ELECTRIC PULSE HEATING OF REACTIVE COMPOSITIONS BY THIN-WALLED CONDUCTORS-HEATERS IN THE MODES OF MULTI-POINT IGNITION OF PROPELLANT CHARGES

The problem of electric pulse heating of a medium by the heater made of metal foil with an ideal thermal contact with the medium is solved. The solution is obtained in the form of rapidly converging series for ohmic heating power, which is given as an arbitrary function of time. Using the obtained solution, a dimensionless criterion is introduced for quasi-homogeneous heating of the heater up to a melting point with intensive heat transfer to environment. It is shown that with a fixed heating duration, the criterion value depends weakly on the type of a heating power function, which allows ignoring parameters of the external electrical circuit of the device while choosing the heater thickness. The definition of a "thin" heater is introduced, which admits of bulk droplet destruction during heating of a reactive medium. In the "thin" heater approximation, quadrature solutions to the thermal problem are obtained under heat exchange according to Newton's law and ideal thermal contact, when the heater power is an arbitrary function of time. Dimensionless similarity parameters of the simulated processes are identified in all solutions, which include thermal and physical characteristics of the heater and medium, as well as the thickness of the heater and the time of its heating up to the melting point. The applicability of the "thin" heater model for calculating the thermal state of a high-energy pyrotechnic coating is shown. As an example, the permissible values of the thickness of the magnesium foil heater are determined, which ensure its uniform heating up to the melting point in 1 and 5 milliseconds under the ideal thermal contact with ignited coating. The obtained quadrature solutions to the thermal problems and the calculated results are applicable in the design of compact electric pulse devices for contact multi-point ignition of various reactive compositions with efficient consumption of electric energy.

Thermal condition of cohesion in a two-layer roll of a rolling mill

A condition of heat exchange between the layershaving different thermalphysic properties in a two-layercylindrical roll of a rolling mill is analyzed foe an ideal thermalcontact. It can be realized with application of the condition ofheat balance of one of the layers in the cylindrical area for ahomogeneous equation of heat conductivity. Analyzed was asimplified target setting in the radial section with a supposition,regarding an averaged in radius temperature distribution in theouter layer. By applying the condition of the thermal balance andby integrating the homogeneous equation of heat conductivity inthe two-layer area a condition of cohesion of an impedance typein case of an ideal thermal contact between the layers wasconstructed.

Plane Thermoelastic Deformation of a Multilayer Foundation with Non-Ideal Thermal Contact between its Layers

We proposed the method of the compliance function for the solution of two-dimensional stationary problem of thermoelasticity for a multilayer foundation (stack of elastic layers coupled with a half plane) with a non-ideal thermal contact between its layers. We constructed the recurrence relations for the auxiliary functions and the compliance functions of neighboring layers of the foundation. We analyzed the influence of thermal resistance on the distribution of stresses and temperature at the points of the lower boundary of the upper layer for a two-layer foundation subjected to the action of thermal loads.

Exfoliation the flexible continuous reinforcements of the free edge of a semiinfinite plate

Exfoliation the not extensible flexible stiffener heated up to the set temperature is investigated in conditions of a plane problem thermoelasticity. The flexible stiffener is placed at edge of the semi-infinite plates in conditions ideal thermal contact and action the stretching loading on the plate. Development of localized zones of prefracture (the weakened contact) is precede to separation the stiffener in vicinities of her ends. They can correspond to regions of damages, plastic deformation, partial break of connection and another precedes. On area outside of zones of prefracture the perfect mechanical contact is remaining. The analytical decision of a problem is shown to problem Koshy for differential equation of the first order and realized its numerical analysis. Physically correct limited stresses and deformations are received in all points of a composition. Tangents stresses also satisfy to relationship of pair law. Basic part of loading from reinforcements to plate is transfer in neighbourhood of reinforcement ends. Interference of power and temperature loadings on flexible stiffener separation is investigated.