Maximum Failure Load Research Articles

Effects of Shoulder Geometry on Microstructures and Mechanical Properties of Probeless Friction Stir Spot Welded Aluminum 7075-T651 Sheets

In this work, three types of probeless tools (archimedes, involute, and concave tools) were designed. A 7075-T651 sheet of 1.0 mm thickness was welded using the designed probeless tools. It was found that the stir zone and hook defect varied a lot for different joints. Plunge depth was the dominant process parameter for joint property. The joint’s maximum failure load (5.73 kN) was obtained with the concave tool when the target plunge depth was 0.55 mm. Two typical joint fracture modes (shear fracture and plug fracture) were found using three designed tools with different plunge depths, rotation speeds, and dwell times. Shoulder geometry presented little influence on heat generation. Compared with involute grooves, archimedes grooves showed to be more effective on the material flow. The properties of the joints with the archimedes tool were more sensitive to welding parameters. Compared with the flat tool, the concave tool decreased the escape of plasticized material, improved the forge force, and optimized the metallurgical bond at the interface.

Structural behaviour of concrete beams reinforced with polyethylene terephthalate (PET) bottles wastes bars

This paper examines the effect of using PET bottle waste as a reinforcement bar in concrete beams. Waste of PET bottles has been cut by a special tool to long strips with width of 6 mm and thickness of 0.5 mm and lengths ranging between 6000 mm for small bottles and 11000 for large bottles. Then, straps areused in the formation of PET bars in three different forms, two braids are formed and twisted bundles form.Each PET bar consists of 36 straps. PET bars are arranged in the same location of rebar as an alternative to the steel bars in the tensile area. Also, it are pre-tightened before casting with a special tool is designedfor this purpose in order to give it a straight texture and reduce the expected elongation. Five concrete beams with dimensions (150*200*1400)mm are used in this study.Two of themare controlledbeams with and witout tension steel reinforcement.The other three beams are reinforced withthree different forms of PET bottle waste bars. The achieved results are encouraged and unprecedented as the models containing rods achieved a maximum failure load of up to 25% of the failure load for specimens containing reinforcing steel bars.This technique enhancesits ability to be used as reinforcing bars in secondary structural members.

Effects of global and local ply-reinforcements of critical components on crush performances of 2D tri-axially braided CFRP J-shaped fuselage frame

With the development of aircraft industry, there is an urgent demand for pursuing higher crashworthiness design standard of fuselage. However, there is a challenge for improving the crush performances of fuselage with low design and fabrication cost. To explore optimal design areas, effects of global and local ply-reinforcements of critical components on crush performances of 2D tri-axially braided CFRP J-shaped fuselage frame are predicted with validated continuum damage model. The finite element model composed of three critical components (e.g. outer flange, web, and inner flange) can accurately predict the experimental maximum failure load and breakage mode. Then, the crush behaviours of fuselage frame with global and local ply-reinforcements are respectively compared among three parts. It is found that local ply-reinforcements slightly increase structural stiffness, failure load, and SEA but global ply-reinforcements present greater improvements, especially for the outer flange and web. Further, effects of ply number of each part on crush behaviours of fuselage frame are predicted. Results show that increasing ply number presents higher performances but the SEA only increases for global ply-reinforcement of outer flange. It is concluded that globally reinforcing the outer flange has the highest reinforcement efficiency with a low increase of weight. This study provides a preferential reinforcement design idea for the fuselage to keep the light-weight and high-strength.

Factors affecting biomechanical strength of Latarjet constructs: A systematic review and meta-regression.

The Latarjet procedure reduces recurrent glenohumeral instability but has potential hardware and graft complications. The procedure has been modified to use various screw types as well as suture buttons. Biomechanical studies have evaluated the effect of these implants on construct strength. With varying results it is unclear whether there is an optimal implant to use. We conducted a systematic review of human cadaveric biomechanical studies evaluating Latarjet ultimate failure load. Two independent reviewers screened articles and included them after full text review. Additional factors including implants used, graft orientation, cortices engaged, drill diameter, and screw characteristics were recorded. Meta-regression was performed on the 145 specimens from eight studies that met inclusion criteria. Screw fixation resulted in a 396.8 N (95% CI, 149.8-643.7) N higher ultimate failure load against shear stresses than suture buttons (p = 0.002). There were no differences between implants for ultimate failure load against tensile forces. Tensile strength was significantly affected by drill diameter with each millimeter of increase reducing the mean ultimate failure load by 127.4 N (95% CI, 41.2-213.6) N (p = 0.004). These results suggest that using screw fixation and minimizing drill diameter can obtain the maximum ultimate failure load against both shear and tensile forces in a Latarjet construct.

Failure load and stress intensity factor of single-lap steel joints bonded with nano-Al2O3 reinforced epoxy adhesive

The failure load of single-lap steel joints (subjected to tensile force) with epoxy/nano-Al2O3 adhesives was analysed experimentally. Spherical-shaped nano-Al2O3 of diameter 23–47 nm and rod-shaped nano-Al2O3 of diameter < 10 nm and length < 50 nm were included in the epoxy adhesive by wt% (0.5, 1.0, 1.5, and 2.0 wt%). Stress intensity factor of the adhesive layer at the corner of single-lap joints was calculated from the failure load. A substantial improvement in the failure load and stress intensity factor of epoxy/nano-Al2O3 adhesives was obtained compared to the base adhesive. The maximum failure load and stress intensity factor of epoxy/nano-Al2O3 adhesives were found at 1.0 wt% of Al2O3 nanorods and 1.5 wt% of Al2O3 nanospheres. The failure load and stress intensity factor of epoxy/nano-Al2O3 adhesives reduced on further addition of nano-Al2O3 (i.e. 1.5 and 2.0 wt% of nanorods and 2.0 wt% of nanospheres). Still, these were more than the base adhesive.

Biomechanical effects of posterior pedicle screw-based instrumentation using titanium versus carbon fiber reinforced PEEK in an osteoporotic spine human cadaver model

BackgroundAim of this biomechanical investigation was to compare the biomechanical effects of a carbon fiber reinforced PEEK and titanium pedicle screw/rod device in osteoporotic human cadaveric spine. MethodsTen human fresh-frozen cadaveric lumbar spines (L1-L5) have been used and were randomized into two groups according to the bone mineral density. A monosegmental posterior instrumentation (L3-L4) using titanium pedicle screws and rods was carried out in group A and using carbon fiber reinforced PEEK in group B. A cyclic loading test was performed at a frequency of 3 Hz, starting with a peak of 500 N for the first 2000 cycles, up to 950 N for 100,000 cycles under a general preload with 100 N. All specimens were evaluated with regard to a potential collapse of the implanted pedicle screws. A CT supported digital measurement of cavities around the pedicle at 3 defined measuring points was performed. Finally, the maximum zero-time failure load of all specimens was determined using a universal testing machine (80% Fmax). FindingsRegarding maximum axial force (group A: 2835 N, group B: 3006 N, p = 0.595) and maximum compression (group A: 11.67 mm, group B: 15.15 mm, p = 0.174) no statistical difference could be shown between the two groups. However, significant smaller cavity formation around the pedicle screws could be observed in group B (p = 0.007), especially around the screw tip (p < 0.001). InterpretationCarbon fiber reinforced PEEK devices seem to be advantageous in terms of microscopic screw loosening compared to titanium devices.

Damage properties of pre-embedded connection of carbon fiber wound composite tubes

In this study, a new connection technology of composite tubes is proposed: carbon fiber (T700/TDE86) filament winding composite tubes with pre-embedded titanium alloy joints, which realize the application of light-weighting heavy load pod for a stratospheric airship. The axial tensile behavior of specimens was determined through experimental tests and by using finite element method. In comparison with the conventional bonding connection joints, the maximum failure load of specimens is higher than 105 kN, indicating the excellent mechanical properties of the novel connecting structure. Damage in the adhesive layer is caused by the opposite movement trend between the embedded titanium and the composite tube, and the main failure mode refers to the fiber tear damage. The ±30° layer near the ends of the titanium joint is subjected to a larger tensile load and is completely damaged because of the failure of the adhesive layer. Subsequently, the inter-layer reaches the ultimate failure strength, delamination takes place, and then the structure loses its loading capacity. Numerical simulation results of the progressive damage process and failure load are in good agreement with the experimental results. Stress analysis indicates that the failure of the adhesive layer is not the dominant factor that causes the structure to lose its load-bearing capacity. Moreover, structural strength is dominated by the tensile strength of the ±30° layers and the interlaminar shear strength between 90° layer and 30° layer. The circumferentially tightened 90° yarns in the grooves are also critical to the load-bearing effect of the structure.

Pulsed laser texturing for improved adhesive-bonded polyethylene (PE) joints

Nanosecond pulsed laser texturing was performed on pigmented polyethylene (PE) specimens with a 1064 nm fiber laser with the aim of improving adhesive-bonded joint strength. A Design-of-Experiments (DoE) was employed to optimize process parameters and determine the effects of average laser power, scanning velocity and hatch spacing on the resulting failure load of PE joints bonded with Teroson 9399. Failure load increased with laser energy dose up to the onset of macroscopic melting. Laser scanning strategies minimizing heat accumulation yielded best results as the energy dose could be increased as much as possible prior to onset of melting. The process exhibited highest sensitivity to heat accumulation in the laser scanning direction, favoring large pulse separation distances in the scanning direction and moderate pulse overlap in the lateral direction. With a focused spot diameter of 60 μm and a repetition rate of 20 kHz, a maximum failure load of 0.93 kN (1.49 MPa, standard deviation 0.01 kN) was achieved with a crossing-line laser scanning strategy, 25 μm hatch spacing, 3 W average power and 2500 mm/s scanning velocity. Under these conditions, purely cohesive failure took place yielding a 79% improvement in failure load over standard primed joints.

Biomechanical Analysis of Four Suturing Techniques for Radial Meniscal Tears Demonstrated the Advantage of the Cross-Tie Grip Suture

Objectives:The “Tie Grip suture” was designed to fix radial meniscal tears more rigidly than simple conventional sutures. However, one shortcoming was residual gapping at the central margin of the tear. We modified the original method to address this point and named it the “Cross Tie Grip suture”. The purpose of this study was to perform biomechanical tests to compare suture strength and stability between four suturing techniques; the original “Tie Grip suture”, the “Cross Tie Grip suture” and two conventional suture methods, the double horizontal and cross sutures. It was hypothesized that the Cross Tie Grip suture will show the least displacement and resist the greatest maximum load.Methods:Forty fresh-frozen porcine knees were dissected to acquire 80 menisci. 20 menisci were tested in each group: original Tie Grip, Cross Tie Grip, double horizontal, and cross suture groups. A radial tear was created from the central margin to 2 mm to the menisco-capsular junction at the middle third of the meniscal body, equidistance from the anterior and posterior horns. Suture configurations are shown in Figure 1. The sutured menisci were set in a custom clamp, with a metric ruler positioned parallel to the clamp to serve as a measurement scale. All menisci underwent preconditioning from 5 to 20 N for 300 cycles at 0.5 Hz. Subsequently, submaximal loading was performed for 500 cycles from 5 to 20 N at 1 Hz. The cycle was paused at cycles 0, 100, 250, and 500 for digital photographs to be taken under a 5 N load. An image processing software (ImageJ; US National Institutes of Health) was utilized to analyze the digital photographs for gap measurement. Load to failure testing was done at 5 mm/min and failure mode was recorded. An a priori power analysis based on preliminary experiments with statistical power of 80%, and significance set at .05, sample size required was at least 18 per group. The data was analyzed by one-way analysis of variance and Tukey-Kramer post hoc test. P-values <0.05 were considered statistically significant.Results:Displacement after 500 submaximal cycles was significantly small in the Cross Tie Grip suture group (0.4 ± 0.3 mm) compared to the 3 other suture methods (Table 1). Displacement was, 0.9 ± 0.6 mm, 1.2 ± 0.7 mm, 1.4 ± 0.6 mm (P < .05) for Tie Grip, double horizontal, and cross suture groups, respectively. Maximum failure load was significantly greater in the Cross Tie Grip (154.9 ± 29.0N) and Tie Grip (145.2± 39.1N) groups compared to the double horizontal (81.2±19.9N) and cross suture (87.3±17.7N) groups (P < .05) (Table 1). Tissue failure was the most common mode of failure in all groups.Conclusions:The Cross Tie Grip suture showed greater resistance to displacement compared to the original method and both conventional methods, the double horizontal and cross sutures. In respect to maximum load, the Cross Tie Grip suture was equivalent to the original method. Both Tie Grip sutures showed greater maximum load compare to the other conventional sutures; double horizontal and cross.Table 1.Ultimate load and submaximal load data. Ultimate failure load was significantly greater in the Cross Tie Grip and Tie Grip groups compared to the double horizontal and cross suture groups. Gapping was significantly small in the Cross Tie Grip and Tie Grip groups compared to the double horizontal and cross suture groups. Displacement after 500 cycles was significantly small in the Cross Tie Grip group. Original tie grip Cross tie grip Double horizontal Cross Ultimate failure load (N)145.2 ± 39.1154.9 ± 29.081.2 ± 19.987.3 ± 17.7Gapping after cyclic load (mm)0 cycles1.2 ± 0.70.7 ± 0.51.7 ± 1.02.4 ± 1.2100 cycles1.6 ± 0.80.1 ± 0.72.2 ± 1.12.8 ± 1.4250 cycles1.8 ± 0.81.2 ± 0.72.5 ± 1.23.4 ± 1.5500 cycles2.1 ± 0.81.3 ± 0.72.9 ± 1.63.8 ± 1.6Displacement after 500 cycles (mm)0.9 ± 0.60.4 ± 0.41.2 ± 0.71.4 ± 0.6

Biomechanical Analysis of Plate Fixation Compared With Various Screw Configurations for Use in the Latarjet Procedure.

Background:The biomechanical properties of coracoid fixation with a miniplate during the Latarjet procedure have not been described.Purpose:To determine the biomechanical properties of miniplate fixation for the Latarjet procedure compared with various screw fixation configurations.Study Design:Controlled laboratory study.Methods:A total of 8 groups (n = 5 specimens per group) were tested at a screw insertion angle of 0°: (1) 3.75-mm single screw, (2) 3.75-mm double screw, (3) 3.75-mm double screw with washers, (4) 3.75-mm double screw with a miniplate, (5) 4.00-mm single screw, (6) 4.00-mm double screw, (7) 4.00-mm double screw with washers, and (8) 4.00-mm double screw with a miniplate. In addition, similar to groups 1 to 3 and 5 to 7, there were 30 additional specimens (n = 5 per group) tested at a screw insertion angle of 15° (groups 9-14). To maintain specimen uniformity, rigid polyurethane foam blocks were used. Testing parameters included a preload of 214 N for 10 seconds, cyclical loading from 184 to 736 N at 1 Hz for 100 cycles, and failure loading at a rate of 15 mm/min until 10 mm of displacement or specimen failure occurred.Results:All single-screw constructs and 77% of 15° screw constructs failed before the completion of cyclical loading. Across all groups, group 8 (4.00-mm double screw with miniplate) demonstrated the highest maximum failure load (P < .001). There were no differences in failure loads among specimens with single-screw fixation (groups 1, 5, 9, and 12; P > .05). All specimens in groups 9, 10, 11, 12, 13, and 14 (insertion angle of 15°) had significantly lower maximum failure loads compared with specimens in groups 2, 3, 4, 6, 7, and 8 (insertion angle of 0°) (P < .001 for all).Conclusion:These results indicate significantly superior failure loads with the miniplate compared with all other constructs. Across all fixation techniques and screw sizes, constructs with screws inserted at 0° performed better than constructs with screws inserted at 15°.Clinical Relevance:The use of a miniplate for coracoid fixation during the Latarjet procedure may provide a more durable construct for the high-demand contact athlete.

Experimental study on structural behaviour of branching steel columns

Few researchers have study the branching column and there is no enough information about it. The objects of this research is to study the structural behaviour of the branching columns and how it effects on the form-finding. These branching columns are experimentally tested and preparation tables to assist with design of it. Experimental work was carried out on the seventeen specimens. All specimens have been tested under static load then evaluated for maximum failure load, maximum vertical displacement and failure mode. The studied variables are the ratio of horizontal spacing between branches to total width of specimen, number of branches and number of branching level. The results showed that when the ratio between the width of the specimen and the overall width was increased, failure load and buckling load was decreased and maximum vertical displacement was increased. When the number of branches increases, the failure load increases slightly, with the vertical displacement increasing. The failure load, buckling load decreased and the vertical displacement greatly increased as the number of branching levels increases. All specimens have failed with buckling mode, and had less failure load and buckling load than the reference specimen.

Fracture mechanisms of hybrid adhesive bonded joints: Effects of the stiffness of constituents

In this study, different single-lap hybrid joints are used to analyse the effects of the stiffness of the adherends and the adhesive on the failure mechanism. The hybrid joints include a combination of (a) different adherends: aluminium (6082 T6) and PolyPhtalamide (PPA) reinforced with 50% of glass fibre (grade HTV-5H1 from Grivory) and (b) different adhesives: epoxy-based adhesive (Loctite EA 9497) and silane-modified polymer-based adhesive (Teroson MS 9399). Six different single-lap joints are fabricated and analysed. The cohesive parameters of different adhesives against different adherends are determined respectively using single-mode coupons and validated with finite element modelling. Single-lap shear tests are conducted to understand different fracture mechanisms of the joints. Finite element (FE) models using the Cohesive Zone Method (CZM) are developed to simulate the failure of the joints and validated by the testing results. Different failure processes obtained from different hybrid joints combinations are discussed further by analysing the stress distributions along the interfaces of the joints. Finally, the relationship between the stiffness of the constituents of a hybrid adhesive joint and its failure mechanism is summarised. The load vs displacement behaviour of the single-lap joints demonstrate that the stiffness of adherends affects the maximum failure load of the joints with rigid adhesive (epoxy). However, the joint with flexible adhesive (polyurethane) is not sensitive to the stiffness of the adherends. In addition, higher shear stress distribution occurs in the interface adjacent to the adherend with lower stiffness, leading to the failure initiation at the PPA side regardless of adhesive types.

Study on microstructure and properties of resistance spot welding of Mg/Ti dissimilar materials

ABSTRACT The dissimilar material of AZ31 Mg alloy and TA15 Ti alloy were welded by resistance spot welding. The influence of welding current on the interface of nuggets is studied. The microstructure, hardness, tensile strength and fracture surface of joints are analysed. The results indicate that when the electrode pressure and welding time are determined, the failure load of the joint can be improved by the increase in the welding current; however, excessively high welding current will cause cracks near the interface. Under the welding current of 14.5 kA, the electrode pressure of 0.22 MPa and the welding time of 200 ms, the maximum failure load of the joint can reach 4.79 kN, which is almost the same as the shear strength of AZ31B magnesium alloy base metal.

Mechanical Behavior of a Composite Lightweight Slab, Consisting of a Laminated Wooden Joist and Ecological Mortar.

The investigation reported in this paper is an evaluation of the mechanical behavior of full-scale ecological mortar slabs manufactured with a mixture of expanded clay and recycled concrete aggregates. The composite mortars form a compressive layer over laminated wooden joists to form a single construction unit. To do so, full-scale flexural tests are conducted of the composite laminated wood-ecological mortar slabs with different types of mortar designs: reference mortar (MR), lightweight mortar dosed with recycled concrete aggregates (MLC), and lightweight mortar dosed with recycled mixed aggregates (MLM). The test results showed that the mortar forming the compression layer and the laminated wooden joists worked in unison and withstood a higher maximum failure load under flexion than the failure load of the wooden joists in isolation. Moreover, the laboratory test results were compared with the simulated values of the theoretical model, generated in accordance with the technical specifications for structural calculations contained in the Spanish building code, and with the results calculated by a computer software package. From the analysis of the results of the calculation methods and the full-scale laboratory test results, it was concluded that the safety margin yielded by the calculations validated the use of those methods on this type of composite slab. In this way, a strong mixed wood–mortar slab was designed, contributing little dead-load to the building structure and its manufacture with recycled aggregate, also contributes to the circular economy of construction materials.

A Synthetic Graft With Multilayered Co-Electrospinning Nanoscaffolds for Bridging Massive Rotator Cuff Tear in a Rat Model

Background: Graft bridging is used in massive rotator cuff tear (MRCT); however, the integration of graft-tendon and graft-bone is still a challenge. Hypothesis: A co-electrospinning nanoscaffold of polycaprolactone (PCL) with an “enthesis-mimicking” (EM) structure could bridge MRCT, facilitate tendon regeneration, and improve graft-bone healing. Study Design: Controlled laboratory study. Methods: First, we analyzed the cytocompatibility of the electrospinning nanoscaffolds, including aligned PCL (aPCL), nonaligned PCL (nPCL), aPCL–collagen I, nPCL–collagen II, and nPCL-nanohydroxyapatite (nHA). Second, for the EM condition, nPCL–collagen II and nPCL-nHA were electrospun layer by layer at one end of the aPCL–collagen I; for the control condition, the nPCL was electrospun on the aPCL. In 40 mature male rats, resection of both the supraspinatus and infraspinatus tendons was performed to create MRCT, and the animals were divided randomly into EM and control groups. In both groups, one end of the layered structure was fixed on the footprint of the rotator cuff, whereas the other end of the layered structure was sutured with the tendon stump. The animals were euthanized for harvesting of tissues for histologic and biomechanical analysis at 4 weeks or 8 weeks postoperatively. Results: All scaffolds showed good cytocompatibility in vitro. The graft-tendon tissue in the EM group had more regularly arranged cells, denser tissue, a significantly higher tendon maturing score, and more birefringence compared with the control group at 8 weeks after operation. Newly formed fibrocartilage could be observed at the graft-bone interface in both groups by 8 weeks, but the EM group had a higher graft-bone healing score and significantly more newly formed fibrocartilage than the control group. An enthesis-like structure with transitional layers was observed in the EM group at 8 weeks. Biomechanically, the values for maximum failure load and stiffness of the tendon-graft-bone complex were significantly higher in the EM group than in the control group at 8 weeks. Conclusion: The co-electrospinning nanoscaffold of aPCL–collagen I could be used as a bridging graft to improve early graft-tendon healing for MRCT in a rat model and enhance early enthesis reconstruction in combination with a multilayered structure of nPCL–collagen II and nPCL-nHA. Clinical Relevance: We constructed a graft to bridge MRCT, enhance graft-tendon healing and graft-bone healing, and reconstruct the enthesis structure.

Behavior of High-Strength Self-Consolidated Reinforced Concrete T-Deep Beams

Background:When a beam is loaded on two opposite faces and the beam’s depth is increased such that either the span-to-depth ratio is smaller than four or the shear-span-to-depth ratio is less than two, it will behave like a deep beam. Strain distribution in deep beams is different from that of ordinary beams because it is nonlinear along with the beam depth. If the beam is cast monolithically with a slab in the slab–beam system, it is considered a T-deep beam. The behavior of the resulting member is more complicated.Objective:The effect of flange width on the behavior of high-strength self-consolidated reinforced concrete T-deep beams was investigated.Methods:Experimental and numerical studies were conducted. Two shear span-to-depth ratios (1.25 and 0.85) were adopted for two groups. Each group consisted of four specimens: one rectangular beam that served as a reference beam and three flanged beams with flange widths of 440, 660 and 880 mm. All specimens had an overall depth of 450 mm, a width of 160 mm and a total length of 1600 mm. The tests were performed under a two-point load with a clear span of 1400 mm. A nonlinear analysis was also performed using ANSYS software.Results:Throughout the study, the performance of the T-deep beams has been investigated in terms of cracking loads, failure loads, modes of failure, loading history, rate of widening of cracks and ductility index. Results revealed that such parameters have a different ranges of effect on the response of T-deep beams. Calibration of the ANSYS model has been done by comparing results of load-deflection curves, cracking and failure loads with that obtained experimentally.Conclusion:The study’s results indicated that increasing the flange width yielded an 88% improvement in the failure load and an approximately 68% improvement in the cracking load. This positive effect of flange width on the failure load was more pronounced in beams with higher shear span to- depth ratios and flange widths of 660 mm. In addition, the beam’s ductility was improved, especially in cases corresponding to a higher shear span-to-depth ratio.The finite element simulation showed good validation in terms of the load-deflection curve with a maximum failure load difference of 9%. In addition, the influence of longitudinal steel reinforcement on the behavior of such members was studied. Some parameters that reflect the effect of changing the flange width on the behavior of deep beams were also presented. Increasing the flange width is more effective when using normal strength concrete than when using high-strength concrete in terms of cracking load, beam stiffness, and failure load.

Investigation of laser joining process of CFRTP and aluminum alloy

ABSTRACT An experimental investigation on the joining process of 6061 aluminum alloy and carbon fiber reinforced thermoplastics composite (CFRTP) has been carried out with swing laser. The application of the swing laser is beneficial to obtain a larger bonding area. The effects of scanning speed are investigated on the interface formation and fracture load of the hybrid joint. In addition, the formation mechanism of the interface and the fracture mode of the hybrid joint are further elucidated. The results indicate that maximum failure load is obtained with appropriate process parameters (scanning speed: 20 mm/s, laser power: 2000 W), whereas the interface morphology under this process parameter demonstrates that the structurally sound connection between CFRTP and aluminum alloy is realized by the mechanical interlocking effect. At a higher scanning speed, the gaps in the interface caused by insufficient heat input per unit length result in a lower failure load, while at a lower scanning speed, the bubbles and gaps at the interface are observed as a result of resin decomposition and trapped pyrolysis gases in the interface, ultimately reducing the failure load of the joint. Moreover, the fracture mode of the hybrid joint is a mixed failure.

Biomechanical comparative analysis of screw fixation and cortical endo-button fixation in Latarjet procedure for anterior dislocation of shoulder joint

To clarify the value of the cortical endo-button as an internal fixator in Latarjet procedure through biomechanical analysis. Ten pairs of shoulder joints from 6-7 months old male pigs were selected. Each pair was randomly divided into screw group and endo-button group. A 25% glenoid defect model was created, and the porcine infraspinatus tendon and its associated bone were used to simulate conjoint tendon and coracoid process in human body. The bone grafts were fixed with two 3.5 mm screws and double cortical endo-buttons with high-strength sutures in screw group and endo-button group, respectively. The prepared glenoid defect model was fixed on a biomechanical test bench and optical markers were fixed on the glenoid and the bone block, respectively. Then fatigue test was performed to observe whether the graft or internal fixator would failed. During the test, the standard deviations of the relative displacement between the graft and the glenoid of two groups were measured by optical motion measure system for comparison. Finally the maximum failure load comparison was conducted and the maximum failure loads of the two groups were measured and compared. There was no tendon tear, bone fracture, and other graft or internal fixation failure in the two groups during the fatigue test. The standard deviation of the relative displacement of the screw group was (0.007 87±0.001 44) mm, and that of the endo-button group was (0.034 88±0.011 10) mm, showing significant difference between the two groups ( t=7.682, P=0.000). The maximum failure load was (265±39) N in screw group and (275±52) N in endo-button group, showing no significant difference between the two groups ( t=1.386, P=0.199). There were 3 ways of failure: rupture at bone graft's tunnel (6/10 from screw group, 3/10 from endo-button group), tendon tear at the cramp (2/10 from screw group, 2/10 from endo-button group), and tendon tear at the internal fixator interface (2/10 from screw group, 5/10 from endo-button group), showing no significant difference between the two groups ( P=0.395). Although the endo-button fixation fails to achieve the same strong fixation stability as the screw fixation, its fixation stability can achieve the clinical requirements. The two fixation methods can provide similar fixation strength when being used in Latarjet procedure.

Simulation of surface preparations to predict the bond behaviour between normal strength concrete and ultra-high performance concrete

Bond strength between the normal strength concrete (NSC) and ultra high performance concrete (UHPC) is determined through slant shear, split tensile and four point bending test. Test methods are selected based on failure criteria such as shear, tension and bending in the typical strengthened structural components. The parameters studied to determine the bond behaviour are surface preparation (chipping and grooving) and nature of bonding (fresh and hardened state of UHPC) are chosen based on the bond studies carried out by many researchers. However, numerical research is required to evaluate the performance of the composite members incorporated with various surface preparations. Hence, the experimental results of composites with different surface preparations are validated through numerical approach by predicting the maximum failure load. The maximum difference between the numerically predicted and the corresponding experimental value is about 12%. Scanned electron microscopic analysis has been performed to determine the morphology of bond surface.

Experimental investigation on reliable and accurate prediction of buckling analysis of thin cylindrical shells with geometric imperfections

The cylindrical shell having a diameter to thickness ratio more than 10 is normally called as thin cylindrical shell. The primary threat to the thin cylindrical shell is axial compressive force. This force leads to buckling and it provokes the failure of shell. Owing to several consequences in terms of loss of injury, property, life & damage of failure incidents, pipeline planners are setting more accentuation both on protection measures against outside impedance and on giving sufficient obstruction against buckling. The universally useful FE code ANSYS is utilized for the improvement of the material disappointment model. A numerical alignment technique is portrayed which empowers the utilization of standard pliable test information for steels and measure of weight as the contribution to the trial arrangement with and without internal pressure. Current work describes the buckling analysis of thin shells and their consequences that arise as a result of geometric imperfections. For experimental purpose beverage can has been selected, and are subjected to manual loading conditions by placing the cans between two discs, and buckling load is determined. Experimental buckling was also calculated for the beverage cans with square and round cutouts and their corresponding deflections have been tabulated. The experimental results are compared with numerical results to identify the deflection, and also confirmation of limit conditions used. The load at which the thin cylindrical shell starts to buckle, yield point and maximum failure load will be determined by the results.