Research

17 pages, 4424 KiB

Open AccessArticle

Establishing the Durability and Reliability of a Dental Bur Based on the Wear

by Filip Ilie and Ioan Alexandru Saracin

Materials 2023, 16(13), 4660; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16134660 - 28 Jun 2023

Viewed by 680

This paper analyzes the phenomenon that conditions the durability and reliability of a type of dental bur based on the wear of the active part and with effect on its quality. For the experimental study, a conical-cylindrical dental bur and a sample dental [...] Read more.

This paper analyzes the phenomenon that conditions the durability and reliability of a type of dental bur based on the wear of the active part and with effect on its quality. For the experimental study, a conical-cylindrical dental bur and a sample dental material in cobalt–chromium alloy, cylindrical shape, tested on a specially made experimental installation were used. In this paper, the most significant parameter was considered (loss of mass, m_w, through the wear of the active part of a tested dental bur), which highlights the studied wear phenomenon. This is useful for the establishment of the durability and reliability of the dental bur by the extension of the lifetime or even optimization of its operation. The wear phenomenon of the active part of dental bur is studied based on the results and experimental data obtained in the work process that was validated by interpolation and led to polynomial functions which approximate very well the dependent parameter, m_w, considered in the experimental program. The results of the interpolation showed that in the first 11 h of work, the dental bur works with high efficiency (allow optimizing operation or offering new ideas for constructive solutions), after which it can be easily decommissioned; i.e., it should be replaced with a new one (establishing some possible criteria for replacing the used dental bur). Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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20 pages, 11057 KiB

Open AccessArticle

Prediction of Extrusion Machine Stem Fatigue Life Using Structural and Fatigue Analysis

by Dong-Yul Kim, Ji-Wook Kim, Jin-Su Ha, A-Ra Jo, Sung-Yun Lee, Myeong-Sik Jeong, Dae-Cheol Ko and Jin-Seok Jang

Materials 2023, 16(8), 3192; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16083192 - 18 Apr 2023

Viewed by 1015

Abstract

In this study, the characteristics of the SKD61 material used for the stem of an extruder were analyzed through structural analysis, tensile testing, and fatigue testing. The extruder works by pushing a cylindrical billet into a die with a stem to reduce its [...] Read more.

In this study, the characteristics of the SKD61 material used for the stem of an extruder were analyzed through structural analysis, tensile testing, and fatigue testing. The extruder works by pushing a cylindrical billet into a die with a stem to reduce its cross-sectional area and increase its length, and it is currently used to extrude complex and diverse shapes of products in the field of plastic deformation processes. Finite element analysis was used to determine the maximum stress on the stem, which was found to be 1152 MPa, lower than the yield strength of 1325 MPa obtained from tensile testing. Fatigue testing was conducted using the stress–life (S–N) method, considering the characteristics of the stem, and statistical fatigue testing was employed to create an S–N curve. The predicted minimum fatigue life of the stem at room temperature was 424,998 cycles at the location with the highest stress, and the fatigue life decreased with increasing temperature. Overall, this study provides useful information for predicting the fatigue life of extruder stems and improving their durability. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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16 pages, 2657 KiB

Open AccessArticle

A Study on the Pressure Mechanism Improvement of a Roller-Type Machine Working Bodies

by Auezhan T. Amanov, Gayrat A. Bahadirov and Ayder M. Nabiev

Materials 2023, 16(5), 1956; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16051956 - 27 Feb 2023

Cited by 7 | Viewed by 1724

Abstract

The parameters of the improved design of the pressure mechanism of a roller technological machine for squeezing wet materials are investigated in this article. The factors influencing the parameters of the pressure mechanism, which provide the required force between the working rolls of [...] Read more.

The parameters of the improved design of the pressure mechanism of a roller technological machine for squeezing wet materials are investigated in this article. The factors influencing the parameters of the pressure mechanism, which provide the required force between the working rolls of a technological machine during the processing of moisture-saturated fibrous materials, such as wet leather, were studied. The processed material is drawn in the vertical direction between the working rolls under their pressure. This study aimed to determine the parameters that make it possible to create the required pressure of the working rolls depending on the change in the thickness of the material being processed. A pressure mechanism of working rolls mounted on levers is proposed. In the design of the proposed device, the length of the levers does not change due to the movement of the sliders when turning the levers; this provides a horizontal direction of the sliders. The change in the pressure force of the working rolls is determined depending on the variation in the nip angle, the coefficient of friction, and other factors. Based on theoretical studies concerning the feed of the semi-finished leather product between the squeezing rolls, graphs were plotted, and conclusions were drawn. An experimental roller stand designated for pressing multi-layer leather semi-finished products has been developed and manufactured. An experiment was carried out to determine the factors affecting the technological process of squeezing excess moisture from wet semi-finished leather products with their multilayer package together with moisture-removing materials by means of their vertical supply on a base plate between rotating squeezing shafts also covered with moisture-removing materials. According to the results of the experiment, the optimal process parameters were selected. It is recommended to carry out the process of squeezing the moisture from two wet semi-finished leather products at a pass rate more than twice as high and with a pressing force of the working shafts two times lower compared to the analog. According to the results of the study, the optimal parameters for the process of squeezing the moisture from two layers of wet leather semi-finished products were chosen, namely the feed rate of 0.34 m/s and a pressing force of the squeezing rollers of 32 kN/m. The use of the proposed roller device allowed an increase of two times or more in the productivity of the process of processing wet leather semi-finished products on the basis of the proposed technique compared to known roller wringers. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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18 pages, 10853 KiB

Open AccessArticle

Experimental Analysis of Channel Steel Member under Tension Load with Damage in the Unconnected Legs

by Ahmed M. Sayed, Hani Alanazi, Aref A. Abadel, Yousef R. Alharbi and Mohd F. Shamsudin

Materials 2023, 16(2), 527; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020527 - 05 Jan 2023

Viewed by 1004

Abstract

Damage occurring to steel element structures is highly possible due to tearing ruptures, corrosion, or the adoption of sudden loads. The damage has a great effect on their capacity to bear load and the corresponding elongation, as well as the distribution of the [...] Read more.

Damage occurring to steel element structures is highly possible due to tearing ruptures, corrosion, or the adoption of sudden loads. The damage has a great effect on their capacity to bear load and the corresponding elongation, as well as the distribution of the stresses in the cross-section of the element. Therefore, in the present research, experimental tests were carried out on 15 specimens of channel steel elements with different damage ratios in the unconnected legs and at different locations along the element’s length. Through the test, the load and the corresponding elongation values were obtained for the control and damaged specimens. From the study of the different variables, it was demonstrated that the damage location does not significantly affect the load capacity, with a maximum difference of 1.9%. With the presence of the damage in only one leg at a ratio of less than or equal to 40%, the prediction of the value of the loss in the load is within the safe limit. However, if this ratio increases, there is a defect in calculating the loss in the load as it is greater than the effect of the damage. If there is any damage in the two legs of the channel together, the prediction of the loss of load is within the safe limit, where the loss is less than the effect of the damage ratio. We propose a model that can predict the capacitance of the axial load of steel channel elements through identifying the ratio of damage in the unconnected leg. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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20 pages, 6473 KiB

Open AccessArticle

Fatigue Life Improvement of Weld Beads with Overlap Defects Using Ultrasonic Peening

by Seung-Hyon Song, Chang-Soon Lee, Tae-Hwan Lim, Auezhan Amanov and In-Sik Cho

Materials 2023, 16(1), 463; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010463 - 03 Jan 2023

Cited by 1 | Viewed by 3501

Abstract

Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects [...] Read more.

Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects without repair welding was studied. We experimentally investigated changes in the mechanical properties of defective welds before and after ultrasonic peening. The weld specimen with an overlap defect contained a large cavity-type defect inside the weld bead, which significantly reduced the fatigue life. When the surface of the defective test piece was peened, the fatigue life of the weld plate was restored, resulting in an equivalent or higher number of cycles to failure, compared to a specimen with a normal weld. The recovery of mechanical properties was attributed to the effect of surface work hardening by ultrasonic peening and the change in stress distribution. Thus, ultrasonic peening could compensate for the deterioration of mechanical properties such as tensile strength, fatigue life, and elongation due to overlap defects, without resorting to repair welding. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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12 pages, 6488 KiB

Open AccessArticle

Implant—Abutment Misfit after Cyclic Loading: An In Vitro Experimental Study

by John Eversong Lucena de Vasconcelos, Jefferson David Melo de Matos, Daher Antonio Queiroz, Guilherme da Rocha Scalzer Lopes, Bruna Caroline Gonçalves Vasconcelos de Lacerda, Marco Antonio Bottino, Cecilia Pedroso Turssi, Roberta Tarkany Basting, Flávia Lucisano Botelho do Amaral and Fabiana Mantovani Gomes França

Materials 2022, 15(15), 5341; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155341 - 03 Aug 2022

Cited by 3 | Viewed by 1750

Abstract

This study aimed to evaluate the influence of thermomechanical cycling (TMC) and type of abutment on the misfit and compressive strength of the implant–abutment interface. Forty 3.75-mm external hexagon implants with 25° angled abutments were divided into four groups (N = 10). Group [...] Read more.

This study aimed to evaluate the influence of thermomechanical cycling (TMC) and type of abutment on the misfit and compressive strength of the implant–abutment interface. Forty 3.75-mm external hexagon implants with 25° angled abutments were divided into four groups (N = 10). Group A: overcast plus TMC; Group B: overcast without TMC; Group C: completely cast plus TMC; Group D: completely cast without TMC. Abutments were fixed to the implants with 32-Ncm torque, and groups A and C specimens were cyclically loaded at 80 N with 2 Hz for 1 million cycles. The misfit on the implant–abutment interface was evaluated by optical microscope (100×) and the compressive strength test was performed in a universal test machine. For statistical analysis, a two-way ANOVA and post hoc Tukey test were used. There was no difference in misfit presented by all the abutments in the absence of TMC (p > 0.05). When TMC was performed, the completely cast abutments showed greater misfit than overcast ones (p = 0.001). Regarding compressive strength, irrespective of TMC performed, the overcast abutments showed higher compressive strength values than completely cast abutments (p = 0.003). Moreover, disregarding the type of abutment used, the absence of TMC provided higher compressive strength values (p < 0.001). It was concluded that thermomechanical cyclic loading aggravated the misfit, especially in completely cast abutments, regardless of material or fabrication technique, and reduced the compressive strength of the two types of abutments tested. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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14 pages, 2949 KiB

Open AccessArticle

Mechanical Parameters of Leather in Relation to Technological Processing of the Footwear Uppers

by Aura Mihai, Arina Seul, Antonela Curteza and Mariana Costea

Materials 2022, 15(15), 5107; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155107 - 22 Jul 2022

Cited by 2 | Viewed by 1688

Abstract

This paper aimed to define two critical mechanical properties of leather—Young’s modulus and Poisson ratio—essential to the virtual simulation of the behaviour of the footwear uppers against the manufacturing operations of stitching and perforating. The following technological aspects were considered to analyse the [...] Read more.

This paper aimed to define two critical mechanical properties of leather—Young’s modulus and Poisson ratio—essential to the virtual simulation of the behaviour of the footwear uppers against the manufacturing operations of stitching and perforating. The following technological aspects were considered to analyse the materials from manufacturing conditions point of view: the number of layers (one layer and two layers), the nature of the materials used for uppers subgroups (calfskin-outer upper, sheep leather-lining, polyester knitted fabric-lining), the overlapping width in the stitching area, the number of parallel stitches (single stitch and double stitch), the punching interval and the type of perforations (simple and with eyelets), resulting in nine kinds of samples. Furthermore, the elasticity (Young’s modulus) and lateral contraction (Poisson’s ratio) were calculated during the tensile strength analysis performed on the SATRA STM 466 equipment. Both mechanical parameters are essential to simulate the behaviour of the virtual footwear prototypes in various conditions. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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19 pages, 11995 KiB

Open AccessArticle

Tribological Characterization of Electrical Discharge Machined Surfaces for AISI 304L

by Muhammad Adnan, Waqar Qureshi, Muhammad Umer and Daniele Botto

Materials 2022, 15(3), 1028; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15031028 - 28 Jan 2022

Cited by 2 | Viewed by 2176

Abstract

Surface treatments are normally carried out after machining. Surface treatment is a costly and time-consuming process. Hence, it makes sense to reduce the requirement of surface treatment as much as possible. Electrical Discharge Machining (EDM) is a frequently used machining process. EDM produces [...] Read more.

Surface treatments are normally carried out after machining. Surface treatment is a costly and time-consuming process. Hence, it makes sense to reduce the requirement of surface treatment as much as possible. Electrical Discharge Machining (EDM) is a frequently used machining process. EDM produces a recast layer on the surface of machined components. The tribological performance of this recast layer is not very well understood. The properties of the recast layer formed as a result of EDM depend upon the discharge current, electrodes and dielectrics. This work aims to study the effects of each on the tribological performance – in terms of the wear depth, friction coefficient, friction force and contact surface temperature of recast layers. Subsequent improvement in the quality of surfaces will significantly reduce the cost and time required to treat surfaces after machining. Hence, various combinations of discharge current, dielectrics and electrodes have been used to characterize and deduce their effects. The tribo-tests are performed in the boundary lubrication regime under pin-on-disc configuration to analyze sliding friction, contact surface temperature and the wear of the recast layers formed on AISI 304L. The surface morphology of the test pins has been performed by Scanning Electron Microscopy (SEM) before and after the tests. The results show that indeed it is possible to control the tribological performance of the recast layers by varying EDM parameters. This approach promises to be a useful methodology to improve the tribological performance of the layers formed after EDM and reduce the time and costs required for surface treatments post machining. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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