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Research On Honeycomb Structure Explosives And Double Sided Explosive Cladding

Posted on:2016-08-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:G H MiaoFull Text:PDF
GTID:1220330467490523Subject:Engineering Mechanics
Abstract/Summary:PDF Full Text Request
Explosive cladding, which has the advantages of simple process, low cost, good performance and energy rich, has become a very important connection method in metal processing. Using large charge weight, single sided explosive cladding, which is relatively primitive, is still used at home and abroad. Most of energy is released in the space in the form of shock wave due to only one side of explosive energy can be used. In such case, single sided explosive cladding has the characteristics of "high noise and low efficiency". The explosives for explosive cladding used mostly at present is powder explosive. Due to it is difficult to control the charge density and uniformity, the detonation velocity of explosives is not stable. In such case, the quality of the product is seriously affected. The following issues, such as heavy workload, serious dust pollution and harmful for workers’mental and physical health remain unresolved. In order to resolve the current issues, honeycomb structure explosives and double sided explosive cldding were used in the present study. Double sided explosive cladding can clad two composite plates simultaneously. Due to constraint of double sided flyer plates, lateral rarefaction waves invasion is prevented. The energy of detonation wave is reduced and the energy utilization ratio is improved. The consumption of explosive is only10~20%for the traditional method.Honeycomb structure explosives, which is made of aluminum honeycomb and emulsion explosives is designed to resolve the backward method of charge. Due to multi-directional constraint of honeycomb material and double sided flyer plates, emulsion explosives with the thickness of5mm can stable detonation. Honeycomb structure explosives can improve the quality of the charge. The detonation parameters of honeycomb structure explosives were tested and calculated, respectively. The results show that:The detonation velocity of honeycomb structure explosives with the thickness of5mm is4510m/s. The detonation pressure driven by honeycomb structure explsives with the thickness of13mm is808MPa. The density on the CJ plane is1.49g/cm3. The velocity of detonation products is1128m/s. The detonation pressures is5.7GPa.The theoretical calculation and experimental study of double sided explosive cladding for steel of No45to steel of Q235and stainless steel to steel of Q235were investigated respectively. The calculation results show that:The explosive cladding window for steel of No45to steel of Q235is222m/s<υp<716m/s,1045m/s<υD<5200m/s. The explosive cladding window for stainless steel to steel of Q235is197m/s <υp<557m/s,851m/s<υD<5200m/s. The experiment results show that:The bond interface with micro wavy create good connection due to almost no transition zone, no cracks and loose like "cavity" exist in micro wavy interface. It shows that double sided explosive cladding is feasible. Based on the results of explosive cladding window, experiment results of steel of No45to steel of Q235and stainless steel to steel of Q235were predicted by Gurney formula, Aziz formula and Deribas formula. The results show that:The experiment results can be better predicted by Deribas formula. It can provide theoretical guidance for explosive cladding manufacture. By using double sided explosive cladding, the energy produced by explosives has been fully utilized. Compared to the existing single sided explosive cladding method, the consumption of explosives for the cladding of steel of No45to steel of Q235and stainless steel to steel of Q235is reduced by83%and77%in the case of cladding the same number of composite plates. The problem of "high noise and low efficiency" existed in explosive cladding has been resolved. Low energy, high efficiency and environmental friendly have come true. The close relationship that the bonding energy increase with increasing explosive ratio was found between bonding interface morphology and explosive ratio. High detonation velocity explosives are used in the experiments rather than low detonation velocity explosives commonly used in explosive cladding(2000-3000m/s). As can be seen from the experiment results, the high velocity explosives can meet the requirements of explosive cladding. The bond interface of micro wavy with high bond strength was produced. Exhausting of air in the gap between base and flyer plates was not affected by the high detonation velocity explosives. Compared with the low velocity explosives, high detonation velocity leads to the higher detonation pressure and higher energy of detonation products. In order to generate the same collision velocity as the low velocity explosives, explosive consumption is relatively less.SPH method established by LS-DYNA has been used to simulate the change law of bonding interface waveform. The simulation results reproduce the phenomenon of jetting and the interfacial waves. It shows that SPH method is effective for explosive cladding. The continuous accumulation of detonation products which effect on interface was not considered. The phenomenon of the size of interface wave increased slowly from initiation end to the terminal of composite plate still appears in the experiments. Investigate its reason:Due to the collision from flyer plate to base plate, the vibration energy was generated in the waiting bond region of composite plate. With the collision point moving forward, the vibration energy caused by anterior collision points was continuous superposition. The vibration energy of the waiting bond plate also continue to strengthen. The collision velocity from intiation to the end of composite plate continues to strengthen. Considering with the detonation wave of explosives moving forward, the continuous accumulation of detonation products which increase the load acting on the waiting bond plate. It shows that the collision velocity will also increase. Combined with the effect of vibration, the change of bonding interface wave is by the continuous accumulation of detonation products and the vibration energy caused by anterior collision points interaction results.SPH method established by LS-DYNA has been used to simulate boundary effect in explosive cladding. The generation mechanism of boundary effect was revealed by brand-new viewpoint:With the effect of rarefaction wave, the detonation products pressure decay rapidly at the initiation end. The collision angle change to negative. The force F acting on the initiation end of the flyer plate can be divided into two parts:Fi and F2. Fi is the downward collision force, namely bonding force. F2is the force which can generate the boundary effect. The magnitude of this force can be expressed as: F2=F sin θ. It shows that the initiation end of flyer plate can be torn at a certain angle. Similar to the initiation end, the detonation products pressure decay rapidly at the terminal of detonation products. The collision angle at the terminal is larger than the collision angle at the centre. The force F" acting on the terminal of the flyer plate can be divided into two parts:F5and F6. F5is the downward collision force, namely bonding force. F6is the force which can generate the boundary effect. The magnitude of this force can be expressed as:F6=F" sin β. A jet is the necessary condition for explosive cladding. The production condition of jet is50<β<25°. At this angle range, F6is8.72%~42.26%of the F". The collision angle of terminal is larger than the centre. It shows that the terminal of flyer plate can be torn at a certain angle. Due to multi-directional constraint of honeycomb material and double sided flyer plates, the effect of rarefaction wave effectively reduces. Using honeycomb structure explosives and double sided explosive cladding, the boundary effect can be effectively controlled without increasing the charge size and flyer plate size. The effective bonding area is much higher. It will not only save costs but also beneficial to environmental friendly.In order to improve computational efficiency, SPH-FEM coupled method established by LS-DYNA has been used to simulate the feasibility experiments in chapter3. The results show that:Due to reduction rate exist in the flyer plate, the displacement of flyer plates under the condition of the charge thickness with10mm and5mm is slightly larger than the stand-off distance6mm. The collision velocity and collision pressure at the centre of the flyer plate is897m/s and17.08GPa under the condition of the charge thickness with10mm. The collision velocity and collision pressure at the centre of the flyer plate is565m/s and11.25GPa under the condition of the charge thickness with5mm. compared with calculation results by three theoretical formulas(Gurney formula, Aziz formula and Deribas formula), it found that the simulation results are relatively close to the Deribas formula, the error is small. The simulation results are consistent with the experimental results. It shows that SPH-FEM coupled method is effective for explosive cladding. It also shows that Deribas formula and SPH-FEM coupled method is important guiding significance for double sided explosive cladding. Under the condition of the charge thickness with10mm and5mm, the collision velocity and collision pressure increases with the increasing of distance. The reason for this phenomenon is the continuous accumulation of detonation products and the vibration energy caused by anterior collision points interaction results.
Keywords/Search Tags:Honeycomb structure explosives, Double sided explosive cladding, Energy efficiency, Boundary effect, Bonding interface, Numerical simulation, SPH-FEM coupled method
PDF Full Text Request
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