Remzi Varol

Influence of electromagnetic fields on bone fracture in rats: role of CAPE.

OBJECTIVE To study the effects of radiation emitted by mobile phones on bone strength and caffeic acid phenethyl ester (CAPE) on the changes induced by radiation. METHODS Forty-eight Sprague-Dawley rats were divided into five groups. Rats in the control group (first group) were left within the experimental setup for 30 min/day for 28 days without radiation exposure. Nine hundred MHz radiation group was broke down into 2 subgroups (group 1/2). Both subgroups were exposed to radiation for 28 days (30 min/day). The next group was also divided into 2 subgroups (group 3/4). Each was exposed to 1800 MHz of radiation for 28 days (30 min/day). The third and fifth groups were also treated with CAPE for 28 days. Treatment groups received ip caffeic acid phenethyl ester (10 micromol/kg per day) before radiation session. Bone fracture was analyzed. RESULTS Breaking force, bending strength, and total fracture energy decreased in the irradiated groups but increased in the treatment groups. CONCLUSION Radiation and CAPE can significantly improve bone.

Novel Type Shot Peening Applications on Railway Axle Steel

In this study, novel type shot peening applications such as severe shot peening (SSP) and dual step peening -DSP- (severe shot peening followed by re-peening -RP-) have been applied to AISI 4340 railway axle steel. Microstructural and mechanical properties are compared with conventionally shot peened (CSP) ones. The new treatments influence thicker surface layer and improve mechanical properties (microhardness and fatigue) by the way of Almen intensity enhancement. Disadvantageously, SSP increase surface roughness to the values that can be hazardous to the expected fatigue life of critical machine parts. However, DSP reduces the values and new approaches could be designed for making surface roughness values comparable with CSP in the aspect of the experimental outputs.

Wear Behavior of Severe Shot Peened and Thermally Oxidized Commercially Pure Titanium

In this study, severe shot peening (SSP) has been performed to commercially pure titanium (Grade 2) specimens in order to expose severe plastic deformations to the material surface. S230 shot media with higher air pressure conditions have been selected for SSP. A nanocrystalline layer has been created by means of severe plastic deformation. The nanograined structure has been investigated via XRD, FESEM, and microhardness methods. SSP specimens have been subjected to thermal oxidation treatment in air at 500 and 700 °C for 2 and 16 h. Severe shot peened commercially pure titanium has a thicker oxide layer when compared to as received ones. The results show that both SSP and thermal oxidation improve the wear characteristics.

Tribological properties of boronized ferrous based PM journal bearings

Abstract Ferrous based PM (powder metallurgical) materials are widely used in journal bearings since they provide a good tribological performance. These bearings are self-lubricating and can be used in places where lubricating is not possible. This also applies to the shaft material which shows adhesive wear. Tribological properties can be improved and adhesive wear can be decreased by boronizing. In this study, tribological properties of ferrous based boronized and non-boronized Fe-graphite, FeCu-graphite and CuSnFe-graphite bearings manufactured by PM method have been determined and compared. Boronizing treatment was carried out at 950° C for 4 hours. The SAE 1050 steel shaft was used as counter abrader. Experiments were carried out at 20 N loads and 1500 rpm every 30 minutes for 2.5 hours.

Effect of Boronizing and Shot Peening on the Fatigue Properties of an Iron Based FeCu-Graphite P/M Material

Abstract Iron based materials manufactured by powder metallurgy (P/M) method are widely used in industry. These materials are very important in applications where no machining is required, they can also be used as journal bearing material due to their self-lubricated property, and can be used for applications in the medical industry. In this study, powder metal parts were manufactured from composites based on FeCu-graphite by P/M method. Fatigue test was carried out on manufactured samples, which were only treated by boronizing or boronizing and shot peeing. The fatigue properties of these parts were investigated by a rotating bending fatigue test rig.