Monolithic Part Research Articles

The application of UHPC on the monolithic part of the Štvanice footbridge

The use of UHPC with fibers is becoming an increasingly common topic in the world. This material is used for its superior mechanical and physical properties and long service life. However, the production cost is high, hence UHPC is used for special applications or for smaller prefabricated parts. This paper focuses on UHPC application for the construction of the Štvanice Footbridge, Prague, the Czech Republic. A monolithic part of the structure was made of UHPC from fresh transport concrete, which was produced by Skanska Transbeton. The special feature is that about 126m3 of fresh concrete was industrially prepared. This concrete achieved the properties of SCC and the final 28 day compressive strength was 120MPa with tensile strength of 18.6 MPa. Due to high hydration heat release rate, an internal water cooling system was designed and sucessfully appled using water from Vltava River.

The use of pile columns during the building construction by the top-down method

The article examines the analysis of publications regarding the use of various types of piles-columns during top-down construction. Today, the following types of piles can be used during construction using the "up-down" technology: bored piles, bored piles with a barrel extension (bell pile), barrettes (barrette), combined piles with a steel core (king post). The article analyzes the buildings that were built by the "up-down" method, as well as the structural characteristics of the piles-columns that were used during their construction. It was established that pile-columns are expected to absorb loads in a wide range from 1.5 to 44.5 MN, on average the calculated load is from 10 to 14 MN. The length of the piles varies from 16 to 67 m, on average - 30...35 m, and they were placed with steps from 1.8 to 4.3 m, on average - 3 m. A growing trend of using combined piles with a metal core (king post) was revealed. Their main advantage is the ability to immediately perceive significant loads from the above-ground part of the building during the simultaneous construction of its underground part and guaranteed indicators of strength and stability of the column. Installation of combined piles with a metal core (king post) involves two stages. At the first stage, a pit is arranged and a reinforcing frame is installed to it, then a concrete mixture is laid to the lower monolithic part of the pile, into which the steel core of the upper part is mounted and it is covered with gravel in the pit. At the second stage, during the construction of the underground floors, the metal core is concreted. At the same time, it was established that the installation and concreting of a metal body is a technologically complex and expensive process that requires a more detailed study of the possibility of improving structural and technological solutions and reducing the cost of work.

Research progress of 3D printing combined with thermoplastic foaming

Thermoplastic foam additive manufacturing is a brand-new industry that perfectly combines the advantages of polymer foaming with AM. The 3D printing industry currently suffers from limited available materials and monolithic part manufacturing, and 3D printed foam offers a new way of thinking to address these challenges. Designing multifunctional components with additive manufacturing gives designers great flexibility, while foaming reduces the weight of materials and costs. The combination of the two allows for the creation of lightweight structural and functional items with differentiated physical properties. This one-of-a-kind and innovative approach can be achieved in the printed section. 3D printing foam, on the other hand, is still in its infancy. This review examines the respective functions and applications of additive manufacturing and foaming, and then attempts to summarize four commonly used 3D printing methods at this stage:1) cellular scaffolds; 2) composite printing foam; 3) post-foaming of printed solid scaffolds; 4) in-situ foam 3D printing. Among these methods, in-situ foam 3D printing is the technique that properly merges the foaming and fused filament fabrication processes. Although in the early stages of research and not yet fully established, this foam 3D printing technique seems to be the trend to replace other foaming processes.

Application of Chain Beam Constraint Model in numerical design Bistable compliant mechanisms

Bistable compliant mechanism is a monolithic part and jointless in the structure, is utilized due to saving energy, precious in operation, and reducing maintenance costs. This mechanism work based on the compression and tension of the flexural beam. Most calculation methods assist the mechanism's characteristics to have challenges because of the nonlinear behavior of the structure. This paper employs the CBCM (Chained Beam Constraints Model) method to analyze and evaluate Bistable compliant mechanisms. The flexural beam of the mechanism is divided into many segments for evaluating the compliant mechanism behavior. This method is verified with the finite element method and the results show insignificant errors. CBCM assists in the design of the compliant Bistable mechanism with high accuracy in a short time.

Development of an information and software model of a specialized concrete work flow to ensure the continuity of the production cycle.

Abstract The subject of the study is the process of automating the calculation of the parameters of the design of the technology of concrete works and the justification of the "standard set" of equipment for the organization of a specialized flow of concreting of a typical floor. The transport-concrete cycle is a synchronized schedule of works of the production cycle for laying concrete mix and the dynamics of the ABS kit movement, ensuring the continuity of concreting, through the use of the selected technological scheme of concreting. It determines the continuity of the technological processes of laying the concrete mixture, based on the requirements of mandatory compliance with the concreting time and reducing the number of technological and organizational interruptions of the parameters of the complex process. Thus, the automation of the presented techniques will significantly facilitate the calculation of the total duration of the construction of the monolithic part of the building and ensure the continuity of work on the construction site The scientific novelty lies in the development of a new information system that will allow calculating organizational and technological parameters. The specialized flow of monolithic concrete works consists of reinforcement, concrete and formwork works taking into account architectural planning, structural and technological factors of the designed buildings and structures. For its successful organization, it is necessary to have a "standard set" of equipment and tooling for the manufacture of reinforcement products, formwork systems and the preparation of commercial concrete mixtures. For a simpler calculation of the total duration of the construction of the monolithic part of the building and uninterrupted operation on the construction site, it was proposed to automate the methods of organization, planning and management of construction.

Calculation Substantiation of the Optimal Anchoring Length of the Working Reinforcement of Precast-Monolithic Piles in the Cryolithozone

The subject of research is the development of rational types of foundations in permafrost. These article is proposed use of prefabricated monolithic piles, providing for a combination of drilling and bored methods of pile foundations. The computational substantiation of the anchoring length of the working reinforcement of precast-monolithic piles under the influence of tangential forces of frost heaving has been carried out. Mathematical modeling of the joint between the prefabricated part of the pile and the monolithic part was carried out in the Ansys software.

Microscale Photopatterning of Through-thickness Modulus in a Monolithic and Functionally Graded 3D Printed Part.

3D printing is transforming traditional processing methods for applications ranging from tissue engineering to optics. To fulfill its maximum potential, 3D printing requires a robust technique for producing structures with precise three-dimensional (x, y and z) control of mechanical properties. Previous efforts to realize such spatial control of modulus within 3D printed parts have largely focused on low-resolution (mm to cm scale) multi-material processes and grayscale approaches that spatially vary the modulus in the x-y plane and energy dose-based (E = I 0 t exp) models that do not account for the resin's sub-linear response to irradiation intensity. Here, we demonstrate a novel approach for through-thickness (z) voxelated control of mechanical properties within a single-material, monolithic part. Control over the local modulus is enabled by a predictive model that incorporates the observed non-reciprocal dose response of the material. The model is validated by an application of atomic force microscopy to map the through-thickness modulus on multi-layered 3D parts. Overall, both smooth gradations (30 MPa change over ≈75 μm) and sharp step-changes (30 MPa change over ≈5 μm) in modulus are realized in poly(ethylene glycol) diacrylate based 3D constructs, paving the way for advancements in tissue engineering, stimuli-responsive 4D printing and graded metamaterials.

Impacts of layout, surface condition and alloying elements on diffusion welding of micro process devices

AbstractThe formation of a monolithic part during diffusion bonding is accompanied by the diffusion of atoms across the bonding planes. At sufficient low roughness, it mainly depends on the temperature and dwell time. At the same time, the diffusion process competes against grain growth. By adjusting an appropriate level of bearing pressure, it is possible to control deformation taking into account additional parameters resulting from mechanical microstructures and the design and aspect ratio of the part. Furthermore, material properties, such as the content of alloying elements, the degree of cold work hardening and the grain size, have an impact on diffusion and deformation behavior. Also the surface condition of mating surfaces is important to diffusion kinetics and the quality of the joint. Especially passivation layers of corrosion‐resistant alloys, such as stainless steels and nickel‐based alloys, impair diffusion. In contrast to this, cold work hardening at low depth below the surface, e. g. by means of a blasting processes, may facilitate formation of a good bond and help to limit grain size. For oxide dispersion‐strengthened materials, additional impacts on diffusion bonding behavior applies.

Increasing Structural Strength of Tillage Machines’ Working Bodies

According to the analysis of published materials, the design with an attachable chisel has enjoyed the broadest use because it has a monolithic nose part with an additional component (chisel) that provides extra strength to this area. The force impact of the soil environment on the facial surface of the plowshare nose is analyzed. In most cases, the plowshare fails by breakdown and deformation in the zones of the nose and the first fastener hole. According to the theory of elasticity, this hole is the point of support for the cantilever beam with an arm extended from the first fastener hole to the blade perpendicular to the weak section line. The cantilever beam with regard to the plowshare nose is a triangle with a continuously increasing cross section from the blade to the first fastener hole; that is why failures may occur in any point along the arm line, whatever the arm length. It has been established that, when the chisel is mounted on the plowshare with side faces made parallel to the landward edge line, the strength of the tip increases on the plowshoe with all the fastener holes arranged in a single line, but the zone of the first fastener hole becomes weaker because extra force is generated that produces the bending torque and the rotational torque under the soil pressure. It has been shown that the plowshare strength in the zone of the first fastener hole is increased by mounting the attachable chisel so that the line along the side faces of the chisel splits the chisel into two equal parts by form and area and passes through the first fastener hole perpendicularly to the weak section and crosses the holes for fastening the chisel to the plowshare frame. Thus, the forces that cause the bending torque in the cantilever beam fastening point, i.e., in the first fastener hole, will be active only along one line perpendicular to the weak section line. This way the strength in the weak section zone close to the first fastener hole will increase because the impact of other extra soil forces will be minimized.

Salt Spray Testing on the Chloride Resistance of Jointed Concrete

Joints existing in segmental precast and pouring constructions have poorer performance than the monolithic parts in concrete structures, of which the mechanical behaviors have been studied by many researchers. However, studies related to the durability of concrete rarely focus on joints. The purpose of this study is to compare the chloride resistances between joints and the monolithic parts. Concrete structures are generally under a certain stress state, so unstressed specimens and specimens under compressive and tensile stresses were prepared. Salt spray tests on specimens with different stress states and different joint types were conducted. Based on the test results of chloride profiles, the chloride resistances of the specimens under different stress states were compared. The results indicate that the monolithic part has a better chloride resistance than the joint, no matter what the stress state is. Moreover, the chloride resistances of the different joints also differ greatly.

Compact illumination optic with three freeform surfaces for improved beam control.

Multi-chip and large size LEDs dominate the lighting market in developed countries these days. Nevertheless, a general optical design method to create prescribed intensity patterns for this type of extended sources does not exist. We present a design strategy in which the source and the target pattern are described by means of "edge wavefronts" of the system. The goal is then finding an optic coupling these wavefronts, which in the current work is a monolithic part comprising up to three freeform surfaces calculated with the simultaneous multiple surface (SMS) method. The resulting optic fully controls, for the first time, three freeform wavefronts, one more than previous SMS designs. Simulations with extended LEDs demonstrate improved intensity tailoring capabilities, confirming the effectiveness of our method and suggesting that enhanced performance features can be achieved by controlling additional wavefronts.

Process Modeling of Composite Materials for Wind-Turbine Rotor Blades: Experiments and Numerical Modeling.

The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes. The investigation focuses on the simulation of temperature distribution for one-sided, self-heated tooling and thick laminates. Experimental data from rotor-blade production and down-scaled laboratory tests are presented. Based on influencing factors that are identified, a physical model is created and implemented as a simulation. This provides an opportunity to simulate temperature and cure-degree distribution for two-dimensional cross sections. The aim of this simulation is to support production processes. Hence, it is modelled as an in situ simulation with direct input of temperature data and real-time capability. A monolithic part of the rotor blade, the main girder, is used as an example for presenting the results.

Ring-Based Stiffening Flexure Applied as a Load Cell With High Resolution and Large Force Range

This paper applies linear elastic theory and Castigliano's first theorem to design nonlinear (stiffening) flexures used as load cells with both large force range and large resolution. Low stiffness at small forces causes high sensitivity, while high stiffness at large forces prevents over-straining. With a standard 0.1 μm deflection sensor, the nonlinear load cell may detect 1% changes in force over five orders of force magnitude. In comparison, a traditional linear load cell functions over only three orders of magnitude. We physically implement the nonlinear flexure as a ring that increasingly contacts rigid surfaces with carefully chosen curvatures as more force is applied. We analytically describe the load cell performance as a function of its geometry. We describe methods for manufacturing the flexure from a monolithic part or multiple parts. We experimentally verify the theory for two load cells with different parameters.

A high-resolution and large force-range load cell by means of nonlinear cantilever beams

In the present work, we describe a nonlinear stiffening load cell with high resolution (the ability to detect 1% changes in the force) that can function over a large force range (5 orders of magnitude), and exhibit minimal hysteresis and intrinsic geometric protection from force overload. The stiffening nature of the load cell causes its deflection and strain to be very sensitive to small forces and less sensitive to large forces. High stiffness at high forces prevents the load cell from over-straining. We physically implement the nonlinear springs with cantilever beams that increasingly contact rigid surfaces with carefully chosen curvatures as more force is applied. We analytically describe the performance of the load cell as a function of its geometric and material parameters. We also describe a method for manufacturing the mechanical component of the load cell out of one monolithic part, which decreases hysteresis and assembly costs. We experimentally verify the theory for two load cells with two different sets of parameters.

Periods and Damping Rates of Fast Sausage Oscillations in Multishelled Coronal Loops

Standing sausage modes are important in interpreting quasi-periodic pulsations in the lightcurves of solar flares. Their periods and damping times play an important role in seismologically diagnosing key parameters like the magnetic field strength in regions where flare energy is released. Usually such applications are based on theoretical results neglecting unresolved fine structures in magnetized loops. However, the existence of fine structuring is suggested on both theoretical and observational grounds. Adopting the framework of cold magnetohydrodynamics (MHD), we model coronal loops as magnetized cylinders with a transverse equilibrium density profile comprising a monolithic part and a modulation due to fine structuring in the form of concentric shells. The equation governing the transverse velocity perturbation is solved with an initial-value-problem approach, and the effects of fine structuring on the periods $P$ and damping times $\tau$ of global, leaky, standing sausage modes are examined. A parameter study shows that fine structuring, be it periodically or randomly distributed, brings changes of only a few percent to $P$ and $\tau$ when there are more than about ten shells. The monolithic part, its steepness in particular, plays a far more important role in determining $P$ and $\tau$. We conclude that when measured values of $P$ and $\tau$ of sausage modes are used for seismological purposes, it is justified to use theoretical results where the effects due to fine structuring are neglected.

Sub-scale Machining of Large Components

A post-processing algorithm for CNC machine NC code was developed for altering NC code based on measurements from a stand-alone coordinate metrology system that measures the orientation and offset of the part and machine coordinate systems (CS). With this post-processing algorithm, the ability to machine a monolithic part larger than the working area of a machine in multiple sections becomes possible. A series of test parts were machined with a Haas Vertical Milling Machine (VMM) and a Leica laser tracker as proof of concept and to determine the errors introduced into the machining process by adding the additional metrology system. Monte Carlo simulations confirm that adding the stand-alone metrology system increases the magnitude of errors to approximately the accuracy of the metrology system itself, about 50 micrometers. The initial set of test parts machined showed errors at a factor of 25 larger than expected. It was determined that a component used to determine the machine's spindle location was introducing significant error into the process. The component was replaced and new parts machined that showed a significant improvement but still with errors larger than expected. Machine squareness errors showed the importance of measuring CS features within the same plane. Finally, it was determined that the definition of the part CS is sensitive to how the part is fixtured to the machine. Sub-scale machining is a viable process for machining large components with a slight increase in feature location error.

Predictive Modeling for Tool Deflection and Part Distortion of Large Machined Components

Machined monolithic components provide the foundation for modern aircraft structures requiring high performance designs in terms of weight, strength, and fatigue properties. Part distortions arising from machining-induced stresses and tool deflection resulting from high dynamic cutting forces frustrate manufacturing and assembly processes, necessitating expensive in-process and post-machining corrective measures aimed at eliminating their effects. Component weight and cost requirements are often compromised by adding thicker component section designs or off-machine part flipping processes as a distortion control mechanism. Similarly, small depths of cut are taken to minimize cutting forces and tool deflection. Additional spring passes are also taken to eliminate any undercut errors introduced by unanticipated deflection and distortion problems. The ability to accurately predict and minimize tool deflections and part distortion via simulations can significantly reduce manufacturing and assembly costs. This paper presents physics-based models for predicting tool deflection and part distortions by considering the appropriate physics for each problem. Dynamic cutting forces predicted by physics-based machining models, and tool compliance properties are incorporated into a detailed linear elastic deflection model in order to predict in-process deflections along a computer numerical control (CNC) machining toolpath. Similarly, bulk stress state and machining-induced stresses for large, monolithic part machining are taken into account for predicting part distortions. Sources of stresses may include heat treatment, quenching, forging, and machining operations. Bulk stress data from heat treatment predictive models can also be imported and mapped onto the workpiece finite element model. CNC part programs, along with stresses arising from corresponding tooling, are processed and analyzed. Results of a validation study for workpiece distortion predictions are presented for a number of monolithic, thin-walled components. Predictions for tool deflection are also compared against experimental measurements for multiple cutting configurations and tool diameters. Good correlation is found between predictions and measurements of deflection.

Design and Implementation of Control System in Ultrasonic Detection Machine for Plate Part

It is provided that when a machine has some thin-walled monolithic structure parts, It can improve equipment stiffness, reduce the weight of the equipment, greatly reducing equipment parts number. But, the casting property of the thin-walled monolithic structure parts are very bad, at the same time, those parts may have a warp in machining processes. So, to a thin-walled monolithic structure part of an important machine, nondestructive inspection should be carried out before assembly. The machine typically was designed to detect if a plate part has some imperfections. The machine includes control system built with SIEMENS CPU224 programmable logic controller (PLC), hydraulic driving system and the ultrasonic detection, etc. The prototype built can detect a key part before assembled, which is used in military, high pressure vessel and huge bridge.

Design of a compact six-component force and moment sensor for aerodynamic testing

The measurement of steady and fluctuating forces acting on a body in a flow is one of the main tasks in wind-tunnel experiments. Usually, a multi-component strain gauge force and moment sensor (also known as balance) is used to generate signals which are processed by means of an adequate instrumentation. To design a wind-tunnel balance, the specifications of the load ranges and the available space (for the placement of the balance inside or outside the model) are required. The main challenge is to conceive the elastic element of the sensor as a monolithic part with a relative simple geometry and to identify the adequate placement of strain gauges to maximize the measuring sensitivities and to diminish the inter-influence of the components. This paper describes the design of a six-component force/moment sensor which is compact, has high measuring sensitivities, and can be used either as internal or as external balance in the aerodynamic testing.

Performance of a micro engine with heptane as working fluid

A micro Newcomen engine is proposed. To overcome the problems of friction and leakage of the micro mechanical parts during engine’s operation, we use a flexible ripple tube to integrate piston and cylinder into one monolithic part. Heptane is used as the working fluid, and it works in the two-phase condition for higher energy output density per thermodynamic cycle. In the experiment, the prototype engine is tested under different operational conditions. It works continuously and generates the net mechanical work of 0.833 J per cycle with an efficiency of 2.77% in the maximum. The experimental results prove its feasibility. However, the prototype engine still requires further improvement and optimization for better performance.