Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets

Dubiel, Tomasz; Grzejda, Rafał

doi:10.3390/lubricants11110460

Open AccessArticle

Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets

by

Tomasz Dubiel

¹ and

Rafał Grzejda

^2,*

¹

Koelner Rawplug IP—Branch in Lancut, 41 Podzwierzyniec Str., 37-100 Lancut, Poland

²

Faculty of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology in Szczecin, 19 Piastow Ave., 70-310 Szczecin, Poland

^*

Author to whom correspondence should be addressed.

Lubricants 2023, 11(11), 460; https://doi.org/10.3390/lubricants11110460

Submission received: 25 September 2023 / Revised: 23 October 2023 / Accepted: 27 October 2023 / Published: 28 October 2023

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Abstract

:

The aim of this article is to investigate the effect of atmospheric conditions on the tightening behaviour of HV bolts in structural bolt sets. The article describes the results of experimental tests carried out for bolt sets of a selected type. The parts of the joined sets were stored according to the specified six different conditions for four weeks before assembly. Paper, cardboard boxes and anticorrosion foils were used as protection against atmospheric conditions. The behaviour of unassembled and assembled bolt sets was also taken into account. The variation in the friction coefficient depending on the clamping force and storage conditions of the bolt sets was demonstrated. This applies both to the contact between the joining elements on the threaded surfaces and to the area between the bolt head and the bearing surface of the nut and washer.

Keywords:

atmospheric conditions; preload; HV bolts; bolt set

1. Introduction

Standardised bolt sets are most commonly used to create bolted connections for which preloading is required [1,2,3]. They are used to join not only steel, but also composite [4,5] or additively manufactured [6,7] components. Among the most advanced sets are HV high-strength bolt sets [8], which can be used in a wide range of structures exposed to various, including aggressive, environmental conditions. For this purpose, such sets are usually coated with hot-dip zinc [9].

Before bolt sets are used for assembly, they are subjected to actual operating conditions and processes onsite, caused by high or low temperatures, as well as storage conditions under varying atmospheric conditions. These different temperature extremes, as well as moisture on the threads of the bolt components, affect the friction coefficients and thus the tightening behaviour of the bolt sets. A change in the tribological properties of the bolts can result in a lower bolt preload being achieved during assembly, or in too high a force being achieved at low torque values, leading to the tensile strength of the bolt being exceeded. All of these effects can lead to bolt failures, resulting in costly and time-consuming failure analyses and assembly interruptions [8,10].

No further specific definitions are provided in the bolting standards [11,12], other than the general requirement that the bolt set should be adequately lubricated as supplied to ensure that seizure does not occur when the set is tightened and that the required preload is achieved. The exception to this is the DASt-Richtlinie 024 standard [13], which requires the protection of sets from dirt and moisture, which affect the quality of lubrication. However, this wording is not precise and allows for overinterpretation. Consequently, there are no precise recommendations in the current standards regarding the effect of specific atmospheric or site conditions on the preload and tightening of bolt sets.

In the generally available scientific and technical literature, the effect of various atmospheric conditions on the tightening behaviour of bolted connections has not been exhaustively studied. Wen et al. [14] identified corrosion occurring under the influence of the external environment as one of the factors that alter the mechanical properties of bolts, accelerating their failure. This phenomenon also occurs in the case of galvanised bolts [15,16]. Nah et al. [17] estimated the tensile forces of high-strength bolts subjected to temperatures ranging from −10 °C to 50 °C. Underwater tightening and preload behaviour of a bolted connection and determination of the slip factor under water was described by Ripsch and Henkel [18]. They developed a test system to determine the slip factor using different media for all traditional types of surface coatings. Omura [19] investigated the susceptibility to hydrogen embrittlement (delayed fracture) of high-strength steel bolts under atmospheric exposure conditions. The hydrogen permeability under atmospheric conditions showed a strong dependence on time of day, season and exposure location. The mechanism of hydrogen penetration was investigated by measuring hydrogen permeation under laboratory wet–dry cyclic conditions. The dominant factors controlling hydrogen penetration were temperature, relative humidity and the amount of sea salt on the steel surface. Stranghöner et al. [10] studied the effect of atmospheric conditions on the preload behaviour of HV and HR bolt sets based on a tightening test of the sets at different temperatures (−20 °C, +23 °C, +50 °C) and selected humidity conditions (including dry, frost, minor direct/indirect rain, variable dry/wet conditions). However, this study did not examine the effect of storage on the quality of the resulting bolted connection. The variation in friction coefficient [20,21] as a function of the point of contact of the different elements of the bolted connection was also not tested.

In order to investigate the effect of atmospheric conditions on the tightening behaviour of HV bolts in structural bolt sets, this article describes the results of experimental tests performed for bolt sets of a selected type stored under different atmospheric conditions. These tests were carried out to examine the validity of the research hypothesis that autumn and winter atmospheric conditions have an effect on the reduction in friction coefficient values in bolt sets. The most important results of this study, which distinguish it from other studies, led to the demonstration of the variability in friction coefficient depending on the place where the friction phenomenon is considered, with a distinction between phenomena occurring between the joining elements on the threaded surfaces as well as between the bolt head and the bearing surface of the nut and the washer.

2. Materials and Methods

The tests were carried out on the EN 14399-4-HV-M24 × 140-10.9/10-tZn-K1 bolt set (Figure 1) supplied by a single manufacturer [12].

The mechanical property class of the set elements was confirmed using tests included in ISO 898-1 [22] and ISO 898-2 [23], and the HV hardness of the washers according to ISO 898-3 [24]. The hot-dip zinc coating applied to the components met the requirements of ISO 10684 [11] and ranged from 50 to 80 µm. After the threading process, the nuts were coated with molybdenum disulphide by the manufacturer. In order to confirm the compliance of the HV bolt set, a connection suitability test was carried out in accordance with EN 14399-2 [25] using the scheme shown in Table 1.

The following designations are used in Table 1:

F_p,C—the required preload calculated according to the formula [26]:

F_{p, C} = 0.7 \cdot f_{u b} \cdot A_{s}

(1)

where f_ub is the nominal tensile strength and A_s is the nominal stress area of the bolt.

2.: ΔΘ_2i,min—the minimum required value of angle difference specified in the relevant product standard according to the formula:

{Δ Θ}_{2 i, m i n} = Θ_{2 i} - Θ_{p i}

(2)

where Θ_2i is the individual value of the angle of rotation of the nut relative to the bolt and Θ_pi is the individual value of the angle of rotation of the nut relative to the bolt at which the bolt force has first reached the value of F_p,C.

A connection suitability test was carried out using a Kistler machine of type 5413-2777 (Figure 2) according to the parameters provided in Table 2. The parameters of the M24 thread outline are provided in Table 3. The expected clamping force and torque for M24 × 140 bolts in class 10.9 were within the ranges of the selected sensors.

The following coefficients were checked as additional parameters:

µ_th—the coefficient of friction between the threaded surfaces of the joining elements;
µ_b—the coefficient of friction between the bolt head and the bearing surfaces;
µ_tot—the coefficient of total friction.

Tightening was performed through the nut; therefore, the friction coefficients were evaluated sequentially, first determining µ_th, then µ_b.

Extending this study to include µ_th and µ_b values allowed for a more detailed analysis of the effect of storage conditions on the behaviour of the nut coating. In order to determine the value of the friction coefficient on the bearing surface, it was important to determine the average value of the mean diameter of the bearing surface. Two standards were used to determine the properties of the connection suitability:

k-factor determined according to the formula:

k = \frac{T}{F \cdot d}

(3)

2.: Total friction coefficient based on the Kellermann–Klein formula (for comparison, see [27]):

T = F \cdot [\frac{1}{2} \cdot \frac{P + 1.154 \cdot π \cdot μ_{t h} \cdot d_{2}}{π - 1.154 \cdot μ_{t h} \cdot \frac{P}{d_{2}}} + μ_{b} \cdot \frac{D_{o} + d_{h}}{4}]

(4)

where T is the individual value of the tightening torque at which the bolt force has first reached the value of F_p,C, F denotes the clamping force, d is the nominal thread diameter of the bolt, P denotes the thread pitch, d₂ is the basic pitch diameter of thread, D_o denotes the outer bearing surface diameter and d_h is washer hole diameter.

TestXpert II software [28] was used to prepare the connection suitability test. The results were generated in .xlsx format, allowing for easy evaluation of the assembly methods. For the assessment, the requirements contained in EN 14399-2 [25] were adopted, as well as the requirements for the combined method K1 according to EN 1090-2 [29] and the modified method according to DASt-Richtlinie 024 [13] (Table 4). For the assembly methods, the achievement of the required preload was verified. In addition, the occurrence of overextension of the bolt was examined by assessing the exceedance of the maximum value of the clamping force obtained in the tests for the assembly method. Exceeding the maximum tensile strength in a bolted connection results in a reduction in the strength of the connection subjected to the load [30].

In order to determine the effect of atmospheric conditions on the bolt set, an autumn–winter period was chosen. The conditions occurring at this time at the test site located in Lancut (Poland) are presented in Figure 3. As can be seen, there was both rain and snow. The temperature took on positive and negative values. Humidity was high, above 70%, throughout the tests.

Bolt sets stored under different conditions were tested, as described in Table 5 and shown in Figure 4. The test results for the bolt sets stored in the defined manner were compared with the results of tests carried out according to EN 14399-2 [25], marked V0.

Six versions of bolt product protection were adopted. The sets were stored in a box or directly on the concrete floor. In this way, the most common means of protection were mapped. In addition, it was decided to protect the nuts with VCI anticorrosion foils, bearing in mind the direct influence of the surface condition of the nuts on the assembly parameters. The research carried out aimed to answer the following questions:

Do wet conditions result in lower k-factors and friction coefficients?
Does the reduction in k-factor lead to a case where the required torque is not achieved for the modified tightening procedure?
Do additional protective measures minimise the environmental effect on the connection assembly?
Is the bolt set still functional after 4 weeks of being outdoors?

3. Results and Discussion

Due to the complexity of the research, the results obtained were divided into two blocks for the purpose of analysis. The focus was on the functionality of the connection, i.e., compliance with the requirements set by industry standards for HV bolts, and on the assessment of changes in the friction coefficient under the effects of atmospheric conditions and storage time.

3.1. Analysis of Storage Methods

The first block analyses the storage methods and the results obtained for the assembly methods. This block can be called functional. The evaluation of sets can be performed in three ways, depending on the function of the evaluator, which may be:

Manufacturer of bolt sets;
Designer;
User or assembler.

From the point of view of the bolt set manufacturer, the test according to EN 14399-2 [25] is crucial to evaluation. The results presented in Table A1 (in Appendix A) summarise the parameters:

F, K1 and k-factor, corresponding to the first stage of the tests, in which the value of the k-factor and the variance of this parameter were determined by assembling the sets with the force F_p,C (fulfilment of the K1 condition occurs when the k-factor values are between 0.100 and 0.160);
F_bi,max, which occurs in the second stage of assembly (for the M24 thread outline, the minimum value of this force is 317.7 kN);
Angle of rotation ΔΘ_2i,min, the achievement of which allows for the connection efficiency and strength of the threaded connection to be checked.

From the manufacturer’s point of view, the bolts maintained compliance with the applicable requirements for four weeks. Importantly, a change of approximately 0.02 in the k-factor was between the requirements of 0.100 and 0.160. This change did not affect the maximum force achieved or the additional angle of rotation.

At the second point of the assessment, attention should be paid to the requirement to achieve a minimum force F_p,C or F_p,C *. The force requirement F_p,C must be met for type B and C shear connections as well as for a type E preloaded connection. In contrast, the force requirement F_p,C * must be satisfied for type A and D connections according to EN 1993-1-8 [31]. Table A1 (in Appendix A) shows the results for the combined K1 and modified methods. In the case of the first method, the minimum value of F_p,C should be 247.1 kN, while for the second method, the minimum F_p,C * is 220 kN. However, simply assessing the strength achieved at the end of the procedure is only a superficial check. This is due to the fact that for the combined K1 method, the assembly ends when the additional angle of rotation is reached, while for the modified method, the required torque value is reached. The principle adopted is that if the assembly is completed and F_p,C or F_p,C * is determined after F_bi,max has been exceeded, the connection is no longer functional and safe. After exceeding the maximum value for the force F_bi,max, the clamping force in the connection decreases, which is caused by a reduction in the bolt neck diameter or deformation of the thread. In the tests, all bolts reached the required clamping force before exceeding the F_bi,max value, so the sets were properly preloaded.

The third point of assessment is the observation of the user of the bolt sets, who assembles the connection. Under assembly conditions, it should be assumed that the sets supplied meet the requirements contained on the label and are as ordered. The assembler may note the aspect of potential breakage of the sets resulting from elongation of the bolts in the neck or excessive torsional stresses. Breakage of the connection can occur as a result of inadequate fit of the threaded parts being joined. On the other hand, if the coating degrades and the friction coefficient increases, the torque increases and, consequently, the torsional stresses increase. This can lead to the destruction of the bolted connection in the threaded part of the bolt immediately in front of the nut. Such an incident did not occur during the tests. Another aspect, which only applies to the modified method, is the failure to achieve the required M_A value. Such a case may occur when the k-factor is too low. In such a case, a significantly higher clamping force is obtained for the M_A value. It may therefore happen that the F_bi,max value is exceeded and, further down the assembly, the torque decreases as the force decreases. This would lead to an inability to reach the M_A value and destruction of the thread or the formation of a neck in the threaded part of the bolt.

An evaluation of the bolt sets under the conditions of four weeks and direct exposure (Figure 5) also highlights possible signs of corrosion, damage to the boxes or deterioration of label visibility. The hot-dip zinc coating on the surface of the set parts protected them from environmental influences for the stated period of time. In turn, the batch identification system on the head of the bolt and nut, even when the boxes or labels are damaged, makes it possible to identify the production batch and match it with the certificates sent by the manufacturer.

3.2. Analysis of Friction Coefficients

The second block of evaluation was the analysis of the friction coefficient parameters. HV bolt sets are mainly analysed by paying attention only to the value of the k-factor. To determine the clamping force, this parameter is sufficient and easy to establish. When analysing the molybdenum disulphide coating process or assessing the storage method, it may not be enough. In the case of HV bolt sets, due to the size of the bearing surface of the nut and contact with the washer, the significance of the friction coefficient on the bearing surface is much higher than for standard ISO 4014 bolt [32] and ISO 4032 nut [33] connections. This also affects the evaluation of the individual parameters and, in particular, more attention should be paid to the µ_b coefficient.

The data in Table A2 (in Appendix A) present a summary for the k-factor, µ_tot, µ_th and µ_b parameters determined in the first part of the tests according to EN 14399-2 [25] after the F_p,C force has been reached.

The changes over a four-week period should be referred to the V0 test. After the first week, characterised by temperatures in the range of −3 to 8 °C, humidity in the range of 73 and 96% and rainfall not exceeding 2 mm for three days, friction coefficients decreased.

The k-factor and µ_tot parameters shown in Figure 6 and Figure 7 correspond to each other. The µ_tot coefficient is the extended equivalent of k-factor. When analysing the change in the µ_tot coefficient over successive weeks, it reached an average value of 0.084. In contrast, for the sets taken from the warehouse, the coefficient varied between 0.102 and 0.113. The spread between individual test values was 0.032, with a maximum score of 0.100 and a minimum score of 0.068.

The variation in the µ_th and µ_b coefficients is summarised in Figure 8 and Figure 9. An important result is that the k-factor does not fall below 0.100. The lowest friction coefficient values were read after 2 weeks when the sets were under snow. In this case, the products contained in the boxes had the lowest friction coefficients values on the bearing surface.

The effect of atmospheric conditions on the performance of the coating on the joining elements is presented for the chosen method of storing the bolt sets in the graphs in Figure 10, Figure 11 and Figure 12. The graphs show the changes in the friction coefficients under clamping force for the first sets of variant V1, starting with the initial test marked as 0 and illustrating the subsequent weeks as 1, 2, 3 and 4. The reduction in friction increased the value of the maximum clamping force achieved.

The change in the k-factor value between 0.100 to 0.160 (Figure 6) for the four weeks of testing was achieved by a small change in µ_b coefficient (Figure 12). The µ_th coefficient varied as shown in Figure 11, where, due to changes in storage time, friction decreased as clamping force increased. The µ_b value changed on average by 0.011 and µ_th by 0.039.

Analysing all the results obtained, also for other methods of storing the bolt sets, it can be concluded that the method of packaging and storing the bolt sets had little effect on the results. Temperature drop, precipitation and increased humidity affected the tested sets in a similar way. The research showed that the nut coating method adopted and the process requirements used satisfactorily reduced variations.

4. Concluding Remarks

The following conclusions can be drawn from the research carried out:

Tests performed in autumn and winter conditions show that the HV bolt sets are still functional for assembly according to the combined method K1 [29] and the modified method [13];
It was found that the friction coefficient for the bolt sets was reduced as a result of the autumn and winter weather conditions in Poland. Thus, the research hypothesis posed in the introduction to this article was proven. The achieved average difference for the k-factor is 0.028 between sets from storage and those exposed to atmospheric conditions;
Despite the large effect of friction on the bearing surface on the µ_tot values, the largest changes occurred for the µ_th parameter.

The authors see room for improvement and a greater reduction in existing changes in the friction coefficient values obtained, especially for the µ_th parameter. As a new research direction, it is possible to point out the investigation of the effect of the application of the topcoat coating [34], widely used in fasteners for the automotive industry, on the variation of the friction coefficient.

The research presented in this article relates to autumn and winter conditions in Poland and the temperature changes that occur there. However, the presented test procedure can be successfully applied to the investigation of bolt sets in temperature conditions occurring in other parts of the world.

Author Contributions

Conceptualization, T.D.; methodology, T.D.; software, T.D.; validation, T.D. and R.G.; formal analysis, T.D.; investigation, T.D.; resources, T.D.; data curation, T.D.; writing—original draft preparation, T.D.; writing—review and editing, R.G.; visualization, T.D. and R.G.; supervision, R.G.; project administration, R.G.; funding acquisition, R.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

All experimental data are available from the corresponding author upon request.

Conflicts of Interest

The authors declare no conflict of interest.

Nomenclature

Symbol	Definition
d	Nominal thread diameter of the bolt
d₂	Basic pitch diameter of thread
d_h	Washer hole diameter
ƒ_ub	Nominal tensile strength
h	Humidity
k	k-factor (torque factor)
n	Number of sets in the tests
p	Precipitation
t	Temperature
A_s	Nominal stress area of the bolt
D_o	Outer bearing surface diameter
F	Clamping force
F_bi,max	Individual value of the maximum bolt force reached during test
F_p,C	Required preload
F_p,C *	Reduced preload
F(M_A)	Preload for the torque in the modified method
F(θ_KV)	Preload for step two in the combined method
M_A	Torque in the modified method
P	Thread pitch
T at F_p,C	Individual value of the torque at which the bolt force has first reached the value of F_p,C
V_k	Coefficient of variation of the k-factor for the preload F_p,C
µ_b	Coefficient of friction between the bolt head and the bearing surfaces
µ_th	Coefficient of friction between the threaded surfaces of the joining elements
µ_tot	Coefficient of total friction
Θ	Angle of rotation of the nut relative to the bolt
Θ_2i	Individual value of the angle Θ
Θ_pi	Individual value of the angle Θ at which the bolt force has first reached the value of F_p,C
ΔΘ_2i	Individual angle difference (Θ_2i–Θ_pi)
ΔΘ_2i,min	Minimum required value of the angle difference ΔΘ_2i specified in the relevant product standard

Appendix A

Table A1. Test results for M24 × 140 sets after 4 weeks of exposure to atmospheric conditions.

			EN 14399-2 [21]						Combined Method K1 [25]			Modified Method [9]
	Week	n	F_p,C	K1	k-Factor	F_bi,max	ΔΘ_2i ≥ ΔΘ_2i,min	Fracture	F(θ_KV) ≥ F_p,C	F(θ_KV)	F_p,C ≥ F_bi,max	F(M_A) ≥ F_p,C *	F(M_A)	F_p,C * ≥ F_bi,max
V0	–	5	5/5	5/5	0.144–0.158 (V_k = 3.65%)	5/5	5/5	0/5	5/5	322.3–344.2	0/5	5/5	223.8–245.5	0/5
V1	1	5	5/5	5/5	0.123–0.131 (V_k = 2.42%)	5/5	5/5	0/5	5/5	358.3–375.4	0/5	5/5	257.4–278.7	0/5
	2	5	5/5	5/5	0.118–0.129 (V_k = 3.70%)	5/5	5/5	0/5	5/5	352.0–369.1	0/5	5/5	259.6–308	0/5
	3	5	5/5	5/5	0.122–0.133 (V_k = 3.40%)	5/5	5/5	0/5	5/5	353.9–367.4	0/5	5/5	250.3–284.7	0/5
	4	5	5/5	5/5	0.121–0.128 (V_k = 2.50%)	5/5	5/5	0/5	5/5	357.0–367.6	0/5	5/5	263.2–282.7	0/5
V2	1	5	5/5	5/5	0.116–0.123 (V_k = 2.10%)	5/5	5/5	0/5	5/5	364.9–373.4	0/5	5/5	283.9–309.5	0/5
V2	3	5	5/5	5/5	0.120–0.126 (V_k = 1.92%)	5/5	5/5	0/5	5/5	362.3–366.5	0/5	5/5	271.8–297.0	0/5
V3	1	5	5/5	5/5	0.114–0.125 (V_k = 4.23%)	5/5	5/5	0/5	5/5	338.4–379.4	0/5	5/5	266.0–321.8	0/5
	2	5	5/5	5/5	0.102–0.124 (V_k = 8.11%)	5/5	5/5	0/5	5/5	360.9–388.0	0/5	5/5	275.2–378.8	0/5
	3	5	5/5	5/5	0.111–0.121 (V_k = 3.56%)	5/5	5/5	0/5	5/5	369.6–381.2	0/5	5/5	284.2–322.1	0/5
	4	5	5/5	5/5	0.125–0.131 (V_k = 1.90%)	5/5	5/5	0/5	5/5	359.5–365.2	0/5	5/5	256.9–272.4	0/5
V4	1	5	5/5	5/5	0.116–0.142 (V_k = 7.95%)	5/5	5/5	0/5	5/5	345.0–377.4	0/5	5/5	235.4–308.5	0/5
V4	3	5	5/5	5/5	0.111–0.121 (V_k = 4.77%)	5/5	5/5	0/5	5/5	370.2–384.1	0/5	5/5	285.2–336.6	0/5
V5	1	5	5/5	5/5	0.121–0.134 (V_k = 3.84%)	5/5	5/5	0/5	5/5	354.4–369.1	0/5	5/5	250.5–285.4	0/5
	2	5	5/5	5/5	0.108–0.128 (V_k = 5.86%)	5/5	5/5	0/5	5/5	355.4 –383.8	0/5	5/5	264.5–347.4	0/5
	3	5	5/5	5/5	0.112–0.123 (V_k = 3.90%)	5/5	5/5	0/5	5/5	365.6–378.4	0/5	5/5	274.4–330.7	0/5
	4	5	5/5	5/5	0.119–0.127 (V_k = 2.57%)	5/5	5/5	0/5	5/5	357.4–366.4	0/5	5/5	264.1–291.2	0/5
V6	1	5	5/5	5/5	0.116–0.134 (V_k = 5.47%)	5/5	5/5	0/5	5/5	356.1–368.9	0/5	5/5	249.0–300.8	0/5
	2	5	5/5	5/5	0.106–0.124 (V_k = 6.25%)	5/5	5/5	0/5	5/5	358.2–388.1	0/5	5/5	278.3–341.3	0/5
	3	5	5/5	4/5	0.114–0.123 (V_k = 3.52%)	5/5	5/5	0/5	5/5	368.7–379.7	0/5	5/5	274.2–312.4	0/5
	4	5	5/5	5/5	0.125–0.13 (V_k = 1.36%)	5/5	5/5	0/5	5/5	356.4–366.4	0/5	5/5	258.6–269.4	0/5

Table A2. k-factor and friction coefficient results for M24 × 140 sets after 4 weeks of exposure to atmospheric conditions.

		k-Factor		µ_tot		µ_th		µ_b
Week	Variant	Average	Min–Max	Average	Min–Max	Average	Min–Max	Average	Min–Max
–	V0	0.150	0.144–0.158	0.107	0.102–0.113	0.144	0.136–0.161	0.078	0.074–0.087
1	V1	0.128	0.123–0.131	0.089	0.084–0.091	0.111	0.100–0.117	0.072	0.069–0.074
	V2	0.120	0.116–0.123	0.083	0.079–0.085	0.101	0.098–0.105	0.069	0.065–0.071
	V3	0.119	0.114–0.125	0.081	0.078–0.087	0.095	0.089–0.106	0.070	0.069–0.072
	V4	0.126	0.116–0.142	0.087	0.079–0.100	0.106	0.093–0.127	0.072	0.065–0.079
	V5	0.126	0.121–0.134	0.087	0.083–0.093	0.110	0.098–0.116	0.069	0.064–0.076
	V6	0.126	0.116–0.134	0.087	0.079–0.094	0.108	0.096–0.116	0.071	0.066–0.080
2	V1	0.123	0.118–0.129	0.084	0.080–0.090	0.109	0.096–0.114	0.066	0.059–0.071
	V3	0.112	0.102–0.124	0.076	0.068–0.086	0.095	0.077–0.111	0.061	0.054–0.068
	V5	0.118	0.108–0.128	0.081	0.073–0.089	0.109	0.096–0.133	0.059	0.054–0.065
	V6	0.114	0.106–0.124	0.077	0.071–0.086	0.103	0.090–0.120	0.057	0.055–0.059
3	V1	0.126	0.122–0.133	0.087	0.084–0.093	0.109	0.100–0.121	0.071	0.066–0.077
	V2	0.123	0.120–0.126	0.085	0.082–0.088	0.105	0.103–0.109	0.069	0.064–0.071
	V3	0.116	0.111–0.121	0.079	0.075–0.083	0.100	0.097–0.103	0.063	0.059–0.070
	V4	0.117	0.111–0.121	0.080	0.075–0.083	0.100	0.092–0.107	0.064	0.057–0.069
	V5	0.117	0.112–0.123	0.080	0.076–0.085	0.100	0.092–0.114	0.064	0.060–0.066
	V6	0.119	0.114–0.123	0.082	0.077–0.085	0.099	0.093–0.104	0.068	0.065–0.071
4	V1	0.125	0.121–0.128	0.087	0.083–0.089	0.107	0.104–0.108	0.071	0.068–0.074
	V3	0.127	0.125–0.131	0.088	0.086–0.091	0.110	0.103–0.120	0.071	0.069–0.074
	V5	0.125	0.119–0.127	0.086	0.082–0.088	0.110	0.102–0.116	0.067	0.065–0.072
	V6	0.128	0.125–0.130	0.089	0.087–0.090	0.111	0.108–0.115	0.071	0.070–0.073

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Figure 1. HV bolt set M24 × 140.

Figure 2. Kistler machine of type 5413-2777.

Figure 3. Atmospheric conditions during the tests: (a) temperature and humidity; (b) total precipitation (designations: t_max—maximum temperature; t_min—minimum temperature; h—humidity; p—precipitation).

Figure 4. Methods of storing the bolt sets, according to Table 5: (a) V1; (b) V2; (c) V3; (d) V4; (e) V5; (f) V6.

Figure 5. Bolt sets exposed to atmospheric conditions: (a) for 2 weeks; (b) for 3 weeks; (c) for 3 weeks, after assembly and disassembly (storage method V6).

Figure 6. Graph of variation of the k–factor over successive weeks of exposure of the M24 × 140 sets to weather, taking into account the method of storage.

Figure 7. Graph of variation in the µ_tot coefficient over successive weeks of exposure of the M24 × 140 sets to weather, taking into account the method of storage.

Figure 8. Graph of variation in the µ_th coefficient over successive weeks of exposure of the M24 × 140 sets to weather, taking into account the method of storage.

Figure 9. Graph of variation in the µ_b coefficient over successive weeks of exposure of the M24 × 140 sets to weather, taking into account the method of storage.

Figure 10. Graph of the dependence of the µ_tot on the clamping force in the case of the first samples tested for storage variant V1.

Figure 11. Graph of the dependence of the µ_th on the clamping force in the case of the first samples tested for storage variant V1.

Figure 12. Graph of the dependence of the µ_b on the clamping force in the case of the first samples tested for storage variant V1.

Table 1. Steps for testing the suitability of the connection according to EN 14399-2 [25] for the EN 14399-4-HV-M24 × 140-10.9/10-tZn-K1 bolt set.

Step 1	To F_p,C = 247.1 kN
Step 2	To ΔΘ_2i,min = 210° or decrease force to F_p,C = 247.1 kN
Removal	Return to starting position

Table 2. Key data used to prepare the study for the Kistler machine of type 5413-2777.

Parameter	Value
Total torque	8000 Nm
Thread/bearing torque	4000 Nm
Clamping force	1000 kN

Table 3. Outline parameters of the M24 thread.

Parameter	Value
Thread pitch	3 mm
Average flange diameter	22.05 mm
Angle of thread	60°
Mean bearing surface diameter	32.9 mm
Nominal diameter	24 mm

Table 4. Evaluated assembly parameters.

	EN 14399-2 [25]	EN 1090-2 [29]	DASt-Richtlinie 024 [13]
k-factor	K1, 0.10–0.16	K1, 0.10–0.16	K1, 0.10–0.16
Clamping force	F_p,C = 247.1 kN	F_p,C = 247.1 kN	F_p,C * = 220 kN ²
Step 1	247.1 kN	560 Nm	600 Nm
Step 2	210°	90°	800 Nm
F_bi,max ¹	318 kN	–	–

¹ F_bi,max is the individual value of the maximum bolt force reached during test; ² F_p,C * is the reduced preload [13].

Table 5. List of storage methods for the bolt sets.

Symbol	Description
V1	A set of products, not assembled, placed directly on a concrete base.
V2	A set of products, assembled, placed directly on a concrete base.
V3	A set of products, not assembled, placed in a box.
V4	A set of products, assembled, placed in a box.
V5	Bolts and washers placed in a box, nuts secured with a VCI anticorrosion foil and placed in a box.
V6	Bolts and washers placed in a box, nuts secured with paper and placed in a box.

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Dubiel, T.; Grzejda, R. Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets. Lubricants 2023, 11, 460. https://doi.org/10.3390/lubricants11110460

AMA Style

Dubiel T, Grzejda R. Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets. Lubricants. 2023; 11(11):460. https://doi.org/10.3390/lubricants11110460

Chicago/Turabian Style

Dubiel, Tomasz, and Rafał Grzejda. 2023. "Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets" Lubricants 11, no. 11: 460. https://doi.org/10.3390/lubricants11110460

APA Style

Dubiel, T., & Grzejda, R. (2023). Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets. Lubricants, 11(11), 460. https://doi.org/10.3390/lubricants11110460

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Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets

Abstract

1. Introduction

2. Materials and Methods

3. Results and Discussion

3.1. Analysis of Storage Methods

3.2. Analysis of Friction Coefficients

4. Concluding Remarks

Author Contributions

Funding

Data Availability Statement

Conflicts of Interest

Nomenclature

Appendix A

References

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