Failure analysis of bolted joints: Effect of friction coefficients in torque–preloading relationship

Croccolo, Dario; Agostinis, Massimiliano De; Vincenzi, Nicolò

doi:10.1016/j.engfailanal.2010.09.015

Cited by 118 publications

(67 citation statements)

References 9 publications

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“…Pitch is one of the parameters in equations (2), (5), and (6). In order to analyze the influence of pitch on torque-initial load relation, coarse thread model for M12 bolt when pitch is 1.75 mm and fine thread models when pitch is 1.5 and 1.25 are established when other parameters are kept constant.…”

Section: Effect Of Pitchmentioning

confidence: 99%

“…Nassar and Zaki 5 conducted experiments to explore the effects of surface coating, tightening speed, and repetitive tightening on the relationship between torque and initial load. Croccolo and colleagues [6][7][8][9] provided a useful experimental methodology to determine the friction coefficients in bolted joints and then to determine the relation between torque and initial load precisely. The assessment of the correct design methodology that allows selecting the appropriate screw to be used in high-duty bolted joints was conducted.…”

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Finite element analysis of relationship between tightening torque and initial load of bolted connections

Zhou

Wang

2015

Advances in Mechanical Engineering

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Proper initial load is necessary to ensure the stability of the bolted connections. In order to apply appropriate torque, the relationship between tightening torque and initial load should be determined. In this study, a detailed threedimensional finite element model of bolted joints was established with consideration of helix angle, pitch, thread type, tooth-type angle, and other details. The process of pre-tightening of bolted joints was simulated to validate the finite element model. The curves for the relationship between the torque and initial load obtained from finite element analysis agree well with those calculated from theoretical equations. Then, the influence of the friction coefficient, pitch, elastic modulus, assembly clearance, and strain-hardening exponent on the relationship was studied. The results show that the friction coefficient between nut and joint has great influence on the relationship between torque and initial load, that is, the larger the friction coefficient, the smaller the initial load of bolt at the same tightening torque. In contrast, the pitch, assembly clearance, Young's modulus, and strain-hardening exponent have little influence on torque-initial load relation. The method used in this study provides a theoretical basis for accurately determining the tightening torque for bolted joints. Bolted joints are widely used in mechanical structures as they are easy to be assembled and disassembled. Threaded joints must be tightened when installed so that the connected components are compressed while the bolt is stretched. The force acting on the bolt introduced by pre-tightening is named initial load. Keywords1 The purpose of pre-tightening is to strengthen reliability and compactness of the connections. However, an excessive initial load will lead to yield and even fracture in the bolt; on the other hand, an insufficient initial load cannot provide the adequate clamping force which is required for maintaining the integrity of the joint and eventually causes structure loosening and failure. So, determining an appropriate initial load is quite important for bolted connections. It is hard to measure the initial load during the assembly process, so the common practice is using torque wrench to regulate the tightening torque. Thus, determining the relationship between the tightening torque and initial load is of remarkable significance in maintaining the reliability of the bolted joints.

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Section: Effect Of Pitchmentioning

confidence: 99%

mentioning

confidence: 99%

Finite element analysis of relationship between tightening torque and initial load of bolted connections

Zhou

Wang

2015

Advances in Mechanical Engineering

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“…Z kolei podatność elementów łączonych coraz częściej wyznacza się za pomocą MES, przy czym na ogół stosuje się następujące modele: W przypadku łączenia pary elementów konstrukcji bardzo często wykorzystuje się połączenia wielośrubowe. Są one typowe dla struktur, w których przed rozpoczęciem ich eksploatacji wprowadza się napięcie wstępne śrub [3,6,17,31]. Siły w śrubach są przykładane według przyjętej kolejności napinania [9,12,16] oraz założonego sposobu napinania [1,32].…”

Section: Podstawy Analizyunclassified

Numerical investigation on the effect of externally exerted loads on particular bolts forces in the multi-bolted flange joint

Grzejda¹

2015

Mechanik

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Rys. 1. Przykład kołnierzowego połączenia wielośrubowego• zbioru śrub, • kołnierzowego elementu łączonego, • warstwy stykowej znajdującej się pomiędzy elementem łą-czonym a ostoją.Dzięki takiemu podejściu każdy podukład może być modelowany i rozwijany oddzielnie.W niniejszej pracy przedstawiono kontynuację badań nad opisanym modelem, a jej celem jest rozwój modelowania podukładu śrub jako części układu wielośrubowego. Rozważania ograniczono do badania wpływu uproszczeń w modelu pojedynczego złącza śrubowego [11] na siły w śrubach w połączeniu obciążonym zewnętrznie siłą eksploatacyjną. Wszystkie analizy przeprowadzono w programie Midas NFX 2014 [20] służącym do obliczania układów liniowych i nieliniowych, obciążonych siłami statycznymi lub dynamicznymi. Podstawy analizyJednym z ważnych zagadnień w przypadku połączenia śrubowego jest analiza obciążenia śrub tworzących to połą-czenie. Biorąc pod uwagę zależności wynikające z wykresu przeciwsobnego połączenia śrubowego, wartość obciążenia roboczego w śrubach F s można wyznaczyć ze wzoru [13]:(1) gdzie: F m -napięcie wstępne, F e -obciążenie zewnętrzne, e s -podatność śruby, e p -podatność kołnierza.Gdy śruby potraktuje się jako elementy liniowe, ich podatność można wyznaczyć w prosty sposób, np. podany w normie VDI 2230 [8]. Z kolei podatność elementów łączonych coraz częściej wyznacza się za pomocą MES, przy czym na ogół stosuje się następujące modele:

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“…A structural steel with a Young's modulus E = 200 GPa, a Poisson's ratio ν = 0.3, a yield stress Sy = 400 MPa and a mass density ρ = 7,850 kg/m 3 has been employed. Modern FEM analysis capabilities, mainly in terms of computational resources, allow the vehicle manufacturer to fix structural issues before performing field tests, hence shortening the overall design and engineering phase, as demonstrated in [1] to [4]. Despites of the noticeable size of the chassis, the single beam used to realize the chassis is generally no longer than 1.5 m. Moreover, the displacements object of investigation are several orders of magnitude smaller than the overall dimensions of the chassis.…”

Section: Fig1 Urban Bus and Respective Chassismentioning

confidence: 99%

Structural Analysis of an Articulated Urban Bus Chassis via FEM: a Methodology Applied to a Case Study

Croccolo¹,

Agostinis²,

Vincenzi³

2011

SV-JME

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Failure analysis of bolted joints: Effect of friction coefficients in torque–preloading relationship

Cited by 118 publications

References 9 publications

Finite element analysis of relationship between tightening torque and initial load of bolted connections

Finite element analysis of relationship between tightening torque and initial load of bolted connections

Numerical investigation on the effect of externally exerted loads on particular bolts forces in the multi-bolted flange joint

Structural Analysis of an Articulated Urban Bus Chassis via FEM: a Methodology Applied to a Case Study

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