Joint Defects Research Articles

Improved YOLOv3 detection method for PCB plug-in solder joint defects based on ordered probability density weighting and attention mechanism

Printed Circuit Board (PCB) is the heart component of electronic products, and its defect detection is the basic requirement of PCB quality control in the production process. Traditional visual detection methods need artificial design features, so their detection accuracy is poor, and the rate of missed and false detection is high. To solve the above problems, this paper proposes an improved YOLOv3 (You Only Look Once) detection method for PCB plug-in solder spot defects based on the combination of the ordered probability density weighting and the attention mechanism. First, in order to obtain a higher priority priori box, the ordered probability density weighting (OWA) method is used to optimize the multiple sets of a priori boxes generated by K-means. Then, to get more effective feature information, the Squeeze-and-Excitation mechanism (SE) is added to the backbone network. In the feature detection network, the Convolutional Block Attention Module (CBAM) attention mechanism is joined, at the same time in the inspection network output layer three layer feature are fusions. Finally, in order to accelerate the convergence speed of model and improve the accuracy of the model, the network loss function was improved by using the generalized joint generalized intersection over union (GIoU), and the COCO data model was applied to PCB solder spot defect training by transfer learning method. After testing, the average detection accuracy of improved network is improved from 84.35% to 96.69%, and the improved network has better convergence than the original network. The study shows that the improved method based on YOLOv3 is more suitable for industrial application of PCB plug-in solder spot defect detection.

Development of a test rig for the diagnosis of arthritic knee joint defects in the case of lower extremity amputees in orthopaedic technology

Abstract If the alignment of a leg prosthesis is inadequate there will be the danger of arthritic defects occurring in the preserved knee joint. Acoustic-kinetic joint analysis in orthopaedic technology allows monitoring of the knee joint of an amputee after the alignment of a leg prosthesis and to recognize early joint defects resulting in adaptation of the alignment of the prothesis. A test rig was developed which includes acoustic emission analysis of the knee, video-based gait analysis, ground reaction force measurement and the measurement of the holding forces of the hands. During the examination a subject must do 3 one-legged knee bends during 10 sec with the preserved leg. To support the subject two grab handles were fixed with force sensors to a frame. A series of 6 measurements were recorded with breaks of 2 min. The recorded forces of the leg show a double hump pattern during the knee bend. The rising edge of the flexion phase was not uniform. The forces show no conclusive uniform pattern. The fitness of the probands acts as an indicator for the pattern of the force signals. The signals of the measurements show the necessity of the support for both hands to execute a one-legged knee bend. The understanding of the 3 measured forces is important for the arthritic diagnosis of the knee joint.

Superlarge living hyaline cartilage graft contributed by the scale-changed porous 3D culture system for joint defect repair

It is known that an excellent hyaline cartilage phenotype, an internal microstructure with safe crosslinking and available size flexibility are the key factors of cartilage grafts that allow for clinical application. Living hyaline cartilage grafts (LhCGs) constructed by phase-transfer hydrogel (PTCC) systems were reported to have a hyaline phenotype and bionic microstructure. By employing chondrocytes to secrete matrix in the hydrogel and then removing the material to obtain material-free tissue in vitro, LhCG technology exhibited superior performance in cartilage repair. However, PTCC systems could only produce small-sized LhCGs because of medium delivery limitations, which hinders the clinical application of LhCGs. In this study, we prepared three different noncrosslinked gelatin microspheres with diameters from 200 μm to 500 μm, which replaced the original pore-forming agent. The new PTCC system with the mixed and gradient porous structure was used for the preparation of superlarge LhCGs with a continuous structure and hyaline phenotype. Compared to the original technique, the porous gradient structure promoted nutrient delivery and cartilage matrix secretion. The small size of the microporous structure promoted the rapid formation of matrix junctions. The experimental group with a mixed gradient increased cartilage matrix secretion significantly by more than 50% compared to the that of the control. The LhCG final area reached 7 cm2 without obvious matrix stratification in the mixed gradient group. The design of the scale-changed porous PTCC system will make LhCGs more promising for clinical application.

Dual beam laser fusion-brazed Ti6Al4V/AA7075 dissimilar lap joint: Crack inhibition via inoculation with TiC nanoparticles

Severe hot cracks defects formed in the aluminum weld metal during laser fusion brazing (LFB) Ti6Al4V/AA7075 dissimilar lap joint. Herein, TiC nanoparticles were used to optimize the microstructure of aluminum weld metal. The wettability of molten aluminum alloy on the titanium was improved due to the increased laser absorptivity of aluminum with the addition of TiC nanoparticles. In contrast to the aluminum weld metal of the LFB joint with coarse cellular and dendrite grains, the LFB-TiC joint had a refined microstructure, consisting of equiaxed grains with segmented secondary phase, both of which intrinsically inhibit the intergranular hot cracking. Most of the TiC nanoparticles are dispersed in the precipitated phase or adsorbed on the boundary surface between the matrix phase and the Mg(Zn,Cu,Al) 2 precipitated phase. The average thickness of TiAl 3 IMC (intermetallic compound) increased to a maximum of 1.73 μm, ensuring interfacial bonding reliability. Benefiting from the inhibition of cracks and the synergy effect of grain refinement strengthening and load-bearing strengthening, the LFB-TiC joint exhibits elevated mechanical performance, the equivalent tensile strength and displacement increased from 289.8 MPa and 0.35 mm of the LFB joint to 487.7 MPa and 0.58 mm of the LFB-TiC joint. The enhancement in ductility is mainly attributed to the grain boundary modification caused by the dispersed TiC nanoparticles. The results show that Ti/Al lap joint with excellent mechanical properties can be obtained by laser fusion brazing method with proper microstructure control. • The hot cracking characteristics of Ti6Al4V/AA7075 laser fusion brazing joint was revealed. • TiC nanoparticles were used to inhibit the hot crack defects in the dissimilar lap joint. • The modified aluminum weld had a refined microstructure, consisting of equiaxed grains with segmented secondary phase. • The crack-free LFB-TiC joint shows improved mechanical properties with the equivalent tensile strength of 487.7 MPa.

Automatic compact camera module solder joint inspection method based on machine vision

Because of the contradiction between the production requirements of compact camera modules (CCMs) to achieve high efficiency and quality and the low efficiency and poor accuracy of traditional solder joint inspection methods, an automatic inspection method of CCM solder joint based on machine vision is proposed. After optimizing the imaging parameters according to the CCM inspection process, the region of interest is dynamically identified based on feature matching and image enhancement methods to remove background interference. On this basis, an improved adaptive particle swarm optimization is used to optimize the kernel extreme learning machine to automatically classify the solder joint defects. Experimental results showed that with its low latency, high precision and robustness, the CCM surface solder joint defect detection and classification method based on machine vision can effectively solve the problem of low efficiency and high cost of the current CCM solder joint defect detection technology.

Application of LARS ligament combined with three-dimensional printed prosthesis in reconstruction of radial hemicarpal joint after tumor resection

To investigate the effectiveness of LARS ligament and three-dimensional (3D) printed prosthesis on the combined reconstruction of radial hemicarpal joint after distal radius tumor resection. The clinical data of 12 patients with combined reconstruction of radial hemicarpal joint with LARS ligament and 3D printed prosthesis after distal radius tumor resection between September 2017 and March 2021 were retrospectively analyzed. There were 7 males and 5 females with an average age of 41.8 years (range, 19-63 years). There were 8 cases on the left side and 4 cases on the right side, and 10 cases of giant cell tumor of bone and 2 cases of osteosarcoma. The disease duration ranged from 1 to 20 months, with an average of 8.1 months. The osteotomy length, operation time, and intraoperative blood loss were recorded, and the wrist function was evaluated by Mayo wrist score and Musculoskeletal Tumor Society (MSTS) score before and after operation. The grip strength of the affected limb was expressed by the percentage of grip strength of the healthy upper limb, and the range of motion (ROM) of the wrist joint was measured, including extension, flexion, radial deviation, and ulnar deviation; the bone ingrowth and osseointegration at the bone-prosthesis interface of the wrist joint were observed by radiographic follow-up; the possible wrist complications were recorded. All 12 patients successfully completed the operation. The osteotomy length was 5.0-10.5 cm (mean, 6.8 cm), and the operation time was 180-250 minutes (mean, 213.8 minutes). The intraoperative blood loss was 30-150 mL (mean, 61.7 mL). All patients were followed up 11-52 months (mean, 30.8 months). Radiographic follow-up showed that bone ingrowth and osseointegration at the bone-prosthesis interface were observed in all patients, and biological fixation was gradually achieved. During the follow-up, the stability, motor function, and ROM of the wrist joint were good. There was no complication such as arthritis, subluxation, prosthesis loosening, and infection, and no tumor recurrence and metastasis. At last follow-up, the Mayo score was 82.1±5.4, and MSTS score was 27.5±1.5, which were significantly improved when compared with those before operation (48.8±13.5, 16.4±1.4; t=-10.761, P<0.001; t=-26.600, P<0.001). The grip strength of the affected side was 59%-88% of that of the healthy side, with an average of 70.5%. The ROM of wrist joint were 55°-80° (mean, 65.42°) in extension, 35°-60° (mean, 44.58°) in flexion, 10°-25° (mean, 17.92°) in radial deviation, 10°-25° (mean, 18.33°) in ulnar deviation. The combined application of LARS ligament and 3D printed prosthesis is an effective way to reconstruct bone and joint defects after distal radius tumor resection. It can improve the function of wrist joint, reduce the incidence of complications, and improve the stability of wrist joint.

Does the use of 3D-printed cones give a chance to postpone the use of megaprostheses in patients with large bone defects in the knee joint?

Revision procedures and the resulting bone loss are a big challenge for orthopedic surgeons. Therefore, we checked what functional outcomes that 3D-printed cone augments can offer to patients with bone defects (Anderson Orthopedic Research Institute [AORI] classification type 2B and 3) in the knee and whether the use of cones can delay the necessity to use a megaprotheses. Data from 64 patients (M = 22; W = 42) who underwent total knee arthroplasty (TKA) revision were included in the analysis. The Knee Society Clinical Rating System (KSS) and the range of motion in the knee joint were used for the functional assessment. The mean follow-up was 28 months (range: 18–44 months). The survival rate for aseptic loosening at follow-up was 100%. Infection occurred in two (3.1%) patients. The mean KSS score increased from 12.75 points preoperatively to 66.56 postoperatively (p < 0.001). The mean range of motion in the knee changed from 61.15° preoperatively to 115.93° postoperatively (p < 0.001). 3D-printed cone augments seem to be a good solution for patients requiring a TKA revision procedure. When used in patients with bone defects classified as 2B and 3 (AORI), they can be a good alternative, delaying the need for megaprotheses.

Outcomes of Semiknee Replacement in Skeletally Immature Bone Sarcoma Patients.

A semiknee mega endoprosthesis (SKMEP) was used to replace the resected distal femur or proximal tibia in skeletally immature bone sarcoma patients. This study investigated the surgical technique, endoprosthesis survival rate, functional outcome, complications, and approaches to resolve limb-length discrepancy (LLD) following this procedure. In total, 15 girls and 16 boys with a mean age of 9.1 years (range, 4-12) and 8.9 years (range, 5-13), respectively, were included in this study. The mean length of the resected distal femur (15 cases) and proximal tibia (16) was 145.0 and 122.8 mm, respectively. Altogether, 19 custom-made SKMEPs and 12 modular units were used to reconstruct the bone and joint defects. The average follow-up was 82.8 months (range, 4-225 months). Five patients died of disease. Seven SKMEPs were revised to total knee endoprosthesis after a mean of 40.3 months. Nineteen patients retained the original SKMEP, and the mean LLD was 4.3 cm (range, 0-10 cm). One case each of Henderson type 1B, type 2A, type 2B, and type 5B failures was observed. Knee subluxation occurred in two cases. Although a slight laxity of the knee was identified on physical examination, the average Musculoskeletal Tumor Society 93(MSTS93) functional score was 84.5% (range, 57-97%). The estimated implant survival was 70.5% at 5 years. This was the largest retrospective study reporting the application of SKMEP in bone sarcoma patients. For selected skeletally immature bone sarcoma patients, SKMEP is an option with satisfactory functional outcomes and survival rates. However, heightening pads or shoes to compensate the LLD were indispensable before subsequent LLD was adjusted by further operation(s).

Vascular injury of immature epiphyses impair stem cell engraftment in cartilage defects

The purpose of our study was to investigate if vascular injury in immature epiphyses affects cartilage repair outcomes of matrix-associated stem cell implants (MASI). Porcine bone marrow mesenchymal stromal stem cells (BMSCs) suspended in a fibrin glue scaffold were implanted into 24 full-thickness cartilage defects (5 mm ø) of the bilateral distal femur of six Göttingen minipigs (n = 12 defects in 6 knee joints of 3 immature pigs; age 3.5–4 months; n = 12 defects in 6 knee joints of 3 mature control pigs; age, 21–28 months). All pigs underwent magnetic resonance imaging (MRI) at 2, 4, 12 (n = 24 defects), and 24 weeks (n = 12 defects). After the last imaging study, pigs were sacrificed, joints explanted and evaluated with VEGF, H&E, van Gieson, Mallory, and Safranin O stains. Results of mature and immature cartilage groups were compared using the Wilcoxon signed-rank test. Quantitative scores for subchondral edema at 2 weeks were correlated with quantitative scores for cartilage repair (MOCART score and ICRS score) at 12 weeks as well as Pineda scores at end of the study, using linear regression analysis. On serial MRIs, mature joints demonstrated progressive healing of cartilage defects while immature joints demonstrated incomplete healing and damage of the subchondral bone. The MOCART score at 12 weeks was significantly higher for mature joints (79.583 ± 7.216) compared to immature joints (30.416 ± 10.543, p = 0.002). Immature cartilage demonstrated abundant microvessels while mature cartilage did not contain microvessels. Accordingly, cartilage defects in immature joints showed a significantly higher number of disrupted microvessels, subchondral edema, and angiogenesis compared to mature cartilage. Quantitative scores for subchondral edema at 2 weeks were negatively correlated with MOCART scores (r = − 0.861) and ICRS scores (r = − 0.901) at 12 weeks and positively correlated with Pineda scores at the end of the study (r = 0.782). Injury of epiphyseal blood vessels in immature joints leads to subchondral bone defects and limits cartilage repair after MASI.

A Study on Welding Characteristics, Mechanical Properties, and Penetration Depth of T-Joint Thin-Walled Parts for Different TIG Welding Currents: FE Simulation and Experimental Analysis

Considering the effect of heat input of tungsten inert gas (TIG) arc welding for T-joint welding of thin-walled parts of aluminum alloy 6061-T6, here, the welding characteristics are analyzed via the finite element method. The experiments are carried out using scanning electron microscope (SEM), optical microscope (OM), and tensile test of specimens to investigate the microstructure variation of the weld zone (WZ), heat-affected zone (HAZ), and base metal (BM), and the mechanical properties of the T-welded joint. The mechanical properties of the T-welded joint are explored and assessed combined with the tensile test in terms of yield strength, tensile strength, and Vickers hardness. Furthermore, the effects of different welding currents on welding penetration variation under welding deformation are thoroughly investigated, and the appearance of porosity and incomplete fusion defects of T-welded joints are clearly illustrated. The results show that the yield and tensile strength of T-welded joints, respectively, account for less than 37% and 74% of the base metal (BM) strength. Moreover, the welding penetration depth and microstructure of T-welded joints are deeply affected by the welding current. The maximum penetration depth is achieved at about 2.18 mm under the maximum welding current, and partial welding defects emerged, affecting and reducing the mechanical properties of the welded joint. It is expected that these results will provide an analysis foundation for optimization of the welding process, suppression of welding defects, and promotion of mechanical properties for thin-walled parts in the future.

Experimental investigation of the effects of adhesive defects on the strength and creep behavior of single-lap adhesive joints at various temperatures

ABSTRACT In this article, the creep behavior and strength of single-lap adhesive joints ( s) including defects have been studied, and the effect of the position of defects on the creep behavior and strength of s have been investigated. The defects were created on various sides of the Araldite 2011 adhesive layer and joints were subjected to the tensile and creep tests. The creep tests were done at three different temperatures; 23 ℃ (Room Temperature), 45 ℃, and 55 ℃. The results showed that the presence of a defect in the adhesive layer caused the greatest decrease in the strength of the joints in the defective joint with the defect in the middle and both sides. Also, the presence of a defect in the adhesive layer increases the creep displacement, which is much higher than the amount of this displacement in the joint without a defect. Increasing temperature to 45 ℃, and 55 ℃ has increased the creep displacement by almost 90%, compared to the creep displacement at room temperature (RT). Based on the results, the presence of defects on both sides has the greatest effect on reducing the strength of the joint (defect in the middle) and increasing the creep displacement (defect in the edge).

Non-metallic inclusions and quality of pipe joints obtained by high-frequency electric resistance welding

An incisive analysis of studies of the most frequent defects of pipe joints obtained by high-frequency electric resistance welding (HFW) is included herein with particular focus on nonmetallic inclusions (NMIs), which are the cause of defects in such welded joints. Their composition, origin and methods of elimination under industrial conditions are discussed. In order to validate the nature of defects the interpretation procedure of the composition of NMIs detected in the discontinuities of welded joints has been developed. Examples of its application on the low-carbon line pipe steels of different grades X52&ndash;X56 are presented. The compositions of NMIs found in 64 defects of welded joints of A 516-55 (09G2S) steel pipes are summarized. These compositions significantly differ from each other and correspond to the different nature of NMIs: indigenous deoxidation products based on spinel MgO∙Al2O3 (8 %), products of steel modification by calcium (62 %), exo-indigenous NMIs with residuals of mould flux (4 %) or MgO (8 %) and indi-exogenous NMIs based on MgO (18 %). The unique variation ranges of the main elements included in these groups of NMIs are used for automated determination of their origin when carrying out metallographic examination of defects by means of the Thixomet image analyzer in the conditions of factory practice. The detailed origin of NMIs makes it possible to indicate the exact location in the technology of ladle treatment and steel casting for their improvement and to enhance on this basis the quality of line pipe joints obtained by HFW.

Effect of lateral misalignment defects of rail joints on dynamic derailment behaviour in railway turnouts

This study aims to investigate the mechanism of wheel jumping derailment in the railway switch panel after a freight wagon passes over a rail joint defect (RJD) situated before the switch. For this purpose, a 3D vehicle-track (turnout) coupled dynamic model that considers the elastic deformation of the rails and wheelsets has been established. Several extreme running conditions, including sharp curves, low-speed railway turnouts, lateral misalignment defects of RJs, and empty wagons are all considered in the simulation model. The vertical wheel rise limit for the railway switch panel is presented for the evaluation of a quasi-static derailment risk. The wheel-rail impact behaviour and the evolution of the derailment processes in the switch panel are revealed, and the effects of wagon load and misalignment width of RJ sections on the vehicle’s dynamic response and running safety are investigated. The results show that the root cause of the high derailment risk in the railway switch is a lower wheel rise limit at the front region of the switch rail when compared with the mainline. This dynamic derailment limit is sensitive to the car-body load and the misalignment width. Severe lateral defects of the RJ before the switch toe should therefore be avoided.

Damage imaging algorithm for non-destructive inspection of CFRP/steel adhesive joints based on ultrasonic guided wave propagation

The paper concerns assessing the quality of the adhesive connection between a steel plate and the reinforcing CFRP laminate. A three-stage algorithm for non-destructive damage imaging was developed. As the first step, an initial study involving dispersion curves of joint components was executed to determine the material parameters and the appropriate excitation frequency. During the second step, damage identification in three-layer joints was performed using the weighted root mean square (WRMS) of the guided wave signals. A novel approach to determine the optimal values of WRMS parameters was proposed. Within the third step, the guided wavefield was recorded by scanning laser vibrometry. Visualization of the distribution of WRMS values on the surface of scanned specimens allowed efficient damage imaging. The application of statistical analysis (histograms) was used to prepare the final damage maps. The results of the investigations showed the high usefulness of the developed approach for imaging both intentionally introduced and unintended defects in adhesive joints.

Deep neural network for diagnostics of railway track components

The problem of increasing the speed of railway transportation and ensuring reliability is associated with constant monitoring of the condition of the railway tracks. The modern track measuring cars are equipped with video cameras and computer equipment for processing the received information. However, manual processing of data by operators in real-time is not possible. The article proposes a deep convolutional neural network for automatically recognizing and classifying defects in rail joints on rail track images. The rail video observation forms the image array during the passage of the track recording car. The formation of classes of rail joints is described. Regular rail joints with connectors, insulating joints, and welded joints are considered. Additional classes are identified, corresponding to various anomalous configurations of rail joints in the images. A modified structure of a pre-trained deep convolutional network is constructed. When preparing training samples, the actual images of rail joints were supplemented with artificial images obtained by affine transformations. The process of training and testing the classifier based on the developed convolutional network is described. The Transfer Learning is used to train the neural network. As a result of the experiments, the accuracy of classifying rail joints and detecting defects was at least 96%.

Risk management of cable termination faults and effective maintenance using partial discharge (PD-LT) device

One of the most important equipment in distribution networks is cable termination. The widespread use of this equipment makes it one of the most important equipment in the electricity industry and at the same time, it includes a major part of the causes of outages in power networks. For example, in 2021, this equipment is the second influential factor in the amount of undistributed energy and the increase of the SAIDI index in Isfahan Electricity Distribution Company and Conventional methods such as periodic inspections and imaging using thermovision cameras and the installation of surge arresters and the construction of parallel earths, etc. has not a significant impact on detecting faulty cable terminations and preventing outages. In this paper, an attempt has been made to obtain a solution to identify and prevent defects in cable terminations and joints by using Partial Discharge measurement by measuring the magnetic field and converting it into an audio unit by a PD-LT device. Initially, 720 cable terminations in the city of Baharestan1 were tested and analyzed. The information obtained was analyzed by Power BI software, which led to the prediction of the useful life of the tested cables. The amount of partial discharge can be a good indicator to measure the risk of failure in distribution networks.

Inflammatory-associated apoptotic markers: are they the culprit to rheumatoid arthritis pain?

Rheumatoid arthritis (RA) is a prolonged inflammatory disease resulting from autoimmune reactions that leads to local and systemic bone erosion, joint defects and functional impairment. Although the inflammation is subsided through the prescription of anti-inflammatory therapeutics, the patients persistently complained of sleepless nights due to flare pain. This indicates the possible contribution of other pathways besides inflammation in leading to RA pain. This review aims to uncover the roles and involvement of several inflammatory-associated apoptotic markers in facilitating pain transmission and processing during the pathogenesis of RA. This narrative review focused on the reports from the previous literature based on the search string of "apoptotic marker AND inflammation AND 'chronic pain' OR 'neuropathic pain' and apoptosis AND 'rheumatoid arthritis' OR arthritis from the databases including Science Direct and Scopus, considering the exclusion criteria of the published abstracts, proceedings or articles on other neuropathic pain types such as painful bowel syndrom, insterstitial cystitis, fibrosis and so on. Several studies in the literature demonstrate a close association between imbalanced apoptotic regulations and an increased number of synovial fibroblasts and inflammatory cells in RA. Cell death or specific cell survival has been linked with increased central hypersensitivity in various types of chronic and neuropathic pain. The RA-related flare pain is possibly contributed by the abnormal regulation of apoptosis through several inflammatory-related pathways, and further studies need to modulate these pathways for the putative anti-nociceptive benefits.

Long-term preservation of metacarpophalangeal joint function in traumatic defects by metatarsophalangeal osteochondral transplantation.

The integrity of the metacarpophalangeal (MCP) joints is essential for finger and hand function. Preservation of range-of-motion is one of the aims in reconstruction of complex injuries to these joints. Osteochondral transplants have shown to be reliable in reconstruction of various joint defects. This series presents three patients with traumatic injuries to four MCP joints, which were reconstructed by seven avascular osteochondral transplants of metatarsophalangeal (MTP) joints. The joints were examined for radiographic signs of resorption or joint space narrowing, and if this would affect the joints' function in the long term. In three patients (40, 45 and 48years) with complex injuries to their MCP joints (one milling, two saw injuries), four joints were reconstructed by three metatarsal head and four osteochondral transplants of the base of the proximal toe phalanges. Beside the joint itself, various soft tissue defects were reconstructed in each patient. The patients were clinically and radiographically examined after 9, 6, respectively, 7years. All patients were satisfied with the result without any pain in the MCP joints. Range-of-motion in the four affected joints rated 25, 60, 75, and 80°, DASH scores rated 13, 29, and 17, respectively. None of the patients complained of problems at their feet. Radiographic examination revealed moderate joint space narrowing in one of the four joints. In another patient, localized osteolysis was found around the screws' heads, so that the screws were removed 7years post-op. Osteochondral transplants for reconstruction of MCP defects are able to preserve function in severely injured joints even in the long term. Joint space narrowing may occur, which is not accompanied by pain, however. Since localized osteolysis can cause screw head prominence, mid-term radiographic follow-up is necessary to prevent damage to the joint. In the long term, remaining bone stock may be adequate for total joint replacement.

Effect of oscillating laser beam on the interface and mechanical properties of Ti/Al fusion welding joint

To solve the problem that cracks and brittle Ti-Al intermetallic compounds restrict the mechanical properties of Ti-Al joint, an effective connection method has been explored for laser welding of TC4 titanium alloy and 7075 aluminum alloy by oscillating laser beam, and the effect of oscillating laser beam on the interface and mechanical properties of Ti/Al fusion welding joint was also investigated. With the application of beam oscillation, some defects like pores and cracks can be avoided in welding joint, the connection width of interface layer is increased, and the diffusion of Al-to-Ti is suppressed due to the reduced interfacial heat input and the stirring effect induced by the keyhole rotating. As a result, Al-rich Ti-Al compound at interface is reduced while Ti-rich compound is formed. Generally, the property of Ti/Al joint can be significantly improved by the reduction of joint defects and the formation of lower brittle TiAl/Ti3Al compounds. As the oscillation frequency increase, the maximum load of the joint increases first but then decreases, and reached the highest value of 1852N when the 150 Hz oscillating frequency is applied, representing 76.38% enhancement compared with that without oscillation. However, under the condition of excessive oscillating frequency, the interface layer is too thin to form an effective connection, which deteriorates the joint properties.

Application of Pulse Sequence Partial Discharge Based Convolutional Neural Network in Pattern Recognition for Underground Cable Joints

In this study, a pulse sequence analysis (PSA) method is presented, which does not measure the voltage signal for the defect-type recognition of power cable joints based on partial discharges (PDs) using convolutional neural networks (CNNs). The PSA showed effective results in comparison to a conventional phase-resolved PD (PRPD) pattern, which is a combination of a PD and voltage signals. The optimal drawing formats of the PSA patterns, including the size, type, color, and marker size of the images, which influence the recognition accuracy, were evaluated. In total, 12 sets of PD data, consisting of three types of cable joint defects, were trained and tested using CNN-based models. The results show that the performance of the PSA-based CNN model is as good as that of a PRPD even when the voltage signal is lost, whereas PRPD mostly fails under such cases. The total recognition accuracy obtained from a PSA-based CNN was 95.3%, whereas that of the PRPD-based CNN was 90.6%. In addition, an advanced and useful application of a PSA pattern is discussed herein.