Rolling Contact Fatigue Life of 13Cr-2Ni-2Mo Stainless Steels which are Surface Treated by Induction Heating (IH) and Wide Peening Cleaning (WPC)

A new surface treatment, wide peening cleaning (WPC), was developed to improve fatigue strength of steels using shot peening and sandblast technologies. The combination of induction heating (IH) and WPC is expected to introduce higher compressive stress on the steels than single IH or single WPC. We investigated effect of IH and WPC on rolling contact fatigue life of 13Cr-2Ni-2Mo stainless steel. Vickers hardness and residual stress measurements, and RCF life evaluation using the Weibull distribution were carried out. It was found that the residual stress was introduced by WPC near the surface to improve life fatigue

CAVITATION AND ELECTROCHEMICAL CHARACTERISTICS IN SEAWATER BY WATER CAVITATION PEENING OF 5083-O Al ALLOY FOR SHIPS

Aluminum (Al) alloy ships are vulnerable to both damage from chlorine ions in seawater environments and cavitation-erosion due to fast relative motion of metal and liquid resulting from lightweight and high-speed vessels moving through seawater. These corrosive processes cause damage to the hulls of ships, resulting in large economic losses. Recently, cavitation peening technology to improve the durability of a material has been in development. The technology works by forming compressive residual stress on the surface layer of the material in order to improve fatigue strength and fatigue life. In this study, we performed a water cavitation peening (WCP) on a 5083-O Al alloy for ships by applying an ultrasonic piezoelectric effect and cavitation effect, as described in ASTM-G32. From these experiments, we determined an optimum WCP duration, 2.5[Formula: see text]min, for sufficient cavitation resistance characteristics. This timing improved cavitation resistance by 48.68% compared to the untreated condition. A comprehensive comparison of all of results revealed that the optimum WCP duration was 3[Formula: see text]min with respect to the point of cavitation and corrosion resistance.

Fatigue Testing of Titanium Alloy Ti6Al4V Used in Medical Devices

Because titanium alloy Ti6Al4V features low density, good corrosion resistance and biocompatibility, it a metal of choice for medicine, used in orthopedics, accident surgery and dentistry. The insertion of elements such as nitrogen, carbon, hydrogen, iron or oxygen improve fatigue strength of this material. This paper presents certain basic fatigue and monotonic tests performed on the alloy. We have proposed a unique sample geometry and sample dimensions smaller than the reference ones. The dimensions of the working part of the sample correspond to the geometry of a dental implant connector. This part of the implant has to withstand stresses that are both intricate and variable in time. We performed monotonic tensile strength tests and uniaxial fatigue tests using the Instron 8874 machine. Then, we examined the samples under a stereoscopic microscope and measured the fracture development angle.

Design of a Lightweight Truck Wheel

The presented research activity is focused on the lightweight construction of a of truck wheel, with the final aim of improving the energy efficiency in compliance with current safety standards. On the basis of the design of a truck wheel currently into production, the objective of reducing the wheel mass is achieved by adopting high-strength materials, optimizing the geometry, and developing a new production process. The approach used for the new wheel design is based on the selection of a proper mission of the vehicle and on the acquisition of the loading spectra defined by using a new measuring wheel. The information obtained is used during the structural analysis phase. Based on the current production process, a number of suitable materials have been selected. Innovative manufacturing processes have been considered for improving the fatigue life of the wheel. Shot peening has been considered as a method to improve fatigue strength. Moreover, the introduction of laser cutting and welding led both to more freedom in the definition of the geometry of the wheel and to the reduction of the effects of geometric notches due to the absence of weld beads. A dedicated indoor test rig was used for durability tests. These activities led to a new truck wheel with reduced mass that is currently in the experimental validation phase.

The Effect of Shot Peening on the Surface Topography and Fatigue Strength of Selected Sheets

Numerous investigations have been performed in an attempt to improve fatigue strength of materials by creating compressive residual stresses in the surface layers as a result of the shot peening process. For example, during exploitation of the separating screener, some parts of screen sieve plate situated near the fixed edge undergo the largest deformation caused by impact bending and need special treatment. In this paper, the results of experimental tests are presented to analyse the effect of micro shot peening on surface layer characteristics and fatigue strength of steel sheet specimens. The effect of shot peening is more visible when fatigue life is taking into account. Thus, the use of shot peening of sheet surface made it possible to increase fatigue life of screener sieve.