Search Results (28)

This paper proposes a novel tube hydro-joining process, which combines piercing, hole flanging, and nut inlaying. The nut punch shape design proposed by this paper can deliver three advantages of no scrap, no oil leakage, and longer flange length, which can achieve stronger clamping force and accordingly increase the pull out load. First, we use the finite element analysis to investigate the elasto-plastic deformation of the aluminum alloy A6063 tube during the hydro-joining process. A punch-shaped nut with a tapered locking part is designed to increase the elasto-binding strength of the pierced tube and the pull out load of the inlayed nut. The effects of hydro-joining loading paths on the formability of the A6063 tubes and punch-shaped nuts are examined. Additionally, the effects of fit zone size, nut punch stroke length, internal pressure, nut diameter, and the die hole diameter on the pull out load and twisting torque are explored. Finally, experiments on hydro-joining of A6063 tubes are conducted to validate the finite element modeling and the simulation results. Full article

CFD-based numerical wave tank models are valuable tools for analyzing the nonlinear interaction between waves and structures. This paper aims to examine the deformation of high-order free surfaces near a vertical, surface-piercing fixed cylinder with various cross-sections under regular head waves, assuming no wave breaking. Additionally, the study investigates the effects of wavelength on wave evolution, nonlinear wave amplification, and the harmonics around the cylinder. The numerical analysis is performed using the CFD toolbox OpenFOAM. The comparison of numerical results for different cross-sections reveals the influence of corner ratio on lateral edge waves and highlights its significant impact on the nonlinear wave field around the cylinder, particularly for short incident waves. The numerical results indicate the important contribution of the cross-section shape together with the corner effect on the lateral edge waves and accordingly the nonlinear wave field surrounding the given column, which involves high harmonics wave amplification up to fourth. The reduction in corner ratio results in a reduction in maximum run-up height from 2.57 to 2.2 in short waves, while for the long waves, it is from 1.61 to 1.45. This research not only enhances our understanding of fluid–structure interactions but also has implications for the design and safety of hydrogen storage and transportation systems. Understanding dynamic pressures and structural responses is crucial for these applications. CFD simulations of wave–cylinder interactions are essential for designing and optimizing offshore hydrogen infrastructure. These simulations model how waves interact with cylindrical structures, such as wind turbine foundations, hydrogen production platforms, and storage tanks. Understanding these interactions is vital for ensuring the structural integrity, efficiency, and sustainability of offshore hydrogen facilities. Full article

Ultra-soft soil is distributed in coastal areas around the world and has poor engineering properties. There is a significant difference in settlement between semi-rigid pile and surrounding soil under embankment load. Based on existing research results, the settlement calculation formula of ultra-soft soil composite foundation reinforced by semi-rigid pile is derived in this paper. Based on the Alamgir displacement model, assuming a three-zone model of pile skin friction with a negative skin friction plastic zone in the upper part of the pile, an elastic zone in the middle part of the pile, and a skin friction-bearing plastic zone in the lower part of the pile, the upward and downward penetrations of pile, and pile–soil slip deformation characteristics are considered. Analytical expressions for settlement calculations of semi-rigid pile composite foundations under embankments were derived based on differential equations for pile–soil load transfer in the unit cell. The influences of pile diameter and the compression modulus of the underlying layer at the pile end on the settlement characteristics of the semi-rigid pile composite foundation are discussed. The results show that the derived theoretical calculation method is in good agreement with the field measurement and laboratory model test results. Ultra-soft soil composite foundations have long settlement stabilization times and large settlement deformations. Penetration deformation occurs at the semi-rigid pile end. The relationship between pile end resistance and pile end piercing deformation is hyperbolic. The compression modulus of the underlying layer has a great influence on pile end penetration. The lower the compression modulus of the underlying layer, the larger the penetration deformation of pile end. The larger the pile diameter is, the smaller the penetration deformation is. Full article

The cross-roll piercing and elongation (CPE) is a forming process performed at high temperatures and high strain rates. The final product quality is strongly dependent on its microstructure. In this study, a finite element method (FEM) model was developed to better understand plastic deformation effects on microstructure during CPE and to analyze alternative thermo-mechanical processing routes. Specific models were used to simulate dynamic and meta-dynamic recrystallization (DRX and MDRX) for the processing of superaustenitic stainless steel (SASS). In addition, the CPE of SASS was investigated experimentally. The microstructure, mechanical properties, and chemical changes of the final product were assessed using optical microscopy, hardness testing, X-ray diffraction, and SEM-EDS. The results revealed higher temperatures and strain rates in the exterior area of the shell after piercing, and MDRX occurred in the whole thickness. However, an average grain size reduction of 13.9% occurred only in the shell middle and inner diameters. During elongation, the highest values of the strain rate and DRX were observed in the inner region, exhibiting a grain size reduction of 38%. Spread in terms of grain size and grain shape anisotropy was found to be less accentuated for tube samples as compared to the pierced shells. Full article

In recent years, the transportation industry has faced the challenge of cutting costs, meeting increasingly stringent environmental regulations, and significantly increasing transportation volumes. One approach to meeting these challenges is to develop new, improved transportation vehicles using new materials and innovative joining techniques. Multi-material structures are becoming an alternative to body parts. Self-pierce riveting technology plays a crucial role in this process, and hybrid structures depend exclusively on it. In this article, recent advances in self-pierce riveting technology are analyzed to meet today’s challenges and future multi-material applications. Full article

The hydro-piercing process is an emerging approach to the direct punching of holes on complex hollow components. During tube hydro-piercing, the deformation in the region adjacent to the pierced hole may range from having a substantially flat form to having a countersunk form. To improve the understanding of deformation behavior in square hole hydro-piercing, an experimental setup was designed and the effects of internal pressure and punch corner radius on the deformation sequence, as well as the collapse behavior, were investigated in this study. At the same time, a numerical simulation was conducted using the Abaqus/Explicit software 6.13. The results showed that the degrees of collapse at three characteristic points were different when the internal pressure was low and that the differences in the degrees of collapse could be reduced by increasing the internal pressure. It was demonstrated that the collapse was related to the internal pressure but had little dependence on the punch corner radius. Full article

In this study, experimental and numerical investigations were carried out to achieve a comprehensive understanding of the impact of surface conditions on self-piercing riveting (SPR) joint quality. Oil lubrication and sandpaper grinding were employed in experimental tests to change surface conditions at rivet/top sheet, top/bottom sheets and bottom sheet/die interfaces. A finite element (FE) model for the SPR process was also adopted to numerically assess the impact of surface conditions. Variations in surface conditions were modelled by changing friction coefficients at contact interfaces. The results revealed that the friction coefficient between the rivet and top sheet (μ₁) imposed significant influences on the interlock (I₁) by affecting the deformation of the rivet shank and top sheet. The friction coefficient between the rivet and bottom sheet (μ₂) showed a lower influence on the joint quality because of a smaller contact area and shorter interaction time. The friction coefficient between the top and bottom sheets (μ₃) led to opposite changing trends of remaining bottom sheet thickness at the joint centre (t_c) and under the rivet tip (t_tip). The friction coefficient between the bottom sheet and die (μ₄) demonstrated crucial influences on the remaining bottom sheet at the joint centre. The riveting force was significantly influenced throughout the whole riveting process by the μ₁, but only affected at the end of the joining process by the other three friction coefficients. Full article

The free transverse vibration of a surface-piercing, vertical cylinder partially submerged in water was studied. The cylinder had an arbitrary non-circular, but symmetric, cross-section in the vibration direction. The water was assumed to be an incompressible and inviscid fluid. The effect of the surface waves of water was neglected in the analysis. The exact solution of velocity potential of water was derived by the method of separation of variables. The unknown coefficients in the solution of the velocity potential were expressed in the form of integral equations, including the dynamic deformation of the beam. Then, the governing differential equation of bending vibration of the cylinder under the hydrodynamic pressure was obtained. The Galerkin method was used to obtain the eigenvalue equation by expanding the wet modes of the cylinder into a series of dry modes. The elliptical cylinders partially submerged in water were taken as the numerical example. The accuracy of the proposed method was evaluated by the convergence studies. As a consequent result, the non-dimensional added virtual mass incremental (NAVMI) factor solutions were compared to the present Galerkin solutions, which can be used as a benchmark test for more sophisticated numerical simulations of computational fluid dynamics. Full article

This study reviewed some simplified methods of finite element analysis (FEA) for connections in cold-formed steel (CFS) structure, and summarized eight simplified methods divided into three categories. Shear performance tests were performed for six groups of self-piercing riveted (SPR) connection in CFS. A constitutive model of shear behavior for SPR connections was proposed, which was simplified from the load–displacement curve of shear performance test results. The models of SPR connection were established in ABAQUS by the eight simplified methods, and then the FEA results and the test results were compared. The applicable scope of each simplified model was explored, and a simplified method of FEA that was most suitable for the shear behavior of the CFS-SPR connection was proposed. Moreover, the shear performance test of the CFS shear wall with SPR was conducted by considering the rivet spacing, and failure modes and load–deformation curves were obtained. On this basis, numerical models of the CFS-SPR connection shear wall were established. By comparing the test results and the FEA results for the CFS-SPR connection shear wall, the feasibility of a simplified method of FEA applied to the CFS-SPR connection was verified. The main failure modes of the CFS-SPR connection were that the rivet tail pulled out from the bottom sheet and the rivet head pulled over from the top sheet. The SPR connection of the CFS frame could be simplified with a pin or a fastener element, and the SPR connection between the steel frame and the sheathing could be simulated by a Cartesian connector or a Spring2 element. The FEA results were highly similar to the test results for the CFS-SPR shear wall. Full article

Curculio glandium females associated with the pedunculate oak were investigated in order to fill the knowledge gap on acorn structure preferences and shell-hardening influence on ovipositional behavior and fecundity. Shell solidification progression of weekly harvested acorns was measured using penetration and force–deformation tests along with fruit mass within a time frame covering weevils’ reproduction period. Captured females were offered regular acorns (uncracked, soft enough to drill into) and older seeds (with natural cracks) for behavior recordings and preferences tests. Young acorns and fruits ripe enough to be too hard for females to drill (artificially pierced and untouched) were used for egg output assessment throughout the shell-hardening progression. Experiments revealed that naturally cracked acorns were chosen significantly more often, which resulted in reduced drilling-phase duration. Egg number did not differ significantly before and after the threshold of acorn hardening; however, having passed it, females significantly more frequently deposited eggs in artificially pierced seeds. Results indicate the opportunistic nature of female preferences. Oviposition in cracked or pierced acorns facilitates the process and lowers competition for relatively shortly available soft and healthy seeds, the first of which reach impenetrability in the third week of August. Full article

To explore the anti-penetration performance of the specially shaped ceramic/metal composite armor, such an armor is designed and fabricated using a semi-cylindrical projectile resistant ceramic and metal back plate, and its anti-penetration performance for the 12.7 mm armor-piercing incendiary (API) projectile (also known as the 0.50 caliber API projectile) is investigated experimentally and numerically. The results show that due to the significant attitude deflection during projectile penetration, the penetration into the designed ceramic composite armor is quite different from that into the conventional homogeneous ceramic/metal composite armor, which can be roughly divided into the following four stages: asymmetric erosion of the projectile, ceramic cone squeezing movement, back plate failure and projectile exit. The failure mode of the back plate is mainly dishing deformation and petaling failure. When obvious attitude deflection occurs to the projectile, the breaches in the back plate are elliptical in varying degrees, and the height and size of petals are apparently different. The area of the composite armor is divided into different zones according to its anti-penetration performance. The influence of the ratio of semi-cylindrical ceramic diameter to projectile core diameter $\xi$ on the anti-penetration performance is studied under constant areal density. The results show that the deflection effect of the composite armor is small when the ratio $\xi$ is less than 2, and the anti-penetration performance is the strongest when $\xi$ is close to 2. With the increase in the initial velocity of the projectile, the deflection effect of the composite armor on the projectile gradually weakened, and the erosion effect gradually increased. Full article

During the single-point incremental forming (SPIF) process, a sheet is formed by a locally acting stress field on the surface consisting of a normal and shear component that is strongly affected by friction of the dragging forming tool. SPIF is usually performed under well-lubricated conditions in order to reduce friction. Instead of lubricating the contact surface of the sheet metal, we propose an innovative, environmentally friendly method to reduce the coefficient of friction by ultrasonic excitation of the metal sheet. By evaluating the tool-workpiece interaction process as non-linear due to large deformations in the metal sheet, the finite element method (FEM) allows for a virtual evaluation of the deformation and piercing parameters of the SPIF process in order to determine destructive loads. Full article

Self-pierce riveting of three thin sheets of 980 MPa steel and 5052 aluminum alloy was performed to investigate the effect of sheet configuration on the deforming behaviors of the sheets and the rivet and joint strength. When the lower sheet was aluminum alloy, the joining range was relatively wide, i.e., the interlock hooking the rivet leg tended to be large. In the sheet configuration in which the upper and lower sheets were A5052 and the middle sheet was 980 MPa steel, the rivet leg spread out moderately and the joint without defects was obtained. In the lower 980 MPa steel sheet, fracture tended to occur due to the low ductility of the lower sheet, and the joining range was narrow with the small interlock although the three sheets were joined by an appropriate die shape. In joint strength of joined three sheets, fracture occurred in the lower-strength aluminum alloy sheet if interlocks of about 300 μm and 150 μm could be formed in the lower aluminum alloy sheet and 980 MPa steel sheet, respectively. Full article

During the self-piercing riveting (SPR) process, residual stress develops due to the high plastic deformation of the sheet materials. In this study, the effect of the residual stress on the fatigue lifetime of SPR joints with dissimilar magnesium AZ31 alloy and aluminum Al5052 alloy sheets was evaluated. The residual stress distribution was derived through a simulation of the SPR process by the FEA (finite element analysis). The measured values by the X-ray diffraction technique confirmed that the validity of the simulation has a maximum error of 17.2% with the experimental results. The fatigue strength of the SPR joint was evaluated at various loading angles using tensile-shear and cross-shaped specimens. It was found that the compressive residual stresses of the joint reduce the stress amplitude by 13% at 10⁶ cycles lifetime, resulting in extension of its lifetime to approximately 3.4 million cycles from 10⁶ cycles lifetime. Finally, it was confirmed that the fatigue life of SPR joints was appropriately predicted within a factor of three using the relationship between the fatigue life and the equivalent stress intensity factor. The fatigue resistance of the magnesium AZ31 alloy on the upper sheet was found to govern fatigue lifetimes of SPR joints of dissimilar magnesium AZ31 alloy sheets. Full article

Microplastics are practically ubiquitous and pose a serious survival challenge for many species. Most of the exposure experiments for determining the toxicological effects of microplastics were performed with a microplastic varying little in shape and size (often purchased microplastic beads), but few studies deal with non-homogeneous samples. We analyzed the effect on Xenopuslaevis larva on the early development of polyester fibers, PEFs, taken from a dryer machine in which 100% polyester fabrics were dried after washing. Three concentrations were tested. The results showed that the gastrointestinal tract, GIT, was the most affected system by PEFs which modified the normal shape of the intestine with an EC₅₀ 96 h value of 6.3 µg mL⁻¹. Fibers were observed to press against the digestive epithelium, deforming the normal architecture of the gut, sometimes pushing deep into the epithelium until piercing it. Physical GIT occlusion was observed in a concentration-dependent manner. However, no other damages were registered. No mortality was observed, but PEF-exposed larvae showed a significant reduction in their mobility. The results of the present paper suggest that environmental samples with their heterogeneity may have adverse effects on X. laevis development. Full article