A.M. Eleiche

Experimental investigation of the ballistic resistance of steel-fiberglass reinforced polyester laminated plates

Abstract The present experimental study is undertaken to investigate the effect of target configuration on ballistic performance when struck by standard bullets of different velocities. At first, single mild steel plates, 1–8 mm thick, are tested, and the effect of thickness and mechanical properties of plate material are explored. Secondly, in-contact laminae comprising an 8 mm-thick target, and spaced laminae of the same total steel thickness, with spacing distances equal to or multiples of the bullet core diameter (6 mm) are tested and the effect of number, thickness, and arrangement of laminae sought. In addition, fiberglass reinforced polyester (FRP) is used as a filler material for targets with spaced steel laminae. The influence of FRPs physical and mechanical properties on the ballistic performance of steel-FRP targets is investigated. In order to perform the ballistic tests, a special setup is constructed, which consists of a launcher, a target clamp and a velocity-measuring device. In each experiment, the change in the projectile velocity (while penetrating the target) divided by the length of penetration is established as a measure of target performance. Results show that single targets are more effective than laminated targets of the same total thickness, regardless of the configuration or striking velocity. It is noted, however, that the difference in performance diminishes as the striking velocity increases. Moreover, the effectiveness of laminated targets, in contact or spaced, increases as the number of laminae comprising each target decreases. Ballistic performance of laminated targets is further enhanced by using the thickest lamina as the back lamina. Results also emphasize the dependence of target performance on mechanical properties. Steel-FRP targets show better performance than weight-equivalent steel targets. Performance of a steel-FRP target is further improved by increasing fiber weight fraction in the FRP.

Fracture toughness properties of high-strength martensitic steel within a wide hardness range

Fracture toughness tests were carried out on six grades of high-strength martensitic steel within the hardness range from 270 to 475 HB. Four types of tests were performed: (a) Charpy V-notch (CVN) impact over the temperature range −120 to 60 °C, (b) plane strain fracture toughness, KIC, near the onset of crack growth, (c) fracture toughness, JIC, near the initiation of slow crack growth, and (d) fracture toughness, JiC, and crack tip opening displacement (CTODiC) at the onset of slow crack growth using direct current potential drop (DCPD) technique. Further, true plane strain fracture toughness, Ko, at the onset of crack initiation was determined. Fracture toughness behavior including the measured and determined values of CVN, KIC, Ko, JIC, KiC, and CTODiC have been interrelated over the entire hardness range using the various analytical and empirical correlations reported in the literature. The results indicate that the steel acquires the optimum fracture toughness properties at a hardness of 305 HB, corresponding to a tempering temperature of 630 °C. Further, the steel exhibits a slight 300 °C temper embrittlement phenomenon.

Low-cycle fatigue in rotating cantilever under bending I: Theoretical analysis

Rotating bending fatigue of a cantilever beam is examined analytically. New relationships are derived to determine the surface strain amplitude, at the mid-point of the tested zone, as a function of the applied nominal bending stress, the vertical and horizontal deflections, and Youngs modulus. A numerical methodology is also derived to calculate the rotating bending fatigue behaviour of a material from its cyclic stress-strain response and strain-life curve, and vice versa

Fatigue crack growth in cantilever bending under displacement control

Fatigue crack growth (FCG) behavior of two martensitic steel grades was investigated using a single edge-notched bend specimen fixed beyond the notched section in cantilever bending under displacement control. This task was made possible by a new and original testing methodology developed on the basis of finite element analyses to define valid boundary conditions and the corresponding stress intensity factor K-expression for the test specimen. The behavior has been described including the nearthreshold zone and the second zone of relatively high FCG rates. Results for the two steel grades were found to correspond well with the empirical models reported in the literature. This confirms the validity of the methodology proposed in the present paper, which can be attributed to: (1) the accurate K-expression for the test specimen, (2) the proper definition of the boundary conditions adopted during testing, and (3) the validity of the adopted boundary conditions.

Modeling of Notch Tensile Behavior of Martensitic Steels

AbstractNotch tensile tests have been carried out on six grades of a high-strength martensitic steel at different hardness levels to investigate the effects of stress triaxiality at the net section and uniaxial tensile properties on fracture behavior. Cylindrical V-notched specimens were used in these tests with the notch-root radius, ρ, ranging from 0.03–1.4 mm, and with the value of the net-to-gross diameter ratio being 0.6. The notch strength ratio (NSR) was found to attain its maximum value at ρ=0.38 mm. The test results were used successfully for screening the fracture toughness behavior of the martensitic steel by extrapolating the corresponding ρ-NSR curve to ρ=0.0. Further, finite element computation of the average stress triaxiality factor (

A Global Collaborative Effort to Enhance Design in a Mechanical Engineering Curriculum in Saudi Arabia

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The shot-peening effect on the HCF behavior of high-strength martensitic steels

) enabled the development of a model more accurate than that reported in the literature for estimating NSR for a ductile material as a function of