Model For Shrinkage Research Articles

Thermo-Viscoelastic Model for Shrinkage and Warpage Prediction During Cooling and Solidification of Automotive Blow Molded Parts

Thermo-Viscoelastic Model for Shrinkage and Warpage Prediction During Cooling and Solidification of Automotive Blow Molded Parts

The Experimental Study on Creep and Shrinkage of High Strength Concrete with Fly Ash

Shrinkage and creep characteristics of concrete are significant factors in the design of prestressed concrete structures. With large scale/span concrete structures developed, the fly ash or other blends are added into high strength concrete to improve the mechanical properties and workability. As a result, the existing shrinkage and creep predicting models have certain limitations. The creep and shrinkage behavior of high strength concrete with fly ash are studied in this paper. Proper predicting model for shrinkage and creep of high strength concrete is recommended. The influence factor of fly ash is proposed as well. These conclusions would be of great useful for structures with fly ash concrete.

Analysis of Volumetric Shrinkage and Optimization of Process Parameters in Injection Molding

Based on experimental method of factorial design, numerical simulation of injection molding using Moldflow software has been done. The effects of the gate number-distribution, melt temperature, packing pressure, packing time, injection time, etc. on volumetric shrinkage and the two-way interactions among factors in injection molding of plastic part have been researched. The regression model for volumetric shrinkage of plastic part has been obtained through multiple linear regression analysis of the experimental data. The optimization model has been established to optimize processing parameters setting leading factors which effect volumetric shrinkage as design variables and regression model of volumetric shrinkage as objective function. The volumetric shrinkage value of plastic part is less than the minimum volumetric shrinkage value of the main experiment, which indicates that the method has a good practical value in engineering.

Deflection Reliability Analysis of PSC Box-Girder Bridge under High-Speed Railway Loads

A high-speed railway (HSR) construction boom has been observed in China during the past few years, in which prestressed concrete (PSC) box-girders are widely used for HSR bridges. Concerns have been raised regarding the long-term deflection of girders under the combined actions of concrete creep, shrinkage, and tendon relaxation, since the time-variant deflection significantly undermines the safety of high-speed trains. This paper presents the time-variant deflection reliability analysis of an existing HSR PSC box-girder bridge, in which a hybrid method, consisting of the response surface (RS) method, the finite element (FE) method and the checking point method (i.e., the JC method), is used. The pre-and post-cracking behaviors of the thin-walled box girder are described by using composite degenerated shell elements with the smeared cracking model and the Hordijk's tension softening relation. In particular, the CEB-FIP model for creep and shrinkage is applied in the finite-element (FE) analyses. By using the probabilistic sensitivity analyses, random variables that significantly affect the time-variant deflection are selected for the reliability calculation. It is found that the deflection reliabilities are high in the early stage of bridge service but decrease rapidly during the first 10 to 20 service years. Higher speed limits result in a significant decrease in deflection reliability indices, which may fall below the target value prior to the expected service life. The proposed methodologies can be used in the design optimization, speed control and making rational maintenance or repair strategies for HSR PSC bridges.

An analysis of embryo development in palm: interactions between dry matter accumulation and water relations in Pritchardia remota (Arecaceae)

AbstractAssessments of seed storage physiology among Arecaceae (palm) species are often inconclusive because seeds exhibit diverse responses to low temperature and moisture conditions. Interrelationships between dry matter accumulation, cell structure and water relations during seed development of the endangered Hawaiian endemic palm, Pritchardia remota, suggest that damage from drying results from mechanical strain. Endosperm and fruits accumulate dry mass through most of the 400 d gestation period, but embryos reached maximum dry mass about 250 d post-anthesis (DPA). Mostly sucrose and some triacylglycerols accumulated in the cytoplasm and vacuoles of embryo cells, and organelles in mature embryo cells de-differentiated. Water content and water potential decreased as embryos matured and embryos contained about 0.45 g H2O (g dry mass)− 1 ( − 26 MPa) at shedding. Mature embryos survived drying to 0.16 g g− 1 ( − 49 MPa), but further drying was lethal. A model of allowable cell shrinkage is consistent with the substantial, but incomplete, desiccation tolerance acquired in P. remota embryos, and provides a new framework to explain variation in critical water contents as embryos develop. We suggest that desiccation tolerance, which distinguishes recalcitrant and orthodox physiologies among seeds, can be quantified by mechanical strain when embryo cells shrink during drying.

Experimental Study on Forecasting Mathematical Model of Drying Shrinkage of Recycled Aggregate Concrete

On the basis of basic law in AASHTO2007 model, the forecasting mathematical model of drying shrinkage of recycled aggregate concrete (RAC) is established by regression analysis and experimental study. The research results show that (1) with the replacement rate of RCA increases, the drying shrinkage value of RAC increases; this trend is even more obvious in the early drying time. (2) The addition of fly ash can inhibit the drying shrinkage of RAC, but the effect is not very obvious. Specifically, the addition of fly ash will increase the shrinkage to some extent when the mixing amount is 20%. (3) The addition of expansive agent can obviously inhibit the shrinkage of RAC; the inhibition affection is better than that of fly ash. (4) The forecasting mathematical models of drying shrinkage of RAC established in this paper have high accuracy and rationality according to experiment validation and error analysis.

Desorption Experimental Analysis and Modeling of Drying Shrinkage and Relative Humidity in Non-Saturated Concrete

Abstract. The paper investigates the gradient of relative humidity over time at different depth from dried surface and the relationship between relative humidity and concrete shrinkage. It shows that a drop in relative humidity over time is remarkable, and that drying shrinkage is linearly related to humidity. By measuring the weight of the sample and calculation of the capillary pressure, the relationship between the saturation and the capillary pressure is presented. Based on the experiment and Kelvin’s law, a model of shrinkage for non-saturated concrete taking the surface energy into account is presented. A comparison of computed and observed drying shrinkage is made, finding that the two values are in agreement very well.

Parametric design and process parameter optimization for bra cup molding via response surface methodology

Seamless and traceless undergarments have rendered foam sheet molding as an important manufacturing technique for the intimate apparel industry. Seamless bra cups are made by one-step forming technology. The three-dimensional (3D) cup shape is formed by using high temperatures and pressures with flexible polyurethane foams. Nevertheless, the mold head design process and control of the bra cup molding process are highly complicated and error prone. There is limited knowledge about the effects of foam properties, molding parameters and foam cup geometric parameters on molding process optimization. This research presents a response surface methodology as the approach for parametric design and process parameter optimization of bra cup molding. The proposed approach integrates 3D scanning via reverse engineering, parameterized-based remeshing and registration algorithm, non-linear mathematical prediction models for cup shape conformity, a model of foam shrinkage and example-based bra cup design and grading to optimize the bra cup development and production process. The experimental results show that this method is highly effective and more timesaving in the design and development of new products, as well as providing consistent quality control of the bra cup molding process.

Study on Prediction Model of Shrinkage and Creep of Prestressed Concrete Beam in Passenger Dedicated Line

To improve the calculation precision of deformation in prestressed concrete bridge in passenger dedicated line and accurately predict the development of shrinkage and creep in bridge, a universal applicable modified model was put forward in this paper based on ACI 209R(1992) shrinkage and creep model. In the modified model, three influence factors-slump, strength and reinforcement - are corrected. And the modified model results were compared with the experimental results. It shows that the modified model can more accurately predict the development of shrinkage and creep of high-speed railway bridge and better accord with the law of it.

Diffusive model of pore shrinkage in final-stage sintering under hydrostatic pressure

A grain-boundary-diffusion model is developed to understand the densification behavior of pores in the final stage of sintering under compressive hydrostatic pressure. From analysis of the diffusive model, the bulk viscosity, densification rate and shrinkage rate of pores are predicted for a dense matrix polycrystal containing spherical pores, and compared with the existing experimental results and models. A transition in the sintering mechanism is predicted from the different pore-size dependence of the shrinkage rate between the diffusive and the viscous flow models. The transition effect is experimentally confirmed by the appearance of a downward inflection in the size distribution of pores during sintering. The upward inflection observed experimentally in the cavity-size distribution after superplastic deformation is also explained by the transition of the mechanism.

Experimental Study on Creep and Shrinkage of High-Strength Plain Concrete and Reinforced Concrete

It is important to accurately estimate creep and shrinkage effects in long-span continuous box girder bridges. Based on the experiments on creep and shrinkage of the plain concrete used in the continuous rigid frame of Sutong Bridge, China, the applicability of ACI 209–82, JTG D62–2004, B3 and GL2000 prediction model for creep and shrinkage on the high-strength concrete is evaluated. Also, a modified model based upon JTG D62–2004 is presented. Results indicate that the accuracy of prediction of creep and shrinkage can be enhanced greatly by carrying out short-term creep and shrinkage measurements on the given concrete and modifying the prediction model parameters accordingly. Furthermore, the presence of steels can have an impact on the time-dependent deformations caused by creep and shrinkage, accordingly, the restraint influence of steels on creep and shrinkage is investigated through the reinforced specimens with different reinforcement ratio. Formulas of influence coefficients of steels on creep and shrinkage are derived, and a good agreement is observed between the calculated values of the influence coefficients of steels on creep and shrinkage and the measured data in each specimen. The reinforced specimens can be also used for calibrating the modified model.

Shrinkage Performance of Adherence of New Steel Fiber-Reinforced Concrete to Old Concrete

Shrinkage experiments were done to determine the influence of the volume fraction of steel fiber-reinforcement on the bonding behavior between new concrete and old concrete. The mechanics of the model of restricted shrinkage upon the adherence of new steel fiber reinforced concrete to old concrete are described. The results demonstrate that the difference of shrinkage between the new and the old concrete can been reduced by adding steel fiber to the new concrete. The decrease of shrinkage difference reduces the shrinkage force at the adhesive interface, which improves the adhesion of new concrete to old concrete and the magnitude of the decrease of shrinkage difference is correlated to the steel fiber volume fraction.

The drying shrinkage of cellulosic fibres and isotropic paper sheets

We present theory for the shrinkage on drying of the cross-sectional area of cellulosic fibres and show that this depends on their initial moisture content only. For the linear shrinkage of cross-sectional dimensions, an additional parameter is required, which we estimate from comparison of the theory with experimental data from the literature. We proceed to combine our model of fibre shrinkage with probabilistic theory for fibre contacts in random fibrous networks to obtain a model for the unrestrained shrinkage of isotropic paper sheets. The expression obtained depends only on the moisture content of fibres and the extent of inter-fibre contact and exhibits good agreement with experimental data for laboratory-formed paper sheets. The results have relevance to the commercial manufacture of paper and potential for application to the study of cellulose nano-composites.

Evolutionary trajectory of white spot syndrome virus (WSSV) genome shrinkage during spread in Asia.

BackgroundWhite spot syndrome virus (WSSV) is the sole member of the novel Nimaviridae family, and the source of major economic problems in shrimp aquaculture. WSSV appears to have rapidly spread worldwide after the first reported outbreak in the early 1990s. Genomic deletions of various sizes occur at two loci in the WSSV genome, the ORF14/15 and ORF23/24 variable regions, and these have been used as molecular markers to study patterns of viral spread over space and time. We describe the dynamics underlying the process of WSSV genome shrinkage using empirical data and a simple mathematical model.Methodology/Principal FindingsWe genotyped new WSSV isolates from five Asian countries, and analyzed this information together with published data. Genome size appears to stabilize over time, and deletion size in the ORF23/24 variable region was significantly related to the time of the first WSSV outbreak in a particular country. Parameter estimates derived from fitting a simple mathematical model of genome shrinkage to the data support a geometric progression (k<1) of the genomic deletions, with k = 0.371±0.150.Conclusions/SignificanceThe data suggest that the rate of genome shrinkage decreases over time before attenuating. Bioassay data provided support for a link between genome size and WSSV fitness in an aquaculture setting. Differences in genomic deletions between geographic WSSV isolates suggest that WSSV spread did not follow a smooth pattern of geographic radiation, suggesting spread of WSSV over long distances by commercial activities. We discuss two hypotheses for genome shrinkage, an adaptive and a neutral one. We argue in favor of the adaptive hypothesis, given that there is support for a link between WSSV genome size and fitness.

Time-Dependent Reliability of PSC Box-Girder Bridge Considering Creep, Shrinkage, and Corrosion

Bridge performance undergoes time-varying changes when exposed to aggressive environments. While much work has been done on bridge reliability under corrosion, little is known about the effects of creep and shrinkage on the reliability of concrete bridges. In this paper, the CEB-FIP model for creep and shrinkage is applied by using finite-element (FE) analysis in conjunction with probabilistic considerations. Verification is made by comparing the analytical findings with existing test data. More specifically, a time-dependent reliability assessment is made for a composite prestressed concrete (PSC) box-girder bridge exposed to a chloride environment. This realized via an advanced probabilistic FE method. The postcracking behavior of the thin-walled box girder is described using composite degenerated shell elements, and importance sampling is used to improve the efficiency of the reliability analyses. It is shown that concrete creep and shrinkage dominate during the early stages of bridge structure deterio...

A Powder Shrinkage Model for Describing Real Layer Thickness during Selective Laser Melting Process

Shrinkage tends to generate when loose metal powder melted in each processing layer along the direction of layer growing during selective laser melting process, resulting in an increased real layer thickness. The shrinkage model for layer shrinkage in SLM process is established. The variation of real layer thickness and the relevant mathematical explanations are discussed in this paper. The results show that the total shrinkage of metal powder layer sharply increases in the initial layers, and then reaches to a plateau value with the increased processing layers. This value is defined by the ratio of sliced layer thickness (h) to relative density (k) during selective laser melting process.

A two-variable linear model of parotid shrinkage during IMRT for head and neck cancer

Purpose To assess anatomical, clinical and dosimetric pre-treatment parameters, possibly predictors of parotid shrinkage during radiotherapy of head and neck cancer (HNC). Materials Data of 174 parotids from four institutions were analysed; patients were treated with IMRT, with radical and adjuvant intent. Parotid shrinkage was evaluated by the volumetric difference (Δ V) between parotid volumes at the end and those at the start of the therapy, as assessed by CT images (MVCT for 40 patients, KVCT for 47 patients). Correlation between Δ Vcc/% and a number of dosimetric, clinical and geometrical parameters was assessed. Univariate as well as stepwise logistic multivariate (MVA) analyses were performed by considering as an end-point a Δ Vcc/% larger than the median value. Linear models of Δ V (continuous variable) based on the most predictive variables found at the MVA were developed. Results Median Δ Vcc/% were 6.95 cc and 26%, respectively. The most predictive independent variables of Δ Vcc at MVA were the initial parotid volume (IPV, OR: 1.100; p = 0.0002) and Dmean (OR: 1.059; p = 0.038). The main independent predictors of Δ V% at MVA were age (OR: 0.968; p = 0.041) and V40 (OR: 1.0338; p = 0.013). Δ Vcc and Δ V% may be well described by the equations: Δ Vcc = −2.44 + 0.076 Dmean (Gy) + 0.279 IPV (cc) and Δ V% = 34.23 + 0.192 V40 (%) − 0.2203 age (year). The predictive power of the Δ Vcc model is higher than that of the Δ V% model. Conclusions IPV/age and Dmean/ V40 are the major dosimetric and clinical/anatomic predictors of Δ Vcc and Δ V%. Δ Vcc and Δ V% may be well described by bi-linear models including the above-mentioned variables.

A PROPOSAL OF PREDICTION MODEL FOR AUTOGENOUS SHRINKAGE OF ULTRA HIGH-STRENGTH CONCRETE

In this paper, a prediction model for autogenous shrinkage of ultra high-strength concrete which include silica fume was proposed by using mixture rule and autogenous shrinkage behavior of cement paste with low water-to-binder ratio. The proposed autogenous shrinkage model consists of two parts with regard to the rate of autogenous shrinkage. Characteristic autogenous shrinkage of ultra high-strength concrete which is rapid autogenous shrinkage up to about 1 day, is expressed by a function of water-to-binder ratio and temperature of fresh concrete. And reaction activity of silica fume in high temperature is expressed by apparent activation energy. The proposed model is evaluated by a comparison with previous data, and it has about accuracy of 30%.

Investigating the effects of ingredient levels on physical quality properties of cooked hamburger patties using response surface methodology and image processing technology

A three-factor central composite design was adopted to determine the interactive effects of fat (15-30%), water (10-20%) and textured soy protein (3-9%) content on the shrinkage, fat loss and moisture loss of hamburger patties after cooking. Image processing was used to estimate the shrinkage of hamburger patties. Textured soy protein (TSP) content was found to be the most important factor for minimizing fat and moisture loss. Both fat and water content were found to be significantly effective (P<0.05) in the model for shrinkage and moisture loss in linear form. The changes in shrinkage due to fat, water and TSP content were also in linear form. The model for fat loss was in linear and quadratic form, whereas the model for moisture loss was in full quadratic form. The models for shrinkage, fat loss and moisture loss had the R-square values of 0.954, 0.969 and 0.964, respectively.

Analytical model for ArF photoresist shrinkage under scanning electron microscopy inspection

Linewidth slimming is a phenomenon occurring specifically in photolithography of 193 nm wavelength (ArF) radiation. Photoresists for this wavelength appear to lose volume when exposed to electron-beam radiation, as when scanned in scanning electron microscopy for critical dimension (linewidth) measurement. This work is an attempt to understand this “shrinkage” from a polymer physics point of view. More specifically, the authors try to check the applicability of free volume theory in polymer systems by calculating some relevant physical properties, assuming that the exposure to e-beam creates an external hardened shell for the material bulk, and continued exposure will deliver heat into the polymer enclosed in a confined space. The authors’ main conclusion is that the free volume loss (annealing) shows qualitative resemblance to experiment, but this effect exclusively is not a sufficient quantitative explanation for the observed shrinkage. A possible explanation for this discrepancy is that their model is limited due to unknown material parameters, or that the annealing is coupled with other effects such as “wringing” solvent out.