Table 9 The influence mechanism of different influence factors.

Single-factor

Percussion energy

As the percussion energy declines, the impact energy of the firing pin decreases, which in turn reduces the amplitude of the plastic stress wave. As a consequence, both plastic deformation and the conversion of plastic work into heat gradually weaken. This reduction leads to a slower heating rate of the primer mixture, causing a delay in the temperature reaching the ignition temperature. This delay restricts the formation of high - temperature zones and hotspots in the extrusion area, resulting in a drop in the combustion rate of the primer mixture and an extended time to pressure initiation.

Interlocking gap

As the interlocking gap increases, when the firing pin is impacted by the hammer, its effective displacement decreases. As a result, the loss of percussion energy increases, and the efficiency of energy transfer and conversion into percussion energy declines. This causes a gradual reduction in both plastic deformation and the conversion of energy through plastic work, leading to a delay in the time it takes to heat up to the ignition temperature. Consequently, insufficient energy dissipation impedes the formation of energetic particles required for hotspot creation, thereby reducing the combustion reaction rate of the primer mixture and, in turn, increasing the time needed for pressure initiation.

Primer charge height

Based on the hotspot theory, a decrease in the charge surface height causes non - homogeneity and non - continuity within the propellant grain, leading to a random decrease in the local plastic deformation of the propellant grain. This reduction in the heat accumulated from plastic work lowers both the probability and the number of hotspots. As a result, the time it takes to heat the primer mixture to the firing temperature is prolonged. Subsequently, the combustion reaction rate of the primer mixture decreases, and the time needed for pressure initiation increases.

Anvil height

When the primer mixture is deformed by impact energy, it is subjected to the pinning action of the anvil after this plastic deformation, which leads to the formation of hotspots beneath the pinned region. As the anvil height increases, the distance between the anvil and the primer mixture grows. As a result, the contact between the primer mixture and the anvil is limited after the plastic deformation. Owing to friction and shear mechanisms, the formation rate of local hotspots within the deformation layer slows down, delaying the time it takes to heat the primer mixture to its firing temperature. Meanwhile, the reaction rate of the primer mixture decreases, which in turn extends the time needed for pressure initiation.

Two-factor coupling

Interlocking gap and primer charge height

As the interlocking gap increases, the percussion energy declines, leading to less plastic deformation of the primer mixture. Meanwhile, the rate of temperature rise induced by the plastic work within the primer mixture slows down, delaying the formation of hotspots.

On the contrary, a reduction in the charge surface height directly weakens the plastic deformation of the primer mixture. As a consequence, the plastic deformation zone narrows, which reduces both the number of hotspots formed and the combustion reaction rate of the primer mixture. Consequently, the time to pressure initiation shows more pronounced variations.

Interlocking gap and anvil height

As the interlocking gap increases, the percussion energy declines, subjecting the primer mixture to a lower load. As a result, the mass points within the primer mixture undergo less plastic deformation under the action of the stress wave. A smaller proportion of the percussion energy is converted into energy for volume - deformation work within the primer mixture, leading to a slower rate of temperature rise due to the heat conversion from plastic work.

Meanwhile, an increase in the anvil height delays the moment when the primer mixture is subjected to pinning action. The greater distance between the primer mixture and the anvil means that more plastic deformation is required for the primer mixture to come into contact with the anvil. Consequently, the proportion of percussion energy used for hotspot formation decreases, which reduces the combustion reaction rate within the primer mixture. As a consequence, the time to pressure initiation shows more pronounced variations.

Anvil height and primer charge height

A change in the anvil height can lead to increased energy dissipation and affect the accumulation of hotspots. Likewise, variations in the charge surface height affect the amount of the primer mixture. As a result, the number of hotspots is impacted, and the combustion reaction rate within the primer mixture decreases. Consequently, the time to pressure initiation shows more pronounced variations.