Silicon dioxide or silica is the earth's most abundant mineral. The primary pulmonary illness attributable to silica exposure is silicosis, which is observed in three forms: classic, accelerated and acute. A case of silicosis is presented in this article who has been working in a stone-cutting plant. He had suffered from symptoms of silicosis one year after employment in this plant (acute form), but his radiologic findings were compatible with accelerated or chronic silicosis. One of the important occupational diseases is silicosis, which is not treatable but is preventable. However, because of lack of appropriate engineering controls or personal protective devices in some workplaces we observe cases of silicosis yet.

Background: Production process of most factory-made products is harmful to our health and environment. Silica is the most important stone used in stone cutting factories. Numerous researches have reported respiratory diseases due to the inhalation of these particles in various occupations. Silicosis is a disease with typical radiographic pattern caused as the result of inhalation of silica particles. According to the intensity of exposures and onset of initiation of clinical symptoms silicosis is classified into three groups of acute, chronic and accelerated forms. The present study evaluated silicosis among stone cutter workers.Materials and Methods: This cross sectional study was performed on stone cutter workers in Malayer city (Azandarian) between 2008 and 2009. Respiratory data of our study participants were collected with a respiratory questionnaire and performing spirometry tests and chest radiography.Results: Among our participants, 16 silicosis cases were diagnosed by radiographic changes. Among them, 10 workers had exposure for more than three years and 6 workers were smokers. Eleven workers had an abnormal radiographic pattern on their chest x-rays. Seven workers had obstructive and 4 workers had restrictive spirometric patterns.Conclusion: Prevalence of silicosis was high among our understudy workers and preventive strategies are required to control it.

A prototype of a straw chopper, equipped with a discharge system was designed and fabricated in the Department of Mechanics of Agricultural Machinery, University of Tehran, Karaj, Iran. To test for the effective performance of the machine, the effects of such parameters as: drum speed (at three levels of: 400, 540, and 800 rpm), screen size (at two levels: 2.5 and 4 cm), and number of blades on each flange (4 and 8 blades), on power requirement for particle size reduction, chopping capacity, and straw particle size distribution were investigated. Based on the results, with increase in drum speed, power requirement as well as threshing capacity increased. There was no significant difference observed between drum speeds of 540 and 800 rpm as regards particle size distribution, while a speed of 400 rpm resulted in longer particles, therefore a drum speed range of 540 to 800 rpm was recommended. With decrease in screen openings' size, the power requirements increased while the threshing capacity decreasing. Screen size of 2.5 cm led to finer particles. With an increase in the number of blades on each flange, the power requirements decreased while the threshing capacity increasing. Since there was no significant difference observed between the numbers of the two sets of blades as regards particle size distribution, it is recommended that 8 blades be installed on each flange. The power requirement can thus be reduced and the cutting capacity increased.

There is a direct relationship between the efficiency of mechanized excavation in hard rocks and that of disc cutters. Disc cutter wear is an important effective factor involved in the functionality of tunnel boring machines. Replacement of disc cutters is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate, and has a major effect on the total time and cost of the tunneling projects. When these machines bore through hard rocks, the cutter wear considerably affects the excavation process. To evaluate the performance of the cutters, first, it is essential to figure out how they operate the rock cutting mechanism; secondly, it is important to identify the key factors that cause the wear. In this work, we attempt to introduce a comprehensive numerical method for estimation of disc cutter wear. The field data including the actual cutter wear more than 1000 pieces and the geological parameters along the Kani-Sib transmission tunnel in the northwest of Iran are compiled in a special database that is subjected to a statistical analysis in order to reveal the genuine wear rule. The results obtained from the numerical method indicate that with an increase in the wear of disk cutter up to 25 mm, the applied normal and rolling forces can be multiplied by 2. 9 and 2. 7, respectively, and by passing the critical wear, the disk cutters lose their optimal performance. This method also shows that confining pressure will increase the wear of the disc cutter. By the proposed formulation, the cutter consumption rate can be predicted with a high accuracy.

Summary In this paper, the effect of cutter edge shape on the failure mechanism of rock has been investigated using particle flow code in two directions (PFC2D). Particle flow code represents a rock mass as an assemblage of bonded rigid particles. The standard process of generating a PFC2D assembly to represent a test model involves: particle generation, packing the particles, isotropic stress installation (stress initialization), floating particle (floater) elimination and bond installation. In PFC2D circular disks are connected with cohesive and frictional bonds and confined with planar walls. The values assigned to the strength bonds influence the macro strength of the sample. Friction is activated by specifying the coefficient of friction and is mobilized as long as particles stay in contact. Tensile cracks occur when the applied normal stress exceeds the specified normal bond strength. Shear cracks are generated as the applied shear stress surplus the specified shear bond strength either by rotation or by shearing of particles. The tensile strength at the contact immediately drops to zero after the bond breaks, while the shear strength decreases to the residual friction value. For all these microscopic behaviours, PFC only requires selection of the basic micro-parameters to define contact and bond stiffness, bond strength and contact friction, but these micro-parameters should provide the macroscale behaviour of the material being modelled. The code uses an explicit finite difference scheme to solve the equation of force and motion, and hence one can readily track initiation and propagation of bond breakage through the system. For this purpose, two numerical models with different tensile strength of 5 MPa and 25 MPa were built and compressed by two different confining pressures of 5 MPa and 25 MPa, respectively. Eight disc cutters with different edge shape peneterate into the model at the rate of 0. 02 m/s till 4 mm of disc peneteration is reached. Totally 16 simulation has been done. The rock materials, below the cutters, show three different mechanical behavior i. e. failure, plastic and elastic behavior. The failure zone is fully fractured. The plastic zone is consisted of partially micro crack with several major fractures. The elastic zone is an undamaged zone. The shape of cutter edge has important effect on extension of three introduce zones. When tensile strength is 5 MPa, the failure stress resulted from penetration of convex-shape cutter is the lowest one, 5. 3 MPa while the number of total cracks is maximum one, 102. It means that the cutter shape controls the failure stress and failure extension when it cuts the weak rock. When tensile strength is 25 MPa, the failure stress resulted from penetration of different cutters is similar, 21 MPa, but the extension of failure is largest under Ushape cutter. It means that the cutter shapes has not any effects on the failure stress when it cuts the hard rock while the U-shape cutter produce the largest failure zone. The results show that convex-shape edge and U-shape edge cutters have the best performance when tensile strength of rock is 5MPa and 25 MPa, respectively. The results also showed that the failure stress increases with increasing tensile strength, while the failure extension decreases.

Introduction: The main producers of lentil are Canada, India, Nepal and China, respectively and Iran is the ninth producer in the world. The hand pulling is the usual method of lentil harvesting. Use of conventional combine because of short leg varieties, wide combine head in dry land and grain losses by cutter bar vibrations is impossible. So a mechanism should be designed to harvest the lentil plants with minimum damage. …

Summary: This study is to simulate the rock fragmentation process with disc cutter in linear cutting machine (LCM) using the numerical method of finite element. The numerical model of rock and disc cutter was built according to the experimental settings, and then, validated with the test data. The rock model was built for Indiana Limestone as it was used in experimental study. The comparison of cutting forces obtained from the numerical simulation with those obtained from LCM test showed a good agreement between the simulation and the test results.Introduction: Use of tunnel boring machine (TBM) for hard rock tunneling has been ever increased due to the growth of technology and society, as well as growing demand. The main role of disc cutters in this machine is rock cutting. An accurate estimation of the forces acting on the disc cutter is very important in machine design. To do so, the cutting forces acting on a single disc cutter as well as its performance in a specific rock are predicted using full-scale linear rock cutting tests. The results are then generalized for TBM design in the same rock.Methodology and Approaches: The commercial finite element code ABAQUS/CAE was used to perform the numerical simulations of the rock cutting process in LCM test. The forces acting on a fresh constant cross section disc and specific energy were simulated. For validation purposes, the results obtained from numerical model were compared with those of experimental results.Results: and Conclusions The model validity was checked by comparing the results recorded from the experiments and those results obtained from numerical simulation. All cutting forces obtained from simulation were located in the confidence interval of experimental data. The analysis results showed that cutting forces and cutting coefficient increased non-linearly with increasing disc penetration. A good agreement was obtained between the numerical results and experimental data. Moreover, the cutting forces obtained from the simulation showed a maximum deviation of 15 and 21% from the experimental average values for normal force in penetration depth of 5 mm and rolling force in 2.5 mm, respectively.

Background: Use of industry and technology must be based on protection of health as well as the environment. In other words, constant development of technology should fulfil human needs and not pose a health hazard.Silicosis is one of the oldest industry-induced occupational pulmonary diseases which is caused through exposure to particles of crystalline silica in respirable sizes and still is a major health hazard in workers exposed to silica all over the world. Since there is no cure for silicosis and in affected patients the disease may continue to progress even after leaving the workforce, dust control in the working environment is the only way to overcome this disease.Materials and Methods: An analytical cross-sectional study was performed on workers of the 27 stone-cutter factories in Malayer- Azandarian during 2001-2002. Sampling method was un-randomized and considering the type of study, all factory workers who were about 100 individuals entered the study. The study was done via clinical examination, questionnaire, spirometry, and chest x-ray.Results: Study results demonstrated that lung examination was abnormal in 21 workers accompanied by respiratory symptoms as follows:Twelve cases had irritative coughs. Four cases had coughs and dyspnea and 5 complained of exertional dyspnea. In 10 of them a significant change was seen in their chest x-ray. Fourteen cases had an abnormal spirogram curve in evaluation of their respiratory status and only in 4 patients spirometry was abnormal.Most patients with silicosis were under the age of 44 and had almost 5 years of working experience. Six patients were smokers. In conclusion, 10 workers had silicosis (10%) (6 cases of simple silicosis and 4 cases of the complicated type) and the diagnosis was confirmed by chest radiography.