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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Aufschlagimpuls}} {{PSM_Infobox}} Initial load, impact impulse or inertial force __FORCETOC__ ==Causes of inertial load== The occurrence of an inertial load (also referred to as inertial force) caused by mass inertia, which is superimposed on the actual deformation behaviour, represents a measurement and evaluation problem in materials testing under dynamic load..."

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{{Language_sel|LANG=ger|ARTIKEL=Aufschlagimpuls}}
{{PSM_Infobox}}
Initial load, impact impulse or inertial force
__FORCETOC__

==Causes of inertial load==

The occurrence of an inertial load (also referred to as inertial force) caused by mass inertia, which is superimposed on the actual deformation behaviour, represents a measurement and evaluation problem in [[Materials Testing|materials testing]] under dynamic loads. Due to the large differences in damping behaviour, the vibration problem is even more pronounced for [[Plastics|plastics]] than for metals.

When the [[Stress|stress]] is applied suddenly during dynamic ([[Impact Loading Plastics|impact]]) tests, a complex reaction occurs in the entire coupled system, which consists of the following components:

* Reaction forces of the test [[Specimen|specimen]],
* Acceleration forces,
* Signal vibrations caused by spring-mass forces,
* Signal vibrations caused by reflected body sound waves,
* High-frequency signal vibrations caused by downstream measuring electronics.

==Relationship between inertial load and maximum load in ICIT==

In an electronically recorded load–time or [[ICIT – Types of Impact Load–Deflection Diagrams|load–deflection diagram]] in the [[Instrumented Charpy Impact Test|instrumented Charpy impact test (ICIT)]], the mass inertia causes a reaction force to occur in the test specimen, the amplitude of which must always be considered in relation to the maximum load (force at the onset of unstable [[Crack Propagation|crack propagation]]). The vibration that occurs is referred to as inertial vibration. The inertial load is independent of the ''a''/''W'' ratio (''a'' – [[Notching|notch depth]], ''W'' – specimen width) of the test [[Specimen|specimen]], but depends on stress parameters such as [[Velocity|velocity]] and temperature.

==Criteria for determining the start of unstable crack propagation==

The decisive factor in determining the point at which unstable [[Crack Propagation|crack propagation]] begins is that the maximum impact load ''F''max

{|
|-
|width="20px"|
|width="500px" | <math>F_{max}\;>\;F_1</math>
|}

must be greater than the inertial load ''F''1. To check this equation, the amplitude of the inertial force can be estimated using the equation

{|
|-
|width="20px"|
|width="500px" | <math>F_1\approx\frac{Z_1\,\cdot\,Z_2}{Z_1+Z_2} \cdot v_I</math>
|}

must be greater than the inertial load ''F''1. To check this equation, the amplitude of the inertial force can be estimated using the equation

{|
|-
|width="20px"|
|width="500px" | <math>Z_{1{,}2}\,=\,c_{1{,}2} \cdot \rho_{1{,}2}</math>
|}

where

{|
|-
|''Z''1,2
|width="15px" |
|spezific sound impedance of [[Specimen|specimen]] and/or pendulum
|-
|''ρ''1,2
|
|[[Density]] of specimen and/or pendulum hammer material
|-
|''c''1,2
|
|[[Sound Velocity|sound velocity]] of specimen and/or pendulum hammer
|-
|''v''I
|
|impact velocity according to ISO 13802
|}

If the maximum impact load is greater than the inertial load, the [[Fracture Mechanics|fracture mechanics]] [[Material Parameter|parameters]] can be determined using static evaluation formulas.

==See also==

* [[ICIT – Influence of Pendulum Hammer Velocity|ICIT– Influence of pendulum hammer velocity]]
* [[ICIT – Experimental Conditions|ICIT– Experimental conditions]]
* [[ICIT – Limits of Fracture Mechanics Evaluation|ICIT– Limits of fracture mechanics evaluation]]
* [[ICIT – Nonlinear Material Behaviour|ICIT– Nonlinear material behaviour]]

'''References'''
* [[Grellmann, Wolfgang|Grellmann, W.]]: Bewertung der Zähigkeitseigenschaften durch bruchmechanische Kennwerte, In: Schmiedel, H. (Ed.): Handbuch der Kunststoffprüfung. Carl Hanser, Munich Vienna (1992), pp. 139–183, (ISBN 3-446-16336-0; see [[AMK-Büchersammlung|AMK-Library]] under A 3)
* [https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.], [[Seidler, Sabine|Seidler, S. (eng.)]]: Kunststoffprüfung. Carl Hanser, Munich (2025) 4th Edition, pp. 256–261 (ISBN 978-3-446-44718-9; E-Book: ISBN 978-3-446-48105-3; see [[AMK-Büchersammlung|AMK-Library]] under A 23)
* ISO 13802 (2025-08): Plastics – Verification of Pendulum Impact-testing Machines – Charpy, Izod and Tensile Impact-testing

[[category:Instrumented Impact Test]]

Inertial Load - Revision history