Ductile damage prediction of AA 5754 sheet during cold forming condition

Mohamed Amer,Mostafa Shazly,Mohamed Mohamed,Abdel Aziz Hegazy 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.10

Aluminium sheet parts manufactured by cold-forming processes are subjected to ductile damage due to the plastic deformation. Tool design based on the experience and failure prediction using simple criteria in sheet metal forming can cause high cost of material scrap and tools modifications. Consequently, the ability to predict ductile damage gives full control of the forming process. This work was conducted to evaluate the predictive capability of different damage models for AA 5754 under cold forming condition. The models are calibrated using published tensile and forming limit diagram data for AA 5754. A set of experimental cup tests for AA 5754 sheet were conducted to validate the selected models. An FE model was developed to simulate the cup test process using LS-DYNA software. The selected models used were the Johnson-Cook, continuum damage model (CDM), Gurson model and the generalized incremental stress state-dependent model (GISSMO) model. The experimental results of the cup tests were compared with the simulation results from different damage models concluding that the Gissmo model was able to show a good agreement with the experimental results.

Water Sorption/Desorption Kinetics and Convective Drying of Eucalyptus globulus Wood

( Mahyoub AMER ),( Bousselham KABOUCHI ),( Salah El ALAMI ),( Brahim AZIZE ),( Mohamed RAHOUTI ),( Abderrahim FAMIRI ),( Abdelwahed FIDAH ) 한국목재공학회 2019 목재공학 Vol.47 No.5

Radial and tangential water diffusion in Eucalyptus globulus wood was investigated using three mature trees from a forest in Khemis Sahel (North Morocco). Absorption and desorption kinetics experiments were conducted at ambient temperature (25 °C) and 30 °C, respectively, and a relative humidity of 60%. The diffusion coefficients in the two directions were determined under imposed hygrothermal conditions; they were greater in the radial direction for the absorption as well as desorption processes. Convective drying under load, preceded by reconditioning and followed up by balancing, revealed the drying conditions that corresponded to the appropriate drying schedules for E. globulus wood. This was verified by measuring the cracks and bowsbefore and after drying of boards.

One-stage Hip Reconstruction for Developmental Hip Dysplasia in Children over 8 Years of Age

Irfan Qadir,Saeed Ahmad,Atiq uz Zaman,Chirag Muhammad Khan,Shahzad Ahmad,Amer Aziz 대한고관절학회 2018 Hip and Pelvis Vol.30 No.4

Purpose: This study was performed to assess the clinical and radiological outcomes following one-stage hip reconstruction, consisting of open reduction femoral shortening and pelvic osteotomy, for neglected developmental dislocation of the hip (DDH). Materials and Methods: This is a retrospective analysis of 77 hips in 65 patients (46 females and 19 males; 12 had bilateral dislocations), operated at a Ghurki Trust Teaching Hospital in Pakistan between 2013 and 2015. The average age at surgery was 11.02±3.43 years. According to the Tönnis classification, there were 10, 14, 22, and 31 patients in grades 1, 2, 3, and 4, respectively. The pelvic procedure utilized in this study was triple osteotomy (47 hips) followed by double and Salter osteotomy (18 and 12 hips, respectively). Postoperative evaluations were conducted using the modified MacKay’s scoring system (functional outcomes) and Severin’s scoring method (radiological assessment). Results: Postoperatively, there were 38 (49.4%), 19 (24.7%), 14 (18.2%), and 6 (7.8%) hips in Severin grade I, II, III and IV, respectively. According to the modified McKay criteria, there were 22 hips (28.6%) in excellent condition, 44 (57.1%) in good condition, 9 (11.7%) in fair condition and 2 (2.6%) in poor condition. Both patients with poor outcomes had an unstable, painful hip with evidence of avascular necrosis of the femoral head. Conclusion: Based on the results presented here, we recommend the single stage procedure of open reduction, femoral shortening and pelvic osteotomy for treatment of DDH in older children with good to excellent functional and radiological outcomes.

Component Alignment in Simultaneous Bilateral versus Unilateral Total Knee Arthroplasty

Irfan Qadir,Bahar Shah,Muhammad Waqas,Umair Ahmad,Shahzad Javed,Amer Aziz 대한슬관절학회 2019 대한슬관절학회지 Vol.31 No.1

Purpose: The purpose of this study was to investigate differences in component alignment between first and second knees in simultaneous bilateral total knee arthroplasty (SBTKA) and unilateral TKA (UTKA).Materials and Methods: 274 SBTKAs and 198 UTKAs were included in study. Patients were divided into three groups as SBTKA on the right knee (group A), SBTKA on the left knee (group B) and UTKA (group C). Femoral and tibial component alignment was checked in both coronal plane (alpha [α] and beta [β] angles) and sagittal plane (gamma [γ] and delta [δ] angles) radiographs.Results: There were no statistically significant differences among groups in the preoperative anatomical varus angle and Kellgren–Lawrence gonarthrosis classification grade (p=0.139 and p=0.329, respectively). In the coronal plane, the alignment of femoral component (α angle) and tibial component (β angle) was similar in all three groups (α angle, 95.01 vs. 95.14 vs. 94.9, p=0.945; β angle, 90.03 vs. 89.67 vs. 89.98, p=0.483). The sagittal plane alignment of femoral component (γ angle) and tibial component (δ angle) did not show significant differences (γ angle, 7.04 vs. 6.98 vs. 7.00, p=0.132; δ angle, 86.56 vs. 87.41 vs. 86.73, p=0.610).Conclusions: The angular alignment of components was similar between SBTKA and UTKA.

Vertebral Endplate Changes Correlate with Presence of Cartilaginous Endplate in the Herniated Disc Tissue: Factor Predicting Failure of Conservative Treatment

Latif Rabia,Imran Sumera,Ahmad Ijaz,Ilyas Muhammad Saad,Aziz Amer,Zehra Uruj 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.2

Study Design: Cross-sectional comparative. Purpose: To characterize the scores of disc degeneration, inflammation, and nerve density in herniated disc samples and associate findings with the presence of vertebral endplate (VEP) changes on magnetic resonance imaging (MRI). Overview of Literature: Considering the role of disc composition in spontaneous regression and persistence of pain during conservative management, it is important to identify the influencing factors. VEP changes are highly associated with disc degeneration, but their correlation with herniated disc composition has not yet been reported. Methods: Fifty-one discs were obtained from patients undergoing surgery for herniated disc. Their ages ranged from 19-65 years, and 31/51 were male. Pre-surgical T1 and T2 weighted lumbar-spine MRIs were analyzed to observe Pfirrmann grade, VEP defects, herniation type, Modic changes, and high-intensity zones (HIZ) at the affected level. Five-micron thick sections were stained with hematoxylin and eosin, Alcian blue periodic acid–Schiff stain; examined for histological degeneration scores (HDS; 0–15), inflammation (0 [absence]–3 [severe]), and presence of cartilaginous endplate (CEP). Three-micron thick sections were stained with protein-gene-product 9.5 and expression was counted/mm2. Data was analyzed, and p<0.05 was considered to indicate statistical significance. Results: VEP defects, Modic changes, and HIZ were respectively observed in 30/51, 16/51, and 6/51 of the samples. CEP was observed in 26/51 samples and in 23/51 with endplate defects. Discs with adjacent VEP defects showed increased HDS (p<0.001) and inflammation (p<0.001). Discs with adjacent Modic changes also revealed increased HDS (p=0.01). Histological sections with CEP showed increased HDS (p<0.001) and inflammation (p<0.001), and nerve density was significantly positively correlated with HDS (r=0.27, p=0.02). Conclusions: VEP changes can modulate degeneration and inflammation of herniated discs. Presence of these changes is highly predictive of the occurrence of CEP in herniated discs, which leads to slow resorption and persistent clinical symptoms.

Outcomes of Direct Infrapectineal Buttress Plate for Quadrilateral Surface Fractures of Acetabulum Using an Anterior Intrapelvic Approach

( Umair Nadeem ),( Irfan Qadir ),( Jahanzeb Mazari ),( Atiq Uz Zaman ),( Amer Aziz ) 대한고관절학회 2021 Hip and Pelvis Vol.33 No.1

Purpose: Reduction and stable fixation of the quadrilateral plate are challenging primarily due to its location in the true pelvis, limited bone stock, juxta-articular nature, and its comminution. The current study aimed to investigate the quality of reduction and functional outcomes after open reduction and internal fixation (ORIF) with infrapectineal buttress plating of the quadrilateral surface via an anterior intrapelvic approach. Materials and Methods: We conducted a retrospective review of twenty-one patients with acetabular fractures involving quadrilateral plate operated at Ghurki Trust Teaching Hospital between January 2017 and December 2018. Radiological assessment of the quality of reduction was conducted using criteria described by Matta. Functional outcomes were evaluated using a modified Postel Merle d’Aubigné score. Results: The current study included 15 males and 6 females with a mean age of 40.67±12.17 years (range, 22- 62 years). The most common fracture pattern was anterior column and posterior hemi-transverse in eight patients followed by true bicolumn and T-type fractures in seven and four patients respectively. Both transverse fractures were transtectal. The quality of reduction according to Matta criteria was anatomical in 14 patients, imperfect in five and poor in two. Functional outcomes were excellent in 47.6% cases, good in 42.9%, and fair in 9.5% cases. Both patients with fair outcomes had non-anatomical reduction, and one required total hip arthroplasty at a later time. Conclusion: Quadrilateral plate reconstruction with an infrapectineal buttress plate applied though an anterior intrapelvic approach provides high rates of anatomical reduction and yields good functional outcomes.