Advances on the Fragmentation-Energy Fan Concept and the Swebrec Function in Modeling Drop Weight Testing

The breakage index equation (BIE), or t10 model from drop weight testing (DWT) data for rocks and ores is used in the design of crushers and mills. Such models are becoming increasingly difficult to visualize as the number of variables increases. The so-called double fan BIE, combined with the Swebrec distribution’s accurate description of the sieving curves, is applied to the modelling of drop-weight test fragmentation. The key parameters are geometric properties visible in the fan plot; slopes of straight lines and their point of convergence. The ability of the double fan BIE to reproduce DWT data had been previously established for 8 rocks with 480 DWT data sets. Here the fidelity of the double fan BIE is further evaluated for 18 new materials, based on 281 data sets. The fidelity of the double fan BIE with three fan lines is on par with the fidelity of the current state-of-the-art models for the new materials. Besides the breakage index equation, the new double fan BIE’s t10 equation produces, without additional parameters or fitted constants, the general breakage surface equation tn for an arbitrary n value as a bonus. The specific sieving curve for any combination of particle size and impact energy is also contained in the same formula. The result is an accurate, compact and transparent model.

Fluoropolymer/GAP Block Copolyurethane Binders: Sensitivity, Mechanical Properties and Reactive Properties with Aluminum

In order to enhance the application properties of GAP in solid propellant, an energetic copolyurethane binder, (poly[3,3-bis(2,2,2-trifluoro-ethoxymethyl)oxetane] glycol-block-glycidylazide polymer (PBFMO-b-GAP) was developed. The PBFMO-b-GAP was prepared using poly[3,3-bis(2,2,2-trifluoro-ethoxymethyl)oxetane] glycol (PBFMO) which preparing from cationic polymerization and GAP as the raw materials, TDI as the coupling agent via a prepolymer process. The molecular structure of copolyurethane was confirmed by FT-IR, NMR, GPC. The impact sensitivity, mechanical properties and thermal behavior of PBFMO-b-GAP were studied by drop weight test, XPS, tensile test, SEM, DSC and TG/DTG respectively. The results proved that the introduction of fluoropolymer can evidently reduce the sensitivity of GAP based polyurethanes and enhance their mechanical behavior (the tensile strength up to 5.75MPa with a breaking elongation of 1660 %). Also, PBFMO-b-GAP exhibited an excellent resistance to thermal decomposition up to 200°C and good compatibility with Al and HMX. Cook-off test was used to investigate the reactive of copolyurethanes and Al, the results indicated that the copolyurethanes could react with Al efficiently and release significantly more heat. Therefore, the energetic copolyurethanes may serve as promising energetic binders for future propellant formulations.

Experimental and Numerical Investigation of Steel Sections under Impact Effect

Experimental and numerical behaviour of steel test specimens with various types of joints is investigated in this study. A drop weight test setup with necessary test equipment is used for this purpose. The mass and drop height of the hammer is taken to be constant so that the same impact energy can be applied on test specimens. The acceleration, displacement, impact load, drop numbers and drop durations, are obtained through experimental study. In addition, development of damage to test specimens is observed during tests. Numerical analyses of behaviour of test specimens under impact load are also conducted to verify test results using the Abaqus software, and a comparison of results is made.

Evaluation of Impact Resistance for Derailment Containment Provision Using Drop Weight Test

In Korea, to prepare for unexpected accidents caused by human errors and natural disasters that cannot be completely prevented, a protective wall (a type of side-structure) against derailed trains has been installed on high-speed railway bridges as one of the physical measures to mitigate the associated damage. However, taking the geometric aspects of a domestic railway bridge's super structure into consideration, such a protective wall is not appropriate, and the corresponding protective performance does not provide adequate security. Hence, a protective wall named Derailment Containment Provision (DCP) was newly developed and installed in the track gauge. In this study, to evaluate the impact resistance of the newly developed DCP, a drop weight experiment was conducted, and the impact behavior corresponding to a specific impact energy was analyzed.

Some Observations About the Drop-weight Explosive Sensitivity Test

The apparent simplicity of the drop-weight apparatus for explosive sensitivity testing hides the reality that it is actually a complex integrated test of both ignition and growth of deflagration. Although the drop-weight test is undeniably a useful screening test for explosive properties, a misunderstanding of the technique’s limitations has blinded many researchers to its limited wider applicability. This monograph discusses how the test actually works, the significant engineering difficulties with standardization between machines, which types of explosives are suited to the test and which are not, and finally offers a few suggestions for alternatives when a more quantified understanding of a material’s response is required for other applications.

Experimental Investigation on Relations Between Impact Resistance and Tensile Properties of Cement-Based Materials Reinforced by Polyvinyl Alcohol Fibers

Cement-based material is brittle and is easily damaged by an impact load with a few blows. The purpose of this paper is to study the relations between the impact resistance and tensile properties of cement-based materials reinforced by polyvinyl alcohol fiber (PVA-FRCM). A drop-weight test and uniaxial tension test were performed. The relations were studied based on the experimental results, including the relation between the blow number and the tensile stress at the first visible cracking (σc) and the relation between the blow number and the tensile strain at the ultimate failure (εf). Results showed that the blow number for the first visible crack for disc impact specimens increases obviously with the increase of σc of slab specimens. The crater diameter and blow number for ultimate failure of the disc specimens increase with the increase of εf of slab specimens. For the PVA-FRCM specimens with larger σc and εf, much more blows are needed to cause both the first visible crack and ultimate failure. Polyvinyl alcohol fibers can reinforce impact resistance and tensile properties of cement-based materials.

Behaviour of Micro Reinforced Concrete with Hooked End Steel Fibres subjected to Impact Loads

Reinforced cement concrete is a common material used for building constructions. In this work a trial has been created to utilize steel fibres in RCC members to extend strength and conjointly to extend resistance to impact load. Hooked end steel fibres (HESF) are used here for the preparation of concrete specimens. Concrete grade of M30 is selected and mix design was carried out for target strength of 38.25 N/mm2 . Varied volume fractions of HESF such as 0%, 1%, 2%, 3% and 4% were added to concrete. Cube, beam and cylindrical specimens were cast with good compaction and cured fully as per standards. Hardened concrete strength of all the specimens with different quantities of HEFS were tested. Simple drop weight test was conducted on the specimens reinforced with different percentages of steel fibres. The impact load is produced by means of dropping a weight of 5.5 kg from 400 mm height. Impact energy of the specimens is derived from number of blows required to produce initial crack (N1) and number of blows to cause complete failure (N2). Impact energy of the specimens with different quantities of fibres are compared. Results indicated that the concrete specimens with 3% volume fraction of fibre has shown best performance and it is also seen that the increase in volume of fibre beyond 3% has resulted in reduced impact energy