in the promotion **of** quality **of** life in a situation **of** de- pendence. Playing this role is not an easy task **and** it is accompanied by sociocultural difficulties that go beyond the psychological **and** physical demands al- ready existent in the activity **of** informal caregiving. With respect to the definitions **of** caregiver **and** in- formal caregiver presented by the literature, there are many **and** not all are unanimous as regards reference to the concepts. In general, when the types **of** care- givers are specified, the main (or primary) caregiver is defined as the person who has the greatest responsibil- ity in the daily care **of** the dependent elderly person, performing the majority **of** day to day tasks; **and** the secondary caregiver, as the one who performs tasks without much regularity, **and** without having much responsibility or power **of** decision, helping the main caregiver only with complementary activities. (3,4) Sec-

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The transition to kindergarten is a part **of** family life cycle **and** an expected devel- opmental change that can induce **stress** **and** as such requires family adjustment. In this paper we deal with the types **and** sources **of** parental **stress** when a child enters the kindergarten **and** during the period **of** his/her adaptation. In the first phase **of** the study we conducted three focus group discussions, in which 20 parents participated. The second phase was designed for the questionnaire survey, in which the sample consisted **of** 163 parents. The data suggest that in parents’ experience the most fre- quent are stressful events related to the child’s reactions **and** changes in the child’s acquired habits. With less frequency parents reported about **stress** related to their own emotional reactions **and** changes in the family functioning. When compared, no significant differences were found between the fathers **and** mothers in terms **of** the frequency **of** the reported **stress**. Generally, parents estimate that stressful experience associated with children’s adaptation to kindergarten does not induce highly intense **stress**. Additionally, we found that mothers perceive the children’s period **of** adapta- tion to kindergarten significantly more stressful than fathers. Research findings can be important for future investigations about the effects **of** parental **stress** in the pe- riod **of** children’s adaptation to kindergarten on optimal family functioning, **and** for the practical implications for working with these families.

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horn microtip diameter, 10 mm. Standard flavonoids solutions **of** 8.0 m g/mL were mixed in same volumetric flasks **and** 30 ml **of** mixtures were kept in brown glass tubes (3 cm in diameter; 10– 20 cm in height). The tubes were immersed in a low-temperature water bath (DC–1006, Safe Corporation, Ningbo, China) to maintain a constant temperature. Five solvents were chosen not only because they are frequently reported for extraction flavonoids, but also they may cause different sonochemical effect. Additionally, we want to know whether flavonoids stability would be affected when ultrasound **intensity** or temperature changes. The solutions were then treated by US with the following parameters (except for the tested factor): probe position, 1 cm from the top **of** the extraction cell; liquid height (the distance from the horn microtip to the bottom **of** the tube), 4 cm; temperature, 5uC; pulse mode: on, 2 s **and** off, 2 s; treatment time, 20 min; **and** US **intensity**, 15.29 W/cm 2 . Samples obtained by standing under the same conditions were used as controls (CK). The ultrasound treated samples (US) **and** CK solutions were filtered through 0.45 m m polyvinylidene fluoride microfiltration membranes (Shanghai Xingya Purification Material Co., Shanghai, China) **and** subsequently stored at –18uC for further HPLC analysis.

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The key stress parameters of a section discontinuity (namely, overburden pressure, normal components of horizontal stress, intensity of tangential stress), for horizontal and non-horizon[r]

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Objective: The aim **of** this study was to assess whether repetitive **opening** **and** **closure** **of** self-ligating bracket clips can cause plastic deformation **of** the clip. Methods: Three types **of** active/interactive ceramic self-ligating brackets (n = 20) were tested: In-Ovation C, Quicklear **and** WOW. A standardized controlled device performed 500 cycles **of** **opening** **and** **closure** movements **of** the bracket clip with proper instruments **and** techniques adapted as recommended by the manu- facturer **of** each bracket type. Two tensile tests, one before **and** one after the repetitive cycles, were performed to assess the stiffness **of** the clips. To this end, a custom-made stainless steel 0.40 x 0.40 mm wire was inserted into the bracket slot **and** adapted to the universal testing machine (EMIC DL2000), after which measurements were recorded. On the loading portion **of** the loading-unloading curve **of** clips, the slope fitted a first-degree equation curve to determine the stiffness/ deflection rate **of** the clip. Results: The results **of** plastic deformation showed no significant difference among bracket types before **and** after the 500 cycles **of** **opening** **and** **closure** (p = 0.811). There were significant differences on stiffness among the three types **of** brackets (p = 0.005). The WOW bracket had higher mean values, whereas Quicklear bracket had lower values, regardless **of** the **opening**/**closure** cycle. Conclusion: Repetitive controlled **opening** **and** **closure** move- ments **of** the clip did not alter stiffness or cause plastic deformation.

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half-plane is assumed to constant along the lateral direction. The problem is reduced to a system **of** singular integral equation **of** the second kind which is solved numerically to compute the contact **stress** distributions. In order to provide more insight into the behaviour **of** the functionally graded steel, contact mechanics analysis is also conducted by means **of** the inite element method. The parametric analyses are performed by considering lat punch proiles. The presented results illustrate the inluences the coeficient **of** Coulomb friction on the distributions **of** the contact stresses **and** **stress** **intensity** **factors**.

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Analysis **of** Fracture Mechanics problems considering cracks with arbitrary shapes **and** mixed **crack** **opening** modes: another important contribution **of** this work consisted in the extension **of** the Splitting Method to the analysis **of** problems containing cracks with arbitrary shapes, as explained in Chapter 2. Obviously, when cracks with arbitrary shapes are considered, mixed **crack** **opening** modes must be also taken into account. When such modeling is available, complex real-life problems can be analyzed, with emphasis on multisite damage problems. For instance, it was possible to find out the most critical pattern **of** cracks attached to holes in a rivet connection.

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Sensitivity analysis was conducted each time for the model described in Section 3, for which it was assumed that the parameters vary in ranges given in Table 1. Table 2 lists parameters influence **of** which was not taken into consideration in sensitivity analysis. According to the fact that these parameters are connected with the phase change diagram, they cannot be changed freely **and** independently from one another. Additionally, in Table 2 physical parameters **of** the mould are included. Table 2.

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Attractive technological paraphernalia is available, from which we can really benefit, but they can also cause more harm than good. Different processes, but intended for similar purposes, were used in the past, such as the construction **and** ornamentation **of** the pyramids that housed the bodies **of** sovereigns (identified with the gods), their belongings, **and** even servants **and** pets, hoping that they could return to use them in another life. Temples were filled with icons that kept “staring” at those being honored, reinforcing the memory **of** their presence in the world **of** the living. It was a ritual meant to ensure that death had come **and** the life within the body was gone, which only represented a brief passage through the path towards eternity.

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