Wear Analysis of Forging Tools Used in an Industrial Production Process—Hot Forging in Closed Dies of the “Head-Disk” of an Engine Valve Forging

The article performs an analysis of the durability of punches applied in the process of producing a valve forging from chromium-nickel steel. A forging of this type is made in two operations: coextrusion of a long shank, followed by finishing forging in closed dies of the valve head. The product obtained in this way (after other additional finishing procedures) constitutes the key element of the combustion engine (resistant to high pressures and temperatures) in motor trucks. Unfortunately, a significant problem in this production process is a relatively low durability of the forging tools, especially the punch used in the second forging operation. The key element at this stage, deciding about the punch’s further operation, is the area of the so-called “calotte”. The short-term life of the tools results from very hard performance conditions present during the forging process (periodical high mechanical and thermal loads, long path of friction). The latter cause intensive abrasive wear as well as high adhesion of the forging material to the tool surface. Based on the performed studies, including the following: technology analysis, numerical modelling, macro analyses combined with 3D scanning of tool sections as well as microstructural tests and hardness measurements, it was established that it is crucial to properly select the process parameters (charge and tool temperature, tribological conditions), as even slight changes introduced into them significantly affect the operation time of the forging tools. Mastering and proper implementation of the analyzed forging technology requires numerous further studies and tests, which will enable its perfection and thus increase the durability of the tools as well as the quality of the produced items.     

Wear Improvement of Tools in the Cold Forging Process for Long Hex Flange Nuts

Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life.     

Wear Mechanisms of the Forging Tool Used in Pre-Forming in a Double Forging System of Truck Parts

Tool life in plastic forming processes is a problem of the utmost importance as it significantly affects the cost of production. Hot forging with hammers and mechanical presses is an example of the technological process in which the load on tools is extremely high and, consequently, the lifetime of tools is short. Considering, additionally, that this applies to large-scale production, from an economic point of view, the key issue will be to extend the tool life, make an accurate prediction of the number of parts that can be forged before the replacement of dies is necessary, and develop a system for quick tool changeover. Initially, however, it is necessary to understand the causes of excessive tool wear, which may lie in phenomena occurring at the level of microstructure. The aim of this article was to outline an example of the coexistence of multiple wear mechanisms in hot forging dies. For the modified chemical composition, the microstructure examinations were performed in selected areas of the tool. The research has revealed the causes of cracks in tools and some irregularities in the preparation of tools for production process.     

Achieving High-Strength and Toughness in a Mg-Gd-Y Alloy Using Multidirectional Impact Forging

High strength and toughness are achieved in the Mg-4.96Gd-2.44Y-0.43Zr alloy by multidirectional impact forging (MDIF). The forged sample has a fine-grained microstructure with an average grain size of ~5.7 µm and a weak non-basal texture, and it was characterized by an optical microscope (OM), scanning electron microscope (SEM), and electron back-scattering diffraction (EBSD). Tensile results exhibit the tensile yield strength (TYS) and static toughness (ST) of as-homogenized alloy dramatically increased after forging and aging, i.e., the TYS increased from 135−5+4 MPa to 337−2+2 MPa, and the ST enhanced from 22.0−0.5+0.3 MJ/m³ to 50.4−5.4+5.3 MJ/m³. Specifically, the forged Mg-Gd-Y-Zr alloy owns higher TYS than that of commercial rolled WE54 (Mg-5.25Y-3.5Nd-0.5Zr) and WE43 (Mg-4.0Y-3.0Nd-0.5Zr) alloys.     

Influence of Test Conditions on Sliding Wear Performance of High Velocity Air Fuel-Sprayed WC–CoCr Coatings

Sliding wear performance of thermal spray WC-based coatings has been widely studied. However, there is no systematic investigation on the influence of test conditions on wear behaviour of these coatings. In order to have a good understanding of the effect of test parameters on sliding wear test performance of HVAF-sprayed WC–CoCr coatings, ball-on-disc tests were conducted under varying test conditions, including different angular velocities, loads and sliding distances. Under normal load of 20 N and sliding distance of 5 km (used as ‘reference’ conditions), it was shown that, despite changes in angular velocity (from 1333 rpm up to 2400 rpm), specific wear rate values experienced no major variation. No major change was observed in specific wear rate values even upon increasing the load from 20 N to 40 N and sliding distance from 5 km to 10 km, and no significant change was noted in the prevailing wear mechanism, either. Results suggest that no dramatic changes in applicable wear regime occur over the window of test parameters investigated. Consequently, the findings of this study inspire confidence in utilizing test conditions within the above range to rank different WC-based coatings.     

Impact of Rotor Material Wear on the Aluminum Refining Process

The paper presents the results of tests carried out during the refining of the AlSi9Cu3(Fe) alloy in industrial conditions at the FDU stand. In the tests, three different rotors made of classical graphite, fine-grained graphite and classical graphite with SiC spraying were tested for the degree of wear. A series of tests was conducted for five cases—0% to 100% of consumption every 25%—corresponding to the cycles of the refining process. The number of cycles corresponding to 100% wear of each rotor was determined as 1112. The results of the rotor wear profile for all types of graphite after the assumed cycles are presented. Comparison of CAD models of new rotors and 3D scans of rotors in the final stage of operation revealed material losses during operational tests. The study assessed the efficiency of the rotor in terms of its service life as well as work efficiency. It was estimated on the basis of the calculated values of the Dichte Index (DI) and the density of the samples solidified in the vacuum. The structure of samples before and after refining at various stages of rotor wear is also presented, and the results are discussed.     

Microstructure and Wear Properties of Laser Cladding WC/Ni-Based Composite Layer on Al–Si Alloy

The microstructural and wear properties of laser-cladding WC/Ni-based layer on Al–Si alloy were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and wear-testing. The results show that, compared with the original specimen, the microhardness and wear resistance of the cladding layer on an Al–Si alloy were remarkably improved, wherein the microhardness of the layer achieved 1100 HV and the average friction coefficient of the layer was barely 0.14. The mainly contributor to such significant improvement was the generation of a WC/Ni-composite layer of Al–Si alloy during laser cladding. Two types of carbides, identified as M₇C₃ and M₂₃C₆, were found in the layer. The wear rate of the layer first increased and then decreased with the increase in load; when the load was 20 N, 60 N and 80 N, the wear rate of layer was1.89 × 10⁻³ mm³·m⁻¹, 3.73 × 10⁻³ mm³·m⁻¹ and 2.63 × 10⁻³ mm³·m⁻¹, respectively, and the average friction coefficient (0.14) was the smallest when the load was 60 N.     

The Wear of Seal Fins during High-Speed Rub between Labyrinth Seal Fins and Honeycomb Stators at Different Incursion Rates

Labyrinth seals as a noncontact sealing technology are widely used in aero-engine. To improve the efficiency of the aero-engine, the clearance between the rotor and stator must be as small as possible. However, the change of the clearance between the rotor and stator because of thermal expansion, vibration, mechanical loading may lead to undesirable high-speed rub, which will lead to the cracking of the seal fins. This paper focuses on the wear of the seal fin after the rub and presents the rubbing tests between seal fins and the metal honeycomb under rubbing speed of 380 m/s and incursion rates between 20 and 180 μm/s, with an incursion depth of 1500 μm and a temperature of 350 °C. The rubbing force and temperature were recorded, and the seal fins were checked by SEM and EDS. The results show that the wear mechanism of seal fins changed from oxidation wear and adhesive wear to delamination wear and then to metal wear with the increasing incursion rate. The axial cracks appeared on the worn surface of the seal fins due to the cracking of tribo-layers under periodic thermomechanical stress. The wear mechanism of the seal fin also has a great influence on the rubbing force and temperature.     

Study of Wear Phenomenon of a Dental Milling Cutter by Statistical–Mathematical Modeling Based on the Experimental Results

The wear phenomenon of a dental milling cutter is studied based on experimental results and data and validated by statistical–mathematical modeling. The results of the statistical–mathematical modeling by the interpolation of the experimental results (data) regarding the wear of the dental milling cutter analyzed and obtained in the work process are presented in this paper. These results (data) are important because they lead to polynomial functions which by interpolation approximate very well the dependent parameter, specifically the wear process (mass lost due to dental milling cutter wear, m_w), considered in the experimental program. The polynomial interpolation functions are valid, only during the experimental testing range of the dental milling cutter, to describe the wear phenomenon; the extrapolations do not lead to satisfactory results. However, by using a controlled interpolation function with an exponential component, the extrapolation of the results is possible. Therefore, the purpose of this paper is the statistical–mathematical modeling by the interpolation of the experimental results of the mass lost due to dental milling cutter wear, m_w, using the deterministic differential model for the work process of it. Thus, interesting conclusions can be drawn relating to the phenomenon. In support of these statements come the results of the statistical–mathematical modeling by the interpolation of the experimental data obtained in the work process of the dental milling cutters, leading to practical applications, such as the extension of the life of dental milling cutter, useful even for its operation optimization; determination of possible criteria for replacing the worn dental milling cutters; the extension of the life of the materials from which dental milling cutters are built; or the provision of ideas for constructive solutions. Based on the modeling results by interpolation, it was found that the dental milling cutter during the milling operation works with high efficiency (mass loss due to wear is very reduced) in the first 11 h of operation, i.e., about a 10% increase in lifetime. After 11 h of operation, mass loss due to wear of the dental milling cutter increases relatively exponentially; thus, it is recommended that, in the normal way, the dental milling cutter be replaced with a new one to ensure high standards of materials processing.     

Microstructure and Wear Resistance of Laser-Clad Ni–Cu–Mo–W–Si Coatings on a Cu–Cr–Zr Alloy

To improve the wear resistance of high-strength and high-conductivity Cu–Cr–Zr alloys in high-speed and heavy load friction environments, coatings including Ni–Cu, Ni–Cu-10(W,Si), Ni–Cu–10(Mo,W,Si), and Ni–Cu–15(Mo,W,Si) (with an atomic ratio of Mo,W to Si of 1:2) were prepared using coaxial powder-feeding laser cladding technology. The microstructure and wear performance of coatings were chiefly investigated. The results revealed that (Mo,W)Si₂ and MoNiSi phases are found in the Ni–Cu–10(Mo,W,Si) and Ni–Cu–15(Mo,W,Si) coating. WSi₂ phases are found in the Ni–Cu–10(W,Si) coating. The degree of grain refinement in Ni–Cu–10(Mo,W,Si) was greater than that of the Ni–Cu–10(W,Si) coating after the effect of Mo. The excellent wear resistance and micro-hardness of the Ni–Cu–15(Mo,W,Si) coating were attributed to the increase in its dispersion phase, which were approximately 34.72 mg/km and 428 HV, 27.1% and 590% higher than the Cu–Cr–Zr substrate, respectively. The existence of silicide plays an important role in grain refinement due to the promotion of nucleation and the inhibition of grain growth. In addition, the wear mechanism transformed from adhesive wear in the Ni–Cu coating with no silicides to abrasive wear in the Ni–Cu–15(Mo,W,Si) coating with high levels of silicides.     

Investigation of the Technological Possibility of Manufacturing Volumetric Shaped Ductile Cast Iron Products in Open Dies

Information about the technological possibility of stamping in open dies, round-shaped forgings made of ductile cast iron, is outlined herein. Cast iron’s propensity for plastic deformation under complex loading conditions is analyzed from the standpoint of the morphology of graphite inclusions, depending on the degree and mechanical scheme of deformation. The research methodology included: the choice of a brand of cast iron with spherical graphite and the technological process of its deformation; mathematical modeling of the deformation process using the DEFORM–3D software package; stamping of an experimental batch of forgings; and microstructural studies of the forging material, together with the data of its stress–strain state and the direction of flow of the material. Under the conditions of comprehensive compression of the workpiece material at the beginning of the deformation process, lateral pressure was created from the tool walls. It was carried out by selecting the size and shape of the initial blank by mathematical modeling. When analyzing the morphology of graphite inclusions, the stress state scheme was determined as the main influencing factor. The greatest change in the shape and size of graphite inclusions of cast iron, including their crushing, corresponds to the condition of the disappearance of all-round compression. When stamping in open dies, this occurs in the area where the material exits from the stamp engraving into the flash gutter. In the process of forming, cast iron showed the possibility of deformation in the deformation intensity index ε_i = 2.5.     

Determination of the Kinetics and Thermodynamic Parameters of Lignocellulosic Biomass Subjected to the Torrefaction Process

The torrefaction process upgrades biomass characteristics and produces solid biofuels that are coal-like in their properties. Kinetics analysis is important for the determination of the appropriate torrefaction condition to obtain the best utilization possible. In this study, the kinetics (Friedman (FR) and Kissinger–Akahira–Sunose (KAS) isoconversional methods) of two final products of lignocellulosic feedstocks, miscanthus (Miscanthus x giganteus) and hops waste (Humulus Lupulus), were studied under different heating rates (10, 15, and 20 °C/min) using thermogravimetry (TGA) under air atmosphere as the main method to investigate. The results of proximate and ultimate analysis showed an increase in HHV values, carbon content, and fixed carbon content, followed by a decrease in the VM and O/C ratios for both torrefied biomasses, respectively. FTIR spectra confirmed the chemical changes during the torrefaction process, and they corresponded to the TGA results. The average E_α for torrefied miscanthus increased with the conversion degree for both models (25–254 kJ/mol for FR and 47–239 kJ/mol for the KAS model). The same trend was noticed for the torrefied hops waste samples; the values were within the range of 14–224 kJ/mol and 60–221 kJ/mol for the FR and KAS models, respectively. Overall, the E_a values for the torrefied biomass were much higher than for raw biomass, which was due to the different compositions of the torrefied material. Therefore, it can be concluded that both torrefied products can be used as a potential biofuel source.     

Preliminary Studies of the Durability of Tools Used to Form Ceramic Tiles Made of Hardox 600 and NC11LV Steel

The study performs a comparative analysis of the wear of tools made of two wear-resistant materials: steel Hardox 600 and NC11LV, used in the process of forming a band for roofing tiles. The analyses were to allow the assessment of the possibility of replacing the standard material for tools in this process with a much less expensive tool steel for cold work after heat treatment (with a large number of carbides), as an alternative material dedicated to tools resistant to intense abrasive wear. The performed investigations included a macroscopic and geometrical analysis with the use of 3D scanning, microstructural analyses conducted by means of a light microscope, as well as an analysis of the topography of the working areas of the tools with the use of SEM, and microhardness tests. The obtained results demonstrate that the tools made of both materials were characterized with a similar level of wear, which, in the most critical area, reached over 4 mm, while the tools made of steel NC11LV worked over a much longer period of time without regeneration, equaling 912 h, and an insert made of steel Hardox 600 operated for 384 h. A higher tool life in the case of NC11LV steel may be the result of higher hardness and the presence of hard carbides.     

The Importance of Echocardiography in Transcatheter Aortic Valve Implantation

Valvular heart diseases cause serious health problems in Turkey as well as in Western countries. According to a study conducted in Turkey, aortic stenosis (AS) is second after mitral valve disease among all valvular heart diseases. AS is frequently observed in elderly patients who have several cardiovascular risk factors and comorbidities. In symptomatic severe AS, surgical aortic valve replacement (AVR) is a definitive treatment. However, in elderly patients with left ventricular dysfunction and comorbidities, the risk of operative morbidity and mortality increases and outweighs the gain obtained from AVR surgery. As a result, almost one‐third of the patients with serious AS are considered ineligible for surgery. Transcatheter aortic valve implantation (TAVI) is an effective treatment in patients with symptomatic severe AS who have high risk for conventional surgery. Since being performed for the first time in 2002, with a procedure success rate reported as 95% and a mortality rate of 5%, TAVI has become a promising method. Assessment of vascular anatomy, aortic annular diameter, and left ventricular function may be useful for the appropriate selection of patients and may reduce the risk of complications. Cardiac imaging methods including 2D and 3D echocardiography and multidetector computed tomography are critical during the evaluation of suitable patients for TAVI as well as during and after the procedure. In this review, we describe the role of echocardiography methods in clinical practice for TAVI procedure in its entirety, i.e. from patient selection to guidance during the procedure, and subsequent monitoring.     

Analysis of the Risk of Wear on Cemented and Uncemented Polyethylene Liners According to Different Variables in Hip Arthroplasty

Wear debris in total hip arthroplasty is one of the main causes of loosening and failure, and the optimal acetabular fixation for primary total hip arthroplasty is still controversial because there is no significant difference between cemented and uncemented types for long-term clinical and functional outcome. To assess and predict, from a theoretical viewpoint, the risk of wear with two types of polyethylene liners, cemented and uncemented, a simulation using the finite element (FE) method was carried out. The risk of wear was analyzed according to different variables: the polyethylene acetabular component’s position with respect to the center of rotation of the hip; the thickness of the polyethylene insert; the material of the femoral head; and the relationship of the cervical–diaphyseal morphology of the proximal end of the femur to the restoration of the femoral offset. In all 72 simulations studied, a difference was observed in favour of a cemented solution with respect to the risk of wear. With regard to the other variables, the acetabular fixation, the thickness of the polyethylene, and the acetabular component positioning were statistically significant. The highest values for the risk of wear corresponded to a smaller thickness (5.3 mm), and super-lateral positioning at 25 mm reached the highest value of the von Mises stress. According to our results, for the reconstruction of the acetabular side, a cemented insert with a thickness of at least 5 mm should be used at the center of rotation.     

Investigation on Microstructure,Mechanical and Wear Properties of HVOF Sprayed Composite Coatings (WC–Co + CR) On Ductile Cast Iron

Recent work indicates that the high-velocity oxy-fuel (HVOF) thermal spraying WC–Co coatings have been used to enhance the wear resistance of various engineering components in a variety of industrial environments. In the present work, WC–Co powder, containing Cr particles in an amount of 10%, was deposited on ductile cast iron with the HVOF thermal spray coating technique. An investigation was conducted to determine the role of Cr particles in the WC–Co coating produced with the HVOF technique on microstructure, mechanical, and wear properties in a system of type: WC-Co coating/ductile cast iron. The microstructure of the HVOF-sprayed WC–Co + Cr coating was characterised by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of a coating with low porosity, compact structure, and good adhesion to the substrate with a typical lamellar structure composed of fine molten Cr particles and finely fragmented WC grains embedded in a Co matrix, reaching the size of nanocrystalline. The scratch test was applied for the analysis of the adhesion of coatings to the substrate. The erosion behaviour and mechanism of material removal was studied and discussed based on microstructural examinations. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the WC–Co + Cr/ductile cast iron, as microhardness and erosion resistance of the coating. It was found that the addition of Cr particles to the WC–Co powder, which causes hardening of the binder phase is a key influence on increased mechanical and wear properties in the studied system. Additionally, due to the construction of nanostructured coatings, suitable proportion of hard and soft phases, the technique sprayed HVOF coatings have advantageous properties such as high density and good slurry erosion resistance.     

Historically Accurate Reconstruction of the Materials and Conservation Technologies Used on the Facades of the Artistic Buildings in Lecce (Apulia,Italy)

The protection of the stone surfaces of the buildings of the city of Lecce (Apulia, Italy) represents an ancient practice, which has always allowed the conservation of the historical-artistic heritage of the city, which nowadays is an international touristic and cultural destination. The identification of ancient recipes, materials and methodologies for the protection of historical buildings plays an important role in establishing correct protocols in order to ensure the durability of stone surfaces over time. This work presents a historically accurate reconstruction of the materials and conservation technologies used on the facades of the artistic buildings in Lecce. Several historical buildings, both civil and religious, have been selected in order to investigate the treatments applied on their facades and to know the traditions spread in the past in the field of building conservation in the Salento territory. Thanks to non-invasive or micro-destructive techniques (optical microscopy, ATR-FTIR spectroscopy, pyrolysis–gas chromatography–mass spectrometry), the characteristic molecular markers of the materials and the products of degradation have been identified, deepening the knowledge of the mechanisms of deterioration and interaction between the stone material, the surface finish and the surrounding environment. The paper is a valuable tool for the knowledge of ancient traditions and the planning of proper restoration works.     

Study of the Optimal Composition and Storage Conditions of the Fricke–XO–Pluronic F–127 Radiochromic Dosimeter

This paper presents the results of research on the Fricke–XO–Pluronic F–127 dosimeter. It consists of a Fricke dosimetric solution and xylenol orange (XO), which are embedded in a matrix of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F–127). Upon irradiation, Fe⁺² ions transform into Fe⁺³, forming a colored complex with XO ([XO-Fe]⁺³). The color intensity is related to the dose absorbed. The optimal composition, storage conditions, and radiation-induced performance of the Fricke–XO–Pluronic F–127 dosimeter were investigated. The optimal composition was found to be 1 mM FAS, 50 mM sulfuric acid (H₂SO₄), 0.165 mM XO in 25% Pluronic F–127. The basic features of this dosimeter are discussed, such as dose sensitivity, linear and dynamic dose range, stability before and after irradiation, storage conditions, dose response for irradiation with 6 and 15 MV photons, and batch-to-batch reproducibility. The obtained results showed a certain potential of the Fricke–XO–Pluronic F–127 for radiotherapy dosimetry.     

Diet‐induced prediabetes: Effects on the activity of the renin–angiotensin–aldosterone system in selected organs

Aims/IntroductionDerangements often observed with type 2 diabetes are associated with disturbances in renin–angiotensin–aldosterone system (RAAS) activity. A positive correlation between local RAAS activity and the complications observed in type 2 diabetes has been noted. However, the detrimental ramifications due to moderate hyperglycemia noted in prediabetes, and the affected organ system and mechanistic pathways are not elucidated. Hence, this study investigated the effects of diet‐induced prediabetes on RAAS in various organs.Materials and MethodsMale Sprague–Dawley rats were separated into two groups: (i) non‐prediabetes through exposure to standard rat chow group; and (ii) diet‐induced prediabetes group by exposure to a high‐fat high‐carbohydrate diet for 32 weeks. RAAS activity in the skeletal muscle, adipose tissue, liver, pancreas and heart was determined through the analysis of RAAS components, such as renin, angiotensinogen, angiotensin‐converting enzyme and angiotensin II type 1 receptor through polymerase chain reaction, as well as the quantification of angiotensin II and aldosterone concentration. Furthermore, nicotinamide adenine dinucleotide phosphate oxidase, superoxide dismutase and glutathione peroxidase 1 concentrations were determined in the skeletal muscle, pancreas and heart, in addition to the hepatic triglycerides.ResultsThe RAAS components were elevated in the diet‐induced prediabetes group when compared with the non‐prediabetes group. This was further accompanied by increased nicotinamide adenine dinucleotide phosphate oxidase and reduced superoxide dismutase and glutathione peroxidase 1 concentrations in the selected organs, in addition to the elevated hepatic triglycerides concentration in the diet‐induced prediabetes by comparison to non‐prediabetes group.ConclusionsDue to these observed changes, we suggest that local RAAS activity in the prediabetes state in selected organs elicits the derangements noted in type 2 diabetes.     

The Performance of Graphene-Enhanced THz Grating: Impact of the Gold Layer Imperfectness

We report the performance of a graphene-enhanced THz grating fabricated by depositing a gold layer on the femtosecond micromachined SiO₂ substrate. The morphology of the gold plated patterned substrate was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), while the quality of the chemical vapor deposition (CVD) graphene was evaluated by Raman spectroscopy. The electromagnetic (EM) response of the metasurface comprising the graphene sheet and the gold plated substrate was studied by THz time domain spectroscopy in the 100 GHz–1 THz frequency range. We employed the finite elements method (FEM) to model the metasurface EM response by adjusting the ac conductivity of the gold layer covering the patterned SiO₂ substrate to reproduce the measured transmission/reflection spectra. The results of the numerical simulation reveal the impact of the imperfectness of the gold layer on the performance of the THz metasurface. The experimental results are well described in terms of the Drude–Smith model of metal conductivity that takes into account the anisotropic scattering of the carriers in thin metal films.