Study on the hydrogen-induced delayed fracture behavior of Q-P980 and MS980

In this paper, the hydrogen diffusion behavior and hydrogen induced delayed fracture (HIDF) of Q-P980 (Q-P: Quenching and Partitioning) and MS980 (MS: Martensitic steel) steels were investigated using hydrogen penetration, slow strain rate tensile (SSRT) tests, thermal desorption spectroscopy (TDS) tests, fracture analysis, and microstructural examination in this paper. The austenite in Q-P980 is massive retained-austenite (RA) with low stability. The TRIP (Transformation Induced Plasticity) effect will occur in the process of strain and change into high carbon martensite. HIDF is caused by a substantial amount of surplus hydrogen being enriched at the border and flaws. The fracture has a broad cleavage surface and is a typical quasi-cleavage fracture. MS980 has been sufficiently tempered, resulting in a substantial quantity of distributed spherical cementite (150nm) precipitating around the lath martensite. This size and form of cementite may successfully trap hydrogen while maintaining the material's mechanical characteristics. And tempering can effectively reduce the local stress level of steel, so MS980 has a very low HE susceptibility. HIDF is related to local stress and hydrogen accumulation. We suppose that Z is a constant and ZC is a critical value which associated to σ and CH (the local stress and local hydrogen concentration), rising as σ and CH rises. The atomic bonds at the crack tip, lattice position and the phase interface will fracture when ZC reaches a particular value Z. Tempering to minimize local stress and carbide precipitation to capture hydrogen are two strategies for reducing hydrogen embrittlement (HE) susceptibility, particularly for dislocation strengthened steel. Microalloying elements can generate precipitates that function as hydrogen traps and obstruct the HELP (Hydrogen Enhanced Localized Plasticity) process, lowering local stress and hydrogen accumulation.

Computer Vision-Based Detection for Delayed Fracture of Bolts in Steel Bridges

The delayed fracture of high-strength bolts occurs frequently in the bolt connections of long-span steel bridges. This phenomenon can threaten the safety of structures and even lead to serious accidents in certain cases. However, the manual inspection commonly used in engineering to detect the fractured bolts is time-consuming and inconvenient. Therefore, a computer vision-based inspection approach is proposed in this paper to rapidly and automatically detect the fractured bolts. The proposed approach is realized by a convolutional neural network- (CNN-) based deep learning algorithm, the third version of You Only Look Once (YOLOv3). A challenge for the detector training using YOLOv3 is that only limited amounts of images of the fractured bolts are available in practice. To address this challenge, five data augmentation methods are introduced to produce more labeled images, including brightness transformation, Gaussian blur, flipping, perspective transformation, and scaling. Six YOLOv3 neural networks are trained using six different augmented training sets, and then, the performance of each detector is tested on the same testing set to compare the effectiveness of different augmentation methods. The highest average precision (AP) of the trained detectors is 89.14% when the intersection over union (IOU) threshold is set to 0.5. The practicality and robustness of the proposed method are further demonstrated on images that were never used in the training and testing of the detector. The results demonstrate that the proposed method can quickly and automatically detect the delayed fracture of high-strength bolts.

A Case of Femoral Neck Insufficiency Fracture due to Tumor-Induced Osteomalacia

Tumor-induced osteomalacia (TIO) is a rare skeletal disease caused by hypersecretion of fibroblast growth factor 23 (FGF-23) from neoplasms of mesenchymal origin; patients with TIO present with insufficiency fractures, progressive bone pain, and delayed fracture unions. Herein, we report the case of a 48-year-old man with an insufficiency fracture in his left femoral neck associated with TIO. The causative tumor located in the patient’s maxillary sinus had been resected; however, complete resection was impossible due to the location of the tumor. Therefore, the patient’s osteomalacia persisted, and he experienced a left femoral neck fracture in the absence of severe trauma. Because delayed fracture union was anticipated in this patient, we performed an internal fixation using an implant with a lateral plate for angular stability and multiple screws for rotational stability. Although fracture union took 15 months, the patient’s postoperative course was uneventful, and he could walk without any symptoms or assistance at his most recent follow-up 30 months after surgery. In TIO, hypersecretion of FGF-23 leads to increased renal excretion of phosphorus, increased bone resorption of calcium and phosphorus, decreased osteoblastic bone mineralization, and decreased gastrointestinal absorption of calcium and phosphorus, leading to insufficiency fractures and delayed fracture unions. Diagnosis of TIO is often delayed due to its rarity and vague symptoms. Total resection of the causative tumor is the optimal treatment; however, in cases wherein complete tumor resection is impossible, drug therapy may be insufficient, and the underlying TIO pathology, including bone fragility, may persist. Early diagnosis of TIO is important for preventing insufficiency fractures; however, when fractures are unavoidable, the surgical treatment of femoral neck fractures in patients with osteomalacia should account for a longer time frame for complete fracture union and therefore utilize implants with sufficient stability.

Delayed fracture union in a case of vitamin D dependent rickets associated with pulmonary tuberculosis - a case report

<p>Rickets is a defect of bone mineralization caused by vitamin D deficiency, seen most significantly at growth plates that result in radiological bony abnormalities like metaphyseal flaring and cupping, physeal widening with focal and generalised osteomalacia.<strong> </strong>Here we present a rare case of 7 years old male, a case of vitamin D3 deficiency rickets in a known case of multi drug resistant pulmonary tuberculosis. The patient had suffered left proximal fibular fracture following trivial fall 1.5 month back and had delayed bony union leading to difficulty in walking and pain. The patient was treated with oral vitamin D supplementation. In vitamin D deficiency rickets, there is decreased bone mineralization leading to weak bones and delayed fracture healing in children. Low serum vitamin D levels also caused decreased immunity with increased susceptibility to respiratory infections like pulmonary tuberculosis. Appropriate treatment with injectable or oral vitamin D3 with adequate exposure of sunlight and proper nutrition is the best modality of treatment.<strong></strong></p><p><strong> </strong></p>

Recent Progress of Low and Medium-Carbon Advanced Martensitic Steels

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm- working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, good cold-formability, superior toughness and fatigue strength, and delayed fracture strength due to a mixture of martensite and retained austenite, compared with the conventional martensitic steels. In addition, the hot- and warm-stamping and forging contribute to enhance the mechanical properties of the AMSs due to grain refining and the improvement of retained austenite characteristics. The case-hardening process (fine particle peening and vacuum carburization) is effective to further increase the fatigue strength.

Comparative Study of Conservative Vs Surgical Management of Clavicle Fractures

Background: Clavicle Fractures is one of the common fractures of upper limb accounting for approximately 40 % of all shoulder fractures. Till recently all clavicle fracture were treated conservatively, but now interest in surgical management is rising. This study was carried out to see if Surgical management outweighs the conservative treatment of Fractures Of Clavicle. Methods: A total of 40 cases satisfying inclusion and exclusion criteria were included in the study. Alternate patients were allocated to operative and conservation groups. In total 20 patients were operated operatively and 20 patients were treated conservatively. Outcome was analysed in terms of radiological union and functional outcome of the patient. Constant and Murley score was used as a score to evaluate final outcome. Results: In this study, the 20 patients who were operated upon had an average union time of 7.8 weeks; 1 patient had delayed fracture union by 12 wks. 20 patients in conservative group had normal union of fractures with 1 patient going into non-union. Average union time in the conservative group was 9.4 weeks, which was more than the 7.8 weeks seen in the group treated operatively. Mal-union was present in 7 of the 20 patients treated conservatively, and 5 of these 7 had a visible deformity. Out of these patients with mal-union 1 had poor functional outcome, 3 had good to excellent outcome and 3 had satisfactory functional outcome. 4 of these had restricted movements terminally and 2 had pain on movement. Conclusions: From our study based on patients of clavicle fractures, it can be concluded that the operative group had significantly higher excellent outcomes as compared to the conservatively- managed group, based on the Constant and Murley score. Keywords: Clavicle Fractures, Constant and Murley Score, Operative Clavicle Fracture Management, Clavicle Fracture Functional Outcome.