Maximum Tensile Load Research Articles

Effect of a cooling method on the structural and mechanical properties of friction stir spot welding with a 2524 aluminum alloy

Friction stir spot welding (FSSW) is a clean, environmentally-friendly and cost-effective welding technology. To weld joints with improved mechanical properties, an FSSW experiment with a 2 mm-thick 2524 aluminum alloy sheet was performed to explore the influence of ambient cooling (AC), forced air cooling (FAC), waterflow cooling (WC), and an increasing rotational speed under WC, and to evaluate the welding method with regard to the resulting structural and tensile properties of the joint. The results showed that cooling-assisted welding reduced the width of the heat-affected zone (HAZ) and marginally increased the microhardness of the welding nugget zone (WNZ). The maximum tensile shear load (L) and effective width (W) values were 4673 N and 1958 μm at FAC, respectively, which were higher than the values of 4296 N and 1763 μm found with AC, respectively; in addition, the minimum values were 2946 N and 948 μm with WC, respectively. These results are not consistent with the idea that the joint strength can typically be improved with WC, because water absorbs a large amount of welding heat and reduces the plastic deformation capacity of the structure, thereby decreasing the W and L of the joint. Increasing the rotation speed of the welding tool can increase the heat input, which requires increasing the rotation speed along with WC. L and W reach their maximum values of 7652 N and 3320 μm, respectively, at 2500 r·min−1. As the rotation speed increases, L and W decrease. All joints underwent ductile fracturing, and the dispersion distribution of the second-phase particles at the bottom of the dimple exhibited good performance.

Performance of Geosynthetic Reinforced MSE Walls with Marginal Backfills at the Onset of Rainfall Infiltration

In the present study, performance of geosynthetic reinforced MSE walls backfilled with locally available marginal lateritic soil at the onset of rainfall infiltration was investigated. Two different types of geosynthetics reinforcements were used. One was a conventional type of geogrids usually used in MSE walls, and the other was composite geogrids. Seepage analysis, stability analysis and strength and deformation analysis were carried out on MSE walls with rainfall simulated for a duration of 3 days. In case of geogrid reinforced soil wall (GR-W), the suction within the backfill was lost completely at the end of 2.176 days of rainfall, whereas suction was maintained even at the end of 3 days of rainfall in walls reinforced with composite geogrids (CGR-W). From the stability analysis, it was observed that the factor of safety of GR-W decreased at the onset of rainfall infiltration with time and reached less than the desirable value of less than 1.5 in 2.125 days of rainfall. The factor of safety of CGR-W was maintained at 1.88 throughout the period of rainfall. The facing deformation in GR-W was found to increase, with a maximum of 3.2 times increase at the end of three days of rainfall. Similarly, there was an increase in maximum tensile load mobilized in the reinforcements in GR-W, whereas in the case of CGR-W, the influence of rainfall was negligible. From the present study, it can be concluded that the presence of composite geogrids improves the overall performance of MSE walls backfilled with marginal lateritic backfills.

The effect of process parameters on the morphology, mechanical strength and electrical resistance of CW laser-welded pure copper hairpins

Manufacturing of high-performance electric motors has become a key industrial goal over recent years due to increasing demand for electrification, in particular in the automotive field. The use of windings comprising pure copper conductors with a rectangular cross section allows the overall performance of electric motors to be increased. In the present work, the influence of processing parameters on weld quality for joining of copper hairpins with near-infrared laser irradiation performed with a specific welding path. After determining a feasible operating window, the effect of process parameters on fusion zone morphology, presence of pores and mechanical and electrical properties was investigated. The results showed that high power and high welding speed lead to joints characterized by less than 1 % pores. A maximum tensile load of 490 N was achieved during tensile tests performed on specimens obtained with optimized welding parameters, with fracture taking place in the heat affected zone (HAZ). Micro-hardness profiles confirmed slight softening near the HAZ, corresponding to a reduction in mechanical strength in this region. Electrical tests highlighted a correlation between mechanical properties and the electrical resistance of the connection.

Model studies on polymer strip reinforced soil retaining walls

Polymer strip (PS) reinforced soil retaining walls (RSRW) are in common use due to the associated construction speed, ease of use, aesthetic appeal and low cost. It is quite significant to estimate the deformation behavior of this types of walls before construction. In this study, firstly, a full-scale field model of PS-RSRW was constructed and instrumented. According to the experimental result, the maximum measured displacements occurred at 30% of the height down from the top of the wall. The maximum tensile loads in the reinforcements were measured at a distance of 40% of the wall height from the face of the wall. Then, a two-dimensional (2D) finite element method (FEM) model was established and calibrated with experimental data from the field model. The predicted displacements of the wall facing showed reasonable agreement with the measured deformations. The reinforcement loads calculated from the validated FEM model were also compared with theoretical methods. Finally, RSRW having different heights were numerically modeled with various combinations of materials utilized for filling and reinforcement. The effects of parameters such as wall height (H), reinforcement length (L) and reinforcement interval (Sv) on the horizontal wall displacement and on the reinforcement loads are investigated through parametric analyses.

Diffusion bonding of 304 austenitic stainless-steel using pressure pulses

Abstract The influence of bonding temperature during impulse pressure assisted diffusion bonding on characteristics of AISI 304 austenitic stainless steel has been reported in this paper. Austenitic stainless steel sheets were joined by impulse pressure assisted diffusion bonding in a temperature range of 850–950 °C. The bond interface was analyzed by tensile shear testing, optical microscope, field emission scanning electron microscope. The soundness of the diffusion bond was evaluated by calculating the interface bonding ratio (ratio of void free interface length to the total interface length). The effect of diffusion bonding temperature on tensile properties and interface bonding ratio was investigated. The maximum tensile shear load carrying capacity of the diffusion bond obtained was 34.42 kN at 950 °C. The structural analysis revealed good joint quality of the diffusion bonds and 91.25% bonding interface ratio at 950 °C bonding temperature.

Lateral bearing capacity analysis of pile foundation using a spring modelling system

Pile foundations are often required to resist lateral loads and moments in addition to their primary use as axially loaded members. The interaction between material strength of axial, moment and shear against load capacity and soil interaction is the most important factors in the pile analysis. This study aims to obtain the lateral bearing capacity of pile foundation using a spring modelling system which will be calculated manually for the Kv spring constant in the vertical direction and the kh coefficient in the horizontal direction using the Nakazawa method and SAP 2000 v14.2.5 program. The result shows that the maximum shear load and the maximum axial tensile load received by the pile is still within the allowable shear load and allowable axial tensile load capacity resulting from the manual calculation. However, the maximum axial compression load and maximum moment is exceeded its each allowable capacity. Hence, it is necessary to re-modelling by adding the depth or number of piles.

Effect of tool pin geometry on microstructure and mechanical properties of friction stir spot welds of 7075-T651 aluminium alloy

7075-T651 aluminium alloy sheets were overlapped and friction stir spot welded using two welding tools having different pin geometries (one with a conical pin and other with a triangular pin) and 800, 1200 and 1600 revolution per minute (rpm) tool rotation speeds at a constant tool plunge and removal speed of 7.3 mm/min, tool plunge depth of 3.8 mm and tool dwell time of 5 s. Microstructure, Vickers microhardness, tensile shear strength, fracture surface after tensile shear test and impact energy of the produced friction stir spot welds were examined. As a result, the welds made via triangular pin tool had considerably higher tensile shear loads than the welds made via conical pin tool since the weld bond widths (stir zones) of the welds made via triangular pin tool were larger. The strongest welds made at 1200 rpm for conical pin tool and triangular pin tool. The tensile shear loads of the welds increased significantly when tool rotation speed increased from 800 to 1200 rpm for both welding tools and then decreased slightly for triangular pin tool and dramatically for conical pin tool with further increasing tool rotation speed from 1200 to 1600 rpm. Maximum tensile shear load of 7.776 kN and impact energy of 16 J obtained in the weld made at 1200 rpm using triangular pin tool. The welds made at 800 rpm had lowest impact energy. The lowest hardness values found in the heat affected zones of the welds. Circumferential fracture mode for conical pin tool welds and nugget pull-out fracture mode for triangular pin tool welds observed after tensile tests.

Redesigning a flexural joint for metal-based additive manufacturing

Traditional rigid mechanisms exhibit problems such as assembly difficulties, friction and lubrification. Flexure-based compliant mechanisms, instead, are monolithic and gain their mobility thanks to proper design and material deflection. Designing and producing a compliant mechanism accurately and conveniently is crucial. Thanks to its capabilities, additive manufacturing (AM) approach can provide optimal design and production and open the way to new, unexploited performances.This study investigates the redesign of a traditional cantilevered pivot. The redesign considers the performance improvements by exploiting the advantages of the AM based on laser powder bed fusion (L-PBF).The maximum tensile and compressive loads of the redesigned joint were identified. The structure was optimised by considering the most critical geometrical parameters in terms of mechanical performance. The geometrical factors comply with the design rules for L-PBF process, to maximise the dimensional and surface accuracies. The new approach to the flexural joint design presented in this paper provided higher mobility if compared with the traditional approach. Therefore, this study makes a major contribution to research on the production of precision alignment mechanisms and scientific instruments.

Mortars produced with an environmentally sustainable rice HUSK silica: Rheological properties

This paper presents an experimental study on the rheological behavior of commercial mortars with a high percentage of Rice Husk Silica (RHS). RHS was used to replace 5%, 10%, 15%, 20% and 30% by mass of Portland cement. The use of the waste material from burning rice husk in the mixtures contributes to a cleaner and more sustainable environment. The rheological behavior of fresh mixtures was investigated along with the time (15, 60, 120 e 180 min) by flow table test, modified Vicat and squeeze flow tests. In this research, an extension version of squeeze flow test was proposed, in which the samples are submitted to load and unload test (tensile test). The flow table results obtained showed that the workability of the mortars decreases as the RHS content increases. About 4% of the workability loss is related to the granular structure of mortars, and 96% about the porous structure of the RHS. In the Modified Vicat test, lower cone penetrations were observed as the RHS content increased, indicating the increase in the viscosities of mortars. Through the squeeze flow test, it was observed an increase in the mortar stiffness with the increase in RHS content and the increase in time. The maximum tensile load obtained in the unload squeeze flow test was higher as the replacement of Portland cement by RHS increased. Therefore, the mortars with higher RHS content are possibly able to retain more water, which may increase the adhesion with the substrate in the hardened state. In sum, the study shows that it is possible to produce eco-friendly mortar with a high quantity of RHS by increasing the time for application.

A decision tree approach for energy efficient friction riveting of polymer/metal multi-material lightweight structures

Friction riveting has emerged out as a promising candidate for joining polymers to metals, since it is energy efficient, fast and eco-friendly without material wastage and pre and post processing and cleaning. For sustainable manufacturing of car ports, automobile panels and aircraft structures, there is a need for joining of polycarbonate to AA 6063 using friction riveting technique. Hence in the present work, Polycarbonate/AA 6063 combination is joined employing friction riveting with a new slotted end rivet. Microstructural examination reveals a visible deformation during the penetration of AA 6063 rivet that provides excellent anchoring. Decision tree is an exploration approach that is applied on friction riveting experimentation data and it has derived meaningful information out of testing data to reach the maximum possible tensile load carrying capacity by a friction riveted joint within the production constrains. The maximum tensile load of 5.75 kN can be achieved when rotational speed, friction time and depth of friction riveting are kept above at 2050 rpm, 37.5 sec and 9 mm respectively. It is helpful in industries during selection of different combination of process parameters to obtain the desirable joining strength. • Successful joining of dissimilar Polycarbonate to AA 6063. • Friction riveting with new slotted end rivet profile. • Decision tree approach, for judicial selection of processing conditions. • Micro-structural investigation on bonding mechanism at the interface.

Experimental verification of a novel anchorage method of CFRP grid in mortar

A novel anchorage method of CFRP grid in mortar named intersect-type anchorage method was proposed in this paper. In order to verify the application feasibility of this novel anchorage method in practical engineering, two phases of pull-out tests including single-direction pull-out tests and bidirectional pull-out tests were carried out. The number of grid points and anchorage conditions were selected as changing parameters. The maximum tensile loads, failure patterns, load–displacement curves of test specimens and load–strain curves of CFRP grids were obtained. The ultimate resistant actions, tensile bearing modes of grid points, tensile stress transfer process, coupling effect between the bond action of vertical grid and the resistant action of grid points and the failure mechanism were discussed. The research results showed that the intersect-type anchorage method is a favorable anchorage method for CFRP grid in mortar and the bond action of vertical grid play a dominant role for the anchorage action of CFRP grid in mortar rather than the resistant action of horizontal grid. In order to make full use of the tensile strength of CFRP grid, the number of grid points in intersecting part was not less than two.

Process Parameters Optimization of Refill Friction Stir Spot Welded Al/Cu Joint by Response Surface Method

Refill friction stir spot welding is a new branch of friction stir welding. In this study, the dissimilar Al/Cu joint was acquired by refill friction stir spot welding. A quadratic regression model was established by Box–Behnken design to explore the relationships between the key process parameters of rotational velocity, plunge depth and welding time and the joint tensile shear load. The results show that the rotational velocity is the most dominant factor for tensile shear load, while the welding time and plunge depth are the second and third effective process parameters. The contour map and response surface present that tensile shear load first increases and then decreases with the increase of the investigated process parameters. The maximum tensile shear load of 4.69 kN is acquired at the optimized rotational velocity of 2500 rpm, plunge depth of 1.7 mm and welding time of 6.2 s.

Study on the effects of fibre volume percentage on banana-reinforced epoxy composite by finite element method

Researchers and engineers have shifted their interest from synthetic fibres to natural fibres. These fibres are not only light weight and high-strength materials but are also more economical than the conventional synthetic fibres. Moreover, the natural fibres are eco-friendly and biodegradable. Banana fibre is a bi-product of banana fruit cultivation and hence abundant in nature. Banana fibre being one of the strongest natural fibres can be used for different applications when reinforced with some binding resin. Epoxy resin has excellent binding properties and is thus suitable matrix for composite formation. As it has been widely discussed in previous studies that fibre loading or fibre volume fraction affects mechanical strengths and properties of natural fibre-reinforced composite, this study is aimed finding the relation between the fibre volume percentage and the load-bearing capacity of banana fibre-reinforced epoxy composite material by data-driven decision method. In the finite element analysis conducted on the banana-epoxy composite, it has been seen that the composite bear maximum tensile load of up to 7956 N, flexural load of up to 411 N and has hardness of up to 167.28. On the basis of this study, it can be said that due to excellent load-bearing properties, banana-epoxy composite can be used for various medium to high-load industrial applications. The following paper also proposes an analytical relation based on the regression model superposition of the results of tensile, flexural and hardness test simulation conducted by finite element analysis software ANSYS 16.0 which was prepared on Minitab 19 software.

Retrospective multicenter cohort analysis of 621 cases of BellaGel silicone breast implants with study of physicochemical properties and surface topography

This study aimed to assess the effectiveness and safety of BellaGel implants after implantation in Asian women and inform surgeons of another option for use in breast augmentation and reconstruction. This study was conducted in eight hospitals from November 27, 2015 to April 30, 2018. All patients underwent augmentation mammoplasty or implant-based breast reconstruction with BellaGel implants. Complication rates were compared between groups, and the cumulative hazard function was compared using the Kaplan-Meier survival analysis. Implants were grouped by surface type, and the cumulative hazard functions of total complication cases were compared. The biomechanical properties of the BellaGel implant and other company representative implants were tested using a mechanical testing machine, and surface topography was analyzed using a 3D laser scanning confocal microscope. There was a significant difference in the incidence of complications between the reconstruction (17.1%) and augmentation (4.7%) groups, but no significant difference in the complication rates of each group. There was no difference in the reoperation or revision rates between the groups. The log rank test showed a statistically significant difference in cumulative hazard function between the groups. Among the three types of implants (smooth, textured, and microtextured), the microtextured type had the lowest complication rate. The BellaGel microtexture implant had the highest maximal tensile load and displacement value. The BellaGel and Silksurface implants had the highest stored energy, although there was no significant difference. BellaGel implants can serve as a criterion for the selection of safe and effective implants among currently available implants.

Experimental and numerical studies for buckling and collapse behaviors of a cracked thin steel panel subjected to sequential tensile and compressive loading

The buckling and collapse behaviors of a cracked thin steel panel subjected to sequential tensile and compressive loading were investigated. An experimental apparatus was developed. Three different test specimens were employed, i.e., an intact panel and cracked panels with different crack lengths. The load-displacement curve and crack opening displacement (COD) were measured during the loading. The experimental results were examined via finite element (FE) computation. The results revealed that the developed experimental apparatus is quite suitable for investigating the buckling and collapse behaviors. Furthermore, the maximum tensile load, ultimate strength and local deformation around the crack were well simulated by the FE computation. The presence of the crack and length of the crack were strongly affected to the buckling and collapse behaviors.

Clarifying effect of welding conditions on microstructure and mechanical properties of friction stir spot-welded DH590 automotive high-strength steel plates

Friction stir spot welding was successfully applied to the 1.2-mm-thick DH590 dual-phase steel plates by using a polycrystalline cubic boron nitride rotating tool. During welding, the rotation speed ranged from 600 to 1000 r/min and the penetration depth ranged from 0.1 to 0.3 mm. In the spot joints, the size of the stir zone increased with the increase in rotation speed as well as the penetration depth of the tool. Comparing with the banded ferrite and martensite structure of the base metal, a mixed microstructure of ferrite and tempered martensite, refined bainite structure and coarse martensite structure were found in the heat-affected zone, thermomechanically affected zone and stir zone of the joints, respectively. Two kinds of interfacial shapes were formed between the upper and lower steel plates, and the formation of the bonded interface was dominated mainly by the penetration depth of the rotating tool rather than the rotation speed. It was revealed that the joints with straight interfaces showed higher shear tensile loads comparing with those with hook-like interfaces. Shear tensile tests showed that the maximum shear tensile load reached about 15.56 kN when the rotation speed and penetration depth were set as 800 r/min and 0.3 mm, respectively. The specimen was fractured through plug failure mode with a total elongation of about 5.6 mm.

Metal–Electrolyte Solution Dual‐Mode Electrospinning Process for In Situ Fabrication of Electrospun Bilayer Membrane

AbstractElectrospun bilayer membranes comprising two layers, one aligned and the other random, have shown great potential in tissue engineering but previous fabrication processes inevitably relied on manual integration and produced limited types of membranes. Here, a metal–electrolyte solution dual‐mode electrospinning (M‐ELES) for fabrication of electrospun bilayer membrane based on a metal–electrolyte solution switchable collector is developed. The switchable collector enables random nanofiber deposition directly over the preexisting aligned nanofiber layer in an in situ manner and integration of the layers through an on‐demand switch from the metal to the electrolyte solution collector. The electrolyte solution can effectively discharge excessive positive charges of the deposited nanofibers and thus maintain the efficiency of random nanofiber deposition, which allows ≈2.5 times faster fabrication as compared to a conventional method. M‐ELES also possess each layer controllability through on‐demand switching, thereby achieving the electrospun bilayer membranes with diverse physical (e.g., aligned nanofiber density) and mechanical (e.g., maximum tensile load up to ≈3 N) properties. As a biomedical application, in vitro wound healing assay using NIH3T3 cells demonstrates that the electrospun bilayer membrane promotes wound coverage through topographical guidance of the aligned nanofiber layer while providing mechanical support by the random nanofiber layer.

Refill Friction Stir Spot Welding of Dissimilar AA6014 Al Alloy and Carbon-Fiber-Reinforced Polymer Composite

Both Al and carbon-fiber-reinforced polymer (CFRP) are being investigated as lightweight materials for automobile applications. To form effective hybrid materials from Al and CFRP, strong bonding between these two dissimilar materials is critical. Here, we analyzed the microstructure and tensile shear strength of joints between an Al alloy (AA 6014) and CFRP fabricated using refill friction stir spot welding (RFSSW). A maximum tensile shear load of 1.6 kN was measured for untreated AA 6014/CFRP specimens. Microscopy images of the Al–CFRP joints exhibited tight bonding along the joint interface without any noticeable defects. Moreover, Al–O–C, C–C, and C=O chemical bonds were detected on the tensile–shear fracture surfaces of both the Al alloy and CFRP sheets using X-ray photoelectron spectroscopy. Micro-mechanical interlocking and chemical bond formation were the key factors contributing to the tensile shear strength of the RFSSW joint. This study demonstrated that the RFSSW technique is a suitable bonding method for manufacturing metal–polymer hybrid structures.

Bonding mechanism of Al/steel interface formed by laser-TIG welding assisted riveting technology

Laser-tungsten inert gas (TIG) welding assisted riveting technology was used to join Q460 high strength steel and AA6061-T651 aluminum alloy. The effect of laser power on the mechanical properties of Al/steel joints was studied. In this study, the welding-riveting hybrid structure was used to weaken the adverse effect of thermal-physical properties differences between aluminum alloy and steel, and the distribution of Fe-Al intermetallic compounds was optimized by adjusting laser power to obtain the joint with the best mechanical properties. Due to the different laser power, there were two fracture modes of Al/steel joints, namely, button-type fracture and pull-out fracture. The failure processes of these two fracture modes were discussed. Under the appropriate welding parameters, the maximum tensile shear load of the joint could reach to 6.3 kN, which was 92.2 % of the Q460 base metal. The Al/steel interface of the joint was mainly composed of Al, Fe4Al13, Fe2Al5, and α-Fe phases. When the favorable orientation relationships of the Fe4Al13/Al system, Fe4Al13/Fe2Al5 system, and Fe2Al5/α-Fe system in the Al/steel interface were selected, there was a semi-coherent-coherent-coherent matching relationship between these phases. The Al/steel interface growth model of the Al/steel joint was discussed in this study.

Effects of rotation speed and dwell time on the mechanical properties and microstructure of dissimilar aluminum‐titanium alloys by friction stir spot welding (FSSW)

AbstractIn this study, the effects of rotation speed and dwell time on the mechanical properties and microstructure of friction stir spot welded joints of dissimilar aluminum and titanium alloys were investigated. Aluminum AA6061 and titanium Ti‐6Al‐4 V alloys were selected as the work piece. The joint quality, mechanical behavior, and microstructural evolution in the welded regions were considerably affected by the welding parameters. The results of scanning electron microscopy showed the formation of Ti3Al intermetallic compounds near the thermomechanical affected zone, which significantly affected the properties of the welding joint. Maximum tensile shear load was produced at 1000 min−1 and 10 s dwell time. Moreover, the welding joint microhardness was improved with increasing the rotation speed.