Selim Gürgen

The effect of carbide particle additives on rheology of shear thickening fluids

In this paper, shear thickening fluids (STFs) including silicon carbide particles are presented. We fabricated a kind of STF based on nanosize fumed silica suspended in a liquid medium, polyethylene glycol, at a constant concentration of 20 wt.%. Then, different particle size silicon carbide (SiC) particles were added to the STF with various amounts. Their rheological properties under various temperatures were tested by using a rheometer. The suspension exhibits different systematic variations with respect to the varied parameters.

The effect of silicon carbide additives on the stab resistance of shear thickening fluid treated fabrics

ABSTRACT Applications of shear thickening fluids (STFs) with ballistic fabrics improve the protection performance of body protective systems. This article presents an innovative view of STF-impregnated ballistic fabrics by integrating silicon carbide (SiC) particles into targets. In this study, SiC particles were added into silica-based STFs, and Twaron fabrics were impregnated with this novel suspension. The effect of the SiC particles in the STFs was investigated with rheological testing. The results show that SiC particles are able to increase the viscosity profile of the suspension. In the stab testing, two types of impactors, such as spikes and knives, were dropped on the composite targets. According to the results, SiC particles enhance the protection performance of the STF-treated ballistic fabrics while keeping the flexibility.

High Performance Fabrics in Body Protective Systems

High performance fabrics are preferable for armor systems due to their lightweight structure and flexibility. High performance fabrics are generally used in body armor design for personal protection. However, these fabrics are utilized to cover the living space in military vehicles such as helicopters and armored vehicles. Besides, pilot seats in combat helicopters are included in utilization area of high performance fabrics. On the other hand armor is defined as a defensive covering to protect body or something against attacking threats. Protection is provided by absorbing the kinetic energy of the attacking threats and stopping them before any damage occurs in the target. This paper offers an overview of high performance fabrics in armor systems.

Numerical Simulation of Roller Hemming Operation on Convex Edge-Convex Surface Parts

This paper presents the roller hemming operation of FEE220BH sheet metal with convex edge-convex surface geometry. The investigation is focused on process parameters of bending angle and roller geometry whose effects have not been investigated in previous studies. A set of numerical simulations is designed to observe the multi response of the process parameters. The objective of the study is to determine the influences of these parameters on deformation, undesired wrinkling formation and hemming force which are directly related to the material reliability and the visual quality in the operation. The results are discussed to improve the outputs of the operation.

Fatigue and corrosion behavior of in-service AA7075 aircraft component after thermo-mechanical and retrogression and re-aging treatments

Fatigue crack growth and corrosion are the two important failure mechanisms for aircraft structural components and, therefore, various treatments have been developed to improve the fatigue and corrosion resistance of aircraft materials. In the present study, thermo-mechanical and retrogression and re-aging treatments were applied to AA7075T7352 specimens, which were extracted from a nearly 40 years in-service F-4 Phantom component. The in-service component was selected in order to observe the influence of thermo-mechanical and retrogression and re-aging treatments on the properties of a used aircraft material and it was expected that the service life of the material is extended in the maintenance stage. In the experimental work, electrical, mechanical, fatigue crack growth, and corrosion tests were carried out using the specimens with T7352 (as-received), thermo-mechanical and retrogression and re-aging conditions. Based on the results, fatigue crack growth resistance of the material benefited from the thermo-mechanical and retrogression and re-aging treatments; however, both treatments lowered the corrosion resistance of the material.

Fatigue failure in aircraft structural components

Abstract Safety in aircraft applications is at the advanced level since any mistake may result in irreversible situations during the services. For this reason, aircraft structural parts are subject to different kinds of inspections from manufacturing stage to service stage. Generally, the parts under arduous conditions are called critical parts and inspected profoundly against the fatigue defects. The most common fatigue failures arise from sharp edges, notch-sensitive areas, and necked-down sections in the structural parts. In this chapter, two case studies about failure of aircraft structural components are discussed. The first case study describes the fracture mechanism in a Cessna-185 aircraft propeller blade due to fatigue crack propagation induced by foreign object damage. The second case study explains the fatigue failure of a cylindrical part in an aircraft flap actuator.