Structural Effects of Heat Treatment Holding-Time on Dynamic and Damping Behaviour of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

The paper reports the structural effects of holding time period, during heat treatment, on the dynamic and damping behavior of a Fe-28Mn-6Si-5Cr (mass. %) shape memory alloy. After casting and hot rolling, solution treatment at 1050 oC was applied for five holding times, 2, 4, 6, 8 and 10 hours, followed by water quenching. The specimens were analyzed by scanning electron microscopy and X-ray diffraction which emphasized that only the 2-hours solution treated specimens contained ε-hexagonal close packed (hcp) martensite and experienced the highest internal friction value. These specimens were tested on a special device which transformed both tension and compression into tensile strain applied to the specimens and proved to be a promising solution for anti-seismic damper

Evaluation of the Fatigue Behavior and Failure Mechanisms of 4340 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

Fatigue behavior of standardized 4340 steel samples uniformly coated with WIP-C1 (Ni/CrC) by cold spray was investigated. In particular, when a crack appeared at the interface between the base material and the coating, the cause of it as well as its shape and size were investigated. Fatigue loading was applied by alternating symmetrical cycles. Scanning electron microscopy was used to study the onset of failure and the subsequent propagation of cracks. The interface between the two materials performed well—in all samples, the initial crack propagation occurred on the surface of the base material, continuing into the coating material and in the interior of the base material. The fatigue durability curve of stress vs. number of cycles (S-N) presented a conventional form for a metallic alloy and the coating material had an influence only on the damage on the surface of the base material

Structural Testing by Torsion of Scalable Wind Turbine Blades

In life service, the wind turbine blades are subjected to compound loading: torsion, bending, and traction, all these resulting in the occurrence of normal and tangential stresses. At some points, the equivalent stresses, due to overlapping effects provided by normal and shear stresses, can have high values, close to those for which the structure can reach to the failure point. If the effects of erosion and clashes with foreign bodies are added, the structure of the blade may lose its integrity. Considering both the complex shape of the blade and internal structure used, the mechanical behavior of the blade, such as the rigidity and resistance along the length of the blade, are usually determined with some uncertainty. This paper presents the results obtained in the non-destructive tests at static torsion of a scalable wind turbine blade. The objective of the paper was to determine the variation of the equivalent stress in the most stressed points of the blade, in relation to the torques applied. To determine the points with the highest stress, a finite element analysis was performed on the scalable wind turbine blade. Electrotensiometric transducers were mounted at different points of the blade, determining the main stresses in the respective points, as well as their variation during the torsion test, by subsequent calculations. The determinations were performed by applying the torque in both senses, in relation to the blade axis, thus concluding the values of the equivalent stress in the two cases

Analysis of the Effect of Fiber Orientation on Mechanical and Elastic Characteristics at Axial Stresses of GFRP Used in Wind Turbine Blades

Due to its physical and mechanical properties, glass-fiber-reinforced polymer (GFRP) is utilized in wind turbine blades. The loads given to the blades of wind turbines, particularly those operating offshore, are relatively significant. In addition to the typical static stresses, there are also large dynamic stresses, which are mostly induced by wind-direction changes. When the maximum stresses resulting from fatigue loading change direction, the reinforcing directions of the material used to manufacture the wind turbine blades must also be considered. In this study, sandwich-reinforced GFRP materials were subjected to tensile testing in three directions. The parameters of the stress–strain curve were identified and identified based on the three orientations in which samples were cut from the original plate. Strain gauge sensors were utilized to establish the three-dimensional elasticity of a material. After a fracture was created by tensile stress, SEM images were taken to highlight the fracture’s characteristics. Using finite element analyses, the stress–strain directions were determined. In accordance to the three orientations and the various reinforcements used, it was established that the wind turbine blades are operational

Obtaining and Tensile Strength Study for Non-Precious Alloys Based Cobalt

This paper presents aspects of obtaining non-precious dental alloys of Co-Cr-Mo alloys system and experimental tests to determine tensile strength, carried on standard flat specimens

Hardness-gradient reversion in FeMnSiCr shape memory alloy modules produced by high-speed high pressure torsion

High pressure torsion (HPT) processing technology, consisting in the obtainment of (ultra)fine bulk metallic structure during 2–3 complete rotations of the superior anvil at low speed (~10-1 rpm) under high applied pressure (~ GPa) applied on the lower anvil, has been modified as to allow the application of elevated number of rotation numbers (~102 rpm). By high-speed high pressure torsion (HS-HPT), coned-disk spring shape modules were processed from an as cast Fe-28Mn-6Si-5Cr (mass %) shape memory alloy (SMA). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies revealed that the modules became nanostructured as an effect of HS-HPT processing. After processing, a hardness gradient was obtained along the truncated cone generator, increasing from inner to outer areas, due to different deformation degrees in these zones. After complete flattening, the measurements revealed that the hardness gradient maintained its value but reversed its variation sense

Hardness-gradient reversion in FeMnSiCr shape memory alloy modules produced by high-speed high pressure torsion

High pressure torsion (HPT) processing technology, consisting in the obtainment of (ultra)fine bulk metallic structure during 2–3 complete rotations of the superior anvil at low speed (~10-1 rpm) under high applied pressure (~ GPa) applied on the lower anvil, has been modified as to allow the application of elevated number of rotation numbers (~102 rpm). By high-speed high pressure torsion (HS-HPT), coned-disk spring shape modules were processed from an as cast Fe-28Mn-6Si-5Cr (mass %) shape memory alloy (SMA). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies revealed that the modules became nanostructured as an effect of HS-HPT processing. After processing, a hardness gradient was obtained along the truncated cone generator, increasing from inner to outer areas, due to different deformation degrees in these zones. After complete flattening, the measurements revealed that the hardness gradient maintained its value but reversed its variation sense

Evaluation of the Fatigue Behavior and Failure Mechanisms of 4340 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

Fatigue behavior of standardized 4340 steel samples uniformly coated with WIP-C1 (Ni/CrC) by cold spray was investigated. In particular, when a crack appeared at the interface between the base material and the coating, the cause of it as well as its shape and size were investigated. Fatigue loading was applied by alternating symmetrical cycles. Scanning electron microscopy was used to study the onset of failure and the subsequent propagation of cracks. The interface between the two materials performed well—in all samples, the initial crack propagation occurred on the surface of the base material, continuing into the coating material and in the interior of the base material. The fatigue durability curve of stress vs. number of cycles (S-N) presented a conventional form for a metallic alloy and the coating material had an influence only on the damage on the surface of the base material