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The fracture of cables is often caused by fatigue phenomena. To analyse the fatigue behaviour of these elements, a device has been designed, manufactured, and validated. This machine can produce different load states for the specimens, combining variable axial loads and variable bending moments. The testing machine has been designed to achieve two goals: to avoid the fracture of the cable in the vicinity of the clamps and to assure that the fracture of the cable is in the middle of the length of the specimen. The type of failure will be due to a combination of global stresses and fretting fatigue phenomena. This work also shows the results of different fatigue tests for a specific strand configuration. Finally, the fracture and contact surfaces of the strand have been analysed with a scanning electron microscope (SEM). The results obtained with this device show that it is adequate for testing cables and strands subjected to different combinations of axial loads and bending moments. [ABSTRACT FROM AUTHOR]

Repair welding for recovery from local damage of a rail head surface is known to cause high residual stress and can accelerate fatigue in the rail. This study examines repair-welded rails by applying experimental and numerical approaches. In the former approach, two newly manufactured rail specimens and four repair-welded rail specimens with two different weld depths were prepared, and their residual stresses were measured with a sectioning method. In the latter approach, a finite element repair welding simulation model was developed that adopted a prescribed temperature method with a moving block as an input heat source, and the thermal strain caused by the volume change due to solid-state phase transformation was considered. Overall, the residual stresses correlated well between the experimental and numerical approaches. The measured high compressive residual stress of −290 MPa seems to be beneficial to prevent a crack initiation in the rail surface. [ABSTRACT FROM AUTHOR]

In the present work, an attempt has been made to study the fatigue crack growth in a part-through circumferentially notched pipe specimen. It has been observed that under four-point bend cyclic load, the crack propagates in a transverse plane in the radial direction initially followed by propagation in the circumferential direction. The crack extension in the circumferential direction resulted crack growth retardation in the radial direction. This behaviour of the fatigue crack growth has been modelled, and a fatigue life prediction methodology based on an exponential model has been applied for prediction of fatigue crack growth. [ABSTRACT FROM AUTHOR]

ABSTRACT A new experimental set-up for drop weight tear tests is proposed. Its principal characteristic is the adoption of inclined supports driving the hinges connected to the specimen. This choice accomplishes the need that the specimen was subjected to a persistent stress field in the ligament, thus approaching the stress field experienced by a crack propagating in a pipeline. This set-up requires a proper processing of the data that is accurately explained in the paper. The tests are conducted under a quasi-static loading but the method has been designed to apply in dynamic tests. [ABSTRACT FROM AUTHOR]

Steam generators are important components of a nuclear reactor. They are subjected to system pressure and force controlled bending moments. Leak before break (LBB) criteria based on a fracture mechanics approach is used to ensure the reliability of the primary heat transport system of nuclear reactors. Experimental studies were recently completed for justifying LBB for the cold end of the shell–nozzle junction of the steam generator of the 500 MWe Fast breeder reactor (FBR) under construction at Kalpakkam. The internal diameter of the main tube is 1120 mm and that of the nozzle is 386.4 mm. The thickness of the main tube is 24 mm while that of the nozzle is 18 mm. Fatigue tests were conducted on two carbon steel and two modified 9Cr1Mo steel shell–nozzle junction specimens at room temperature under constant internal pressure and cyclic in-plane bending moment. Fracture tests were conducted on these components until collapse after the fatigue test. FEM analysis was also performed to identify critical locations and factor of safety for fatigue loading and collapse. The objective of the studies was to obtain the factor of safety for crack initiation, through-wall and critical crack size, and collapse. The studies demonstrated adequate factor of safety for all the above LBB criteria. [ABSTRACT FROM AUTHOR]

This study focused on the crack-healing behaviour of three commercial Al2O3–ceramic-matrix composites: TiCP/Al2O3, ZrO2/Al2O3 and SiCW/Al2O3. Vickers indentation was used to introduce surface flaws with different loads of 49, 98 and 196 N. Then the cracked specimens were annealed in air for 1 h at 1000, 1200 and 1400 °C. The annealing treatment was also conducted at 1200 °C in vacuum for 1 h. Results showed that the annealing treatments increased the indentation strength, but the extent of the increase was different. When annealed in air, the main crack-healing mechanism of TiCP/Al2O3 and SiCW/Al2O3 composites was chemical reaction. When annealed in vacuum, stress relaxation caused much less strength recovery. The main crack-healing mechanism of ZrO2/Al2O3 was the existence of low melting eutectic and the rearrangement of grains caused by ZrO2(m)→ ZrO2(t) transformation in the crack-opening process zone. The effects of annealing temperature, atmosphere and indentation load on the degree of strength recovery were all related to the crack-healing mechanisms. [ABSTRACT FROM AUTHOR]

The propagation of a surface flaw in a cylindrical shaft subjected to rotary bending is analysed using a two-parameter theoretical model. The stress-intensity factor distribution along the crack front is numerically determined for any position of the flaw with respect to the bending moment axis. The crack front is assumed to present an elliptical-arc shape with aspect ratio α = a/b (a, b = ellipse semi-axes), whereas the relative depth ξ of the deepest point on the front is equal to the ratio between the maximum crack depth, a, and the bar diameter, D. The results for rotary bending are compared to those for reversed cyclic bending. [ABSTRACT FROM AUTHOR]

In Part I of this paper, using the modal superposition method, equations for dynamic SIF calculations are derived for an arbitrary linear model of an impact bend specimen. In this paper (Part II), modal parameters and other data which are necessary for the DSIF determination have been calculated for three types of specimen model: the Euler–Bernoulli beam model, and two- (2D) and three-dimensional (3D) solid models. For the latter two cases, calculations were performed using the finite element program ADINA. Results for the 2D model of the specimen were fitted by polynomials for a wide range of specimen geometry parameters and Poisson’s ratio values. Considerable differences were observed between the beam model parameters and the 2D or 3D ones. The differences in results for the 2D and 3D models are small and mainly connected with non-uniformity of the SIF distribution along the front of a through-crack in the 3D solid. Results of processing one- and three-point bend test data reported in the literature are presented. Numerical DSIF values are compared with the experimental ones. [ABSTRACT FROM AUTHOR]