Evaluation of Fatigue and Fracture properties of Al-Li Alloys - Annual Report 1988-89.

This annual report describes results obtained to-date on fatigue and fracture properties of Lital-A aluminium lithium alloy. Low cycle fatigue data on 12 .5mm thick material and R-curve results on thinner 1, 2 and 3mm thick material are presented. Fatigue crack growth data under constant amplitude loading reflecting the effect of stress ratio, rolling direction and material thickness are presented. Typical results on the effect of rolling direction under spectrum loading are shown. Fatigue crack growth behaviour of Lital-A series of Al-Li alloys is different from conventional Al-alloys . Lital-A exhibits a higher threshold stress intensity and lower fracture toughness, resulting in less favorable damage tolerance properties

Random load sequence for full scale fatigue test of MiG-21M airframe

Random load sequence for the full scale fatigue test of Mig-21M airframe is derived from flight data. Loads corresponding to 'g' peak/trough are derived from information on Mach number, angle of attack and weight of the aircraft. The random load sequence will be applied flight-by-flight on the airframe during the full scale test. These loads will be simulated with the help of 16 servo-hydraulic actuators. The loading actions of each of these actuators are derived. This report describes, in detail, the derivation of the random load sequence and the loading action on the multi-actuator test rig to be used in the Mig-21M airframe. A mini-load sequence is derived by omitting lower g-ranges on the basis of their cumulative damage contribution. It is suggested that this mini-load sequence be used in the full scale test of Mig-21M airframe

Fatigue crack growth behaviour of aluminum-lithium alloy

Fatigue crack growth behavior was investigated in 8090 plate and sheet material under constant-amplitude as well as spectrum loading. The effect of rolling direction, thickness, stress ratio, spectrum load truncation, and omission level on crack growth were studied. 8090-T85113; plate material has significant anisotropy in crack growth behavior under spectrum loading. No significant effect of plate thickness on crack growth was observed. Lower truncation level led to reduced growth rate at a given reference stress intensity. Crack closure level in spectrum load test was higher compared to constant amplitude closure level

Observation of crack closure using a crack mouth opening displacement gauge

A crack mouth opening displacement (CMOD) gauge has been designed to estimate the crack length as well as the crack opening stress level in an automated fatigue crack propagation test programme. The CMOD gauge accurately predicts crack tip opening levels in K-controlled tests with constant K, K increasing or K decreasing. In all three K-controlled tests with a single 100% overload cycle, the CMOD gauge does not measure the crack tip opening stress level over a large range of crack lengths after the application of the overload. The CMOD gauge measures the stress level at which the overload plastic zone site opens. Caution should thus be exercised in using the crack opening stress level, estimated by the CMOD gauge, to explain fatigue crack propagation under arbitrary load sequences from the viewpoint of crack closure phenomena

Does Late Presentation of Displaced Supracondylar Humerus Fracture in Children Influence Outcomes of Surgery?

Introduction: Displaced Supracondylar Humerus Fracture (SCHF) in children is usually treated with percutaneous pinning on emergency basis in fresh cases. Though there are spectrum of modalities treatment reported, still paucity of literature available to compare between cross versus lateral pinning in late presented cases with massive swelling and poor soft tissue condition. Aim: To compare the efficacy and safety of percutaneous medial-lateral cross Kirschner wire (K-wire) and two lateral K-wire fixation in treatment of displaced SCHF in children. Materials and Methods: We retrospectively reviewed the functional and radiological result of treatment in 58 children (aged 2-12 years) with displaced SCHF presented more than two days duration after injury. Among 58 patients, (n=31) treated with cross K-wire (Group A) and (n=27) treated two lateral K-wire fixation (Group B). Statistical analysis of different variables was performed using SPSS software (version 20.0; SPSS, Chicago, Illinois). A p-value of <0.05 was considered to be statistically significant. Results: Both the group were similar in terms of mean demographic variables. Mean delay of presentation was 4.07 days and 4.87 days in Group A versus Group B respectively. In Group A, three patient had iatrogenic ulnar nerve injury. There were also no significant differences (p>0.05) between groups with respect to the Baumann angle, change in the Baumann angle, Flynn grade, carrying angle, elbow range of motion, return to function, or complications. Conclusion: Although both the technique appears to be equally effective in term of stability and outcomes. But lateral pinning has a definite edge over cross pinning in respect to reduced incidence of iatrogenic ulnar nerve injury, especially in late presenters with severe swelling and poor soft tissue conditions

PATTERN OF MEDICATION USE AMONG ELDERLY INPATIENTS IN A TERTIARY CARE HOSPITAL OF NORTHEAST INDIA

Objectives: The objective of the present study was to assess the pattern of medication use among elderly inpatients of internal Medicine Wards and to evaluate inappropriate prescribing with the help of Beers criteria 2019. Methods: It was a retrospective hospital data-based study. Data were obtained from treatment charts of elderly inpatients stored in the Medical Records Department. Total 236 treatment record charts of patients ≥60 years of either sex was obtained from the period of July 2015 to December 2015 and the information were noted in predesigned pro forma. Results: The mean±SD age of the patients was 69.07±7.72 years with male preponderance (58.5%). Maximum number of patients were having respiratory disorders (57.6%), followed by kidney diseases (20.8%), cardiovascular diseases (18.6%), and so on. A total of 2683 drugs were prescribed with average number of 10.68±4.74 drugs per prescription. Only 363 formulations were prescribed by their generic names and 29.1% drugs were prescribed as fixed dose combinations. Polypharmacy was seen in 91.5% and 39%, respectively, in hospital stay and during discharge. About 60.5% drugs were prescribed from the National list of essential medicine. Total 57 drugs were found to be potentially inappropriate. About 22% patients received at least one drug which was potentially inappropriate according to Beers criteria and around 14% drugs were prescribed inappropriately. Conclusion: This study suggests that use of potentially inappropriate medications is common in elderly patients, some of them associated with high degree of risk in terms of worsening of the co-morbidity or drug-drug interactions. There is a need for nationwide assessment and strategies that may reduce or overcome such high prevalence