Damage Depth Research Articles

Detection and numerical simulation of blasting-induced damage in shallow-buried twin tunnels with small spacing

In order to study the damage effect of blasting load on the surrounding rock of shallow-buried small spacing twin tunnels, the shallow-buried tunneling section of the south extension project of Shunhe Expressway is taken as the engineering background. Firstly, based on the dynamic damage evolution and Hoffman failure criterion, an anisotropic dynamic damage constitutive model for rock materials is established. Then, by using the secondary development function of the LSDYNA software, the constitutive model is applied to the numerical simulation of the tunnel blasting damage. Finally, based on the acoustic wave measurement theory, the wave velocities in the surrounding rock of the shallow-buried small spacing twin tunnels before and after blasting were measured by using non-metallic ultrasonic detectors, and the damage of the surrounding rock is evaluated from changes in wave velocity. The applicability of the anisotropic dynamic damage constitutive model and the accuracy of the numerical results are verified by comparing the numerical simulation results with the field test results. The numerical simulation results show that the maximum damage radius of single-hole blasting is 0.58 m, and the maximum damage depth is 1.88 m. According to the damage threshold of the rock mass, the horizontal failure range of the rock mass can reach 0.14 m, and the failure depth is 1.70m. According to the field test, the damage degree of the middle intercalated rock is higher than that of the other parts of the surrounding rock in the alternate blasting excavation of the double track tunnel. The damage depth of the surrounding rock caused by blasting excavation is about 0.5 m, which is close to the simulation results, and verifying the accuracy of the anisotropic dynamic damage constitutive model. The research results have a certain guiding role on the blasting excavation and damage control of shallow-buried twin tunnels with small spacing..

Corrosion and mechanical behavior of 17G1S-U pipeline steel and its weld joint of in the terms simulating operational conditions

Corrosion and mechanical behavior of weld joint samples of the straight-weld pipe of 17G1S-U pipeline steel in the conditions simulating the operating conditions of internal and external corrosion has been studied. It is shown that the initiation of local corrosion of welded joints from the inner surface of the pipeline is due to thin-film corrosion in a two-phase medium (hydrocarbon-water) under deformation conditions. The depth of local damages of the base metal and weld metal can reach 0.337 mm and 0.381 mm. Stress corrosion cracking is a danger for the outer surface which is under cathodic protection. Maintaining the potential at the level of the maximum protective potential -1050 mV increases the stress corrosion cracking inclination of pipeline 17G1S-U steel and its weld joint, due to deterioration of the plastic properties of the metal during longtime exposure at cathodic polarization: decreasing in the relative elongation of the base metal is equal near 11 %, weld joint – by 20%. The KS susceptibility, estimated by the KS coefficient, under these conditions is equal to 1.8 for 17G1S-U steel, 1.5 for weld joint.

Infrared and ultrasonic intelligent damage recognition of composite materials based on deep learning.

With the large-scale application of composite materials in military aircraft, various composite material detection technologies with infrared nondestructive and ultrasonic nondestructive testing as the core have played an important role in detecting composite material component damage in military aircraft. At present, the damage of composite materials is mostly recognized manually, which is time-consuming, laborious, and inefficient. It can effectively improve detection efficiency and accuracy by using intelligent detection methods to detect and recognize damage. Moreover, the effect of infrared detection is significantly reduced with increasing detection depth, while ultrasonic detection has shallow-blind areas. A cascade fusion R-CNN network is proposed in order to comprehensively identify composite material damage. This network realizes the intelligent fusion recognition of infrared and ultrasonic damage images of composite materials. The network is based on a cascade R-CNN network, using fusion modules and BiFPN for improvement. For the infrared image and ultrasonic C-scan image data set established in this paper, the algorithm can identify the type and location of damage detected by infrared and ultrasonic testing. Its recognition accuracy is 99.3% and mean average precision (mAP) is 90.4%. In the detection process, the characteristics of infrared and ultrasonic images are used to realize the recognition of damage depth. Compared to SSD, YOLOv4, faster R-CNN and cascade R-CNN, the network proposed in this paper is better and more effective.

Modelling and understanding edge glow effects on material failure resulting from artificial lightning strike

This paper examines the influence of edge glow effects (arcing of current from specimen side surfaces) on the prediction of material failure during an artificial lightning strike. A novel modelling approach is proposed to incorporate edge glow effects. Finite Element simulations are undertaken to examine modelling strategies and results compared against experimental data. Simulations also examine the influence of inter-ply properties, as together with edge glow modelling, these may be expected to impact the predicted current path through a test specimen. Unprotected carbon fibre/epoxy composite material and Society of Automotive Engineers (SAE) lightning test Waveform A are studied. Inter-ply thermal and electrical conductivities are modified either wholly or partly (by 50% or 100%) from a reference magnitude. Results reveal that changes to inter-ply contact can affect the damage area and depth predictions, varying damage area predictions by up to 22%. However, it is shown that edge glow effects produce an even more significant change in the prediction of thermal damage behaviour, reducing predicted damage areas, by up to 55%, and increasing damage depth by 14%.

Регулирование коррозионной повреждаемости магниевых сплавов за счет использования вакуумных циркониевых покрытий

Magnesium alloys have a unique combination of properties in terms of specific strength, modulus of elasticity and biocompatibility, which allows them to be considered as one of the most promising materials for use as temporary bioresorbable implants capable of being replaced by bone tissue in the process of gradual dissolution in the human body, thereby eliminating the need for repeated surgical intervention to remove the implant after healing. In this regard, the world scientific community pays much attention to works aimed at developing methods for controlling the corrosion damage of magnesium alloys. The presented study demonstrates that such precision control can be realized using vacuum zirconium coatings, while Zr itself is already actively used in medicine. It has been shown that the application of a zirconium coating on the MA14 (ZK60) alloy, which is currently considered as one of the possible candidates for use in medical practice, with thicknesses of 0.4 μm and 0.8 μm, can reduce the corrosion damage estimated by the hydrogen yield, based on 110 hours per 1.3 and 1.6 times, respectively. The favorable effect of the zirconium coating on the resistance to corrosion processes is confirmed by the results obtained using a laser confocal microscope: a decrease in both the total corroded area and the depth of corrosion damage was recorded in three-dimensional images of the sample surface. In addition, in the work using scanning electron microscopy, a comprehensive study of the obtained coatings is presented, which made it possible to characterize its structure and chemical composition. The adhesion characteristics of the coating were evaluated by scratching on a tester and showed that for a coating with a thickness of 0.8 μm, fracture is observed at an indentation load of the conical indenter of the order of 0.5 N.

Influence of oblique low velocity impact on damage behavior of 2D and 3D woven composites: Experimental and numerical methods

The aim of this study is to determine whether 3D woven composites exhibit better mechanical performance in comparison with 2D ones under oblique low velocity impact. For this purpose several glass/unsaturated polyester composite specimens were tested using drop-weight impact test machine in different angles including 0°, 10°, 20°, 30° and 40°. In addition, the finite element package ABAQUS was used to simulate oblique impact event. The impact parameters such as contact force, contact duration, absorbed energy, impactor displacement, as well as damage parameters like damage initiation time and force, damage depth and area and damage intensity were examined. The results showed that absorbed energy, damage initiation time and force as well as damage area on the front side of samples increase with rising impact angle, while damage intensity, damage depth and damage area on the back side of the composites decrease. From evaluation of absorbed energy and damage intensity parameters, it was conclusive that the mechanical performance superiority of 3D composites decreases with increasing impact angle.

Study on HfO 2 /SiO 2 high reflective film damage induced by 248nm UV excimer laser

The deep ultraviolet optical thin films play an important role in excimer lasers, deep ultraviolet lithography machine and other laser systems. In this paper, the experiment on damage in HfO2/ SiO2 high reflective film irradiated by 248nm ultraviolet excimer laser was carried out. And the high reflection film is coated with a layer of SiO2 as a protective film. The damage morphology and depth of the samples were observed and analyzed by means of DIC microscope and surface profiler system. In this experiment, the laser-induced damage threshold of HfO2/ SiO2 high reflective film coated with SiO2 protective film was calculated by zero damage probability. Based on the surface characteristics of the damage points, we established the model to analyze the damage mechanism of the high reflectance film by using Finite Element Method(FEM). The experimental results show that the damage threshold of 248nm excimer laser to the highly reflective film is 3.086J/cm2. When the incident laser energy is 3.33J/cm2, stress damage appears on the surface of the highly reflective film. With the increase of laser energy, the high reflective film will appear melting damage and corrugated damage.

3D Modelling of the Scattering of the Fundamental Anti-Symmetric Lamb Mode (A0) Propagating within a Point-Impacted Transverse-Isotropic Composite Plate

The present paper deals with an effort to model impact damage in 3D-FE simulation. In this work, we studied the scattering behavior of an incident A0 guided wave mode propagating towards an impacted damaged zone created within a quasi-isotropic composite plate. Besides, barely visible impact damage of the desired energy was created and imaged using ultrasonic bulk waves in order to measure the size of the damage. The 3D-FE frequency domain model is then used to simulate the scattering of an incident guided wave at a frequency below an A1 cut-off with a wavelength comparable to the size of the damaged zone. The damage inside the plate is modeled as a conical-shaped geometry with decayed elastic stiffness properties. The model was first validated by comparing the directivity of the scattered fields for the A0 Lamb mode predicted numerically with the experimental measurements. The modeling of the impact zone with conical-shape geometry showed that the scattering directivity of the displacement field depends significantly on the size (depth and width) of the conical damage created during the point-impact of the composite with potential applications allowing the determination of the geometric characteristics of the impacted areas.

Application of contrast-enhanced ultrasound in the diagnosis of burn depth.

BackgroundThe diagnosis of burn depth often relies on the subjective judgment of plastic surgeons. Contrast-enhanced ultrasound (CEUS) can visualize the microcirculation well and has potential value in diagnosing the depth of burn wounds. We assessed the depth of the burn wounds by CEUS, and compared the results with histological examination.MethodsTwo rhesus monkeys were used, and multiple burn wounds with different depths were made on their backs. The echo of the dermis and subcutaneous tissue were observed for each wound, and the thickness of the dermis was measured. CEUS was performed to evaluate the depth of burn wounds and compared with pathological results.Results(I) After scalding, dermal tissue edema occurred, and the thickness of the dermis measured by a US tended to increase gradually, related to the time of scalding and the order of measurement. (II) With the prolongation of the burn time, the depth of filling by contrast agent gradually increased, from the superficial dermis to the deep dermis and subcutaneous tissue, indicating that the depth of tissue damage gradually increased. This was consistent with the pathological observation. The thickness of the healthy dermis was about 1.3–1.8 mm, and 2.7–4.1 mm after scalding. The depth of the burn wounds was 0.9–4.1 mm, accounting for 32–100% of the full skin thickness.ConclusionsCEUS is a convenient and fast examination method that is consistent with pathological diagnosis of the depth of burn wounds and could prove valuable for the accurate assessment of burn injuries.

Damage Detection on a Beam with Multiple Cracks: A Simplified Method Based on Relative Frequency Shifts

Identifying cracks in the incipient state is essential to prevent the failure of engineering structures. Detection methods relying on the analysis of the changes in modal parameters are widely used because of the advantages they present. In our previous research, we found that eigenfrequencies were capable of indicating the position and depth of damage when sufficient vibration modes were considered. The damage indicator we developed was based on the relative frequency shifts (RFS). To calculate the RFSs for various positions and depths of a crack, we established a mathematical relation that involved the squared modal curvatures in the healthy state and the deflection of the healthy and damaged beam under dead mass, respectively. In this study, we propose to calculate the RFS for beams with several cracks by applying the superposition principle. We demonstrate that this is possible if the cracks are far enough from each other. In fact, if the cracks are close to each other, the superposition method does not work and we distinguish two cases: (i) when the cracks affect the same beam face, the frequency drop is less than the sum of the individual frequency drops, and (ii) on the contrary, cracks on opposite sides cause a decrease in frequency, which is greater than the sum of the frequency drop due to individual damage. When the RFS curves are known, crack assessment becomes an optimization problem, the cost function being the distance between the measured RFSs and all possible RFSs for several vibration modes. Thus, the RFS constitutes a benchmark that characterizes damage using only the eigenfrequencies. We can accurately locate multiple cracks and estimate their severity through experiments and thus prove the reliability of the proposed method.

Study on Deformation and Failure Characteristics of Surrounding Rock of Overlying Roadway under Upward Mining in the Deep Mine

To study the impact of mining of the lower protective layer on the deformation and failure characteristics of the upper roadway, these characteristics of an 879 gas drainage roadway were studied and analyzed during the mining of the II 1051 working face of the Zhuxianzhuang coal mine using similar simulation experiments and numerical simulation methods. The results indicate that with the continuous excavation of the working face, the range of impact of the mining stress gradually spreads and exceeds the level of the roadway. At the present time, the roadway is in a mining stress-rising area. The two sides of the roadway are sheared, and the roof and floor are under tension–shear composite failure. The floor is the most gravely damaged—the depth of its damage is 2.5 m, and the depths of damage on either side and of the roof are approximately 1–2 m. During the advancing process of the working face, the deformation of the roadway increases slowly at first, then increases sharply, and tends to be stable thereafter. The deformation of the floor is the largest, followed by those of the two sides and the roof; the values are 800, 400, and 300 mm, respectively.

Model test study on damage depth of concrete target under penetration and explosion

In order to study the influence of the cavity on the explosion effect caused by the penetration of concrete target, model tests of penetration and explosion of concrete target at the velocity of 450–700 m/s were carried out. Based on 10 sets of test results and dimensional analysis, the effect of penetration result on the depth of blast hole is studied. Results indicate that the dimensionless impact coefficient Ip can be used to characterize the penetration effects such as penetration depth, hole volume and penetration damage value, regardless of length-diameter ratio of charge, the increase of damage depth is mainly influenced by dimensionless impact coefficient Ip and explosion coefficient Ie. Based on the experimental data, influence rule of the depth of crater is obtained for the length-diameter ratio of 5: (1) when the Ip is small, the penetration depth is small, the change of Ie has little influence on the depth of crater he; (2) with the increase of Ip, he increases at a decreasing rate, influence of Ie on he increases; (3) with the increase of Ip to a certain extent, he tends to reachsaturation value, influence of Ie on he tends to be stable.

Reasonable Scope of Kilometer Drilling in Lower Layer of Extrathick Coal Seam: A Case Study of Tingnan Coal Mine, China

When stratified mining is adopted in high-gas and extrathick coal seam, a large amount of pressure-relief gas of the lower layer flows into the upper layer goaf along the cracks in the layer, resulting in upper layer working face to frequently exceed the gas limit. And ordinary drilling can no longer meet the requirements of the pressure-relief gas drainage of the lower layer. The 205 working face of Tingnan Coal Mine is taken as the test background in this paper, and based on the “pressure-relief and flow-increase” effect of the lower layer under the action of mining stress during the upper layer mining, the gas drainage of kilometer directional drilling in lower layer is studied. According to the distribution characteristics of support pressure before and after the working face, the pressure-relief principle, fracture development characteristics, and gas migration law of the lower layered coal body are analyzed in the process of advancing the upper layered working face in the extrathick coal seam with high gas. The maximum depth of goaf damage is calculated theoretically, and the Flac3D numerical simulation of the failure deformation of the 205 working face floor is carried out. It is found that the maximum depth of plastic failure of the lower layer is about 13 m. According to the plastic deformation of the lower layer under different vertical depths and the movement of coal and rock mass, it is determined that the reasonable range of kilometer directional drilling in the lower layer is 6–9 m below the floor vertical depth. From 15 m to 45 m in the two parallel grooves, there is no fracture failure with a sharp increase or decrease in the displacement in the local range. Meanwhile, in this part, the roof falling behind is not easy to compaction, and the displacement of the floor is large, which does not cause plastic damage. The degree of pressure relief is more sufficient, and the permeability of the lower layer is good. Therefore, drilling should be arranged as much as possible along the working face in this tendency range. The determination of reasonable arrangement range of kilometer directional drilling in extrathick coal seam provides reference index and theoretical guidance for industrial test of working face and also provides new ideas for gas control of stratified mining face in high-gas and extrathick coal seam.

Optimizing the microstructure of a new machinable bioactive glass-ceramic

ObjectivesThis study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics. MethodsDifferential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed. ResultsWe found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi2O3) and lithium disilicate (LS2, Li2Si2O5). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD). ConclusionThis bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases.

Evaluasi Kelas Kemampuan Lahan dan Usaha Perbaikan di Sebagian Das Riawajo Kabupaten Sikka

Agricultural activity in several villages in the Riawajo Watershed (DAS) is very high. The high agricultural activity will affect the quality of the watershed. For this reason, it is necessary to conduct research on evaluating land capability classes in the Riawajo watershed, Sikka Regency. The variables observed were soil texture, salinity, soil structure, slope, effective depth of soil, erosion damage, rock conditions, flood threat, and drainage. The data is processed by the arithmetic matching method. The results showed that the agricultural lands in the villages in the Riawajo watershed were in the first class and were still able to support their agricultural activities.

THE CONCEPT OF A COMPREHENSIVE PROGNOSTIC MODEL OF THE EFFECTIVENESS OF IMPLEMENTATION OF MINIMALLY INVASIVE INTERVENTIONS IN THE TREATMENT OF CARIOUS PATHOLOGY

The research presents a prognostic model of the effectiveness of minimally invasive interventions in the dental patients’ treatment of carious pathology, which was developed to reduce the impact of iatrogenic interventions, increase the results of biological, biomechanical and financial feasibility of treatment.
 The aim of research is to develop a mathematical representation of a comprehensive prognostic model of the minimally invasive treatment effectiveness of carious pathology.
 Materials and methods of research. Comprehensive prognostic model of comparative efficiency of minimally invasive implementation of treatment protocols of carious pathology included consideration of relative risk indicators of biological complications (secondary caries and affected tissue pulp), decreased biomechanical forecast of the tooth (based on the performance index IROPZ and IHRKCHZ) and the financial feasibility of these methods, taking into account the ratio of material costs and unit labor intensity of the biological level and biomechanical forecast of the functioning of the dentition unit.
 Results of the research. The factors were identified during the scientific research; it was provided that the volume of iatrogenic interventions in the dental patients’ treatment of caries can be minimized. The structure of a complex prognostic model of the effectiveness of realization minimally invasive methods of treating caries of hard tooth tissues was developed. A comparative assessment of the biological, biomechanical and financial feasibility of treatment of carious pathology depending on the depth of damage to the hard tissues of the tooth using classical (invasive) and mini-invasive methods of treatment was held. The study showed that the implementation of minimally invasive approaches to the treatment of carious pathology in terms of risk and complications in secondary destructive changes of dental hard tissues and pulp tissue damage contributes to the effectiveness of limited nuclear interventions with controlled enamel reduction and determination of connection of restoration with the bottom of the formed cavity. The highest biomechanical feasibility of minimally invasive dissection protocols has been established in the defects treatment within the enamel in order to minimize unreasonable enamel reduction and dentin tissues, carious cavities treatment at the border of medium-deep types of lesions to limit the caries spreading in the cavities deep localization in order to prevent the development of associated lesions of the pulp complex, which in terms of biological prognosis can provoke the development of irreversible changes.
 Conclusion. As a result of scientific research and comparative analysis of the effectiveness of caries treatment by mini-invasive methods of intervention, the fact of improving the biological and biomechanical prognosis of the affected units of the dentition compared to the results of treatment of pathological lesions by surgery in accordance with classical protocols, confirming the developed complex prognostic model of efficiency of use of minimally invasive methods of treatment of carious pathology of dental patients. However, the creation of a unified comprehensive forecasting model, which would include the most complete reflection of all these criteria and was at the same time reliable, is impossible. Biological stacking relative risk indicators in the process of secondary development and pulpitis indicate the excess of minimally invasive treatment in all analyzed clinical cases, cases of initial treatment in relation to the risk of pulp production and cases in the center of caries relative to the risk of the previous year.

Residual compression property and response of honeycomb sandwich structures subjected to single and repeated quasi-static indentation

Abstract This paper investigated the response and residual compression properties of honeycomb sandwich structures subjected to single quasi-static indentation (QSI) and repeated QSI (RQSI). The damage depth after repeated low-velocity impact (LVI) was considered as the governing parameter during the QSI experiments. Three-dimensional digital image correlation method was applied to determine deformation of the front panels after LVI and QSI to describe damage to honeycomb structures. For specimens with the same depth, it is found that the residual strength of QSI was less than that of LVI and close to that of RQSI. Results indicated that it is more reasonable to describe the damage by volume than by depth.

Predictors for external and internal pancreatic fistulas after pancreatic necrosis

Aim . To analyze the outcomes of pancreatic necrosis depending on the depth and localization of damage to the pancreatic tissue, to determine the main risk factors for the development of external and internal pancreatic fistulas. Materials and methods. The analysis of long-term results of treatment of pancreatic necrosis in 81 patients was carried out: 53 patients were treated at the stage of acute pancreatitis in our clinic, 28 – in other medical institutions. The algorithm of the survey included a CT scan with contrast enhancement, fistulography, MRI-pancreatocholangiography and/or endoscopic retrograde cholangiopancreatography. The influence of various factors on the development of pseudocysts and pancreatic fistulas was estimated using the Spearman correlation coefficient. Results. Signs of damage to the pancreatic duct were detected in 19 (36%) of 53 patients: 9 were diagnosed with pseudocysts, 10 had external pancreatic fistulas. The daily flow rate of pancreatic juice ( α -amylase activity >20950 u/l) was 300–350 ml. Interventions (minimally invasive, open surgery) required 10 patients (52.6%). The correlation coefficient of external pancreatic fistulas with the depth of pancreatic necrosis was 0.46 ( р = 0.00005), the CT severity index according to Balthazar – 0.05 ( р = 0.63), the localization of necrosis in the neck – 0.31 ( р = 0.006), the amount of drainage discharge – 0.55 ( р = 0.000001), the activity of α -amylase fluid – 0.53 ( р = 0.000002). There was a significant positive correlation of mediastinal pancreatogenic cysts with pseudocysts located on the posterior surface of the pancreas ( r = 0.7; p = 0.003), pleural effusion with high activity of α -amylase ( r = 0.87, р = 0.0005) and alcoholic etiology of acute pancreatitis ( r = 0.75, р = 0.002). Conclusion. Predictors of resistant to conservative treatment external pancreatic fistulas are deep necrosis, especially in the area of the neck of the pancreas, the discharge flow rate through the drainage is more than 150 ml with an α -amylase activity of more than 1000 u/l. A risk factor for the development of internal pancreatic fistulas with penetration into the mediastinum is the localization of pseudocysts on the posterior surface of the pancreas in the body and tail area.

Study of the corrosion resistance of aluminum alloy AMg6 and steel 12Kh18N10T in conditions of loading under the impact of environmental factors

Stress corrosion cracking is one of the most dangerous types of corrosion damage in metallic materials. We present the results of studying the impact of environmental factors on the susceptibility of AMg6 aluminum alloy and 12Kh18N10T stainless steel to stress corrosion cracking under four-point bending. Tests of loaded samples were carried out in laboratory and field conditions of the moderately warm climate of the coastal zone over a period of six months. The samples were examined daily with fixation of the time to their destruction and upon completion of the tests the appearance of the samples and the depth of intergranular corrosion on microsections were assessed. A 3D relief was constructed using macro photography of the surface with the determination of the depth of corrosion foci. We also carried out a comparative analysis of the frequency of stress-induced destruction of steel samples of various grades both in atmospheric and laboratory conditions. It is shown that in atmospheric conditions characterized by the presence of dust particles acting as concentrators for the formation of corrosion foci, the aggressiveness of the corrosive effect of the environment increases, whereas the general corrosion resistance of materials decreases. The most pronounced effect of the environment was recorded in AMg6 alloy samples when exposed under a ventilated canopy in conditions of periodic spraying of seawater aerosols. The depth of surface corrosion damage was up to 0.1 mm. When the test samples were exposed under other conditions (salt fog chamber and louvered storage) the corrosion damage was absent. The results obtained can be used to predict the corrosion resistance of the products made of AMG6 alloy and 12Kh18N10T steel when operated in conditions of loading under the impact of environmental factors.

EVALUATION OF DAMAGE OF ROUNDWOOD ASSORTIMENTS CAUSED BY VARIED CONSTRUCTION, TECHNICAL SOLUTIONS AND CONDITIONS OF HARVESTER HEAD FEED ROLLERS

The purpose of this study was to evaluate the depth of damages caused by harvester head feed roller spikes to birtch veneer logs, harvested according to top diameter group (18x25cm, 25cm), spruce sawlogs (6x10cm), spruce and pine sawlogs according to top diameter group (10x14cm, 14x18cm). Thirteen technical solutions and conditions of the harvester head soft feed rollers (Moipu Standard, Rib), standard feed rollers (Multi-Tree Handling (MTH), Steel Thumbnail) and agreesive feed rollers (TP) were tested in this study.Regulation parameters of hydraulic system and angles of delimbing knife blades during the harvesting of stems in different woodland types and seasonality using single grip harvesters: John Deere 1270E, John Deere 1070E and John Deere 1070D equipped with harvester heads: H754; H480C and H460 were examined in clearcutting and thinning operations in twenty four wood felling sites in Kurzeme and Vidzeme region of Latvia.