Lifetime Analysis of Dies Manufactured by Conventional Processes and Reconditioned by Deposition Welding Operation.

The refurbishment of dies by the deposition welding of wear areas is an efficient and economical process. The aim of this study was to conduct a comparative analysis of the lifetimes of different types of dies for the manufacturing of wagon wheels. The analyzed dies were manufactured by conventional processes (Type I) and reconditioned through a deposition welding procedure using a dedicated electrode (Type II). The Anderson-Darling test was conducted to analyze the goodness of fit of the lifetime data specific to the die types. The maximum likelihood estimation method (MLE) with a 95% confidence interval (CI) was applied in order to estimate the lifetime distribution parameters. It was found that the lifetimes of type II dies were longer than those of type I dies. The mean time to failure (MTTF) recorded for reconditioned dies was 426 min, while the mean time to failure of dies manufactured by conventional processes was approximatively 253 min. In addition, an accentuated hazard rate for type I dies compared to type II dies was observed. The results of this analysis emphasized the fact that dies can be restored to their initial operating capacity by successfully using deposition welding procedures that confer a high resistance to operational loads. At the same time, the use of these procedures allows for the sustainable development of resources and waste management.

The Displacements Study of Birch Veneer Layers from Composition of Plywood during Water Jet Cutting Using the Finite Element Method (FEA).

This paper presents a study of the deformations of the birch veneer layer of plywood composed of veneer sheets, each with a thickness of 1.4 mm. Displacements in the longitudinal and transverse directions were analyzed in each layer of veneer from the composition of the board. Cutting pressure was applied to the surface equal to the diameter of the water jet, located in the center of the laminated wood board. Finite element analysis (FEA) does not study the breaking of the material or its elastic deformation, but only what happens from a static point of view when maximum pressure acts on the board, which causes detachment of the veneer particles. The results of the finite element analysis indicate maximum values of 0.0012 mm in the longitudinal direction of the board located in the proximity of the application of the maximum force of the water jet. Additionally, in order to analyze the recorded differences between both longitudinal and transversal displacements, estimation of statistical parameters with 95% confidence intervals (CI) was applied. The comparative results indicate that the differences are not significant for the displacements under study.

Chainsaw operators' exposure to occupational risk factors and incidence of professional diseases specific to the forestry field.

Purpose. This article focuses on detailed studies regarding the analysis of occupational risk factors on health and occupational disease, namely, the influence of noise, hand-arm vibration, wet bulb globe temperature (WBGT) index and exposure to particulates. Methods. This study measured the equivalent acoustic level (LAeq), daily vibration exposure (A(8)), WBGT index and particulate concentration in the respirable area of the worker. The inferential analysis consisted of the application of specific statistical methods: a probability plot with 95% confidence interval, the Anderson-Darling statistic and 87th percentile estimation. A sample of 107 chainsaw operators was medically evaluated, out of which 30 workers were suspected of having professional pathologies and were hospitalized in the university clinic. Results. The measurements highlight: exceeding the legal limit for noise exposure; 13% of cases exceeding the limit of 2.5 m/s2 for hand-arm vibration; dust exposure generally within legal limits; WBGT shows the thermal stress of the workers. Following the medical evaluation, osteomusculoskeletal disorders (25.23%), Raynaud's syndrome (0.93%) and bilateral hearing loss (3.74%) were identified. Conclusions. Analysis of the levels of exposure to the risk factors, the typology and the incidence of occupational diseases requires the need to adopt new preventive measures.

Reliability Estimation of Parameters of Helical Wind Turbine with Vertical Axis.

Due to the prolonged use of wind turbines they must be characterized by high reliability. This can be achieved through a rigorous design, appropriate simulation and testing, and proper construction. The reliability prediction and analysis of these systems will lead to identifying the critical components, increasing the operating time, minimizing failure rate, and minimizing maintenance costs. To estimate the produced energy by the wind turbine, an evaluation approach based on the Monte Carlo simulation model is developed which enables us to estimate the probability of minimum and maximum parameters. In our simulation process we used triangular distributions. The analysis of simulation results has been focused on the interpretation of the relative frequency histograms and cumulative distribution curve (ogive diagram), which indicates the probability of obtaining the daily or annual energy output depending on wind speed. The experimental researches consist in estimation of the reliability and unreliability functions and hazard rate of the helical vertical axis wind turbine designed and patented to climatic conditions for Romanian regions. Also, the variation of power produced for different wind speeds, the Weibull distribution of wind probability, and the power generated were determined. The analysis of experimental results indicates that this type of wind turbine is efficient at low wind speed.