Karakteristik Fiber Metal Laminate Akibat Beban Impak Balistik Dari Peluru Kaliber 9 mm Full Metal Jacket (FMJ)

<p class="Abstract"><span lang="EN-GB">Estimated damage levels from ballistics impact zone provide valuable information to make bulletproof materials more effective. Therefore, this study aims to determine the impact of ballistics including hole shape, hole depth, macro, and microstructure on fiber metal laminate. The characteristics of ballistics impact for each configuration target is obtained from experiment and comparison based on simulations with finite element method. Test experiments used short-barreled fire guns at a distance of 5 meters with a normal attack angle based on the National Institute of Justice standard. Simulation with Johnson-Cook plasticity models for aluminum plate and orthotropic material model for kevlar/epoxy. The experiment and simulation results showed that the projectile is able to perforate the first layer (aluminum plate) and the second layer (Kevlar/epoxy) while the last layer (backplate) is deformed to form a bulge. The aluminum plate is perforated by the failure of petaling formation on the backside and spread of dimple fracture around the area of the petal which indicates ductile fracture while kevlar/epoxy is perforated by projectile with failure of fiber fracture on primary yarn, fiber pull-out, fiber stretching and fiber rupture.</span></p>

Effect of Powder Recycling on the Fracture Behavior of Electron Beam Melted Alloy 718

Understanding the effect of powder feedstock alterations during multicycle additive manufacturing on the quality of built components is crucial to meet the requirements on critical parts for aerospace engine applications. In this study, powder recycling of Alloy 718 during electron beam melting was studied to understand its influence on fracture behavior of Charpy impact test bars. High resolution scanning electron microscopy was employed for fracture surface analysis on test bars produced from virgin and recycled powder. For all investigated samples, an intergranular type of fracture, initiated by non-metallic phases and bonding defects, was typically observed in the regions close to or within the contour zone. The fracture mode in the bulk of the samples was mainly moderately ductile dimple fracture. The results show a clear correlation between powder degradation during multi-cycle powder reuse and the amount of damage relevant defects observed on the fracture surfaces. In particular, samples produced from recycled powder show a significant amount of aluminum-rich oxide defects, originating from aluminum-rich oxide particulates on the surface of the recycled powder.

Numerical approach to dimple fracture under very short pulse loading

Dimple fracture of aluminum alloy 7075-T651 subjected to various stress intensity pulses with durations of 20, 40 and 80 μs is investigated by discrete dislocation dynamics and the Gurson-Tvergaard-Needleman constitutive model (GTN-model). A dominant void ahead of macro crack tip is modeled by a micro crack. The evolution of principal stress component along the inner ligament is computed by the sum of the crack tip stress field and the interaction stress field of dislocations emitted from both the micro crack and macro crack. The yielding flow of GTN-model is used to estimate void volume fraction, which is used for a fracture initiation criterion. The numerical results of the dimple fracture are obtained in a reasonable agreement with the experimental ones.

The Influence of Thermal Exposure and Hydrogen Charging on the Notch Tensile Properties and Fracture Behaviour of Dissimilar T91/TP316H Weldments

The effects of ageing and hydrogen charging on the notch tensile properties and fracture behaviour of individual heat-affected zones (HAZ) and Ni-based weld metal (Ni WM) of T91/TP316H weldments were investigated. After the post-weld heat treatment at 750 °C for 1 h the weldments were annealed at 600 °C for 1000 h and 5000 h, respectively. All heat-treated states were studied in condition without as well as with hydrogen charging. Thermal expositions led to additional precipitation and microstructure coarsening but their influence on tensile strength was insignificant. In contrast, remarkable plasticity decrease and the fracture mode transition from ductile dimple tearing to transgranular cleavage were observed. The combined effects of thermal exposure and hydrogen charging were more complex. Whereas the regions of Ni WM and TP316H HAZ did not show any significant change in strength, the hydrogen effect caused the strength increase in T91 HAZ. Although the hydrogen embrittling effects were clearly manifested by decreasing plasticity, their significance was getting smaller with increasing annealing duration. The fracture behaviour of thermally exposed and hydrogen charged regions exhibited mixed fracture modes including transgranular cleavage, intergranular dimple fracture and intergranular decohesion.

Microstructure and Mechanical Properties of Cobalt Alloy Coating Deposited by Electro-Spark

Stellite190 cobalt alloy coating was deposited on 45 carbon steel by electro-spark deposition. Formation mechanism, microstructure, phase composition and mechanical properties of the coating were researched, fracture mechanism of the coating was analyzed. The results indicate that, the coating has dense and well distributed microstructure, mainly composed of Co, (CoCrW)6C, Cr7C3. The coating presents excellent mechanical properties with a tensile strength of 731.83 MPa, a bonding strength of 213.01 MPa and good peeling resistance. The mechanism for tensile fracture of the coating is dimple fracture, and for shear fracture is cleavage fracture.

Effect of Tempering Temperature on Mechanical Properties of High Strength Wear Resistant Cast Steel

This paper mainly studied the high temperature quenching oil quenching, tempering temperature on the influence of high strength steel mechanical properties of wear resistant. The results show that high strength and toughness wear-resistant cast steel with 880°C× 30min after oil quenching, the hardness of 38.6HRC steel, the impact toughness value reaches 40.18J/cm2. After 200°C, 400°C and 600°C tempering, with the increase of the tempering temperature, the hardness decreased linearly, as by 600°C tempering, the hardness has been reduced to 22.3HRC. Impact toughness with the tempering temperature, the overall upward trend, the impact toughness of some reduced at 400°C, the highest impact toughness value reaches 113.34J/cm2. From the fracture morphology can be seen, with the increase of tempering temperature, ductile fracture increased, by 600°C tempering is dimple fracture, obviously can not see the traces of brittle fracture.

Effects of Trace ZrC on the Microstructure and Properties of Molybdenum Alloy

The present study describes the effect of trace ZrC additive on the microstructure and properties of Mo-Ti-Zr alloy fabricated by powder metallurgy method. The results indicate that, ZrC addition effectively enhanced the tensile strength of the alloy both at room-temperature and high-temperature, the alloy with 0.4wt% ZrC has the highest tensile strength, which is 611MPa and 513MPa at 25°C and 800°C, respectively. The tensile fracture mainly consists of intergranular rupture at room temperature, while dimple fracture occurred at high temperature, which indicating higher elongation. Through observation from the micrograph and EDS analysis, ZrxOyCz second-phase particles were observed,which is derived from part of ZrC particles reacted with the oxygen and can suppress the oxygen segregation on grain boundary.

Effect of Y on Microstructure and Mechanical Properties of Aluminium Alloy

The effects of yttrium (Y) on microstructures and mechanical properties of aluminium alloy were investigated in detail by scanning electronic microscope (SEM), energy dispersive spectrum (EDS),X-ray diffraction and tensile test. The results show that the trend of alloys tensile strength and elongation with increasing of the Y content is a broken line. When the Y content is increased up to 0.30%, the tensile strength and elongation are 105MPa and 10.50% respectively, meanwhile, the fractograph exhibited typical ductile dimple fracture pattern. Then the alloy performance is best. The high strength of aluminum alloy is attributed to the size of Al2Y phase. Addition of Y above 0.30% in aluminum alloy may generate more the coarse Al2Y particle. It can induce the decrease in the material performance.

Effects of Rare Earth on the Inclusions and Mechanical Properties of Austenitic Stainless Steel

The effects of rare earth metals on the inclusions and the mechanical properties of 21Cr11Ni austenitic steel were studied by scanning electron microscope (SEM) and energy spectrum analysis. The results show that the morphologies and sizes of inclusions in 21Cr11Ni stainless steel are changed, and rare earth played a very good role of modifying inclusions. The fracture mode of 21Cr11Ni stainless steel is typical cleavage fracture, but quasi-cleavage and dimple fracture after adding RE into the steel. The transverse impact toughness of 21Cr11Ni stainless steel is improved obviously by RE. In comparison with 21Cr11Ni stainless steel without RE, the transverse impact toughness of 21Cr11Ni stainless steel with RE is increased 25.33% at-40°C, and the room temperature strength are improved, the elongation and reduction of area have been improved 9.18%, 12.71% respectively.