Influence of laser peening on fatigue crack initiation of notched aluminum plates

Vignaud Granados-Alejo,Carlos Rubio-Gonzalez,Yazmin Parra-Torres,J. Antonio Banderas,Gilberto Gómez-Rosas 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.6

Notches such as slots are typical geometric features on mechanical components that promote fatigue crack initiation. Unlike for components with open hole type notches, there are no conventional treatments to enhance fatigue behavior of components with slots. In this work we evaluate the viability of applying laser shock peening (LSP) to extend the fatigue life of 6061-T6 aluminum components with slots. The feasibility of using LSP is evaluated not only on damage free notched specimens, but also on samples with previous fatigue damage. For the LSP treatment a convergent lens was used to deliver 0.85 J and 6 ns laser pulses 1.5 mm in diameter by a Q-switch Nd: YAG laser, operating at 10 Hz with 1064 nm of wavelength. Residual stress distribution was assessed by the hole drilling method. A fatigue analysis of the notched specimens was conducted using the commercial code FE-Safe and different multiaxial fatigue criteria to predict fatigue lives of samples with and without LSP. The residual stress field produced by the LSP process was estimated by a finite element simulation of the process. A good comparison of the predicted and experimental fatigue lives was observed. The beneficial effect of LSP in extending fatigue life of notched components with and without previous damage is demonstrated.

Axial-Shear-Flexural Interaction Behavior of a Double-Span Steel Beam Under a Column-Loss State Using the Pushdown Method

Nur Ezzaryn Asnawi Subki,Hazrina Mansor,Yazmin Sahol Hamid,Gerard A. R. Parke 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.3

The axial-shear-flexural interaction behavior of a double-span steel beam in a column-loss state is a complex phenomenon that demands more explanation. Nowadays, it is common practice to study the column loss scenario of a double-span steel beam using the pushdown method. Generally, two pushdown methods are commonly used: the Monotonic Pushdown Force (MPF) and the Distributed Pushdown Force (DPF) methods. Many current researchers adopted the MPF approach due to its practical and straightforward instrumentation for experimental testing compared to the DPF approach. However, the DPF approach would better approximate the actual collapse behavior of the structure in a column-loss event since it resembles the proper form of gravity loads. This paper aimed to demonstrate how these two approaches result in significantly different behavior in double-span steel beam collapse, particularly on the axial-shear-flexural interaction behavior. A finite element analysis using ABAQUS software was undertaken on a validated double-span steel beam model. In the MPF approach, the results have highlighted the importance of the tensile catenary action in the overall structural resistance of the double-span beam against collapse. The tensile catenary action dominated the load-resisting mechanism of the double-span beam at a large deformation state and interrupted the flexural resistance development. The stretching effect induced by the tensile catenary action has avoided the inelastic local buckling and allowed for greater rotation capacity on the beam assembly. However, under the DPF approach, the double-span beam has limited tensile catenary action build-up with high shear force development after the plastic hinge formation. The significant effects of the high shear force development on the double-span beam behavior were highlighted in this study.

Trends in post osteoporotic hip fracture care from 2010 to 2014 in a private hospital in Malaysia

Swan Sim Yeap,M.F.R. Nur Fazirah,C. Nur Aisyah,Siti Yazmin Zahari Sham,Intan Nureslyna Samsudin,Subashini C. Thambiah,Fen Lee Hew,Boon Ping Lim,Yew Siong Siow,Siew Pheng Chan 대한골다공증학회 2017 Osteoporosis and Sarcopenia Vol.3 No.2

Objective: Following an osteoporotic fracture, pharmacological treatment is recommended to increase bone mineral density and prevent future fractures. However, the rate of starting treatment after an osteoporotic hip fracture remains low. The objective of this study was to survey the treatment rate following a low-trauma hip fracture at a tertiary private hospital in Malaysia over a period of 5 years. Methods: The computerised hospital discharge records were searched using the terms “hip,” “femur,” “femoral,” “trochanteric,” “fracture,” or “total hip replacement” for all patients over the age of 50, admitted between 2010 and 2014. The medical charts were obtained and manually searched for demographic data and treatment information. Hip operations done for nonelow-trauma-related fracture and arthritis were excluded. Results: Three hundred seventy patients over the age of 50 years were admitted with a hip fracture, of which 258 (69.7%) were low trauma, presumed osteoporotic, hip fractures. The median age was 79.0 years (interquartile range [IQR], 12.0). Following a hip fracture, 36.8% (95 of 258) of the patients received treatment, but out of these, 24.2% (23 of 95) were on calcium/vitamin D only. The median duration of treatment was 1 month (IQR, 2.5). In 2010, 56.7% of the patients received treatment, significantly more than subsequent years 2011e2014, where approximately only 30% received treatment. Conclusions: Following a low-trauma hip fracture, approximately 72% of patients were not started on active antiosteoporosis therapy. Of those who were, the median duration of treatment was 1 month. This represents a missed opportunity for the prevention of future fractures.

Myeloperoxidase Is Associated with Insulin Resistance and Inflammation in Overweight Subjects with First-Degree Relatives with Type 2 Diabetes Mellitus

Anel Gómez García,Mireya Rivera Rodríguez,Carlos Gómez Alonso,Daysi Yazmin Rodríguez Ochoa,Cleto Alvarez Aguilar 대한당뇨병학회 2015 Diabetes and Metabolism Journal Vol.39 No.1

Background: Family history of type 2 diabetes mellitus (T2DM) is one of risk factors for that in future a subject can develop diabetes. Insulin resistance (IR) is important in the pathogenesis of T2DM. There is evidence that oxidative stress plays an important role in the etiology and/or progression of diabetes. Myeloperoxidase (MPO) participates in developing of inflammation. The objective was to investigate if MPO is associated with IR and inflammation in individuals with first-degree relatives of T2DM. Methods: Cross-sectional study in 84 overweight individuals with family history of T2DM divided in two groups according to IR, group with IR (homeostasis model assessment [HOMA] ≥2.5; n=43) and control group (CG; HOMA <2.5; n=41). Complete clinical history and a venous blood sample were collected for measuring glucose and lipids profile, insulin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), MPO, glutathione reductase (GRd), glutathione peroxidase, and superoxide dismutase. Results: MPO, TNF-α, and IL-6 were higher in patients with IR than in CG (MPO: 308.35 [190.85 to 445.42] vs. 177.35 [104.50 to 279.85], P=0.0001; TNF-α: 13.46 [10.58 to 18.88] vs. 9.39 [7.53 to 11.25], P=0.0001; IL-6: 32.93 [24.93 to 38.27] vs. 15.60 [12.93 to 26.27]; P=0.0001, respectively). MPO was associated with IR (rho de Spearman=0.362, P=0.001). In the analysis of lineal regression, MPO predicts IR (β, 0.263; t, 2.520; P=0.014). In the univariate analysis, MPO had an odds ratio of 9.880 for risk of IR (95% confidence interval, 2.647 to 36.879). Conclusion: MPO had relation with IR and inflammation parameters in overweight subjects with first-degree relatives of T2DM. We need studies on a casual relationship and molecular mechanisms among the increased serum MPO levels, inflammation markers, and IR.

Different reference ranges affect the prevalence of osteoporosis and osteopenia in an urban adult Malaysian population

Swan Sim Yeap,Subashini C. Thambiah,Intan Nureslyna Samsudin,Geeta Appannah,Nurunnaim Zainuddin,Safarina Mohamad-Ismuddin,Nasrin Shahifar,Salmiah Md-Said,Siti Yazmin Zahari Sham,Subapriya Suppiah,Fen 대한골다공증학회 2020 Osteoporosis and Sarcopenia Vol.6 No.4

Objectives: To determine the prevalence of osteopenia (OPe) and osteoporosis (OP) in an urban adult population in Malaysia, and to compare the change in the prevalence when using a Caucasian compared to an Asian reference range. Methods: A cross-sectional random sample of the population aged between 45 and 90 years from the state of Selangor, Malaysia, was invited to attend a bone health check-up. Participants with diseases known to affect bone metabolism or who were on treatment for OP were excluded. Bone mineral density was measured using dual energy X-ray absorptiometry. Based on the World Health Organization definitions, the prevalence of OPe and OP was calculated using the Asian and Caucasian T-scores. Results: A total of 342 subjects (222 females, 120 males), with a mean age of 59.68 (standard deviation: 8.89) years, who fulfilled the study criteria were assessed. Based on the Asian reference range, there were 140 (40.9%) subjects with OPe and 48 (14.0%) with OP. On applying the Caucasian reference range, there were 152 (44.4%) subjects with OPe and 79 (23.1%) with OP, with significant increases in males, females, and Chinese ethnic groups. Overall, 75 (21.9%) of subjects had a change in their diagnostic status. T-scores were consistently lower when the Caucasian reference range was used. Conclusions: In a healthy urban Malaysian population, the prevalence of OP is 14.0% and OPe is 40.9%. Application of a Caucasian reference range significantly increased the number of subjects with OP and may potentially lead to over-treatment.