Plate Specimens Research Articles

A new bone adhesive to fix mandible fractures in New Zealand Rabbits: cytotoxicity assay and comparison of bone formation with conventional plate and screw method

Statement of the Problem: Using plate and screws as the conventional bone fixation method in maxillofacial fractures leads to many complications as plate exposure, infection or unpleasant feeling on touching. Finding a substitute fixation method has been a far desire for many years.
 Purpose: This study compared the new bone formation using an experimental bone adhesive containing a functional monomer (benzophenone tetracarboxylic di-methacrylate, BTDMA) and the conventional plate and screw in fractured mandibles of rabbit.
 Materials and Method: This is an experimental animal study. The artificial fractures were induced at the mandibular angles of three male New Zealand rabbits. Screw and plate were used as control and titanium mesh with the resin-based bone adhesive containing 15 wt. % BTDMA monomer were applied as treatment. The mandible radiography were obtained and the density of the fracture line was compared to the control. The newly formed bone was assessed by a microscope.
 Results: The results obtained from the MTT cytotoxicity assay showed that 70% of cells were able to grow in the presence of the adhesive. The radiographic density of mesh-adhesive specimens was 119.88±76.29, while conventional plate specimens' density was 120.38±73.89. The average new bone formation score in the mesh specimens and plate specimens was 3.67±4.62 and 7±4.36, respectively. There was no significant difference between the two groups. The application of bone adhesive containing 15% BTDMA monomer in a group of the rabbits showed lamellar bone formation.
 Conclusion: Using bone adhesives containing BTDMA could lead to a new bone formation with high density in the case of adequate bonding to the fractured area.

A Study of Weld Seams on Low Carbon Steel ABS Grade a Marine Plates Using SMAW Process

Understanding the impact of welding parameters and welder skill on weld quality is crucial. However, it is the lack of comprehensive studies that consider the welding parameters and welder-introduced defects when analyzing the mechanical and metallurgical behaviors of low carbon steel welds using the SMAW process. The research aims to study and assess the impact of weld seams of low carbon steel ABS Grade A marine plate of 12.7mm thick using manual SMAW process as per AWS D1.1 structural welding code requirements and fulfilments of ASME Section IX pressurized equipment welding code requirements too. Different voltages, currents, and travel speeds were used to weld the test specimen plates. After the manual SMAW process, a series of testing techniques, including non-destructive tests, such as VT and RT, and destructive tests, such as tensile tests, bend tests, impact tests, microhardness tests, and metallographic examination has been conducted to assess/evaluate on the welded seam profiles and analyses/determines whether the accepted welded seam profiles have fulfilled the relevant welding code requirements. From the series of assessments and analyses, it is confirmed that the welded test specimen 1 having the welding parameters (i.e., voltage 23 V, current 70 A, and travel speeds 56.52 – 312.50 mm/min, having a range of heat inputs from 0.31kJ/mm to 1.71kJ/mm) is accepted as the quality good weld seam.

Crack propagation and induced vibration characteristics of cracked cantilever plates under resonance state: Experiment and simulation

Cracks in aero-engine blades have caused great economic losses and safety hazards in the past decades. High cycle fatigue, as one of the main causes of blade crack propagation, has been of increasing interest in recent years. In this paper, the cantilever plate specimens are selected as the research object to analyze the real crack propagation path and the change of resonance frequencies under the resonance state. First, a joint simulation analysis method based on FRANC3D and ANSYS software is proposed for the analysis of the crack propagation path. The proposed method is verified through crack propagation experiments. Second, a dynamic model for cantilever plates with a real crack propagation path is proposed based on the shell element theory. Finally, the associations between crack propagation lengths and resonance frequencies are studied. Some interesting phenomena are found: the resonance frequency decreases as the crack propagation length increases and the resonance frequencies show a slow decrease, then a constant decrease, and finally a rapid decrease; the nearer the initial crack location is to the root of the cantilever plate, the greater the curvature of the crack propagation path. This study can provide a better understanding of blade fatigue and the reference for analysis of blade crack propagation paths.

Residual stress associated with crystalline phase transformation of 3–6 mol% yttria-stabilized zirconia ceramics induced by mechanical surface treatments

Monolithic dental prostheses made of 3–6 mol% yttria-stabilized zirconia (3–6YSZ) have gained popularity owing to their improved material properties and semi-automated fabrication processes. In this study, we aimed to evaluate the influence of mechanical surface treatments, such as polishing, grinding, and sandblasting, on the residual stress of 3–6YSZ used for monolithic prostheses in association with crystalline phase transformation. Plate specimens were prepared from five dental zirconia blocks: Aadva Zirconia ST (3YSZ), Aadva Zirconia NT (6YSZ), Katana HT (4YSZ), Katana STML (5YSZ), and Katana UTML (6YSZ). The specimens were either polished using 1, 3, or 9 μm diamond suspensions, ground using 15, 35, or 55 μm diamond discs, or sandblasted at 0.2, 0.3, or 0.4 MPa. The residual stress, crystalline phase, and hardness were analyzed using the cosα method, X-ray diffraction (XRD), and Vickers hardness test, respectively. Additionally, we analyzed the residual stress on the surfaces of monolithic zirconia crowns (MZCs) made of 4YSZ, 5YSZ, and 6YSZ, which were processed using clinically relevant procedures, including manual grinding, followed by polishing using a dental electric motor on the external surface, and sandblasting on the internal surface. Residual stress analysis demonstrated that grinding and sandblasting, particularly the latter, resulted in the generation of compressive residual stress on the surfaces of the plate specimens. XRD revealed that the ground and sandblasted specimens contained a larger amount of the rhombohedral phase than that of the polished specimens, which may be a cause of the residual stress. Sandblasting significantly increased the Vickers hardness compared to polishing, which may possibly be due to the generation of compressive residual stress. In the case of MZCs, compressive residual stress was detected not only on the sandblasted surface, but also on the polished surface. The difference in the residual stress between the plate and crown specimens may be related to the force applied during the automated and manual grinding and polishing procedures. Further studies are required to elucidate the effects of the compressive residual stress on the clinical performance of MZCs.

Tensile behavior of CFRP-Steel composite laminates

Carbon-fiber/epoxy steel composite laminate (CSL) is a type of fiber metal laminate formed by stacking thin layers of carbon-fiber/epoxy and steel sheet. To investigate the stress–strain relationship under monotonic tensile and cyclic tensile, comprehensive experiments were conducted on five groups, including four groups of CSL specimens with different steel volume fractions (SVF) and one group of control steel plate specimens. Furthermore, stable post-yield modules and comparatively small residual deformation could be observed from CSLs curves. Based on the experimental failure mode, the theoretical models were proposed, and the numerical simulation was established, and verified by the test results. Theoretical calculations and numerical analysis were performed to estimate the effect of varying the SVF on the mechanical performance of the CSL, particularly in the absorption and energy dissipation coefficients.

Experimental study on fatigue behavior of cracked steel plates repaired with adhesively bonded steel patches

Fatigue cracking is prone to occur in orthotropic steel decks (OSDs) due to its complex geometry. To guarantee structural safety and extend the fatigue life of OSDs in steel bridges, the repair technique of adhesively bonded steel patches, which has the advantage of lower cost, easy operation, and not damaging the original structure, is experimentally studied using simplified cracked steel plate specimens. Four repair schemes were considered including bare plate, single-sided patched, double-sided patched, and stop-hole repaired. The failure mode, fatigue crack propagation, and adhesive damage were studied to evaluate the effects of steel patch repair. The morphological analysis was performed to investigate the fatigue fracture characteristics and metal interface performance. The outcomes showed that adhesively bonded steel patches could significantly improve the fatigue life of cracked steel plates and the strengthening was more effective for double-sided patched specimens than single-sided patched specimens. In comparison, the repair effect of the stop-hole method is limited for cracked specimens.

Experimental investigation of failure diffusion in brittle materials subjected to low-speed impact

The generalized driving force and local shear resistance are introduced to reveal the intrinsic mechanism of failure diffusion in brittle materials subjected to low-speed impact. Two experiment techniques (i.e. the Split Hopkinson pressure bar (SHPB) test and sphere penetration test), four specimen configurations (i.e. cuboid, trapezoid, sphere, and plate specimens), and three transparent brittle materials (i.e. polymethyl methacrylate (PMMA), glass, and transparent ceramics ALON) are employed in the present study. The generation and propagation of the failure front in the specimens are traced and analyzed based on the high-speed photography and the DIC method. The calculated equivalent strain fields vary greatly with configurations of specimens. The generalized driving force (e.g. calculated based on the strain field) and the shearing diffusion resistance (e.g. calculated based on the strain field and the transmission stress profile) are then proposed to illustrate respectively the deformation-gradient induced driving force and the local shear in the shear-activated process of failure diffusion. The results show that they both increase rapidly in the formation process of the failure front and decrease to almost zero after the specimen is failed; while the velocity of the failure front increases exponentially with the increase of the driving force, and decreases with the increase of local shearing resistance. The relations of the two generalized forces to the geometric structures are obtained, and the local dynamic strength is firstly revealed by the evolution of the shearing resistance. The results are helpful for the profound understanding of the failure mechanism of brittle material subjected to impact loading.

Fracture assessment of U-notched diagonally loaded square plates additively manufactured from ABS with different raster orientations

This paper investigates the fracture behavior of 3D-printed notched specimens under various combinations of mode I and mode II loadings, including pure mode I and pure mode II loadings. The study employs fused deposition modeling (FDM) to fabricate U-notched diagonally loaded square plate (UNDLSP) specimens using Acrylonitrile Butadiene Styrene (ABS) filaments. To experimentally measure the fracture load and fracture initiation angles, 120 UNDLSP specimens are 3D printed with different notch tip radii, notch orientation angles, and [0, 90], [45, −45] raster orientations. Tensile characteristics and translaminar fracture toughness of ABS plates with [0, 90] and [45, −45] raster orientations are obtained using dog-bone and cracked DLSP samples, respectively. Considering the layered nature and anisotropy of the material, the virtual isotropic material concept (VIMC) is utilized along with two well-known stress-based brittle fracture models: the maximum tangential stress (MTS) and the mean stress (MS) criteria. The test results are predicted using the fracture limit curves and fracture initiation angle curves developed for these fracture models in terms of the notch stress intensity factors (NSIFs). Furthermore, a general equation is established to estimate the fracture initiation angle of U-notched ABS specimens under mixed mode I/II loading, irrespective of geometry, raster orientation, and notch tip radius, based on the curves obtained from the MTS and MS criteria. The fracture surfaces of the UNDLSP specimens are examined using scanning electron microscopy (SEM) to study the micro-mechanisms involved in the fracture process. The findings indicate that both the VIMC-UMTS and VIMC-UMS criteria accurately predict the experimentally achieved fracture loads. Additionally, it is observed that the fracture initiation angle curves for both criteria are nearly identical and accurate. The significance of this research is not only providing numerous new experimental results on mixed mode I/II fracture of notched 3D-printed ABS plates, but also providing simple, fast, accurate, and robust criteria for predicting the critical loads of such plates, without the need for conducting layer-by-layer failure analysis using progressive damage models.

Characterizing the bending behavior of underground utility tunnel roofs in a fabricated composite shell system

The traditional underground utility tunnel system is characterized by a lengthy construction period, material waste, and poor engineering quality. This study proposes the prefabricated composite shell system underground utility tunnel as a new type of prefabricated underground utility tunnel system. This system uses 20 mm thick high-performance cement-based materials as permanent templates, with steel reinforcement skeletons placed in the cavity between the two side molds, and concrete can be poured after on-site hoisting and positioning to form an integrated tunnel. This study first systematically introduces the system design method of the prefabricated composite shell system underground utility tunnel and clarifies its component and connection structures. Then, bending tests are conducted on the composite shell tunnel top plate specimens, and a cast-in-place top plate specimen is selected as a control group. A suitable bearing capacity calculation formula for composite shell top plates is derived and proposed based on test phenomena and results analysis. The results showed that the prefabricated outer template and internal cast-in-place concrete of the composite shell top plate specimen have good collaborative performance. Its bearing capacity, stiffness, and failure phenomena are consistent with those of cast-in-place components, as are its mechanical properties. In addition, the proposed bearing capacity calculation formula for a composite shell top plates is highly accurate and can guide the design of such components.

Modified Maximum Likelihood Estimation Metal Magnetic Memory Quantitative Identifying Model of Weld Defect Levels Based on Dempster–Shafer Theory

Metal magnetic memory (MMM) is a nondestructive testing technology based on the magnetomechanical effect, which is widely used in the qualitative detection of stress concentration zones for welded joints. However, there is inevitable residual stress after welding, which brings the bottleneck of quantitative identification between the weld residual stress concentration and the early hidden damage. In order to overcome the bottleneck of quantitative identification of weld defect levels with MMM technology, a modified maximum likelihood estimation (MLE) MMM quantitative identifying model is first proposed. The experimental materials are Q235B welded plate specimens. Fatigue tension experiments were operated to find the MMM feature laws of critical hidden crack by comparing with synchronous X-ray detection results. Six MMM characteristic parameters, which are, ΔHp(x), Gxmax, Zxmax, ΔHp(y), Gymax and Zymax, are extracted corresponding to the normal state, the hidden crack state and the macroscopic crack, respectively. The MLE values of the six parameters are obtained by the kernel density functions with optimized bandwidth from the view of mathematical statistics. Furthermore, the modified MLE MMM quantitative identifying model is established based on D–S theory to overcome the partial overlap of MLE values among different defect levels, of which the uncertainty is as low as 0.3%. The verification result from scanning electron microscopy (SEM) is consistent with the prediction of the modified MLE MMM model, which provides a new method for quantitative identification of weld defect levels.

Quenched‐and‐tempered high‐strength steels at elevated temperatures: Mechanical properties and effects of plate thickness

AbstractHigh‐strength steels can be used in civil structures that demand high strength/weight ratios, but their advantages may be weakened by fire. For this reason, this study has been concerned with the mechanical properties of a type of quenched‐and‐tempered high‐strength steel at elevated temperatures up to 800°C, the steel grade is S690. A standard axial tensile test was conducted on plate specimens with a reduced section. The test results demonstrated that the stress–strain curves of S690 steel at elevated temperatures had no distinctive yield plateau but post‐yield hardening, the effective yield strengths and elastic modulus deteriorated dramatically with the increasing temperature due to microstructure changes. Besides, this study also investigated the effects of steel plate thickness on said temperature‐dependent mechanical properties. The plate thicknesses are 8 and 12 mm nominally. The comparisons showed that, different from the trend at room temperature where the thinner steel plates usually have higher strength than their thicker counterparts, the thinner plates exhibited lower strengths at elevated temperatures, this implies that with the same cross‐sectional area, a steel member formed by thinner plates would have a lower cross‐sectional load‐carrying capacity under fire.

Plastic-deformation-history effects on the cyclic ductile fracture of steel sheet under high triaxiality

This paper presents the experimental and modeling studies of the plastic deformation history effects on the cyclic ductile fracture of thin steel sheet under high triaxiality. The center-holed plate specimens with three cutting radiuses are tested respectively under three cyclic loading protocols, i.e., the ascending-descending (AD), the descending-ascending (DA), and the random deformation amplitude. The prestrain-induced enhanced ductility effect is identified through comparisons between AD and DA testing, as the earlier applied large deformation might reduce the damage accumulation rate when the subsequent lower deformation amplitude is applied. A new cyclic void-induced damage model (CVOID model) is proposed to characterize the damage accumulation and succeeding softening evolution. The damage accumulation is attributed to the void growth and shrinkage subjected to cyclic deformation, which will trigger the softening initiation and development due to the internal micro-crack propagation. Furthermore, a new plasticity state variable is introduced to quantify the current plastic deformation state to consider the reduced damage rate dependent on the prestrain effect. Using the proposed CVOID model, the full-range cyclic hardening–softening behaviors can be accurately predicted under all concerned triaxialities and loading protocols, especially under random cyclic loading. It achieves better prediction of the cyclic softening behaviors than three conventional models (i.e., the CVGM, SWDFM, and the JIA cyclic fracture model), as indicated by the profound percentage errors of the accumulated critical deformation (AcD) lower than 2.1% compared with the errors from 20% to 60% via the existing models.

Equipment and Methodology for Studying the Behavior of High-Strength Steels Under Static Pressing of Plate Specimens

Equipment and Methodology for Studying the Behavior of High-Strength Steels Under Static Pressing of Plate Specimens

Influence of prestressing force on performance of concrete plates under impact loading

An experimental and numerical study has been performed to explore the performance of one-way pretensioned concrete plates against impact loading. The impact resistance, experimental results and damage within the pretensioned concrete have been compared with the non-pretensioned concrete. The plate specimens of concrete grades M40 and M60 have been pretensioned to prestress level 10 and 20% of the compressive strength of the concrete. While, all the tendons employed in the non-pretensioned concrete were kept unstressed. The plates were struck at the mid-span by a steel mass (242.85 kg) dropped from 0.5 to 1.0 m heights. The numerical simulations have been executed using explicit finite element code considering the Holmquist–Johnson–Cook (HJC) and the metal plasticity model for concrete and steel, correspondingly. The performance of the plates is governed by the grade of concrete, impact energy and level of the prestress within the concrete. The induced prestress within the concrete enhanced the stiffness and, consequently, the impact resistance of the pretensioned concrete plates. The pretensioned concrete hence witnessed increased impact force and reduced deflection by 18.1% and 11.0%, correspondingly, compared to the non-pretensioned concrete. The splitting and punching crack within the plates became pronounced once the drop height increased from 0.5 m to 1.0 m. The simulations have estimated the peak impact force and reaction within 19.7% and 15.5% deviation, respectively. The displacement and energy absorption have been calculated using an analytical methodology closely correlated with the actual results within 18% and 14% deviation, respectively. Further, the simulations performed on two-way pretensioned concrete have shown improved performance of the plates witnessing no splitting crack and uniform crack distribution compared to one-way pretensioned concrete.

Thermally-induced responses of triaxially woven fabric composites

The article examines the thermal responses of one-ply triaxially woven fabric composites (TWFCs). A temperature change experimental observation is first conducted on plate and slender strip specimens of TWFCs. Computational simulations are then performed with analytical and simple, geometrically-similar model configurations to capture thereby offering insights into the anisotropic thermal effects of the experimentally observed deformation. It is revealed that the leading cause of the observed thermal responses is the advancement of a locally formed twisting deformation mode. Therefore, a newly defined thermal deformation description called the coefficient of thermal twist is then characterized for TWFCs for different loading cases.

Two Coupled Analysis Strategies for Melt-Ablation Modeling of Thermal Protection Material in Supersonic Gas-Particle Two-Phase Impingement Flow

In this study, two analysis strategies were used to investigate the melt-ablation process of the copper specimen plate in the scaled ducted launcher. The reliability of the simulation results of the two analysis strategies was confirmed by comparing the two-way fluid-thermal-ablation coupled analysis (two-way FTA-CA) strategy with two-way fluid-thermal-ablation loosely coupled analysis (two-way FTA-LCA) strategy. Then, the accuracy of the FTA-LCA strategy was validated by comparing the simulation results of the FTA-LCA strategy and experimental results from the experimental scale test. Finally, the FTA-LCA strategy used in this study can not only estimate the impingement surface heat flux into the copper plate when the inverse heat conduction analysis (IHCA) is not possible, but also provide the analysis solution accuracy and the considerable gain in computational efficiency for predicting the long-duration ablation problem in supersonic gas-particle two-phase exhaust plume impingement flow.

Mixed mode brittle fracture of stereolithographic 3D-printed parts

Technical advances in additive manufacturing (AM), also known as three-dimensional (3D) printing, have led to applications of this technology in creation of end-use items. Consequently, performance and the mechanical strength of AMed parts have become of significant importance. In this research, fracture behavior and crack propagation of AMed cracked plates are investigated. To this aim, the stereolithography (SLA) technique is used to fabricate square plate specimens with a hole in the center and radial cracks that started at the perimeter of the central hole. Here, full range of mixed-mode fracture (from pure mode I to pure mode II) are obtained by altering the angle between the crack and the applied load. We used the finite element method to determine stress intensity factors. This study deals with a series of experiments on 3D-printed cracked plates to study mixed-mode fracture and crack propagation in brittle fracture of SLA 3D-printed components. Additionally, the digital image correlation technique was used to determine strain field on the surface of the specimens. As SLA is one of the most commonly used concepts in polymer 3D printing and has garnered significant attention for fabrication of complex structural elements, the outcomes of this study are useful for next developments and innovative designs of 3D-printed polymeric components.

A Study on the Applicability of Cathodic Protection for the Outdoor Sculptures Corrosion

In this study, we proposed the sacrificial anode cathodic protection method as a countermeasure to reduce the corrosion of the steel sculptures under outdoor conditions and proved the anticorrosive effect experimentally. To affix the Mg sacrificial anode and the steel plate specimen, an adhesive bonding strength test was conducted with three types of conductive adhesives. Hence, the suitability of the conductive epoxy adhesive was confirmed, and a C-clamp experiment was conducted to supplement the connection. In addition, by applying a sacrificial anode suitable for the soil where the artwork is installed, the field applicability was reviewed through an artificial determination of resistance to cyclic corrosion conditions test(salt fog/dry/humid) to prove the suitability of the cathodic protection method by sacrificial anode. Hence, corrosion monitoring is in progress by test-laying steel plate specimens in an outdoor sculpture park to identify natural deterioration. In the future, based on the results of the outdoor exposure test, we plan to determine the proper method of bonding the sacrificial anode and the steel sculpture, and the replacement period of the sacrificial anode.

Stress amplification effect and fatigue strength evaluation of marine thin plate welded structure considering welding deformation: Theoretical and experimental analysis

Due to the low bending stiffness of thin plate welded joints, welding deformations such as welding dislocation, welding angle deformation and initial welding deformation are easy to occur in the welding process. The existence of these deformations will cause additional stress concentration effect and reduce the fatigue performance of thin-plate welded structures. Therefore, the influence of various welding deformations should be considered when evaluating the fatigue strength of the welded joints of thin plates. Combined with the test data, the calculation formula of stress amplification factor considering various welding deformations proposed by this paper is compared with the calculation formula in the existing literature and finite element calculation results. Moreover, the analytical formula is applied to the fatigue assessment of 5059 aluminum alloy welded joints. According to the evaluation results, it is found that the structural stress method and equivalent structural stress method based on the proposed bending stress amplification coefficient formula have good evaluation results for aluminum alloy thin plate specimens with welding deformations. Fatigue strength class curves suitable for thin plate aluminum alloy welded joints corresponding to different fatigue evaluation methods are further suggested.

Phase Field Modeling of Crack Growth with Viscoplasticity

The fracture of viscoplastic materials is a complex process due to its time-dependent and plastic responses. Numerical simulation for fractures plays a significant role in crack prediction and failure analysis. In recent years, the phase field model has become a competitive approach to predict crack growth and has been extended to inelastic materials, such as elasto-plastic, viscoelastic and viscoplastic materials, etc. However, the contribution of inelastic energy to crack growth is seldom studied. For this reason, we implement the fracture phase field model coupled with a viscoplastic constitutive in a finite element framework, in which the elastic energy and inelastic energy are used as crack driving forces. The implicit algorithm for a viscoplastic constitutive is presented; this procedure is suitable for other viscoplastic constitutive relations. The strain rate effect, creep effect, stress relaxation effect and cyclic loading responses are tested using a single-element model with different inelastic energy contributions. A titanium alloy plate specimen and a stainless-steel plate specimen under tension are studied and compared with the experimental observations in the existing literature. The results show that the above typical damage phenomenon and fracture process can be well reproduced. The inelastic energy significantly accelerates the evolution of the phase field of viscoplastic materials. For cyclic loadings, the acceleration effect for low frequency is more significant than for high frequency. The influence of the weight factor of inelastic energy β on the force-displacement curve mainly occurs after reaching the maximum force point. With the increase of β, the force drops faster in the force-displacement curve. The inelastic energy has a slight effect on the crack growth paths.