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A Study on Laser Welding of Dissimilar Materials between Aluminum and Copper (Ⅱ) - Development of Laser Welding Quality Verification Technique -

The quality management of laser welding is crucial for EV battery manufacturing as it directly affects vehicle safety. However, there is currently no test standard to evaluate the quality of laser-welded structures. Visual inspection and tensile testing have been used to examine the quality of lap joint laser welding. However, it is dangerous to determine the optimal welding parameters only by tensile strength. The aim of this study was to determine the optimal laser welding parameters by conducting tests for various load directions, such as peel, moment, and low-cycle fatigue tests. As a results, in the case of Al/Cu welding that is highly brittle, the peel test demonstrated greater discrimination than the tensile test. In contrast, the moment test was more effective at determining the strength of the local interface joints. Lastly, the fatigue test yielded similar outcomes to the tensile test. It is challenging to completely replace the tensile test results and utilize them independently. Hence, it is recommended to utilize them exclusively as sub-tests to establish the ideal laser welding conditions.

Aerodynamic Load Variation and Wind-Induced Vibration Analysis of Tower Cranes Under Full Wind Angles

When tower cranes are applied in coastal engineering, the wind-induced vibration under complex wind loads along the coast will be exceptionally obvious. It is increasingly important to explore the wind-induced vibration characteristics of different sections of tower cranes under full wind angles. This paper first establishes a three-dimensional numerical wind tunnel model that can be used for the simulation of tower cranes under full wind angles and analyzes the aerodynamic load variation of the tower crane under full wind angles. Secondly, the tower crane structure is divided into sub-regions, and the AR model method in the linear filtering method is used to simulate the three-dimensional wind speed time history. Further, the wind speed time history is applied to the finite element transient analysis, and based on the Newmark-beta method, the acceleration and displacement responses of different sections of the tower crane structure under fluctuating wind are systematically studied. Finally, the equivalent static wind load of different sections of the tower crane is evaluated by using the gust load factor method. The results indicate that the wind load of the tower crane exhibits an obvious three-dimensional effect, and the crosswind load cannot be ignored in the analysis of wind stability. The different sections of the tower crane structure show low-frequency vibration characteristics, and the low-frequency band is dominated by down-wind vibration, while the high-frequency band often experiences crosswind vibration. The amplification effect of the tower crane on fluctuating wind loads will increase with the increase of the height of the tower crane and the length of the jib, and the amplification effect on fluctuating wind loads in the crosswind direction is more obvious. The equivalent static wind load on the top of the tower crane reaches the maximum when the angle between the jib and the incoming wind is 60°.

Efficient reliability-based concurrent topology optimization method under PID-driven sequential decoupling framework

The continuous improvement of advanced equipment performance has promoted the development of detailed structural design. The detailed design of the structure should meet many requirements such as high reliability, strong robustness, lightweight, and high efficiency. This paper proposes a proportional-integral-derivative-driven efficient reliability-based concurrent topology optimization strategy under the sequential framework. Considering the uncertainty of load position, load direction, load amplitude, and material properties, an efficient reliability-based concurrent topology optimization model is constructed based on the sequential strategy. Based on effectively quantifying the nonlinear characteristics brought by multi-source uncertainty, a constraint refinement movement strategy based on the proportional-integral-derivative controller is proposed, which to some extent overcomes the tedious calculation of uncertainty quantification. This paper provides sensitivity information on macroscopic and microscopic level set functions under displacement constraints. Four numerical examples demonstrate the effectiveness, efficiency, and generalization ability of the proposed method.

Identification of failure behaviors of underground structures under dynamic loading using machine learning

Understanding the dynamic responses of hard rocks is crucial during deep mining and tunneling activities and when constructing nuclear waste repositories. However, the response of deep massive rocks with openings of different shapes and orientations to dynamic loading is not well understood. Therefore, this study investigates the dynamic responses of hard rocks of deep underground excavation activities. Split Hopkins Pressure Bar (SHPB) tests on granite with holes of different shapes (rectangle, circle, vertical ellipse (elliptical short (ES) axis parallel to the impact load direction), and horizontal ellipse (elliptical long (EL) axis parallel to the impact load direction)) were carried out. The influence of hole shape and location on the dynamic responses was analyzed to reveal the rocks' dynamic strengths and cracking characteristics. We used the ResNet18 (convolutional neural network-based) network to recognize crack types using high-speed photographs. Moreover, a prediction model for the stress-strain response of rocks with different openings was established using Deep Neural Network (DNN). The results show that the dynamic strengths of the granite with EL and ES holes are the highest and lowest, respectively. The strength-weakening coefficient decreases first and then increases with an increase of thickness-span ratio (h/L). The weakening of the granite with ES holes is the most obvious. The ResNet18 network can improve the analyzing efficiency of the cracking mechanism, and the trained model's recognition accuracy reaches 99%. Finally, the dynamic stress-strain prediction model can predict the complete stress-strain curve well, with an accuracy above 85%.

Bearing capacity of modified suction caissons in clay overlying sand under monotonic horizontal loading

The modified suction caisson (MSC) is an innovative foundation for fixing offshore wind turbines, consisting of an internal caisson (IC) and an external skirt (ES). In this study, the Plaxis3D is conducted on the bearing capacity of the MSC in clay overlying sand under monotonic horizontal loading. The parameters of the aspect ratio of the IC, the size of the ES, the clay thickness, and the soil strength are considered. Results show that the horizontal ultimate bearing capacity of the MSC decreases as the length ratio of the ES to IC decreases. Moreover, the width of the ES enhances the horizontal bearing capacity of the MSC higher than the length of the ES. With the increase of the clay thickness, the rotation center of the TSC and MSC exhibits two and three stage change patterns, respectively. When the clay and sand are the inhomogeneous soils, the horizontal ultimate bearing capacity of the MSC is enhanced by 8.96% compared to the homogeneous soils. Additionally, the passive and active earth pressures around the MSC are mainly generated at the front and rear side of the loading direction, respectively. This study will provide theoretical guidance for the design of the MSC.

Determining technological parameters for obtaining ta15 titanium alloy blanks with improved mechanical characteristics using the electron-beam 3D printing method

The object of this study is the process of electron beam 3D printing of articles made of TA15 titanium alloy powder. Peculiarities of the structure and properties formation of alloy blanks, obtained by this method have been described. Influence of process parameters (electron beam power and geometric scanning parameters) on the characteristics of the material were considered. Step of displacement of the beam trajectory changed from 0.1 to 0.25 mm with an interval of 0.05 mm. Specific energy of the electron beam varied from 20 to 70 J/mm3 for every trajectory displacement step. The macrostructure was examined visually while the microstructure was studied by optical microscopy. Mechanical properties were determined by uniaxial tension and impact bending tests. It was established that depending on the 3D printing parameters the macrostructure of most samples is dense but with unfavorable parameters non-fusions or shrinkage porosity defects may form. The microstructure of the dendritic type has an α´+β lamellar-acicular morphology, its dispersity and shape of α´–phase areas vary depending on the process parameters. A scanning step of 0.2 mm and a beam energy of 40 J/mm3 allows obtaining a dispersed microstructure in which there are no non-fusions and shrinkage micropores. The value of the Rm is 27 %, and the R0.2 is 24 % higher than that of the alloy obtained by the conventional technology of electron beam melting. The A5 is 3.2 times higher. However, impact toughness of the sample with dendrite unfavorable orientation to the direction of load applying may be lower compared to conventional technology. The results could be used for devising commercial technology of high strength titanium alloys parts produced by 3D printing

Study of the stress-strain state of the loess soil base of an eccentrically loaded tower foundations, with taking into account the possible water saturation of the soil

This article provides the design of the tower shallow foundations using numerical simulation in the "Midas GTS NX" software. The foundations are four separate structures that perceive the bearing reactions from the tower supports. Depending on the wind load direction, the support reactions change both quantitatively and qualitatively. So, one foundation can accept a compressive force, the other one can accept a pull-out force. In this study, two variants of wind loading are considered: the wind load acts on the tower face or on the tower edge. The geological conditions of the research site are taken as simplified. The soil base consists of one engineering-geological element, which is a loess soil. Numerical simulation of the soil massif was implemented by using volumetric finite elements. An elastic-plastic deformation law and a Mohr–Coulomb failure criterion were applied for these finite elements. The design provided for the calculation of the tower foundation on a natural basis and with the arrangement of a compacted sub-base. Research was carried out for the foundations of the tower construction in four stages: 1) soil base in its natural state; 2) arranged compacted sub-base; 3) natural basis with local water saturation of the soil; 4) compacted sub-base with local water saturation of the soil massif. Simulation of the arrangement of the compacted sub-base occurs by replacing the stiffness of the finite element at a certain stage of the calculation. The soil water saturation simulation algorithm is performed in a similar way - there is a change in the physical and mechanical characteristics of certain finite elements. The localization of saturation zones was chosen from the conditions of the most unfavorable combinations of loads and vertical movements of the foundations. An analysis of the stress-strain state of the soil base of foundations under the tower on a natural base and with the arrangement of a compacted sub-base was performed. The scheme of the applied load on the foundation and the possible local water saturation of the loess soil at the base of the foundations were taken into account

Wire and arc additive manufacturing for strengthening of metallic components

Wire and arc additive manufacturing (WAAM), also known as wire arc directed energy deposition (WA-DED), offers valuable capabilities not only for manufacturing but also for strengthening and repairing aging components. This paper employs the finite element (FE) method to investigate the influence of deposition parameters on the strengthening efficiency of damaged steel plates strengthened by WAAM material. The study calibrates the inherent strain method (ISM) with thermo-mechanical analysis to accurately predict residual stresses (RS) in manufactured samples, demonstrating that the ISM enhances computational efficiency while effectively predicting RS. It thoroughly examines key parameters such as the deposition direction, maximum thickness, and the geometric configuration of the WAAM material, including shapes and in-plane dimensions. The results indicate that deposition perpendicular to the loading direction provides better performance compared to deposition along the loading direction as it induces less normal and through-thickness stresses. Furthermore, this research determines the optimal maximum thickness for the WAAM material, showing that an increase in thickness can lead to higher maximum tensile stresses at the interface between the newly WAAM material and the underlying base plate. The study also establishes the optimal in-plane dimensions for the WAAM material. The results suggest placing the maximum thickness of WAAM material near the damaged area and gradually decreasing it in two directions to ensure sufficient stiffness around the cracked area, while avoiding an abrupt change in stiffness. This approach generates appropriate compressive stresses around the crack tip and decreases maximum tensile stresses in the plate. The study further illustrates that employing a proper printing strategy without a subsequent machining process can effectively reduce the maximum tensile stress in the steel plate while minimizing material usage.

The Chinese Knot inspired anisotropic TC4 lattice Structures: Ultra-high specific strength in engineering materials

Lattice structures possess high specific strength, multi-functionality through innovative structural designs. Here, we proposed an efficient method for the construction of lattice structures by elongating two-dimensional planar patterns along the load direction, which enabled the efficient utilization of 100 % materials for load bearing. Inspired by Chinese Knot (CK), a series of meticulously crafted TC4 lattice structures were fabricated by using selective laser melting. These structures feature nine tubular units arranged in a 3 × 3 matrix interconnected by sixteen parallel plates, and their failure modes were subsequently investigated by uniaxial compression tests. The results show that the specific compressive strength of the CK structure enhances as increasing the density. The detachment between the plate and tube, and the buckling of the plate, lead to the premature failure, which in turn leads to substantial variations in strength, estimated at approximately 80 MPa at ∼ 1.5 g/cm3. When the thickness of the plate exceeds 0.5 mm, and the tube wall thickness exceeds 0.04 mm, the CK structures show high stability and exhibit a 45° shear failure mode. Notably, the specific strength of the CK structure can surpass 330 MPa∙cm3/g, which represents the peak level of specific compressive strength compared to the current TC4 lattice structures.

Study on the Energy Absorption Performance of Triply Periodic Minimal Surface (TPMS) Structures at Different Load-Bearing Angles.

As engineering demands for structural energy absorption intensify, triply periodic minimal surface (TPMS) structures, known for their light weight and exceptional energy absorption, are increasingly valued in aerospace, automotive, and shipping engineering. In this study, the energy absorption performance of three typical TPMS structures was evaluated (i.e., Gyroid, Diamond, and IWP) using quasi-static compression tests at various load-bearing angles. The results showed that while there is little influence of load-bearing angles on the energy absorption performance of Gyroid structures, its energy absorption is the least of the three structures. In contrast, Diamond structures have notable fluctuation in energy absorption at certain angles. Moreover, IWP (I-graph and Wrapped Package-graph) structures, though highly angle-sensitive, achieve the highest energy absorption. Further analysis of deformation behaviors revealed that structures dominated by bending deformation are stable under multi-directional loads but less efficient in energy absorption. Conversely, structures exhibiting mainly tensile deformation, despite their load direction sensitivity, perform best in energy absorption. By integrating bending and tensile deformations, energy absorption was enhanced through a multi-stage platform response. The data and conclusions revealed in the present study can provide valuable insights for future applications of TPMS structures.

Prediction of Placental Abruption of Pregnant Women Drivers with Various Collision Velocities, Seatbelt Positions and Placental Positions-Analysis with Novel Pregnant Occupant Model.

The aims of this study were as follows: the (a) creation of a pregnant occupant finite element model based on pregnant uterine data from sonography, (b) development of the evaluation method for placental abruption using this model and (c) analysis of the effects of three factors (collision speed, seatbelt position and placental position) on the severity of placental abruption in simulations of vehicle collisions. The 30-week pregnant occupant model was developed with the uterine model including the placenta, uterine-placental interface, fetus, amniotic fluid and surrounding ligaments. A method for evaluating the severity of placental abruption on this pregnant model was established, and the effects of these factors on the severity of the injury were analyzed. As a result, a higher risk of placental abruption was observed in high collision speeds, seatbelt position over the abdomen and anterior-fundal placenta. Lower collision speeds and seatbelt position on the iliac wings prevented severe placental abruption regardless of placental positions. These results suggested that safe driving and keeping seatbelt position on the iliac wings were essential to decrease the severity of this injury. From the analysis of the mechanism for placental abruption, the following hypothesis was proposed: a shear at adhesive sites between the uterus and placenta due to direct seatbelt loading to the uterus.

Empowered or enchained? Exploring consumer perspectives on Direct Load Control

Demand Response has become a central focus in policy discussions, attracting heightened attention for its potential key role in fostering enhanced demand flexibility. Direct Load Control (DLC) holds particular promise, requiring reduced consumer involvement compared to strategies relying on manual responses to time-varying pricing. However, the participation rate of residential consumers in DLC programs remains low, emphasizing the need for a more profound understanding of consumers' perspectives on DLC. Drawing from 15 in-depth interviews with Swedish households participating in a program involving direct load control of heat pumps, this study aims to explore the experiences and perceptions of consumers, providing in-depth understanding on factors that may serve as motivators, barriers and enablers for participation. Key findings include: financial benefits and interest in technology were the main motivations for participation; pre-existing knowledge and awareness of energy-related matters shaped consumers’ attitudes to DLC; trust in the service provider was a key enabling factor for participation. The study further suggests that DLC does not inevitably lead to a perceived loss of control among participants, but, if implemented in alignment with their specific conditions, needs and preferences, may also foster a sense of empowerment.

Combined axial load-biaxial bending interaction method for L-shaped CFSP shear walls

This paper reports the development of axial load and biaxial bending interaction method for L-shaped concrete-filled steel plate (CFSP) composite shear walls based on fiber section analysis model using the uniaxial constitutive relationship of materials. Owing to the complex interaction between the two perpendicular wall limbs (web and flange) of an L-shaped shear wall, the contour shape of the My-Mz curve is asymmetric. Linear transformation was employed to reduce the asymmetry of the contour shape, eliminate the influence of dimension, and perform parametric analysis. The analysis results indicate that when 0° ≤ θ(neutral axis angle) ≤ 90°, the influence of width-to-thickness ratio (hw1/bw) and shape coefficient (γ) on the coefficient that controls the contour shape (α) was negligible. The effect of shape coefficient (γ), steel content ratio (ρ), compressive strength of unconfined concrete (fc0), and yield strength of steel plate (fyp) on α is not significant for −180° ≤ θ ≤ −90°. Further, simplified equations were suggested to determine α. The axial load-moment interaction curve expressions for distinctive loading directions were determined by establishing the calculation method for the curve's characteristic points (axial load capacity, bending capacity, boundary points). Subsequently, the characteristic points were combined with the contour shape of the axial load-moment interaction curve derived by fitting the finite element simulation data to generate the axial load-moment interaction curve equations. A design approach was finally formulated based on the equations for the biaxial moment capacity curve and the axial load-moment interaction curves of the characteristic loading directions.

Control of edgewise vibration of a pre-twisted rotating beam with shunted piezoelectric tuned mass damper

The edgewise vibration control of a pre-twisted beam, rotating in the vertical plane, is considered in this study. A piezoelectric tuned mass damper (PTMD) comprising a spring–mass–damper system and a piezoelectric transducer with its associated shunt circuit is considered the control device. A finite element formulation of the pre-twisted rotating beam with the attached PTMD is developed while considering the effect of centrifugal stiffening due to rotation and the effect of gravity force. The natural frequencies of the beam (without PTMD) obtained using the present formulation are corroborated by comparing them with the results derived from Ansys. A single PTMD attached at the tip end of the beam can effectively suppress the response of the beam subjected to a distributed load in the edgewise direction. The best values of resistance and inductance of the shunt circuit are obtained through a parametric study on the peak and root mean square value of the beam tip response. A qualitative difference in the uncontrolled as well as in the controlled responses can be noticed while considering the effect of the gravity load component in the edgewise direction. Further, it has been observed that the conventional Tuned Mass Damper (TMD) provides better control than the PTMD system for ideally tuned conditions, however, the control performance of TMD degrades rapidly as compared to the PTMD in the presence of detuning. This demonstrates the effectiveness of PTMD in a practical implementation where achieving the perfectly tuned condition is seldom realized. The control performance of PTMD marginally degrades when the beam is subjected to multi-directional excitation. Hence, the proposed control system has the potential for application in rotating beam-type structures, such as wind turbine blades.

Tailoring mechanical properties of FDM-3D-printed parts through titanium dioxide-reinforced resin filling technique

Fused deposition modeling (FDM) is a type of additive manufacturing that falls under the category of material extrusion. Building an object using FDM involves layer-by-layer selective deposition of melted material along a predetermined path. However, FDM parts are inherently anisotropic, meaning their mechanical properties vary depending on the direction of loading, which makes them prone to failure under transverse loads. This study introduces a novel post-processing technique to enhance the mechanical properties of FDM parts. Unlike conventional FDM printing, this study explores a post-processing technique where TiO2-infused resin is injected into the internal voids of printed parts to reinforce their structure. Compared to unfilled counterparts, resin filled structures exhibited significant improvements in tensile strength (up to 40%) and impact energy (up to 28%). A 20% infill density was found to offer a cost-effective balance between material usage and performance, while 2% wt. TiO2 achieved the optimal balance between reinforcement and dispersion, exceeding the performance gains of other concentrations. SEM analysis confirmed effective TiO2 dispersion at lower concentrations, leading to smoother surfaces and potentially improved mechanical properties. This technique presents a promising approach for fabricating high-performance FDM parts with enhanced strength and toughness.

Experimental investigation of pseudo-ductility in plain weft-knitted epoxy composite laminates under tension

The inherent brittleness of unidirectional fiber-reinforced composites represents a major complication in their broad practical applications. However, exploiting different reinforcement architectures can offer an opportunity for highly desirable ductile fracture nature. This article is aimed at investigating experimentally the tensile behavior of an epoxy laminate reinforced by different layers of plain weft-knitted fabrics. The fabricated laminates were subjected to uniaxial tension in different loading directions, and the corresponding tensile responses were recorded. Basic mechanical properties were characterized and digital image correlation (DIC) was employed to capture surface deformations. Tensile test results demonstrated strong nonlinearity and pseudo-ductility as well as loading-direction dependence in this type of composite laminates. Fracture tests were conducted showing high fracture toughness ranging from 10 to 20 MPa·m1/2. Typical damage modes were characterized using microscopy, which were coupled to a few distinct tensile deformation stages. This work demonstrates that weft-knitted composites are promising in permitting great amounts of pseudo-ductility with clear warning before complete failure. It is also expected to contribute to the understanding of the specific role of weft knit fabrics in composite laminates.

Lode-dependent anisotropic-asymmetric yield function for isotropic and anisotropic hardening of pressure-insensitive materials. Part II: Stress invariant-based coupled quadratic and non-quadratic function

This research couples a Lode-dependent anisotropic-asymmetric (LAA) frame (Lou and Yoon, 2023. International Journal of Plasticity, 166, 103,647) with a stress-invariant-based coupled quadratic-non-quadratic (CQN) anisotropic hardening function to analytically characterize the anisotropic-asymmetric hardening of sheet metals under uniaxial tension and uniaxial compression. Experiments are conducted for AA2A12-O under uniaxial tension, uniaxial compression, equibiaxial tension, plane strain tension and shear. Anisotropy is investigated by conducting the experiments along different loading directions from the rolling. The flow curves are obtained from these experimental data at distinct stress states and loading directions. The plastic hardening is represented by the CQN-coupled LAA function to verify its accuracy. The CQN-coupled LAA model is also utilized to represent the plastic flow of DP980 under uniaxial tension, uniaxial compression, shear and plane strain tension along different loading directions as well as equibiaxial tension. The application to AA2A12-O and DP980 demonstrates that the CQN-coupled LAA function is capable of modeling plastic hardening behaviors under uniaxial tension, uniaxial compression, equibiaxial tension and equibiaxial compression and dramatically improving the prediction accuracy of flow curves under plane strain tension.

Multi-objective optimization of prosthetic multi-cells foam liner

Restoring mobility using prosthetic limbs anchored in custom sockets is the primary goal of amputee rehabilitation. The contact pressure at the stump-liner interface is critical for improving prosthetic socket design and enhancing amputee satisfaction and comfort. This study aimed to develop and optimize a new customized multicellular foam liner model by identifying the optimal configuration of the liner’s cells to achieve minimal contact pressure between the transtibial limb (stump) and the prosthetic interface while simultaneously minimizing the stump’s immersion in the foam liner. The study employed a multi-objective optimization using the NSGA-II genetic algorithm to optimize the material configurations of the liner cells. The objective function was based on a finite element (FE) model of the customized foam liner, composed of 40 cells, each using one of six foam materials with varying firmness. The optimization process yielded nine different configurations representing the Pareto front. Contact pressure and immersion, represented by displacement in the load direction, were reduced from 140 KPa and 9 mm to 10 KPa and less than 1 mm, respectively. The results obtained in this study motivate future clinical trials on the efficacy of customized multicellular foam liners. These findings provide in-depth insights into prosthesis design and customization, potentially leading to further development in the use of foam rather than silicone for liner manufacturing.

Design and Simulation of Seats for Emergency Landing Conditions in Electrical VTOLs

Emerging electrification technologies in aviation and recent advances drive the increased usage of electrical vertical take-off and landing (VTOL) air vehicles. Weight considerations are predominant due to the weaker powertrain and lower payload capacity. Moreover, most systems are automated, and there is no distinction between pilot and passenger seats anymore. Conventional aircraft seating typically exhibits excessive weight, necessitating the development of lightweight troop seats with simple designs and textile seat pans and backrests. This research focuses primarily on the design aspects of these lightweight troop seats. There are already guiding military standards and civilian codes for physical tests for passenger or pilot seats. Nevertheless, there needs to be a comprehensive document combining all of these and explaining how simulation tools can be practically used for the same purpose. Consequently, a generic design was generated based on the troop seat of military helicopters, which was then tested and simulated virtually by finite element analysis according to MIL-S-85510, CS27, and CS29 standards. After finalizing the static tests for forward, rearward, lateral, downward, and upward g forces on a 10-degree floor deformation in the longitudinal axis, implicit dynamic tests were conducted with loading in longitudinal and vertical directions as specified by the MIL-S-85510 standards. Then, hotspot analysis is made for stress interpretation. As a result, a near-optimum design was achieved with stresses 10% lower than the yield stress of the materials, which can be used on board an electrical VTOL.

Modelling of Multi-Bolted Systems at the Pretension Stage – Part 1: Mechanical Characteristics of the Contact between the Joined Elements

The subject of the paper is the modelling of multi-bolted connections that are at the pretensioning stage. Taking a systematic approach to the modelling issue, the connection was treated as a composite of four subsystems: a bolt set, a pair of joined elements and a contact layer between them. The first part of the paper describes experimental studies to determine the contact stiffness of a pair of elements separated from an exemplary asymmetric multi-bolted connection. The normal loading and unloading direction of the contact joint was considered. The tests were performed with the use of an INSTRON 8850 servo-hydraulic testing machine equipped with an extensometer. A normal stiffness characteristic in the form of an exponential function was proposed for the tested contact joint. It will be applied in the second part of the paper, in which finite element modelling of the multi-bolted connection will be presented.