Form Deviation Research Articles

On the Influence of the Characteristic Frequency and Broadband of Seismic Effects on the Vertical Rod Oscillations

The problems of longitudinal oscillations of high vertical rods with orientation to the application of results in the problems of seismic calculations are considered. Mathematical models of free, forced harmonic and forced random oscillations caused by kinematic disturbances of the lower end are obtained. Application of methods of separation of variables and finite differences in combination with visualization of calculations in Matlab environment gave own values and own functions, and then amplitudes and mean square deviations of oscillations. It is shown how the preliminary consideration of harmonic oscillations significantly simplified the solution of the stochastic problem. Influence of characteristic frequency and broadband parameter of input random process on the form and standard deviation of longitudinal oscillations is studied.

Improving geometry element regression analysis for dimensional X-ray computed tomography measurements using locally determined quality values

X-ray computed tomography (CT) enables the determination of numerous dimensional measurands with a single scan. However, measurements are often affected by artefacts, which are mainly caused by the effects of the complex physical interactions between the used radiation, the measurement object and the detector as well as the algorithms used for measurement data processing. Surface regions affected by artefacts lead to an inaccurate surface determination and therefore to increased measurement deviations and uncertainties of geometric measurements. This contribution aims to demonstrate the possibility of detecting negatively affected surface regions by a qualitative examination of the underlying volume data in the region of each determined surface point. This classification is used to improve different kinds of sphere measurements, which are evaluated by performing regression analysis onto the measured point clouds. Because of the available qualitative classification for each surface point, it is possible to apply a suitable weighting metric before applying the regression analysis in order to reduce the influence of lowly classified surface areas onto the measurement result. The workflow is demonstrated with a calibrated multi-sphere specimen. The results show that a significant reduction of the measurement errors associated with the evaluation of sphere centre distances, sphere form and radius deviations, respectively, can be achieved, while using the regression analysis tools of the commercial software VGStudio Max (Volume Graphics GmbH).

Computed tomography enabling virtual assembly

Computed tomography (CT) is the only dimensional measurement technology that captures holistic geometric information of the complete object. The availability of equally and densely distributed measurement data gathered by CT enables the consideration of local form deviations of the object's surface for the definition of a datum system. A datum system describes a coordinate system that is used for referencing geometrical tolerances. Therefore, the datum definition by an approximation of datum features is replaced by a fitting method called virtual assembly (VA), where the datum surfaces are registered in order to simulate the real, physical workpiece contact. Besides describing the theory, in this paper the method is evaluated using a linear guide assembly as an example that is compared to the real assembly of the object.

Digital twin of composite assembly manufacturing process

Industry is facing the management of geometrical deviations along the entire lifecycle of the product. It is helped by digital twin tools that may minimise the geometrical deviations from nominal of products. The new digital twin tools allow to manage geometrical variations through a set of steps fully related by modern information and communication technologies that establish a continuous and unambiguous flow of information among the different steps of this digital process along the whole product lifecycle. They are based on data coming from manufacturing, assembly and inspection. The available large data sets from manufacturing and inspection allow to develop new and more accurate simulation models that realistically consider form deviations and process signature, i.e. the pattern left by the manufacturing process on the produced part surfaces. The present work introduces a digital twin tool to support the lightweight design of assemblies in composite material. It establishes a continuous and unambiguous flow of variation information from the part design to assembly, passing through manufacturing by considering the manufacturing signature. It was applied to a case study and the obtained results agree with the experimental ones.

Vibrational Impact on Milled Surface Irregularities

The methodology and results of a simultaneous study of causally linked parameters of mechanical vibration (cause) and surface irregularities (consequence) in flat milling with an end mill are given. The features of measurement and analysis of surface quality parameters through the application of the separation frequency method of profilogram harmonic components on the surface roughness, waviness, and the deviation of the profile are reviewed. A new method of profilogram digital processing is developed, comprising the steps of its digitization, low-pass filtering, and the formation of the roughness profile. The initial theoretical positions on modeling mechanical (elastic) waves which are caused by vibration in the cutting zone and propagate in a solid, liquid, and gas (air) media are presented. The results of experimental studies of milled surface profilogram and the vibro-displacement signal in the milling are given. Keywords: part performance, surface finish, surface integrity, vibro-acceleration, vibro-velocity, vibro-displacement, roughness, waviness, form deviation.

System of metrological assurance of traceability of measurements of mass geometry characteristics

A system of metrological support is proposed that allows testing for type approval, verification and calibration of stands for measuring mass, coordinates of mass center and moments of inertia. The mathematical model of a special standard has been developed. It is based on the analytical principles for the determination of the mass center coordinates and inertia moments of homogeneous bodies with a regular geometric shape. The standard consists of a set of modules and fasteners of a special shape. Each module is a reference measure of both mass, center of mass coordinates, and moments of inertia, and can be used either separately or in a set with other modules. A scheme for transferring units of values from state primary standards of mass and length to stands using special standards has been developed. A method for calibration of special standards has been developed. It includes indirect measurements of the coordinates of the center of mass and moments of inertia based on the results of direct measurements of the mass and geometric dimensions of the standard modules’ elements, as well as measurements of the form deviations and deviations of position of the standard modules’ surfaces and static balancing of the standard. Technical requirements for special standards have been developed to minimize methodological measurement uncertainties when reproducing units of values by the standard. A line of special standards was created, their certification and approval in Rosstandart was carried out. Stand verification methods using special standards have been developed and approved. The type approval of two stands was carried out using special standards. The decision to grant a patent for the invention “Method for determining the error of the stand for measuring the characteristics of the mass geometry of products and a device for its implementation” was received.

Straightness, flatness and cylindricity characterization using discrete Legendre polynomials

In dimensional metrology the straightness, flatness or cylindricity of surfaces is commonly measured at a limited number of equidistant points on the surface. This paper describes some opportunities and characteristics of discrete Legendre polynomials to describe and analyze such measurements. The reference surface can be adequately described using a few lower order polynomials while the higher order polynomials describe the form deviations and these are independent of different reference surface definitions. Cylindricity can be described by combining Fourier coefficients for the circumference with discrete Legendre polynomials for measurements taken along the axis. Some application examples are given.

Analysis of the Influence of Surface Integrity of Cemented Carbides Machined by Sinking EDM on Flexural Fatigue

Abstract Bulk forming is a manufacturing technology characterized by high tool loads. In order to reduce form deviations and increase surface qualities this manufacturing technology aims for even higher process forces, which result in larger stresses during the forming process. Consequently, the tool life of steel tools decreases drastically. A material that offers an alternative are cemented carbides due to their ability to withstand enormous compressive stresses and their resistance to wear. However, for the same reason, cemented carbides are hard to machine with conventional cutting technologies. A cost-efficient alternative is electrical discharge machining (EDM), because of its independence from mechanical material properties. Due to the brittle character of cemented carbides, one of the challenges in EDM, the reduction of the influence on the surface integrity, becomes a paramount concern. Thermal stresses caused by machining can initiate cracks that may lead to a failure of the tool after a few load cycles. The risk of crack initiation can be reduced with an appropriate machining strategy. In order to correlate the influence of surface integrity with flexural strength, load-controlled fatigue tests are conducted with two different types of cemented carbides that have each been machined with three different EDM-strategies. Along with the fatigue evaluation, the cross sections of the specimens are examined regarding their surface integrity. With these results it is possible to evaluate the impact of surface integrity of EDMed cemented carbides on the flexural fatigue.

Tolerance analysis tools for fixture design: a comparison

Abstract Fixtures are used to rapidly, accurately and securely position workpieces during machining, such that all machined parts fall within the design specifications. However, the geometrical deviations of both the fixture and the datum surfaces of the workpieces involve a geometrical deviation of the part machined surface. Workpiece and locators constitute an assembly. Therefore, the aim of the present work is to apply models and software commonly used for tolerance analysis to estimate the deviation from the nominal location of a drilled hole due to both locators’ position deviation and form deviation of the part datum into contact with locators.

Performance of SAE 52100 steel grinding using MQL technique with pure and diluted oil

Grinding is one of the highest dimensional accuracy machining processes in the industry. To obtain the smallest form and geometrical workpiece deviation, it is necessary to add cutting fluids as the aim of ensuring the tolerances established for this process, by reducing the machining temperature, due to its cooling capacity, facilitating the cutting by its capacity lubricant. Currently, it is known that together with conventional fluid, there are problems related to environmental pollution and damage to the operator’s health. Some techniques have come up to alleviate these problems; one of them is the minimum quantity lubricant (MQL) that has been outstanding for obtaining results close to flood application. This technique has stood out concerning the surface integrity and geometric and dimensional precision of the machined workpiece since a smaller quantity of cutting fluid is directed precisely in the cutting region. However, the reduced cooling capacity of MQL has promoted the researches to perfect this technique. In this way, this research aims to analyze the consequences of the water addition in this method to minimize the probability of thermal damages in the workpiece when applied in the grinding of SAE 52100 steel which is widely used in the manufacture of bearings, shafts, blades, and various other components where there is a need for high hardness and high abrasion resistance. The analysis of the output parameters evaluated the performance of the technique: surface roughness (Ra), roundness error, diametrical wheel wear, viscosity, cutting power, metallography, and microhardness. Beyond this, it evaluated the behavior of each lubri-refrigeration method concerning the ground surface through scanning electron and confocal microscopy, and it used optical microscopy to analyze of the grinding wheel cutting surface. The results of the water increment in the MQL were superior to those of the MQL (oil-pure) in almost all aspects, remaining inferior only in the cutting power. Also, the 1:5 dilution (oil-water) presented close and satisfactory results when compared to traditional cutting fluid (flood); it becomes an excellent alternative for insertion environmentally correct cutting fluids in today’s industry.

A comprehensive study of three dimensional deviation analysis methods for aero-engine rotors assembly

Rotor assembly is a core tache in the whole process of aero-engine manufacturing. The assembly deviation analysis is an effective tool to control deviation propagation. For aero-engine rotors assembly, the traditional deviation control methods focus on the modeling of plane dimension chain and extremum analysis, which is difficult to comprehensively consider the rich geometrical errors and their relationship to each other; meanwhile, the precision prediction is too conservative to reduce the parts’ rework frequency and adjusting difficulty; In addition, traditional methods overemphasize the promotion of parts’ machining precision, and ignore the means of overall stack optimization. In recent years, three dimensional deviation analysis and control methods have a lot of developments. These methods synthetically consider the matters of size deviation, form and location deviation, fixing structure and the positioning relationship. The poor concentricity problem of gyro black assembly can be exactly described, which is beneficial to control assembly deviation. This paper deals with aero-engine rotors assembly problem from two perspectives: deviation expression and deviation propagation, gives the difficulties of this topic, and provides a detailed review on the most recent approaches about partial deviation expression and three dimensional chain propagation. Finally, a perspective overview of the future research about aero-engine rotors assembly is presented, such as rotors deformation, surface morphology representation and matching, and the relationship between assembly precision geometry and performance physical quantity.

3D-customized thin-walled ceramic mouldings produced by deep drawing of green tapes

Thin-walled 3D-customized ceramic components can be used, e.g. for inert and thermal resistant housings as well as special surface structured kiln furniture. For manufacturing such components, deep drawing of ceramic green tapes has been used. The technology has been almost not applied for processing of ceramic green tapes. A new approach was developed to realize a homogenous ceramic particle packing and hence uniform green density within a deep drawn green tape. After debinding and sintering, defect-free model structures with a dense microstructure (density > 99%) were achieved. Within this study, the deep drawing of ceramic green tapes by using a new approach was investigated. The developed approach brings several beneficial properties together, e.g. a reproducible form deviation and more importantly a homogeneous particle distribution allowing homogeneous and dense structures. With this results, the transformation of non-complex and cheap ceramic green tapes to 3D-customized and near-net-shape thin-walled mouldings becomes possible.

Precision contact displacement meter

Modern machine building, instrument making, robotics, optical production, aircraft industry and other industries where mechanical devices are manufactured and used, are closely linked to the need for accurate measurement of the movement of objects and measurements of their linear dimensions. The variety of areas of use of devices for measuring linear displacements and distances, the constant growth of the requirements for the accuracy of the sensors, the range of measurable quantities, as well as the orientation to solving specific practical problems, suggest that the development and research of new meters for linear displacements and distance meters, as well as improvements of existing sensors are an important and relevant task. Practical examples of problems solved by existing meters of linear quantities are the control and measurement of the geometric characteristics of the product (dimensional measurement, dimensional deviation of form and location of surfaces); ensuring precise positioning of separate units of assembly units when they are assembled in precision instrumentation; precise positioning of moving elements, etc. Among the various technical solutions for the creation of high-precision measuring devices, the meters should be noted with the contact method of measurement and the use of inductive converters with a digital reference measurement result. Contact displacement meters using inductive sensors are characterized by the ease of production and use. They are unpretentious to the environment and have rather high metrological characteristics.

Software Dedicated to Determining a Strategy of Coordinate Measurements

The paper presents the developed software dedicated to determining a measurement strategy of contact coordinate measurements conducted by using coordinate measuring machines. The created software enables to calculate locations of the scanning lines along free-form surfaces of measured workpieces. The presented program was developed by using the MATLAB software. The created program was tested based on the selected examples of curvilinear surfaces. Measurement points were located in the parts of surfaces characterized by the biggest form deviations resulting from machining processes. The calculated deviations were the results of simulations performed by using selected CAM software. The presented software increases the efficiency of measurement processes.

Biomolecular Aspects of Schizophrenia

Abstract
 Schizophrenia is a common psychiatric disorder, which is characterized by severe distortion of reality; disturbances in thoughts, feelings and behavior; according to DSM V is a disorder form deviations fundamentals and characteristics of thought and perception, and by the innapropriate or blunted affect. The influence of genetics is believed to have a role in psychiatric disorders, especially if the disorder has occurred in young adults or adolescents. The pathophysiology of schizophrenia is closely related to disorders of the biomolecular aspects of the central nervous system. Dopamine activity in the striatal area and prefrontal cortex is a mechanism believed to be the cause of the emergence of positive and negative symptoms in schizophrenia. Meanwhile, neuronal cell apoptosis and increased oxidants, especially in the basal ganglia and prefrontal cortex areas cause worsening of negative symptoms experienced by schizophrenic patients.

Additive Manufacturing of Complex Components through 3D Plasma Metal Deposition—A Simulative Approach

This study examines simulative experimental investigations on the additive manufacturing of complex component geometries using 3D plasma metal deposition (3DPMD). Here, complex contour surfaces for a cross-rolling tool were produced from weld metals in multilayer technology through 3DPMD. As a consequence of the special features of 3DPMD with large-weld metal volumes, greatly differing properties between base material/deposited material and asymmetrical heat input, the resulting shrinkage, deformation and residual stresses are particularly critical. These lead to dimensional and form deviations as well as the formation of cracks, which has a negative influence on the quality of the plasma deposition-welded component structures. By means of the thermo-elastic-plastic simulation model, the temperature field distribution, deformation, and residual stresses occurring during additive 3DPMD of tool contours were predicted and analyzed. The temperature field distribution and its gradients were determined using the ellipsoid heat-source model for the 3DPMD process. On this basis, a coupled thermo-elastic-plastic structural–mechanical analysis was performed. Accordingly, the results achieved were used for the production of almost-net-shaped tool contour surfaces with predefined layer properties. The acquired simulation results of the temperature fields, deformation, and residual stress condition show good alignment with the experimental results.

A kinematic approach for error modelling in drilling

PurposeThe purpose of this paper is to model how geometric errors of a machined surface (or manufacturing errors) are related to locators’ error, workpiece form error and machine tool volumetric error. A kinematic model is presented that puts into relationship the locator error, the workpiece form deviations and the machine tool volumetric error.Design/methodology/approachThe paper presents a general and systematic approach for geometric error modelling in drilling because of the geometric errors of locators positioning, of workpiece datum surface and of machine tool. The model can be implemented in four steps: (1) calculation of the deviation in the workpiece reference frame because of deviations of locator positions; (2) evaluation of the deviation in the workpiece reference frame owing to form deviations in the datum surfaces of the workpiece; (3) formulation of the volumetric error of the machine tool; and (4) combination of those three models.FindingsThe advantage of this approach lies in that it enables the source errors affecting the drilling accuracy to be explicitly separated, thereby providing designers and/or field engineers with an informative guideline for accuracy improvement through suitable measures, i.e. component tolerancing in design, machining and so on. Two typical drilling operations are taken as examples to illustrate the generality and effectiveness of this approach.Research limitations/implicationsSome source errors, such as the dynamic behaviour of the machine tool, are not taken into consideration, which will be modelled in practical applications.Practical implicationsThe proposed kinematic model may be set by means of experimental tests, concerning the industrial specific application, to identify the values of the model parameters, such as standard deviation of the machine tool axes positioning and rotational errors. Then, it may be easily used to foresee the location deviation of a single or a pattern of holes.Originality/valueThe approaches present in the literature aim to model only one or at most two sources of machining error, such as fixturing, machine tool or workpiece datum. This paper goes beyond the state of the art because it considers the locator errors together with the form deviation on the datum surface into contact with the locators and, then, the volumetric error of the machine tool.

Design, additive manufacturing, processing, and characterization of metal mirror made of aluminum silicon alloy for space applications

Metal mirrors are used for spaceborne optical systems, such as telescopes and spectrometers. In addition to the optical performance, the mechanical needs and the mass restrictions are important aspects during the design and manufacturing process. Using the additive manufacturing process, optimized internal lightweight structures are realized to reduce the weight of the system while keeping the mechanical stability. A mass reduction of ≈60.5 % is achieved. Using the aluminum silicon alloy AlSi40, the thermal mismatch of the mirror base body to a necessary electroless nickel-polishing layer is minimized. Based on an exemplary mirror design, the optimization of the interior lightweight structure is described, followed by the manufacturing process from additive manufacturing to diamond turning, plating, and polishing. Finally, the results of surface metrology and light scattering measurements are presented. A final form deviation below 80 nm p . − v . and a roughness of ∼1 nm rms could be demonstrated.

Improvement of the replication quality of randomly micro-textured injection-moulding components using a multi-scale surface analysis

In this work, the relations between the replication quality of random, coarse textured, surfaces with the injection-moulding process has been analysed through 3D areal characterisation techniques. The multi-scale surface approach has been applied to effectively separate the main surface components, roughness, waviness and form. Amplitude, functional, hybrid and spatial parameters, as well as alternative surface characteristics such as the number of micro-cavities (NG), grain area (GA¯) and grain volume (GV),¯ were used as a way to determine the influence of the manufacturing process on the replication quality of the mould texture, either at the macro- or micro-scale. A model to quantify the effect of the injection-moulding parameters on surface texture replication has been obtained through a 24 factorial design of experiments. It was found that the holding pressure was the main parameter to enhance the mould texture replication, followed by the melt and mould temperatures. The injection volumetric flow rate did not have a significant effect on the texture replication ratio. The surface analysis, at the human eye resolution, only allows the detection of macro-defects such as form deviation. On the other hand, the surface characterisation at the micro-scale allows the detection of roughness differences, up to 30% on average, as a function of the injection conditions.

On machine test of Inverse Projected-Fringe system for measurement of form deviation and surface profile of axisymmetric objects

An in-situ Inverse Projected-Fringe system for on-machine inspection of axisymmetric parts is developed. Parts considered for this study are specular with RMS surface roughness >1 μm and have large slopes with radii of about 50 mm. The in-situ system is developed based on the previously reported Inverse Projected-Fringe technique in order to determine the on-machine measurement repeatability and reproducibility for industrial applications. In order to measure the whole part, a stereo arrangement and a new data fusion technique are used to increase the field of view of the system. A measurement trace with the highest Signal to Noise Ratio (SNR) is selected to achieve the best accuracy. The repeatability and reproducibility tests of the system are reported. It is shown the in-situ Inverse Projected-Fringe system is capable of measuring the form deviation from a master-part with repeatability and reproducibility of ±1 to ±7 μm, equivalent to a dynamic range of one part in 25,000 to one part in 3,600, respectively for the areas with higher SNR to lower SNR. Simultaneously, the RMS surface roughness has been measured with an accuracy of ±1.2 μm or better.