EN 10319-2:2006

Metallic materials - Tensile stress relaxation testing - Part 2: Procedure for bolted joint models

This part of EN 10319 specifies the test method for determining the stress relaxation of bolts tensioned in bolted joint models subjected throughout the test to overall constant strain and constant temperature conditions.

Metallische Werkstoffe - Relaxationsversuch unter Zugbeanspruchung - Teil 2: Prüfverfahren mit Schraubenverbindungsmodellen

In diesem Teil von EN 10319 ist das Prüfverfahren zur Bestimmung der Spannungsrelaxation von Schraubenbolzen unter Zugbelastung in Schraubenverbindungsmodellen festgelegt, die während der Prüfung unter konstanter Dehnung und konstanter Temperatur gehalten werden.

Matériaux métalliques - Essai de relaxation en traction - Partie 2: Mode opératoire pour modèles d'assemblages boulonnés

La présente partie de l’EN 10319 spécifie la méthode d’essai pour la détermination de la relaxation de
contrainte de boulons en traction dans des modèles d’assemblages boulonnés et soumis tout au long de
l’essai à des conditions de déformation globalement constante et de température constante.

Kovinski materiali – Preskušanje sprostitve pri natezni obremenitvi – 2. del: Postopek za modele vijačnih zvez

General Information

• Status: Published
• Publication Date: 17-Oct-2006
• Withdrawal Date: 29-Apr-2007
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Drafting Committee: ECISS/TC 1/WG 2 - Stress relaxation testing
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 27-Nov-2023
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 10319-2:2007 - Metallic materials - Tensile stress relaxation testing - Part 2: Procedure for bolted joint models

Overview

EN 10319-2:2006 is the CEN European standard that specifies a laboratory procedure for measuring tensile stress relaxation of bolts installed in bolted joint models under constant overall strain and constant temperature conditions. It is Part 2 of the EN 10319 series (Part 1 covers procedures for testing machines). The standard defines the test principle, required apparatus, specimen preparation, measurement methods and reporting conventions for metallic materials subjected to stress relaxation testing in bolted assemblies.

Key topics and technical requirements

• Scope & principle
  • Test determines how bolt stress relaxes when held at a specified elastic strain and temperature for a set time, then unloaded to measure residual stress.
  • Residual and initial stresses are derived from measured strains using the elastic modulus at test temperature (ET), or dynamic modulus ETd if ET is unavailable: σo = ET·εeo and σrt = ET·εer.
• Bolted joint models
  • Two model types: Model A (extension measured by overall length) and Model B (strain measured on cylindrical section with strain gauges).
  • Bolts, nuts and flanges should be same material and arranged to minimize bending/torsion; unloading is performed by destroying a flange or nut.
• Measurement systems
  • Extension (Model A): dial gauge accuracy ±0.001 mm; reference bars recommended.
  • Strain (Model B): two opposite active strain gauges (≥6 mm gauge length) with passive compensating gauges on a reference piece; accuracy ~ ±1×10⁻⁶ strain.
  • Temperature measurement: indicator resolution ≥0.5 °C, measuring accuracy ±1 °C; thermocouple placement and shielding rules apply.
• Temperature control tolerances
  • Permitted deviation between indicated temperature Ti and specified T, and maximum admissible temperature gradient:
    • T ≤ 600 °C: Ti − T = ±3 °C, gradient ≤ 2 °C
    • 600 < T ≤ 800 °C: Ti − T = ±4 °C, gradient ≤ 3 °C
    • 800 < T ≤ 1000 °C: Ti − T = ±5 °C, gradient ≤ 3 °C
  • Minimum thermocouple recommendations and calibration requirements are specified.

Applications and users

• Practical uses: characterizing bolt relaxation behavior, lifetime prediction of bolted assemblies at elevated temperature, material selection, and design validation where long-term preload retention is critical (e.g., pressure vessels, boilers, engines, structural connections).
• Typical users: mechanical and materials test laboratories, bolt and fastener manufacturers, R&D engineers, quality assurance teams, and standards bodies developing joint design criteria.

Related standards

• EN 10319-1: Procedure for testing machines (companion document to Part 2)
• Other CEN/CENELEC metallic materials testing standards (refer to national bodies for up-to-date cross-references)

Keywords: EN 10319-2, tensile stress relaxation testing, bolted joint models, stress relaxation of bolts, metallic materials testing, CEN standard.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Metallic materials - Tensile stress relaxation testing - Part 2: Procedure for bolted joint modelsMatériaux métalliques - Essai de relaxation en traction - Partie 2: Mode opératoire pour modeles d'assemblages boulonnésMetallische Werkstoffe - Relaxationsversuch unter Zugbeanspruchung - Teil 2: Prüfverfahren mit SchraubenverbindungsmodellenTa slovenski standard je istoveten z:EN 10319-2:2006SIST EN 10319-2:2007en77.040.10Mehansko preskušanje kovinMechanical testing of metalsICS:SLOVENSKI
STANDARDSIST EN 10319-2:200701-marec-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 10319-2October 2006ICS 77.040.10 English VersionMetallic materials - Tensile stress relaxation testing - Part 2:Procedure for bolted joint modelsMatériaux métalliques - Essai de relaxation en traction -Partie 2: Mode opératoire pour modèles d'assemblagesboulonnésMetallische Werkstoffe - Relaxationsversuch unterZugbeanspruchung - Teil 2: Prüfverfahren mitSchraubenverbindungsmodellenThis European Standard was approved by CEN on 6 August 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 10319-2:2006: E

Information concerning different types of thermocouples.21 Annex B (informative)
Information concerning methods of calibration of thermocouples.22 Bibliography.23

3.8.1 specified initial elastic strain (εεεεeo) initial elastic strain of the bolt at the beginning of the test
NOTE The specified initial elastic strain is calculated from the extension during tensioning ∆Lo (reo/LLo∆=ε) or is measured directly on the cylindrical length of the bolt with strain gauges. 3.8.2 residual elastic strain (εεεεer) strain calculated from the reverse extension ∆Lt (rterLL∆ε=) or directly measured in the cylindrical length of the bolt with strain gauges during unloading of the bolt at the end of the test 3.9 stress at any time during the test, force divided by the original cross-sectional area (So) of the bolt between: A distinction is made between: 3.9.1 initial stress (σσσσοοοο) stress at the start of the test, expressed as a product of the static elastic modulus ET at the test temperature and the specific initial elastic strain εeo eoTεσ×=Eo
(1) 3.9.2 residual stress (σσσσrt) value to which the stress of the bolt has relaxed at the specified time t, after the test, expressed as the product of the elastic modulus ET or ETd and the residual elastic strain erTrtεσ×=E
(2) NOTE The dynamic modulus of elasticity ETd should be taken, if the static modulus of elasticity ET at test temperature is not available. 4 Symbols and designations The symbols and corresponding designations are given in Table 1.

Specified initial elastic strain εer
Residual elastic strain ET GPa Static modulus of elasticity at test temperature ETd GPa Dynamic modulus of elasticity at test temperature σo MPaa Initial stress σrt MPa Residual stress at time t t h Test duration T °C Specified temperature Ti °C Indicated temperature a 1 MPa=1 N/mm2. 5 Principle The test consists of tensioning a test piece in the form of a bolt in a bolted joint model device to a specified initial elastic strain, subjecting the bolt to that strain for specific temperature and time and determining the residual stress in the bolt by unloading at the end of the test. The constant tensile strain and residual stress are derived from an extension measurement referring to the overall length of the bolt (bolted joint model A) or from strain gauge measurements at the cylindrical length of the bolt (bolted joint model B), all measurements being performed at room temperature. 6 Apparatus 6.1 Bolted joint model device 6.1.1 General In the bolted joint model, a bolt with a cylindrical length and threaded ends is tensioned by two nuts against a flange (Figure 1). Bolts, flanges and nuts shall be of the same material.

± 3 2 600 < T ≤ 800 ± 4 3 800 < T ≤ 1 000
± 5 3 For specified temperatures greater than 1 000 °C, the permitted values shall be defined by agreement between the parties concerned. The indicated temperatures Ti, are the temperatures measured at the surface of the cylindrical length of the test piece, errors from all sources being taken into account. NOTE Instead of measuring the temperature at the surface of the bolted joint model, it is permitted to indirectly measure the temperature of each heating zone of the furnace provided it is demonstrated that the tolerance defined above is fulfilled. The variation of the room temperature during all extension measurements shall not exceed ± 2 °C. 6.3.3
Temperature measurement 6.3.3.1 General Temperature indicator shall have a resolution (sensitivity) of at least 0,5 °C and the temperature measuring equipment shall have an accuracy of ± 1 °C. 6.3.3.2 Number of thermocouples It is recommended that at least one thermocouple should be used for each bolted joint model and where only one thermocouple is used, it should be positioned at the middle of the bolted joint model. In the case of indirect temperature measurement, regular control measurements are required to determine the differences between the thermocouple(s) of each heating zone and a significant number of model bolts within a given zone. The non-systematic components of the temperature differences shall not exceed ± 2 °C up to 800 °C and ± 3 °C above 800 °C. The total number of thermocouples may not be reduced to less than three, if the thermocouples located at suitable places in the furnace and the indicated temperature do not exceed the permitted deviations given in Table 2. 6.3.3.3 Thermocouples In all cases, thermocouple junction shall make good thermal contact with the surface of the bolted joint model and shall be screened from direct radiation from the heating source. The remaining portions of the wires within the furnace shall be thermally shielded and electrically insulated. NOTE This clause is not applicable in the case of indirect temperature measurement. 6.3.4 Calibration of the thermocouples and temperature measuring system NOTE Information concerning different types of thermocouples is given in Annex A.
...