Spring Pitch Research Articles

Exploring Recycled Polyethylene Terephthalate (PET) Based Cushioning Design to Reduce Bruise Damage in Pears

Post-harvest activities, which include sorting, loading, unloading, and transporting, are potential factors that cause mechanical damage and bruises to fresh produce. This would directly impact fruit shelf-life and, therefore, cause economic losses. This study developed a finite element (FE) model for pear fruit where a steel impactor drop-based test was utilized. The FE model was validated by evaluating it as the experimental model in order to identify bruises of the pear fruit. Therefore, to minimize bruises on the pear fruit, a recycled polyethylene terephthalate (PET) spring-based design was proposed in order to serve as a cushioning design for pear fruits. Design of experiments and response surface methodology were performed in order to minimize the fruit bruise susceptibility response subject to different spring design parameters. The results revealed that reduced spring pitch and increased coil thickness would significantly minimize bruises of pear fruit. The recycled PET proposed design proved its efficiency in reducing FE pear fruit model bruises by about 50%. This study provides insights on assessing bruise susceptibility using finite element analysis and reusing plastic for fresh produce packaging, thus reducing loops in supply chains and achieving a circular economy.

Use of customized 3-dimensional printed mandibular prostheses with a dental implant pressure-reducing device in mandibular body defect: A finite element study performing multiresponse surface methodology

Background/purposeSegmental body defects of the mandible result in the complete loss of the affected region. In our previous study, we investigated the clinical applicability of a customized mandible prosthesis (CMP) with a pressure-reducing device (PRD) in an animal study. In this study, we further incorporated dental implants into the CMP and explored the use of dental implant PRD (iPRD) designs. Materials and methodsBy employing a finite element analysis approach, we created 4 types of CMP: CMP, CMP with iPRD, CMP-PRD, and CMP-PRD with iPRD. We developed 2 parameters for the iPRD: cone length (CL) in the upper part and spring pitch (SP) in the lower part. Using the response surface methodology (RSM), we determined the most suitable structural assignment for the iPRD. ResultsOur results indicate that CMP-PRD had the highest von Mises stress value for the entire assembly (1076.26 MPa). For retentive screws and abutments, CMP with iPRD had the highest von Mises stress value (319.97 and 452.78 MPa, respectively). CMP-PRD had the highest principal stress (131.66 MPa) in the anterior mandible. The iPRD reduced principal stress in both the anterior and posterior mandible. Using the RSM, we generated 25 groups for comparison to achieve the most favorable results for the iPRD and we might suggest the CL to 12 mm and the SP to 0.4 mm in the further clinical trials. ConclusionUse of the PRD and iPRD in CMP may resolve the challenges associated with CMP, thereby promoting its usage in clinical practice.

Experimental Analysis of Heat Transfer in a Triple Tube Heat Exchanger with Spring Turbulator Using CuO/Water Nanofluid

An Experiment has been performed to find out effect of coiled spring turbulators on the heat transfer and pressure drop in a triple tube heat exchanger using water and CuO/water (0.8%vol/vol) as working media. Two spring turbulators having pitch 5 mm and 10 mm with a common wire diameter of 1 mm are being used. The experiment was carried out under turbulent flow at different Reynolds numbers varying between 4000 to 16,000. In this experiment, the variation in the rate of heat transfer and friction factor have been analyzed for parallel and counter flow arrangements. The combination of the lower-pitched insert with CuO attained the maximum heat transfer increment in the counter flow pattern. For counter flow arrangement, augmentation in Nusselt number for a triple tube with lower spring pitch with CuO nanofluid is 63.33%, which is higher in comparison to the plain triple tube with water as working fluid. The maximum thermal performance value is observed for plain tube with CuO nanofluid having the value 1.04 at Reynolds number of 4000.

Effect of NiTi parameters on the mechanical properties of integrated braided stents

Stent insertion can serve as an effective therapy method for patients with esophageal stricture but stents with inappropriate mechanical properties lead to restenosis. To prepare a stent matching the esophageal environmental mechanics, both the NiTi spring yarn and polyester multifilament were used to produce seven kinds of stents by braiding technology. The mechanical properties of the stents were tested including compression, flexibility, and antimigration behavior. Results showed that three different parameters including spring consistency with tracks, spring content, and spring pitch altered the effective number of coils and elastic modulus, and affected the compression strength, flexibility and migration resistance of the stent. In particular, the integrated braided stent with full consistency, 12 NiTi spiral yarns, and spring pitch of 1.00 mm had the best mechanical properties among all the prototypes in this research. The compression strength, bending strength, and migration resistance were 1048.75 cN, 46.35 cN, and 3.74 N, respectively. In summary, this research presents a new preparation method for esophageal stent manufacture in the treatment of inoperable esophageal malignancies.

Finite Element Study on Forming Helical Springs by Wire Bending with a Plate

Coil springs, widely used as mechanical elements, will enter another new production outlook due to the application of CNC wire bending machines and as the era of On-Demand Manufacturing is approaching. This article tries to follow the trend and use finite element analysis investigating parameters, such as the angle, shift distance, and wire diameter, applied in a CNC bending machine with a swivel plate as the die on the formed cylindrical helical coil springs. The results show that the angle of the swivel plate normal to the wire feeding direction and shift distance have a significant effect on the spring diameter, while the wire diameter has a significant effect on the spring pitch. The result will be used as a reference for the industry to develop On-Demand Manufacturing machinery applications in the future.

Optimization of melting time of solar thermal energy storage unit containing spring type heat transfer enhancer by Taguchi based grey relational analysis

The major concern of this research study was determining the optimum parameters affecting melting time of paraffin wax used for storing artificial solar energy and time dependant enhancement ratio of thermal energy storage unit using Taguchi based grey relational analysis. The influence of the varied wire diameter, spring diameter and spring pitch on the performance of melting time and time dependant enhancement ratio of latent heat thermal energy storage unit was examined. L9 (three factors, three levels) orthogonal array was selected to design experiments. The obtained experimental results were optimized using grey relational analysis taking account the optimization as a single-objective problem instead of multi-objective problem. The optimal levels as the highest wire diameter and spring pitch and the lowest spring diameter with grey relational analysis was determined. The contribution ratios of parameters were identified by applying ANOVA analysis to find out which factor had more impact on melting time and time dependant enhancement ratio. The correlation equations of melting time and time dependant enhancement ratio depending on determining parameters were carried out by using the Regression analysis. The confirmation results revealed that the obtained data from Regression analysis were line up with the experimental results according to error analysis.

Advanced static and dynamic analysis method for helical springs of non-linear geometries

Current design and analysis methods of helical springs are significantly confined to a simple and linear domain. The traditional spring formula is only effective for analyzing helical springs with linear geometric properties like constant coil diameter, unchanged spring pitch and no coil contact. An advanced analytical spring model is proposed in this study to address the non-linear effects of variable coil diameter, spring pitch and coil contact that exist in helical springs of arbitrary shapes. It aims to expand the available spring design and analysis domain to a wider non-linear space. In addition, it is coupled with the modal spring model to explain and predict the dynamic vibrational response of non-linear beehive springs. It is found that the proposed model has an excellent accuracy in estimating mechanical properties of non-linear springs in both static and dynamic conditions by comparing with experimental and FE results. This model may lead to an innovative method for developing innovative tools of spring design and performance analysis that could be beneficial to a wide range of engineering applications.

Theoretical studies of oscillations of the cleaning working bodies spiral potato separator

Purpose. Increase of efficiency of potato tubers cleaning process from impurities of new construction of spiral separator taking into account and activation of vibrating process of its cleaning spiral springs. Methods. The research was carried out with the use of higher mathematics, theoretical mechanics, elasticity theory and methods of programming and numerical calculations with the help of PC. Results. For the developed construction of the spiral separator of potato heap, which consists of cantilever mounted cleaning spiral springs, the mathematical model of free ends of spiral oscillations under the influence of external load is developed. An equivalent bending scheme of the cantilever spiral under the action of uniformly distributed load, selected corresponding axes of coordinates and parameters characterizing the vibrational process of the spiral end are determined. For such an equivalent scheme, a differential equation of cleaning spiral oscillations in partial derivatives is made for the first time. After the corresponding transformations, the differential equation was numerically solved according to the program, by means of a PC. This made it possible to find the dependence of the change in the winding pitch of the cleaning spiral spring as a result of its deformation, in particular, the simultaneous longitudinal stretching and transverse deflection, on its length. Also new analytical dependences of the reduced moment of inertia of the section of the cantilever spring are received, on the basis of which graphic dependences of change of its value on length of a spiral spring at the set diameter, pitch of skills, angle of rise of a coil and angular speed of rotation have been received on the PC. Conclusions 1.The calculated mathematical model of vibrations of the working bodies of the spiral separator of potato heap is constructed, as a result the differential equation of transverse bending vibrations of its console cleaning spiral spring is made. 2.On the basis of the differential equation solution of transverse bending oscillations of the cleaning spiral spring the analytical expressions describing the law of vibrational process and deflection of the spiral spring at any moment of time for any point of its longitudinal axis are received. 3.Analytical dependencies are obtained to determine the variable pitch of a curved coil spring at any given time and for any inter-turn lumen during this oscillatory process. 4.At the angular velocity of the spiral spring, which is equal to ω = 30 rad∙s-1, the density of the material of which the spring is made, = 7700 kg∙m-3, modulus of elasticity Е = 2∙1011 Pa, the radius of the bar = 8.5 mm, uniformly distributed spiral spring load by potato heap intensity 1000 Н∙m-1 the total spring deflection along its length varies from 0 to 0.25 m. 5.The obtained analytical expressions of restriction on the maximum change of the cleaning spiral spring pitch at its fluctuations from the condition that potato tubers do not fall into the spring inter-turn space taking into account structural and kinematic parameters of the cleaning spiral spring, the material from which it is made, technological modes of operation and tubers' sizes. 6.As the numerical calculations on the PC show, a cleaning spiral spring with the above parameters and an initial winding pitch S = 48 mm at the considered transverse oscillations at the expense of deformation can change a step up to 54 mm that will provide not falling out of a potato tuber outside of a separator of a potato heap. Keywords: potatoes, digging, impurities, cantilever spiral spring, oscillations, differential equation, numerical calculations on PC.

Experimental investigations on the effect of geometrical properties of helical wire turbulators on thermal performance of a helically coiled tube

As like to straight tubes, experts try to use heat transfer enhancement techniques to improve the thermal performance of helical tubes. Present study provides an experimental investigation on the effect of geometrical properties of spiral wire turbulator on thermal performance of helical tube. Spiral wire is the only kind of turbulator which can be easily inserted into helical tubes. The quality and quantity of helical wire turbulator inside helical tubes are different with strait tubes, due to the presence of centrifugal forces. Besides variation of geometrical properties of spiral wires (including spring pitch, wire diameter and spring diameter) can significantly influence on thermal behavior of helical tubes. In this study spiral wire with different geometrical properties (four different spring pitch and four different wire diameter) is employed and the thermal behavior of helical heat exchanger is experimentally investigated. The helical tube containing spiral wire was put under constant heat flux supplied by means of an electrical heater. In order to calculate the convective heat transfer coefficient, the inlet, outlet and wall temperature of helical tube was measured. The results revealed that variation of the pitch and wire diameter have significant effect on thermal performance of helical heat exchanger. Increment in spring pitch and wire diameter of spiral tube caused increment in Nu (Nusselt) number up to 73% and 70% respectively. Also it was revealed that increment in wire diameter increases the heat transfer coefficient whereas the effect of increment of spring pitch on heat transfer coefficient is vice versa and the increment of spring pitch decrease the heat transfer coefficient.

Smooth muscle-like tissue constructs with circumferentially oriented cells formed by the cell fiber technology.

The proper functioning of many organs and tissues containing smooth muscles greatly depends on the intricate organization of the smooth muscle cells oriented in appropriate directions. Consequently controlling the cellular orientation in three-dimensional (3D) cellular constructs is an important issue in engineering tissues of smooth muscles. However, the ability to precisely control the cellular orientation at the microscale cannot be achieved by various commonly used 3D tissue engineering building blocks such as spheroids. This paper presents the formation of coiled spring-shaped 3D cellular constructs containing circumferentially oriented smooth muscle-like cells differentiated from dedifferentiated fat (DFAT) cells. By using the cell fiber technology, DFAT cells suspended in a mixture of extracellular proteins possessing an optimized stiffness were encapsulated in the core region of alginate shell microfibers and uniformly aligned to the longitudinal direction. Upon differentiation induction to the smooth muscle lineage, DFAT cell fibers self-assembled to coiled spring structures where the cells became circumferentially oriented. By changing the initial core-shell microfiber diameter, we demonstrated that the spring pitch and diameter could be controlled. 21 days after differentiation induction, the cell fibers contained high percentages of ASMA-positive and calponin-positive cells. Our technology to create these smooth muscle-like spring constructs enabled precise control of cellular alignment and orientation in 3D. These constructs can further serve as tissue engineering building blocks for larger organs and cellular implants used in clinical treatments.

Design and Development of a Livestock Feed Mixer with Spring-Controlled Packaging Unit

A vertical livestock feed mixer with spring-controlled packaging unit was designed, constructed and tested. This design had in focus a weighing and gauging mechanism which made possible a semi-automatic packaging in conjunction with feed mixing and discharge operations. The main components of the machine included a double-wall cylindrical mixing chamber consisting of recycling gate, discharge gate, evacuating gate, window and a screw conveyor inside an inner cylinder. The packaging mechanism is attached to the discharge gate and the base of the frame with the frame serving as the structural support for the machine and its contents. The main design parameters included screw conveyor features such as helix angle, fill ratio, normal pressure due to bulk load on screw shaft, axial force per pitch, total screw torque, capacity and power requirements of the screw conveyor. The design concept of the packaging mechanism involved determination of free length of spring, total active length, pitch of spring, spring index, stiffness of spring, maximum shear stress and total spring rate. In a hitch-free operation, the machine was designed to package 25 kg of mixed feed ingredients at a time. In operation, the feed ingredients are scooped and moved upward by the rotary movement of the screw conveyor and then sprayed back into the smaller cylinder without passing through the internal tube. A preliminary testing was carried out on the machine to determine the actual discharge rate and hence the performance of the packaging mechanism. Results revealed that an average discharge rate of 0.356 kg/s was obtained. Powered by a 2 hp single phase electric motor, the machine has a mixing capacity of 4.124 m3/h with a production cost of $470.

Heat transfer characteristics in a sudden expansion pipe equipped with swirl generators

This investigation is aimed at studying the heat transfer characteristics and pressure drop for turbulent airflow in a sudden expansion pipe equipped with propeller type swirl generator or spiral spring with several pitch ratios. The investigation is performed for the Reynolds number ranging from 7500 to 18,500 under a uniform heat flux condition. The experiments are also undertaken for three locations for the propeller fan ( N = 15 blades and blade angle of 65°) and three pitch ratios for the spiral spring ( P/ D = 10, 15 and 20). The influences of using the propeller rotating freely and inserted spiral spring on heat transfer enhancement and pressure drop are reported. In the experiments, the swirl generator and spiral spring are used to create a swirl in the tube flow. Mean and relative mean Nusselt numbers are determined and compared with those obtained from other similar cases. The experimental results indicate that the tube with the propeller inserts provides considerable improvement of the heat transfer rate over the plain tube around 1.69 times for X/ H = 5. While for the tube with the spiral spring inserts, an improvement of the heat transfer rate over the plain tube around 1.37 times for P/ d = 20. Thus, because of strong swirl or rotating flow, the propeller location and the spiral spring pitch become influential on the heat transfer enhancement. The increase in pressure drop using the propeller is found to be three times and for spiral spring 1.5 times over the plain tube. Correlations for mean Nusselt number, fan location and spiral spring pitch are provided.

Pressure Contact Micro-Springs in Small Pitch Flip-Chip Packages

This work investigates electrical pressure contacts based on a micro-spring with orders of magnitude smaller pitch and force than conventional pressure contacts. The springs are beams which curl out of the surface and can be used for wafer-scale testing and packaging. They are fabricated with standard wafer-scale thin film techniques and have been previously demonstrated on active silicon integrated circuits. Single springs and their electrical contacts are characterized with force versus compression and compression versus resistance measurements. Flip-chip packages with hundreds of micro-springs were assembled with 20-mum pad pitch and 40-mum spring pitch. Each spring operates with a force of approximately 0.01 g and contacts a gold pad. These packages are shown to have stable resistance values during both in-situ thermocycle (0degC to 125degC) and humidity testing (60degC at 95%RH). Spring electrical contacts inside the package are shown not to degrade during environmental testing through measurements of four-wire resistance and electrical isolation structures. High-speed glitch measurements are performed to confirm that the pressure contact does not have intermittent opens during thermocycling. These results suggest that a low-force solder-free pressure spring contact is a viable technology for next generation flip-chip packaging

Performance of Wire Springs as Extended Heat Transfer Surface for Compact Heat Exchangers

Use of thin metal wire structures as a new type of extended heat transfer surface is proposed. As one of the most basic shapes of such wire structures, heat transfer performance of spring shaped fins is experimentally investigated under relatively low Reynolds number conditions. The averaged heat transfer coefficient is evaluated by a single-blow method while the pressure drop is measured at a steady state flow condition. The effects of the geometric parameters such as the wire diameter, the spring pitch and the pitch ratio were systematically examined and the obtained data were compared with that of a conventional offset fin, which is commercially available. It was found that the geometric parameters of the spring fins and the arrangement of spring fins in the test section affect their heat transfer performance. Some types of spring fins showed better heat transfer performance than a conventional offset fin, when they are evaluated in terms of the total heat transfer at a constant pumping power.

Quasi‐Homogeneous and Pseudospin Modes of Zirconium‐Wire Combustion in Air

A novel experimental technique is proposed for examining the transition mechanism from quasi‐homogeneous to heterogeneous combustion — burning of a variable‐pitch spring. Depending on the pitch of air‐combustible zirconium springs, two combustion modes are possible. Quasi‐homogeneous (layer‐by‐layer) combustion is observed in the case of small‐pitch springs; as the spring pitch increases, quasi‐homogeneous combustion transforms into heterogeneous (pseudo‐spin) combustion. Conditions for the occurrence of various combustion modes, depending on the spring diameter and pitch, are studied.

High-Density Multipin Connector for High-Speed Pulse Propagation

A Procedure for designing connectors suitable for gigabit per second (Gbit/s) rate pulse propagation is presented. A design chart for a multipin connector satisfying both electrical and mechanical requirements is obtained. The design procedure is as follows. First, the effect of varying the arrangement of ground contact springs on characteristic impedance is investigated using the finite-element method. Next, the effect of varying contact spring size and contact spring pitch is analyzed with respect to characteristic impedance and crosstalk. Finally, a design chart is constructed for the multipin connector by combining the mechanical characteristics of the contact springs with the aforementioned electrical characteristics. Based on the resulting design chart, a prototype multipin connector for a pin grid array is fabricated. The empirically derived electrical characteristics of the prototype connector are in good agreement with those predicted analytically.