Technological features of repair cracks in ship plates by comb cutting method

Ремонт трещин в судовых пластинах является наиболее ответственной и сложной операцией Задача получения заданных размеров проплава с обратной стороны свариваемого металла резко усложняется в тех случаях, когда доступ к обратной стороне шва затруднен или вообще невозможен, выполнение двухсторонних сварных швов на наружной обшивке корпуса судна, в большинстве случаев для доступа к поврежденным районам, приводит к увеличению числа сопутствующих работ по демонтажу (монтажу) оборудования и влияет на нормативные сроки ремонта судов, в том числе и при стоянке судов в доке. В данной работе излагаются результаты исследования эффективности технологии ремонта трещин, в судовых пластинах, путем ориентации сварочной ванны вдоль плоскости повреждения, за счет гребенчатой разделки поврежденного района с различной геометрией кромок. Представлены результаты аналитического исследования и факторных экспериментов оценки прочности сварных соединений с различной геометрией гребенчатой разделки, при односторонней сварке, с использованием различных сварочных материалов и варьировании режимов сварки. Приведены результаты металлографического исследования (на макрошлифах) полученных сварных соединений. Предложены технологически эффективные, для практического применения в судоремонте, параметры гребенчатой разделки трещин в судовых пластинах. Repair of cracks in the ship plates is the most responsible and complex operation The task of obtaining the specified dimensions of the melt on the reverse side of the welded metal is sharply complicated in cases where access to the reverse side of the seam is difficult or even impossible, the implementation of double-sided welds on the outer skin of the hull of the vessel, in most cases for access to damaged areas, leads to an increase in the number of related works on the dismantling (installation) of equipment and affects the normative terms of repair of vessels, including when ships are parked in the dock. This paper presents the results of the study of the effectiveness of the technology of repair of cracks in the ship plates, by orienting the welding bath along the damage plane, due to the comb cutting of the damaged area with different geometry of the edges. The results of analytical research and factor experiments assessment of the strength of welded joints with different geometry of comb cutting, with one-sided welding, using different welding materials and varying welding modes. The results of metallographic research (on macro-grinds) of the obtained welded joints are given. Technologically effective parameters of comb cutting of cracks in ship plates are proposed for practical application in ship repair.

Lift-off reduction and patella tracking in Total Knee Arthroplasty (TKA) using a 3D printed patient-specific knee model

The patellofemoral joint is greatly influenced by the geometry and position of the femur during knee flexion. After knee replacement surgery, the joint geometry is changed by the surface replacement and its kinematics by the orientation of the cutting planes planned by the surgeon. The technique presented in this study verifies the compatibility of the cutting method during total knee arthroplasty (TKA) with the geometry of the joint and the kinematics of knee flexion. To confirm the benefit of this method, three patient-specific knee models were printed in 3D. All models were made from the patient’s CT data and the patient’s measurement of flexion motion obtained with an infrared stereo camera. The models are operated according to three different techniques: Kinematic Alignment (KA), Measured Resection (MR) with 3 degrees of external rotation and MR with 9 degrees of external rotation. The resulting postoperative knees from the different alignment techniques are compared to the patient’s preoperative knee. The results show that the movement of the patella is modified after surgery on the model. The different alignments also lead to a variation in the behavior of the tibiofemoral joint. Based on these three examples, MR with an external orientation of the prosthesis results in a patellar movement closer to the preoperative movement. The KA method also reproduces the patella movement almost identically, but a lift-off appears at the tibiofemoral joint. The error observed for each cutting method between the pre-and postoperative patella position varies by a maximum of 5 degrees of rotation and 5 mm of translation, showing that the configuration has an overall small impact on the patellar movement. This study of three cases shows the importance of the preparation of the operation and the adjustment of the prosthesis for each specific patient using the 3D printed model.

Manufacture of Gilded Threads in the 15-17th Centuries

Since ancient times, gilded threads have been used to decorate textiles in different cultures around the world. In the article, the author examines the threads manufacturing in the 16-17th centuries in Europe and Western Asia, trying to answer two, as it seems to him, the main questions: what was the method of gilding and what was the method of cutting if width error was less than 10 μm. It is assumed that the main gilding method was the diffusion one, and the main cutting method used rollers and a sharp blade at a small angle. The first one has not been proven but the second has been proved. The article lists all marks, diffusion and adhesion coefficients, human angular resolution, and much more.

Characteristic Tearing Energy and Fatigue Crack Propagation of Filled Natural Rubber

Below the incipient characteristic tearing energy (T0), cracks will not grow in rubber under fatigue loading. Hence, determination of the characteristic tearing energy T0 is very important in the rubber industry. A rubber cutting experiment was conducted to determine the T0, using the cutting method proposed originally by Lake and Yeoh. Then, a fatigue crack propagation experiment on a edge-notched pure shear specimen under variable amplitude loading was studied. A method to obtain the crack propagation rate da/dN from the relationship of the crack propagation length (Δa) with the number of cycles (N) is proposed. Finally, the T0 obtained from the cutting method is compared with the value decided by the fatigue crack propagation experiment. The values of T0 obtained from the two different methods are a little different.

Theoretical Study and Experiment Validation on Drilling Cutting Weight during the Whole Process of Drilling

In mining engineering, coal and gas outburst is extremely dangerous dynamic disaster, which will cause serious casualties and property losses. As a method to predict coal burst, the drilling cutting method has been widely used in coal mines. The drilling cutting weight is an important index of the drilling cutting method. In theoretical calculation, scholars usually assume that the coal is isotropic and homogeneous before drilling to deduce the formula of drilling cutting weight. However, in actual mining engineering, drilling cutting is usually carried out in the plastic coal body in front of the working face. Therefore, in the present study, the theoretical formula of the drilling cutting weight in the plastic coal mass is deduced, as well as in the elastic coal mass. The results show that the drilling cutting weight calculated based on the deduced formula increases with the increase of drilling depth in the plastic coal mass, which is consistent with the field measurement results. The fragmentation degrees of coal around the drilling hole are also considered by introducing cohesion, which changes linearly along the radial direction of the drilling hole. The results show that the smaller the cohesion, the greater the drilling cutting weight. The calculation formula for drilling cutting in elastic coal mass is also given. The dilatancy effect of coal around the drilling hole is also considered by introducing expansion coefficient n, which changes linearly along the radial direction of the drilling hole. There is a good match between the theoretical calculation results and the laboratory test results. The obtained results are helpful for the prediction and prevention of coal burst.