Theoretical study of temperature in the contact zone cBN cutting tool

Однією з сучасних світових тенденцій розвитку технологій лезової обробки є обробка матеріалів високої твердості. У той же час, зі збільшенням режимів обробки та твердості оброблюваного матеріалу має місце суттєве збільшення температури в зоні контакту, що впливає на стійкість та зношування різального інструменту та стає одним із факторів, що обмежує продуктивність процесу різання. Зниження температури на контактних ділянках інструмента мінімізує інтенсивність взаємодії між інструментальнім і оброблюваним матеріалами в зоні різання, що зменшує знос інструмента.The article is devoted to solving of actual scientific and technical task of increasing of tool life of the cutting tool equipped of cBN-Based PSHM while turning hardened steels. The concept of increasing of tool life of the PCBN cutting tools when turning hardened steel has been proposed, which is based on the reducing of temperature in the cutting zone. It was implemented by applying boron nitride coating with amorphous structure (BNam) on the working surfaces of the PCBN. Based on experimental data on the size of the contact area, contact loads and the topography of the contact areas of tools, the calculation of the value of temperature flashes was conducted. It was found that the change in temperature has an extreme character with a maximum of 2036 °C and 1044 °C on the sticking and sliding zones of contact area respectively. Wherein, it was revealed that a sufficient level of temperature for chemical interaction between instrumental and processed materials can be realized only in the sticking zone. The use of BNam coating reduces the temperature to 1770 °C in the sticking and to 893 °C in the sliding contact zones, hence reducing the intensity of reaction of the chemical interaction in the sticking zone of the contact area. On the basis of research and industrial tests of the obtained results it was found that exploitation of cBN tools coated with BN am allows one to increase the tool life of tool in comparison with the same tool without coating.Одной из современных мировых тенденций развития технологий лезвийной обработки является обработка материалов высокой твердости инструментом, оснащенным ПКНБ. В то же время, с ростом режимов обработки и твердости обрабатываемого материала имеет место существенное увеличение температуры в зоне контакта, что влияет на стойкость и интенсивность изнашивания режущего инструмента и становится одним из факторов, ограничивающим производительность процесса резания. Снижение температуры на контактном участке инструмента минимизирует интенсивность взаимодействия инструментального и обрабатываемого материалов в зоне резания, что способствует уменьшению износа инструмента

Recovery surgery for extracapsular extension of squamous cell cancer metastasizing to the lymph nodes in the neck

Metastatic neck lymph nodes in massive lesion of their tissue with tumor cells are accompanied by extracapsular extension to the adjacent structures in a number of cases. The greatest problem in clinical oncology is when even extended radical neck dissection fails to completely remove tumor tissue that is macroscopically detectable after surgical resection. In this situation, there is a continued growth of tissue mass that is left on the neck. Thus, the unresectable extracapsular spread of neck lymph node metastases to the adjacent tissues reduces the duration of life in the patients and worsens its quality.The basis for this investigation is clinical observations of patients who have been operated on at the Nizhny Novgorod Regional Clinical Oncology Dispensary (Hospital Two) in the period 2005 to 2016. Histologically, the tumors were squamous cell carcinomas. In this period, there have been 24 Crile operations (radical neck dissection) that are cytoreductive. A primary tumor has been (n = 15) or has not been (n = 9) previously excised. The extracapsular spread of metastatic lymph nodes corresponded to levels IIa, IIb, and III. Cytoreductive cervical lymphadenectomy with the pectoralis musculocutaneous flap covering an unresectable tumor for extracapsular unresectable squamous cell carcinoma metastasizing to the neck lymph nodes should be considered the operation of recovery. This type of surgery is warranted, as tumor mass reduction by eliminating the source of intoxication allows further antitumor treatment (radiotherapy or chemotherapy or their combination) that is contraindicated in patients with tumor lysis in the neck. When the cause of death is the exceedingly continued growth of an unresectable component of radio- and chemoresistant variants of tumor tissue on the neck, the covering of the component with a pectoralis major flap delays a fatal outcome in incurable patients to improve a number of quality-of-life indicators

Создание и применение инструментальной керамики на основе сверхтвердых структурированных композитов

The state-of-the-art of development and improvement of superhard composites based on the cubic boron nitride have been considered. Such composites are used for equipment of cutting tools for machining of materials with high mechanical properties.Рассмотрены современные подходы к созданию и совершенствованию сверхтвердых композитов на основе кубического нитрида бора для оснащения режущих инструментов для обработки конструкционных материалов с высокими механическими свойствами

Pectoral and trapezoidal flaps for reconstruction of full-thickness post-resection defect in combination treatment of locally advanced buccal cancer

The study objective is to compare short-term results of reconstruction of a full-thickness defect of the cheek using pectoral and trapezoidal flaps.Materials and methods. Examination and treatment of 21 patients with locally advanced buccal cancer were performed at the Nizhny Novgorod Regional Clinical Oncologic Dispensary in 2007–2018.Results. Flap necrosis developed in 7 (33 %) patients: in 3 patients total, in 4 – marginal. No postoperative mortality was observed. For pectoral flap reconstruction, necrosis was observed in 2 cases (marginal necrosis of the skin graft). For trapezoidal flap buccal reconstruction, necrosis was observed in 5 patients (total in 3, marginal in 2).Conclusion. Use of a trapezoidal flap is limited due to its anatomical characteristics and is associated with higher rate of necrosis despite better esthetic characteristics compared to a pectoral flap. Despite its larger volume compared to trapezoidal flap, pectoral flap has better blood supply which leads to low rate of necrosis