Tensile Failure Load Research Articles

Statistical and Metallurgical Analysis of Dissimilar Friction Stir Spot Welded Aluminum/Copper Metals

In this paper, friction stir spot welding of 2-mm-thick AA 1060 Al to T2 Cu is conducted. The effects of dwell time, tool rotational speed and shoulder plunge depth on tensile shear failure load (TSFL) are investigated. A quadratic regression model is proposed to fit the relationship between TSFL of the joint and the welding process parameters. The analysis-of-variance results show that the rotational speed is the most significant factor affecting the TSFL. Joint fabricated at the low rotational speed is weak-bonded by discontinuous intermetallic layers due to the insufficient heat input. Increasing the rotational speed can improve the TSFL by promoting intermetallics formation at the interface, while an excessive increase in rotational speed results in formation of microcrack at the interface, which seriously compromises the tensile property of the joint. Shoulder plunge depth, tool rotational speed and dwell time of 0.1 mm, 2371 r/min and 4.96 s, respectively, were identified as the optimal combination of welding process parameters. Results of microstructure characterization show that the joint produced at the optimized process parameters is well metallurgically bonded by a 1.9-μm-thick laminated intermetallics layer which comprises CuAl and CuAl2 sublayers. Result of fracture path reveals that the fracture firstly extends along the interfacial CuAl2 layer by a brittle mode and then propagates through the aluminum matrix in the stir zone by a ductile mode.

Experimental analysis of tensile and compressive failure load in single-lap adhesive joint of green composites

In this study, the tensile and compressive performance of adhesively bonded single-lap joint of green composites (bamboo fiber/Polylactic acid (PLA)) has been experimentally investigated. The green composites have been fabricated by film stacking method in compression molding. The important factors affecting the performance of the adhesively bonded joint such as overlapping length of the specimen (20, 40, and 60 mm) and width of the specimen (20, 26, and 32 mm) have been studied for epoxy, polyurethane, and parent polymer (PLA) used as bonding materials for joining of developed green composites. From the experimental analysis, it has been found that the higher levels of width and overlapping length of the joint specimen offer better tensile and compressive strength of the joint specimen. The failure loads of the joint specimens have been found to be more for epoxy as compared to PLA and polyurethane used for the purpose of joining. The relative significance of the chosen input parameters has also been found by performing analysis of variance (ANOVA). The most significant parameter has been found to be the width of the specimen for tensile failure load and type of bonding material for compressive failure load. The failure mode analysis has revealed that adhesive and cohesive failures are the major mode of failure of the adhesively bonded green composites under tensile and compressive loadings.

Flax roving twisting preparation for weaving and effect of the weft layers number on the physical and mechanical properties of 3D interlock flax fabric

The feasibility to manufacture a 3D warp interlock preform from 1000 Tex flax roving is investigated by means of a prototype machine developed to GEMTEX laboratory. The provided flax roving has low tensile failure load because of lack of twist so it isn’t suitable for weaving. The first step was dedicated to improve the tensile properties of the roving through twisting process and identifies the optimal twist level. Experimental campaign is conducted by applying different twist level and evaluates the roving tensile properties. The ultimate tensile load increases as roving twist level increases until a threshold at which the tensile load declines as twist level increases. While the failure strain increases continuously as twist level increases. Five fabrics are produced with the same flax roving, 3D weave architecture and warp number and weft column number per unit length. Only the number of weft layers varies. The physical and tensile properties of these five flax fabrics are characterized experimentally. A considerable effect on the thickness and areal density of the fabric is reported. The difference in the waviness length between the two types of the warp roving (reinforcing and binding) has a significant impact on the tensile behavior of the fabrics in warp direction through the appearance of two phases on the force-strain curve. Otherwise, the variation of the number of layers does not induce a remarkable impact of the fabric structure on the tensile performance of the constituting roving.

Process parameter optimization and performance comparison of AISI 430 and AISI 1018 in resistance spot welding process

Resistance spot welding (RSW) process plays an important role in the sheet metal fabrication process, in which metal joining is obtained by heat developed through electric resistance against the current flow in the metals contact area. In this work, the impact of weld time, squeeze time, weld current and hold time on weld strength of 1.2 mm thickness ferritic stainless steel (AISI 430) and low carbon mild steel (AISI 1018) sheets by using RSW process were investigated and compared. The Design of experiment (DoE) was used to formulate the number of experiments with variations in input conditions. Welding of similar metals of AISI 430 and AISI 1018 was done according to the number of experiments obtained using DoE. The welded samples were subjected to tensile shear failure load and micro-hardness testing. The output responses were analyzed through Response surface methodology (RSM) to find the optimum control parameters to achieve higher weld strength.

Experimental investigations on interfacial characterization and mechanical performance of ultrasonic spot welded Al/brass joints

The dissimilar joining of aluminum (AA 1100) to brass (UNS C27000) in the electric power industry is highly required to transmit the electricity efficiently. However, it's hard to join these materials using fusion welding process because of the broad differences in their physical, mechanical and chemical properties, and the evaporation of zinc constituent during the welding process. Thus, it is directed the researchers to find a new technique to tackle this problem. It seems that ultrasonic metal welding (USMW) is one such promising method that is developed nowadays. In this study, lap joints of AA 1100 aluminum alloy and UNS C27000 copper alloy have been produced using USMW and the effects of process parameters on the mechanical strength and interface microstructure have also investigated. The tensile shear failure load firstly increases with the rise of weld time up to 0.55 s of weld time followed by a rapid decrement in the value due to excessive plastic deformation in the weld zone. It is confirmed from the energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD) results that USWed aluminum to brass produces intermetallic compounds (IMC), and its thickness is getting wider with the increase in weld time. A composite eutectic structure of Al and Al2Cu is the first compound formed in the middle of the weld zone.

Dissimilar joining of Al/SS sheets with interlayers by ultrasonic spot Welding: Microstructure and mechanical properties

Ultrasonic spot welding (USW) has received a great deal of attention by the automobile manufacturer to build lightweight structural components. However, the versatility of using this process is still limited due to the substantial instabilities in weld quality. These fluctuations are mainly due to the lack of scientific understanding of this process and poor control of intermetallic compound formation. Therefore, this study is focused on the improving of the joint strength and its quality by ultrasonic welding of Al3003 and SS304 sheets with molybdenum (Mo) and zinc (Zn) powder as interlayers. The results revealed that the optimum thickness for Mo and Zn interlayers are found to be 0.11 mm and 0.15 mm, respectively. In comparison, Al3003/SS304 joints with Zn interlayer exhibits the maximum tensile shear failure load about 626.44 N at 1.5 s of weld time, which is better than those of the joints produced with Mo interlayer. The microstructural morphologies at the weld interface reveal the different characteristics like mechanical interlocking at the outside zone of the sonotrode knurl indentation, wavy type region under the sonotrode knurl, and swirling like diffusion zone inside the sonotrode knurl.

Analysis of tensile failure load of single-lap green composite specimen welded by high-frequency ultrasonic vibration

Ultrasonic welding is a solid-state fusion bonding method which is mostly use to bond thermoplastic parts by means of high-frequency ultrasonic vibration by producing heat at the interface of the joint. It is an eco-friendly, cost-effective, and time-saving method of making joint which requires no additional parts or materials unlike mechanical fastener and bonding materials used in mechanical and adhesive joining. In the present work, high-frequency (20 kHz) ultrasonic vibration was applied to join green composite specimens. The green composite specimens were fabricated using bamboo fiber as reinforcement and poly(lactic) acid (PLA) as a binding polymer. Both these constituents of the composite are biodegradable in nature. The green composites were fabricated by stacking the fiber mats and polymer layer alternatively using hot compression. The overlapping length and the width of the lap-joint specimens were kept constant to 50 and 32 mm, respectively. The strength of the welded lap-joint specimen was evaluated by conducting tensile tests. The influence of the welding parameters such as holding pressure (1, 2, 3, 4, and 5 bar), holding time (1000, 3000, 5000, 7000, and 9000 ms), and welding time (1000, 3000, 5000, 7000, and 9000 ms) on the tensile failure load of the welded specimen were studied by varying one factor at a time. The load-displacement behavior and failure mode of the welded specimen under different experimental conditions were also studied to investigate the ultrasonic welding behavior of the developed green composites.

Dynamic fracture investigations of ultra-high performance concrete by spalling tests

Ultra-High Performance Concrete (UHPC) is an innovative cement based material with superior strength for engineering structures. The mechanical properties of the cementitious composite depend on its exact composition and need to be determined experimentally. Whereas several standard tests for the static loading regime exist, dynamic data such as tensile strength and failure load are difficult to measure.This contribution presents an experimental method to identify the material properties under impact loading. By means of a modified Hopkinson pressure bar, cylindrical UHPC specimens of different compositions without fiber are examined in strain rates of approximately 30s-1. Assuming uniaxial wave propagation, the resulting stress states are analyzed and the specimens’ dynamic elastic modulus, tensile strength and specific fracture energy are determined. Numerical fracture simulations in the sense of an inverse analysis prove the experimental approach valid. The agreement between both, experimental observations and numerical results, show that the obtained parameter are reliable and suitable for predictive simulations.

Characterizing fracture response of cracked transversely graded materials

Property gradation along a crack front makes conventional fracture mechanics analyses challenging. This issue is addressed in the present study through a combination of full-field measurements and modeling. We develop a novel experimental setup that consists of a synchronous dual Digital Image Correlation (DIC) system, facilitating in situ measurement of displacement and strain fields on both sides of a transversely precracked multi-layered structure subjected to uniaxial tensile load. By measuring the evolution of stress intensity factors developed on the opposite sides of the sample, we explore the mechanisms of crack initiation and propagation in the examined graded sample. Our experimental measurements are supplemented by a finite element analysis that elucidates the deformation and fracture response of the internal layers for which surface measurement is not possible. Finally, based on experimental and numerical observations, we develop a simple model that allows for prediction of critical far-field loads at which transversely graded structures fail. The capability of our proposed model in predicting tensile failure loads is demonstrated through a brief study of the influence of gradient function on the load bearing and fracture resistance in various graded structures.

Pull-out tests on handcrafted headed studs

The aim of this paper is to contribute towards better understanding of the behaviour of site-welded headed studs embedded in normal-weight concrete. The axial failure loads of these studs estimated by design codes and other calculation methods are conservative and inaccurate for concrete cone detachment. The concrete tensile strength and embedded length of the steel shank are believed to be the most influential factors on the final pull-out resistance of headed studs. In an experimental programme, ten headed studs with varying head thickness were pulled out from concrete blocks of strength 25 MPa or 35 MPa. The failure loads, failure modes and steel yield loads were used as parameters to verify the efficiency of the studs and to evaluate which design methodology gave estimated final resistances closest to the experimental values. Two collapse types were observed: one was located along the shank when the applied load exceeded the steel tensile failure load while the other was in the concrete and occurred when the applied load exceeded the concrete ultimate tensile strength, creating a conical failure surface. The two head thicknesses were found to be satisfactory and the theoretical loads underestimated the concrete tensile strength.

Characterization of PAN based Carbon Tow for Structural Composites

Fibers are load carrying component in a fiber reinforced polymer composite materials. Tensile properties of composite are affected by the properties of the fiber. Polyacrylonitrile (PAN) based carbon fibers are widely used as a reinforcement in composite materials because of its high tensile strength and tensile modulus. Stringent characterisation of PAN based carbon tow is paramount for the fabrication of high performance advanced composite products. This paper presents characterization of PAN based carbon tow for structural composites. The physical and chemical parameters of carbon tow namely tex, density, diameter of single fiber, sizing content and carbon content were characterized for carbon fiber. Tensile properties of PAN based carbon tow can be determined by mono filament test and liquid resin impregnated tow tensile test. In the present study, tensile strength and modulus of PAN based fiber was evaluated by mono filament test. It was observed that tensile failure load was varying from filament to filament for same lot of fiber in mono filament test. High scattering in tensile strength values of filaments was observed due to statically distributed surface flaws on the filaments. Coefficient of variance for tensile strength of filament by mono filament tensile test was varied from 12-25 % from one lot to other lot of carbon tow. Liquid resin impregnated tow tensile test was conducted with specified resin system with low temperature cure cycle, to get more consistent and more accurate values of fiber tensile strength, modulus and % strain. Carbon tow was characterized by laminate level mechanical properties namely NOL ring hoop tensile strength and ILSS with high temperature curing epoxy resin system, which is used for fabrication of actual structural composite product.

Effect of nanostructured reinforcement of adhesive on thermal cycling performance of a single-lap joint with composite adherends

Nanostructure of adhesive increased the failure load of bonded joints. Adhesively bonded joints are often exposed to alternating warm and cold temperatures in many applications. Hence investigation of their thermal cycle performance is very important. In the present study, the tensile strength of adhesively bonded single lap composite joints (SLCJs) was experimentally investigated under ambient temperature and thermal cycling conditions. In the study, carbon fiber fabric reinforced (CFFR) composites (0/90°) with Plain Weave (PW) were used as the adherend; DP460 tough and DP125 flexible adhesive types were used as the adhesive and 1 wt% Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the nanostructures. Six different thermal cycles were applied to SLCJs and their tensile failure loads and failure surfaces were investigated. As a result, when the joints obtained through nanostructure non-reinforced adhesives are exposed to thermal cycle, a significant decrease appears in the failure load of the joint. Yet, adding nanostructure to the adhesive enhances the thermal cycle performance of the joint. This enhancement in the thermal cycle resistance changes depending on the structural features of the adhesive, the type of nanostructure and thermal cycle condition.

Experimental analysis of tensile and compressive failure load in single-lap bolted joint of green composites

In this study, bamboo/PLA green composites have been fabricated using a compression moulding to investigate the single-lap bolted joining behaviour of the developed composites. The factors affecting the strength of the joint such as hole quality and geometrical parameters have been experimentally investigated. The cutting parameters (feed and speed) and drill geometries have been optimised using Taguchi’s method to obtain the lower drilling induced forces. The optimised parameters have been used for making hole in composite specimens to facilitate the bolted joint. The influence of the input parameters on the induced forces has also been analysed through analysis of variance (ANOVA). The behaviour of bolted joint specimens has been investigated by evaluating the tensile and compressive failure loads. The influence of width to diameter ratio (w/d) (2.5, 3.25, and 4), edge to diameter ratio (e/d) (1.5, 2.25, and 3.125), and bolt fastening torque (10, 15, and 20 N-m) on the failure load has been statistically analysed by performing ANOVA. Both tensile and compressive failure load was found to be increased at a higher value of w/d, e/d, and bolt fastening torque. From statistical analysis, w/d was found to be the most significant parameter followed by bolt fastening torque and e/d.

Ultrasonic spot welding of 5182 aluminum alloy: Evolution of microstructure and mechanical properties

The present study is focused on the evaluation of microstructures, tensile lap shear strength and fatigue resistance of ultrasonic spot welded joints of lightweight AA 5182 aluminum alloy. The temperature quickly increased during ultrasonic spot welding (USW), with the peak temperature increasing with increasing welding energy. A “necklace”-like ultrafine structure occurred at the weld interface due to the presence of dynamic recrystallization. The tensile lap shear strength increased with decreasing number of impedance setting. When the impedance was set below 5, the tensile lap shear failure load of nearly 6 kN was attained, surpassing the requirement for the average peak load of AWS D17.2 standards. The tensile lap shear strength, failure energy, and critical stress intensity factor first increased, reached their maximum and then decreased with increasing welding energy. The maximum tensile lap shear strength of ∼150 MPa was achieved at a welding energy of 4000 J and an impedance setting of 2. The load-controlled fatigue behavior displayed a bi-linear characteristic due to the change in the failure mode from interfacial failure at the higher cyclic loads to transverse-through thickness (TTT) crack growth mechanism at the lower cyclic loads.

Comparison of RSM and ANN model in the prediction of the tensile shear failure load of spot welded AISI 304 /316 L dissimilar sheets

Resistance spot welding process is broadly used for joining sheet metals in automobile, aerospace, chemical and biomedical industries. In this research work, mechanical property, macro and microstructure of resistance spot welded dissimilar steel sheets of grades AISI 304 and high corrosion resistance AISI 316 L are studied. Experiments are conducted by changing the process parameters such as welding current, electrode pressure, welding time and squeeze time using central composite design of response surface methodology. The empirical model predicted by the response surface methodology (RSM) is compared with back propagation algorithm model of artificial neural network (ANN). By numerical optimisation tool of design expert software, the optimal process parameters setting for attaining the maximum tensile shear failure load is identified. The results of the properly trained ANN model (R2 value of 99.04%) proved that it is more accurate than RSM model (R2 value of 96.33%).

In vitro investigation of the impact of remaining tooth structure on the tensile failure loads of overdenture copings.

BackgroundThe purpose of this in vitro study was to evaluate the impact of the remaining tooth structure on the retention of overdenture cast metal copings.Material and MethodsA freshly extracted intact mandibular human canine (length 25 mm) was selected and endodontically treated. An incisal reduction of 4 mm with no ferrule preparation was performed and a post space of 12 mm was created. By using polyvinyl siloxane duplication material and autopolymerizing polymethylmethacrylate resin, ten resin teeth analogs (control group) were obtained. A second set of ten resin teeth analogs (group 1) was created by preparing on the original natural tooth a 360o ferrule design of 1 mm in height and by using the same procedural technique. The canine was further reduced by an additional 1 mm, resulting in a ferrule of 2 mm in height, measured from the initial incisal reduction, thus a third set of ten resin teeth analogs (group 2) was created. For every tooth analog in all groups a dome-shaped metal coping was cast and luted with a glass ionomer cement. All specimens were subjected to tensile load testing until decementation occurred.ResultsThe specimens in the control group exhibited a mean failure load of 87.21 ± 18.26 N, while the 1 mm ferrule group recorded a higher mean failure load of 125.43 ± 8.79 N and the 2 mm ferrule group recorded the highest mean failure load of 146.12 ± 23.38 N. One-way ANOVA revealed significant differences (F= 28.04, p<0.001) in the tensile failure loads between all of the groups being tested.ConclusionsThe metal copings with a 2 mm ferrule design exhibited the highest retention values, followed by the 1 mm ferrule and the no ferrule design, with the differences among them being statistically significant. Key words:Ferrule effect, In vitro study, Metal copings, Overdenture, Tensile stress.

Comparison of RSM and ANN model in the prediction of the tensile shear failure load of spot welded AISI 304/316 L dissimilar sheets

Comparison of RSM and ANN model in the prediction of the tensile shear failure load of spot welded AISI 304/316 L dissimilar sheets

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

BackgroundDouble hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size. MethodsSemitendinosus, gracilis, and quadriceps tendons were harvested from 10 matched pairs of human cadaver lower extremities. Within each pair, a routine hamstring ACL graft (control) consisting of the semitendinosus and gracilis tendons, and an quadriceps augmented hamstrings graft of equal size comprised of the semitendinosus and quadriceps tendons, were prepared. A freeze-clamp mount was used to biomechanically test each graft construct. Tensile failure load, displacement, energy absorbed, and stiffness were determined and statistically compared within each pair and mode of graft failure was established. ResultsNo statistically significant differences were found between the quadriceps augmented hamstrings graft versus standard control grafts. Average values for peak failure load and graft displacement at the point of first failure were nearly identical. All ACL graft constructs failed at the mid-substance. ConclusionsThis study demonstrates no statistical difference in the biomechanical properties of an isolated hamstring ACL autograft versus a quadriceps augmented ACL autograft of equal size at time zero. Clinical relevanceThis is a potentially new and reliable method for quadriceps tendon autograft augmentation of hamstring autograft for ACL reconstruction.

Ultrasonic spot welding of dissimilar 2024Al alloy and SiCp/2009Al composite

Dissimilar welding of 2024Al alloy to SiC/2009Al composite was conducted via solid-state ultrasonic spot welding technique. Defect-free sound spot welds were successfully achieved. SiCp particles were observed to migrate from the composite side to 2024Al side along with the interfacial interlocking during the intense high-frequency rubbing, which increased with increasing welding energy. The microhardness across the ultrasonic spot welded similar and dissimilar joints remained nearly constant. The tensile lap shear failure load increased with increasing welding energy, and satisfied the requirements of AWS standard D17.2 for spot welding. In addition to room temperature tensile lap shear tests, all the similar and dissimilar joints were subjected to tensile tests at varying temperatures and their respective results were discussed.

Stochastic critical stress intensity factor response of single edge notched laminated composite plate using displacement correlation method

The second-order statistics of critical stress intensity factor (SIF) of single edge notched fiber reinforced composite plates with random system properties and subjected to uniaxial tensile loadings is investigated. This paper is an extension of reference (Lal and Kapania, 2013) by the present authors by considering more number of input random system parameters for higher accuracy. A C0 finite element method based on a higher-order shear deformation plate theory using displacement correlation method via isoparametric quarter point element is proposed for basic formulation. A stochastic finite element method using first-order perturbation technique and Monte Carlo simulation (MCS) is employed to examine the mean, coefficient of variance, and probability density faction of critical first mode SIF. The effect of different fiber orientations, crack length, plate thickness, a number of layers, and the lamination schemes with random system properties on the statistics of SIF of single edge crack laminated composite plate is evaluated. The tensile failure load is predicted using Hashin’s failure criteria. The present approach is validated with results available in literature and by employing independent MCS.