Modelling of process parameters in dynamic form-cladding

Abstract

Explosive form-cladding is a dynamic process, in which plastic deformation of two sheet metals alongwith solid state welding between them is accomplished by single detonation of an explosive charge. The process parameters include (a) the depth to diameter (h/D) ratio of the dies, (b) the mass of the explosive per unit mass of the cladder (c/m ratio) and (c) the density ratio of the (:ladder and backer. An attempt was made to express the rate of success of the explosive form-cladding endeavours in terms of the process parameters.All experiments were open air, contact operations and were schemed using design of experiments. A granular explosive, with a detonation velocily of 280(I m/s, was the energy generator. Aluminium and copper sheets (1.2 mm thick) were cladder plates and low carbon steel sheet (1.2 mm thick) were backer plates. Analysis Of Variance (ANOVA) was employed to evaluate the significance of the parameters and their interactions on the process.Key words : explosive torm-cladding, design of experiments, ANOVA, model, adequacy check. I N T R O D U C T I O NExplosive torm-cladding is a high energy rate material processing technique in which forming and cladding of two sheet metal blanks are accomplished in one step. The shock wave, produced by the detonation of an explosive. travels outwards from the centre to accelerate and detbrm the cladder. The cladder plate is impacted against the backer plate. Both the plates are accelerated, simultaneously, towards the die surface. Plastic deformation of the two plates and the cladding between them is thus accomplished in single detonation [1]. The parameters include (a) the depth to diameter (h/D) ratio of the dies, Co) the mass of explosive per unit mass of cladder plate (e/m ratio) and (c) the density ratio of the cladder and backer plate (p~,~,,,). An attempt was made to formulate a model, enveloping the above parameters, to predict the rate of success of the explosive form-cladding operations. E X P E R I M E N T A L S E T U P DiesTwo hemispherical tool steel dies of 133 mm outer diameter were fabricated Liberal die entrant radius was provided on each die to ensure smooth flow of metals during deformation. A vacuum vent of 2 mm diameter was drilled at the bottom of the (tie. Four 14 mm diameter holes, equispaced on the die annulus, were also drilled. The other ends of the holes were countersunk at the bottom face of the dies to accomodate the bolt heads. The depth of the dies were 19 mm and 62.5 mm and diameters were 95 mm and 125 mm respectively, thus varying the h/D ratio from 0.2 to 0.5. BlanksThe cladder and backer plates were of 1133 mm diameter and 1.2 mm thick. Four 14 mm holes were drilled on the annulus of each, to coincide with the holes drilled on the die. The cladder and backer material composition are

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“…formülünden bulunabilir. Burada A, örsün derinlik/çap oranını, B, patlayıcı kütlesinin uçucu plaka kütlesine oranını, C ise uçucu ve ana plaka malzemelerinin yoğunluklarının oranını ifade etmektedir [28]. Raghukandan (2003) düşük karbon çeliğine, patlayıcı olarak toz halinde nitrogliserin kullanılarak bakır plakanın kaynatılmasını incelediği çalışmasında deneysel verileri kullanarak ANOVA analizi yapmış ve kayma ve çekme durumundaki bağlama kuvvetinin formüllerini elde etmişlerdir [29].…”

Effect on Explosive Cladding of TITAN 12/SS 304 L Plates under Multiple Conditions (Design Matrix)

“…Comparison of F calculated values with F critical values will give insight into the significance of the process parameters and their interactions with the process. This analysis was done using F-distribution at 1% significant level and the F critical value (from F-table) is 12.25 that is F (1,7) at 99% confidence level is 12.25. Therefore all factors have real effect on the response function h (amplitude), ?…”

“…The independently controllable predominant process parameters were identified [2,5,6] to enable to carry out experimental work and develop the mathematical models: they were stand-off distance (D), e/m ratio, where e is mass of explosive and m is mass of flyer + buffer, (M), and angle of inclination (A). As per the previous work done by Rathinasabapathi et al [7], the upper and lower levels of the parameters are coded as +1 and -1, respectively, and the coded value s of any intermediate levels are calculated by using the fo llowing expression [8].…”

Micro Structural Studies On Explosively Clad Cu/Ss, Br/Ss and Al/Ss Plates

“…The combination of the pressure, heat and plastic flow on the materials can produce an interface bond having strength equal to or greater than that of the parent material [1]. While the process can be used to weld two or more pieces of similar materials, its major industrial potential lies in the fact that it can be used to clad dissimilar materials, many of which are impossible to join by any other methods [2][3][4][5]. The aim of this study is to investigate the various microstructural features like wave formation and straight interface present in the explosive cladding of Cu/Ss, Br/Ss and Al/Ss combinations.…”