Penetrometers

Expendable Doppler penetrometer components. (From Beard, R.M. 1985. Expendable Doppler penetrometer for deep ocean sediment strength measurements. In Laboratory and In Situ Determination of the Strength of Marine Soils, STP 883, Chaney, R.C., and Demars, K.R., eds., ASTM, Philadelphia, PA, 101-124, 1985. Reprinted with permission. Copyright ASTM.) 

A number of techniques have been developed to convert the total penetration force to sediment shear strength. They t5qjically involve splitting up the force into various components which correspond to different elements of an assumed mode of soil failure. A soil penetration model based on Newton s second law has been presented by True (1975). If the penetrometer motion is known, then the soil strength can be determined. 

Se is the strain rate effect (varies between 1 and 2 as a function of velocity) 

Su is the undrained shear strength of sediment Nc is the bearing capacity factor (usually 9) 

8 is the side adhesion factor (usually assumed equal to 1) 

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Penetrating stains Penetration resistance Penetration theory Penetrometers Peng-Robinson equation DL-Pemcillamine Penicillamine [52-67-5]... 

Tertiary amines are also effective as accelerators in cobalt redox systems to advance the cure rate (Eig. 6). Hardness development measured by Shore D or Barcol D634-1 penetrometer can be used to demonstrate this benefit, which is useful in increasing mold turnover at ambient temperatures. 

Most instmments make use of a probe geometry which gives an increasing area of contact as penetration proceeds. In this way, at some depth of penetration, the resisting force can become sufficient to balance the appHed force on the indentor. Unfortunately, many geometries, eg, diamonds, pyramids, and cones, do not permit the calculation of basic viscoelastic quantities from the results. Penetrometers of this type include the Pfund, Rockwell, Tukon, and Buchholz testers, used to measure indentation hardness which is dependent on modulus. 

For dynamic water resistance, the BaUy Penetrometer Test, lUP/10 (52) measures water penetration. 

A coherent plastic layer from a few mm to 2—3 cm thick separates the semicoke and coke from the unfused coal in the coke oven. Coking properties are assessed in Russia and some other countries by a measurement of the thickness of this plastic layer. A standardized test widely used in eastern Europe is the best known of this type (6) and involves a penetrometer used to measure the thickness of the plastic layer in a column of coal heated from the bottom. The various standard tests give results that are similar but do not give close correlations with each other. 

Fig. 7. Root and shoot dry weight of wheat after 22 days of growth (5-leaf Stage) at various soil penetrometer resistances. Variations in penetrometer resistance were obtained by varying soil bulk density and water content. Symbols are as follows. Shape refers to bulk density (g cm ) 0,1.17 A, 1.29 , 1.37 <0, 1.41 V, 1.45. Shade refers to water content (g g dry soil) open symbols, 0.22 or 0.23 half-shaded, 0.25 closed, 0.27. Points are means s.E. (n = 6). Modified from Masle Passioura (1988).

This treatise wants to give a short but not necessarily complete overview of the standard rheological equipment of a modem laboratory in the food industry, starting off with purely empirical rheometers like the Ridgelimeter, the Pectinometer of Herbstreith Fox, and penetrometers, passing over to more sophisticated rheometers, capable to give fundamental data. 

Penetrometers are easy to use giving good results and correlating well with the sensory assessment of gels etc. Nevertheless these instruments yield a purely empirical method working on the principal of linear compression, penetration or back extrusion. 

At the penetrometers the form and the weight of the probe are preselected depending on the test material. The penetration speed or the penetration depth can not be preselected. The penetration measurements are based on the gravitational force applied by the probe. 

Three useful tests have been used to evaluate the working and setting properties of experimental cements. These are the parallel plate plas-tometer, the penetrometer and the oscillating rheometer. They are described in the following sections of this chapter. 

G. M. Whiteley, The deformation of soil by penetrometers and root tips of Pisiim sativum. Plant Soil 7/7 210 (1989). 

The traditional subsurface rock characterization technique includes collection of field samples and subsequent analysis in the laboratory for both mineralog-ical and chemical data. A borehole or penetrometer sampler initially collects... 

Fia. 7. Effect of n-heptyl additives on fluidity as measured with a precision penetrometer (arbitrary numbers) for Rutile-Plexol 201 and HiSil-Plexol 201 Gels. 

A penetrometer consisting of a weighted needle and depth gauge may be used to estimate Tr In this crude test, the penetration of the weighted needle is monitored as the temperature of the polymer, in contact with the needle, is increased. 

The so-called brittle point, associated with sample failure in impact tests, may be determined qualitatively using a penetrometer or a Shore durometer (an instrument used to measure resistance of a sample to penetration by a blunt needle) to measure the change in penetration hardness with temperature. Also, a thin film of a polymer may be readily folded at temperatures above T but may crack when folded at temperatures below Tr... 

The stability of foams is usually measured by the volume of liquid drained from a foam during a specific time at room temperature (10. 15. 17) or by a decrease in foam volume over time. Methods employed to measure foam stability include the rate of fall of a perforated weight through a column of foam (20. 22), the penetration of a penetrometer cone (17), or the ability to support a series of specific weights (277. 

The lower limit of the elastic range, the glass transition temperature, can be easily determined by refractometric, volumetric, or other well known methods. The upper limit suffers from an exact definition the transition from the fixed liquid to the liquid state occurs without transformation. But as the viscosity decreases exponentially with the temperature it is very convenient to define a 1 flow-temperature by penetrometer measurements. If the rate of temperature rise is kept constant, this temperature is reproducible within 1° or 2°C. The penetrometer indicates a temperature where macroscopically one would call the substance liquid. ... 

The same state diagram can be taken as a function, not of the chain length, but of the amount of plasticizer which is added to a polymer of given molecular weight. A new type of penetrometer, which uses a penetrating rod, has been constructed for... 

After curing, the Unconfined Compressive Strength (UCS) of the samples was measured by using a penetrometer. The reagent ratio that resulted in the desired UCS (1.5-2.5 tons/ft ) was utilized for further leach-ability testing. 

De Man (1983) has reviewed this property of fats. Consistency is defined as (1) an ill-defined and subjectively assessable characteristic of a material that depends on the complex stress-flow relation or as (2) the property by which a material resists change of shape. Spreadabil-ity, a term used in relation to consistency, is the force required to spread the fat with a knife. The definition is similar to that for hardness the resistance of the surface of a body to deformation. The most widely used simple compression test in North America is the cone penetrometer method (AOCS Method Cc 16-60, 1960). More sophisticated rheological procedures are also available. Efforts have been made to calibrate instrumental tests with sensory response. With the cone penetrometer method, penetration depth is used as a measure of firmness. Hayakawa and De Man (1982) studied the hardness of fractions obtained by crystallization of milk fat. Hardness values obtained with a constant speed penetrometer reflected trends in their TG composition and solid fat content. 

TEXTURAL MEASUREMENTS USING A PUNCTURE PROBE OR A CONE PENETROMETER... 

Puncture probes and cone penetrometers provide a simple means for determining the textural properties of many structured foods (see sample results in Figure H2.2.1). 

Figure H2.2.1 Force/deformation curves illustrating three puncture probe tests (50 mm/min deformation rate) of an apple specimen and a cone penetrometer test (10 mm/min deformation rate) of Cheddar cheese, all at room temperature.

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