Effect Of Hole Size Research Articles

Effects of Hole Sizes and Stack Thicknesses on Mechanical Properties and Failure Behavior of Pre-holed Self-piercing Riveted Steel-Aluminum Joints

Effects of Hole Sizes and Stack Thicknesses on Mechanical Properties and Failure Behavior of Pre-holed Self-piercing Riveted Steel-Aluminum Joints

Embedment strength and foundation modulus at an angle to the grain for fully threaded bolts

ABSTRACT As the main parameter, embedment strength is used to assess the load-carrying capacity of timber joints with dowel-type fasteners and foundation modulus is used to assess their stiffness. The embedment properties, i.e. embedment strength and foundation modulus, are system properties, which depend not only upon the material properties but also upon the load-to-grain angle and surface conditions of fasteners. The formulae for the embedment strengths of dowels and bolts in the design standards of timber structures are almost exclusively derived from the embedment tests on smooth dowels, with the surface conditions different from those of alternative fully threaded bolts in timber structures. Moreover, there are hardly any formulae for determining the foundation modulus. In this study, the embedment tests at different angles to the grain were carried out using the fully threaded bolts with different diameters in oversized holes as they would be used in practice. The load-to-grain angle had statistically significant effects on these embedment properties. The empirical formulae for the embedment strength and foundation modulus were derived. The embedment tests on fully threaded bolts and smooth dowels in tight-fitting holes were also performed to explore the effects of bolt hole sizes and surface conditions.

Improvement of airflow uniformity and noise reduction with optimized V-shape configuration of perforated plate in the air distributor

The air distributor is the end component of the ventilation system, and its performance directly determines the comfortable and pleasant feeling of the residence. A perforated plate can be added to the air distributor to convert dynamic pressure into static pressure first and then distribute the air flow, which provides better self-adjustment compared with the embedded guide vane structure. However, the perforated plate can lead to a contradiction between head loss, noise and distribution uniformity. To reconcile this problem, a novel V-shape configuration of the perforated plate was put forward in this study. The internal flow and aeroacoustic properties of different types of perforated plates were systematically studied, and a full-scale test platform was built to verify the flow characteristics. The effects of hole size and installation position of the perforated plate on the uniform distribution of air flow were analyzed by the parametric analysis method. Then, the sound pressure level of the optimized perforated plate air distributor was further analyzed. The results show that, with the optimized perforated plate structure, the uniform flow performance was improved by about 30% and the overall sound pressure level was reduced by up to 12 dB.

Ply-Blocking Phenomenon and Hole Size Effects in Modeling Progressive Damage in Fiber-Reinforced Plastics Laminates

Abstract This work presents a 3D progressive damage model based on Puck’s failure theory and linear damage evolution in fiber-reinforced plastic (FRP) laminates. It includes shear nonlinearity, in situ strengths, equivalent stress–strain, and mixed-mode fracture energy, and is implemented in abaqus/explicitTM through VUMAT subroutine. Various test cases were performed to validate the model and demonstrate its applications. The shear nonlinearity test shows that transverse compression retards matrix microcracking while transverse tension accelerates it. The open hole tension (OHT) test of laminates shows that delamination initiates around the holes and free edges, spreads the most, and propagates in different directions at different interfaces. Later, interfiber damage in 45 deg or −45 deg plies initiates and spreads at a slight inclination to the tip of the hole. Finally, fiber damage in 0 deg plies initiates at the tip of the hole, spreads the least, and propagates perpendicular to the loading direction. The ply-blocked laminates show around 30% higher strength and fracture strain than non-ply-blocked laminate due to delay in damage propagation, and are less sensitive to the hole size. Accordingly, their OHT strength reduces by 14.3% as opposed to 21.14% in the non-ply-blocked laminates, when the hole size increases from 6 to 9 mm. The damage location, magnitude, and propagation were corroborated with experimental findings in the literature.

Simulation and experiment on pneumatic defrosting of evaporators with heat storage

In order to solve the problem of frosting on surface of the evaporators in rapid freezing equipment, a new defrosting system was proposed based on pneumatic defrosting and heat storage defrosting. A three-dimensional flow model including an evaporator and a thermal flow defrosting system was established to observe the temperature distributions of the fins and gas flowing outside the evaporator and to reflect the defrosting effect. The correctness of the model was verified by a freezing experiment. On this basis, the effects of the nozzle placement hole sizes, hot air inlet temperatures and velocities on the fins and cold air temperatures were simulated. The results show that the appropriate horizontal distance between the nozzle and the evaporator is 40 mm considering the large area of heat transfer. The initial temperatures of the hot gas and nozzle sizes have little effects on the heat exchange areas, but the initial velocities of the hot gas have great effects on the heat exchange areas. It takes 180 s for the air outlet temperature of the heat accumulator with the decrease of the temperature from 44 °C to 25 °C. The frost on the surface of the fin melts rapidly within the time that the heat accumulator can maintain a certain temperature range. More studies are required to perform defrosting experiments by choosing appropriate heat storage materials and elevating gas pressure and temperature.

Cell culture design for homogeneous proliferation of cells in three-dimensional nonwoven polymer scaffolds

The objective of this study is to establish strategies to uniformly proliferate cells in a three-dimensional nonwoven polyethylene terephthalate (PET)/ethylene vinyl alcohol (EVOH) scaffold by simple adjustments in seeding and culture methods and the scaffold design. The combined dynamic and static seeding (intermittent agitations at 300 rpm with 1 h interval) resulted in the highest seeding efficiency (71%) comparing to the static and continuous agitating seeding methods. Cell-attached scaffolds were cultivated under different conditions. The stirring culture permitted cells to proliferate to a significantly greater extent than the static or agitating cultures, although faster cell proliferation in the outer region of the scaffold was observed. Next, based on this observation, scaffolds were opened with holes to alleviate the cell aggregation. The effect of hole size and number of scaffolds on the distribution of cells proliferated in the scaffold was evaluated. Two of 1-mm holes showed to be an optimal adjustment to allow cells to proliferate in a homogeneous manner. After 14 days culture, both of the holes were filled by cells proliferated with a fourfold increase in the cell number. The cell viability in the scaffolds was also high upon evaluating the live/dead and 3[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) staining examinations. Different cell types of 3T3-L1, C3H/10T1/2, and KUM6 cells showed similar behavior of cell proliferation and distribution in the scaffold, indicating the applicability of the established procedure. It is concluded that the nonwoven PET/EVOH scaffold serves as a potential cell culture substrate for an efficient cell proliferation.

Formability investigation of perforated austenitic SS 304L sheets using SPIF

Incremental sheet forming (ISF) is a progressive and highly flexible method of producing sheet metallic components in batches of limited quantities. It is also used for making prototypes at a low cost. Advantages of ISF are: higher sheet formability; elimination of molds and dies or use of simple molds and dies; formed parts with a good surface finish; use of commonly available vertical CNC milling machine and the possibility of quick changes in design. The low accuracy of formed parts and slow speed of the process are the disadvantages of ISF. Perforated metallic sheets have many applications in different industries because of their attractive display exposable to the atmospheric air and lighter weight than nonperforated metallic sheets. Its formability varies with the hole dimensions, ligament width, material chemistry, and forming parameters. In this paper, the effects of hole size, and other input parameters on the formability of the sheet are investigated. One millimeter thick SS 304L perforated sheets with 2 mm and 3 mm diameter holes are used for the present work. FLD and FLSD were drawn after performing the straight groove and wall angle tests. The highest formability was observed in the sheet with 2 mm diameter holes. XRD line profile analysis was done and correlated the formability with the crystallite size and dislocation density. SEM micrographs of fracture surfaces were taken and the fractographic parameters were correlated with formability. FE simulation was done using the optimized process parameters and the simulation results were compared with the experimental results. Contour and spiral tool path comparison was done numerically and experimentally.

Study the Effect of Face Sheets Material on Strength of Sandwich Plates with Circular Hole

This study aims to investigate the effect of changing skins material on the strength of sandwich plates with circular hole when subjected to mechanical loads. Theoretical, numerical and experimental analyses are done for sandwich plates with hole and with two face sheet materials. Theoretical analysis is performed by using sandwich plate theory which depends on the first order shear deformation theory for plates subjected to tension and bending separately. Finite element method was used to analyse numerically all cases by ANSYS program.
 The sandwich plates were investigated experimentally under bending and buckling load separately. The relationship between stresses and the ratio of hole diameter to plate width (d/b) are built, by studying the effect of hole size on strength of sandwich plates. The maximum stress were developed at the hole region in sandwich plates clarified the dropped in their strength. So, the experimental maximum stress was found by means of multiplying the experimental nominal stress obtained from Stress-strain curve by the stress concentration factor.
 All results which obtained, theoretically, numerically and experimentally are compared to find that the hole weaken the strength of sandwich plates because of the stress concentration and that weakness is depending on the hole size and the face sheets materials.

Failure Mechanism of Tensile CFRP Composite Plates with Variable Hole Diameter

Real thin-walled composite structures such as aircraft or automotive structures are exposed to the development of various types of damage during operation. The effect of circular hole size on the strength of a thin-walled plate made of carbon fibre-reinforced polymer (CFRP) was investigated in this study. The test object was subjected to tensile testing to investigate the strength and cracking mechanism of the composite structure with variable diameter of the central hole. The study was performed using two independent test methods: experimental and numerical. With increasing diameter of the central hole, significant weakening of the composite plate was observed. The study showed qualitative and quantitative agreement between the experimental and numerical results. The results confirmed the agreement of the proposed FEM model with the experimental test. The novelty of this study is the use of the popular XFEM technique to describe the influence of the hole size on the cracking and failure of the composite structure. In addition, the study proposes a new method for determining the experimental and numerical damage and failure loads of a composite plate under tension.

The realization of parallel airflow after flow rectification by the perforated plate under complex inflows

The parallel push-pull ventilation system uses uniform, low turbulence, and wide parallel airflow to achieve low diffusion transport of pollutants and reduce the system's energy consumption. Complex inflows caused by local connectors (fans, elbows, and reducers) in front of the air supply device seriously affect the air supply distribution. Currently, most existing studies focus on the performance of parallel push-pull ventilation systems, while lacking theoretical support and parameter guidance to rectify these complex inflows into parallel airflow. This study investigates parallel airflow after rectifying various complex inflows using perforated plates. Within the study context, three typical complex inflows models (fan, elbow, and reducer inflows) are established using dominant numerical and supporting experimental methods. In addition, the rectification effects of inflow velocity, porosity, and hole size of the perforated plate on various complex inflows are compared. The results show that the perforated plate's porosity and hole size should be reasonably matched under different complex inflows to achieve a uniform and low turbulence parallel flow. The perforated plate should have a porosity between 40% and 55% and a dimensionless hole size between 0.014 and 0.031 for elbow and reducer inflows. Swirling flow causes a reduction in the perforated plate's rectification capacity for fan inflow, requiring lower porosity and hole size, while also meaning that the resistance increases significantly. Overall, the study results are anticipated to aid in achieving supply airflow with parallel airflow.

Engineered origami crease perforations for optimal mechanical performance and fatigue life

Perforating crease lines has been widely adopted as a practical method for designing thick engineering origami structures. Perforations inevitably reduce crease stiffness and thus affects the mechanical characteristics and fatigue performance of origami structures. It is therefore important to understand the effect of perforations on the performance of origami creases. The purpose of this study is to propose a perforated crease with desirable folding response and fatigue performance for engineering origami structures. Drawing on the literature on engineering origami, ten perforated creases are proposed, including single- and double-sided slots, oblong holes, elongated holes, moon holes, and barbell holes. Next, finite element analysis is used to assess their folding and unfolding responses, and to predict their fatigue lives combined with FE-SAFE. It is demonstrated that the crease with three rows of oblong holes is the optimal design, which has excellent mechanical characteristics and fatigue performance. A parametric analysis is then carried out to investigate the effect of sheet thickness, hole size, and holes arrangement on the performance of the optimal perforated crease. It is revealed that increasing sheet thickness, hole distance, or row distance exerts a positive effect on reaction forces, while increasing hole length or hole width produces a negative effect. Additionally, the fatigue life is severely reduced as sheet thickness or hole length increases, while it enhances with increasing hole width or hole distance. On the other hand, variations in row distance have an insignificant effect on the fatigue life. The parametric analysis presented in this study can provide guidance for the application of optimal perforated creases to engineering origami structures.

Seismic behavior of an innovative bolted connection with dual-slot hole for modular steel buildings

Although a significant advantage for modular steel buildings (MSBs) is suitable for rapid construction, the unexpected installation error and initial defects of components in the construction site may lead to the failure of rapid assembly or even connection between modules. Aiming at the error sensitivity problem of module splicing, this paper proposes a new type of bolted connection with dual-slot hole and two kinds of connection strengthening methods, including diagonal brace strengthening and flange strengthening. To proceed, tests on four full-scale connections with cyclic loads were performed for seismic behavior. The test results presented the specimens’ failure mode, strength and stiffness properties, ductility, and energy dissipation capacity. Following that, the finite element model was validated against test data, and the influence of slot hole size and displacement effect was discussed. Finally, the hysteretic model was given. The results indicated that the proposed connection has reliable load-bearing, stable energy dissipation, and fast splicing capacity. The connection may be classified as semi-rigid type according to the stiffness feature for the structural behavior of MSBs. Both diagonal brace and flange strengthening can effectively improve the connections’ load-bearing capacity but weaken the energy dissipation capacity. The research results could serve as an effective reference for the inter-module bolted connection design of MSBs.

Investigational studies of crystalline, optical, dielectric, thermal, mechanical, second besides third order nonlinear optical properties of urea itaconic acid solitary material

In this research work, we used low temperature growth technique (Slow cooling method) for the growth of nonlinear optical and antimicrobial activity of fully-fledged organic Urea Itaconic acid (UITA) crystal. The model was crystallised with a monoclinic crystal structure in the centrosymmetric space group P21/c. The single crystal X-ray diffraction (SXRD) method was used to determine the crystal characteristics of the compounds. To validate the presence of separate functional groups, a Fourier transform infra-red test is utilised. The crystallinity and phase purity of the entire crystal is confirmed by the X-ray diffraction pattern of the detected Bragg peaks. The optical transmission window and shorter UITA wavelength cut-off were established using UV-Vis-NIR studies. Defects were also analysed by the dielectric loss, dielectric constant and AC conductivity studies. The mechanical stability of growing crystal was required to identify using Vickers microhardness analysis and by the Hays-Kendall approach, the effect of hole size (ISE) and the proportional stability model (PSRM) was adequately explained. Using energy dispersion spectrometry, the presence of urea and itaconic acid was confirmed. The differential thermal analysis (DTA) and thermogravimetric (TG) technique were studied by thermal effects of crystal. Using Z scan method the good third order nonlinear response for different planes (1 0 0), (0 0 1) and (1 1 − 1) of the UITA crystal sample were determined. Potentially threatening microbe’s activity utilised to analysis antimicrobial chattels. UITA sample were taken into the solubility and width of the metastable region. The good crystal perfection is showed that the grown crystals using by HRXRD and etching studies. Using on classical nucleation theory, the final nucleation constraints such as phase to phase strain, Gibbs free energy transformation, critical radius, molecular count in the critical nucleus and nucleation rate were calculated for the UITA sample. Second Order NLO behaviour of the grown crystals were confirmed by Kurtz powder procedure.

Evaluation of multi-hole diesel injectors spray under evaporating conditions: Effects of adjacent spray plumes on the macroscopic and mixture characteristics of target spray

Previously, diesel sprays of multi-hole injectors were simulated in an environment where only a single spray plume was simulated. Although boundaries were declared as symmetry, the impact of aerodynamic forces between spray plumes was always neglected. In the present work, all spray plumes of diesel injectors are simulated in a cylindrical box mesh considering external effects including umbrella angle, space between nozzle holes, and hole length to hole diameter ratio. To examine the nozzle hole size effect, two 10-hole diesel injectors with hole diameters of 0.101 and 0.133 mm are investigated under 120 MPa injection pressure. Likewise, to understand the effect of injection pressure, the 0.101 mm hole diameter injector is studied under 120 and 140 MPa rail pressures. In experiments, Laser Absorption Scattering diagnostic technique is applied to visualize the vapor phase, measure mixture concentration and characterize air entrainment. Since Diesel fuel does not absorb UV light, Tracer fuel with the composition of 97.5% of n-tridecane and 2.5% α-Methylnaphthalene is used. On the contrary, sprays are simulated in the Eulerian-Lagrangian two-phase fluid framework using KHRT Breakup and Multicomponent Evaporation models. Parameters such as injection rate and initial spray trajectory angle are measured experimentally and used as input for the spray simulation. Computational results correspond with experiments particularly in terms of Penetration and Equivalence Ratio while Spray Angle deviates.

Notched tensile strength of long discontinuous glass fiber reinforced nylon composite

In this study, the hole size effect in the open hole tension (OHT) of discontinuous glass fiber-polyamide 6 organosheet composite material was studied. Organosheet used in this study is a novel long discontinuous fiber-reinforced polymer composite with long glass fiber and in-situ polymerized polyamide 6 (nylon) matrix. A progressive failure analysis (PFA) using finite-element model was proposed to predict OHT strength using measured fiber orientation distribution. The generated virtual ogranosheet samples were used to conduct OHT Monte Carlo simulations to predict variability in strength. The notch sensitivity was observed experimentally and analyzed using PFA model, which captured interactions between various failure modes. The experimental and PFA results of OHT strength were used for calibrating analytical models, Point Stress Criterion (PSC) and Modified Point Stress Criterion (MPSC). Both, experimental and modeling approaches, yielded nearly identical analytical curves, indicating that virtual testing of organosheet can be used for OHT characterization of organosheet. The results show that the notched strength of organosheet with the diameter of 2 mm was at the same level as strength of unnotched organosheet. The notch insensitivity was attributed to the increased plasticity in the matrix due to ductility in nylon.

The effect of longitudinal hole shape and size on the flexural behavior of RC beams

The building's electro-mechanical piping systems can pass through transverse or longitudinal holes inside the reinforced concrete (RC) secondary beams, thus increasing the available floor height. These holes induced a reduction in the beam stiffness and strength. This work analytically and experimentally investigates the impact of longitudinal hole shape on the flexural behavior of RC beams. The interaction between hole shape and hole location has also been studied. The test program includes nine beams with the same cross section dimensions and steel reinforcement. Holes have been made using two circular PVC pipes (50 and 75 mm in diameter), and wooden medium-density fiberboard (MDF) square tubes (50×50 mm) and rectangular tubes (50×100 mm). Each hole shape was installed at two locations (90 and 160 mm) from the top of the beam. All beams were tested to failure using a four-point bending test. The results show that the hole shape and size up to half the beam width does not affect the failure mode compared to the solid control beam. The reduction in the ultimate strength of hollow beams compared to the control beam depends on the hole shape and size, with a maximum reduction of 20%. The developed analytical models were validated using experimental test results and can be employed to accurately predict the full flexural behavior of hollow RC beams, including cracking, yielding, and ultimate moments/loads.

The effect of stiffness and hole size on nipple compression in infant suckling.

During infant feeding, the nipple is an important source of sensory information that affects motor outputs, including ones dealing with compression of the nipple, suction, milk bolus movement, and swallowing. Despite known differences in behavior across commercially available nipples, little is known about the in vivo effects of nipple property variation. Here we quantify the effect of differences in nipple stiffness and hole size on an easily measured metric representing infant feeding behavior: nipple compression. We bottle-fed 7-day old infant pigs (n = 6) on four custom fabricated silicone nipples. We recorded live X-ray fluoroscopic imaging data of feeding on nipples of two levels of hardness/stiffness and two hole sizes. We tested for differences in nipple compression at the nipple's maximum compression across different nipple types using a mixed model analysis of variance. Stiffer nipples and those with smaller holes were compressed less than compliant nipples and nipples with larger holes (p < 0.001). We also estimated the force applied on the nipple during feeding and found that more force was applied to the compliant nipple with disproportionately larger strains. Our results suggest that infant pigs' nipple compression depends on material type and hole size, which is likely detected by the infant pigs' initial assessment of compressibility and flow. By isolating nipple properties, we demonstrated a relationship between properties and suckling behavior. Our results suggest that sensory information affects feeding behaviors and may also inform clinical treatment of poor feeding performance.

Assessment of end-two-flange web crippling strength of roll-formed aluminium alloy perforated channels by experimental testing, numerical simulation, and deep learning

This work presents a deep-learning model referred to as a deep belief network (DBN) to investigate the end-two-flange (ETF) web crippling behaviour of roll-formed aluminium alloy lipped channels (both unfastened and fastened to the supports) with centred and offset web circular holes. A total of 1,080 data points was generated for training the DBN, using an elasto-plastic finite element model that was validated using 30 new experimental results presented in this paper. When the DBN predictions were compared to the experimental results, they were found to be 5% conservative on an average. A parametric analysis was then carried out using the DBN predictions, to study the effects of hole size, hole position, section thickness, and the bearing plate on web crippling strength of perforated roll-formed aluminium alloy channels. The DBN predictions were utilised to evaluate the performance of the current design rules of American Iron and Steel Institute (AISI 2016), Australian and New Zealand Standards (i.e., AS/NZS 1664, AS/NZS 4600:2018), and Eurocode (CEN 2007). The current design standards were demonstrated to be over conservative in predicting the web crippling strength of roll-formed aluminium alloy perforated channels. From the parametric analysis, new web crippling strength and web crippling strength reduction factor formulae for roll-formed aluminium alloy perforated channels were proposed. Additionally, a reliability analysis revealed that the proposed equations accurately predicted the ETF web crippling strength of roll-formed aluminium alloy perforated lipped channels.

Evaluating the adequacy of dynamic pressure remote sensing method in a model gas turbine combustor

Direct measurement of dynamic pressure in a combustor using a flush sensor mounting generally shortens the lifetime and lowers the measurement accuracy of the sensor due to its direct exposure to hot-burnt gases. Thus, indirect remote sensing methods are typically employed in combustion systems; however, the measurements may contain errors. Therefore, in this study, the feasibility of a remote sensing method for measuring dynamic pressure is verified by conducting an acoustic forcing experiment in a model gas turbine combustor. Sensing performance of the sensor adapters are evaluated based on their measurement locations for a driving frequency of 50–5000 Hz. In an experiment with different measurement locations, mode shapes corresponding to a resonant frequency of 160 Hz are clearly observed. Furthermore, in a sensor-adapter performance experiment, the effects of hole-size and length of a dynamic pressure propagation tube on the sensing characteristics are investigated and the optimum design shape is obtained. The results indicate an increase in the accuracy of dynamic pressure measurements and a subsequent decrease in the risk of combustion instability accidents. Therefore, the findings of this study and optimal design methodology for remote sensing equipment could positively contribute to the safe operation of gas turbines.

Effect of web perforations on end-two-flange web crippling behaviour of roll-formed aluminium alloy unlipped channels through experimental test, numerical simulation and deep learning

Aluminium alloy has recently become popular in New Zealand’s construction sector as a sustainable building material. However, in roll-formed aluminium alloy (RFA) channel beams, particularly those having web holes, cripples at points of concentrated or localised loading. In this paper, end-two-flange (ETF) web crippling behaviour of RFA unlipped channels having web holes was investigated using experimental tests, numerical simulations and a deep learning model referred as deep belief network (DBN). A total of 1080 data points was generated to train the DBN, using a finite element (FE) model that was validated using 30 new experimental results reported in this paper. Compared to the test data, the DBN predictions were conservative by around 6%. Using the DBN predictions, a comprehensive parametric study was undertaken which used the validated FE model in order to explore the effects of hole size, hole location, section thickness, and bearing plate on the web crippling strength of RFA channels having web holes. Web crippling strengths obtained from the DBN, tests and finite element analysis (FEA) were utilised to evaluate the performance of current design specifications from the American Iron and Steel Institute (AISI), Australian/New Zealand Standards (AS/NZS 1664; AS/NZS 4600:2018) and Eurocode (CEN 2006, 2007). It is shown that the current design rules are not reliable to predict the web crippling strength of RFA unlipped channels with web holes. As a consequence of the parametric analysis, new web crippling strength and web crippling strength reduction factor formulae for perforated RFA unlipped channels were proposed. A reliability analysis was then conducted, which confirmed that the proposed equations are capable of predicting the ETF web crippling strength of perforated RFA unlipped channels.