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{{Language_sel|LANG=ger|ARTIKEL=Zugversuch und Schallemissionsanalyse}}
{{PSM_Infobox}}
Tensile test and acoustic emission analysis
__FORCETOC__

==Introduction==

In the [[Quasi-static Test Methods|quasi-static]] [[Tensile Test|tensile test]], the [[Sound Emission|sound emissions]] occurring during loading on single-notched [[Specimen|test specimens]] are used to evaluate the damage kinetics. Due to the use of [[Notch|notched]] [[Specimen|test specimens]], it is possible to specify a defined distance between the acoustic emission source and the sensor position and thus derive reproducible conditions. However, a disadvantage is that, due to the increased notch stress and local deformation, it is not possible to provide information on stress and strain. Due to the [[Notch Sensitivity|notch effect]] and the influence of the sensor position on the recording of the [[Sound Emission|sound emission]], different experimental conditions apply and the test was carried out in accordance with ISO 527-1 [1].

==Experimental==

A polypropylene (PP/20) reinforced with 20 wt.-% [[Short-fibre Reinforced Plastics|short glass fibres]] was investigated. Due to the non-polar nature of polypropylene, maleic anhydride was used as a coupling agent to optimise the bonding of the fibres to the matrix ([[Fibre–Matrix Adhesion|fibre–matrix adhesion]]). Kardelky and Schröder demonstrated in [2] and [3] that Echtblau achieves the best mechanical properties compared to other nucleating agents for PP/GF composites at a content of 0.01 % by mass. For this reason, Echtblau was used as the nucleating agent. Injection-moulded [[Multipurpose Test Specimen|multi-purpose test specimens]] in accordance with ISO 527-2 [4] with a total length ''l''3 of 170 mm were available for the investigations.

The depth of the notch made with a metal blade (see also: [[Notch Geometry|notch geometry]]) was 2 mm with a [[Notch Sensitivity#Influence of the notch radius on the notch impact strength|notch radius]] of 0.3 µm and a sensor–notch distance of 30 mm. The Zwick Z020 [[Material Testing Machine|universal testing machine]] ([https://www.zwickroell.com/ ZwickRoell GmbH & Co. KG, Ulm]]) was used for the tests at a [[Crosshead Speed|crosshead speed]] of 10 mm/min at room temperature.

The 3-channel AMSY-4 measuring system (VALLEN-SYSTEME GMBH, ICKING, GERMANY) with an AEP-3 preamplifier and an AE204A broadband sensor was used to perform the [[Sound Emission Testing|sound emission measurements]]. The bandwidths of the preamplifier and the sensor were 95–1000 kHz as well as 150–650 kHz. Impedance matching during application of the sensor to the test specimen surface was achieved using beeswax as an adhesive, and constant contact pressure was ensured by using a clamp. '''Figure 1''' shows a clamped [[Specimen|test specimen]] equipped with the acoustic sensor.

{| border="0"
|[[File:Zugv_SEA_HybMeth_Bild2a.jpg]]
|
{| border=0
|-valign="top"
|width="25px"|A –
|Acoustic broadband sensor, applied to the test specimen with coupling medium
|-valign="top"
|B –
|Clamp attached
|-valign="top"
|C –
|Safety cable to catch the sensor and prevent damage
|}
|}
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Test setup for sound emission measurements in the tensile arrangement
|}

==Example==

The distribution functions for the peak amplitude values ''A''p, the event duration ''t''ED and the cumulative rate representation of the energy ''E''AE are shown for PP/20 together with the force-traverse path diagram in '''Figures 2a–c'''.

{|
|-
|[[File:TT_SEA_Fig-4a.jpg|300px]]
|[[File:TT_SEA_Fig-4b.jpg|300px]]
|-
|[[File:TT_SEA_Fig-4c.jpg|300px]]
|
|}
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |Representation of the distribution functions of the amplitude values ''A''p, the event duration ''t''ED and cumulative rate representation of the energy ''E''AE, as well as the division into three acoustically different ranges for PP/20 (a–c) [5]
|}

For PP/20, unstable [[Crack Propagation|crack propagation]] was determined and, in comparison with the unnotched [[Specimen|test specimens]] (results not shown), the [[Notching|insertion]] of a sharp [[Notch|notch]] results in a lower [[Strength|strength]] level due to the formation of a [[Multiaxial Stress State|triaxial stress state]] and the higher [[Deformation Rate|deformation rate]] at the notch tip.

From the distribution functions, three acoustically different areas can be derived on the basis of the ''hit'' density, which are illustrated in the graphical representation in '''Figure 2''' by vertical lines and were adopted for the event duration ''t''ED and for the rate representation of the energy ''E''AE. The amplitudes and event duration in areas II and III are characterised by an overlap of the values in the areas preceding them ('''Table 1'''). Area I is characterised by low acoustic activity, and the transition from area II to area III shows a disproportionate increase in [[Acoustic Emission|acoustic emission]]. Before the ultimate [[Component Failure|failure]] of the [[Material & Werkstoff|material]], most [[Sound Emission|sound emissions]] per unit of time are detected with the highest amplitude values and maximum energies, which can be attributed to the increase in material damage.

{| border="1px" style="border-collapse:collapse"
|+ '''Table 1''': Assignment of amplitude and event duration values to the acoustic ranges for PP materials
!! style="width:160px; background:#DCDCDC" | acoustic range
!! style="width:160px; background:#DCDCDC" | corresponding amplitudes
!! style="width:160px; background:#DCDCDC" | corresponding event duration
|-
|style="text-align:center" | I
|40–50 dB
|< 20 <math>\mu</math>s
|-
|style="text-align:center" | II
|50–68 dB
|20–200 <math>\mu</math>s
|-
|style="text-align:center" | III
|> 68 dB
|> 200 <math>\mu</math>s
|}

To interpret the results, [[Scanning Electron Microscopy|SEM images]] of the corresponding [[Fracture Surface|fracture surfaces]] of PP/20 were taken in order to qualitatively evaluate the [[Fibre–Matrix Adhesion|adhesion conditions]] and [[Deformation Mechanisms|damage mechanisms]]. '''Figures 3a–b''' show an overview and a detailed image. Glass fibre breaks (i), numerous pulled-out glass fibres not wetted with matrix material (ii), holes resulting from pull-out (iii) and severely plastically stretched matrix webs (iv) are visible. Based on the [[Fracture Surface|fracture surfaces]], it cannot be clearly determined whether the glass fibres broke during the manufacturing process or as a result of unstable [[Crack Propagation|crack propagation]].

[[File:Zugv_SEA_HybMeth_Bild5.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 3''':
|width="600px" |REM image (a) and detailed section (b) of the [[Fracture Surface|fracture surface]] of PP/20; i – fibre fracture, ii – fibre not wetted with matrix material, iii – hole resulting from pull-out, and iv – plastically stretched matrix bridges between the glass fibres
|}

It is not possible to assess the adhesion conditions on the basis of the [[Fracture Surface|fracture surfaces]] obtained in [[Quasi-static Test Methods|quasi-static tests]], as there is an impermissible influence, i.e. uncovering of the fibres during the pull-out. In this case, preparation must be carried out at a high [[Test Speed|test speed]] and/or at low temperatures [6, 7]. An evaluation of the adhesion conditions can be carried out, for example, on [[Fracture Surface|fracture surfaces]] obtained from the [[Instrumented Charpy Impact Test|instrumented Charpy impact test]] (ICIT). If the fibres are well bonded to the matrix, force is transferred between the matrix and the fibre during loading. In contrast to impact/dynamic loading (see: [[Impact Loading Plastics|impact loading plastics]]), the [[Deformation|deformation]] and thus energy absorption of the matrix in the [[Quasi-static Test Methods|quasi-static test]] is greater, as illustrated by the strongly plastically deformed matrix areas on the [[Fracture Surface|fracture surface]].

==See also==

* [[Tensile Test|Tensile test]]
* [[Sound Emission|Sound emission]]
* [[Sound Emission Experimental Conditions|Sound emission experimental conditions]]
* [[Sound Emission Analysis|Sound emission analysis]]
* [[Sound Emission Testing|Sound emission testing]]

==References==

{|
|-valign="top"
|[1]
|ISO 527-1 (2019-07): Plastics – Determination of Tensile Properties – Part 1: General Principles
|-valign="top"
|[2]
|Kardelky, S.: Einfluss der Nukleierungsmittelart auf die Deformations- und Bruchmechanismen von medial beanspruchten PP/GF-Verbunden. Diplomarbeit. Martin-Luther-Universität Halle-Wittenberg (2002); see [[AMK-Library]] under B 3-101)
|-valign="top"
|[3]
|Schröder, D.: Kombinierte Wirkung des Faservolumen- und Nukleierungsmittelgehaltes auf das mechanische Eigenschaftsniveau von PP/GF-Verbunden. Diplomarbeit. Martin-Luther-Universität Halle-Wittenberg (2003); see [[AMK-Library]] under B 3-102)
|-valign="top"
|[4]
|ISO 527-2 (2025-06): Plastics – Determination of Tensile Properties – Part 2: Test Conditions for Moulding and Extrusion Plastics
|-valign="top"
|[5]
|Schoßig, M.: Bewertung der Schädigungsmechanismen von kurzglasfaserverstärkten Polyolefinen durch simultane Aufzeichnung der Schallemissionen unter quasistatischer und dynamischer Beanspruchung. Dissertation. Martin-Luther-Universität Halle-Wittenberg (2010), (ISBN 978-3-8348-1483-8); see [[AMK-Library]] under B 1-21) [https://www.polymerservice-merseburg.de/fileadmin/inhalte/psm/veroeffentlichungen/Schossig_Promotion_Inhaltsverzeichnis.pdf Content as pdf]
|-valign="top"
|[6]
|VDI 3822 Blatt 2.1.2 (2024-06): Failure Analysis – Defects of Thermoplastic Products Made of Plastics Caused by Faulty Processing
|-valign="top"
|[7]
|VDI 3822 Blatt 2.1.10 (2024-07): Failure Analysis – Significant Instrumental Analysis Methods for Failure Analysis of Products Made of Plastics
|}

[[Category:Hybrid Methods]]

Tensile Test and Sound Emission Analysis - Revision history