Joint Material Research Articles

A photoactive Dual-cationic Covalent Organic Framework Encapsulated Sodium Nitroprusside as controllable NO-releasing material for joint cation/photothermal/NO antibacterial therapy

The rational design and preparation of novel multifunctional materials harboring with combinational antibacterial activities have great demand in the fields of biomedicine. Herein, a novel antibacterial agent (DC-COF-SNP) based on a photoactive dual-cationic covalent organic framework (COF) encapsulated sodium nitroprusside (SNP) hybrid was developed. DC-COF consisted by imidazolium and viologen cation, showed a prominent broad spectrum antibacterial activity itself via damaging the negatively charged cell membrane of bacteria. Under laser irradiation, DC-COF with concurrently excellent photo-stability and high photothermal conversion efficiency (38.71%) presented an efficient photothermal antibacterial activity. Meanwhile, the electronegative SNP could be strongly absorbed in the positively charged COF, avoiding the self-decomposition of SNP. DC-COF-SNP displayed controllable NO release property under intermittent laser irradiation. As a result, a synergistic and amplified multi modalities antibacterial effect of cation, NO gas, and photothermal therapy was achieved, which could be employed as a wide spectrum antibacterial agent against both Gram-negative and Gram-positive bacteria. Therefore, this work paves an avenue for the rational preparation of promising combinational antimicrobial agents with controllable gas release capacity, thus, achieving higher therapeutic effect.

Bio-inspired hydrogel-polymer brush bi-layered coating dramatically boosting the lubrication and wear-resistance

Surface modification is of great significance in improving the interfacial properties of bioimplants, especially friction and wear of artificial joint materials (e. g. polyetheretherketone, PEEK). Herein, inspired by the layered structure and gradient modulus of natural articular joint, hydrogel-polymer brush bilayered coating was developed to functionalize rigid PEEK (PBHP). The resulting PBHP material showed similar layered structure with natural articular joint. The load-bearing hydrogel layer and lubricating polymer brush layer exhibited corresponding moduli with natural cartilage and superficial biomacromolecules layer, respectively. Tribological tests demonstrated that the obtained material showed outstanding lubrication (friction coefficient<0.07), high load-bearing capability (load>20 N) and excellent wear-resistant capability (sliding cycles>10,000). The “hard PEEK-elastic hydrogel-soft polymer brush” layered material may find potential applications in artificial joint replacement.

Outstanding Bio-Tribological Performance Induced by the Synergistic Effect of 2D Diamond Nanosheet Coating and Silk Fibroin.

Due to their excellent biocompatibility, outstanding mechanical properties, high strength-to-weight ratio, and good corrosion resistance, titanium (Ti) alloys are extensively used as implant materials in artificial joints. However, Ti alloys suffer from poor wear resistance, resulting in a considerably short lifetime. In this study, we demonstrate that the chemical self-assembly of novel two-dimensional (2D) diamond nanosheet coatings on Ti alloys combined with natural silk fibroin used as a novel lubricating fluid synergistically results in excellent friction and wear performance. Linear-reciprocating sliding tests verify that the coefficient of friction and the wear rate of the diamond nanosheet coating under silk fibroin lubrication are reduced by 54 and 98%, respectively, compared to those of the uncoated Ti alloy under water lubrication. The lubricating mechanism of the newly designed system was revealed by a detailed analysis of the involved microstructural and chemical changes. The outstanding tribological behavior was attributed to the establishment of artificial joint lubrication induced by the cross binding between the diamond nanosheets and silk fibroin. Additionally, excellent biocompatibility of the lubricating system was verified by cell viability, which altogether paves the way for the application of diamond coatings in artificial Ti joint implants.

(Digital Presentation) Crack-Free Ni-P Film for Power Devices

Demands for power devices are expanding with the electrification of automobiles. Power devices are soldered using Ni-P films prepared by an electrochemical method to withstand required high currents. However, cracks are inevitably induced in Ni-P films during high mounting temperatures. Ni-P films play an important role as a solder joint material and the P concentration is a critical factor that affects the mechanical properties of Ni-P films. Therefore, in this work, we focused on the P concentration and tried to prepare Ni-P films without cracks induced by high heat treatments. Ni-P films with different P concentration were formed on an Al substrate by an electroplating using a Watt bath and then investigated the relationship between the P concentration and the generation of cracks by X-ray diffraction and thermal expansion analyses. By the heat treatment at 300 °C or higher, Ni-P compounds mainly composed of Ni3P was formed in the Ni-P film with P concentration of 8 wt.% or more and the film shrank by 0.11%. In contrast, the 2 wt.% or less P- Ni film did not cause the formation of Ni3P and little shrinkage was observed even after the high treatment at 400 °C. The obtained results indicate that the phase transition to Ni-P compounds by the heat treatment is responsible for the mechanical disintegration, that is, the P concentration in the film is closely related to the generation of cracks. We propose the method for suppressing cracks by controlling the P concentration in the Ni film. Figure 1

Effect of humid and thermal environments on the performance of an epoxy resin pavement filling joint material

Modified epoxy resins have shown good results for the repair of pavement cracks. However, as the grouting material is directly exposed to the atmosphere, its performance is affected by humid and heat, resulting in a certain deterioration in its performance and service life. To explore the influence of humid and heat on an epoxy resin joint filling material (EPFM), EPFM was treated in humid and thermal environments for varying periods of time in this study, and the water absorption characteristics, mechanical properties, and road performance of the EPFM were tested. The stress relaxation index was used to evaluate the stress relaxation performance of the EPFM after humid and heat treatments. The results show that in a humid environment, EPFM undergoes a three-stage water absorption process, and the increase in water content reduces its glass transition temperature. In low-temperature environments, the tensile and shear strengths of the EPFM are reduced, but the deformation properties are enhanced under different stress patterns. In a high-temperature environment, the internal macromolecular structure of the EPFM is damaged, causing a significant reduction in its toughness. Under the −10 °C test conditions, the tensile strength reaches a maximum of 31 MPa, and the elongation at breaking decreases to less than 60 %. Through stress relaxation tests, it is found that compared with the thermal environment, water further weakens the stress relaxation performance of the EPFM.

Grasp Stability and Design Analysis of a Flexure-Jointed Gripper Mechanism via Efficient Energy-Based Modeling

For flexure-based gripper mechanisms, the arrangement and design of joint elements may be chosen to allow enclosure of objects in grasping. This must provide stable containment under load, without causing excessive stress within the joint materials. This paper describes an energy-based model formulation for a cable-driven flexure-jointed gripper mechanism that can accurately describe the nonlinear load-deflection behavior for a grasped object. The approach is used to investigate the limits of grasp performance for a gripper with two single-joint fingers through simulation studies, including the accurate prediction of stability limits due to joint buckling. Hardware experiments are set up and conducted to validate the theoretical model over a range of loading conditions that exceed limits for stable grasping. Parametric design studies are also presented to show the influence of joint geometry on both grasp stability and flexure peak stress. Considering the intersection of feasible design sets, generated from simulation data over a range of possible object geometries, is shown to be an effective approach for selecting gripper design parameters.

An Electrical Contacts Study for Tetrahedrite-Based Thermoelectric Generators.

High electrical and thermal contact resistances can ruin a thermoelectric device’s performance, and thus, the use of effective diffusion barriers and optimization of joining methods are crucial to implement them. In this work, the use of carbon as a Cu11Mn1Sb4S13 tetrahedrite diffusion barrier, and the effectiveness of different fixation techniques for the preparation of tetrahedrite/copper electrical contacts were investigated. Contacts were prepared using as jointing materials Ni and Ag conductive paints and resins, and a Zn-5wt% Al solder. Manual, cold- and hot-pressing fixation techniques were explored. The contact resistance was measured using a custom-made system based on the three points pulsed-current method. The legs interfaces (Cu/graphite/tetrahedrite) were investigated by optical and scanning electron microscopies, complemented with energy-dispersive X-ray spectroscopy, and X-ray diffraction. No interfacial phases were formed between the graphite and the tetrahedrite or Cu, pointing to graphite as a good diffusion barrier. Ag water-based paint was the best jointing material, but the use of hot pressing without jointing materials proves to be the most reliable technique, presenting the lowest contact resistance values. Computer simulations using the COMSOL software were performed to complement this study, indicating that high contact resistances strongly reduce the power output of thermoelectric devices.

Biomimetic chitosan-derived bifunctional lubricant with superior antibacterial and hydration lubrication performances

The lubrication deficiency in joints is a major cause of osteoarthritis. One of the most commonly used treatment means is to inject artificial lubricants, but there is a potential risk of infection during the injection process. Therefore, developing artificial lubricants with dual functions of friction-reduction and antibacterial is urgent. In this work, a novel polysaccharide-derived lubricant with simultaneous anti-bacteria and water-lubrication properties, called CS-MPC-N, is developed by grafting 2‑methacryloyloxylethyl phosphorylcholine (MPC) and nisin peptide onto backbone of chitosan (CS). Compared to the control CS, CS-MPC-N exhibits good lubrication and friction-reduction properties because of its excellent water solubility. Especially, CS-MPC-N shows low friction coefficient (0.03 ∼ 0.05) at the sliding interfaces of artificial joints materials or even natural articular cartilages. Moreover, CS-MPC-N can effectively inhibit the proliferation of Staphylococcus aureu, exhibiting excellent antibacterial effect. This kind of novel polysaccharide-derived lubricant is expected to be used in treating infectious arthritis.

Stress ratio effect on crack growth behavior of dissimilar friction stir welded butt joint between AA6061 and AA7075 alloys

Many engineering components are subjected to random nature of loading during their life period. In this work, the fatigue crack growth in friction stir welded dissimilar AA6061 and AA7075 was investigated under different stress ratio. AA6061 was kept on the advancing side due to having a higher solidus temperature and softer than AA7075 for smooth material flow. The microstructure characterization, tensile and crack growth behavior was studied. It was observed that the joint material exhibited lower strength and ductility as compared to the base material. About 41%, 34%, and 66% reduction in tensile strength, yield strength, and percentage of elongation as compared to AA6061 (base material) were observed. About 27% higher hardness in the HAZ of retreating side than the advancing side was noticed. The crack deflection and tortuosity features were observed in the fatigue fractured specimens. In this paper, a comparative study using different crack growth models has been studied and a simple crack growth rate equation has been proposed considering the crack closure effect.

Separation and Extraction of Mixed Grinding Chips of Artificial Joints with Different Densities by Multiple Centrifugal Separations

Aseptic loosening caused by the wear and tear of the artificial joint prosthesis after implantation is one of the main causes of artificial joint failure. Therefore, it is important to investigate the wear debris generated due to wear when developing new artificial joint materials. Aseptic loosening is related to the size, number, and morphology of wear debris, and this study proposed the separation and extraction of mixed wear debris with different density ratios of artificial joints by centrifugation to study the characteristics of different artificial joint wear and wear debris extraction rates. The results showed that multiple centrifugations to separate the mixed wear debris were able to reintroduce the wear debris on the wall of the centrifuge tube into the solution and that the wear debris extraction rate was increased. Suspensions with different density ratios of artificially jointed mixed wear debris were effectively separated by this method. The total extraction rate of the three repeated extractions compared to the first extraction rate, the extraction rate of CoCrMo wear debris increased by 6.7%, ultra-high molecular weight polyethylene (UHMWPE) wear debris increased by 15.1–23.44%, ZrO2 wear debris increased by 10.91%, and that of polyether ether ketone (PEEK) wear debris increased by 9.95%. This method for separating and extracting wear debris from artificial joints can realize the separation of mixed wear debris from artificial joints and obtain a high extraction rate and high-quality wear debris images, investigate the wear mechanism of artificial joint implants, and provide valuable information on the wear performance of new artificial joint implants under investigation.

Failure Analysis of Drill Pipe during Working Process in a Deep Well: A Case Study

The failure of a 101.6 mm drill pipe was studied by combining experimental testing and finite element simulation. The macro analysis, metallographic structure and energy spectrum, chemical composition and a mechanical property test of the failed drill pipe sample were firstly carried out. Then, a three-dimensional finite element model of drill pipe failure was established based on the experimental results. Finally, the failure mechanism of drill pipe was analyzed and the mitigation measures were put forward. The results showed that solids settling sticking was the direct cause of fracture failure of the drill pipe joint. Due to the violent friction and wear between the drill pipe joint and the settled sand, the large amount of heat generated caused the microstructure of the joint material to undergo phase transformation and the bearing capacity to be reduced. Finally, fracture occurs under tensile and torsional loads.

Recent progress of bioinspired cartilage hydrogel lubrication materials

AbstractHydrogels have been considered as potential candidates for cartilage replacement due to their high‐water content, extreme network hydration, excellent biocompatibility and tunable mechanical properties. Currently, the development of high‐performance cartilage‐inspired hydrogel lubrication materials has become a hot topic in the field of biomedical materials. This review focusses on the recent development of cartilage‐inspired high‐strength hydrogels from the viewpoints of bionic surface/interface and biotribology. Specifically, the composition structure and extraordinary lubrication mechanism of the natural articular cartilage are overviewed first. Subsequently, some of the novel biomimetic design strategies for preparing high strength cartilage hydrogels with various network structures are summarised in detail, while systematic evaluation of lubrication properties and mechanisms are discussed. Furthermore, new surface modification means for improving the lubrication feature of high strength cartilage hydrogel materials are presented. In addition, in order to demonstrate the application potential of cartilage hydrogels in clinical, several bonding methods to decorate hydrogels onto surfaces of natural bone tissues or artificial joint materials are introduced. Finally, current challenges and future research directions are discussed for cartilage‐inspired hydrogel lubrication materials.

A review study on fatigue behavior of aluminum 6061 T-6 and 6082 T-6 alloys welded by MIG and FS welding methods

The aluminum alloys are widely used due to their light weight, the moderate strength and good corrosion resistance. The main applications include food processing equipment, chemical containers, aerospace and railway transport systems. The objective of this study is to compare the microstructure and fatigue behavior of Al 6061 T-6 and Al 6082 T-6 alloys welded by metal inert gas (MIG) and friction stir (FS) welding techniques. The tensile strength of Al 6061 T-6 and Al 6082 T-6 alloys were analyzed for both welding technique, which mainly depends on welding parameters used during welding process. The Grain size and microstructures of the MIG & FS weld joints of Al 6061 T-6 and Al 6068 T-6 have been studied at various welding process parameters. The microstructure study was carried out by using metallurgical microscope with image analyzer system. The micro hardness study was carried out by using digital vickers micro hardness tester for both weld joint materials.

Anti-friction mechanism of textured artificial joint material under the walking conditions of human

The tribological properties of artificial joints can be significantly affected by surface textures. In this study, micro textures were prepared by laser surface texturing on the 316 L stainless steel. The relationship between surface and tribological properties of the material was proposed, and the tribological behavior was verified by different micro-pit area ratios and aspect ratios under the conditions of human walking. The results indicate that the tribological properties of the textured 316 L stainless steel are greatly correlated with surface roughness and wettability. Within the parameter range of this study, the friction of textured surfaces has been significantly reduced when the area ratio of micro-pits is 10% and the aspect ratio is 0.52. In addition, the anti-friction mechanism of textured surface is that micro-pits could store worn debris and provide secondary lubrication, and that many air bubbles between interfaces would enhance bearing capacity and interface slip when the material surface is hydrophobic.

Exploring Cu-Ge alloys as filler materials for high vacuum brazing application of W and CuCrZr

Cu-Ge system was evaluated for its application as a filler material in W-CuCrZr joints proposed as heat sink components of the future fusion power plants. The selected compositions were rich in Cu, with the aim of retaining the ductility that characterizes copper metal. Three compositions (Cu-13.5Ge, Cu-19.5Ge and Cu-33.2Ge) and two manufacturing routes (flexible and rigid tapes) were evaluated and characterized thermally, microstructurally and mechanically. The brazing temperature decreased as the Ge content increased, giving rise to less base material thermal affectation. The microstructure was dominated by several peritectic reactions that hinder the solid state diffusion control, and three main phases (Cu solid solution, ε and ζ) were detected both in the solidified filler drop and in the joint braze. In addition, the rigid filler manufacturing route seemed to produce more continuous joints due to its more homogeneous composition. The mechanical properties indicated that both lower and richer Ge compositions gave rise to joints with higher strength.

Mechanical Properties and Pavement Usability of Modified Asphalt-Based Joint Material of Cement Concrete Pavement

Abstract The virgin-asphalt-based joint materials of cement concrete pavement are subjected to damages because of repeated vehicle load and environmental factors. The styrene-butadiene-styrene (SBS), shape memory polyurethane (PU), and organosilicon (OS) modified asphalt-based joint materials were prepared to improve mechanical properties and pavement usability of virgin-asphalt-based joint materials of cement concrete pavement. The tensile, compressive, shear property, low-temperature ductility, high-temperature fluidity, and elastic recovery performance were tested to select a suitable modifier and confirm its dosage for preparing modified asphalt-based joint material. Results indicate that mechanical properties, ductility, fluidity, and elastic recovery of asphalt joint materials are improved by SBS, PU, and OS modifiers. Especially, the modification effect of PU modifier at the dosage of 8 wt % is most satisfactory, successively followed by OS and SBS. The PU at the dosage of 8 % is proposed to develop a new modified asphalt-based joint material, reducing the failures of joint material and improving the durability of cement concrete pavement.

Analysis of Cracked Rail of the Crane of Type A120

The aim of the work was to find out the causes of cracking of the A120 crane track rail. Although the track was regularly inspected by defectoscopic techniques, after five years of operation, the rail was broken at the weldment. The elemental composition of the welded joint materials was verified and the mechanical properties were determined. A fractographic description of the fracture surface was performed and the structure of the material was evaluated. Several factors contributed to the formation of crack, the combination of which led to a rail failure. Defects of the welded joint, acting as notches, from which they initiated fatigue cracks, unfavourable microstructure of the weld metal, low toughness of the base material and operating environment and conditions were dominant.

Effect of the IMC layer geometry on a solder joint thermomechanical behavior

PurposeIn a printed circuit board assembly (PCBA), the coefficient of thermal expansion (CTE) mismatch between the solder joint materials has a detrimental impact on reliability. The mechanical stresses caused by the thermal changes of the assembly lead to fatigue and sometimes the failure of the solder joints. The purpose of this study is to propose a novel pad design to obtain an interrupted solder/substrate interface, to improve the PCBA reliability.Design/methodology/approachAn interruption in the continuous intermetallic compound (IMC) layer of a solder joint was implemented, by the deposition of a silicone film in the pad, changing its geometry. That change allows a redistribution of stresses in the most ductile zone of the solder joint, the solder. The stress concentration at the solder/substrate interface is reduced, as well as the general state of stress at the solder joint.FindingsA new way was developed to reduce the stress on the solder joints, caused by thermal variations, because of the different components CTEs mismatch. This new method consists of interrupting the IMC layers of the solder joint, strategically, redirecting the usual stresses to a more ductile area of the joint, the solder. This is an innovative method that allows increase the lifetime of PCBAs and the equipments.Originality/valueIn this study, a new pad design concept for higher solder joint reliability was developed to reduce the shear stress in the solder joints because of the CTE mismatch between all the solder joint components.

Simultaneous enhancement of anti-friction and wear resistance performances via porous substrate and FeCoNiTiAl high entropy alloy coating of artificial joint materials

It remains an extreme challenge to fabricate artificial joint materials with applicability of mechanical properties compared with bones, superior biocompatibility, anti-friction and wear resistance performances. Here, we report an effective strategy to simultaneously enhance the anti-friction and wear resistance performance of Ti6Al4V substrate through optimizing the porosity and sputtering a high-entropy alloy (HEA) coating. The progressive scratch experiments are carried out to equivalently imitate the scratch deformation process induced by hard particles and evaluate the anti-friction and wear resistance performances, which directly reveal the significantly decreased coefficient of friction (COF) of porous substrate based on suitable pore diameter covered with HEA coating compared with pure Ti6Al4V substrate. The porous design is verified to effectively weaken the stress shielding effect and simultaneously improve the hydrodynamic lubrication. Attributed to the coupling effects of pore structure-induced “flexibility” and HEA coating-induced surface hardening, the composite structure exhibits low COF value, wear volume and enhanced scratch resistance. The design concept would facilitate the development of novel medical implant materials with requirements of anti-friction and wear resistance.

A review of joining techniques for thermoplastic composite materials

Composite materials have found widespread applications in the automotive, aerospace, and building industries. Several components are joined together for these applications, by some temporary or permanent bonding approach. The increased use of different materials and their combinations such as composites makes the whole joining process something to be thoroughly considered before continuing. Several aspects need to be studied before spending significant time and financial resources. Considering these challenges in this paper we have provided a review of the investigations that have been made on fiber-reinforced composite joints. The level of development in various types of joints and joining techniques such as mechanical bonding, adhesive bonding, and fusion bonding along with their advantages and disadvantages is given. Several parameters affecting the performance of composite joints such as joint configuration, material selection and properties, geometric parameters, dominating failure modes, and environmental factors are described briefly. To verify the performance of composite joints, guidance on joint testing is given (both destructive and non-destructive).