Heat Flow Calorimetry and Others Thermal Technics Applied in … 2019/Talks for...

armasuisseScience and TechnologyarmasuisseScience and Technology

Heat Flow Calorimetry and Others Thermal Technics Applied in the Ammunition Surveillance and Shelf Life Prediction

A. Sarbach, P. Folly, B. Roduit, C. Luyet, M. Hartmann 15.05.2019

VBS / armasuisse / S+T / SAHSTK 2019

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Examples of ammunition


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Samples - preparation• Propellants in ammunition

Pyrotechnic PropellantExplosive


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Samples - preparation• Propellant in an missile

http://lazysupply.co/tow-missile-diagram.html

Pyrotechnic PropellantExplosive


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Multi temperature ageing procedure

Sealed Aluminum bag

Propellant

Oven at constant temperature


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Techniques of analysis - Thermal

High Flow Calorimetry (STANAG 4582)

Typical Heat Flow Calorimetry results 10.6 days at 80C


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Techniques of analysis - Thermal

Vacuum stability test (STANAG 4556)

Typical VST results 40 h @ 90C

Volume of Released Gas per 5.001 g of Sample = 11.399 ml

Raw Data Smoothed Data Linear Regression Quadratic Regression

Time (min)2,4002,2002,0001,8001,6001,4001,2001,0008006004002000

Gas

Pre

ssur

e (k

Pa)

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0


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Sparse experimental data


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Sparse experimental data


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Gas evolution (VST) test


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Commonly applied kinetic models

Reaction modelsf(alpha)

S-shaped model:

(1-)n m


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Reaction rate

Arrhenius

11)1(1exp 11

mn

TREA

dtd

S-shaped-model approach


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Akaike & Bayesian Information Criteria

Model selection: Akaike & Bayesian Information Criteria (AIC & BIC)

Method for comparing models based on information theory:

(I) Can be used to compare two (or more) models(II) Takes into account not only the quality of fit such as the

sum of residual squares, but also the number of points and model parameters

(III) Determines which model is more likely to be correct and quantify how much more likely (regression parameter ‘w’)


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Statistical results (AIC & BIC)


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verification


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Heat evolution (HFC) test


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Pressure firing (PF) test


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Stabilizer depletion test (HPLC)


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70C

Stabilizer depletion (HPLC)Simulated change of the stabilizer content at different temperatures


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35C70C

Stabilizer depletion (HPLC)Simulated change of the stabilizer content at different temperatures


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Stabilizer depletion (HPLC)

70C 35C

acceptable limit (0.2 mass %)

11.8 days at 70Ccorresponds to

10.7 years at 35C

Simulated change of the stabilizer content at different temperatures


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TTT diagram

HPLC

(70C, 11.8 days)

(35C, 10.7years)

11.8 days at 70Ccorresponds to

10.7 years at 35C

Temperature – Time – Transformation (TTT) diagramPresented dependencies depict the equivalent time-temperature points for which

the aging progress is the same.


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HFCVSTHPLC

PF

SAFE

UNSAFE

TTT diagramTemperature – Time – Transformation (TTT) diagram

for the 4 limits of propellant properties calculated from the best kinetic model.


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Propellant properties reaching limits

First limit

Second limit Third limit

Fourth limit

VSTPF

HPLC HFC

Propellant properties


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Conclusion• If you want to make a good life time prediction of

propellants you need to perform • a stabilizer depletion test• a thermal stability test

• You also need to know the storage conditions and the start values of your powder.

• The security issues between safety and reliability are linked but the consequences are not identical.

• Without these information your prediction would only be a rough estimation.


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Thank-you for your attention

Questions ?

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Heat Flow Calorimetry and Others Thermal Technics Applied in … 2019/Talks for...

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