Modeling of influence of planar defects on plasticity of powder materials by computational methods of micromechanics

Based on the energy concept of the critic stress state, a three-parameter model of plasticity of the Cam-Clay type was formulated. For this phenomenological model, the dependences of the determining parameters on the porosity and damage were found by the method of micromechanical averaging on the unit cell corresponding to the porous damaged material of powder origin. The plastic multi-responce (different yield strength in tension and compression) behavior of this material is found by micromechanical averaging on a unit cell. According to the mechanics of composites, the geometry of the cell represents the structure of a heterogeneous material and the boundary conditions on a unit cell make it possible to relate the stress-strain state at the macro- and meso-level. The averaging was carried out by computer simulation using the finite element method with an adaptive mesh, which was automatically condensed in places of a large gradient of the stress-strain state. The structure of the representative cell corresponds to a powder origin material with "imperfect", partially stratified, interparticle contacts. In the proposed model the rheological response of a porous damaged material is specified by three moduli, and the structure of such a material is described by two internal state parameters: porosity and the degree of delamination of interparticle contacts. That is, the rheological moduli are functions of porosity and damage. Accordingly, a number of values of each of the moduli were calculated for a certain discrete range of density and damage. The advantage of this approach is precisely in focusing on powder origin materials and not generally on any damaged materials, which makes it possible to take into account the real structure of the damaged material using the methods of mechanics of microheterogeneous materials. According to the simulation results, in particular, it was found that the yield strength for shear is significantly (30%) less sensitive to damage than the yield strength for uniaxial tension. Keywords: theory of plasticity, powder materials, micromechanics, damaged materials, stress-strain state.

Preservation of audio-visual archives in Zambia

Audio-visual records and archives constitute a fundamental heritage that satisfies multiple needs, including education, training, research and entertainment. As such, there is a need to appropriately preserve and conserve them so they can be accessed for as long as they are needed. In spite of their significant role in safeguarding cultural heritage, audio-visual records and archives, are often neglected and accorded less attention than paper-based records, especially in developing countries. Hence, there is a risk of losing information held in audio-visual form. That is why this study looked at how the National Archives of Zambia (NAZ) and the Zambia National Broadcasting Corporation (ZNBC) preserve audio-visual materials to ensure long-term accessibility of the information. The study investigated the types of audio-visual collections held, the storage equipment used, measures put in place to ensure long-term accessibility of audio-visual materials, the disaster preparedness plans in place to safeguard audio-visual archives and the major challenges encountered in the preservation of audio-visual materials. The findings of the study revealed that films (microfilm and microfiche), photographs and manuscripts, and video (video tapes) and sound recordings (compact cassette) constitute the biggest audio-visual collection preserved. The equipment used to store audio-visual materials included open shelves, specialised cabinets, electronic database for digitised materials, aisle mobiles and cupboards. The measures taken to ensure the long-term accessibility of audio-visual collection included digitisation and migration of endangered records and archives; fumigation of storage areas; conservation of damaged materials and regulation of temperatures and humidity in the storage areas. The disaster preparedness plans in place mostly covered structure insurance; protection against fire and water by way of installing fire extinguishers; smoke sensors; fire detectors and construction of purpose-built structures. The major challenges faced were financial constraints; technological obsolescence; lack of playback equipment; limited training; lack of strong back-up systems and inadequate storage facilities.

Preservation of audio-visual archives in Zambia

Audio-visual records and archives constitute a fundamental heritage that satisfies multiple needs, including education, training, research and entertainment. As such, there is a need to appropriately preserve and conserve them so they can be accessed for as long as they are needed. In spite of their significant role in safeguarding cultural heritage, audio-visual records and archives, are often neglected and accorded less attention than paper-based records, especially in developing countries. Hence, there is a risk of losing information held in audio-visual form. That is why this study looked at how the National Archives of Zambia (NAZ) and the Zambia National Broadcasting Corporation (ZNBC) preserve audio-visual materials to ensure long-term accessibility of the information. The study investigated the types of audio-visual collections held, the storage equipment used, measures put in place to ensure long-term accessibility of audio-visual materials, the disaster preparedness plans in place to safeguard audio-visual archives and the major challenges encountered in the preservation of audio-visual materials. The findings of the study revealed that films (microfilm and microfiche), photographs and manuscripts, and video (video tapes) and sound recordings (compact cassette) constitute the biggest audio-visual collection preserved. The equipment used to store audio-visual materials included open shelves, specialised cabinets, electronic database for digitised materials, aisle mobiles and cupboards. The measures taken to ensure the long-term accessibility of audio-visual collection included digitisation and migration of endangered records and archives; fumigation of storage areas; conservation of damaged materials and regulation of temperatures and humidity in the storage areas. The disaster preparedness plans in place mostly covered structure insurance; protection against fire and water by way of installing fire extinguishers; smoke sensors; fire detectors and construction of purpose-built structures. The major challenges faced were financial constraints; technological obsolescence; lack of playback equipment; limited training; lack of strong back-up systems and inadequate storage facilities.

Formulation of Unique Standard Protocol To Assess Degree of Deterioration in RCC Buildings

The repairs strategy adopted is replacement of damaged materials without dealing with the real problems. Many engineers unintentionally attempt treating the symptoms, instead of dealing with the cause. Such an approach may offer a quick action with minimum inconvenience to the occupants. But in this process, there is a strong possibility that the source and cause for the distress remain unattended and continue to cause problem even after the superficial repairs have been executed. If structural defects are dealt with in this fashion, it remains only as defects camouflaged beneath finishes, which gives a false sense of safety to the occupants allowing the problem to continue without getting treated. A rational approach to any repair and rehabilitation work to consider the source of the problem and the symptoms together identified on a standard scale is needed. Repairs, maintenance , rehabilitation is an integral part during life span of the structure. Neglecting or avoiding the same results in a potential loss of structure which may ultimately result in loss of human life. Structural Audit is the most commonly used parameter/system which gives a detailed structural information regarding the actual insight of the structure. There are also detailed systems available as far as repairs or rehabilitation is concerned. There is a gap which needs to be bridged between the assessment and the actual repair process. There needs to be a standard system developed which will act as a protocol regarding assessment of the degree of deterioration of the structure.

Delineating the complex mechanistic interplay between autophagy and monocyte to macrophage differentiation: a functional perspective

Autophagy is an extremely essential cellular process aimed to clear redundant and damaged materials. In this study, we demonstrated that mTOR dependent classical autophagy is ubiquitously triggered in differentiating monocytes. Moreover, autophagy plays a decisive role in sustaining the process of monocyte to macrophage differentiation. We have delved deeper into understanding the underlying mechanistic complexities that trigger autophagy during differentiation. We have also shown that autophagy directs monocyte differentiation via protein degradation. Further, we delineated the complex cross-talk between autophagy and cell-cycle arrest in differentiating monocytes. This study also inspects the contribution of adhesion on various steps of autophagy and its ultimate impact on monocyte differentiation. Our study reveals new mechanistic insights into the process of autophagy associated with monocyte differentiation and would undoubtedly help to understand the intricacies of the process better for the effective design of therapeutics as autophagy and autophagy-related processes have enormous importance in human patho-physiology.

Estimation of Uniaxial Material Properties by Miniature Small Punch Testing to Support Post-Irradiation Examination of RPV Steels

The small punch (SP) test technique is expected to become a more common tool for estimating tensile properties since the technique has been approved for standardization and will be published early 2020 as EN-10371. The testing technique is naturally of interest in the nuclear field due to the small amount of material needed for estimating the properties of both virgin and irradiation damaged materials. In the project STRUMAT-LTO, supported within the Sustainable Nuclear Energy Technology Platform (SNETP), there is intention to use both miniature uniaxial test specimen as well as miniature SP specimen to assess the influence of high fluence irradiation on mechanical properties of the samples of the joint NRG-JRC irradiation campaign LYRA-10. The alloys represented in the irradiation campaign are variations of VVER and PWR reactor pressure vessel steels with tailor made chemical compositions. Four of the PWR model steels are tested here with miniature uniaxial specimens using the SP technique at room temperature (RT) and 100°C in as-received material state and at RT for heat treated (450°C / 40 h) material. The SP samples were extracted from used KLST (miniature Charpy) specimens. The results of this test program are expected to provide the basis for the future development of material property determination of irradiated materials.

Analysis of Elastic Nonlinearity Using Continuous Waves: Validation and Applications

The nonlinear elastic response of consolidated granular or damaged materials is the result of the combination of nonlinear attenuation and velocity, coupled with hysteresis, which is linked to non equilibrium effects (often termed conditioning). Thus, a preliminary step towards the comprehension of the physical mechanisms responsible of the nonlinear elastic behaviours consists in quantifying and separating the various contributions. To this purpose, an approach based on a semi-analytical treatment of signals resulting from a monochromatic continuous wave excitation can be successfully implemented. Its validation is discussed here, applying the proposed approach to the analysis of numerical data obtained by using a finite difference spring model code. The accuracy, sensibility and robustness of the protocol are verified in different nonlinear conditions.

Analisis Pengendalian Kualitas Cacat Produk Kaleng 307 di PT.X Menggunakan Metode Six Sigma

Pengendalian kualitas merupakan sebuah teknik yang dapat dilakukan mulai dari tahap sebelum proses produksi hingga proses produksi berakhir. Six sigma merupakan sebuah metodologi terstruktur untuk memperbaiki proses dengan menggunakan statistik dan problem solving tools secara intensif menuju target 3,4 kegagalan per satu juta kesempatan. PT. X bergerak di bidang industri pembuatan kaleng makanan dengan salah satu produknya adalah kaleng tipe two piece cans 307. Berdasarkan informasi perusahaan, pada proses produksi kaleng tipe tersebut seringkali ditemukan produk mengalami cacat yang merugikan perusahaan. Penelitian ini dilakukan untuk mengetahui bagaimana cara yang tepat untuk meminimalkan cacat kaleng tipe tersebut dengan menggunakan metode six sigma. Hasil penelitian diketahui bahwa penyebab utama cacat adalah pekerja kurang teliti, setting clearence dies yang terlalu rapat, dies kemasukan afval, pisau press tumpul, bahan kotor dan rusak, perawatan mesin yang tidak dilakukan secara berkala, area produksi tidak rapi dan bising. Nilai DPMO sebesar 2844 yang dikonversikan kedalam sigma level yakni 4.27. Usulan perbaikan dengan Five-M Checklist meliputi memberikan pelatihan dan memperketat pengawasan kepada pekerja, melakukan setting mesin sesuai prosedur serta ubah clearence dies menjadi 0,24 mm, memperketat pemeriksaan bahan baku kaleng, melaksanakan perawatan mesin sesuai dengan jadwal yang telah ditentukan, menjaga kebersihan dan kerapian area produksi. Quality control is a technique that can be carried out from before the production process until the production process ends. Six sigma is a structured solution to process improvement using statistics and problem solving tools that intensively reach the target of 3.4 recovery per one million opportunities. PT. X is engaged in the industry of making cans with one of its products is a 307 two-piece can. Based on company information, in the production process, cans are found to find products that can save the company. This research was conducted to find out the right way to overcome this type of defect by using the six sigma method. The results of the study are known to be related to the fact that workers do not have meticulous, clear dead settings that are too tight, afval conceded dies, blunt press blades, dirty and damaged materials, machine maintenance that is not officially done, production area is not neat and noisy. The DPMO value is 2844 which is converted into sigma level which is 4.27. Proposed improvements with the Five-M Checklist provide training and tighten supervision to workers, make machine arrangements according to procedures and change clearly to 0.24 mm, tighten inspection of tin raw materials, manage engine maintenance according to agreed schedules, care about cleanliness and neatness production area.