Average Failure Load Research Articles

Progressive failure analysis of woven and non‐woven CFRP composite/steel bolted joints

AbstractDue to recent advancements in textile fabrication, woven fabric reinforcements are used in composite structures as an alternative to traditional unidirectional fiber reinforcing layups. In this paper, experimental work was performed to study the behavior of multiple bolt‐lapped joints under uniaxial tension. Different bolt numbers, composite layups, and fabric configurations were studied. Single‐ and double‐lap configurations were used to investigate the effect of secondary stresses. It was found that the P‐δ curves of lapped joints exhibit four primary stages: a linear elastic stage, followed by a nonlinear hardening stage, then linear hardening leading up to the peak, and finally a softening stage. For double‐lapped non‐woven joints, the curves encompass only the first three stages; however, for woven composites, the last stage is very small. In addition, among the laminates, the non‐woven laminate sustains the highest normalized failure load, except in the staggered case, where the quasi‐isotropic woven laminate exhibits higher strength. Conversely, the bidirectional woven laminate demonstrates the lowest loads and the highest deformation.Highlights A study compared bolted joint performance of woven and uni‐based composites. Lapped joints with different bolt arrangements were experimentally studied. P‐δ curves showed elastic, nonlinear, linear hardening, and softening stages. Woven laminates showed higher displacements compared to non‐woven laminates. Secondary bending induced additional stress with less impact on woven samples. Bearing failure predominated, with variations in extent of bearing damage.

Biomechanical evaluation of Gamma 3 nail with anti-rotation screw fixation for unstable femoral neck fractures: a biomechanical study

This study aims to evaluate the biomechanical performance of the Gamma 3 nail with an anti-rotation screw (GNS) and compare it to two established gold-standard methods for treating unstable femoral neck fractures (UFNFs). Synthetic bone models were prepared with Pauwels’ type III osteotomy and an additional posterior wedge. Three different implant configurations were tested: three cannulated crews (3CS) in an inverted triangle configuration, a dynamic hip screw with an anti-rotation screw (DHSS), and GNS. Non-destructive cyclic axial loading was applied at 7° adduction, with 1000 cycles ranging from 100 to 1000 N. Subsequently, a construct failure test was conducted using progressive axial compression, and fracture reduction loss was recorded. The average axial stiffness was 321 ± 52 N/mm for 3CS, 430 ± 71 N/mm for DHSS, and 519 ± 104 N/mm for GNS. The average ultimate failure loads were 2699.3 N for 3CS, 3427.1 N for DHSS, and 3758.9 N for GNS. GNS demonstrated significantly greater axial stiffness compared to the other two groups (P < 0.05). Both DHSS and GNS exhibited similar failure loading, which were greater than those of 3CS (P < 0.05). GNS offers the advantages of a minimally invasive and intramedullary implant with comparable stability to the DHSS system. Moreover, GNS demonstrated superior biomechanical performance compared to 3 CS configuration.

Flexural Strength of Reinforced Concrete Structures Exposed to Corrosive Media

This study investigated the effect of corrosion on the flexural behavior and midspan deflection of reinforced concrete beam members. Control, corroded, and resin-coated concrete beam specimens were tested to determine their failure load, midspan deflection, rebar diameter measurements, and mechanical properties. The results showed that corrosion significantly reduced the flexural strength and increased the midspan deflection of beams due to weakening of the reinforcing steel. The average failure load of corroded beams decreased by 25.73% compared to the control beams. Similarly, the average midspan deflection of corroded beams increased by 103.8% over the control beams. Measurements of rebar diameters before and after corrosion revealed reductions of up to 0.87% in corroded samples, substantiating corrosion-induced thinning. Additionally, mechanical properties testing showed decreases in ultimate tensile strength, yield strength, and strain ratio while increasing ductility for corroded rebars. Resin coating prevented much of the strength loss and provided protective benefits near that of the control specimens. The relationship between failure load, midspan deflection, diameter measurements, mechanical properties and corrosion damage was investigated through analytical comparisons. Corroded samples consistently demonstrated lower failure loads, higher deflections, reduced diameters and strengths versus controls. Conversely, coated samples performed similarly to controls, validating the coating's effectiveness. This research quantitatively confirms literature reports that corrosion degrades reinforced concrete through weakening of rebar-concrete bond and steel deterioration over time if left unprotected. The findings emphasize the importance of mitigating corrosion to ensure structural integrity, safety and durability of reinforced concrete infrastructure.

Biomechanical Comparison of All-Suture, All-Inside Meniscus Repair Devices in a Human Cadaveric Meniscus Model.

Newer all-suture, all-inside meniscus repair devices utilize soft suture anchors. The purpose of this study was to compare the biomechanical performance of 4 meniscus repair devices in human cadaver menisci: the JuggerStitch (all-suture, all-inside), the FiberStitch (all-suture, all-inside), a polyether ether ketone (PEEK) all-inside, and an inside-out device. Forty human cadaver menisci were tested after creating 20 mm longitudinal tears in the posterior meniscus. Each knee was randomized to 1 of 4 meniscus repair groups: JuggerStitch (all-suture, all-inside), FiberStitch (all-suture, all-inside), FAST-FIX 360 (PEEK-based anchor all-inside), and inside-out (with BroadbandTM tape meniscus needles). For each meniscus, 2 devices were used to prepare vertical mattress repair construct. The specimens were tested by pre-conditioning 20 cycles between 5 N and 30 N and then the tear diastasis was measured, followed by distraction to failure phase after imposing a displacement at a rate of 0.5 mm/s. Ten menisci were tested in each of the 4 groups. After pre-conditioning, there was no significant difference in the gap formation among groups (P = 0.212). The average failure load for the JuggerStitch, FiberStitch, PEEK all-inside, and inside-out was 384 N, 311 N, 207 N, and 261 N, respectively, with a significant difference between groups (P = 0.034). Post hoc analysis showed the JuggerStitch failure load was higher than the PEEK all-inside and inside-out (P = 0.005, and P = 0.045, respectively). There was no significant difference between the failure load of the JuggerStitch and FiberStitch (P = 0.225). The JuggerStitch all-suture device, FiberStitch all-suture device, PEEK all-inside, and inside-out devices have similar biomechanical properties for gapping and stiffness. The JuggerStitch all-suture, all-inside device has superior failure load compared with the PEEK all-inside and inside-out repair for longitudinal meniscus tear repair.

Use of Electrocautery to Facilitate Suture Passage Through the Greater Trochanter of the Femur: A Biomechanical Study.

The specific aims of this study were to evaluate (1) the axial force reduction of suture passage utilizing electrocautery when applied to the greater trochanter of the femur, (2) the temperature change caused while using electrocautery for suture passage, and (3) the failure loads and failure modes utilizing this technique. Five matched pairs of fresh-frozen femurs were used and classified into two groups: with electrocautery on needle (study group) and without electrocautery on needle (control group). Two bicortical, osseous tunnels were made around the insertion of the gluteus medius tendon. Each specimen was sequentially tested in a needle penetration test and a single load-to-failure test. A #5 Ethibond suture with a straight needle was used. Electrocautery reduced the peak axial force for bone penetration in 40% (near cortex) and 70% (far cortex) of the trials, and no significant difference was detected between groups or between two osseous tunnels. The average peak force was significantly higher for the far cortex for both groups and for both osseous tunnels compared to the near cortex. There was no significant change in temperature of the tunnel site with electrocautery. Ninety percent of the samples experienced bone tunnel failure for the study group compared to 70% in the control group. The average ultimate failure load for the study group was lower compared with the control group, but this finding was not statistically significant (range: 6%-15%). Suture passage using electrocautery may not significantly decrease the peak force needed to pass a needle directly through the greater trochanter.

Influence of Strain Rate on Metallurgical and Mechanical Properties of Friction Stir Spot Welded Aluminium Joints

Nowadays, the substitution of copper with aluminium is widely pursued in order to save weight and material costs, for battery components and wire connectors. Additionally, cost reductions can be further enhanced with effective reduction of energy consumption through efficient manufacturing. Therefore, friction stir spot welding as a solid-state welding technique is a potential choice with low energy demands and high joining performances. However, the joining of aluminium and its alloys with solid-state welding techniques is still a challenging task due to a persistent and chemically stable aluminium oxide layer formed at the sheets prior to the welding, due to the reaction between aluminium and atmospheric oxygen. In this paper, the influence of strain rate induced during friction stir spot welding process on the metallurgical, mechanical and electrical properties of friction stir spot welding of AA 5754-H111 was studied. The strain rate was calculated according to the rotational speed of the tool and the effective (average) radius and depth of the stir zone. It was observed that the specimens welded with a lower strain rate endured a 15 % higher average strain failure load compared to the specimens welded at a higher share rate. The microhardness profiles of the specimens obtained at low strain rates imply strain hardening mechanisms in the weld zone, while the microhardness of specimens welded at high strain rates expressed thermal softening. It was also found that the friction welded sheets, regardless of the strain rate, show increased electrical resistance compared to the base material, however, it decreases with an increase in strain rate. Microstructural analysis reveals a stress-induced metallurgical transformation in the narrow zone around the weld-faying interface.

Electrolyte-supported solid oxide fuel cells with ultra-thin honeycomb structure prepared by digital light processing 3D printing technology

A significant challenge in electrolyte-supported solid oxide fuel cells (SOFCs) pertains to the substantial thickness of the electrolyte, resulting in elevated operational temperatures that hinder commercial viability. In this research, we utilized digital light processing (DLP) 3D printing technology to fabricate ultra-thin honeycomb electrolyte-supported SOFCs and subsequently evaluated their performance. Through the use of ultraviolet absorbers, we achieved a shallow curing depth (60.3 μm), which facilitated the creation of ultra-thin electrolyte samples. We investigated the mechanical properties of electrolytes with various honeycomb structures, finding that the square honeycomb structure exhibited the highest mechanical integrity, with an average failure load of 1.01 N. Finally, we assessed the electrochemical performance, observing a substantial power density of 215.4 mW/cm2, representing a twofold increase compared to the 114 mW/cm2 achieved by the same method in a flat primary cell.

Printing strategies to fabricate a disk through the fused deposition modeling method

The fused deposition modeling (FDM) technique is widely used in different industries due to its low cost and ability to produce complex geometries from polymers. In this technique, some manufacturing parameters are essential because of their effects on the mechanical performance of the final fabricated part. The current study investigated the impact of path strategy and printing speed, two key manufacturing factors, on the mechanical performance of printed disks. Six types of path strategies of rasters corresponding to the loading direction, namely unidirectional-vertical, unidirectional-horizontal, unidirectional-45, cross, cross-45, and concentrate, were used for printing some disks, and compressive tests were done on them. The results showed that these path strategies’ average compressive failure loads were 2955, 4957, 2342, 4640, 3971, and 5893 N, respectively. The lower compressive strength of the unidirectional path pattern was due to the weak zones that were located between the printed layers and rasters. Besides, three printing speeds of 40, 60, and 80 mm/s were considered to fabricate the disks with a concentrate path pattern, and compressive experiments were performed. The results showed that the 40 mm/s printing speed conducted a compressive failure load of 4544 N, while 60 and 80 mm/s resulted in 3008 and 2828 N, respectively. Finally, inter-layer strength as a major factor in controlling the compressive strength of the disks was comprehensively discussed.

Experimental study on the mechanical properties of three‐dimensional braided composite circular tubes with preembedded licker‐in

AbstractThis study investigates the tensile and compression properties of three‐dimensional five‐direction (3D5D) braided composite circular tubes with preembedded titanium alloy licker‐ins. The influence of the braided angle, braided thickness, and braided configuration on the bearing capacity is analyzed, and the microdamage morphology and failure mechanism of the tube structure are examined using scanning electron microscopy. Results show that the 3D5D braided tube has a larger tensile failure load than the 3D full five‐direction braided tube of the same outer diameter. In circular tubes of the same braided configuration and outer diameter, the compression failure load increases with the wall thickness, and the C‐ø30t3 circular tube achieves the maximum compression failure load. The damage morphology is characterized by the pulling‐off failure of the licker‐in joint. The T‐ø30t2.5 and T‐ø25t3 circular tubes achieve a large failure load, with an average tensile load of over 120 kN. The failure morphology is characterized by the cracking of the fiber at the end of the tube after the licker‐in joint has been pulled off. The average tensile failure load of the T‐ø30t3 circular tubes is over 105 kN, and the failure morphology reveals a broken licker‐in joint, indicating design deficiencies that require further optimization. The findings of this paper can provide an important scientific basis for the lightweight and high‐strength connection design for 3D braided composites in near‐space aerostats and their flight applications.

Open-Source Designs for Distributed Manufacturing of Low-Cost Customized Walkers

To improve accessibility, this article describes a static, four-legged walker that can be constructed from materials and fasteners commonly available from hardware stores coupled by open-source 3D-printed joints. The designs are described in detail, shared under an open-source license, and fabricated with a low-cost open-source desktop 3D printer and hand tools. The resulting device is loaded to failure to determine the maximum load that the design can safely support in both vertical and horizontal failure modes. The experimental results showed that the average vertical failure load capacity was 3680 ± 694.3 N, equivalent to 375.3 ± 70.8 kg of applied weight with the fractured location at the wood dowel handlebars. The average horizontal load capacity was 315.6 ± 49.4 N, equivalent to 32.2 ± 5.1 kg. The maximum weight capacity of a user of 187.1 ± 29.3 kg was obtained, which indicates that the open-source walker design can withstand the weight requirements of all genders with a 95% confidence interval that includes a safety factor of 1.8 when considering the lowest deviation weight capacity. The design has a cost at the bottom of the range of commercial walkers and reduces the mass compared to a commercial walker by 0.5 kg (19% reduction). It can be concluded that this open-source walker design can aid accessibility in low-resource settings.

The Influence of Tool Geometry on the Mechanical Properties and the Microstructure of AA6061-T6 Aluminum Alloy Friction Stir Spot Welding.

In this work, the influence of the tool geometry on friction stir spot welding (FSSW) was studied on sheets made of AA6061-T6 aluminum alloy. Four different AISI H13 tools with simple cylindrical and conical pin profiles and 12 mm and 16 mm shoulder diameters were used to perform the FSSW joints. Sheets of 1.8 mm thickness were used during the experimental work to prepare the lap-shear specimens. The FSSW joints were performed at room temperature. For each joining condition, four specimens were carried out. Three specimens were used to find the value of the average tensile shear failure load (TSFL), while the fourth one was used to examine the micro-Vickers hardness profile and to observe the microstructure of the cross-section of the FSSW joints. The investigation concluded that higher mechanical properties corresponding to the finer microstructure were obtained by the conical pin profile and the higher shoulder diameter compared with the specimens performed using the cylindrical pin tool and lower shoulder diameter due to the higher strain hardening and the higher frictional heat generation, respectively.

Assessment of the Compression Properties of Different Giant Bamboo Species for Sustainable Construction

In this study, compression mechanical properties of five giant bamboo species from different continents were investigated based on the ISO 22157:2019 standard. The selected species have been used for rural construction for centuries. The chosen bamboo species for this study, which are considered strong candidates to be used in modern construction as well, are as follows: Phyllostachys edulis (Moso), Guadua angustifolia (Guadua), Gigantochloa apus (Tali), Gigantochloa atroviolacea (Black Java), and Phyllostachys bambusoides (Madake). The excellent properties of bamboo species in tension are well established. Hence, this article principally focuses on the behaviour of selected giant species in compression to be used as structural members. In this study, the mentioned bamboo species were gathered from different continents of origin to be critically assessed, analysed, and compared with one another to better understand their compression behaviour as structural columns. The compression properties of these bamboo species have not been evaluated and compared with one another in an academic study so far. The results show that all tested species were able to provide mean compressive strengths greater than 50 MPa, which makes them highly promising construction material candidates for modern construction. The Guadua test series was able to provide outstanding consistency in the presented compression behaviour and strengths among all the tested species. The specimens with the maximum sustained load belonged to the Tali species. The greatest average failure load belonged to the Moso species. The greatest mean compressive strength measured was 88.9 MPa, reported for Madake species with smaller diameters compared to the other test series. Among the specimens with larger diameters, the greatest mean ultimate strengths were for Moso, Guadua, and Tali species with 69.9 MPa, 60.7 MPa, and 59.1 MPa compressive strengths, respectively.

Axial compressive performances of stiffened composite panels: Experimental and numerical study

Axial compressive performances of stiffened composite panel were studied in this manuscript. In experimental study, buckling phenomenon of three specimens appear at 413kN, 403kN and 403kN respectively while catastrophic failure appears at 964kN, 934kN and 970kN respectively. Thus average failure load is 2.35 times average buckling load, which indicate the large postbuckling capacity. Only local buckling appears in skin bay without buckling in stiffeners. Buckling strain and failure strain were proposed by the average value of several typical position strains at buckling and failure moment respectively. Average failure strain is −6483 με, which is 2.75 times buckling strain (-2354 με). The relationship between buckling and failure strain is similar to that of buckling and failure load. Failure modes contain debonding and fracture of stiffeners, the splitting and wrapped skin. In numerical study, finite element model considering the Hashin damage, cohesive element and geometry imperfection were built. Buckling load and failure load by FE results have −1.2% and −3.9% error compared to experimental ones, indicating the FE results have good accuracy. FE results show that debonding initiation is close to the moment of final catastrophic failure, about 92.7% failure load. Moreover, debonding area percentage have an accelerating increase trend with the compressive load increasing.

Morphometric and Biomechanical Comparison of the Scapular Spine and Coracoid Graft in Anterior Shoulder Instability

Background: The scapular spine has been described as a relatively new bone graft alternative used in glenoid augmentation. The classic Latarjet procedure, which transfers the coracoid as a graft, is regarded as the gold standard. The comparison of these 2 techniques has not been fully reported. Purpose: To compare the anatomic and biomechanical properties of glenoid augmentation using scapular spine graft or coracoid graft. Study Design: Controlled laboratory study. Methods: The study used 20 fresh-frozen human cadaveric shoulders. A 25% anterior glenoid defect was created, and the specimens were divided randomly to receive glenoid augmentation by scapular spine or coracoid grafts. For both procedures, the grafts were secured to the glenoid defect with 2 screws. Morphometric data, including the glenoid articular area, amount of restoration, and graft dimensions, were obtained. A biomechanical test was conducted in a direct-loading scenario. The construct stiffness, cyclic displacement, and ultimate failure of each specimen were collected. Results: No significant difference was found in glenoid articular restoration between the scapular spine group and the coracoid group (31% vs 33%, respectively; P = .311). Morphometric analysis indicated that coracoid grafts exhibited significantly greater thickness and height than scapular spine grafts. In biomechanical results, the scapular spine group exhibited significantly greater construct stiffness than the coracoid group (206.3 ± 58.8 vs 148.3 ± 76.0 N/mm, respectively; P = .023). The average failure load in the scapular spine group was not significantly higher than that in the coracoid group. No significant differences in cyclic displacement were found between the 2 techniques. Conclusion: In a simulated 25% anterior glenoid bony defect, a scapular spine graft was comparable with the classic Latarjet procedure in restoring the glenoid articular dimension and exhibited superior construct stiffness in a cadaveric model. Clinical Relevance: The scapular spine may serve as an alternative graft choice in glenoid augmentation surgery considering the amount of articular restoration and initial fixation stability.

Experimental study on mixing ratio effect of hybrid graphene nanoplatelet/nano-silica reinforcement on the static and fatigue life of aluminum-to-GFRP bonded joints under four-point bending

In the scenario of nanoparticle-reinforcement, synergistic effect of adding two or more nanoparticles types to the adhesive can be introduced as a solution to achieve more efficient bonded joints. This paper aims to investigate the influence of hybrid insertion of graphene nanoplatelet (GNP) and silica nanoparticle (SNP) additives with various GNP + SNP mixing ratios on the static strength, endurance, and crack initiation life of aluminum-to-GFRP bonded joints under four-point bending. Four specimen groups were prepared: I) neat, II) hybrid-type reinforcements with different mixing ratios of 30 %GNP + 70 %SNP, III) 50 %GNP + 70 %SNP, and IV) 70 %GNP + 30 %SNP. Static tests indicated that, for 0.5 and 1.0 wt%, 70 %GNP + 30 %SNP had the maximum average static failure load, while, for 1.5 wt%, 30 %GNP + 70 %SNP resulted in the highest static strength. Under a fatigue load of 50 %, the longest endurance and crack initiation life was obtained for 70 %GNP + 30 %SNP hybrid-reinforced group. However, under higher fatigue loads of 70 %, variations in hybrid mixing ratio had a negligible effect on crack initiation phase for 0.5 and 1.0 wt%. Under fatigue loads of 70 % and 1.5 wt%, 30 %GNP + 70 %SNP group had 3.4 % and 2.6 %, and 5.1 % longer crack initiation life than 50 %GNP + 50 %SNP and 70 %GNP + 30 %SNP groups, respectively. Finally, major microstructural reinforcing mechanisms were interpreted using scanning electron microscopy (SEM).

Butted friction stir forming of AA6061-T6 to low carbon steel

Friction stir welding (FSW) is a popular method for creating dissimilar material joints in the aerospace and automotive industries. This work proposes a new FSW derivative process: butted friction stir forming (BFSF). BFSF has the distinction of joining two abutting workpieces to a lapped third workpiece. Additionally, the process does not require modification to traditional FSW equipment and tooling. In this study, BFSF combines two workpieces of aluminum alloy 6061-T6 in a butt weld configuration throughout the process. As the FSW tool traverses, it travels over preformed, threaded holes in low carbon ASTM A36 hot rolled steel at regular spacing. Downward force combined with the stirring action of the tool displaces material into the hole, filling the threads and forming a mechanical interlock. Testing of various screw sizes and thread pitches allowed the determination of the optimal joint configuration. Aluminum die-cut bolts of each size established a point of comparison for base material strength. Of the sizes tested, the ANSI metric M profile M9-1.25 screw had the highest mechanical strength. In cross-tensile testing, the average failure load was 3915 N. Shear testing produced a failure load of 5749 N. The M9-1.25 formed screws had a 33.6% decrease in strength compared to the die-cut bolts. While this strength reduction is higher than is often experienced in traditional FSW, the results of this study are a valid proof of concept for further development in BFSF methods.

Biomechanical comparison of the femoral neck system and the dynamic hip screw in basicervical femoral neck fractures

The purpose of this study was to compare the fixation stability of proximal fragments and the mechanical characteristics in proximal femur models of basicervical femoral neck fracture fixed by the femoral neck system (FNS) versus the dynamic hip screw. The mean axial stiffness was 234 ± 35 N/mm in the FNS group and 253 ± 42 N/mm in the DHS group, showing no significant difference (p = 0.654). Mean values for x-axis rotation, y-axis rotation, and z-axis rotation after cycle load were 2.2 ± 0.5°, 6.5 ± 1.5°, and 2.5 ± 0.6°, respectively, in the FNS group and 2.5 ± 0.7°, 5.8 ± 2.1°, and 2.2 ± 0.9°, respectively, in the DHS group, showing no significant differences (p = 0.324, p = 0.245, and p = 0.312, respectively). The mean values of cranial and axial migration of screws within the femoral head were 1.5 ± 0.3 and 2.1 ± 0.2 mm, respectively, in the FNS group and 1.2 ± 0.3 and 2.4 ± 0.3 mm, respectively, in the DHS group, showing no significant differences (p = 0.425 and p = 0.625, respectively). The average failure load at vertical load was 1342 ± 201 N in the FNS group and 1450 ± 196 N in the DHS group, showing no significant difference (p = 0.452). FNS fixation might provide biomechanical stability comparable to that of DHS for treating displaced basicervical femoral neck fractures in young adults.

Influence of Hydrothermal Aging under Two Typical Adhesives on the Failure of BFRP Single Lap Joint

Facing increasingly serious resource crises, energy conservation is becoming the development trend of various delivery vehicles, and lightweight is an important way to achieve energy conservation. In this paper, the basalt fiber-reinforced resin composite material (BFRP) was selected to study the effect of its bonding structure, and it was used to make BFRP-BFRP joints. Two adhesives, Araldite®2012 and Araldite®2015, were used to make single-lap joints and dumbbell-shaped specimens. Aging environments of 80 °C/95% RH and 80 °C/pure water were used for the 0-day (unageing), 10-day, 20-day, and 30-day aging tests, respectively. According to Fick’s second law, the moisture absorption change model of two adhesives was established, and it was found that the water absorption process could be divided into two stages, which explains the precipitation of water molecules and the reaction of water molecules with functional groups. The maximum average failure load and load-displacement curves under different environments and different joints were obtained by using the electronic universal tensile machine, and the exposure time was more important than the effect of humidity. At the same time, the change law of failure strength and ductility were analyzed. The change of Tg (Glass transition temperature) was analyzed by differential scanning calorimetry (DSC) equipment, and the results showed that molecular chain rupture was the reason for the decrease of Tg. It could be seen from the joint failure mode distribution that Araldite®2012 adhesive was easily affected by the environment, and the joint of Araldite®2015 adhesive was affected by the combined effect of the adhesive and BFRP.

Valgus fatigue and nonlinear damage accretion of the anterior bundle of the elbow medial collateral ligament (AMCL)

Failure by fatigue is one mechanism by which ligaments can rupture, with the accumulation of damage gradually degrading the ligament strength. Baseball pitchers who perform repeated high-level throwing continuously subject the medial ligament complex of the elbow to extreme levels of loading, which can lead to fatigue and eventual rupture. This study sought to investigate this behavior and quantify the fatigue properties of the anterior bundle of the medial collateral ligament (AMCL) with respect to valgus elbow torque. Eleven pairs of cadaveric elbow specimens were used for this study. One side of each pair was tested in vertical elongation at four flexion angles and then tested to failure at 90° of flexion. The contralateral specimens were tested in valgus fatigue at 90° of flexion using a specialized apparatus with application of known moments based on the elongation failure load. The average tensile failure load for the AMCL was 595.3 ± 201.9 N. During cycling, the average increase in the maximum valgus rotation angle was 4.77° ± 2.82°. The average maximum stretch of the AMCL middle band increased from 1.066 ± 0.017 to 1.076 ± 0.018 near the time of fatigue failure. The average cycles to failure for specimens tested at 90% and 80% of the estimated failure torque were 3211 ± 4721.33 and 25063 ± 30487.58, respectively. The nonlinear non-dimensional fatigue life and damage accretion results work in conjunction to predict the fatigue properties for a valgus elbow motion of arbitrary torque magnitude at 90° of elbow flexion.

Influence of rotational speed on the electrical and mechanical properties of the friction stir spot welded aluminium alloy sheets

AbstractAn efficient and productive joining technique to weld aluminium has become a priority challenge for promoting the use of aluminium in the electrical industry. One of the challenges is to obtain welds with superior mechanical properties with the consistent quality of weld surface as well as low electrical resistance. In this paper, the influence of rotational speed during the friction stir spot welding of AA 5754-H111 was studied to analyse the mechanical and electrical properties of the welds. The results from two rotational speeds (1000 rpm and 4500 rpm) are presented and compared to the base material. It was observed that the samples welded at 1000 rpm showed a higher average shear failure load (~ 1.1 kN) compared to the samples welded at 4500 rpm (~ 0.94 kN). The microhardness of the samples welded at 1000 rpm was higher than that of the base material, while the microhardness of samples welded at 4500 rpm was lower. It was also found that the friction welded sheets, regardless of the rotational speed used, showed increased electrical resistance compared to the base material, albeit this increase for the samples welded at 1000 rpm was about 42%, compared to samples welded at 4500 rpm where this increase was just 14%.