Additional Fasteners Research Articles

Devising a calculation method for modern structures of current-conducting elements in large electric machines in a three-dimensional statement

The jumpers of rotor pole-to-pole connections are highly stressed elements in a hydraulic generator structure. These assemblies often fail due to deformation that exceeds the size of an air gap. Existing methods do not take into account the thermal component and attempts to improve the design are not based on mathematical models that make it possible to perform calculations with an accuracy of more than 50 %. The method devised in this work makes it possible to obtain boundary conditions of the third kind on the basis of three-dimensional mathematical modeling of the ventilation system of the hydraulic unit without simplifications. The method accuracy is explained by taking into account the spatial thermal component. The heat transfer coefficient determined by this method in the pole-to-pole connections area was ~250 W/(m2·K). Using FEM, mathematical modeling of the thermal stress state of pole-to-pole connections was carried out, taking into account mechanical and thermal factors. This made it possible to design the improved connection structure with additional fastening elements, which make it possible to reduce the displacement to 0.03 mm, and the stress to 53 MPa at the rotor rotation frequency of 880 rpm. This design makes it possible to enable reliable operation of the hydraulic unit under the condition of increasing the rotor rotation frequency to overspeed with disconnected combinatorial dependence, provided that the actual stresses are 0.95 % of the material yield strength. The convergence of the values obtained by the proposed method and by the HSS method exceeded 99 %. The practical result is the proposals for the hydraulic generator design modernization

Toward Cost-Effective Timber Shell Structures through the Integration of Computational Design, Digital Fabrication, and Mechanical Integral ‘Half-Lap’ Joints

In a global context, where the construction industry is a major source of CO2 emissions and resource use, is dependent on concrete and its risks, and lags behind in digitalization, a clear need arises to direct architecture towards more practical, efficient, and sustainable practices. This research introduces an alternative technique for building timber space structures, aiming to expand its applications in areas with limited access to advanced technologies such as CNCs with more than five axes and industrial robotic arms. This involves reconfiguring economic and ecological constraints to maximize the structural and architectural advantages of these systems. The method develops a parametric tool that integrates computational design and manufacturing based on two-axis laser cutting for shells with segmented hexagonal plywood plates. It uses a modified ‘half-lap joint’ mechanical joint, also made of plywood and without additional fasteners, ensuring a precise and robust connection. The results demonstrate the compatibility of the geometry with two-axis CNC machines, which simplifies manufacturing and reduces the cuts required, thus increasing economic efficiency. The prototype, with a span of 1.5 m and composed of 63 plywood panels and 163 connectors, each 6 mm thick, supported a point load of 0.8 kN with a maximum displacement of 5 mm, weighing 15.1 kg. Assembly and disassembly, carried out by two students, took 5 h and 1.45 h, respectively, highlighting the practicality and accessibility of the method. In conclusion, the technique for building timber shells based on two-axis CNC is feasible and effective, proven by practical experimentation and finite element analysis.

Эффективность различных оперативных способов лечения переломов ключицы

Fractures of the clavicle in frequency occupy one of the first places in case of damage to the musculoskeletal system. In this connection, many methods have been developed for the treatment of clavicle fractures; however, an effective method of fixation, devoid of shortcomings, remains the subject of research. The aim: to evaluate the effectiveness of various surgical methods for the treatment of clavicle fractures on the example of the Multidisciplinary clinic named after Professor Kh.Zh. Makazhan (Karaganda, Kazakhstan). Methods. A retrospective study was conducted in 276 patients with clavicle fractures older than 10 years. Of the total number of patients, the largest number are men - 221 patients (80.07%), women - 55 patients (19.92%). The use of intramedullary osteosynthesis (using pins, rods) was about 9% or 25 of all operated patients. With the help of an overlay plate, fixation was performed in 86% of patients (238 people), while out of 238 patients operated on with an overlay plate, 152 patients were operated on due to repeated referral from other clinics, and the remaining 86 were operated on urgently. Treatment with the rod apparatus was carried out in 1 patient. Results. As a result of treatment, the majority of patients achieved satisfactory results. However, when using intramedullary osteosynthesis (with the help of a pin, a rod), in 6 patients out of 25 operated by this method, the fixator migrated, and therefore bone osteosynthesis was performed. In patients treated with overlay plates, migration of the structure or the development of diastasis was not observed. As a result of the treatment with the rod apparatus, no complications were observed either. Conclusion. Based on the obtained statistical data, we see that plate osteosynthesis provides more rigid fixation, and additional fastening of autografts is performed in the treatment of false joints, which is effective for further fusion of fragments. However, despite the effectiveness of plate osteosynthesis, its disadvantages require the development of a new fixator for intramedullary osteosynthesis.

3D Printer planning the production of weapon parts in the shortest possible time

This study presents a mathematical model to optimise the production of weapon parts using a 3D printer using parallel machine planning. After the battle with the enemy is over, many weapons will be damaged. Damaged weapons are classified as full, medium or minor damage. Among these, weapons with minor damage can be used again immediately after repair, simply by replacing the damaged or missing part. However, due to the constant movement of troops around the battlefield, carrying thousands of weapon parts is not practical. To remedy this situation, a 3D printer can be carried in a separate unit and the necessary parts can be produced in the field to repair even minor weapon damage. A model for scheduling the production of the necessary parts in a short period after each battle is over is proposed for this purpose. A set of multiple 3D printers can operate as a parallel machine and produce different parts. The 3D printers can produce a finished product for each part simultaneously or produce two separate parts for each part, but if they make individual parts, this increases the burden on that part due to the production of additional fasteners for assembly. That is, in the case of making individual parts, the total production time for that part will be longer compared to the case of making the finished product immediately. Nevertheless, this study confirms that by introducing a sub-batch fabrication concept of weapon parts, the production time can be reduced when planning the production schedule of a 3D printer.

Результаты внедрения комплекса мероприятий по обеспечению микроклиматических параметров рудничной атмосферы на объектах НШПП «Яреганефть» ООО «ЛУКОЙЛ-Коми»

The Yarega field is currently the only one in Russia where oil production is carried out by the thermal mining method. The deposit was discovered in 1932, and it is located in the southern part of the Timan-Pechora province, in the Ukhta district of the Komi Republic. The oil of the Yarega field has a high viscosity, and in order to ensure its production, the oil-bearing formation is thermally affected by steam supply through steam-falling (injection) wells into the rock mass. Depending on the development system used, steam injection can be carried out both through surface vertical wells and through underground hollow ascending wells. A combination of these methods is also possible. The heated oil-containing liquid from the producing wells located in the underground mining galleries of the mine is delivered to the surface using the existing collection and transportation system. The uniqueness of the technology of thermal mining production of heavy oil creates additional difficulties in the development of various technical solutions due to the lack of experience in operating such objects in Russia. This oil extraction technology is accompanied by an increase in the temperature and humidity of the mine atmosphere in mine workings, due to the presence of heat sources and areas where steam enters the mine working. Despite the applied technical solutions (increasing ventilation performance, cooling the air by spraying cold water, erecting additional concrete fasteners), there is a possibility of the microclimatic parameters of the air in the mine workings going beyond the established limits. In order to normalize the parameters of the mine atmosphere, a whole complex of technical and organized measures is being implemented, including thermal insulation of heat sources using modern materials. The article discusses various technologies for the use of thermal insulation coatings, analyzes their efficiency and offers solutions for choosing the optimal ways to reduce the temperature and humidity of air in the mine workings.

CONTROL OF EQUIPMENT FOR INCREMENTAL FORMING USING A LASER TRACKER

The technological equipment geometry control has a significant impact on the overall quality and performance of the product in many manufacturing processes such as multi-position assembly and stamping as well as on productivity and production costs. One of the most promising means of technology equipment geometry control in the digital economy condition is a laser tracker. The robotic incremental sheet forming process assumes the necessary flexibility and profitability due to a very flexible tool chain. In this case, the trajectory of the universal tool is set using a processing program determined by the product geometry. The technological equipment geometry control of the robotic complex for incremental sheet forming was carried out in 2 stages. At the first stage, the measurements were carried out manually in the absolute range measuring system mode. At the second stage, a dynamic measurement of the blank plane displacement was carried out automatically in the interferometer mode during forming process. It was shown that the largest slipway deviation more than 1 mm and it occurs in the direction of the main application of force, i.e. in the product manufacture depth. This value can have a serious impact on the of manufacturing parts geometry accuracy. Based on the measurement results, it can be concluded that it is necessary to increase the rigidity of the frame, either by adding additional fasteners, or by using more rigid materials of its construction.

Novel Drone Design Using an Optimization Software with 3D Model, Simulation, and Fabrication in Drone Systems Research

This paper presents the design of a small size Unmanned Aerial Vehicle (UAV) using the 3DEXPERIENCE software. The process of designing the frame parts involves many methods to ensure the parts can meet the requirements while conforming to safety and industry standards. The design steps start with the selection of materials that can be used for the drone, which are polylactic acid (PLA), acrylonitrile styrene acrylate (ASA), and acrylonitrile butadiene styrene (ABS). The drone frame consists of four main parts, which are the center top cover (50 g), the side top cover (10 g), the middle cover (30 g), and the drone’s arm (80 g). A simulation was carried out to determine the stress, displacement, and weight of the drone’s parts. Additionally, a trade-off study was conducted to finalize the shapes of the parts and the various inputs based on their priorities. The outcome of this new design can be represented in design concepts, which involve the use of the snap hook function to assemble two body parts together, namely the middle cover and the center top cover, without the need of an additional fastener.

Micro-notches as a novel connection system for timber-concrete composite slabs

Timber-concrete composite slabs are more and more in use: the combination of timber and concrete combines the advantages of both materials and offer a valid solution for the increasing demand for sustainable construction. The connection between timber and concrete is the crucial element, yet its potential regarding material and time expenses is not exploited. This paper presents the novel connection system micro-notches, an interlocking concept between timber and concrete with indentations in the millimetre range. Micro-notches provide a continuous shear transfer without additional steel fasteners such as screws or dowels. The paper presents the development of the micro-notch concept in an extensive experimental program supplemented with analytical and numerical models, a calculation model, and practice-relevant guidelines. The results of the investigations show that micro-notches feature an approximately rigid composite action between timber and concrete and a sufficient shear strength for the use in office and residential buildings.

Розробка конструкції механічного самоцентрованого пристрою для встановлення оптичних деталей

Під час роботи над створенням оптичної лави для моделювання оптичних систем приладів виникла проблема із встановленням окремих оптичних деталей без оправ та додаткових елементів кріплення. При чому, це в більшості своїй деталі типу тіл обертання, але діаметр їх може значно відрізнятись. Тому постало завдання розробити конструкцію пристрою, що дозволить закріплювати на оптичній лаві оптичні деталі типу сферичних лінз; дзеркал сферичних та плоских; плоско-паралельних пластин та інших осесиметричних деталей. Діапазон діаметрів деталей, що планується закріплювати знаходиться у межах 30…90 мм, товщина по краю – до 10 мм. Головна умова – пристрій має центрувати деталі, автоматично розташовувати їх по вісі пристрою при закріпленні. Закріплення має відбуватись швидко, без застосування проміжних елементів та деталей. 
 Проведено дослідження відомих конструкцій, визначено оптимальний варіант конструкції, спроєктовано вузол та виготовлено за допомогою 3D-друку. Результати аналізу виготовленого пристрою та його випробувань довели працездатність конструкції та її ефективність, визначено шляхи щодо модернізації конструкції задля усунення виявлених недоліків.
 
 While working on the creation of an optical bench for modeling optical systems of devices, there was a problem with the installation of individual optical parts without frames and additional fasteners. Moreover, it is mostly a part of the type of rotating bodies, but their diameter can vary significantly. Therefore, the task arose to develop a design of the device that will fix on the optical bench optical parts such as spherical lenses; spherical and flat mirrors; plane-parallel plates and other axisymmetric parts. The range of diameters of the details which are planned to be fixed is within 30…90 mm, thickness on edge - to 10 mm. The main condition - the device must center the parts, automatically place them on the axis of the device when fixing. Fastening should be quick, without the use of intermediate elements and parts. Research of known constructions is carried out, the optimum variant of a design is defined, the knot is designed and made by means of 3D-printing. The results of the analysis of the manufactured device and its tests proved the efficiency of the structure and its efficiency, identified ways to upgrade the structure to eliminate the identified shortcomings.

Potential of shear-clinching technology for joining of three sheets

The load-specific design of car bodies often requires the joining of more than two sheets. However, due to the additional interfaces and the mutual influence of the joining partners, joining of multi-layer sheets is challenging. This applies for welding technologies and in particular for joining by forming processes, which are often limited by the mechanical properties of the joining partners or require additional fasteners. The shear-clinching technology combines shear-cutting and clinching and therefore allows the joining by forming of high-strength materials without additional fasteners or pre-holing. Yet, the process has only been analyzed for two sheets. Thus, the potential of the technology for joining three sheets is investigated within the scope of this work. Starting from a two-sheet joint with punch-sided AA5182-O and die-sided DP600, the upper and the lower sheet are subsequently replaced by two sheets with half the thickness. The shear-clinching process, the joint formation and the resulting load-bearing capacity are analyzed for the joining of three sheets and compared to the two-sheet reference. Shear-clinching of three sheets with DP600 in the middle and the bottom layer was successfully conducted. Under shear load, the load-bearing capacity is comparable to the two-sheet specimens. However, applying tensile load leads to a two-staged failure of the joint and therefore to lower testing forces. When the force is applied to the top and the bottom layer, the joint strength is distinctly reduced, independent from the load direction.

Influence of Tool Wear on the Load-Bearing Capacity of Shear-Clinched Joints

Shear-clinching allows the joining by forming of dissimilar materials with high differences between their mechanical properties without additional fasteners. Since the lower joining partner is indirectly shear cut during the process, even ultra-high strength materials can be joined. However, the cutting of the high-strength materials as well as the extrusion of the upper joining partner leads to high process forces and therefore to high tool loads. This applies in particular for the die, which is highly stressed during the cutting phase and therefore plastically deformed. Within the scope of this work, the influence of the occurring wear on the formation of the joint and its load-bearing capacity is analyzed for a scope of 500 strokes. For this purpose, press hardened 22MnB5 is used as lower joining partner. Its high strength leads to the plastic deformation of the cutting edge, which increases within the first 200 strokes. Afterwards only minor changes occur. Yet, no effect of the occurring wear on the joint formation and the joint strength, which was tested under shear and tensile load, could be determined. Functioning joints could still be produced for more than 500 strokes as the load-bearing capacity remained on a comparable level.

The mechanics of built-up cold-formed steel members

Abstract The paper presents methods of analysis of built-up sections in which the discrete locations of fasteners is accounted for explicitly, rather than by smearing their effect using continuous shear flexibility as in current approaches. By considering fasteners at discrete points, it is possible to analyse the effects of placing additional fasteners at the ends (end fastener groups), to account directly for actual support conditions and to determine the optimum locations of fasteners. The paper first outlines the linear analysis of beams in flexure and introduces the notion of the effective flexural rigidity to account for partial composite actions. Closed form solutions are provided for five load and end support cases to demonstrate the application of the analysis. Next, the paper describes the linear analysis of built-up sections in torsion, considering first uniform torsion followed by non-uniform torsion. Closed form solutions are obtained for the effective torsion rigidity (GJeff) of built-up sections featuring closed loops. A framework is also presented for determining the effective torsion rigidity (EIw,eff) of open built-up sections in non-uniform torsion. The paper concludes with the analysis of built-up sections subject to flexural buckling. A general variational buckling equation is derived followed by an energy-type method for calculating buckling loads for common end support conditions, including columns supported on flexible end tracks. Closed form solutions are presented for up to seven rows of fasteners longitudinally. While by nature approximate, the solutions are shown to be highly accurate. Comparisons are made between the presented closed form solutions and buckling load predictions obtained using current design provisions.

Mathematical modelling of a new implant for interbody lumbar spinal fusion

Objective: using mathematical modeling with the finite element method to develop a model of the interbody implant with an additional fastening element and to evaluate the stress-strain state of the system «vertebral body – implant». Methods: models were designed in SolidWorks software. Two designed schemes with implants were developed and studied: 1) titanium cylindrical; 2) titanium cylindrical with an additional fastening element — a spike. The condition of the Ist stage of the study is the absence of movements of the elements of the contact pair «implant – vertebral body», the IInd — a small relative slip between them with zero friction. Bending loads on the segment were created. Re­sults: the application of an additional fastener significantly in­creases the rigidity of the entire system. Redistribution of stresses occurs with their decrease in the implant with an additional fastening element by 30 % than without it. The equivalent stresses of cortical tissues for the first and second calculation schemes of the first stage of the study turned out to be close in values, the difference is 2 %. For stage II, the difference was 43 %, higher stresses were observed in the case of implant with a spike. Contact pressure indices in models with two types of implants in the absence of movements in the «implant – vertebral body» system are close, the difference is 5 %. In the case of modeling of a small relative slip between them with zero friction (stage II), the difference in values rises up to 54 %, and the lower pressure corresponds to the implant model with a spike. Conclusions: the use of an improved design of the interbody implant with an additional fastening element in the form of a spike is more effective to achieve stabilization in the system of the «vertebral body – implant» compared with a conventional cylindrical implant.

Experimental investigation on the shear properties of notched connections in mass timber panel-concrete composite floors

Mass timber panel-concrete composite floors efficiently combine the structural merits of timber and concrete and are gaining interests from builders and designers. Among different connection systems in the composite floors, the notched connection is both structurally superior and cost effective. However, due to the lack of design methodology, the use of notched connection in mass timber panel-concrete composite floor systems is hindered. This study investigated some important factors that could affect the structural performance of notched connections through experimental studies. Ten types of notched connections were made with varying factors including geometry of the connection, orientation of timber and presence of additional steel fasteners in the connection, and tested under shear load. Test results show that stiffness, load-carrying capacity and failure pattern vary among different configurations, and geometry of the connection and orientation of timber are the most important factors that influence the connection performance. Results from this study could serve as an important reference for the optimal design of the notches in the composite floors, as well as improving the existing design rules and verifying the analytical models for the notched connections.

A study on fracture behavior due to crack propagation at compact tension specimen composed of inhomogeneous metal materials with holes near crack

This paper aims at studying on the fracture behavior due to crack propagation at compact tension specimen composed of inhomogeneous metal materials with holes near main crack. In this study, the experiments were performed for compact tension specimens produced by the mutual bonding metals of stainless steel and brass, and the simulation analyses to verify these experiments were conducted. When the preceding study results are confirmed, the design of structures with no holes near a crack becomes more durable on the strength aspect than the design of structures with holes existing near the crack. The design for highest strength is possible if no holes are pierced in inhomogeneous metal materials bonded with adhesives. On the other hand, in case the holes due to additional bolt and rivet fastening must be pierced, the most similar tendency to that of materials without holes is exhibited when the hole center is placed by about 20 mm from the crack tip. A great difference in strength occurs according to the hole position near the main crack at inhomogeneous metal materials bonded with adhesives. So, the design considering this aspect is deemed important. The data for different positions where the crack propagations occur can be confirmed at analysis and experimental results. Therefore, the changes inside the material that are actually difficult to confirm due to the crack growth characteristics at inhomogeneous materials can be expected through an analysis. The fracture behavior of inhomogeneous metal materials bonded by adhesives was investigated through the experiment and analysis. The basic data through this study could be secured at contributing to the developed design of light-weight composite materials as well as bonding the technology for mutually different materials.

Fundamental mechanisms and their interactions in shear‐clinching technology and investigation of the process robustness

AbstractThe compliance with increasingly stricter emission standards is a challenge for the automotive industry, which requires the utilization of lightweight materials e. g. aluminium and high‐strength steels. Hereby, the load‐optimized design of body parts and the reduction of wall thicknesses are enabled. But, due to the use of dissimilar materials, common joining technologies are reaching their limits. On the one hand, joining by welding is often not possible because of different melting temperatures. On the other hand, joining by forming with additional fasteners increases the cycle time and the costs. However, joining by forming without fasteners is often limited by the mechanical properties of the joining partners. The innovative shear‐clinching technology combines shear‐cutting and clinching in a single stage process and thereby enables joining by forming of materials with high differences regarding their mechanical properties. However, by the combination of the sub‐processes cutting and joining, the complexity of the technology is increased. Thus, within the scope of this work, the fundamental mechanisms in shear‐clinching and their interactions as well as the robustness of the process are analysed, in order to promote the applicability of the technology.

An Experimental Study of the Inductance Parameters of a Smoothing Filter Reactor with a Completely Closed Magnetic Flux

The use of advanced structural concepts for development of electric power equipment of dc traction power supply systems allows one to triple the power density per unit volume. An armored rod radial–cylindrical magnetic system with massive nonlaminated design elements, which is split into sections by nonmagnetic gaps, allows one to provide high mechanical strength without using additional fasteners and pressing elements. This design also provides an admissible level of hysteresis and eddy current losses, as well as meeting the requirements for unconditional linearization of a magnetic flux in the range of working currents. The latter is caused by the performance of smoothing reactors as parts of high-power rectifiers that feed rolling stock.

Experimental and numerical study on the interfacial bonding characteristics of FRP-to-concrete joints with mechanical fastening

Premature debonding is the major barrier to FRP (fibre-reinforced polymer) utilization in FRP-reinforced concrete structures and restricts the promotion of structural bearing capability. The additional mechanical fasteners could restrain the interfacial debonding, which has been suggested by many research studies. However, the mechanism of FRP-to-concrete with mechanical fastening in HB joints still needs to be further studied to make it into a structural design. This study carried out 7 single-shear tests to study the interfacial bonding characteristics with mechanical fastening, and a reliable bond-slip relationship was obtained. The 2D numerical model was built based on the unified bond-slip model and verified through the test results. Parameter analysis was implemented to analyse the further design method, which is not yet clear, including the fastener spacing, number, distributed pattern and external bonding length at the fastener’s two sides.

Cult caves building on the territory of European Russia

The paper deals with cult caves building on the territory of European Russia. The author draws attention to the fact that the process primarily depended on the nature of rock formation where the caves were constructed. In a softer and loose ground the walls and the ceiling were strengthened by armour stone or bricks after taking up the rocks. There was no need in additional fastening of hard rocky ground. The waling was done according to the beds and rock jointing. An adze, a spade, a crowbar as well as other metal tools were used. Construction works proceeded both during the daytime and at night. The space was lighted with candles. The work was organized by the community formed during the cave construction with an active support of the local population. Drawings and plans of venerated underground holy places in Christian pilgrimage centres could be used for construction works. In case of making the cave construction official a professional architect could be invited, the example of it could be Belogorskaya cave which is the longest one in Russia. Intensity of work depended on the age and gender characteristics of the employed and official authorities.

Muhu vammuste lõikelistest eripäradest / Characteristics of the sewing patterns of Muhu overcoats

As the song festival, our main event involving folk costumes, takes place in the summer, when outer garments are not particularly necessary, such garments have received relatively little interest from researchers as an everyday part of folk costume. In this article, I shall examine the characteristics of the patterns of women’s overcoats in Muhu, sharing information I came across when making an overcoat for myself, and when studying, measuring and describing the overcoats found in the collections of Estonian museums.
 A total of 19 overcoats can be found in the collections of Estonian museums. The focus of this article is strictly on Muhu women’s overcoats. Outer garments have been covered before in various books on Estonian folk costumes, but the characteristics of the patterns of Muhu overcoats, including the side gussets, have not been studied in depth. Side gussets are triangular pieces of fabric located at the side seams of the front pieces of the overcoats. In most cases, the gusset is located at the hip or slightly lower; they tend to vary in size between coats (see Table 1). The museum items also included overcoats with gussets added to the shoulders and lower edges. Presumably, these pieces, which seem at first glance unnecessary, have been added for practical purposes.
 Such overcoats were made for special occasions in the life of a girl or young woman, such as for confirmations and weddings. The overcoat was also worn on top of the sheepskin winter coat to keep the latter clean. As a rule, the textile overcoats found in museums were sheep brown originally and could later be coloured black with alder bark.
 All the overcoats studied here were made in a similar way: they consist of four main pieces, with two-piece sleeves, differing only in their manner of sewing and decoration. The material used was hand-woven and fulled wool fabric. The process of wool fulling is long and complex; after textile mills emerged in Estonia, fabric was often taken there to be fulled. When the fabric was ready for sewing, it was narrow, just ca 60 centimetres wide. This meant that extreme care was needed in placing the pattern on the fabric so that as little of the fabric as possible would go to waste.
 The neck would be V-shaped at the front and at the back, with a black or dark blue baize binding decorated with both a rolled hem in orange and by embroidery. The chest part would be decorated with square pieces made of an orange fine wool background with embroidered wool ornaments. The central back seam was similar in all the museum examples, employing an extremely interesting technological solution. The width of the seam varies along the length of the entire seam –wider at the waist (up to 7 cm) so as to shape the waistline, and much narrower at the bottom in order to increase the width of the coat.
 The back pieces of all the overcoats came down longer than at the front, forming a gently sloping triangle at the central back seam. The lower edge of the overcoat was stitched with a couching stitch, and a coloured wool yarn finished off the closed hem. The coats were fastened with hooks at the front; a coloured ribbon, known locally as taht, located at chest-level could be used as an additional fastener.
 The front pieces and gussets of all the women’s overcoats studied here were joined with a lapped seam. To understand why gussets are necessary, I decided to experiment with placing the patterns on the fabric. Figure 4 clearly shows that placing the patterns meant for the front and back pieces with the shoulder seams facing one other ensured that the fabric would be used as economically as possible. The shoulder seam of the back piece intersects with the side seam of the front piece, which results in triangular cut-outs at the sides.
 Gussets are needed at the lower edges of the sides if the piece does not fit the width of the fabric and so the length of the lower edge needs increasing. Several pieces found in museums also have gussets at the shoulders: if the front and back pieces are placed very close to one other on a narrow piece of fabric, the side of the back piece intersects with the shoulder seam of the front piece. We can thus conclude that the gussets are a sign of a thrifty use of fabric which has been made into a decorative element by means of the stitching.
 Keywords: overcoats, folk costumes, Muhu, patterns, cut-out